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Sample records for nanocrystalline cobalt substituted

  1. Structural and magnetic properties of nanocrystalline stannic substituted cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, Y.M., E-mail: ymabbas@live.com [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Mansour, S.A. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Physics Department, Faculty of Science, King AbdulAziz University, Rabegh (Saudi Arabia); Ibrahim, M.H. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Physics Department, Faculty of Science, King AbdulAziz University (Saudi Arabia); Ali, Shehab. E., E-mail: shehab_ali@science.suez.edu.eg [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt)

    2012-09-15

    The structural and magnetic properties of the spinel ferrite system Co{sub 1+x}Fe{sub 2-2x}Sn{sub x}O{sub 4} (x=0.0-1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm{sup -1} and 425 cm{sup -1}, which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. - Highlights: Black-Right-Pointing-Pointer The spinel ferrite system has been formed at 1000 Degree-Sign C by using ceramic techniques. Black-Right-Pointing-Pointer Structural and microstructural evolutions have been studied using XRD and the Rietveld method. Black-Right-Pointing-Pointer The refinement result showed cationic distribution in the lattice is partially an inverse spinel. Black-Right-Pointing-Pointer The transmission electronic microscope analysis confirmed the X-ray results. Black-Right-Pointing-Pointer Magnetic properties of the samples were characterized by using a vibrating sample magnetometer.

  2. Structural and magnetic properties of nanocrystalline stannic substituted cobalt ferrite

    International Nuclear Information System (INIS)

    Abbas, Y.M.; Mansour, S.A.; Ibrahim, M.H.; Ali, Shehab. E.

    2012-01-01

    The structural and magnetic properties of the spinel ferrite system Co 1+x Fe 2−2x Sn x O 4 (x=0.0–1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm −1 and 425 cm −1 , which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. - Highlights: ► The spinel ferrite system has been formed at 1000 °C by using ceramic techniques. ► Structural and microstructural evolutions have been studied using XRD and the Rietveld method. ► The refinement result showed cationic distribution in the lattice is partially an inverse spinel. ► The transmission electronic microscope analysis confirmed the X-ray results. ► Magnetic properties of the samples were characterized by using a vibrating sample magnetometer.

  3. Microstructure characterization and cation distribution of nanocrystalline cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, Y.M., E-mail: ymabbas@live.com [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Mansour, S.A.; Ibrahim, M.H. [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Ali, Shehab E., E-mail: shehab_physics@yahoo.com [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt)

    2011-11-15

    Nanocrystalline cobalt ferrite has been synthesized using two different methods: ceramic and co-precipitation techniques. The nanocrystalline ferrite phase has been formed after 3 h of sintering at 1000 deg. C. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. The transmission electronic microscope analysis confirmed the X-ray results. The magnetic properties of the samples were characterized using a vibrating sample magnetometer. - Highlights: > The refinement result showed that the cationic distribution over the sites in the lattice is partially an inverse spinel. > The transmission electronic microscope analysis confirmed the X-ray results. > The magnetic properties of the samples were characterized using a vibrating sample magnetometer.

  4. Microstructure characterization and cation distribution of nanocrystalline cobalt ferrite

    International Nuclear Information System (INIS)

    Abbas, Y.M.; Mansour, S.A.; Ibrahim, M.H.; Ali, Shehab E.

    2011-01-01

    Nanocrystalline cobalt ferrite has been synthesized using two different methods: ceramic and co-precipitation techniques. The nanocrystalline ferrite phase has been formed after 3 h of sintering at 1000 deg. C. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. The transmission electronic microscope analysis confirmed the X-ray results. The magnetic properties of the samples were characterized using a vibrating sample magnetometer. - Highlights: → The refinement result showed that the cationic distribution over the sites in the lattice is partially an inverse spinel. → The transmission electronic microscope analysis confirmed the X-ray results. → The magnetic properties of the samples were characterized using a vibrating sample magnetometer.

  5. Nanocrystalline Iron-Cobalt Alloys for High Saturation Indutance

    Science.gov (United States)

    2016-02-24

    film deposited just like the pick-up of a turn-table music player. The contact pads provide the electrical contacts to the starting and end point of...anisotropy using the geometry of the thin toroid. We have shown experimentally that the thin film toroid calculations may be applicable to up to millimeter...thin film as well as bulk devices. 15. SUBJECT TERMS Micromagnetic Calculations, Nanocrystalline cobalt-iron, Thin Film Toroids 16. SECURITY

  6. Correlation between crystallographic texture, microstructure and magnetic properties of pulse electrodeposited nanocrystalline Nickel–Cobalt alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Amit; Chhangani, Sumit; Madhavan, R.; Suwas, Satyam, E-mail: satyamsuwas@materials.iisc.ernet.in

    2017-07-15

    Highlights: • Nano-crystalline Ni–Co materials with varying composition has been deposited by pulse electrodeposition. • Overall weakening of <1 1 1> texture and strengthening of <2 0 0> fibre texture is observed with increasing cobalt content. • Higher thermal stability of Ni–70Co is interpreted in terms of low mobility twins and texture. • A clear transition from soft to hard magnetic character is observed with an increase cobalt content. - Abstract: This paper reports the evolution of microstructure and texture in Nickel–Cobalt electrodeposits fabricated by pulse electrodeposition (PED) technique and the correlation of these attributes with the magnetic properties. The structural and microstructural investigation using X-ray diffraction and transmission electron microscopic studies indicate the presence of nanocrystalline grains and nano-twins in the electrodeposits. Convoluted Multiple Whole profile fitting reveals an increase in dislocation density and twin density with increasing cobalt content in the as-deposited samples. Strengthening of <1 1 1> fibre texture and weakening of <2 0 0> fibre texture with increasing cobalt concentration has been observed with X-ray texture analysis. A corresponding significant increase in the saturation magnetization and coercivity observed with increasing cobalt content. A significant improvement in the soft magnetic character in the electrodeposits in terms of increase in saturation magnetization and decrease in coercivity has been observed with thermal annealing.

  7. Tailoring the magnetic properties and magnetorheological behavior of spinel nanocrystalline cobalt ferrite by varying annealing temperature

    Czech Academy of Sciences Publication Activity Database

    Sedlacik, M.; Pavlinek, V.; Peer, Petra; Filip, Petr

    2014-01-01

    Roč. 18, č. 43 (2014), s. 6919-6924 ISSN 1477-9226 R&D Projects: GA ČR GA202/09/1626 Grant - others:GA MŠk(CZ) ED2.1.00/03.0111 Institutional support: RVO:67985874 Keywords : spinel nanocrystalline cobalt ferrite * nanoparticles * magnetorheological effect Subject RIV: BK - Fluid Dynamics Impact factor: 4.197, year: 2014

  8. Inversion degree and saturation magnetization of different nanocrystalline cobalt ferrites

    International Nuclear Information System (INIS)

    Concas, G.; Spano, G.; Cannas, C.; Musinu, A.; Peddis, D.; Piccaluga, G.

    2009-01-01

    The inversion degree of a series of nanocrystalline samples of CoFe 2 O 4 ferrites has been evaluated by a combined study, which exploits the saturation magnetization at 4.2 K and 57 Fe Moessbauer spectroscopy. The samples, prepared by sol-gel autocombustion, have different thermal history and particle size. The differences observed in the saturation magnetization of these samples are explained in terms of different inversion degrees, as confirmed by the analysis of the components in the Moessbauer spectra. It is notable that the inversion degrees of the samples investigated are set among the highest values reported in the literature.

  9. Structural and magnetic study of dysprosium substituted cobalt ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Hemaunt, E-mail: hvatsal@gmail.com [Department of Physics, Govind Ballabh Pant University of Agr. & Technology, Pantnagar, Uttarakhand 263145 (India); Srivastava, R.C. [Department of Physics, Govind Ballabh Pant University of Agr. & Technology, Pantnagar, Uttarakhand 263145 (India); Pal Singh, Jitendra [Advanced Analysis Centre, Korea Institute of Science and Technology, Seoul 02792 (Korea, Republic of); Negi, P. [Department of Physics, Govind Ballabh Pant University of Agr. & Technology, Pantnagar, Uttarakhand 263145 (India); Agrawal, H.M. [Advanced Analysis Centre, Korea Institute of Science and Technology, Seoul 02792 (Korea, Republic of); Das, D. [UGC-DAE CSR Kolkata Centre, Kolkata 700098 (India); Hwa Chae, Keun [Advanced Analysis Centre, Korea Institute of Science and Technology, Seoul 02792 (Korea, Republic of)

    2016-03-01

    The present work investigates the magnetic behavior of Dy{sup 3+} substituted cobalt ferrite nanoparticles. X-ray diffraction studies reveal presence of cubic spinel phases in these nanoparticles. Raman spectra of these nanoparticles show change in intensity of Raman bands, which reflects cation redistribution in cubic spinel lattice. Saturation magnetization and coercivity decrease with increase of Dy{sup 3+}concentration in these nanoparticles. Room temperature Mössbauer measurements show the cation redistribution in these nanoparticles and corroborates the results obtained from Raman Spectroscopic measurements. Decrease in magnetization of Dy{sup 3+} substituted cobalt ferrite is attributed to the reduction in the magnetic interaction and cation redistribution. - Highlights: • Slight decrease in crystallite size after Dy{sup 3+} doping. • Saturation magnetization and coercivity decrease after Dy{sup 3+} doping. • Mössbauer measurements show the cation redistribution in the samples.

  10. Effect of rare earth substitution in cobalt ferrite bulk materials

    International Nuclear Information System (INIS)

    Bulai, G.; Diamandescu, L.; Dumitru, I.; Gurlui, S.; Feder, M.; Caltun, O.F.

    2015-01-01

    The study was focused on the influence of small amounts of rare earth (RE=La, Ce, Sm, Gd, Dy, Ho, Er, Yb) addition on the microstructure, phase content and magnetic properties of cobalt ferrite bulk materials. The X-Ray diffraction measurements confirmed the formation of the spinel structure but also the presence of secondary phases of RE oxides or orthoferrite in small percentages (up to 3%). Density measurements obtained by Archimedes method revealed a ~1 g cm −3 decrease for the RE doped cobalt ferrite samples compared with stoichiometric one. Both the Mössbauer and Fourier Transform Infrared Spectrocopy analysis results confirmed the formation of the spinel phase. The saturation magnetization and coercive field values of the doped samples obtained by Vibrating Sample Magnetometry were close to those of the pure cobalt ferrite. For magnetostrictive property studies the samples were analyzed using the strain gauge method. Higher maximum magnetostriction coefficients were found for the Ho, Ce, Sm and Yb doped cobalt ferrite bulk materials as related to the stoichiometric CoFe 2 O 4 sample. Moreover, improved strain derivative was observed for these samples but at higher magnetic fields due to the low increase of the coercive field values for doped samples. - Highlights: • Substitution by a large number of rare earth elements was investigated. • First reported results on magnetostriction measurements of RE doped cobalt ferrite. • The doped samples presented an increased porosity and a decreased grain size. • Increased magnetostrctive response was observed for several doped samples

  11. Peroxidase-like activity of nanocrystalline cobalt selenide and its application for uric acid detection

    Directory of Open Access Journals (Sweden)

    Zhuang QQ

    2017-04-01

    Full Text Available Quan-Quan Zhuang,1 Zhi-Hang Lin,1 Yan-Cheng Jiang,1 Hao-Hua Deng,2 Shao-Bin He,1,3 Li-Ting Su,4 Xiao-Qiong Shi,2 Wei Chen2 1Department of Pharmacy, Affiliated Quanzhou First Hospital of Fujian Medical University, Quanzhou, 2Department of Pharmaceutical Analysis, School of Pharmacy, Fujian Medical University, Fuzhou, 3Department of Pharmacy, Quanzhou Infectious Disease Hospital, 4Department of Pharmaceutical Analysis, Quanzhou Medical College, Quanzhou, People’s Republic of China Abstract: Dendrite-like cobalt selenide nanostructures were synthesized from cobalt and selenium powder precursors by a solvothermal method in anhydrous ethylenediamine. The as-prepared nanocrystalline cobalt selenide was found to possess peroxidase-like activity that could catalyze the reaction of peroxidase substrates in the presence of H2O2. A spectrophotometric method for uric acid (UA determination was developed based on the nanocrystalline cobalt selenide-catalyzed coupling reaction between N-ethyl-N-(3-sulfopropyl-3-methylaniline sodium salt and 4-aminoantipyrine (4-AAP in the presence of H2O2. Under optimum conditions, the absorbance was proportional to the concentration of UA over the range of 2.0–40 µM with a detection limit of 0.5 µM. The applicability of the proposed method has been validated by determination of UA in human serum samples with satisfactory results. Keywords: enzyme mimics, cobalt selenide, peroxidase-like activity, uric acid, human serum

  12. Investigation of nanocrystalline thin cobalt films thermally evaporated on Si(100) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kozłowski, W., E-mail: wkozl@std2.phys.uni.lodz.pl [Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of Łódź, Pomorska 149/153, 90-236 Łódź (Poland); Balcerski, J.; Szmaja, W. [Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of Łódź, Pomorska 149/153, 90-236 Łódź (Poland); Piwoński, I. [Department of Materials Technology and Chemistry, Faculty of Chemistry, University of Łódź, Pomorska 163, 90-236 Łódź (Poland); Batory, D. [Institute of Materials Science and Engineering, Łódź University of Technology, Stefanowskiego 1/15, 90-924 Łódź (Poland); Miękoś, E. [Department of Inorganic and Analytical Chemistry, Faculty of Chemistry, University of Łódź, Tamka 12, 91-403 Łódź (Poland); and others

    2017-03-15

    We have made a quantitative study of the morphological and magnetic domain structures of 100 nm thick nanocrystalline cobalt films thermally evaporated on naturally oxidized Si(100) substrates. The morphological structure is composed of densely packed grains with the average grain size (35.6±0.8) nm. The grains exhibit no geometric alignment and no preferred elongation on the film surface. In the direction perpendicular to the film surface, the grains are aligned in columns. The films crystallize mainly in the hexagonal close-packed phase of cobalt and possess a crystallographic texture with the hexagonal axis perpendicular to the film surface. The magnetic domain structure consists of domains forming a maze stripe pattern with the average domain size (102±6) nm. The domains have their magnetizations oriented almost perpendicularly to the film surface. The domain wall energy, the domain wall thickness and the critical diameter for single-domain particle were determined. - Highlights: • 100 nm thick nanocrystalline cobalt films on Si(100) were studied quantitatively. • The grains are densely packed and possess the average size (35.6±0.8) nm. • The films have a texture with the hexagonal axis perpendicular to the film surface. • The magnetic domains form a maze stripe pattern with the average size (102±6) nm. • The domains are magnetized almost perpendicularly to the film surface.

  13. Magnetic and Structural Investigations of Nanocrystalline Cobalt-Ferrite

    Directory of Open Access Journals (Sweden)

    I. Sharifi

    2012-10-01

    Full Text Available Cobalt ferrite is an important magnetic material due to their large magneto-crystalline anisotropy, high cohercivity, moderate saturation magnetization and chemical stability.In this study, cobalt ferrites Nanoparticles have been synthesized by the co-precipitation method and a new microemulsion route. We examined the cation occupancy in the spinel structure based on the “Rietveld with energies” method. The Xray measurements revealed the production of a broad single ferrite cubic phase with the average particle sizes of about 12 nm and 7nm, for co-precipitation and micro-emulsion methods, respectively. The FTIR measurements between 400 and 4000 cm-1 confirmed the intrinsic cation vibrations of the spinelstructure for the two methods. Furthermore, the Vibrating Sample Magnetometer (VSM was carried out at room temperature to study the structural and magnetic properties. The results revealed that by changing the method from co-precipitation to the reverse micelle the material exhibits a softer magnetic behavior in such a way that both saturation magnetization and coercivity decrease from 58 to 29 emu/g and from 286 to 25 Oe, respectively.

  14. The effect of cobalt substitution on magnetic hardening of magnetite

    Energy Technology Data Exchange (ETDEWEB)

    Mozaffari, M., E-mail: mozafari@sci.ui.ac.ir [Department of Physics, Faculty of Science, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of); Hadadian, Y. [Physics Department, Razi University, Taghebostan, Kermanshah (Iran, Islamic Republic of); Aftabi, A. [Department of Physics, University of Kurdistan, Sanandaj 66177-15175 (Iran, Islamic Republic of); Oveisy Moakhar, M. [Physics Department, Razi University, Taghebostan, Kermanshah (Iran, Islamic Republic of)

    2014-03-15

    In this work cobalt-substituted magnetite (Co{sub x}Fe{sub 1−x}Fe{sub 2}O{sub 4}, x=0, 0.25, 0.50 and 0.75) nanoparticles were synthesized by coprecipitation method and their structural and magnetic properties were investigated. X-ray diffraction was carried out and the results show that all of the samples have single phase spinel structure. Microstructure of the samples was studied using a field emission scanning electron microscope and the results show that particle sizes of the prepared nanoparticles were uniform and in the 50–55 nm range. Room temperature magnetic properties of the nanoparticles were measured by an alternating gradient force magnetometer and the results revealed that substituting cobalt for iron in magnetite structure, changes the magnetite from a soft magnetic material to a hard one. So that coercivity changes from 0 (a superparamagnetic state) to 337 Oe (a hard magnetic material), which is a remarkable change. Curie temperatures of the samples were determined by recording their susceptibility-temperature (χ–T) curves and the results show that by increasing cobalt content, Curie temperature of the samples also increases. Also χ–T curves of the samples were recorded from above Curie temperature to room temperature (first cooling), while the curves in the second heating and second cooling have the same behaviour as the first cooling curve. The results depict that all samples have different behaviour in the first cooling and in the first heating processes. This shows remarkable changes of the cation distribution in the course of first heating. - Highlights: • It is possible to get Co substituted magnetite nanoparticles by coprecipitation method. • Prepared nanoparticles have different cation distribution in comparison with that of bulk counterparts. • Co substitution increases coercivity of the magnetite.

  15. Substitution of cobalt alloying in PWR primary circuit gate valves

    International Nuclear Information System (INIS)

    Cachon, L.; Sudreau, F.; Brunel, L.

    1995-01-01

    The object of this study is qualify cobalt-free alternative alloys for valve applications. This paper focus on tribological characterization of numerous coatings is done by using the first one, of a classical type. Then tests are performed with the second one which simulates solicitations supported by gate valves in primary circuit of PWR. 35% Ni-Cr - 65% Cr 3 C 2 coating, deposited by detonation gun technology, gives us hope to find a substitute of Stelite 6. (author). 5 refs., 16 figs., 2 tabs

  16. Manganese substituted cobalt ferrite magnetostrictive materials for magnetic stress sensor applications

    OpenAIRE

    Paulsen, J. A.; Ring, A. P.; Lo, C. C. H.; Snyder, John Evan; Jiles, David

    2005-01-01

    Metal bonded cobalt ferrite composites have been shown to be promising candidate materials for use in magnetoelastic stress sensors, due to their large magnetostriction and high sensitivity of magnetization to stress. However previous results have shown that below 60 °C the cobalt ferrite material exhibits substantial magnetomechanical hysteresis. In the current study, measurements indicate that substituting Mn for some of the Fe in the cobalt ferrite can lower the Curie temperature of the ma...

  17. Neutron diffraction studies on cobalt substituted BiFeO3

    Science.gov (United States)

    Ray, J.; Biswal, A. K.; Acharya, S.; Babu, P. D.; Siruguri, V.; Vishwakarma, P. N.

    2013-02-01

    A dilute concentration of single phase Cobalt substituted Bismuth ferrite, BiFe1-XCoXO3; (x=0, 0.02) is prepared by sol-gel auto combustion method. Room temperature neutron diffraction patterns show no change in the crystal and magnetic structure upon cobalt doping. The calculation of magnetic moments shows 3.848 μB for Fe+ and 2.85 μB for Co3+. The cobalt is found to be in intermediate spin state.

  18. Magnetic and magnetoelastic properties of M-substituted cobalt ferrites (M=Mn, Cr, Ga, Ge)

    Energy Technology Data Exchange (ETDEWEB)

    Song, Sang-Hoon [Iowa State Univ., Ames, IA (United States)

    2007-12-15

    Magnetic and magnetoelastic properties of a series of M-substituted cobalt ferrites, CoMxFe2-xO4 (M=Mn, Cr, Ga; x=0.0 to 0.8) and Ge-substituted cobalt ferrites Co1+xGexFe2-2xO4 (x=0.0 to 0.6) have been investigated.

  19. Tailoring the magnetic properties and magnetorheological behavior of spinel nanocrystalline cobalt ferrite by varying annealing temperature.

    Science.gov (United States)

    Sedlacik, Michal; Pavlinek, Vladimir; Peer, Petra; Filip, Petr

    2014-05-14

    Magnetic nanoparticles of spinel nanocrystalline cobalt ferrite were synthesized via the sol-gel method and subsequent annealing. The influence of the annealing temperature on the structure, magnetic properties, and magnetorheological effect was investigated. The finite crystallite size of the particles, determined by X-ray diffraction and the particle size observed via transmission electron microscopy, increased with the annealing temperature. The magnetic properties observed via a vibrating sample magnetometer showed that an increase in the annealing temperature leads to the increase in the magnetization saturation and, in contrast, a decrease in the coercivity. The effect of annealing on the magnetic properties of ferrite particles has been explained by the recrystallization process at high temperatures. This resulted in grain size growth and a decrease in an imposed stress relating to defects in the crystal lattice structure of the nanoparticles. The magnetorheological characteristics of suspensions of ferrite particles in silicone oil were measured using a rotational rheometer equipped with a magnetic field generator in both steady shear and small-strain oscillatory regimes. The magnetorheological performance expressed as a relative increase in the magnetoviscosity appeared to be significantly higher for suspensions of particles annealed at 1000 °C.

  20. The magnetic properties of amorphous and nanocrystalline cobalt-rare earth films

    Science.gov (United States)

    Thomas, Richard Allen

    Magnetic materials are of great technological importance for their use in transformers, electric motors, computer disks and hard drives, etc. Understanding the intrinsic physical properties of magnetic materials is essential in order to develop new and better materials for these applications. Presented here is a study of the magnetic properties of amorphous and nanocrystalline cobalt-rare earth (Co-R, where R = Y, Pr, Gd, and Dy) films composed of very small crystalline grains, about 2--200 nm in size. The films are produced by co-sputtering two single element targets onto a single substrate. Many are then annealed briefly to produce magnetic films composed of nanoscale crystallites. The magnetic properties of these films depend largely on the relative strengths of the exchange interaction, which tends to align the spins within a group of crystallites, and the magnetocrystalline anisotropy, which tends to align the spins within each crystallite to an easy direction defined by the crystal lattice. The ratio of these two competing interactions varies strongly with grain size as predicted by the random magnetic anisotropy model. The coercivity, remanent magnetization, initial magnetization, etc., are discussed in light of the predictions made by the models of Callen et al (1977), Chi and Alben (1977), Chudnovsky (1986), and Fukunaga and Inoue (1992).

  1. Nanocrystallinity effects on osteoblast and osteoclast response to silicon substituted hydroxyapatite.

    Science.gov (United States)

    Casarrubios, Laura; Matesanz, María Concepción; Sánchez-Salcedo, Sandra; Arcos, Daniel; Vallet-Regí, María; Portolés, María Teresa

    2016-11-15

    Silicon substituted hydroxyapatites (SiHA) are highly crystalline bioceramics treated at high temperatures (about 1200°C) which have been approved for clinical use with spinal, orthopedic, periodontal, oral and craniomaxillofacial applications. The preparation of SiHA with lower temperature methods (about 700°C) provides nanocrystalline SiHA (nano-SiHA) with enhanced bioreactivity due to higher surface area and smaller crystal size. The aim of this study has been to know the nanocrystallinity effects on the response of both osteoblasts and osteoclasts (the two main cell types involved in bone remodelling) to silicon substituted hydroxyapatite. Saos-2 osteoblasts and osteoclast-like cells (differentiated from RAW-264.7 macrophages) have been cultured on the surface of nano-SiHA and SiHA disks and different cell parameters have been evaluated: cell adhesion, proliferation, viability, intracellular content of reactive oxygen species, cell cycle phases, apoptosis, cell morphology, osteoclast-like cell differentiation and resorptive activity. This comparative in vitro study evidences that nanocrystallinity of SiHA affects the cell/biomaterial interface inducing bone cell apoptosis by loss of cell anchorage (anoikis), delaying osteoclast-like cell differentiation and decreasing the resorptive activity of this cell type. These results suggest the potential use of nano-SiHA biomaterial for preventing bone resorption in treatment of osteoporotic bone. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Substitutional Boron in Nanodiamond, Bucky-Diamond, and Nanocrystalline Diamond Grain Boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, Amanda S.; Sternberg, Michael G.

    2006-10-05

    Although boron has been known for many years to be a successful dopant in bulk diamond, efficient doping of nanocrystalline diamond with boron is still being developed. In general, the location, configuration, and bonding structure of boron in nanodiamond is still unknown, including the fundamental question of whether it is located within grains or grain boundaries of thin films and whether it is within the core or at the surface of nanoparticles. Presented here are density functional tight-binding simulations examining the configuration, potential energy surface, and electronic charge of substitutional boron in various types of nanocrystalline diamond. The results predict that boron is likely to be positioned at the surface of isolated particles and at the grain boundary of thin-film samples.

  3. Investigation of superparamagnetism in pure and chromium substituted cobalt nanoferrite

    Energy Technology Data Exchange (ETDEWEB)

    Raghasudha, M., E-mail: raghasudha_m@yahoo.co.in [Department of Chemistry, University College of Science, Osmania University, Hyderabad 500007, Telangana (India); Ravinder, D. [Department of Physics, University College of Science, Osmania University, Hyderabad 500007, Telangana (India); Veerasomaiah, P. [Department of Chemistry, University College of Science, Osmania University, Hyderabad 500007, Telangana (India)

    2016-12-15

    Nanostructured magnetic materials with the chemical composition CoFe{sub 2}O{sub 4} and CoCr{sub 0.9}Fe{sub 1.1}O{sub 4} were synthesized through Citrate-gel chemical synthesis with a crystallite size of 6.5 nm and 10.7 nm respectively. Structural characterization of the samples was performed by X-ray diffraction analysis and magnetic properties were studied using Vibrating Sample Magnetometer (VSM). Magnetization measurements as a function of applied magnetic field ±10 T at various temperatures 5 K, 25 K, 310 K and 355 K were carried out. Field cooled (FC) and Zero field cooled (ZFC) magnetization measurements under a magnetic field of 100 Oe for temperature ranging from 5–400 K were studied. The blocking temperature (T{sub b}) for both the ferrites was observed to be around 355 K. Below blocking temperature they showed ferromagnetic behavior and above which they are superparamagnetic in nature that favors their application in the biomedical field. The substitution of paramagnetic Cr{sup 3+} ions for magnetic Fe{sup 3+} ion in cobalt ferrite has resulted in a decrease in magnetization and the coercivity of the samples. CoCr{sub 0.9}Fe{sub 1.1}O{sub 4} nanoferrites with observed low coercivity of 338 Oe make them desirable in high frequency transformers due to their very soft magnetic behavior. - Highlights: • Particle size of CoFe{sub 2}O{sub 4} and CoCr{sub 0.9}Fe{sub 1.1}O{sub 4} is 6.5 nm and 10.7 nm respectively. • At 5 K and 25 K the materials were ferromagnetic in nature with high coercivity. • Materials show superparamagnetic behavior above room temperature. • Blocking temperature is at around 355 K where coercivity and remanence are zero. • Materials are suitable for hyperthermia cancer therapy.

  4. Enhanced magneto-optical Kerr effect in rare earth substituted nanostructured cobalt ferrite thin film prepared by sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Avazpour, L.; Toroghinejad, M.R. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Shokrollahi, H., E-mail: Shokrollahi@sutech.ac.ir [Electroceramics Group, Department of Materials Science and Engineering, Shiraz University of Technology, Shiraz 13876-71557 (Iran, Islamic Republic of)

    2016-11-30

    Highlights: • The nanostructured rare earth doped Co-ferrite thin film was synthesized by the sol–gel method. • The coercivity of as high as 1.8 kOe is achieved for 20% substituted cobalt ferrite. • The average particle diameter of particulate film is decreasing by increasing substitute content. • Kerr spectra of films shifted to higher energies. • Kerr rotation angle increased to 1.65° for 0.1 Eu doped thin film. - Abstract: A series of rare-earth (RE)-doped nanocrystalline Co{sub x} RE{sub (1−x)} Fe{sub 2}O{sub 4} (x = 0, 0.1, 0.2 and RE: Nd, Eu) thin films were prepared on silicon substrates by a sol–gel process, and the influences of different RE{sup 3+} ions on the microstructure, magnetism and polar magneto-optical Kerr effect of the deposited films were investigated. Also this research presents the optimization process of cobalt ferrite thin films deposited via spin coating, by studying their structural and morphological properties at different thicknesses (200, 350 nm) and various heat treatment temperatures 300–850 °C. Nanoparticulate polycrystalline thin film were formed with heat treatment above 400 °C but proper magnetic properties due to well crystallization of the film were achieved at about 650 °C. AFM results indicated that the deposited thin films were crack-free exhibiting a dense nanogranular structure. The root-mean square (RMS) roughness of the thin films was in the range of 0.2–3.2 nm. The results revealed that both of the magnetism and magneto optical Kerr (MOKE) spectra of Co{sub x} RE{sub (1−x)} Fe{sub 2}O{sub 4} films could be mediated by doping with various RE ions. The Curie temperature of substituted samples was lower than pristine cobalt ferrite thin films. In MOKE spectra both dominant peaks were blue shifted with addition of RE ions. For low concentration dopant the inter-valence charge transfer related rotation was enhanced and for higher concentration dopant the crystal field rotation peak was enhanced

  5. and aluminum-substituted cobalt ferrite prepared by co-precipitation

    Indian Academy of Sciences (India)

    Structural and magnetic properties of zinc- and aluminum-substituted cobalt ferrite prepared by co-precipitation method. S T ALONE1,∗ and K M JADHAV2. 1Shiv Chhatrapati College, Aurangabad 431 004, India. 2Department of Physics, Dr. B. A. Marathwada University, Aurangabad 431 004, India. ∗Corresponding author.

  6. Sinus Floor Elevation and Augmentation Using Synthetic Nanocrystalline and Nanoporous Hydroxyapatite Bone Substitute Materials: Preliminary Histologic Results.

    Science.gov (United States)

    Belouka, Sofia-Maria; Strietzel, Frank Peter

    To compare the tissue composition of augmented sites after using two different synthetic bone substitute materials, nanocrystalline and nanoporous hydroxyapatite (HA), for sinus floor elevation and augmentation. Forty-four patients received 88 titanium screw implants (Camlog Promote plus) of 4.3-mm diameter and 11- or 13-mm length, placed simultaneously during sinus floor elevation and augmentation. Nanocrystalline (Ostim) or nanoporous (NanoBone) HA were used exclusively. Bone substitute materials and implant lengths were allocated by randomization. Bone biopsy specimens were obtained from the former area of the lateral access window at implant exposure during healing abutment placement after 6 months. Biopsy specimens were prepared and examined histologically and histomorphometrically. All implants were osseointegrated at the time of exposure. Clinically and histologically, no signs of inflammation in the augmented sites were present. The histomorphometric analysis of 44 biopsy specimens revealed 31.8% ± 11.6% newly formed bone for sites augmented with nanocrystalline HA and 34.6% ± 9.2% for nanoporous HA (P = .467). The proportion of remaining bone substitute material was 28.4% ± 18.6% and 30% ± 13%, respectively (P = .453). The proportion of soft tissue within the biopsy specimens was 39.9% ± 11.1% and 35.4% ± 6.8%, respectively (P = .064). No significant differences were found between the area fractions of bone, bone substitute material, and soft tissue concerning the bone substitute material utilized. Within the present study, both synthetic bone substitute materials, nanocrystalline and nanoporous HA, were found to support bone formation in sinus floor elevation and augmentation procedures by osteoconductivity. They were not completely resorbed after 6 months. The amounts of newly formed bone, soft tissue, and bone substitute material remnants were found to be similar, indicating that both materials are likewise suitable for sinus floor elevation and

  7. Cu 2 + and Al 3 + co-substituted cobalt ferrite

    Indian Academy of Sciences (India)

    X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field emissionscanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM) are used for studying the effect of variation in the Cu–Al substitution and its impact on particle size, magnetic properties such as Ms and Hc.

  8. Synthesis of nanocrystalline cobalt ferrite through soft chemistry methods: A green chemistry approach using sesame seed extract

    Energy Technology Data Exchange (ETDEWEB)

    Gingasu, Dana [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021, Bucharest (Romania); Mindru, Ioana, E-mail: imandru@yahoo.com [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021, Bucharest (Romania); Mocioiu, Oana Catalina; Preda, Silviu; Stanica, Nicolae; Patron, Luminita [Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021, Bucharest (Romania); Ianculescu, Adelina; Oprea, Ovidiu [Politehnica University of Bucharest, Faculty of Chemistry, 1-7 Polizu Street, 011061, Bucharest (Romania); Nita, Sultana; Paraschiv, Ileana [National Institute for Chemical Pharmaceutical Research and Development, 112 Calea Vitan, 031299, Bucharest (Romania); Popa, Marcela; Saviuc, Crina [University of Bucharest, Faculty of Biology, Microbiology Department, Research Institute of the University of Bucharest-ICUB, Life, Environmental and Earth Sciences Division, 91-95 Splaiul Independentei, Bucharest (Romania); Bleotu, Coralia [Stefan S. Nicolau Institute of Virology, Cellular and Molecular Pathology Department, 285 Mihai Bravu Avenue, Bucharest (Romania); Chifiriuc, Mariana Carmen [University of Bucharest, Faculty of Biology, Microbiology Department, Research Institute of the University of Bucharest-ICUB, Life, Environmental and Earth Sciences Division, 91-95 Splaiul Independentei, Bucharest (Romania)

    2016-10-01

    The nanocrystalline cobalt ferrites (CoFe{sub 2}O{sub 4}) were obtained through self-combustion and wet ferritization methods using aqueous extracts of sesame (Sesamum indicum L) seeds. The multimetallic complex compounds were characterized by Fourier transform infrared spectroscopy (FTIR), UV-VIS spectroscopy and thermal analysis. Phase identification, morphological evolution and magnetic properties of the obtained cobalt ferrites were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), FTIR and magnetic measurements. FE-SEM investigations revealed the particle size of CoFe{sub 2}O{sub 4} obtained by wet ferritization method ranged between 3 and 20.45 nm. Their antimicrobial, anti-biofilm and cytotoxic properties were evaluated. - Highlights: • CoFe{sub 2}O{sub 4} were obtained by two chemical synthesis methods. • Sesame seed extract was used as gelling or chelating agent. • The morphological features of CoFe{sub 2}O{sub 4} nanoparticles were evaluated. • CoFe{sub 2}O{sub 4} exhibited good microbicidal and anti-biofilm features.

  9. The substitution of nickel for cobalt in hot isostatically pressed powder metallurgy UDIMET 700 alloys

    Science.gov (United States)

    Harf, F. H.

    1985-01-01

    Nickel was substituted in various proportions for cobalt in a series of five hot-isostatically-pressed powder metallurgy alloys based on the UDIMET 700 composition. These alloys were given 5-step heat treatments appropriate for use in turbine engine disks. The resultant microstructures displayed three distinct sizes of gamma-prime particles in a gamma matrix. The higher cobalt-content alloys contained larger amounts of the finest gamma-prime particles, and had the lowest gamma-gamma-prime lattice mismatch. While all alloys had approximately the same tensile properties at 25 and 650 gamma C, the rupture lives at 650 and 760 C peaked in the alloys with cobalt contents between 12.7 and 4.3 pct. Minimum creep rates increased as cobalt contents were lowered, suggesting their correlation with the gamma-prime particle size distribution and the gamma-gamma-prime mismatch. It was also found that, on overaging at temperatures higher than suitable for turbine disk use, the high cobalt-content alloys were prone to sigma phase formation.

  10. Fe(II)-substituted cobalt ferrite nanoparticles against multidrug resistant microorganisms

    Science.gov (United States)

    Žalnėravičius, Rokas; Paškevičius, Algimantas; Mažeika, Kęstutis; Jagminas, Arūnas

    2018-03-01

    The present study is focused on the determination the influence of cobalt content in the magnetic cobalt ferrite nanoparticles (Nps) on their antibacterial efficiency against gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria and several Candida species, in particular C. parapsilosis and C. albicans. For the synthesis of Fe(II) substituted cobalt ferrite Nps by co-precipitation way, the L-lysine was used as the capping biocompatible agent and the particle size was successfully controlled to be in the range of 5-6.4 nm. The antimicrobial efficiencies of the CoxFe1-xFe2O4@Lys Nps, where x varies from 0.2 to 1.0, were evaluated through the quantitative analysis by comparing with that of Fe3O4@Lys Nps and L-lysine. In this way, it was evidenced that increase in the Co2+ content in the similar sized cobalt ferrite Nps resulted in an increase in their antimicrobial potency into 93.1-86.3 % for eukaryotic and into 96.4-42.7 % for prokaryotic strains. For characterization the composition, structure, and morphology of the tested herein Nps inductively coupled plasma optical emission spectrometry, X-ray diffraction, high-resolution transmission electron microscopy, Mössbauer, and FTIR spectroscopy techniques were conferred.

  11. Structural and magnetic properties correlated with cation distribution of Mo-substituted cobalt ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Heiba, Z.K. [Faculty of Science, Taif University, P.O. Box: 888, Al-Haweiah, Taif (Saudi Arabia); Physics Department, Faculty of Science, Ain Shams University, Cairo (Egypt); Mostafa, Nasser Y., E-mail: nmost69@yahoo.com [Faculty of Science, Taif University, P.O. Box: 888, Al-Haweiah, Taif (Saudi Arabia); Chemistry Department, Faculty of Science, Suez Canal University, Ismailia 41522 (Egypt); Abd-Elkader, Omar H. [Department of Zoology, Science College, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Electron Microscope and Thin Films Department, National Research Center (NRC), El-Behooth Street, Dokki, Cairo 12622 (Egypt)

    2014-11-15

    Mo-substituted cobalt ferrite nanoparticles; CoFe{sub 2−2x}Mo{sub x}O{sub 4} (0.0≤x≤0.3) were prepared by a one-step solution combustion synthesis technique. The reactants were metal nitrates and glycine as a fuel. The samples were characterized using an X-ray diffraction (XRD), a transmission electron microscope (TEM) and a vibrating sample magnetometer (VSM). XRD analysis revealed a pure single phase of cubic spinel ferrites for all samples with x up to 0.3. The lattice parameter decreases with Mo{sup 6+} substitution linearly up to x=0.15, then nonlinearly for x≥0.2. Rietveld analysis and saturation magnetization (M{sub s}) revealed that Mo{sup 6+} replaced Fe{sup 3+} in the tetrahedral A-sites up to x=0.15, then it replaced Fe{sup 3+} in both A-sites and B-sites for x≥0.2. The saturation magnetization (M{sub s}) increases with increasing Mo{sup 6+} substitution up to x=0.15 then decreases. The crystallite size decreased while the microstrain increased with increasing Mo{sup 6+} substitution. Inserting Mo{sup 6+} produces large residents of defects and cation vacancies. - Highlights: • Nano-sized Mo-substituted cobalt ferrite CoFe{sub 2−2x}Mo{sub x}O{sub 4} (0.0≤x≤0.3) were prepared by solution combustion. • The change in M{sub s} with increasing Mo-substitution was investigated. • The cations distributions of ferrites were obtained from Rietveld analysis. • Inserting Mo{sup 6+} produces large residents of defects and cation vacancies.

  12. Cobalt

    Science.gov (United States)

    Slack, John F.; Kimball, Bryn E.; Shedd, Kim B.; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    Cobalt is a silvery gray metal that has diverse uses based on certain key properties, including ferromagnetism, hardness and wear-resistance when alloyed with other metals, low thermal and electrical conductivity, high melting point, multiple valences, and production of intense blue colors when combined with silica. Cobalt is used mostly in cathodes in rechargeable batteries and in superalloys for turbine engines in jet aircraft. Annual global cobalt consumption was approximately 75,000 metric tons in 2011; China, Japan, and the United States (in order of consumption amount) were the top three cobalt-consuming countries. In 2011, approximately 109,000 metric tons of recoverable cobalt was produced in ores, concentrates, and intermediate products from cobalt, copper, nickel, platinum-group-element (PGE), and zinc operations. The Democratic Republic of the Congo (Congo [Kinshasa]) was the principal source of mined cobalt globally (55 percent). The United States produced a negligible amount of byproduct cobalt as an intermediate product from a PGE mining and refining operation in southeastern Montana; no U.S. production was from mines in which cobalt was the principal commodity. China was the leading refiner of cobalt, and much of its production came from cobalt ores, concentrates, and partially refined materials imported from Congo (Kinshasa).The mineralogy of cobalt deposits is diverse and includes both primary (hypogene) and secondary (supergene) phases. Principal terrestrial (land-based) deposit types, which represent most of world’s cobalt mine production, include primary magmatic Ni-Cu(-Co-PGE) sulfides, primary and secondary stratiform sediment-hosted Cu-Co sulfides and oxides, and secondary Ni-Co laterites. Seven additional terrestrial deposit types are described in this chapter. The total terrestrial cobalt resource (reserves plus other resources) plus past production, where available, is calculated to be 25.5 million metric tons. Additional resources of

  13. Biologically inspired rosette nanotubes and nanocrystalline hydroxyapatite hydrogel nanocomposites as improved bone substitutes

    International Nuclear Information System (INIS)

    Zhang Lijie; Webster, Thomas J; Rodriguez, Jose; Raez, Jose; Myles, Andrew J; Fenniri, Hicham

    2009-01-01

    Today, bone diseases such as bone fractures, osteoporosis and bone cancer represent a common and significant public health problem. The design of biomimetic bone tissue engineering materials that could restore and improve damaged bone tissues provides exciting opportunities to solve the numerous problems associated with traditional orthopedic implants. Therefore, the objective of this in vitro study was to create a biomimetic orthopedic hydrogel nanocomposite based on the self-assembly properties of helical rosette nanotubes (HRNs), the osteoconductive properties of nanocrystalline hydroxyapatite (HA), and the biocompatible properties of hydrogels (specifically, poly(2-hydroxyethyl methacrylate), pHEMA). HRNs are self-assembled nanomaterials that are formed from synthetic DNA base analogs in water to mimic the helical nanostructure of collagen in bone. In this study, different geometries of nanocrystalline HA were controlled by either hydrothermal or sintering methods. 2 and 10 wt% nanocrystalline HA particles were well dispersed into HRN hydrogels using ultrasonication. The nanocrystalline HA and nanocrystalline HA/HRN hydrogels were characterized by x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Mechanical testing studies revealed that the well dispersed nanocrystalline HA in HRN hydrogels possessed improved mechanical properties compared to hydrogel controls. In addition, the results of this study provided the first evidence that the combination of either 2 or 10 wt% nanocrystalline HA and 0.01 mg ml -1 HRNs in hydrogels greatly increased osteoblast (bone-forming cell) adhesion up to 236% compared to hydrogel controls. Moreover, this study showed that HRNs stimulated HA nucleation and mineralization along their main axis in a way that is very reminiscent of the HA/collagen assembly pattern in natural bone. In summary, the presently observed excellent properties of the biomimetic nanocrystalline HA/HRN hydrogel composites

  14. Investigation of Structural, Morphological, Magnetic Properties and Biomedical applications of Cu2+ Substituted Uncoated Cobalt Ferrite Nanoparticles

    Directory of Open Access Journals (Sweden)

    M. Margabandhu

    Full Text Available ABSTRACT In the present work, Cu2+ substituted cobalt ferrite (Co1-xCuxFe2O4, x = 0, 0.3, 0.5, 0.7 and 1 magnetic nanopowders were synthesized via chemical co-precipitation method. The prepared powders were investigated by various characterization methods such as X-ray diffraction analysis (XRD, scanning electron microscope analysis (SEM, vibrating sample magnetometer analysis (VSM and fourier transform infrared spectroscopy analysis (FTIR. The XRD analysis reveals that the synthesized nanopowders possess single phase centred cubic spinel structure. The average crystallite size of the particles ranging from 27-49 nm was calculated by using Debye-scherrer formula. Magnetic properties of the synthesized magnetic nanoparticles are studied by using VSM. The VSM results shows the magnetic properties such as coercivity, magnetic retentivity decreases with increase in copper substitution whereas the saturation magnetization shows increment and decrement in accordance with Cu2+ substitution in cobalt ferrite nanoparticles. SEM analysis reveals the morphology of synthesized magnetic nanoparticles. FTIR spectra of Cu2+ substituted cobalt ferrite magnetic nanoparticles were recorded in the frequency range 4000-400cm-1. The spectrum shows the presence of water adsorption and metal oxygen bonds. The adhesion nature of Cu2+ substituted cobalt ferrite magnetic nanoparticles with bacteria in reviewed results indicates that the synthesized nanoparticles could be used in biotechnology and biomedical applications.

  15. Nanocrystalline Cobalt-doped SnO2 Thin Film: A Sensitive Cigarette Smoke Sensor

    Directory of Open Access Journals (Sweden)

    Patil Shriram B.

    2011-11-01

    Full Text Available This article discusses a sensitive cigarette smoke sensor based on Cobalt doped Tin oxide (Co-SnO2 thin films deposited on glass substrate by a conventional Spray Pyrolysis technique. The Co-SnO2 thin films have been characterized by X-ray Diffraction (XRD, Scanning Electron Microscopy (SEM and Energy Dispersive X-ray Spectroscopy (EDAX. The XRD spectrum shows polycrystalline nature of the film with a mixed phase comprising of SnO2 and Co3O4. The SEM image depicts uniform granular morphology covering total substrate surface. The compositional analysis derived using EDAX confirmed presence of Co in addition to Sn and O in the film. Cigarette smoke sensing characteristics of the Co-SnO2 thin film have been studied under atmospheric condition at different temperatures and smoke concentration levels. The sensing parameters such as sensitivity, response time and recovery time are observed to be temperature dependent, exhibiting better results at 330 oC.

  16. Chemical bonding and magnetic properties of gadolinium (Gd) substituted cobalt ferrite

    International Nuclear Information System (INIS)

    Puli, Venkata Sreenivas; Adireddy, Shiva; Ramana, C.V.

    2015-01-01

    Graphical abstract: Room temperature Raman spectra of CoFe 2−x Gd x O 4 (CFGO, x = 0.0–0.3) compounds as a function of wavenumber (cm −1 ). - Highlights: • Gd substituted ferrites were synthesized under controlled concentration. • Gd ion induced lattice dynamical changes are significant. • Enhanced magnetization is observed upon Gd-incorporation in cobalt ferrite. • A correlation between lattice dynamics and magnetic properties is established. - Abstract: Polycrystalline gadolinium (Gd) substituted cobalt ferrites (CoFe 2−x Gd x O 4 ; x = 0–0.3, referred to CFGO) ceramics have been synthesized by solid state reaction method. Chemical bonding, crystal structure and magnetic properties of CFGO compounds have been evaluated as a function of Gd-content. X-ray diffraction (XRD) and Raman spectroscopic analyses confirmed the formation of inverse spinel cubic structure. However, a secondary ortho-ferrite phase (GdFeO 3 ) nucleates for higher values of Gd-content. A considerable increase in the saturation magnetization has been observed upon the initial substitution of Gd (x = 0.1). The saturation magnetization drastically decreases at higher Gd content (x ⩾ 0.3). No contribution from ortho-ferrite GdFeO 3 phase is noted to the magnetic properties. The increase in the magnetic saturation magnetization is attributed to the higher magnetic moment of Gd 3+ (4f 7 ) residing in octahedral sites is higher when compared to that of Fe 3+ (3d 5 ) and as well due to the migration of Co 2+ (3d 7 ) ions from the octahedral to the tetrahedral sites with a magnetic moment aligned anti-parallel to those of rare earth (RE 3+ ) ions in the spinel lattice. Increase in coercivity with increase in Gd 3+ is content is attributed to magnetic anisotropy in the ceramics

  17. Cobalt

    International Nuclear Information System (INIS)

    Stolyarova, I.A.; Bunakova, N.Yu.

    1983-01-01

    The neutron-activation method for determining cobalt in rocks, polymetallic and iron ores and rockforming minerals at 2x10 -6 -5x10 -3 % content is developed. Cobalt determination is based on the formation under the effect of thermal neutrons of nuclear reactor of the 60 Co radioactive isotope by the 59 Co (n, γ) 60 Co reaction with radiation energy of the most intensive line of 1333 keV. Cobalt can be determined by the scheme of the multicomponent analysis from the sample with other elements. Co is determined in the solution after separation of all determinable by the scheme elements. The 60 Co intensity is measured by the mUltichannel gamma-spectrometer with Ge(Li)-detector

  18. Acrylate intercalation and in situ polymerization in iron-, cobalt-, or manganese-substituted nickel hydroxides.

    Science.gov (United States)

    Vaysse, C; Guerlou-Demourgues, L; Duguet, E; Delmas, C

    2003-07-28

    A chimie douce route based on successive redox and exchange reactions has allowed us to prepare new hybrid organic-inorganic materials, composed of polyacrylate macromolecules intercalated into layered double hydroxides (LDHs), deriving from Ni(OH)(2). Monomer intercalation and in situ polymerization mechanisms have appeared to be strongly dependent upon the nature of the substituting cation in the slabs. In the case of iron-based LDHs, a phase containing acrylate monomeric intercalates has been isolated and identified by X-ray diffraction and infrared spectroscopy. Second, interslab free-radical polymerization of acrylate anions has been successfully initiated using potassium persulfate. In cobalt- or manganese-based LDHs, one-step polymerization has been observed, leading directly to a material containing polyacrylate intercalate.

  19. Improved electrical properties of cadmium substituted cobalt ferrites nano-particles for microwave application

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Rabia [Institute of Chemical Sciences, Gomal University, D. I. Khan (Pakistan); Hussain Gul, Iftikhar, E-mail: iftikhar.gul@scme.nust.edu.pk [Thermal Transport Laboratory (TTL), Materials Engineering Department, School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology - NUST, H-12 Campus, Islamabad (Pakistan); Zarrar, Muhammad [Thermal Transport Laboratory (TTL), Materials Engineering Department, School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology - NUST, H-12 Campus, Islamabad (Pakistan); Anwar, Humaira [Islamabad Model College for Girls G-10/2, Islamabad (Pakistan); Khan Niazi, Muhammad Bilal [Department of Chemicals Engineering, SCME, NUST, H-12 Campus, Islamabad (Pakistan); Khan, Azim [Institute of Chemical Sciences, Gomal University, D. I. Khan (Pakistan)

    2016-05-01

    Cadmium substituted cobalt ferrites with formula Cd{sub x}Co{sub 1−x}Fe{sub 2}O{sub 4} (x=0.0, 0.2, 0.35, 0.5), have been synthesized by wet chemical co-precipitation technique. Electrical, morphological and Structural properties of the samples have been studied using DC electrical resistivity and Impedance analyzer, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively. XRD, SEM and AFM have been used to study the structural parameters such as measured density, lattice constant, X-ray density, crystallite size and morphology of the synthesized nano-particles. Debye–Scherrer formula has been used for the estimation of crystallite sizes. The estimated crystallite sizes were to be 15–19±2 nm. Hopping length of octahedral and tetrahedral sites have been calculated using indexed XRD data. The porosity and lattice constant increased as Cd{sup 2+}concentration increases. DC electrical resistivity was performed using two probe technique. The decrease of resistivity with temperature confirms the semiconducting nature of the samples. The dielectric properties variation has been studied at room temperature as a function of frequency. Variation of dielectric properties from 100 Hz to 5 MHz has been explained on the basis of Maxwell and Wagner’s model and hoping of electrons on octahedral sites. To separates the grains boundary and grains of the system Cd{sub x}Co{sub 1−x}Fe{sub 2}O{sub 4} the impedance analysis were performed. - Highlights: • Preparation of homogeneous, spherical and single phase well crystallized cobalt ferrites. • A simple and economical PEG assisted wet chemical co-precipitation method has been used. • Increased in DC electrical resistivity and activation energy. • Decease in dielectric constant used for microwave absorber. • AC conductivity of Cd{sup 2+} substituted Co-ferrites increases.

  20. Improved electrical properties of cadmium substituted cobalt ferrites nano-particles for microwave application

    International Nuclear Information System (INIS)

    Ahmad, Rabia; Hussain Gul, Iftikhar; Zarrar, Muhammad; Anwar, Humaira; Khan Niazi, Muhammad Bilal; Khan, Azim

    2016-01-01

    Cadmium substituted cobalt ferrites with formula Cd x Co 1−x Fe 2 O 4 (x=0.0, 0.2, 0.35, 0.5), have been synthesized by wet chemical co-precipitation technique. Electrical, morphological and Structural properties of the samples have been studied using DC electrical resistivity and Impedance analyzer, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively. XRD, SEM and AFM have been used to study the structural parameters such as measured density, lattice constant, X-ray density, crystallite size and morphology of the synthesized nano-particles. Debye–Scherrer formula has been used for the estimation of crystallite sizes. The estimated crystallite sizes were to be 15–19±2 nm. Hopping length of octahedral and tetrahedral sites have been calculated using indexed XRD data. The porosity and lattice constant increased as Cd 2+ concentration increases. DC electrical resistivity was performed using two probe technique. The decrease of resistivity with temperature confirms the semiconducting nature of the samples. The dielectric properties variation has been studied at room temperature as a function of frequency. Variation of dielectric properties from 100 Hz to 5 MHz has been explained on the basis of Maxwell and Wagner’s model and hoping of electrons on octahedral sites. To separates the grains boundary and grains of the system Cd x Co 1−x Fe 2 O 4 the impedance analysis were performed. - Highlights: • Preparation of homogeneous, spherical and single phase well crystallized cobalt ferrites. • A simple and economical PEG assisted wet chemical co-precipitation method has been used. • Increased in DC electrical resistivity and activation energy. • Decease in dielectric constant used for microwave absorber. • AC conductivity of Cd 2+ substituted Co-ferrites increases.

  1. Al-substituted {alpha}-cobalt hydroxide synthesized by potentiostatic deposition method as an electrode material for redox-supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Vinay [Art, Science and Technology Center for Cooperative Research, Kyushu University, Kasuga-shi, Fukuoka 816-8580 (Japan); Japan Science and Technology Agency, Kawaguchi-shi, Saitama 332-0012 (Japan); Gupta, Shubhra; Miura, Norio [Art, Science and Technology Center for Cooperative Research, Kyushu University, Kasuga-shi, Fukuoka 816-8580 (Japan)

    2008-03-01

    Al-substituted {alpha}-cobalt hydroxide was prepared by a potentiostatic deposition process at -1.0 V (vs. Ag/AgCl) onto stainless steel electrodes by using a mixed aqueous solution of cobalt nitrate and aluminum nitrate. Their structure and surface morphology were studied by using X-ray diffraction analysis, energy dispersive X-ray spectroscopy and scanning electron microscopy. The SEM images showed changes in the nanostructure of {alpha}-cobalt hydroxide by the addition of Al. Galvanostatic charge-discharge curves showed a drastic improvement in the capacitive characteristics of {alpha}-cobalt hydroxide, with a specific energy increase from 11.3 to 18.7 Wh kg{sup -1} by the substitution of just 8 at.% Al, and a specific capacitance of 843 F g{sup -1} between 0 and 0.4 V. The cycle stability data suggest no significant changes in the discharge characteristics of {alpha}-cobalt hydroxide by the addition of Al. (author)

  2. Chemical bonding and magnetic properties of gadolinium (Gd) substituted cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Puli, Venkata Sreenivas, E-mail: vspuli@utep.edu [Department of Mechanical Engineering, University of Texas, El Paso, TX 79968 (United States); Adireddy, Shiva [Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118 (United States); Ramana, C.V. [Department of Mechanical Engineering, University of Texas, El Paso, TX 79968 (United States)

    2015-09-25

    Graphical abstract: Room temperature Raman spectra of CoFe{sub 2−x}Gd{sub x}O{sub 4} (CFGO, x = 0.0–0.3) compounds as a function of wavenumber (cm{sup −1}). - Highlights: • Gd substituted ferrites were synthesized under controlled concentration. • Gd ion induced lattice dynamical changes are significant. • Enhanced magnetization is observed upon Gd-incorporation in cobalt ferrite. • A correlation between lattice dynamics and magnetic properties is established. - Abstract: Polycrystalline gadolinium (Gd) substituted cobalt ferrites (CoFe{sub 2−x}Gd{sub x}O{sub 4}; x = 0–0.3, referred to CFGO) ceramics have been synthesized by solid state reaction method. Chemical bonding, crystal structure and magnetic properties of CFGO compounds have been evaluated as a function of Gd-content. X-ray diffraction (XRD) and Raman spectroscopic analyses confirmed the formation of inverse spinel cubic structure. However, a secondary ortho-ferrite phase (GdFeO{sub 3}) nucleates for higher values of Gd-content. A considerable increase in the saturation magnetization has been observed upon the initial substitution of Gd (x = 0.1). The saturation magnetization drastically decreases at higher Gd content (x ⩾ 0.3). No contribution from ortho-ferrite GdFeO{sub 3} phase is noted to the magnetic properties. The increase in the magnetic saturation magnetization is attributed to the higher magnetic moment of Gd{sup 3+} (4f{sup 7}) residing in octahedral sites is higher when compared to that of Fe{sup 3+} (3d{sup 5}) and as well due to the migration of Co{sup 2+} (3d{sup 7}) ions from the octahedral to the tetrahedral sites with a magnetic moment aligned anti-parallel to those of rare earth (RE{sup 3+}) ions in the spinel lattice. Increase in coercivity with increase in Gd{sup 3+} is content is attributed to magnetic anisotropy in the ceramics.

  3. Effect of Cr{sup 3+} substitution on electric and magnetic properties of cobalt ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Panda, R.K., E-mail: physics.panda@gmail.com [Department of Physics, National Institute of Technology, Rourkela, 769 008 (India); Muduli, R. [Department of Physics, National Institute of Technology, Rourkela, 769 008 (India); Jayarao, G. [Department of Ceramic Engineering, National Institute of Technology, Rourkela, 769 008 (India); Sanyal, D. [Variable Energy Cyclotron Centre, Kolkata, 700064 (India); Behera, D. [Department of Physics, National Institute of Technology, Rourkela, 769 008 (India)

    2016-06-05

    This work describes the effect of incorporation of Cr{sup 3+} into CoFe{sub 2}O{sub 4} nanoparticles on its magnetic and electric properties, prepared by auto combustion method. The samples of CoFe{sub 2-x}Cr{sub x}O4 (x = 0, 0.15, 0.3) series were characterized by x-ray diffraction and field emission scanning electron microscopy to find out the average particle size. The substitution of Cr{sup 3+} caused a significant reduction in particle size of the modified systems. Room temperature Moessbauer spectroscopy and magnetic characterization were performed. Analysis of extracted parameters concluded that Cr{sup 3+} replaced the Fe{sup 3+} at B-site (octahedral). The decrease in magnetization at B-site was found responsible for the observed reduced saturation magnetization and coercivity. Impedance spectroscopic analysis has revealed the suppression of electrode-sample surface conduction effect and enhancement of material resistivity. The latter was confirmed by dc resistivity measurement. All these results were explained on the basis of occupancy of Cr{sup 3+} at B-site, surface anisotropy potential and reduced particle size. - Highlights: • Cr substitution reduced the particle size in nano-cobalt ferrite. • Mossbauer study revealed that the Cr{sup 3+} replaced the Fe{sup 3+} at B-site. • Decrease in saturation magnetization and coercivity with the addition of Cr{sup 3+}. • Reduction of surface conduction and rise in resistance observed in modified systems.

  4. Effect of Gd3+ substitution on structural, magnetic, dielectric and optical properties of nanocrystalline CoFe2O4

    Science.gov (United States)

    Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Kumar, Arun; Singh, Mahavir

    2017-03-01

    Nanoparticles of CoGdxFe2-xO4 with x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.15 were synthesized by co-precipitation method. Gd3+ substitution effect on different properties of nanocrystalline CoFe2O4 has been studied. X-ray diffraction and Raman spectroscopy confirmed the formation of single phase cubic mixed spinel structure. Cation distribution has been proposed from Rietveld refined data. Mössbauer spectra at room temperature showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Mössbauer parameters suggested that Gd3+ ions occupy the octahedral site in CoFe2O4. Room temperature magnetic measurements exhibited that the saturation magnetization decreased from 91 emu/gm to 54 emu/gm for x=0.0 to 0.15 samples. The coercivity decreased from 1120 Oe to 340 Oe for x=0.0 to 0.07 samples and increased from 400 Oe to 590 Oe for x=0.10 and 0.15 samples, respectively. Raman analysis showed that the degree of inversion with Gd3+ substitution supporting the variation of coercivity. Electron spin resonance spectra revealed the dominancy of superexchange interactions in these samples. Optical band gap measurement suggested that all samples are indirect band gap materials and band gap has been decreased with Gd3+ substitution. Both dielectric constant and dielectric loss is found to decrease because of the decrease in hopping rate with the Gd3+ substitution for Fe3+ at the octahedral sites. Low dielectric loss suggested the applicability of Gd3+ doped CoFe2O4 nanoparticles for high frequency microwave device applications.

  5. Following the Formation of Active Co(III) Sites in Cobalt Substituted Aluminophosphates Catalysts by In-Situ Combined UV-VIS/XAFS/XRD Technique

    International Nuclear Information System (INIS)

    Sankar, Gopinathan; Fiddy, Steven; Harvey, Ian; Hayama, Shusaku; Bushnell-Wye, Graham; Beale, Andrew M.

    2007-01-01

    Cobalt substituted aluminophosphates, CoAlPO-34 (Chabazite structure) and DAF-8 (Phillipsite structure) were investigated by in situ combined XRD/EXAFS/UV-VIS technique. In-situ combined XRD, Co K-edge EXAFS and UV-Vis measurements carried out during the calcination process reveal that CoAlPO-34 containing 10 wt percent cobalt is stable and the cobalt ions are converted from Co(II) in the as synthesised form to Co(III); DAF-8 containing about 25 percent cobalt is not stable and does not show change in oxidation state

  6. Acid mine drainage simulated leaching behavior of goethite and cobalt substituted goethite

    Science.gov (United States)

    Penprase, S. B.; Kimball, B. E.

    2015-12-01

    Though most modern day mining aims to eliminate the seepage of acid mine drainage (AMD) to the local watershed, historical mines regularly receive little to no remediation, and often release acidic, metal-rich drainage and particles to the environment. Treatment of AMD often includes neutralizing pH to facilitate the precipitation of Fe-oxides and dissolved trace metals, thereby forming Trace Metal Substituted (TMS) forms of known minerals, such as goethite (α-FeOOH). The stability of TMS precipitates is not fully understood. As a result, we conducted a 20 day leach experiment using laboratory synthesized pure (Gt) and cobalt-substituted (CoGt) goethites with a dilute ultrapure HCl solution (pH = 3.61) at T = 23.3±2.5ºC. Leached solids were characterized using X-ray diffraction (XRD) and scanning electron microscopy paired with energy dispersive spectroscopy (SEM-EDS). Leach solutions were sampled for pH and conductivity, and dissolved chemistry was determined with Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Preliminary results indicate Gt and CoGt filtered leach solutions experienced constant pH (Gt = 3.9 ± 0.1, CoGt = 6.8 ± 0.2) and conductivity (Gt = 69 ± 6.6 μS/cm, CoGt = 81 ± 16 μS/cm) for t = 0-20 days. Micro-focused XRD results indicate that leached solids did not change in mineralogy throughout the experiment, and SEM images show minor disintegration along mineral grain edges, but little overall change in shape. Preliminary ICP-MS results show lower dissolved Fe concentrations for CoGt (1.1 ± 1.1 ppb) compared to Gt (17 ± 8.9 ppb) over time. Dissolved Co concentrations ranged from 560 - 830 ppb and increased over time. Compared to leaching of pure Gt, leaching of CoGt generated significantly higher pH, slightly higher conductivity, and significantly less dissolved Fe. During the CoGt leach, Co was preferentially leached over Fe. The differences in leaching behavior between pure and TMS goethite in the laboratory have implications for

  7. Structural and chemical reactivity modifications of a cobalt perovskite induced by Sr-substitution. An in situ XAS study

    International Nuclear Information System (INIS)

    Hueso, Jose L.; Holgado, Juan P.; Pereñíguez, Rosa; Gonzalez-DelaCruz, V.M.; Caballero, Alfonso

    2015-01-01

    LaCoO 3 and La 0.5 Sr 0.5 CoO 3−δ perovskites have been studied by in situ Co K-edge XAS. Although the partial substitution of La(III) by Sr(II) species induces an important increase in the catalytic oxidation activity and modifies the electronic state of the perovskite, no changes could be detected in the oxidation state of cobalt atoms. So, maintaining the electroneutrality of the perovskite requires the generation of oxygen vacancies in the network. The presence of these vacancies explains that the substituted perovskite is now much more reducible than the original LaCoO 3 perovskite. As detected by in situ XAS, after a consecutive reduction and oxidation treatment, the original crystalline structure of the LaCoO 3 perovskite is maintained, although in a more disordered state, which is not the case for the Sr doped perovskite. So, the La 0.5 Sr 0.5 CoO 3−δ perovskite submitted to the same hydrogen reduction treatment produces metallic cobalt, while as determined by in situ XAS spectroscopy the subsequent oxidation treatment yields a Co(III) oxide phase with spinel structure. Surprisingly, no Co(II) species are detected in this new spinel phase. - Highlights: • A Sr-substituted lanthanum cobalt perovskite has been prepared by spray pyrolysis. • It has been established that Co(III) cations are present in both perovskites. • LaCoO 3 is a less reducible phase than the substituted La 0.5 Sr 0.5 CoO 3−δ . • After reoxidation of reduced La 0.5 Sr 0.5 CoO 3−δ , a 100% Co(III) spinel is obtained

  8. High-temperature Thermoelectric and Microstructural Characteristics of Ga Substituted on the Co-site in Cobalt-based Oxides

    DEFF Research Database (Denmark)

    Van Nong, Ngo; Yanagiya, S.; Sonne, Monica

    2011-01-01

    The effects of Ga substitution on the Co-site on the high-temperature thermoelectric properties and microstructure are investigated for the misfitlayered Ca3Co4O9 and the complex perovskite-related Sr3RECo4O10.5 (RE = rare earth) cobalt-based oxides. For both systems, substitution of Ga for Co...... results in a simultaneous increase in the Seebeck coefficient (S) and the electrical conductivity (σ), and the influence is more significant in the high temperature region. The power factor (S 2 σ) is thereby remarkably improved by Ga substitution, particularly at high temperatures. Texture factor......0.05O9 shows the best ZT value of 0.45 at 1200 K, which is about 87.5% higher than the nondoped one, a considerable improvement....

  9. Effect of Gd"3"+ substitution on structural, magnetic, dielectric and optical properties of nanocrystalline CoFe_2O_4

    International Nuclear Information System (INIS)

    Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Kumar, Arun; Singh, Mahavir

    2017-01-01

    Nanoparticles of CoGd_xFe_2_−_xO_4 with x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.15 were synthesized by co-precipitation method. Gd"3"+ substitution effect on different properties of nanocrystalline CoFe_2O_4 has been studied. X-ray diffraction and Raman spectroscopy confirmed the formation of single phase cubic mixed spinel structure. Cation distribution has been proposed from Rietveld refined data. Mössbauer spectra at room temperature showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Mössbauer parameters suggested that Gd"3"+ ions occupy the octahedral site in CoFe_2O_4. Room temperature magnetic measurements exhibited that the saturation magnetization decreased from 91 emu/gm to 54 emu/gm for x=0.0 to 0.15 samples. The coercivity decreased from 1120 Oe to 340 Oe for x=0.0 to 0.07 samples and increased from 400 Oe to 590 Oe for x=0.10 and 0.15 samples, respectively. Raman analysis showed that the degree of inversion with Gd"3"+ substitution supporting the variation of coercivity. Electron spin resonance spectra revealed the dominancy of superexchange interactions in these samples. Optical band gap measurement suggested that all samples are indirect band gap materials and band gap has been decreased with Gd"3"+ substitution. Both dielectric constant and dielectric loss is found to decrease because of the decrease in hopping rate with the Gd"3"+ substitution for Fe"3"+ at the octahedral sites. Low dielectric loss suggested the applicability of Gd"3"+ doped CoFe_2O_4 nanoparticles for high frequency microwave device applications. - Highlights: • Gd"3"+ ions were successfully added in to the spinel lattice of CoFe_2O_4. • Magnetic hysteresis loss is influenced by Gd"3"+ doping. • All doped samples exhibit normal dielectric dispersion behaviour of spinel ferrites. • UV–vis diffuse spectroscopy concludes band gap is reduced by Gd"3"+ doping.

  10. EPR-study of reversible oxygenation process of coordination compounds of cobalt(II) with S-substituted N1,N4-di(salicylidene)-isothiosemicarbazides

    International Nuclear Information System (INIS)

    Gerbeleu, N.V.; Revenko, M.D.; Rusu, V.G.; Shames, A.T.

    1987-01-01

    The reaction between molecular oxygen and coordination compounds of cobalt(II) with S-substituted N 1 ,N 4 -di(salicylidene)isothiosemicarbazides in dimethyl sulfoxide solution was studied by the EPR method. It was found that paramagnetic monomeric adducts and diamagnetic μ-peroxo-dimers are formed. The spin-Hamiltonian parameters of the EPR spectra of the initial cobalt complexes, as well as of the paramagnetic adducts were determined. The nature of the Co-O 2 bond is discussed

  11. Study on soft magnetic properties of Finemet-type nanocrystalline alloys with Mo substituting for Nb

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Dehui; Zhou, Bingwen; Jiang, Boyu; Ya, Bin; Zhang, Xingguo [School of Materials Science and Engineering, Dalian University of Technology, Dalian (China)

    2017-10-15

    The thermal stability, microstructure, and soft magnetic properties as a function of annealing time were studied for Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 3-x}Mo{sub x} (x = 0, 1, 2, 3) (atom percent, at.%,) ribbons. It was found that substituting Nb by Mo reduced the thermal stability. After 15 min short time vacuum annealing, Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 2}Mo{sub 1} and Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 1}Mo{sub 2} samples obtained higher permeability and similar coercivity compared to the original Finemet alloy (Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 3}), Mo substituting Nb reduced the optimum annealing time in Finemet-type alloys, and meanwhile marginally increased the saturation magnetization. Substituting all Nb by Mo led to the earlier formation of non-soft magnetic phase, thus deteriorated the soft magnetic properties. XRD and TEM structural analysis showed that in Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 2}Mo{sub 1} and Fe{sub 73.5}Si{sub 13.5}B{sub 9}Cu{sub 1}Nb{sub 1}Mo{sub 2} samples (annealed for 15 min), nanocrystals ∝10 nm in size were obtained, and the good soft magnetic properties of these alloys could be attributed to the small grain size. The relationship between annealing time, soft magnetic properties, and microstructure was established. Reducing annealing time and temperature to obtain best soft magnetic properties could cut down the production costs of Finemet-type alloys. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Yttrium-substituted nanocrystalline TiO 2 photoanodes for perovskite based heterojunction solar cells

    KAUST Repository

    Qin, Peng; Domanski, Anna L.; Chandiran, Aravind Kumar; Berger, Rü diger; Butt, Hans-Jü rgen; Dar, M. Ibrahim; Moehl, Thomas; Tetreault, Nicolas; Gao, Peng; Ahmad, Shahzada; Nazeeruddin, Mohammad K.; Grä tzel, Michael

    2014-01-01

    We report the use of Y3+-substituted TiO2 (0.5%Y-TiO2) in solid-state mesoscopic solar cells, consisting of CH3NH3PbI3 as the light harvester and spiro-OMeTAD as the hole transport material. A power conversion efficiency of 11.2% under simulated AM 1.5 full sun illumination was measured. A 15% improvement in the short-circuit current density was obtained compared with pure TiO2, due to the effect of Y3+ on the dimensions of perovskite nanoparticles formed on the semiconductor surface, showing that the surface modification of the semiconductor is an effective way to improve the light harvesters' morphology and electron transfer properties in the solid-state mesoscopic solar cells. © 2013 The Royal Society of Chemistry.

  13. Yttrium-substituted nanocrystalline TiO 2 photoanodes for perovskite based heterojunction solar cells

    KAUST Repository

    Qin, Peng

    2014-01-01

    We report the use of Y3+-substituted TiO2 (0.5%Y-TiO2) in solid-state mesoscopic solar cells, consisting of CH3NH3PbI3 as the light harvester and spiro-OMeTAD as the hole transport material. A power conversion efficiency of 11.2% under simulated AM 1.5 full sun illumination was measured. A 15% improvement in the short-circuit current density was obtained compared with pure TiO2, due to the effect of Y3+ on the dimensions of perovskite nanoparticles formed on the semiconductor surface, showing that the surface modification of the semiconductor is an effective way to improve the light harvesters\\' morphology and electron transfer properties in the solid-state mesoscopic solar cells. © 2013 The Royal Society of Chemistry.

  14. Defect dynamics in Li substituted nanocrystalline ZnO: A spectroscopic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, S., E-mail: sghoshphysics@gmail.com [Department of Material Science, Indian Association for the Cultivation of Science, 2A and 2B Raja S.C. Mullick Road, Jadavpur, Kolkata 700032 (India); Nambissan, P.M.G.; Thapa, S. [Applied Nuclear Physics Division, Saha Institute of Nuclear Physics, Sector 1, Block AF, Bidhannagar, Kolkata 700064 (India); Mandal, K. [Department of Condensed Matter Physics and Material Sciences, S.N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700098 (India)

    2014-12-01

    Very recently, vacancy-type defects have been found to play a major role in stabilizing d{sup 0} ferromagnetism in various low dimensional ZnO systems. In this context, the evolution of vacancy-type defects within the ZnO nanocrystals due to the doping of ZnO by alkali metal lithium (Li) is investigated using X-ray photoelectron (XPS), photoluminescence (PL) and positron annihilation spectroscopy (PAS). Li-doping is found to have significant effects in modifying the vacancy-type defects, especially the Zn vacancy (V{sub Zn}) defects within the ZnO lattice. XPS measurement indicated that initially the Li{sup 1+} ions substitute at Zn{sup 2+} sites, but when Li concentration exceeds 7 at%, excess Li starts to move through the interstitial sites. The increase in positron lifetime components and the lineshape S-parameter obtained from coincident Doppler broadening spectra with Li-doping indicated an enhancement of V{sub Zn} defect concentration within the doped ZnO lattice. The vacancy type defects, initially of the predominant configuration V{sub Zn+O+Zn} got reduced to neutral ZnO divacancies due to the partial recombination by the doped Li{sup 1+} ions but, when the doping concentration exceeded 7 at% and Li{sup 1+} ions started migrating to the interstitials, positron diffusion is partly impeded and this results in reduced probability of annihilation. PL spectra have shown intense green and yellow-orange emission due to the stabilization of a large number of V{sub Zn} defects and Li substitutional (Li{sub Zn}) defects respectively. Hence Li can be a very useful dopant in stabilizing and modifying significant amount of Zn vacancy-defects which can play a useful role in determining the material behavior.

  15. Defect dynamics in Li substituted nanocrystalline ZnO: A spectroscopic analysis

    Science.gov (United States)

    Ghosh, S.; Nambissan, P. M. G.; Thapa, S.; Mandal, K.

    2014-12-01

    Very recently, vacancy-type defects have been found to play a major role in stabilizing d0 ferromagnetism in various low dimensional ZnO systems. In this context, the evolution of vacancy-type defects within the ZnO nanocrystals due to the doping of ZnO by alkali metal lithium (Li) is investigated using X-ray photoelectron (XPS), photoluminescence (PL) and positron annihilation spectroscopy (PAS). Li-doping is found to have significant effects in modifying the vacancy-type defects, especially the Zn vacancy (VZn) defects within the ZnO lattice. XPS measurement indicated that initially the Li1+ ions substitute at Zn2+ sites, but when Li concentration exceeds 7 at%, excess Li starts to move through the interstitial sites. The increase in positron lifetime components and the lineshape S-parameter obtained from coincident Doppler broadening spectra with Li-doping indicated an enhancement of VZn defect concentration within the doped ZnO lattice. The vacancy type defects, initially of the predominant configuration VZn+O+Zn got reduced to neutral ZnO divacancies due to the partial recombination by the doped Li1+ ions but, when the doping concentration exceeded 7 at% and Li1+ ions started migrating to the interstitials, positron diffusion is partly impeded and this results in reduced probability of annihilation. PL spectra have shown intense green and yellow-orange emission due to the stabilization of a large number of VZn defects and Li substitutional (LiZn) defects respectively. Hence Li can be a very useful dopant in stabilizing and modifying significant amount of Zn vacancy-defects which can play a useful role in determining the material behavior.

  16. Defect dynamics in Li substituted nanocrystalline ZnO: A spectroscopic analysis

    International Nuclear Information System (INIS)

    Ghosh, S.; Nambissan, P.M.G.; Thapa, S.; Mandal, K.

    2014-01-01

    Very recently, vacancy-type defects have been found to play a major role in stabilizing d 0 ferromagnetism in various low dimensional ZnO systems. In this context, the evolution of vacancy-type defects within the ZnO nanocrystals due to the doping of ZnO by alkali metal lithium (Li) is investigated using X-ray photoelectron (XPS), photoluminescence (PL) and positron annihilation spectroscopy (PAS). Li-doping is found to have significant effects in modifying the vacancy-type defects, especially the Zn vacancy (V Zn ) defects within the ZnO lattice. XPS measurement indicated that initially the Li 1+ ions substitute at Zn 2+ sites, but when Li concentration exceeds 7 at%, excess Li starts to move through the interstitial sites. The increase in positron lifetime components and the lineshape S-parameter obtained from coincident Doppler broadening spectra with Li-doping indicated an enhancement of V Zn defect concentration within the doped ZnO lattice. The vacancy type defects, initially of the predominant configuration V Zn+O+Zn got reduced to neutral ZnO divacancies due to the partial recombination by the doped Li 1+ ions but, when the doping concentration exceeded 7 at% and Li 1+ ions started migrating to the interstitials, positron diffusion is partly impeded and this results in reduced probability of annihilation. PL spectra have shown intense green and yellow-orange emission due to the stabilization of a large number of V Zn defects and Li substitutional (Li Zn ) defects respectively. Hence Li can be a very useful dopant in stabilizing and modifying significant amount of Zn vacancy-defects which can play a useful role in determining the material behavior

  17. Effect of Cu-Cr co-substitution on magnetic properties of nanocrystalline magnesium ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com [Surface and Solid State Chemistry Laboratory, Department of Chemistry, Quaid-I-Azam University, Islamabad 45320 (Pakistan); Ahmad, Zahoor [Surface and Solid State Chemistry Laboratory, Department of Chemistry, Quaid-I-Azam University, Islamabad 45320 (Pakistan); Melikhov, Yevgen [Wolfson Centre for Magnetics, School of Engineering, Cardiff University, Cardiff CF24 3AA (United Kingdom); Nlebedim, Ikenna Cajetan [Ames Laboratory of US Department of Energy, Ames, IA 50011 (United States)

    2012-03-15

    This study deals with the temperature and composition dependence of magnetization and magnetic anisotropy of Cu{sup 2+}-Cr{sup 3+} co-substituted magnesium ferrite, Mg{sub 1-x}Cu{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x=0.0-0.5). The synthesized materials are characterized using thermo gravimetric analysis, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray fluorescence, Moessbauer spectrometer, superconducting quantum interference device magnetometer and vibrating sample magnetometer. The M-H loops measured up to 50 kOe at 300, 200 and 100 K, revealed narrow hysteresis curves with a coercive field and saturation magnetization varying for different compositions. The high field regimes of these loops are modeled using the Law of Approach to saturation to extract anisotropy information and saturation magnetization. Both the saturation magnetization and the anisotropy constant are observed to increase with the decrease in temperature while decrease with the Cu-Cr co-substituents for all the samples. Explanation of the observed behavior is proposed in terms of the preference of the co-substituent ions of Cu{sup 2+} and Cr{sup 3+} and their predominant choice to substitute into the octahedral sites of the cubic spinel lattice. - Highlights: Black-Right-Pointing-Pointer Mg{sub 1-x}Cu{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} was synthesized by novel PEG assisted microemulsion method. Black-Right-Pointing-Pointer Present paper dealt with magnetic properties of Mg{sub 1-x}Cu{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4}. Black-Right-Pointing-Pointer XRD patterns revealed tetragonal distorted cubic structure of Mg{sub 1-x}Cu{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4}. Black-Right-Pointing-Pointer Mossbauer spectroscopy confirmed that Cu-Cr occupy octahedral sites. Black-Right-Pointing-Pointer High field regime of M-H loops was modeled using Law of Approach to saturation.

  18. Heating-induced inner-sphere substitution and reduction-oxidation reactions of the solid phenanthroline containing cobalt (2) and cobalt (3) complexes

    International Nuclear Information System (INIS)

    Palade, D.M.

    1996-01-01

    The results of the differential thermal and thermogravimetric analyses of solid phenanthroline-containing complexes of cobalt (2) and cobalt (3) in the atmosphere of the air have been analyzed. Mechanism of redox reactions occurring when cobalt (3) complexes are heated has been discussed. It is shown that some of gaseous products of the redox processes appear as a result of secondary reactions and not the processes of the ligands oxidation by Co 3+ . The influence of certain inner-sphere and coordinated anions (of I, inclusively) on cobalt (3) complexes behaviour during heating has been considered

  19. On-surface manipulation of atom substitution between cobalt phthalocyanine and the Cu(111) substrate

    DEFF Research Database (Denmark)

    Shen, Kongchao; Narsu, Bai; Ji, Gengwu

    2017-01-01

    On-surface fabrication of controllable nanostructures is an appealing topic in the field of molecular electronics. Herein, the adsorption of cobalt phthalocyanine (CoPc) on a Cu(111) surface is investigated utilizing a combination of photoelectron spectroscopy (PES) and density functional theory ...... state environment may offer an encouraging approach towards the artificial engineering of organometallic nanostructures and related properties for surface catalysts, molecular electronics and so on....... and thermal annealing, and the tendency to form Co–Cu alloy at the interface. While CoPc has been successfully utilized in electrocatalysts for fuel cell applications and CuPc is commonly used as a leading material in organic solar cells, this report of interface transmetalation from CoPc to CuPc in a solid...

  20. Correlation of reactivity with structural factors in a series of Fe(II) substituted cobalt ferrites

    International Nuclear Information System (INIS)

    Sileo, Elsa E.; Garcia Rodenas, Luis; Paiva-Santos, Carlos O.; Stephens, Peter W.; Morando, Pedro J.; Blesa, Miguel A.

    2006-01-01

    A series of powdered cobalt ferrites, Co x Fe 3- x O 4 with 0.66≤x II , were synthesized by a mild procedure, and their Fe and Co site occupancies and structural characteristics were explored using X-ray anomalous scattering and the Rietveld refinement method. The dissolution kinetics, measured in 0.1 M oxalic acid aqueous solution at 70 deg. C, indicate in all cases the operation of a contracting volume rate law. The specific rates increased with the Fe II content following approximately a second-order polynomial expression. This result suggests that the transfer of Fe III controls the dissolution rate, and that the leaching of a first layer of ions Co II and Fe II leaves exposed a surface enriched in slower dissolving octahedral Fe III ions. Within this model, inner vicinal lattice Fe II accelerates the rate of Fe III transfer via internal electron hopping. A chain mechanism, involving successive electron transfers, fits the data very well. - Graphical abstract: The electron exchange between octahedral Fe II and Fe III ions has important consequences on the specific dissolution rates. Display Omitted

  1. Histological and histomorphometrical analysis of a silica matrix embedded nanocrystalline hydroxyapatite bone substitute using the subcutaneous implantation model in Wistar rats

    Energy Technology Data Exchange (ETDEWEB)

    Ghanaati, Shahram; Orth, Carina; Barbeck, Mike; Kirkpatrick, Charles James [Institute of Pathology, University Medical Center of the Johannes Gutenberg University Mainz, Langenbeckstrasse 1, 55101 Mainz (Germany); Willershausen, Ines [Institute for Dental Material Sciences and Technology, University Medical Center of the Johannes Gutenberg University Mainz, Anselm-Franz-von-Bentzel-Weg 14, 55128 Mainz (Germany); Thimm, Benjamin W [Institute for Biomechanics, ETH Zuerich, Wolfgang-Pauli-Str.10, 8093 Zuerich (Switzerland); Booms, Patrick [Leeds Institute of Molecular Medicine, Section of Medicine, Surgery and Anaesthesia, University of Leeds (United Kingdom); Stuebinger, Stefan; Landes, Constantin; Sader, Robert Anton, E-mail: ghanaati@uni-mainz.d [Department for Oral, Cranio-Maxillofacial and Facial Plastic Surgery, Medical Center of the Goethe University Frankfurt, Theodor-Stein-Kai 7, 60596 Frankfurt am Main (Germany)

    2010-06-01

    The clinical suitability of a bone substitute material is determined by the ability to induce a tissue reaction specific to its composition. The aim of this in vivo study was to analyze the tissue reaction to a silica matrix-embedded, nanocrystalline hydroxyapatite bone substitute. The subcutaneous implantation model in Wistar rats was chosen to assess the effect of silica degradation on the vascularization of the biomaterial and its biodegradation within a time period of 6 months. Already at day 10 after implantation, histomorphometrical analysis showed that the vascularization of the implantation bed reached its peak value compared to all other time points. Both vessel density and vascularization significantly decreased until day 90 after implantation. In this time period, the bone substitute underwent a significant degradation initiated by TRAP-positive and TRAP-negative multinucleated giant cells together with macrophages and lymphocytes. Although no specific tissue reaction could be related to the described silica degradation, the biomaterial was close to being fully degraded without a severe inflammatory response. These characteristics are advantageous for bone regeneration and remodeling processes.

  2. Histological and histomorphometrical analysis of a silica matrix embedded nanocrystalline hydroxyapatite bone substitute using the subcutaneous implantation model in Wistar rats

    International Nuclear Information System (INIS)

    Ghanaati, Shahram; Orth, Carina; Barbeck, Mike; Kirkpatrick, Charles James; Willershausen, Ines; Thimm, Benjamin W; Booms, Patrick; Stuebinger, Stefan; Landes, Constantin; Sader, Robert Anton

    2010-01-01

    The clinical suitability of a bone substitute material is determined by the ability to induce a tissue reaction specific to its composition. The aim of this in vivo study was to analyze the tissue reaction to a silica matrix-embedded, nanocrystalline hydroxyapatite bone substitute. The subcutaneous implantation model in Wistar rats was chosen to assess the effect of silica degradation on the vascularization of the biomaterial and its biodegradation within a time period of 6 months. Already at day 10 after implantation, histomorphometrical analysis showed that the vascularization of the implantation bed reached its peak value compared to all other time points. Both vessel density and vascularization significantly decreased until day 90 after implantation. In this time period, the bone substitute underwent a significant degradation initiated by TRAP-positive and TRAP-negative multinucleated giant cells together with macrophages and lymphocytes. Although no specific tissue reaction could be related to the described silica degradation, the biomaterial was close to being fully degraded without a severe inflammatory response. These characteristics are advantageous for bone regeneration and remodeling processes.

  3. Nanocrystalline hydroxyapatite bone substitute leads to sufficient bone tissue formation already after 3 months: histological and histomorphometrical analysis 3 and 6 months following human sinus cavity augmentation.

    Science.gov (United States)

    Ghanaati, Shahram; Barbeck, Mike; Willershausen, Ines; Thimm, Benjamin; Stuebinger, Stefan; Korzinskas, Tadas; Obreja, Karina; Landes, Constantin; Kirkpatrick, Charles J; Sader, Robert A

    2013-12-01

    In this study the de novo bone formation capacity of a nanocrystalline hydroxyapatite bone substitute was assessed 3 and 6 months after its insertion into the human sinus cavity. Sinus cavity augmentation was performed in a total of 14 patients (n = 7 implantation after 3 months; n = 7 implantation after 6 months) with severely atrophic maxillary bone. The specimens obtained after 3 and 6 months were analyzed histologically and histomorphometrically with special focus on bone metabolism within the residual bone and the augmented region. This study revealed that bone tissue formation started from the bone-biomaterial-interface and was directed into the most cranial parts of the augmented region. There was no statistically significant difference in new bone formation after 3 and 6 months (24.89 ± 10.22% vs 31.29 ± 2.29%), respectively. Within the limits of the present study and according to previously published data, implant insertion in regions augmented with this bone substitute material could be considered already after 3 months. Further clinical studies with bone substitute materials are necessary to validate these findings. © 2012 Wiley Periodicals, Inc.

  4. Tuning of magnetic property by lattice strain in lead substituted cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Rajnish [Department of Physics, Indian Institute of Technology Patna, Bihta, Patna 801103 (India); Singh, Rakesh Kr. [Aryabhatta Center for Nanoscience and Nanotechnology, Aryabhatta Knowledge University, Patna 800001 (India); Zope, Mukesh Kumar [Indira Gandhi Institute of Medical Sciences, Sheikhpura, Patna 800014 (India); Kar, Manoranjan, E-mail: mano@iitp.ac.in [Department of Physics, Indian Institute of Technology Patna, Bihta, Patna 801103 (India)

    2017-06-15

    Highlights: • Increase of lattice parameter due to Pb substitution in CFO. • Magnetism due to lattice strain in nonmagnetic (Pb) substituted CFO. • Saturation magnetization increases up to 2% Pb concentration. • Magnetocrystalline anisotropy constant increases up to 2% Pb concentration. • Existence of non-collinear spin structure which can be explained by three sublattice model of Yafet and Kittel. - Abstract: Co{sub 1−x}Pb{sub x}Fe{sub 2}O{sub 4} (x = 00–0.15) have been synthesized using citric acid modified sol-gel method. Samples for x ≤ 0.02 have been ball milled to reduce the particle size. Hence, all the materials under the study are in almost equal crystallite size (∼15 nm). The phase purity and structural study have been carried out using X-ray powder diffraction (XRD) technique. The Rietveld refinement of XRD patterns reveals the increasing lattice parameter with the lead (Pb) concentration. Detailed analysis of the Raman spectroscopy data supports the XRD pattern analysis results. Magnetic hysteresis loop measurements have been performed using Vibrating Sample Magnetometer (VSM) at room temperature over field range of ±20 kOe. Magnetocrystalline anisotropy constant was calculated using Law of Approach (LA) to saturation, which shows increasing behavior till 2% Pb concentration. The large difference in experimental and theoretical saturation magnetic moment per formula unit shows existence of three sublattice model suggested by Yafet-Kittel.

  5. Surface properties of self-assembled monolayer films of tetra-substituted cobalt, iron and manganese alkylthio phthalocyanine complexes

    Energy Technology Data Exchange (ETDEWEB)

    Akinbulu, Isaac Adebayo; Khene, Samson [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.z [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa)

    2010-09-30

    Self-assembled monolayer (SAM) films of iron (SAM-1), cobalt (SAM-2) and manganese (SAM-3) phthalocyanine complexes, tetra-substituted with diethylaminoethanethio at the non-peripheral positions, were formed on gold electrode in dimethylformamide (DMF). Electrochemical, impedimentary and surface properties of the SAM films were investigated. Cyclic voltammetry was used to investigate the electrochemical properties of the films. Ability of the films to inhibit common faradaic processes on bare gold surface (gold oxidation, solution redox chemistry of [Fe(H{sub 2}O){sub 6}]{sup 3+}/[Fe(H{sub 2}O){sub 6}]{sup 2+} and underpotential deposition (UDP) of copper) was investigated. Electrochemical impedance spectroscopy (EIS), using [Fe(CN){sub 6}]{sup 3-/4-} redox process as a probe, offered insights into the electrical properties of the films/electrode interfaces. Surface properties of the films were probed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The films were employed for the electrocatalytic oxidation of the pesticide, carbofuran. Electrocatalysis was evidenced from enhanced current signal and less positive oxidation potential of the pesticide on each film, relative to that observed on the bare gold electrode. Mechanism of electrocatalytic oxidation of the pesticide was studied using rotating disc electrode voltammetry.

  6. Implantation of silicon dioxide-based nanocrystalline hydroxyapatite and pure phase beta-tricalciumphosphate bone substitute granules in caprine muscle tissue does not induce new bone formation

    Directory of Open Access Journals (Sweden)

    Ghanaati Shahram

    2013-01-01

    Full Text Available Abstract Background Osteoinductive bone substitutes are defined by their ability to induce new bone formation even at heterotopic implantation sites. The present study was designed to analyze the potential osteoinductivity of two different bone substitute materials in caprine muscle tissue. Materials and methods One gram each of either a porous beta-tricalcium phosphate (β-TCP or an hydroxyapatite/silicon dioxide (HA/SiO2-based nanocrystalline bone substitute material was implanted in several muscle pouches of goats. The biomaterials were explanted at 29, 91 and 181 days after implantation. Conventional histology and special histochemical stains were performed to detect osteoblast precursor cells as well as mineralized and unmineralized bone matrix. Results Both materials underwent cellular degradation in which tartrate-resistant acid phosphatase (TRAP-positive osteoclast-like cells and TRAP-negative multinucleated giant cells were involved. The ß-TCP was completely resorbed within the observation period, whereas some granules of the HA-groups were still detectable after 180 days. Neither osteoblasts, osteoblast precursor cells nor extracellular bone matrix were found within the implantation bed of any of the analyzed biomaterials at any of the observed time points. Conclusions This study showed that ß-TCP underwent a faster degradation than the HA-based material. The lack of osteoinductivity for both materials might be due to their granular shape, as osteoinductivity in goat muscle has been mainly attributed to cylindrical or disc-shaped bone substitute materials. This hypothesis however requires further investigation to systematically analyze various materials with comparable characteristics in the same experimental setting.

  7. Low temperature magneto-dielectric measurements on BiFeO3 lightly substituted by cobalt

    International Nuclear Information System (INIS)

    Ray, J.; Biswal, A. K.; Vishwakarma, P. N.

    2015-01-01

    Dielectric and magnetodielectric measurements are done on BiFe 1−x Co x O 3 : x = 0, 0.01, and 0.02 in the temperature range 70–300 K and up to magnetic field 1.3 T. The dielectric data are well described by Haverliak–Negami expression plus an additional term for the Maxwell Wagner (MW) type relaxations, whose contribution is dominant near room temperature. The parameters obtained from the fitting of data using the above mentioned expression, suggest slowing down of relaxation and approach towards ideal Debye type relaxations, as the temperature is lowered. The dielectric relaxations obey polaronic variable range hopping model with distinct activation energies (E a ) in the extrinsic (6.67T 3/4  meV) and intrinsic (2.88T 3/4  meV) regions for the parent sample (x = 0), and thus a distinct transition from extrinsic to intrinsic behavior is seen at 215 K while lowering the temperature. This distinct transition is missing for Co substituted samples probably due to the extrinsic region values of E a (3.42T 3/4  meV and 2.42T 3/4  meV for x = 0.01 and 0.02, respectively) comparable to that of the intrinsic region (see x = 0). The magnetodielectric measurement shows positive magnetodielectricity (MD) in the intrinsic region (T < 215 K for x = 0) and negative MD in the extrinsic region (T > 215 K for x = 0). The extrinsic region is found to be dominated by MW and magnetoresistance effects, whereas MD in intrinsic regions is due to the spin reorientation transitions. The Co substitution is found to increase the extrinsic and non-Debye contributions to dielectricity, which becomes so large that no spin reorientation transitions are seen in x = 0.02 sample. The pyroelectric active region in x = 0 is found to be dominated by the diffusive behavior having contribution of the form ω −0.5

  8. Hydrogel-embedded nanocrystalline hydroxyapatite granules (elastic blocks based on a cross-linked polyvinylpyrrolidone as bone grafting substitute in a rat tibia model

    Directory of Open Access Journals (Sweden)

    Dau M

    2017-10-01

    in EB (21 and 63 days. Furthermore, no significant differences regarding the level of TRAP-positive marked cells in each group were observed. Conclusion: The bone substitute (EB with the cross-linked PVP-based hydrogel carrier leads at the beginning to a higher amount of remaining carrier material and remaining bone substitute. This delayed degradation is supposed to be the reason for the observed lower level of bone remodeling and is caused by the irradiation changes (cross links in the structure in PVP.Keywords: bone substitute, cross-linked, nanocrystalline hydroxyapatite, rat animal model, polyvinylpyrrolidone, irradiation, silica, osseointegration

  9. The practical limits for enhancing magnetic property combinations for bulk nanocrystalline NdFeB alloys through Pr, Co and Dy substitutions

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Z.W. [Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD (Singapore)]. E-mail: phylz@nus.edu.sg; Davies, H.A. [Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD (Singapore)

    2007-06-15

    Pr, Co and Dy additions have been employed to improve the combinations of magnetic properties for nanocrystalline Nd {sub x} Fe{sub 94-} {sub x} B{sub 6} melt spun alloys. The dependences of the magnetic properties on the solute element concentrations have been extensively investigated and the relationships between the measured remanence, maximum energy product (BH){sub max} and intrinsic coercivity for several compositional series are discussed. The composition ranges for these elemental substitutions which can be used to achieve the highest values of (BH){sub max} are identified. It is found that, when we employ individual or combined substitutions of Pr and Dy for Nd and Co for Fe in NdFeB alloys with various RE:Fe ratios, the practical limit of (BH){sub max} lies in the range {approx}160-180 kJ/m{sup 3}, combined with a coercivity in the range {approx}400-800 kA/m.

  10. Effect of cobalt substitution on the magnetic properties of nickel chromite

    Science.gov (United States)

    Mohanty, P.; Sheppard, C. J.; Prinsloo, A. R. E.; Roos, W. D.; Olivi, L.; Aquilanti, G.

    2018-04-01

    It is of interest to study the magneto-structural coupling in geometrically frustrated antiferromagnets, where structural distortion elevates the ground state degeneracy, leading to a long-range magnetic order. In this regard a cubic spinel compound of the form AB2O4 is currently drawing much attention, where A refers to tetrahedral and B to octahedral sites. In the particular case of NiCr2O4 the material undergoes several structural phase transitions associated with the magnetic ordering. It is therefore necessary to study the magnetic behaviour of NiCr2O4 by substituting either A or B sites, or both systematically with suitable cations. The current work therefore aims at the modification of magnetic properties of NiCr2O4 by doping with Co2+ at A sites. In order to achieve the afore mentioned, (Ni1-xCox)Cr2O4 (0 ≤ x ≤ 1) were prepared using chemical co-precipitation techniques. X-ray diffraction (XRD) results indicate that the samples are in the expected phase without any trace of Cr2O3 impurities after calcination. Transmission electron microcopy (TEM) analyses of these samples show that the particles are mostly bi-pyramidal in shape, with sizes ranging from 50 nm to 100 nm. In the present study the ferrimagnetic transition temperatures (TC) of the various samples were determined utilizing magnetization as function of temperature measurements. TC for NiCr2O4 and CoCr2O4 was determined to be 82.4 ± 0.8 K and 99.5 ± 0.5 K, respectively. These values are higher than those previously reported in the literature for both these compounds. Substitution of Ni by Co, results in an increase in the TC, giving values of 89.2 ± 0.7 K and 90.6 ± 0.9 K for (Ni0.5Co0.5)Cr2O4 and (Ni0.25Co0.75)Cr2O4, respectively. The (Ni0.5Co0.5)Cr2O4 sample demonstrated a high coercivity of 3.6 ± 0.1 T and a shift in the hysteresis loop observed under field cooled measurement, not previously reported in literature. X-ray photoelectron spectroscopy (XPS) of (Ni0.5Co0.5)Cr2O4 suggests

  11. Soapnut extract mediated synthesis of nanoscale cobalt substituted NdFeB ferromagnetic materials and their characterization

    Science.gov (United States)

    Rao, G. V. S. Jayapala; Prasad, T. N. V. K. V.; Shameer, Syed; Rao, M. Purnachandra

    2018-04-01

    Neodymium iron boron (NdFeB) permanent magnets have high energy product with suitable magnetic and physical properties for an array of applications including power generation and motors. However, synthetic routes of NdFeB permanent magnets involve critical procedures with high energy and needs scientific skills. Herein, we report on soapnut extract mediated synthesis of nanoscale cobalt substituted NdFeB (Co-NdFeB) permanent magnetic powders (Nd: 15%, Fe: 77.5%, B: 7.5% and Co with molar ratios: 0.5, 1, 1.5 and 2). A 10 ml of 10% soapnut extract was added to 90 ml of respective chemical composition and heated to 60 °C for 30 min and aged for 24 h. The dried powder was sintered at 500 °C for 1 h. The characterization of the prepared nanoscale Co-NdFeB magnetic powders was done using the techniques such as Dynamic Light Scattering (DLS for size and zeta potential measurements), X-ray diffraction (XRD) for structural determination, Scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS) for surface morphological and elemental analysis, Fourier transform infrared spectroscopy (FT-IR) for the identification of functional groups associated and hysteresis loop studies to quantify the magnetization. The results revealed that particles were in irregular and tubular shaped and highly stable (Zeta potential: -44.4 mV) with measured size <100 nm. XRD micrographs revealed a tetragonal crystal structure and FTIR showed predominant N-H and O-H stretching indicates the involvement of these functional groups in the reduction and stabilization process of Co-NdFeB magnetic powders. Hysteresis studies signify the effect of an increase in Co concentration.

  12. Influence of La3+ Substitution on Structure, Morphology and Magnetic Properties of Nanocrystalline Ni-Zn Ferrite.

    Directory of Open Access Journals (Sweden)

    Y K Dasan

    Full Text Available Lanthanum substituted Ni-Zn ferrite nanoparticles (Ni0.5Zn0.5LaxFe1-xO4; 0.00 ≤x≤ 1.00 synthesized by sol-gel method were presented. X-ray diffraction patterns reveal the typical single phase spinel cubic ferrite structure, with the traces of secondary phase for lanthanum substituted nanocrystals. In addition, the structural analysis also demonstrates that the average crystallite size varied in the range of 21-25 nm. FTIR spectra present the two prominent absorption bands in the range of 400 to 600 cm-1 which are the fingerprint region of all ferrites. Surface morphology of both substituted and unsubstituted Ni-Zn ferrite nanoparticle samples was studied using FESEM technique and it indicates a significant increase in the size of spherical shaped particles with La3+ substitution. Magnetic properties of all samples were analyzed using vibrating sample magnetometer (VSM. The results revealed that saturation magnetization (Ms and coercivity (Hc of La3+ substituted samples has decreased as compared to the Ni-Zn ferrite samples. Hence, the observed results affirm that the lanthanum ion substitution has greatly influenced the structural, morphology and magnetic properties of Ni-Zn ferrite nanoparticles.

  13. Effect of Dy3+ substitution on structural and magnetic properties of nanocrystalline Ni-Cu-Zn ferrites

    Science.gov (United States)

    Kabbur, S. M.; Ghodake, U. R.; Nadargi, D. Y.; Kambale, Rahul C.; Suryavanshi, S. S.

    2018-04-01

    Nanocrystalline Ni0.25Cu0.30Zn0.45DyxFe2-xO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1 and 0.125 mol.) ferrimagnetic oxides have been synthesized by sol-gel autocombustion route. X-ray diffraction study reveals the formation of spinel cubic structure with an expansion of the unit cell by Dy addition. Bertaut method was employed to propose the site occupancy i.e. cation distribution for elements at A-tetrahedral and B-octahedral sites of spinel lattice. The intrinsic vibrational absorption bands i.e. υ1 (712-719 cm-1) and υ2 (496-506 cm-1) are observed for tetrahedral and octahedral sites respectively. The microstructural aspect confirms the formation of an average grain size (∼7-99 nm) with presence of expected elements. Magnetization studies reveal that the magnetic moments are no longer linear but exhibit canting effect due to spin frustration. The frequency dispersion spectrum of initial permeability has been explained based on grain size, saturation magnetization and anisotropy constant. Thermal hysteresis curve (initial permeability versus temperature) indicates magnetic disordering to paramagnetic state at Néel temperature (TN). High values of TN show that the present ferrite samples are cation-ordered with d-electrons contributing towards the magnetic interaction at the sublattice.

  14. Effect of Gd{sup 3+} substitution on structural, magnetic, dielectric and optical properties of nanocrystalline CoFe{sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Seema [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida 201307 (India); Kumar, Manoj, E-mail: mkumar.phy@gmail.com [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida 201307 (India); Chhoker, Sandeep [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida 201307 (India); Kumar, Arun; Singh, Mahavir [Department of Physics, Himachal Pradesh University, Shimla 5 (India)

    2017-03-15

    Nanoparticles of CoGd{sub x}Fe{sub 2−x}O{sub 4} with x=0.0, 0.03, 0.05, 0.07, 0.10 and 0.15 were synthesized by co-precipitation method. Gd{sup 3+} substitution effect on different properties of nanocrystalline CoFe{sub 2}O{sub 4} has been studied. X-ray diffraction and Raman spectroscopy confirmed the formation of single phase cubic mixed spinel structure. Cation distribution has been proposed from Rietveld refined data. Mössbauer spectra at room temperature showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Mössbauer parameters suggested that Gd{sup 3+} ions occupy the octahedral site in CoFe{sub 2}O{sub 4}. Room temperature magnetic measurements exhibited that the saturation magnetization decreased from 91 emu/gm to 54 emu/gm for x=0.0 to 0.15 samples. The coercivity decreased from 1120 Oe to 340 Oe for x=0.0 to 0.07 samples and increased from 400 Oe to 590 Oe for x=0.10 and 0.15 samples, respectively. Raman analysis showed that the degree of inversion with Gd{sup 3+} substitution supporting the variation of coercivity. Electron spin resonance spectra revealed the dominancy of superexchange interactions in these samples. Optical band gap measurement suggested that all samples are indirect band gap materials and band gap has been decreased with Gd{sup 3+} substitution. Both dielectric constant and dielectric loss is found to decrease because of the decrease in hopping rate with the Gd{sup 3+} substitution for Fe{sup 3+} at the octahedral sites. Low dielectric loss suggested the applicability of Gd{sup 3+} doped CoFe{sub 2}O{sub 4} nanoparticles for high frequency microwave device applications. - Highlights: • Gd{sup 3+} ions were successfully added in to the spinel lattice of CoFe{sub 2}O{sub 4}. • Magnetic hysteresis loss is influenced by Gd{sup 3+} doping. • All doped samples exhibit normal dielectric dispersion behaviour of spinel ferrites. • UV–vis diffuse spectroscopy concludes band gap is reduced by Gd{sup 3+} doping.

  15. Structural, electrical, magnetic and dielectric properties of rare-earth substituted cobalt ferrites nanoparticles synthesized by the co-precipitation method

    Energy Technology Data Exchange (ETDEWEB)

    Nikumbh, A.K., E-mail: aknik@chem.unipune.ac.in; Pawar, R.A.; Nighot, D.V.; Gugale, G.S.; Sangale, M.D.; Khanvilkar, M.B.; Nagawade, A.V.

    2014-04-15

    Pure nanoparticles of the rare-earth substituted cobalt ferrites CoRE{sub x}Fe{sub 2−x}O{sub 4} (where RE=Nd, Sm and Gd and x=0.1 and 0.2) were prepared by the chemical co-precipitation method. X-ray diffraction, Transmission electron microscopy (TEM), d.c. electrical conductivity, Magnetic hysteresis and Thermal analysis are utilized in order to study the effect of variation in the rare-earth substitution and its impact on particle size, magnetic properties like M{sub S}, H{sub C} and Curie temperature. The phase identification of the materials by X-ray diffraction reveals the single-phase nature of the materials. The lattice parameter increased with rare-earth content for x≤0.2. The Transmission electron micrographs of Nd-, Sm- and Gd-substituted CoFe{sub 2}O{sub 4} exhibit the particle size 36.1 to 67.8 nm ranges. The data of temperature variation of the direct current electrical conductivity showed definite breaks, which corresponds to ferrimagnetic to paramagnetic transitions. The thermoelectric power for all compound are positive over the whole range of temperature. The dielectric constant decreases with frequency and rare-earth content for the prepared samples. The magnetic properties of rare-earth substituted cobalt ferrites showed a definite hysteresis loop at room temperature. The reduction of coercive force, saturation magnetization, ratio M{sub R}/M{sub S} and magnetic moments may be due to dilution of the magnetic interaction.

  16. Hydrogen/deuterium fractionation factors of the aqueous ligand of cobalt in Co(H2O)62+ and Co(II)-substituted carbonic anhydrase

    International Nuclear Information System (INIS)

    Kassebaum, J.W.

    1988-01-01

    The author has measured the hydrogen/deuterium fractionation factor for the rapidly exchanging aqueous ligands of cobalt in Co(H 2 O) 6 2+ and in three Co(II)-substituted isozymes of carbonic anhydrase. The fractionation factor was determined from NMR relaxation rates at 300 MHz of the protons of water in mixed solutions of H 2 O and D 2 O containing these complexes. In each case, the paramagnetic contribution to 1/T 2 was greater than to 1/T 1 , consistent with a chemical shift mechanism affecting 1/T 2 . The fractionation factors obtained from T 2 were 0.73 ± 0.02 for Co(H 2 O) 6 2+ , 0.72 ± 0.02 for Co(II)-substituted carbonic anhydrase I, 0.77 ± 0.01 for Co(II)-substituted carbonic anhydrase II, and 1.00 ± 0.07 for Co(Il)-substituted carbonic anhydrase III. He concluded that fractionation factors in these cases determined from T 1 and T 2 measured isotope preferences for different populations of ligand sites. Since T 2 has a large contribution from a chemical shift mechanism, the fractionation factor determined from T 2 has a large contribution of the fractionation of inner shell ligands. The fractionation factor of Co(H 2 O) 6 2+ was used to interpret the solvent hydrogen isotope effects on the formation of complexes of cobalt with the bidentate ligands glycine, N,N-dimethylglycine, and acetylacetone. The contribution of the fractionation factor of the inner water shell in Co(H 2 O) 6 2+ did not account completely for the measured isotope effect, and that the hydrogen/deuterium fractionation of outer shell water makes a large contribution to the isotope effect on the formation of these complexes

  17. Effect of Titanium Substitution on Magnetic Properties and Microstructure of Nanocrystalline Monophase Nd-Fe-B Magnets

    Directory of Open Access Journals (Sweden)

    Wang Cong

    2012-01-01

    Full Text Available Nd12.3Fe81.7−xTixB6.0  (x=0.5–3.0 ribbons have been prepared by rapid quenching and subsequent annealing treatment. Effect of Ti substitution and annealing treatment on the microstructure, magnetic properties, and crystallization behavior of the ribbons was systematically investigated by the methods of differential scanning calorimeter (DSC, X-ray diffraction (XRD, transmission electron microscopy (TEM, and vibrating sample magnetometer (VSM. It is found that Ti addition may increase the crystallization temperature and stabilize the amorphous phase. Ti element inhibits the grain growth during crystallization process and finally refines the microstructure. The exchange coupling interactions and magnetic properties of the ribbons increase with increasing x from 0.5 to 1 and then decrease with further increasing x≥1.5. Optimum magnetic properties with (BHmax⁡=151.6 kJ/m3, Hci=809.2 kA/m, Jr=1.02 T are achieved in the Nd12.3Fe80.7Ti1B6.0 ribbons annealed at 600°C for 10 min.

  18. Effect of rare earth substitution on properties of barium strontium titanate ceramic and its multiferroic composite with nickel cobalt ferrite

    International Nuclear Information System (INIS)

    Pahuja, Poonam; Kotnala, R.K.; Tandon, R.P.

    2014-01-01

    Highlights: • Rare earth ions Dy 3+ , Gd 3+ and Sm 3+ have been substituted in Ba 0.95 Sr 0.05 TiO 3 (BST). • Ni 0.8 Co 0.2 Fe 2 O 4 has been used as ferrimagnetic phase to obtain composites. • Substitution of these ions increases dielectric constant of BST and composites. • Magnetoelectric coefficient of composites increases on substitution of these ions. - Abstract: Effect of substitution of rare earth ions (Dy 3+ , Gd 3+ and Sm 3+ ) on various properties of Ba 0.95 Sr 0.05 TiO 3 (BST) i.e. the composition Ba 0.95−1.5x Sr 0.05 R x TiO 3 (where x = 0.00, 0.01, 0.02, 0.03 and R are rare earths Dy, Gd, Sm) and that of their multiferroic composite with Ni 0.8 Co 0.2 Fe 2 O 4 (NCF) has been studied. Shifting of peaks corresponding to different compositions in the X-ray diffraction pattern confirmed the substitution of rare earth ions at both Ba 2+ and Ti 4+ sites in BST. It is clear from scanning electron microscopy (SEM) images that rare earth substitution in BST increases its grain size in both pure and composite samples. Substitution of rare earth ions results in increase in value of dielectric constant of pure and composite samples. Sm substitution in BST significantly decreases its Curie temperature. Dy substituted pure and composite samples possess superior ferroelectric properties as confirmed by polarization vs electric field (P–E) loops. Composite samples containing Dy, Gd and Sm substituted BST as ferroelectric phase possess lower values of remanent and saturation magnetizations in comparison to composite sample containing pure BST as ferroelectric phase (BSTC). Rare earth substituted composite samples possess higher value of magnetoelectric coefficient as compared to that for BSTC

  19. Residual dipolar couplings in sup 3 sup 1 P MAS spectra of PPh sub 3 substituted cobalt complexes

    CERN Document Server

    Szalontai, G

    2002-01-01

    Residual dipolar couplings between sup 3 sup 1 P- sup 5 sup 9 Co spin pairs were studied in sup 3 sup 1 P MAS spectra of mono- and dinuclear cobalt-triphenylphosphine complexes. These spectra can provide important information such as the scalar coupling between the dipolar phosphorus and the quadrupolar cobalt nuclei normally not available from solution phase studies. In case of complementary (NQR or x-ray) data even the relative orientation of the interacting shielding, dipolar, scalar couplings, and electric field gradient tensors or internuclear distances can be determined. Examples are shown both for well resolved and practically unresolved cases, factors which possibly control the spectral resolution are discussed in detail. (author)

  20. Effects of the substitution of iron for cobalt on the crystal and magnetic properties of PrCo4-xFexM (M=Al and Ga)

    International Nuclear Information System (INIS)

    Zlotea, C.; Isnard, O.

    2003-01-01

    We report on the structural and magnetic properties of PrCo 4-x Fe x M where x=0-4 and M=Al and Ga. The iron solubility limit in these phases is determined by means of X-ray diffraction and scanning electron microscopy. Our study confirms that single phase samples crystallizing in the CaCu 5 -type structure are stabilized for x 5 structure but with a slight preference for the 3g site. The saturation magnetization and the Curie temperature increase upon the iron substitution. The PrCo 4-x Fe x M compounds present spin reorientation transitions, whatever the substituting M and the Fe content. The substitution of iron for cobalt induces a significant increase of the spin reorientation temperature. Neutron and X-ray powder diffraction experiments as well as magnetic measurements are combined in order to clarify the effects of the presence of iron on the magnetocrystalline anisotropy and the spin reorientation transition. Finally, the magnetic phase diagrams of PrCo 4-x Fe x M (M=Al and Ga) have been determined in the whole ordered temperature range

  1. Synthesis, structural investigation and magnetic properties of Zn2+ substituted cobalt ferrite nanoparticles prepared by the sol–gel auto-combustion technique

    International Nuclear Information System (INIS)

    Raut, A.V.; Barkule, R.S.; Shengule, D.R.; Jadhav, K.M.

    2014-01-01

    Structural morphology and magnetic properties of the Co 1−x Zn x Fe 2 O 4 (0.0≤x≥1.0) spinel ferrite system synthesized by the sol–gel auto-combustion technique using nitrates of respective metal ions have been studied. The ratio of metal nitrates to citric acid was taken at 1:3. The as prepared powder of cobalt zinc ferrite was sintered at 600 °C for 12 h after TG/DTA thermal studies. Compositional stoichiometry was confirmed by energy dispersive analysis of the X-ray (EDAX) technique. Single phase cubic spinel structure of Co–Zn nanoparticles was confirmed by XRD data. The average crystallite size (t), lattice constant (a) and other structural parameters of zinc substituted cobalt ferrite nanoparticles were calculated from XRD followed by SEM and FTIR. It is observed that the sol–gel auto-combustion technique has many advantages for the synthesis of technologically applicable Co–Zn ferrite nanoparticles. The present investigation clearly shows the effect of the synthesis method and possible relation between magnetic properties and microstructure of the prepared samples. Increase in nonmagnetic Zn 2+ content in cobalt ferrite nanoparticles is followed by decrease in n B , M s and other magnetic parameters. Squareness ratio for the Co-ferrite was 1.096 at room temperature. - Highlights: • Co–Zn nanoparticles are prepared by sol–gel auto-combustion method. • Structural properties were characterized by XRD, SEM, and FTIR. • Compositional stoichiometry was confirmed by EDAX analysis. • Magnetic parameters were measured by the pulse field hysteresis loop technique

  2. Synthesis, structural investigation and magnetic properties of Zn{sup 2+} substituted cobalt ferrite nanoparticles prepared by the sol–gel auto-combustion technique

    Energy Technology Data Exchange (ETDEWEB)

    Raut, A.V., E-mail: nano9993@gmail.com [Vivekanand Arts and Sardar Dalipsingh Commerce and Science College, Aurangabad, 431004 Maharastra (India); Barkule, R.S.; Shengule, D.R. [Vivekanand Arts and Sardar Dalipsingh Commerce and Science College, Aurangabad, 431004 Maharastra (India); Jadhav, K.M., E-mail: drjadhavkm@gmail.com [Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, 431004 Maharastra (India)

    2014-05-01

    Structural morphology and magnetic properties of the Co{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (0.0≤x≥1.0) spinel ferrite system synthesized by the sol–gel auto-combustion technique using nitrates of respective metal ions have been studied. The ratio of metal nitrates to citric acid was taken at 1:3. The as prepared powder of cobalt zinc ferrite was sintered at 600 °C for 12 h after TG/DTA thermal studies. Compositional stoichiometry was confirmed by energy dispersive analysis of the X-ray (EDAX) technique. Single phase cubic spinel structure of Co–Zn nanoparticles was confirmed by XRD data. The average crystallite size (t), lattice constant (a) and other structural parameters of zinc substituted cobalt ferrite nanoparticles were calculated from XRD followed by SEM and FTIR. It is observed that the sol–gel auto-combustion technique has many advantages for the synthesis of technologically applicable Co–Zn ferrite nanoparticles. The present investigation clearly shows the effect of the synthesis method and possible relation between magnetic properties and microstructure of the prepared samples. Increase in nonmagnetic Zn{sup 2+} content in cobalt ferrite nanoparticles is followed by decrease in n{sub B}, M{sub s} and other magnetic parameters. Squareness ratio for the Co-ferrite was 1.096 at room temperature. - Highlights: • Co–Zn nanoparticles are prepared by sol–gel auto-combustion method. • Structural properties were characterized by XRD, SEM, and FTIR. • Compositional stoichiometry was confirmed by EDAX analysis. • Magnetic parameters were measured by the pulse field hysteresis loop technique.

  3. Evolution of the mössbauer spectra of ludwigite Co3 - x Fe x O2BO3 with substitution of iron for cobalt

    Science.gov (United States)

    Knyazev, Yu. V.; Ivanova, N. B.; Bayukov, O. A.; Kazak, N. V.; Bezmaternykh, L. N.; Vasiliev, A. D.

    2013-06-01

    A concentration series of single crystals of iron-cobalt ludwigites Co3 - x Fe x O2BO3 ( x = 0.0125, 0.025, 0.050, 0.10, 1.0) has been synthesized. The structure has been studied using X-ray diffraction and Mössbauer effect. A preferred occupation of nonequivalent crystallographic positions by iron in the ludwigite structure has been revealed. It has been found that the valence of substituting iron ions is three. It has been revealed that the structure of the γ-resonance spectrum of Co2FeO2BO3 is complicated due to a composition disorder in the system.

  4. Surface chemistry and electrocatalytic behaviour of tetra-carboxy substituted iron, cobalt and manganese phthalocyanine monolayers on gold electrode

    International Nuclear Information System (INIS)

    Mashazi, Philani N.; Westbroek, Philippe; Ozoemena, Kenneth I.; Nyokong, Tebello

    2007-01-01

    Surface chemistry and electrocatalytic properties of self-assembled monolayers of metal tetra-carboxylic acid phthalocyanine complexes with cobalt (Co), iron (Fe) and manganese (Mn) as central metal ions have been studied. These phthalocyanine molecules are immobilized on gold electrode via the coupling reaction between the ring substituents and pre-formed mercaptoethanol self-assembled monolayer (Au-ME SAM). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed chemisorption of mercaptoethanol via sulfur group on gold electrode and also coupling reaction between phthalocyanines and Au-ME SAM. Electrochemical parameters of the immobilized molecules show that these molecules are densely packed with a perpendicular orientation. The potential applications of the gold modified electrodes were investigated towards L-cysteine detection and the analysis at phthalocyanine SAMs. Cobalt and iron tetra-carboxylic acid phthalocyanine monolayers showed good oxidation peak for L-cysteine at potentials where metal oxidation (M III /M II ) takes place and this metal oxidation mediates the catalytic oxidation of L-cysteine. Manganese tetra-carboxylic acid phthalocyanine monolayer also exhibited a good catalytic oxidation peak towards L-cysteine at potentials where Mn IV /Mn III redox peak occurs and this redox peak mediates L-cysteine oxidation. The analysis of cysteine at phthalocyanine monolayers displayed good analytical parameters with good detection limits of the orders of 10 -7 mol L -1 and good linearity for a studied concentration range up to 60 μmol L -1

  5. EPR-study of reversible oxygenation process of coordination compounds of cobalt(II) with S-substituted N/sup 1/,N/sup 4/-di(salicylidene)-isothiosemicarbazides

    Energy Technology Data Exchange (ETDEWEB)

    Gerbeleu, N.V.; Revenko, M.D.; Rusu, V.G.; Shames, A.T.

    1987-09-01

    The reaction between molecular oxygen and coordination compounds of cobalt(II) with S-substituted N/sup 1/,N/sup 4/-di(salicylidene)isothiosemicarbazides in dimethyl sulfoxide solution was studied by the EPR method. It was found that paramagnetic monomeric adducts and diamagnetic ..mu..-peroxo-dimers are formed. The spin-Hamiltonian parameters of the EPR spectra of the initial cobalt complexes, as well as of the paramagnetic adducts were determined. The nature of the Co-O/sub 2/ bond is discussed.

  6. Alkyl group dependence on structure and magnetic properties in layered cobalt coordination polymers containing substituted glutarate ligands and 4,4'-bipyridine

    International Nuclear Information System (INIS)

    Nettleman, Joseph H.; Supkowski, Ronald M.; LaDuca, Robert L.

    2010-01-01

    Five two-dimensional divalent cobalt coordination polymers containing 4,4'-bipyridine (bpy) and substituted or unsubstituted glutarate ligands have been prepared hydrothermally and structurally characterized by single-crystal X-ray diffraction. [Co(mg)(bpy)] n (1, mg=3-methylglutarate) forms a (4,4) rhomboid grid structure based on the connection of {Co 2 (CO 2 ) 2 } dimeric units. Using the more sterically encumbered ligands 3,3-dimethylglutarate (dmg) and 3-ethyl, 3-methylglutarate (emg) generated {[Co(dmg)(bpy)(H 2 O)].2H 2 O} n (2) and {[Co(emg)(bpy)(H 2 O)].H 2 O} n (3), respectively. These complexes manifest {Co(CO 2 )} n chains linked into 2-D by aliphatic dicarboxylate and bpy ligands. The 'tied-back' substituted glutarate ligand 1,1-cyclopentanediacetate (cda) afforded [Co(cda)(bpy)] n (4), and the unsubstituted glutarate (glu) generated [Co(glu)(bpy)] n (5), both of which exhibit a topology similar to that of 1. The magnetic properties of complexes 1-4 were analyzed successfully with a recently developed phenomenological chain model accounting for both magnetic coupling (J) and zero-field splitting effects (D), even though 1 and 4 contain isolated, discrete {Co 2 (CO 2 ) 2 } dimers. The D parameter in this series varied between 21.8(8) and 48.0(9) cm -1 . However weak antiferromagnetic coupling was observed in 1 (J=-2.43(4) cm -1 ) and 4 (J=-0.89(2) cm -1 ), while weak ferromagnetic coupling appears to be operative in both 2 (J=0.324(5) cm -1 ) and 3 (J=0.24(1) cm -1 ). - Five two-dimensional divalent cobalt coordination polymers containing 4,4'-bipyridine (bpy) and substituted or unsubstituted glutarate ligands have been prepared and structurally characterized by single-crystal X-ray diffraction. Three contain dimeric {Co 2 (CO 2 ) 2 } units, while two manifest {Co(CO 2 )} n chains, depending on the steric bulk of the substituent. The magnetic properties of the complexes were analyzed successfully with a recently developed phenomenological chain model

  7. Synthesis and characterization of nickel substituted cobalt ferrite nanoparticles by sol–gel auto-combustion method

    Energy Technology Data Exchange (ETDEWEB)

    Hankare, P.P., E-mail: p_hankarep@rediffmail.com [Solid State Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur, Maharashtra 416 004 (India); Sanadi, K.R., E-mail: sanadikishor@gmail.com [Solid State Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur, Maharashtra 416 004 (India); Garadkar, K.M. [Solid State Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur, Maharashtra 416 004 (India); Patil, D.R. [Material Research Laboratory, Department of Physics, R.L. College, Parola, Jalgaon, Maharashtra 425 111 (India); Mulla, I.S. [Emeritus Scientist-CSIR, Centre for Materials for Electronics and Technology (C-MET), Panchawati, Pune 411 008 (India)

    2013-03-15

    Highlights: ► Co{sub 1−x}Ni{sub x}Fe{sub 2}O{sub 4} Mixed Metal oxides. ► Sol–gel auto-combustion method. ► Cubic spinel symmetry. ► Nanocrystaline material. ► Semiconducting nature. -- Abstract: Nanocrystalline Co{sub 1−x}Ni{sub x}Fe{sub 2}O{sub 4} (where x = 0.0, 0.25, 0.50, 0.75, 1) were successfully synthesized by sol–gel method using citrate–nitrate precursors. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were effectively utilized to investigate the different structural parameters. XRD showed single cubic spinel phase for all the samples. The decrease in lattice parameter and increase in crystallite size of the ferrispinel was observed with increasing nickel content. The surface morphology and elemental composition were studied by Scanning electron microscope (SEM) and Energy Dispersive X-ray analysis (EDAX) respectively. The nanosize of the synthesized material had been identified by TEM investigation and which is lies in between 20–25 nm. The semiconducting nature of the samples was studied by variation of resistivity and thermal emf with temperature.

  8. Nanocrystalline solids

    International Nuclear Information System (INIS)

    Gleiter, H.

    1991-01-01

    Nanocrystalline solids are polycrystals, the crystal size of which is a few (typically 1 to 10) nanometres so that 50% or more of the solid consists of incoherent interfaces between crystals of different orientations. Solids consisting primarily of internal interfaces represent a separate class of atomic structures because the atomic arrangement formed in the core of an interface is known to be an arrangement of minimum energy in the potential field of the two adjacent crystal lattices with different crystallographic orientations on either side of the boundary core. These boundary conditions result in atomic structures in the interfacial cores which cannot be formed elsewhere (e.g. in glasses or perfect crystals). Nanocrystalline solids are of interest for the following four reasons: (1) Nanocrystalline solids exhibit an atomic structure which differs from that of the two known solid states: the crystalline (with long-range order) and the glassy (with short-range order). (2) The properties of nanocrystalline solids differ (in some cases by several orders of magnitude) from those of glasses and/or crystals with the same chemical composition, which suggests that they may be utilized technologically in the future. (3) Nanocrystalline solids seem to permit the alloying of conventionally immiscible components. (4) If small (1 to 10 nm diameter) solid droplets with a glassy structure are consolidated (instead of small crystals), a new type of glass, called nanoglass, is obtained. Such glasses seem to differ structurally from conventional glasses. (orig.)

  9. Am and Eu extraction from acidic media by synergistic mixtures of substituted bis-tetrazolyl pyridines with chlorinated cobalt dicarbollide

    International Nuclear Information System (INIS)

    Smirnov, I.V.; Chirkov, A.V.; Babain, V.A.; Pokrovskaya, E.Yu.; Artamonova, T.A.

    2009-01-01

    Americium (Am) and europium (Eu) extraction from HNO 3 and HClO 4 media by a synergistic mixture of 2.6-bis(1-aryl-1H-tetrazol-5-yl)pyridines (ATP) with chlorinated cobalt dicarbollide (CCD) was studied by using m-nitrobenzotrifluoride, phenyltrifluoromethyl sulfone, and 1,2-dichloroethane as diluents. We examined the effects of diluents, of the aqueous phase composition and the nature of substituents in the ATP aryl ring on Am/Eu extraction efficiency and selectivity. The Am/Eu separation factor was found to be close to 100 at the optimal ratio of ATPs: CCD ∝ 1:1. We also studied the extraction of 85 Sr, 137 Cs and 133 Ba; a PhATP-CCD mixture provided the separation of the Sr/Ba pair with a factor of 35. A high resistance of 2,6-bis-aryltetrazolyl pyridines to 6 M nitric and perchloric acids at 95 C was demonstrated. (orig.)

  10. Effects of disorder on the intrinsically hole-doped iron-based superconductor KC a2F e4A s4F2 by cobalt substitution

    Science.gov (United States)

    Ishida, Junichi; Iimura, Soshi; Hosono, Hideo

    2017-11-01

    In this paper, the effects of cobalt substitution on the transport and electronic properties of the recently discovered iron-based superconductor KC a2F e4A s4F2 , with Tc=33 K , are reported. This material is an unusual superconductor showing intrinsic hole conduction (0.25 holes /F e2 + ). Upon doping of Co, the Tc of KC a2(Fe1-xC ox) 4A s4F2 gradually decreased, and bulk superconductivity disappeared when x ≥0.25 . Conversion of the primary carrier from p type to n type upon Co-doping was clearly confirmed by Hall measurements, and our results are consistent with the change in the calculated Fermi surface. Nevertheless, neither spin density wave (SDW) nor an orthorhombic phase, which are commonly observed for nondoped iron-based superconductors, was observed in the nondoped or electron-doped samples. The electron count in the 3 d orbitals and structural parameters were compared with those of other iron-based superconductors to show that the physical properties can be primarily ascribed to the effects of disorder.

  11. Temperature and composition dependence of magnetic properties of cobalt-chromium co-substituted magnesium ferrite nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com [Surface and Solid State Chemistry Laboratory, Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Ahmad, Zahoor [Surface and Solid State Chemistry Laboratory, Department of Chemistry, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Meydan, Turgut; Melikhov, Yevgen [Wolfson Center for Magnetics, School of Engineering, Cardiff University, Cardiff CF24 3AA (United Kingdom)

    2012-11-15

    The temperature and composition dependence of magnetic properties of Co-Cr co-substituted magnesium ferrite, Mg{sub 1-x}Co{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} (x=0.0-0.5), prepared by novel polyethylene glycol assisted microemulsion method, are studied. The synthesized materials are characterized by the Moessbauer spectrometer and standard magnetic measurements. Major hysteresis loops are measured up to the magnetic field of 50 kOe at 300, 200 and 100 K. The high field regimes of these loops are modeled using the Law of Approach to saturation to determine the first-order cubic anisotropy coefficient and saturation magnetization. Both the saturation magnetization and the anisotropy coefficient are observed to increase with the decrease in temperature for all Co-Cr co-substitution levels. Also, both the saturation magnetization and the anisotropy coefficient achieved maximum value at x=0.3 and x=0.2, respectively. Explanation of the observed behavior is proposed in terms of the site occupancy of the co-substituent, Co{sup 2+} and Cr{sup 3+} in the cubic spinel lattice. - Highlights: Black-Right-Pointing-Pointer Mg{sub 1-x}Co{sub x}Cr{sub x}Fe{sub 2-x}O{sub 4} are synthesized by novel PEG assisted microemulsion method. Black-Right-Pointing-Pointer Co-Cr occupied octahedral site confirmed by the Moessbauer analysis. Black-Right-Pointing-Pointer High field regime of M-H loops are modeled using the Law of Approach to saturation. Black-Right-Pointing-Pointer The values of M{sub S}, M{sub r}, H{sub C} and K{sub 1} are found to increase with decreasing temperature.

  12. High precision measurement of the hyperfine fields of substitutional and defect associated Cd in single crystalline hcp cobalt

    CERN Document Server

    Correia, J G; Melo, A A; Soares, J C

    1996-01-01

    The hyperfine fields of Cd in single crystalline hcp Co were measured after simultaneous implantation of 111mCd and 111In. High statistics measurements could be done separately for each parent isotope combining the e--g and g-g PAC techniques. The hyperfine coupling constants wL(CdCo)=422.8(1) Mrad/s and w0(CdCo)=6.14(11) Mrad/s are determined for Cd probes in undisturbed substitutional sites. Several defect associated sites in the hcp Co lattice are clearly seen in the data. Most of the radiation damage created by the ion implantation anneals out at temperatures below 503 K, with only one dominating component surviving at this temperature. This defect is assigned as a probe atom in an interstitial site, surrounded by a vacancy tetrahedron. The corresponding magnetic field and electric field gradient are collinear with the c-axis of the Co lattice, and the respective coupling constants are wL(defect)= 216.7(2) Mrad/s and w0(defect)= 45.3(6) Mrad/s.

  13. Kinetic study of the substitution of pyridine by cyanide in the bis(pyridine)cobalt(III)hematoporphyrin-IX: distinguishing between Isub(d) and D mechanism

    International Nuclear Information System (INIS)

    Birush, M.; Pribanicj, M.

    1977-01-01

    ''Mass-law (rate) retardation'' effect shows that the reaction between the cyanide ion and bis(pyridine)cobalt(III)hematoporphyrin-IX complex to give (CN) 2 cobalt(III)hematoporphyrin-IX occurs by a purely dissociative (D but not Isub(d)) mechanism in chloroform. Limiting rate constant at the excess of cyanide ion concentration at 25 deg C was found to be 2.5x10 -3 S -1 and the competition ratio of pyridine (ksub(-) 1 ) and the cyanide ion (k 2 ) for a five coordinate intermediate (pyridin) cobalt(III)hematoporphyrin-IX complex was obtained as ksub(-) 1 /k 2 =0.35. (author)

  14. A study of magnetoplumbite-type (M-type) cobalt-titanium-substituted barium ferrite, BaCoxTixFe12-2xO19 (x = 1-6)

    International Nuclear Information System (INIS)

    Teh, G.B.; Saravanan, N.; Jefferson, D.A.

    2007-01-01

    Cobalt(II)-titanium(IV)-substituted barium ferrite forming the chemical formula of BaCo x Ti x Fe 12-2x O 19 (x = 1-6) have been investigated using X-ray diffraction spectroscopy (XRD), Superconducting Quantum Interference Device (SQUID) and high-resolution transmission electron microscopy (HRTEM). The specimen of magnetoplumbite (M-type) Co-Ti-substituted BaFe 12 O 19 were synthesised via sol-gel method using ethylene glycol as precursor. Significant increase in line broadening of the XRD patterns were observed indicating the decrease of particle sizes due to the Co(II)-Ti(IV) substitution. BaCo 3 Ti 3 Fe 6 O 19 showed the highest coercivity but moderate saturation and remnant magnetisations. HRTEM imaging showed that Co(II)-Ti(IV) substitution in the system of BaCo x Ti x Fe 12-2x O 19 (x = 1-6) produced no drastic change in the structure of the M-type ferrites. Most of the M-types crystals examined by HRTEM displayed a long axis perpendicular to the c-axis of the M-type structure. Disordered crystals showing the intergrowth between Co-Ti-substituted barium ferrite and the spinel-structured iron oxide were detected

  15. A study of magnetoplumbite-type (M-type) cobalt-titanium-substituted barium ferrite, BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 1-6)

    Energy Technology Data Exchange (ETDEWEB)

    Teh, G.B. [Department of Bioscience and Chemistry, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Kuala Lumpur (Malaysia)], E-mail: tehgb@mail.utar.edu.my; Saravanan, N. [Department of Bioscience and Chemistry, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Kuala Lumpur (Malaysia); Jefferson, D.A. [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

    2007-10-15

    Cobalt(II)-titanium(IV)-substituted barium ferrite forming the chemical formula of BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 1-6) have been investigated using X-ray diffraction spectroscopy (XRD), Superconducting Quantum Interference Device (SQUID) and high-resolution transmission electron microscopy (HRTEM). The specimen of magnetoplumbite (M-type) Co-Ti-substituted BaFe{sub 12}O{sub 19} were synthesised via sol-gel method using ethylene glycol as precursor. Significant increase in line broadening of the XRD patterns were observed indicating the decrease of particle sizes due to the Co(II)-Ti(IV) substitution. BaCo{sub 3}Ti{sub 3}Fe{sub 6}O{sub 19} showed the highest coercivity but moderate saturation and remnant magnetisations. HRTEM imaging showed that Co(II)-Ti(IV) substitution in the system of BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 1-6) produced no drastic change in the structure of the M-type ferrites. Most of the M-types crystals examined by HRTEM displayed a long axis perpendicular to the c-axis of the M-type structure. Disordered crystals showing the intergrowth between Co-Ti-substituted barium ferrite and the spinel-structured iron oxide were detected.

  16. Structural and magnetic properties of Co substituted Li{sub 0.5}Fe{sub 2.5}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Patil, R.P., E-mail: raj_rbm_raj@yahoo.co.in [Department of Chemistry, M.H. Shinde Mahavidyalaya, Tisangi 416206, MH (India); Patil, S.B. [Department of Physics, Krantisinh Nana Patil College Walwa, Sangli 416313, MH (India); Jadhav, B.V. [Department of Chemistry, Changu Kana Thakur Arts, Commerce and Science College, New Panvel 400035, MH (India); Delekar, S.D.; Hankare, P.P. [Department of Chemistry, Shivaji University, Kolhapur 416004, MH (India)

    2016-03-01

    Nanocrystalline Li{sub 0.5}Fe{sub 2.5−x}Co{sub x}O{sub 4} (2.5≥x≥0) system was prepared by sol–gel route. Formation of single phase cubic spinel structure for all the compositions was confirmed from their X-ray diffraction studies. These ferrite samples existed as homogenous and uniform grains as observed from Scanning Electron Microscopy technique. The magnetic studies indicated that, the ferrimagnetic behavior decreases with Cobalt substitution. In general, the substitution of cobalt plays an important role in changing the structural and magnetic properties of these ferrites. - Highlights: • Novel Co doped Li{sub 0.5}Fe{sub 2.5}O{sub 4} system. • Sol–gel method synthesized Co–Lithium ferrites. • Single Phase Cubic spinel structure. • Homogenous and uniform grain size of samples. • Ferrimagnetic behavior for all the samples.

  17. Nanocrystalline ceramic materials

    Science.gov (United States)

    Siegel, Richard W.; Nieman, G. William; Weertman, Julia R.

    1994-01-01

    A method for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material.

  18. Effect of amine substituted at ortho and para positions on the electrochemical and electrocatalytic properties of cobalt porphyrins self-assembled on glassy carbon surface

    International Nuclear Information System (INIS)

    Muthukumar, Palanisamy; John, S. Abraham

    2014-01-01

    Highlights: •The self-assembly of ortho and para isomers of Co(II)aminoporphyrin on GCE was studied. •The electrochemical and electrocatalytic properties were examined. •The Co(II)MTpAP showed two redox waves whereas Co(II)MToAP showed a single redox peak. •Both the SAMs greatly catalyzed the dioxigen reduction when compared to GCE. -- Abstract: This work addresses the influence of amine group substituted at para and ortho positions of the phenyl groups on the electrochemical and electrocatalytic properties of cobalt porphyrins self-assembled on glassy carbon electrode (GCE). We have synthesized meso-tetra(para-aminophenyl)porphyrinatocobalt(II) (Co(II)MTpAP) and meso-tetra(ortho-aminophenyl)porphyrinatocobalt(II) (Co(II)MToAP) and were self-assembled on GCE through Michael addition of nucleophilic amine with olefinic GCE surface. Cyclic voltammetry, reflectance spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques were employed to confirm the formation of the self-assembled monolayers (SAMs) of Co(II)MTpAP and Co(II)MToAP on GCEs. Interestingly, the SAM of Co(II)MTpAP in 0.1 M H 2 SO 4 shows two redox waves at 0.37 and 0.60 V whereas the SAM of Co(II)MToAP shows a single redox wave at 0.32 V, indicating the influence of amine group position in the phenyl ring on the redox chemistry of porphyrin. In contrary, the SAMs of the corresponding free base porphyrins prepared under identical conditions show a single redox wave around 0.36 V. Thus, we have assigned the redox wave at 0.37 V to Co(II)Por 1− /Co(II)Por 2− and 0.60 V to Co III/II redox couples for the SAM of Co(II)MTpAP. In the case of Co(II)MToAP, we have assigned the redox wave at 0.32 V due to both Co(II)Por 1− /Co(II)Por 2− and Co III/II . The surface coverage estimated from the charge consumed for the oxidation of Co III/II was used to study the thermodynamics and kinetics of Co(II)MTpAP and Co(II)MToAP self-assembled on GCE. Further, the electrochemical reduction of dioxygen

  19. Evidence of spin transition and charge order in cobalt substituted La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3

    CERN Document Server

    Srivastava, C M; Gundurao, T K; Nigam, A K; Bahadur, D

    2003-01-01

    The transport and magnetic studies of a series of compounds having the general formula La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 Mn sub 1 sub - sub x Co sub x O sub 3 (0.1 = 0.25 there is a clear spin transition at low temperature from the high to the low spin state of trivalent cobalt and this leads to change in ferromagnetic (FM) and antiferromagnetic (AFM) phases. For x >= 0.25 there are two transitions for each value of x: the upper one gives the FM and AFM spin arrangement depending upon whether the DE or the SE dominates; the lower one is obtained due to the transition from the high to the low spin state of the trivalent cobalt ion.

  20. Study the effect of Gd{sup 3+} incorporation into nanocrystalline (Ni–Ti) substituted Mn–Zn ferrites on its structure and functional properties

    Energy Technology Data Exchange (ETDEWEB)

    Rady, K.E., E-mail: k_rady_2001@yahoo.com [Engineering Basic Sciences Department, Faculty of Engineering, Menoufia University, Shebin El-El, Kom (Egypt); Shams, M.S. [Department of Physics and Engineering Mathematics, Faculty of Electronic Engineering, Menoufia University, Menouf (Egypt)

    2017-03-15

    Ferrite samples with general chemical formula Mn{sub 0.9}Zn{sub 0.1}Ni{sub 0.05}Ti{sub 0.05}Gd{sub t}Fe{sub 1.9−t}O{sub 4}; (0.0≤ t≤0.05; step 0.01) were prepared using solid state reaction technique and the effect of Gd{sup 3+} ions incorporation on its physical properties has been studied. From the obtained results, XRD analysis reveals that the samples have a cubic spinel single phase structure for 0.0≤ t≤0.02; while for t≥0.03 a small peak of secondary phase (Gd{sub 3}Fe{sub 5}O{sub 12}) appears and becomes more noticeable with increasing Gd content. The lattice parameter (a) of the prepared samples was found to be initially increases and then decreases with increasing Gd content which may be attributed to the difference in the ionic radii of the cations involved and the solubility limit of Gd{sup 3+} ions. The crystallite size of the samples was estimated using Scherrer's equation and ranged from 96 nm to 107 nm. A vibrating sample magnetometer (VSM) was used at room temperature in order to study the effect of Gd content on the magnetic hysteresis parameters of the prepared ferrites such as saturation magnetization and coercivity. DC molar magnetic susceptibility (χ{sub M}) for the prepared samples was measured using Faraday's method as a function of temperature and the Curie temperature was calculated from the magnetic susceptibility measurements. Also the DC resistivity of the samples was measured at room temperature. The obtained results show that, the substitution by Gd{sup 3+} ions improves the electrical properties of the samples by increasing it DC electrical resistivity by 118% and consequently decreases it eddy current loss while the saturation magnetization slightly decreased by 14% only. The sample of t=0.01 shows a high dc magnetic susceptibility, high saturation magnetization (43.1 emu/g), high electric resistivity 12×10{sup 3} Ω.m and high Curie temperature (496 K), which is useful in some technological applications such

  1. Fabrication, microstructure, and mechanical properties of high strength cobalt sub-micron structures

    International Nuclear Information System (INIS)

    Jin Sumin; Burek, Michael J.; Evans, Robert D.; Jahed, Zeinab; Leung, Michael C.; Evans, Neal D.; Tsui, Ting Y.

    2012-01-01

    The mechanical properties exhibited by sub-micron scale columnar structures of cobalt, fabricated by electron beam lithography and electroplating techniques, were investigated through uniaxial compression. Transmission electron microscopy analyses show these specimens possess a microstructure with sub-micron grains which are elongated and aligned near to the pillar loading axis. In addition, small nanocrystalline cobalt crystals are also present within the columnar structure. These specimens display exceptional mechanical strength comparable with both bulk polycrystalline and nanocrystalline cobalt deposited by electroplating. Size-dependent softening with shrinking sample dimensions is also observed in this work. Additionally, the strength of these sub-micron structures appears to be strain rate sensitive and comparable with bulk nanocrystalline cobalt specimens.

  2. Structural and magnetic properties of Ni0.8M0.2Fe2O4 (M = Cu, Co) nano-crystalline ferrites

    Science.gov (United States)

    Vijaya Babu, K.; Satyanarayana, G.; Sailaja, B.; Santosh Kumar, G. V.; Jalaiah, K.; Ravi, M.

    2018-06-01

    Nano-crystalline nickel ferrites are interesting materials due to their large physical and magnetic properties. In the present work, two kinds of spinel ferrites Ni0.8M0.2Fe2O4 (M = Cu, Co) are synthesized by using sol-gel auto-combustion method and the results are compared with NiFe2O4. The structural properties of synthesized ferrites are determined by using X-ray powder diffraction; scanning electron microscope and Fourier transform infrared spectroscopy. The cation distribution obtained from X-ray diffraction show that cobalt/copper occupies only tetrahedral site in spinel lattice. The lattice constant increases with the substitution of cobalt/copper. The structural parameters like bond lengths, tetrahedral and octahedral edges have been varied with the substitution. The microstructural study is carried out by using SEM technique and the average grain size is increased with nickel ferrite. The initial permeability (μi) is improving with the substitution. The observed g-value from ESR is approximately equal to standard value.

  3. Synthesis of zinc substituted cobalt ferrites via reverse micelle technique involving in situ template formation: A study on their structural, magnetic, optical and catalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Charanjit; Jauhar, Sheenu [Department of Chemistry, Panjab University, Chandigarh 160014 (India); Kumar, Vinod [ICON Analytical Equipment (P) Ltd., Mumbai 400018 (India); Singh, Jagdish [Institute Instrumentation Centre, Indian Institute of Technology–Roorkee (India); Singhal, Sonal, E-mail: sonal1174@gmail.com [Department of Chemistry, Panjab University, Chandigarh 160014 (India)

    2015-04-15

    Nano-crystalline particles of visible light responsive Zn–Co ferrites having formula Zn{sub x}Co{sub 1-x}Fe{sub 2}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were successfully synthesized via reverse micelle technique. Sodium dodecyl sulfate was used as a surfactant/templating agent. The ferrite formation was confirmed using powder X-Ray Diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy. The spherical shape of the ferrite particles was established by High Resolution Transmission Electron Microscope (HR-TEM) analysis. From the magnetic studies, the ferromagnetic nature of CoFe{sub 2}O{sub 4} was known. However, the nano-particles exhibited a transition from ferromagnetic to super-paramagnetic upon increasing the zinc concentration. In addition, the photo-Fenton activity of ferrites was also studied by carrying out degradation of Rhodamine B (RhB) dye under visible light irradiation. The catalytic activity increased with increase in zinc ion concentration. - Highlights: • Controlled dimensions of Zn–Co ferrite nanoparticles by microemulsion technique. • Spherical shape with uniform size distribution of ∼5 nm was achieved. • Significant shift from ferromagnetic to superparamagnetic with Zn{sup 2+} ion doping. • Improved photocatalytic activity with Zn{sup 2+} ion doping.

  4. Structural, morphological and dielectric studies of zirconium substituted CoFe2O4 nanoparticles

    Directory of Open Access Journals (Sweden)

    S. Anand

    2017-12-01

    Full Text Available In this work, the influence of zirconium substitution in cubic spinel nanocrystalline CoFe2O4 on the structural, morphological and dielectric properties are reported. Zirconium substituted cobalt ferrite Co1-xZrxFe2O4 (x = 0.7 nanoparticles were synthesized by sol-gel route. The structural and morphological investigations using powder X-ray diffraction and high resolution scanning electron microscope (HRSEM analysis are reported. Scherrer plot, Williamson–Hall analysis and Size-strain plot method were used to calculate the crystallite size and lattice strain of the samples. High purity chemical composition of the sample was confirmed by energy dispersive X-ray analysis. The atoms vibration modes of as synthesized nanoparticles were recorded using Fourier transform infrared (FTIR spectrometer in the range of 4000–400 cm-1. The temperature-dependent dielectric properties of zirconium substituted cobalt ferrite nanoparticles were also carried out. Relative dielectric permittivity, loss tangent and AC conductivity were measured in the frequency range 50 Hz to 5 MHz at temperatures between 323 K and 473 K. The dielectric constant and dielectric loss values of the sample decreased with increasing in the frequency of the applied signal.

  5. Effect of Tb and Al substitution within the rare earth and cobalt sublattices on magnetothermal properties of Dy{sub 0.5}Ho{sub 0.5}Co{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Chzhan, V.B., E-mail: lemuriform@gmail.com [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119334 (Russian Federation); National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Tereshina, E.A. [Institute of Physics CAS, Prague 18221 (Czech Republic); Mikhailova, A.B. [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119334 (Russian Federation); Politova, G.A. [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119334 (Russian Federation); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw 53-421 (Poland); Tereshina, I.S. [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119334 (Russian Federation); Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Kozlov, V.I. [Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Ćwik, J. [International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw 53-421 (Poland); Nenkov, K. [IFW Dresden, P.O. Box 270116, 01171 Dresden (Germany); Alekseeva, O.A.; Filimonov, A.V. [Peter the Great St. Petersburg Polytechnic University, St. Petersburg 195251 (Russian Federation)

    2017-06-15

    Highlights: • Single-phase (Tb,Dy,Ho)(Co,Al){sub 2} alloys synthesized using high-purity metals. • Temperature dependence of lattice parameters measured in a wide temperature range. • Tb and Al substitution increase the Curie temperature in Dy{sub 0.5}Ho{sub 0.5}Co{sub 2.} • The MCE measured by direct and indirect methods. • Materials with ‘table-like’ MCE are found. - Abstract: The effect of Tb and Al substitution within the rare earth and cobalt sublattices on structural and magnetothermal properties of Dy{sub 0.5}Ho{sub 0.5}Co{sub 2} has been studied. Multicomponent Laves phase alloys Tb{sub x}(Dy{sub 0.5}Ho{sub 0.5}){sub 1−x}Co{sub 2−y}Al{sub y} (x = 0, 0.3, 0.4, 0.5; y = 0, 0.25) synthesized using high-purity metals have been studied using X-ray diffraction analysis, heat capacity and magnetocaloric measurements. Dy{sub 0.5}Ho{sub 0.5}Co{sub 2} has a first order phase transition at the Curie temperature T{sub C} ≈ 110 K. Both Tb and Al substitution leads to increase of the T{sub C}. The increasing Tb content leads to the decreases slightly the MCE and all the transitions near the Curie temperature are of the first order. As for the Al-containing compounds, MCE measurements show that the phase transition type changes from the first to the second-order. The advantage of Tb{sub x}(Dy{sub 0.5}Ho{sub 0.5}){sub 1−x}Co{sub 1.75}Al{sub 0.25} as compared with Al-free alloys is ‘table-like’ behavior of MCE.

  6. Electromagnetic properties of nanocrystalline Al substituted ...

    Indian Academy of Sciences (India)

    The temperature variation of magnetic properties were measured in the temperature ... ties of these compounds are dependent on the distribution of cations between .... the higher binding energy and bond strength of Al–O com- pared to Fe–O ...

  7. Thermally Stable Nanocrystalline Steel

    Science.gov (United States)

    Hulme-Smith, Christopher Neil; Ooi, Shgh Woei; Bhadeshia, Harshad K. D. H.

    2017-10-01

    Two novel nanocrystalline steels were designed to withstand elevated temperatures without catastrophic microstructural changes. In the most successful alloy, a large quantity of nickel was added to stabilize austenite and allow a reduction in the carbon content. A 50 kg cast of the novel alloy was produced and used to verify the formation of nanocrystalline bainite. Synchrotron X-ray diffractometry using in situ heating showed that austenite was able to survive more than 1 hour at 773 K (500 °C) and subsequent cooling to ambient temperature. This is the first reported nanocrystalline steel with high-temperature capability.

  8. Cation distribution controlled dielectric, electrical and magnetic behavior of In{sup 3+} substituted cobalt ferrites synthesized via solid-state reaction technique

    Energy Technology Data Exchange (ETDEWEB)

    Pandit, Rabia, E-mail: rabiabest@gmail.com [Department of Physics, National Institute of Technology, Hamirpur, H.P 177 005 (India); Sharma, K.K., E-mail: kk.gautam@yahoo.co.in [Department of Physics, National Institute of Technology, Hamirpur, H.P 177 005 (India); Kaur, Pawanpreet [Department of Physics, National Institute of Technology, Hamirpur, H.P 177 005 (India); Kumar, Ravi [Centre for Material Science and Engineering, National Institute of Technology, Hamirpur, H.P 177 005 (India)

    2014-12-15

    We report the structural, cation distribution, dielectric, electrical and magnetic properties of CoFe{sub 2−x}In{sub x}O{sub 4} (0.0 ≤ x ≤ 0.6) ferrites. Rietveld fitted X-ray diffraction (XRD) patterns confirm the formation of single phase cubic spinel structure with Fd3m space group for all the samples. The comprehensive analysis of XRD based cation distribution has been performed to see the effect of In{sup 3+} ions substitution on various structural parameters such as site ionic radii, edge and bond lengths, interionic distances etc. The dielectric constant and tangent loss have been studied as a function of temperature and frequency. The dielectric data presented in electric modulus form reveals the presence of non-Debye relaxation behavior in considered ferrites. Both the AC and DC conductivities as a function of temperature are found to decrease with increasing In{sup 3+} content. The power law behavior of AC-conductivity indicates a strong correlation among electrons in these systems. The isothermal magnetization versus applied field curves with high field slope and significant coercivity suggest that studied materials are highly anisotropic with canted spin structures and exhibit ferrimagnetic behavior at 300 K. Magnetization gets enhanced up to 40% of In{sup 3+} substitution. The observed low dielectric losses and high resistivity can find their application in power transformers at high frequencies. - Highlights: • Rietveld refinement of CoIn{sub x}Fe{sub 2−x}O{sub 4} samples shows single phase cubic spinel structure. • Cation distribution matches well with experimental integrated intensity ratios. • Strength of magnetic interactions is found to increase with increasing In{sup 3+} substitution. • The present systems are highly correlated. • These material are promising candidate for power transformers at high frequencies.

  9. Cobalt Ferrite Nanocrystallites for Sustainable Hydrogen Production Application

    Directory of Open Access Journals (Sweden)

    Rajendra S. Gaikwad

    2011-01-01

    Full Text Available Cobalt ferrite, CoFe2O4, nanocrystalline films were deposited using electrostatic spray method and explored in sustainable hydrogen production application. Reflection planes in X-ray diffraction pattern confirm CoFe2O4 phase. The surface scanning microscopy photoimages reveal an agglomeration of closely-packed CoFe2O4 nanoflakes. Concentrated solar-panel, a two-step water splitting process, measurement technique was preferred for measuring the hydrogen generation rate. For about 5 hr sustainable, 440 mL/hr, hydrogen production activity was achieved, confirming the efficient use of cobalt ferrite nanocrystallites film in hydrogen production application.

  10. Dodecatungstocobaltate and Sn (IV)-Substituted Polyoxometalate ...

    African Journals Online (AJOL)

    NICO

    work metals, or substituting different cations for the protons to make their acidic or neutral ... corrosive materials in comparison with traditional Lewis acids. The importance of .... salt by treatment with potassium chloride. Finally, the cobalt (II).

  11. Nanocrystalline Aluminum Truss Cores for Lightweight Sandwich Structures

    Science.gov (United States)

    Schaedler, Tobias A.; Chan, Lisa J.; Clough, Eric C.; Stilke, Morgan A.; Hundley, Jacob M.; Masur, Lawrence J.

    2017-12-01

    Substitution of conventional honeycomb composite sandwich structures with lighter alternatives has the potential to reduce the mass of future vehicles. Here we demonstrate nanocrystalline aluminum-manganese truss cores that achieve 2-4 times higher strength than aluminum alloy 5056 honeycombs of the same density. The scalable fabrication approach starts with additive manufacturing of polymer templates, followed by electrodeposition of nanocrystalline Al-Mn alloy, removal of the polymer, and facesheet integration. This facilitates curved and net-shaped sandwich structures, as well as co-curing of the facesheets, which eliminates the need for extra adhesive. The nanocrystalline Al-Mn alloy thin-film material exhibits high strength and ductility and can be converted into a three-dimensional hollow truss structure with this approach. Ultra-lightweight sandwich structures are of interest for a range of applications in aerospace, such as fairings, wings, and flaps, as well as for the automotive and sports industries.

  12. Effect of Cr substitution on magnetic and magnetic entropy change of La{sub 0.65}Eu{sub 0.05}Sr{sub 0.3}Mn{sub 1−x}Cr{sub x}O{sub 3} (0.05≤x≤0.15) rhombohedral nanocrystalline near room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bellouz, R., E-mail: bellouzridha@yahoo.fr [Laboratoire de Physico-chimie des Matériaux, Département de Physique, Faculté des Sciences de Monastir,Université de Monastir, 5019 (Tunisia); Oumezzine, M. [Laboratoire de Physico-chimie des Matériaux, Département de Physique, Faculté des Sciences de Monastir,Université de Monastir, 5019 (Tunisia); Hlil, E.K. [Institut Néel, National Centre for Scientific Research, Université Joseph Fourier, B.P. 166, 38042 Grenoble (France); Dhahri, E. [Laboratoire de Physique appliqué, Département de physique, Faculté des Sciences de Sfax, 3018 (Tunisia)

    2015-02-01

    We have studied the effect of Cr substitution on magnetic and magnetocaloric properties in nanocrystalline La{sub 0.65}Eu{sub 0.05}Sr{sub 0.3}Mn{sub 1−x}Cr{sub x}O{sub 3} (x=0.05, 0.1 and 0.15). The materials were prepared using the Pechini sol–gel method. All the studied samples were crystallized into a single phase rhombohedral structure with R−3C space group. Magnetic measurements indicate that the ferromagnetic double exchange interaction is weakened with increasing Cr concentration, resulting in a shift in T{sub C} from 338 K to 278 K as x varied between 0.05 and 0.15. Detailed analyzes in the vicinity of the ferromagnetic (FM)–paramagnetic (PM) phase-transition temperature prove the samples undergoing a second-order phase transition. The magnetocaloric effect is calculated from the measurement of initial isothermal magnetization versus magnetic field at various temperatures. The maximum magnetic entropy change |ΔS{sub M}{sup max}| is found to decrease with increasing of Cr content from 4.04 J/Kg K for x=0.05–0.78 J/KgK for x=0.15 upon 5 T applied field change. The relative cooling power (RCP) of La{sub 0.65}Eu{sub 0.05}Sr{sub 0.3}Mn{sub 1−x}Cr{sub x}O{sub 3} series is nearly 54% of pure Gd, which will be an interesting system for application in room temperature refrigeration. - Highlights: • Nanocrystalline materials La{sub 0.65}Eu{sub 0.05}Sr{sub 0.3}Mn{sub 1−x}Cr{sub x}O{sub 3} were obtained. • The Cr substitution decreases the T{sub C} from 338 K for x=0.05–278 K for x=0.15. • The relative cooling power of La{sub 0.65}Eu{sub 0.05}Sr{sub 0.3}Mn{sub 1−x}Cr{sub x}O{sub 3} is nearly 54% of pure Gd. • Arrott plot analyses was applied to study the order of the magnetic transition. • La{sub 0.65}Eu{sub 0.05}Sr{sub 0.3}Mn{sub 1−x}Cr{sub x}O{sub 3} samples show second order PM–FM transition at T=T{sub C}.

  13. Cation substitution induced blue-shift of optical band gap

    Indian Academy of Sciences (India)

    Cation substitution induced blue-shift of optical band gap in nanocrystalline Zn ( 1 − x ) Ca x O thin films deposited by sol–gel dip coating technique ... thin films giving 13.03% enhancement in theenergy gap value due to the electronic perturbation caused by cation substitution as well as deterioration in crystallinity.

  14. Cobalt release from inexpensive jewellery

    DEFF Research Database (Denmark)

    Thyssen, Jacob Pontoppidan; Jellesen, Morten Stendahl; Menné, Torkil

    2010-01-01

    . Conclusions: This study showed that only a minority of inexpensive jewellery purchased in Denmark released cobalt when analysed with the cobalt spot test. As fashion trends fluctuate and we found cobalt release from dark appearing jewellery, cobalt release from consumer items should be monitored in the future......Objectives: The aim was to study 354 consumer items using the cobalt spot test. Cobalt release was assessed to obtain a risk estimate of cobalt allergy and dermatitis in consumers who would wear the jewellery. Methods: The cobalt spot test was used to assess cobalt release from all items...

  15. Synthesis of nanocrystalline fluorinated hydroxyapatite

    Indian Academy of Sciences (India)

    Fluorinated hydroxyapatite; nanocrystalline; microwave synthesis; dissolution. ... HA by the presence of other ions such as carbonate, magnesium, fluoride, etc. ... Fourier transform infrared spectroscopy (FT–IR) and laser Raman spectroscopy.

  16. Cobalt sensitization and dermatitis

    DEFF Research Database (Denmark)

    Thyssen, Jacob P

    2012-01-01

    : This clinical review article presents clinical and scientific data on cobalt sensitization and dermatitis. It is concluded that cobalt despite being a strong sensitizer and a prevalent contact allergen to come up on patch testing should be regarded as a very complex metal to test with. Exposure...

  17. Characterizing deformed ultrafine-grained and nanocrystalline materials using transmission Kikuchi diffraction in a scanning electron microscope

    International Nuclear Information System (INIS)

    Trimby, Patrick W.; Cao, Yang; Chen, Zibin; Han, Shuang; Hemker, Kevin J.; Lian, Jianshe; Liao, Xiaozhou; Rottmann, Paul; Samudrala, Saritha; Sun, Jingli; Wang, Jing Tao; Wheeler, John; Cairney, Julie M.

    2014-01-01

    Graphical abstract: -- Abstract: The recent development of transmission Kikuchi diffraction (TKD) in a scanning electron microscope enables fast, automated orientation mapping of electron transparent samples using standard electron backscatter diffraction (EBSD) hardware. TKD in a scanning electron microscope has significantly better spatial resolution than conventional EBSD, enabling routine characterization of nanocrystalline materials and allowing effective measurement of samples that have undergone severe plastic deformation. Combining TKD with energy dispersive X-ray spectroscopy (EDS) provides complementary chemical information, while a standard forescatter detector system below the EBSD detector can be used to generate dark field and oriented dark field images. Here we illustrate the application of this exciting new approach to a range of deformed, ultrafine grained and nanocrystalline samples, including duplex stainless steel, nanocrystalline copper and highly deformed titanium and nickel–cobalt. The results show that TKD combined with EDS is a highly effective and widely accessible tool for measuring key microstructural parameters at resolutions that are inaccessible using conventional EBSD

  18. Elicitation threshold of cobalt chloride

    DEFF Research Database (Denmark)

    Fischer, Louise A; Johansen, Jeanne D; Voelund, Aage

    2016-01-01

    : On the basis of five included studies, the ED10 values of aqueous cobalt chloride ranged between 0.0663 and 1.95 µg cobalt/cm(2), corresponding to 30.8-259 ppm. CONCLUSIONS: Our analysis provides an overview of the doses of cobalt that are required to elicit allergic cobalt contactdermatitis in sensitized...

  19. Structural and magnetic properties of the products of the transformation of ferrihydrite: Effect of cobalt dications

    Energy Technology Data Exchange (ETDEWEB)

    Camacho, K.I. [Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional Unidad Saltillo, Av. Industria Metalúrgica 1062, Parque Industrial Ramos Arizpe, Ramos Arizpe, Coahuila C.P.25000, México (Mexico); Pariona, N. [Red de Estudios Moleculares Avanzados, Instituto de Ecología A.C., Carretera Antigua a Coatepec 351, El Haya, 91070 Xalapa, Veracruz (Mexico); Martinez, A.I., E-mail: arturo.martinez@cinvestav.edu.mx [Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional Unidad Saltillo, Av. Industria Metalúrgica 1062, Parque Industrial Ramos Arizpe, Ramos Arizpe, Coahuila C.P.25000, México (Mexico); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Río de Janeiro 22290-180 (Brazil); Herrera-Trejo, M. [Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional Unidad Saltillo, Av. Industria Metalúrgica 1062, Parque Industrial Ramos Arizpe, Ramos Arizpe, Coahuila C.P.25000, México (Mexico); Perry, Dale L. [Mailstop 70A1150, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States)

    2017-05-01

    The effect of cobalt dications on the transformation of 2-line ferrihydrite (2LF) has been studied. The products of the transformation reaction were characterized by X-ray diffraction, Mössbauer spectroscopy (MS), transmission electron microscopy (TEM), magnetometry, and first-order reversal curve (FORC) diagrams. It was found that the concentration of cobalt dications plays an important role on the structural and magnetic properties of the products; i.e., for low cobalt concentrations, cobalt-substituted hematite is formed, while higher concentrations promote the formation of cobalt-substituted magnetite. Structural results revealed that formation of other iron oxide polymorphs is avoided and residual 2LF is always present in the final products. In this way, hematite/2LF and magnetite/2LF nanocomposites were formed. For all the samples, magnetic measurements yielded non-saturated hysteresis loops at a maximum field of 12 kOe. For cobalt-substituted hematite/2LF samples, FORC diagrams revealed the presence of multiple single-domain (SD) components which generate interaction coupling between SD with low and high coercivity. Moreover, for cobalt-substituted magnetite/2LF samples, the FORC diagrams revealed the components of wasp-waist hysteresis loops which consist of mixtures of SD and superparamagnetic particles. One of the goals of the present study is the rigorous, experimental documentation of ferrihydrite/hematite mixtures as a function of reaction conditions for use as analytical standards research. - Highlights: • Co(II) may stabilize ferrihydrite against transformation to more crystalline oxides. • The transformation is strongly dependent on the Co(II)/Fe(III) atomic ratio. • Cobalt-substituted hematite and cobalt-substituted magnetite were the products. • FORC diagrams identified the interaction coupling between single-domains.

  20. Structural and magnetic properties of the products of the transformation of ferrihydrite: Effect of cobalt dications

    International Nuclear Information System (INIS)

    Camacho, K.I.; Pariona, N.; Martinez, A.I.; Baggio-Saitovitch, E.; Herrera-Trejo, M.; Perry, Dale L.

    2017-01-01

    The effect of cobalt dications on the transformation of 2-line ferrihydrite (2LF) has been studied. The products of the transformation reaction were characterized by X-ray diffraction, Mössbauer spectroscopy (MS), transmission electron microscopy (TEM), magnetometry, and first-order reversal curve (FORC) diagrams. It was found that the concentration of cobalt dications plays an important role on the structural and magnetic properties of the products; i.e., for low cobalt concentrations, cobalt-substituted hematite is formed, while higher concentrations promote the formation of cobalt-substituted magnetite. Structural results revealed that formation of other iron oxide polymorphs is avoided and residual 2LF is always present in the final products. In this way, hematite/2LF and magnetite/2LF nanocomposites were formed. For all the samples, magnetic measurements yielded non-saturated hysteresis loops at a maximum field of 12 kOe. For cobalt-substituted hematite/2LF samples, FORC diagrams revealed the presence of multiple single-domain (SD) components which generate interaction coupling between SD with low and high coercivity. Moreover, for cobalt-substituted magnetite/2LF samples, the FORC diagrams revealed the components of wasp-waist hysteresis loops which consist of mixtures of SD and superparamagnetic particles. One of the goals of the present study is the rigorous, experimental documentation of ferrihydrite/hematite mixtures as a function of reaction conditions for use as analytical standards research. - Highlights: • Co(II) may stabilize ferrihydrite against transformation to more crystalline oxides. • The transformation is strongly dependent on the Co(II)/Fe(III) atomic ratio. • Cobalt-substituted hematite and cobalt-substituted magnetite were the products. • FORC diagrams identified the interaction coupling between single-domains.

  1. Nitrogen induced ferromagnetism in Cobalt doped BaTiO3

    Directory of Open Access Journals (Sweden)

    Chandrima Mitra

    2012-09-01

    Full Text Available The electronic structure and magnetism of Cobalt doped BaTiO3 (BaTi1−xCoxO3 is investigated. Substitutional Nitrogen on an Oxygen site is found to play an important role in inducing net magnetic moments in the system. The presence of a Nitrogen atom as nearest neighbour to a Cobalt atom is crucial in producing spin splitting of both the Nitrogen and Cobalt states thereby introducing a net local magnetic moment. The introduction of Nitrogen is further found to enhance ferromagnetic interactions between Cobalt atoms.

  2. Elevated temperature study of Nd-Fe-B--based magnets with cobalt and dysprosium additions

    International Nuclear Information System (INIS)

    Gauder, D.R.; Froning, M.H.; White, R.J.; Ray, A.E.

    1988-01-01

    This paper discusses the elevated temperature performance of Nd-Fe-B magnets containing 0--15 wt. % cobalt substitutions for iron and 0--10 wt. % dysprosium substitutions for neodymium. Test samples were prepared using conventional powder metallurgy techniques. Elevated temperature hysteresis loop and open-circuit measurements were performed on the samples to investigate irreversible losses and long term aging losses at 150 0 C. Magnets with high amounts of both cobalt and dysprosium exhibited lower losses of coercivity and magnetization. Dysprosium had more influence on the elevated temperature performance of the material than did cobalt

  3. Co+ -ion implantation induced doping of nanocrystalline CdS thin films: structural, optical, and vibrational properties

    International Nuclear Information System (INIS)

    Chandramohan, S.; Sarangi, S.N.; Majumder, S.; Som, T.; Kanjilal, A.; Sathyamoorthy, R.

    2009-01-01

    Full text: Transition metal (Mn, Fe, Co and Ni) doped CdS nanostructures and nanocrystalline thin films have attracted much attention due to their anticipated applications in magneto-optical, non-volatile memory and future spintronics devices. Introduction of impurities in substitutional positions is highly desirable for such applications. Ion implantation is known to provide many advantages over conventional methods for efficient doping and possibility of its seamless integration with device processing steps. It is not governed by equilibrium thermodynamics and offers the advantages of high spatial selectivity and to overcome the solubility limits. In this communication, we report on modifications of structural morphological, optical, and vibrational properties of 90 keV Co + -ion implanted CdS thin films grown by thermal evaporation. Co + -ion implantation was performed in the fluence range of 0.1-3.6x10 16 ions cm -2 These fluences correspond to Co concentration in the range of 0.34-10.8 at % at the peak position of profile. Implantation was done at an elevated temperature of 573 K in order to avoid amorphization and to enhance the solubility of Co ions in the CdS lattice. Films were characterized by glancing angle X-ray diffraction (GAXRD), atomic force microscopy (AFM), optical absorption, and micro-Raman spectroscopy. Implantation does not lead to any secondary phase formation either in the form of impurity or the metallic clusters. However, implantation improves the crystalline quality of the samples and leads to supersaturation of Co ions in the CdS lattice. Thus, nanocrystalline CdS thin films can be considered as a good radiation- resistant material, which can be employed for prolonged use in solar cells for space applications. The optical band gap is found to decrease systematically with increasing ion fluence from 2.39 to 2.28 eV. Implantation leads to agglomeration of grains and a systematic increase in the surface roughness. Both GAXRD and micro

  4. Nanocrystalline diamond films for biomedical applications

    DEFF Research Database (Denmark)

    Pennisi, Cristian Pablo; Alcaide, Maria

    2014-01-01

    Nanocrystalline diamond films, which comprise the so called nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD), represent a class of biomaterials possessing outstanding mechanical, tribological, and electrical properties, which include high surface smoothness, high corrosion...... performance of nanocrystalline diamond films is reviewed from an application-specific perspective, covering topics such as enhancement of cellular adhesion, anti-fouling coatings, non-thrombogenic surfaces, micropatterning of cells and proteins, and immobilization of biomolecules for bioassays. In order...

  5. Strength and structure of nanocrystalline titanium

    International Nuclear Information System (INIS)

    Noskova, N.I.; Pereturina, I.A.; Elkina, O.A.; Stolyarov, V.V.

    2004-01-01

    Investigation results on strength and plasticity of nanocrystalline titanium VT-1 are presented. Specific features of plastic deformation on tension of this material specimens in an electron microscope column are studied in situ. It is shown that nanocrystalline titanium strength and plasticity at room temperature are dependent on the structure and nanograin size. It is revealed that deformation processes in nanocrystalline titanium are characterized by activation of deformation rotational modes and microtwinning [ru

  6. Nanocrystalline diamond coatings for machining

    Energy Technology Data Exchange (ETDEWEB)

    Frank, M.; Breidt, D.; Cremer, R. [CemeCon AG, Wuerselen (Germany)

    2007-07-01

    This history of CVD diamond synthesis goes back to the fifties of the last century. However, the scientific and economical potential was only gradually recognized. In the eighties, intensive worldwide research on CVD diamond synthesis and applications was launched. Industrial products, especially diamond-coated cutting tools, were introduced to the market in the middle of the nineties. This article shows the latest developments in this area, which comprises nanocrystalline diamond coating structures. (orig.)

  7. Structure and thermal stability of nanocrystalline materials

    Indian Academy of Sciences (India)

    In addition, study of the thermal stability of nanocrystalline materials against significant grain growth is both scientific and technological interest. A sharp increase in grain size (to micron levels) during consolidation of nanocrystalline powders to obtain fully dense materials may consequently result in the loss of some unique ...

  8. cobalt (ii), nickel (ii)

    African Journals Online (AJOL)

    DR. AMINU

    Department of Chemistry Bayero University, P. M. B. 3011, Kano, Nigeria. E-mail: hnuhu2000@yahoo.com. ABSTRACT. The manganese (II), cobalt (II), nickel (II) and .... water and common organic solvents, but are readily soluble in acetone. The molar conductance measurement [Table 3] of the complex compounds in.

  9. Dynamic recovery in nanocrystalline Ni

    International Nuclear Information System (INIS)

    Sun, Z.; Van Petegem, S.; Cervellino, A.; Durst, K.; Blum, W.; Van Swygenhoven, H.

    2015-01-01

    The constant flow stress reached during uniaxial deformation of electrodeposited nanocrystalline Ni reflects a quasi-stationary balance between dislocation slip and grain boundary (GB) accommodation mechanisms. Stress reduction tests allow to suppress dislocation slip and bring recovery mechanisms into the foreground. When combined with in situ X-ray diffraction it can be shown that grain boundary recovery mechanisms play an important role in producing plastic strain while hardening the microstructure. This result has a significant consequence for the parameters of thermally activated glide of dislocations, such as athermal stress and activation volume, which are traditionally derived from stress/strain rate change tests

  10. Size effects of nano-spaced basal stacking faults on the strength and deformation mechanisms of nanocrystalline pure hcp metals

    Science.gov (United States)

    Wang, Wen; Jiang, Ping; Yuan, Fuping; Wu, Xiaolei

    2018-05-01

    The size effects of nano-spaced basal stacking faults (SFs) on the tensile strength and deformation mechanisms of nanocrystalline pure cobalt and magnesium have been investigated by a series of large-scale 2D columnar and 3D molecular dynamics simulations. Unlike the strengthening effect of basal SFs on Mg alloys, the nano-spaced basal SFs are observed to have no strengthening effect on the nanocrystalline pure cobalt and magnesium from MD simulations. These observations could be attributed to the following two reasons: (i) Lots of new basal SFs are formed before (for cobalt) or simultaneously with (for magnesium) the other deformation mechanisms (i.e. the formation of twins and the edge dislocations) during the tensile deformation; (ii) In hcp alloys, the segregation of alloy elements and impurities at typical interfaces, such as SFs, can stablilise them for enhancing the interactions with dislocation and thus elevating the strength. Without such segregation in pure hcp metals, the edge dislocations can cut through the basal SFs although the interactions between the dislocations and the pre-existing SFs/newly formed SFs are observed. The nano-spaced basal SFs are also found to have no restriction effect on the formation of deformation twins.

  11. Substitutional analysis

    CERN Document Server

    Rutherford, Daniel Edwin

    2013-01-01

    Classic monograph, suitable for advanced undergraduates and graduate students. Topics include calculus of permutations and tableaux, semi-normal representation, orthogonal and natural representations, group characters, and substitutional equations. 1968 edition.

  12. Analysis of radioactive cobalt

    International Nuclear Information System (INIS)

    1977-01-01

    This is a manual published by Science and Technology Agency, Japan, which prescribes on the analysis method for radioactive cobalt which is a typical indexing nuclide among the radioactive nuclides released from nuclear facilities. Since the released cobalt is mainly discharged to coastal region together with waste water, this manual is written for samples of sea water, sea bottom sediments and marine organisms. Radioactive cobalt includes the nuclides of 57 co, 58 Co, 60 Co, etc., the manual deals with them as a whole as 60 Co of long half life. Though 60 Co analysis has become feasible comparatively simply due to scintillation or semi-conductor spectrometry, trace 60 Co analysis is performed quantitatively by co-precipitation or collection into alumina and scintillation spectrometry. However, specific collecting operation and γ-γ coincidence measurement have been required so far. This manual employs 60 Co collection by means of ion-exchange method and measurement with low background GM counting system, to analyze quantitatively and rapidly low level 60 Co. It is primarily established as the standard analyzing method for the survey by local autonomous bodies. It is divided into 4 chapters including introduction sea water, marine organisms, and sea bottom sediments. List of required reagents is added in appendix. (Wakatsuki, Y.)

  13. Chemical synthesis of hexagonal indium nitride nanocrystallines at low temperature

    Science.gov (United States)

    Wang, Liangbiao; Shen, Qianli; Zhao, Dejian; Lu, Juanjuan; Liu, Weiqiao; Zhang, Junhao; Bao, Keyan; Zhou, Quanfa

    2017-08-01

    In this study, hexagonal indium nitride nanocystallines with high crystallinity have been prepared by the reaction of InCl3·4H2O, sulfur and NaNH2 in an autoclave at 160 °C. The crystal structures and morphologies of the obtained InN sample are characterized by X-ray diffraction and scanning electron microscope. As InCl3·4H2O is substituted by In(NO3)3·4.5H2O, InN nanocrystallines could also be obtained by using the similar method. The photoluminescence spectrum shows that the InN emits a broad peak positioned at 2.3 eV.

  14. Self-subunit swapping occurs in another gene type of cobalt nitrile hydratase.

    Directory of Open Access Journals (Sweden)

    Yi Liu

    Full Text Available Self-subunit swapping is one of the post-translational maturation of the cobalt-containing nitrile hydratase (Co-NHase family of enzymes. All of these NHases possess a gene organization of , which allows the activator protein to easily form a mediatory complex with the α-subunit of the NHase after translation. Here, we discovered that the incorporation of cobalt into another type of Co-NHase, with a gene organization of , was also dependent on self-subunit swapping. We successfully isolated a recombinant NHase activator protein (P14K of Pseudomonas putida NRRL-18668 by adding a Strep-tag N-terminal to the P14K gene. P14K was found to form a complex [α(StrepP14K(2] with the α-subunit of the NHase. The incorporation of cobalt into the NHase of P. putida was confirmed to be dependent on the α-subunit substitution between the cobalt-containing α(StrepP14K(2 and the cobalt-free NHase. Cobalt was inserted into cobalt-free α(StrepP14K(2 but not into cobalt-free NHase, suggesting that P14K functions not only as a self-subunit swapping chaperone but also as a metallochaperone. In addition, NHase from P. putida was also expressed by a mutant gene that was designed with a order. Our findings expand the general features of self-subunit swapping maturation.

  15. Bilirubin adsorption on nanocrystalline titania films

    International Nuclear Information System (INIS)

    Yang Zhengpeng; Si Shihui; Fung Yingsing

    2007-01-01

    Bilirubin produced from hemoglobin metabolism and normally conjugated with albumin is a kind of lipophilic endotoxin, and can cause various diseases when its concentration is high. Bilirubin adsorption on the nanocrystalline TiO 2 films was investigated using quartz crystal microbalance, UV-vis and IR techniques, and factors affecting its adsorption such as pH, bilirubin concentration, solution ionic strength, temperature and thickness of TiO 2 films were discussed. The amount of adsorption and parameters for the adsorption kinetics were estimated from the frequency measurements of quartz crystal microbalance. A fresh surface of the nanocrystalline TiO 2 films could be photochemically regenerated because holes and hydroxyl radicals were generated by irradiating the nanocrystalline TiO 2 films with UV light, which could oxidize and decompose organic materials, and the nanocrystalline TiO 2 films can be easily regenerated when it is used as adsorbent for the removal of bilirubin

  16. Blood doping by cobalt. Should we measure cobalt in athletes?

    Directory of Open Access Journals (Sweden)

    Guidi Gian

    2006-07-01

    Full Text Available Abstract Background Blood doping is commonplace in competitive athletes who seek to enhance their aerobic performances through illicit techniques. Presentation of the hypothesis Cobalt, a naturally-occurring element with properties similar to those of iron and nickel, induces a marked and stable polycythemic response through a more efficient transcription of the erythropoietin gene. Testing the hypothesis Although little information is available so far on cobalt metabolism, reference value ranges or supplementation in athletes, there is emerging evidence that cobalt is used as a supplement and increased serum concentrations are occasionally observed in athletes. Therefore, given the athlete's connatural inclination to experiment with innovative, unfair and potentially unhealthy doping techniques, cobalt administration might soon become the most suited complement or surrogate for erythropoiesis-stimulating substances. Nevertheless, cobalt administration is not free from unsafe consequences, which involve toxic effects on heart, liver, kidney, thyroid and cancer promotion. Implications of the hypothesis Cobalt is easily purchasable, inexpensive and not currently comprehended within the World Anti-Doping Agency prohibited list. Moreover, available techniques for measuring whole blood, serum, plasma or urinary cobalt involve analytic approaches which are currently not practical for antidoping laboratories. Thus more research on cobalt metabolism in athletes is compelling, along with implementation of effective strategies to unmask this potentially deleterious doping practice

  17. Nickel, cobalt, and their alloys

    CERN Document Server

    2000-01-01

    This book is a comprehensive guide to the compositions, properties, processing, performance, and applications of nickel, cobalt, and their alloys. It includes all of the essential information contained in the ASM Handbook series, as well as new or updated coverage in many areas in the nickel, cobalt, and related industries.

  18. Cobalt source calibration

    International Nuclear Information System (INIS)

    Rizvi, H.M.

    1999-01-01

    The data obtained from these tests determine the dose rate of the two cobalt sources in SRTC. Building 774-A houses one of these sources while the other resides in room C-067 of Building 773-A. The data from this experiment shows the following: (1) The dose rate of the No.2 cobalt source in Building 774-A measured 1.073 x 10 5 rad/h (June 17, 1999). The dose rate of the Shepherd Model 109 Gamma cobalt source in Building 773-A measured 9.27 x 10 5 rad/h (June 25, 1999). These rates come from placing the graduated cylinder containing the dosimeter solution in the center of the irradiation chamber. (2) Two calibration tests in the 774-A source placed the graduated cylinder with the dosimeter solution approximately 1.5 inches off center in the axial direction. This movement of the sample reduced the measured dose rate 0.92% from 1.083 x 10 5 rad/h to 1.073 x 10 5 rad/h. and (3) A similar test in the cobalt source in 773-A placed the graduated cylinder approximately 2.0 inches off center in the axial direction. This change in position reduced the measured dose rate by 10.34% from 1.036 x 10 6 to 9.27 x 10 5 . This testing used chemical dosimetry to measure the dose rate of a radioactive source. In this method, one determines the dose by the chemical change that takes place in the dosimeter. For this calibration experiment, the author used a Fricke (ferrous ammonium sulfate) dosimeter. This solution works well for dose rates to 10 7 rad/h. During irradiation of the Fricke dosimeter solution the Fe 2+ ions ionize to Fe 3+ . When this occurs, the solution acquires a slightly darker tint (not visible to the human eye). To determine the magnitude of the change in Fe ions, one places the solution in an UV-VIS Spectrophotometer. The UV-VIS Spectrophotometer measures the absorbency of the solution. Dividing the absorbency by the total time (in minutes) of exposure yields the dose rate

  19. Unithiol - a cobalt antidote

    International Nuclear Information System (INIS)

    Cherkes, A.I.; Braver-Chernobul'skaya, B.S.

    1977-06-01

    The blockade of the sulfhydryl groups of the proteins leads to a disturbance of the normal activity of many enzymes and thus of the functioning of the organs and tissue. The search for antidotes against these substances which inactivate the enzymes led to the synthesis of a large group of thiols in the Ukrainian Scientific Research Sanitary Chemical Institute. The most active is sodium dithiol-2,3-dimercaptonpropansulphonate CH 2 SH-CHSH-CH 2 SO 3 Na x H 2 O, named unithiol. Its antidote activity is discussed in detail, especially concerning cobalt intoxication. (HK) [de

  20. Operator substitution

    NARCIS (Netherlands)

    Hautus, M.L.J.

    1994-01-01

    Substitution of an operator into an operator-valued map is defined and studied. A Bezout-type remainder theorem is used to derive a number of results. The tensor map is used to formulate solvability conditions for linear matrix equations. Some applications to system theory are given, in particular

  1. Solvent substitution

    International Nuclear Information System (INIS)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general ''Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated

  2. Tonemic Substitution

    African Journals Online (AJOL)

    Ezenwafor

    grammatical constructions. The choice of substitutable tonemes as observed from the analyzed data is highly. Ezenwafordependent on the intuitive judgement of the native speaker. This work shows with adequate data, that regular tonemic changes are not always meaningful in Ekwulobia lect. Such tonemic alternations are ...

  3. Solvent substitution

    Energy Technology Data Exchange (ETDEWEB)

    1990-01-01

    The DOE Environmental Restoration and Waste Management Office of Technology Development and the Air Force Engineering and Services Center convened the First Annual International Workshop on Solvent Substitution on December 4--7, 1990. The primary objectives of this joint effort were to share information and ideas among attendees in order to enhance the development and implementation of required new technologies for the elimination of pollutants associated with industrial use of hazardous and toxic solvents; and to aid in accelerating collaborative efforts and technology transfer between government and industry for solvent substitution. There were workshop sessions focusing on Alternative Technologies, Alternative Solvents, Recovery/Recycling, Low VOC Materials and Treatment for Environmentally Safe Disposal. The 35 invited papers presented covered a wide range of solvent substitution activities including: hardware and weapons production and maintenance, paint stripping, coating applications, printed circuit boards, metal cleaning, metal finishing, manufacturing, compliance monitoring and process control monitoring. This publication includes the majority of these presentations. In addition, in order to further facilitate information exchange and technology transfer, the US Air Force and DOE solicited additional papers under a general Call for Papers.'' These papers, which underwent review and final selection by a peer review committee, are also included in this combined Proceedings/Compendium. For those involved in handling, using or managing hazardous and toxic solvents, this document should prove to be a valuable resource, providing the most up-to-date information on current technologies and practices in solvent substitution. Individual papers are abstracted separated.

  4. Impurity diffusion of cobalt in plutonium

    International Nuclear Information System (INIS)

    Charissoux, Christian; Calais, Daniel.

    1975-01-01

    The sectioning method for investigation of the impurity diffusion of 60 Co in the fcc and bcc phases of plutonium gives the following results: 344-426 deg C: D=1.2x10 -2 exp(-12700/RT)cm 2 /s in delta Pu(fcc); 484-621 deg C: D=1.4x10 -3 exp(-9900/RT)cm 2 /s in epsilon Pu(bcc). Cobalt is a fast diffuser in plutonium; the diffusion coefficient being unaffected by phase changes delta'→delta; delta'→epsilon, the diffusion mechanism is probably dissociative in both phases, the solute becoming interstitial by: solute (substitution) reversible solute (interstitial) + vacancy [fr

  5. Cu and Al co-substituted cobalt ferrite: structural analysis ...

    Indian Academy of Sciences (India)

    ... 400 cm−1 (v2). They are attributed to the tetrahedral and octahedral group complexes of the spinel .... Intensity (a.u.). 2 (degree) ... Heating iron-hydroxides in air is known to yield haematite ... M–O distance in tetrahedral and octahedral sites.

  6. Structural elucidation of nanocrystalline biomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Maltsev, S.

    2008-10-23

    Bone diseases, such as osteoporosis and osteoarthritis, are the second most prevalent health problem worldwide. In Germany approximately 5 millions people are affected by arthritis. Investigating biomineralization processes and bone molecular structure is of key importance for developing new drugs for preventing and healing bone diseases. Nuclear magnetic resonance (NMR) was the primary technique used due to its advantages in characterising poorly ordered and disordered materials. Compared to all the diffraction techniques that widely applied in structural investigations, the usefulness of NMR is independent of long range molecular order. This makes NMR an outstanding technique for studies of complex/amorphous materials. Conventional NMR experiments (single pulse, spin-echo, cross polarization (CP), etc.) as well as their modifications and high-end techniques (2D HETCOR, REDOR, etc.) were used in this work. Combining the contributions from different techniques enhances the information content of the investigations and can increase the precision of the overall conclusions. Also XRD, TEM and FTIR were applied to different extent in order to get a general idea of nanocrystalline hydroxyapatite crystallite structure. Results: - A new approach named 'Solid-state NMR spectroscopy using the lost I spin magnetization in polarization transfer experiments' has been developed for measuring the transferred I spin magnetization from abundant nuclei, which is normally lost when detecting the S spin magnetization. - A detailed investigation of nanocrystalline hydroxyapatite core was made to prove that proton environment of the phosphates units and phosphorus environment of hydroxyl units are the same as in highly crystalline hydroxyapatite sample. - Using XRD it was found that the surface of the hydroxyapatite nanocrystals is not completely disordered, as it was suggested before, but resembles the hydroxyapatite structure with HPO{sub 4}{sup 2-} (and some CO{sub 3}{sup

  7. Structural elucidation of nanocrystalline biomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Maltsev, S

    2008-10-23

    Bone diseases, such as osteoporosis and osteoarthritis, are the second most prevalent health problem worldwide. In Germany approximately 5 millions people are affected by arthritis. Investigating biomineralization processes and bone molecular structure is of key importance for developing new drugs for preventing and healing bone diseases. Nuclear magnetic resonance (NMR) was the primary technique used due to its advantages in characterising poorly ordered and disordered materials. Compared to all the diffraction techniques that widely applied in structural investigations, the usefulness of NMR is independent of long range molecular order. This makes NMR an outstanding technique for studies of complex/amorphous materials. Conventional NMR experiments (single pulse, spin-echo, cross polarization (CP), etc.) as well as their modifications and high-end techniques (2D HETCOR, REDOR, etc.) were used in this work. Combining the contributions from different techniques enhances the information content of the investigations and can increase the precision of the overall conclusions. Also XRD, TEM and FTIR were applied to different extent in order to get a general idea of nanocrystalline hydroxyapatite crystallite structure. Results: - A new approach named 'Solid-state NMR spectroscopy using the lost I spin magnetization in polarization transfer experiments' has been developed for measuring the transferred I spin magnetization from abundant nuclei, which is normally lost when detecting the S spin magnetization. - A detailed investigation of nanocrystalline hydroxyapatite core was made to prove that proton environment of the phosphates units and phosphorus environment of hydroxyl units are the same as in highly crystalline hydroxyapatite sample. - Using XRD it was found that the surface of the hydroxyapatite nanocrystals is not completely disordered, as it was suggested before, but resembles the hydroxyapatite structure with HPO{sub 4}{sup 2-} (and some CO{sub 3}{sup 2

  8. One-pot, three-component synthesis of highly substituted pyridines ...

    Indian Academy of Sciences (India)

    Administrator

    trile in the presence of nanocrystalline magnesium oxide provides the highly substituted pyridine derivatives in moderate to ..... NAP–MgO (0⋅1 g), ethanol (5 mL) at reflux temperature b ... difference in the electronic and steric properties of.

  9. Radio cobalt in French rivers

    International Nuclear Information System (INIS)

    Lambrechts, A.; Baudin-Jaulent, Y.

    1996-01-01

    The isotopes 58 and 60 of cobalt present in liquid wastes from nuclear plants or from fuel reprocessing plant of Marcoule are fixed in the different compartments of French rivers. The activity levels of radio-cobalt vary according to the sampled compartments nature (bryophyta > immersed plants > sediment > fish). Elsewhere, laboratory experimentations show that the contamination of fish occurs essentially from the water way rather than from food. Cobalt is mainly fixed by kidneys; muscles is no more than 30 % of the total fish activity. (author)

  10. THE COORDINATION COMPOUNDS OF COBALT (II, III) WITH DITHIOCARBAMIC ACID DERIVATIVES — MODIFICATORS OF HYDROLYTIC ENZYMES ACTIVITY

    OpenAIRE

    L. D. Varbanets; О. V. Matselyukh; N. А. Nidyalkova; Е. V. Аvdiyuk; А. V. Gudzenko; I. I. Seifullina; G. N. Маsаnоvets; N. V. Khitrich

    2013-01-01

    Chloride, bromide and isothiocyanate complexes of cobalt(II) with N-substituted thiocarbamoyl-N?-pentamethylenesulfenamides (1)–(12), and also complexes of cobalt(II, Ш) with derivatives of morpholine-4-carbodithioic acid (13)–(18) have been used as modificators of enzymes of hydrolytic action — Bacillus thurin-giensis ІМВ В-7324 peptidases, Bacillus subtilis 147 and Aspergillus flavus var. oryzae 80428 amylases, Eupenicillium erubescens 248 and Cryptococcus albidus 1001 rhamnosidases. It was...

  11. Evaluation of structural, morphological and magnetic properties of CuZnNi (Cu_xZn_0_._5_−_xNi_0_._5Fe_2O_4) nanocrystalline ferrites for core, switching and MLCI’s applications

    International Nuclear Information System (INIS)

    Akhtar, Majid Niaz; Khan, Muhammad Azhar; Ahmad, Mukhtar; Nazir, M.S.; Imran, M.; Ali, A.; Sattar, A.; Murtaza, G.

    2017-01-01

    The influence of Cu substitution on the structural and morphological characteristics of Ni–Zn nanocrystalline ferrites have been discussed in this work. The detailed and systematic magnetic characterizations were also done for Cu substituted Ni–Zn nanoferrites. The nanocrystalline ferrites of Cu substituted Cu_xZn_0_._5_−_xNi_0_._5Fe_2O_4 ferrites (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized using sol gel self-combustion hybrid method. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM) were used to investigate the properties of Cu substituted nanocrystalline ferrites. Single phase structure of Cu substituted in Ni–Zn nanocrystalline ferrites were investigated for all the samples. Crystallite size, lattice constant and volume of the cell were found to increase by increasing Cu contents in spinel structure. The better morphology with well-organized nanocrystals of Cu–Zn–Ni ferrites at x=0 and 0.5 were observed from both FESEM and TEM analysis. The average grain size was 35–46 nm for all prepared nanocrystalline samples. Magnetic properties such as coercivity, saturation, remanence, magnetic squareness, magneto crystalline anisotropy constant (K) and Bohr magneton were measured from the recorded M–H loops. The magnetic saturation and remanence were increased by the incorporation of Cu contents. However, coercivity follow the Stoner-Wolforth model except for x=0.3 which may be due to the site occupancy and replacement of Cu contents from octahedral site. The squareness ratio confirmed the super paramgnetic behaviour of the Cu substituted in Ni–Zn nanocrystalline ferrites. Furthermore, Cu substituted Ni–Zn nanocrystalline ferrites may be suitable for many industrial and domestic applications such as components of transformers, core, switching, and MLCI’s due to variety of the soft magnetic characteristics. - Highlights: • Cu substituted

  12. Cobalt: for strength and color

    Science.gov (United States)

    Boland, Maeve A.; Kropschot, S.J.

    2011-01-01

    Cobalt is a shiny, gray, brittle metal that is best known for creating an intense blue color in glass and paints. It is frequently used in the manufacture of rechargeable batteries and to create alloys that maintain their strength at high temperatures. It is also one of the essential trace elements (or "micronutrients") that humans and many other living creatures require for good health. Cobalt is an important component in many aerospace, defense, and medical applications and is a key element in many clean energy technologies. The name cobalt comes from the German word kobold, meaning goblin. It was given this name by medieval miners who believed that troublesome goblins replaced the valuable metals in their ore with a substance that emitted poisonous fumes when smelted. The Swedish chemist Georg Brandt isolated metallic cobalt-the first new metal to be discovered since ancient times-in about 1735 and identified some of its valuable properties.

  13. Cobalt release from implants and consumer items and characteristics of cobalt sensitized patients with dermatitis

    DEFF Research Database (Denmark)

    Thyssen, Jacob Pontoppidan; Menne, Torkil; Liden, Carola

    2012-01-01

    -containing dental alloys and revised hip implant components.Results. Six of eight dental alloys and 10 of 98 revised hip implant components released cobalt in the cobalt spot test, whereas none of 50 mobile phones gave positive reactions. The clinical relevance of positive cobalt test reactions was difficult......-tested dermatitis patients in an attempt to better understand cobalt allergy.Materials and methods. 19 780 dermatitis patients aged 4-99 years were patch tested with nickel, chromium or cobalt between 1985 and 2010. The cobalt spot test was used to test for cobalt ion release from mobile phones as well as cobalt...

  14. Nanocrystalline permanent magnets with enhanced properties

    International Nuclear Information System (INIS)

    Leonowicz, M.

    2002-01-01

    Parameters of permanent magnets result from the combination of intrinsic properties such as saturation magnetization, magnetic exchange, and magnetocrystalline energy, as well as microstructural parameters such as phase structure, grain size, and orientation. Reduction of grain size into nanocrystalline regime (∼ 50 nm) leads to the enhanced remanence which derives from ferromagnetic exchange coupling between highly refined grains. In this study the fundamental phenomena, quantities, and structure parameters, which define nanophase permanent magnets are presented and discussed. The theoretical considerations are confronted with experimental data for nanocrystalline Sm-Fe-N type permanent magnets. (author)

  15. Direct Coating of Nanocrystalline Diamond on Steel

    Science.gov (United States)

    Tsugawa, Kazuo; Kawaki, Shyunsuke; Ishihara, Masatou; Hasegawa, Masataka

    2012-09-01

    Nanocrystalline diamond films have been successfully deposited on stainless steel substrates without any substrate pretreatments to promote diamond nucleation, including the formation of interlayers. A low-temperature growth technique, 400 °C or lower, in microwave plasma chemical vapor deposition using a surface-wave plasma has cleared up problems in diamond growth on ferrous materials, such as the surface graphitization, long incubation time, substrate softening, and poor adhesion. The deposited nanocrystalline diamond films on stainless steel exhibit good adhesion and tribological properties, such as a high wear resistance, a low friction coefficient, and a low aggression strength, at room temperature in air without lubrication.

  16. Electroplated zinc-cobalt alloy

    International Nuclear Information System (INIS)

    Carpenter, D.E.O.S.; Farr, J.P.G.

    2005-01-01

    Recent work on the deposition and use of ectrodeposited zinc-cobalt alloys is surveyed. Alloys containing lower of Nuclear quantities of cobalt are potentially more useful. The structures of the deposits is related to their chemical and mechanical properties. The inclusion of oxide and its role in the deposition mechanism may be significant. Chemical and engineering properties relate to the metallurgical structure of the alloys, which derives from the mechanism of deposition. The inclusion of oxides and hydroxides in the electroplate may provide evidence for this mechanism. Electrochemical impedance measurements have been made at significant deposition potentials, in alkaline electrolytes. These reveal a complex electrode behaviour which depends not only on the electrode potential but on the Co content of the electrolyte. For the relevant range of cathodic potential zinc-cobalt alloy electrodeposition occurs through a stratified interface. The formation of an absorbed layer ZnOH/sup +/ is the initial step, this inhibits the deposition of cobalt at low cathodic potentials, so explaining its 'anomalous deposition'. A porous layer of zinc forms on the adsorbed ZnOH/sup +/ at underpotential. As the potential becomes more cathodic, cobalt co- deposits from its electrolytic complex forming a metallic solid solution of Co in Zn. In electrolytes containing a high concentration of cobalt a mixed entity (ZnCo)/sub +/ is assumed to adsorb at the cathode from which a CoZn intermetallic deposits. (author)

  17. Formation and structure of nanocrystalline Al-Mn-Ni-Cu alloys

    International Nuclear Information System (INIS)

    Latuch, J.; Krasnowski, M.; Ciesielska, B.

    2002-01-01

    This paper reports the results of the short investigation on the effect of Cu additions upon the nanocrystallization behaviour of an Al-Mn-Ni alloy. 2 at.% Cu added to the base alloy of Al 85 Mn 10 Ni 5 alloy by substitution for Mn(mischmetal). The control of cooling rate did not cause the formation of nanocrystals of fcc-Al phase. The nanocrystalline structure fcc-Al + amorphous phase in quarternary alloy was obtained by isothermal annealing and continuous heating method, but the last technique is more effective. The volume fraction, lattice parameter, and size of Al-phase were calculated. (author)

  18. Fe(Co)SiBPCCu nanocrystalline alloys with high Bs above 1.83 T

    Science.gov (United States)

    Liu, Tao; Kong, Fengyu; Xie, Lei; Wang, Anding; Chang, Chuntao; Wang, Xinmin; Liu, Chain-Tsuan

    2017-11-01

    Fe84.75-xCoxSi2B9P3C0.5Cu0.75 (x = 0, 2.5 and 10) nanocrystalline alloys with excellent magnetic properties were successfully developed. The fully amorphous alloy ribbons exhibit wide temperature interval of 145-156 °C between the two crystallization events. It is found that the excessive substitution of Co for Fe greatly deteriorates the magnetic properties due to the non-uniform microstructure with coarse grains. The alloys with x = 0 and 2.5 exhibit high saturation magnetization (above 1.83 T), low core loss and relatively low coercivity (below 5.4 A/m) after annealing. In addition, the Fe84.75Si2B9P3C0.5Cu0.75 nanocrystalline alloy also exhibits good frequency properties and temperature stability. The excellent magnetic properties were explained by the uniform microstructure with small grain size and the wide magnetic domains of the alloy. Low raw material cost, good manufacturability and excellent magnetic properties will make these nanocrystalline alloys prospective candidates for transformer and motor cores.

  19. COBALT SALTS PRODUCTION BY USING SOLVENT EXTRACTION

    Directory of Open Access Journals (Sweden)

    Liudmila V. Dyakova

    2010-06-01

    Full Text Available The paper deals with the extracting cobalt salts by using mixtures on the basis of tertiary amine from multicomponent solutions from the process of hydrochloride leaching of cobalt concentrate. The optimal composition for the extraction mixture, the relationship between the cobalt distribution coefficients and modifier’s nature and concentration, and the saltingout agent type have been determined. A hydrochloride extraction technology of cobalt concentrate yielding a purified concentrated cobalt solution for the production of pure cobalt salts has been developed and introduced at Severonikel combine.

  20. Biomimetic three-dimensional nanocrystalline hydroxyapatite and magnetically synthesized single-walled carbon nanotube chitosan nanocomposite for bone regeneration

    Science.gov (United States)

    Im, Owen; Li, Jian; Wang, Mian; Zhang, Lijie Grace; Keidar, Michael

    2012-01-01

    Background Many shortcomings exist in the traditional methods of treating bone defects, such as donor tissue shortages for autografts and disease transmission for allografts. The objective of this study was to design a novel three-dimensional nanostructured bone substitute based on magnetically synthesized single-walled carbon nanotubes (SWCNT), biomimetic hydrothermally treated nanocrystalline hydroxyapatite, and a biocompatible hydrogel (chitosan). Both nanocrystalline hydroxyapatite and SWCNT have a biomimetic nanostructure, excellent osteoconductivity, and high potential to improve the load-bearing capacity of hydrogels. Methods Specifically, three-dimensional porous chitosan scaffolds with different concentrations of nanocrystalline hydroxyapatite and SWCNT were created to support the growth of human osteoblasts (bone-forming cells) using a lyophilization procedure. Two types of SWCNT were synthesized in an arc discharge with a magnetic field (B-SWCNT) and without a magnetic field (N-SWCNT) for improving bone regeneration. Results Nanocomposites containing magnetically synthesized B-SWCNT had superior cytocompatibility properties when compared with nonmagnetically synthesized N-SWCNT. B-SWCNT have much smaller diameters and are twice as long as their nonmagnetically prepared counterparts, indicating that the dimensions of carbon nanotubes can have a substantial effect on osteoblast attachment. Conclusion This study demonstrated that a chitosan nanocomposite with both B-SWCNT and 20% nanocrystalline hydroxyapatite could achieve a higher osteoblast density when compared with the other experimental groups, thus making this nanocomposite promising for further exploration for bone regeneration. PMID:22619545

  1. Chemical vapor deposition of nanocrystalline diamond films

    International Nuclear Information System (INIS)

    Vyrovets, I.I.; Gritsyna, V.I.; Dudnik, S.F.; Opalev, O.A.; Reshetnyak, O.M.; Strel'nitskij, V.E.

    2008-01-01

    The brief review of the literature is devoted to synthesis of nanocrystalline diamond films. It is shown that the CVD method is an effective way for deposition of such nanostructures. The basic technological methods that allow limit the size of growing diamond crystallites in the film are studied.

  2. Synthesis and characterization of nanocrystalline zinc ferrite

    DEFF Research Database (Denmark)

    Jiang, J.S.; Yang, X.L.; Gao, L.

    1999-01-01

    Nanocrystalline zinc ferrite powders with a partially inverted spinel structure were synthesized by high-energy ball milling in a closed container at ambient temperature from a mixture of alpha-Fe2O3 and ZnO crystalline powders in equimolar ratio. From low-temperature and in-field Mossbauer...

  3. Multiphase Nanocrystalline Ceramic Concept for Nuclear Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Mecartnery, Martha [Univ. of California, Irvine, CA (United States); Graeve, Olivia [Univ. of California, San Diego, CA (United States); Patel, Maulik [Univ. of Liverpool (United Kingdom)

    2017-05-25

    The goal of this research is to help develop new fuels for higher efficiency, longer lifetimes (higher burn-up) and increased accident tolerance in future nuclear reactors. Multiphase nanocrystalline ceramics will be used in the design of simulated advanced inert matrix nuclear fuel to provide for enhanced plasticity, better radiation tolerance, and improved thermal conductivity

  4. Multiphase Nanocrystalline Ceramic Concept for Nuclear Fuel

    International Nuclear Information System (INIS)

    Mecartnery, Martha; Graeve, Olivia; Patel, Maulik

    2017-01-01

    The goal of this research is to help develop new fuels for higher efficiency, longer lifetimes (higher burn-up) and increased accident tolerance in future nuclear reactors. Multiphase nanocrystalline ceramics will be used in the design of simulated advanced inert matrix nuclear fuel to provide for enhanced plasticity, better radiation tolerance, and improved thermal conductivity

  5. Characterization of nanocrystalline silicon germanium film and ...

    African Journals Online (AJOL)

    The nanocrystalline silicon-germanium films (Si/Ge) and Si/Ge nanotubes have low band gaps and high carrier mobility, thus offering appealing potential for absorbing gas molecules. Interaction between hydrogen molecules and bare as well as functionalized Si/Ge nanofilm and nanotube was investigated using Monte ...

  6. Comparative metallurgical study of thick hard coatings without cobalt

    International Nuclear Information System (INIS)

    Clemendot, F.; Van Duysen, J.C.; Champredonde, J.

    1992-07-01

    Wear and corrosion of stellite type hard coatings for valves of the PWR primary system raise important problems of contamination. Substitution of these alloys by cobalt-free hard coatings (Colmonoy 4 and 4.26, Cenium 36) should allow to reduce this contamination. A comparative study (chemical, mechanical, thermal, metallurgical), as well as a corrosion study of these coatings were carried out. The results of this characterization show that none of the studied products has globally characteristics as good as those of grade 6 Stellite currently in service

  7. Phosphorus introduction mechanism in electrodeposited cobalt films

    International Nuclear Information System (INIS)

    Kravtchenko, Jean-Francois

    1973-01-01

    The cathodic reduction of hypophosphite, phosphite and phosphate ions was studied using chrono-potentiometry and voltammetry. Then cobalt was deposited at constant current from a bath containing one of these three compounds. The current, while giving an electrodeposition of cobalt, also enhances at the same time a chemical deposition of cobalt. It is shown that high coercive forces in cobalt films are much more related to this chemical deposition than to the simple fact that the films contain some phosphorus. (author) [fr

  8. A multilayer innovative solution to improve the adhesion of nanocrystalline diamond coatings

    Energy Technology Data Exchange (ETDEWEB)

    Poulon-Quintin, A., E-mail: poulon@icmcb-bordeaux.cnrs.fr [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Faure, C.; Teulé-Gay, L.; Manaud, J.P. [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France)

    2015-03-15

    Highlights: • Improvement of the NCD adhesion on WC-12%Co substrates for tooling applications using a multi-interlayer additional system. • Reduction of the graphite layer thickness and continuity at the interface with the diamond. • Transmission electron microscopy study for a better understanding of the diffusion phenomena occurring at the interfaces. - Abstract: Nano-crystalline diamond (NCD) films grown under negative biased substrates by chemical vapor deposition (CVD) are widely used as surface overlay coating onto cermet WC-Co cutting tools to get better performances. To improve the diamond adhesion to the cermet substrate, suitable multi-layer systems have been added. They are composed of a cobalt diffusion barrier close to the substrate (single and sequenced nitrides layers) coated with a nucleation extra layer to improve the nucleus density of diamond during CVD processing. For all systems, before and after diamond deposition, transmission electron microscopy (TEM) has been performed for a better understanding of the diffusion phenomena occurring at the interfaces and to evaluate the presence of graphitic species at the interface with the diamond. Innovative multilayer system dedicated to the regulation of cobalt diffusion coated with a bilayer system optimized for the carbon diffusion control, is shown as an efficient solution to significantly reduce the graphite layer formation at the interface with the diamond down to 10 nm thick and to increase the adhesion of NCD diamond layer as scratch-tests confirm.

  9. Molecular mechanics calculations on cobalt phthalocyanine dimers

    NARCIS (Netherlands)

    Heuts, J.P.A.; Schipper, E.T.W.M.; Piet, P.; German, A.L.

    1995-01-01

    In order to obtain insight into the structure of cobalt phthalocyanine dimers, molecular mechanics calculations were performed on dimeric cobalt phthalocyanine species. Molecular mechanics calculations are first presented on monomeric cobalt(II) phthalocyanine. Using the Tripos force field for the

  10. Transport of cobalt-60 industrial radiation sources

    Science.gov (United States)

    Kunstadt, Peter; Gibson, Wayne

    This paper will deal with safety aspects of the handling of Cobalt-60, the most widely used industrial radio-isotope. Cobalt-60 is a man-made radioisotope of Cobalt-59, a naturally occurring non radioactive element, that is made to order for radiation therapy and a wide range of industrial processing applications including sterilization of medical disposables, food irradiation, etc.

  11. Accumulation of cobalt by cephalopods

    International Nuclear Information System (INIS)

    Nakahara, Motokazu

    1981-01-01

    Accumulation of cobalt by cephalopod mollusca was investigated by radiotracer experiments and elemental analysis. In the radiotracer experiments, Octopus vulgaris took up cobalt-60 from seawater fairly well and the concentration of the nuclide in whole body attained about 150 times the level of seawater at 25th day at 20 0 C. Among the tissues and organs measured, branchial heart which is the specific organ of cephalopods showed the highest affinity for the nuclide. The organ accumulated about 50% of the radioactivity in whole body in spite of its little mass as 0.2% of total body weight. On the other hand, more than 90% of the radioactivity taken up from food (soft parts of Gomphina melanaegis labelled with cobalt-60 previously in an aquarium) was accumulated in liver at 3rd day after the single administration and then the radioactivity in the liver seemed to be distributed to other organs and tissues. The characteristic elution profiles of cobalt-60 was observed for each of the organs and tissues in Sephadex gel-filtration experiment. It was confirmed by the gel-filtration that most of cobalt-60 in the branchial heart was combined with the constituents of low molecular weights. The average concentration of stable cobalt in muscle of several species of cephalopods was 5.3 +- 3.0 μg/kg wet and it was almost comparable to the fish muscle. On the basis of soft parts, concentration of the nuclide closed association among bivalve, gastropod and cephalopod except squid that gave lower values than the others. (author)

  12. Cobalt production in RAPS-1

    International Nuclear Information System (INIS)

    Krishnan, P.D.; Purandare, H.D.

    1978-01-01

    At present in RAPS-1 radioisotope Co 60 is produced by irradiating Co 59 in the adjusters which perform the function of regulation of reactivity, power and xenon override. But the manrem expenditure of the crew handling the charge and discharge of the adjusters is going to be prohibitively high. It is therefore proposed to irradiate Co 59 in the fuel channel positions. The physics optimisation study for such irradiation is presented. The burnup penalty and loss of power are estimated to produce the required quantity of Co 60 after optimising the number of cobalt pencils in a bundle and the positions of the cobalt producing channels in the reactor core. (author)

  13. Cobalt(II) and Cobalt(III) Coordination Compounds.

    Science.gov (United States)

    Thomas, Nicholas C.; And Others

    1989-01-01

    Presents a laboratory experiment which illustrates the formation of tris(phenanthroline)cobalt complexes in the 2+ and 3+ oxidation states, the effect of coordination on reactions of the ligand, and the use of a ligand displacement reaction in recovering the transformed ligand. Uses IR, UV-VIS, conductivity, and NMR. (MVL)

  14. Assessment of polyphase sintered iron-cobalt-iron boride cermets

    International Nuclear Information System (INIS)

    Nowacki, J.; Pieczonka, T.

    2004-01-01

    Sintering of iron, cobalt and boron powders has been analysed. As a result iron-iron boride, Fe-Fe 2 B and iron/cobalt boride with a slight admixture of molybdenum, Fe - Co - (FeMoCo) 2 B cermets have been produced. Iron was introduced to the mixture as the Astalloy Mo Hoeganaes grade powder. Elemental amorphous boron powder was used, and formation of borides occurred both during heating and isothermal sintering periods causing dimensional changes of the sintered body. Dilatometry was chosen to control basic phenomena taking place during multiphase sintering of investigated systems. The microstructure and phase constituents of sintered compacts were controlled as well. The cermets produced were substituted to: metallographic tests, X-ray analysis, measurements of hardness and of microhardness, and of wear in the process of sliding dry friction. Cermets are made up of two phases; hard grains of iron - cobalt boride, (FeCo) 2 B (1800 HV) constituting the reinforcement and a relatively soft and plastic eutectic mixture Fe 2 B - Co (400-500 HV) constituting the matrix. (author)

  15. Influence of cobalt doping on structural and magnetic properties of BiFeO3 nanoparticles

    Science.gov (United States)

    Khan, U.; Adeela, N.; Javed, K.; Riaz, S.; Ali, H.; Iqbal, M.; Han, X. F.; Naseem, S.

    2015-11-01

    Nanocrystalline cobalt-doped bismuth ferrites with general formula of BiFe1- δ Co δ O3 (0 ≤ δ ≤ 0.1) have been synthesized using solution evaporation method. Structure and phase identification was performed with X-ray diffraction (XRD) technique. The results confirm the formation of rhombohedral-distorted Perovskite structure with R3c symmetry. A decrease in lattice parameters and an increase in X-ray density have been observed with increasing cobalt concentration in BiFeO3. Particle size determined by transmission electron microscope was in good agreement with XRD, i.e., 39 nm. Room-temperature coercivity and saturation magnetization of nanoparticles were increased up to 7.5 % of cobalt doping. Low-temperature magnetic measurements of selected sample showed increasing behavior in saturation magnetization, coercivity, effective magnetic moments, and anisotropy constant. An increase in coercivity with decrease in temperature followed theoretical model of Kneller's law, while modified Bloch's model was employed for saturation magnetization in temperature range of 5-300 K.

  16. Effect of Co addition on the magnetic properties and microstructure of FeNbBCu nanocrystalline alloys

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Lin [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China); Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 (China); School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Yang, Weiming [School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Liu, Haishun, E-mail: liuhaishun@126.com [School of Sciences, China University of Mining and Technology, Xuzhou 221116 (China); Men, He [Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 (China); Wang, Anding, E-mail: anding@nimte.ac.cn [Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 (China); Chang, Chuntao [Ningbo Institute of Industrial Technology, Chinese Academy of Sciences, Ningbo 315201 (China); Shen, Baolong, E-mail: blshen@seu.edu.cn [School of Materials Science and Engineering, Southeast University, Nanjing 211189 (China)

    2016-12-01

    Through gradient substitution of Co for Fe, the magnetic properties and microstructures of (Fe{sub 1−x}Co{sub x}){sub 83}Nb{sub 2}B{sub 14}Cu{sub 1} (x=0.1, 0.2, 0.3, 0.4, 0.5) nanocrystalline alloys were investigated. Because of the strong ferromagnetic exchange coupling between Co and Fe, substantial improvement in saturation magnetization was achieved with proper levels of Co addition. Meanwhile, the Curie temperature increased noticeably with increasing Co addition. After heat treatment, the (Fe{sub 0.9}Co{sub 0.1}){sub 83}Nb{sub 2}B{sub 14}Cu{sub 1} nanocrystalline alloy showed a refined microstructure with an average grain size of 10–20 nm, exhibiting a comparatively high saturation magnetization of 1.82 T and a lower coercivity of 12 A/m compared to other Hitperm-type alloys with higher Co contents. Additionally, the Curie temperature reached 1150 K upon introduction of Co. As the soft magnetic properties are strengthened by adding a small amount of Co, the combination of fine, soft magnetic properties and low cost make this nanocrystalline alloy a potential magnetic material. - Highlights: • New (Fe{sub 1−x}Co{sub x}){sub 83}Nb{sub 2}B{sub 14}Cu{sub 1} nanocrystalline alloys are successfully synthesized. • Minor Co addition improves the Curie temperature of (Fe{sub 1−x}Co{sub x}){sub 83}Nb{sub 2}B{sub 14}Cu{sub 1} alloy system. • (Fe{sub 1−x}Co{sub x}){sub 83}Nb{sub 2}B{sub 14}Cu{sub 1} nanocrystalline alloys exhibit high saturation magnetization above 1.82 T.

  17. Biomimetic three-dimensional nanocrystalline hydroxyapatite and magnetically synthesized single-walled carbon nanotube chitosan nanocomposite for bone regeneration

    Directory of Open Access Journals (Sweden)

    Im O

    2012-04-01

    Full Text Available Owen Im1, Jian Li2, Mian Wang2, Lijie Grace Zhang2,3, Michael Keidar2,31Department of Biomedical Engineering, Duke University, Durham, NC; 2Department of Mechanical and Aerospace Engineering, 3Institute for Biomedical Engineering and Institute for Nanotechnology, The George Washington University, Washington, DC, USABackground: Many shortcomings exist in the traditional methods of treating bone defects, such as donor tissue shortages for autografts and disease transmission for allografts. The objective of this study was to design a novel three-dimensional nanostructured bone substitute based on magnetically synthesized single-walled carbon nanotubes (SWCNT, biomimetic hydrothermally treated nanocrystalline hydroxyapatite, and a biocompatible hydrogel (chitosan. Both nanocrystalline hydroxyapatite and SWCNT have a biomimetic nanostructure, excellent osteoconductivity, and high potential to improve the load-bearing capacity of hydrogels.Methods: Specifically, three-dimensional porous chitosan scaffolds with different concentrations of nanocrystalline hydroxyapatite and SWCNT were created to support the growth of human osteoblasts (bone-forming cells using a lyophilization procedure. Two types of SWCNT were synthesized in an arc discharge with a magnetic field (B-SWCNT and without a magnetic field (N-SWCNT for improving bone regeneration.Results: Nanocomposites containing magnetically synthesized B-SWCNT had superior cytocompatibility properties when compared with nonmagnetically synthesized N-SWCNT. B-SWCNT have much smaller diameters and are twice as long as their nonmagnetically prepared counterparts, indicating that the dimensions of carbon nanotubes can have a substantial effect on osteoblast attachment.Conclusion: This study demonstrated that a chitosan nanocomposite with both B-SWCNT and 20% nanocrystalline hydroxyapatite could achieve a higher osteoblast density when compared with the other experimental groups, thus making this nanocomposite

  18. Structure, microstructure and photoluminescence of nanocrystalline Ti-doped gahnite

    International Nuclear Information System (INIS)

    Vrankić, M.; Gržeta, B.; Mandić, V.; Tkalčec, E.; Milošević, S.; Čeh, M.; Rakvin, B.

    2012-01-01

    Highlights: ► Ti-doped gahnite samples with 0–11.6 at.% Ti were synthesized for the first time. ► The samples had crystallite size of 16.6–20.5 nm and lattice strain of 0.07–0.26%. ► Titanium entered the gahnite structure as Ti 4+ , substituting for octahedral Al 3+ . ► Ti-doped gahnite showed the UV absorption and blue emission under UV excitation. - Abstract: A series of Ti-doped ZnAl 2 O 4 (gahnite) samples with doping levels of 0, 1.8, 3.8, 5.4 and 11.6 at.% Ti in relation to Al were prepared by a sol–gel technique. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), EPR spectroscopy, UV–vis reflectance spectroscopy and photoluminescence (PL) studies. Diffraction patterns indicated that all samples were nanocrystalline, with a spinel-type structure, space group Fd3 ¯ m. Titanium doping of gahnite caused an increase of unit-cell parameter and diffraction line broadening. The structure of samples was refined by the Rietveld method, simultaneously with the analysis of diffraction line broadening. TEM investigations confirmed that samples had spinel-type structure, and showed that samples contained evenly shaped particles of about 20 nm in size. Ti-doped samples exhibited strong absorption at wavelength exc = 308 nm.

  19. Electron transfer reactions of macrocyclic compounds of cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Heckman, R.A.

    1978-08-01

    The kinetics and mechanisms of reduction of H/sub 2/O/sub 2/, Br/sub 2/, and I/sub 2/ by various macrocyclic tetraaza complexes of cobalt(II), including Vitamin B/sub 12r/, were studied. The synthetic macrocycles studied were all 14-membered rings which varied in the degree of unsaturation,substitution of methyl groups on the periphery of the ring, and substitution within the ring itself. Scavenging experiments demonstrated that the reductions of H/sub 2/O/sub 2/ produce free hydroxyl radicals only in the case of Co((14)ane)/sup 2 +/ but with none of the others. In the latter instances apparently H/sub 2/O/sub 2/ simultaneously oxidizes the metal center and the ligand. The reductions of Br/sub 2/ and I/sub 2/ produce an aquohalocobalt(III) product for all reductants (except B/sub 12r/ + Br/sub 2/, which was complicated by bromination of the corrin ring). The mechanism of halogen reduction was found to involve rate-limiting inner-sphere electron transfer from cobalt to halogen to produce a dihalide anion coordinated to the cobalt center. This intermediate subsequently decomposes in rapid reactions to halocobalt(III) and halogen atom species or reacts with another cobalt(II) center to give two molecules of halocobalt(III). The reductions of halomethylcobaloximes and related compounds and diamminecobaloxime by Cr/sup 2 +/ were also studied. The reaction was found to be biphasic in all cases with the reaction products being halomethane (for the halomethylcobaloximes), Co/sup 2 +/ (in less than 100 percent yield), a Cr(III)-dimethylglyoxime species, a small amount of free dmgH/sub 2/, and a highly-charged species containing both cobalt and chromium. The first-stage reaction occurs with a stoichiometry of 1:1 producing an intermediate with an absorption maximum at 460 nm for all starting reagents. The results were interpreted in terms of inner-sphere coordination of the cobaloxime to the Cr(II) and electron transfer through the oxime N-O bond.

  20. Radiation influence on properties of nanocrystalline alloy

    International Nuclear Information System (INIS)

    Holkova, D.; Sitek, J.; Novak, P.; Dekan, J.

    2016-01-01

    Our work is focused on the studied of structural changes amorphous and nanocrystalline alloys after irradiation with electrons. For the analysis of these alloy we use two spectroscopic methods: Moessbauer spectroscopy and XRD. Measurements of nanocrystalline (Fe 3 Ni 1 ) 81 Nb 7 B 12 samples before and after electrons irradiation by means of Moessbauer spectroscopy and XRD showed that the electrons causes changes in magnetic structure which is reflected changes of direction of net magnetic moment. Structural changes occurs in the frame of error indicated by both spectroscopic methods. We can confirm that this kind alloys a resistive again electrons irradiation up to doses of 4 MGy. We observed in this frame only beginning of the radiation damage. (authors)

  1. Ultrafast Terahertz Conductivity of Photoexcited Nanocrystalline Silicon

    DEFF Research Database (Denmark)

    Cooke, David; MacDonald, A. Nicole; Hryciw, Aaron

    2007-01-01

    The ultrafast transient ac conductivity of nanocrystalline silicon films is investigated using time-resolved terahertz spectroscopy. While epitaxial silicon on sapphire exhibits a free carrier Drude response, silicon nanocrystals embedded in glass show a response that is best described by a class...... in the silicon nanocrystal films is dominated by trapping at the Si/SiO2 interface states, occurring on a 1–100 ps time scale depending on particle size and hydrogen passivation......The ultrafast transient ac conductivity of nanocrystalline silicon films is investigated using time-resolved terahertz spectroscopy. While epitaxial silicon on sapphire exhibits a free carrier Drude response, silicon nanocrystals embedded in glass show a response that is best described...

  2. Simple, heart-smart substitutions

    Science.gov (United States)

    Coronary artery disease - heart smart substitutions; Atherosclerosis - heart smart substitutions; Cholesterol - heart smart substitutions; Coronary heart disease - heart smart substitutions; Healthy diet - heart ...

  3. Solubility of Carbon in Nanocrystalline -Iron

    OpenAIRE

    Alexander Kirchner; Bernd Kieback

    2012-01-01

    A thermodynamic model for nanocrystalline interstitial alloys is presented. The equilibrium solid solubility of carbon in -iron is calculated for given grain size. Inside the strained nanograins local variation of the carbon content is predicted. Due to the nonlinear relation between strain and solubility, the averaged solubility in the grain interior increases with decreasing grain size. The majority of the global solubility enhancement is due to grain boundary enrichment however. Therefor...

  4. The cobalt-60 container scanner

    International Nuclear Information System (INIS)

    Jigang, A.; Liye, Z.; Yisi, L.; Haifeng, W.; Zhifang, W.; Liqiang, W.; Yuanshi, Z.; Xincheng, X.; Furong, L.; Baozeng, G.; Chunfa, S.

    1997-01-01

    The Institute of Nuclear Energy Technology (INET) has successfully designed and constructed a container (cargo) scanner, which uses cobalt-60 of 100-300 Ci as radiation source. The following performances of the Cobalt-60 container scanner have been achieved at INET: a) IQI (Image Quality Indicator) - 2.5% behind 100 mm of steel; b) CI (Contrast Indicator) - 0.7% behind 100 mm of steel; c) SP (Steel Penetration) - 240 mm of steel; d) Maximum Dose per Scanning - 0.02mGy; e) Throughput - twenty 40-foot containers per hour. These performances are equal or similar to those of the accelerator scanners. Besides these nice enough inspection properties, the Cobalt-60 scanner possesses many other special features which are better than accelerator scanners: a) cheap price - it will be only or two tenths of the accelerator scanner's; b) low radiation intensity - the radiation protection problem is much easier to solve and a lot of money can be saved on the radiation shielding building; c) much smaller area for installation and operation; d) simple operation and convenient maintenance; e) high reliability and stability. The Cobalt-60 container (or cargo) scanner is satisfied for boundary customs, seaports, airports and railway stations etc. Because of the nice special features said above, it is more suitable to be applied widely. Its high properties and low price will make it have much better application prospects

  5. Cobalt 60 commercial irradiation facilities

    International Nuclear Information System (INIS)

    West, G.

    1985-01-01

    The advantage of using cobalt 60 for ionizing treatment is that it has excellent penetration. Gamma plants are also very efficient, in as much as there is very little mechanical or electrical equipment in a gamma irradiation facility. The average efficiency of a gamma plant is usually around 95% of all available processing time

  6. Characterization of amorphous and nanocrystalline carbon films

    International Nuclear Information System (INIS)

    Chu, Paul K.; Li Liuhe

    2006-01-01

    Amorphous and nanocrystalline carbon films possess special chemical and physical properties such as high chemical inertness, diamond-like properties, and favorable tribological proprieties. The materials usually consist of graphite and diamond microstructures and thus possess properties that lie between the two. Amorphous and nanocrystalline carbon films can exist in different kinds of matrices and are usually doped with a large amount of hydrogen. Thus, carbon films can be classified as polymer-like, diamond-like, or graphite-like based on the main binding framework. In order to characterize the structure, either direct bonding characterization methods or the indirect bonding characterization methods are employed. Examples of techniques utilized to identify the chemical bonds and microstructure of amorphous and nanocrystalline carbon films include optical characterization methods such as Raman spectroscopy, Ultra-violet (UV) Raman spectroscopy, and infrared spectroscopy, electron spectroscopic and microscopic methods such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, transmission electron microscopy, and electron energy loss spectroscopy, surface morphology characterization techniques such as scanning probe microscopy (SPM) as well as other characterization methods such as X-ray reflectivity and nuclear magnetic resonance. In this review, the structures of various types of amorphous carbon films and common characterization techniques are described

  7. Deposition and properties of cobalt- and ruthenium-based ultra-thin films

    Science.gov (United States)

    Henderson, Lucas Benjamin

    (0), yields cobalt-phosphorus films without any co-reactant. However, the molecule does not contain sufficient amounts of amorphizing agents to fully eliminate grain boundaries, and the resulting film is nanocrystalline.

  8. THE COORDINATION COMPOUNDS OF COBALT (II, III WITH DITHIOCARBAMIC ACID DERIVATIVES — MODIFICATORS OF HYDROLYTIC ENZYMES ACTIVITY

    Directory of Open Access Journals (Sweden)

    L. D. Varbanets

    2013-02-01

    Full Text Available Chloride, bromide and isothiocyanate complexes of cobalt(II with N-substituted thiocarbamoyl-N?-pentamethylenesulfenamides (1–(12, and also complexes of cobalt(II, Ш with derivatives of morpholine-4-carbodithioic acid (13–(18 have been used as modificators of enzymes of hydrolytic action — Bacillus thurin-giensis ІМВ В-7324 peptidases, Bacillus subtilis 147 and Aspergillus flavus var. oryzae 80428 amylases, Eupenicillium erubescens 248 and Cryptococcus albidus 1001 rhamnosidases. It was shown that cobalt (II, Ш compounds influence differently on the activity of enzymes tested, exerted both inhibitory and stimulatory action. It gives a possibility to expect that manifestation of activity by complex molecule depends on ligand and anion presence — Cl–, Br– or NCS–. The high activating action of cobalt(II complexes with N-substituted thiocarbamoyl-N?-pentamethylenesulphenamides (1–(12 on elastase and fibrinolytic activity of peptidases compared to tris(4-morpholinecarbodithioatocobalt(ІІІ (14 and products of its interaction with halogens (15–(17, causes inhibitory effect that is probably due to presence of a weekly S–N link, which is easy subjected to homolytic breaking. The studies of influences of cobalt(II complexes on activity of C. аlbidus and E. еrubescens ?-Lrhamnosidases showed, that majority of compounds inhibits of its activity, at that the most inhibitory effect exerts to C. аlbidus enzyme.To sum up, it is possible to state that character of influence of cobalt(II complexes with N-substituted thiocarbamoyl-N?-pentamethylenesulphenamides, and also cobalt(II, Ш complexes with derivatives of morpholine-4-carbodithioic acid varies depending on both strain producer and enzyme tested. The difference in complex effects on enzymes tested are due to peculiarities of building and functional groups of their active centers, which are also responsible for binding with modificators.

  9. Bone healing around nanocrystalline hydroxyapatite, deproteinized bovine bone mineral, biphasic calcium phosphate, and autogenous bone in mandibular bone defects

    DEFF Research Database (Denmark)

    Broggini, Nina; Bosshardt, Dieter D; Jensen, Simon S

    2015-01-01

    The individual healing profile of a given bone substitute with respect to osteogenic potential and substitution rate must be considered when selecting adjunctive grafting materials for bone regeneration procedures. In this study, standardized mandibular defects in minipigs were filled...... with nanocrystalline hydroxyapatite (HA-SiO), deproteinized bovine bone mineral (DBBM), biphasic calcium phosphate (BCP) with a 60/40% HA/β-TCP (BCP 60/40) ratio, or particulate autogenous bone (A) for histological and histomorphometric analysis. At 2 weeks, percent filler amongst the test groups (DBBM (35.65%), HA......-SiO (34.47%), followed by BCP 60/40 (23.64%)) was significantly higher than the more rapidly substituted autogenous bone (17.1%). Autogenous bone yielded significantly more new bone (21.81%) over all test groups (4.91%-7.74%) and significantly more osteoid (5.53%) than BCP 60/40 (3%) and DBBM (2...

  10. Photoacoustic study of nanocrystalline silicon produced by mechanical grinding

    Energy Technology Data Exchange (ETDEWEB)

    Poffo, C.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Lima, J.C. de, E-mail: fsc1jcd@fisica.ufsc.b [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Souza, S.M.; Triches, D.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Grandi, T.A. [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Trindade, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Biasi, R.S. de [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, 22290-270 Rio de Janeiro, RJ (Brazil)

    2011-04-01

    Mechanical grinding (MG) was used to produce nanocrystalline silicon and its thermal and transport properties were investigated by photoacoustic absorption spectroscopy (PAS). The experimental results suggest that in as-milled nanocrystalline silicon for 10 h the heat transfer through the crystalline and interfacial components is similar, and after annealed at 470 {sup o}C the heat transfer is controlled by crystalline component.

  11. Photoacoustic study of nanocrystalline silicon produced by mechanical grinding

    International Nuclear Information System (INIS)

    Poffo, C.M.; Lima, J.C. de; Souza, S.M.; Triches, D.M.; Grandi, T.A.; Biasi, R.S. de

    2011-01-01

    Mechanical grinding (MG) was used to produce nanocrystalline silicon and its thermal and transport properties were investigated by photoacoustic absorption spectroscopy (PAS). The experimental results suggest that in as-milled nanocrystalline silicon for 10 h the heat transfer through the crystalline and interfacial components is similar, and after annealed at 470 o C the heat transfer is controlled by crystalline component.

  12. Solid state consolidation nanocrystalline copper-tungsten using cold spray

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Aaron Christopher [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sarobol, Pylin [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Argibay, Nicolas [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Clark, Blythe [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Diantonio, Christopher [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    It is well known that nanostructured metals can exhibit significantly improved properties compared to metals with conventional grain size. Unfortunately, nanocrystalline metals typically are not thermodynamically stable and exhibit rapid grain growth at moderate temperatures. This severely limits their processing and use, making them impractical for most engineering applications. Recent work has shown that a number of thermodynamically stable nanocrystalline metal alloys exist. These alloys have been prepared as powders using severe plastic deformation (e.g. ball milling) processes. Consolidation of these powders without compromise of their nanocrystalline microstructure is a critical step to enabling their use as engineering materials. We demonstrate solid-state consolidation of ball milled copper-tantalum nanocrystalline metal powder using cold spray. Unfortunately, the nanocrystalline copper-tantalum powder that was consolidated did not contain the thermodynamically stable copper-tantalum nanostructure. Nevertheless, this does this demonstrates a pathway to preparation of bulk thermodynamically stable nanocrystalline copper-tantalum. Furthermore, it demonstrates a pathway to additive manufacturing (3D printing) of nanocrystalline copper-tantalum. Additive manufacturing of thermodynamically stable nanocrystalline metals is attractive because it enables maximum flexibility and efficiency in the use of these unique materials.

  13. Cobalt release from inexpensive jewellery: has the use of cobalt replaced nickel following regulatory intervention?

    Science.gov (United States)

    Thyssen, Jacob Pontoppidan; Jellesen, Morten S; Menné, Torkil; Lidén, Carola; Julander, Anneli; Møller, Per; Johansen, Jeanne Duus

    2010-08-01

    Before the introduction of the EU Nickel Directive, concern was raised that manufacturers of jewellery might turn from the use of nickel to cobalt following the regulatory intervention on nickel exposure. The aim was to study 354 consumer items using the cobalt spot test. Cobalt release was assessed to obtain a risk estimate of cobalt allergy and dermatitis in consumers who would wear the jewellery. The cobalt spot test was used to assess cobalt release from all items. Microstructural characterization was made using scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS). Cobalt release was found in 4 (1.1%) of 354 items. All these had a dark appearance. SEM/EDS was performed on the four dark appearing items which showed tin-cobalt plating on these. This study showed that only a minority of inexpensive jewellery purchased in Denmark released cobalt when analysed with the cobalt spot test. As fashion trends fluctuate and we found cobalt release from dark appearing jewellery, cobalt release from consumer items should be monitored in the future. Industries may not be fully aware of the potential cobalt allergy problem.

  14. Cobalt-Catalyzed C(sp(2))-H Borylation: Mechanistic Insights Inspire Catalyst Design.

    Science.gov (United States)

    Obligacion, Jennifer V; Semproni, Scott P; Pappas, Iraklis; Chirik, Paul J

    2016-08-24

    A comprehensive study into the mechanism of bis(phosphino)pyridine (PNP) cobalt-catalyzed C-H borylation of 2,6-lutidine using B2Pin2 (Pin = pinacolate) has been conducted. The experimentally observed rate law, deuterium kinetic isotope effects, and identification of the catalyst resting state support turnover limiting C-H activation from a fully characterized cobalt(I) boryl intermediate. Monitoring the catalytic reaction as a function of time revealed that borylation of the 4-position of the pincer in the cobalt catalyst was faster than arene borylation. Cyclic voltammetry established the electron withdrawing influence of 4-BPin, which slows the rate of C-H oxidative addition and hence overall catalytic turnover. This mechanistic insight inspired the next generation of 4-substituted PNP cobalt catalysts with electron donating and sterically blocking methyl and pyrrolidinyl substituents that exhibited increased activity for the C-H borylation of unactivated arenes. The rationally designed catalysts promote effective turnover with stoichiometric quantities of arene substrate and B2Pin2. Kinetic studies on the improved catalyst, 4-(H)2BPin, established a change in turnover limiting step from C-H oxidative addition to C-B reductive elimination. The iridium congener of the optimized cobalt catalyst, 6-(H)2BPin, was prepared and crystallographically characterized and proved inactive for C-H borylation, a result of the high kinetic barrier for reductive elimination from octahedral Ir(III) complexes.

  15. Polytypic transformations during the thermal decomposition of cobalt hydroxide and cobalt hydroxynitrate

    International Nuclear Information System (INIS)

    Ramesh, Thimmasandra Narayan

    2010-01-01

    The isothermal decomposition of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature leads to the formation of Co 3 O 4 . The phase evolution during the decomposition process was monitored using powder X-ray diffraction. The transformation of cobalt hydroxide to cobalt oxide occurs via three phase mixture while cobalt hydroxynitrate to cobalt oxide occurs through a two phase mixture. The nature of the sample and its preparation method controls the decomposition mechanism. The comparison of topotactical relationship between the precursors to the decomposed product has been reported in relation to polytypism. - Graphical abstract: Isothermal thermal decomposition studies of cobalt hydroxide and cobalt hydroxynitrate at different intervals of temperature show the metastable phase formed prior to Co 3 O 4 phase.

  16. Recovery of Cobalt as Cobalt Oxalate from Cobalt Tailings Using Moderately Thermophilic Bioleaching Technology and Selective Sequential Extraction

    Directory of Open Access Journals (Sweden)

    Guobao Chen

    2016-07-01

    Full Text Available Cobalt is a very important metal which is widely applied in various critical areas, however, it is difficult to recover cobalt from minerals since there is a lack of independent cobalt deposits in nature. This work is to provide a complete process to recover cobalt from cobalt tailings using the moderately thermophilic bioleaching technology and selective sequential extraction. It is found that 96.51% Co and 26.32% Cu were extracted after bioleaching for four days at 10% pulp density. The mean compositions of the leach solutions contain 0.98 g·L−1 of Co, 6.52 g·L−1 of Cu, and 24.57 g·L−1 of Fe (III. The copper ion was then recovered by a solvent extraction process and the ferric ions were selectively removed by applying a goethite deironization process. The technological conditions of the above purification procedures were deliberately discussed. Over 98.6% of copper and 99.9% of ferric ions were eliminated from the leaching liquor. Cobalt was finally produced as cobalt oxalate and its overall recovery during the whole process was greater than 95%. The present bioleaching process of cobalt is worth using for reference to deal with low-grade cobalt ores.

  17. Evaluation of structural, morphological and magnetic properties of CuZnNi (Cu{sub x}Zn{sub 0.5−x}Ni{sub 0.5}Fe{sub 2}O{sub 4}) nanocrystalline ferrites for core, switching and MLCI’s applications

    Energy Technology Data Exchange (ETDEWEB)

    Akhtar, Majid Niaz, E-mail: majidniazakhtar@ciitlahore.edu.pk [Department of Physics, COMSATS Institute of Information Technology, Lahore, 54000 Pakistan (Pakistan); Khan, Muhammad Azhar [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur, 63100 Pakistan (Pakistan); Ahmad, Mukhtar [Department of Physics, COMSATS Institute of Information Technology, Lahore, 54000 Pakistan (Pakistan); Nazir, M.S. [Department of Chemical Engineering, COMSATS Institute of Information Technology, Lahore, 54000 Pakistan (Pakistan); Imran, M.; Ali, A.; Sattar, A. [Department of Physics, COMSATS Institute of Information Technology, Lahore, 54000 Pakistan (Pakistan); Murtaza, G. [Centre for Advanced Studies in Physics, G.C. University, Lahore (Pakistan)

    2017-01-01

    The influence of Cu substitution on the structural and morphological characteristics of Ni–Zn nanocrystalline ferrites have been discussed in this work. The detailed and systematic magnetic characterizations were also done for Cu substituted Ni–Zn nanoferrites. The nanocrystalline ferrites of Cu substituted Cu{sub x}Zn{sub 0.5−x}Ni{sub 0.5}Fe{sub 2}O{sub 4} ferrites (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized using sol gel self-combustion hybrid method. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM) were used to investigate the properties of Cu substituted nanocrystalline ferrites. Single phase structure of Cu substituted in Ni–Zn nanocrystalline ferrites were investigated for all the samples. Crystallite size, lattice constant and volume of the cell were found to increase by increasing Cu contents in spinel structure. The better morphology with well-organized nanocrystals of Cu–Zn–Ni ferrites at x=0 and 0.5 were observed from both FESEM and TEM analysis. The average grain size was 35–46 nm for all prepared nanocrystalline samples. Magnetic properties such as coercivity, saturation, remanence, magnetic squareness, magneto crystalline anisotropy constant (K) and Bohr magneton were measured from the recorded M–H loops. The magnetic saturation and remanence were increased by the incorporation of Cu contents. However, coercivity follow the Stoner-Wolforth model except for x=0.3 which may be due to the site occupancy and replacement of Cu contents from octahedral site. The squareness ratio confirmed the super paramgnetic behaviour of the Cu substituted in Ni–Zn nanocrystalline ferrites. Furthermore, Cu substituted Ni–Zn nanocrystalline ferrites may be suitable for many industrial and domestic applications such as components of transformers, core, switching, and MLCI’s due to variety of the soft magnetic characteristics. - Highlights

  18. Derivative spectrophotometry of cobalt alloys

    International Nuclear Information System (INIS)

    Spitsyn, P.K.

    1985-01-01

    The method of derivative spectrophotometry is briefly described, and derivative absorption spectra are presented for samarium, cobalt, and commercial Sm-Co alloys. It is shown that the use of derivative spectrophotometry not only improves the accuracy and selectivity of element determinations but also simplifies the analysis of alloys. Results of a statistical evaluation of the metrological characteristics of the analytical procedure described here are presented. 8 references

  19. EFTF cobalt test assembly results

    International Nuclear Information System (INIS)

    Rawlins, J.A.; Wootan, D.W.; Carter, L.L.; Brager, H.R.; Schenter, R.E.

    1988-01-01

    A cobalt test assembly containing yttrium hydride pins for neutron moderation was irradiated in the Fast Flux Test Facility during Cycle 9A for 137.7 equivalent full power days at a power level fo 291 MW. The 36 test pins consisted of a batch of 32 pins containing cobalt metal to produce Co-60, and a set of 4 pins with europium oxide to produce Gd-153, a radioisotope used in detection of the bone disease Osteoporosis. Post-irradiation examination of the cobalt pins determined the Co-60 produced with an accuracy of about 5 %. The measured Co-60 spatially distributed concentrations were within 20 % of the calculated concentrations. The assembly average Co-60 measured activity was 4 % less than the calculated value. The europium oxide pins were gamma scanned for the europium isotopes Eu-152 and Eu-154 to an absolute accuracy of about 10 %. The measured europium radioisotpe anc Gd-153 concentrations were within 20 % of calculated values. In conclusion, the hydride assembly performed well and is an excellent vehicle for many Fast Flux Test Facility isotope production applications. The results also demonstrate that the calculational methods developed by the Westinghouse Hanford Company are very accurate. (author)

  20. Magnetic behavior of nanocrystalline nickel ferrite

    International Nuclear Information System (INIS)

    Nathani, H.; Gubbala, S.; Misra, R.D.K.

    2005-01-01

    In the previous papers [R.D.K. Misra, A. Kale, R.S. Srivatsava, O. Senkov, Mater. Sci. Technol. 19 (2003) 826; R.D.K. Misra, A. Kale, B. Hooi, J.Th. DeHosson, Mater. Sci. Technol. 19 (2003) 1617; A. Kale, S. Gubbala, R.D.K. Misra, J. Magn. Magn. Mater. 277 (2004) 350; S. Gubbala, H. Nathani, K. Koizol, R.D.K. Misra, Phys. B 348 (2004) 317; R.D.K. Misra, S. Gubbala, A. Kale, W.F. Egelhoff, Mater. Sci. Eng. B. 111 (2004) 164], we reported the synthesis, structural characterization and magnetic behavior of nanocrystalline ferrites of inverse and mixed spinel structure made by reverse micelle technique that enabled a narrow particle size distribution to be obtained. In the present paper, the reverse micelle approach has been extended to synthesize nanocrystalline ferrites with varying surface roughness of 8-18 A (the surface roughness was measured by atomic force microscopy) and the magnetic behavior studied by SQUID magnetometer. Two different kinds of measurement were performed: (a) zero-field cooling (ZFC) and field cooling (FC) magnetization versus temperature measurements and (b) magnetization as a function of applied field. The analysis of magnetic measurement suggests significant influence of surface roughness of particles on the magnetic behavior. While the superparamagnetic behavior is retained by the nanocrystalline ferrites of different surface roughness at 300 K, the hysteresis loop at 2 K becomes non-squared and the coercivity increases with increase in surface roughness. This behavior is discussed in terms of broken bonds and degree of surface spin disorder

  1. Cobalt accumulation and circulation by blackgum trees

    International Nuclear Information System (INIS)

    Thomas, W.A.

    1975-01-01

    Blackgum (Nyssa sylvatica Marsh.) trees accumulate far greater concentrations of cobalt in mature foliage than do other species on the same site (363 ppM in ash of blackgum, compared with about 3 ppM by mockernut hickory and about 1 ppM by red maple, tulip tree, and white oak). Cobalt concentrations in dormant woody tissues of blackgum also significantly exceed those in the other four species. Inoculation of six blackgums with 60 Co revealed that cobalt remains mobile in the trees for at least 3 years. Foliar concentrations of stable cobalt increase uniformly until senescence. In late August, foliage accounts for only 9 percent of total tree weight but 57 percent of total tree cobalt. Losses of cobalt from trees occur almost entirely by leaf abscission, and the loss rates of weight and cobalt from decomposing litter are similar. Retention of cobalt in the biologically active soil layers perpetuates zones of cobalt concentration created by this species in woodlands

  2. Transparent nanocrystalline diamond coatings and devices

    Science.gov (United States)

    Sumant, Anirudha V.; Khan, Adam

    2017-08-22

    A method for coating a substrate comprises producing a plasma ball using a microwave plasma source in the presence of a mixture of gases. The plasma ball has a diameter. The plasma ball is disposed at a first distance from the substrate and the substrate is maintained at a first temperature. The plasma ball is maintained at the first distance from the substrate, and a diamond coating is deposited on the substrate. The diamond coating has a thickness. Furthermore, the diamond coating has an optical transparency of greater than about 80%. The diamond coating can include nanocrystalline diamond. The microwave plasma source can have a frequency of about 915 MHz.

  3. Simulations of intergranular fracture in nanocrystalline molybdenum

    DEFF Research Database (Denmark)

    Frederiksen, Søren Lund; Jacobsen, Karsten Wedel; Schiøtz, Jakob

    2004-01-01

    Using molecular dynamics simulations we investigate the plastic deformation of nanocrystalline molybdenum with a grain size of 12 nm at high strain rates. The simulations are performed with an interatomic potential which is obtained through matching of atomic forces to a database generated...... with density-functional calculations. The simulations show the plastic deformation to involve both grain boundary processes and dislocation migration which in some cases lead to twin boundary formation. A large component of the strain is accommodated through the formation of cracks in the grain boundaries...

  4. Microstructure and tribological property of nanocrystalline Co–W alloy coating produced by dual-pulse electrodeposition

    International Nuclear Information System (INIS)

    Su Fenghua; Huang Ping

    2012-01-01

    Highlights: ► The nanocrystalline Co–W alloy coating were produced by dual-pulse electrodeposition from aqueous bath with cobalt sulfate and sodium tungstate. ► The correlation between the electrodeposition condition, the microstructure and alloy composition, and the hardness and tribological properties of electrodeposited Co–W alloy coatings were established. ► By careful control of the electrodeposition condition and the bath composition, the Co–W alloy coating excellent performance of microhardness and tribological properties, can exhibit excellent performances of microhardness and tribological properties. - Abstract: The nanocrystalline Co–W alloy coatings were produced by dual-pulse electrodeposition from aqueous bath with cobalt sulfate and sodium tungstate (Na 2 WO 4 ). Influence of the current density and Na 2 WO 4 concentration in bath on the microstructure, morphology and hardness of the Co–W alloy coatings were investigated using an X-ray diffraction, a scanning electronic microscope and a Vickers hardness tester, respectively. In addition, the friction and wear properties of the Co–W alloy coating electrodeposited under different condition were evaluated with a ball-on-disk UMT-3MT tribometer. The correlation between the electrodeposition condition, the microstructure and alloy composition, and the hardness and tribological properties of the deposited Co–W alloy coatings were discussed in detail. The results showed that the microhardness of the deposited Co–W alloy coating was significantly affected by its average grain size, W content and crystal orientation. Smaller grain size, higher W content and strong hcp (1 0 0) orientation favor the improvement of the hardness for Co–W alloy coatings. The deposited Co–W alloy coating could obtain the maximum microhardness over 1000 kgf mm −2 by careful control of the electrodeposition conditions. The tribological properties of the electrodeposited Co–W alloy coating were greatly

  5. Synthesis of cobalt ferrite with enhanced magnetostriction properties by the sol−gel−hydrothermal route using spent Li-ion battery

    International Nuclear Information System (INIS)

    Yao, Lu; Xi, Yuebin; Xi, Guoxi; Feng, Yong

    2016-01-01

    The combination of a sol–gel method and a hydrothermal method was successfully used for synthesizing the nano-crystalline cobalt ferrite powders with a spinel structure using spent Li-ion batteries as the raw materials. The phase composition, microstructure, magnetic properties and magnetostriction coefficient of cobalt ferrite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), magnetometer and magnetostrictive measurement instrument. The microstructure of the products exhibited hedgehog-like microspheres with particle size of approximately 5 μm. The different crystalline sizes and the microstructure of cobalt ferrites precursor were controlled by varying the hydrothermal time, which significantly affected the super-exchange and the deflection direction of the magnetic domain, and led to the change of the magnetic properties of sintered cylindrical samples. The saturation magnetization and maximum magnetostriction coefficient were 81.7 emu/g and −158.5 ppm, respectively, which was larger than that of products prepared by the sol-gel sintered method alone. - Graphical abstract: The magnetostriction of cobalt ferrites with a spinel structure was successfully prepared using the sol–gel–hydrothermal route using spent Li-ion batteries. On the basis of the aforementioned SEM observation, the formation of a hedgehog-like microsphere structure might involve two important steps: Ostwald ripening and self-assembly. - Highlights: • The cobalt ferrites were prepared by the sol–gel–hydrothermal route. • The cobalt ferrites show hedgehog-like microsphere particles in shape. • The microspheres size increased with increasing hydrothermal time. • The magnetostriction properties of the cobalt ferrite were enhanced.

  6. Synthesis and properties of nickel-doped nanocrystalline barium hexaferrite ceramic materials

    Science.gov (United States)

    Waqar, Moaz; Rafiq, Muhammad Asif; Mirza, Talha Ahmed; Khalid, Fazal Ahmad; Khaliq, Abdul; Anwar, Muhammad Sabieh; Saleem, Murtaza

    2018-04-01

    M-type barium hexaferrite ceramics have emerged as important materials both for technological and commercial applications. However, limited work has been reported regarding the investigation of nanocrystalline Ni-doped barium hexaferrites. In this study, nanocrystalline barium hexaferrite ceramics with the composition BaFe12- x Ni x O19 (where x = 0, 0.3 and 0.5) were synthesized by sol-gel method and characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer and precision impedance analyzer. All the synthesized samples had single magnetoplumbite phase having space group P63/mmc showing the successful substitution of Ni in BaFe12O19 without the formation of any impurity phase. Average grain size of undoped samples was around 120 nm which increased slightly with the addition of Ni. Saturation magnetization ( M s) and remnant magnetization ( M r) increased with the addition of Ni, however, coercivity ( H c) decreased with the increase in Ni from x = 0 to x = 0.5. Real and imaginary parts of permittivity decreased with the increasing frequency and increased with Ni content. Dielectric loss and conductivity showed slight variation with the increase in Ni concentration.

  7. Microhardness studies of nanocrystalline lead molybdate

    International Nuclear Information System (INIS)

    Anandakumar, V.M.; Abdul Khadar, M.

    2009-01-01

    Nanocrystalline lead molybdate (PbMoO 4 ) of four different grain sizes were synthesized through chemical precipitation technique and the grain sizes and crystal structure are determined using the broadening of X-ray diffraction patterns and transmission electron microscopy. The microhardness of nanocrystalline lead molybdate (PbMoO 4 ) with different grain sizes were measured using a Vicker's microhardness tester for various applied loads ranging from 0.049 to 1.96 N. The microhardness values showed significant indentation size effect at low indentation loads. The proportional specimen resistance model put forward by Li and Bradt and energy balance model put forward by Gong and Li were used to analyze the behaviour of measured microhardness values under different indentation loads. The microhardness data obtained for samples of different grain sizes showed grain size dependent strengthening obeying normal Hall-Petch relation. The dependence of compacting pressure and annealing temperature on microhardness of the nanostructured sample with grain size of ∼18 nm were also studied. The samples showed significant increase in microhardness values as the compacting pressure and annealing time were increased. The variation of microhardness of the material with pressure of pelletization and annealing time are discussed in the light of change of pore size distribution of the samples.

  8. Grain growth studies on nanocrystalline Ni powder

    International Nuclear Information System (INIS)

    Rane, G.K.; Welzel, U.; Mittemeijer, E.J.

    2012-01-01

    The microstructure of nanocrystalline Ni powder produced by ball-milling and its thermal stability were investigated by applying different methods of X-ray diffraction line-profile analysis: single-line analysis, whole powder-pattern modelling and the (modified) Warren–Averbach method were employed. The kinetics of grain growth were investigated by both ex-situ and in-situ X-ray diffraction measurements. With increasing milling time, the grain-size reduction is accompanied by a considerable narrowing of the size distribution and an increase in the microstrain. Upon annealing, initial, rapid grain growth occurs, accompanied by the (almost complete) annihilation of microstrain. For longer annealing times, the grain-growth kinetics depend on the initial microstructure: a smaller microstrain with a broad grain-size distribution leads to linear grain growth, followed by parabolic grain growth, whereas a larger microstrain with a narrow grain-size distribution leads to incessant linear grain growth. These effects have been shown to be incompatible with grain-boundary curvature driven growth. The observed kinetics are ascribed to the role of excess free volume at the grain boundaries of nanocrystalline material and the prevalence of an “abnormal grain-growth” mechanism.

  9. Cobalt 60 availability for radiation processing

    International Nuclear Information System (INIS)

    Fraser, F.M.

    1986-01-01

    In the last 20 years, the steady and significant growth in the application of radiation processing to industrial sterilization has been seen. The principal application of this technology is the sterilization of disposable medical products, food irradiation, the irradiation of personal care goods and so on. At present, more than 70 million curies of cobalt-60 supplied by Atomic Energy of Canada Ltd. have been used for gamma processing in these applications. This is estimated to be more than 80 % of the total cobalt-60 in service in the world. Commercial food irradiation has an exciting future, and as to the impact of food irradiation on the availability of cobalt-60 over the next ten years, two principal factors must be examined, namely, the anticipated demand for cobalt-60 in all radiation processing applications, and the supply of cobalt-60 to reliably meet the expected demand. As for the cobalt-60 in service today, 90 % is used for the sterilization of disposable medical products, 5 % for food irradiation, and 5 % for other application. The demand for up to 30 million curies of cobalt-60 is expected over the next 10 years. Today, it is estimated that over 150,000 tons of spices, fruit and fish are irradiated. The potential cobalt-60 production could exceed 110 million curies per year. Gamma processing application will demand nearly 50 million curies in 1990. (Kako, I.)

  10. Cobalt allergy in hard metal workers

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, T; Rystedt, I

    1983-03-01

    Hard metal contains about 10% cobalt. 853 hard metal workers were examined and patch tested with substances from their environment. Initial patch tests with 1% cobalt chloride showed 62 positive reactions. By means of secondary serial dilution tests, allergic reactions to cobalt were reproduced in 9 men and 30 women. Weak reactions could not normally be reproduced. A history of hand eczema was found in 36 of the 39 individuals with reproducible positive test reactions to cobalt, while 21 of 23 with a positive initial patch test but negative serial dilution test had never had any skin problems. Hand etching and hand grinding, mainly female activities and traumatic to the hands, were found to involve the greatest risk of cobalt sensitization. 24 individuals had an isolated cobalt allergy. They had probably been sensitized by hard metal work, while the individuals, all women, who had simultaneous nickel allergy had probably been sensitized to nickel before their employment and then became sensitized to cobalt by hard metal work. A traumatic occupation, which causes irritant contact dermatitis and/or a previous contact allergy or atopy is probably a prerequisite for the development of cobalt allergy.

  11. Diagnostic Value of the Cobalt (58Co) Excretion Test in Iron Deficiency Anemia

    International Nuclear Information System (INIS)

    Sihn, Hyun Chung; Hong, Kee Suck; Cho, Kyung Sam; Song, In Kyung; Koh, Chang Soon; Lee, Mun Ho

    1976-01-01

    The diagnosis of iron deficiency rests upon the correct evaluation of body iron stores. Morphological interpretation of blood film and the red cell indices are not reliable and often absent in mild iron deficiency. Serum iron levels and iron-binding capacity are more sensitive indices of iron deficiency, but they are often normal in iron depletion and mild iron deficiency anemia. They are also subject ro many variables which may introduce substantial errors and influenced by many pathologic and physiologic states. Examination of the bone marrow aspirate for stainable iron has been regarded as one of the most sensitive and reliable diagnostic method for detecting iron deficiency, but this also has limitations. Thus, there is still need for a more practical, but sensitive and reliable substitute as a screening test of iron deficiency. Pollack et al. (1965) observed that the intestinal absorption of cobalt was raised in iron, deficient rats and Valberg et al. (1969) found that cobalt absorption was elevated in patients with iron deficiency. A direct correlation was demonstrated between the amounts of radioiron and radiocobalt absorbed. Unlike iron, excess cobalt was excreted by the kidney, the percentage of radioactivity in the urine being directly related to the percentage absorbed from the gastro-intestinal tract. Recently a test based on the urinary excretion of an oral dose of 57 Co has been proposed as a method for detecting iron deficiency. To assess the diagnostic value of urinary cobalt excretion test cobaltous chloride labelled with 1 μCi of 58 Co was given by mouth and the percentage of the test dose excreted in the urine was measured by a gamma counter. The mean 24 hour urinary cobalt excretion in control subjects with normal iron stores was 6.1%(1.9-15.2%). Cobalt excretion was markedly increased in patients with iron deficiency and excreted more than 29% of the dose. In contrast, patients with anemia due to causes other than iron deficiency excreted less

  12. The manufacture of synthetic non-sintered and degradable bone grafting substitutes.

    Science.gov (United States)

    Gerike, W; Bienengräber, V; Henkel, K-O; Bayerlein, T; Proff, P; Gedrange, T; Gerber, Th

    2006-02-01

    A new synthetic bone grafting substitute (NanoBone, ARTOSS GmbH, Germany) is presented. This is produced by a new technique, the sol-gel-method. This bone grafting substitute consists of nanocrystalline hydroxyapatite (HA) and nanostructured silica (SiO2). By achieving a highly porous structure good osteoconductivity can be seen. In addition, the material will be completely biodegraded and new own bone is formed. It has been demonstrated that NanoBone is biodegraded by osteoclasts in a manner comparable to the natural bone remodelling process.

  13. High-speed jet electrodeposition and microstructure of nanocrystalline Ni-Co alloys

    International Nuclear Information System (INIS)

    Qiao Guiying; Jing Tianfu; Wang Nan; Gao Yuwei; Zhao Xin; Zhou Jifeng; Wang Wei

    2005-01-01

    The jet electrodeposition from watts baths with a device of electrolyte jet was carried out to prepare nano-crystalline cobalt-nickel alloys. The influence of the concentration of Co 2+ ions in the electrolyte and electrolysis parameters, such as the cathodic current density, the temperature as well as the electrolyte jet speed, on the chemistry and microstructure of Ni-Co-deposit alloys were investigated. Experimental results indicated that increasing the Co 2+ ions concentration in the bath, the electrolyte jet speed and decreasing of the cathodic current density and decrease of the electrolyte temperature all results in an increase of cobalt content in the alloy. Detailed microstructure changes upon the changes of alloy composition and experimental conditions were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD results show the Ni-Co solid solution was formed through the jet electrodeposition. Phase constitution of solid solution changes progressively under different electrolyte concentration. Alloys with low Co concentration exhibit single phase of face-centered cubic (fcc) structure; The Co concentration over 60.39 wt.%, the alloys are composed of face-centered cubic (fcc) phase and hexagonal close-packed (hcp) phase. Furthermore, the formation of the nanostructured Ni-Co alloy deposit is investigated. Increasing the Co 2+ ions concentration in the bath, the cathodic current density, the electrolyte temperature and the electrolyte jet speed all result in the finer grains in the deposits. Additives such as saccharin in the electrolyte also favor the formation of the finer grains in the alloy deposits

  14. Nanocrystalline hydroxyapatite doped with selenium oxyanions: a new material for potential biomedical applications.

    Science.gov (United States)

    Kolmas, Joanna; Oledzka, Ewa; Sobczak, Marcin; Nałęcz-Jawecki, Grzegorz

    2014-06-01

    Selenium-substituted hydroxyapatites containing selenate SeO4(2-) or selenite SeO3(2-) ions were synthesized using a wet precipitation method. The selenium content was determined by atomic absorbance spectrometry. The raw, unsintered powders were also characterized using powder X-ray diffraction, middle-range FT-IR spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopic microanalysis. The synthesized apatites were found to be pure and nanocrystalline with a crystal size similar to that in bone mineral. The incorporation of selenium oxyanions into the crystal lattice was confirmed. The toxicity of hydroxyapatites containing selenite or selenate ions was evaluated with a protozoan assay and bacterial luminescence test. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Superconductivity and low temperature electrical transport in B-doped CVD nanocrystalline diamond

    Directory of Open Access Journals (Sweden)

    Milos Nesladek, Jiri J. Mares, Dominique Tromson, Christine Mer, Philippe Bergonzo, Pavel Hubik and Jozef Kristofik

    2006-01-01

    Full Text Available In this work, we report on superconductivity (SC found in thin B-doped nanocrystalline diamond films, prepared by the PE-CVD technique. The thickness of the films varies from about 100 to 400 nm, the films are grown on low-alkaline glass at substrate temperatures of about 500–700 °C. The SIMS measurements show that films can be heavily doped with boron in concentrations in the range of 3×1021 cm−3. The Raman spectra show Fano resonances, confirming the substitutional B-incorporation. The low temperature magnetotransport measurements reveal a positive magnetoresistance. The SC transition is observed at about Tc=1.66 K. A simple theory exploiting the concept of weak localization accounting for this transition is proposed.

  16. Structure and magnetic properties of nanocrystalline Fe75Si25 powders prepared by mechanical alloying

    International Nuclear Information System (INIS)

    Kalita, M.P.C.; Perumal, A.; Srinivasan, A.

    2008-01-01

    Nanocrystalline Fe 75 Si 25 powders were prepared by mechanical alloying in a planetary ball mill. The evolution of the microstructure and magnetic properties during the milling process were studied by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer measurements. The evolution of non-equilibrium solid solution Fe (Si) during milling was accompanied by refinement of crystallite size down to 10 nm and the introduction of high density of dislocations of the order of 10 17 m -2 . During the milling process, Fe sites get substituted by Si. This structural change and the resulting disorder are reflected in the lattice parameters and average magnetic moment of the powders milled for various time periods. A progressive increase of coercivity was also observed with increasing milling time. The increase of coercivity could be attributed to the introduction of dislocations and reduction of powder particle size as a function of milling time

  17. Cobalt sorption onto Savannah River Plant soils

    International Nuclear Information System (INIS)

    Hoeffner, S.L.

    1985-06-01

    A laboratory study of cobalt-60 sorption was conducted using Savannah River Plant soil and groundwater from the low-level waste burial ground. Systematic variation of soil and water composition indicates that cobalt sorption is most strongly a function of pH. Over a pH range of 2 to 9, the distribution coefficient ranged from 2 to more than 10,000 mL/g. Changes in clay content and in K + , Ca 2+ , or Mg 2+ concentrations influence cobalt sorption indirectly through the slight pH changes which result. The ions Na + , Cl - , and NO 3 - have no effect on cobalt sorption. Ferrous ion, added to groundwater to simulate the condition of water at the bottom of the waste trenches, accounts for part of the decrease in cobalt sorption observed with trench waters. 17 refs., 3 figs., 4 tabs

  18. Cobalt-60 production in CANDU reactors

    International Nuclear Information System (INIS)

    Ross, Michel; Lemire, Christian

    2002-01-01

    CANDU reactors can produce cobalt-60 very efficiently and with an interesting return on investment. This paper discusses what is needed to convert a CANDU reactor into a cobalt-60 producer: what are the different phases, the safety studies required, the physical modifications needed, and what is the minimum involvement of the utility owning the plant. The past ten years of experience of Hydro-Quebec as a cobalt-60 producer will be reviewed, including the management of the risk of both incident and electricity generation loss, and including the benefits for the utility and its personnel. Originally a simple metal used for centuries as a pigment, cobalt-59 today is transformed into cobalt-60, a radioactive element of unprecedented value. Well known in medicine for cancer treatment, cobalt-60 is also used to sterilize a wide range of disposable medical products used in hospitals and to sanitize pharmaceutical and cosmetic products. Cobalt-60 is proving to be a new and effective solution, in the food sector, for preserving harvests and controlling food-borne diseases, or to advantageously replace certain gases and chemical products which are suspected of being harmful or carcinogenic. There are also other applications, such as: hardening of some plastics, treatment of sewage sludge and elimination of harmful insect populations. With a half-life of 5,3 years, cobalt-60 is a metal not found in nature. It is a radioactive isotope produced by exposing stable nuclei of cobalt-59 to neutrons. One of the best places to find such an important neutron source is a nuclear reactor. High energy gamma rays are then emitted during the process of radioactive decay, where cobalt-60 seeks again its stable state

  19. Effects of surface crystallization and oxidation in nanocrystalline FeNbCuSiB(P) ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Butvinová, B., E-mail: beata.butvinova@savba.sk [Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia); Butvin, P. [Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia); Brzózka, K. [Department of Physics, University of Technology and Humanities in Radom, Krasickiego 54, 26-600 Radom (Poland); Kuzminski, M. [Institute of Physics PAS, Al. Lotnikow 36/42, 02-668 Warsaw (Poland); Maťko, I.; Švec Sr, P. [Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia); Chromčíková, M. [Institute of Inorg. Chem. SAS, Centrum VILA, Študentská 2, 911 50 Trenčín (Slovakia)

    2017-02-15

    Si-poor Fe{sub 74}Nb{sub 3}Cu{sub 1}Si{sub 8}B{sub 14−x}P{sub x}, (x=0, 3) nanocrystalline ribbon-form alloys often form surfaces, which exert in-plane force on underlying ribbon interior when nanocrystallized in even modest presence of oxygen. Mostly unwanted hard-ribbon-axis magnetic anisotropy is standard result. Essential sources of the surface-caused stress have been sought and influence of P instead of B substitution on this effect was studied too. Preferred surface crystallization (PSC) was found to be the major reason. However P substitution suppresses PSC and promotes Fe-oxide formation, which eases the stress, softens the surfaces and provides different annealing evolution of surface properties. - Highlights: • Ar anneal of low-Si FeNbCuBSi ribbons produce surfaces that stress ribbon interior. • The stress comes mainly from preferred crystallization of surfaces. • Partial substitution of B by P changes annealing evolution of surface properties. • Without P, more crystalline surfaces significantly reduce ribbon's elasticity. • P suppresses surface crystallinity, promotes oxides and reduces mutual stress.

  20. Electrochemical passivation behaviour of nanocrystalline Fe80Si20 ...

    Indian Academy of Sciences (India)

    Abstract. Passivation behaviour of nanocrystalline coating (Fe80Si20) obtained by in situ mechanical alloying route .... is controlled by the iron oxide film in case of alloys with ..... the surface is covered, thus, producing effective protection of.

  1. Optimization of nanocrystalline γ-alumina coating for direct spray ...

    Indian Academy of Sciences (India)

    Modifications of the partial gas percentage influences the optical properties and composition ... O2 flow in the Ar ambient and substrate temperature on struc- ture and properties of ..... nism to explain mechanical behaviour of nanocrystalline.

  2. Tailoring and patterning the grain size of nanocrystalline alloys

    International Nuclear Information System (INIS)

    Detor, Andrew J.; Schuh, Christopher A.

    2007-01-01

    Nanocrystalline alloys that exhibit grain boundary segregation can access thermodynamically stable or metastable states with the average grain size dictated by the alloying addition. Here we consider nanocrystalline Ni-W alloys and demonstrate that the W content controls the grain size over a very broad range: ∼2-140 nm as compared with ∼2-20 nm in previous work on strongly segregating systems. This trend is attributed to a relatively weak tendency for W segregation to the grain boundaries. Based upon this observation, we introduce a new synthesis technique allowing for precise composition control during the electrodeposition of Ni-W alloys, which, in turn, leads to precise control of the nanocrystalline grain size. This technique offers new possibilities for understanding the structure-property relationships of nanocrystalline solids, such as the breakdown of Hall-Petch strength scaling, and also opens the door to a new class of customizable materials incorporating patterned nanostructures

  3. Amorphous and nanocrystalline materials preparation, properties, and applications

    CERN Document Server

    Inoue, A

    2001-01-01

    Amorphous and nanocrystalline materials are a class of their own. Their properties are quite different to those of the corresponding crystalline materials. This book gives systematic insight into their physical properties, structure, behaviour, and design for special advanced applications.

  4. Protein-modified nanocrystalline diamond thin films for biosensor applications.

    Science.gov (United States)

    Härtl, Andreas; Schmich, Evelyn; Garrido, Jose A; Hernando, Jorge; Catharino, Silvia C R; Walter, Stefan; Feulner, Peter; Kromka, Alexander; Steinmüller, Doris; Stutzmann, Martin

    2004-10-01

    Diamond exhibits several special properties, for example good biocompatibility and a large electrochemical potential window, that make it particularly suitable for biofunctionalization and biosensing. Here we show that proteins can be attached covalently to nanocrystalline diamond thin films. Moreover, we show that, although the biomolecules are immobilized at the surface, they are still fully functional and active. Hydrogen-terminated nanocrystalline diamond films were modified by using a photochemical process to generate a surface layer of amino groups, to which proteins were covalently attached. We used green fluorescent protein to reveal the successful coupling directly. After functionalization of nanocrystalline diamond electrodes with the enzyme catalase, a direct electron transfer between the enzyme's redox centre and the diamond electrode was detected. Moreover, the modified electrode was found to be sensitive to hydrogen peroxide. Because of its dual role as a substrate for biofunctionalization and as an electrode, nanocrystalline diamond is a very promising candidate for future biosensor applications.

  5. Effect of nanocrystalline surface of substrate on microstructure and ...

    Indian Academy of Sciences (India)

    surface layers or bulk nanocrystalline metals and alloys more effectively. ... severe plastic deformation on surface layers of bulk met- als at high strains and strain rates. .... scanning electron microscopy (SEM) (Zeiss, model: Sigma. VP), energy ...

  6. Nanocrystalline Ni-Co Alloy Synthesis by High Speed Electrodeposition

    OpenAIRE

    Idris, Jamaliah; Christian, Chukwuekezie; Gaius, Eyu

    2013-01-01

    Electrodeposition of nanocrystals is economically and technologically viable production path for the synthesis of pure metals and alloys both in coatings and bulk form. The study presents nanocrystalline Ni-Co alloy synthesis by high speed electrodeposition. Nanocrystalline Ni-Co alloys coatings were prepared by direct current (DC) and deposited directly on steel and aluminum substrates without any pretreatment, using high speed electrodeposition method. The influence of the electrolysis par...

  7. Electrochemistry of Inorganic Nanocrystalline Electrode Materials for Lithium Batteries

    Directory of Open Access Journals (Sweden)

    C. W. Kwon

    2003-01-01

    much different from that of traditional crystalline ones because of their significant ‘surface effects’. In connection with that, the nanocrystalline cathode materials are reported to have an enhanced electrochemical activity when the first significative electrochemical step is insertion of Li ions (discharge process. The “electrochemical grafting” concept will be given as a plausible explanation. As illustrative examples, electrochemical behaviors of nanocrystalline manganese oxydes are presented.

  8. Reversal of exchange bias in nanocrystalline antiferromagnetic-ferromagnetic bilayers

    International Nuclear Information System (INIS)

    Prados, C; Pina, E; Hernando, A; Montone, A

    2002-01-01

    The sign of the exchange bias in field cooled nanocrystalline antiferromagnetic-ferromagnetic bilayers (Co-O and Ni-O/permalloy) is reversed at temperatures approaching the antiferromagnetic (AFM) blocking temperature. A similar phenomenon is observed after magnetic training processes at similar temperatures. These effects can be explained assuming that the boundaries of nanocrystalline grains in AFM layers exhibit lower transition temperatures than grain cores

  9. Influence of cobalt doping on structural and magnetic properties of BiFeO{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Khan, U. [Chinese Academy of Sciences, Institute of Physics (China); Adeela, N., E-mail: adeela16@gmail.com [Centre for High Energy Physics, University of the Punjab (Pakistan); Javed, K. [Chinese Academy of Sciences, Institute of Physics (China); Riaz, S. [Centre for Solid State Physics, University of the Punjab (Pakistan); Ali, H. [Chinese Academy of Sciences, Institute of Physics (China); Iqbal, M. [Centre for High Energy Physics, University of the Punjab (Pakistan); Han, X. F. [Chinese Academy of Sciences, Institute of Physics (China); Naseem, S., E-mail: shahzad-naseem@yahoo.com [Centre for Solid State Physics, University of the Punjab (Pakistan)

    2015-11-15

    Nanocrystalline cobalt-doped bismuth ferrites with general formula of BiFe{sub 1−δ}Co{sub δ}O{sub 3} (0 ≤ δ ≤ 0.1) have been synthesized using solution evaporation method. Structure and phase identification was performed with X-ray diffraction (XRD) technique. The results confirm the formation of rhombohedral-distorted Perovskite structure with R3c symmetry. A decrease in lattice parameters and an increase in X-ray density have been observed with increasing cobalt concentration in BiFeO{sub 3}. Particle size determined by transmission electron microscope was in good agreement with XRD, i.e., 39 nm. Room-temperature coercivity and saturation magnetization of nanoparticles were increased up to 7.5 % of cobalt doping. Low-temperature magnetic measurements of selected sample showed increasing behavior in saturation magnetization, coercivity, effective magnetic moments, and anisotropy constant. An increase in coercivity with decrease in temperature followed theoretical model of Kneller’s law, while modified Bloch’s model was employed for saturation magnetization in temperature range of 5–300 K.Graphical Abstract.

  10. Size dependence of elastic mechanical properties of nanocrystalline aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wenwu; Dávila, Lilian P., E-mail: ldavila@ucmerced.edu

    2017-04-24

    The effect of grain size on the elastic mechanical properties of nanocrystalline pure metal Al is quantified by molecular dynamics simulation method. In this work, the largest nanocrystalline Al sample has a mean grain size of 29.6 nm and contains over 100 millions atoms in the modeling system. The simulation results show that the elastic properties including elastic modulus and ultimate tensile strength of nanocrystalline Al are relatively insensitive to the variation of mean grain size above 13 nm yet they become distinctly grain size dependent below 13 nm. Moreover, at a grain size <13 nm, the elastic modulus decreases monotonically with decreasing grain size while the ultimate tensile strength of nanocrystalline Al initially decreases with the decrease of the grain size down to 9 nm and then increases with further reduction of grain size. The increase of ultimate tensile strength below 9 nm is believed to be a result of an extended elasticity in the ultrafine grain size nanocrystalline Al. This study can facilitate the prediction of varied mechanical properties for similar nanocrystalline materials and even guide testing and fabrication schemes of such materials.

  11. Nanocrystalline Steels’ Resistance to Hydrogen Embrittlement

    Directory of Open Access Journals (Sweden)

    Skołek E.

    2015-04-01

    Full Text Available The aim of this study is to determine the susceptibility to hydrogen embrittlement in X37CrMoV5-1 steel with two different microstructures: a nanocrystalline carbide-free bainite and tempered martensite. The nanobainitic structure was obtained by austempering at the bainitic transformation zone. It was found, that after hydrogen charging, both kinds of microstructure exhibit increased yield strength and strong decrease in ductility. It has been however shown that the resistance to hydrogen embrittlement of X37CrMoV5-1 steel with nanobainitic structure is higher as compared to the tempered martensite. After hydrogen charging the ductility of austempered steel is slightly higher than in case of quenched and tempered (Q&T steel. This effect was interpreted as a result of phase composition formed after different heat treatments.

  12. Limitation of biocompatibility of hydrated nanocrystalline hydroxyapatite

    Science.gov (United States)

    Minaychev, V. V.; Teleshev, A. T.; Gorshenev, V. N.; Yakovleva, M. A.; Fomichev, V. A.; Pankratov, A. S.; Menshikh, K. A.; Fadeev, R. S.; Fadeeva, I. S.; Senotov, A. S.; Kobyakova, M. I.; Yurasova, Yu B.; Akatov, V. S.

    2018-04-01

    Nanostructured hydroxyapatite (HA) in the form of hydrated paste is considered to be a promising material for a minor-invasive surgical curing of bone tissue injure. However questions about adhesion of cells on this material and its biocompatibility still remain. In this study biocompatibility of paste-formed nanosized HA (nano-HA) by in vitro methods is investigated. Nano-HA (particles sized about 20 nm) was synthesized under conditions of mechano-acoustic activation of an aqueous reaction mixture of ammonium hydrophosphate and calcium nitrate. It was ascertained that nanocrystalline paste was not cytotoxic although limitation of adhesion, spreading and growth of the cells on its surface was revealed. The results obtained point on the need of modification of hydrated nano-HA in the aims of increasing its biocompatibility and osteoplastic potential.

  13. Stability of nanocrystalline electrochemically deposited layers

    DEFF Research Database (Denmark)

    Pantleon, Karen; Somers, Marcel A. J.

    2009-01-01

    have different microstructure and properties compared to bulk materials and the thermodynamic non-equilibrium state of as-deposited layers frequently results in changes of the microstructure as a function of time and/or temperature. The evolving microstructure affects the functionality and reliability......The technological demand for manufacturing components with complex geometries of micrometer or sub-micrometer dimensions and ambitions for ongoing miniaturization have attracted particular attention to electrochemical deposition methods. Thin layers of electrochemically deposited metals and alloys...... of electrodeposited components, which can be beneficial, as for the electrical conductivity of copper interconnect lines, or detrimental, as for reduced strength of nickel in MEMS applications. The present work reports on in-situ studies of the microstructure stability of as-deposited nanocrystalline Cu-, Ag- and Ni...

  14. Application Potential of Nanocrystalline Ribbons Still Pending

    Science.gov (United States)

    Butvin, Pavol; Butvinová, Beata; Švec, Peter; Sitek, Jozef

    2010-09-01

    Nanocrystalline soft-magnetic ribbons promised a wide-spread practical use when introduced at the beginning of nineties. After 20 years of extensive research there are still unclear material problems which are thought to be the principal reason why these materials show but marginal use. Poorly controllable magnetic anisotropy due to spontaneous intrinsic macroscopic stress that comes from an inevitable heterogeneity of the ribbon materials is pointed to in this work. Certain stress-based mechanisms are shown to induce the unintended anisotropy in the already familiar Finemets as well as in the newer Hitperms. Hysteresis loops, domain structure and power loss is used to reveal the anisotropy consequences and particular connected but still unanswered questions are pinpointed.

  15. Reinforced plastics and aerogels by nanocrystalline cellulose

    Energy Technology Data Exchange (ETDEWEB)

    Leung, Alfred C. W.; Lam, Edmond; Chong, Jonathan; Hrapovic, Sabahudin; Luong, John H. T., E-mail: john.luong@cnrc-nrc.gc.ca [National Research Council Canada (Canada)

    2013-05-15

    Nanocrystalline cellulose (NCC), a rigid rod-like nanoscale material, can be produced from cellulosic biomass in powder, liquid, or gel forms by acid and chemical hydrolysis. Owing to its unique and exceptional physicochemical properties, the incorporation of a small amount of NCC into plastic enhances the mechanical strength of the latter by several orders of magnitudes. Carbohydrate-based NCC poses no serious environmental concerns, providing further impetus for the development and applications of this green and renewable biomaterial to fabricate lightweight and biodegradable composites and aerogels. Surface functionalization of NCC remains the main focus of NCC research to tailor its properties for dispersion in hydrophilic or hydrophobic media. It is of uttermost importance to develop tools and protocols for imaging of NCC in a complex matrix and quantify its reinforcement effect.

  16. Nanocrystalline diamond coatings for mechanical seals applications.

    Science.gov (United States)

    Santos, J A; Neto, V F; Ruch, D; Grácio, J

    2012-08-01

    A mechanical seal is a type of seal used in rotating equipment, such as pumps and compressors. It consists of a mechanism that assists the connection of the rotating shaft to the housings of the equipments, preventing leakage or avoiding contamination. A common cause of failure of these devices is end face wear out, thus the use of a hard, smooth and wear resistant coating such as nanocrystalline diamond would be of great importance to improve their working performance and increase their lifetime. In this paper, different diamond coatings were deposited by the HFCVD process, using different deposition conditions. Additionally, the as-grown films were characterized for, quality, morphology and microstructure using scanning electron microscopy (SEM) and Raman spectroscopy. The topography and the roughness of the films were characterized by atomic force microscopy (AFM).

  17. Arsenic removal by magnetic nanocrystalline barium hexaferrite

    International Nuclear Information System (INIS)

    Patel, Hasmukh A.; Byun, Jeehye; Yavuz, Cafer T.

    2012-01-01

    Nanoscale magnetite (Fe 3 O 4 ) ( 12 O 19 , BHF) is a well-known permanent magnet (i.e., fridge magnets) and attractive due to its low cost in making large quantities. BHF offers a viable alternative to magnetite nanocrystals for arsenic removal since it features surfaces similar to iron oxides but with much enhanced magnetism. Herein, we employ BHF nanocrystalline materials for the first time in arsenic removal from wastewater. Our results show better (75 %) arsenic removal than magnetite of the similar sizes. The BHF nanoparticles, 6.06 ± 0.52 nm synthesized by thermolysis method at 320 °C do not show hexagonal phase, however, subsequent annealing at 750 °C produced pure hexagonal BHF in >200 nm assemblies. By using BHF, we demonstrate that nanoparticle removal is more efficient and fixed bed type cartridge applications are more possible.

  18. Effect of calcinations temperature on the luminescence intensity and fluorescent lifetime of Tb3+-doped hydroxyapatite (Tb-HA nanocrystallines

    Directory of Open Access Journals (Sweden)

    Hairong Yin

    2017-06-01

    Full Text Available Hydroxyapatite luminescent nanocrystallines doped with 6 mol.% Tb3+ (Tb-HA were prepared via chemical deposition method and calcined at different temperature, and the effects of calcinations temperature on the luminescence intensity and fluorescent lifetime were studied. TEM image of Tb-HA revealed that the shape of nanocrystallines changed from needle-like to short rod-like and sphere-like with the increase of calcinations temperature; while the particles sizes decreased from 190 nm to 110 nm. The crystallinity degree increased. The typical emission peaks attributed to Tb3+ ions were observed in emission spectra of 6 mol.% Tb-HA under 378 nm excitation. The luminescent intensity of Tb-HA, which showed the fluorescence quenching, firstly enhanced and then decreased at 700 °C; while the fluorescent lifetime increased firstly and then decreased after 600 °C. Furthermore, the ratio of intensity between 545 nm and 490 nm corresponding to electric-dipole and magnetic-dipole transition (IR: IO increases firstly and then decreases, which revealed that the proportion of substitute type and site of Ca2+ ions by Tb3+ ions were helpful to realize the substitute process and functional structure design.

  19. Functionalization of nanocrystalline diamond films with phthalocyanines

    Energy Technology Data Exchange (ETDEWEB)

    Petkov, Christo [Institute of Nanostructure Technologies and Analytics (INA), Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel (Germany); Reintanz, Philipp M. [Institute of Chemistry, Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel (Germany); Kulisch, Wilhelm [Institute of Nanostructure Technologies and Analytics (INA), Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel (Germany); Degenhardt, Anna Katharina [Institute of Chemistry, Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel (Germany); Weidner, Tobias [Max Planck Institute for Polymer Research, Mainz (Germany); Baio, Joe E. [School of Chemical, Biological and Environmental Engineering, Oregon State University, Corvallis, OR (United States); Merz, Rolf; Kopnarski, Michael [Institut für Oberflächen- und Schichtanalytik (IFOS), Kaiserslautern (Germany); Siemeling, Ulrich [Institute of Chemistry, Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel (Germany); Reithmaier, Johann Peter [Institute of Nanostructure Technologies and Analytics (INA), Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel (Germany); Popov, Cyril, E-mail: popov@ina.uni-kassel.de [Institute of Nanostructure Technologies and Analytics (INA), Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel (Germany)

    2016-08-30

    Highlights: • Grafting of phthalocyanines on nanocrystalline diamond films with different terminations. • Pc with different central atoms and side chains synthesized and characterized. • Attachment of Pc on H- and O-terminated NCD studied by XPS and NEXAFS spectroscopy. • Orientation order of phthalocyanine molecules on NCD surface. - Abstract: Phthalocyanine (Pc) derivatives containing different central metal atoms (Mn, Cu, Ti) and different peripheral chains were synthesized and comprehensively characterized. Their interaction with nanocrystalline diamond (NCD) films, as-grown by hot-filament chemical vapor deposition or after their modification with oxygen plasma to exchange the hydrogen termination with oxygen-containing groups, was studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The elemental composition as determined by XPS showed that the Pc were grafted on both as-grown and O-terminated NCD. Mn, Cu and Ti were detected together with N stemming from the Pc ring and S in case of the Ti-Pc from the peripheral ligands. The results for the elemental surface composition and the detailed study of the N 1s, S 2p and O 1s core spectra revealed that Ti-Pc grafted better on as-grown NCD but Cu-Pc and Mn-Pc on O-terminated films. Samples of Mn-Pc on as-grown and O-terminated NCD were further investigated by NEXAFS spectroscopy. The results showed ordering of the grafted molecules, laying flat on the H-terminated NCD surface while only the macrocycles were oriented parallel to the O-terminated surface with the peripheral chains perpendicular to it.

  20. Nickel acts as an adjuvant during cobalt sensitization

    DEFF Research Database (Denmark)

    Bonefeld, Charlotte Menne; Nielsen, Morten Milek; Vennegaard, Marie T.

    2015-01-01

    Metal allergy is the most frequent form of contact allergy with nickel and cobalt being the main culprits. Typically, exposure comes from metal-alloys where nickel and cobalt co-exist. Importantly, very little is known about how co-exposure to nickel and cobalt affects the immune system. We...... investigated these effects by using a recently developed mouse model. Mice were epicutaneously sensitized with i) nickel alone, ii) nickel in the presence of cobalt, iii) cobalt alone, or iv) cobalt in the presence of nickel, and then followed by challenge with either nickel or cobalt alone. We found...... that sensitization with nickel alone induced more local inflammation than cobalt alone as measured by increased ear-swelling. Furthermore, the presence of nickel during sensitization to cobalt led to a stronger challenge response to cobalt as seen by increased ear-swelling and increased B and T cell responses...

  1. Electroformed Nanocrystalline Coatings: An Advanced Alternative to Hard Chrome Electroplating

    Science.gov (United States)

    2003-11-21

    100mL/min. The vials were then analyzed for any traces of cobalt, iron, chloride, sulphate, and for two additives. A summary of the emission results...observed that correspond to cobalt- phosphites , indicating that the phosphorus is present in the deposits in a solid solution state (similar to XRD...precipitation of cobalt- phosphites from the supersaturated solid solution at elevated temperatures. Figure 4-2 shows the variation in hardness as a

  2. Cobalt-60 production in CANDU power reactors

    International Nuclear Information System (INIS)

    Slack, J.; Norton, J.L.; Malkoske, G.R.

    2003-01-01

    MDS Nordion has been supplying cobalt-60 sources to industry for industrial and medical purposes since 1946. These cobalt-60 sources are used in many market and product segments. The major application is in the health care industry where irradiators are used to sterilize single use medical products. These irradiators are designed and built by MDS Nordion and are used by manufacturers of surgical kits, gloves, gowns, drapes and other medical products. The irradiator is a large shielded room with a storage pool for the cobalt-60 sources. The medical products are circulated through the shielded room and exposed to the cobalt-60 sources. This treatment sterilizes the medical products which can then be shipped to hospitals for immediate use. Other applications for this irradiation technology include sanitisation of cosmetics, microbial reduction of pharmaceutical raw materials and food irradiation. The cobalt-60 sources are manufactured by MDS Nordion in their Cobalt Operations Facility in Kanata. More than 75,000 cobalt-60 sources for use in irradiators have been manufactured by MDS Nordion. The cobalt-60 sources are double encapsulated in stainless steel capsules, seal welded and helium leak tested. Each source may contain up to 14,000 curies. These sources are shipped to over 170 industrial irradiators around the world. This paper will focus on the MDS Nordion proprietary technology used to produce the cobalt-60 isotope in CANDU reactors. Almost 55 years ago MDS Nordion and Atomic Energy of Canada developed the process for manufacturing cobalt-60 at the Chalk River Labs, in Ontario, Canada. A cobalt-59 target was introduced into a research reactor where the cobalt-59 atom absorbed one neutron to become cobalt-60. Once the cobalt-60 material was removed from the research reactor it was encapsulated in stainless steel and seal welded using a Tungsten Inert Gas weld. The first cobalt-60 sources manufactured using material from the Chalk River Labs were used in cancer

  3. Cobalt-60 production in CANDU power reactors

    International Nuclear Information System (INIS)

    Malkoske, G.R.; Norton, J.L.; Slack, J.

    2002-01-01

    MDS Nordion has been supplying cobalt-60 sources to industry for industrial and medical purposes since 1946. These cobalt-60 sources are used in many market and product segments, but are primarily used to sterilize single-use medical products including; surgical kits, gloves, gowns, drapes, and cotton swabs. Other applications include sanitization of cosmetics, microbial reduction of pharmaceutical raw materials, and food irradiation. The technology for producing the cobalt-60 isotope was developed by MDS Nordion and Atomic Energy of Canada Limited (AECL) almost 55 years ago using research reactors at the AECL Chalk River Laboratories in Ontario, Canada. The first cobalt-60 source produced for medical applications was manufactured by MDS Nordion and used in cancer therapy. The benefits of cobalt-60 as applied to medical product manufacturing, were quickly realized and the demand for this radioisotope quickly grew. The same technology for producing cobalt-60 in research reactors was then designed and packaged such that it could be conveniently transferred to a utility/power reactor. In the early 1970's, in co-operation with Ontario Power Generation (formerly Ontario Hydro), bulk cobalt-60 production for industrial irradiation applications was initiated in the four Pickering A CANDU reactors. As the demand and acceptance of sterilization of medical products grew, MDS Nordion expanded its bulk supply by installing the proprietary Canadian technology for producing cobalt-60 in additional CANDU reactors. CANDU is unique among the power reactors of the world, being heavy water moderated and fuelled with natural uranium. They are also designed and supplied with stainless steel adjusters, the primary function of which is to shape the neutron flux to optimize reactor power and fuel bum-up, and to provide excess reactivity needed to overcome xenon-135 poisoning following a reduction of power. The reactor is designed to develop full power output with all of the adjuster

  4. Influence of cobalt content on the structure and hard magnetic properties of nanocomposite (Fe,Co)-Pt-B alloys

    Energy Technology Data Exchange (ETDEWEB)

    Grabias, A., E-mail: agnieszka.grabias@itme.edu.pl [Institute of Electronic Materials Technology, Wólczyńska 133, 01-919 Warsaw (Poland); Kopcewicz, M. [Institute of Electronic Materials Technology, Wólczyńska 133, 01-919 Warsaw (Poland); Latuch, J.; Oleszak, D. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Pękała, M. [Department of Chemistry, University of Warsaw, Al. Żwirki i Wigury 101, 02-089 Warsaw (Poland); Kowalczyk, M. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland)

    2017-07-15

    Highlights: • Nanocomposite alloys were formed by annealing of the rapidly quenched alloys. • Magnetically hard L1{sub 0} (Fe,Co)Pt and soft (Fe,Co){sub 2}B or (Fe,Co)B were formed. • Mössbauer spectra revealed Co substitution for Fe in L1{sub 0} FePt, FeB and Fe{sub 2}B phases. • Annealed alloys exhibit hard magnetic properties which depend on phase compositions. • Co addition was found to decrease the magnetization and the energy product. - Abstract: The influence of Co content on the structural and hard magnetic properties of two sets of nanocrystalline Fe{sub 52−x}Co{sub x}Pt{sub 28}B{sub 20} (x = 0–26) and Fe{sub 60−y}Co{sub y}Pt{sub 25}B{sub 15} (y = 0–40) alloys was studied. The alloys were prepared as ribbons by the rapid quenching technique. The nanocomposite structure in the alloys was obtained by annealing at 840–880 K for 30 min. Structural characterization of the samples was performed using the Mössbauer spectroscopy and X-ray diffraction. Magnetic properties of the samples were studied by the measurements of the hysteresis loops and of the magnetization at increasing temperatures. An amorphous phase prevailed in the as-quenched Fe{sub 52−x}Co{sub x}Pt{sub 28}B{sub 20} alloys while a disordered solid solution of fcc-(Fe,Co)Pt was a dominating phase in the Fe{sub 60−y}Co{sub y}Pt{sub 25}B{sub 15} ribbons. Differential scanning calorimetry measurements revealed one or two exothermic peaks at temperatures up to 993 K, depending on the composition of the alloys. Thermal treatment of the samples led to the formation of the magnetically hard ordered L1{sub 0} tetragonal (Fe,Co)Pt nanocrystallites and magnetically softer phases of (Fe,Co)B (for Fe{sub 52−x}Co{sub x}Pt{sub 28}B{sub 20}) or (Fe,Co){sub 2}B (for Fe{sub 60−y}Co{sub y}Pt{sub 25}B{sub 15}). Detailed Mössbauer spectroscopy studies revealed that cobalt substituted for iron in both the L1{sub 0} phase and in iron borides. The nanocomposite Fe{sub 60−y}Co{sub y

  5. The cobalt-mediated [2+2+2]cycloaddition of thiophenes and benzofurans to alkynes

    Energy Technology Data Exchange (ETDEWEB)

    Malaska, M.J.

    1991-01-01

    The cobalt-mediated [2+2+2]cycloaddition of thiophenes and benzofurans to alkynes was investigated. The cocyclization of 2-propynyloxymethylthiophenes provided two types of cyclohexadiene complexes. It was found that one of these complexes could be converted to the other by a thermal rearrangement. This novel transformation was investigated by deuterium-labelling and kinetic studies, and a mechanism was proposed. The complexes could be oxidatively demetallated to provide the liberated organic framework. Further reorganization of these dienes were observed during the decomplexation process and in the presence of CpCo(C[sub 2]H[sub 4])[sub 2]. In this manner several new heterocyclic ring systems could be constructed from 2-substituted thiophenes. Following the success of the thiophene cyclizations, the cocyclization of the benzofuran nucleus was examined. Reagents and conditions were developed that provide an efficient synthesis of alkynols from carboxylic acids; other functional group interconversions of the alkynols were briefly studied. The synthesis and cyclization of 1-[7-methoxy-4-benzofuranyl]-3-butyn-2-ol produced a cobalt complex containing the A,B,C, and D rings of the morphine skeleton. A synthetic advantage of this methodology would be the ease of substitution at pharmaco-logically relevant C-6 and C-7 positions of the morphine framework. Synthetic routes using a cobalt cyclization strategy were proposed.

  6. Medicineringsfejl ved generisk substitution

    DEFF Research Database (Denmark)

    Rölfing, Jan

    2012-01-01

    Generic substitution is a major cause of medical mistakes in the general population. Danish legislation obligates pharmacies to substitute prescribed medicine with the cheapest equivalent formulation, despite variations in product name, packaging, shape and colour. Consequently, medical mistakes...... occur. Scientific evidence on the consequences of generic substitution is sparse. Call upon fellow health workers to report medical mistakes to the national entities and scientific peers, in order to increase awareness and scientific evidence about the problem....

  7. A phenomenological variational multiscale constitutive model for intergranular failure in nanocrystalline materials

    KAUST Repository

    Siddiq, A.; El Sayed, Tamer S.

    2013-01-01

    We present a variational multiscale constitutive model that accounts for intergranular failure in nanocrystalline fcc metals due to void growth and coalescence in the grain boundary region. Following previous work by the authors, a nanocrystalline

  8. Nickel and cobalt base alloys

    International Nuclear Information System (INIS)

    Houlle, P.

    1994-01-01

    Nickel base alloys have a good resistance to pitting, cavernous or cracks corrosion. Nevertheless, all the nickel base alloys are not equivalent. Some differences exit between all the families (Ni, Ni-Cu, Ni-Cr-Fe, Ni-Cr-Fe-Mo/W-Cu, Ni-Cr-Mo/W, Ni-Mo). Cobalt base alloys in corrosive conditions are generally used for its wear and cracks resistance, with a compromise to its localised corrosion resistance properties. The choice must be done from the perfect knowledge of the corrosive medium and of the alloys characteristics (chemical, metallurgical). A synthesis of the corrosion resistance in three medium (6% FeCl 3 , 4% NaCl + 1% HCl + 0.1% Fe 2 (SO 4 ) 3 , 11.5% H 2 SO 4 + 1.2% HCl + 1% Fe 2 (SO 4 ) 3 + 1% CuCl 2 ) is presented. (A.B.). 11 refs., 1 fig., 12 tabs

  9. Preparation of high purity cobalt

    International Nuclear Information System (INIS)

    Isshiki, M.; Fukuda, Y.; Igaki, K.

    1985-01-01

    A combination of anion exchange separation, electrolytic extraction, floating zone refining and dry hydrogen treatment was used to purify cobalt. The effectiveness of each purification process was confirmed by measurements of the residual resistivity ratio (RRR) and activation analyses. Proton activation analysis revealed that all the main metallic impurities except iron were effectively removed by a combination of these processes. The effective removal of oxygen, nitrogen and carbon by dry hydrogen treatment was confirmed by activation analyses using 3 He ion beams, proton beams and γ rays. It was found that the rate-controlling step in the decarburization process was a surface reaction. The maximum RRR obtained for the purified specimen was 334, which is higher than previously reported values. (Auth.)

  10. Cobalt bis(dicarbollides)(1-) covalently attached to the calyx[4]arene platform: the first combination of organic bowl-shaped matrices and inorganic metallaborane cluster anions

    NARCIS (Netherlands)

    Grüner, Bohumír; Mikulasek, Libor; Baca, Jirí; Cisarova, Ivana; Böhmer, Volker; Danila, Crenguta; Reinoso garcia, M.M.; Verboom, Willem; Reinhoudt, David; Casnati, Alessandro; Ungaro, Rocco

    2005-01-01

    Various calix[4]arene and resorc[4]arene ionic compounds substituted by cobalt bis(dicarbollide) anions (1) have been prepared for the first time. From tBu-calix[4]arene (A) the complete series of mono-, di-, tri- and tetrasubstituted derivatives bearing one to four cluster anions on the lower rim

  11. Cobalt-60 control in Ontario Hydro reactors

    International Nuclear Information System (INIS)

    Lacy, C.S.

    1988-01-01

    This paper discusses the impact of specifying reduced Cobalt-59 in the primary heat transport circuit materials of construction on the radiation fields developed around the primary circuit. An eight-fold reduction in steam generator radiation fields due to Cobalt-60 has been observed for two identical sets of reactors, one with and one without Cobalt-59 control. The comparison is between eight reactors at the Pickering Nuclear Generating Station (PNGS). Units 5 to 8 (PNGS-B) are identical to Units 1 to 4 (PNGS-A) except that PNGS-B has reduced impurity Cobalt-59 in the alloys of construction and a reduced use of stellite. The effects of chemistry control are also discussed

  12. Nano cobalt oxides for photocatalytic hydrogen production

    KAUST Repository

    Mangrulkar, Priti A.; Joshi, Meenal M.; Tijare, Saumitra N.; Polshettiwar, Vivek; Labhsetwar, Nitin K.; Rayalu, Sadhana Suresh

    2012-01-01

    of various operating parameters in hydrogen generation by nano cobalt oxide was then studied in detail. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  13. An elevator for cobalt-60 source

    International Nuclear Information System (INIS)

    Tang Zaimin; Liang Donghu

    1990-07-01

    The elevator used for cobalt-60 source is a key device in the irradiation industry. It plays an important role in the safety and control of irradiation operation as well as the utilization rate of radiation source. From 1983 to 1986, Beijing Institute of Nuclear Engineering undertook designing of various size irradiation projects for different uses. Since then a kind of cobalt-60 source elevator suited for the irradiator of wet-source-storage has been chosen. It is reliable in the operation and complete in the function. An automatic control circuit brings the systems of cobalt-60 source elevator into an interlock system which ensures the irradiation operation safety. Besides introducing the structural features and performance of this elevator, the conditions of safety interlocking in raising or lowering the cobalt-60 source is also discussed. The discussion is from the safety viewpoint of operating an irradiator and irradiation technology

  14. Transport properties of cobalt at low temperatures

    DEFF Research Database (Denmark)

    Radharkishna, P.; Nielsen, Mourits

    1965-01-01

    Measurements are made of electrical resistivity, absolute thermoelectric power, and thermal conductivity of polycrystalline cobalt between 1.2 and 6 K; results are discussed on basis of inter-electronic scattering.......Measurements are made of electrical resistivity, absolute thermoelectric power, and thermal conductivity of polycrystalline cobalt between 1.2 and 6 K; results are discussed on basis of inter-electronic scattering....

  15. COBALT COMPOUNDS AS ANTIDOTES FOR HYDROCYANIC ACID.

    Science.gov (United States)

    EVANS, C L

    1964-12-01

    The antidotal potency of a cobalt salt (acetate), of dicobalt edetate, of hydroxocobalamin and of cobinamide against hydrocyanic acid was examined mainly on mice and rabbits. All the compounds were active antidotes for up to twice the LD50; under some conditions for larger doses. The most successful was cobalt acetate for rabbits (5xLD50), which was effective at a molar cyanide/cobalt (CN/Co) ratio of 5, but had as a side-effect intense purgation. Hydroxocobalamin was irregular in action, but on the whole was most effective for mice (4.5xLD50 at a molar ratio of 1), and had no apparent side effects. Dicobalt edetate, at molar ratios of up to 2, was more effective for rabbits (3xLD50) than for mice (2xLD50), but had fewer side effects than cobalt acetate. The effect of thiosulphate was to augment the efficacy of dicobalt edetate and, in mice, that of hydroxocobalamin; but, apparently, in rabbits, to reduce that of hydroxocobalamin. Cobinamide, at a molar ratio of 1, was slightly more effective than hydroxocobalamin on rabbits and also less irregular in its action. Cobalt acetate by mouth was effective against orally administered hydrocyanic acid. The oxygen uptake of the body, reduced by cyanide, is rapidly reinstated when one of the cobalt antidotes has been successfully administered.

  16. Review: Plasma-enhanced chemical vapor deposition of nanocrystalline diamond

    Directory of Open Access Journals (Sweden)

    Katsuyuki Okada

    2007-01-01

    Full Text Available Nanocrystalline diamond films have attracted considerable attention because they have a low coefficient of friction and a low electron emission threshold voltage. In this paper, the author reviews the plasma-enhanced chemical vapor deposition (PE-CVD of nanocrystalline diamond and mainly focuses on the growth of nanocrystalline diamond by low-pressure PE-CVD. Nanocrystalline diamond particles of 200–700 nm diameter have been prepared in a 13.56 MHz low-pressure inductively coupled CH4/CO/H2 plasma. The bonding state of carbon atoms was investigated by ultraviolet-excited Raman spectroscopy. Electron energy loss spectroscopy identified sp2-bonded carbons around the 20–50 nm subgrains of nanocrystalline diamond particles. Plasma diagnostics using a Langmuir probe and the comparison with plasma simulation are also reviewed. The electron energy distribution functions are discussed by considering different inelastic interaction channels between electrons and heavy particles in a molecular CH4/H2 plasma.

  17. Thermodynamic and experimental study on phase stability in nanocrystalline alloys

    International Nuclear Information System (INIS)

    Xu Wenwu; Song Xiaoyan; Lu Nianduan; Huang Chuan

    2010-01-01

    Nanocrystalline alloys exhibit apparently different phase transformation characteristics in comparison to the conventional polycrystalline alloys. The special phase stability and phase transformation behavior, as well as the essential mechanisms of the nanocrystalline alloys, were described quantitatively in a nanothermodynamic point of view. By introducing the relationship between the excess volume at the grain boundary and the nanograin size, the Gibbs free energy was determined distinctly as a function of temperature and the nanograin size. Accordingly, the grain-size-dependence of the phase stability and phase transformation characteristics of the nanocrystalline alloy were calculated systematically, and the correlations between the phase constitution, the phase transformation temperature and the critical nanograin size were predicted. A series of experiments was performed to investigate the phase transformations at room temperature and high temperatures using the nanocrystalline Sm 2 Co 17 alloy as an example. The phase constitution and phase transformation sequence found in nanocrystalline Sm 2 Co 17 alloys with various grain-size levels agree well with the calculations by the nanothermodynamic model.

  18. Cobalt release from inexpensive jewellery: has the use of cobalt replaced nickel following regulatory intervention?

    DEFF Research Database (Denmark)

    Thyssen, Jacob Pontoppidan; Jellesen, Morten S; Menné, Torkil

    2010-01-01

    Before the introduction of the EU Nickel Directive, concern was raised that manufacturers of jewellery might turn from the use of nickel to cobalt following the regulatory intervention on nickel exposure.......Before the introduction of the EU Nickel Directive, concern was raised that manufacturers of jewellery might turn from the use of nickel to cobalt following the regulatory intervention on nickel exposure....

  19. Synthesis of new cobalt aluminophosphate framework by opening a cobalt methylphosphonate layered material

    Czech Academy of Sciences Publication Activity Database

    Zaarour, M.; Pérez, O.; Boullay, P.; Martens, J.; Mihailova, B.; Karaghiosoff, K.; Palatinus, Lukáš; Mintova, S.

    2017-01-01

    Roč. 19, č. 34 (2017), s. 5100-5105 ISSN 1466-8033 Institutional support: RVO:68378271 Keywords : cobalt aluminophosphate * cobalt methylphosphonate * layered materials * crystallic structure * X-ray diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.474, year: 2016

  20. AN ELECTROPLATING METHOD OF FORMING PLATINGS OF NICKEL, COBALT, NICKEL ALLOYS OR COBALT ALLOYS

    DEFF Research Database (Denmark)

    1997-01-01

    An electroplating method of forming platings of nickel, cobalt, nickel alloys or cobalt alloys with reduced stresses in an electrodepositing bath of the type: Watt's bath, chloride bath or a combination thereof, by employing pulse plating with periodic reverse pulse and a sulfonated naphthalene...

  1. Control of carbon nanotube growth using cobalt nanoparticles as catalyst

    International Nuclear Information System (INIS)

    Huh, Yoon; Green, Malcolm L.H.; Kim, Young Heon; Lee, Jeong Yong; Lee, Cheol Jin

    2005-01-01

    We have controllably grown carbon nanotubes using uniformly distributed cobalt nanoparticles as catalyst. Cobalt nanoparticles with a uniform size were synthesized by chemical reaction and colloidal solutions including the cobalt nanoparticles were prepared. The cobalt nanoparticles were uniformly distributed on silicon substrates by a spin-coating method. Carbon nanotubes with a uniform diameter were synthesized on the cobalt nanoparticles by thermal chemical vapor deposition of acetylene gas. The density and vertical alignment of carbon nanotubes could be controlled by adjusting the density of cobalt (Co) nanoparticles

  2. Characterisation of Suspension Precipitated Nanocrystalline Hydroxyapatite Powders

    International Nuclear Information System (INIS)

    Mallik, P K; Swain, P.K.; Patnaik, S.C

    2016-01-01

    Hydroxyapatite (HA) is a well-known biomaterial for coating on femoral implants, filling of dental cavity and scaffold for tissue replacement. Hydroxyapatite possess limited load bearing capacity due to their brittleness. In this paper, the synthesis of nanocrystalline hydroxyapatite powders was prepared by dissolving calcium oxide in phosphoric acid, followed by addition of ammonia liquor in a beaker. The prepared solution was stirred by using magnetic stirrer operated at temperature of 80°C for an hour. This leads to the formation of hydroxyapatite precipitate. The precipitate was dried in oven for overnight at 100°C. The dried agglomerated precipitate was calcined at 800°C in conventional furnace for an hour. The influence of calcium oxide concentration and pH on the resulting precipitates was studied using BET, XRD and SEM. As result, a well-defined sub-rounded morphology of powders size of ∼41 nm was obtained with a salt concentration of 0.02 M. Finally, it can be concluded that small changes in the reaction conditions led to large changes in final size, shape and degree of aggregation of the hydroxyapatite particles. (paper)

  3. Thermally Stimulated Currents in Nanocrystalline Titania

    Directory of Open Access Journals (Sweden)

    Mara Bruzzi

    2018-01-01

    Full Text Available A thorough study on the distribution of defect-related active energy levels has been performed on nanocrystalline TiO2. Films have been deposited on thick-alumina printed circuit boards equipped with electrical contacts, heater and temperature sensors, to carry out a detailed thermally stimulated currents analysis on a wide temperature range (5–630 K, in view to evidence contributions from shallow to deep energy levels within the gap. Data have been processed by numerically modelling electrical transport. The model considers both free and hopping contribution to conduction, a density of states characterized by an exponential tail of localized states below the conduction band and the convolution of standard Thermally Stimulated Currents (TSC emissions with gaussian distributions to take into account the variability in energy due to local perturbations in the highly disordered network. Results show that in the low temperature range, up to 200 K, hopping within the exponential band tail represents the main contribution to electrical conduction. Above room temperature, electrical conduction is dominated by free carriers contribution and by emissions from deep energy levels, with a defect density ranging within 1014–1018 cm−3, associated with physio- and chemi-sorbed water vapour, OH groups and to oxygen vacancies.

  4. Arsenic removal by magnetic nanocrystalline barium hexaferrite

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Hasmukh A.; Byun, Jeehye; Yavuz, Cafer T., E-mail: yavuz@kaist.ac.kr [Graduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST) (Korea, Republic of)

    2012-07-15

    Nanoscale magnetite (Fe{sub 3}O{sub 4}) (<15 nm) is known to remove arsenic efficiently but is very difficult to separate or require high magnetic fields to separate out from the waste water after treatment. Anisotropic hexagonal ferrite (BaFe{sub 12}O{sub 19}, BHF) is a well-known permanent magnet (i.e., fridge magnets) and attractive due to its low cost in making large quantities. BHF offers a viable alternative to magnetite nanocrystals for arsenic removal since it features surfaces similar to iron oxides but with much enhanced magnetism. Herein, we employ BHF nanocrystalline materials for the first time in arsenic removal from wastewater. Our results show better (75 %) arsenic removal than magnetite of the similar sizes. The BHF nanoparticles, 6.06 {+-} 0.52 nm synthesized by thermolysis method at 320 Degree-Sign C do not show hexagonal phase, however, subsequent annealing at 750 Degree-Sign C produced pure hexagonal BHF in >200 nm assemblies. By using BHF, we demonstrate that nanoparticle removal is more efficient and fixed bed type cartridge applications are more possible.

  5. Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

    International Nuclear Information System (INIS)

    Qi, B.; Andrew, J. S.; Arnold, D. P.

    2017-01-01

    This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe_6_6Co_3_4) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe_2O_4) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

  6. Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

    Energy Technology Data Exchange (ETDEWEB)

    Qi, B. [University of Florida, Interdisciplinary Microsystems Group, Department of Electrical and Computer Engineering (United States); Andrew, J. S. [University of Florida, Department of Materials Science and Engineering (United States); Arnold, D. P., E-mail: darnold@ufl.edu [University of Florida, Interdisciplinary Microsystems Group, Department of Electrical and Computer Engineering (United States)

    2017-03-15

    This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe{sub 66}Co{sub 34}) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

  7. Nanocrystalline and ultrafine grain copper obtained by mechanical attrition

    Directory of Open Access Journals (Sweden)

    Rodolfo Rodríguez Baracaldo

    2010-01-01

    Full Text Available This article presents a method for the sample preparation and characterisation of bulk copper having grain size lower than 1 μm (ultra-fine grain and lower than 100 nm grain size (nanocrystalline. Copper is initially manufactured by a milling/alloying me- chanical method thereby obtaining a powder having a nanocrystalline structure which is then consolidated through a process of warm compaction at high pressure. Microstructural characterisation of bulk copper samples showed the evolution of grain size during all stages involved in obtaining it. The results led to determining the necessary conditions for achieving a wide range of grain sizes. Mechanical characterisation indicated an increase in microhardness to values of around 3.40 GPa for unconsolida- ted nanocrystalline powder. Compressivee strength was increased by reducing the grain size, thereby obtaining an elastic limit of 650 MPa for consolidated copper having a ~ 62 nm grain size.

  8. Creep behavior of a nanocrystalline Fe-B-Si alloy

    International Nuclear Information System (INIS)

    Xiao, M.; Kong, Q.P.

    1997-01-01

    The research of nanocrystalline materials has attracted much attention in the world. In recent years, there have been several studies on their creep behavior. Among these, the authors have studied the tensile creep of a nanocrystalline Ni-P alloy (28 nm) at temperatures around 0.5 Tm (Tm is the melting point). The samples were prepared by the method of crystallization of amorphous ribbon. Based on the data of stress exponent and activation energy, they suggested that the creep was controlled by boundary diffusion; while the creep of the same alloy with a larger grain size (257 nm) was controlled by a different mechanism. In the present paper, the authors extend the research to the creep of a nanocrystalline Fe-B-Si alloy. The samples are also prepared by crystallization of amorphous ribbon. The samples such prepared have an advantage that the interfaces are naturally formed without artificial compaction and porosity

  9. Ferromagnetism appears in nitrogen implanted nanocrystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Remes, Zdenek [Institute of Physics ASCR v.v.i., Cukrovarnicka 10, 162 00 Prague 6 (Czech Republic); Sun, Shih-Jye, E-mail: sjs@nuk.edu.tw [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan (China); Varga, Marian [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan (China); Chou, Hsiung [Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Hsu, Hua-Shu [Department of Applied Physics, National Pingtung University of Education, Pingtung 900, Taiwan (China); Kromka, Alexander [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan (China); Horak, Pavel [Nuclear Physics Institute, 250 68 Rez (Czech Republic)

    2015-11-15

    The nanocrystalline diamond films turn to be ferromagnetic after implanting various nitrogen doses on them. Through this research, we confirm that the room-temperature ferromagnetism of the implanted samples is derived from the measurements of magnetic circular dichroism (MCD) and superconducting quantum interference device (SQUID). Samples with larger crystalline grains as well as higher implanted doses present more robust ferromagnetic signals at room temperature. Raman spectra indicate that the small grain-sized samples are much more disordered than the large grain-sized ones. We propose that a slightly large saturated ferromagnetism could be observed at low temperature, because the increased localization effects have a significant impact on more disordered structure. - Highlights: • Nitrogen implanted nanocrystalline diamond films exhibit ferromagnetism at room temperature. • Nitrogen implants made a Raman deviation from the typical nanocrystalline diamond films. • The ferromagnetism induced from the structure distortion is dominant at low temperature.

  10. Correlation of thermodynamics and grain growth kinetics in nanocrystalline metals

    International Nuclear Information System (INIS)

    Song Xiaoyan; Zhang Jiuxing; Li Lingmei; Yang Keyong; Liu Guoquan

    2006-01-01

    We investigated the correlation of thermodynamics and grain growth kinetics of nanocrystalline metals both theoretically and experimentally. A model was developed to describe the thermodynamic properties of nanograin boundaries, which could give reliable predictions in the destabilization characteristics of nanograin structures and the slowing down of grain growth kinetics at a constant temperature. Both the temperature-varying and isothermal nanograin growth behaviors in pure nanocrystalline Co were studied to verify the thermodynamic predictions. The experimental results showing that discontinuous nanograin growth takes place at a certain temperature and grain growth rate decreases monotonically with time confirm our thermodynamics-based description of nanograin growth characteristics. Therefore, we propose a thermodynamic viewpoint to explain the deviation of grain growth kinetics in nanocrystalline metals from those of polycrystalline materials

  11. Effet de la substitution du cuivre par du lithium sur les proprietes de l'oxyde spinelle lithium(x)cuivre(y-x)cobalt(3-y)oxygen(4) etudie pour l'electrocatalyse de la reaction de degagement de l'oxygene en milieu alcalin

    Science.gov (United States)

    Fatih, Khalid

    L'electrolyse de l'eau demeure la seule technologie industrielle de generation de l'hydrogene et de l'oxygene tres purs sans rejet de CO2 dans l'atmosphere, ce qui le rend tres attrayant par rapport a la combustion de carburants fossiles qui provoque presentement de serieux problemes environnementaux. Dans le but d'ameliorer le rendement de ce procede, nous avons developpe de nouveaux materiaux d'anode peu couteux, a base de l'oxyde mixte CuyCo3-yO 4, qui possedent une cinetique rapide pour la reaction de degagement de l'oxygene (RDO). Cette reaction suscite un interet particulier en raison de la surtension d'activation relativement elevee a l'anode qui cause la principale perte de rendement du procede. Une etude systematique a ete effectuee sur la substitution du Cu par du Li (0 a 40%), afin d'elucider les proprietes electrocatalytiques des oxydes LixCuy-xCo3-yO4. Ces oxydes, prepares sous forme de poudres par decomposition thermique des nitrates precurseurs entre 300 et 500°C, ont montre (DRX et FTIR) une structure spinelle inverse non-stcechiometrique avec une diminution du volume de la maille cristalline. La surface specifique par BET est d'environ 6 m2 g-1. Le pcn, obtenu par titrage acido-basique, a indique une diminution de la force du lien M-OH avec le taux du Li dans l'oxyde. Les analyses par XPS, realisees sur des films d'oxyde prepares par nebulisation reactive sur un substrat lisse de nickel, revelent un enrichissement de la surface en Cu a partir de 30% Li, et la presence des cations de surface Co2+, Co3+, Cu +, Cu2+ et Cu3+. La concentration de ce dernier montre un maximum a 10 et 20% Li. Suite a la substitution du Cu par du Li, la compensation de la charge serait assuree principalement par la formation d'especes Cu3+ pour les oxydes contenant jusqu'a 20% Li, et par la formation d'especes Co3+ aux taux de substitution superieurs. Les micrographies MEB montrent une morphologie hemispherique des particules d'oxyde reparties uniformement sur le substrat

  12. 40 CFR 721.981 - Substituted naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex.

    Science.gov (United States)

    2010-07-01

    ... naphthalenyl-substituted azonaphthol chromium complex. 721.981 Section 721.981 Protection of Environment...-substituted naphthalenyl-substituted azonaphthol chromium complex. (a) Chemical substance and significant new... naphtholoazo-substituted naphthalenyl-substituted azonaphthol chromium complex (PMN P-93-1631) is subject to...

  13. Phase evolution and its effects on the magnetic performance of nanocrystalline SmCo7 alloy

    International Nuclear Information System (INIS)

    Zhang Zhexu; Song Xiaoyan; Xu Wenwu

    2011-01-01

    The evolution of the phase constitution and the microstructure, as well as their effects on magnetic performance, were investigated systematically using a prepared nanocrystalline single-phase SmCo 7 alloy as the starting material for a series of annealing processes. The SmCo 7 (1:7 H) phase was discovered to have a good single-phase stability from room temperature up to 600 deg. C. The destabilization of the SmCo 7 phase results in the formation of the Sm 2 Co 17 (2:17 R) and SmCo 5 (1:5 H) phases, which exist as phase-transformation twins and particulate precipitates, respectively, with a completely coherent relationship with the 1:7 H parent phase. For the first time the formation mechanism of the 2:17 R phase-transformation twins has been proposed, in which the ordered substitution of 1/3 of the Sm atoms by Co-Co dumbbell pairs along two particular crystal directions was demonstrated. The characteristic width values of the 2:17 R phase-transformation twins, as deduced from this model of the mechanism, were unambiguously verified by the experimental results. Among the SmCo 7 alloys with various phase constitutions and microstructures, the best magnetic properties were obtained in the nanocrystalline 1:7 H single-phase alloys. The present work may promote a new understanding of nanoscale-stabilized single-phase SmCo 7 and its potential applications as unique high-temperature permanent magnets.

  14. Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg₂Ni-type Alloy by Melt Spinning.

    Science.gov (United States)

    Zhang, Yang-Huan; Li, Bao-Wei; Ren, Hui-Ping; Li, Xia; Qi, Yan; Zhao, Dong-Liang

    2011-01-18

    Mg₂Ni-type Mg₂Ni 1-x Co x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1) alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg₂Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD) of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio () of the (x = 0.4) alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio () from 54.5 to 70.2%, the hydrogen diffusion coefficient (D) from 0.75 × 10 - 11 to 3.88 × 10 - 11 cm²/s and the limiting current density I L from 150.9 to 887.4 mA/g.

  15. Synthesis of Samarium Cobalt Nanoblades

    Energy Technology Data Exchange (ETDEWEB)

    Darren M. Steele

    2010-08-25

    As new portable particle acceleration technologies become feasible the need for small high performance permanent magnets becomes critical. With particle accelerating cavities of a few microns, the photonic crystal fiber (PCF) candidate demands magnets of comparable size. To address this need, samarium cobalt (SmCo) nanoblades were attempted to be synthesized using the polyol process. Since it is preferable to have blades of 1-2 {micro}m in length, key parameters affecting size and morphology including method of stirring, reaction temperature, reaction time and addition of hydroxide were examined. Nanoparticles consisting of 70-200 nm spherical clusters with a 3-5 nm polyvinylpyrrolidone (PVP) coating were synthesized at 285 C and found to be ferromagnetic. Nanoblades of 25nm in length were observed at the surface of the nanoclusters and appeared to suggest agglomeration was occurring even with PVP employed. Morphology and size were characterized using a transmission electron microscope (TEM). Powder X-Ray Diffraction (XRD) analysis was conducted to determine composition but no supportive evidence for any particular SmCo phase has yet been observed.

  16. Bimodal microstructure and deformation of cryomilled bulk nanocrystalline Al-7.5Mg alloy

    International Nuclear Information System (INIS)

    Lee, Z.; Witkin, D.B.; Radmilovic, V.; Lavernia, E.J.; Nutt, S.R.

    2005-01-01

    The microstructure, mechanical properties and deformation response of bimodal structured nanocrystalline Al-7.5Mg alloy were investigated. Grain refinement was achieved by cryomilling of atomized Al-7.5Mg powders, and then cryomilled nanocrystalline powders blended with 15 and 30% unmilled coarse-grained powders were consolidated by hot isostatic pressing followed by extrusion to produce bulk nanocrystalline alloys. Bimodal bulk nanocrystalline Al-7.5Mg alloys, which were comprised of nanocrystalline grains separated by coarse-grain regions, show balanced mechanical properties of enhanced yield and ultimate strength and reasonable ductility and toughness compared to comparable conventional alloys and nanocrystalline metals. The investigation of tensile and hardness test suggests unusual deformation mechanisms and interactions between ductile coarse-grain bands and nanocrystalline regions

  17. Texture-dependent twin formation in nanocrystalline thin Pd films

    International Nuclear Information System (INIS)

    Wang, B.; Idrissi, H.; Shi, H.; Colla, M.S.; Michotte, S.; Raskin, J.P.; Pardoen, T.; Schryvers, D.

    2012-01-01

    Nanocrystalline Pd films were produced by electron-beam evaporation and sputter deposition. The electron-beam-evaporated films reveal randomly oriented nanograins with a relatively high density of growth twins, unexpected in view of the high stacking fault energy of Pd. In contrast, sputter-deposited films show a clear 〈1 1 1〉 crystallographic textured nanostructure without twins. These results provide insightful information to guide the generation of microstructures with enhanced strength/ductility balance in high stacking fault energy nanocrystalline metallic thin films.

  18. Engineering of giant magnetoimpedance effect of amorphous and nanocrystalline microwires

    Directory of Open Access Journals (Sweden)

    V. Zhukova

    2016-12-01

    Full Text Available We present our studies of the factors affecting soft magnetic properties and giant magnetoimpedance effect in thin amorphous and nanocrystalline microwires. We showed that the magnetoelastic anisotropy is one of the most important parameters that determine magnetic softness and GMI effect of glass-coated microwires  and annealing can be very effective for manipulation the magnetic properties of amorphous ferromagnetic glass-coated microwires. Considerable magnetic softening and increasing of the GMI effect is observed in Fe-rich nanocrystalline FINEMET-type glass-coated microwires after the nanocrystallization.

  19. Inter- and intra-agglomerate fracture in nanocrystalline nickel.

    Science.gov (United States)

    Shan, Zhiwei; Knapp, J A; Follstaedt, D M; Stach, E A; Wiezorek, J M K; Mao, S X

    2008-03-14

    In situ tensile straining transmission electron microscopy tests have been carried out on nanocrystalline Ni. Grain agglomerates (GAs) were found to form very frequently and rapidly ahead of an advancing crack with sizes much larger than the initial average grain size. High-resolution electron microscopy indicated that the GAs most probably consist of nanograins separated by low-angle grain boundaries. Furthermore, both inter- and intra-GA fractures were observed. The observations suggest that these newly formed GAs may play an important role in the formation of the dimpled fracture surfaces of nanocrystalline materials.

  20. High-pressure structural behaviour of nanocrystalline Ge

    International Nuclear Information System (INIS)

    Wang, H; Liu, J F; He, Y; Wang, Y; Chen, W; Jiang, J Z; Olsen, J Staun; Gerward, L

    2007-01-01

    The equation of state and the pressure of the I-II transition have been studied for nanocrystalline Ge using synchrotron x-ray diffraction. The bulk modulus and the transition pressure increase with decreasing particle size for both Ge-I and Ge-II, but the percentage volume collapse at the transition remains constant. Simplified models for the high-pressure structural behaviour are presented, based on the assumption that a large fraction of the atoms reside in grain boundary regions of the nanocrystalline material. The interface structure plays a significant role in affecting the transition pressure and the bulk modulus

  1. Production of nanocrystalline metal powders via combustion reaction synthesis

    Science.gov (United States)

    Frye, John G.; Weil, Kenneth Scott; Lavender, Curt A.; Kim, Jin Yong

    2017-10-31

    Nanocrystalline metal powders comprising tungsten, molybdenum, rhenium and/or niobium can be synthesized using a combustion reaction. Methods for synthesizing the nanocrystalline metal powders are characterized by forming a combustion synthesis solution by dissolving in water an oxidizer, a fuel, and a base-soluble, ammonium precursor of tungsten, molybdenum, rhenium, or niobium in amounts that yield a stoichiometric burn when combusted. The combustion synthesis solution is then heated to a temperature sufficient to substantially remove water and to initiate a self-sustaining combustion reaction. The resulting powder can be subsequently reduced to metal form by heating in a reducing gas environment.

  2. Electricity/oil substitution

    International Nuclear Information System (INIS)

    Melvin, J.G.

    1980-09-01

    The extent to which electricity could substitute for imported oil in Canada is assessed and it is concluded that the bulk of projected oil imports could be displaced. This substitution of electricity for oil could be largely completed within two decades, with existing technology, using Canadian resources. The substitution of electricity for imported oil would result in relatively low energy costs and would stimulate economic growth. Energy self-sufficiency through the substitution of electricity for oil is uniquely a Canadian option; it is not open to other industrial countries. The option exists because of Canada's resources of oil sands for essential liquid fuels, hydraulic and nuclear electrical potential, and natural gas as an interim source of energy. While other countries face an energy crisis due to declining supplies of oil, Canada faces opportunities. The policies of Federal and Provincial governments, as perceived by individual decision makers, will have a major influence on Canada's ability to realize opportunities. (auth)

  3. Cobalt: A vital element in the aircraft engine industry

    Science.gov (United States)

    Stephens, J. R.

    1981-01-01

    Recent trends in the United States consumption of cobalt indicate that superalloys for aircraft engine manufacture require increasing amounts of this strategic element. Superalloys consume a lion's share of total U.S. cobalt usage which was about 16 million pounds in 1980. In excess of 90 percent of the cobalt used in this country was imported, principally from the African countries of Zaire and Zambia. Early studies on the roles of cobalt as an alloying element in high temperature alloys concentrated on the simple Ni-Cr and Nimonic alloy series. The role of cobalt in current complex nickel base superalloys is not well defined and indeed, the need for the high concentration of cobalt in widely used nickel base superalloys is not firmly established. The current cobalt situation is reviewed as it applies to superalloys and the opportunities for research to reduce the consumption of cobalt in the aircraft engine industry are described.

  4. Assessment of cobalt levels in wastewater, soil and vegetable ...

    African Journals Online (AJOL)

    User

    Key words: Cobalt level, Kubanni River, soil, vegetable, wastewater. INTRODUCTION. Cobalt is ... metals released into the environment from a variety of anthropogenic activities ..... Heavy Metal Stress in Plants, 2nd Edition,. Springer,. United.

  5. Synthesis and phosphatase activity of a Cobalt(II) phenanthroline ...

    Indian Academy of Sciences (India)

    MAMONI GARAI

    2017-09-19

    Sep 19, 2017 ... Synthesis and phosphatase activity of a Cobalt(II) phenanthroline complex. MAMONI GARAIa ... tion, cobalt complexes have gained importance because of their application as ... 2.3 Physical measurements. Infrared spectrum ...

  6. Copper removal using electrosterically stabilized nanocrystalline cellulose.

    Science.gov (United States)

    Sheikhi, Amir; Safari, Salman; Yang, Han; van de Ven, Theo G M

    2015-06-03

    Removal of heavy metal ions such as copper using an efficient and low-cost method with low ecological footprint is a critical process in wastewater treatment, which can be achieved in a liquid phase using nanoadsorbents such as inorganic nanoparticles. Recently, attention has turned toward developing sustainable and environmentally friendly nanoadsorbents to remove heavy metal ions from aqueous media. Electrosterically stabilized nanocrystalline cellulose (ENCC), which can be prepared from wood fibers through periodate/chlorite oxidation, has been shown to have a high charge content and colloidal stability. Here, we show that ENCC scavenges copper ions by different mechanisms depending on the ion concentration. When the Cu(II) concentration is low (C0≲200 ppm), agglomerates of starlike ENCC particles appear, which are broken into individual starlike entities by shear and Brownian motion, as evidenced by photometric dispersion analysis, dynamic light scattering, and transmission electron microscopy. On the other hand, at higher copper concentrations, the aggregate morphology changes from starlike to raftlike, which is probably due to the collapse of protruding dicarboxylic cellulose (DCC) chains and ENCC charge neutralization by copper adsorption. Such raftlike structures result from head-to-head and lateral aggregation of neutralized ENCCs as confirmed by transmission electron microscopy. As opposed to starlike aggregates, the raftlike structures grow gradually and are prone to sedimentation at copper concentrations C0≳500 ppm, which eliminates a costly separation step in wastewater treatment processes. Moreover, a copper removal capacity of ∼185 mg g(-1) was achieved thanks to the highly charged DCC polyanions protruding from ENCC. These properties along with the biorenewability make ENCC a promising candidate for wastewater treatment, in which fast, facile, and low-cost removal of heavy metal ions is desired most.

  7. Tribological properties of nanocrystalline diamond films

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, A.; Fenske, G.R.; Krauss, A.R.; Gruen, D.M.; McCauley, T.; Csencsits, R.T. [Argonne National Lab., IL (United States). Energy Technology Div.

    1999-11-01

    In this paper, we present the friction and wear properties of nanocrystalline diamond (NCD) films grown in Ar-fullerene (C{sub 60}) and Ar-CH{sub 4} microwave plasmas. Specifically, we will address the fundamental tribological issues posed by these films during sliding against Si{sub 3}N{sub 4} counterfaces in ambient air and inert gases. Grain sizes of the films grown by the new method are very small (10-30 nm) and are much smoother (20-40 nm, root mean square) than those of films grown by the conventional H{sub 2}-CH{sub 4} microwave-assisted chemical vapor deposition process. Transmission electron microscopy (TEM) revealed that the grain boundaries of these films are very sharp and free of nondiamond phases. The microcrystalline diamond films grown by most conventional methods consist of large grains and a rough surface finish, which can cause severe abrasion during sliding against other materials. The friction coefficients of films grown by the new method (i.e. in Ar-C{sub 60} and Ar-CH{sub 4} plasmas) are comparable with those of natural diamond, and wear damage on counterface materials is minimal. Fundamental tribological studies indicate that these films may undergo phase transformation during long-duration, high-speed and/or high-load sliding tests and that the transformation products trapped at the sliding interfaces can intermittently dominate friction and wear performance. Using results from a combination of TEM, electron diffraction, Raman spectroscopy, and electron energy loss spectroscopy, we describe the structural chemistry of the debris particles trapped at the sliding interfaces and elucidate their possible effects on friction and wear of NCD films in dry N{sub 2}. Finally, we suggest a few potential applications in which NCD films can improve performance and service lives. (orig.)

  8. Magnetic properties of nanocrystalline CoFe{sub 2}O{sub 4} powders prepared at room temperature: variation with crystallite size

    Energy Technology Data Exchange (ETDEWEB)

    Rajendran, M.; Pullar, R.C.; Bhattacharya, A.K. E-mail: ashokbhattacharya@warwick.ac.uk; Das, D.; Chintalapudi, S.N.; Majumdar, C.K

    2001-06-01

    The magnetic properties of nanocrystalline CoFe{sub 2}O{sub 4} powders prepared by a redox process at room temperature have been studied by vibrating sample magnetometer (VSM). The average crystallite size of the powders varied from 6 to 20 nm by changing the synthesis conditions and the corresponding saturation magnetisation (M{sub s}) value ranged from 9 to 38 emu g{sup -1}. On heating, the crystallite size increased with corresponding increase in M{sub s} values. At 1073 K all samples achieved M{sub s} values close to 73 emu g{sup -1}. On increasing the crystallite size, the coercivity (H{sub c}) increased passed through a maximum and dropped. Cobalt ferrite powder with an average crystallite size of 6 nm prepared at room temperature achieved desirable values of M{sub s}=60 emu g{sup -1} and H{sub c}=1.42 kOe after thermal annealing at 973 K. The Moessbauer spectra were recorded for CoFe{sub 2}O{sub 4} having a range of crystallite sizes at room temperature and at low temperatures down to 40 K. The magnetic and Moessbauer results are provided for nanocrystalline CoFe{sub 2}O{sub 4} as a function of crystallite size and measurement temperature.

  9. The physiological effect of cobalt on watermelon cultivation

    International Nuclear Information System (INIS)

    Yao Naihua; Jin Yafang; Sun Yaochen; Huang Yiming

    1993-01-01

    Cobalt has essential physiological action on both animals and plants. For the latter it can raise plant's nitrogen-fixing ability and saccharine content. Spray of cobalt mixed with other nutritive elements can improve the germinatit of seeds and the yield of fruit. For specifying the nutritive function of cobalt upon watermelon, isotope 60 Co was mixed into a complex leaf nutritive aqua and the regularity of transferring and absorbing cobalt in the watermelon's body was investigated

  10. Relaxation resistance of heat resisting alloys with cobalt

    International Nuclear Information System (INIS)

    Borzdyka, A.M.

    1977-01-01

    Relaxation resistance of refractory nickel-chromium alloys containing 5 to 14 % cobalt is under study. The tests involve the use of circular samples at 800 deg to 850 deg C. It is shown that an alloy containing 14% cobalt possesses the best relaxation resistance exceeding that of nickel-chromium alloys without any cobalt by a factor of 1.5 to 2. The relaxation resistance of an alloy with 5% cobalt can be increased by hardening at repeated loading

  11. Manipulating radicals: Using cobalt to steer radical reactions

    OpenAIRE

    Chirilă, A.

    2017-01-01

    This thesis describes research aimed at understanding and exploiting metallo-radical reactivity and explores reactions mediated by square planar, low-spin cobalt(II) complexes. A primary goal was to uncover novel reactivity of discrete cobalt(III)-bound carbene radicals generated upon reaction of the cobalt(II) catalysts with carbene precursors. Another important goal was to replace cobalt(II)-porphyrin catalysts with cheaper and easier to prepare metallo-radical analogues. Therefore the cata...

  12. Fracturing of revision of a cobalt-chrome femoral head after fracturing of a ceramic femoral head, with diffuse metallosis. Case report

    Directory of Open Access Journals (Sweden)

    Pedro Miguel Dantas Costa Marques

    2013-04-01

    Full Text Available We presente a case of a fracture of a cobalt-chrome femoral head after revision of a hip total prosthesis with ceramic femoral head fracture. During surgery we found the cobalt-chrome femoral head fracture, wear of the polyethylene and massive metallosis in muscular and cartilaginous tissue. Both femoral stem and acetabular cup were stable and without apparent wearing. After surgical debridement, we promoted the substitution of the femoral head and the acetabular polyethylene by similar ones. After 12 months of follow-up, the patient has no pain complaints, function limit or systemic signs associated with malign metallosis

  13. Valence states of cobalt and crystal structure peculiarities of solid solution YBa2Cu3-xCoxO6+σ

    International Nuclear Information System (INIS)

    Voronin, V.I.; Goshchinskij, B.N.; Mitberg, Eh.B.; Leonidov, I.A.; Kozhevnikov, V.L.

    2000-01-01

    Crystal structure of solid solution YBa 2 Cu 3-x Co x O 6+σ , where x = 0.2, 0.4, 0.6 and 0.8, is studied by the method of powder neutron diffraction. Charge states of the cation are calculated using the interatomic distances obtained. It is shown that cobalt in Cu1 position has valency 3 + and octahedral coordination at x = 0.2 and 0.4. Increase in doping degree involves both transition of a portion of cobalt ions in the positions mentioned to the state with valence 4 + and tetrahedral coordination and partial substitution of copper in Cu2 position [ru

  14. Perfluorinated cobalt phthalocyanine effectively catalyzes water electrooxidation

    KAUST Repository

    Morlanes, Natalia Sanchez

    2014-12-08

    Efficient electrocatalysis of water oxidation under mild conditions at neutral pH was achieved by a fluorinated cobalt phthalocyanine immobilized on fluorine-doped tin oxide (FTO) surfaces with an onset potential at 1.7 V vs. RHE. Spectroscopic, electrochemical, and inhibition studies indicate that phthalocyanine molecular species are the operational active sites. Neither free cobalt ions nor heterogeneous cobalt oxide particles or films were observed. During long-term controlled-potential electrolysis at 2 V vs. RHE (phosphate buffer, pH 7), electrocatalytic water oxidation was sustained for at least 8 h (TON ≈ 1.0 × 105), producing about 4 μmol O2 h-1 cm-2 with a turnover frequency (TOF) of about 3.6 s-1 and no measurable catalyst degradation.

  15. Characterization of a Cobalt-Tungsten Interconnect

    DEFF Research Database (Denmark)

    Harthøj, Anders; Holt, Tobias; Caspersen, Michael

    2012-01-01

    is to act both as a diffusion barrier for chromium and provide better protection against high temperature oxidation than a pure cobalt coating. This work presents a characterization of a cobalt-tungsten alloy coating electrodeposited on the ferritic steel Crofer 22 H which subsequently was oxidized in air......A ferritic steel interconnect for a solid oxide fuel cell must be coated in order to prevent chromium evaporation from the steel substrate. The Technical University of Denmark and Topsoe Fuel Cell have developed an interconnect coating based on a cobalt-tungsten alloy. The purpose of the coating...... for 300 h at 800 °C. The coating was characterized with Glow Discharge Optical Spectroscopy (GDOES), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). The oxidation properties were evaluated by measuring weight change of coated samples of Crofer 22 H and Crofer 22 APU as a function...

  16. Solubility of cobalt in primary circuit solutions

    International Nuclear Information System (INIS)

    Lambert, I.; Joyer, F.

    1992-01-01

    The solubility of cobalt ferrite (CoFe 2 O 4 ) was measured in PWR primary circuit conditions, in the temperature range 250-350 deg C, and the results were compared with the ones obtained on magnetite and nickel ferrite. As in the former cases, it was found that, in the prevailing primary circuit conditions, the solubility of the cobalt ferrite was minimum at temperatures around 300 deg C, for cobalt as well as for iron. The equilibrium iron concentration is significantly lower than in the case of magnetite. The results are discussed in relation with the POTHY code, based only on thermodynamic laws and data, used for the prediction of the primary circuit chemistry

  17. Total quality management of cobalt-60 sources

    International Nuclear Information System (INIS)

    Malkoske, G.R.

    1999-01-01

    Total Quality Management of Cobalt-60 sources by a supplier requires a life cycle approach to source management. This covers various aspects, including design, manufacturing, installation, field inspection, source surveillance and return of cobalt-60 sources at the end of their useful life. The Total Quality Management approach demonstrates a strong industry commitment to the beneficial use of gamma technology for industrial irradiation applications in both developed nations and in those nations who are developing their infrastructure and techniques for the beneficial use of this technology. MDS Nordion continues to demonstrate its support and commitment to the industry by developing and implementing state-of-the-art standards for the safe use of cobalt-60 sources

  18. Preliminary studies of cobalt complexation in groundwater

    International Nuclear Information System (INIS)

    Warwick, P.; Shaw, P.; Williams, G.M.; Hooker, P.J.

    1988-01-01

    A relatively non-invasive method has been used to separate complexed from free cobalt-60 in groundwater, using the weak cationic adsorption properties of Sephadex gels, and a mobile phase of natural groundwater. Results show the kinetics of Co complex formation in groundwater to be slow, and that the equilibrium position is affected by temperature, cobalt concentration and the ionic/organic strength of the groundwater. The addition of DAEA cellulose to the groundwater to remove humic material, also removed the majority of organic species which absorb UV at 254 nm, but 45% of the original total organic carbon remained, and the amount of complexed cobalt left in solution was only reduced to 76% of its former concentration. This suggests that the completed Co species separated by the method described in this paper are a mixture of inorganic and organic compounds, and studies are therefore continuing to establish their exact nature. (author)

  19. Preliminary studies of cobalt complexation in groundwater

    International Nuclear Information System (INIS)

    Warwick, P.; Shaw, P.; Williams, G.M.; Hooker, P.J.

    1988-01-01

    A relatively non-invasive method has been used to separate complexed from free cobalt-60 in groundwater, using the weak cationic adsorption properties of Sephadex gels, and a mobile phase of natural groundwater. Results show the kinetics of Co complex formation in groundwater to be slow, and that the equilibrium position is affected by temperature, cobalt concentration and the ionic/organic strength of the groundwater. The addition of DEAE cellulose to the groundwater to remove humic material, also removed the majority of organic species with absorb UV at 254 nm, but 45% of the original total organic carbon remained, and the amount of complexed cobalt left in solution was only reduced to 76% of its former concentration. This suggests that the complexed Co species separated by the method described in this paper are a mixture of inorganic and organic compounds, and studies are therefore continuing to establish their exact nature. (orig.)

  20. Palladium-cobalt particles as oxygen-reduction electrocatalysts

    Science.gov (United States)

    Adzic, Radoslav [East Setauket, NY; Huang, Tao [Manorville, NY

    2009-12-15

    The present invention relates to palladium-cobalt particles useful as oxygen-reducing electrocatalysts. The invention also relates to oxygen-reducing cathodes and fuel cells containing these palladium-cobalt particles. The invention additionally relates to methods for the production of electrical energy by using the palladium-cobalt particles of the invention.

  1. Feasibility Study for Cobalt Bundle Loading to CANDU Reactor Core

    International Nuclear Information System (INIS)

    Park, Donghwan; Kim, Youngae; Kim, Sungmin

    2016-01-01

    CANDU units are generally used to produce cobalt-60 at Bruce and Point Lepreau in Canada and Embalse in Argentina. China has started production of cobalt-60 using its CANDU 6 Qinshan Phase III nuclear power plant in 2009. For cobalt-60 production, the reactor’s full complement of stainless steel adjusters is replaced with neutronically equivalent cobalt-59 adjusters, which are essentially invisible to reactor operation. With its very high neutron flux and optimized fuel burn-up, the CANDU has a very high cobalt-60 production rate in a relatively short time. This makes CANDU an excellent vehicle for bulk cobalt-60 production. Several studies have been performed to produce cobalt-60 using adjuster rod at Wolsong nuclear power plant. This study proposed new concept for producing cobalt-60 and performed the feasibility study. Bundle typed cobalt loading concept is proposed and evaluated the feasibility to fuel management without physics and system design change. The requirement to load cobalt bundle to the core was considered and several channels are nominated. The production of cobalt-60 source is very depend on the flux level and burnup directly. But the neutron absorption characteristic of cobalt bundle is too high, so optimizing design study is needed in the future

  2. Feasibility Study for Cobalt Bundle Loading to CANDU Reactor Core

    Energy Technology Data Exchange (ETDEWEB)

    Park, Donghwan; Kim, Youngae; Kim, Sungmin [KHNP Central Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    CANDU units are generally used to produce cobalt-60 at Bruce and Point Lepreau in Canada and Embalse in Argentina. China has started production of cobalt-60 using its CANDU 6 Qinshan Phase III nuclear power plant in 2009. For cobalt-60 production, the reactor’s full complement of stainless steel adjusters is replaced with neutronically equivalent cobalt-59 adjusters, which are essentially invisible to reactor operation. With its very high neutron flux and optimized fuel burn-up, the CANDU has a very high cobalt-60 production rate in a relatively short time. This makes CANDU an excellent vehicle for bulk cobalt-60 production. Several studies have been performed to produce cobalt-60 using adjuster rod at Wolsong nuclear power plant. This study proposed new concept for producing cobalt-60 and performed the feasibility study. Bundle typed cobalt loading concept is proposed and evaluated the feasibility to fuel management without physics and system design change. The requirement to load cobalt bundle to the core was considered and several channels are nominated. The production of cobalt-60 source is very depend on the flux level and burnup directly. But the neutron absorption characteristic of cobalt bundle is too high, so optimizing design study is needed in the future.

  3. 21 CFR 73.1015 - Chromium-cobalt-aluminum oxide.

    Science.gov (United States)

    2010-04-01

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

  4. Cobalt-free nickel-base superalloys

    International Nuclear Information System (INIS)

    Koizumi, Yutaka; Yamazaki, Michio; Harada, Hiroshi

    1979-01-01

    Cobalt-free nickel-base cast superalloys have been developed. Cobalt is considered to be a beneficial element to strengthen the alloys but should be eliminated in alloys to be used for direct cycle helium turbine driven by helium gas from HTGR (high temp. gas reactor). The elimination of cobalt is required to avoid the formation of radioactive 60 Co from the debris or scales of the alloys. Cobalt-free alloys are also desirable from another viewpoint, i.e. recently the shortage of the element has become a serious problem in industry. Cobalt-free Mar-M200 type alloys modified by the additions of 0.15 - 0.2 wt% B and 1 - 1.5 wt% Hf were found to have a creep rupture strength superior or comparable to that of the original Mar-M200 alloy bearing cobalt. The ductility in tensile test at 800 0 C, as cast or after prolonged heating at 900 0 C (the tensile test was done without removing the surface layer affected by the heating), was also improved by the additions of 0.15 - 0.2% B and 1 - 1.5% Hf. The morphology of grain boundaries became intricated by the additions of 0.15 - 0.2% B and 1 - 1.5% Hf, to such a degree that one can hardly distinguish grain boundaries by microscopes. The change in the grain boundary morphology was considered, as suggested previously by one of the authors (M.Y.), to be the reason for the improvements in the creep rupture strength and tensile ductility. (author)

  5. Radiation induced ligand loss from cobalt complexes

    International Nuclear Information System (INIS)

    Funston, A. M.; McFadyen, W.D.; Tregloan, P.A.

    2000-01-01

    Full text: Due to the rapid nature of ligand dissociation from cobalt(II) complexes the study of the rate of ligand dissociation necessitates the use of a technique such as pulse radiolysis. This allows the rapid reduction of the corresponding cobalt(III) complex by a reducing radical, such as the aquated electron, to form the cobalt(II) complex. However, to date, no systematic study of either the mechanism of reduction or the influence of the electronic structure on the rate of ligand dissociation has been carried out. In order to understand these processes more fully the mechanism of reduction of a range of related cobalt(III) complexes by the aquated electron and the subsequent rate of ligand dissociation from the resulting cobalt(II) complexes is being investigated. It has been found that a number of processes are observed following the initial rapid reaction of the cobalt(III) complex with the aquated electron. Ultimately ligand loss is observed. Depending upon the complex, the initial processes observed may include the formation of coordinated radicals and electron transfer within the complex. For complexes containing aromatic ligands such as 2,2'-bipyridine, 1,10-phenanthroline and dipyrido[3,2-a:2',3'-c]phenazine the formation of a coordinated radical is observed as the initial reduction step. The kinetics of ligand dissociation of these complexes has been determined. The loss of monodentate ligands is fast and has been indistinguishable from the reduction processes when aromatic ligands are also present in the complex. However, for diamine chelates and diimine chelates spectra of the transient species can be resolved

  6. Fast response time alcohol gas sensor using nanocrystalline F

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 36; Issue 4. Fast response time alcohol gas sensor using nanocrystalline F-doped SnO2 films derived via sol–gel method. Sarbani Basu Yeong-Her Wang C Ghanshyam Pawan Kapur. Volume 36 Issue 4 August 2013 pp 521-533 ...

  7. High-pressure structural behavior of nanocrystalline Ge

    DEFF Research Database (Denmark)

    Wang, H.; Liu, J. F.; Yan, H.

    2007-01-01

    The equation of state and the pressure of the I-II transition have been studied for nanocrystalline Ge using synchrotron x-ray diffraction. The bulk modulus and the transition pressure increase with decreasing particle size for both Ge-I and Ge-II, but the percentage volume collapse at the transi...

  8. Induced anisotropy effect in nanocrystalline cores for GFCBs

    Energy Technology Data Exchange (ETDEWEB)

    Waeckerle, T. E-mail: thierry.waeckerle@imphy.usinor.com; Verin, Ph.; Cremer, P.; Gautard, D

    2000-06-02

    Nanocrystalline materials are very efficient for GFCB cores with flat hysteresis loop, especially if permeability may be raised in keeping low the remanent induction. This can be achieved with peculiar field annealing . A thermodynamic model is proposed to explain the experimental evidence.

  9. Bioactive nanocrystalline wollastonite synthesized by sol–gel ...

    Indian Academy of Sciences (India)

    The sol–gel combustion method was employed to synthesize the nanocrystalline wollastonite by taking the raw eggshell powder as a calcium source and TEOS as a source of silicate. Glycine was .... 94·37% CaCO3, hence in order to prepare 1 M Ca2+ ion solu- ... requires an acid or base catalyst hence the pH of the solu-.

  10. High Pressure X-Ray Diffraction Studies on Nanocrystalline Materials

    Science.gov (United States)

    Palosz, B.; Stelmakh, S.; Grzanka, E.; Gierlotka, S.; Pielaszek, R.; Bismayer, U.; Werner, S.; Palosz, W.

    2003-01-01

    Application of in situ high pressure powder diffraction technique for examination of specific structural properties of nanocrystals based on the experimental data of SiC nanocrystalline powders of 2 to 30 nrn diameter in diameter is presented. Limitations and capabilities of the experimental techniques themselves and methods of diffraction data elaboration applied to nanocrystals with very small dimensions (nanoparticles of different grain size.

  11. Bioactive nanocrystalline wollastonite synthesized by sol–gel ...

    Indian Academy of Sciences (India)

    The sol–gel combustion method was employed to synthesize the nanocrystalline wollastonite by taking the raw eggshell powder as a calcium source and TEOS as a source of silicate. Glycine was used as a reductant or fuel and nitrate ions present in metal nitrate acts as an oxidizer. The phase purity of the wollastonite was ...

  12. New route to the fabrication of nanocrystalline diamond films

    International Nuclear Information System (INIS)

    Varshney, Deepak; Morell, Gerardo; Palomino, Javier; Resto, Oscar; Gil, Jennifer; Weiner, Brad R.

    2014-01-01

    Nanocrystalline diamond (NCD) thin films offer applications in various fields, but the existing synthetic approaches are cumbersome and destructive. A major breakthrough has been achieved by our group in the direction of a non-destructive, scalable, and economic process of NCD thin-film fabrication. Here, we report a cheap precursor for the growth of nanocrystalline diamond in the form of paraffin wax. We show that NCD thin films can be fabricated on a copper support by using simple, commonplace paraffin wax under reaction conditions of Hot Filament Chemical Vapor Deposition (HFCVD). Surprisingly, even the presence of any catalyst or seeding that has been conventionally used in the state-of-the-art is not required. The structure of the obtained films was analyzed by scanning electron microscopy and transmission electron microscopy. Raman spectroscopy and electron energy-loss spectroscopy recorded at the carbon K-edge region confirm the presence of nanocrystalline diamond. The process is a significant step towards cost-effective and non-cumbersome fabrication of nanocrystalline diamond thin films for commercial production

  13. Quartz crystal microbalance gas sensor with nanocrystalline diamond sensitive layer

    Czech Academy of Sciences Publication Activity Database

    Varga, Marián; Laposa, A.; Kulha, Pavel; Kroutil, J.; Husák, M.; Kromka, Alexander

    2015-01-01

    Roč. 252, č. 11 (2015), s. 2591-2597 ISSN 0370-1972 R&D Projects: GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:68378271 Keywords : gas sensor * nanocrystalline diamond * quartz resonator * thickness shear mode Subject RIV: JB - Sensor s, Measurment, Regulation Impact factor: 1.522, year: 2015

  14. Transparent nanocrystalline ZnO films prepared by spin coating

    Energy Technology Data Exchange (ETDEWEB)

    Berber, M. [SusTech GmbH and Co. KG, Petersenstr. 20, 64287 Darmstadt, Hessen (Germany)]. E-mail: mete.berber@sustech.de; Bulto, V. [SusTech GmbH and Co. KG, Petersenstr. 20, 64287 Darmstadt, Hessen (Germany); Kliss, R. [SusTech GmbH and Co. KG, Petersenstr. 20, 64287 Darmstadt, Hessen (Germany); Hahn, H. [SusTech GmbH and Co. KG, Petersenstr. 20, 64287 Darmstadt, Hessen (Germany); Forschungszentrum Karlsruhe, Institute for Nanotechnology, Postfach 3640, 76021 Karlsruhe (Germany); Joint Research Laboratory Nanomaterials, TU Darmstadt, Institute of Materials Science, Petersenstr. 23, 64287 Darmstadt (Germany)

    2005-09-15

    Dispersions of zinc oxide nanoparticles synthesized by the electrochemical deposition under oxidizing conditions process with organic surfactants, were spin coated on glass substrates. After sintering, the microstructure, surface morphology, and electro-optical properties of the transparent nanocrystalline zinc oxide films have been investigated for different coating thicknesses and organic solvents.

  15. Transparent nanocrystalline ZnO films prepared by spin coating

    International Nuclear Information System (INIS)

    Berber, M.; Bulto, V.; Kliss, R.; Hahn, H.

    2005-01-01

    Dispersions of zinc oxide nanoparticles synthesized by the electrochemical deposition under oxidizing conditions process with organic surfactants, were spin coated on glass substrates. After sintering, the microstructure, surface morphology, and electro-optical properties of the transparent nanocrystalline zinc oxide films have been investigated for different coating thicknesses and organic solvents

  16. Nanocrystalline spinel ferrites by solid state reaction route

    Indian Academy of Sciences (India)

    Wintec

    Nanocrystalline spinel ferrites by solid state reaction route. T K KUNDU* and S MISHRA. Department of Physics, Visva-Bharati, Santiniketan 731 235, India. Abstract. Nanostructured NiFe2O4, MnFe2O4 and (NiZn)Fe2O4 were synthesized by aliovalent ion doping using conventional solid-state reaction route. With the ...

  17. Electrodeposited nanocrystalline bronze alloys as replacement for Ni

    NARCIS (Netherlands)

    Hovestad, A.; Tacken, R.A.; Mannetje, H.H.'t

    2008-01-01

    Nanocrystalline white-bronze, CuSn, electroplating was investigated as alternative to Ni plating as undercoat for noble metals in jewellery applications. A strongly acidic plating bath was developed with an organic additive to suppress hydrogen evolution and obtain bright coatings. Polarization

  18. Development of Bulk Nanocrystalline Cemented Tungsten Carbide for Industrial Applicaitons

    Energy Technology Data Exchange (ETDEWEB)

    Z. Zak Fang, H. Y. Sohn

    2009-03-10

    This report contains detailed information of the research program entitled "Development of Bulk Nanocrystalline Cemented Tungsten Carbide Materials for Industrial Applications". The report include the processes that were developed for producing nanosized WC/Co composite powders, and an ultrahigh pressure rapid hot consolidation process for sintering of nanosized powders. The mechanical properties of consolidated materials using the nanosized powders are also reported.

  19. Adhesion of osteoblasts on chemically patterned nanocrystalline diamonds

    Czech Academy of Sciences Publication Activity Database

    Kalbáčová, M.; Michalíková, Lenka; Barešová, V.; Kromka, Alexander; Rezek, Bohuslav; Kmoch, S.

    2008-01-01

    Roč. 245, č. 10 (2008), s. 2124-2127 ISSN 0370-1972 R&D Projects: GA AV ČR KAN400100701 Institutional research plan: CEZ:AV0Z10100521 Keywords : cell growth * nanocrystalline diamond * surface termination Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.166, year: 2008

  20. Oxygen reduction on nanocrystalline ruthenia-local structure effects

    DEFF Research Database (Denmark)

    Abbott, Daniel F.; Mukerjee, Sanjeev; Petrykin, Valery

    2015-01-01

    Nanocrystalline ruthenium dioxide and doped ruthenia of the composition Ru1-xMxO2 (M = Co, Ni, Zn) with 0 ≤ x ≤ 0.2 were prepared by the spray-freezing freeze-drying technique. The oxygen reduction activity and selectivity of the prepared materials were evaluated in alkaline media using the RRDE ...

  1. Osteoblastic cells trigger gate currents on nanocrystalline diamond transistor

    Czech Academy of Sciences Publication Activity Database

    Ižák, Tibor; Krátká, Marie; Kromka, Alexander; Rezek, Bohuslav

    2015-01-01

    Roč. 129, May (2015), 95-99 ISSN 0927-7765 R&D Projects: GA ČR GAP108/12/0996 Grant - others:AVČR(CZ) M100101209 Institutional support: RVO:68378271 Keywords : field-effect transistors * nanocrystalline diamond * osteoblastic cells * leakage currents Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.902, year: 2015

  2. Luminescence of nanocrystalline ZnSe:Mn2+

    NARCIS (Netherlands)

    Suyver, J.F.; Wuister, S.F.; Kelly, J.J.; Meijerink, A.

    2000-01-01

    The luminescence properties of nanocrystalline ZnSe:Mn^(2+) prepared via an inorganic chemical synthesis are described. Photoluminescence spectra show distinct ZnSe and Mn^(2+) related emissions, both of which are excited via the ZnSe host lattice. The Mn^(2+) emission wavelength and the

  3. Cation distributions on rapidly solidified cobalt ferrite

    Science.gov (United States)

    De Guire, Mark R.; Kalonji, Gretchen; O'Handley, Robert C.

    1990-01-01

    The cation distributions in two rapidly solidified cobalt ferrites have been determined using Moessbauer spectroscopy at 4.2 K in an 8-T magnetic field. The samples were obtained by gas atomization of a Co0-Fe2O3-P2O5 melt. The degree of cation disorder in both cases was greater than is obtainable by cooling unmelted cobalt ferrite. The more rapidly cooled sample exhibited a smaller departure from the equilibrium cation distribution than did the more slowly cooled sample. This result is explained on the basis of two competing effects of rapid solidification: high cooling rate of the solid, and large undercooling.

  4. EXAFS Determination of the Structure of Cobalt in Carbon-Supported Cobalt and Cobalt-Molybdenum Sulfide Hydrodesulfurization Catalysts.

    NARCIS (Netherlands)

    Koningsberger, D.C.; Bouwens, S.M.A.M.; Veen, J.A.R. van; Beer, V.H.J. de; Prins, R.

    1991-01-01

    The structure of the cobalt present in carbon-supported Co and Co-Mo sulfide catalysts was studied by means of X-ray absorption spectroscopy at the Co K-edge and by X-ray photoelectron spectroscopy (XPS). Thiophene hydrodesulfurization activities were used to measure the catalytic properties of

  5. Strain rate sensitivity studies on bulk nanocrystalline aluminium by nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Varam, Sreedevi; Rajulapati, Koteswararao V., E-mail: kvrse@uohyd.ernet.in; Bhanu Sankara Rao, K.

    2014-02-05

    Nanocrystalline aluminium powder synthesized using high energy ball milling process was characterized by X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The studies indicated the powder having an average grain size of ∼42 nm. The consolidation of the powder was carried out by high-pressure compaction using a uni-axial press at room temperature by applying a pressure of 1.5 GPa. The cold compacted bulk sample having a density of ∼98% was subjected to nanoindentation which showed an average hardness and elastic modulus values of 1.67 ± 0.09 GPa and 83 ± 8 GPa respectively at a peak force of 8000 μN and a strain rate of 10{sup −2} s{sup −1}. Achieving good strength along with good ductility is challenging in nanocrystalline metals. When enough sample sizes are not available to measure ductility and other mechanical properties as per ASTM standards, as is the case with nanocrystalline materials, nanoindentation is a very promising technique to evaluate strain rate sensitivity. Strain rate sensitivity is a good measure of ductility and in the present work it is measured by performing indentation at various loads with varying loading rates. Strain rate sensitivity values of 0.024–0.054 are obtained for nanocrystalline Al which are high over conventional coarse grained Al. In addition, Scanning Probe Microscopy (SPM) image of the indent shows that there is some plastically flown region around the indent suggesting that this nanocrystalline aluminium is ductile.

  6. Antibacterial activity of cobalt(II complexes with some benzimidazole derivatives

    Directory of Open Access Journals (Sweden)

    S. O. PODUNAVAC-KUZMANOVIC

    2008-12-01

    Full Text Available The antibacterial activities of cobalt(II complexes with two series of benzimidazoles were evaluated in vitro against three Gram-positive bacterial strains (Bacillus cereus, Staphylococcus aureus, and Sarcina lutea and one Gram-negative isolate (Pseudomonas aeruginosa. The minimum inhibitory concentration was determined for all the complexes. The majority of the investtigated complexes displayed in vitro inhibitory activity against very persistent bacteria. They were found to be more active against Gram-positive than Gram-negative bacteria. It may be concluded that the antibacterial activity of the compounds is related to the cell wall structure of the tested bacteria. Comparing the inhibitory activities of the tested complexes, it was found that the 1-substituted-2-aminobenzimidazole derivatives were more active than complexes of 1-substituted-2-amino-5,6-dimethylbenzimidazoles. The effect of chemical structure on the antibacterial activity is discussed.

  7. Preparation of nanocrystalline Ce1-xSmx(Fe,Co)11Ti by melt spinning and mechanical alloying

    Science.gov (United States)

    Wuest, H.; Bommer, L.; Huber, A. M.; Goll, D.; Weissgaerber, T.; Kieback, B.

    2017-04-01

    Permanent magnetic materials based on Ce(Fe, Co)12-xTix with the ThMn12 structure are promising candidates for replacing NdFeB magnets. Its intrinsic magnetic properties are not far below the values of Nd2Fe14B, and the high amount of Fe and the fact that Ce is much more abundant and less expensive than Nd encourages the reasonable interest in these compounds. Nanocrystalline magnetic material of the composition Ce1-xSmxFe11-yCoyTi (x=0-1 and y=0; 1.95) has been produced by both melt spinning and mechanical alloying. Alloys containing only Ce as rare earth element (x=0) show coercivities below 77 kA/m, while for x=1 Hc,J values up to 392 kA/m are reached. Coercivity shows rather an exponential than a linear dependence on the gradual substitution of Ce by Sm.

  8. Passivation and corrosion behaviours of cobalt and cobalt-chromium-molybdenum alloy

    International Nuclear Information System (INIS)

    Metikos-Hukovic, M.; Babic, R.

    2007-01-01

    Passivation and corrosion behaviour of the cobalt and cobalt-base alloy Co30Cr6Mo was studied in a simulated physiological solution containing chloride and bicarbonate ions and with pH of 6.8. The oxido-reduction processes included solid state transformations occurring at the cobalt/electrolyte interface are interpreted using theories of surface electrochemistry. The dissolution of cobalt is significantly suppressed by alloying it with chromium and molybdenum, since the alloy exhibited 'chromium like' passivity. The structural and protective properties of passive oxide films formed spontaneously at the open circuit potential or during the anodic polarization were studied using electrochemical impedance spectroscopy in the wide frequency range

  9. Bone substitute biomaterials

    CERN Document Server

    Mallick, K

    2014-01-01

    Bone substitute biomaterials are fundamental to the biomedical sector, and have recently benefitted from extensive research and technological advances aimed at minimizing failure rates and reducing the need for further surgery. This book reviews these developments, with a particular focus on the desirable properties for bone substitute materials and their potential to encourage bone repair and regeneration. Part I covers the principles of bone substitute biomaterials for medical applications. One chapter reviews the quantification of bone mechanics at the whole-bone, micro-scale, and non-scale levels, while others discuss biomineralization, osteoductivization, materials to fill bone defects, and bioresorbable materials. Part II focuses on biomaterials as scaffolds and implants, including multi-functional scaffolds, bioceramics, and titanium-based foams. Finally, Part III reviews further materials with the potential to encourage bone repair and regeneration, including cartilage grafts, chitosan, inorganic poly...

  10. [Delegation yes, substitution no!].

    Science.gov (United States)

    Schroeder, A

    2014-08-01

    The aging of society leads on the one hand to increasing case numbers and on the other hand to a reduction in the number of physicians available for patient treatment. The delegation and substitution of medical duties as a tried and tested method is increasingly being recommended in order to compensate for the lack of physicians. The Berufsverband der Deutschen Urologen (BDU, Professional Association of German Urologists) supports the guiding principle of the Bundesärztekammer (Federal Medical Council) of "delegation yes, substitution no" and rejects a substitution of medical duties by non-medical academic health personnel. Against the background of the demographic changes, the increasing need for treatment and the current deficiency of junior physicians, a more extensive inclusion of well-qualified and experienced non-medical personnel by the delegation of medically responsible duties (medical scope of practice) can be an appropriate measure to maintain a good medical service in practices, hospitals and nursing homes.

  11. Aryl substitution of pentacenes

    Directory of Open Access Journals (Sweden)

    Andreas R. Waterloo

    2014-07-01

    Full Text Available A series of 11 new pentacene derivatives has been synthesized, with unsymmetrical substitution based on a trialkylsilylethynyl group at the 6-position and various aryl groups appended to the 13-position. The electronic and physical properties of the new pentacene chromophores have been analyzed by UV–vis spectroscopy (solution and thin films, thermoanalytical methods (DSC and TGA, cyclic voltammetry, as well as X-ray crystallography (for 8 derivatives. X-ray crystallography has been specifically used to study the influence of unsymmetrical substitution on the solid-state packing of the pentacene derivatives. The obtained results add to our ability to better predict substitution patterns that might be helpful for designing new semiconductors for use in solid-state devices.

  12. Aryl substitution of pentacenes

    Science.gov (United States)

    Waterloo, Andreas R; Sale, Anna-Chiara; Lehnherr, Dan; Hampel, Frank

    2014-01-01

    Summary A series of 11 new pentacene derivatives has been synthesized, with unsymmetrical substitution based on a trialkylsilylethynyl group at the 6-position and various aryl groups appended to the 13-position. The electronic and physical properties of the new pentacene chromophores have been analyzed by UV–vis spectroscopy (solution and thin films), thermoanalytical methods (DSC and TGA), cyclic voltammetry, as well as X-ray crystallography (for 8 derivatives). X-ray crystallography has been specifically used to study the influence of unsymmetrical substitution on the solid-state packing of the pentacene derivatives. The obtained results add to our ability to better predict substitution patterns that might be helpful for designing new semiconductors for use in solid-state devices. PMID:25161729

  13. Muon substituted free radicals

    International Nuclear Information System (INIS)

    Burkhard, P.; Fischer, H.; Roduner, E.; Strub, W.; Gygax, F.N.; Brinkman, G.A.; Louwrier, P.W.F.; McKenna, D.; Ramos, M.; Webster, B.C.

    1984-01-01

    Spin polarized energetic positive muons are injected as magnetic probes into unsaturated organic liquids. They are implemented via fast chemical processes ( -10 s) in various molecules. Of particular interest among these are muonium substituted free radicals. The technique allows determination of accurate rate coefficients for fast chemical reactions of radicals. Furthermore, radiochemical processes occuring in picoseconds after injection of the muon are studied. Of fundamental interest are also the structural and dynamical implications of substituting a proton by a muon, or in other terms, a hydrogen atom by a muonium atom. Selected examples for each of these three types of experiments are given. (Auth.)

  14. Structural, magnetic and electrical characterization of Mg–Ni nano-crystalline ferrites prepared through egg-white precursor

    Energy Technology Data Exchange (ETDEWEB)

    Gabal, M.A., E-mail: mgabalabdonada@yahoo.com [Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Al Angari, Y.M. [Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Zaki, H.M. [Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Physics Department, Faculty of Science, Zagazig University, Zagazig (Egypt)

    2014-08-01

    Soft Ni–Mg nano-crystalline ferrites with the general formula Ni{sub 1−x}Mg{sub x}Fe{sub 2}O{sub 4} (0≤x≤1) were synthesized through egg-white method. The precursor decomposition was followed by thermal analysis techniques. The obtained ferrites were characterized by X-ray diffraction, Fourier transform infrared and transmission electron microscopy measurements. X-ray diffraction showed the cubic spinel structure with crystallite size variation within the range 20–45 nm. The different structural data obtained were discussed in the view of ionic radii of the entire ions and their distribution within the lattice. The appropriate suggested cation distribution was then confirmed through Fourier transform infrared as well as electrical and magnetic properties measurements. Transmission electron microscopy exhibited a nano-crystal aggregation phenomenon. The observed size of the spherical particles agrees well with that obtained by X-ray diffraction. Hysteresis loop measurements revealed dilution in the obtained magnetic parameters by Mg-substitution due to the preferential occupancy of Mg{sup 2+} ions by the octahedral sites. Ac-electrical conductivity as a function of temperature and frequency exhibited a semi-conducting behavior with conductivity decreases by increasing Mg-content. The change in the slope of the curve indicates the changing in the conduction mechanism from electron hopping to polaron mechanism by increasing temperature. The obtained structural, electrical and magnetic properties were explained based on the cation distribution among tetrahedral and octahedral sites. - Highlights: • Ni–Mg nano-crystalline ferrites were synthesized through egg-white method. • An appropriate cation distribution was suggested. • Conductivity revealed a change in conduction mechanism by increasing temperature. • The effect of Mg-substitution on different properties was studied.

  15. Cobalt reduction of NSSS valve hardfacings for ALARA

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Joo Hak; Lee, Sang Sub [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1994-07-01

    This report informs NSSS designer that replacement of materials is one of the major means of ALARA implementation, and describes that NSSS valves with high-cobalt hardfacing are significant contributors to post-shutdown radiation fields caused by activation of cobalt-59 to cobalt-60. Generic procedures for implementing cobalt reduction programs for valves are presented. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. The nuclear safety issues involved with changing valve hardfacing materials are discussed. The common methods used to deposit hardfacing materials are described together with an explanation of the wear measurements. Wear resistance, corrosion resistance, friction coefficient, and mechanical properties of candidate hardfacing alloys are given. World-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The use of low-cobalt or cobalt-free alloys in other nuclear plant components is described. 17 figs., 38 tabs., 18 refs. (Author).

  16. Cobalt reduction of NSSS valve hardfacings for ALARA

    International Nuclear Information System (INIS)

    Kim, Joo Hak; Lee, Sang Sub

    1994-07-01

    This report informs NSSS designer that replacement of materials is one of the major means of ALARA implementation, and describes that NSSS valves with high-cobalt hardfacing are significant contributors to post-shutdown radiation fields caused by activation of cobalt-59 to cobalt-60. Generic procedures for implementing cobalt reduction programs for valves are presented. Discussions are presented of the general and specific design requirements for valve hardfacing in nuclear service. The nuclear safety issues involved with changing valve hardfacing materials are discussed. The common methods used to deposit hardfacing materials are described together with an explanation of the wear measurements. Wear resistance, corrosion resistance, friction coefficient, and mechanical properties of candidate hardfacing alloys are given. World-wide nuclear utility experience with cobalt-free hardfacing alloys is described. The use of low-cobalt or cobalt-free alloys in other nuclear plant components is described. 17 figs., 38 tabs., 18 refs. (Author)

  17. Water splitting: Taking cobalt in isolation

    Science.gov (United States)

    Wang, Aiqin; Zhang, Tao

    2016-01-01

    The sustainable production of hydrogen is key to the delivery of clean energy in a hydrogen economy; however, lower-cost alternatives to platinum electrocatalysts are needed. Now, isolated, earth-abundant cobalt atoms dispersed over nitrogen-doped graphene are shown to efficiently electrolyse water to generate hydrogen.

  18. Synthesis and Characterization of Cobalt Ferrite Nanoparticles ...

    African Journals Online (AJOL)

    prepared material. It was observed that surface modification such as with silica coating on the cobalt ferrite will have significant effect on the structural and magnetic properties. It is also observed that, silica coated nanoparticles could be used in biomedical applications (Hong et al., 2013). In this work we have chosen sol-gel ...

  19. Nano cobalt oxides for photocatalytic hydrogen production

    KAUST Repository

    Mangrulkar, Priti A.

    2012-07-01

    Nano structured metal oxides including TiO 2, Co 3O 4 and Fe 3O 4 have been synthesized and evaluated for their photocatalytic activity for hydrogen generation. The photocatalytic activity of nano cobalt oxide was then compared with two other nano structured metal oxides namely TiO 2 and Fe 3O 4. The synthesized nano cobalt oxide was characterized thoroughly with respect to EDX and TEM. The yield of hydrogen was observed to be 900, 2000 and 8275 mmol h -1 g -1 of photocatalyst for TiO 2, Co 3O 4 and Fe 3O 4 respectively under visible light. It was observed that the hydrogen yield in case of nano cobalt oxide was more than twice to that of TiO 2 and the hydrogen yield of nano Fe 3O 4 was nearly four times as compared to nano Co 3O 4. The influence of various operating parameters in hydrogen generation by nano cobalt oxide was then studied in detail. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  20. Sputtering on cobalt with noble gas ions

    International Nuclear Information System (INIS)

    Sarholt-Kristensen, L.; Johansen, A.; Johnson, E.

    1983-01-01

    Single crystals of cobalt have been bombarded with 80 keV Ar + ions and with 80 keV and 200 keV Xe + ions in the [0001] direction of the hcp phase and the [111] direction of the fcc phase. The sputtering yield has been measured as function of target temperature (20 0 C-500 0 C), showing a reduction in sputtering yield for 80 keV Ar + ions and 200 keV Xe + ions, when the crystal structure changes from hcp to fcc. In contrast to this, bombardment with 80 keV Xe + ions results in an increase in sputtering yield as the phase transition is passed. Sputtering yields for [111] nickel are in agreement with the sputtering yields for fcc cobalt indicating normal behaviour of the fcc cobalt phase. The higher sputtering yield of [0001] cobalt for certain combinations of ion mass and energy may then be ascribed to disorder induced partly by martensitic phase transformation, partly by radiation damage. (orig.)

  1. Properties of Resistive Hydrogen Sensors as a Function of Additives of 3 D-Metals Introduced in the Volume of Thin Nanocrystalline SnO2 Films

    Science.gov (United States)

    Sevast'yanov, E. Yu.; Maksimova, N. K.; Potekaev, A. I.; Sergeichenko, N. V.; Chernikov, E. V.; Almaev, A. V.; Kushnarev, B. O.

    2017-11-01

    Analysis of the results of studying electrical and gas sensitive characteristics of the molecular hydrogen sensors based on thin nanocrystalline SnO2 films coated with dispersed Au layers and containing Au+Ni and Au+Co impurities in the bulk showed that the characteristics of these sensors are more stable under the prolonged exposure to hydrogen in comparison with Au/SnO2:Sb, Au films modified only with gold. It has been found that introduction of the nickel and cobalt additives increases the band bending at the grain boundaries of tin dioxide already in freshly prepared samples, which indicates an increase in the density Ni of the chemisorbed oxygen. It is important that during testing, the band bending eφs at the grain boundaries of tin dioxide additionally slightly increases. It can be assumed that during crystallization of films under thermal annealing, the 3d-metal atoms in the SnO2 volume partially segregate on the surface of microcrystals and form bonds with lattice oxygen, the superstoichiometric tin atoms are formed, and the density Ni increases. If the bonds of oxygen with nickel and cobalt are stronger than those with tin, then, under the prolonged tests, atomic hydrogen will be oxidized not by lattice oxygen, but mainly by the chemisorbed one. In this case, stability of the sensors' characteristics increases.

  2. NATO Advanced Research Workshop on Properties and Applications of Nanocrystalline Alloys from Amorphous Precursors

    CERN Document Server

    Idzikowski, Bogdan; Miglierini, Marcel

    2005-01-01

    Metallic (magnetic and non-magnetic) nanocrystalline materials have been known for over ten years but only recent developments in the research into those complex alloys and their metastable amorphous precursors have created a need to summarize the most important accomplishments in the field. This book is a collection of articles on various aspects of metallic nanocrystalline materials, and an attempt to address this above need. The main focus of the papers is put on the new issues that emerge in the studies of nanocrystalline materials, and, in particular, on (i) new compositions of the alloys, (ii) properties of conventional nanocrystalline materials, (iii) modeling and simulations, (iv) preparation methods, (v) experimental techniques of measurements, and (vi) different modern applications. Interesting phenomena of the physics of nanocrystalline materials are a consequence of the effects induced by the nanocrystalline structure. They include interface physics, the influence of the grain boundaries, the aver...

  3. Single cobalt sites in mesoporous N-doped carbon matrix for selective catalytic hydrogenation of nitroarenes

    KAUST Repository

    Sun, Xiaohui

    2017-11-20

    A supported cobalt catalyst with atomically dispersed Co-Nx sites (3.5 wt% Co) in a mesoporous N-doped carbon matrix (named Co@mesoNC) is synthesized by hydrolysis of tetramethyl orthosilicate (TMOS) in a Zn/Co bimetallic zeolitic imidazolate framework (BIMZIF(Co,Zn)), followed by high-temperature pyrolysis and SiO2 leaching. A combination of TEM, XRD XPS and X-ray absorption spectroscopy studies confirm the absence of cobalt nanoparticles and indicate that these highly dispersed cobalt species are present in the form of Co-Nx. The exclusive formation of Co-Nx sites in the carbon matrix is attributed to the presence of a large amount of Zn and N in the BIMZIF precursor together with the presence of SiO2 in the pore space of this framework, extending the initial spatial distance between cobalt atoms and thereby impeding their agglomeration. The presence of SiO2 during high-temperature pyrolysis is proven crucial to create mesoporosity and a high BET area and pore volume in the N-doped carbon support (1780 m2 g−1, 1.54 cm3 g−1). This heterogeneous Co@mesoNC catalyst displays high activity and selectivity (>99%) for the selective hydrogenation of nitrobenzene to aniline at mild conditions (0.5–3 MPa, 343–383 K). When more challenging substrates (functionalized nitroarenes) are hydrogenated, the catalyst Co@mesoNC displays an excellent chemoselectivity to the corresponding substituted anilines.The presence of mesoporosity improves mass transport of reactants and/or products and the accessibility of the active Co-Nx sites, and greatly reduces deactivation due to fouling.

  4. Single cobalt sites in mesoporous N-doped carbon matrix for selective catalytic hydrogenation of nitroarenes

    KAUST Repository

    Sun, Xiaohui; Olivos-Suarez, Alma I.; Osadchii, Dmitrii; Romero, Maria Jose Valero; Kapteijn, Freek; Gascon, Jorge

    2017-01-01

    A supported cobalt catalyst with atomically dispersed Co-Nx sites (3.5 wt% Co) in a mesoporous N-doped carbon matrix (named Co@mesoNC) is synthesized by hydrolysis of tetramethyl orthosilicate (TMOS) in a Zn/Co bimetallic zeolitic imidazolate framework (BIMZIF(Co,Zn)), followed by high-temperature pyrolysis and SiO2 leaching. A combination of TEM, XRD XPS and X-ray absorption spectroscopy studies confirm the absence of cobalt nanoparticles and indicate that these highly dispersed cobalt species are present in the form of Co-Nx. The exclusive formation of Co-Nx sites in the carbon matrix is attributed to the presence of a large amount of Zn and N in the BIMZIF precursor together with the presence of SiO2 in the pore space of this framework, extending the initial spatial distance between cobalt atoms and thereby impeding their agglomeration. The presence of SiO2 during high-temperature pyrolysis is proven crucial to create mesoporosity and a high BET area and pore volume in the N-doped carbon support (1780 m2 g−1, 1.54 cm3 g−1). This heterogeneous Co@mesoNC catalyst displays high activity and selectivity (>99%) for the selective hydrogenation of nitrobenzene to aniline at mild conditions (0.5–3 MPa, 343–383 K). When more challenging substrates (functionalized nitroarenes) are hydrogenated, the catalyst Co@mesoNC displays an excellent chemoselectivity to the corresponding substituted anilines.The presence of mesoporosity improves mass transport of reactants and/or products and the accessibility of the active Co-Nx sites, and greatly reduces deactivation due to fouling.

  5. Hazardous solvent substitution

    International Nuclear Information System (INIS)

    Twitchell, K.E.

    1995-01-01

    This article is an overview of efforts at INEL to reduce the generation of hazardous wastes through the elimination of hazardous solvents. To aid in their efforts, a number of databases have been developed and will become a part of an Integrated Solvent Substitution Data System. This latter data system will be accessible through Internet

  6. Carbolanthanation of substituted alkynes

    International Nuclear Information System (INIS)

    Kalinin, V.N.; Kazimirchuk, E.I.; Vitt, S.V.; Khandozhko, V.N.; Beletskaya, I.P.

    1993-01-01

    Using the reaction between CH 3 YbI and substituted alkynes as an example, agents can enter into carbolanthanation reaction via transfer of a methyl group to carbon atom of acetylene bond with the production of a new olefin carbanion. 5 refs.; 1 fig.; 3 tabs

  7. Theoretical study on recoilless fractions of simple cubic monatomic nanocrystalline particles

    International Nuclear Information System (INIS)

    Huang Jianping; Wang Luya

    2002-01-01

    Recoilless fractions of simple cubic monatomic nanocrystalline particles are calculated by using displacement-displacement Green's function. The numerical results show that the recoilless fractions on the surface of monatomic nanocrystalline particles are smaller than those in the inner, and they decrease when the particle size increase, the recoilless fractions of whole monatomic nanocrystalline particles increase when the particle size increase. These effects are more evident when the temperature is higher

  8. Vibrational thermodynamics of Fe90Zr7B3 nanocrystalline alloy from nuclear inelastic scattering

    DEFF Research Database (Denmark)

    Stankov, S.; Miglierini, M.; Chumakov, A. I.

    2010-01-01

    Recently we determined the iron-partial density of vibrational states (DOS) of nanocrystalline Fe(90)Zr(7)B(3) (Nanoperm), synthesized by crystallization of an amorphous precursor, for various stages of nanocrystallization separating the DOS of the nanograins from that of the interfaces [S. Stank......, vibrational entropy, and lattice specific heat as the material transforms from amorphous, through nanocrystalline, to fully crystallized state. The reported results shed new light on the previously observed anomalies in the vibrational thermodynamics of nanocrystalline materials....

  9. Cellulose-precursor synthesis of nanocrystalline Co0.5Cu0.5Fe2O4 spinel ferrites

    International Nuclear Information System (INIS)

    Ounnunkad, Kontad; Phanichphant, Sukon

    2012-01-01

    Highlights: ► Synthesis of spinel copper cobalt nanoferrite particles from a cellulose precursor for the first time. Control of nanosize and properties of nanoferrites can take place by varying the calcining temperature. The simple, low cost, easy cellulose process is a choice of nanoparticle processing technology. -- Abstract: Nanocrystalline Cu 0.5 Co 0.5 Fe 2 O 4 powders were prepared via a metal-cellulose precursor synthetic route. Cellulose was used as a fuel and a dispersing agent. The resulting precursors were calcined in the temperature range of 450–600 °C. The phase development of the samples was determined by using Fourier transform infrared (FT-IR) spectroscopy and powder X-ray diffraction (XRD). The field-dependent magnetizations of the nanopowders were measured by vibrating sample magnetometer (VSM). All XRD patterns are of a spinel ferrite with cubic symmetry. Microstructure of the ferrites showed irregular shapes and uniform particles with agglomeration. From XRD data, the crystallite sizes are in range of 16–42 nm. Saturation magnetization and coercivity increased with increasing calcining temperature due to enhancement of crystallinity and reduction of oxygen vacancies.

  10. Room temperature ferromagnetism of nanocrystalline Nd1.90Ni0.10O3-δ

    Science.gov (United States)

    Sarkar, B. J.; Mandal, J.; Dalal, M.; Bandyopadhyay, A.; Chakrabarti, P. K.

    2018-05-01

    Nanocrystalline sample of Ni2+ doped neodymium oxide (Nd1.90Ni0.10O3-δ, NNO) is synthesized by co-precipitation method. Analysis of X-ray diffraction (XRD) pattern by Rietveld refinement method confirms the desired phase of NNO and complete substitution of Ni2+ ions in the Nd2O3 lattice. Analyses of transmission electron microscopy (TEM) and Raman spectroscopy of NNO recorded at room temperature (RT) also substantiate this fact. Besides, no traces of impurities are found in the analyses of XRD, TEM and Raman data. Room temperature hysteresis loop of NNO suggests the presence of weak ferromagnetism (FM) in low field region ( 600 mT), but in high field region paramagnetism of the host is more prominent. Magnetization vs. temperature ( M- T) curve in the entire temperature range (300-5 K) is analyzed successfully by a combined equation generated from three-dimensional (3D) spin wave model and Curie-Weiss law, which suggests the presence of mixed paramagnetic phase together with ferromagnetic phase in the doped sample. The onset of magnetic ordering is analyzed by oxygen vacancy mediated F-center exchange (FCE) coupling mechanism.

  11. Nanocrystalline hydroxyapatite doped with selenium oxyanions: A new material for potential biomedical applications

    International Nuclear Information System (INIS)

    Kolmas, Joanna; Oledzka, Ewa; Sobczak, Marcin; Nałęcz-Jawecki, Grzegorz

    2014-01-01

    Selenium-substituted hydroxyapatites containing selenate SeO 4 2− or selenite SeO 3 2− ions were synthesized using a wet precipitation method. The selenium content was determined by atomic absorbance spectrometry. The raw, unsintered powders were also characterized using powder X-ray diffraction, middle-range FT-IR spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopic microanalysis. The synthesized apatites were found to be pure and nanocrystalline with a crystal size similar to that in bone mineral. The incorporation of selenium oxyanions into the crystal lattice was confirmed. The toxicity of hydroxyapatites containing selenite or selenate ions was evaluated with a protozoan assay and bacterial luminescence test. - Highlights: • We synthesized and analyzed hydroxyapatites doped with selenium oxyanions. • We used various analytical methods, i.e. XRD, TEM, AAS and FT-IR. • We confirmed incorporation of SeO 3 2− and SeO 4 2− into the crystal lattice. • The toxicity of the materials was studied

  12. Nanocrystalline hydroxyapatite doped with selenium oxyanions: A new material for potential biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Kolmas, Joanna, E-mail: joanna.kolmas@wum.edu.pl [Medical University of Warsaw, Faculty of Pharmacy, Department of Inorganic and Analytical Chemistry, ul. Banacha 1, 02-097 Warsaw (Poland); Oledzka, Ewa; Sobczak, Marcin [Medical University of Warsaw, Faculty of Pharmacy, Department of Inorganic and Analytical Chemistry, ul. Banacha 1, 02-097 Warsaw (Poland); Nałęcz-Jawecki, Grzegorz [Medical University of Warsaw, Faculty of Pharmacy, Department of Environmental Health Sciences, ul. Banacha 1, 02-097 Warsaw (Poland)

    2014-06-01

    Selenium-substituted hydroxyapatites containing selenate SeO{sub 4}{sup 2−} or selenite SeO{sub 3}{sup 2−} ions were synthesized using a wet precipitation method. The selenium content was determined by atomic absorbance spectrometry. The raw, unsintered powders were also characterized using powder X-ray diffraction, middle-range FT-IR spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopic microanalysis. The synthesized apatites were found to be pure and nanocrystalline with a crystal size similar to that in bone mineral. The incorporation of selenium oxyanions into the crystal lattice was confirmed. The toxicity of hydroxyapatites containing selenite or selenate ions was evaluated with a protozoan assay and bacterial luminescence test. - Highlights: • We synthesized and analyzed hydroxyapatites doped with selenium oxyanions. • We used various analytical methods, i.e. XRD, TEM, AAS and FT-IR. • We confirmed incorporation of SeO{sub 3}{sup 2−} and SeO{sub 4}{sup 2−} into the crystal lattice. • The toxicity of the materials was studied.

  13. Efficient photoluminescence of Dy3+ at low concentrations in nanocrystalline ZrO2

    International Nuclear Information System (INIS)

    Diaz-Torres, L.A.; Rosa, E. de la; Salas, P.; Romero, V.H.; Angeles-Chavez, C.

    2008-01-01

    Nanocrystalline ZrO 2 :Dy 3+ were prepared by sol-gel and the structural and photoluminescence properties characterized. The crystallite size ranges from 20 to 50 nm and the crystalline phase is a mixture of tetragonal and monoclinic structure controlled by dopant concentration. Strong white light produced by the host emission band centered at ∼460 nm and two strong Dy 3+ emission bands, blue (488 nm) and yellow (580 nm), under direct excitation at 350 nm were observed. The highest efficiency was obtained for 0.5 mol% of Dy 3+ . Emission is explained in terms of high asymmetry of the host suggesting that Dy 3+ are substituted mainly into Zr 4+ lattice sites at the crystallite surface. Luminescence quenching is explained in terms of cross-relaxation of intermediate Dy 3+ levels. - Graphical abstract: White light emission from ∼70 nm ZrO 2 :Dy 3+ nanocrystals. The highest efficiency was obtained for 0.5 mol% of dopant and the dominant crystalline structure was monoclinic

  14. A preliminary study in osteoinduction by a nano-crystalline hydroxyapatite in the mini pig.

    Directory of Open Access Journals (Sweden)

    Karsten K H Gundlach

    2011-04-01

    Full Text Available To test the probable osteoinductive properties of NanoBone, a new highly non-sintered porous nano-crystalline hydroxylapatite bone substitute embedded into a silica gel matrix, granules were implanted subcutaneously and intramuscularly into the back region of 18 mini pigs. After periods of 5 and 10 weeks as well as 4 and 8 months, implantation sites were investigated using histological and histomorphometric procedures. Signs of early osteogenesis could already be detected after 5 weeks. The later periods were characterized by increasing membranous osteogenesis in and around the granules leading to the formation of bone-like structures showing periosteal and tendon-like structures with bone marrow and focal chondrogenesis. Bone formation was better in the subcutaneous than in the intramuscular implantation sites. This ectopic osteogenesis is discussed with regard to the nanoporosity and microporosity of the material, physico-chemical interactions at its surface, the differentiation of osteoblasts, the role of angiogenesis and the probable involvement of growth factors. The results of this preliminary study indicate that this biomaterial has osteoinductive potential and induces the formation of bone structures, mainly in subcutaneous adipose tissue in the pig.

  15. A preliminary study in osteoinduction by a nano-crystalline hydroxyapatite in the mini pig.

    Science.gov (United States)

    Götz, Werner; Lenz, Solvig; Reichert, Christoph; Henkel, Kai-Olaf; Bienengräber, Volker; Pernicka, Laura; Gundlach, Karsten K H; Gredes, Tomasz; Gerber, Thomas; Gedrange, Tomasz; Heinemann, Friedhelm

    2010-12-01

    To test the probable osteoinductive properties of NanoBone, a new highly non-sintered porous nano-crystalline hydroxylapatite bone substitute embedded into a silica gel matrix, granules were implanted subcutaneously and intramuscularly into the back region of 18 mini pigs. After periods of 5 and 10 weeks as well as 4 and 8 months, implantation sites were investigated using histological and histomorphometric procedures. Signs of early osteogenesis could already be detected after 5 weeks. The later periods were characterized by increasing membranous osteogenesis in and around the granules leading to the formation of bone-like structures showing periosteal and tendon-like structures with bone marrow and focal chondrogenesis. Bone formation was better in the subcutaneous than in the intramuscular implantation sites. This ectopic osteogenesis is discussed with regard to the nanoporosity and microporosity of the material, physico-chemical interactions at its surface, the differentiation of osteoblasts, the role of angiogenesis and the probable involvement of growth factors. The results of this preliminary study indicate that this biomaterial has osteoinductive potential and induces the formation of bone structures, mainly in subcutaneous adipose tissue in the pig.

  16. An investigation on the preparation of nanocrystalline hydrous zirconia from zirconium tungstate

    Science.gov (United States)

    Antunes, M.; Perottoni, C. A.; Gouvêa, D.; Machado, G.; Zorzi, J. E.

    2018-02-01

    Hydrous nanocrystalline zirconia was prepared from an unusual precursor—the bimetallic oxide zirconium tungstate (ZrW2O8)—in alkaline medium. Different experimental conditions (NaOH concentration, time and temperature) were used to investigate the effects on crystallographic, morphological, chemical and thermal characteristics of the products. The resulting materials are composed of particles with a crystal structure similar to that of cubic ZrO2 (or a mixture of tetragonal and cubic phases, depending on the synthesis conditions), with particle size around 5 nm and crystallites around 3 nm in diameter. These particles form high surface area agglomerates, exhibiting mesoporosity and capacity for adsorption of water and carbon dioxide. The synthesis mechanism appears to be constituted, first, by a chemical substitution reaction between the WO4 tetrahedra and hydroxyl ions, with subsequent solubilization of the structure. Indeed, excess hydroxyls in the medium form colloidal zirconium ions which polymerize/condense, generating crystalline nuclei in a process facilitated by heterogeneous nucleation and supersaturation. The presence of residual tungsten in all samples appears to be a key element for stabilizing the size and crystalline structure of the materials produced.

  17. The cytotoxicity and genotoxicity of soluble and particulate cobalt in human lung fibroblast cells

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Leah J.; Holmes, Amie L. [Wise Laboratory of Environmental and Genetic Toxicology, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Maine Center for Environmental Toxicology and Health, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Department of Applied Medical Science, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Kandpal, Sanjeev Kumar; Mason, Michael D. [Department of Chemical and Biological Engineering, University of Maine, Orono, ME (United States); Zheng, Tongzhang [Department of Environmental Health Sciences, Yale School of Public Health, New Haven, CT (United States); Wise, John Pierce, E-mail: John.Wise@usm.maine.edu [Wise Laboratory of Environmental and Genetic Toxicology, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Maine Center for Environmental Toxicology and Health, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States); Department of Applied Medical Science, University of Southern Maine, 96 Falmouth St., P.O. Box 9300, Portland, ME 04101-9300 (United States)

    2014-08-01

    Cobalt exposure is increasing as cobalt demand rises worldwide due to its use in enhancing rechargeable battery efficiency, super-alloys, and magnetic products. Cobalt is considered a possible human carcinogen with the lung being a primary target. However, few studies have considered cobalt-induced toxicity in human lung cells. Therefore, in this study, we sought to determine the cytotoxicity and genotoxicity of particulate and soluble cobalt in human lung cells. Cobalt oxide and cobalt chloride were used as representative particulate and soluble cobalt compounds, respectively. Exposure to both particulate and soluble cobalt induced a concentration-dependent increase in cytotoxicity, genotoxicity, and intracellular cobalt ion levels. Based on intracellular cobalt ion levels, we found that soluble cobalt was more cytotoxic than particulate cobalt while particulate and soluble cobalt induced similar levels of genotoxicity. However, soluble cobalt induced cell cycle arrest indicated by the lack of metaphases at much lower intracellular cobalt concentrations compared to cobalt oxide. Accordingly, we investigated the role of particle internalization in cobalt oxide-induced toxicity and found that particle-cell contact was necessary to induce cytotoxicity and genotoxicity after cobalt exposure. These data indicate that cobalt compounds are cytotoxic and genotoxic to human lung fibroblasts, and solubility plays a key role in cobalt-induced lung toxicity. - Highlights: • Particulate and soluble cobalt are cytotoxic and genotoxic to human lung cells. • Soluble cobalt induces more cytotoxicity compared to particulate cobalt. • Soluble and particulate cobalt induce similar levels of genotoxicity. • Particle-cell contact is required for particulate cobalt-induced toxicity.

  18. Effect of Nanocrystalline Hydroxyapatite Socket Preservation on Orthodontically Induced Inflammatory Root Resorption

    Science.gov (United States)

    Seifi, Massoud; Arayesh, Ali; Shamloo, Nafise; Hamedi, Roya

    2015-01-01

    Objective Orthodontically induced inflammatory root resorption (OIIRR) is considered to be an important sequel associated with orthodontic tooth movement (OTM). OTM after Socket preservation enhances the periodontal condition before orthodontic space closure. The purpose of this study is to investigate the histologic effects of NanoBone®, a new highly nonsintered porous nano-crystalline hydroxyapatite bone on root resorption following OTM. Materials and Methods This experimental study was conducted on four male dogs. In each dog, four defects were created at the mesial aspects of the maxillary and mandibular first premolars. The defects were filled with NanoBone®. We used the NiTi closed coil for mesial movement of the first premolar tooth. When the experimental teeth moved approximately halfway into the defects, after two months, the animals were sacrificed and we harvested the area of interest. The first premolar root and adjacent tissues were histologically evaluated. The three-way ANOVA statistical test was used for comparison. Results The mean root resorption in the synthetic bone substitute group was 22.87 ± 11.25×10-4mm2 in the maxilla and 21.41 ± 11.25×10-4mm2 in the mandible. Statistically, there was no significant difference compared to the control group (p>0.05). Conclusion The use of a substitution graft in the nano particle has some positive effects in accessing healthy periodontal tissue following orthodontic procedures without significant influence on root resorption (RR). Histological evaluation in the present study showed osteoblastic activity and remodeling environment of nanoparticles in NanoBone®. PMID:25685742

  19. Effect of nanocrystalline hydroxyapatite socket preservation on orthodontically induced inflammatory root resorption.

    Science.gov (United States)

    Seifi, Massoud; Arayesh, Ali; Shamloo, Nafise; Hamedi, Roya

    2015-01-01

    Orthodontically induced inflammatory root resorption (OIIRR) is considered to be an important sequel associated with orthodontic tooth movement (OTM). OTM after Socket preservation enhances the periodontal condition before orthodontic space closure. The purpose of this study is to investigate the histologic effects of NanoBone®, a new highly nonsintered porous nano-crystalline hydroxyapatite bone on root resorption following OTM. This experimental study was conducted on four male dogs. In each dog, four defects were created at the mesial aspects of the maxillary and mandibular first premolars. The defects were filled with NanoBone®. We used the NiTi closed coil for mesial movement of the first premolar tooth. When the experimental teeth moved approximately halfway into the defects, after two months, the animals were sacrificed and we harvested the area of interest. The first premolar root and adjacent tissues were histologically evaluated. The three-way ANOVA statistical test was used for comparison. The mean root resorption in the synthetic bone substitute group was 22.87 ± 11.25×10(-4)mm(2) in the maxilla and 21.41 ± 11.25×10(-4)mm(2) in the mandible. Statistically, there was no significant difference compared to the control group (p>0.05). The use of a substitution graft in the nano particle has some positive effects in accessing healthy periodontal tissue following orthodontic procedures without significant influence on root resorption (RR). Histological evaluation in the present study showed osteoblastic activity and remodeling environment of nanoparticles in NanoBone®.

  20. Paramagnetic centers in nanocrystalline TiC/C system

    International Nuclear Information System (INIS)

    Guskos, N.; Bodziony, T.; Maryniak, M.; Typek, J.; Biedunkiewicz, A.

    2008-01-01

    Electron paramagnetic resonance is applied to study the defect centers in nanocrystalline titanium carbide dispersed in carbon matrix (TiC x /C) synthesized by the non-hydrolytic sol-gel process. The presence of Ti 3+ paramagnetic centers is identified below 120 K along with a minor contribution from localized defect spins coupled with the conduction electron system in the carbon matrix. The temperature dependence of the resonance intensity of the latter signal indicates weak antiferromagnetic interactions. The presence of paramagnetic centers connected with trivalent titanium is suggested to be the result of chemical disorder, which can be further related to the observed anomalous behavior of conductivity, hardness, and corrosion resistance of nanocrystalline TiC x /C

  1. Electrophoretic Nanocrystalline Graphene Film Electrode for Lithium Ion Battery

    International Nuclear Information System (INIS)

    Kaprans, Kaspars; Bajars, Gunars; Kucinskis, Gints; Dorondo, Anna; Mateuss, Janis; Gabrusenoks, Jevgenijs; Kleperis, Janis; Lusis, Andrejs

    2015-01-01

    Graphene sheets were fabricated by electrophoretic deposition method from water suspension of graphene oxide followed by thermal reduction. The formation of nanocrystalline graphene sheets has been confirmed by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The electrochemical performance of graphene sheets as anode material for lithium ion batteries was evaluated by cycling voltammetry, galvanostatic charge-discharge cycling, and electrochemical impedance spectroscopy. Fabricated graphene sheets exhibited high discharge capacity of about 1120 mAh·g −1 and demonstrated good reversibility of lithium intercalation and deintercalation in graphene sheet film with capacity retention over 85 % after 50 cycles. Results show that nanocrystalline graphene sheets prepared by EPD demonstrated a high potential for application as anode material in lithium ion batteries

  2. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    Science.gov (United States)

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-01-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

  3. Nanocrystalline electrodeposited Ni-Mo-C cathodes for hydrogen production

    International Nuclear Information System (INIS)

    Hashimoto, K.; Sasaki, T.; Meguro, S.; Asami, K.

    2004-01-01

    Tailoring active nickel alloy cathodes for hydrogen evolution in a hot concentrated hydroxide solution was attempted by electrodeposition. The carbon addition to Ni-Mo alloys decreased the nanocrystalline grain size and remarkably enhanced the activity for hydrogen evolution, changing the mechanism of hydrogen evolution. The Tafel slope of hydrogen evolution was about 35 mV per decade. This suggested that the rate-determining step is desorption of adsorbed hydrogen atoms by recombination. As was distinct from the binary Ni-Mo alloys, after open circuit immersion, the overpotential, that is, the activity of nanocrystalline Ni-Mo-C alloys for hydrogen evolution was not changed, indicating the sufficient durability in the practical electrolysis

  4. Nanocrystalline Ni-Co Alloy Synthesis by High Speed Electrodeposition

    Directory of Open Access Journals (Sweden)

    Jamaliah Idris

    2013-01-01

    Full Text Available Electrodeposition of nanocrystals is economically and technologically viable production path for the synthesis of pure metals and alloys both in coatings and bulk form. The study presents nanocrystalline Ni-Co alloy synthesis by high speed electrodeposition. Nanocrystalline Ni-Co alloys coatings were prepared by direct current (DC and deposited directly on steel and aluminum substrates without any pretreatment, using high speed electrodeposition method. The influence of the electrolysis parameters, such as cathodic current density and temperature at constant pH, on electrodeposition and microstructure of Ni-Co alloys were examined. A homogeneous surface morphology was obtained at all current densities of the plated samples, and it was evident that the current density and temperature affect the coating thickness of Ni-Co alloy coatings.

  5. Grain boundary and triple junction diffusion in nanocrystalline copper

    Energy Technology Data Exchange (ETDEWEB)

    Wegner, M., E-mail: m.wegner@uni-muenster.de; Leuthold, J.; Peterlechner, M.; Divinski, S. V., E-mail: divin@uni-muenster.de [Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Straße 10, D-48149, Münster (Germany); Song, X., E-mail: xysong@bjut.edu.cn [College of Materials Science and Engineering, Beijing University of Technology, 100124 Beijing (China); Wilde, G. [Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Straße 10, D-48149, Münster (Germany); Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, 200444 Shanghai (China)

    2014-09-07

    Grain boundary and triple junction diffusion in nanocrystalline Cu samples with grain sizes, 〈d〉, of ∼35 and ∼44 nm produced by spark plasma sintering were investigated by the radiotracer method using the {sup 63}Ni isotope. The measured diffusivities, D{sub eff}, are comparable with those determined previously for Ni grain boundary diffusion in well-annealed, high purity, coarse grained, polycrystalline copper, substantiating the absence of a grain size effect on the kinetic properties of grain boundaries in a nanocrystalline material at grain sizes d ≥ 35 nm. Simultaneously, the analysis predicts that if triple junction diffusion of Ni in Cu is enhanced with respect to the corresponding grain boundary diffusion rate, it is still less than 500⋅D{sub gb} within the temperature interval from 420 K to 470 K.

  6. Effect of power on the growth of nanocrystalline silicon films

    International Nuclear Information System (INIS)

    Kumar, Sushil; Dixit, P N; Rauthan, C M S; Parashar, A; Gope, Jhuma

    2008-01-01

    Nanocrystalline silicon thin films were grown using a gaseous mixture of silane, hydrogen and argon in a plasma-enhanced chemical vapor deposition system. These films were deposited away from the conventional low power regime normally used for the deposition of device quality hydrogenated amorphous silicon films. It was observed that, with the increase of applied power, there is a change in nanocrystalline phases which were embedded in the amorphous matrix of silicon. Atomic force microscopy micrographs show that these films contain nanocrystallite of 20-100 nm size. Laser Raman and photoluminescence peaks have been observed at 514 cm -1 and 2.18 eV, respectively, and particle sizes were estimated using the same as 8.24 nm and 3.26 nm, respectively. It has also been observed that nanocrystallites in these films enhanced the optical bandgap and electrical conductivity

  7. Effect of power on the growth of nanocrystalline silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sushil; Dixit, P N; Rauthan, C M S; Parashar, A; Gope, Jhuma [Plasma Processed Materials Group, National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012 (India)], E-mail: skumar@mail.nplindia.ernet.in

    2008-08-20

    Nanocrystalline silicon thin films were grown using a gaseous mixture of silane, hydrogen and argon in a plasma-enhanced chemical vapor deposition system. These films were deposited away from the conventional low power regime normally used for the deposition of device quality hydrogenated amorphous silicon films. It was observed that, with the increase of applied power, there is a change in nanocrystalline phases which were embedded in the amorphous matrix of silicon. Atomic force microscopy micrographs show that these films contain nanocrystallite of 20-100 nm size. Laser Raman and photoluminescence peaks have been observed at 514 cm{sup -1} and 2.18 eV, respectively, and particle sizes were estimated using the same as 8.24 nm and 3.26 nm, respectively. It has also been observed that nanocrystallites in these films enhanced the optical bandgap and electrical conductivity.

  8. Research Update: Phonon engineering of nanocrystalline silicon thermoelectrics

    Directory of Open Access Journals (Sweden)

    Junichiro Shiomi

    2016-10-01

    Full Text Available Nanocrystalline silicon thermoelectrics can be a solution to improve the cost-effectiveness of thermoelectric technology from both material and integration viewpoints. While their figure-of-merit is still developing, recent advances in theoretical/numerical calculations, property measurements, and structural synthesis/fabrication have opened up possibilities to develop the materials based on fundamental physics of phonon transport. Here, this is demonstrated by reviewing a series of works on nanocrystalline silicon materials using calculations of multiscale phonon transport, measurements of interfacial heat conduction, and synthesis from nanoparticles. Integration of these approaches allows us to engineer phonon transport to improve the thermoelectric performance by introducing local silicon-oxide structures.

  9. Size dependence of the optical spectrum in nanocrystalline silver

    International Nuclear Information System (INIS)

    Taneja, Praveen; Ayyub, Pushan; Chandra, Ramesh

    2002-01-01

    We report a detailed study of the optical reflectance in sputter-deposited, nanocrystalline silver thin films in order to understand the marked changes in color that occur with decreasing particle size. In particular, samples with an average particle size in the 20 to 35 nm range are golden yellow, while those with a size smaller than 15 nm are black. We simulate the size dependence of the observed reflection spectra by incorporating Mie's theory of scattering and absorption of light in small particles, into the bulk dielectric constant formalism given by Ehrenreich and Philipp [Phys. Rev. 128, 1622 (1962)]. This provides a general method for understanding the reflected color of a dense collection of nanoparticles, such as in a nanocrystalline thin film. A deviation from Mie's theory is observed due to strong interparticle interactions

  10. THz generation from a nanocrystalline silicon-based photoconductive device

    International Nuclear Information System (INIS)

    Daghestani, N S; Persheyev, S; Cataluna, M A; Rose, M J; Ross, G

    2011-01-01

    Terahertz generation has been achieved from a photoconductive switch based on hydrogenated nanocrystalline silicon (nc-Si:H), gated by a femtosecond laser. The nc-Si:H samples were produced by a hot wire chemical vapour deposition process, a process with low production costs owing to its higher growth rate and manufacturing simplicity. Although promising ultrafast carrier dynamics of nc-Si have been previously demonstrated, this is the first report on THz generation from a nc-Si:H material

  11. Electrochemical passivation behaviour of nanocrystalline Fe 80 Si ...

    Indian Academy of Sciences (India)

    Passivation behaviour of nanocrystalline coating (Fe80Si20) obtained by in situ mechanical alloying route is studied and compared with that of the commercial pure iron and cast Fe80Si20 in sodium borate buffer solution at two different pH values (7.7 and 8.4). The coating reveals single passivation at a pH of 7.7 and ...

  12. A study of the structure and crystallisation of nanocrystalline zirconia

    International Nuclear Information System (INIS)

    Tucker, M.

    1999-12-01

    Nanocrystalline zirconia, prepared via, calcination of the hydroxide, has been studied using a variety of experimental techniques. Two chemical routes, a precipitation and a sol-gel route, were used to prepare the hydroxide. Neutron and X-ray diffraction, EXAFS, NMR and SANS have been used to study the structure and crystallisation, during in-situ and ambient condition measurements. The structural information from the diffraction data has been complimented by the other techniques to provide information on the short, medium and longer range structure of nanocrystalline zirconia. Pure and yttrium doped samples were studied, this enabled the affects of doping and preparation routes to be investigated. The amorphous hydroxide was found to have a, monoclinic-like structure for all samples, independent of preparation route or yttrium content. The crystallisation temperature was lowest for the pure precipitation sample and was increased by the addition of yttrium or by preparation via, the sol-gel route. For the precipitation samples, in addition to the crystallisation temperature being raised, doping with yttrium also had an effect on the size of the crystallites obtained at high temperatures. Due to the different incorporation method of the yttrium into the sol-gel samples the effect on crystallite size and crystallisation temperature, as seen for the precipitation samples, were not evident for the sol-gel samples. The neutron and NMR data clearly show hydrogen remains in the samples well after crystallisation has become evident. The structural picture of nanocrystalline zirconia consisting of small crystallites surrounded by material containing, or terminated by, hydroxyl groups, is supported by all the results and methods used in this thesis. The in-situ and ambient conditions data is combined into a coherent growth picture of the nanocrystalline material from the hydroxide until at high enough temperatures the bulk or polycrystalline material is formed. (author)

  13. Critical currents and fields of disordered nanocrystalline superconductors

    International Nuclear Information System (INIS)

    Yavary, H.; Shahzamanian, M.A.; Rabbani, H.

    2007-01-01

    Full text: There is an enormous effort directed at increasing the upper critical field of the superconducting materials because this upper critical field provides a fundamental limit to the maximum field a magnet system can produce. High-energy particle accelerators and medical resonance imaging body scanners are limited by the for NbTi (10 T). Gigahertz class nuclear-magnetic-resonance and high field laboratory magnets are limited by for Nb 3 Sn (23 T) [1]. However, the values of critical current density are too low for industrial use, possibly because of degraded or nonsuperconducting phases, such as MoS 2 or Mo 2 S 3 , at the grain boundaries or because the pinning site density is not high enough. It has long been known that decreasing the grain size of low-temperature superconducting (LTS) materials, such as Nb 3 Sn, increases the density of flux pinning sites and hence. Nanocrystalline materials are characterized by ultrafine grains and a high density of grain boundaries [2]. Hence nanocrystalline materials can exhibit unusual physical, chemical, and mechanical properties with respect to conventional polycrystalline materials. The purpose of this paper is to investigate the structure of currents and fields in disordered nanocrystalline superconducting materials by the use of quasiclassical many body techniques. The Keldish Greens functions are used to calculate the current density of the system. Since the disorder and microstructure of these nanocrystalline materials are on a sufficiently short length scale as to increase both the density of pinning site and the upper critical field. (authors)

  14. Investigation of microstructure thermal evolution in nanocrystalline Cu

    International Nuclear Information System (INIS)

    Zhou Kai; Li Hui; Pang Jinbiao; Wang Zhu

    2011-01-01

    The microstructure of nanocrystalline Cu prepared by compacting nanoparticles (50-60 nm in diameter) under high pressures has been studied by means of positron lifetime spectroscopy and X-ray diffraction. These nanoparticles were produced by two different methods. We found that there are order regions interior to the grains and disorder regions at the grain boundaries with a wide distribution of interatomic distances. The mean grain sizes of the nanocrystalline Cu samples decrease after being annealed at 900 o C and increase during aging at 180 o C, which are observed by X-ray diffraction, revealing that the atoms exchange between the two regions. The positron lifetime results clearly indicate that the vacancy clusters formed in the annealing process are unstable and decomposed at the aging time below 6 hours. In addition, the partially oxidized surfaces of the nanoparticles hinder grain growth when the samples age at 180 o C, and the vacancy clusters inside the disorder regions, which are related to Cu 2 O, need longer aging time to decompose. The disorder regions remain after the heat treatment in this work, in spite of the grain growth, which will be good for the samples keeping the properties of nanocrystalline material. -- Research highlights: → We use a digital positron lifetime spectrometer correlated with XRD to study the microstructure evolution of nanocrystalline Cu during thermal treatment. → An atomic scale microstructure of grain boundary is characterized. Further, the surface oxidation of the nanoparticles is considered. → The disorder regions remain after the heat treatment in this work, in spite of grain growth.

  15. Stress-induced magnetic anisotropy in nanocrystalline alloys

    International Nuclear Information System (INIS)

    Varga, L.K.; Gercsi, Zs.; Kovacs, Gy.; Kakay, A.; Mazaleyrat, F.

    2003-01-01

    Stress-annealing experiments were extended to both nanocrystalline alloy families, Finemet and Nanoperm (Hitperm), and, for comparison, to amorphous Fe 62 Nb 8 B 30 alloy. For both Finemet and bulk amorphous, stress-annealing results in a strong induced transversal anisotropy (flattening of hysteresis loop) but yields longitudinal induced anisotropy (square hysteresis loop) in Nanoperm and Hitperm. These results are interpreted in terms of back-stress theory

  16. Possible origin of superior corrosion resistance for electrodeposited nanocrystalline Ni

    International Nuclear Information System (INIS)

    Roy, I.; Yang, H.W.; Dinh, L.; Lund, I.; Earthman, J.C.; Mohamed, F.A.

    2008-01-01

    We present here for the first time observations that grain boundaries in electrodeposited (ED) nanocrystalline (nc) Ni are predominantly of Σ3 character. The results presented are based on orientation imaging microscopy (OIM) performed to produce electron backscatter diffraction (EBSD) maps. This large volume fraction of coherent low sigma coincidence site lattice (CSL) boundaries appears to be consistent with the superior corrosion resistance of ED nc-Ni in comparison with its coarse-grained counterpart

  17. Thermoelectric nanocrystalline YbCoSb laser prepared layers

    Czech Academy of Sciences Publication Activity Database

    Jelínek, Miroslav; Zeipl, Radek; Kocourek, Tomáš; Remsa, Jan; Navrátil, Jiří

    2016-01-01

    Roč. 122, č. 3 (2016), s. 1-5, č. článku 155. ISSN 0947-8396 R&D Projects: GA ČR(CZ) GA13-33056S Institutional support: RVO:68378271 ; RVO:61389013 Keywords : nanocrystalline YbCoSb * thermoelectric layers * pulsed laser deposition Subject RIV: BM - Solid Matter Physics ; Magnetism; CA - Inorganic Chemistry (UMCH-V) Impact factor: 1.455, year: 2016

  18. Microwave PECVD of nanocrystalline diamond with rf induced bias nucleation

    Czech Academy of Sciences Publication Activity Database

    Frgala, Z.; Jašek, O.; Karásková, M.; Zajíčková, L.; Buršíková, V.; Franta, D.; Matějková, Jiřina; Rek, Antonín; Klapetek, P.; Buršík, Jiří

    2006-01-01

    Roč. 56, Suppl. B (2006), s. 1218-1223 ISSN 0011-4626 R&D Projects: GA ČR(CZ) GA202/05/0607 Institutional research plan: CEZ:AV0Z20650511; CEZ:AV0Z20410507 Keywords : nanocrystalline diamond * plasma enhanced chemical vapor deposition * self-bias Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.568, year: 2006

  19. Nanocrystalline SiC film thermistors for cryogenic applications

    Science.gov (United States)

    Mitin, V. F.; Kholevchuk, V. V.; Semenov, A. V.; Kozlovskii, A. A.; Boltovets, N. S.; Krivutsa, V. A.; Slepova, A. S.; Novitskii, S. V.

    2018-02-01

    We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K-300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.

  20. Quantum transport in boron-doped nanocrystalline diamond

    Czech Academy of Sciences Publication Activity Database

    Mareš, Jiří J.; Hubík, Pavel; Krištofik, Jozef; Kindl, Dobroslav; Nesládek, Miloš

    2008-01-01

    Roč. 14, č. 7-8 (2008), s. 161-172 ISSN 0948-1907 R&D Projects: GA ČR GA202/07/0525; GA AV ČR IAA1010404; GA ČR(CZ) GA202/06/0040 Institutional research plan: CEZ:AV0Z10100521 Keywords : nanocrystalline diamond film * ballistic transport * superconductivity * Josephson’s effects Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.483, year: 2008

  1. Ferromagnetism appears in nitrogen implanted nanocrystalline diamond films

    Czech Academy of Sciences Publication Activity Database

    Remeš, Zdeněk; Sun, S. J.; Varga, M.; Chou, H.; Hsu, H.S.; Kromka, A.; Horák, Pavel

    2015-01-01

    Roč. 394, Nov (2015), s. 477-480 ISSN 0304-8853 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk(CZ) LD14011 EU Projects: European Commission(XE) COST Action MP1202 HINT Institutional support: RVO:68378271 ; RVO:61389005 Keywords : diamond * nonmetallic ferromagnetic materials * fine-particle systems * nanocrystalline materials Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.357, year: 2015

  2. Electrodeposition and characterization of nanocrystalline CoNiFe films

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.; Wang, Q.P. [Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Cai, C. [School of Chemistry and chemical engineering, Ningxia University, Yinchuan 750021 (China); Yuan, Y.N. [Department of Materials and Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Cao, F.H. [Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Zhang, Z., E-mail: eaglezzy@zjuem.zju.edu.cn [Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Zhang, J.Q. [Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027 (China); State Key Laboratory for Corrosion and Protection of Metals, Shenyang 110016 (China)

    2012-02-29

    Nanocrystalline Co{sub 45}Ni{sub 10}Fe{sub 24} films have been fabricated using cyclic voltammetry technique from the solutions containing sulfate, then characterized by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometer. Meanwhile, Electrochemical Impedance Spectroscopy technique has been employed to probe into the nucleation/growth behavior of Co{sub 45}Ni{sub 10}Fe{sub 24} films. The results show that, the obtained Co{sub 45}Ni{sub 10}Fe{sub 24} film possesses low coercivity of 973.3 A/m and high saturation magnetic flux density of 1.59 Multiplication-Sign 10{sup 5} A/m. Under the experimental conditions, the nucleation/growth process of Co{sub 45}Ni{sub 10}Fe{sub 24} films is mainly under activation control. With the increase of the applied cathodic potential bias, the charge transfer resistance for CoNiFe deposition decreases exponentially. - Highlights: Black-Right-Pointing-Pointer Nanocrystalline Co{sub 45}Ni{sub 10}Fe{sub 24} film is obtained using cyclic voltammetry technique. Black-Right-Pointing-Pointer Nanocrystalline Co{sub 45}Ni{sub 10}Fe{sub 24} possesses low coercivity of 973.3 A/m. Black-Right-Pointing-Pointer Nanocrystalline Co{sub 45}Ni{sub 10}Fe{sub 24} possesses high saturation magnetic flux density. Black-Right-Pointing-Pointer The nucleation/growth process of CoNiFe films is mainly under activation control. Black-Right-Pointing-Pointer The charge transfer resistance for CoNiFe deposition decreases exponentially.

  3. [Currently available skin substitutes].

    Science.gov (United States)

    Oravcová, Darina; Koller, Ján

    2014-01-01

    The current trend of burn wound care has shifted to more holistic approach of improvement in the long-term form and function of the healed burn wounds and quality of life. Autologous split or full-thickness skin graft are the best definitive burn wound coverage, but it is constrained by the limited available sources, especially in major burns. Donor site morbidities in term of additional wounds and scarring are also of concern of the autograft application. This has demanded the emergence of various skin substitutes in the management of acute burn injury as well as post burn reconstructions. This paper reviews currently available skin substitutes, produced in not for-profit skin banks as well as commercially available. They are divided according to type of material included, as biological, biosynthetic and synthetic and named respectively.

  4. Uncertainty propagation in a multiscale model of nanocrystalline plasticity

    International Nuclear Information System (INIS)

    Koslowski, M.; Strachan, Alejandro

    2011-01-01

    We characterize how uncertainties propagate across spatial and temporal scales in a physics-based model of nanocrystalline plasticity of fcc metals. Our model combines molecular dynamics (MD) simulations to characterize atomic-level processes that govern dislocation-based-plastic deformation with a phase field approach to dislocation dynamics (PFDD) that describes how an ensemble of dislocations evolve and interact to determine the mechanical response of the material. We apply this approach to a nanocrystalline Ni specimen of interest in micro-electromechanical (MEMS) switches. Our approach enables us to quantify how internal stresses that result from the fabrication process affect the properties of dislocations (using MD) and how these properties, in turn, affect the yield stress of the metallic membrane (using the PFMM model). Our predictions show that, for a nanocrystalline sample with small grain size (4 nm), a variation in residual stress of 20 MPa (typical in today's microfabrication techniques) would result in a variation on the critical resolved shear yield stress of approximately 15 MPa, a very small fraction of the nominal value of approximately 9 GPa. - Highlights: → Quantify how fabrication uncertainties affect yield stress in a microswitch component. → Propagate uncertainties in a multiscale model of single crystal plasticity. → Molecular dynamics quantifies how fabrication variations affect dislocations. → Dislocation dynamics relate variations in dislocation properties to yield stress.

  5. XRD and HREM studies of nanocrystalline Cu and Pd

    International Nuclear Information System (INIS)

    Nieman, G.W.; Weertmen, J.R.; Siegel, R.W.

    1991-01-01

    Consolidated powders of nanocrystalline Cu and Pd have been studied by x-ray diffraction (XRD) and high resolution electron microscopy (HREM) as part of an investigation of the mechanical behavior of nanocrystalline pure metals. XRD line broadening measurements were made to estimate rain size, qualitative grain size distribution and average long range strains in a number of samples. Mean grain sized range from 4-60 nm and have qualitatively narrow grain size distributions. Long range lattice strains are of the order of 0.2-3% in consolidated samples. These strains apparently persist and even increase in Cu samples after annealing at 0.35 Tm (498K) for 2h, accompanied by an apparent increase in grain size of ≥2x. Grain size, grain size distribution width and internal strains vary somewhat among samples produced under apparently identical processing conditions. HREM studies show that twins, stacking faults and low-index facets are abundant in as-consolidated nanocrystalline Cu samples. In this paper methodology, results and analysis of XRD and HREM experiments are presented

  6. Size-dependent deformation behavior of nanocrystalline graphene sheets

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhi [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, Shaanxi (China); Huang, Yuhong [College of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062, Shaanxi (China); Ma, Fei, E-mail: mafei@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, Shaanxi (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Sun, Yunjin [Faculty of Food Science and Engineering, Beijing University of Agriculture, Beijing Key Laboratory of Agricultural Product Detection and Control of Spoilage Organisms and Pesticide Residue, Beijing Laboratory of Food Quality and Safety, Beijing 102206 (China); Xu, Kewei, E-mail: kwxu@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, Shaanxi (China); Department of Physics and Opt-electronic Engineering, Xi’an University of Arts and Science, Xi’an 710065, Shaanxi (China); Chu, Paul K., E-mail: paul.chu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

    2015-08-15

    Highlights: • MD simulation is conducted to study the deformation of nanocrystalline graphene. • Unexpectedly, the elastic modulus decreases with the grain size considerably. • But the fracture stress and strain are nearly insensitive to the grain size. • A composite model with grain domains and GBs as two components is suggested. - Abstract: Molecular dynamics (MD) simulation is conducted to study the deformation behavior of nanocrystalline graphene sheets. It is found that the graphene sheets have almost constant fracture stress and strain, but decreased elastic modulus with grain size. The results are different from the size-dependent strength observed in nanocrystalline metals. Structurally, the grain boundaries (GBs) become a principal component in two-dimensional materials with nano-grains and the bond length in GBs tends to be homogeneously distributed. This is almost the same for all the samples. Hence, the fracture stress and strain are almost size independent. As a low-elastic-modulus component, the GBs increase with reducing grain size and the elastic modulus decreases accordingly. A composite model is proposed to elucidate the deformation behavior.

  7. Remediation of arsenic and lead with nanocrystalline zinc sulfide.

    Science.gov (United States)

    Piquette, Alan; Cannon, Cody; Apblett, Allen W

    2012-07-27

    Nanocrystalline (1.7 ± 0.3 nm) zinc sulfide with a specific surface area up to 360 m(2) g(-1) was prepared from the thermal decomposition of a single-source precursor, zinc ethylxanthate. Zinc ethylxanthate decomposes to cubic zinc sulfide upon exposure to temperatures greater than or equal to 125 °C. The resulting zinc sulfide was tested as a water impurity extractant. The target impurities used in this study were As(5+), As(3+), and Pb(2+). The reaction of the nanocrystalline ZnS with Pb(2+) proceeds as a replacement reaction where solid PbS is formed and Zn(2+) is released into the aqueous system. Removal of lead to a level of less than two parts per billion is achievable. The results of a detailed kinetics experiment between the ZnS and Pb(2+) are included in this study. Unlike the instance of lead, both As(5+) and As(3+) adsorb on the surface of the ZnS extractant as opposed to an ion-exchange process. An uptake capacity of > 25 mg g(-1) for the removal of As(5+) is possible. The uptake of As(3+) appears to proceed by a slower process than that of the As(5+) with a capacity of nearly 20 mg g(-1). The nanocrystalline zinc sulfide was extremely successful for the removal of arsenic and lead from simulated oil sand tailing pond water.

  8. Cobalt Fischer-Tropsch catalysts: influence of cobalt dispersion and titanium oxides promotion

    Energy Technology Data Exchange (ETDEWEB)

    Azib, H

    1996-04-10

    The aim of this work is to study the effect of Sol-Gel preparation parameters which occur in silica supported cobalt catalysts synthesis. These catalysts are particularly used for the waxes production in natural gas processing. The solids have been characterized by several techniques: transmission electron microscopy (TEM), X-ray absorption near edge spectroscopy (XANES), programmed temperature reduction (TPR), infrared spectroscopy (IR), ultraviolet spectroscopy (UV), Magnetism, thermodesorption of H{sub 2} (TPD). The results indicate that the control of the cobalt dispersion and oxide phases nature is possible by modifying Sol-Gel parameters. The catalytic tests in Fischer-Tropsch synthesis were conducted on a pilot unit under pressure (20 atm) and suggested that turnover rates were independent of Co crystallite size, Co phases in the solids (Co deg., cobalt silicate) and titanium oxide promotion. On the other methane, the C{sub 3}{sup +} hydrocarbon selectivity is increased with increasing crystallite size. Inversely, the methane production is favoured by very small crystallites, cobalt silicate increase and titanium addition. However, the latter, used as a cobalt promoter, has a benefic effect on the active phase stability during the synthesis. (author). 149 refs., 102 figs., 71 tabs.

  9. Electrocatalytic performance evaluation of cobalt hydroxide and cobalt oxide thin films for oxygen evolution reaction

    Science.gov (United States)

    Babar, P. T.; Lokhande, A. C.; Pawar, B. S.; Gang, M. G.; Jo, Eunjin; Go, Changsik; Suryawanshi, M. P.; Pawar, S. M.; Kim, Jin Hyeok

    2018-01-01

    The development of an inexpensive, stable, and highly active electrocatalyst for oxygen evolution reaction (OER) is essential for the practical application of water splitting. Herein, we have synthesized an electrodeposited cobalt hydroxide on nickel foam and subsequently annealed in an air atmosphere at 400 °C for 2 h. In-depth characterization of all the films using X-ray diffraction (XRD), X-ray photoelectron emission spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) techniques, which reveals major changes for their structural, morphological, compositional and electrochemical properties, respectively. The cobalt hydroxide nanosheet film shows high catalytic activity with 290 mV overpotential at 10 mA cm-2 and 91 mV dec-1 Tafel slope and robust stability (24 h) for OER in 1 M KOH electrolyte compared to cobalt oxide (340 mV). The better OER activity of cobalt hydroxide in comparison to cobalt oxide originated from high active sites, enhanced surface, and charge transport capability.

  10. A computer controlled tele-cobalt unit

    International Nuclear Information System (INIS)

    Brace, J.A.

    1982-01-01

    A computer controlled cobalt treatment unit was commissioned for treating patients in January 1980. Initially the controlling computer was a minicomputer, but now the control of the therapy unit is by a microcomputer. The treatment files, which specify the movement and configurations necessary to deliver the prescribed dose, are produced on the minicomputer and then transferred to the microcomputer using minitape cartridges. The actual treatment unit is based on a standard cobalt unit with a few additional features e.g. the drive motors can be controlled either by the computer or manually. Since the treatment unit is used for both manual and automatic treatments, the operational procedure under computer control is made to closely follow the manual procedure for a single field treatment. The necessary safety features which protect against human, hardware and software errors as well as the advantages and disadvantages of computer controlled radiotherapy are discussed

  11. Creep-fatigue of low cobalt superalloys

    Science.gov (United States)

    Halford, G. R.

    1982-01-01

    Testing for the low cycle fatigue and creep fatigue resistance of superalloys containing reduced amounts of cobalt is described. The test matrix employed involves a single high temperature appropriate for each alloy. A single total strain range, again appropriate to each alloy, is used in conducting strain controlled, low cycle, creep fatigue tests. The total strain range is based upon the level of straining that results in about 10,000 cycles to failure in a high frequency (0.5 Hz) continuous strain-cycling fatigue test. No creep is expected to occur in such a test. To bracket the influence of creep on the cyclic strain resistance, strain hold time tests with ore minute hold periods are introduced. One test per composition is conducted with the hold period in tension only, one in compression only, and one in both tension and compression. The test temperatures, alloys, and their cobalt compositions that are under study are given.

  12. Process for obtaining cobalt and lanthanum nickelate

    International Nuclear Information System (INIS)

    Tapcov, V.; Samusi, N.; Gulea, A.; Horosun, I.; Stasiuc, V.; Petrenco, P.

    1999-01-01

    The invention relates to the process for obtaining polycrystalline ceramics of cobalt and lanthanum nickelate with the perovskite structure from coordinative hetero metallic compounds. The obtained products can be utilized in the industry in the capacity of catalysts. Summary of the invention consists in obtaining polycrystalline ceramics LaCoO 3 and LaNiO 3 with the perovskite structure by pyrolysis of the parent compounds, namely, the coordinative hetero metallic compounds of the lanthanum cobalt or lanthanum nickel. The pyrolysis of the parent compound runs during one hour at 800 C. The technical result of the invention consists in lowering the temperature of the parent compound pyrolysis containing the precise ratio of metals necessary for ceramics obtaining

  13. Cobalt oxides from crystal chemistry to physics

    CERN Document Server

    Raveau, Bernard

    2012-01-01

    Unparalleled in the breadth and depth of its coverage of all important aspects, this book systematically treats the electronic and magnetic properties of stoichiometric and non-stoichiometric cobaltites in both ordered and disordered phases. Authored by a pioneer and a rising star in the field, the monograph summarizes, organizes and streamlines the otherwise difficult-to-obtain information on this topic. An introductory chapter sets forth the crystal chemistry of cobalt oxides to lay the groundwork for an understanding of the complex phenomena observed in this materials class. Special emphasis is placed on a comprehensive discussion of cobaltite physical properties in different structural families. Providing a thorough introduction to cobalt oxides from a chemical and physical viewpoint as a basis for understanding their intricacies, this is a must-have for both experienced researchers as well as entrants to the field.

  14. Photoionization of cobalt impuritiesin zinc oxide

    Czech Academy of Sciences Publication Activity Database

    Ivanov, V.; Godlewski, M.; Dejneka, Alexandr

    2015-01-01

    Roč. 252, č. 9 (2015), s. 1988-1992 ISSN 0370-1972 R&D Projects: GA MŠk(CZ) LM2011029; GA ČR GAP108/12/1941 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : absorption band * cobalt * photoionization * electron spin resonance * pulsed mode * ZnO Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.522, year: 2015

  15. Speciation studies of cobalt in sea water

    International Nuclear Information System (INIS)

    Toteja, R.S.D.; Sudersanan, M.; Iyer, R.K.

    1995-01-01

    Recent results on the speciation of cobalt in simulated and actual sea water is reported using ion exchangers. The influence of magnesium ions in affecting the composition of ion exchangers and subsequent interpretation of the results is discussed. The results indicated that Co +2 may predominate in both the simulated and actual sea water and the presence of other constituents in sea water does not affect the nature of complex species present. (author). 2 refs., 3 tabs., 1 fig

  16. Literature study on the physiology of cobalt

    International Nuclear Information System (INIS)

    Erzberger, A.

    1986-12-01

    This literature study analyses the metabolism of cobalt in the human body, focussing on its resorption and the influence of various parameters like its chemical form, antagonisms, etc. on the level of resorption rate. The value currently recommended by ICRP for resorption rates (f 1 factor) of 0,3 or 0,05 for man is examined for its confirmation or non-confirmation in literature. (orig./MG) [de

  17. Enhanced magnetocrystalline anisotropy in deposited cobalt clusters

    Energy Technology Data Exchange (ETDEWEB)

    Eastham, D.A.; Denby, P.M.; Kirkman, I.W. [Daresbury Laboratory, Daresbury, Warrington (United Kingdom); Harrison, A.; Whittaker, A.G. [Department of Chemistry, University of Edinburgh, Edinburgh (United Kingdom)

    2002-01-28

    The magnetic properties of nanomaterials made by embedding cobalt nanocrystals in a copper matrix have been studied using a SQUID magnetometer. The remanent magnetization at temperatures down to 1.8 K and the RT (room temperature) field-dependent magnetization of 1000- and 8000-atom (average-size) cobalt cluster samples have been measured. In all cases it has been possible to relate the morphology of the material to the magnetic properties. However, it is found that the deposited cluster samples contain a majority of sintered clusters even at cobalt concentrations as low as 5% by volume. The remanent magnetization of the 8000-atom samples was found to be bimodal, consisting of one contribution from spherical particles and one from touching (sintered) clusters. Using a Monte Carlo calculation to simulate the sintering it has been possible to calculate a size distribution which fits the RT superparamagnetic behaviour of the 1000-atom samples. The remanent magnetization for this average size of clusters could then be fitted to a simple model assuming that all the nanoparticles are spherical and have a size distribution which fits the superparamagnetic behaviour. This gives a value for the potential energy barrier height (for reversing the spin direction) of 2.0 {mu}eV/atom which is almost four times the accepted value for face-centred-cubic bulk cobalt. The remanent magnetization for the spherical component of the large-cluster sample could not be fitted with a single barrier height and it is conjectured that this is because the barriers change as a function of cluster size. The average value is 1.5 {mu}eV/atom but presumably this value tends toward the bulk value (0.5 {mu}eV/atom) for the largest clusters in this sample. (author)

  18. Cobalt metabolism and toxicology-A brief update

    Energy Technology Data Exchange (ETDEWEB)

    Simonsen, Lars Ole, E-mail: LOSimonsen@dadlnet.dk; Harbak, Henrik; Bennekou, Poul

    2012-08-15

    Cobalt metabolism and toxicology are summarized. The biological functions of cobalt are updated in the light of recent understanding of cobalt interference with the sensing in almost all animal cells of oxygen deficiency (hypoxia). Cobalt (Co{sup 2+}) stabilizes the transcriptional activator hypoxia-inducible factor (HIF) and thus mimics hypoxia and stimulates erythropoietin (Epo) production, but probably also by the same mechanism induces a coordinated up-regulation of a number of adaptive responses to hypoxia, many with potential carcinogenic effects. This means on the other hand that cobalt (Co{sup 2+}) also may have beneficial effects under conditions of tissue hypoxia, and possibly can represent an alternative to hypoxic preconditioning. Cobalt is acutely toxic in larger doses, and in mammalian in vitro test systems cobalt ions and cobalt metal are cytotoxic and induce apoptosis and at higher concentrations necrosis with inflammatory response. Cobalt metal and salts are also genotoxic, mainly caused by oxidative DNA damage by reactive oxygen species, perhaps combined with inhibition of DNA repair. Of note, the evidence for carcinogenicity of cobalt metal and cobalt sulfate is considered sufficient in experimental animals, but is as yet considered inadequate in humans. Interestingly, some of the toxic effects of cobalt (Co{sup 2+}) have recently been proposed to be due to putative inhibition of Ca{sup 2+} entry and Ca{sup 2+}-signaling and competition with Ca{sup 2+} for intracellular Ca{sup 2+}-binding proteins. The tissue partitioning of cobalt (Co{sup 2+}) and its time-dependence after administration of a single dose have been studied in man, but mainly in laboratory animals. Cobalt is accumulated primarily in liver, kidney, pancreas, and heart, with the relative content in skeleton and skeletal muscle increasing with time after cobalt administration. In man the renal excretion is initially rapid but decreasing over the first days, followed by a second, slow

  19. Structural, Magnetic and Microwave Properties of Nanocrystalline Ni-Co-Gd Ferrites

    Science.gov (United States)

    Nikzad, Alireza; Parvizi, Roghaieh; Rezaei, Ghasem; Vaseghi, Behrooz; Khordad, Reza

    2018-02-01

    A series of Co- and Gd-substituted NiFe2O4 ferrite nanoparticles with the formula Ni1- x Co x Fe2- y Gd y O4 (where x = 0.0-1.0 and y = 0.0-0.1) have been successfully synthesized using a hydrothermal method. X-ray diffraction and field emission scanning electron microscopy results indicated that a highly crystallized spherical ferrite nanoparticle structure was obtained along with an increase in the lattice parameters. Compositional analysis of the prepared nanoferrite powders has been carried out using energy-dispersive x-ray (EDX) spectra. The EDX analysis reveals the presence of Ni, Co, Gd and Fe elements in the specimens. Magnetization and the coercive field improved dramatically with an increase in the amount of cobalt and gadolinium added, attributed to the redistribution of cations in the spinel nanoferrite structure. Saturation magnetization and coercivity values up to 99 emu/g and 918 Oe, respectively, were measured using a vibration sample magnetometer at room temperature. Comparative microwave absorption experiments demonstrated that the reflection loss (RL) properties enhanced with increasing substitution of cations in the Ni-ferrite spinel structure for an absorber thickness of 1.8 mm. A maximum RL of - 26.7 dB was obtained for substituted Ni-Co-Gd nanoferrite with x = 1.0 and y = 0.1 at a frequency of 9.4 GHz with a bandwidth of 3.6 GHz (RL ≤ - 10 dB). Experimental results revealed that the synthesized nanoparticles possessed great potential in microwave absorption applications.

  20. Uptake of radionuclides caesium and cobalt

    International Nuclear Information System (INIS)

    Lukac, P.; Foldesova, M.

    1995-01-01

    By means of chemical treatment ammonium, potassium, sodium and H-form of zeolite were prepared. The chemical modifications of zeolite were carried out with: 2M solution of NaNO 3 , NH 4 NO 3 , KNO 3 ; 0,1M solution of HCl; NaOH solution of different concentration. The method of model radioactive solution was used to find the sorption ability for cesium and cobalt every modified zeolite. The model solution were 0.05M solution of cobalt labelled by 60 Co or cesium labelled by 137 Cs. The highest sorption ability was observed for zeolite modified by NaOH. The influence of pH on uptake of cesium and cobalt by modified zeolite was searched as well. The experimental data (leaching tests, compressive strength measurement and porosity) were measured for the case the Cs and Cs from model water solution and radioactive waste water were up taken on chemically modified zeolite and were subsequently incorporated into cement casts on blast furnace cement slags basis. The leachability was tested in water, in basis solution and in acid solution. The leachability in water and basic solution was negligible, in acid solution it was less than 4% which is inside of value of applied measure method. The compressive strength, porosity and leaching experiment are hopefully and show good mechanical stability and good retention of observed radionuclides in samples exposed in leaching solutions. (J.K.)

  1. Uptake of radionuclides caesium and cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Lukac, P; Foldesova, M [Slovak Technical Univ., Bratislava (Slovakia)

    1996-12-31

    By means of chemical treatment ammonium, potassium, sodium and H-form of zeolite were prepared. The chemical modifications of zeolite were carried out with: 2M solution of NaNO{sub 3}, NH{sub 4}NO{sub 3}, KNO{sub 3}; 0,1M solution of HCl; NaOH solution of different concentration. The method of model radioactive solution was used to find the sorption ability for cesium and cobalt every modified zeolite. The model solution were 0.05M solution of cobalt labelled by {sup 60}Co or cesium labelled by {sup 137}Cs. The highest sorption ability was observed for zeolite modified by NaOH. The influence of pH on uptake of cesium and cobalt by modified zeolite was searched as well. The experimental data (leaching tests, compressive strength measurement and porosity) were measured for the case the Cs and Cs from model water solution and radioactive waste water were up taken on chemically modified zeolite and were subsequently incorporated into cement casts on blast furnace cement slags basis. The leachability was tested in water, in basis solution and in acid solution. The leachability in water and basic solution was negligible, in acid solution it was less than 4% which is inside of value of applied measure method. The compressive strength, porosity and leaching experiment are hopefully and show good mechanical stability and good retention of observed radionuclides in samples exposed in leaching solutions. (J.K.).

  2. Plasma sprayed samarium--cobalt permanent magnets

    International Nuclear Information System (INIS)

    Willson, M.C.; Janowiecki, R.J.

    1975-01-01

    Samarium--cobalt permanent magnets were fabricated by arc plasma spraying. This process involves the injection of relatively coarse powder particles into a high-temperature gas for melting and spraying onto a substrate. The technique is being investigated as an economical method for fabricating cobalt--rare earth magnets for advanced traveling wave tubes and cross-field amplifiers. Plasma spraying permits deposition of material at high rates over large areas with optional direct bonding to the substrate, and offers the ability to fabricate magnets in a variety of shapes and sizes. Isotropic magnets were produced with high coercivity and good reproducibility in magnetic properties. Post-spray thermal treatments were used to enhance the magnetic properties of sprayed deposits. Samarium--cobalt magnets, sprayed from samarium-rich powder and subjected to post-spray heat treatment, displayed energy products in excess of 9 million gauss-oersteds and coercive forces of approximately 6000 oersteds. Bar magnet arrays were constructed by depositing magnets on ceramic substrates. (auth)

  3. Sintered cobalt-rare earth intermetallic product

    International Nuclear Information System (INIS)

    Benz, M.C.

    1975-01-01

    A process is described for preparing novel sintered cobalt--rare earth intermetallic products which can be magnetized to form permanent magnets having stable improved magnetic properties. A cobalt--rare earth metal alloy is formed having a composition which at sintering temperature falls outside the composition covered by the single Co 5 R intermetallic phase on the rare earth richer side. The alloy contains a major amount of the Co 5 R intermetallic phase and a second solid CoR phase which is richer in rare earth metal content than the Co 5 R phase. The specific cobalt and rare earth metal content of the alloy is substantially the same as that desired in the sintered product. The alloy, in particulate form, is pressed into compacts and sintered to the desired density. The sintered product is comprised of a major amount of the Co 5 R solid intermetallic phase and up to about 35 percent of the product of the second solid CoR intermetallic phase which is richer in rare earth metal content than the Co 5 R phase

  4. The cobalt radioactive isotopes in environment

    International Nuclear Information System (INIS)

    2007-01-01

    For the year 1993 the total activity released in cobalt is 69 GBq for the whole of nuclear power plants. The part of activity in cobalt for La Hague in 1993 is 8 GBq of 58 Co and 2 GBq of 60 Co. The radioactive isotopes released by nuclear power plants or the reprocessing plant of La Hague under liquid effluents are shared by half between 58 Co and 60 Co. The exposure to sealed sources is the most important risk for the cobalt. The risk of acute exposure can associate a local irradiation of several decades of grays inducing a radiological burns, deep burn to treat in surgery by resection or graft even amputation. A global irradiation of organism for several grays induces an acute irradiation syndrome, often serious. At long term the stochastic effects are represented by leukemia and radio-induced cancers. The increase of probability of their occurrence is 1% by sievert. We must remind that the natural spontaneous probability is 25%. (N.C.)

  5. Hot corrosion of low cobalt alloys

    Science.gov (United States)

    Stearns, C. A.

    1982-01-01

    The hot corrosion attack susceptibility of various alloys as a function of strategic materials content are investigated. Preliminary results were obtained for two commercial alloys, UDIMET 700 and Mar-M 247, that were modified by varying the cobalt content. For both alloys the cobalt content was reduced in steps to zero. Nickel content was increased accordingly to make up for the reduced cobalt but all other constituents were held constant. Wedge bar test samples were produced by casting. The hot corrosion test consisted of cyclically exposing samples to the high velocity flow of combustion products from an air-fuel burner fueled with jet A-1 and seeded with a sodium chloride aqueous solution. The flow velocity was Mach 0.5 and the sodium level was maintained at 0.5 ppm in terms of fuel plus air. The test cycle consisted of holding the test samples at 900 C for 1 hour followed by 3 minutes in which the sample could cool to room temperature in an ambient temperature air stream.

  6. Measurement for cobalt target activity and its axial distribution

    International Nuclear Information System (INIS)

    Li Xingyuan; Chen Zigen.

    1985-01-01

    Cobalt target activity and its axial distribution are measured in process of producing radioactive isotopes 60 Co by irradiation in HFETR. Cobalt target activity is obtained with measured data at 3.60 m and 4.60 m, relative axial distribution of cobalt target activity is obtained with one at 30 cm, and axial distribution of cobalt target activity(or specific activity) is obtained with both of data. The difference between this specific activity and measured result for 60 Co teletherapy sources in the end is less than +- 5%

  7. Cobalt metabolism and toxicology—A brief update

    International Nuclear Information System (INIS)

    Simonsen, Lars Ole; Harbak, Henrik; Bennekou, Poul

    2012-01-01

    Cobalt metabolism and toxicology are summarized. The biological functions of cobalt are updated in the light of recent understanding of cobalt interference with the sensing in almost all animal cells of oxygen deficiency (hypoxia). Cobalt (Co 2+ ) stabilizes the transcriptional activator hypoxia-inducible factor (HIF) and thus mimics hypoxia and stimulates erythropoietin (Epo) production, but probably also by the same mechanism induces a coordinated up-regulation of a number of adaptive responses to hypoxia, many with potential carcinogenic effects. This means on the other hand that cobalt (Co 2+ ) also may have beneficial effects under conditions of tissue hypoxia, and possibly can represent an alternative to hypoxic preconditioning. Cobalt is acutely toxic in larger doses, and in mammalian in vitro test systems cobalt ions and cobalt metal are cytotoxic and induce apoptosis and at higher concentrations necrosis with inflammatory response. Cobalt metal and salts are also genotoxic, mainly caused by oxidative DNA damage by reactive oxygen species, perhaps combined with inhibition of DNA repair. Of note, the evidence for carcinogenicity of cobalt metal and cobalt sulfate is considered sufficient in experimental animals, but is as yet considered inadequate in humans. Interestingly, some of the toxic effects of cobalt (Co 2+ ) have recently been proposed to be due to putative inhibition of Ca 2+ entry and Ca 2+ -signaling and competition with Ca 2+ for intracellular Ca 2+ -binding proteins. The tissue partitioning of cobalt (Co 2+ ) and its time-dependence after administration of a single dose have been studied in man, but mainly in laboratory animals. Cobalt is accumulated primarily in liver, kidney, pancreas, and heart, with the relative content in skeleton and skeletal muscle increasing with time after cobalt administration. In man the renal excretion is initially rapid but decreasing over the first days, followed by a second, slow phase lasting several weeks, and

  8. Pharmacokinetics of inorganic cobalt and a vitamin B12 supplement in the Thoroughbred horse: Differentiating cobalt abuse from supplementation.

    Science.gov (United States)

    Hillyer, L L; Ridd, Z; Fenwick, S; Hincks, P; Paine, S W

    2018-05-01

    While cobalt is an essential micronutrient for vitamin B 12 synthesis in the horse, at supraphysiological concentrations, it has been shown to enhance performance in human subjects and rats, and there is evidence that its administration in high doses to horses poses a welfare threat. Animal sport regulators currently control cobalt abuse via international race day thresholds, but this work was initiated to explore means of potentially adding to application of those thresholds since cobalt may be present in physiological concentrations. To devise a scientific basis for differentiation between presence of cobalt from bona fide supplementation and cobalt doping through the use of ratios. Six Thoroughbred horses were given 10 mL vitamin B 12 /cobalt supplement (Hemo-15 ® ; Vetoquinol, Buckingham, Buckinghamshire, UK., 1.5 mg B 12 , 7 mg cobalt gluconate = 983 μg total Co) as an i.v. bolus then an i.v. infusion (15 min) of 100 mg cobalt chloride (45.39 mg Co) 6 weeks later. Pre-and post-administration plasma and urine samples were analysed for cobalt and vitamin B 12 . Urine and plasma samples were analysed for vitamin B 12 using an immunoassay and cobalt concentrations were measured via ICP-MS. Baseline concentrations of cobalt in urine and plasma for each horse were subtracted from their cobalt concentrations post-administration for the PK analysis. Compartmental analysis was used for the determination of plasma PK parameters for cobalt using commercially available software. On administration of a vitamin B 12 /cobalt supplement, the ratio of cobalt to vitamin B 12 in plasma rapidly increased to approximately 3 and then rapidly declined below a ratio of 1 and then back to near baseline over the next week. On administration of 100 mg cobalt chloride, the ratio initially exceeded 10 in plasma and then declined with the lower 95% confidence interval remaining above a ratio of 1 for 7 days. For two horses with extended sampling, the plasma ratio remained above one for

  9. Accumulation and recovery of defects in ion-irradiated nanocrystalline gold

    Energy Technology Data Exchange (ETDEWEB)

    Chimi, Y. E-mail: chimi@popsvr.tokai.jaeri.go.jp; Iwase, A.; Ishikawa, N.; Kobiyama, M.; Inami, T.; Okuda, S

    2001-09-01

    Effects of 60 MeV {sup 12}C ion irradiation on nanocrystalline gold (nano-Au) are studied. The experimental results show that the irradiation-produced defects in nano-Au are thermally unstable because of the existence of a large volume fraction of grain boundaries. This suggests a possibility of the use of nanocrystalline materials as irradiation-resistant materials.

  10. Enhanced Activity of Nanocrystalline Zeolites for Selective Catalytic Reduction of NOx

    International Nuclear Information System (INIS)

    Sarah C. Larson; Vicki H. Grassian

    2006-01-01

    Nanocrystalline zeolites with discrete crystal sizes of less than 100 nm have different properties relative to zeolites with larger crystal sizes. Nanocrystalline zeolites have improved mass transfer properties and very large internal and external surface areas that can be exploited for many different applications. The additional external surface active sites and the improved mass transfer properties of nanocrystalline zeolites offer significant advantages for selective catalytic reduction (SCR) catalysis with ammonia as a reductant in coal-fired power plants relative to current zeolite based SCR catalysts. Nanocrystalline NaY was synthesized with a crystal size of 15-20 nm and was thoroughly characterized using x-ray diffraction, electron paramagnetic resonance spectroscopy, nitrogen adsorption isotherms and Fourier Transform Infrared (FT-IR) spectroscopy. Copper ions were exchanged into nanocrystalline NaY to increase the catalytic activity. The reactions of nitrogen dioxides (NO x ) and ammonia (NH 3 ) on nanocrystalline NaY and CuY were investigated using FT-IR spectroscopy. Significant conversion of NO 2 was observed at room temperature in the presence of NH 3 as monitored by FT-IR spectroscopy. Copper-exchanged nanocrystalline NaY was more active for NO 2 reduction with NH 3 relative to nanocrystalline NaY

  11. A novel method to synthesize cobalt oxide (Co3O4) nanowires from cobalt (Co) nanobowls

    DEFF Research Database (Denmark)

    Srivastava, Akhilesh Kumar; Madhavi, S.; Ramanujan, R.V.

    2010-01-01

    A novel method suitable for the synthesis of the cobalt oxide (Co3O4) nanowires at targeted regions is presented in this report. Cobalt (Co) nanobowls synthesized by colloidal crystal directed assembly were transformed into Co3O4 nanowires by a simple heat treatment process. Co nanobowls exhibited...... a two phase (h.c.p. + f.c.c.) microstructure while single phase microstructure was observed for Co3O4 nanowires. Ferromagnetic Co nanobowls showed a dependence of coercivity on bowl size while Co3O4 exhibited weak ferromagnetic behavior....

  12. Calix[4]arenes Substituted on the Narrow Rim with Malononitrile and Cobalt Bis(dicarbollide) Anion

    Czech Academy of Sciences Publication Activity Database

    Zhao, J.; Bolte, M.; Dordea, C.; Grüner, Bohumír; Böhmer, V.

    2009-01-01

    Roč. 41, č. 23 (2009), s. 4063-4067 ISSN 0039-7881 R&D Projects: GA ČR GA104/09/0668 Institutional research plan: CEZ:AV0Z40320502 Keywords : carboranes * metallacarboranes * dicarbollides Subject RIV: CA - Inorganic Chemistry Impact factor: 2.572, year: 2009

  13. and aluminum-substituted cobalt ferrite prepared by co-precipitation ...

    Indian Academy of Sciences (India)

    Spinal ferrites having the general formula Co1-ZnFe2-AlO4 ( = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were prepared using the wet chemical co-operation technique. The samples were annealed at 800°C for 12 h and were studied by means of X-ray diffraction, magnetization and low field AC susceptibility measurements.

  14. Magnetoresistance of drop-cast film of cobalt-substituted magnetite nanocrystals.

    Science.gov (United States)

    Kohiki, Shigemi; Nara, Koichiro; Mitome, Masanori; Tsuya, Daiju

    2014-10-22

    An oleic acid-coated Fe2.7Co0.3O4 nanocrystal (NC) self-assembled film was fabricated via drop casting of colloidal particles onto a three-terminal electrode/MgO substrate. The film exhibited a large coercivity (1620 Oe) and bifurcation of the zero-field-cooled and field-cooled magnetizations at 300 K. At 10 K, the film exhibited both a Coulomb blockade due to single electron charging as well as a magnetoresistance of ∼-80% due to spin-dependent electron tunneling. At 300 K, the film also showed a magnetoresistance of ∼-80% due to hopping of spin-polarized electrons. Enhanced magnetic coupling between adjacent NCs and the large coercivity resulted in a large spin-polarized current flow even at 300 K.

  15. Electrical Properties and Dipole Relaxation Behavior of Zinc-Substituted Cobalt Ferrite

    Science.gov (United States)

    Supriya, Sweety; Kumar, Sunil; Kar, Manoranjan

    2017-12-01

    Co1- x Zn x Fe2O4 ceramics with x = 0.00, 0.05, 0.10, 0.15 and 0.20 were synthesized by a modified citric acid sol-gel method. The crystalline phase of the samples was characterized by the powder x-ray diffraction technique (XRD) and the Rietveld analysis of the XRD patterns. The morphology and particle size were studied using field emission scanning electron microscopy. Fourier transform infrared spectroscopy studies were consistent with the XRD results. The impedance measurements were carried out from 100 Hz to 10 MHz at different temperatures from 40°C to 300°C. The frequency dispersion of dielectric was analyzed with a modified Debye equation. The activation energy derived from the dielectric constant and the impedance follows the Arrhenius law and are comparable with each other. The dielectric relaxation and impedance relaxation are correlated in terms of activation energy, show a good temperature stability of the dielectrics and are useful for their applications in microelectronic devices such as filters, capacitors, resonators, etc.

  16. Effect of grain size on corrosion of nanocrystalline copper in NaOH solution

    International Nuclear Information System (INIS)

    Luo Wei; Xu Yimin; Wang Qiming; Shi Peizhen; Yan Mi

    2010-01-01

    Research highlights: → Coppers display an active-passive-transpassive behaviour with duplex passive film. → Grain size variation has little effect on the overall corrosion behaviour of Cu. → Little effect on corrosion may be due to duplex passivation in NaOH solution. → Bulk nanocrystalline Cu show bamboo-like flake corrosion structure. - Abstract: Effect of grain size on corrosion of bulk nanocrystalline copper was investigated using potentiodynamic polarization measurements in 0.1 M NaOH solution. Bulk nanocrystalline copper was prepared by inert gas condensation and in situ warm compress (IGCWC) method. The grain sizes of all bulk nanocrystalline samples were determined to be 48, 68 and 92 nm using X-ray diffraction (XRD). Results showed that bulk coppers displayed an active-passive-transpassive behaviour with duplex passive films. From polycrystalline to nanocrystalline, grain size variation showed little effect on the overall corrosion resistance of copper samples.

  17. Infrared absorption study of hydrogen incorporation in thick nanocrystalline diamond films

    International Nuclear Information System (INIS)

    Tang, C.J.; Neves, A.J.; Carmo, M.C.

    2005-01-01

    We present an infrared (IR) optical absorbance study of hydrogen incorporation in nanocrystalline diamond films. The thick nanocrystalline diamond films were synthesized by microwave plasma-assisted chemical vapor deposition and a high growth rate about 3.0 μm/h was achieved. The morphology, phase quality, and hydrogen incorporation were assessed by means of scanning electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). Large amount of hydrogen bonded to nanocrystalline diamond is clearly evidenced by the huge CH stretching band in the FTIR spectrum. The mechanism of hydrogen incorporation is discussed in light of the growth mechanism of nanocrystalline diamond. This suggests the potential of nanocrystalline diamond for IR electro-optical device applications

  18. In vitro corrosion, cytotoxicity and hemocompatibility of bulk nanocrystalline pure iron

    International Nuclear Information System (INIS)

    Nie, F L; Zheng, Y F; Wei, S C; Hu, C; Yang, G

    2010-01-01

    Bulk nanocrystalline pure iron rods were fabricated by the equal channel angular pressure (ECAP) technique up to eight passes. The microstructure and grain size distribution, natural immersion and electrochemical corrosion in simulated body fluid, cellular responses and hemocompatibility were investigated in this study. The results indicate that nanocrystalline pure iron after severe plastic deformation (SPD) would sustain durable span duration and exhibit much stronger corrosion resistance than that of the microcrystalline pure iron. The interaction of different cell lines reveals that the nanocrystalline pure iron stimulates better proliferation of fibroblast cells and preferable promotion of endothelialization, while inhibits effectively the viability of vascular smooth muscle cells (VSMCs). The burst of red cells and adhesion of the platelets were also substantially suppressed on contact with the nanocrystalline pure iron in blood circulation. A clear size-dependent behavior from the grain nature deduced by the gradual refinement microstructures was given and well-behaved in vitro biocompatibility of nanocrystalline pure iron was concluded.

  19. Effects of precursors on the crystal structure and photoluminescence of CdS nanocrystalline

    International Nuclear Information System (INIS)

    Fu Zuoling; Zhou Shihong; Shi Jinsheng; Zhang Siyuan

    2005-01-01

    A series of cadmium sulfide (CdS) nanocrystalline were synthesized by precipitation from a mixture of aqueous solutions of cadmium salts and sulfur salts without adding any surface-termination agent. Their crystal structures and particle sizes were determined by X-ray diffraction (XRD). The CdS nanocrystalline precipitated from different precursors exhibited three cases: cubic phase, hexagonal phase and a hybrid of cubic and hexagonal phases. The photoluminescence (PL) of cadmium salt precursors and CdS nanocrystalline is also analyzed. Similar spectral band structure of cadmium salt precursors and CdS nanocrystalline is found. The PL of 3.4, 2.4 and 2.0 nm sized CdS nanocrystalline with the same crystal structure indicated quantum confinement effect

  20. Hexavalent Chromium Substitution Projects

    Science.gov (United States)

    2011-05-12

    Hexavalent Chromium Substitution Projects Date (12 May 2011) Gene McKinley ASC/WNV (937) 255-3596 Gene.McKinley@wpafb.af.mil Aeronautical Systems...valid OMB control number. 1. REPORT DATE 12 MAY 2011 2. REPORT TYPE 3. DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Hexavalent ...A-10) – AETC (T-6, T-38 and T1A) • Both Cr Primers & Non-Cr primers as well as Cr Surface Treatment – F-22 8 Non- Chrome Tie-coat & touch-up

  1. Muonium substituted molecules

    International Nuclear Information System (INIS)

    Cox, S.F.J.

    1990-12-01

    The manner in which Muon Spin Rotation and Level Crossing Resonance are used to characterise muonium substituted organic radicals is described, and illustrated with spectra for the ethyl radical and related species. Comparison with electron spin resonance data for the unsubstituted radicals reveals significant structural and hyperfine isotope effects which can be traced to the effects of zero point motion. The first comparable results for a diamagnetic species, exhibiting a quadrupole isotope effect by comparison with conventional nuclear quadrupole resonance data, are presented and discussed. (author)

  2. Nanoferrites of nickel doped with cobalt: Influence of Co{sup 2+} on the structural and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, A.P.G. [Federal University of Rio Grande do Norte, Chemical Institute, Natal-RN 59078-970 (Brazil); Gomes, D.K.S., E-mail: dkarinne@yahoo.com.br [Federal University of Rio Grande do Norte, Graduate Program in Materials Science and Engineering, Laboratory of Catalysis and Materials, Natal-RN 59078-970 (Brazil); Coordination of Improvement of Higher Education Personnel, CAPES/PNPD (Brazil); Araújo, J.H., E-mail: humberto@dfte.ufrn.br [Federal University of Rio Grande do Norte, Department of Theoretical and Experimental Physics, Laboratory of Magnetism and Magnetic Materials, Natal-RN 59078-970 (Brazil); Melo, D.M.A., E-mail: daraujomelo@gmail.com [Federal University of Rio Grande do Norte, Chemical Institute, Natal-RN 59078-970 (Brazil); Oliveira, N.A.S. [Federal University of Rio Grande do Norte, Chemical Institute, Natal-RN 59078-970 (Brazil); Braga, R.M., E-mail: renata@cear.ufpb.br [Federal University of Paraíba, DEER-CEAR, João Pessoa–PB 58051-970 (Brazil)

    2015-01-15

    Nanoferrites of nickel substituted with cobalt of composition Ni{sub 1−x}Co{sub x}Fe{sub 2}O{sub 4} (0≤x≤0.75), were synthesized by combustion reaction assisted in microwaves. The influence of the substitution of Ni{sup 2+} by Co{sup 2+} content and the concentration of Co{sup 2+} in the structural and magnetic properties was investigated. The powders were prepared by combustion according to the concept of chemical propellants and heated in a microwave oven with a power of 7000 kW. The synthesized powders were characterized by absorption spectroscopy in the infrared region (FTIR), X-ray diffraction (XRD) together with Rietveld refinement, surface area (BET) method, scanning electron microscopy (MEV) and magnetic measurements (MAV). The results indicated that it was possible to obtain nickel ferrite doped with cobalt in all compositions and that an increase of cobalt concentration caused an increase in particle size (9.78–21.63 nm), a reduction in surface area, and reduction in magnetic concentrations greater than 50%. - Highlights: • Nanoferrites Ni{sub 1–x}Co{sub x}Fe{sub 2}O{sub 4}(0≤x≤0.75) synthesized by combustion reaction assisted. • The structural and magnetic properties of substitution of Ni{sup 2+} by Co{sup 2+} were investigate. • Combustion reaction takes spinel phase with suitable magnetic properties. • The ferrites presented characteristics of soft and intermediate magnetic materials.

  3. Study of complex formation of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel

    International Nuclear Information System (INIS)

    Ismailova, M.M.; Egorova, L.A.; Khamidov, B.O.

    1993-01-01

    Present article is devoted to study of complex formation of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel. The condition of cobalt in various rate of oxidation in acrylamide aqueous solutions was studied. The concentration conditions of stability of system Co(II)-Co(III) were defined. The composition of coordination compounds of cobalt (II) and cobalt (III) in acrylamide aqueous solutions and in the phase of acrylamide hydrogel was determined.

  4. Reactions of metal-substituted myoglobins with excess electrons studied by pulse radiolysis and low-temperature gamma-radiolysis

    International Nuclear Information System (INIS)

    Miki, Hideho; Nakajima, Atushi; Ogasawara, Masaaki; Tamura, Mamoru

    1990-01-01

    Reactions of metal-substituted myoglobins with excess electrons in electron-pulse-irradiated aqueous solutions at room temperature and γ-irradiated aqueous matrices at 77 K were studied for the purpose of probing the functional role of heme iron. The rate constants for the reactions of various myoglobins with hydrated electrons were not much different from each other, and were close to those of diffusion-controlled reactions. In contrast, the reduction rates of myoglobins with dithionite depended markedly on the kind of central metals in the myoglobins. The difference was interpreted in terms of Marcus' theory for electron-transfer reactions. Effects of the 6-coordinate structure of the cobalt(III) species on the reaction with dithionite was also discussed. The steady-state optical-absorption measurements of γ-irradiated matrices containing cobaltimyoglobin at 77 K demonstrated the reduction of cobalt(III) species by excess electrons produced by the action of ionizing radiation. It was shown, by electron-spin resonance spectroscopy, that a 6-coordinated cobalt(II) species produced at 77 K transformed to a 5-coordinate one at higher temperatures, as reported previously. However, structural relaxation was not observed by optical spectroscopy either in the solutions or in the low-temperature matrices. It was concluded, therefore, that the intermediate 6-coordinate cobalt(II) species gave an optical absorption spectrum which was indistinguishable from that of the relaxed 5-coordinate cobalt(II) species. (author)

  5. Resources, recycle, and substitution

    International Nuclear Information System (INIS)

    Wymer, R.G.

    A two-fold strategy appears necessary to ensure that the resource needs of the developed and developing nations are met. First, recycle and substitution must be encouraged in those instances where they do find application. Although these measures have limited applicability, they may be of vital importance in those instances where they do apply; in any event, they buy time. Second, practical and economical technologies must be developed to exploit the lower-grade and marginal ores and the oftentimes abundant but highly refractory ores, as well as to greatly increase the recovery of secondary elements present in the ores - elements whose form and amounts in the ores make them economically unrecoverable by themselves, but which are economically recoverable as by-products. It is often the case that if these elements are not recovered during the initial mining and milling operations, they are rendered unrecoverable, in a practical sense, forever. Furthermore, they may even become environmental pollutants. Specific examples of recovery from refractory ores, by-product recovery, and recycle are given. Also, some suggestions of substitutes for important resources are tabulated

  6. X-ray absorption and emission study of amorphous and nanocrystalline GaN films containing buried N2

    International Nuclear Information System (INIS)

    Ruck, B.J.; Koo, A.; Budde, F.; Granville, S.; Trodahl, H.J.

    2004-01-01

    Full text: It has been predicted that amorphous gallium nitride (a-GaN) may possess a well-defined wide band gap, and is thus a potential substitute for the more expensive crystalline form used in short wavelength optoelectronic devices. Experimental investigations of disordered GaN have lent support to this prediction, but the picture is complicated because the properties of the amorphous state are not unique, and instead depend on the exact nature of the disordered structure. We have pioneered a novel ion-assisted growth technique that produces GaN films with a microstructure that ranges from nanocrystalline, with crystallite size of order 3 nm, to fully amorphous, depending on the exact growth conditions. This presentation will give an overview of our research into the properties of disordered GaN, including characterization of the physical structure of the films and their electronic energy levels, and also their photoconductive response. In particular I will focus on synchrotron radiation studies of samples with a range of different microstructures. X-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) provide particularly powerful tools for examining a sample's empty and filled electronic energy levels, respectively. The details of the absorption and emission processes make it possible to obtain atom-specific information and to investigate the symmetry of the electronic levels. An example of the information obtained is shown. The thin solid curve shows XAS data, which is a measure of the nitrogen /7-projected density of unfilled electronic states in this nanocrystalline GaN sample. The thick solid curve shows XES data from the same sample, which provides complementary information about the occupied valence band states. Although the spectral features are broader in fully amorphous films than in nanocrystalline samples, a well-defined band gap exists in both cases with magnitude similar to that of crystalline GaN. There are additional feature

  7. Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg2Ni-type Alloy by Melt Spinning

    Directory of Open Access Journals (Sweden)

    Hui-Ping Ren

    2011-01-01

    Full Text Available Mg2Ni-type Mg2Ni1−xCox (x = 0, 0.1, 0.2, 0.3, 0.4 alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD and transmission electron microscopy (TEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1 alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4 alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg2Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s to 30 m/s, the hydrogen absorption saturation ratio ( of the (x = 0.4 alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio ( from 54.5 to 70.2%, the hydrogen diffusion coefficient (D from 0.75 × 10−11 to 3.88 × 10−11 cm2/s and the limiting current density IL from 150.9 to 887.4 mA/g.

  8. Dosing of anaerobic granular sludge bioreactors with cobalt: Impact of cobalt retention on methanogenic activity

    KAUST Repository

    Fermoso, Fernando G.

    2010-12-01

    The effect of dosing a metal limited anaerobic sludge blanket (UASB) reactor with a metal pulse on the methanogenic activity of granular sludge has thus far not been successfully modeled. The prediction of this effect is crucial in order to optimize the strategy for metal dosage and to prevent unnecessary losses of resources. This paper describes the relation between the initial immobilization of cobalt in anaerobic granular sludge cobalt dosage into the reactor and the evolution of methanogenic activity during the subsequent weeks. An operationally defined parameter (A0· B0) was found to combine the amount of cobalt immobilized instantaneously upon the pulse (B0) and the amount of cobalt immobilized within the subsequent 24. h (A0). In contrast with the individual parameters A0 and B0, the parameter A0· B0 correlated significantly with the methanogenic activity of the sludge during the subsequent 16 or 35. days. This correlation between metal retention and activity evolution is a useful tool to implement trace metal dosing strategies for biofilm-based biotechnological processes. © 2010.

  9. Cobalt(I) and Cobalt(III) Cyclopentadienyl Complexes with New Silicon-branched Fluorous Tags

    Czech Academy of Sciences Publication Activity Database

    Strašák, Tomáš; Čermák, Jan; Červenková Šťastná, Lucie; Sýkora, Jan; Fajgar, Radek

    2014-01-01

    Roč. 159, MAR 2014 (2014), s. 15-20 ISSN 0022-1139 R&D Projects: GA ČR(CZ) GAP106/12/1372 Institutional support: RVO:67985858 Keywords : fluorous tag * cobalt complex * cyclopentadienyl complex Subject RIV: CC - Organic Chemistry Impact factor: 1.948, year: 2014

  10. The radiation response of mesoporous nanocrystalline zirconia thin films

    Energy Technology Data Exchange (ETDEWEB)

    Manzini, Ayelén M.; Alurralde, Martin A. [Comisión Nacional de Energía Atómica, Centro Atómico Constituyentes, Av. General Paz 1499, 1650 San Martin, Provincia de Buenos Aires (Argentina); Giménez, Gustavo [Instituto Nacional de Tecnología Industrial - CMNB, Av. General Paz 5445, 1650 San Martín, Provincia de Buenos Aires (Argentina); Luca, Vittorio, E-mail: vluca@cnea.gov.ar [Comisión Nacional de Energía Atómica, Centro Atómico Constituyentes, Av. General Paz 1499, 1650 San Martin, Provincia de Buenos Aires (Argentina)

    2016-12-15

    The next generation of nuclear systems will require materials capable of withstanding hostile chemical, physical and radiation environments over long time-frames. Aside from its chemical and physical stability, crystalline zirconia is one of the most radiation tolerant materials known. Here we report the first ever study of the radiation response of nanocrystalline and mesoporous zirconia and Ce{sup 3+}-stabilized nanocrystalline zirconia (Ce{sub 0.1}Zr{sub 0.9}O{sub 2}) thin films supported on silicon wafers. Zirconia films prepared using the block copolymer Brij-58 as the template had a thickness of around 60–80 nm. In the absence of a stabilizing trivalent cation they consisted of monoclinic and tetragonal zirconia nanocrystals with diameters in the range 8–10 nm. Films stabilized with Ce{sup 3+} contained only the tetragonal phase. The thin films were irradiated with iodine ions of energies of 70 MeV and 132 keV at low fluences (10{sup 13} - 10{sup 14} cm{sup −2}) corresponding to doses of 0.002 and 1.73 dpa respectively, and at 180 keV and high fluences (2 × 10{sup 16} cm{sup −2}) corresponding to 82.4 dpa. The influence of heavy ion irradiation on the nanocrystalline structure was monitored through Rietveld analysis of grazing incidence X-ray diffraction (GIXRD) patterns recorded at angles close to the critical angle to ensure minimum contribution to the diffraction pattern from the substrate. Irradiation of the mesoporous nanocrystalline zirconia thin films with 70 MeV iodine ions, for which electronic energy loss is dominant, resulted in slight changes in phase composition and virtually no change in crystallographic parameters as determined by Rietveld analysis. Iodine ion bombardment in the nuclear energy loss regime (132–180 keV) at low fluences did not provoke significant changes in phase composition or crystallographic parameters. However, at 180 keV and high fluences the monoclinic phase was totally eliminated from the GIXRD

  11. 21 CFR 189.120 - Cobaltous salts and its derivatives.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Cobaltous salts and its derivatives. 189.120 Section 189.120 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... malt beverages as a foam stabilizer and to prevent “gushing.” (b) Food containing any added cobaltous...

  12. Study to use graded cobalt adjuster in 540 MWe PHWR

    International Nuclear Information System (INIS)

    Raj, Manish; Fernando, M.P.S.; Pradhan, A.S.; Kumar, A.N.

    2007-01-01

    Full text: There are 17 adjusters in 540 MWe PHWR, which are essentially provided for xenon override function. They also provide flux flattening being in the central region of the reactor core. The present design of adjusters consists of stainless steel tube. The adjuster rods are grouped into 8 banks for movement. Since adjusters are normally fully inserted during reactor operation, they are best suited for production of cobalt 60. The nickel-plated cobalt in the form of either slugs or pellet are used for the design of cobalt pencils. The number of pencils can be varied to optimize the reactivity load and cobalt 60 production requirement. The worth and activity of cobalt adjusters have been worked out considering different pin configuration for the adjuster assembly. To start with we have assumed all adjusters throughout its length are of the same configuration. The flux depression factors within the cobalt pencils have been considered in the estimations of the specific and total cobalt 60 activities. The option of using graded cobalt adjusters, where different pin configuration along the length is considered for better flux flattening

  13. Removal of Cobalt Ions by Precipitate Foam Flotation

    Energy Technology Data Exchange (ETDEWEB)

    Jung, In Ha; Lee, Jung Won [Korea Atomic Energy Research Institute, Taejon (Korea)

    1998-09-30

    Simulated waste liquid containing 50 ppm cobalt ion was tested by precipitate flotation using a sodium lauryl sulfate as a collector. The effects of initial cobalt ion concentration, pH, surfactant concentration, flotation time, gas flow rate and foreign ions on removal efficiency of cobalt ion were studied. Pretreatment of the waste liquid with 35% H{sub 2}O{sub 2} prior to precipitate flotation made shift of optimal flotation pH from the strong alkalinity to weak alkaline range and made a favorable flotation of cobalt ion in wide range of pH. For the result of this experiment, 99.8% removal efficiency was obtained on the conditions of initial cobalt ion concentration 50 ppm, pH 9.5, gas flow rate 70 ml/min, flotation time 30 min. The simulate ion was formed to be the most harmful ion against removal of cobalt by precipitate flotation of the species which were tested. The presence of 0.1 M of SO{sub 4}{sup 2-} ion decreased removal efficiency of cobalt to 90% while the cobalt were almost entirely removed in the absence of sulfate ion. (author). 11 refs., 8 figs.

  14. Adsorption Study of Cobalt on Treated Granular Activated Carbon

    OpenAIRE

    Y. V. Hete; S. B. Gholase; R. U. Khope

    2012-01-01

    This study is carried out for the removal of cobalt from aqueous solution using granular activated carbon in combination with p-nitro benzoic acid at temperature 25±1 °C. The adsorption isotherm of cobalt on granular activated carbon has been determined and the data fitted reasonably well to the Langmuir and Freundlich isotherm for activated carbon.

  15. Adsorption Study of Cobalt on Treated Granular Activated Carbon

    Directory of Open Access Journals (Sweden)

    Y. V. Hete

    2012-01-01

    Full Text Available This study is carried out for the removal of cobalt from aqueous solution using granular activated carbon in combination with p-nitro benzoic acid at temperature 25±1 °C. The adsorption isotherm of cobalt on granular activated carbon has been determined and the data fitted reasonably well to the Langmuir and Freundlich isotherm for activated carbon.

  16. Microwave Mapping Demonstration Using the Thermochromic Cobalt Chloride Equilibrium

    Science.gov (United States)

    Nguyen, Vu D.; Birdwhistell, Kurt R.

    2014-01-01

    An update to the thermochromic cobalt(II) chloride equilibrium demonstration is described. Filter paper that has been saturated with aqueous cobalt(II) chloride is heated for seconds in a microwave oven, producing a color change. The resulting pink and blue map is used to colorfully demonstrate Le Châtelier's principle and to illuminate the…

  17. The role of cobalt on the creep of Waspaloy

    Science.gov (United States)

    Jarrett, R. N.; Chin, L.; Tien, J. K.

    1984-01-01

    Cobalt was systematically replaced with nickel in Waspaloy (which normally contains 13% Co) to determine the effects of cobalt on the creep behavior of this alloy. Effects of cobalt were found to be minimal on tensile strengths and microstructure. The creep resistance and the stress rupture resistance determined in the range from 704 to 760 C (1300 to 1400 C) were found to decrease as cobalt was removed from the standard alloy at all stresses and temperatures. Roughly a ten-fold drop in rupture life and a corresponding increase in minimum creep rate were found under all test conditions. Both the apparent creep activation energy and the matrix contribution to creep resistance were found to increase with cobalt. These creep effects are attributed to cobalt lowering the stacking fault energy of the alloy matrix. The creep resistance loss due to the removal of cobalt is shown to be restored by slightly increasing the gamma' volume fraction. Results are compared to a previous study on Udimet 700, a higher strength, higher gamma' volume fraction alloy with similar phase chemistry, in which cobalt did not affect creep resistance. An explanation for this difference in behavior based on interparticle spacing and cross-slip is presented.

  18. Potential for cobalt recovery from lateritic ores in Europe

    Science.gov (United States)

    Herrington, R.

    2012-04-01

    Cobalt is one of the 'critical metals' identified under the EU Raw Materials Initiative. Annually the global mine production of cobalt is around 55,000 tonnes,with Europe's industries consuming around 30% of that figure. Currently Europe produces around 27 tonnes of cobalt from mines in Finland although new capacity is planned. Co-bearing nickel laterite ores being mined in Greece, Macedonia and Kosovo where the cobalt is currently not being recovered (ores have typical analyses of 0.055% Co and >1% Ni,). These ores are currently treated directly in pyrometallurgical plants to recover the contained nickel and this process means there is no separate cobalt product produced. Hydrometallurgical treatment of mineralogically suitable laterite ores can recover the cobalt; for example Cuba recovers 3,500 tonnes of cobalt from its laterite mining operations, which are of a similar scale to the current European operations. Implementation of hydrometallurgical techniques is in its infancy in Europe with one deposit in Turkey planning to use atmospheric heap leaching to recover nickel and copper from oxide-dominated ores. More widespread implementation of these methods to mineralogically suitable ore types could unlock the highly significant undeveloped resources (with metal contents >0.04% Co and >1% Ni), which have been defined throughout the Balkans eastwards into Turkey. At a conservative estimate, this region has the potential to supply up to 30% of the EU cobalt requirements.

  19. Highly selective cobalt-catalyzed hydrovinylation of styrene

    NARCIS (Netherlands)

    Grutters, M.M.P.; Müller, C.; Vogt, D.

    2006-01-01

    The hydrovinylation reaction is a codimerization of a 1,3-diene or vinyl arene and ethene with great potential for fine chemicals and pharmaceuticals. For the first time, enantioselective cobalt-catalyzed hydrovinylations of styrene were achieved with a cobalt-based system bearing a chiral

  20. Preparation of nanocrystalline Ce{sub 1−x}Sm{sub x}(Fe,Co){sub 11}Ti by melt spinning and mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Wuest, H., E-mail: holger.wuest@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Bommer, L., E-mail: lars.bommer@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Huber, A.M., E-mail: arne.huber@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Goll, D., E-mail: dagmar.goll@htw-aalen.de [Aalen University, Materials Research Institute, Beethovenstr. 1, 73430 Aalen (Germany); Weissgaerber, T., E-mail: thomas.weissgaerber@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Kieback, B., E-mail: bernd.kieback@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Technische Universität Dresden, Institute for Materials Science, Helmholtzstraße 7, 01069 Dresden (Germany)

    2017-04-15

    Permanent magnetic materials based on Ce(Fe, Co){sub 12−x}Ti{sub x} with the ThMn{sub 12} structure are promising candidates for replacing NdFeB magnets. Its intrinsic magnetic properties are not far below the values of Nd{sub 2}Fe{sub 14}B, and the high amount of Fe and the fact that Ce is much more abundant and less expensive than Nd encourages the reasonable interest in these compounds. Nanocrystalline magnetic material of the composition Ce{sub 1−x}Sm{sub x}Fe{sub 11−y}Co{sub y}Ti (x=0−1 and y=0; 1.95) has been produced by both melt spinning and mechanical alloying. Alloys containing only Ce as rare earth element (x=0) show coercivities below 77 kA/m, while for x=1 H{sub c,J} values up to 392 kA/m are reached. Coercivity shows rather an exponential than a linear dependence on the gradual substitution of Ce by Sm. - Highlights: • CeFe{sub 11}Ti nanocrystalline samples demonstrate values of H{sub c,J} up to 77 kA/m. • SmFe{sub 11}Ti nanocrystalline samples demonstrate values of H{sub c,J} up to 392 kA/m. • Dependence of H{sub c,J} on x in Ce{sub 1−x}Sm{sub x(}Fe, Co){sub 11}Ti obeys non-linear dependence. • Optimum annealing shifts to from 800 °C for CeFe{sub 11}Ti to 900 °C for SmFe{sub 11}Ti.

  1. On the effects of partial substitution of Co for Fe in FINEMET and Nb-containing HITPERM alloys

    CERN Document Server

    Blazquez, J S; Conde, C F; Conde, A; Greneche, J M

    2003-01-01

    A comparative study of the effects of partial substitution of Co for Fe on thermal stability, crystallization and magnetic properties of Co-containing FINEMET and HITPERM alloys series is presented. The difference in metalloid and Nb content between the two alloy series and the presence of Si in the nanocrystals in the case of FINEMET alloys appear as key parameters. A recrystallization process involving the alpha-Fe type phase in nanocrystalline alloys of both series is evident from thermomagnetic results as a significant decrease in magnetization at the second crystallization stage.

  2. Cobalt ferrite nanoparticles under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Saccone, F. D.; Ferrari, S.; Grinblat, F.; Bilovol, V. [Instituto de Tecnologías y Ciencias de la Ingeniería, “Ing. H. Fernández Long,” Av. Paseo Colón 850 (1063), Buenos Aires (Argentina); Errandonea, D., E-mail: daniel.errandonea@uv.es [Departamento de Fisica Aplicada, Institut Universitari de Ciència dels Materials, Universitat de Valencia, c/ Doctor Moliner 50, E-46100 Burjassot, Valencia (Spain); Agouram, S. [Departamento de Física Aplicada y Electromagnetismo, Universitat de València, 46100 Burjassot, Valencia (Spain)

    2015-08-21

    We report by the first time a high pressure X-ray diffraction and Raman spectroscopy study of cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles carried out at room temperature up to 17 GPa. In contrast with previous studies of nanoparticles, which proposed the transition pressure to be reduced from 20–27 GPa to 7.5–12.5 GPa (depending on particle size), we found that cobalt ferrite nanoparticles remain in the spinel structure up to the highest pressure covered by our experiments. In addition, we report the pressure dependence of the unit-cell parameter and Raman modes of the studied sample. We found that under quasi-hydrostatic conditions, the bulk modulus of the nanoparticles (B{sub 0} = 204 GPa) is considerably larger than the value previously reported for bulk CoFe{sub 2}O{sub 4} (B{sub 0} = 172 GPa). In addition, when the pressure medium becomes non-hydrostatic and deviatoric stresses affect the experiments, there is a noticeable decrease of the compressibility of the studied sample (B{sub 0} = 284 GPa). After decompression, the cobalt ferrite lattice parameter does not revert to its initial value, evidencing a unit cell contraction after pressure was removed. Finally, Raman spectroscopy provides information on the pressure dependence of all Raman-active modes and evidences that cation inversion is enhanced by pressure under non-hydrostatic conditions, being this effect not fully reversible.

  3. Cobalt60 plaques in recurrent retinoblastoma

    Energy Technology Data Exchange (ETDEWEB)

    Fass, D.; McCormick, B.; Abramson, D.; Ellsworth, R. (Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, NY, NY (USA))

    1991-08-01

    Cobalt60 plaque irradiation is one treatment option for patients with recurrent retinoblastoma following conventional external beam irradiation (ERT). Tumorocidal doses can be delivered without excessive risk of normal tissue injury. In patients not considered candidates for xenon arc or cryotherapy, 60Co is an alternative to enucleation. Between 1968 and 1987, 85 patients were treated with 60Co plaques, 72 of whom had failed prior ERT. Age at diagnosis ranged from 1 week to 4 years. There are 37 males and 35 females. Seventy-one patients had bilateral disease and one had unilateral. Three patients had both eyes plaqued. Prior ERT ranged from 30 to 70 Gy (mean 4200 Gy). Time from initial therapy to failure ranged from 13 to 60 months. Cobalt plaques of 10 mm, 15 mm, or 10 {times} 15 mm were used depending on tumor size and location. Dose prescribed to the apex of the tumor ranged from 30 to 50 Gy (median 40 Gy) given over 3 to 8 days. Twelve patients had two plaque applications; three patients had three plaque applications. All patients were followed with routine ophthalmoscopic examinations. Follow-up ranged from 2 to 22 years (mean 8.7). Seven patients died of metastatic disease; 10 patients developed non-ocular second tumors. Thirty patients required enucleation. Twenty-two patients had clear tumor progression, two patients had radiation complications, and six patients had a combination of tumor growth and complications. Cobalt60 can salvage eyes in retinoblastoma patients failing ERT. Currently, the authors are using I125 in an attempt to spare normal ocular tissue and reduce subsequent complications.

  4. Cobalt60 plaques in recurrent retinoblastoma

    International Nuclear Information System (INIS)

    Fass, D.; McCormick, B.; Abramson, D.; Ellsworth, R.

    1991-01-01

    Cobalt60 plaque irradiation is one treatment option for patients with recurrent retinoblastoma following conventional external beam irradiation (ERT). Tumorocidal doses can be delivered without excessive risk of normal tissue injury. In patients not considered candidates for xenon arc or cryotherapy, 60Co is an alternative to enucleation. Between 1968 and 1987, 85 patients were treated with 60Co plaques, 72 of whom had failed prior ERT. Age at diagnosis ranged from 1 week to 4 years. There are 37 males and 35 females. Seventy-one patients had bilateral disease and one had unilateral. Three patients had both eyes plaqued. Prior ERT ranged from 30 to 70 Gy (mean 4200 Gy). Time from initial therapy to failure ranged from 13 to 60 months. Cobalt plaques of 10 mm, 15 mm, or 10 x 15 mm were used depending on tumor size and location. Dose prescribed to the apex of the tumor ranged from 30 to 50 Gy (median 40 Gy) given over 3 to 8 days. Twelve patients had two plaque applications; three patients had three plaque applications. All patients were followed with routine ophthalmoscopic examinations. Follow-up ranged from 2 to 22 years (mean 8.7). Seven patients died of metastatic disease; 10 patients developed non-ocular second tumors. Thirty patients required enucleation. Twenty-two patients had clear tumor progression, two patients had radiation complications, and six patients had a combination of tumor growth and complications. Cobalt60 can salvage eyes in retinoblastoma patients failing ERT. Currently, the authors are using I125 in an attempt to spare normal ocular tissue and reduce subsequent complications

  5. Nanocrystalline CdTe thin films by electrochemical synthesis

    Directory of Open Access Journals (Sweden)

    Ramesh S. Kapadnis

    2013-03-01

    Full Text Available Cadmium telluride thin films were deposited onto different substrates as copper, Fluorine-doped tin oxide (FTO, Indium tin oxide (ITO, Aluminum and zinc at room temperature via electrochemical route. The morphology of the film shows the nanostructures on the deposited surface of the films and their growth in vertical direction. Different nanostructures developed on different substrates. The X-ray diffraction study reveals that the deposited films are nanocrystalline in nature. UV-Visible absorption spectrum shows the wide range of absorption in the visible region. Energy-dispersive spectroscopy confirms the formation of cadmium telluride.

  6. Preparation of porous ceramics from nanocrystalline zirconia and its microstructure

    International Nuclear Information System (INIS)

    Nikitin, D.S.; Zhukov, V.A.; Kul'kov, S.N.; Perkov, V.V.; Buyakova, S.P.

    2004-01-01

    The behaviour of ZrO 2 (Y) nanocrystalline powder under pressing, the effect of forming pressure, the temperature and the time of sintering on the structure of the sintered porous ceramics are under study. It is shown that on pressing the fracturing of powder particles and their agglomerates takes place even at low pressures (≅50 MPa). The change of densification mechanisms is revealed - from quasi-liquid displacement of powder particles at the beginning of mechanical action to fracture of coarse structural elements. It is established that a strong skeleton responsible for needed porosity is formed even at the initial stage of sintering [ru

  7. Nanocrystalline iron nitride films with perpendicular magnetic anisotropy

    International Nuclear Information System (INIS)

    Gupta, Ajay; Dubey, Ranu; Leitenberger, W.; Pietsch, U.

    2008-01-01

    Nanocrystalline α-iron nitride films have been prepared using reactive ion-beam sputtering. Films develop significant perpendicualr magnetic anisotropy (PMA) with increasing thickness. A comparison of x-ray diffraction patterns taken with scattering vectors in the film plane and out of the film plane provides a clear evidence for development of compressive strain in the film plane with thickness. Thermal annealing results in relaxation of the strain, which correlates very well with the relaxation of PMA. This suggests that the observed PMA is a consequence of the breaking of the symmetry of the crystal structure due to the compressive strain

  8. Elemental separation in nanocrystalline Cu-Al alloys

    Science.gov (United States)

    Wang, Y. B.; Liao, X. Z.; Zhao, Y. H.; Cooley, J. C.; Horita, Z.; Zhu, Y. T.

    2013-06-01

    Nanocrystallization by high-energy severe plastic deformation has been reported to increase the solubility of alloy systems and even to mix immiscible elements to form non-equilibrium solid solutions. In this letter, we report an opposite phenomenon—nanocrystallization of a Cu-Al single-phase solid solution by high-pressure torsion separated Al from the Cu matrix when the grain sizes are refined to tens of nanometers. The Al phase was found to form at the grain boundaries of nanocrystalline Cu. The level of the separation increases with decreasing grain size, which suggests that the elemental separation was caused by the grain size effect.

  9. Tailoring the wettability of nanocrystalline TiO 2 films

    Science.gov (United States)

    Liang, Qiyu; Chen, Yan; Fan, Yuzun; Hu, Yong; Wu, Yuedong; Zhao, Ziqiang; Meng, Qingbo

    2012-01-01

    The water contact angle (WCA) of nanocrystalline TiO2 films was adjusted by fluoroalkylsilane (FAS) modification and photocatalytic lithography. FAS modification made the surface hydrophobic with the WCA up to ∼156°, while ultraviolet (UV) irradiation changed surface to hydrophilic with the WCA down to ∼0°. Both the hydrophobicity and hydrophilicity were enhanced by surface roughness. The wettability can be tailored by varying the concentration of FAS solution and soaking time, as well as the UV light intensity and irradiation time. Additionally, with the help of photomasks, hydrophobic-hydrophilic micropatterns can be fabricated and manifested via area-selective deposition of polystyrene particles.

  10. Mueller matrix spectroscopic ellipsometry study of chiral nanocrystalline cellulose films

    Science.gov (United States)

    Mendoza-Galván, Arturo; Muñoz-Pineda, Eloy; Ribeiro, Sidney J. L.; Santos, Moliria V.; Järrendahl, Kenneth; Arwin, Hans

    2018-02-01

    Chiral nanocrystalline cellulose (NCC) free-standing films were prepared through slow evaporation of aqueous suspensions of cellulose nanocrystals in a nematic chiral liquid crystal phase. Mueller matrix (MM) spectroscopic ellipsometry is used to study the polarization and depolarization properties of the chiral films. In the reflection mode, the MM is similar to the matrices reported for the cuticle of some beetles reflecting near circular left-handed polarized light in the visible range. The polarization properties of light transmitted at normal incidence for different polarization states of incident light are discussed. By using a differential decomposition of the MM, the structural circular birefringence and dichroism of a NCC chiral film are evaluated.

  11. Stacking fault-mediated ultrastrong nanocrystalline Ti thin films

    Science.gov (United States)

    Wu, K.; Zhang, J. Y.; Li, G.; Wang, Y. Q.; Cui, J. C.; Liu, G.; Sun, J.

    2017-11-01

    In this work, we prepared nanocrystalline (NC) Ti thin films with abundant stacking faults (SFs), which were created via partial dislocations emitted from grain boundaries and which were insensitive to grain sizes. By employing the nanoindentation test, we investigated the effects of SFs and grain sizes on the strength of NC Ti films at room temperature. The high density of SFs significantly strengthens NC Ti films, via dislocation-SF interactions associated with the reported highest Hall-Petch slope of ˜20 GPa nm1/2, to an ultrahigh strength of ˜4.4 GPa, approaching ˜50% of its ideal strength.

  12. Electron holography of Fe-based nanocrystalline magnetic materials (invited)

    International Nuclear Information System (INIS)

    Shindo, Daisuke; Park, Young-Gil; Gao, Youhui; Park, Hyun Soon

    2004-01-01

    Magnetic domain structures of nanocrystalline magnetic materials were extensively investigated by electron holography with a change in temperature or magnetic field applied. In both soft and hard magnetic materials, the distribution of lines of magnetic flux clarified in situ by electron holography was found to correspond well to their magnetic properties. An attempt to produce a strong magnetic field using a sharp needle made of a permanent magnet, whose movement is controlled by piezo drives has been presented. This article demonstrates that the attempt is promising to investigate the magnetization process of hard magnetic materials by electron holography

  13. Influence of Cr doping on the stability and structure of small cobalt oxide clusters

    Energy Technology Data Exchange (ETDEWEB)

    Tung, Nguyen Thanh; Lievens, Peter; Janssens, Ewald, E-mail: ewald.janssens@fys.kuleuven.be [Laboratory of Solid-State Physics and Magnetism, KU Leuven, B-3001 Leuven (Belgium); Tam, Nguyen Minh; Nguyen, Minh Tho [Department of Chemistry, KU Leuven, B-3001 Leuven (Belgium)

    2014-07-28

    The stability of mass-selected pure cobalt oxide and chromium doped cobalt oxide cluster cations, Co{sub n}O{sub m}{sup +} and Co{sub n−1}CrO{sub m}{sup +} (n = 2, 3; m = 2–6 and n = 4; m = 3–8), has been investigated using photodissociation mass spectrometry. Oxygen-rich Co{sub n}O{sub m}{sup +} clusters (m ⩾ n + 1 for n = 2, 4 and m ⩾ n + 2 for n = 3) prefer to photodissociate via the loss of an oxygen molecule, whereas oxygen poorer clusters favor the evaporation of oxygen atoms. Substituting a single Co atom by a single Cr atom alters the dissociation behavior. All investigated Co{sub n−1}CrO{sub m}{sup +} clusters, except CoCrO{sub 2}{sup +} and CoCrO{sub 3}{sup +}, prefer to decay by eliminating a neutral oxygen molecule. Co{sub 2}O{sub 2}{sup +}, Co{sub 4}O{sub 3}{sup +}, Co{sub 4}O{sub 4}{sup +}, and CoCrO{sub 2}{sup +} are found to be relatively difficult to dissociate and appear as fragmentation product of several larger clusters, suggesting that they are particularly stable. The geometric structures of pure and Cr doped cobalt oxide species are studied using density functional theory calculations. Dissociation energies for different evaporation channels are calculated and compared with the experimental observations. The influence of the dopant atom on the structure and the stability of the clusters is discussed.

  14. Hot Corrosion of Cobalt-Base Alloys

    Science.gov (United States)

    1975-06-01

    Alloys 20. ABSTRACT (Continue on revet -se tside lf necessary and identify by block number) ~ lThe sodium sulfate-induced hot corrosion of cobalt and...Figures 12 and 13. The Na2 SO 4 was observed to form puddles on the oxide-covered specimen surface. An oxide slag was usually suspended in the... slag (black arrows) were suspended (30 sees at 1000°C in air). b) After washing the Na2SO 4 from the specimen, the exposed oxide surface was highly

  15. Future of U.S. cobalt irradiation

    International Nuclear Information System (INIS)

    Clouser, J.F.

    1995-01-01

    An examination of future cobalt needs requires us to review our base business, customer trends, technology trends, and people, the human aspect of our business. I am approaching this discussion from the perspective of a contract supplier of gamma irradiation services in the United States. The base business is comprised primarily of the sterilization of medical devices followed by containers, labware, food products, and other items. Since the core business is serving the medical industry, trends observed within medical device manufacturers can impact our growth and the type of services needed to support that industry. (author)

  16. HYDROCARBON FORMATION ON POLYMER-SUPPORTED COBALT

    Energy Technology Data Exchange (ETDEWEB)

    Benner, Linda S.; Perkins, Patrick; Vollhardt, K.Peter C.

    1980-10-01

    In this report we detail the synthesis catalytic chemistry of polystyrene supported {eta}{sup 5} ~cyclopentadienyl- dicarbonyl cobalt, CpCo(CO){sub 2}. This material is active in the hydrogenation of CO to saturated linear hydrocarbons and appears to retain its "homogeneous", mononuclear character during the course of its catalysis, During ·the course of our work 18% and 20% crosslinked analogs of polystyrene supported CpCo(CO){sub 2} were shown to exhibit limited catalytic activity and no CO activation.

  17. Bifunctional cobalt F-T catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Miller, J.G.; Coughlin, P.K.; Yang, C.L.; Rabo, J.A.

    1986-03-01

    Results on the catalytic screening of Fischer-Tropsch catalysts containing shape selective components are reported. Catalysts consist of promoted cobalt intimately contacted with Union Carbide molecular sieves and were tested using a Berty type internally recycled reactor. Methods of preparation, promoters and shape selective components were varied and aimed at improving catalyst performance. Catalysts were developed demonstrating high C/sub 5/ + yields with high olefin content and low methane production while maintaining stability under both low and high H/sub 2/:CO ratio conditions.

  18. Nitrogen oxides storage catalysts containing cobalt

    Science.gov (United States)

    Lauterbach, Jochen; Snively, Christopher M.; Vijay, Rohit; Hendershot, Reed; Feist, Ben

    2010-10-12

    Nitrogen oxides (NO.sub.x) storage catalysts comprising cobalt and barium with a lean NO.sub.x storage ratio of 1.3 or greater. The NO.sub.x storage catalysts can be used to reduce NO.sub.x emissions from diesel or gas combustion engines by contacting the catalysts with the exhaust gas from the engines. The NO.sub.x storage catalysts can be one of the active components of a catalytic converter, which is used to treat exhaust gas from such engines.

  19. Study of Malayaite and Malayaite Cobalt Pigment

    International Nuclear Information System (INIS)

    Pina, C.; Arriola, H.; Nava, N.

    2005-01-01

    Calcium tin silicate, CaSnSiO 5 , called Malayaite is synthesized with equimolecular quantities of calcium oxide, silica and stannic oxide followed by a thermic process. In this work, the synthesis of Malayaite and the structure of a Malayaite-based pigment, Sn/Co pink, is investigated by X-ray diffraction and Mossbauer spectroscopy. The results indicate Malayaite and Cassiterite formation, but the ion cobalt incorporated in the Malayaite structure, diminishes the Cassiterite proportion and causes larger asymmetry in the environment of the tin atom.

  20. Low-Cobalt Powder-Metallurgy Superalloy

    Science.gov (United States)

    Harf, F. H.

    1986-01-01

    Highly-stressed jet-engine parts made with less cobalt. Udimet 700* (or equivalent) is common nickel-based superalloy used in hot sections of jet engines for many years. This alloy, while normally used in wrought condition, also gas-atomized into prealloyed powder-metallurgy (PM) product. Product can be consolidated by hot isostatically pressing (HIPPM condition) and formed into parts such as turbine disk. Such jet-engine disks "see" both high stresses and temperatures to 1,400 degrees F (760 degrees C).

  1. Association between cobalt allergy and dermatitis caused by leather articles

    DEFF Research Database (Denmark)

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

    2015-01-01

    BACKGROUND: Cobalt is a strong skin sensitizer and a prevalent contact allergen. Recent studies have recognized exposure to leather articles as a potential cause of cobalt allergy. OBJECTIVES: To examine the association between contact allergy to cobalt and a history of dermatitis resulting from...... exposure to leather. METHODS: A questionnaire case-control study was performed: the case group consisted of 183 dermatitis patients with a positive patch test reaction to cobalt chloride and a negative patch test reaction to potassium dichromate; the control group consisted of 621 dermatitis patients who...... did not react to either cobalt or chromium in patch testing. Comparisons were made by use of a χ(2) -test, Fisher's exact, and the Mann-Whitney test. Logistic regression analyses were used to test for associations while taking confounding factors into consideration. RESULTS: Leather was observed...

  2. Total body irradiation with a reconditioned cobalt teletherapy unit.

    Science.gov (United States)

    Evans, Michael D C; Larouche, Renée-Xavière; Olivares, Marina; Léger, Pierre; Larkin, Joe; Freeman, Carolyn R; Podgorsak, Ervin B

    2006-01-01

    While the current trend in radiotherapy is to replace cobalt teletherapy units with more versatile and technologically advanced linear accelerators, there remain some useful applications for older cobalt units. The expansion of our radiotherapy department involved the decommissioning of an isocentric cobalt teletherapy unit and the replacement of a column-mounted 4-MV LINAC that has been used for total body irradiation (TBI). To continue offering TBI treatments, we converted the decommissioned cobalt unit into a dedicated fixed-field total body irradiator and installed it in an existing medium-energy LINAC bunker. This article describes the logistical and dosimetric aspects of bringing a reconditioned cobalt teletherapy unit into clinical service as a total body irradiator.

  3. The acceleration of dissolved cobalt's ecological stoichiometry due to biological uptake, remineralization, and scavenging in the Atlantic Ocean

    Science.gov (United States)

    Saito, Mak A.; Noble, Abigail E.; Hawco, Nicholas; Twining, Benjamin S.; Ohnemus, Daniel C.; John, Seth G.; Lam, Phoebe; Conway, Tim M.; Johnson, Rod; Moran, Dawn; McIlvin, Matthew

    2017-10-01

    The stoichiometry of biological components and their influence on dissolved distributions have long been of interest in the study of the oceans. Cobalt has the smallest oceanic inventory of inorganic micronutrients and hence is particularly vulnerable to influence by internal oceanic processes including euphotic zone uptake, remineralization, and scavenging. Here we observe not only large variations in dCo : P stoichiometry but also the acceleration of those dCo : P ratios in the upper water column in response to several environmental processes. The ecological stoichiometry of total dissolved cobalt (dCo) was examined using data from a US North Atlantic GEOTRACES transect and from a zonal South Atlantic GEOTRACES-compliant transect (GA03/3e and GAc01) by Redfieldian analysis of its statistical relationships with the macronutrient phosphate. Trends in the dissolved cobalt to phosphate (dCo : P) stoichiometric relationships were evident in the basin-scale vertical structure of cobalt, with positive dCo : P slopes in the euphotic zone and negative slopes found in the ocean interior and in coastal environments. The euphotic positive slopes were often found to accelerate towards the surface and this was interpreted as being due to the combined influence of depleted phosphate, phosphorus-sparing (conserving) mechanisms, increased alkaline phosphatase metalloenzyme production (a zinc or perhaps cobalt enzyme), and biochemical substitution of Co for depleted Zn. Consistent with this, dissolved Zn (dZn) was found to be drawn down to only 2-fold more than dCo, despite being more than 18-fold more abundant in the ocean interior. Particulate cobalt concentrations increased in abundance from the base of the euphotic zone to become ˜ 10 % of the overall cobalt inventory in the upper euphotic zone with high stoichiometric values of ˜ 400 µmol Co mol-1 P. Metaproteomic results from the Bermuda Atlantic Time-series Study (BATS) station found cyanobacterial isoforms of the

  4. Experimental evidence for cobalt(III)-carbene radicals: key intermediates in cobalt(II)-based metalloradical cyclopropanation

    NARCIS (Netherlands)

    Lu, H.; Dzik, W.I.; Xu, X.; Wojtas, L.; de Bruin, B.; Zhang, X.P.

    2011-01-01

    New and conclusive evidence has been obtained for the existence of cobalt(III)-carbene radicals that have been previously proposed as the key intermediates in the underlying mechanism of metalloradical cyclopropanation by cobalt(II) complexes of porphyrins. In the absence of olefin substrates,

  5. EXAFS and XRD studies of nanocrystalline cerium oxide: the effect of preparation method on the microstructure

    International Nuclear Information System (INIS)

    Savin, S.L.P.; Chadwick, A.V.; Smith, M.E.; O'Dell, L.A.

    2007-01-01

    There is considerable interest in nanocrystalline materials due to their unusual properties, such as enhanced ionic conductivity in the case of nanocrystalline ionic solids. This has potential commercial applications, particularly for oxide ion conductors. However, a detailed knowledge of the microstructure is important in fully understanding the novel properties exhibited by nanocrystalline materials. The final microstructure of a material is dependent on the preparation method used, for example, sol-gel and ball-milling methods are commonly used in the preparation of nanocrystalline oxides. Additionally, there is a problem in maintaining the materials in nanocrystalline form when they are subjected to elevated temperatures. We have been exploring strategies to restrict the growth of nanocrystalline oxides and have found that adding a small amount of an inert material, e.g. SiO 2 or Al 2 O 3 , is particularly effective. We will report XRD and EXAFS studies of nanocrystalline ceria prepared by sol-gel, sol-gel pinned and ball-milling methods and the effect of preparation method on the final microstructure. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Cobalt- and platinum-rich ferromanganese crusts and associated substrate rocks from the Marshall Islands

    Science.gov (United States)

    Hein, J.R.; Schwab, W.C.; Davis, A.

    1988-01-01

    Ferromanganese crusts cover most hard substrates on seafloor edifices in the central Pacific basin. Crust samples and their associated substrates from seven volcanic edifices of Cretaceous age along the Ratak chain of the Marshall Islands are discussed. The two most abundant substrate lithologies recovered were limestone, dominantly fore-reef slope deposits, and volcanic breccia composed primarily of differentiated alkalic basalt and hawaiite clasts in a phosphatized carbonate matrix. The degree of mass wasting on the slopes of these seamounts is inversely correlated with the thickness of crusts. Crusts are generally thin on limestone substrate. Away from areas of active mass-wasting processes, and large atolls, crusts may be as thick as 10 cm maximum. The dominant crystalline phase in the Marshall Islands crusts is ??-MnO2 (vernadite). High concentrations of cobalt, platinum and rhodium strongly suggest that the Marshall Islands crusts are a viable source for these important metals. Many metals and the rare earth elements vary significantly on a fine scale through most crusts, thus reflecting the abundances of different host mineral phases in the crusts and changes in seawater composition with time. High concentrations of cobalt, nickel, titanium, zinc, lead, cerium and platinum result from a combination of their substitution in the iron and manganese phases and their oxidation potential. ?? 1988.

  7. Efficient hydrogen evolution catalysis using ternary pyrite-type cobalt phosphosulphide

    KAUST Repository

    Cabán-Acevedo, Miguel

    2015-09-14

    The scalable and sustainable production of hydrogen fuel through water splitting demands efficient and robust Earth-abundant catalysts for the hydrogen evolution reaction (HER). Building on promising metal compounds with high HER catalytic activity, such as pyrite structure cobalt disulphide (CoS 2), and substituting non-metal elements to tune the hydrogen adsorption free energy could lead to further improvements in catalytic activity. Here we present a combined theoretical and experimental study to establish ternary pyrite-type cobalt phosphosulphide (CoPS) as a high-performance Earth-abundant catalyst for electrochemical and photoelectrochemical hydrogen production. Nanostructured CoPS electrodes achieved a geometrical catalytic current density of 10 mA cm at overpotentials as low as 48mV, with outstanding long-term operational stability. Integrated photocathodes of CoPS on n -p-p silicon micropyramids achieved photocurrents up to 35 mA cm at 0 V versus the reversible hydrogen electrode (RHE), onset photovoltages as high as 450 mV versus RHE, and the most efficient solar-driven hydrogen generation from Earth-abundant systems.

  8. Thermal properties of rare earth cobalt oxides and of La1- x Gd x CoO3 solid solutions

    Science.gov (United States)

    Orlov, Yu. S.; Dudnikov, V. A.; Gorev, M. V.; Vereshchagin, S. N.; Solov'ev, L. A.; Ovchinnikov, S. G.

    2016-05-01

    Powder X-ray diffraction data for the crystal structure, phase composition, and molar specific heat for La1‒ x Gd x CoO3 cobaltites in the temperature range of 300-1000 K have been analyzed. The behavior of the volume thermal expansion coefficient in cobaltites with isovalent doping in the temperature range of 100-1000 K is studied. It is found that the β( T) curve exhibits two peaks at some doping levels. The rate of the change in the occupation number for the high-spin state of cobalt ions is calculated for the compounds under study taking into account the spin-orbit interaction. With the Birch-Murnaghan equation of state, it is demonstrated that the low-temperature peak in the thermal expansion shifts with the growth of the pressure toward higher temperatures and at pressure P ˜ 7 GPa coincides with the second peak. The similarity in the behavior of the thermal expansion coefficient in the La1- x Gd x CoO3 compounds with the isovalent substitution and the undoped LnCoO3 compound (Ln is a lanthanide) is considered. For the whole series of rare earth cobalt oxides, the nature of two specific features in the temperature dependence of the specific heat and thermal expansion is revealed and their relation to the occupation number for the high-spin state of cobalt ions and to the insulator-metal transition is established.

  9. SYNTHESIS OF THERMALLY STABLE METAL SUBSTITUTED ...

    African Journals Online (AJOL)

    Preferred Customer

    Opre et al. [22, 23] also studied the selective oxidation of alcohols with oxygen on cobalt promoted ruthenium-hydroxyapatite. Earlier, hydroxyapatites were used as supports in a many studies [24-28]. Recently, our group has also successfully used cobalt, iridium and platinum hydroxyapatites as catalysts for solvent-free.

  10. Preparation and characterization of electrodeposited cobalt nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Irshad, M. I., E-mail: imrancssp@gmail.com; Mohamed, N. M., E-mail: noranimuti-mohamed@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia); Ahmad, F., E-mail: faizahmad@petronas.com.my; Abdullah, M. Z., E-mail: zaki-abdullah@petronas.com.my [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia)

    2014-10-24

    Electrochemical deposition technique has been used to deposit cobalt nanowires into the nano sized channels of Anodized Aluminium Oxide (AAO) templates. CoCl{sub 2}Ðœ‡6H2O salt solution was used, which was buffered with H{sub 3}BO{sub 3} and acidified by dilute H{sub 2}SO{sub 4} to increase the plating life and control pH of the solution. Thin film of copper around 150 nm thick on one side of AAO template coated by e-beam evaporation system served as cathode to create electrical contact. FESEM analysis shows that the as-deposited nanowires are highly aligned, parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. The TEM results show that electrodeposited cobalt nanowires are crystalline in nature. The Hysteresis loop shows the magnetization properties for in and out of plane configuration. The in plane saturation magnetization (Ms) is lower than out of plane configuration because of the easy axis of magnetization is perpendicular to nanowire axis. These magnetic nanowires could be utilized for applications such as spintronic devices, high density magnetic storage, and magnetic sensor applications.

  11. Preparation and characterization of electrodeposited cobalt nanowires

    International Nuclear Information System (INIS)

    Irshad, M. I.; Mohamed, N. M.; Ahmad, F.; Abdullah, M. Z.

    2014-01-01

    Electrochemical deposition technique has been used to deposit cobalt nanowires into the nano sized channels of Anodized Aluminium Oxide (AAO) templates. CoCl 2 Ðœ‡6H2O salt solution was used, which was buffered with H 3 BO 3 and acidified by dilute H 2 SO 4 to increase the plating life and control pH of the solution. Thin film of copper around 150 nm thick on one side of AAO template coated by e-beam evaporation system served as cathode to create electrical contact. FESEM analysis shows that the as-deposited nanowires are highly aligned, parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. The TEM results show that electrodeposited cobalt nanowires are crystalline in nature. The Hysteresis loop shows the magnetization properties for in and out of plane configuration. The in plane saturation magnetization (Ms) is lower than out of plane configuration because of the easy axis of magnetization is perpendicular to nanowire axis. These magnetic nanowires could be utilized for applications such as spintronic devices, high density magnetic storage, and magnetic sensor applications

  12. Investigations on the formation of cobalt thiomolybdates

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, S [Paraiba Univ., Joao Pessoa (Brazil). Dept. de Engenharia Quimica

    1984-06-01

    The reactions between Co/sup 2 +/ and different thiomolybdate anions (MoS/sup 2 -//sub 4/, Mo/sub 4/S/sup 6 -//sub 15/, Mo/sub 2/S/sup 2 -//sub 7/ and Mo/sub 4/S/sup 2 -//sub 13/) have been investigated by means of glass electrode and conductometric titrations between the reactants at several concentrations. The results provide definite evidence for the formation of CoS.MoS/sub 3/ and 3CoS.4MoS/sub 3/ around pH 7.1 and 5.9, respectively. The titrations of cobalt chloride with Na/sub 2/S.2MoS/sub 3/ and Na/sub 2/S.4MoS/sub 3/ failed to provide any dependable results for the formation of the corresponding cobalt thiomolybdates. The accuracy and reproducibility of these titrations are of high order. Analytical investigations of these compounds have also been carried out and substantiate the results of the pH and conductometric measurements.

  13. Spin-dependent transport in cobalt nanocontacts

    Energy Technology Data Exchange (ETDEWEB)

    Sarau, G.

    2007-04-16

    The magnetoresistance response of cobalt nanocontacts with varying geometries formed between two extended electrodes has been experimentally investigated and linked to micromagnetic simulations. The contribution of the nanoconstriction to the measured magnetoresistance signal has been separated from that of the electrode bulk. The different nanocontact geometries exhibit different shape anisotropies resulting in a characteristic behavior of the magnetization at each nanocontact. The magnetization reversal processes are explained on the basis of the anisotropic magnetoresistance and domain wall scattering effects. The domain wall resistance takes positive values, which is in agreement with models based on the spin mistracking inside the domain wall. The 4 K MR measurements are found to be influenced by the exchange bias effect between the ferromagnetic cobalt electrodes and the antiferromagnetic oxidized Co surface. When cooling down in an applied magnetic field, the uniform biased Co layer behaves as if it possesses a unidirectional anisotropy axis along the field cooling direction. In the zero field cooling case, the exchange bias varies locally throughout the sample giving rise to non-reproducible successive MR traces. (orig.)

  14. A spot test for detection of cobalt release – early experience and findings

    DEFF Research Database (Denmark)

    Thyssen, Jacob P.; Menné, Torkil; Johansen, Jeanne D.

    2010-01-01

    Background: It is often difficult to establish clinical relevance of metal exposure in cobalt-allergic patients. Dermatologists and patients may incorrectly assume that many metallic items release cobalt at levels that may cause cobalt dermatitis. Cobalt-allergic patients may be unaware that they...

  15. A spot test for detection of cobalt release - early experience and findings

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Menné, Torkil; Johansen, Jeanne D

    2010-01-01

    It is often difficult to establish clinical relevance of metal exposure in cobalt-allergic patients. Dermatologists and patients may incorrectly assume that many metallic items release cobalt at levels that may cause cobalt dermatitis. Cobalt-allergic patients may be unaware that they are exposed...

  16. Magnetic properties of nanocrystalline pyrrhotite prepared by high-energy milling

    DEFF Research Database (Denmark)

    Balaz, P.; Godocikova, E.; Alacova, A.

    2004-01-01

    The nanocrystalline pyrrhotite was prepared by high-energy milling of lead sulphide with elemental Fe acting as reducing element. X-ray diffractometry, Mossbauer spectroscopy and VSM magnetometry were used to determine the properties of nanocrystalline iron sulphide prepared by the corresponding...... mechanochemical reaction. Pyrrhotite Fe1-xS together with the residual Fe metal were identified by the X-ray diffractometry. The kinetic studies performed by Mossbauer spectroscopy and VSM magnetometry allowed us to follow in more details the progress of the nanocrystalline magnetic phase formation during...

  17. Syntheses of nanocrystalline BaTiO3 and their optical properties

    Science.gov (United States)

    Yu, J.; Chu, J.; Zhang, M.

    Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

  18. Fabrication and structure of bulk nanocrystalline Al-Si-Ni-mishmetal alloys

    International Nuclear Information System (INIS)

    Latuch, Jerzy; Cieslak, Grzegorz; Kulik, Tadeusz

    2007-01-01

    Al-based alloys of structure consisting of nanosized Al crystals, embedded in an amorphous matrix, are interesting for their excellent mechanical properties, exceeding those of the commercial crystalline Al-based alloys. Recently discovered nanocrystalline Al alloys containing silicon (Si), rare earth metal (RE) and late transition metal (Ni), combine high tensile strength and good wear resistance. The aim of this work was to manufacture bulk nanocrystalline alloys from Al-Si-Ni-mishmetal (Mm) system. Bulk nanostructured Al 91-x Si x Ni 7 Mm 2 (x = 10, 11.6, 13 at.%) alloys were produced by ball milling of nanocrystalline ribbons followed by high pressure hot isostating compaction

  19. Interface effects on effective elastic moduli of nanocrystalline materials

    International Nuclear Information System (INIS)

    Wang Gangfeng; Feng Xiqiao; Yu Shouwen; Nan Cewen

    2003-01-01

    Interfaces often play a significant role in many physical properties and phenomena of nanocrystalline materials (NcMs). In the present paper, the interface effects on the effective elastic property of NcMs are investigated. First, an atomic potential method is suggested for estimating the effective elastic modulus of an interface phase. Then, the Mori-Tanaka effective field method is employed to determine the overall effective elastic moduli of a nanocrystalline material, which is regarded as a binary composite consisting of a crystal or inclusion phase with regular lattice connected by an amorphous-like interface or matrix phase. Finally, the stiffening effects of strain gradients are examined on the effective elastic property by using the strain gradient theory to analyze a representative unit cell. Our analysis shows two physical mechanisms of interfaces that influence the effective stiffness and other mechanical properties of materials. One is the softening effect due to the distorted atomic structures and the increased atomic spacings in interface regions, and another is the baffling effect due to the existence of boundary layers between the interface phase and the crystalline phase

  20. A variational multiscale constitutive model for nanocrystalline materials

    KAUST Repository

    Gurses, Ercan

    2011-03-01

    This paper presents a variational multi-scale constitutive model in the finite deformation regime capable of capturing the mechanical behavior of nanocrystalline (nc) fcc metals. The nc-material is modeled as a two-phase material consisting of a grain interior phase and a grain boundary effected zone (GBAZ). A rate-independent isotropic porous plasticity model is employed to describe the GBAZ, whereas a crystal-plasticity model which accounts for the transition from partial dislocation to full dislocation mediated plasticity is employed for the grain interior. The constitutive models of both phases are formulated in a small strain framework and extended to finite deformation by use of logarithmic and exponential mappings. Assuming the rule of mixtures, the overall behavior of a given grain is obtained via volume averaging. The scale transition from a single grain to a polycrystal is achieved by Taylor-type homogenization where a log-normal grain size distribution is assumed. It is shown that the proposed model is able to capture the inverse HallPetch effect, i.e., loss of strength with grain size refinement. Finally, the predictive capability of the model is validated against experimental results on nanocrystalline copper and nickel. © 2010 Elsevier Ltd. All rights reserved.

  1. Low cost and efficient photovoltaic conversion by nanocrystalline solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Graetzel, M. [Institut de Chimie Physique, Ecole Polytechnique Federal de Lausanne (Switzerland)

    1996-09-01

    Solar cells are expected to provide environmentally friendly solutions to the world`s energy supply problem. Learning from the concepts used by green plants we have developed a molecular photovoltaic device whose overall efficiency for AM 1.5 solar light to electricity has already attained 8-11%. The system is based on the sensitization of nanocrystalline oxide films by transition metal charge transfer sensitizers. In analogy to photosynthesis, the new chemical solar cell achieves the separation of the light absorption and charge carrier transport processes. Extraordinary yields for the conversion of incident photons into electric current are obtained, exceeding 90% for transition metal complexes within the wavelength range of their absorption band. The use of molten salt electrolytes together with coordination complexes of ruthenium as sensitizers and adequate sealing technology has endowed these cells with a remarkable stability making practical applications feasible. Seven industrial cooperations are presently involved in the development to bring these cells to the market. The first cells will be applied to supply electric power for consumer electronic devices. The launching of production of several products of this type is imminent and they should be on the market within the next two years. Quite aside from their intrinsic merits as photovoltaic device, the mesoscopic oxide semiconductor films developed in our laboratory offer attractive possibilities for a number of other applications. Thus, the first example of a nanocrystalline rocking chair battery will be demonstrated and its principle briefly discussed.

  2. Mechanical properties of nanocrystalline palladium prepared by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Castrup, Anna; Hahn, Horst [Forschungszentrum Karlsruhe (Germany); Technical University of Darmstadt (Germany); Scherer, Torsten; Ivanisenko, Yulia; Choi, In-Suk; Kraft, Oliver [Forschungszentrum Karlsruhe (Germany)

    2009-07-01

    Nanocrystalline metals and alloys with grain sizes well below 100 nm often demonstrate unique deformation behaviour and therefore attract a great interest in material science. The understanding of deformation mechanisms operating in nanocrystalline materials is important to predict their mechanical properties. In the present study Pd films of 1{mu}m thickness were prepared using UHV rf magnetron sputtering on dog bone shaped Kapton substrates and on Si/SiO2 wafers. The films were sputtered using multilayer technology with an individual layer thickness of 10 nm. This resulted in grain sizes of about 20 nm. Initial microstructure and texture were characterized using conventional XRD measurements and transmission electron microscopy (TEM) in both cross section- and plane view. The mechanical properties were investigated using tensile testing and nanoindentation at several strain rates. An increased hardness and strength as compared to coarse grained Pd was observed, as well as high strain rate sensitivity. The microstructure in the gauge section after tensile testing was again analyzed using TEM in order to reveal signatures of deformation mechanisms like dislocation motion or twinning.

  3. Visualizing decoupling in nanocrystalline alloys: A FORC-temperature analysis

    Science.gov (United States)

    Rivas, M.; Martínez-García, J. C.; Gorria, P.

    2016-02-01

    Devitrifying ferromagnetic amorphous precursors in the adequate conditions may give rise to disordered assemblies of densely packed nanocrystals with extraordinary magnetic softness well explained by the exchange coupling among multiple crystallites. Whether the magnetic exchange interaction is produced by direct contact or mediated by the intergranular amorphous matrix has a strong influence on the behaviour of the system above room temperature. Multi-phase amorphous-nanocrystalline systems dramatically harden when approaching the amorphous Curie temperature (TC) due to the hard grains decoupling. The study of the thermally induced decoupling of nanosized crystallites embedded in an amorphous matrix has been performed in this work by the first-order reversal curves (FORCs) analysis. We selected a Fe-rich amorphous alloy with TC = 330 K, in order to follow the evolution of the FORC diagrams obtained below and above such temperature in samples with different percentages of nanocrystalline phase. The existence of up to four regions exhibiting unlike magnetic behaviours is unambiguously determined from the temperature evolution of the FORC.

  4. Nanocrystalline functional materials and nanocomposites synthesis through aerosol routes

    Directory of Open Access Journals (Sweden)

    Milošević Olivera B.

    2003-01-01

    Full Text Available This paper represents the results of the design of functional nanocrystalline powders and nanocomposites using chemical reactions in aerosols. The process involves ultrasonic aerosol formation (mist generators with the resonant frequencies of 800 kHz, 1.7 and 2.5 MHz from precursor salt solutions and control over the aerosol decomposition in a high-temperature tubular flow reactor. During decomposition, the aerosol droplets undergo evaporation/drying, precipitation and thermolysis in a single-step process. Consequently, spherical, solid, agglomerate-free submicronic particles are obtained. The particle morphology, revealed as a composite structure consisting of primary crystallites smaller than 20 nm was analysed by several methods (XRD, DSC/DTA, SEM, TEM and discussed in terms of precursor chemistry and process parameters. Following the initial attempts, a more detailed aspect of nanocrystalline particle synthesis was demonstrated for the case of nanocomposites based on ZnO-MeO (MeO=Bi Cr+, suitable for electronic applications, as well as an yttrium-aluminum base complex system, suitable for phosphorus applications. The results imply that parts of the material structure responsible for different functional behaviour appear through in situ aerosol synthesis by processes of intraparticle agglomeration, reaction and sintering in the last synthesis stage.

  5. New atom probe approaches to studying segregation in nanocrystalline materials

    International Nuclear Information System (INIS)

    Samudrala, S.K.; Felfer, P.J.; Araullo-Peters, V.J.; Cao, Y.; Liao, X.Z.; Cairney, J.M.

    2013-01-01

    Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. - Highlights: ► New data treatment methods allow delineation of grain boundaries, even without segregation. ► Proxigrams calculated from the surfaces accurately show the extent of segregation. ► Tessellation of the data volume can be used to map the Gibbsian interfacial excess

  6. Nanocrystalline zinc oxide for the decontamination of sarin

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, T.H. [Defense R and D Establishment, Jhansi Road, 474002, Gwalior, MP (India); Prasad, G.K., E-mail: gkprasad@lycos.com [Defense R and D Establishment, Jhansi Road, 474002, Gwalior, MP (India); Singh, Beer; Acharya, J.; Srivastava, A.R.; Vijayaraghavan, R. [Defense R and D Establishment, Jhansi Road, 474002, Gwalior, MP (India)

    2009-06-15

    Nanocrystalline zinc oxide materials were prepared by sol-gel method and were characterized by X-ray diffraction, scanning electron microscopy, thermogravimetry, nitrogen adsorption and infrared spectroscopy techniques. The data confirmed the formation of zinc oxide materials of zincite phase with an average crystallite size of {approx}55 nm. Obtained material was tested as destructive adsorbent for the decontamination of sarin and the reaction was followed by GC-NPD and GC-MS techniques. The reaction products were characterized by GC-MS and the data explored the role of hydrolysis reaction in the detoxification of sarin. Sarin was hydrolyzed to form surface bound non-toxic phosphonate on the surface of nano-zinc oxide. The data also revealed the values of rate constant and half-life to be 4.12 h{sup -1} and 0.16 h in the initial stages of the reaction and 0.361 h{sup -1} and 1.9 h at the final stages of the reaction for the decontamination reaction on nanocrystalline ZnO.

  7. Nanocrystalline zinc oxide for the decontamination of sarin

    International Nuclear Information System (INIS)

    Mahato, T.H.; Prasad, G.K.; Singh, Beer; Acharya, J.; Srivastava, A.R.; Vijayaraghavan, R.

    2009-01-01

    Nanocrystalline zinc oxide materials were prepared by sol-gel method and were characterized by X-ray diffraction, scanning electron microscopy, thermogravimetry, nitrogen adsorption and infrared spectroscopy techniques. The data confirmed the formation of zinc oxide materials of zincite phase with an average crystallite size of ∼55 nm. Obtained material was tested as destructive adsorbent for the decontamination of sarin and the reaction was followed by GC-NPD and GC-MS techniques. The reaction products were characterized by GC-MS and the data explored the role of hydrolysis reaction in the detoxification of sarin. Sarin was hydrolyzed to form surface bound non-toxic phosphonate on the surface of nano-zinc oxide. The data also revealed the values of rate constant and half-life to be 4.12 h -1 and 0.16 h in the initial stages of the reaction and 0.361 h -1 and 1.9 h at the final stages of the reaction for the decontamination reaction on nanocrystalline ZnO.

  8. Nanocrystalline materials: recent advances in crystallographic characterization techniques

    Directory of Open Access Journals (Sweden)

    Emilie Ringe

    2014-11-01

    Full Text Available Most properties of nanocrystalline materials are shape-dependent, providing their exquisite tunability in optical, mechanical, electronic and catalytic properties. An example of the former is localized surface plasmon resonance (LSPR, the coherent oscillation of conduction electrons in metals that can be excited by the electric field of light; this resonance frequency is highly dependent on both the size and shape of a nanocrystal. An example of the latter is the marked difference in catalytic activity observed for different Pd nanoparticles. Such examples highlight the importance of particle shape in nanocrystalline materials and their practical applications. However, one may ask `how are nanoshapes created?', `how does the shape relate to the atomic packing and crystallography of the material?', `how can we control and characterize the external shape and crystal structure of such small nanocrystals?'. This feature article aims to give the reader an overview of important techniques, concepts and recent advances related to these questions. Nucleation, growth and how seed crystallography influences the final synthesis product are discussed, followed by shape prediction models based on seed crystallography and thermodynamic or kinetic parameters. The crystallographic implications of epitaxy and orientation in multilayered, core-shell nanoparticles are overviewed, and, finally, the development and implications of novel, spatially resolved analysis tools are discussed.

  9. Magnetic induction heating of FeCr nanocrystalline alloys

    International Nuclear Information System (INIS)

    Gómez-Polo, C.; Larumbe, S.; Pérez-Landazábal, J.I.; Pastor, J.M.; Olivera, J.; Soto-Armañanzas, J.

    2012-01-01

    In this work the thermal effects of magnetic induction heating in (FeCr) 73.5 Si 13.5 Cu 1 B 9 Nb 3 amorphous and nanocrystalline wires were analyzed. A single piece of wire was immersed in a glass capillary filled with water and subjected to an ac magnetic field (frequency, 320 kHz). The initial temperature rise enabled the determination of the effective Specific Absorption Rate (SAR). Maximum SAR values are achieved for those samples displaying high magnetic susceptibility, where the eddy current losses dominate the induction heating behavior. Moreover, the amorphous sample with Curie temperature around room temperature displays characteristic features of self-regulated hyperthermia. - Highlights: ► Amorphous and nanocrystalline Fe based alloys with tailored Curie temperature of the amorphous phase. ► Induction heating effects under the action of a ac magnetic field. ► Self-regulated characteristics based on the control of the Curie temperature. ► Dominant role of the eddy-current losses in the self-heating phenomena.

  10. Magnetotransport in nanocrystalline SmB6 thin films

    Directory of Open Access Journals (Sweden)

    Jie Yong

    2015-07-01

    Full Text Available SmB6 has been predicted to be a prototype of topological Kondo insulator (TKI but its direct experimental evidence as a TKI is still lacking to date. Here we report on our search for the signature of a topological surface state and investigation of the effect of disorder on transport properties in nanocrystalline SmB6 thin films through longitudinal magnetoresistance and Hall coefficient measurements. The magnetoresistance (MR at 2 K is positive and linear (LPMR at low field and become negative and quadratic at higher field. While the negative part is understood from the reduction of the hybridization gap due to Zeeman splitting, the positive dependence is similar to what is observed in other topological insulators (TI. We conclude that the LPMR is a characteristic of TI and is related to the linear dispersion near the Dirac cone. The Hall resistance shows a sign change around 50K. It peaks and becomes nonlinear around 10 K then decreases below 10 K. This indicates that carriers with opposite signs emerge below 50 K. These properties indicate that the surface states are robust and probably topological in our nanocrystalline films.

  11. New atom probe approaches to studying segregation in nanocrystalline materials

    Energy Technology Data Exchange (ETDEWEB)

    Samudrala, S.K.; Felfer, P.J.; Araullo-Peters, V.J. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); The Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Cao, Y.; Liao, X.Z. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); Cairney, J.M., E-mail: julie.cairney@sydney.edu.au [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); The Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia)

    2013-09-15

    Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. - Highlights: ► New data treatment methods allow delineation of grain boundaries, even without segregation. ► Proxigrams calculated from the surfaces accurately show the extent of segregation. ► Tessellation of the data volume can be used to map the Gibbsian interfacial excess.

  12. New atom probe approaches to studying segregation in nanocrystalline materials.

    Science.gov (United States)

    Samudrala, S K; Felfer, P J; Araullo-Peters, V J; Cao, Y; Liao, X Z; Cairney, J M

    2013-09-01

    Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Mechanically alloyed PrFeB nanocrystalline magnets

    International Nuclear Information System (INIS)

    Kaszuwara, W.; Leonowicz, M.

    1998-01-01

    Mechanically alloyed PrFeB nanocrystalline magnets were prepared by extensive ball milling of Pr, Fe and Fe 80 B 20 powders, followed by diffusion annealing. After milling, the material consisted of nanocrystalline α-Fe crystallites embedded in amorphous Pr-rich matrix. Thermomagnetic and calorimetric investigations of the transformations which occurred during annealing showed that the amorphous phase crystallised at 240 C, leading to the formation of crystalline Pr having lattice constants 10% greater than those shown in the ASTM data. This fact indicated that mechanical alloying and low temperature annealing led to the formation of a solid solution of either Fe or B in Pr, which does not exist in the equilibrium state. The Pr 2 Fe 14 B phase was subsequently formed within a temperature range of 420-620 C. The magnetic properties of magnets depend on the phase structure and grain size. Milling time appears to be a decisive processing parameter for the tailoring of the magnetic properties. Depending on the phase structure, the coercivities varied from 100 to 1200 kA/m and, respectively, the remanences from 0.98 T to 0.6 T. The highest maximum energy product was 80 kJ/m 3 . (orig.)

  14. Investigation of nanocrystalline Gd films loaded with hydrogen

    KAUST Repository

    Hruška, Petr; Čí žek, Jakub; Dobroň, Patrik; Anwand, Wolfgang; Mü cklich, Arndt; Gemma, Ryota; Wagner, Stefan; Uchida, Helmut; Pundt, Astrid

    2015-01-01

    The present work reports on microstructure studies of hydrogen-loaded nanocrystalline Gd films prepared by cold cathode beam sputtering on sapphire (112¯0) substrates. The Gd films were electrochemically step-by-step charged with hydrogen and the structural development with increasing concentration of absorbed hydrogen was studied by transmission electron microscopy and in-situ   X-ray diffraction using synchrotron radiation. The relaxation of hydrogen-induced stresses was examined by acoustic emission measurements. In the low concentration range absorbed hydrogen occupies preferentially vacancy-like defects at GBs typical for nanocrystalline films. With increasing hydrogen concentration hydrogen starts to occupy interstitial sites. At the solid solution limit the grains gradually transform into the ββ-phase (GdH2). Finally at high hydrogen concentrations xH>2.0xH>2.0 H/Gd, the film structure becomes almost completely amorphous. Contrary to bulk Gd specimens, the formation of the γγ-phase (GdH3) was not observed in this work.

  15. Currency substitution in Eastern Europe

    NARCIS (Netherlands)

    van Aarle, B.; Budina, N.

    1995-01-01

    Monetary instability during the transition process from a command economy to a market economy has induced a considerable increase in currency substitution in Eastern Europe. Currency substitution itself affects monetary stability since it reduces the stability of velocity. This paper investigates

  16. Why Does Trigonometric Substitution Work?

    Science.gov (United States)

    Cunningham, Daniel W.

    2018-01-01

    Modern calculus textbooks carefully illustrate how to perform integration by trigonometric substitution. Unfortunately, most of these books do not adequately justify this powerful technique of integration. In this article, we present an accessible proof that establishes the validity of integration by trigonometric substitution. The proof offers…

  17. Substitution of matrices over rings

    NARCIS (Netherlands)

    Hautus, M.L.J.

    1995-01-01

    For a given commutative ring with an identity element, we define and study the substitution of a matrix with entries in into a matrix polynomial or rational function over . A Bezout-type remainder theorem and a "partial-substitution rule" are derived and used to obtain a number of results. The

  18. Substitution in recreation choice behavior

    Science.gov (United States)

    George L. Peterson; Daniel J. Stynes; Donald H. Rosenthal; John F. Dwyer

    1985-01-01

    This review discusses concepts and theories of substitution in recreation choice. It brings together the literature of recreation research, psychology, geography, economics, and transportation. Parallel and complementary developments need integration into an improved theory of substitution. Recreation decision behavior is characterized as a nested or sequential choice...

  19. Biological background of dermal substitutes

    NARCIS (Netherlands)

    van der Veen, V. C.; van der Wal, M.B.; van Leeuwen, M.C.; Ulrich, M.; Middelkoop, E.

    2010-01-01

    Dermal substitutes are of major importance in treating full thickness skin defects, both in acute and chronic wounds. In this review we will outline specific requirements of three classes of dermal substitutes:-natural biological materials, with a more or less intact extracellular matrix

  20. Synthesis of cobalt boride nanoparticles using radio frequency thermal plasma

    International Nuclear Information System (INIS)

    Lapitan, Jr. Lorico DS.; Ying Ying Chen; Seesoek Choe; Watanabe, Takayuki

    2012-01-01

    Nano size cobalt boride particles were synthesized from vapor phase using a 30 kw-4 MHz radio frequency (RF) thermal plasma. Cobalt and boron powder mixtures used as precursors in different composition and feed rate were evaporated immediately in the high temperature plasma and cobalt boride nanoparticles were produced through the quenching process. The x-ray diffractometry (XRD) patterns of cobalt boride nanoparticles prepared from the feed powder ratio of 1:2 and 1:3 for Co: B showed peaks that are associated with the Co 2 B and CoB crystal phases of cobalt boride. The XRD analysis revealed that increasing the powder feed rate results in a higher mass fraction and a larger crystalline diameter of cobalt boride nanoparticles. The images obtained by field emission scanning electron microscopy (FE-SEM) revealed that cobalt boride nanoparticles have a spherical morphology. The crystallite size of the particles estimated with XRD was found to be 18-22 nm. (author)