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Sample records for cr fe-silicon layers

  1. Process for depositing Cr-bearing layer

    DOEpatents

    Ellis, T.W.; Lograsso, T.A.; Eshelman, M.A.

    1995-05-09

    A method of applying a Cr-bearing layer to a substrate, comprises introducing an organometallic compound, in vapor or solid powder form entrained in a carrier gas to a plasma of an inductively coupled plasma torch or device to thermally decompose the organometallic compound and contacting the plasma and the substrate to be coated so as to deposit the Cr-bearing layer on the substrate. A metallic Cr, Cr alloy or Cr compound such as chromium oxide, nitride and carbide can be provided on the substrate. Typically, the organometallic compound is introduced to an inductively coupled plasma torch that is disposed in ambient air so to thermally decompose the organometallic compound in the plasma. The plasma is directed at the substrate to deposit the Cr-bearing layer or coating on the substrate. 7 figs.

  2. Process for depositing Cr-bearing layer

    DOEpatents

    Ellis, Timothy W.; Lograsso, Thomas A.; Eshelman, Mark A.

    1995-05-09

    A method of applying a Cr-bearing layer to a substrate, comprises introducing an organometallic compound, in vapor or solid powder form entrained in a carrier gas to a plasma of an inductively coupled plasma torch or device to thermally decompose the organometallic compound and contacting the plasma and the substrate to be coated so as to deposit the Cr-bearing layer on the substrate. A metallic Cr, Cr alloy or Cr compound such as chromium oxide, nitride and carbide can be provided on the substrate. Typically, the organometallic compound is introduced to an inductively coupled plasma torch that is disposed in ambient air so to thermally decompose the organometallic compound in the plasma. The plasma is directed at the substrate to deposit the Cr-bearing layer or coating on the substrate.

  3. The impact of Cr adhesion layer on CNFET electrical characteristics

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Chikkadi, Kiran; Muoth, Matthias; Hierold, Christofer; Haluska, Miroslav

    2016-01-01

    The effect of a Cr adhesion layer on the transfer characteristics of Cr/Au-contacted carbon nanotube field-effect transistors (CNFETs) based on individual single-walled carbon nanotubes (SWNTs) is presented in this paper. We show that a very thin Cr layer (≈0.4 nm) already has an impact on the carrier transport in Schottky-barrier-modulated CNFETs. The ratio of the p- and n-branch current is reduced by eight times when the Cr adhesion layer thickness is increased from 0 to 8 nm. We suggest a change in Schottky barrier height at the contact as the determining mechanism for this result. Additionally, superior lifetime of devices is observed even for non-passivated CNFETs with preserved clean SWNT/Cr/Au-contacts using Cr layer thinner than 2 nm. Our experiments show that the role of the adhesion layer in metal/nanotube contacts should be explicitly considered when designing CNTFET-based circuits, developing CNFET fabrication processes, and analyzing the corresponding properties of the electrical contacts.

  4. The impact of Cr adhesion layer on CNFET electrical characteristics.

    PubMed

    Liu, Wei; Chikkadi, Kiran; Muoth, Matthias; Hierold, Christofer; Haluska, Miroslav

    2016-01-08

    The effect of a Cr adhesion layer on the transfer characteristics of Cr/Au-contacted carbon nanotube field-effect transistors (CNFETs) based on individual single-walled carbon nanotubes (SWNTs) is presented in this paper. We show that a very thin Cr layer (≈0.4 nm) already has an impact on the carrier transport in Schottky-barrier-modulated CNFETs. The ratio of the p- and n-branch current is reduced by eight times when the Cr adhesion layer thickness is increased from 0 to 8 nm. We suggest a change in Schottky barrier height at the contact as the determining mechanism for this result. Additionally, superior lifetime of devices is observed even for non-passivated CNFETs with preserved clean SWNT/Cr/Au-contacts using Cr layer thinner than 2 nm. Our experiments show that the role of the adhesion layer in metal/nanotube contacts should be explicitly considered when designing CNTFET-based circuits, developing CNFET fabrication processes, and analyzing the corresponding properties of the electrical contacts.

  5. Synthesis and characterization of Cd-Cr and Zn-Cd-Cr layered double hydroxides intercalated with dodecyl sulfate

    SciTech Connect

    Guo Ying; Zhang He; Zhao Lan; Li Guodong; Chen Jiesheng . E-mail: chemcj@mail.jlu.edu.cn; Xu Lin

    2005-06-15

    Cd-Cr and Zn-Cd-Cr layered double hydroxides (CdCr-LDH and ZnCdCr-LDH) containing alkyl sulfate as the interlamellar anion have been prepared through a coprecipitation technique. The resulting compounds were characterized using X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Magnetic property measurements indicate that antiferromagnetic interactions occur between the chromium ions in the two compounds at low temperatures. The introduction of zinc influences the ligand field of Cr{sup III} and the Cr{sup III}-Cr{sup III} interactions in the LDH compound. It is found that both CdCr-LDH and ZnCdCr-LDH can be delaminated by dispersion in formamide, leading to translucent and stable colloidal solutions.

  6. Surface morphological evolution of epitaxial CrN(001) layers

    SciTech Connect

    Frederick, J.R.; Gall, D.

    2005-09-01

    CrN layers, 57 and 230 nm thick, were grown on MgO(001) at T{sub s}=600-800 deg. C by ultrahigh-vacuum magnetron sputter deposition in pure N{sub 2} discharges from an oblique deposition angle {alpha}=80 deg. . Layers grown at 600 deg. C nucleate as single crystals with a cube-on-cube epitaxial relationship with the substrate. However, rough surfaces with cauliflower-type morphologies cause the nucleation of misoriented CrN grains that develop into cone-shaped grains that protrude out of the epitaxial matrix to form triangular faceted surface mounds. The surface morphology of epitaxial CrN(001) grown at 700 deg. C is characterized by dendritic ridge patterns extending along the orthogonal <110> directions superposed by square-shaped super mounds with <100> edges. The ridge patterns are attributed to a Bales-Zangwill instability while the supermounds form due to atomic shadowing which leads to the formation of epitaxial inverted pyramids that are separated from the surrounding layer by tilted nanovoids. Growth at 800 deg. C yields complete single crystals with smooth surfaces. The root-mean-square surface roughness for 230-nm-thick layers decreases from 18.8 to 9.3 to 1.1 nm as T{sub s} is raised from 600 to 700 to 800 deg. C. This steep decrease is due to a transition in the roughening mechanism from atomic shadowing to kinetic roughening. Atomic shadowing is dominant at 600 and 700 deg. C, where misoriented grains and supermounds, respectively, capture a larger fraction of the oblique deposition flux in comparison to the surrounding epitaxial matrix, resulting in a high roughening rate that is described by a power law with an exponent {beta}>0.5. In contrast, kinetic roughening controls the surface morphology for T{sub s}=800 deg. C, as well as the epitaxial fraction of the layers grown at 600 and 700 deg. C, yielding relatively smooth surfaces and {beta}{<=}0.27.

  7. Computational prediction and characterization of single-layer CrS2

    NASA Astrophysics Data System (ADS)

    Zhuang, Houlong L.; Johannes, Michelle D.; Blonsky, Michael N.; Hennig, Richard G.

    2014-01-01

    Using first-principles calculations, we predict a previously unreported bulk CrS2 phase that is stable against competing phases and a low energy dynamically stable single-layer CrS2 phase. We characterize the electronic, optical, and piezoelectric properties of this single-layer material. Like single-layer MoS2, CrS2 has a direct bandgap and valley polarization. The optical bandgap of CrS2 is 1.3 eV, close to the ideal bandgap of 1.4 eV for photovoltaic applications. Applying compressive strain increases the bandgap and optical absorbance, transforming it into a promising photocatalyst for solar water splitting. Finally, we show that single-layer CrS2 possesses superior piezoelectric properties to single-layer MoS2.

  8. Computational prediction and characterization of single-layer CrS{sub 2}

    SciTech Connect

    Zhuang, Houlong L.; Blonsky, Michael N.; Hennig, Richard G.; Johannes, Michelle D.

    2014-01-13

    Using first-principles calculations, we predict a previously unreported bulk CrS{sub 2} phase that is stable against competing phases and a low energy dynamically stable single-layer CrS{sub 2} phase. We characterize the electronic, optical, and piezoelectric properties of this single-layer material. Like single-layer MoS{sub 2}, CrS{sub 2} has a direct bandgap and valley polarization. The optical bandgap of CrS{sub 2} is 1.3 eV, close to the ideal bandgap of 1.4 eV for photovoltaic applications. Applying compressive strain increases the bandgap and optical absorbance, transforming it into a promising photocatalyst for solar water splitting. Finally, we show that single-layer CrS{sub 2} possesses superior piezoelectric properties to single-layer MoS{sub 2}.

  9. Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Wang, Zhangzhong

    2016-09-01

    A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel's wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer's oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10-4 mm3/N m, which was only 45.2% of the untreated sample.

  10. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Tobar, M. J.; Yáñez, A.; Amigó, V.; Candel, J. J.

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed.

  11. Electroless deposition of NiCrB diffusion barrier layer film for ULSI-Cu metallization

    NASA Astrophysics Data System (ADS)

    Wang, Yuechun; Chen, Xiuhua; Ma, Wenhui; Shang, Yudong; Lei, Zhengtao; Xiang, Fuwei

    2017-02-01

    NiCrB films were deposited on Si substrates using electroless deposition as a diffusion barrier layer for Cu interconnections. Samples of the prepared NiCrB/SiO2/Si and NiCrB/Cu/NiCrB/SiO2/Si were annealed at temperatures ranging from 500 °C to 900 °C. The reaction mechanism of the electroless deposition of the NiCrB film, the failure temperature and the failure mechanism of the NiCrB diffusion barrier layer were investigated. The prepared samples were subjected to XRD, XPS, FPP and AFM to determine the phases, composition, sheet resistance and surface morphology of samples before and after annealing. The results of these analyses indicated that the failure temperature of the NiCrB barrier film was 900 °C and the failure mechanism led to crystallization and grain growth of the NiCrB barrier layer after high temperature annealing. It was found that this process caused Cu grains to reach Si substrate through the grain boundaries, and then the reaction between Cu and Si resulted in the formation of highly resistive Cu3Si.

  12. Developments of the Physical and Electrical Properties of NiCr and NiCrSi Single-Layer and Bi-Layer Nano-Scale Thin-Film Resistors

    PubMed Central

    Cheng, Huan-Yi; Chen, Ying-Chung; Li, Chi-Lun; Li, Pei-Jou; Houng, Mau-Phon; Yang, Cheng-Fu

    2016-01-01

    In this study, commercial-grade NiCr (80 wt % Ni, 20 wt % Cr) and NiCrSi (55 wt % Ni, 40 wt % Cr, 5 wt % Si) were used as targets and the sputtering method was used to deposit NiCr and NiCrSi thin films on Al2O3 and Si substrates at room temperature under different deposition time. X-ray diffraction patterns showed that the NiCr and NiCrSi thin films were amorphous phase, and the field-effect scanning electronic microscope observations showed that only nano-crystalline grains were revealed on the surfaces of the NiCr and NiCrSi thin films. The log (resistivity) values of the NiCr and NiCrSi thin-film resistors decreased approximately linearly as their thicknesses increased. We found that the value of temperature coefficient of resistance (TCR value) of the NiCr thin-film resistors was positive and that of the NiCrSi thin-film resistors was negative. To investigate these thin-film resistors with a low TCR value, we designed a novel bi-layer structure to fabricate the thin-film resistors via two different stacking methods. The bi-layer structures were created by depositing NiCr for 10 min as the upper (or lower) layer and depositing NiCrSi for 10, 30, or 60 min as the lower (or upper) layer. We aim to show that the stacking method had no apparent effect on the resistivity of the NiCr-NiCrSi bi-layer thin-film resistors but had large effect on the TCR value. PMID:28344296

  13. Developments of the Physical and Electrical Properties of NiCr and NiCrSi Single-Layer and Bi-Layer Nano-Scale Thin-Film Resistors.

    PubMed

    Cheng, Huan-Yi; Chen, Ying-Chung; Li, Chi-Lun; Li, Pei-Jou; Houng, Mau-Phon; Yang, Cheng-Fu

    2016-02-25

    In this study, commercial-grade NiCr (80 wt % Ni, 20 wt % Cr) and NiCrSi (55 wt % Ni, 40 wt % Cr, 5 wt % Si) were used as targets and the sputtering method was used to deposit NiCr and NiCrSi thin films on Al₂O₃ and Si substrates at room temperature under different deposition time. X-ray diffraction patterns showed that the NiCr and NiCrSi thin films were amorphous phase, and the field-effect scanning electronic microscope observations showed that only nano-crystalline grains were revealed on the surfaces of the NiCr and NiCrSi thin films. The log (resistivity) values of the NiCr and NiCrSi thin-film resistors decreased approximately linearly as their thicknesses increased. We found that the value of temperature coefficient of resistance (TCR value) of the NiCr thin-film resistors was positive and that of the NiCrSi thin-film resistors was negative. To investigate these thin-film resistors with a low TCR value, we designed a novel bi-layer structure to fabricate the thin-film resistors via two different stacking methods. The bi-layer structures were created by depositing NiCr for 10 min as the upper (or lower) layer and depositing NiCrSi for 10, 30, or 60 min as the lower (or upper) layer. We aim to show that the stacking method had no apparent effect on the resistivity of the NiCr-NiCrSi bi-layer thin-film resistors but had large effect on the TCR value.

  14. Computational discovery of ferromagnetic semiconducting single-layer CrSnTe3

    DOE PAGES

    Zhuang, Houlong L.; Xie, Yu; Kent, P. R. C.; ...

    2015-07-06

    Despite many single-layer materials being reported in the past decade, few of them exhibit magnetism. Here we perform first-principles calculations using accurate hybrid density functional methods (HSE06) to predict that single-layer CrSnTe3 (CST) is a ferromagnetic semiconductor, with band gaps of 0.9 and 1.2 eV for the majority and minority spin channels, respectively. We determine the Curie temperature as 170 K, significantly higher than that of single-layer CrSiTe3 (90K) and CrGeTe3 (130 K). This is due to the enhanced ionicity of the Sn-Te bond, which in turn increases the superexchange coupling between the magnetic Cr atoms. We further explore themore » mechanical and dynamical stability and strain response of this single-layer material for possible epitaxial growth. Lastly, our study provides an intuitive approach to understand and design novel single-layer magnetic semiconductors for a wide range of spintronics and energy applications.« less

  15. Sealing of hard CrN and DLC coatings with atomic layer deposition.

    PubMed

    Härkönen, Emma; Kolev, Ivan; Díaz, Belén; Swiatowska, Jolanta; Maurice, Vincent; Seyeux, Antoine; Marcus, Philippe; Fenker, Martin; Toth, Lajos; Radnoczi, György; Vehkamäki, Marko; Ritala, Mikko

    2014-02-12

    Atomic layer deposition (ALD) is a thin film deposition technique that is based on alternating and saturating surface reactions of two or more gaseous precursors. The excellent conformality of ALD thin films can be exploited for sealing defects in coatings made by other techniques. Here the corrosion protection properties of hard CrN and diamond-like carbon (DLC) coatings on low alloy steel were improved by ALD sealing with 50 nm thick layers consisting of Al2O3 and Ta2O5 nanolaminates or mixtures. In cross sectional images the ALD layers were found to follow the surface morphology of the CrN coatings uniformly. Furthermore, ALD growth into the pinholes of the CrN coating was verified. In electrochemical measurements the ALD sealing was found to decrease the current density of the CrN coated steel by over 2 orders of magnitude. The neutral salt spray (NSS) durability was also improved: on the best samples the appearance of corrosion spots was delayed from 2 to 168 h. On DLC coatings the adhesion of the ALD sealing layers was weaker, but still clear improvement in NSS durability was achieved indicating sealing of the pinholes.

  16. Thermal stability and separation characteristics of anti-sticking layers of Pt/Cr films for the hot slumping technique

    NASA Astrophysics Data System (ADS)

    Ma, Shuang; Wen, Ming-Wu; Wang, Zhan-Shan

    2016-07-01

    The thermal stability and separation characteristics of anti-sticking layers of Pt/Cr films are studied in this paper. Several types of adhesion layers were investigated: 10.0 nm Pt, 1.5 nm Cr + 50.0 nm Pt, 2.5 nm Cr + 50.0 nm Pt and 3.5 nm Cr + 50.0 nm Pt fabricated using direct current magnetron sputtering. The variation of layer thickness, roughness, crystallization and surface topography of Pt/Cr films were analyzed by grazing incidence X-ray reflectometry, large angle X-ray diffraction and optical profiler before and after heating. 2.5 nm Cr + 50.0 nm Pt film exhibits the best thermal stability and separation characteristics according to the heating and hot slumping experiments. The film was also applied as an anti-sticking layer to optimize the maximum temperature of the hot slumping technique. Supported by CAS XTP project XDA04060605

  17. Enhanced Corrosion Resistance of PVD-CrN Coatings by ALD Sealing Layers.

    PubMed

    Wan; Zhang, Teng Fei; Ding, Ji Cheng; Kim, Chang-Min; Park, So-Won; Yang, Yang; Kim, Kwang-Ho; Kwon, Se-Hun

    2017-12-01

    Multilayered hard coatings with a CrN matrix and an Al2O3, TiO2, or nanolaminate-Al2O3/TiO2 sealing layer were designed by a hybrid deposition process combined with physical vapor deposition (PVD) and atomic layer deposition (ALD). The strategy was to utilize ALD thin films as pinhole-free barriers to seal the intrinsic defects to protect the CrN matrix. The influences of the different sealing layers added in the coatings on the microstructure, surface roughness, and corrosion behaviors were investigated. The results indicated that the sealing layer added by ALD significantly decreased the average grain size and improved the corrosion resistance of the CrN coatings. The insertion of the nanolaminate-Al2O3/TiO2 sealing layers resulted in a further increase in corrosion resistance, which was attributed to the synergistic effect of Al2O3 and TiO2, both acting as excellent passivation barriers to the diffusion of corrosive substances.

  18. Frication Property of Mo-Cr-Infiltrated Steel Layer by Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Xu, Jinyong; Kang, Zhicheng; Liu, Yanping; Wang, Jianzhong; Gao, Yuan; Xu, Zhong

    2006-07-01

    Introduced in this article is the technique to acquire a high performance strengthened layer on carbon steel samples, namely, plasma alloying on the surface of Q235 steel and heat treatment technology. With this technique the alloying elements of Mo, Cr, and C can be obtained on the surface of Q235 steel samples. The content of the constituent elements is approximately up to high speed steels (HSS). The surface property required for the HSS after hardening and low tempering is attained. In the test, the alloying elements Mo and Cr were penetrated into the Q235 steel samples by glow discharge sputtering so that the content of the alloyed layer on the surface of the Q235 steel samples was about 20% Mo and 10% Cr. Two kinds of experiments were conducted. One was to carry out ultra-saturated carburization. The alloyed layer's composition was similar to molybdenum HSS with surface carburizing of more than 2.0%. The carbides of the alloyed layer were compact, uniform and disperse without a coarse eutectic ledeburite structure. The another was ion nitriding after the alloying elements of Mo and Cr were penetrated. The first process included hardening with low tempering and hardening with cryogenic treatment for 2 hr and low tempering. The second one was ion nitriding only. It was found that the surface hardness after cryogenic treatment is up to 1600 HV, much higher than that without cryogenic treatment. The abrasion test results indicate that, without the penetrated alloy elements Mo and Cr and without cryogenic treatment and ion nitriding, the friction coefficient is lower by one order of magnitude. The change in relative resistance is similar to the change in the friction coefficient, but without a proportional relationship.

  19. Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution

    NASA Technical Reports Server (NTRS)

    Boclair, J. W.; Braterman, P. S.; Jiang, J.; Lou, S.; Yarberry, F.

    1999-01-01

    Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

  20. Transparent ferrimagnetic semiconducting CuCr2O4 thin films by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Tripathi, T. S.; Yadav, C. S.; Karppinen, M.

    2016-04-01

    We report the magnetic and optical properties of CuCr2O4 thin films fabricated by atomic layer deposition (ALD) from Cu(thd)2, Cr(acac)3, and ozone; we deposit 200 nm thick films and anneal them at 700 °C in oxygen atmosphere to crystallize the spinel phase. A ferrimagnetic transition at 140 K and a direct bandgap of 1.36 eV are determined for the films from magnetic and UV-vis spectrophotometric measurements. Electrical transport measurements confirm the p-type semiconducting behavior of the films. As the ALD technique allows the deposition of conformal pin-hole-free coatings on complex 3D surfaces, our CuCr2O4 films are interesting material candidates for various frontier applications.

  1. Analysis of the microstructure of Cr-Ni surface layers deposited on Fe{sub 3}Al by TIG

    SciTech Connect

    Ma Haijun . E-mail: hjma123@mail.sdu.edu.cn; Li Yajiang; Wang Juan

    2006-12-15

    A series of Cr-Ni alloys were overlaid on a Fe{sub 3}Al surface by tungsten inert gas arc welding (TIG) technology. The microstructure of the Cr-Ni surface layers were analysed by means of optical metallography, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that when the appropriate TIG parameters were used and Cr25-Ni13 and Cr25-Ni20 alloys were used for the overlaid materials, the Cr-Ni surface layers were crack-free. The matrix of the surface layer was austenite (A), pro-eutectoid ferrite (PF), acicular ferrite (AF), carbide-free bainite (CFB) and lath martensite (LM), distributed on the austenitic grain boundaries as well as inside the grains. The phase constituents of the Cr25-Ni13 surface layer were {gamma}-Fe, Fe{sub 3}Al, FeAl, NiAl, an Fe-C compound and an Fe-C-Cr compound. The microhardness of the fusion zone was lower than that of the Fe{sub 3}Al base metal and Cr25-Ni13 surface layer.

  2. Cr-doped TiSe2 - A layered dichalcogenide spin glass

    SciTech Connect

    Luo, Huixia; Tao, Jing; Krizan, Jason W.; Seibel, Elizabeth M.; Xie, Weiwei; Sahasrabudhe, Girija S.; Bergman, Susanna L.; Phelan, Brendan F.; Wang, Zhen; Zhang, Jiandi; Cava, R. J.

    2015-09-17

    We report the magnetic characterization of the Cr-doped layered dichalcogenide TiSe2. The temperature dependent magnetic susceptibilities are typical of those seen in geometrically frustrated insulating antiferromagnets. The Cr moment is close to the spin-only value, and the Curie–Weiss temperatures (θcw) are between –90 and –230 K. Freezing of the spin system, which is glassy, characterized by peaks in the ac and dc susceptibility and specific heat, does not occur until below T/θcw = 0.05. The CDW transition seen in the resistivity for pure TiSe2 is still present for 3% Cr substitution but is absent by 10% substitution, above which the materials are metallic and p-type. Structural refinements, magnetic characterization, and chemical considerations indicate that the materials are of the type Ti1–xCrxSe2-x/2 for 0 ≤ x ≤ 0.6.

  3. Magnetic states of multilayer Fe /Cr structures with ultrathin iron layers

    NASA Astrophysics Data System (ADS)

    Drovosekov, A. B.; Kreines, N. M.; Kholin, D. I.

    2010-08-01

    The evolution of the magnetic properties of Fe /Cr superlattices is studied as the nominal thickness of the iron layers is reduced to atomic values, when these layers are no longer continuous. The studies were done on multilayer samples with Fe thicknesses of 2-6Å and chromium spacer thicknesses of 10 and 20Å. The samples were prepared by molecular beam epitaxy. The static magnetization and complex magnetic susceptibility were measured and FMR spectra taken. It was found that, depending on the thickness of the Fe layers and temperature, different magnetic phases are realized in the system: supermagnetism, magnetic ordering, and a nonergodic state characterized by a dependence of the magnetization of a sample on its magnetic prehistory. The observed nonergodic phase is found to exhibit spin glass properties. A qualitative phase diagram of the magnetic states of this system is constructed.

  4. Metal oxide semiconductor gas sensors utilizing a Cr-zeolite catalytic layer for improved selectivity

    NASA Astrophysics Data System (ADS)

    Mann, D. P.; Paraskeva, T.; Pratt, K. F. E.; Parkin, I. P.; Williams, D. E.

    2005-05-01

    A novel method of improving the selectivity of metal oxide sensors has been developed. The addition of zeolites, catalytically modified with chromium, results in controlled selectivity to alkanes based on shape and size effects. The cracking patterns of n-alkanes over Cr-zeolite Y and Cr-zeolite β between 200 °C and 400 °C have been ascertained using a novel system involving a heated zeolite bed, thermal desorber and GC/MS. The findings correlate with discrimination shown when the respective zeolites are incorporated as a catalytic layer on chromium titanium oxide (CTO) gas sensors used in a proprietary sensor array system to ascertain their suitability for inclusion into an electronic nose.

  5. Identification of delamination failure of boride layer on common Cr-based steels

    NASA Astrophysics Data System (ADS)

    Taktak, Sukru; Tasgetiren, Suleyman

    2006-10-01

    Adhesion is an important aspect in the reliability of coated components. With low-adhesion of interfaces, different crack paths may develop depending on the local stress field at the interface and the fracture toughness of the coating, substrate, and interface. In the current study, an attempt has been made to identify the delamination failure of coated Cr-based steels by boronizing. For this reason, two commonly used steels (AISI H13, AISI 304) are considered. The steels contain 5.3 and 18.3 wt.% Cr, respectively. Boriding treatment is carried out in a slurry salt bath consisting of borax, boric acid, and ferrosilicon at a temperature range of 800 950 °C for 3, 5, and 7 h. The general properties of the boron coating are obtained by mechanical and metallographic characterization tests. For identification of coating layer failure, some fracture toughness tests and the Daimler-Benz Rockwell-C adhesion test are used.

  6. Zoned Cr, Fe-spinel from the La Perouse layered gabbro, Fairweather Range, Alaska

    USGS Publications Warehouse

    Czamanske, G.K.; Himmelberg, G.R.; Goff, F.E.

    1976-01-01

    Zoned spinel of unusual composition and morphology has been found in massive pyrrhotite-chalcopyrite-pent-landite ore from the La Perouse layered gabbro intrusion in the Fairweather Range, southeastern Alaska. The spinel grains show continuous zoning from cores with up to 53 wt.% Cr2O3 to rims with less than 11 wt.% Cr2O3. Their composition is exceptional because they contain less than 0.32 wt.% MgO and less than 0.10 wt.% Al2O3 and TiO2. Also notable are the concentrations of MnO and V2O3, which reach 4.73 and 4.50 wt.%, respectively, in the cores. The spinel is thought to have crystallized at low oxygen fugacity and at temperatures above 900??C, directly from a sulfide melt that separated by immiscibility from the gabbroic parental magma. ?? 1976.

  7. Non-Gaussian resistance noise in misfit layer compounds: Bi-Se-Cr

    NASA Astrophysics Data System (ADS)

    Peng, Lintao; Freedman, Alex; Clarke, Samantha; Freedman, Danna; Grayson, M.

    Misfit layer ternary compounds Bi-Se-Cr have been synthesized and structurally and magnetically characterized. However, the nature of the magnetic ordering below the transition temperature remains debatable between ferromagnetic and spin-glass. These misfit layer compounds consist of two alternating chalcogenide layers of CrSe2 and BiSe along the c-axis. Whereas the a-axis is lattice matched, the lattice mismatch along the b-axis introduces non-periodic modulation of atomic position leading to quasi-crystalline order along the b-axis alone. We explore unconventional electrical transport properties in the noise spectrum of these compounds. After thinning down the compounds to nanoscale, Van der Pauw devices are fabricated with standard electron beam lithography process. Large resistance noise was observed at temperature below the Cure temperature. The magnitude of resistance noise is much greater than trivial intrinsic noises like thermal Johnson noise and increases as temperature decreases. The probability density function of the relative noise shows 2-4 peaks among different observations which indicate strong non-Gaussian statistic property suggesting glassy behaviors in this material.

  8. Kerr rotation and perpendicular magnetic anisotropy of CoCr films with Al ultrathin interlayers and single-layer CoCr films

    NASA Astrophysics Data System (ADS)

    Hirata, Toyoaki; Takahashi, Takakazu; Hoshi, Youichi; Naoe, Masahiko

    1991-11-01

    The Co81Cr19/Al multilayered films were prepared by using the plasma-free sputtering apparatus. The specimen films with the thicknesses of Co81Cr19 and Al layers lCo-Cr and lAl of 50-170 and 7-14 Å, respectively, were investigated for the Kerr rotation angle θK and the reflectance R of the multilayered films with total thickness of 1500 Å. Films with lCo-Cr and lAl of 138 and 7 Å, respectively, had a θK of 0.21° and R of 0.7 which is larger than Co81Cr19 single-layer films prepared by conventional sputtering where θK and R are 0.036° and 0.4-0.5, respectively. These results indicate that the films were entirely homogeneous, that is, the surface and interior of the films may be almost the same for composition, microstructure and magnetic properties. Consequently, the Co81Cr19 thin films with Al ultrathin interlayers may be useful for microcrystalline magneto-optical media with a high C/N ratio.

  9. Coupling of Crystal Structure and Magnetism in the Layered, Ferromagnetic Insulator CrI 3

    DOE PAGES

    McGuire, Michael A.; Dixit, Hemant; Cooper, Valentino R.; ...

    2014-12-23

    Here, we examine the crystallographic and magnetic properties of single crystals of CrI3, an easily cleavable, layered and insulating ferromagnet with a Curie temperature of 61 K. Our X-ray diffraction studies reveal a first-order crystallographic phase transition occurring near 210–220 K upon warming, with significant thermal hysteresis. The low-temperature structure is rhombohedral (Rmore » $$\\bar{3}$$, BiI3-type) and the high-temperature structure is monoclinic (C2/m, AlCl3-type). Evidence for coupling between the crystallographic and magnetic degrees of freedom in CrI3 was found; we observed an anomaly in the interlayer spacing at the Curie temperature and an anomaly in the magnetic susceptibility at the structural transition. First-principles calculations reveal the importance of proper treatment of the long-ranged interlayer forces, and van der Waals density functional theory does an excellent job of predicting the crystal structures and their relative stability. Our calculations suggest that the ferromagnetic order found in the bulk material may persist into monolayer form, suggesting that CrI3 and other chromium trihalides may be promising materials for spintronic and magnetoelectronic research.« less

  10. Cr-doped TiSe2 - A layered dichalcogenide spin glass

    DOE PAGES

    Luo, Huixia; Tao, Jing; Krizan, Jason W.; ...

    2015-09-17

    We report the magnetic characterization of the Cr-doped layered dichalcogenide TiSe2. The temperature dependent magnetic susceptibilities are typical of those seen in geometrically frustrated insulating antiferromagnets. The Cr moment is close to the spin-only value, and the Curie–Weiss temperatures (θcw) are between –90 and –230 K. Freezing of the spin system, which is glassy, characterized by peaks in the ac and dc susceptibility and specific heat, does not occur until below T/θcw = 0.05. The CDW transition seen in the resistivity for pure TiSe2 is still present for 3% Cr substitution but is absent by 10% substitution, above which themore » materials are metallic and p-type. Structural refinements, magnetic characterization, and chemical considerations indicate that the materials are of the type Ti1–xCrxSe2-x/2 for 0 ≤ x ≤ 0.6.« less

  11. Perpendicular Magnetic Anisotropy in FePt Patterned Media Employing a CrV Seed Layer.

    PubMed

    Kim, Hyunsu; Noh, Jin-Seo; Roh, Jong Wook; Chun, Dong Won; Kim, Sungman; Jung, Sang Hyun; Kang, Ho Kwan; Jeong, Won Yong; Lee, Wooyoung

    2011-12-01

    A thin FePt film was deposited onto a CrV seed layer at 400°C and showed a high coercivity (~3,400 Oe) and high magnetization (900-1,000 emu/cm(3)) characteristic of L 10 phase. However, the magnetic properties of patterned media fabricated from the film stack were degraded due to the Ar-ion bombardment. We employed a deposition-last process, in which FePt film deposited at room temperature underwent lift-off and post-annealing processes, to avoid the exposure of FePt to Ar plasma. A patterned medium with 100-nm nano-columns showed an out-of-plane coercivity fivefold larger than its in-plane counterpart and a remanent magnetization comparable to saturation magnetization in the out-of-plane direction, indicating a high perpendicular anisotropy. These results demonstrate the high perpendicular anisotropy in FePt patterned media using a Cr-based compound seed layer for the first time and suggest that ultra-high-density magnetic recording media can be achieved using this optimized top-down approach.

  12. Surface-charging behavior of Zn-Cr layered double hydroxide.

    PubMed

    Rojas Delgado, R; Arandigoyen Vidaurre, M; De Pauli, C P; Ulibarri, M A; Avena, M J

    2004-12-15

    A Zn-Cr layered double hydroxide (LDH) having the formula Zn(2)Cr(OH)(6)Cl(0.7)(CO(3))(0.15)2.1H(2)O was synthesized and characterized by powder X-ray diffraction, infrared spectroscopy, acid-base potentiometric titration, mass titration, electrophoretic mobility, and modeling of the electrical double layer. Adsorption of alizarin was also performed in order to show some particular features of the HDL. Net hydroxyl adsorption, which increases with increasing pH and decreasing supporting electrolyte concentration, takes place above pH 5. The electrophoretic mobility of the particles was always positive and it decreased when the pH was higher than 9. An isoelectric point of 12 could be estimated by extrapolating the data. The modified MUSIC model was used to estimate deprotonation constants of surface groups and different adsorption models were compared. Good fit of hydroxyl adsorption and electrophoresis could be achieved by considering both OH(-)/Cl(-) exchange at structural sites and proton desorption from surface hydroxyl groups. The modeling, in agreement with alizarin adsorption, indicates that most of the structural positive charge of the LDH is screened at the surface by exchanged anions and negatively charged surface groups. It also suggests that only structural charge sites initially neutralized by chloride ions are active for anion exchange. The remaining sites are blocked by carbonate and do not participate in the exchange.

  13. Effects of varying CoCrV seed layer deposition pressure on Ru crystallinity in perpendicular magnetic recording media

    SciTech Connect

    Joost, W.; Das, A.; Alford, T. L.

    2009-10-01

    The effects of varying deposition parameters of a CoCrV seed layer under Ru on the structural and interfacial properties of both layers were studied. While sputtering power showed little effect on film structure, sputtering pressure during deposition of the seed layer had a significant effect on the structural properties of the seed layer. In particular, the grain morphology and crystallinity of the seed layer varied considerably with deposition pressure. Deposition of Ru using a constant recipe for all samples demonstrated the effect of varying seed layer deposition pressure on the Ru layer. The strain energy of the Ru film, a measurement of contraction due to the registry with the seed layer, was greatest at moderate seed layer sputtering pressures, while the Ru(0002) peak area was greatest at low sputtering pressures. The competing contributions of interfacial energy and strain energy describe this effect, with interfacial energy dominating at low sputtering pressures.

  14. Nanostaircases: An atomic shadowing instability during epitaxial CrN(001) layer growth

    SciTech Connect

    Frederick, J.R.; Gall, D.

    2005-08-01

    Epitaxial CrN(001) layers, 57 and 230 nm thick, were grown on MgO(001) at 700 deg. C by ultrahigh-vacuum magnetron sputter deposition in pure N{sub 2} discharges. An oblique deposition angle {alpha}=80 deg. was utilized to purposely increase the effect of atomic shadowing on surface morphological and microstructural evolution. The layers are single crystals with a surface morphology that is characterized by dendritic ridge patterns extending along orthogonal <110> directions superposed by square-shaped supermounds with <100> edges. The ridge patterns are due to a two-dimensional growth instability related to a gradient in the adatom density while the supermounds form due to atomic shadowing. The supermounds protrude out of the surface and capture a larger deposition flux than the surrounding layer. This leads to both vertical and lateral growth and the formation of inverted pyramids that are epitaxially embedded in a single crystalline matrix. The inverted pyramids are terminated by 1-3-nm-wide tilted voids that form nanostaircases due to kinetic faceting along orthogonal {l_brace}100{r_brace} planes.

  15. Effect of Alloy 625 Buffer Layer on Hardfacing of Modified 9Cr-1Mo Steel Using Nickel Base Hardfacing Alloy

    NASA Astrophysics Data System (ADS)

    Chakraborty, Gopa; Das, C. R.; Albert, S. K.; Bhaduri, A. K.; Murugesan, S.; Dasgupta, Arup

    2016-04-01

    Dashpot piston, made up of modified 9Cr-1Mo steel, is a part of diverse safety rod used for safe shutdown of a nuclear reactor. This component was hardfaced using nickel base AWS ER NiCr-B alloy and extensive cracking was experienced during direct deposition of this alloy on dashpot piston. Cracking reduced considerably and the component was successfully hardfaced by application of Inconel 625 as buffer layer prior to hardface deposition. Hence, a separate study was undertaken to investigate the role of buffer layer in reducing the cracking and on the microstructure of the hardfaced deposit. Results indicate that in the direct deposition of hardfacing alloy on modified 9Cr-1Mo steel, both heat-affected zone (HAZ) formed and the deposit layer are hard making the thickness of the hard layer formed equal to combined thickness of both HAZ and deposit. This hard layer is unable to absorb thermal stresses resulting in the cracking of the deposit. By providing a buffer layer of Alloy 625 followed by a post-weld heat treatment, HAZ formed in the modified 9Cr-1Mo steel is effectively tempered, and HAZ formed during the subsequent deposition of the hardfacing alloy over the Alloy 625 buffer layer is almost completely confined to Alloy 625, which does not harden. This reduces the cracking susceptibility of the deposit. Further, unlike in the case of direct deposition on modified 9Cr-1Mo steel, dilution of the deposit by Ni-base buffer layer does not alter the hardness of the deposit and desired hardness on the deposit surface could be achieved even with lower thickness of the deposit. This gives an option for reducing the recommended thickness of the deposit, which can also reduce the risk of cracking.

  16. Localised Ag(+) vibrations at the origin of ultralow thermal conductivity in layered thermoelectric AgCrSe2.

    PubMed

    Damay, F; Petit, S; Rols, S; Braendlein, M; Daou, R; Elkaïm, E; Fauth, F; Gascoin, F; Martin, C; Maignan, A

    2016-03-22

    In materials science, the substructure approach consists in imagining complex materials in which a particular property is associated with a distinct structural feature, so as to combine different chosen physical characteristics, which otherwise have little chance to coexist. Applied to thermoelectric materials, it has been used to achieve simultaneously phonon-glass and electron-crystal properties. Mostly studied for its superionic conductivity, AgCrSe2 is a naturally layered compound, which achieves very low thermal conductivity, ~0.4 W.K(-1).m(-1) at RT (room temperature), and is considered a promising thermoelectric. The Cr atoms of the [CrSe2]∞ layer bear a spin S = 3/2, which orders below TN = 55 K. Here we report low temperature inelastic neutron scattering experiments on AgCrSe2, alongside the magnetic field evolution of its thermal and electrical transport. We observe a very low frequency mode at 3 meV, ascribed to large anharmonic displacements of the Ag(+) ions in the [Ag]∞ layer, and 2D magnetic fluctuations up to 3 TN in the chromium layer. The low thermal conductivity of AgCrSe2 is attributed to acoustic phonon scattering by a regular lattice of Ag(+) oscillating in quasi-2D potential wells. These findings highlight a new way to achieve localised phonon modes in a perfectly crystalline solid.

  17. Localised Ag+ vibrations at the origin of ultralow thermal conductivity in layered thermoelectric AgCrSe2

    PubMed Central

    Damay, F.; Petit, S.; Rols, S.; Braendlein, M.; Daou, R.; Elkaïm, E.; Fauth, F.; Gascoin, F.; Martin, C.; Maignan, A.

    2016-01-01

    In materials science, the substructure approach consists in imagining complex materials in which a particular property is associated with a distinct structural feature, so as to combine different chosen physical characteristics, which otherwise have little chance to coexist. Applied to thermoelectric materials, it has been used to achieve simultaneously phonon-glass and electron-crystal properties. Mostly studied for its superionic conductivity, AgCrSe2 is a naturally layered compound, which achieves very low thermal conductivity, ~0.4 W.K−1.m−1 at RT (room temperature), and is considered a promising thermoelectric. The Cr atoms of the [CrSe2]∞ layer bear a spin S = 3/2, which orders below TN = 55 K. Here we report low temperature inelastic neutron scattering experiments on AgCrSe2, alongside the magnetic field evolution of its thermal and electrical transport. We observe a very low frequency mode at 3 meV, ascribed to large anharmonic displacements of the Ag+ ions in the [Ag]∞ layer, and 2D magnetic fluctuations up to 3 TN in the chromium layer. The low thermal conductivity of AgCrSe2 is attributed to acoustic phonon scattering by a regular lattice of Ag+ oscillating in quasi-2D potential wells. These findings highlight a new way to achieve localised phonon modes in a perfectly crystalline solid. PMID:27000414

  18. Heat treatment of nitrided layer formed on X37CrMoV5-1 hot working tool steel

    NASA Astrophysics Data System (ADS)

    Ciski, A.; Wach, P.; Tacikowski, J.; Babul, T.; Šuchmann, P.

    2017-02-01

    The paper presents the technology consisting of combination of the nitriding process with subsequent austenitizing at temperature above eutectoid temperature of the Fe-C system and further rapid cooling. Such treatment will cause formation of the martensite in the area of the primarily nitrided layer and the additional precipitation hardening by tempering of heat treated steel. The article shows that the heat treatment process of nitrided layer formed on X37CrMoV5-1 steel leads to strengthening of surface layer, the substrate and the core of nitrided part. Heat treatment of nitrided steel with the tempering in inert (nitrogen) or active (ammonia) atmosphere can increase the thickness of the layer formed by short-term nitriding process. After the nitriding process of X37CrMoV5-1 steel the nitrided layer had a thickness of about 160 μm, while a subsurface layer of iron nitrides had a thickness of 7 μm. After subsequent quenching and tempering processes, the nitrided layer undergoes additional diffusion and its thickness is increased to about 220 μm (inert atmosphere) or 280 μm (active atmosphere). If the tempering process is carried out in an inert atmosphere, the primarily formed layer of iron nitrides disappears. Tempering in an active atmosphere leads to forming of white layer with a thickness of 7 μm. Basic properties of nitrided layers formed in such way, like the hardness and the wear resistance, are presented.

  19. Enhancing the blocking temperature of perpendicular-exchange biased Cr2O3 thin films using buffer layers

    NASA Astrophysics Data System (ADS)

    Shimomura, Naoki; Pati, Satya Prakash; Nozaki, Tomohiro; Shibata, Tatsuo; Sahashi, Masashi

    2017-02-01

    In this study, we investigated the effect of buffer layers on the blocking temperature (TB) of perpendicular exchange bias of thin Cr2O3/Co exchange coupled films with a Ru spacer and revealed a high TB of 260 K for 20-nm-thick Cr2O3 thin films. By comparing the TB values of the 20-nm-thick Cr2O3 films on Pt and α-Fe2O3 buffers, we investigated the lattice strain effect on the TB. We show that higher TB values can be obtained using an α-Fe2O3 buffer, which is likely because of the lattice strain-induced increase in Cr2O3 magnetocrystalline anisotropy.

  20. Calculations of the electronic levels, spin-Hamiltonian parameters and vibrational spectra for the CrCl3 layered crystals

    NASA Astrophysics Data System (ADS)

    Avram, C. N.; Gruia, A. S.; Brik, M. G.; Barb, A. M.

    2015-12-01

    Calculations of the Cr3+ energy levels, spin-Hamiltonian parameters and vibrational spectra for the layered CrCl3 crystals are reported for the first time. The crystal field parameters and the energy level scheme were calculated in the framework of the Exchange Charge Model of crystal field. The spin-Hamiltonian parameters (zero-field splitting parameter D and g-factors) for Cr3+ ion in CrCl3 crystals were obtained using two independent techniques: i) semi-empirical crystal field theory and ii) density functional theory (DFT)-based model. In the first approach, the spin-Hamiltonian parameters were calculated from the perturbation theory method and the complete diagonalization (of energy matrix) method. The infrared (IR) and Raman frequencies were calculated for both experimental and fully optimized geometry of the crystal structure, using CRYSTAL09 software. The obtained results are discussed and compared with the experimental available data.

  1. Impact toughness of a gradient hardened layer of Cr5Mo1V steel treated by laser shock peening

    NASA Astrophysics Data System (ADS)

    Xia, Weiguang; Li, Lei; Wei, Yanpeng; Zhao, Aimin; Guo, Yacong; Huang, Chenguang; Yin, Hongxiang; Zhang, Lingchen

    2016-04-01

    Laser shock peening (LSP) is a widely used surface treatment technique that can effectively improve the fatigue life and impact toughness of metal parts. Cr5Mo1V steel exhibits a gradient hardened layer after a LSP process. A new method is proposed to estimate the impact toughness that considers the changing mechanical properties in the gradient hardened layer. Assuming a linearly gradient distribution of impact toughness, the parameters controlling the impact toughness of the gradient hardened layer were given. The influences of laser power densities and the number of laser shots on the impact toughness were investigated. The impact toughness of the laser peened layer improves compared with an untreated specimen, and the impact toughness increases with the laser power densities and decreases with the number of laser shots. Through the fracture morphology analysis by a scanning electron microscope, we established that the Cr5Mo1V steel was fractured by the cleavage fracture mechanism combined with a few dimples. The increase in the impact toughness of the material after LSP is observed because of the decreased dimension and increased fraction of the cleavage fracture in the gradient hardened layer.

  2. Effect of oxide layer modification of CoCr stent alloys on blood activation and endothelial behavior.

    PubMed

    Milleret, Vincent; Ziogas, Algirdas; Buzzi, Stefano; Heuberger, Roman; Zucker, Arik; Ehrbar, Martin

    2015-04-01

    CoCr alloys, in particular MP35N and L605, are extensively used in biomedical implants, for example for coronary stents. In practice, these alloys present a moderately hydrophobic surface which leads to significant platelet adhesion and consequently to risk of early thrombosis or in-stent restenosis. Surface modification of biomedical implants is known to alter their biological performances. In this study we focused on the alteration of in vitro biological responses of human cells contacting CoCr surfaces with engineered oxide layers. XPS analysis was performed to determine the composition of the oxide layer of differently treated CoCr while the bulk properties were not modified. An extensive characterization of the surfaces was performed looking at surface roughness, wettability and charge. After static exposure to blood, strongly reduced platelet and increased polymorphonuclear neutrophil adhesion were observed on treated versus untreated surfaces. Comparisons of treated and untreated samples provide evidence for wettability being an important player for platelet adhesion, although multiple factors including surface oxide chemistry and charge might control polymorphonuclear neutrophil adhesion. The differently treated surfaces were shown to be equally suitable for endothelial cell proliferation. We herein present a novel approach to steer biological properties of CoCr alloys. By adjusting their oxide layer composition, substrates were generated which are suitable for endothelial cell growth and at the same time show an altered (reduced) blood contact activation. Such treatments are expected to lead to stents of highly reproducible quality with minimal thrombogenicity and in-stent restenosis, while maintaining rapid re-endothelialization after coronary angioplasty.

  3. Enhanced sequestration of Cr(VI) by nanoscale zero-valent iron supported on layered double hydroxide by batch and XAFS study.

    PubMed

    Sheng, Guodong; Hu, Jun; Li, Hui; Li, Jiaxing; Huang, Yuying

    2016-04-01

    Herein, the reduction of nanoscale zero-valent iron (NZVI) and adsorption of layered double hydroxides (LDH) to sequester Cr(VI) were well combined by the immobilization of NZVI onto LDH surface (NZVI/LDH). The characterization results revealed that LDH decreased NZVI aggregation and thus increased Cr(VI) sequestration. The batch results indicated that Cr(VI) sequestration by NZVI/LDH was higher than that of NZVI, and superior to the sum of reduction and adsorption. The LDH with good anion exchange property allowed the adsorption of Cr(VI), facilitating interfacial reaction by increasing the local concentration of Cr(VI) in the NZVI vicinity. X-ray absorption near edge structure (XANES) results indicated that Cr(VI) was almost completely reduced to Cr(III) by NZVI/LDH, but Cr(VI) was partly reduced to Cr(III) by NZVI with a trace of Cr(VI) adsorbed on corrosion products. The coordination environment of Cr from extended X-ray absorption fine structure (EXAFS) analysis revealed that LDH could be a good scavenger for the insoluble products produced during reaction. So, the insoluble products on NZVI could be reduced, and its reactivity could be maintained. These results demonstrated that NZVI/LDH exhibits multiple functionalities relevant to the remediation of Cr(VI)-contaminated sites.

  4. Photocatalytic O{sub 2} evolution from water over Zn–Cr layered double hydroxides intercalated with inorganic anions

    SciTech Connect

    Hirata, Naoya; Tadanaga, Kiyoharu; Tatsumisago, Masahiro

    2015-02-15

    Graphical abstract: The photocatalytic activity of Zn–Cr LDHs intercalated with various inorganic anions was studied by O{sub 2} evolution from aqueous solution of AgNO{sub 3} as a sacrificial agent. All the prepared LDHs showed photocatalytic activity under either UV and/or visible light irradiation. The interlayer anions affected the photocatalytic activity of the LDHs. - Highlights: • Zn–Cr layered double hydroxides intercalated with inorganic anions were synthesized. • Photocatalytic activity of the LDHs was studied by O{sub 2} evolution. • All the prepared LDHs showed photocatalytic activity under either UV and/or visible light irradiation. • The interlayer anions affected the photocatalytic activity of the LDHs. - Abstract: Zn–Cr layered double hydroxides (LDHs) intercalated with inorganic anions (CO{sub 3}{sup 2−}, Cl{sup −}, SO{sub 4}{sup 2−} and NO{sub 3}{sup −}) were synthesized by the co-precipitation method and the anion exchange process. The photocatalytic activity of the LDHs was studied by O{sub 2} evolution from aqueous solution of AgNO{sub 3} as a sacrificial agent. All the prepared LDHs showed photocatalytic activity under either UV and/or visible light irradiation. Besides, the interlayer anions affected the photocatalytic activity of the LDHs. After irradiation, Ag particles were formed on the LDHs by accepting the electrons generated during the photocatalytic reaction.

  5. AC Electrical Conduction of Cr-Doped SrTiO3 Thin Films with an Oxygen-Deficient Interface Layer

    NASA Astrophysics Data System (ADS)

    Phan, Bach Thang; Eom, Ki Tae; Lee, Jaichan

    2017-01-01

    The ac electrical conduction of Cr-doped SrTiO3 thin films with an oxygen-deficient interface layer was investigated as a function of temperature and frequency. The Cr-doped SrTiO3 (Cr-STO) thin films with an ultra-thin (˜2 nm) oxygen-deficient layer inserted between the top electrode and the Cr-STO layer exhibited two ac conduction mechanisms, i.e., variable-range hopping and small-polaron hopping conduction, accompanied by a relaxation process. Since high oxygen deficiency induces large lattice distortion in the depletion layer, the first relaxation process occurs at low frequencies in the thin oxygen depletion layer Cr-SrTiO3-δ , and the corresponding conduction behavior follows the small-polaron tunneling model. In the high frequency range, an additional relaxation process is involved and is associated with the variable-range hopping between the localized states in the band gap of the thick Cr-SrTiO3 layer.

  6. The study of the chemical and phase composition of the diffusion interaction zone in layered composite Cr20Ni80-AD1

    NASA Astrophysics Data System (ADS)

    Shmorgun, V. G.; Iskhakova, L. D.; Bogdanov, A. I.; Taube, A. O.; Ermakov, R. P.

    2017-02-01

    The paper presents the research of chemical and phase composition of the zone of diffusion interaction in the layered composite Cr20Ni80-AD1. It is shown that interlayer border of bimetal Cr20Ni80-AD1 is a complex mixture of phases with the main phases in its composition in solid-phase interaction: Al3Ni2 and Al14.687Cr3.443Ni0.87, and in the liquid phase - Al3Ni2, Al0.987Cr0.017, Al14.687Cr3.44Ni0.87 and Al45Cr7. It is shown, that conditions of holding time of the heat treatment do not affect the phase and chemical composition of the diffusion zone.

  7. Coupling of Crystal Structure and Magnetism in the Layered, Ferromagnetic Insulator CrI 3

    SciTech Connect

    McGuire, Michael A.; Dixit, Hemant; Cooper, Valentino R.; Sales, Brian C.

    2014-12-23

    Here, we examine the crystallographic and magnetic properties of single crystals of CrI3, an easily cleavable, layered and insulating ferromagnet with a Curie temperature of 61 K. Our X-ray diffraction studies reveal a first-order crystallographic phase transition occurring near 210–220 K upon warming, with significant thermal hysteresis. The low-temperature structure is rhombohedral (R$\\bar{3}$, BiI3-type) and the high-temperature structure is monoclinic (C2/m, AlCl3-type). Evidence for coupling between the crystallographic and magnetic degrees of freedom in CrI3 was found; we observed an anomaly in the interlayer spacing at the Curie temperature and an anomaly in the magnetic susceptibility at the structural transition. First-principles calculations reveal the importance of proper treatment of the long-ranged interlayer forces, and van der Waals density functional theory does an excellent job of predicting the crystal structures and their relative stability. Our calculations suggest that the ferromagnetic order found in the bulk material may persist into monolayer form, suggesting that CrI3 and other chromium trihalides may be promising materials for spintronic and magnetoelectronic research.

  8. Influence of nature of precursors on the formation and structure of Cu Ni Cr mixed oxides from layered double hydroxides

    NASA Astrophysics Data System (ADS)

    Zhang, Lihong; Zhu, Jia; Jiang, Xiaorui; Evans, David G.; Li, Feng

    2006-08-01

    Analogous layered double hydroxides (LDHs) with the Cu2+/Ni2+/Cr3+ molar ratio of 1/2/1 on the brucite-like layers and interlayer anions (viz sulfate, nitrate and carbonate, respectively) were synthesized by a coprecipitation method. For the first time, the effects of interlayer anions on the structural properties of as-synthesized LDHs and resulting calcined products at 773 K were investigated by means of powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), simultaneous thermogravimetric and differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction (TPR). The results indicate that the nature of interlayer anions involved within the hydrotalcite (HT)-like structure has a larger influence on the thermal stability of LDHs precursors. Calcination of well-crystallized LDHs leads to the formation of mixed metal oxides including CuO, NiO and Cu2+-, Ni2+- and Cr3+-containing spinel phases, the composition distributions of which obtained from LDHs precursors depend on the nature of interlayer anions, thus resulting in the difference of the reducibility of reducible metal species in the calcined LDHs. Moreover, the surface basicity of the calcined material, which is related to the different behaviour of LDHs precursors during the thermal decomposition depending on the interlayer anions, increases progressively following the order of calcined LDHs from sulfate to nitrate and carbonate.

  9. Alloying the X40CrMoV5-1 steel surface layer with tungsten carbide by the use of a high power diode laser

    NASA Astrophysics Data System (ADS)

    Dobrzański, L. A.; Bonek, M.; Hajduczek, E.; Klimpel, A.

    2005-07-01

    The paper presents the effect of alloying with tungsten carbide on properties of the X40CrMoV5-1 steel surface layer, using the high power diode laser (HPDL). Selection of laser operating conditions is discussed, as well as thickness of the alloying layer, and their influence on structure and chemical composition of the steel. Analysis of the influence of the process conditions on the thicknesses of the alloyed layer and heat-affected zone is presented.

  10. Néel temperature of Cr{sub 2}O{sub 3} in Cr{sub 2}O{sub 3}/Co exchange-coupled system: Effect of buffer layer

    SciTech Connect

    Pati, Satya Prakash E-mail: phy-satya@yahoo.co.in; Shimomura, Naoki; Nozaki, Tomohiro; Sahashi, Masashi; Shibata, Tatsuo

    2015-05-07

    The lattice parameter dependence of the Néel temperature T{sub N} of thin Cr{sub 2}O{sub 3} in a Cr{sub 2}O{sub 3}/Co exchange-coupled system is investigated. Lattice-mismatch-induced strain is generated in Cr{sub 2}O{sub 3} by using different buffer layers. The lattice parameters are determined from out-of-plane and in-plane X-ray diffraction measurements. The Néel temperature is detected by direct temperature-dependent magnetization measurement as well as the temperature-dependent interface exchange coupling energy. It is observed that in-plane lattice contraction can enhance T{sub N} in Cr{sub 2}O{sub 3}, which is consistent with theoretical calculations.

  11. Combining CrIS double CO2 bands for detecting clouds located in different layers of the atmosphere

    NASA Astrophysics Data System (ADS)

    Lin, Lin; Zou, Xiaolei; Weng, Fuzhong

    2017-02-01

    Detection of clouds within certain vertical layers of the atmosphere from satellite infrared instruments is challenging, especially of those optically thin clouds due to their small thermal contrasts to the background. This study develops a new method for cloud detection by using the Cross-track Infrared Sounder (CrIS) hyperspectral radiances at shortwave ( 4.3 µm) and longwave ( 15 µm) CO2 bands. Specifically, CrIS longwave channels are first paired with shortwave channels based on weighting function altitudes and sensitivity to clouds. A linear relationship of brightness temperatures between each paired channel is then derived for predicting the shortwave channel from the longwave channel in clear-sky conditions. A cloud emission and scattering index (CESI) can finally be defined as the difference of the paired shortwave channel between the clear-sky, regression model predicted and the observed brightness temperatures. Spatial distributions of such derived CESI for several paired channels in the troposphere are examined for a winter storm that occurred in the eastern part of the United States during 22-24 January 2016. It is shown that the CESI values over the storm regions with optically thin cirrus, fog, and supercooled water clouds are positively larger than those over optically thick opaque ice and overshooting clouds or in clear-sky conditions. Of particular interest is that an area of fog and water clouds over Gulf of Mexico, which are indicated by the Visible Infrared Imaging Radiometer Suite day and night band observations, is identified by the CESI. The global distribution of CESIs derived from CrIS double CO2 bands with weighting functions peak around 321 hPa agrees well with the distribution of ice cloud optical thickness from the Atmospheric Infrared Sounder version 6 cloud product data set in both daytime and nighttime.

  12. The effect of chloride ions on the corroded surface layer of 00Cr22Ni5Mo3N duplex stainless steel under cavitation.

    PubMed

    Wan, Tong; Xiao, Ning; Shen, Hanjie; Yong, Xingyue

    2016-11-01

    The effects of Cl(-) on the corroded surface layer of 00Cr22Ni5Mo3N duplex stainless steel under cavitation in chloride solutions were investigated using nanoindentation in conjunction with XRD and XPS. The results demonstrate that Cl(-) had a strong effect on the nano-mechanical properties of the corroded surface layer under cavitation, and there was a threshold Cl(-) concentration. Furthermore, a close relationship between the nano-mechanical properties and the cavitation corrosion resistance of 00Cr22Ni5Mo3N duplex stainless steel was observed. The degradation of the nano-mechanical properties of the corroded surface layer was accelerated by the synergistic effect between cavitation erosion and corrosion. A key factor was the adsorption of Cl(-), which caused a preferential dissolution of the ferrous oxides in the passive film layer on the corroded surface layer. Cavitation further promoted the preferential dissolution of the ferrous oxides in the passive film layer. Simultaneously, cavitation accelerated the erosion of the ferrite in the corroded surface layer, resulting in the degradation of the nano-mechanical properties of the corroded surface layer on 00Cr22Ni5Mo3N duplex stainless steel under cavitation.

  13. Development of CVD-W coatings on CuCrZr and graphite substrates with a PVD intermediate layer

    NASA Astrophysics Data System (ADS)

    Song, Jiupeng; Lian, Youyun; Lv, Yanwei; Liu, Junyong; Yu, Yang; Liu, Xiang; Yan, Binyou; Chen, Zhigang; Zhuang, Zhigang; Zhao, Ximeng; Qi, Yang

    2014-12-01

    In order to apply tungsten (W) coatings by chemical vapor deposition (CVD) for repairing or updating the plasma facing components (PFCs) of the first wall and divertor in existing or future tokomaks, where CuCrZr or graphite is the substrate material, an intermediate layer by physical vapor deposition (PVD) has been used to accommodate the interface stress due to the mismatch of thermal expansion or act as a diffusion barrier between the CVD-W coating and the substrate. The prepared CuCrZr/PVD-Cu/CVD-W sample with active cooling has passed thermal fatigue tests by electron beam with an absorbed power of 2.2 MW/m2, 50 s on/50 s off, for 100 cycles. Another graphite/PVD-Si/CVD-W sample without active cooling underwent thermal fatigue testing with an absorbed power density of 4.62 MW/m2, 5 s on/25 s off, for 200 cycles, and no catastrophic failure was found.

  14. Antisite Defects in Layered Multiferroic CuCr0.9In0.1P2S6

    DOE PAGES

    He, Qian; Belianinov, Alex; Dziaugys, Andrius; ...

    2015-10-06

    The CuCr1-xInxP2S6 system represents a large family of metal chalcogenophosphates that are unique and promising candidates for 2D materials with functionalities such as ferroelectricity. We carried out detailed microstructural and chemical characterization of these compounds using aberration-corrected STEM, in order to understand the origin of these different ordering phenomena. Quantitative STEM-HAADF imaging and analysis identified the stacking order of an 8-layer thin flake, which leads to the identification of anti-site In3+(Cu+) doping. We believe that these findings will pave the way towards understanding the ferroic coupling phenomena in van der Waals lamellar compounds, as well as the potential applications inmore » 2-D electronics.« less

  15. Computational discovery of ferromagnetic semiconducting single-layer CrSnTe3

    SciTech Connect

    Zhuang, Houlong L.; Xie, Yu; Kent, P. R. C.; Ganesh, P.

    2015-07-06

    Despite many single-layer materials being reported in the past decade, few of them exhibit magnetism. Here we perform first-principles calculations using accurate hybrid density functional methods (HSE06) to predict that single-layer CrSnTe3 (CST) is a ferromagnetic semiconductor, with band gaps of 0.9 and 1.2 eV for the majority and minority spin channels, respectively. We determine the Curie temperature as 170 K, significantly higher than that of single-layer CrSiTe3 (90K) and CrGeTe3 (130 K). This is due to the enhanced ionicity of the Sn-Te bond, which in turn increases the superexchange coupling between the magnetic Cr atoms. We further explore the mechanical and dynamical stability and strain response of this single-layer material for possible epitaxial growth. Lastly, our study provides an intuitive approach to understand and design novel single-layer magnetic semiconductors for a wide range of spintronics and energy applications.

  16. Interactions of Cu with CoSi2, CrSi2 and TiSi2 with and without TiNx barrier layers

    NASA Astrophysics Data System (ADS)

    Olowolafe, J. O.; Li, Jian; Mayer, J. W.

    1990-12-01

    Interactions of Cu with CoSi2, CrSi2, and TiSi2 with and without interposed TiNx layers have been studied using Rutherford backscattering spectrometry, Auger electron spectrometry, x-ray diffraction, and in situ sheet resistivity measurements. Cu diffuses through a preformed CoSi2 layer to form the structure CoSi2/Cu3Si/Si(100). No dissociation of CoSi2 has been observed. For the Cu/CrSi2/Si system, the outdiffusion of Si leads to the formation of Cu3Si/CrSi2/Si at temperatures above 300 °C. At about the same temperature, Cu diffuses into a TiSi2 layer and to the TiSi2/Si interface to react with both Ti and Si forming Cu3Ti, Cu3Si, and Cu4Si phases. A 50-nm TiNx layer prepared by reactive sputtering was observed to be an effective diffusion barrier between Cu and CoSi2 or CrSi2. A 30-nm layer of TiNx simultaneously grown with TiSi2 by rapid thermal annealing proved effective between Cu and TiSi2 up to 500 °C.

  17. The Role of Carbides in Formation of Surface Layer on Steel X153CrMoV12 Due to Low-Pressure Nitriding (Vacuum Nitriding)

    NASA Astrophysics Data System (ADS)

    Januszewicz, B.; Wołowiec, E.; Kula, P.

    2015-05-01

    The mechanism of formation of surface layer on steel X153CrMoV12 in the process of vacuum nitriding (low-pressure nitriding) in a universal vacuum furnace in an atmosphere of dissociated ammonia at a pressure of 30 × 102 Pa (30 mbar) is studied by the methods of light microscopy and measurement of microhardness. The chemical composition of the nitrided layers is determined.

  18. Residual stress and crack initiation in laser clad composite layer with Co-based alloy and WC + NiCr

    NASA Astrophysics Data System (ADS)

    Lee, Changmin; Park, Hyungkwon; Yoo, Jaehong; Lee, Changhee; Woo, WanChuck; Park, Sunhong

    2015-08-01

    Although laser cladding process has been widely used to improve the wear and corrosion resistance, there are unwanted cracking issues during and/or after laser cladding. This study investigates the tendency of Co-based WC + NiCr composite layers to cracking during the laser cladding process. Residual stress distributions of the specimen are measured using neutron diffraction and elucidate the correlation between the residual stress and the cracking in three types of cylindrical specimens; (i) no cladding substrate only, (ii) cladding with 100% stellite#6, and (iii) cladding with 55% stellite#6 and 45% technolase40s. The microstructure of the clad layer was composed of Co-based dendrite and brittle eutectic phases at the dendritic boundaries. And WC particles were distributed on the matrix forming intermediate composition region by partial melting of the surface of particles. The overlaid specimen exhibited tensile residual stress, which was accumulated through the beads due to contraction of the coating layer generated by rapid solidification, while the non-clad specimen showed compressive. Also, the specimen overlaid with 55 wt% stellite#6 and 45 wt% technolase40s showed a tensile stress higher than the specimen overlaid with 100% stellite#6 possibly, due to the difference between thermal expansion coefficients of the matrix and WC particles. Such tensile stresses can be potential driving force to provide an easy crack path ways for large brittle fractures combined with the crack initiation sites such as the fractured WC particles, pores and solidification cracks. WC particles directly caused clad cracks by particle fracture under the tensile stress. The pores and solidification cracks also affected as initiation sites and provided an easy crack path ways for large brittle fractures.

  19. Experimental petrology constraints on the recycling of mafic cumulate: a focus on Cr-spinel from the Rum Eastern Layered Intrusion, Scotland

    NASA Astrophysics Data System (ADS)

    Leuthold, Julien; Blundy, Jonathan D.; Brooker, Richard A.

    2015-08-01

    Reactive liquid flow is a common process in layered intrusions and more generally in episodically refilled magma chambers. Interaction between newly injected melt and cumulates, or crystal mushes, perturbs the liquid line of descent of the melt and modifies mineral chemistry and texture. We present insights into the effects of assimilation of mafic cumulate rocks (gabbro, troctolite) by cogenetic Mg-rich basalt liquid using one-atmosphere, controlled fO2 phase equilibrium experiments on picritic parental liquid to the Rum layered intrusion, Scotland. For picrite-only experiments at fO2 = QFM, Cr-spinel (Cr# = Cr/[Cr + Al + Fe3+] = 0.43; Fe# = Fe2+/[Mg + Fe2+] = 0.32) saturates at 1320 °C, olivine (Fo88) at ~1290 °C, plagioclase (An77) at 1200 °C, and clinopyroxene (Mg#: 0.81) at 1180 °C. In melting experiments on picrite + gabbro mixtures, plagioclase (1230 °C, An80) and clinopyroxene (1200 °C, Mg#: 0.85) saturation temperature and mode are increased significantly. Cr-spinel in these experiments has a distinctive, low Fe#. In melting experiments on picrite + troctolite mixtures, plagioclase (An86) saturates at 1240 °C and clinopyroxene (Mg#: 0.81) at 1170 °C. Al-rich spinel crystallizes at high temperature (>1220 °C) and becomes more Cr-rich upon cooling, reaching the highest Cr# = 0.47 at 1180 °C (0.54 at QFM-1.2). The experimental results confirm that plagioclase and clinopyroxene stability plays a major role in determining the composition of coexisting spinel. Comparing our experimental results to the Rum Eastern Layered Intrusion, we propose a model for the precipitation of spinel from picrite-troctolite hybrid melt that is compatible with the observed olivine, plagioclase, and clinopyroxene chemistry.

  20. Superb adsorption capacity of hierarchical calcined Ni/Mg/Al layered double hydroxides for Congo red and Cr(VI) ions.

    PubMed

    Lei, Chunsheng; Zhu, Xiaofeng; Zhu, Bicheng; Jiang, Chuanjia; Le, Yao; Yu, Jiaguo

    2017-01-05

    The preparation of hierarchical porous materials as catalysts and sorbents has attracted much attention in the field of environmental pollution control. Herein, Ni/Mg/Al layered double hydroxides (NMA-LDHs) hierarchical flower-like hollow microspheres were synthesized by a hydrothermal method. After the NMA-LDHs was calcined at 600°C, NMA-LDHs transformed into Ni/Mg/Al layered double oxides (NMA-LDOs), which maintained the hierarchical flower-like hollow structure. The crystal phase, morphology, and microstructure of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy elemental mapping, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption methods. Both the calcined and non-calcined NMA-LDHs were examined for their performance to remove Congo red (CR) and hexavalent chromium (Cr(VI)) ions in aqueous solution. The maximum monolayer adsorption capacities of CR and Cr(VI) ions over the NMA-LDOs sample were 1250 and 103.4mg/g at 30°C, respectively. Thermodynamic studies indicated that the adsorption process was endothermic in nature. In addition, the addition of coexisting anions negatively influenced the adsorption capacity of Cr(VI) ions, in the following order: CO3(2-)>SO4(2-)>H2PO4(-)>Cl(-). This work will provide new insight into the design and fabrication of advanced adsorption materials for water pollutant removal.

  1. Effect of aqueous solution and load on the formation of DLC transfer layer against Co-Cr-Mo for joint prosthesis.

    PubMed

    Guo, Feifei; Zhou, Zhifeng; Hua, Meng; Dong, Guangneng

    2015-09-01

    Diamond-like carbon (DLC) coating exhibits excellent mechanical properties such as high hardness, low friction and wear, which offer a promising solution for the metal-on-metal hip joint implants. In the study, the hydrogen-free DLC coating with the element Cr as the interlay addition was deposited on the surface of the Co-Cr-Mo alloy by a unbalanced magnetron sputtering method. The coating thickness was controlled as 2 µm. Nano-indentation test indicated the hardness was about 13 GPa. DLC coated Co-Cr-Mo alloy disc against un-coated Co-Cr-Mo alloy pin (spherical end SR9.5) comprised the friction pairs in the pin-on-disc tribotest under bovine serum albumin solution (BSA) and physiological saline(PS).The tribological behavior under different BSA concetrations(2-20 mg/ml), and applied load (2-15N) was investigated.DLC transfer layer did not form under BSA solution, even though different BSA concetration and applied load changed. The coefficient of friction(COF) under 6 mg/ml BSA at 10 N was the lowest as 0.10. A higher COF of 0.13 was obtained under 20 mg/ml BSA. The boundary absorption layer of protein is the main factor for the counterparts. However, the continous DLC transfer layer was observed under PS solution, which make a lower COF of 0.08.

  2. Spin dependent transport properties of Mn-Ga/MgO/Mn-Ga magnetic tunnel junctions with metal(Mg, Co, Cr) insertion layer

    SciTech Connect

    Liang, S. H.; Tao, L. L.; Liu, D. P. Han, X. F.; Lu, Y.

    2014-04-07

    We report a first principles theoretical investigation of spin polarized quantum transport in Mn{sub 2}Ga/MgO/Mn{sub 2}Ga and Mn{sub 3}Ga/MgO/Mn{sub 3}Ga magnetic tunneling junctions (MTJs) with the consideration of metal(Mg, Co, Cr) insertion layer effect. By changing the concentration of Mn, our calculation shows a considerable disparity in transport properties: A tunneling magnetoresistance (TMR) ratio of 852% was obtained for Mn{sub 2}Ga-based MTJs, however, only a 5% TMR ratio for Mn{sub 3}Ga-based MTJs. In addition, the influence of insertion layer has been considered in our calculation. We found the Co insertion layer can increase the TMR of Mn{sub 2}Ga-based MTJ to 904%; however, the Cr insertion layer can decrease the TMR by 668%; A negative TMR ratio can be obtained with Mg insertion layer. Our work gives a comprehensive understanding of the influence of different insertion layer in Mn-Ga based MTJs. It is proved that, due to the transmission can be modulated by the interfacial electronic structure of insertion, the magnetoresistance ratio of Mn{sub 2}Ga/MgO/Mn{sub 2}Ga MTJ can be improved by inserting Co layer.

  3. Enhanced heteroepitaxial growth of CoCrPt-SiO{sub 2} perpendicular magnetic recording media on optimized Ru intermediate layers

    SciTech Connect

    Srinivasan, Kumar; Piramanayagam, S. N.

    2008-01-15

    The crystallographic growth, interfacial roughness, and magnetic properties of CoCrPt-SiO{sub 2} perpendicular magnetic recording media prepared on various types of Ru intermediate growth layers were systematically investigated based on high angle and omega offset x-ray diffraction scans, rocking curve scans, synchrotron radiation based grazing incidence reflectivity scans, and magneto-optical Kerr hysteresis loops. For samples that make use of one Ru growth layer, voltage bias applied on the Ru layer was seen to have two observable effects: (1) the dispersion in the Ru(00{center_dot}2) perpendicular texture increased, but that of the Co(00{center_dot}2) remained unchanged, leading to identical layered growth and (2) the in-plane a-lattice parameter of the Ru decreased leading to enhanced heteroepitaxy with the Co. There was no significant change in the Ru-Co interfacial roughness with changing the bias on the Ru layer. The bias effect can be used to optimize the design of the Ru intermediate layers. A scheme that makes use of two Ru growth layers consisting of a bottom Ru layer prepared under zero bias, which is inserted below a second Ru layer prepared under biased conditions, is shown to lead to significant benefits such as improved texture without affecting the magnetic properties. This is due to the different functional roles ascribed to each of the Ru growth layers.

  4. Lubricity and stability of poly(2-methacryloyloxyethyl phosphorylcholine) polymer layer on Co-Cr-Mo surface for hemi-arthroplasty to prevent degeneration of articular cartilage.

    PubMed

    Kyomoto, Masayuki; Moro, Toru; Saiga, Ken-ichi; Miyaji, Fumiaki; Kawaguchi, Hiroshi; Takatori, Yoshio; Nakamura, Kozo; Ishihara, Kazuhiko

    2010-02-01

    Migration of the artificial femoral head to the inside of the pelvis due to the degeneration of acetabular cartilage has emerged as a serious issue in resurfacing or bipolar hemi-arthroplasty. Surface modification of cobalt-chromium-molybdenum alloy (Co-Cr-Mo) is one of the promising means of improving lubrication for preventing the migration of the artificial femoral head. In this study, we systematically investigated the surface properties, such as lubricity, biocompatibility, and stability of the various modification layers formed on the Co-Cr-Mo with the biocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer by dip coating or grafting. The cartilage/poly(MPC) (PMPC)-grafted Co-Cr-Mo interface, which mimicked a natural joint, showed an extremely low friction coefficient of <0.01, as low as that of a natural cartilage interface. Moreover, the long-term stability in water was confirmed for the PMPC-grafted layer; no hydrolysis of the siloxane bond was observed throughout soaking in phosphate-buffered saline for 12 weeks. The PMPC-grafted Co-Cr-Mo femoral head for hemi-arthroplasty is a promising option for preserving acetabular cartilage and extending the duration before total hip arthroplasty.

  5. A novel way to estimate the nanoindentation hardness of only-irradiated layer and its application to ion irradiated Fe-12Cr alloy

    NASA Astrophysics Data System (ADS)

    Kim, Hoon-Seop; Lee, Dong-Hyun; Seok, Moo-Young; Zhao, Yakai; Kim, Woo-Jin; Kwon, Dongil; Jin, Hyung-Ha; Kwon, Junhyun; Jang, Jae-il

    2017-04-01

    While nanoindentation is a very useful tool to examine the mechanical properties of ion irradiated materials, there are some issues that should be considered in evaluating the properties of irradiated layer. In this study, in order to properly extract the hardness of only-irradiated layer from nanoindentation data, a new procedure is suggested in consideration of the geometry of indentation-induced plastic zone. By applying the procedure to an ion irradiated Fe-12Cr alloy, the reasonable results were obtained, validating its usefulness in the investigation of practical effect of irradiation on the mechanical behavior of future nuclear materials.

  6. Fabrication of wear-resistant layers with lamellar eutectic structure by laser surface alloying using the in situ reaction between Cr and B4C

    NASA Astrophysics Data System (ADS)

    Sun, You-zheng; Li, Jin-bao; Wellburn, Daniel; Liu, Chang-sheng

    2016-11-01

    To improve the wear resistance of Cr5 steel, wear-resistant layers with lamellar eutectic microstructure were fabricated by laser surface alloying (LSA), which is dependent on the in situ reaction between Cr and B4C. Our results indicated that the hypoeutectic structures of the LSA layers were divided into interdendritic eutectic structures and dendrites. The area fraction of the eutectic structures increased with increasing laser scanning speed, which improved the hardness and wear resistance of the LSA layers. The average hardness of the LSA layer prepared at a scanning speed of 8 mm/s was HV0.2 883.9, which was 1.8 times greater than that of the traditional quenched layer (approximately HV 480). After sliding for 659.4 m, the specimen prepared at a scanning speed of 8 mm/s exhibited a volume loss of 0.0323 mm3, which was only 29.5% of the volume loss of the traditional quenched specimen.

  7. Nucleation of graphene layers on magnetic oxides: Co3O4(111) and Cr2O3(0001) from theory and experiment

    DOE PAGES

    Beatty, John; Cheng, Tao; Cao, Yuan; ...

    2016-12-14

    We report directly grown strongly adherent graphene on Co3O4(111) by carbon molecular beam epitaxy (C MBE) at 850 K and density functional theory (DFT) findings that the first graphene layer is reconstructed to fit the Co3O4 surface, while subsequent layers retain normal graphene structure. This adherence to the Co3O4 structure results from partial bonding of half the carbons to top oxygens of the substrate. This structure is validated by X-ray photoelectron spectroscopy and low-energy electron diffraction studies, showing layer-by-layer graphene growth with ~0.08 electrons/carbon atom transferred to the oxide from the first graphene layer, in agreement with DFT. In contrast,more » for Cr2O3 DFT finds no strong bonding to the surface and C MBE on Cr2O3(0001) yields only graphite formation at 700 K, with C desorption above 800 K. As a result, strong graphene-to-oxide charge transfer aids nucleation of graphene on incommensurate oxide substrates and may have implications for spintronics.« less

  8. Structure and microstructure of the high pressure synthesised misfit layer compound [Sr{sub 2}O{sub 2}][CrO{sub 2}]{sub 1.85}

    SciTech Connect

    Castillo-Martinez, E.; Schoenleber, A.; Smaalen, S. van; Arevalo-Lopez, A.M.; Alario-Franco, M.A.

    2008-08-15

    The strontium chromium oxide [Sr{sub 2}O{sub 2}][CrO{sub 2}]{sub 1.85} misfit layer compound has been synthesised at high-pressure and high-temperature conditions. Electron diffraction patterns and high-resolution transmission electron microscopy images along [001] show the misfit character of the different layers composing the structure with a supercell along the incommensurate parameter b{approx}7b{sub 1}{approx}13b{sub 2}. The modulated crystal structure has been refined within the superspace formalism against single-crystal X-ray diffraction data, employing the (3+1)-dimensional superspace group C'nmb(0{sigma}{sub 2}0)0 0 s. The compound has a composite structure with lattice parameters a{sub 1}=5.182(1) A, b{sub 1}=5.411(1) A, c{sub 1}=18.194(3) A for the first, SrO, subsystem and the same a and c, but with b{sub 2}=2.925(1) A for the second, CrO{sub 2}, subsystem. The layer stacking is similar to that of orthorhombic PbS(TiS{sub 2}){sub 1.18}, but with a much stronger intersubsytem bonding in the case of the oxide. The intersubsystem lattice mismatch is mainly handled by displacement modulations of the Sr atoms, correlated with modulations of the valence, the coordination and the anisotropic displacement parameters. - Graphical abstract: A strontium chromium oxide, [Sr{sub 2}O{sub 2}][CrO{sub 2}]{sub 1.85}, with an orthorhombic misfit layer structure has been synthesised under high pressure. Mainly modulations on the Sr position, ADPs and coordination save the subsystems lattice mismatch.

  9. Photocatalytic decomposition of Congo red under visible light irradiation using MgZnCr-TiO2 layered double hydroxide.

    PubMed

    Ma, Chi; Wang, Fenghua; Zhang, Chang; Yu, Zhigang; Wei, Jingjing; Yang, Zhongzhu; Li, Yongqiu; Li, Zihao; Zhu, Mengying; Shen, Liuqing; Zeng, Guangming

    2017-02-01

    The new nanophotocatalyst MgZnCr-TiO2 was prepared by co-precipitation under different molar ratio of metals (Zn:Cr) and the loaded amount of TiO2. And it was characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy et al. Langmuir model fitted well the adsorption isotherm with the value of R(2) 0.9765, the maximum adsorption capacity was 526.32 mg g(-1), the adsorption followed pseudo second order kinetic by MgZnCr-TiO2 (1:1:2-0.05). The photocatalytic oxidation of Congo red was used to determine the photocatalytic performance of MgZnCr-TiO2 (1:1:2-0.05) under visible light irradiation, and the removal rate reached 98% after reaction for 40 min. The degradation mechanism of Congo red also was proposed, and the MgZnCr-TiO2 (1:1:2-0.05) was stable after five cycles. Compared to the adsorption, Congo red was removed fundamentally by photocatalysis and it is expected to be an effective way to eliminate Congo red.

  10. Three-dimensional hierarchical flower-like Mg-Al-layered double hydroxides: highly efficient adsorbents for As(v) and Cr(vi) removal

    NASA Astrophysics Data System (ADS)

    Yu, Xin-Yao; Luo, Tao; Jia, Yong; Xu, Ren-Xia; Gao, Chao; Zhang, Yong-Xing; Liu, Jin-Huai; Huang, Xing-Jiu

    2012-05-01

    3D hierarchical flower-like Mg-Al-layered double hydroxides (Mg-Al-LDHs) were synthesized by a simple solvothermal method in a mixed solution of ethylene glycol (EG) and water. The formation mechanism of the flower-like Mg-Al-LDHs was proposed. After calcination, the flower-like morphology could be completely preserved. With relatively high specific surface areas, Mg-Al-LDHs and calcined Mg-Al-LDHs with 3D hierarchical nanostructures were tested for their application in water purification. When tested as adsorbents in As(v) and Cr(vi) removal, the as-prepared calcined Mg-Al-LDHs showed excellent performance, and the adsorption capacities of calcined Mg-Al-LDHs for As(v) and Cr(vi) were better than those of Mg-Al-LDHs. The adsorption isotherms, kinetics and mechanisms for As(v) and Cr(vi) onto calcined Mg-Al-LDHs were also investigated. The high uptake capability of the as-prepared novel 3D hierarchical calcined Mg-Al-LDHs make it a potentially attractive adsorbent in water purification. Also, this facile strategy may be extended to synthesize other LDHs with 3D hierarchical nanostructures, which may find many other applications due to their novel structural features.3D hierarchical flower-like Mg-Al-layered double hydroxides (Mg-Al-LDHs) were synthesized by a simple solvothermal method in a mixed solution of ethylene glycol (EG) and water. The formation mechanism of the flower-like Mg-Al-LDHs was proposed. After calcination, the flower-like morphology could be completely preserved. With relatively high specific surface areas, Mg-Al-LDHs and calcined Mg-Al-LDHs with 3D hierarchical nanostructures were tested for their application in water purification. When tested as adsorbents in As(v) and Cr(vi) removal, the as-prepared calcined Mg-Al-LDHs showed excellent performance, and the adsorption capacities of calcined Mg-Al-LDHs for As(v) and Cr(vi) were better than those of Mg-Al-LDHs. The adsorption isotherms, kinetics and mechanisms for As(v) and Cr(vi) onto calcined

  11. Magnetic entropy change plateau in a geometrically frustrated layered system: FeCrAs-like iron-pnictide structure as a magnetocaloric prototype

    NASA Astrophysics Data System (ADS)

    Florez, J. M.; Vargas, P.; Garcia, C.; Ross, C. A.

    2013-06-01

    Monte Carlo modeling suggests that the magnetothermal features of the Fe2P-structured FeCrAs-like compound offer a promising route for the design of magnetocaloric materials. The prototype structure is modeled as antiferromagnetically coupled layered Heisenberg systems mimicking the distorted Kagome/triangular stacked architecture of FeCrAs iron-pnictide. The magnetic entropy change ΔSm(T) presents a plateau-like behavior which can be tailored by tuning either the JCr-Fe/JCr-Cr exchange energy ratio or the magnetic field. The plateau is defined by cooperative spin ordering within a ferrimagnetic region which exists between two critical temperatures separating at the lower bound ({T}_{{c}}^{a}) a canted antiferromagnetic phase and at the upper bound ({T}_{{c}}^{d}) the thermally disordered phase. The refrigerant capacity and adiabatic change of temperature are A(H)({T}_{{c}}^{d}-{T}_{{c}}^{a}) and A(H)Tp/Cm respectively, with {T}_{{c}}^{a}\\lt {T}_{{p}}\\lt {T}_{{c}}^{d}, A(H) an increasing positive function of the field defining the height of the plateau and Cm the magnetic specific heat, whose critical behavior is related to the {T}_{{c}}^{a,d} values.

  12. Multi-layered black phosphorus as saturable absorber for pulsed Cr:ZnSe laser at 2.4 μm.

    PubMed

    Wang, Zhaowei; Zhao, Ruwei; He, Jingliang; Zhang, Baitao; Ning, Jian; Wang, Yiran; Su, Xiancui; Hou, Jia; Lou, Fei; Yang, Kejian; Fan, Yisong; Bian, Jintian; Nie, Jinsong

    2016-01-25

    A high-quality black phosphorus (BP) saturable-absorber mirror (SAM) was successfully fabricated with the multi-layered BP, prepared by liquid-phase exfoliation (LPE) method. The modulation depth and saturation power intensity of BP absorber were measured to be 10.7% and 0.96 MW/cm(2), respectively. Using the BP-SAM, we experimentally demonstrated the mid-infrared (mid-IR) pulse generation from a BP Q-switched Cr:ZnSe laser for the first time to our best knowledge. Stable Q-switched pulse as short as 189 ns with an average output power of 36 mW was realized at 2.4 μm, corresponding to a repetition rate of 176 kHz and a single pulse energy of 205 nJ. Our work sufficiently validated that multi-layer BP could be used as an optical modulator for mid-IR pulse laser sources.

  13. Effect of process temperature on structure and magnetic properties of perpendicularly magnetized D022-Mn3Ge thin films on a Cr buffer layer

    NASA Astrophysics Data System (ADS)

    Sugihara, Atsushi; Suzuki, Kazuya; Miyazaki, Terunobu; Mizukami, Shigemi

    2015-08-01

    We investigated the effect of post-annealing on the perpendicular magnetic anisotropy constant (Ku) and surface roughness (Ra) of Mn3Ge thin films grown at comparatively low temperatures (room temperature, 150, 200, and 250 °C) on Cr buffer layers. The films grown at ≥200 °C exhibit a D022-ordered crystal structure in an as-deposited state. The post-annealing process demonstrates differences in trends between the 200-°C-grown film and the 250-°C-grown film. The 200-°C-grown film displays significant degradation of Ku and an increase in Ra upon annealing at >300 °C because of its poor thermal durability, while the 250-°C-grown film is still intact even at 500 °C. The 250-°C-grown film post-annealed at 300 °C displays relatively high Ku while Ra remains low. It may be possible to grow D022-Mn3Ge with higher Ku and low Ra using a buffer-layer material with a lattice-matched crystal structure with D022-Mn3Ge and higher thermal durability than Cr.

  14. The connection analysis between the dilution of the deposited Fe-Cr-V-Mo-C layer by the basic metal and the parameters of its microstructure

    NASA Astrophysics Data System (ADS)

    Degterev, A. S.; Gnusov, S. F.

    2017-02-01

    In this work, the structure of the Fe-Cr-V-Mo-C coatings received by plasma transferred arc cladding was investigated. Coatings were deposited on plates with a thickness of 10 mm and made from constructional steel (steel 20). The correlation analysis of relationships between dilution of the deposited layers by the basic metal and the parameters of their microstructure was carried out. The parameters were as follows: volume fraction, a size, a shape factor, the distance between particles, the number of particles of vanadium carbide, volume fraction of the eutectic on the basis of carbide M7C3 and the distances between its colonies, as well as the volume fraction of the α-phase in the alloy matrix.

  15. A study of the influence of the metallurgical state on shear band and white layer generation in 100Cr6 steel: application to machining

    NASA Astrophysics Data System (ADS)

    Habak, Malek; Lebrun, Jean-Lou; Morel, Anne

    2007-04-01

    The aim of this paper is to better understand the material behaviour involved in machining operations. During machining, the workpiece experiences large strains, high strain rate, high temperatures, complex loading histories, and recovery. To reproduce these loadings and to understand the behaviour of 100Cr6 bearing steel, quasi-static and dynamics mechanical shearing tests were carried out. These tests made it possible to reproduce the primary shear zone observed on the chips after cutting using specimens with special geometries "hat-shaped specimens". The geometry of these specimens results in a localised shearing zone when loaded in compression. Two metallurgical states of the material were investigated (with and without carbides). For each state, three material hardnesses are used (46, 51 and 55HRc). The tests parameters investigated were the strain rate and temperature. For all tests, the microstructures of the shear zones were examined. Results show that the presence of carbides has the tendency to increase the material resistance. The micrographic observations of the sheared zones highlighted the effect of the microstructure and the link between the thermo-mechanical effects and the characteristics of the white zones. It is possible to produce a white layer, similar to those obtained in machining, by quasi-static and dynamic shearing tests. The presence of carbides has a strong effect on the generation of the shear bands and the white layers. Increasing the test temperature and strain rate tends to increase the width of shear band and white layers. A comparison between the white layers obtained by the dynamic tests and those observed on the chip in hard turning are carried out. The results show good agreement.

  16. Spin-density-wave antiferromagnetism of Cr in Fe/Cr(001) superlattices

    SciTech Connect

    Fullerton, E.E.; Bader, S.D.; Robertson, J.L.

    1996-10-01

    The antiferromagnetic spin-density-wave (SDW) order of Cr layers in Fe/Cr(001) superlattices was investigated by neutron scattering. For Cr thickness 51-190 {Angstrom}, a transverse SDW is formed for all temperatures below Neel temperature with a single wavevector Q normal to the layers. A coherent magnetic structure forms with the nodes of the SDW near the Fe-Cr interfaces. For thinner Cr layers, the magnetic scattering can be described by commensurate antiferromagnetic order.

  17. Plasma enhanced chemical vapor deposition of metalboride interfacial layers as diffusion barriers for nanostructured diamond growth on cobalt containing alloys CoCrMo and WC-Co

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.

    This work is a compilation of theory, finite element modeling and experimental research related to the use of microwave plasma enhanced chemical vapor deposition (MPECVD) of diborane to create metal-boride surface coatings on CoCrMo and WC-Co, including the subsequent growth of nanostructured diamond (NSD). Motivation for this research stems from the need for wear resistant coatings on industrial materials, which require improved wear resistance and product lifetime to remain competitive and satisfy growing demand. Nanostructured diamond coatings are a promising solution to material wear but cannot be directly applied to cobalt containing substrates due to graphite nucleation. Unfortunately, conventional pre-treatment methods, such as acid etching, render the substrate too brittle. Thus, the use of boron in a MPECVD process is explored to create robust interlayers which inhibit carbon-cobalt interaction. Furthermore, modeling of the MPECVD process, through the COMSOL MultiphysicsRTM platform, is performed to provide insight into plasma-surface interactions using the simulation of a real-world apparatus. Experimental investigation of MPECVD boriding and NSD deposition was conducted at surface temperatures from 700 to 1100 °C. Several well-adhered metal-boride surface layers were formed: consisting of CoB, CrB, WCoB, CoB and/or W2CoB2. Many of the interlayers were shown to be effective diffusion barriers against elemental cobalt for improving nucleation and adhesion of NSD coatings; diamond on W2CoB2 was well adhered. However, predominantly WCoB and CoB phase interlayers suffered from diamond film delamination. Metal-boride and NSD surfaces were evaluated using glancing-angle x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), cross-sectional scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), micro-Raman spectroscopy, nanoindentation, scratch testing and epoxy pull testing. COMSOL MultiphysicsRTM was used to construct a

  18. ZnCr layered double hydroxide (LDH) nanosheets assisted formation of hierarchical flower-like CdZnS@LDH microstructures with improved visible-light-driven H2 production.

    PubMed

    Yao, Lihua; Wei, Ding; Yan, Dongpeng; Hu, Changwen

    2015-03-01

    The development of new semiconductor photocatalysts toward splitting water has supplied a promising way to obtain sustainable and clean hydrogen energy. Herein, CdZnS@layered double hydroxide (LDH) composites with a hierarchical flower-like microstructure have been fabricated with the aid of ZnCr-LDH nanosheets as templates. XRD, SEM and HRTEM show that the ZnCr-LDH nanosheets are uniformly dispersed within the composites. The surface of the hierarchical structures is rough and composed of numerous nanocrystals of CdZnS. The HRTEM images indicate that the surface of CdZnS nanocrystals is mainly composed of the (111) plane. Moreover, the visible-light-driven H2 production performance of the CdZnS in the presence and absence of ZnCr-LDH nanosheets has been measured. The results show that ZnCr-LDH nanosheets play an important role in the hierarchical morphology and photocatalytic activity of the as-prepared samples. In the water-splitting process, the visible-light-driven H2 -production rate of hierarchical flower-like CdZnS@LDH is 4.03 times and nearly 10 times higher than that of pristine CdZnS microsphere and pure commercial CdS, respectively. Therefore, this work not only achieves enhanced catalytic performance of the CdZnS by the introduction of ZnCr-LDH nanosheets, but also supplies an insight into the relationship between the hierarchical morphology and the semiconductor photocatalytic activity.

  19. Deformation and fracture of a composite material based on a high-strength maraging steel covered with a melt-quenched Co69Fe4Cr4Si12B11 alloy layer

    NASA Astrophysics Data System (ADS)

    Sevost'yanov, M. A.; Kolmakov, A. G.; Molokanov, V. V.; Zabolotnyi, V. T.; Umnov, P. P.; Umnova, N. V.

    2011-04-01

    Multifractal analysis is used to study the deformation and fracture of a promising composite material consisting of a wire base made of K17N9M14 maraging steel covered with a surface layer made from a Co69Fe4Cr4Si12B11 amorphous alloy. As compared to its components, this material has a substantially better set of the mechanical properties.

  20. Nucleation of graphene layers on magnetic oxides: Co3O4(111) and Cr2O3(0001) from theory and experiment

    SciTech Connect

    Beatty, John; Cheng, Tao; Cao, Yuan; Driver, M. Sky; Goddard, III, William A.; Kelber, Jeffry A.

    2016-12-14

    We report directly grown strongly adherent graphene on Co3O4(111) by carbon molecular beam epitaxy (C MBE) at 850 K and density functional theory (DFT) findings that the first graphene layer is reconstructed to fit the Co3O4 surface, while subsequent layers retain normal graphene structure. This adherence to the Co3O4 structure results from partial bonding of half the carbons to top oxygens of the substrate. This structure is validated by X-ray photoelectron spectroscopy and low-energy electron diffraction studies, showing layer-by-layer graphene growth with ~0.08 electrons/carbon atom transferred to the oxide from the first graphene layer, in agreement with DFT. In contrast, for Cr2O3 DFT finds no strong bonding to the surface and C MBE on Cr2O3(0001) yields only graphite formation at 700 K, with C desorption above 800 K. As a result, strong graphene-to-oxide charge transfer aids nucleation of graphene on incommensurate oxide substrates and may have implications for spintronics.

  1. Effect of Si, Sc, Cr doping on the structural, optical and discharge characteristics of MgO thin films as protective layer for plasma display panels

    NASA Astrophysics Data System (ADS)

    Singh, Chandra Bhal; Barik, U. K.; Sarkar, Surajit; Singh, Vandana; Ram, Sanjay K.; Dwivedi, Harish K.; Kumar, Satyendra

    2012-10-01

    We report the effect of Si, Cr, Sc doping in the crystalline structure, optical and discharge characteristics of MgO thin films. Silicon and multiple (Si, Cr, Sc) doped MgO thin films demonstrate higher secondary electron emission (SEE). Si doping with Cr and Sc doping in MgO films shows much higher SEE as compared to pure and only Si doped MgO films. The importance of optimum amount of Sc doping is seen in our study where SEE reduced with further increase in Sc doping. The structural attributes of MgO films are correlated to the observed changes in discharge characteristics in the context of varying amount of Si, Sc, and Cr doping.

  2. Investigation of Coronal Leakage of Root Fillings after Smear Layer Removal with EDTA or Er,Cr:YSGG Laser through Capillary Flow Porometry

    PubMed Central

    Vergauwen, Tom Edgard Maria; Michiels, Rafaël; Torbeyns, Dries; Meire, Maarten; De Moor, Roeland Jozef Gentil

    2014-01-01

    No studies have been performed evaluating the marginal seal of root fillings after direct exposure of root canal (RC) walls to Er,Cr:YSGG laser irradiation. Therefore, 75 root filled teeth (5 × 15–cold lateral condensation) were analyzed for through-and-through leakage (TTL) using capillary flow porometry (CFP). The cleaning protocol determined the experimental groups: (1) irrigation with NaOCl 2.5% and EDTA 17% or standard protocol (SP), (2) SP + Er,Cr:YSGG lasing (dried RC), (3) NaOCl 2.5% + Er,Cr:YSGG lasing (dried RC), (4) SP + Er,Cr:YSGG lasing (wet RC), and (5) NaOCl 2.5% + Er,Cr:YSGG lasing (wet RC). Groups 6 to 10 consisted of the same filled teeth with resected apices. Resection was performed after the first CFP measurement. CFP was used to assess minimum, mean flow, and maximum pore diameters after 48 h. Statistics were performed using nonparametric tests (P > 0.05). Additional three roots per group were submitted to SEM of the RC walls. TTL was observed in all groups without statistically significant differences between the different groups for minimum, mean, and maximum pore diameter (P > 0.05). In this study, the use of EDTA and/or Er,Cr:YSGG laser did not reduce through-and-through leakage in nonresected and resected roots. PMID:24696685

  3. Surface morphological, electrical and transport properties of rapidly annealed double layers Ru/Cr Schottky structure on n-type InP

    NASA Astrophysics Data System (ADS)

    Shanthi Latha, K.; Rajagopal Reddy, V.

    2017-02-01

    The electrical and transport properties of a fabricated bilayer Ru/Cr/n-InP Schottky diode (SD) have been investigated at different annealing temperatures. Atomic force microscopy results have showed that the overall surface morphology of the Ru/Cr/n-InP SD is fairly smooth at elevated temperatures. High barrier height is achieved for the diode annealed at 300 °C compared to the as-deposited, annealed at 200 and 400 °C diodes. The series resistance and shunt resistance of the Ru/Cr/n-InP SD are estimated by current-voltage method at different annealing temperatures. The barrier heights and series resistance are also determined by Cheung's and modified Norde functions. The interface state density of the Ru/Cr/n-InP SD is found to be decreased after annealing at 300 °C and then slightly increased upon annealing at 400 °C. The difference between barrier heights obtained from current-voltage and capacitance-voltage is also discussed. Experimental results have showed that the Poole-Frenkel emission is found to be dominant in the lower bias region whereas Schottky emission is dominant in the higher bias region for the Ru/Cr/n-InP SDs irrespective of annealing temperatures.

  4. Elaboration, characterization of CrN- based coatings

    SciTech Connect

    Tlili, B.; Nouveau, C.; Guillemot, G.

    2011-01-17

    Cr, CrN and CrAlN monolayers were synthesized by RF dual magnetron sputtering on AISI4140 steel and silicon substrates at 200 deg. C. Multilayers coatings based on the three mono-layers such as CrN/CrAlN and Cr/CrN/CrAlN were also synthesized only on Si. The physico-chemical and mechanical properties of the layers were determined by AFM, SEM+WDS, stress, roughness and nanoindentation measurements. The influence of the thickness on the mechanical properties of the monolayers stresses has been studied and as a consequence we compared the mono and multilayers stress state.

  5. Spin resolved photoelectron spectroscopy of [Mn6(III)Cr(III)]3+ single-molecule magnets and of manganese compounds as reference layers.

    PubMed

    Helmstedt, Andreas; Müller, Norbert; Gryzia, Aaron; Dohmeier, Niklas; Brechling, Armin; Sacher, Marc D; Heinzmann, Ulrich; Hoeke, Veronika; Krickemeyer, Erich; Glaser, Thorsten; Bouvron, Samuel; Fonin, Mikhail; Neumann, Manfred

    2011-07-06

    Properties of the manganese-based single-molecule magnet [Mn(6)(III)Cr(III)](3+) are studied. It contains six Mn(III) ions arranged in two bowl-shaped trinuclear triplesalen building blocks linked by a hexacyanochromate and exhibits a large spin ground state of S(t) = 21/2. The dominant structures in the electron emission spectra of [Mn(6)(III)Cr(III)](3+) resonantly excited at the L(3)-edge are the L(3)M(2, 3)M(2, 3), L(3)M(2, 3)V and L(3)VV Auger emission groups following the decay of the primary p(3/2) core hole state. Significant differences of the Auger spectra from intact and degraded [Mn(6)(III)Cr(III)](3+) show up. First measurements of the electron spin polarization in the L(3)M(2, 3)V and L(3)VV Auger emission peaks from the manganese constituents in [Mn(6)(III)Cr(III)](3+) resonantly excited at the L(3)-edge near 640 eV by circularly polarized synchrotron radiation are reported. In addition spin resolved Auger electron spectra of the reference substances MnO, Mn(2)O(3) and Mn(II)(acetate)(2)·4H(2)O are given. The applicability of spin resolved electron spectroscopy for characterizing magnetic states of constituent atoms compared to magnetic circular dichroism (MCD) is verified: the spin polarization obtained from Mn(II)(acetate)(2)·4H(2)O at room temperature in the paramagnetic state compares to the MCD asymmetry revealed for a star-shaped molecule with a Mn(4)(II)O(6) core at 5 K in an external magnetic field of 5 T.

  6. Study on feasibility of producing an amorphous surface layer of Fe49Cr18Mo7B16C4Nb3 by pulsed Nd:YAG laser surface melting

    NASA Astrophysics Data System (ADS)

    Mojaver, Reza; Mojtahedi, Faezeh; Shahverdi, Hamid Reza; Torkamany, Mohammad Javad

    2013-01-01

    This work aims to investigate whether an amorphous surface layer can be obtained when as-cast Fe49Cr18Mo7B16C4Nb3 alloy is submitted to pulsed Nd:YAG laser surface melting. The experiments were conducted in the various laser scanning speeds. The microstructures of laser treated zones were investigated by X-ray diffraction XRD and Field Emission Scanning Electron Microscope (FESEM) and their microhardness were measured, too. The chemical composition of different points of each sample was analyzed by energy-dispersive X-ray spectroscopy EDS. Although the estimated cooling rates in surface layers were higher than the required cooling rate to achieve full amorphization, but the present experiments were unable to retain complete glassy microstructure on surface and a mixture of amorphous (low volume fraction) and ultrafine grained phases were produced in surface of samples. Based on the findings, it was understood that the overlapping of successive pulses and element redistributions occurred in pulsed laser melting could severely restrict amorphization. The influence of laser scan speed and laser power on heat input, melting ratio, compositional changes and cracking in laser treated zone were discussed separately. It is suggested that the limited range of laser variables in pulsed Nd:YAG laser melting may help to produce a sound amorphous phase of as-cast Fe49Cr18Mo7B16C4Nb3 alloy.

  7. Effect of Cr content on the corrosion performance of low-Cr alloy steel in a CO2 environment

    NASA Astrophysics Data System (ADS)

    Xu, Lining; Wang, Bei; Zhu, Jinyang; Li, Wei; Zheng, Ziyi

    2016-08-01

    Low-Cr alloy steel demonstrates lower corrosion rate than does C steel in a high-temperature and high-pressure CO2-containing environment. This study aimed to clarify the role of the Cr content in mitigating corrosion and reports the performance of 1%Cr, 2%Cr, 3%Cr, 4%Cr, 5%Cr, and 6.5%Cr steels. The results show that low-Cr alloy steel in CO2 at 80 °C and 0.8 MPa possesses spontaneous prepassivation characteristics when the Cr content is 3% or higher. Furthermore, the formation and peel-off of a prepassivation film on 3%Cr-6.5%Cr steels surfaces during polarization demonstrate that adequate amount of Cr in the steel substrate can cause protective layer. The main component of prepassivation film on 3%Cr steel is Cr(OH)3. Thus, the role of Cr is revealed. An adequate amount of Cr in the steel substrate causes the formation of protective Cr(OH)3 layer, which helps low-Cr steel to possess prepassivation characteristics. Prepassivation is the reason why low-Cr steel has a lower corrosion rate than C steel.

  8. Switching of perpendicular exchange bias in Pt/Co/Pt/α-Cr{sub 2}O{sub 3}/Pt layered structure using magneto-electric effect

    SciTech Connect

    Toyoki, Kentaro; Shiratsuchi, Yu Kobane, Atsushi; Harimoto, Shotaro; Onoue, Satoshi; Nomura, Hikaru; Nakatani, Ryoichi

    2015-05-07

    Switching of the perpendicular exchange bias polarity using a magneto-electric (ME) effect of α-Cr{sub 2}O{sub 3} was investigated. From the change in the exchange bias field with the electric field during the ME field cooling, i.e., the simultaneous application of both magnetic and electric fields during the cooling, we determined the threshold electric field to switch the perpendicular exchange bias polarity. It was found that the threshold electric field was inversely proportional to the magnetic field indicating that the EH product was constant. The high EH product was required to switch the exchange bias for the film possessing the high exchange anisotropy energy density, which suggests that the energy gain by the ME effect has to overcome the interfacial exchange coupling energy to reverse the interfacial antiferromagnetic spin.

  9. Magnetic phase transitions and entropy change in layered NdMn{sub 1.7}Cr{sub 0.3}Si{sub 2}

    SciTech Connect

    Md Din, M. F. Dou, S. X.; Wang, J. L.; Campbell, S. J.; Studer, A. J.; Avdeev, M.; Kennedy, S. J.; Gu, Q. F.; Zeng, R.

    2014-01-27

    A giant magnetocaloric effect has been observed around the Curie temperature, T{sub C} ∼ 42 K, in NdMn{sub 1.7}Cr{sub 0.3}Si{sub 2} with no discernible thermal and magnetic hysteresis losses. Below 400 K, three magnetic phase transitions take place around 380 K, 320 K and 42 K. Detailed high resolution synchrotron and neutron powder diffraction (10–400 K) confirmed the magnetic transitions and phases as follows: T{sub N}{sup intra} ∼ 380 K denotes the transition from paramagnetism to intralayer antiferromagnetism (AFl), T{sub N}{sup inter} ∼ 320 K represents the transition from the AFl structure to the canted antiferromagnetic spin structure (AFmc), while T{sub C} ∼ 42 K denotes the first order magnetic transition from AFmc to canted ferromagnetism (Fmc + F(Nd)) due to ordering of the Mn and Nd sub-lattices. The maximum values of the magnetic entropy change and the adiabatic temperature change, around T{sub C} for a field change of 5 T are evaluated to be −ΔS{sub M}{sup max} ∼ 15.9 J kg{sup −1} K{sup −1} and ΔT{sub ad}{sup max} ∼ 5 K, respectively. The first order magnetic transition associated with the low levels of hysteresis losses (thermal <∼0.8 K; magnetic field <∼0.1 T) in NdMn{sub 1.7}Cr{sub 0.3}Si{sub 2} offers potential as a candidate for magnetic refrigerator applications in the temperature region below 45 K.

  10. Antisite Defects in Layered Multiferroic CuCr0.9In0.1P2S6

    SciTech Connect

    He, Qian; Belianinov, Alex; Dziaugys, Andrius; Maksymovych, Petro; Vysochanskii, Yulian; Kalinin, Sergei V.; Borisevich, Albina Y.

    2015-10-06

    The CuCr1-xInxP2S6 system represents a large family of metal chalcogenophosphates that are unique and promising candidates for 2D materials with functionalities such as ferroelectricity. We carried out detailed microstructural and chemical characterization of these compounds using aberration-corrected STEM, in order to understand the origin of these different ordering phenomena. Quantitative STEM-HAADF imaging and analysis identified the stacking order of an 8-layer thin flake, which leads to the identification of anti-site In3+(Cu+) doping. We believe that these findings will pave the way towards understanding the ferroic coupling phenomena in van der Waals lamellar compounds, as well as the potential applications in 2-D electronics.

  11. Influence of doping and doping level on magnetoelectric coupling in layered composites Tb1-xDyxFe2-y/Ba-Ti1-zMzO3+δ (M = Fe, Cr, Mn, Co)

    NASA Astrophysics Data System (ADS)

    Zhang, N.; Fan, J. F.; Cao, H. X.; Wei, J. J.

    2010-06-01

    Perovskites BaTi1-zMzO3+δ (M = Fe, Cr, Mn, Co) has been sol-gel synthesized. Their transformation point of ferroelectric to paraelectric and the latent heat of the transformation were found a little lower than those for pure BaTiO3 (BTO), respectively. Layered composites Tb1-xDyxFe2-y-BaTi1-zMzO3+δ have been fabricated. Their magnetoelectric (ME) effect has been investigated. All the bilayers containing the doped BTO displayed a stronger ME effects than that containing pure BTO does. The bilayer Tb1-xDyxFe2-y-BaTi0.99Cr0.01O3+δ was observed to show a larger ME coupling in the composites containing other doped BTO. While Tb1-xDyxFe2-y-BaTi0.985Fe0.015O3+δ showed the largest ME effects in the bilayers Tb1-xDyxFe2-y-BaTi1-zFezO3+δ (0 ≤ z ≤ 0.02). Additionally, the ME voltage coefficient for the trilayers Tb1-xDyxFe2-y-BaTi0.99M0.01O3+δ-Tb1-xDyxFe2-y was observed to be two or three times larger than that observed in the bilayers composed by the same substances. Theoretical analyses have been given for these observations. All the results suggest that the doped BTO can be a new choice of piezoelectrics in fabricating layered ME composites.

  12. Photochromic lens mirror-coated with Cr

    NASA Astrophysics Data System (ADS)

    Shin, Sungho; Lee, Myeongkyu

    2007-11-01

    We have designed and fabricated mirror-coated photochromic lenses for use in sunglasses. These lenses consisted of a Cr thin film sandwiched between two SiO2 layers on the front surface and an anti-reflection (AR) coating on the backside. The SiO2 films above and below the Cr layer were introduced as the protection and buffer layers, respectively. The AR coating was to suppress back-reflection from the lens surface. Deposition of all coating layers were carried out by an e-beam evaporator under Ar atmosphere at P = 10-5 Torr and T = 70 °C. As expected, the overall transmittance decreased with increasing Cr thickness. For a Cr layer of 5 nm thickness, it changed from about 45% in the bleached state down to 25% after exposure to sunlight. This is consistent with the transmission range typically required for sunglasses.

  13. Magnetic resonance in a Cu-Cr-S structure

    SciTech Connect

    Vorotynov, A. M. Abramova, G. M.; Pankrats, A. I.; Petrakovskii, G. A.; Zharkov, S. M.; Zeer, G. M.; Tugarinov, V. I.; Rautskii, M. V.; Sokolov, V. V.

    2013-11-15

    A layered Cu-Cr-S structure composed of single-crystal CuCrS{sub 2} layers and thin CuCr{sub 2}S{sub 4} plates embedded in them has been investigated by the magnetic resonance and scanning electron microscopy methods. The Curie temperature and saturation magnetization of the spinel phase of the investigated samples have been determined. The thickness of the CuCr{sub 2}S{sub 4} layers has been estimated. The dependence of the growncrystal topology on synthesis conditions has been established. An interpretation of the anomalous behavior of the magnetostatic oscillation intensity is offered.

  14. Biocompatible Ferromagnetic Cr-Trihalide Monolayers

    NASA Astrophysics Data System (ADS)

    Sun, Qiang

    Cr with an electronic configuration of 3d54s1 possesses the largest atomic magnetic moment (6µB) of all elements in the 3d transition metal series. Furthermore, the trivalent chromium (Cr3+) is biocompatible and is widely found in food and supplements. Here using first principles calculations combined with Monte Carlo simulations based on Ising model, we systematically study a class of 2D ferromagnetic monolayers CrX3 (X = Cl, Br, I). The feasibility of exfoliation from their layered bulk phase is confirmed by the small cleavage energy and high in-plane stiffness. Spin-polarized calculations, combined with self consistently determined Hubbard U that accounts for strong correlation energy, demonstrate that CrX3 (X =Cl, Br, I) monolayers are ferromagnetic and Cr is trivalent and carries a magnetic moment of 3µB, the resulting Cr3+ ions are biocompatible. The corresponding Curie temperatures for CrCl3 CrBr3 CrI3 are are found to 66, 86, and 107 K, respectively, which can be increased to 323, 314, 293 K by hole doping. The biocompatibility and ferromagnetism render these Cr-containing trichalcogenide monolayers unique for applications.

  15. Magnetic resonance in a gallium-doped Cu-Cr-S structure

    NASA Astrophysics Data System (ADS)

    Vorotynov, A. M.; Pankrats, A. I.; Abramova, G. M.; Velikanov, D. A.; Bovina, A. F.; Sokolov, V. V.; Filatova, I. Yu.

    2016-04-01

    A layered Cu-Cr-S structure doped with Ga ions and consisting of single-crystal CuCrS2 layers, embedded with thin plates of spinel phases CuCr2S4 and CuGa x Cr2- x S4, has been studied using the magnetic resonance and magnetic susceptibility methods. The Curie temperature and the saturation magnetization of the spinel phases of the samples have been determined. The spinel phase layer thickness has been estimated.

  16. Manganese containing layer for magnetic recording media

    DOEpatents

    Lambeth, David N.; Lee, Li-Lien; Laughlin, David E.

    1999-01-01

    The present invention provides for a magnetic recording media incorporating Mn-containing layers between a substrate and a magnetic layer to provide media having increased coercivity and lower noise. The Mn-containing layer can be incorporated in a rotating, translating or stationary recording media to operate in conjunction with magnetic transducing heads for recording and reading of magnetic data, as well as other applications. The magnetic recording medium of the invention preferably includes a Co or Co alloy film magnetic layer, and Mn-containing layer, preferably comprised of VMn, TiMn, MnZn, CrMnMo, CrMnW, CrMnV, and CrMnTi, and most preferably a CrMn alloy, disposed between the substrate and the magnetic layer to promote an epitaxial crystalline structure in the magnetic layer. The medium can further include seed layers, preferably polycrystalline MgO for longitudinal media, underlayers, and intermediate layers. Underlayers and intermediate layers are comprised of materials having either an A2 structure or a B2-ordered crystalline structure disposed between the seed layer and the magnetic layer. Materials having an A2 structure are preferably Cr or Cr alloys, such as CrV, CrMo, CrW and CrTi. Materials having a B2-ordered structure having a lattice constant that is substantially comparable to that of Cr, such as those preferably selected from the group consisting of NiAl, AILCo, FeAl, FeTi, CoFe, CoTi, CoHf, CoZr, NiTi, CuBe, CuZn, A-LMn, AlRe, AgMg, and Al.sub.2 FeMn.sub.2, and is most preferably FeAl or NiAl.

  17. Magnetic and energetic properties of low-index Cr surfaces and Fe/Cr interfaces: A first-principles study

    NASA Astrophysics Data System (ADS)

    Soulairol, R.; Fu, Chu-Chun; Barreteau, C.

    2011-10-01

    Density functional theory calculations are performed to investigate the impact of magnetism on the energetics of low-index Cr surfaces and Fe/Cr interfaces, that is, Cr(100), Cr(110), Fe/Cr(100), and Fe/Cr(110). We have also determined the stability of various Cr magnetic structures, particularly the spin-density waves, in the presence of these surfaces and interfaces. We show that the most stable structure of the spin-density wave is mainly dictated by the subtle balance between bulk and surface/interface influences, and strongly dependent on the surface/interface orientation. Regarding the Cr surfaces, we confirm the role of magnetism to lower the surface energy of Cr(100) with respect to Cr(110). Among all the possible orientations of the wave vector, only the out-of-plane wave is found to be stable near Cr(100) surfaces with the high-moment sites located at the surface layer. At variance, the in-plane wave is shown to be the most stable one, consistent with experimental data for very thin Cr(110) films. Concerning the Fe/Cr interfaces, magnetic frustrations are identified to be responsible for a higher formation energy of Fe/Cr(110) compared to that of Fe/Cr(100). This unusual anisotropy of interface energies is clearly different from the corresponding interfaces between Cr and a nonmagnetic element, Cu. Two ways are suggested to relax partially the magnetic frustrations at the (110) interface and to lower its formation energy. Noncollinear magnetic configurations can be developed where local moments of Fe and Cr atoms are perpendicular to each other. Also, in order to preserve phase coherence, in-plane spin-density waves show a very stable magnetic structure with the nodes at the interface layer. The presence of low-moment sites at Fe/Cr(110) offer another way to relax the magnetic frustrations and lower the interfacial energy.

  18. Atomic scale structure investigations of epitaxial Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Kąc, M.; Morgiel, J.; Polit, A.; Zabila, Y.; Marszałek, M.

    2014-06-01

    Fe/Cr multilayers were deposited by molecular beam epitaxy on the MgO(1 0 0) substrate. Structural properties of the samples were analyzed by low energy electron diffraction, high resolution transmission electron microscopy (HRTEM), as well as by X-ray reflectivity, conversion electron Mössbauer spectroscopy (CEMS) and Auger electron spectroscopy. Investigations revealed multilayered system built of well-ordered Fe and Cr thin films with (1 0 0) orientation. A high geometrical perfection of the system, i.e. planar form of interfaces and reproducible thickness of layers, was also proven. Fe/Cr interface roughness was determined to be 2-3 atomic layers. CEMS studies allowed to analyze at atomic scale the structure of buried Fe/Cr interfaces, as well as to distinguish origin of interface roughness. Roughnesses resulting from interface corrugations and from the Fe-Cr interdiffusion at interfaces were observed. Fe/Cr multilayers showed strong antiferromagnetic coupling of Fe layers.

  19. In-situ transmission electron microscopy study of surface oxidation for Ni–10Cr and Ni–20Cr alloys

    SciTech Connect

    Luo, Langli; Zou, Lianfeng; Schreiber, Daniel K.; Baer, Donald R.; Bruemmer, Stephen M.; Zhou, Guangwen; Wang, Chong-Min

    2016-03-01

    The early-stage oxidation of Ni (001) thin films alloyed with 10 or 20 at% Cr at 700 °C has been directly visualized using environmental transmission electron microscopy. Independent of Cr concentration, the oxidation initiates via the nucleation of surface NiO islands and subsurface Cr2O3. The NiO grows and transitions into a continuous film, followed by the nucleation and growth of NiCr2O4 islands through the outer oxide. The Cr concentration plays a more critical role in the later stages of the oxidation. A continuous and more protective Cr2O3 sublayer is established for Ni-20at% Cr, while the Cr2O3 sublayer for Ni-10at%Cr is discontinuous for Ni-10at%Cr. Oxidation persists on the lower Cr alloy where NiO whiskers are observed to preferentially nucleate and grow from the NiCr2O4 islands. It is suggested that short-circuit diffusion of Ni occurs along the NiCr2O4 interfaces through the discontinuous Cr2O3 layer in Ni-10at%Cr to facilitate the selective nucleation of NiO whiskers on the NiCr2O4 surfaces. Conversely, the protective nature of the continuous Cr2O3 film in Ni-20at%Cr blocks this short-circuit pathway and prevents the formation of additional NiO on the surface in the early stage oxidation.

  20. Spallanzani Cr. Floor

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03632 Spallanzani Cr. Floor

    This image was taken by one of the Mars Student Imaging Project (MSIP) teams. Their target is the unusual floor deposits in Spallanzani Crater. The wind may have affected the surface of the layered deposit. Small dunes have formed near the southern margin.

    Image information: VIS instrument. Latitude 57.9S, Longitude 86.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  1. Spin polarization at Fe/Cr interfaces

    NASA Astrophysics Data System (ADS)

    Pizzagalli, L.; Freyss, M.; Moraitis, G.; Stoeffler, D.; Demangeat, C.; Dreyssé, H.; Vega, A.; Miethaner, S.; Bayreuther, G.

    1997-04-01

    It is shown that contradictory experimental data on magnetic moments and spin order at Fe/Cr interfaces can be explained by structural irregularities at the interfaces. The spin-polarized electronic charge distribution was calculated by using a self-consistent tight-binding model combined with a real-space recursion method. It was used to interpret the total magnetic moment of Cr(001) films and of Cr/Fe(001) sandwiches molecular beam epitaxy grown on Fe(001) from in situ measurements with an alternating gradient magnetometer during film growth. While a strong decrease of the sample moment during Cr deposition was observed on a very smooth surface, no moment change occurred for a strongly faceted surface. The different results of both experiments are consistent with the calculations if we take into account (i) a possible ferrimagnetic c(2×2) spin configuration of a Cr monolayer on Fe(001) which might be favorable in clusters of a certain size and for high step densities; (ii) a possible interchange of one Cr and Fe monolayer at the interface; and (iii) a multidomain configuration with zero net moment of a thin Fe layer on a Cr surface due to a high step density.

  2. Interlayer coupling in Fe/Cr/Gd multilayer structures

    SciTech Connect

    Drovosekov, A. B. Kreines, N. M.; Savitsky, A. O.; Kravtsov, E. A.; Blagodatkov, D. V.; Ryabukhina, M. V.; Milyaev, M. A.; Ustinov, V. V.; Pashaev, E. M.; Subbotin, I. A.; Prutskov, G. V.

    2015-06-15

    The effect of the chromium layer thickness on the magnetic state of an [Fe/Cr/Gd/Cr]{sub n} multilayer structure is studied. A series of Fe/Cr/Gd structures with Cr spacer thicknesses of 4–30 Å is studied by SQUID magnetometry and ferromagnetic resonance in the temperature range 4.2–300 K. The obtained experimental results are described in terms of an effective field model, which takes into account a biquadratic contribution to the interlayer coupling energy and a nonuniform magnetization distribution inside the gadolinium layer (which was detected earlier). Depending on the magnetic field and temperature, the following types of magnetic ordering are identified at various chromium layer thicknesses: ferromagnetic, antiferromagnetic, and canted ordering. A comparison of the experimental and calculated curves allowed us to determine the dependence of the bilinear (J{sub 1}) and biquadratic (J{sub 2}) exchange constants on chromium layer thickness t{sub Cr}. Weak oscillations at a period of about 18 Å are detected in the J{sub 1}(t{sub Cr}) dependence in the range 8–30 Å. The interlayer coupling oscillations in the system under study are assumed to be related to the RKKY exchange interaction mechanism via the conduction electrons of Cr.

  3. Magnetic properties of Al/57Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Jani, Snehal; Lakshmi, N.; Jain, Vishal; Reddy, V. R.; Gupta, Ajay; Venugopalan, K.

    2013-06-01

    Conversion Electron Mössbauer Spectroscopy (CEMS) and DC magnetization are used to compare magnetic properties of as-deposited multilayer (MLS) and Fe2CrAl thin film made from Al/57Fe/Cr MLS deposited by ion beam sputtering and then annealed in UHV. Interdiffusion of elements on annealing sample-1 at 500°C leads to formation of a single, disordered film of Fe2CrAl as evidenced by hyperfine field values obtained by CEMS in the film which compares well with that in bulk Fe2CrAl. CEMS also shows contributions from Fe, Fe/Cr and Fe/Al interfaces in the MLS. Saturation magnetization of as-deposited sample-1 is much less than pure Fe due to reduced Fe thickness because of interface formation and also reduction in Fe-Fe interaction due to intervening Al and Cr layers.

  4. Sorption of Pb(II), Cr(III), Cu(II), As(III) to peat, and utilization of the sorption properties in industrial waste landfill hydraulic barrier layers.

    PubMed

    Koivula, Minna P; Kujala, Kauko; Rönkkömäki, Hannu; Mäkelä, Mauri

    2009-05-15

    The low conductivity landfill barrier layers protect the groundwater and soil by limiting the water flow through the bottom layers of the landfill material. Many materials used in hydraulic barrier layers also have sorption properties which could be used to reduce environmental risks. The adsorption of lead, chromium, copper, and arsenic to peat was studied with a batch-type test and a column test for compacted peat, both without pH adjustment in acidic conditions. Peat adsorbed all the metals well, 40000mg/kg of lead, 13000mg/kg of chromium, and 8400mg/kg of copper in the column test. Arsenic was only tested in a batch-type test, and in that peat adsorbed 60mg/kg of arsenic. The column test showed heavy metals to be adsorbed on the surface layers of the compacted peat sample, on the first centimeter of the sample. The adsorption was much greater in the column test than in the batch-type test, partly due to the different pH conditions and the buffer capacity of the peat in the column test. The liquid/solid ratio of the column experiment represented a time period of approximately 40 years in a landfill, under Finnish climate conditions. The hydraulic conductivity of the peat decreased as it was compressed, but it already met the hydraulic conductivity limits set by European Union legislation for the hydraulic barrier layer (1x10(-9)m/s at a pressure of 150kPa for a 5-m layer), with a pressure of 50kPa. The results show that peat would be an excellent material to construct compacted, low hydraulic conductivity layers with adsorption properties in, e.g. industrial waste landfills.

  5. Enhanced Electrochemical Lithium Storage Activity of LiCrO2 by Size Effect

    SciTech Connect

    Feng, G.; Li, L; Liu, J; Liu, N; Li, H; Yang, X; Huang, X; Chen, L; Nam, K; Yoon, W

    2009-01-01

    Cr8O21 was chemically lithiated using a lithium-biphenyl-dimethoxyethane solution. Lithiated Cr8O21 shows a structure in which as-formed LiCrO2 units are sandwiched between Cr2O3 superlattice layers. Chemically lithiated Cr8O21 shows a delithiation capacity of 200 mAh g-1. It means that LiCrO2 units in lithiated Cr8O21 are electrochemically active. This finding is opposite to previous reports that LiCrO2 materials have very poor Li-storage capacities. Our new result implies that LiCrO2 with extremely small domain size could show enhanced reactivity. This proposal is proved unambiguously by the fact that LiCrO2 powder materials with smaller grain size (<20 nm) show much higher capacities than LiCrO2 materials with larger grain size (>50 nm). In addition, it is found that the cation mixing is more significantly in LiCrO2 materials with smaller grain size, which seems a key factor for the storage and transport of lithium in layered Cr-based materials. The cation mixing may also explain the result that the lattice parameters of LiCrO2 do not change significantly upon lithium extraction and insertion, investigated by in situ and ex situ XRD techniques.

  6. Microstructure Effect of Intermediate Coat Layer on Corrosion Behavior of HVAF-Sprayed Bi-Layer Coatings

    NASA Astrophysics Data System (ADS)

    Sadeghimeresht, Esmaeil; Markocsan, Nicolaie; Nylén, Per

    2017-01-01

    The inherent pores and carbides of Cr3C2-NiCr coatings significantly reduce the corrosion resistance, the former by providing preferential paths for ion diffusion and the latter by forming cathodic sites in galvanic couples (between NiCr and Cr3C2). Adding a dense intermediate layer (intermediate coat layer) between the Cr3C2-NiCr coating (top coat) and substrate increases the corrosion protection of the coating if the layer acts as cathode in connection to the top coat. In the present work, NiCr, NiAl, and NiCoCrAlY layers were deposited by high-velocity air-fuel process as intermediate coat layers for the Cr3C2-NiCr top coat. Effects of coating microstructure on corrosion behavior of single- and bi-layer coatings were studied by open-circuit potential and polarization tests in 3.5 wt.% NaCl at room temperature. A zero resistance ammeter technique was used to study the galvanic corrosion of the coupled top and intermediate coat layers. Methods such as SEM and XRD were employed to characterize the as-sprayed and corroded coatings and to investigate the corrosion mechanisms. The results showed that the NiCoCrAlY coating not only presented a more positive corrosion potential ( Ecorr) than the Cr3C2-NiCr coating, but also provided a better passive layer than the single-phase NiCr and NiAl coatings.

  7. A Novel Single-Step Surface-Treatment Process for Forming Cr-Nitride Coatings on Steels

    NASA Astrophysics Data System (ADS)

    Lu, X. J.; Xiang, Z. D.

    2017-02-01

    A novel single-step surface-treatment process is demonstrated for forming Cr-nitride coatings on steels. The process was carried out at 1327 K (1100 °C) for two steel grades with differing carbon concentrations. For steel grade with 0.42 to 0.5C (wt pct), the coatings formed consisted of an outer Cr2N layer and an inner Cr-carbide layer with a Cr-enriched interdiffusion zone underneath. However, for steel grade with C ≤ 0.17 wt pct, the inner Cr-carbide layer was absent.

  8. Kinetics of borided 31CrMoV9 and 34CrAlNi7 steels

    SciTech Connect

    Efe, Goezde Celebi; Ipek, Mediha; Ozbek, Ibrahim; Bindal, Cuma

    2008-01-15

    In this study, kinetics of borides formed on the surface of 31CrMoV9 and 34CrAlNi7 steels borided in solid medium consisting of Ekabor II at 850-900-950 deg. C for 2, 4, 6 and 8 h were investigated. Scanning electron microscopy and optical microscopy examinations showed that borides formed on the surface of borided steels have columnar morphology. The borides formed in the coating layer confirmed by X-ray diffraction analysis are FeB, Fe{sub 2}B, CrB, and Cr{sub 2}B. The hardnesses of boride layers are much higher than that of matrix. It was found that depending on process temperature and time the fracture toughness of boride layers ranged from 3.93 to 4.48 MPa m{sup 1/2} for 31CrMoV9 and from 3.87 to 4.40 MPa m{sup 1/2} for 34CrAlNi7 steel. Activation energy, growth rate and growth acceleration of boride layer calculated according to these kinetic studies revealed that lower activation energy results in the fast growth rate and high growth acceleration.

  9. Reduction of Cr(VI) to Cr(III) by green rust - sulphate

    NASA Astrophysics Data System (ADS)

    Skovbjerg, L.; Stipp, S.

    2003-04-01

    Chromium is widely used in industrial processes such as leather tanning, electro-plating and as colour pigments. Unfortunately, hexavalent chromium is both toxic and very soluble so it can be a problem for groundwater resources. Given the right redox conditions, however, Cr(VI) can be reduced to trivalent chromium, which is much less soluble and is an essential trace nutrient. Fe(II), an element common in soil and sediments under anaerobic conditions, can serve as a reducing agent for Cr(VI). Green Rust (GR) is a layered Fe(II),Fe(III)-hydroxide with various anions compensating charge in the interlayers. It is very effective in reducing Cr(VI) to Cr(III). GR exists in nature and is thought to be precursor for the formation of Fe(III)-oxides and oxyhydroxides at the redox boundary. It may be that the formation of GR is a key process in the effectiveness of reactive barriers for groundwater remediation that are based on Fe(0). The purpose of this work is to investigate the mechanisms controlling Cr(VI) reduction by Green Rust, to examine the effect of Cr adsorption and incorporation on GR morphology and composition, and to define the role of parameters such as interlayer anion, initial Cr(VI) concentration and time. We are using freshly synthesised material that has not been dried to avoid structural changes that may accompany dehydration and rehydration. X-Ray Diffraction (XRD) is used to characterise mineral structural changes and Atomic Force Microscopy (AFM), to examine changes in morphology as reactions take place. By adjusting the concentration of Cr(VI), we can control the rate of surface change and we can observe the nanoscale particles directly.

  10. Superemission of Cr nanolayers

    SciTech Connect

    Khmelinskii, Igor; Makarov, Vladimir

    2016-08-15

    Highlights: • Development of novel nanodevices for superemission generation. • Development of nanolasers based on metal nanofilms. • Development of theory of nanolasers based on metal nanofilms. - Abstract: We continue our studies of metal nanolayers started earlier [1]. Presently, we investigate absorption, emission and superemission in Cr nanolayers. We provide experimental estimates of the energy density and power density of superemission of Cr nanolayers, along with estimates of the diffraction-limited light divergence. We report that the divergence of the superemission along the direction normal to the nanolayer corresponds to that of a point source, with the divergence angle of ca. 0.2 rad. Additionally, we report surprising long-range transfer of the excitation energy in Cr metal films, at macroscopic distances of 1 cm.

  11. Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.

    PubMed

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

    2011-09-28

    Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ∼1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (∼0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical

  12. Crystal structure and magnetic properties of Fe/Cr/Gd superlattices

    NASA Astrophysics Data System (ADS)

    Ryabukhina, M. V.; Kravtsov, E. A.; Naumova, L. I.; Proglyado, V. V.; Khaidukov, Yu. N.; Ustinov, V. V.

    2017-02-01

    Results of investigations of structural and magnetic properties of Fe/Cr/Gd superlattices that differ in the thicknesses of the Cr interlayer have been reported. The insertion of the Cr interlayer between Gd and Fe layers has been found to lead to structural changes in Gd layers and the appearance of an additional fcc phase in them along with the main hcp phase. The new fcc phase is uniformly distributed across the thickness of the layer and is not localized near layer boundaries or in the center of Gd layers. Polarized-neutron reflectometry was used to show that the aforementioned structural changes are accompanied by a substantial (two-fold to threefold) decrease in the average magnetization of gadolinium over a wide temperature range. Near interfaces of the Gd layer, a layer appears that is two-to-three monatomic layers thick and characterized by increased magnetic moment.

  13. Cr incorporated phase transformation in Y2O3 under ion irradiation

    PubMed Central

    Li, N.; Yadav, S. K.; Xu, Y.; Aguiar, J. A.; Baldwin, J. K.; Wang, Y. Q.; Luo, H. M.; Misra, A.; Uberuaga, B. P.

    2017-01-01

    Under irradiation, chemical species can redistribute in ways not expected from equilibrium behavior. In oxide-dispersed ferritic alloys, the phenomenon of irradiation-induced Cr redistribution at the metal/oxide interfaces has drawn recent attention. Here, the thermal and irradiation stability of the FeCr/Y2O3 interface has been systematically studied. Trilayer thin films of 90 nm Fe - 20 at.% Cr (1st layer)/100 nm Y2O3 (2nd layer)/135 nm Fe - 20 at.% Cr (3rd layer) were deposited on MgO substrates at 500 °C. After irradiation, Cr diffuses towards and enriches the FeCr/Y2O3 interface. Further, correlated with Cr redistributed into the oxide, an amorphous layer is generated at the interface. In the Y2O3 layer, the original cubic phase is observed to transform to the monoclinic phase after irradiation. Meanwhile, nanosized voids, with relatively larger size at interfaces, are also observed in the oxide layer. First-principles calculations reveal that Cr substitution of Y interstitials in Y2O3 containing excess Y interstitials is favored and the irradiation-induced monoclinic phase enhances this process. Our findings provide new insights that may aid in the development of irradiation resistant oxide-dispersed ferritic alloys. PMID:28091522

  14. Cr incorporated phase transformation in Y2O3 under ion irradiation

    NASA Astrophysics Data System (ADS)

    Li, N.; Yadav, S. K.; Xu, Y.; Aguiar, J. A.; Baldwin, J. K.; Wang, Y. Q.; Luo, H. M.; Misra, A.; Uberuaga, B. P.

    2017-01-01

    Under irradiation, chemical species can redistribute in ways not expected from equilibrium behavior. In oxide-dispersed ferritic alloys, the phenomenon of irradiation-induced Cr redistribution at the metal/oxide interfaces has drawn recent attention. Here, the thermal and irradiation stability of the FeCr/Y2O3 interface has been systematically studied. Trilayer thin films of 90 nm Fe - 20 at.% Cr (1st layer)/100 nm Y2O3 (2nd layer)/135 nm Fe - 20 at.% Cr (3rd layer) were deposited on MgO substrates at 500 °C. After irradiation, Cr diffuses towards and enriches the FeCr/Y2O3 interface. Further, correlated with Cr redistributed into the oxide, an amorphous layer is generated at the interface. In the Y2O3 layer, the original cubic phase is observed to transform to the monoclinic phase after irradiation. Meanwhile, nanosized voids, with relatively larger size at interfaces, are also observed in the oxide layer. First-principles calculations reveal that Cr substitution of Y interstitials in Y2O3 containing excess Y interstitials is favored and the irradiation-induced monoclinic phase enhances this process. Our findings provide new insights that may aid in the development of irradiation resistant oxide-dispersed ferritic alloys.

  15. Ferromagnetic resonance studies of exchange coupled ultrathin Py/Cr/Py trilayers

    NASA Astrophysics Data System (ADS)

    Topkaya, R.; Erkovan, M.; Öztürk, A.; Öztürk, O.; Aktaş, B.; Özdemir, M.

    2010-07-01

    Magnetic properties of ultrathin Py/Cr/Py trilayers have been investigated as a function of Cr spacer layer thickness by using ferromagnetic resonance (FMR) and vibrating sample magnetometer (VSM) techniques. The Cr spacer layer thickness was increased from 4 to 40 Å with 1 Å steps to determine the dependence of interlayer exchange coupling between ferromagnetic layers on the spacer layer thickness. Two strong and well resolved peaks were observed which correspond to a strong (acoustic) and weak (optic) modes of magnetization precession in the effective dc field due to the exciting external microwave field as the external dc field orientation comes close to the film normal. The separation of the two modes in the field axis depends on the thickness of Cr spacer layer. An interchange in the relative positions of the acoustic and optic modes has been observed for a particular thickness of Cr spacer layer as well. A computer program for magnetically exchange coupled N magnetic layers was written to simulate the experimental FMR spectra and to obtain the magnetic parameters of ultrathin Py/Cr/Py trilayers. FMR data have been analyzed from every aspect by using this program and interlayer exchange coupling constant was calculated for the prepared structures. It was found that the relative position of the peaks depends on the nature (sign) of the interlayer exchange coupling between ferromagnetic layers through Cr spacer layer. In Py/Cr/Py trilayers, strength of the interlayer exchange coupling constant oscillates and changes its sign with Cr spacer layer thickness with a period of about 11 Å.

  16. Segregation, precipitation, and α -α' phase separation in Fe-Cr alloys

    NASA Astrophysics Data System (ADS)

    Kuronen, A.; Granroth, S.; Heinonen, M. H.; Perälä, R. E.; Kilpi, T.; Laukkanen, P.; Lâng, J.; Dahl, J.; Punkkinen, M. P. J.; Kokko, K.; Ropo, M.; Johansson, B.; Vitos, L.

    2015-12-01

    Iron-chromium alloys, the base components of various stainless steel grades, have numerous technologically and scientifically interesting properties. However, these features are not yet sufficiently understood to allow their full exploitation in technological applications. In this work, we investigate segregation, precipitation, and phase separation in Fe-Cr systems analyzing the physical mechanisms behind the observed phenomena. To get a comprehensive picture of Fe-Cr alloys as a function of composition, temperature, and time the present investigation combines Monte Carlo simulations using semiempirical interatomic potential, first-principles total energy calculations, and experimental spectroscopy. In order to obtain a general picture of the relation of the atomic interactions and properties of Fe-Cr alloys in bulk, surface, and interface regions several complementary methods have to be used. Using the exact muffin-tin orbitals method with the coherent potential approximation (CPA-EMTO) the effective chemical potential as a function of Cr content (0-15 at. % Cr) is calculated for a surface, second atomic layer, and bulk. At ˜10 at. % Cr in the alloy the reversal of the driving force of a Cr atom to occupy either bulk or surface sites is obtained. The Cr-containing surfaces are expected when the Cr content exceeds ˜10 at. %. The second atomic layer forms about a 0.3 eV barrier for the migration of Cr atoms between the bulk and surface atomic layer. To get information on Fe-Cr in larger scales we use semiempirical methods. However, for Cr concentration regions less than 10 at. %, the ab initio (CPA-EMTO) result of the important role of the second atomic layer to the surface is not reproducible from the large-scale Monte Carlo molecular dynamics (MCMD) simulation. On the other hand, for the nominal concentration of Cr larger than 10 at. % the MCMD simulations show the precipitation of Cr into isolated pockets in bulk Fe-Cr and the existence of the upper limit of

  17. Calcium polysulfide treatment of Cr(VI)-contaminated soil.

    PubMed

    Chrysochoou, Maria; Ferreira, Daniel R; Johnston, Chad P

    2010-07-15

    Batch treatability studies for a Cr(VI)-contaminated glacial soil from a Cr plating facility were conducted using 1X and 2X the stoichiometric ratio of calcium polysulfide (CPS). The pH of the treated soil increased from 6 to 11 upon CPS addition, but progressively returned to 8-8.5 over the course of 1 year. The 1X dosage maintained a highly reducing environment up to 21 days of monitoring with the samples exposed to atmospheric oxygen, while 2X was reducing up to 180 days of curing. The EPA regulatory method for solid Cr(VI) could not reliably predict Cr(VI) in the treated solid due to ongoing reduction during the test. SPLP results showed that the CPS created an apparent Cr(VI) mobilization during the first 60 days of treatment, with subsequent decrease in soluble Cr(VI) up to 1 year of monitoring. Synchrotron micro-X-ray analyses at 60 days curing showed that Cr(VI) was predominantly bound as highly insoluble PbCrO(4) that precipitated in the interstitial pores of the soil, with very little to no Cr(VI) associated with the abundant iron oxyhydroxides. Despite its spatial accessibility and due to its low solubility, PbCrO(4) was recalcitrant to treatment, which proceeded only very slowly as judged by the SPLP data. It is concluded that, while CPS has a long residence time in the environment and is a promising reductant, in situ reduction is not an efficient treatment method for soils with highly insoluble Cr(VI) compounds, especially in surficial layers such as the one studied.

  18. Investigation of magnetic properties and electronic structure of layered-structure borides AlT{sub 2}B{sub 2} (T=Fe, Mn, Cr) and AlFe{sub 2–x}Mn{sub x}B{sub 2}

    SciTech Connect

    Chai, Ping; Stoian, Sebastian A.; Tan, Xiaoyan; Dube, Paul A.; Shatruk, Michael

    2015-04-15

    The ternary phases AlT{sub 2}B{sub 2} (T=Fe, Mn, Cr) and quaternary phases AlFe{sub 2–x}Mn{sub x}B{sub 2} have been synthesized by arc-melting and characterized by powder X-ray diffraction, magnetic measurements, Mössbauer spectroscopy, and electronic band structure calculations. All the compounds adopt the AlFe{sub 2}B{sub 2}-type structure, in which infinite zigzag chains of B atoms are connected by Fe atoms into [Fe{sub 2}B{sub 2}] slabs that alternate with layers of Al atoms along the b axis. The magnetic measurements reveal that AlFe{sub 2}B{sub 2} is a ferromagnet with T{sub C}=282 K while AlMn{sub 2}B{sub 2} and AlCr{sub 2}B{sub 2} do not show magnetic ordering in the studied temperature range of 1.8–400 K. A systematic investigation of solid solutions AlFe{sub 2−x}Mn{sub x}B{sub 2} showed a non-linear change in the structural and magnetic behavior. The ferromagnetic ordering temperature is gradually decreased as the Mn content (x) increases. The Mössbauer spectra reveal the presence of non-magnetic (NM) and ferromagnetic (FM) spectral components in all Mn-containing samples, with the amount of NM fraction increasing as the Mn content increases. While for the AlFe{sub 2−x}Mn{sub x}B{sub 2} samples with x=0.0 and 0.4 the hyperfine splitting of the FM spectral component collapses at temperatures close to the Curie temperatures determined from the magnetic measurements, for the x=1.2 and 1.6 samples the FM fraction exhibits a sizable unquenched hyperfine splitting at room temperature, a finding that is inconsistent with the observed magnetic properties. Along with the increase in the amount of the NM fraction, this observation suggests formation of Fe-rich and Mn-rich regions in the structure of the solid solutions. Quantum-chemical calculations and crystal orbital Hamilton population analysis provide a clear explanation of the distinction in properties for this series of compounds and also reveal the importance of electronic factors in modifying the

  19. The stability of DLC film on nitrided CoCrMo alloy in phosphate buffer solution

    NASA Astrophysics Data System (ADS)

    Zhang, T. F.; Liu, B.; Wu, B. J.; Liu, J.; Sun, H.; Leng, Y. X.; Huang, N.

    2014-07-01

    CoCrMo alloy is often used as the material for metal artificial joint, but metal debris and metal ions are the main concern on tissue inflammation or tissue proliferation for metal prosthesis. In this paper, nitrogen ion implantation and diamond like carbon (DLC) film composite treatment was used to reduce the wear and ion release of biomedical CoCrMo substrate. The mechanical properties and stability of N-implanted/DLC composite layer in phosphate buffer solution (PBS) was evaluated to explore the full potential of N-implanted/DLC composite layer as an artificial joint surface modification material. The results showed that the DLC film on N implanted CoCrMo (N-implanted/DLC composite layer) had the higher surface hardness and wear resistance than the DLC film on virgin CoCrMo alloy, which was resulted from the strengthen effect of the N implanted layer on CoCrMo alloy. After 30 days immersion in PBS, the structure of DLC film on virgin CoCrMo or on N implanted CoCrMo had no visible change. But the adhesion and corrosion resistance of DLC on N implanted CoCrMo (N-implanted/DLC composite layer) was weakened due to the dissolution of the N implanted layer after 30 days immersion in PBS. The adhesion reduction of N-implanted/DLC composite layer was adverse for in vivo application in long term. So researcher should be cautious to use N implanted layer as an inter-layer for increasing CoCrMo alloy load carrying capacity in vivo environment.

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

    SciTech Connect

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

    2015-10-15

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

  1. Layer Resolved Imaging of Magnetic Domain Motion in Epitaxial Heterostructures

    NASA Astrophysics Data System (ADS)

    Zohar, Sioan; Choi, Yongseong; Love, David; Mansell, Rhodri; Barnes, Crispin; Keavney, David; Rosenberg, Richard

    We use X-ray Excited Luminescence Microscopy (XELM) to image the elemental and layer resolved magnetic domain structure of an epitaxial Fe/Cr wedge/Co heterostructure in the presence of large magnetic fields. The observed magnetic domains exhibit several unique behaviors that depend on the Cr thickness (tCr) modulated interlayer exchange coupling (IEC) strength. For Cr thickness tCr?Cr?>?1.5?nm, strongly coupled parallel Co-Fe reversal and weakly coupled layer independent reversal are observed, respectively. The transition between these two reversal mechanisms for 0.34?Cr?

  2. Microstructures and mechanical properties of sputtered Cu/Cr multilayers

    SciTech Connect

    Misra, A.; Kung, H.; Mitchell, T.E.; Jervis, T.R.; Nastasi, M.

    1998-03-01

    The microstructures and mechanical properties of Cu/Cr multilayers prepared by sputtering onto {l_brace}100{r_brace} Si substrates at room temperature are presented. The films exhibit columnar grain microstructures with nanoscale grain sizes. The interfaces are planar and abrupt with no intermixing, as expected from the phase diagram. The multilayers tend to adopt a Kurdjumov-Sachs (KS) orientation relationship: {l_brace}110{r_brace}Cr // {l_brace}111{r_brace}Cu, <111>Cr // <110>Cu. The hardness of the multilayered structures, as measured by nanoindentation, increase with decreasing layer thickness for layer thicknesses ranging from 200 nm to 50 nm, whereas for lower thicknesses the hardness of the multilayers is independent of the layer thickness. Dislocation-based models are used to interpret the variation of hardness with layer periodicity. The possible effects of factors such as grain size within the layers, density and composition of films and residual stress in the multilayers are highlighted. Comparisons are made to the mechanical properties of sputtered polycrystalline Cu/Nb multilayers which, like Cu/Cr, exhibit sharp fcc/bcc interfaces with no intermixing and a KS orientation relationship, but have a small shear modulus mismatch.

  3. Molecular-beam epitaxy of CrSi2 on Si(111)

    NASA Technical Reports Server (NTRS)

    Fathauer, R. W.; Grunthaner, P. J.; Lin, T. L.; Chang, K. T.; Mazur, J. H.

    1988-01-01

    The growth of CrSi2 on Si(111) in a commercial MBE system with a base pressure in the low 10 to the -11th torr range is reported. CrSi2 layers grown on Si(111) exhibit a strong tendency to form islands. Two particular epitaxial relationships are identified. Thick (210 nm) layers have been grown by four different techniques, with best results obtained by codepositing Cr and Si at elevated temperature. The grain size is observed to increase with substrate temperature, reaching 1-2 microns in a layer deposited at 825 C.

  4. Backbending in 50Cr

    NASA Astrophysics Data System (ADS)

    Martínez-Pinedo, G.; Poves, A.; Robledo, L. M.; Caurier, E.; Nowacki, F.; Retamosa, J.; Zuker, A.

    1996-11-01

    The collective yrast band and the high spin states of the nucleus 50Cr are studied using the spherical shell model and the cranked Hartree-Fock-Bogoliubov method. The two descriptions lead to nearly the same values for the relevant observables. A first backbending is predicted at I=10ħ corresponding to a collective to noncollective transition. At J=16ħ a second backbending occurs, associated to a configuration change that can also be interpreted as a spherical to triaxial transition.

  5. CR reliability testing

    NASA Astrophysics Data System (ADS)

    Honeyman-Buck, Janice C.; Rill, Lynn; Frost, Meryll M.; Staab, Edward V.

    1998-07-01

    The purpose of this work was to develop a method for systematically testing the reliability of a CR system under realistic daily loads in a non-clinical environment prior to its clinical adoption. Once digital imaging replaces film, it will be very difficult to revert back should the digital system become unreliable. Prior to the beginning of the test, a formal evaluation was performed to set the benchmarks for performance and functionality. A formal protocol was established that included all the 62 imaging plates in the inventory for each 24-hour period in the study. Imaging plates were exposed using different combinations of collimation, orientation, and SID. Anthropomorphic phantoms were used to acquire images of different sizes. Each combination was chosen randomly to simulate the differences that could occur in clinical practice. The tests were performed over a wide range of times with batches of plates processed to simulate the temporal constraints required by the nature of portable radiographs taken in the Intensive Care Unit (ICU). Current patient demographics were used for the test studies so automatic routing algorithms could be tested. During the test, only three minor reliability problems occurred, two of which were not directly related to the CR unit. One plate was discovered to cause a segmentation error that essentially reduced the image to only black and white with no gray levels. This plate was removed from the inventory to be replaced. Another problem was a PACS routing problem that occurred when the DICOM server with which the CR was communicating had a problem with disk space. The final problem was a network printing failure to the laser cameras. Although the units passed the reliability test, problems with interfacing to workstations were discovered. The two issues that were identified were the interpretation of what constitutes a study for CR and the construction of the look-up table for a proper gray scale display.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  7. TI--CR--AL--O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2000-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  8. Hot Corrosion Performance of AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa Coatings Deposited by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Tao, Chong; Wang, Lei; Cheng, Nailiang; Hu, Hengfa; Liu, Yang; Song, Xiu

    2016-04-01

    AlO-CrO/NiCoCrAlYTa and AlO/NiCoCrAlYTa coatings were deposited on 316L stainless steel substrate using atmospheric plasma spraying, respectively, in order to improve the oxidation and corrosion resistance. The hot corrosion performance of the coatings at 700 and 900 °C were studied, and the detailed microstructures and phase composition of the coatings were analyzed using x-ray diffraction, scanning electron microscope with energy dispersive spectrometer, and transmission electron microscope. The results show that both coatings are structurally featured by slatted layers, consisting of amorphous phase, Cr2O3, Ni3Al, and Al2O3. The hot corrosion resistance of AlO-CrO/NiCoCrAlYTa coating is better than that of AlO/NiCoCrAlYTa coating. This improvement is attributed to lower porosity and more compact Cr2O3 in AlO-CrO/NiCoCrAlYTa coating which performs better than Al2O3 in blocking further inward progress of corrosion and oxidization.

  9. Layer-by-layer co-immobilization of soluble complement receptor 1 and heparin on islets.

    PubMed

    Luan, Nguyen Minh; Teramura, Yuji; Iwata, Hiroo

    2011-09-01

    Early graft loss due to instant blood-mediated inflammatory reactions (IBMIRs) is a major obstacle of clinical islet transplantation; inhibition of blood coagulation and complement activation is necessary to inhibit IBMIRs. Here, human soluble form complement receptor 1 (sCR1) and heparin were co-immobilized onto the surfaces of islet cells. sCR1 molecules carrying thiol groups were immobilized through maleimide-poly(ethylene glycol)-phospholipids anchored in the lipid bilayers of islet cells. Heparin was immobilized on the sCR1 layer via the affinity between sCR1 and heparin, and additional layers of sCR1 and heparin were formed layer-by-layer. The sCR1 and heparin molecules in these layers maintained anti-complement activation and anti-coagulation activities, respectively. This promising method could be employed to reduce the number of islet cells required to reverse hyperglycemia and prolong graft survival in both allo- and xeno-islet transplantation.

  10. Atomistic investigation of Cr influence on primary radiation damage in Fe-12 at.% Cr grain boundaries

    NASA Astrophysics Data System (ADS)

    Esfandiarpour, A.; Feghhi, S. A. H.; Arjhangmehr, A.

    2016-08-01

    In this paper, we investigate the influence of Cr on the primary radiation damage in Fe-12 at.% Cr with different atomic grain boundaries (GBs). Four different GB structures, two twists and two symmetric tilt boundaries are selected as the model structures. The primary radiation damage near each GB in α-Fe and Fe-12 at.% Cr is simulated using Molecular Dynamics for 9 keV primary knock-on atoms with velocity vectors perpendicular to the GB plane. In agreement with previous works, the results indicate that the atomic GBs are biased toward interstitials and due to the reduction of ‘in-cascade’ interstitial-vacancy annihilation rates, vacancies accumulate in the bulk grains. The minimum defect production occurs when the overlap between cascade center and GB plane is maximum; in contrast, the number of residual defects in the bulk (vacancies and interstitials) increases when the overlap decreases. Moreover, we find that the presence of Cr hardly affects the number of residual defects in the grain interiors, and causes a Cr-enrichment in the surviving self-interstitial atoms in bulk during relaxation of the primary cascades—also in agreement with previous studies. Further, in order to study the effect of 12 at.% Cr on the energetic and kinetic properties of vacancies near the atomic GBs, we calculate formation energies and diffusion barriers of defects using Molecular Static and climbing-Nudged Elastic Band methods. The results reveal that the vacancies energetically and kinetically tend to form and cluster around the GB plane due to the substantial reduction of their formation energies and migration barriers in layers close to the GB center and are immobile on the simulated time frame (~ps).

  11. Transient Oxidation of a γ-Ni-28Cr-11Al Alloy

    SciTech Connect

    Hu, L; Hovis, D B; Heuer, A H

    2012-04-02

    γ-NiCrAl alloys with relatively low Al contents tend to form a layered oxide scale during the early stages of oxidation, rather than an exclusive α-Al2O3 scale, the so-called 'thermally grown oxide' (TGO). A layered oxide scale was established on a model γ-Ni-28Cr-11Al (at.%) alloy after isothermal oxidation for several minutes at 1100 °C. The layered scale consisted of an NiO layer at the oxide/gas interface, an inner Cr2O3 layer, and an α-Al2O3 layer at the oxide/alloy interface. The evolution of such an NiO/Cr2O3/Al2O3 layered structure on this alloy differs from that proposed in earlier work. During heating, a Cr2O3 outer layer and a discontinuous inner layer of Al2O3 initially formed, with metallic Ni particles dispersed between the two layers. A rapid transformation occurred in the scale shortly after the sample reached maximum temperature (1100°C), when two (possibly coupled) phenomena occurred: (i) the inner transition alumina transformed to α-Al2O3, and (ii) Ni particles oxidized to form the outer NiO layer. Subsequently, NiO reacted with Cr2O3 and Al2O3 to form spinel. Continued growth of the oxide scale and development of the TGO was dominated by growth of the inner α-Al2O3 layer.

  12. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    NASA Astrophysics Data System (ADS)

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-08-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content.

  13. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    PubMed Central

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-01-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content. PMID:26269034

  14. Surface modification to improve fireside corrosion resistance of Fe-Cr ferritic steels

    DOEpatents

    Park, Jong-Hee; Natesan, Krishnamurti; Rink, David L.

    2010-03-16

    An article of manufacture and a method for providing an Fe--Cr ferritic steel article of manufacture having a surface layer modification for corrosion resistance. Fe--Cr ferritic steels can be modified to enhance their corrosion resistance to liquid coal ash and other chemical environments, which have chlorides or sulfates containing active species. The steel is modified to form an aluminide/silicide passivating layer to reduce such corrosion.

  15. Recent progress in the study of protective rust-layer formation on weathering steel

    SciTech Connect

    Yamashita, M.; Misawa, T.

    1998-12-31

    Latest understanding of protective rust layer on weathering steel and its application for structural steels is discussed. Phase transformation of the weathering steel rust layer during long-time exposure brings {alpha}-(Fe{sub 1{minus}x},Cr{sub x})OOH, Cr-substituted goethite, as the final protective rust layer. It is said that the Cr content in the Cr-substituted goethite layer increases gradiently with reaching the rust-steel interface. This increase in the Cr content gives densely packed fine crystal structure end cation selective ability, which impedes the penetration of aggressive corrosives including anions such as Cl{sup {minus}} and SO{sub 4}{sup 2{minus}}. Quite recently, new surface-treatment technique employing Cr{sub 2}(SO{sub 4}){sub 3}, was proposed, which provides a possibility for obtaining the protective rust layer in a relatively short period even in the severe environment such as coastal region.

  16. Intermediate coating layer for high temperature rubbing seals for rotary regenerators

    DOEpatents

    Schienle, James L.; Strangman, Thomas E.

    1995-01-01

    A metallic regenerator seal is provided having multi-layer coating comprising a NiCrAlY bond layer, a yttria stabilized zirconia (YSZ) intermediate layer, and a ceramic high temperature solid lubricant surface layer comprising zinc oxide, calcium fluoride, and tin oxide. Because of the YSZ intermediate layer, the coating is thermodynamically stable and resists swelling at high temperatures.

  17. Molecular-Beam Epitaxy Of CrSi2 on Si(111)

    NASA Technical Reports Server (NTRS)

    Fathauer, Robert W.; Grunthaner, Paula J.; Lin, True-Lon; Jamieson, David N.; Mazur, Jurek H.

    1989-01-01

    Crystalline layers grown in commercial apparatus. Experiments show CrSi2 grown on (111) face of single-crystal Si substrate by molecular-beam epitaxy. Epitaxial CrSi2 produced thus far not in desired single-crystal form. Because CrSi2 semiconductor with band gap of 0.3 eV, experimental process potential for monolitic integration of microelectronic devices based on CrSi2 (e.g., infrared detectors) with signal-processing circuitry based on Si.

  18. Oxygen-induced immediate onset of the antiferromagnetic stacking in thin Cr films on Fe(001)

    SciTech Connect

    Berti, Giulia Brambilla, Alberto; Calloni, Alberto; Bussetti, Gianlorenzo; Finazzi, Marco; Duò, Lamberto; Ciccacci, Franco

    2015-04-20

    We investigated the magnetic coupling of ultra-thin Cr films grown at 600 K on a Fe(001)-p(1 × 1)O substrate by means of spin-polarized photoemission spectroscopy. Our findings show that the expected antiferromagnetic stacking of the magnetization in Cr(001) layers occurs right from the first atomic layer at the Cr/Fe interface. This is at variance with all previous observations in similar systems, prepared in oxygen-free conditions, which always reported on a delayed onset of the magnetic oscillations due to the occurrence of significant chemical alloying at the interface, which is substantially absent in our preparation.

  19. Characterization of Fe–Cr alloy metallic interconnects coated with LSMO using the aerosol deposition process

    SciTech Connect

    Huang, Jian-Jia; Fu, Yen-Pei; Wang, Jian-Yih; Cheng, Yung-Neng; Lee, Shyong; Hsu, Jin-Cherng

    2014-03-01

    Graphical abstract: - Highlights: • Lanthanum strontium manganite (LSMO) as the protective layer for metallic interconnects was successfully prepared by aerosol deposition method (AD). • The microstructure, electrical resistance and composition for LSMO-coated Fe–Cr alloys undergoing high temperature, long-hour oxidation were investigated. • The denser protective layer prepared by AD might effectively prohibit the growth of oxidized scale after long time running at 800 °C in air. - Abstract: A Fe–Cr alloy, used for metallic interconnects, was coated with a protective layer of lanthanum strontium manganite (LSMO) using the aerosol deposition method (AD). The effects of the LSMO protective layer, which was coated on the Fe–Cr interconnects using AD, on the area specific resistance (ASR) during high temperature oxidation and the Cr evaporation behaviors were systematically investigated in this paper. The microstructures, morphologies, and compositions of the oxidized scales that appeared on the LSMO-coated Fe–Cr alloy after annealing at 800 °C for 750 h in air were examined using SEM equipped with EDS. The EPMA mapping of the LSMO-coated Fe–Cr interconnects undergoing long term, high-temperature oxidation was used to explain the formation layers of the oxidized scale, which consists of (Mn,Cr){sub 3}O{sub 4} and Cr{sub 2}O{sub 3} layers. Moreover, the experimental results revealed that the AD process is a potential method for preparing denser protective layers with highly desirable electrical properties for metallic interconnects.

  20. Exchange bias effect in NiMnSb/CrN heterostructures deposited by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Sharma Akkera, Harish; Barman, Rahul; Kaur, Navjot; Choudhary, Nitin; Kaur, Davinder

    2013-05-01

    Exchange bias has been studied in various Ni50Mn36.8Sb13.2/CrN heterostructures with different CrN thicknesses (15 nm-80 nm), grown on Si (100) substrate using magnetron sputtering. The shift in hysteresis loop up to 51 Oe from the origin was observed at 10 K for Ni-Mn-Sb film without CrN layer. On the other hand, a significant shifting of hysteresis loop was observed with antiferromagnetic (AFM) CrN layer in Ni50Mn36.8Sb13.2/CrN heterostructure. The exchange coupled 140 nm Ni50Mn36.8Sb13.2/35 nm CrN heterostructure exhibited a relatively large exchange coupling field of 148 Oe at 10 K compared to other films, which may be related to uncompensated and pinned AFM spins at FM-AFM interface and different AFM domain structures for different thicknesses of CrN layer. Further nanoindentation measurements revealed the higher values of hardness and elastic modulus of about 12.7 ± 0.38 GPa and 179.83 ± 1.24 GPa in Ni50Mn36.8Sb13.2/CrN heterostructures making them promising candidate for various multifunctional MEMS devices.

  1. Oxidation behavior of TD-NiCr in a dynamic high temperature environment

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.; Young, C. T.; Herring, H. W.

    1974-01-01

    The oxidation behavior of TD-NiCr has been studied in static and high-speed flowing air environments at 1100 and 1200 C. It has been found that the stable oxide morphologies formed on the specimens exposed to the static and dynamic environments were markedly different. The faceted crystal morphology characteristic of static oxidation was found to be unstable under high-temperature, high-speed flow conditions and was quickly replaced by a porous NiO 'mushroom' type structure. Also, it was found that the rate of formation of CrO3 from Cr2O3 was greatly enhanced by high gas velocity conditions. The stability of Cr2-O3 was found to be greatly improved by the presence of an outer NiO layer, even though the NiO layer was very porous. An oxidation model is proposed to explain the observed microstructures and overall oxidation behavior of TD-NiCr alloys.

  2. Formation of Cr2O3 Diffusion Barrier Between Cr-Contained Stainless Steel and Cold-Sprayed Ni Coatings at High Temperature

    NASA Astrophysics Data System (ADS)

    Xu, Ya-Xin; Luo, Xiao-Tao; Li, Cheng-Xin; Yang, Guan-Jun; Li, Chang-Jiu

    2016-02-01

    A novel approach to prepare a coating system containing an in situ grown Cr2O3 diffusion barrier between a nickel top layer and 310SS was reported. Cold spraying was employed to deposit Ni(O) interlayer and top nickel coating on the Cr-contained stainless steel substrate. Ni(O) feedstock was prepared by mechanical alloying of pure nickel powders in ambient atmosphere, acting as an oxygen provider. The post-spray annealing was adopted to grow in situ Cr2O3 layer between the substrate and nickel coating. The results revealed that the diffusible oxygen can be introduced into nickel powders by mechanical alloying. The oxygen content increases to 3.25 wt.% with the increase of the ball milling duration to 8 h, while Ni(O) powders maintain a single phase of Ni. By annealing the sample in Ar atmosphere at 900 °C, a continuous Cr2O3 layer of 1-2 μm thick at the interface between 310SS and cold-sprayed Ni coating is formed. The diffusion barrier effect evaluation by thermal exposure at 750 °C shows that the Cr2O3 oxide layer effectively suppresses the outward diffusion of Fe and Cr in the substrate effectively.

  3. Effect of CrO3 Sealing Time on Anodized A12024-T3

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  4. Chromium oxide as a metal diffusion barrier layer: An x-ray absorption fine structure spectroscopy study

    NASA Astrophysics Data System (ADS)

    Ahamad Mohiddon, Md.; Lakshun Naidu, K.; Ghanashyam Krishna, M.; Dalba, G.; Ahmed, S. I.; Rocca, F.

    2014-01-01

    The interaction at the interface between chromium and amorphous Silicon (a-Si) films in the presence of a sandwich layer of chromium oxide is investigated using X-ray absorption fine structure (XAFS) spectroscopy. The oxidized interface was created, in situ, prior to the deposition of a 400 nm tick a-Si layer over a 50 nm tick Cr layer. The entire stack of substrate/metallic Cr/Cr2O3/a-Si was then annealed at temperatures from 300 up to 700 °C. Analysis of the near edge and extended regions of each XAFS spectrum shows that only a small fraction of Cr is able to diffuse through the oxide layer up to 500 °C, while the remaining fraction is buried under the oxide layer in the form of metallic Cr. At higher temperatures, diffusion through the oxide layer is enhanced and the diffused metallic Cr reacts with a-Si to form CrSi2. At 700 °C, the film contains Cr2O3 and CrSi2 without evidence of unreacted metallic Cr. The activation energy and diffusion coefficient of Cr are quantitatively determined in the two temperature regions, one where the oxide acts as diffusion barrier and another where it is transparent to Cr diffusion. It is thus demonstrated that chromium oxide can be used as a diffusion barrier to prevent metal diffusion into a-Si.

  5. Layer resolved magnetic domain imaging of epitaxial heterostructures in large applied magnetic fields

    NASA Astrophysics Data System (ADS)

    Zohar, S.; Choi, Y.; Love, D. M.; Mansell, R.; Barnes, C. H. W.; Keavney, D. J.; Rosenberg, R. A.

    2015-02-01

    We use X-ray Excited Luminescence Microscopy to investigate the elemental and layer resolved magnetic reversal in an interlayer exchange coupled (IEC) epitaxial Fe/Cr wedge/Co heterostructure. The transition from strongly coupled parallel Co-Fe reversal for Cr thickness tCr < 0.34 nm to weakly coupled layer independent reversal for tCr > 1.5 nm is punctuated at 0.34 < tCr < 1.5 nm by a combination of IEC guided domain wall motion and stationary zig zag domain walls. Domain walls nucleated at switching field minima are guided by IEC spatial gradients and collapse at switching field maxima.

  6. Redox and complexation chemistry of the Cr(VI)/Cr(V)/Cr(IV)-D-glucuronic acid system.

    PubMed

    González, Juan Carlos; García, Silvia; Bellú, Sebastián; Salas Peregrín, Juan Manuel; Atria, Ana María; Sala, Luis Federico; Signorella, Sandra

    2010-03-07

    When excess uronic acid over Cr(VI) is used, the oxidation of D-glucuronic acid (Glucur) by Cr(VI) yields D-glucaric acid (Glucar) and Cr(III) as final products. The redox reaction involves the formation of intermediate Cr(IV) and Cr(V) species, with Cr(VI) and Cr(V) reacting with Glucur at comparable rates. The rate of disappearance of Cr(VI), and Cr(V) increases with [H(+)] and [substrate]. The experimental results indicated that Cr(IV) is a very reactive intermediate since its disappearance rate is much faster than Cr(VI)/Cr(V) and decreases when [H(+)] rises. Even at high [H(+)] Cr(IV) intermediate was involved in fast steps and does not accumulate in the reaction. Kinetic studies show that the redox reaction between Glucur and Cr(VI) proceeds through a mechanism combining one- and two-electron pathways for the reduction of intermediate Cr(IV) by the organic substrate: Cr(VI) --> Cr(IV) --> Cr(II) and Cr(VI) --> Cr(IV) --> Cr(III). The mechanism is supported by the observation of free radicals, CrO(2)(2+) (superoxoCr(III) ion) and Cr(V) as reaction intermediates. The EPR spectra show that five-co-ordinate oxo-Cr(V) bischelates are formed at pH < or = 4 with the uronic acid bound to Cr(V) through the carboxylate and the alpha-OH group of the furanose form. Five-co-ordinated oxo-Cr(V) monochelates are observed as minor species in addition to the major five-co-ordinated oxo-Cr(V) bischelates. At pH 7.5 the EPR spectra show the formation of a Cr(V) complex where the cis-diol groups of Glucur participate in the bonding to Cr(V). In vitro, our studies on the chemistry of Cr(V) complexes can provide information on the nature of the species that are likely to be stabilized in vivo. In particular, the EPR pattern of Glucur-Cr(V) species can be used as a finger print to identify Cr(V) complexes formed in biological systems.

  7. The effect of Be and Cr electrode deposition rate on the performance of MIS solar cells

    NASA Astrophysics Data System (ADS)

    Moharram, A. H.; Panayotatos, P.; Yeh, J. L.; Lalevic, B.

    1985-07-01

    An experimental study has been performed on MIS solar cells with Be, Cr and layered Cr-Be electrodes on single crystal Si, Wacker and Monsanto poly-Si substrates. Electrical characterization in the dark and under illumination was correlated to X-ray and Auger spectroscopy results. It was found that the electrode deposition rate directly affects the oxygen content of the electrodes for all metal-substrate configurations. This oxygen is believed to originate from the deposition ambient as well as from the SiO2 layer. In the case of cells with Cr and layered Cr-Be electrodes oxygen acts to reduce the electrode work function (thus increasing the open-circuit voltage) in direct proportion to the relative content of oxygen to chromium.

  8. Cr/B4C multilayer mirrors: Study of interfaces and X-ray reflectance

    DOE PAGES

    Burcklen, C.; Soufli, R.; Gullikson, E.; ...

    2016-03-24

    Here, we present an experimental study of the effect of layer interfaces on the x-ray reflectance in Cr/B4C multilayer interference coatings with layer thicknesses ranging from 0.7 nm to 5.4 nm. The multilayers were deposited by magnetron sputtering and by ion beam sputtering. Grazing incidence x-ray reflectometry, soft x-ray reflectometry, and transmission electron microscopy reveal asymmetric multilayer structures with a larger B4C-on-Cr interface, which we modeled with a 1–1.5 nm thick interfacial layer. Reflectance measurements in the vicinity of the Cr L2,3 absorption edge demonstrate fine structure that is not predicted by simulations using the currently tabulated refractive index (opticalmore » constants) values for Cr.« less

  9. Adhesion property and high-temperature oxidation behavior of Cr-coated Zircaloy-4 cladding tube prepared by 3D laser coating

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    A 3D laser coating technology using Cr powder was developed for Zr-based alloys considering parameters such as: the laser beam power, inert gas flow, cooling of Zr-based alloys, and Cr powder control. This technology was then applied to Zr cladding tube samples to study the effect of Cr coating on the high-temperature oxidation of Zr-based alloys in a steam environment of 1200 °C for 2000s. It was revealed that the oxide layer thickness formed on the Cr-coated tube surface was about 25-times lower than that formed on a Zircaloy-4 tube surface. In addition, both the ring compression and the tensile tests were performed to evaluate the adhesion properties of the Cr-coated sample. Although some cracks were formed on the Cr-coated layer, the Cr-coated layer had not peeled off after the two tests.

  10. Hot Corrosion Behavior of Stainless Steel with Al-Si/Al-Si-Cr Coating

    NASA Astrophysics Data System (ADS)

    Fu, Guangyan; Wu, Yongzhao; Liu, Qun; Li, Rongguang; Su, Yong

    2017-03-01

    The 1Cr18Ni9Ti stainless steel with Al-Si/Al-Si-Cr coatings is prepared by slurry process and vacuum diffusion, and the hot corrosion behavior of the stainless steel with/without the coatings is studied under the condition of Na2SO4 film at 950 °C in air. Results show that the corrosion kinetics of stainless steel, the stainless steel with Al-Si coating and the stainless steel with Al-Si-Cr coating follow parabolic laws in several segments. After 24 h corrosion, the sequence of the mass gain for the three alloys is the stainless steel with Al-Si-Cr coating < the stainless steel with Al-Si coating < the stainless steel without any coating. The corrosion products of the three alloys are layered. Thereinto, the corrosion products of stainless steel without coating are divided into two layers, where the outside layer contains a composite of Fe2O3 and FeO, and the inner layer is Cr2O3. The corrosion products of the stainless steel with Al-Si coating are also divided into two layers, of which the outside layer mainly consists of Cr2O3, and the inner layer is mainly SiO2. The corrosion film of the stainless steel with Al-Si-Cr coating is thin and dense, which combines well with substrate. Thereinto, the outside layer is mainly Cr2O3, and the inside layer is Al2O3. In the matrix of all of the three alloys, there exist small amount of sulfides. Continuous and protective films of Cr2O3, SiO2 and Al2O3 form on the surface of the stainless steel with Al-Si and Al-Si-Cr coatings, which prevent further oxidation or sulfide corrosion of matrix metals, and this is the main reason for the much smaller mass gain of the two alloys than that of the stainless steel without any coatings in the 24 h hot corrosion process.

  11. Ferromagnetic resonance investigation of Py/Cr multilayer system

    NASA Astrophysics Data System (ADS)

    Erkovan, M.; Öztürk, S. T.; Topkaya, R.; Özdemir, M.; Aktaş, B.; Öztürk, O.

    2011-07-01

    The multilayer thin films consisting of alternating stacks of ferromagnetic Permalloy (Py) and ultra thin non-magnetic (sub-nanometer) spacer (Cr) layers have been investigated by using ferromagnetic resonance (FMR) and dc magnetization measurement techniques. The non-magnetic spacer layer thickness changes from 0.5 Å to 2.5 Å by 0.5 Å steps. Polycrystalline composite metallic films were grown on Si substrate by usual magnetron sputtering techniques at UHV conditions. The magnetic hysteresis curves were recorded by conventional dc magnetization. The ac and dc magnetic properties were investigated by using ferromagnetic resonance. FMR measurements were carried out for different directions of external dc magnetic field in order to search magnetic anisotropy. Two strong and well defined peaks (acoustic and optic mode) were observed in FMR spectrum as the magnetic field direction approaches to the film normal. Their positions and relative intensities helped to characterize coupling species. The magnetic parameters have been deduced by using a theoretical model. It has been found that the exchange coupling parameter between ferromagnetic layers through non-magnetic Cr spacer is ferromagnetic in nature and strongly decreases with increasing spacer layer thickness. The magnetic anisotropy parameters strictly depend on magnetic layer thickness while the dc magnetization is almost constant for a few nanometer thick Permalloy as well. We observed only ferromagnetic coupling between ferromagnetic layers in all samples.

  12. Growth of InN nanorods prepared by plasma-assisted molecular beam epitaxy with varying Cr thicknesses

    NASA Astrophysics Data System (ADS)

    Liu, K. W.; Young, S. J.; Chang, S. J.; Hsueh, T. H.; Chen, Y. Z.; Chen, K. J.; Hung, H.; Wang, S. M.; Wu, Y. L.

    2012-05-01

    This study investigates how the thickness of Cr deposited on the Si substrate after the nitridation process influences the AIN buffer layer and the InN nanorods. Atomic force microscopy results reveal that different thicknesses of Cr form varying sizes of CrN nanoislands. The results of scanning electron microscopy and X-ray diffraction show that a Cr deposition thickness of 10 nm results in CrN nanoislands after the nitridation process, improving the quality and density of InN nanorods. A Cr layer that was too thick led to polycrystalline InN growth. The results of transmission electron microscopy indicate a baseball bat-like InN nanorod growth mechanism.

  13. Repassivation of 13% Cr steel dependent on brine pH

    SciTech Connect

    Skogsberg, J.W.; Walker, M.L.

    2000-02-01

    A joint laboratory project, involving an oil production and oil well service company, investigated repassivation of martensitic 13% Cr steel. The rate at which this alloy is repassivated after losing its protective passive oxide layer to hydrochloric acid (HCI) depended on the pH of the spent acid returns. Test samples of 13% Cr cut from oilfield tubing were subjected to a fluid sequence of (1) initial brine, (2) HCI, (3) spent acid, and (4) final brine. In 9 days, the samples regained their passive oxide layers. When spent acid was taken out of the fluid sequence, the samples regained passive oxide layers in 3 days.

  14. Nonmixing layers

    NASA Astrophysics Data System (ADS)

    Gaillard, Pierre; Giovangigli, Vincent; Matuszewski, Lionel

    2016-12-01

    We investigate the impact of nonideal diffusion on the structure of supercritical cryogenic binary mixing layers. This situation is typical of liquid fuel injection in high-pressure rocket engines. Nonideal diffusion has a dramatic impact in the neighborhood of chemical thermodynamic stability limits where the components become quasi-immiscible and ultimately form a nonmixing layer. Numerical simulations are performed for mixing layers of H2 and N2 at a pressure of 100 atm and temperature around 120-150 K near chemical thermodynamic stability limits.

  15. Threshold photodissociation of Cr+2

    NASA Astrophysics Data System (ADS)

    Lessen, D. E.; Asher, R. L.; Brucat, P. J.

    1991-08-01

    A one-photon photodissociation threshold for supersonically cooled Cr+2 is determined to be 2.13 eV. This threshold provides a strict upper limit to the adiabatic binding energy of the ground state of chromium dimer cation if the initial internal energy of the parent ion may be neglected. From the difference in the IPs of chromium atom and dimer, an upper limit to the dissociation of Cr2 is placed at 1.77 eV.

  16. Spallanzani Layers

    NASA Technical Reports Server (NTRS)

    2006-01-01

    31 March 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a layered, light-toned mesa among other layered materials exposed in a mound that covers much of the floor of Spallanzani Crater.

    Location near: 58.3oS, 273.9oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    The new metastable compound Cr1+xSb with x up to 0.6 has been prepared via a thin film approach using modulated elemental reactants and investigated by in-situ X-ray reflectivity, X-ray diffraction, differential scanning calorimetry, energy dispersive X-ray analysis as well as transmission electron microscopy and atomic force microscopy. The new Cr-rich antimonide crystallizes in a structure related to the Ni2In-type structure, where the crystallographic position (1/3, 2/3, 3/4) is partially occupied by excess Cr. The elemental layers of the pristine material interdiffused significantly before Cr1+xSb crystallized. A change in the activation energy was observed for the diffusion process when crystal growth starts. First-principles electronic structure calculations provide insight into the structural stability, magnetic properties and resistivity of Cr1+xSb. 2 interdiffused amorphous film 3 metastable crystalline phase 4 thermodynamic stable phase (and by-product)

  18. Inelastic neutron scattering of the itinerant magnets Cr2Te3 and tr-Cr5Te8

    NASA Astrophysics Data System (ADS)

    Aczel, Adam; Granroth, Garrett; Ghimire, Nirmal; McGuire, Michael; Mandrus, David; Nagler, Steve

    2012-02-01

    Itinerant magnets based on transition metal chalcogenide compounds are of current interest, in part due to their relationship to the parent compounds of Fe-based superconductors. Two particularly interesting systems in this family are the chromium tellurides Cr2Te3 and trigonal (tr) Cr5Te8. These materials crystallize in layered structures with alternating partially and fully-occupied planes of Cr atoms stacked along the c-axis. Magnetization measurements along different crystallographic directions show a net ferromagnetic response and large magnetic anisotropy. In addition, the saturation moments are smaller than predicted by an ionic model; consistent with itinerant behavior. Previous neutron diffraction results for Cr2Te3 revealed an ordered moment of < 0.2 μB in the partially-occupied planes. We examined the magnetic excitations in these materials by powder neutron spectroscopy measurements using the SEQUOIA instrument at the SNS. We find similar moment sizes for the magnetic Cr atoms of both systems. However, despite their similar crystal structures, ordered moment sizes, and chemical compositions, their magnetic excitation spectra are strikingly different. We compare our data to the predictions of various models in an effort to determine the relevant exchange parameters, put constraints on their magnitudes, and understand the differences between the inelastic magnetic spectra. We find that exchange along the c-direction is critical to explain our data.

  19. Film Thickness Influences on the Thermoelectric Properties of NiCr/NiSi Thin Film Thermocouples

    NASA Astrophysics Data System (ADS)

    Chen, Y. Z.; Jiang, H. C.; Zhang, W. L.; Liu, X. Z.; Jiang, S. W.

    2013-06-01

    NiCr/NiSi thin film thermocouples (TFTCs) with a multi-layer structure were fabricated on Ni-based superalloy substrates (95 mm × 35 mm × 2 mm) by magnetron sputtering and electron beam evaporation. The five-layer structure is composed of NiCrAlY buffer layer (2 μm), thermally grown Al2O3 bond layer (200 nm), Al2O3 insulating layer (10 μm), NiCr/NiSi TFTCs (1 μm), and Al2O3 protective layer (500 nm). Influences of thermocouple layer thickness on thermoelectric properties were investigated. Seebeck coefficient of the samples with the increase in thermocouple layer thickness from 0.5 μm to 1 μm increased from 27.8 μV/°C to 33.8 μV/°C, but exhibited almost no change with further increase in thermocouple layer thickness from 1 μm to 2 μm. Dependence on temperature of the thermal electromotive force of the samples almost followed standard thermocouple characteristic curves when the thickness of the thermocouple layer was 1 μm and 2 μm. Sensitive coefficient K of the samples increased greatly with the increase in thickness of the thermocouple layer from 0.5 μm to 1 μm, but decreased insignificantly with the increase in thermocouple layer thickness from 1 μm to 2 μm, and continuously decreased with the increase in temperature. The sensitive coefficient and the stability of NiCr/NiSi TFTCs were both improved after annealing at 600°C.

  20. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms.

    PubMed

    Cui, You-Wei; Li, Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM), followed the pseudo-second-order model, with a rapid adsorption rate. Cr(VI) adsorption was positively associated with the absorbent dose, pH, temperature, and initial Cr(VI) concentration; coexisting anions had little impact. The maximum Cr(VI) adsorption capacity was 17.35 mg/g. Cr(VI) adsorption on La-RM was a mono-layer adsorption pattern, following the Langmuir isotherm model. Thermodynamic parameters showed the adsorption was spontaneous and endothermic. The adsorption of Cr(VI) on La-RM occurred as a result of LaOCl formation on the RM surface, which in turn further reacted with Cr(VI) in the wastewater. This study highlighted a method for converting industrial waste into a valuable material for wastewater treatment. The novel absorbent could be used as a potential adsorbent for treating Cr(VI)-contaminating wastewater, due to its cost-effectiveness and high adsorption capability.

  1. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms

    PubMed Central

    Cui, You-Wei; Li, Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    2016-01-01

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM), followed the pseudo-second-order model, with a rapid adsorption rate. Cr(VI) adsorption was positively associated with the absorbent dose, pH, temperature, and initial Cr(VI) concentration; coexisting anions had little impact. The maximum Cr(VI) adsorption capacity was 17.35 mg/g. Cr(VI) adsorption on La-RM was a mono-layer adsorption pattern, following the Langmuir isotherm model. Thermodynamic parameters showed the adsorption was spontaneous and endothermic. The adsorption of Cr(VI) on La-RM occurred as a result of LaOCl formation on the RM surface, which in turn further reacted with Cr(VI) in the wastewater. This study highlighted a method for converting industrial waste into a valuable material for wastewater treatment. The novel absorbent could be used as a potential adsorbent for treating Cr(VI)-contaminating wastewater, due to its cost-effectiveness and high adsorption capability. PMID:27658113

  2. Enhanced photoelectrochemical and optical performance of ZnO films tuned by Cr doping

    NASA Astrophysics Data System (ADS)

    Salem, M.; Akir, S.; Massoudi, I.; Litaiem, Y.; Gaidi, M.; Khirouni, K.

    2017-04-01

    In this paper, pure and Cr-doped nanostructured Zinc oxide thin films were synthesized by simple and low cost co-precipitation and spin-coating method with Cr concentration varying between 0.5 and 5 at.%. Crystalline structure of the prepared films was investigated by X-ray diffraction (XRD) and Raman spectroscopy techniques. XRD analysis indicated that the films were indexed as the hexagonal phase of wurtzite-type structure and demonstrated a decrease in the crystallite size with increasing Cr doping content. Cr doping revealed a significant effect on the optical measurements such as transmission and photoluminescence properties. The optical measurements indicated that Cr doping decreases the optical band gap and it has been shifted from 3.41 eV for pure ZnO film to 3.31 eV for 5 at.% Cr-doped one. The photoelectrochemical (PEC) sensing characteristics of Cr-doped ZnO layers were investigated. Amongst all photo-anodes with different Cr dopant concentration, the 2 at.% Cr incorporated ZnO films exhibited fast response and higher photoconduction sensitivity.

  3. Structure and mechanical properties of nanoscale multilayered CrN/ZrSiN coatings

    SciTech Connect

    Zhang, Z. G.; Rapaud, O.; Allain, N.; Baraket, M.; Dong, C.; Coddet, C.

    2009-07-15

    Nanocrystalline/amorphous CrN/ZrSiN multilayer coatings with a bilayer thickness ranging from 11 to 153 nm were prepared by reactive magnetron sputtering technique. The microstructure and mechanical properties of these thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and nanoindentation. The formation of nanocrystalline CrN and nanocomposite ZiSiN in the single layer coatings was identified by XRD and FTIR. The periodic structure of the as-deposited multilayer coatings was confirmed by TEM observation. Nanoindentation tests showed that both the values of hardness (H) and reduced elastic modulus (E{sub r}) of CrN/ZrSiN multilayers remained almost constant despite varying the bilayer thickness. The multilayer coatings exhibited higher H of 30 GPa and higher resistance to plastic deformation when compared to the single layer CrN and ZrSiN coatings.

  4. Cu-Cr Literature Review

    SciTech Connect

    Need, Ryan F.

    2012-08-09

    Cu-Cr alloys are part of a class of face-centered cubic (FCC)-body-centered cubic (BCC) composites that includes similar alloys, such as Cu-Nb and Cu-Ta. When heavily deformed, these FCC-BCC materials create 'in situ' composites with a characteristic structure-nanoscale BCC filaments in a ductile FCC matrix. The strength of these composites is vastly greater than predicted by the rule of mixtures, and has been shown to be inversely proportional to the filament spacing. Lower raw materials costs suggest that Cu-Cr alloys may offer more economical solution to high-strength, high-conductivity wire than either their Nb or Ta counterparts. However, Cr is also more brittle and soluble in Cu than Nb or Ta. These qualities necessitate thermal treatments to remove solute atoms from the Cu matrix, improve conductivity, and maintain the ductility of the Cr filaments. Through the use of different thermomechanical processing routes or the addition of select dopants, alloys with strength in excess of 1 GPa at 70% IACS have been achieved. To date, previous research on Cu-Cr alloys has focused on a relatively small number of alloy compositions and processing methods while the effects of dopants and ageing treatments have only been studied independently. Consequently, there remains considerable opportunity for the development and optimization of these alloys as a leading high-strength, high-conductivity material.

  5. CuCrZr alloy microstructure and mechanical properties after hot isostatic pressing bonding cycles

    NASA Astrophysics Data System (ADS)

    Frayssines, P.-E.; Gentzbittel, J.-M.; Guilloud, A.; Bucci, P.; Soreau, T.; Francois, N.; Primaux, F.; Heikkinen, S.; Zacchia, F.; Eaton, R.; Barabash, V.; Mitteau, R.

    2014-04-01

    ITER first wall (FW) panels are a layered structure made of the three following materials: 316L(N) austenitic stainless steel, CuCrZr alloy and beryllium. Two hot isostatic pressing (HIP) cycles are included in the reference fabrication route to bond these materials together for the normal heat flux design supplied by the European Union (EU). This reference fabrication route ensures sufficiently good mechanical properties for the materials and joints, which fulfil the ITER mechanical specifications, but often results in a coarse grain size for the CuCrZr alloy, which is not favourable, especially, for the thermal creep properties of the FW panels. To limit the abnormal grain growth of CuCrZr and make the ITER FW fabrication route more reliable, a study began in 2010 in the EU in the frame of an ITER task agreement. Two material fabrication approaches have been investigated. The first one was dedicated to the fabrication of solid CuCrZr alloy in close collaboration with an industrial copper alloys manufacturer. The second approach investigated was the manufacturing of CuCrZr alloy using the powder metallurgy (PM) route and HIP consolidation. This paper presents the main mechanical and microstructural results associated with the two CuCrZr approaches mentioned above. The mechanical properties of solid CuCrZr, PM CuCrZr and joints (solid CuCrZr/solid CuCrZr and solid CuCrZr/316L(N) and PM CuCrZr/316L(N)) are also presented.

  6. Doping and Thermal Conductivity Studies of CrSiTe3

    NASA Astrophysics Data System (ADS)

    Haglund, Amanda; Yan, Jiaqiang; Keppens, Veerle; Mandrus, David

    CrSiTe3 is a layered material with a 2-dimensional crystal structure, and has recently become of more interest due to the possibility of using its ferromagnetic and semiconducting properties for spintronics applications. To further investigate the properties of CrSiTe3, we doped it with various transition elements on the Cr site in an attempt to tune and control the magnetism, as well as study changes in the thermal conductivity. We synthesized pure CrSiTe3 and doped samples through flux growth, producing plate-like bulk crystals. Crystal quality was checked by x-ray diffraction and energy dispersive spectroscopy, and then thermal conductivity and magnetization measurements were obtained on the doped materials to compare variations from the pristine CrSiTe3.

  7. Properties of Cr2AlC MAX phase thin films prepared by reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Buck, Zachary; Donato, Tyler; Rotella, Christopher; Lunk, Carl; Lofland, S. E.; Hettinger, J. D.

    2012-02-01

    Mn+ 1AXn (MAX) phases, where n is 1, 2, and 3, M is an early transition metal, A is an A-group element, and X is either C or N, are ternary carbides with unique properties such as low density, easy machinability, and good oxidation resistance. The MAX phase Cr2AlC is of particular interest for industrial applications to its excellent high-temperature oxidation resistance and relatively low synthesis temperature. We prepared Cr2AlC thin films on c-axis oriented single crystal Al2O3, glassy carbon and Si thermal oxide substrates using reactive magnetron sputtering as precursor materials for carbide-derived carbon (CDC) films for ``on-chip'' supercapacitors. Film deposition was optimized using elemental composition data obtained by WDXRF. Optimized films were characterized using XRD and scanning electron microscopy. It was found that textured Cr2AlC films only form when the composition was Al-rich allowing the formation of a Cr5Al8 interfacial layer. As film composition was optimized, the interfacial layer did not form but the XRD peaks associated with the Cr2AlC also decreased in magnitude. Extremely high-textured films were grown when a thin buffer layer of CrAl2 was deposited on the substrate before depositing the Cr2AlC films. This result suggests that Cr2AlC films may not be ideal for CDC applications since the films may ``lift-off'' during conversion due to the existence of the naturally occurring buffer-layer.

  8. Method for forming a barrier layer

    DOEpatents

    Weihs, Timothy P.; Barbee, Jr., Troy W.

    2002-01-01

    Cubic or metastable cubic refractory metal carbides act as barrier layers to isolate, adhere, and passivate copper in semiconductor fabrication. One or more barrier layers of the metal carbide are deposited in conjunction with copper metallizations to form a multilayer characterized by a cubic crystal structure with a strong (100) texture. Suitable barrier layer materials include refractory transition metal carbides such as vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), chromium carbide (Cr.sub.3 C.sub.2), tungsten carbide (WC), and molybdenum carbide (MoC).

  9. High-pressure BaCrO{sub 3} polytypes and the 5H–BaCrO{sub 2.8} phase

    SciTech Connect

    Arévalo-López, Angel M.; Paul Attfield, J.

    2015-12-15

    Polytypism of BaCrO{sub 3} perovskites has been investigated at 900–1100 °C and pressures up to 22 GPa. Hexagonal 5H, 4H, and 6H perovskites are observed with increasing pressure, and the cubic 3C perovskite (a=3.99503(1) Å) is observed in bulk form for the first time at 19–22 GPa. An oxygen-deficient material with limiting composition 5H–BaCrO{sub 2.8} is synthesised at 1200 °C under ambient pressure. This contains double tetrahedral Cr{sup 4+} layers and orders antiferromagnetically below 260 K with a (0 0 1/2) magnetic structure. - Graphical abstract: Hexagonal 5H, 4H, and 6H perovskites polytypes of BaCrO{sub 3} are observed with increasing pressure and the cubic 3C perovskite is stabilised in bulk form for the first time at 19–22 GPa. Oxygen-deficient 5H–BaCrO{sub 2.8} synthesised at ambient pressure contains double tetrahedral Cr{sup 4+} layers and orders antiferromagnetically below 260 K with a (0 0 1/2) magnetic structure.

  10. Enhanced removal of trace Cr(VI) ions from aqueous solution by titanium oxide-Ag composite adsorbents.

    PubMed

    Liu, Si Si; Chen, Yong Zhou; De Zhang, Li; Hua, Guo Min; Xu, Wei; Li, Nian; Zhang, Ye

    2011-06-15

    Titanium oxide-Ag composite (TOAC) adsorbents were prepared by a facile solution route with Ag nanoparticles being homogeneously dispersed on layered titanium oxide materials. The as-synthesized TOAC exhibited a remarkable capability for trace Cr(VI) removal from an aqueous solution, where the concentration of Cr(VI) could be decreased to a level below 0.05 mg/L within 1h. We have systematically investigated the factors that influenced the adsorption of Cr(VI), for example, the pH value of the solution, and the contact time of TOAC with Cr(VI). We found that the adsorption of Cr(VI) was strongly pH-dependent. The adsorption behavior of Cr(VI) onto TOAC fitted well the Langmuir isotherm and a maximum adsorption capacity of Cr(VI) as 25.7 mg/g was achieved. The adsorption process followed the pseudo-second-order kinetic model, which implied that the adsorption was composed of two steps: the adsorption of Cr(VI) ions onto TOAC followed by the reduction of Cr(VI) to Cr(III) by Ag nanoparticles. Our results revealed that TOAC with high capacity of Cr(VI) removal had promising potential for wastewater treatment.

  11. Dynamic oxidation behavior of TD-NiCr alloy with different surface pretreatments

    NASA Technical Reports Server (NTRS)

    Young, C. T.; Tenney, D. R.; Herring, H. W.

    1975-01-01

    Oxidation tests of TD-NiCr alloy with different surface pretreatments were conducted in a Mach-5 arc-jet at 1200 C and 0.002 lb/sec flowing air environment. The mechanisms responsible for the observed oxidation behavior are examined. The presence of atomic oxygen in the air stream plays a significant role in determining the oxidation characteristic of the alloy. The rate of Cr2O3 vaporization by formation of volatile CrO3 is greatly enhanced by the flowing conditions. The typical microstructure of oxides formed in the dynamic tests consists of an external layer of NiO with a porous mushroom-type morphology, an intermediate layer of NiO and Cr2O3 oxide mixture, and a continuous inner layer of Cr2O3 in contact with the Cr-depleted alloy substrate. Three basic processes underlying the formation of mushroom-type NiO are identified and discussed. The oxidation rate is determined by the rate of vaporization of NiO. Surface pretreatment has a significant effect on the oxidation behavior of the alloy in the early stage of oxidation, but becomes less important as exposure time increases. Mechanical polishing induces surface recrystallization, but promotes the concurrence of external growth of NiO and internal oxidation of the alloy in the dynamic atmosphere.

  12. Ultrathin nanosheets of CrSiTe3. A semiconducting two-dimensional ferromagnetic material

    DOE PAGES

    Lin, Ming -Wei; Zhung, Houlong L.; Yan, Jiaqiang; ...

    2015-11-27

    Finite range ferromagnetism and antiferromagnetism in two-dimensional (2D) systems within an isotropic Heisenberg model at non-zero temperature were originally proposed to be impossible. However, recent theoretical studies using an Ising model have recently shown that 2D magnetic crystals can exhibit magnetism. Experimental verification of existing 2D magnetic crystals in this system has remained elusive. In this work we for the first time exfoliate the CrSiTe3, a bulk ferromagnetic semiconductor, to mono- and few-layer 2D crystals onto a Si/SiO2 substrate. The Raman spectra show the good stability and high quality of the exfoliated flakes, consistent with the computed phonon spectra ofmore » 2D CrSiTe3, giving a strong evidence for the existence of 2D CrSiTe3 crystals. When the thickness of the CrSiTe3 crystals is reduced to few-layers, we observed a clear change in resistivity at 80~120 K, consistent with the theoretical calculations on the Curie temperature (Tc) of ~80 K for the magnetic ordering of 2D CrSiTe3 crystals. As a result, the ferromagnetic mono- and few-layer 2D CrSiTe3 indicated here should enable numerous applications in nano-spintronics.« less

  13. The influence of Cr and Al pack cementation on low carbon steel to improve oxidation resistance

    NASA Astrophysics Data System (ADS)

    Prasetya, Didik; Sugiarti, Eni; Destyorini, Fredina; Thosin, Kemas Ahmad Zaini

    2012-06-01

    Pack chromizing and aluminizing has been widely used for many years to improve hot temperature oxidation and corrosion resistance of metals. The coating process involves packing the steel in a powder mixture which contain aluminum and chromium source, and inert filler (usually alumina), and halide activator NH4Cl. Al and Cr were deposited onto carbon steel by pack cementation process using elemental Al and Cr powder as Al and Cr source, whereas NiCo alloys codeposited by electrodeposition. The position of Al and Cr could be under or over Ni-Co alloys deposited. Pack cementation was heated on dry inert gas at temperature 800 °C about 5 hours and 20 minute for Cr and Al respectively. Al and Cr was successfully deposited. Laying down effect of Al and Cr onto carbon steel whether up and down toward NiCo alloys coating have affected to oxidation resistance. The pack aluminizing as top layer given best resitance to restrain excessive oxide scale, in contrast pack chromizing reveal bad oxidation resistance, moreover occured spallation on layer.

  14. Key Role of Rutile Structure for Layered Magnetism in Chromium Compounds

    NASA Astrophysics Data System (ADS)

    Kondo, Yasuhiro; Hotta, Takashi

    CrCl2 and CrF2 with the distorted Rutile-type crystal structure are known to exhibit different antiferromagnetic (AF) structures at low temperatures. CrF2 has a simple N_eel structure in common with other uorides, whereas CrCl2 exhibits a characteristic layered AF structure. We provide a simple scenario to understand the emergence of such layered AF structure on the basis of an orbital degenerate double-exchange model on the Rutile-type structure lattice.

  15. Characteristics of CrAlSiN + DLC coating deposited by lateral rotating cathode arc PVD and PACVD process

    NASA Astrophysics Data System (ADS)

    Lukaszkowicz, Krzysztof; Sondor, Jozef; Balin, Katarzyna; Kubacki, Jerzy

    2014-09-01

    Coating system composed of CrAlSiN film covered by diamond-like carbon (DLC)-based lubricant, deposited on hot work tool steel substrate was the subject of the research. The CrAlSiN and DLC layers were deposited by PVD lateral rotating ARC-cathodes (LARC) and PACVD technology on the X40CrMoV5-1 respectively. HRTEM investigation shows an amorphous character of DLC layer. It was found that the tested CrAlSiN layer has a nanostructural character with fine crystallites while their average size is less than 10 nm. Based on the XRD pattern of the CrAlSiN, the occurrence of fcc phase was only observed in the coating, the texture direction <3 1 1> is perpendicular to the sample surface. Combined SEM, AES and ToF-SIMS studies confirmed assumed chemical composition and layered structure of the coating. The chemical distribution of the elements inside the layers and at the interfaces was analyzed by SEM and AES methods. It was shown that additional CrN layer is present between substrate and CrAlSiN coating. The atomic concentration of the particular elements of DLC and CrAlSiN layer was calculated from the XPS measurements. In sliding dry friction conditions the friction coefficient for the investigated elements is set in the range between 0.05 and 0.07. The investigated coating reveals high wear resistance. The coating demonstrated a dense cross-sectional morphology as well as good adhesion to the substrate.

  16. A study of interdiffusion in beta + gamma/gamma + gamma prime Ni-Cr-Al. M.S. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Carol, L. A.

    1985-01-01

    Ternary diffusion in the NiCrAl system at 1200 C was studied with beta + gamma/gamma + gamma prime infinite diffusion couples. Interdiffusion resulted in the formation of complex, multiphase diffusion zones. Concentration/distance profiles for Cr and Al in the phases present in the diffusion zone were measured after 200 hr. The Ni-rich portion of the NiCrAl phase diagram (1200 C) was also determined. From these data, bulk Cr and Al profiles were calculated and translated to diffusion paths on the ternary isotherm. Growth layer kinetics of the layers present in the diffusion zone were also measured.

  17. Conceptual design and experiments of electrochemistry-flushing technology for the remediation of historically Cr(Ⅵ)-contaminated soil.

    PubMed

    Li, Dong; Sun, Delin; Hu, Siyang; Hu, Jing; Yuan, Xingzhong

    2016-02-01

    A conceptual design and experiments, electrochemistry-flushing (E-flushing), using electrochemistry to enhance flushing efficiency for the remediation of Cr(Ⅵ)-contaminated soil is presented. The rector contained three compartments vertically superposed. The upper was airtight cathode compartment containing an iron-cathode. The middle was soil layer. The bottom was anode compartment containing an iron-anode and connected to a container by circulation pumps. H2 and OH(-) ions were produced at cathode. H2 increased the gas pressure in cathode compartment and drove flushing solution into soil layer forming flushing process. OH(-) ions entered into soil layer by eletromigration and hydraulic flow to enhance the desorption of Cr(Ⅵ). High potential gradient was applied to accelerate the electromigration of desorbed Cr(Ⅵ) ions and produced joule heat to increase soil temperature to enhance Cr(Ⅵ) desorption. In anode compartment, Fe(2+) ions produced at iron-anode reduced the desorbed Cr(Ⅵ) into Cr(3+) ions, which reacted with OH(-) ions forming Cr(OH)3. Experimental results show that Cr(Ⅵ) removal efficiency of E-flushing experiments was more than double of flushing experiments and reached the maximum of removal efficiency determined by desorption kinetics. All electrochemistry processes were positively used in E-flushing technology.

  18. Physical, Mechanical, and Dry Sliding Wear Properties of Fe-Cr-W-C Hardfacing Alloys Under Different Tungsten Addition

    NASA Astrophysics Data System (ADS)

    Hajihashemi, Mahdi; Shamanian, Morteza; Azimi, Ghasem

    2015-04-01

    In this study, the effects of tungsten on microstructure and wear performance of Fe-Cr-C claddings were evaluated. In this regard, tungsten inert gas surfacing process was employed to deposit Fe-Cr-C and Fe-Cr-C-W hardfacing alloys on plain carbon steel substrate using preplaced powders. Phase composition, microstructure, and wear behavior of clad layers were investigated using X-ray diffraction analysis, optical and scanning electron microscopy, and reciprocating wear tests, respectively. The claddings were well bonded to the substrate and showed a uniform microstructure. Cr7C3 and WC carbides were detected in the deposited layers. Further investigations indicated that the hardness and wear resistance can be improved by adding tungsten into Fe-Cr-C hardfacing alloys.

  19. Effect of Cr on the passive film formation mechanism of steel rebar in saturated calcium hydroxide solution

    NASA Astrophysics Data System (ADS)

    Liu, Ming; Cheng, Xuequn; Li, Xiaogang; Pan, Yue; Li, Jun

    2016-12-01

    Passive films grow on the surface of Cr-modified steels subjected to saturated Ca(OH)2 solution. Electrochemical techniques, such as measurement of open circuit potentials, polarization curves, and electrochemical impedance spectroscopy combined with X-ray photoelectron spectrometer and auger electron spectroscopy, were applied to study the influence of low Cr content on the passive film formation mechanism of steel rebar in saturated Ca(OH)2 solution. Results show that Cr inhibits the formation of passive film at the beginning of its formation. Corrosion current density decreases and polarization resistance increases with the extension of the immersion time. A stable passive film takes at least three days to form. The passive film resistance of HRB400 carbon steel is higher than that of Cr-modified steels in the early stage of immersion (<72 h). The polarization resistance of Cr-modified steel is larger after a stable passive film is formed (>72 h), and Cr promotes the formation of a denser and more compact passive film. The stable passive film is primarily made up of iron oxides with a thickness of 5-6 nm. Cr are involved in the formation of passive films, thereby resulting in a film that consists of an inner layer that contains Cr-Fe oxides and an outer layer that contains Fe oxides, whose thickness presents a slight increase as the content of Cr increases.

  20. Oxidation of Cr(III) to Cr(VI) during chlorination of drinking water.

    PubMed

    Lindsay, Dana R; Farley, Kevin J; Carbonaro, Richard F

    2012-07-01

    Drinking water treatment typically uses strong oxidants such as chlorine which are capable of converting Cr(III) to Cr(VI). The rates and extent of Cr(III) oxidation by chlorine are not well established. Cr(III) oxidation experiments were therefore conducted in distilled deionized water and New York City tap water dosed initially with Cr(III) and supplemented with sodium hypochlorite to increase free chlorine residual. Reaction progress was monitored using capillary electrophoresis which quenched reactions and allowed for quantification of Cr(VI). Three different forms of Cr(III) were used as reactants: a Cr(III) nitrate salt, Cr(III)-EDTA, and Cr(III) hydroxide. Rates of Cr(VI) production for all three forms of Cr(III) were rapid, on the order of hours. However, oxidation rates slowed and a plateau in Cr(VI) concentrations was reached. This resulted in less than 100% conversion of Cr(III) to Cr(VI) even at relatively high chlorine doses (10 to 100 mg L(-1) as Cl(2)). The loss of free chlorine due to a non-Cr chlorine demand, the precipitation of Cr(III) to Cr(OH)(3)(s), and the partial oxidation of Cr(III) to intermediate oxidation states (i.e. Cr(IV) and Cr(V)) were examined and eliminated as possible explanations for this behavior. Consumption of chlorine via reaction with intermediate oxidation states of Cr is therefore offered as a possible explanation for the plateau in Cr(VI) concentrations.

  1. Removal of Cr(VI) from groundwater by Fe(0)

    NASA Astrophysics Data System (ADS)

    Gao, Yanjiao; Liu, Rui

    2016-12-01

    This research was conducted to investigate the treatment of hexavalent chromium (Cr(VI)) by iron powder (Fe(0)) columns of simulated permeable reactive barriers with and without calcium carbonate (CaCO3). Two columns filled with Fe(0) were used as Cr(VI) removal equipment running at a flow velocity of 10 ml/min at room temperature. After 200 days running of the two columns, the results showed that Fe(0) was an effective material for Cr(VI) reduction with an average removal rate of above 84.6%. The performance of Column 2 with CaCO3 was better than Column 1 without CaCO3 in terms of average Cr(VI) removal rate. The presence of CaCO3 buffered the increasing pH caused by Fe(0) corrosion in Column 2 and enhanced the removal rate of Column 2. Scanning Electron Microscopy (SEM) images of Fe(0) in the three stages of running of the two columns illustrated that the coat layer of Column 1 was a little thicker than that of Column 2. Energy-dispersive spectrometry (EDS) results showed that the surface of Fe(0) of Column 2 contained more chromium elements. Raman spectroscopy found that all iron oxide was generated on the Fe(0) surface of Column 1 and Column 2 and chromium class objects were only detected on Fe(0) surface in Column 2.

  2. Textured growth of the high moment material Gd(0 0 0 1)/Cr(0 0 1)/Fe(0 0 1)

    NASA Astrophysics Data System (ADS)

    Stromberg, F.; Antoniak, C.; von Hörsten, U.; Keune, W.; Sanyal, B.; Eriksson, O.; Wende, H.

    2011-07-01

    By magnetic coupling of Fe and Gd via Cr interlayers, the large local moment of Gd can be combined with the high Curie temperature of Fe. The textured growth of a Gd film is studied here by preparing trilayer systems of Fe/Cr/Gd on MgO(1 0 0) substrates by molecular-beam epitaxy (MBE). The thickness of the Cr interlayer was varied between 3 and 5 monolayers. The structural quality of the samples was confirmed by in situ RHEED and ex situ XRD measurements. Epitaxial Cr(0 0 1)/Fe(0 0 1) growth was observed, as expected. By use of 57Fe-CEMS (conversion electron Mössbauer spectroscopy) in combination with the 57Fe tracer layer method the Fe/Cr interface could be examined on an atomic scale and well separated Fe/Gd layers for all Cr thicknesses were confirmed. The unusual Gd/Cr crystallographic relationship of Gd(0 0 0 1)parCr(0 0 1), with domains of the hexagonal Gd basal planes randomly oriented in the sample plane and not in registry with the underlying Cr(0 0 1) lattice, was found from combined RHEED and x-ray measurements. Annealing of the samples resulted in a remarkable improvement of the crystalline structure of the Gd layers. On the other hand, the appearance of a single line in the CEM spectrum leads to the conclusion that during annealing a small amount of Fe diffuses into the Cr layer. The electronic structure and magnetism of this system are investigated by first-principles theory.

  3. Surface stabilized GMR nanorods of silver coated CrO2 synthesized via a polymer complex at ambient pressure

    NASA Astrophysics Data System (ADS)

    Biswas, S.; Singh, G. P.; Ram, S.; Fecht, H.-J.

    2013-08-01

    Stable anisotropic nanorods of surface modified CrO2 (˜18 nm diameter) with a correlated diamagnetic layer (2-3 nm thickness) of silver efficiently tailors useful magnetic and magnetoresistance (MR) properties. Essentially, it involves a core-shell structure that is developed by displacing part of Cr4+ ions by Ag atoms on the CrO2 surface (topotactic surface layer) via an etching reaction of a CrO2-polymer complex with Ag+ ions in hot water followed by heating the dried sample at 300-400 °C in air. The stable Ag-layer so obtained in the form of a shell protects CrO2 such that it no longer converts to Cr2O3 in ambient pressure during the processing. X-ray diffractogram of the Rutile type tetragonal CrO2 structure (lattice parameters a=0.4429 nm and c=0.2950 nm) includes weak peaks of a minority phase of an fcc-Ag (a=0.4086 nm). The silver surface layer, which manifests itself in a doublet of the 3d5/2 and 3d3/2 X-ray photoelectron bands of binding energies 368.46 eV and 374.48 eV, respectively, suppresses almost all Cr bands to appear in a measurable intensity. The sample exhibits a distinctly enhanced MR-value, e.g., (-) 7.6% at 77 K, than reported values in compacted CrO2 powders or composites. Such a large MR-value in the Coulomb blockade regime (<100 K) arises not only due to the suppressed spin flipping at low temperature but also from a spin dependent co-tunneling through an interlinked structure of silver and silver coated CrO2 nanorods.

  4. Inhibited Aluminization of an ODS FeCr Alloy

    SciTech Connect

    Vande Put Ep Rouaix, Aurelie; Pint, Bruce A

    2012-01-01

    Aluminide coatings are of interest for fusion energy applications both for compatibility with liquid Pb-Li and to form an alumina layer that acts as a tritium permeation barrier. Oxide dispersion strengthened (ODS) ferritic steels are a structural material candidate for commercial reactor concepts expected to operate above 600 C. Aluminizing was conducted in a laboratory scale chemical vapor deposition reactor using accepted conditions for coating Fe- and Ni-base alloys. However, the measured mass gains on the current batch of ODS Fe-14Cr were extremely low compared to other conventional and ODS alloys. After aluminizing at two different Al activities at 900 C and at 1100 C, characterization showed that the ODS Fe-14Cr specimens formed a dense, primarily AlN layer that prevented Al uptake. This alloy batch contained a higher (> 5000 ppma) N content than the other alloys coated and this is the most likely reason for the inhibited aluminization. Other factors such as the high O content, small ({approx} 140 nm) grain size and Y-Ti oxide nano-clusters in ODS Fe-14Cr also could have contributed to the observed behavior. Examples of typical aluminide coatings formed on conventional and ODS Fe- and Ni-base alloys are shown for comparison.

  5. Cr/B4C multilayer mirrors: Study of interfaces and X-ray reflectance

    SciTech Connect

    Burcklen, C.; Soufli, R.; Gullikson, E.; Meltchakov, E.; Dennetiere, D.; Polack, F.; Capitanio, B.; Thomasset, M.; Jerome, A.; de Rossi, S.; Delmotte, F.

    2016-03-24

    Here, we present an experimental study of the effect of layer interfaces on the x-ray reflectance in Cr/B4C multilayer interference coatings with layer thicknesses ranging from 0.7 nm to 5.4 nm. The multilayers were deposited by magnetron sputtering and by ion beam sputtering. Grazing incidence x-ray reflectometry, soft x-ray reflectometry, and transmission electron microscopy reveal asymmetric multilayer structures with a larger B4C-on-Cr interface, which we modeled with a 1–1.5 nm thick interfacial layer. Reflectance measurements in the vicinity of the Cr L2,3 absorption edge demonstrate fine structure that is not predicted by simulations using the currently tabulated refractive index (optical constants) values for Cr.

  6. New needle-crystalline CR detector

    NASA Astrophysics Data System (ADS)

    Leblans, Paul J. R.; Struye, Luc; Willems, Peter

    2001-06-01

    The storage phosphor RbBr:Tl+ can be grown in needles via vacuum deposition. Thanks to reduced lateral light diffusion thick needle screens still offer acceptable resolution. Due to its low intrinsic X-ray absorption, however, a RbBr:Tl+ needle screen does not lead to a better absorption/resolution compromise than a BaFBr1-xIx:Eu2+ powder screen. CsBr:Eu2+ does combine high specific X-ray absorption and the possibility of needle growth. Its blue emission, peaking at 440 nm and near IR stimulation band, with maximum at 685 nm, make it well suited for use in CR systems. Sensitivity and sharpness of a 500 (mu) thick CsBr:Eu2+ needle screen were measured in a flying-spot scanner. The number of photostimulated light quanta per absorbed X-ray quantum is higher than for BaFBr1-xIx:Eu2+. At 70 kVp and 0.5 mm Cu filtration, equal sharpness is obtained for 85% vs. 46% X-ray absorption in BaFBr1-xIx:Eu2+ screens. DQE was measured at 2.5 (mu) Gy, 70 kVp, and 0.5 mm Cu filtration for a CsBr:Eu2+ needle screen in a flying-spot scanner. Up to 3 lp/mm, DQE was 2 times higher than for state-of-the-art CR systems and equal to the DQE claimed for flat panel DR systems, based on a-Si photodiodes combined with a CsI:Tl scintillator layer.

  7. Anti-wetting Cu/Cr coating with micro-posts array structure fabricated by electrochemical approaches

    NASA Astrophysics Data System (ADS)

    Zhou, Yufeng; Hang, Tao; Li, Feng; Li, Ming

    2013-04-01

    Microposts structured Cu/Cr multilayer coating was prepared by a simple two-step approach combining electroless and electro deposition. Surface morphologies of the as-prepared Cu/Cr multilayer coating characterized by field emission scanning electron microscopy show that this multilayer coating exhibits micro-posts arrayed structure with a layer of Cr uniformly covering the circular conical surface of Cu micro-cones array. The wettability test shows that the contact angle of Cu/Cr multilayer surface with water drop can be greater than 140° by optimizing the electrodeposition time of Cr. The mechanism of hydrophobicity of both the micro-cones arrayed and micro-posts arrayed structures was briefly discussed by comparing two different wetting modes. Due to its good anti-wetting property and unique structure, the micro-posts arrayed Cu/Cr multilayer coating is expected for extensive practical applications.

  8. The General Isothermal Oxidation Behavior of Cu-8Cr-4Nb

    NASA Technical Reports Server (NTRS)

    Thomas-Ogbuji, L. U.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Oxidation kinetics of Cu-8Cr-4Nb was investigated by TGA (thermogravimetric) exposures between 500 and 900-C (at 25-50 C intervals) and the oxide scale morphologies examined by microscopy and micro-analysis. Because Cu-8Cr-4Nb is comprised of fine Cr2Nb precipitates in a Cu matrix, the results were interpreted by comparison with the behavior of copper (OFHC) and 'NARloy-Z' (a rival candidate material for thrust cell liner applications in advanced rocket engines) under the same conditions. While NARloy-Z and Cu exhibited identical oxidation behavior, Cu-8Cr-4Nb differed markedly in several respects: below approx. 700 C its oxidation rates were significantly lower than those of Cu; At higher temperatures its oxidation rates fell into two categories: an initial rate exceeding that of Cu, and a terminal rate comparable to that of Cu. Differences in oxide morphologies paralleled the kinetic differences at higher temperature: While NARloy-Z and Cu produced a uniform oxide scale of Cu2O inner layer and CuO outer layer, the inner (Cu2O) layer on Cu-8Cr-4Nb was stratified, with a highly porous/spongy inner stratum (responsible for the fast initial kinetics) and a dense/blocky outer stratum (corresponding to the slow terminal kinetics). Single and spinel oxides of Nb and Cr were found at the interface between the oxide scale and Cu-8Cr-4Nb substrate and it appears that these oxides were responsible for its suppressed oxidation rates at the intermediate temperatures. No difference was found between Cu-8Cr-4Nb oxidation in air and in oxygen at 1.0 atm.

  9. A Cr Isotope Proxy For Ocean Deoxygenation

    NASA Astrophysics Data System (ADS)

    Holmden, C. E.; Scheiderich, K. D.; Amini, M.; Francois, R. H. G. M.; Bacconais, I.

    2015-12-01

    The concentration and distribution of Cr in the oceans is strongly controlled by its oxidation state. Cr(VI) (as soluble chromate) is the dominant oxidation state in oxygenated seawater. Chromate is typically greater than 70% of total dissolved Cr in the open ocean, consistent with thermodynamic predictions. However, lower than average chromate concentrations in coastal seas and oxygen minimum zones suggest that chromate is being removed in these settings by reduction to Cr(III), which favours particle reactive species. Cr is an element whose isotopes are fractionated by redox changes. Reduction of Cr(VI) causes light isotopes of Cr to be enriched in the product Cr(III). Accordingly, any local-scale increase in reductive Cr removal fluxes will cause the seawater Cr concentration to decrease and the δ53Cr value to increase. A recent study of Cr isotopes in the oceans1 supports this prediction. Cr isotopes show a range of δ53Cr values correlating inversely with Cr concentration. The fractionation factor deduced from this correlation is -0.80 ±0.03 ‰ (2s) on a global scale. The difference in solubility of oxidized and reduced Cr in seawater, and the isotopic fractionation between them, is the basis on which the Cr isotope proxy may be used for tracing ocean deoxygenation events in the geological past. More specifically, changes in the size of the chromate inventory of seawater, both locally and globally, should be traceable from reconstructions of seawater-derived Cr isotope variations in marine sedimentary successions. Geological records of Cr isotope changes in the oceans during past deoxygenation events may be used to gauge the impact of global warming on future deoxygenation of the oceans, particularly if proxy records of temperature and ocean pH are also reconstructed. However, study of the modern ocean Cr cycle is still in its early stages, and important knowledge gaps need to be filled going forward. In this talk, we present results of our seawater Cr

  10. Chromizing of 3Cr Steel

    SciTech Connect

    Ravi, Vilupanur; Harrison, Bradley; Koch, Jordan; Ly, Alexander; Schissler, Andrew; Pint, Bruce A; Haynes, James A

    2011-01-01

    Grade 315 steel (Fe-2.9 Cr-1.7 W-0.7 Mo-0.3 Mn-0.3 Si-0.2 V-0.1 Ni-0.13 C-0.01 N) was chromized by the halide-activated pack cementation (HAPC) process. Key process parameters, i.e., coating temperatures and pack compositions, were investigated. Ammonium chloride-activated packs in the 700-1000 C range produced coatings nominally in the 1-8 {micro}m range, as determined by optical and scanning electron microscopy (SEM). Coatings applied in the 900-1000 C temperature range resulted in Cr-rich coatings. The predominant phase in the coating was identified as Cr23C6 by X-ray diffraction. In addition, the presence of chromium nitride, Cr2N, was observed in the coating. The power generation industry is faced with an ever-increasing demand for energy while simultaneously having to reduce carbon emissions. These goals can be facilitated by increasing plant efficiency through the use of higher operating temperatures and pressures. Traditional construction materials, e.g., the ferritic Grade 22 high strength low alloy steel, are limited to operations below {approx} 550 C. Therefore, new materials are required for future plants designed to operate up to 650 C and possibly higher. These new materials need to have improved tensile strength, ductility, toughness, corrosion resistance, and creep properties at elevated temperatures. Oak Ridge National Laboratory (ORNL) is investigating the oxidation and creep behavior of various coatings on Grade 315 steel (Fe-2.9 Cr-1.7 W-0.7 Mo-0.3 Mn-0.3 Si-0.2 V-0.1 Ni-0.13 C-0.01 N), a super-bainitic steel developed for superior creep properties. Thin, chemical vapor-deposited (CVD) aluminide coatings were used to compensate for the reduced corrosion and oxidation resistance that resulted from the low chromium content of the alloy. However, the aluminized Grade 315 alloys performed less-than-favorably under conditions relevant to fossil boilers, leading to the conclusion that higher chromium contents are required for the formation of

  11. Hf-W Chronology of CR Chondrites

    NASA Astrophysics Data System (ADS)

    Budde, G.; Kruijer, T. S.; Kleine, T.

    2017-02-01

    Hf-W systematics of CR chondrites define an age of 3.7 Ma after CAIs for CR chondrule formation. CR metal and silicates have complementary nucleosynthetic W and Mo isotope anomalies due to the uneven distribution of a presolar s-process carrier.

  12. An investigation on corrosion protection of chromium nitride coated Fe-Cr alloy as a bipolar plate material for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Pan, T. J.; Zhang, B.; Li, J.; He, Y. X.; Lin, F.

    2014-12-01

    The corrosion properties of chromium nitride (CrN) coating are investigated to assess the potential use of this material as a bipolar plate for proton exchange membrane fuel cells (PEMFCs). Conductive metallic ceramic CrN layers are firstly deposited onto Fe-Cr alloy using a multi-arc ion plating technique to increase the corrosion resistance of the base alloy. Electrochemical measurements indicate that the corrosion resistance of the substrate alloy is greatly enhanced by the CrN coating. The free corrosion potential of the substrate is increased by more than 50 mV. Furthermore, a decrease in three orders of magnitude of corrosive current density for the CrN-coated alloy is observed compared to the as-received Fe-Cr alloy. Long-term immersion tests show that the CrN layer is highly stable and effectively acts as a barrier to inhibit permeation of corrosive species. On the contrary, corrosion of the Fe-Cr alloy is rather severe without the protection of CrN coating due to the active dissolution. Finally, the corresponding electrochemical impedance models are proposed to elucidate the corrosion process of the CrN/Fe-Cr alloy submerged in a simulated PEMFCs environment.

  13. Magnetic interaction reversal in watermelon nanostructured Cr-doped Fe nanoclusters

    SciTech Connect

    Kaur, Maninder; Dai, Qilin; Bowden, Mark; Engelhard, Mark; Wu, Yaqiao; Tang, Jinke; Qiang, You

    2013-01-01

    Cr-doped core-shell Fe/Fe-oxide nanoclusters (NCs) were synthesized at varied atomic percentages of Cr from 0 at. % to 8 at. %. The low concentrations of Cr (<10 at. %) were selected in order to inhibit the complete conversion of the Fe-oxide shell to Cr2O3 and the Fe core to FeCr alloy. The magnetic interaction in Fe/Fe-oxide NCs (rv25 nm) can be controlled by antiferromagnetic Cr-dopant. We report the origin of r-FeCr phase at very low Cr concentration (2 at. %) unlike in previous studies, and the interaction reversal from dipolar to exchange interaction in watermelon-like Cr-doped core-shell NCs. The giant magnetoresistance (GMR) effect,1,2 where an antiferromagnetic (AFM) exchange coupling exists between two ferromagnetic (FM) layers separated by a certain type of magnetic or non-magnetic spacer,3 has significant potential for application in the magnetic recording industry. Soon after the discovery of the GMR, the magnetic properties of multilayer systems (FeCr) became a subject of intensive study. The application of bulk iron-chromium (Fe-Cr) alloys has been of great interest, as these alloys exhibit favorable prop- erties including corrosion resistance, high strength, hardness, low oxidation rate, and strength retention at elevated temper- ature. However, the structural and magnetic properties of Cr-doped Fe nanoclusters (NCs) have not been investigated in-depth. Of all NCs, Fe-based clusters have unique magnetic properties as well as favorable catalytic characteristics in reactivity, selectivity, and durability.4 The incorporation of dopant of varied type and concentration in Fe can modify its chemical ordering, thereby optimizing its electrical, optical, and magnetic properties and opening up many new applications. The substitution of an Fe atom (1.24 A°) by a Cr atom (1.25 A° ) can easily modify the magnetic properties, since (i) the curie temperature (Tc ) of Fe is 1043 K, while Cr is an itinerant AFM with a bulk Neel temperature TN =311 K, and (ii) Fe

  14. (BiSe)1.23CrSe2 and (BiSe)1.22(Cr1.2Se2)2: magnetic anisotropy in the first structurally characterized Bi-Se-Cr ternary compounds.

    PubMed

    Clarke, Samantha M; Freedman, Danna E

    2015-03-16

    Compounds containing both heavy main group elements and paramagnetic transition metals form a fertile area for the study of magnetic anisotropy. We pursued the synthesis, characterization, and magnetic measurements of Bi-Se-Cr compounds: a ternary system with no structurally characterized materials. Those efforts led to the isolation of two novel misfit layer compounds, namely, (BiSe)1.23CrSe2 (1) and (BiSe)1.22(Cr1.2Se2)2 (2). The crystal structure of 1 consists of alternating BiSe and CrSe2 layers along the c-axis, and 2 is composed of alternating BiSe and (Cr1.2Se2)2 layers along the c-axis. Lattice mismatch occurs in both compounds along the b-axis and leads to positional modulation of the atoms. Field- and temperature-dependent measurements were performed to assess the degree of magnetic anisotropy. Temperature-dependent susceptibility measurements on aligned crystals of 1 display increased bifurcation of zero-field cooled and field cooled data when crystals are oriented with H perpendicular to c than when the crystals are oriented with H parallel to c. Magnetic anisotropy is less pronounced in 2 where both crystallographic orientations exhibit bifurcation at 26 K. The complexity of the magnetic behavior in both compounds likely signifies a competition between CrSe2 intralayer ferromagnetic coupling and interlayer antiferromagnetic coupling. These results highlight the exciting magnetic properties that can arise from the exploration of new ternary phases.

  15. C-Cr-Fe (181)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 2 http://dx.doi.org/10.1007/97.etType="URL"/> 'Systems from B-Be-Fe to Co-W-Zr' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'C-Cr-Fe (181)' with the content:

  16. C-Cr-H (182)

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 2 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from B-Be-Fe to Co-W-Zr' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'C-Cr-H (182)' with the content:

  17. Flux States and Topological Phases from Spontaneous Time-Reversal Symmetry Breaking in CrSi (Ge )Te3 -Based Systems

    NASA Astrophysics Data System (ADS)

    Liu, Jianpeng; Park, Se Young; Garrity, Kevin F.; Vanderbilt, David

    2016-12-01

    We study adatom-covered single layers of CrSiTe3 and CrGeTe3 using first-principles calculations based on hybrid functionals. We find that the insulating ground state of a monolayer of La (Lu) deposited on single-layer CrSiTe3 (CrGeTe3 ) carries spontaneously generated current loops around the Cr sites. These "flux states" induce antiferromagnetically ordered orbital moments on the Cr sites and are also associated with nontrivial topological properties. The calculated Chern numbers for these systems are predicted to be ±1 even in the absence of spin-orbit coupling, with sizable gaps on the order of 100 meV. The flux states and the associated topological phases result from spontaneous time-reversal symmetry breaking due to the presence of nonlocal Coulomb interactions.

  18. [Composition and morphology of oxides on porcelain fused to Ni-Cr alloys. Be containing alloys].

    PubMed

    Watanabe, T

    1989-06-01

    Bonding strength between porcelain and Ni-Cr alloy for the porcelain fused-to metal crown in which Be is contained in the alloy is known to be higher than those in which Be is not contained. Since, bonding between porcelain and alloy is the reaction of oxides and porcelain, the bonding is thought to be influenced by the quality the oxides film which forms on the alloy surface. The purpose of this study was to determine the composition and morphology of the oxides formed on both Be containing and non-Be contained Ni-Cr alloys. The oxides analysis was done using an EPMA and Auger analysis. Also, the Porcelain/Ni-Cr alloy interface was observed by a scanning electron microscope (SEM). The following results are indicated from this investigation: 1. The oxides from the alloys not containing Be are corundum type Cr2O3 and spinel type NiCr2O4. These oxide layers are uniform, thick and porous and the adhesion to alloy is poor. 2. The oxides from alloy containing Be is BeO only. The BeO is uniform, thin and condensed. The adhesion to the alloy is good. 3. The oxide layer formed when the porcelain is fused to alloy containing Be is thin (1 micron average) and has good adhesion to alloy. 4. Be is selectively oxidized and controlled the form of Cr2O3 and NiO.

  19. Sorption of phosphate and Cr(VI) by Fe(III) and Cr(III) hydroxides.

    PubMed

    Tzou, Y M; Wang, M K; Loeppert, R H

    2003-05-01

    Understanding the chemical behavior and interactions of Cr(VI) ( e.g., HCrO(4)(-)) and other anions, such as orthophosphate (P) with insoluble metal hydroxides ( i.e., Cr[III] and Fe[III]) in disposal landfills or in chromite ore processing residue (CORP)-enriched soil is very important in predicting the movement and the fate of Cr(VI). This study evaluates the sorption behavior of P and Cr(VI) by Fe(III) ( i.e., ferrihydrite), Cr(III) ( i.e., Cr[OH](3)), and coprecipitated Fe(III)/Cr(III) hydroxides. These metal hydroxide sorbents were synthesized, and sorption of P and Cr(VI) were conducted at different pH using a batch technology. Our results show that P and Cr(VI) sorption by metal hydroxides decreased with increasing suspension pH. Greater decrease in P sorption was observed when Cr(III) was present in the structures of hydroxides. Following the sorption of low concentration of P ( i.e., 0.5 mM), the sorption of subsequently added Cr(VI) by hydroxides was less influenced. However, Cr(VI) sorption was greatly inhibited when high concentration of P ( i.e., 10 mM) prereacted with hydroxides, particularly in Fe(III) hydroxide system. Results also indicated that high concentration of Cr(VI) (10 mM) could dissolve Cr(III) hydroxide at pH 3 and reprecipitate as an amorphous form of Cr(VI) and Cr(III) compound at pH about 6.5. Although coprecipitation of Cr(VI) with Cr(III) can inhibit Cr(VI) movement through soil profiles, the inhibition seems to be low due to the gradual release of Cr(VI) with increasing pH.

  20. Equilibrium isotopic fractionation and isotopic exchange kinetics between Cr(III) and Cr(VI)

    NASA Astrophysics Data System (ADS)

    Wang, Xiangli; Johnson, Thomas M.; Ellis, Andre S.

    2015-03-01

    We determined the equilibrium isotope fractionation between Cr(III) and Cr(VI), defined as Δ53CrVI-III = δ53Cr(VI) - δ53Cr(III), and the rates of isotopic exchange between the two redox species under different conditions. In high Cr concentration, low-pH experiments we determined the Δ53CrV-III between CrO42- and Cr(H2O)63+ to be 5.2 ± 0.3‰ and 5.5 ± 0.3‰ at 60 °C and 40 °C, respectively. At 25 °C, the system only progressed 25% toward isotopic equilibrium after 684 days. By extrapolating from the 60 °C and 40 °C experiments we estimated the Δ53CrVI-III between CrO42- and Cr(H2O)63+ to be 5.8 ± 0.5‰ at 25 °C. Isotope exchange rates between dissolved Cr(III) and dissolved Cr(VI) at 25 °C, 40 °C, and 60 °C were determined to be 3.13 × 10-5 M day-1, 6.83 × 10-4 M day-1, and 8.37 × 10-3 M day-1, respectively. In low concentration, neutral-pH experiments we determined the isotopic exchange rates between dissolved Cr(VI) and solid Cr(III) oxyhydroxide at 25 °C. In these experiments, significant isotopic exchange was found on time scales of months, though the magnitude of isotopic shifts was limited by the small mass of Cr(III) available for exchange on the surfaces of Cr(III) oxyhydroxide particles. Exchange rates were relatively fast, compared to rates obtained from high concentration, low-pH experiments. This faster isotopic exchange is attributed to adsorption of Cr(VI) to Cr(III) particle surfaces, which keeps Cr(III) and Cr(VI), and potentially intermediate species Cr(V), in close proximity long enough to allow multiple electron transfers. The isotopic exchange rate at neutral-pH was found to conform to the rate law R = k·[Cr(VI)]adsorbed, in which R is the isotopic exchange rate (M day-1); k is the rate constant, determined to be 0.00047 day-1; [CrO42-]adsorbed is the concentration of Cr(VI) adsorbed to Cr(III) oxyhydroxide (M). The impact of isotopic exchange on the 53Cr/52Cr ratio of the dissolved Cr(VI) depends on the relative masses

  1. Double Layers in Astrophysics

    NASA Technical Reports Server (NTRS)

    Williams, Alton C. (Editor); Moorehead, Tauna W. (Editor)

    1987-01-01

    Topics addressed include: laboratory double layers; ion-acoustic double layers; pumping potential wells; ion phase-space vortices; weak double layers; electric fields and double layers in plasmas; auroral double layers; double layer formation in a plasma; beamed emission from gamma-ray burst source; double layers and extragalactic jets; and electric potential between plasma sheet clouds.

  2. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids were observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. The voids resulted from an excess number of oxygen vacancies near the oxidemetal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidation of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al, Cr)2O3 and Ni(Al, Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationship between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  3. Some TEM observations of Al2O3 scales formed on NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Smialek, J.; Gibala, R.

    1979-01-01

    The microstructural development of Al2O3 scales on NiCrAl alloys has been examined by transmission electron microscopy. Voids have been observed within grains in scales formed on a pure NiCrAl alloy. Both voids and oxide grains grew measurably with oxidation time at 1100 C. The size and amount of porosity decreased towards the oxide-metal growth interface. It was postulated that the voids resulted from an excess number of oxygen vacancies near the oxide-metal interface. Short-circuit diffusion paths were discussed in reference to current growth stress models for oxide scales. Transient oxidations of pure, Y-doped, and Zr-doped NiCrAl was also examined. Oriented alpha-(Al,Cr)2O3 and Ni(Al,Cr)2O4 scales often coexisted in layered structures on all three alloys. Close-packed oxygen planes and directions in the corundum and spinel layers were parallel. The close relationships between oxide layers provided a gradual transition from initial transient scales to steady state Al2O3 growth.

  4. Phonon density of states in epitaxial Fe/Cr(001) superlattices

    SciTech Connect

    Ruckert, T.; Keune, W.; Sturhahn, W.; Hu, M. Y.; Sutter, J. P.; Toellner, T. S.; Alp, E. E.

    1999-10-21

    Incoherent nuclear resonant absorption of synchrotron radiation at the 14.413 keV nuclear resonance of {sup 57}Fe was employed to measure directly the Fe-projected (partial) photon density of states (DOS) in epitaxial [Fe(8.7ML)/Cr(8ML)]{sub 200} superlattices and alloy films MBE-grown on MgO(001). Isotopically depleted {sup 56}Fe was used which gives no resonance signal. 0.7 monolayers (ML) thick {sup 57}Fe-probe layer (1{angstrom}) of 95.5% enrichment were placed either at the {sup 56}Fe-on-Cr interfaces or at the center of the {sup 56}Fe layers, thus providing a nuclear resonance signal from different places in the films. In addition, the authors prepared an epitaxial film which contains only a 1{angstrom}-thick {sup 57}Fe submonolayer in Cr(001) and no {sup 56}Fe layers. Moreover, they prepared a 7000 {angstrom}-thick epitaxial {sup 57}Fe{sub 0.03}Cr{sub 0.97}(001) alloy film. The measurements were performed at 300 K with 2.3 meV energy resolution around 14.413 keV. The phonon DOS of the center site was found to be very similar to that of bulk bcc Fe. Compared to the center site, the DOS of the other samples show distinct differences. In particular, longitudinal vibrations of Fe atoms are suppressed at the Fe/Cr interfaces.

  5. Reflective and transmissive CR ScanHead technology on needle image plates

    NASA Astrophysics Data System (ADS)

    Frankenberger, Jorg; Mair, Stephan; Herrmann, Clemens; Lamotte, Johan; Fasbender, Robert

    2005-04-01

    The image quality of needle-image-plate (NIP) Computed Radiography (CR) scanners based on ScanHead technology was optimized. In order to get the best image quality for different applications, the influence of the phosphor layer thickness on the detective quantum efficiency (DQE) for different beam qualities was investigated. We compared a cassette-based, reflective CR-NIP-scanner to a new, transmissive flat-panel CR scanner with fixed, mounted NIP. The image quality was analyzed by DQE- and modulation transfer function (MTF) measurements supported by an observer study. The NIP systems reached DQE values up to three times higher than that of high-quality, state of the art CR scanners independent of the scanning principle. This allows a dose reduction by a factor of two to three without loss of image quality for both scanning systems. For high tube voltages, the variation of the phosphor layer thickness results in a DQE maximum at relatively large thicknesses. For lower tube voltages the DQE is less dependent on the layer thickness, reaching excellent values already at considerably lower thicknesses. Consequently, CR scanners can be adapted to different applications by using NIPs with different thicknesses. This could be easily realized for the cassette based system, but not for the flat-panel system with fixed IP. The latter demands a compromise with respect to the phosphor thickness, to yield superior image quality for all applications.

  6. Microstructure and Mechanical Properties of Cr-SiC Particles-Reinforced Fe-Based Alloy Coating

    NASA Astrophysics Data System (ADS)

    Wang, Fu-cheng; Du, Xiao-dong; Zhan, Ma-ji; Lang, Jing-wei; Zhou, Dan; Liu, Guang-fu; Shen, Jian

    2015-12-01

    In this study, SiC particles were first coated with Cr to form a layer that can protect the SiC particles from dissolution in the molten pool. Then, the Cr-SiC powder was injected into the tail of molten pool during plasma-transferred arc welding process (PTAW), where the temperature was relatively low, to prepare Cr-SiC particles reinforced Fe-based alloy coating. The microstructure and phase composition of the powder and surface coatings were analyzed, and the element distribution and hardness at the interfacial region were also evaluated. The protective layer consists of Cr3Si, Cr7C3, and Cr23C6, which play an important role in the microstructure and mechanical properties. The protective layer is dissolved in the molten pool forming a flocculent region and a transition region between the SiC particles and the matrix. The tribological performance of the coating was also assessed using a ring-block sliding wear tester with GGr15 grinding ring under 490 and 980 N load. Cr-SiC particles-reinforced coating has a lower wear rate than the unreinforced coating.

  7. Giant Magnetoresistance and Coercivity of electrodeposited multilayered FeCoNi/Cu and CrFeCoNi/Cu

    NASA Astrophysics Data System (ADS)

    Shakya, P.; Cox, B.; Davis, D.

    2012-02-01

    The effect of Cr addition on electrodeposited multilayered nanowires CrFeCoNi/Cu was investigated from a magnetic property perspective: current perpendicular to the plane-Giant Magnetoresistance (CPP-GMR) and Coercivity (BH loops). The magnetic behavior of multilayered nanowires of CrFeNiCo/Cu was also affected by the alloy deposition potential, alloy pulsing time (layer thickness) and number of bilayers. Furthermore, the addition of Cr influenced both the nanowires GMR and Coercivity. Cr addition to the ferromagnetic FeCoNi layer induced a reduction in the room temperature GMR from 10.64% to 5.62%; however, the magnetic saturation field decreased from 0.45 to 0.27 T. The increase in the number of bilayers, from 1000 to 2500, resulted in a higher GMR value, 14.56% with 0.35 T magnetic saturation field. Addition of Cr to the ferromagnetic layer decreased the coercivity from 0.015 to 0.0054 T. Low saturation field CPP-GMR nanowires showing low coercivity at room temperature opens a new door for magnetic sensing devices. To the best of our knowledge, this is the first study on electrodeposited CrFeCoNi/Cu multilayered nanowires.

  8. Corrosion Behavior of NiCrFe Alloy 600 in High Temperature, Hydrogenated Water

    SciTech Connect

    SE Ziemniak; ME Hanson

    2004-11-02

    The corrosion behavior of Alloy 600 (UNS N06600) is investigated in hydrogenated water at 260 C. The corrosion kinetics are observed to be parabolic, the parabolic rate constant being determined by chemical descaling to be 0.055 mg dm{sup -2} hr{sup -1/2}. A combination of scanning and transmission electron microscopy, supplemented by energy dispersive X-ray spectroscopy and grazing incidence X-ray diffraction, are used to identify the oxide phases present (i.e., spinel) and to characterize their morphology and thickness. Two oxide layers are identified: an outer, ferrite-rich layer and an inner, chromite-rich layer. X-ray photoelectron spectroscopy with argon ion milling and target factor analysis is applied to determine spinel stoichiometry; the inner layer is (Ni{sub 0.7}Fe{sub 0.3})(Fe{sub 0.3}Cr{sub 0.7}){sub 2}O{sub 4}, while the outer layer is (Ni{sub 0.9}Fe{sub 0.1})(Fe{sub 0.85}Cr{sub 0.15}){sub 2}O{sub 4}. The distribution of trivalent iron and chromium cations in the inner and outer oxide layers is essentially the same as that found previously in stainless steel corrosion oxides, thus confirming their invariant nature as solvi in the immiscible spinel binary Fe{sub 3}O{sub 4}-FeCr{sub 2}O{sub 4} (or NiFe{sub 2}O{sub 4}-NiCr{sub 2}O{sub 4}). Although oxidation occurred non-selectively, excess quantities of nickel(II) oxide were not found. Instead, the excess nickel was accounted for as recrystallized nickel metal in the inner layer, as additional nickel ferrite in the outer layer, formed by pickup of iron ions from the aqueous phase, and by selective release to the aqueous phase.

  9. Ozone Layer Protection

    MedlinePlus

    ... EPA United States Environmental Protection Agency Search Search Ozone Layer Protection Share Facebook Twitter Google+ Pinterest Contact Us Ozone Layer Protection Welcome to EPA's ozone layer protection web ...

  10. Novel Cu-Cr alloy matrix CNT composites with enhanced thermal conductivity

    NASA Astrophysics Data System (ADS)

    Kong, Jian; Zhang, Chao-ying; Cheng, Xiang

    2013-09-01

    Carbon nanotubes (CNTs) are incorporated into the Cu-Cr matrix to fabricate bulk CNT/Cu-Cr composites by means of a powder metallurgy method, and their thermal conductivity behavior is investigated. It is found that the formation of Cr3C2 interfacial layer improves the interfacial bonding between CNTs and Cu-Cr matrix, producing a reduction of interfacial thermal resistance, and subsequently enhancing the thermal conductivity of the composites. The thermal conductivity of the composites increases by 12 % and 17 % with addition of 5 vol.% and 10 vol.% CNTs, respectively. The experimental results are also theoretically analyzed using an effective medium approximation (EMA) model, and it is found that the EMA model combined with a Debye model can provide a satisfactory agreement to the experimental data.

  11. Process for producing Ti-Cr-Al-O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2001-01-01

    Thin films of Ti-Cr-Al-O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti-Cr-Al-O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti-Cr-Al-O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti-Cr-Al-O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  12. Flat panel display using Ti-Cr-Al-O thin film

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2002-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  13. Perpendicular magnetic properties of CoCr films on GaAs

    NASA Astrophysics Data System (ADS)

    Manago, T.; Kuramochi, H.; Akinaga, H.

    2005-01-01

    CoCr films were deposited on three types of GaAs substrates, GaAs(001), GaAs(111), and Al oxide/GaAs(001). The perpendicular magnetic properties were investigated by magneto-optical Kerr-effect measurements. The direct deposition of the CoCr film on the GaAs substrate did not show any perpendicular magnetic properties. This fact indicates that the lattice distortion influenced by the GaAs lattice suppresses the perpendicular magnetism. The CoCr film on the Al oxide layer showed a tilted squarelike hysteresis loop. The thickness dependence of the hysteresis loop and the magnetic force microscopy showed that the onset thickness of ferromagnetism was 6.5nm. The domain size of the CoCr films monotonously decreases with the increasing thickness (6.5-75nm).

  14. Efficiency enhancement of CIGS compound solar cell fabricated using homomorphic thin Cr2O3 diffusion barrier formed on stainless steel substrate

    NASA Astrophysics Data System (ADS)

    Sim, Jae-Kwan; Lee, Seung-Kyu; Kim, Jin-Soo; Jeong, Kwang-Un; Ahn, Haeng-Keun; Lee, Cheul-Ro

    2016-12-01

    It is known that the efficiency of flexible Cu(In,Ga)Se2 (CIGS) solar cells fabricated on stainless-steel (STS) substrates deteriorates due to iron (Fe) and Cr impurities diffusing into the CIGS absorber layer. To overcome this problem, a nanoscale homomorphic chromium oxide layer was formed as a diffusion barrier by thermal oxidation on the surface of STS substrates for 1 min at 600 °C in oxygen atmosphere. By TEM and grazing-incidence X-ray diffraction (GIXRD), it was confirmed that the formed oxide layer on surface of STS substrates was a Cr2O3 layer. It was found that the formed homomorphic Cr2O3 thin layer of about 15 nm thickness was an effective diffusion barrier to reduce impurity diffusion into the CIGS layer by secondary ion mass spectroscopy (SIMS). In contrast to the efficiency of CIGS solar cell without homomorphic Cr2O3 diffusion layer is 8.6%, whereas with diffusion barrier it increases to 10.6% because of impurities such as Fe and Cr from the STS substrate into the CIGS layer. It reveals that the layer formed on the surface of STS substrate by thermal oxidation process plays an important role in increasing the performance of CIGS solar cells.

  15. Comparison of different chelating agents to enhance reductive Cr(VI) removal by pyrite treatment procedure.

    PubMed

    Kantar, Cetin; Ari, Cihan; Keskin, Selda

    2015-06-01

    New technologies involving in-situ chemical hexavalent chromium [Cr(VI)] reduction to trivalent chromium [Cr(III)] with natural Fe(II)-containing minerals can offer viable solutions to the treatment of wastewater and subsurface systems contaminated with Cr(VI). Here, the effects of five different chelating agents including citrate, EDTA, oxalate, tartrate and salicylate on reductive Cr(VI) removal from aqueous systems by pyrite were investigated in batch reactors. The Cr(VI) removal was highly dependent on the type of ligand used and chemical conditions (e.g., ligand concentration). While salicylate and EDTA had no or little effect on Cr(VI) removal, the ligands including citrate, tartrate and oxalate significantly enhanced Cr(VI) removal at pH < 7 relative to non-ligand systems. In general, the efficiency of organic ligands on Cr(VI) removal decreased in the order: citrate ≥ oxalate ≈ tartrate > EDTA > salicylate ≈ non-ligand system. Organic ligands enhanced Cr(VI) removal by 1) removing surface oxide layer via the formation of soluble Fe-Cr-ligand complexes, and 2) enhancing the reductive iron redox cycling for the regeneration of new surface sites. While citrate, oxalate and tartrate eliminated the formation of surface Cr (III)-Fe(III)-oxides, the surface phase Cr (III) species was observed in the presence of EDTA and salicylate indicating that Cr(III) complexed with EDTA and salicylate sorbed or precipitated onto pyrite surface, thereby blocking the access of CrO4(2-) to pyrite surface. The binding of Fe(III) with the disulfide reactive sites (≡Fe-S-S-Fe(III)) was essential for the regeneration of new surface sites through pyrite oxidation. Although Fe(III)-S species was detected at the pyrite surface in the presence of citrate, oxalate and tartrate, Fe(III) complexed with EDTA and salicylate did not strongly interact with the disulfide reactive sites due to the formation of non-sorbing Fe(III)-ligand complexes. The absence of surface Fe

  16. Ti3CrCu4: A possible 2-D ferromagnetic spin fluctuating system

    NASA Astrophysics Data System (ADS)

    Dhar, S. K.; Provino, A.; Manfrinetti, P.; Kulkarni, R.; Goyal, Neeraj; Paudyal, D.

    2016-05-01

    Ti3CrCu4 is a new ternary compound which crystallizes in the tetragonal Ti3Pd5 structure type. The Cr atoms form square nets in the a-b plane (a = 3.124 Å) which are separated by an unusually large distance c = 11.228 Å along the tetragonal axis, thus forming a -2-D Cr-sublattice. The paramagnetic susceptibility is characterized by a low effective moment, μeff = 1.1 μB, a low paramagnetic Curie temperature θP (below 7 K) and a temperature independent χ0 = 6.7 x 10-4 emu/mol. The magnetization at 1.8 K increases rapidly with field nearly saturating to 0.2 μB/f.u. The zero field heat capacity C/T shows an upturn below 7 K (˜190 mJ/mol K2 at ˜0.1K) which is suppressed in applied magnetic fields and interpreted as suggesting the presence of spin fluctuations. The resistivity at low temperatures shows non-Fermi liquid behavior. Overall, the experimental data thus reveal an unusual magnetic state in Ti3CrCu4, which likely has its origin in the layered nature of the Cr sub-lattice and ferromagnetic spin fluctuations. Density functional theoretical calculations reveal a sharp Cr density of states peak just above the Fermi level, indicating the propensity of Ti3CrCu4 to become magnetic.

  17. Microstructures and Thermal Properties of Cold-Sprayed Cu-Cr Composite Coatings

    NASA Astrophysics Data System (ADS)

    Kikuchi, S.; Yoshino, S.; Yamada, M.; Fukumoto, M.; Okamoto, K.

    2013-08-01

    Copper-based composites for thermal conductive components were prepared via the cold spray process, and the deposition efficiency and adhesion morphology of feedstock powders on Cu substrate were evaluated. Cu-based composites were fabricated using Cu-Cr mixed powders with their mixture ratio of 20, 35, 50, and 65 mass% Cr onto oxygen-free copper substrate with N2 carrier gas. Cu-Cr composite coatings were investigated for their Cr content ratio, microstructures, and thermal conductivity. The Cr content ratio in the coating was approximately 50-60% of feedstock mixture ratio due to the low formability of the hard particles. Transmission electron microscopy characterizations revealed that an oxygen-rich layer exists at the Cr particle/Cu substrate interface, which contributes to the deposition of the Cr particles. After the heat treatment at 1093 K, the coatings showed denser cross-sectional structures than those before the heat treatment, and the thermal conductivity was improved as a result of the recrystallization of Cu matrix.

  18. Development of multilayer oxidation resistant coatings on Cr-50Nb alloy

    NASA Astrophysics Data System (ADS)

    Zheng, Haizhong; Xiong, Lingling; Luo, Qinhao; Lu, Shiqiang

    2015-12-01

    To protect Cr-50Nb alloys from high-temperature oxidation, the Al2O3/Si-Al multilayer coatings were produced by pack cementation process, followed by sol-gel process and hot pressing. The results indicate that the multilayer coating is dense and exhibits good adherence to the substrate, which consists of a compact Al2O3 outer layer and an inner layer composed of Si, Al, Cr, Nb. Uncoated Cr-50Nb alloy occurs catastrophic oxidation at the initial oxidation stage at 1200 °C. However, the scale spalling resistance of the multilayer coating is improved significantly, and the multilayer coating exhibits good resistance to oxidation. During cyclic oxidation in air at 1200 °C for 100 h, the weight loss is 0.13 mg/cm2 and the mass gain is 3.38 mg/cm2.

  19. Transient oxidation of multiphase Ni-Cr base alloys

    SciTech Connect

    Baran, G.; Meraner, M.; Farrell, P.

    1988-06-01

    Four commercially available Ni-Cr-based alloys used with porcelain enamels were studied. Major alloying elements were Al, Be, Si, B, Nb, and Mo. All alloys were multiphase. During heat treatments simulating enameling conditions, phase changes occurred in most alloys and were detected using hardness testing, differential thermal analysis (DTA), and microscopy. Oxidation of these alloys at 1000/degrees/C for 10 min produced an oxide layer consisting principally of chromium oxide, but the oxide morphology varied with each alloy depending on the alloy microstructure. Controlling alloy microstructure while keeping the overall composition unchanged may be a means of preventing wrinkled poorly adherent scales from forming.

  20. Highly Corrosion Resistant and Sandwich-like Si3N4/Cr-CrNx/Si3N4 Coatings Used for Solar Selective Absorbing Applications.

    PubMed

    Zhang, Ke; Du, Miao; Haoa, Lei; Meng, Jianping; Wang, Jining; Mi, Jing; Liu, Xiaopeng

    2016-12-14

    Highly corrosion resistant, layer-by-layer nanostructured Si3N4/Cr-CrNx/Si3N4 coatings were deposited on aluminum substrate by DC/RF magnetron sputtering. Corrosion resistance experiments were performed in 0.5, 1.0, 3.0, and 5.0 wt % NaCl salt spray at 35 °C for 168 h. Properties of the coatings were comprehensively investigated in terms of optical property, surface morphology, microstructure, elemental valence state, element distribution, and potentiodynamic polarization. UV-vis-near-IR spectrophotometer and FTIR measurements show that the change process in optical properties of Si3N4/Cr-CrNx/Si3N4/Al coatings can be divided into three stages: a rapid active degradation stage, a steady passivation stage, and a transpassivation degradation stage. With the increase in the concentration of NaCl salt spray, solar absorptance and thermal emittance experienced a slight degradation. SEM images reveal that there is an increase in surface defects, such as microcracks and holes and -cracks. XRD and TEM measurements indicate that the phase structure changed partially and the content of CrOx and Al2O3 has increased. Auger electron spectroscopy shows that the elements of Cr, N, and O have undergone a minor diffusion. Electrochemical polarization curves show that the as-deposited Si3N4/Cr-CrNx/Si3N4/Al coatings have excellent corrosion resistance of 3633.858 kΩ, while after corroding in 5.0 wt % NaCl salt spray for 168 h the corrosion resistance dropped to 13.759 kΩ. However, these coatings still have an outstanding performance of high solar absorptance of 0.924 and low thermal emittance of 0.090 after corroding in 3.0 wt % NaCl salt spray for 120 h. Thus, the Si3N4/Cr-CrNx/Si3N4/Al coating is a good choice for solar absorber coatings applied in the high-saline environment.

  1. Core layering

    NASA Astrophysics Data System (ADS)

    Jacobson, S. A.; Rubie, D. C.; Hernlund, J. W.; Morbidelli, A.

    2015-12-01

    We have created a planetary accretion and differentiation model that self-consistently builds and evolves Earth's core. From this model, we show that the core grows stably stratified as the result of rising metal-silicate equilibration temperatures and pressures, which increases the concentrations of light element impurities into each newer core addition. This stable stratification would naturally resist convection and frustrate the onset of a geodynamo, however, late giant impacts could mechanically mix the distinct accreted core layers creating large homogenous regions. Within these regions, a geodynamo may operate. From this model, we interpret the difference between the planetary magnetic fields of Earth and Venus as a difference in giant impact histories. Our planetary accretion model is a numerical N-body integration of the Grand Tack scenario [1]—the most successful terrestrial planet formation model to date [2,3]. Then, we take the accretion histories of Earth-like and Venus-like planets from this model and post-process the growth of each terrestrial planet according to a well-tested planetary differentiation model [4,5]. This model fits Earth's mantle by modifying the oxygen content of the pre-cursor planetesimals and embryos as well as the conditions of metal-silicate equilibration. Other non-volatile major, minor and trace elements included in the model are assumed to be in CI chondrite proportions. The results from this model across many simulated terrestrial planet growth histories are robust. If the kinetic energy delivered by larger impacts is neglected, the core of each planet grows with a strong stable stratification that would significantly impede convection. However, if giant impact mixing is very efficient or if the impact history delivers large impacts late, than the stable stratification can be removed. [1] Walsh et al. Nature 475 (2011) [2] O'Brien et al. Icarus 223 (2014) [3] Jacobson & Morbidelli PTRSA 372 (2014) [4] Rubie et al. EPSL 301

  2. Chemical filtration of Cr (VI) with electrospun chitosan nanofiber membranes.

    PubMed

    Li, Lei; Li, Yanxiang; Yang, Chuanfang

    2016-04-20

    Chitosan nanofibers (average diameter of 75nm) were electrospun on polyester (PET) scrim to form composite nanofiber membranes with controlled pore size. The membranes were then stacked as a membrane bed for chemical filtration of Cr (VI) of 1-5mg/L. The performance of the bed with respect to loading capacity at breakthrough, bed saturation and utilization efficiency were carefully investigated. The results showed that while these three parameters were dependent on pH, flow rate, flow distribution and packed pattern of the membrane, the latter two were less affected by feed Cr (VI) concentration and bed length. The maximum bed loading capacity for 1mg/L Cr (VI) filtration at breakthrough was found to be 16.5mg-chromium/g-chitosan, higher than the static adsorption capacity of 11.0mg-chromium/g-chitosan using nanofiber mats, indicating the membranes' better potential for dynamic adsorption. The minimum bed length required to avoid breakthrough was determined to be three layers of stacked membranes with nanofiber deposition density of 1g/m(2) by applying bed depth service time (BDST) model.

  3. Diffusive Interaction Between Ni-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Tkacz-Śmiech, Katarzyna; Danielewski, Marek; Bożek, Bogusław; Berent, Katarzyna; Zientara, Dariusz; Zajusz, Marek

    2017-03-01

    In high-temperature coatings, welded parts, and a range of other applications, components in the contact zone interdiffuse at elevated temperatures and may react to change the phase composition. The diffusion zone can be complex and can consist of sequential layers of intermediate phases, solid solutions, and in the case of multicomponent systems also of multiphase layers. In this work, the interdiffusion in Ni-Cr-Al alloys is studied experimentally and modeled numerically. The diffusion multiples were prepared by hot isostatic pressing and post-annealing at 1473 K (1200 °C). The concentration profiles were measured with wide-line EDS technique which allowed obtaining high-accuracy diffusion paths. The experimental profiles and diffusion paths were compared with numerical results simulated with application of very recent model of interdiffusion in muticomponent-multiphase systems. The calculated and experimental data show good agreement.

  4. Cr isotope fractionation factors for Cr(VI) reduction by a metabolically diverse group of bacteria

    NASA Astrophysics Data System (ADS)

    Basu, Anirban; Johnson, Thomas M.; Sanford, Robert A.

    2014-10-01

    Reduction of Cr(VI) is an important process that determines the geochemical behavior, mobility and bioavailability of Cr in both terrestrial and marine environments. Many metabolically diverse microorganisms possess Cr(VI) reduction capacity. Cr(VI) reduction fractionates Cr isotopes and thus 53Cr/52Cr ratios can be used to monitor Cr(VI) reduction and redox conditions. The magnitude of isotopic fractionation (ε) for a variety of microbial reduction mechanisms must be known for accurate interpretation of observed shifts in 53Cr/52Cr ratios. We determined isotopic fractionation factors for Cr(VI) reduction by metal reducers Geobacter sulfurreducens and Shewanella sp. strain NR, a denitrifying soil bacterium Pseudomonas stutzeri DCP-Ps1, and a sulfate reducer Desulfovibrio vulgaris. All bacteria investigated in this study produced significant Cr isotope fractionation. The fractionation (ε) for G. sulfurreducens, Shewanella sp. (NR), P. stutzeri DCP-Ps1, and D. vulgaris were -3.03‰ ± 0.12‰, -2.17‰ ± 0.22‰, -3.14‰ ± 0.13‰, and -3.01‰ ± 0.11‰, respectively. Despite differences in microbial strains in this study, the ε did not vary significantly except for Shewanella sp. (NR). Our results suggest that strong isotopic fractionation is induced during Cr(VI) reduction under electron donor poor (∼300 μM) conditions.

  5. Simulation of tunable Cr:YSO Q-switched Cr:LiSAF laser

    NASA Astrophysics Data System (ADS)

    Chen, Hsiu-Fen; Hsieh, Shang-Wei; Kuo, Yen-Kuang

    2005-01-01

    In this work, we numerically investigate the passive Q-switching performance of the tunable Cr:YSO Q-switched Cr:LiSAF laser over its entire tuning range. Specifically, the optical performance of the Cr:YSO Q-switched Cr:LiSAF laser as functions of the initial population in the ground state of the Cr:YSO saturable absorber, the pumping rate, the reflectivity of the output coupler, and the dissipative loss inside the laser cavity are studied. Simulation results show that the Cr:YSO is an effective saturable absorber Q switch for the Cr:LiSAF laser over its entire tuning range. Unlike the Cr:YSO Q-switched alexandrite laser and the Cr:YSO Q-switched Cr:LiCAF laser, the Cr:YSO Q-switched Cr:LiSAF laser has similar passive Q-switching performance when the laser polarization is along each of the three principal axes of the Cr:YSO. The results obtained numerically in this work are in good agreement with those obtained experimentally by other researchers. Our simulation results indicate that, a Q-switched laser pulse with an output energy of 10 mJ and a pulse width of 17 ns may be obtained at 850 nm, the peak of its tuning spectrum.

  6. Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4 and CoCr2O4

    SciTech Connect

    Ziemniak SE, Anovitz LM, Castelli RA, Porter WD

    2007-01-09

    High temperature heat capacity measurements were obtained for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} using a differential scanning calorimeter. These data were combined with previously-available, overlapping heat capacity data at temperatures up to 400 K and fitted to 5-parameter Maier-Kelley C{sub p}(T) equations. Expressions for molar entropy were then derived by suitable integration of the Maier-Kelley equations in combination with recent S{sup o}(298) evaluations. Finally, a database of high temperature equilibrium measurements on the formation of these oxides was constructed and critically evaluated. Gibbs energies of Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4} were referenced by averaging the most reliable results at reference temperatures of 1100, 1400 and 1373 K, respectively, while Gibbs energies for ZnCr{sub 2}O{sub 4} were referenced to the results of Jacob [Thermochim. Acta 15 (1976) 79-87] at 1100 K. Thermodynamic extrapolations from the high temperature reference points to 298.15 K by application of the heat capacity correlations gave {Delta}{sub f}G{sup o}(298) = -1049.96, -1339.40, -1428.35 and -1326.75 kJ mol{sup -1} for Cr{sub 2}O{sub 3}, FeCr{sub 2}O{sub 4}, ZnCr{sub 2}O{sub 4} and CoCr{sub 2}O{sub 4}, respectively.

  7. Thermodynamic Assessment of Chrome-Spinel Formation in Laser-Sintered Coatings with Cr2O3 Particles

    NASA Astrophysics Data System (ADS)

    Krivilyov, Mikhail; Kharanzhevskiy, Evgeny; Reshetnikov, Sergey; Beyers, Lesley J.

    2016-06-01

    Formation of a thin passive layer has been performed using short pulse laser dispersion of Cr2O3 particles in a C22 steel substrate. As a result, the coating's corrosion resistance is substantially improved compared to unprocessed samples. Microstructure analysis by TEM, XPS, and XRD showed that laser processing leads to dissolution of Cr2O3 with formation of Cr and Fe oxides, chrome-spinel, and metallic Cr dispersed in alpha and gamma Fe. Thermodynamic assessment revealed that the formation of pure chromium is caused by reduction of Cr2O3 and oxidation of iron. This reaction is promoted by shifting of chemical equilibrium at elevated temperatures in the molten zone under short pulse laser processing.

  8. Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

    DOEpatents

    Singh, Prabhakar; Ruka, Roswell J.

    1995-01-01

    A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO.sub.3 particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr.sub.2 O.sub.3 on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO.sub.3 layer coated with CaO and Cr.sub.2 O.sub.3 surface deposit at from about 1000.degree. C. to 1200.degree. C. to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO.sub.3 layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power.

  9. Method and closing pores in a thermally sprayed doped lanthanum chromite interconnection layer

    DOEpatents

    Singh, P.; Ruka, R.J.

    1995-02-14

    A dense, substantially gas-tight electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an air electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element or elements selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by thermal spraying doped LaCrO{sub 3} particles, either by plasma arc spraying or flame spraying; (C) depositing a mixture of CaO and Cr{sub 2}O{sub 3} on the surface of the thermally sprayed layer; and (D) heating the doped LaCrO{sub 3} layer coated with CaO and Cr{sub 2}O{sub 3} surface deposit at from about 1,000 C to 1,200 C to substantially close the pores, at least at a surface, of the thermally sprayed doped LaCrO{sub 3} layer. The result is a dense, substantially gas-tight, highly doped, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the nonselected portion of the air electrode. A fuel electrode can be applied to the solid electrolyte, to form an electrochemical cell, for example for generation of electrical power. 5 figs.

  10. Studies on Transient-Stage-Scale Growth on Fe-22wt.% Cr Alloys Containing 120 PPM La + 270 PPM Ce

    DTIC Science & Technology

    2009-02-01

    diffuse towards the surface where a scale rich in spinel starts to form. This spinel evolves becoming richer in Cr and Mn and nodules made out of chromium ... chromium content iron alloys Abstract Reactive elements (RE), such as Ce, La or Y, are known to improve oxidation resistance of Fe based alloys that...but when the oxidation time is long enough, Cr and Mn oxides will bury it under an oxides layer. This indicates the formation of chromium and

  11. GALPROP: New Developments in CR Propagation Code

    NASA Technical Reports Server (NTRS)

    Moskalenko, I. V.; Jones, F. C.; Mashnik, S. G.; Strong, A. W.; Ptuskin, V. S.

    2003-01-01

    The numerical Galactic CR propagation code GALPROP has been shown to reproduce simultaneously observational data of many kinds related to CR origin and propagation. It has been validated on direct measurements of nuclei, antiprotons, electrons, positrons as well as on astronomical measurements of gamma rays and synchrotron radiation. Such data provide many independent constraints on model parameters while revealing some contradictions in the conventional view of Galactic CR propagation. Using a new version of GALPROP we study new effects such as processes of wave-particle interactions in the interstellar medium. We also report about other developments in the CR propagation code.

  12. Introduction to AIRS and CrIS

    NASA Technical Reports Server (NTRS)

    Susskind, Joel

    2004-01-01

    "Introduction to AIRS and CrIS" is a chapter in a book dealing with various aspects of remote sensing. AIRS and CrIS are both high spectral resolution IR sounding instruments, which were recently launched (AIRS) or will soon be launched (CrIS). The chapter explains the general principles of infra-red remote sensing, and explains the significance and information content of high spectral resolution IR measurements. The chapter shows results obtained using AIRS observations, and explains why similar quality results should be obtainable from CrIS data.

  13. Nucleation of Cr precipitates in Fe-Cr alloy under irradiation

    SciTech Connect

    Dai, Y. Y.; Ao, L.; Sun, Qing- Qiang; Yang, L.; Nie, JL; Peng, SM; Long, XG; Zhou, X. S.; Zu, Xiaotao; Liu, L.; Sun, Xin; Terentyev, Dimtry; Gao, Fei

    2015-04-01

    The nucleation of Cr precipitates induced by overlapping of displacement cascades in Fe-Cr alloys has been investigated using the combination of molecular dynamics (MD) and Metropolis Monte Carlo (MMC) simulations. The results reveal that the number of Frenkel pairs increases with the increasing of overlapped cascades. Overlapping cascades could promote the formation of Cr precipitates in Fe-Cr alloys, as analyzed using short range order (SRO) parameters to quantify the degree of ordering and clustering of Cr atoms. In addition, the simulations using MMC approach show that the presence of small Cr clusters and vacancy clusters formed within cascade overlapped region enhance the nucleation of Cr precipitates, leading to the formation of large Cr dilute precipitates.

  14. Diffusion of cations in chromia layers grown on iron-base alloys

    SciTech Connect

    Lobnig, R.E.; Hennesen, K.; Grabke, H.J. ); Schmidt, H.P.

    1992-02-01

    Diffusion of the cations Cr, Fe, Mn, and Ni in Cr{sub 2}O{sub 3} has been investigated at 1,173 K. The diffusion measurements were performed on chromia layers grown on the model alloys Fe-20Cr and Fe-20Cr-12Ni in order to consider effects of small amounts of dissolved alien cations in Cr{sub 2}O{sub 3}. The samples were diffusion annealed in H{sub 2}-H{sub 2}O at an oxygen partial pressure close to the Cr{sub 2}O{sub 3}/Cr equilibrium. For all tracers the lattice-diffusion coefficients are 3-5 orders of magnitude smaller than the grain-boundary diffusion coefficients. The lattice diffusivity of Mn is about two orders of magnitude greater than the other lattice-diffusion coefficients, especially in Cr{sub 2}O{sub 3} grown on Fe-20Cr-12Ni. The values of the diffusion coefficients for Cr, Fe, and Ni are in the same range. Diffusion of the tracers in Cr{sub 2}O{sub 3} grown on different alloys did not show significant differences with the exception of Mn.

  15. Wetted Foam Liquid DT Layer ICF Experiments at the NIF

    NASA Astrophysics Data System (ADS)

    Olson, R. E.; Leeper, R. J.; Peterson, R. R.; Yi, S. A.; Zylstra, A. B.; Kline, J. L.; Bradley, P. A.; Yin, L.; Wilson, D. C.; Haines, B. M.; Batha, S. H.

    2016-10-01

    A key physics issue in indirect-drive ICF relates to the understanding of the limitations on hot spot convergence ratio (CR), principally set by the hohlraum drive symmetry, the capsule mounting hardware (the ``tent''), and the capsule fill tube. An additional key physics issue relates to the complex process by which a hot spot must be dynamically formed from the inner ice surface in a DT ice-layer implosion. These physics issues have helped to motivate the development of a new liquid DT layer wetted foam platform at the NIF that provides an ability to form the hot spot from DT vapor and experimentally study and understand hot spot formation at a variety of CR's in the range of 12<CR<25. Flexibility in CR will provide a means for exploring variations in the partitioning of available energy between the hot spot and the low adiabat cold fuel during the stagnation process and can allow for a fundamentally different (and potentially more robust) process of hot spot formation. This new experimental platform is currently being used in a series of experiments to discover a range of CR's at which DT layered implosions will have understandable performance - providing a sound basis from which to determine the requirements for ICF ignition. This work was performed under the auspices of the U. S. DOE by LANL under contract DE-AC52-06NA25396.

  16. Epitaxial Cr on n-SrTiO3(001)—An ideal Ohmic contact

    SciTech Connect

    Capan, Cigdem; Sun, Guangyuan; Bowden, Mark E.; Chambers, Scott A.

    2012-01-30

    Epitaxial Cr metallizations grown on n-SrTiO3(001) by molecular beam epitaxy are shown to result in an ordered interface with Cr bound to O in the terminal TiO2 layer, no reduction of the SrTiO3, and a near-perfect Ohmic contact. Cr/n-SrTiO3(001) thus constitutes an ideal interface between a pure metal and wide gap oxide in which interface redox chemistry does not occur, and the Fermi level remains unpinned.

  17. LET Spectrum Measurements In CR-39 PNTD With AFM

    SciTech Connect

    Johnson, C. E.; DeWitt, J. M.; Benton, E. R.; Yasuda, N.; Benton, E. V.

    2011-06-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range ({approx}<10 {mu}m) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching ({approx}<1 {mu}m) following by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features inherently present in the post-etch detector surface. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/{mu}m. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to 1 GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  18. LET Spectrum Measurements In CR-39 PNTD With AFM

    NASA Astrophysics Data System (ADS)

    Johnson, C. E.; DeWitt, J. M.; Benton, E. R.; Yasuda, N.; Benton, E. V.

    2011-06-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range (˜<10 μm) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching (˜<1 μm) following by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features inherently present in the post-etch detector surface. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/μm. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to 1 GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  19. LET spectrum measurements in Cr-39 PNTD with AFM

    SciTech Connect

    Johnson, Carl Edward; De Witt, Joel M; Benton, Eric R; Yasuda, Nakahiro; Benton, Eugene V

    2010-01-01

    Energetic protons, neutrons, and heavy ions undergoing collisions with target nuclei of varying Z can produce residual heavy recoil fragments via intra-nuclear cascade/evaporation reactions. The particles produced in these non-elastic collisions generally have such extremely short range ({approx}< 10 {mu}m) that they cannot be directly observed by conventional detection methods including CR-39 plastic nuclear track detector (PNTD) that has been chemically etched for analysis by standard visible light microscopy. However, high-LET recoil fragments having range on the order of several cell diameters can be produced in tissue during radiotherapy using proton and carbon beams. We have developed a method to analyze short-range, high-LET tracks in CR-39 plastic nuclear track detector (PNTD) using short duration chemical etching ({approx}< 1 {mu}m) followed by automated atomic force microscope (AFM) scanning. The post-scan data processing used in this work was based on semi-automated matrix analysis opposed to traditional grey-scale image analysis. This method takes advantage of the 3-D data obtained via AFM to achieve robust discrimination of nuclear tracks from other features. Through automation of AFM scanning, sufficient AFM scan frames were obtained to attain an LET spectrum spanning the LET range from 200-1500 keV/{mu}m. In addition to our experiments, simulations were carried out with the Monte Carlo transport code, FLUKA. To demonstrate this method, CR-39 PNTD was exposed to the proton therapy beam at Loma Linda University Medical Center (LLUMC) at 60 and 230 MeV. Additionally, detectors were exposed to I GeV protons at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL). For these exposures CR-39 PNTD, Al and Cu target foils were used between detector layers.

  20. Suppressing the chromium disproportionation reaction in O3-type layered cathode materials for high capacity sodium-ion batteries

    DOE PAGES

    Cao, Ming -Hui; Wang, Yong; Shadike, Zulipiya; ...

    2017-02-14

    Chromium-based layered cathode materials suffer from the irreversible disproportionation reaction of Cr4+ to Cr3+ and Cr6+, which hinders the reversible multi-electron redox of Cr ions in layered cathodes, and limits their capacity and reversibility. To address this problem, a novel O3-type layer-structured transition metal oxide of NaCr1/3Fe1/3Mn1/3O2 (NCFM) was designed and studied as a cathode material. A high reversible capacity of 186 mA h g–1 was achieved at a current rate of 0.05C in a voltage range of 1.5 to 4.2 V. X-ray diffraction revealed an O3 → (O3 + P3) → (P3 + O3'') → O3'' phase-transition pathway formore » NCFM during charge. X-ray absorption, X-ray photoelectron and electron energy-loss spectroscopy measurements revealed the electronic structure changes of NCFM during Na+ deintercalation/intercalation processes. It is confirmed that the disproportionation reaction of Cr4+ to Cr3+ and Cr6+ can be effectively suppressed by Fe3+ and Mn4+ substitution. Lastly, these results demonstrated that the reversible multi-electron oxidation/reduction of Cr ions can be achieved in NCFM during charge and discharge accompanied by CrO6 octahedral distortion and recovery.« less

  1. Suppressing the chromium disproportionation reaction in O3-type layered cathode materials for high capacity sodium-ion batteries

    SciTech Connect

    Cao, Ming-Hui; Wang, Yong; Shadike, Zulipiya; Yue, Ji-Li; Hu, Enyuan; Bak, Seong-Min; Zhou, Yong-Ning; Yang, Xiao-Qing; Fu, Zheng-Wen

    2017-01-01

    Chromium-based layered cathode materials suffer from the irreversible disproportionation reaction of Cr4+ to Cr3+ and Cr6+, which hinders the reversible multi-electron redox of Cr ions in layered cathodes, and limits their capacity and reversibility. To address this problem, a novel O3-type layer-structured transition metal oxide of NaCr1/3Fe1/3Mn1/3O2 (NCFM) was designed and studied as a cathode material. A high reversible capacity of 186 mA h g-1 was achieved at a current rate of 0.05C in a voltage range of 1.5 to 4.2 V. X-ray diffraction revealed an O3 → (O3 + P3) → (P3 + O3'') → O3'' phase-transition pathway for NCFM during charge. X-ray absorption, X-ray photoelectron and electron energy-loss spectroscopy measurements revealed the electronic structure changes of NCFM during Na+ deintercalation/intercalation processes. It is confirmed that the disproportionation reaction of Cr4+ to Cr3+ and Cr6+ can be effectively suppressed by Fe3+ and Mn4+ substitution. These results demonstrated that the reversible multi-electron oxidation/reduction of Cr ions can be achieved in NCFM during charge and discharge accompanied by CrO6 octahedral distortion and recovery.

  2. A low-Cr metallic interconnect for intermediate-temperature solid oxide fuel cells

    SciTech Connect

    Geng, Shujiang; Zhu, Jiahong; Brady, Michael P; Anderson, Harlan; ZHOU, XIADONG; YANG, ZHENGUO

    2007-01-01

    Solid oxide fuel cells (SOFCs) have attracted significant attention due to the potential for environmentally-friendly power generation with high efficiency, fuel flexibility, and zero/no emissions. However, the main hurdles thwarting the commercial introduction of SOFCs are the stack cost and durability, particularly related to the long-term stability of stack/cell materials such as the interconnect 1-3. There has been recent interest in utilizing the Cr2O3-forming alloys as interconnect for intermediate-temperature SOFCs4-6. As a consequence, volatile Cr species from the Cr2O3 scale can cause severe degradation of electrical and catalytic properties of the cathode7-9. Here, we report a new low-Cr Fe-Co-Ni base alloy that demonstrates a close match in coefficient of thermal expansion (CTE) with adjacent cell components; good oxidation resistance; and low oxide scale area specific resistance (ASR). The formation of a Cr-free (Fe,Co,Ni)3O4 spinel outer layer over the chromia inner layer upon thermal exposure effectively reduces the chromium evaporation.

  3. Ultrathin nanosheets of CrSiTe3. A semiconducting two-dimensional ferromagnetic material

    SciTech Connect

    Lin, Ming -Wei; Zhung, Houlong L.; Yan, Jiaqiang; Ward, Thomas Zac; Puretzky, Alexander A.; Rouleau, Christopher M.; Gai, Zheng; Liang, Liangbo; Meunier, Vincent; Ganesh, Panchapakesan; Kent, Paul R. C.; Sumpter, Bobby G.; Mandrus, David G.; Geohegan, David B.; Xiao, Kai

    2015-11-27

    Finite range ferromagnetism and antiferromagnetism in two-dimensional (2D) systems within an isotropic Heisenberg model at non-zero temperature were originally proposed to be impossible. However, recent theoretical studies using an Ising model have recently shown that 2D magnetic crystals can exhibit magnetism. Experimental verification of existing 2D magnetic crystals in this system has remained elusive. In this work we for the first time exfoliate the CrSiTe3, a bulk ferromagnetic semiconductor, to mono- and few-layer 2D crystals onto a Si/SiO2 substrate. The Raman spectra show the good stability and high quality of the exfoliated flakes, consistent with the computed phonon spectra of 2D CrSiTe3, giving a strong evidence for the existence of 2D CrSiTe3 crystals. When the thickness of the CrSiTe3 crystals is reduced to few-layers, we observed a clear change in resistivity at 80~120 K, consistent with the theoretical calculations on the Curie temperature (Tc) of ~80 K for the magnetic ordering of 2D CrSiTe3 crystals. As a result, the ferromagnetic mono- and few-layer 2D CrSiTe3 indicated here should enable numerous applications in nano-spintronics.

  4. Band Structure Simulations of the Photoinduced Changes in the MgB2:Cr Films

    PubMed Central

    Kityk, Iwan V.; Fedorchuk, Anatolii O.; Ozga, Katarzyna; AlZayed, Nasser S.

    2015-01-01

    An approach for description of the photoinduced nonlinear optical effects in the superconducting MgB2:Cr2O3 nanocrystalline film is proposed. It includes the molecular dynamics step-by-step optimization of the two separate crystalline phases. The principal role for the photoinduced nonlinear optical properties plays nanointerface between the two phases. The first modified layers possess a form of slightly modified perfect crystalline structure. The next layer is added to the perfect crystalline structure and the iteration procedure is repeated for the next layer. The total energy here is considered as a varied parameter. To avoid potential jumps on the borders we have carried out additional derivative procedure.

  5. Tissue accumulation and urinary excretion of Cr in chromium picolinate (CrPic)-supplemented lambs.

    PubMed

    Dallago, Bruno Stéfano Lima; Lima, Bárbara Alcântara Ferreira; Braz, Shélida Vasconcelos; Mustafa, Vanessa da Silva; McManus, Concepta; Paim, Tiago do Prado; Campeche, Aline; Gomes, Edgard Franco; Louvandini, Helder

    2016-05-01

    Chromium (Cr) concentrations in liver, kidney, spleen, heart, lymph node, skeletal muscle, bone, testis and urine of lambs were measured to trace the biodistribution and bioaccumulation of Cr after oral supplementation with chromium picolinate (CrPic). Twenty-four Santa Inês lambs were treated with four different concentrations of CrPic: placebo, 0.250, 0.375 and 0.500 mg of CrPic/animal/day for 84 days. The basal diet consisted of Panicum maximum cv Massai hay and concentrate. Cr concentrations were measured by ICP-MS measuring (52)Cr as collected mass. There was a positive linear relationship between dose administered and the accumulation of Cr in the heart, lungs and testis. Urinary excretion of Cr occurred in a time and dose-dependent manner, so the longer or more dietary Cr provided, the greater excretion of the element. As some non-carcass components (such as lungs or heart) are added to bone and visceral meal to feed animals, there is a risk of bioaccumulation and biomagnification due to Cr offered as CrPic in the diet.

  6. Observation of ferromagnetism above 900 K in Cr-GaN and Cr-AlN

    NASA Astrophysics Data System (ADS)

    Liu, H. X.; Wu, Stephen Y.; Singh, R. K.; Gu, Lin; Smith, David J.; Newman, N.; Dilley, N. R.; Montes, L.; Simmonds, M. B.

    2004-11-01

    We report ferromagnetism at over 900K in Cr-GaN and Cr-AlN thin films. The magnetic properties vary as a function of Cr concentration with 60%, and 20%, of the Cr being magnetically active at 3% doping in GaN, and 7% in AlN, respectively. In the GaN sample with the highest magnetically active Cr (60%), channeling Rutherford backscattering indicates that over 70% of Cr impurities are located on substitutional sites. These results give indisputable evidence that substitutional Cr defects are involved in the magnetic behavior. While Cr-AlN is highly resistive, Cr-GaN exhibits properties characteristic of hopping conduction including T-1/2 resistivity dependence and small Hall mobility (0.06cm2/Vs). A large negative magnetoresistance is attributed to the influence of the magnetic field on the quantum interference between the many paths linking two hopping sites. The results strongly suggest that ferromagnetism in Cr-GaN and Cr-AlN can be attributed to the double exchange mechanism as a result of hopping between near-midgap substitutional Cr impurity bands.

  7. Zinc-oxide charge trapping memory cell with ultra-thin chromium-oxide trapping layer

    SciTech Connect

    El-Atab, Nazek; Rizk, Ayman; Nayfeh, Ammar; Okyay, Ali K.

    2013-11-15

    A functional zinc-oxide based SONOS memory cell with ultra-thin chromium oxide trapping layer was fabricated. A 5 nm CrO{sub 2} layer is deposited between Atomic Layer Deposition (ALD) steps. A threshold voltage (V{sub t}) shift of 2.6V was achieved with a 10V programming voltage. Also for a 2V V{sub t} shift, the memory with CrO{sub 2} layer has a low programming voltage of 7.2V. Moreover, the deep trapping levels in CrO{sub 2} layer allows for additional scaling of the tunnel oxide due to an increase in the retention time. In addition, the structure was simulated using Physics Based TCAD. The results of the simulation fit very well with the experimental results providing an understanding of the charge trapping and tunneling physics.

  8. Advanced oxidation process based on the Cr(III)/Cr(VI) redox cycle.

    PubMed

    Bokare, Alok D; Choi, Wonyong

    2011-11-01

    Oxidative degradation of aqueous organic pollutants, using 4-chlorophenol (4-CP) as a main model substrate, was achieved with the concurrent H(2)O(2)-mediated transformation of Cr(III) to Cr(VI). The Fenton-like oxidation of 4-CP is initiated by the reaction between the aquo-complex of Cr(III) and H(2)O(2), which generates HO(•) along with the stepwise oxidation of Cr(III) to Cr(VI). The Cr(III)/H(2)O(2) system is inactive in acidic condition, but exhibits maximum oxidative capacity at neutral and near-alkaline pH. Since we previously reported that Cr(VI) can also activate H(2)O(2) to efficiently generate HO(•), the dual role of H(2)O(2) as an oxidant of Cr(III) and a reductant of Cr(VI) can be utilized to establish a redox cycle of Cr(III)-Cr(VI)-Cr(III). As a result, HO(•) can be generated using both Cr(III)/H(2)O(2) and Cr(VI)/H(2)O(2) reactions, either concurrently or sequentially. The formation of HO(•) was confirmed by monitoring the production of p-hydroxybenzoic acid from [benzoic acid + HO(•)] as a probe reaction and by quenching the degradation of 4-CP in the presence of methanol as a HO(•) scavenger. The oxidation rate of 4-CP in the Cr(III)/H(2)O(2) solution was highly influenced by pH, which is ascribed to the hydrolysis of Cr(III)(H(2)O)(n) into Cr(III)(H(2)O)(n-m)(OH)(m) and the subsequent condensation to oligomers. The present study proposes that the Cr(III)/H(2)O(2) combined with Cr(VI)/H(2)O(2) process is a viable advanced oxidation process that operates over a wide pH range using the reusable redox cycle of Cr(III) and Cr(VI).

  9. Role of Y in the oxidation resistance of CrAlYN coatings

    NASA Astrophysics Data System (ADS)

    Domínguez-Meister, S.; El Mrabet, S.; Escobar-Galindo, R.; Mariscal, A.; Jiménez de Haro, M. C.; Justo, A.; Brizuela, M.; Rojas, T. C.; Sánchez-López, J. C.

    2015-10-01

    CrAlYN coatings with different aluminum (4-12 at.%) and yttrium (2-5 at.%) contents are deposited by d.c. reactive magnetron sputtering on silicon and M2 steel substrates using metallic targets and Ar/N2 mixtures. The influence of the nanostructure and chemical elemental distribution on the oxidation resistance after heating in air at 1000 °C is studied by means of cross-sectional scanning electron microscopy (X-SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GD-OES). The sequential exposure to the metallic targets during the synthesis leads to a multilayer structure where concentration of metallic elements (Cr, Al and Y) is changing periodically. A good oxidation resistance is observed when Al- and Y-rich regions are separated by well-defined CrN layers, maintaining crystalline coherence along the columnar structure. This protective behavior is independent of the type of substrate and corresponds to the formation of a thin mixed (Al, Cr)-oxide scale that protects the film underneath. The GD-OES and XRD analysis have demonstrated that Y acts as a reactive element, blocking the Fe and C atoms diffusion from the steel and favoring higher Al/Cr ratio in the passivation layer after heating. The coating with Y content around 4 at.% exhibited the best performance with a thinner oxide scale, a delay in the CrN decomposition and transformation to Cr2N, and a more effective Fe and C blocking.

  10. Development of new layered selenide oxides with perovskite-type oxide layers

    NASA Astrophysics Data System (ADS)

    Ushiyama, Koichi; Ogino, Hiraku; Kishio, Kohji; Shimoyama, Jun-Ichi

    2010-03-01

    Several Fe-based superconductors with perovskite-type oxide layers, such as Sr2ScFePO3 (Tc ˜ 17 K)^[1], were discovered in our previous study. These compounds are composed of alternate stacking of superconducting layers with antifluorite structure and perovskite-type blocking layers. Since both layers are flexible in terms of chemical composition, development of various new functional materials can be expected from this family. In the present study, we have attempted to synthesize new layered selenide oxides with CuSe layers and discovered more than ten compounds, such as Sr2MCu2Se2O2 (M = Mn, Co, Ni, Cu, Zn) and Sr2MCuSeO3 (M = Sc, Cr, Mn, Fe, Ga, In), thus far. These indicated that the CuSe layer can accommodate various types of blocking layers, which may lead various functions. Among them, Sr2Cu3Se2O2 has a potential as for the mother compound of superconductor, if appropriate concentration of carrier is introduced to the CuO2 layer. Crystal structure and physical properties of these newly found compounds will be reported. [1] H. Ogino et al., Supercond. Sci. Technol. 22 (2009) 075008

  11. Effects of adhesion layer on Ag nanorod growth mode and morphology using glancing angle physical vapor deposition

    NASA Astrophysics Data System (ADS)

    Davies, Matthew P.; McKinney, Casey S.; Serrano, Joel M.; Mullen, Thomas J.; Stagon, Stephen P.

    2017-01-01

    This letter reports on the transition from a non-wetting to an effectively wetting growth mode of silver (Ag) nanorods when an adhesion layer is used during glancing angle physical vapor deposition growth. When deposited onto a silicon substrate without an adhesion layer, Ag nanorods grow from partially interconnected non-wetting islands with diameters of ˜100 nm, although many connect with their neighbors due to small rod-to-rod spacing. When a 1 nm thick Cr adhesion layer is used, which is shown not to completely coat the substrate, the growth mode becomes effectively wetting through the coalescence of closely spaced nuclei, and both Ag nanorod diameter and spacing increase. Alternatively, when a thicker 10 nm Cr adhesion layer is used, the growth mode becomes mixed, as both small effective wetting regions and film gaps exist. For the cases of no adhesion layer and 1 nm Cr adhesion layer, the nanorods are oriented at ˜23° from the substrate but lay down onto the substrate when a 10 nm thick Cr adhesion layer is used. Thin film adhesion tests demonstrate that both 1 nm and 10 nm Cr adhesion layers offer an enhanced performance over no adhesion layer or a glancing angle adhesion layer.

  12. Microstructure and Properties of FeCrB Alloy Coatings Prepared by Wire-Arc Spraying

    NASA Astrophysics Data System (ADS)

    Yao, H. H.; Zhou, Z.; Wang, Y. M.; He, D. Y.; Bobzin, K.; Zhao, L.; Öte, M.; Königstein, T.

    2017-02-01

    To improve the heat transfer ability and wear resistance of drying cylinders in paper production machines, a series of Fe87- x Cr13B x ( x = 1 wt.%, 1.5 wt.%, 2 wt.%, 2.5 wt.%, 3 wt.%, and 4 wt.%) cored wires have been produced and used to prepare coatings by wire-arc spraying, in comparison with conventional X30Cr13 solid wire. All coatings presented dense layered structure with porosity of around 4%. The boron content in the cored wires significantly affected the thermal conductivity of the coating, which is attributed to the combined effects of the crystal structure, grain size, and oxide content of the coating. In the investigated range, the coating with 2 wt.% boron content exhibited the highest thermal conductivity, reaching 8.83 W/m-K, greater than that of X30Cr13 coating (5.45 W/m-K). Furthermore, the microhardness and relative wear resistance of the FeCrB coatings obtained from cored wires with boron addition were greatly increased compared with commercial X30Cr13 coating. Therefore, wire-arc-sprayed FeCrB coating has promise as an effective and economic approach to improve the heat transfer behavior and wear resistance of drying cylinders in the paper industry.

  13. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    DOE PAGES

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; ...

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory insidemore » the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.« less

  14. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    SciTech Connect

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

  15. K4Nb6O17·4.5H2O: a novel dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III).

    PubMed

    Ma, Yuli; Liu, Xiaoqing; Li, Yang; Su, Yiguo; Chai, Zhanli; Wang, Xiaojing

    2014-08-30

    A series of orthorhombic phase K4Nb6O17·4.5H2O was synthesized via a hydrothermal approach. When presented in an acidic pH range, K4Nb6O17·4.5H2O showed a strong ability in quick reduction from Cr(VI) to Cr(III). The resulted Cr(III) ions were removed by an effective adsorption through simply adjusting the solution pH from strong acidity to near neutrality, owing to the sample's unique nano-sheet structure with a wide layer spacing. The Cr(III) ions adsorbed onto samples were released again for reusing by eluting with 1molL(-1) HCl solution, and K4Nb6O17·4.5H2O regenerated by immersing in a KOH solution. The reduction efficiency of Cr(VI) was still up to 98% after irradiation for 60min, and the removal efficiency of Cr(III) ions was as high as 83% even after five cycles. Therefore, K4Nb6O17·4.5H2O is clearly demonstrated to be an excellent dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III). The relevant materials reported herein might be found various environment-related applications.

  16. Passive behaviour of alloy corrosion-resistant steel Cr10Mo1 in simulating concrete pore solutions with different pH

    NASA Astrophysics Data System (ADS)

    Ai, Zhiyong; Jiang, Jinyang; Sun, Wei; Song, Dan; Ma, Han; Zhang, Jianchun; Wang, Danqian

    2016-12-01

    The passive behaviour of new alloy corrosion-resistant steel Cr10Mo1 and plain carbon steel (as a comparison) in simulating concrete pore solutions of different pH (ranging from 13.5 to 9.0) under open circuit potential conditions, was evaluated by various electrochemical techniques: potentiodynamic polarization, capacitance measurements and electrochemical impedance spectroscopy. The chemical composition and structure of passive films were investigated by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The electrochemical responses of passive films show that Cr10Mo1 steel has an increasing passivity with pH decreasing while carbon steel dose conversely, revealing carbonation does no negative effect on passivation of the corrosion-resistant steel. SIMS reveals that the passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer mainly consisting of Fe oxides and hydroxides, and an inner layer enriched in Cr species, while only a Fe-concentrated layer for carbon steel. According to the XPS analysis results, as the pH decreases, more stable and protective Cr oxides are enriched in the film on Cr10Mo1 steel while Fe oxides gradually decompose. Higher content of Cr oxides in the film layer provides Cr10Mo1 corrosion-resistant steel more excellent passivity at lower pH.

  17. Cr-Free Metallic-Ceramic Coatings

    DTIC Science & Technology

    2014-11-01

    PT6-, etc. Nov. 2014 ASM/TSS Aerospace Ctgs. Conf. & Expo. 4 • Al-Chromate/Phosphate Slurries Contain Hexavalent Chromium PEL = 5...Aluminum Metallic-Ceramics Al-Cr2O7/PO4 • Zero VOC’s. • 13.0 wt. % inorganic phosphates • 3.3 wt. % Cr+6 (hexavalent chromium ) before curing

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

    SciTech Connect

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

    2016-02-16

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

  19. Isolation and Cr(VI) reduction characteristics of quinone respiration in Mangrovibacter plantisponsor strain CR1.

    PubMed

    Lian, Jing; Li, Zifu; Xu, Zhifang; Guo, Jianbo; Hu, Zhenzhen; Guo, Yankai; Li, Min; Yang, Jingliang

    2016-07-01

    A Cr(VI)-reducing Mangrovibacter plantisponsor strain, CR1, was isolated from tannery effluent sludge and had quinone respiration characteristics. Its chromate (CrO4 (2-) ) resistance, quinone respiration characteristics, and Cr(VI) reduction efficiencies were evaluated in detail. Strain CR1 exhibited a high Cr(VI) resistance with a minimal inhibitory concentration (MIC) of 32 mM in LB medium, and its quinone respiration could occur when an electron donor and strain CR1 both existed in the reaction system. Cr(VI) reduction by strain CR1 was significantly enhanced by a factor of 0.4-4.3 with five different quinone compounds: anthraquinone-2,7-disulfonate, anthraquinone-1-sulfonate, anthraquinone-2-sulfonate (AQS), anthraquinone-2,6-disulfonate, and anthraquinone-1,5-disulfonate. AQS was the best electron shuttle among them, and the greatest enhancement to the Cr(VI) bio-reduction was achieved with 0.96 mM AQS. The correlation between the reaction constant k (mg Cr(VI) g(-1) dry cell weight H(-1) ) and thermodynamic temperature T (K) was expressed as an Arrhenius equation lnk=-7662.9/T+27.931(R2=0.9486); the activation energy Ea was 63.71 kJ mol(-1) , and the pre-exponential factor A was 1.35 × 10(12)  mg Cr(VI) g(-1) dry cell weight H(-1) . During the Cr(VI) reduction process, the pH tended to become neutral, and the oxidation-reduction potential decreased to -440 mV. The efficient reduction of Cr(VI) mediated by a quinone respiration strain shows potential for the rapid anaerobic removal of Cr(VI).

  20. Distribution of hexavalent Cr species across the clay mineral surface-water interface.

    PubMed

    Fritzen, Mauricia B; Souza, Aloisio J; Silva, Tiago A G; Souza, Luciana; Nome, Rene A; Fiedler, Haidi D; Nome, Faruk

    2006-04-15

    The adsorption isotherms of Cr(VI) on kaolinite, montmorillonite, and alumina were adequately treated with Langmuir model showing behavior characteristic of single-layer adsorption. The efficiency of the adsorbents in removing Cr(VI) from water follows the order alumina > kaolinite > montmorillonite > silica. Speciation studies indicate that hydrogen chromate ions were the major adsorbed species and simultaneous adsorption of dichromate ion occurred at concentrations greater than approximately 10(-3) mol L(-1). It is most probable that the mechanism of adsorption of the hydrogen chromate ion at the surface of alumina is predominantly electrostatic adsorption, with outer sphere complex formation.

  1. Generation of a novel Cr2 gene allele by homologous recombination that abrogates production of Cr2 but is sufficient for expression of Cr1

    PubMed Central

    Donius, Luke R.; Orlando, Christopher M.; Weis, Janis J.; Weis, John H.

    2014-01-01

    The enhancing effects of the complement system for humoral immunity have primarily focused upon the recognition of complement-bound foreign antigens by a co-receptor complex of the antigen-specific B cell receptor (BCR) and complement receptor 2 (Cr2). In vivo experiments using Cr2 gene deficient mice (which lack the expression of both the Cr1 and Cr2 proteins) do demonstrate depressed humoral responses to immunization but cannot be used to define specific contributions of the singular Cr1 or Cr2 proteins on B cell functions. To study the effect of a Cr2 deficiency in a Cr1 sufficient environment we created a mouse line in which the alternative splice site required for the expression of the Cr2 isoform was removed. This mouse line, Cr2KO, still expressed Cr1 on B cells but was deficient for the full length Cr2 protein. Surprisingly a new alternative splice within the Cr2 gene created a truncated product that encoded a novel protein termed iCr2 that was expressed on the surface of the cells. The Cr2KO mouse thus provides a new model system for the analysis of Cr1 and Cr2 functions in the immune response of the mouse. PMID:24012440

  2. Anticorrosion nitrided layers on unalloyed and alloyed steels

    NASA Astrophysics Data System (ADS)

    Wach, P.; Michalski, J.; Burdyński, K.; Ciski, A.

    2017-02-01

    In the paper, nitrided layers on unalloyed and alloyed steels and their corrosion properties are presented. Nitrided layers in the controlled gas nitriding process on C10 and 42CrMo4 steels were formed. Two types of nitrided layers are presented: with nitride iron layers above and below 15 µm. Nitrided layer with nitride layer above 15 µm has good corrosion resistance, but after nitriding of machine parts were subsequently oxidised and impregnated. In the second type of nitrided layer, the surface layers of iron nitrides had a thickness of 3.0 to 11.0 µm. Nitrided layers with a surface layer of iron nitrides with the γ’ (Fe4N) structure were formed on unalloyed steel and investigated. The so-formed layers were subject to basic metallographic, X-ray diffraction and corrosion resistance studies carried out by electrochemical methods and in a neutral salt spray chamber. It was found that the layers consisting only of γ’ phase had a good corrosion resistance. Necessary requirements for achieving an enhanced resistance comprise their complete tightness and thickness not lower than 9.0 µm. Thinner layers had good electrochemical properties but did not exhibit corrosion resistance in the salt spray chamber.

  3. Hafnium influence on the microstructure of FeCrAl alloys

    NASA Astrophysics Data System (ADS)

    Geanta, V.; Voiculescu, I.; Stanciu, E.-M.

    2016-06-01

    Due to their special properties at high temperatures, FeCrAl alloys micro-alloyed with Zr can be regarded as potential materials for use at nuclear power plants, generation 4R. These materials are resistant to oxidation at high temperatures, to corrosion, erosion and to the penetrating radiations in liquid metal environments. Also, these are able to form continuously, by the self-generation process of an oxide coating with high adhesive strength. The protective oxide layers must be textured and regenerable, with a good mechanical strength, so that crack and peeling can not appear. To improve the mechanical and chemical characteristics of the oxide layer, we introduced limited quantities of Zr, Ti, Y, Hf, Ce in the range of 1-3%wt in the FeCrAl alloy. These elements, with very high affinity to the oxygen, are capable to stabilize the alumina structure and to improve the oxide adherence to the metallic substrate. FeCrAl alloys microalloyed with Hf were prepared using VAR (Vacuum Arc Remelting) unit, under high argon purity atmosphere. Three different experimental alloys have been prepared using the same metallic matrix of Fe-14Cr-5Al, by adding of 0.5%wt Hf, 1.0%wt Hf and respectively 1.5%wt Hf. The microhardness values for the experimental alloys have been in the range 154 ... 157 HV0.2. EDAX analyses have been performed to determine chemical composition on the oxide layer and in the bulk of sample and SEM analyze has been done to determine the microstructural features. The results have shown the capacity of FeCrAl alloy to form oxide layers, with different texture and rich in elements such as Al and Hf.

  4. Changes induced in a ZnS:Cr-based electroluminescent waveguide structure by intrinsic near-infrared laser radiation

    SciTech Connect

    Vlasenko, N. A. Oleksenko, P. F.; Mukhlyo, M. A.; Veligura, L. I.

    2013-08-15

    The causes of changes that occur in a thin-film electroluminescent metal-insulator-semiconductor-insulator-metal waveguide structure based on ZnS:Cr (Cr concentration of {approx}4 Multiplication-Sign 10{sup 20} cm{sup -3}) upon lasing ({lambda} Almost-Equal-To 2.6 {mu}m) and that induce lasing cessation are studied. It is established that lasing ceases because of light-scattering inhomogeneities formed in the structure and, hence, optical losses enhance. The origin of the inhomogeneities and the causes of their formation are clarified by studying the surface topology and the crystal structure of constituent layers of the samples before and after lasing. The studies are performed by means of atomic force microscopy and X-ray radiography. It is shown that a substantial increase in the sizes of grains on the surface of the structure is the manifestation of changes induced in the ZnS:Cr film by recrystallization. Recrystallization is initiated by local heating by absorbed laser radiation in existing Cr clusters and quickened by a strong electric field (>1 MV cm{sup -1}). The changes observed in the ZnS:Cr film are as follows: the textured growth of ZnS crystallites, an increase in the content of Cr clusters, and the appearance of some CrS and a rather high ZnO content. Some ways for improving the stability of lasing in the ZnS:Cr-based waveguide structures are proposed.

  5. Microstructures and friction-wear behaviors of cathodic arc ion plated CrC coating at high temperatures

    NASA Astrophysics Data System (ADS)

    Dejun, Kong; Shouyu, Zhu

    2016-11-01

    A CrC coating was deposited on YT14 cemented carbide cutting tools by a CAIP (cathodic arc ion plating). The surface and interface morphologies, chemical composition, and phases of the obtained coating were analyzed with a field emission scanning electronic microscope (FESEM), energy dispersive spectroscope (EDS), and x-ray diffraction (XRD), respectively. The COFs (coefficient of frictions) and worn morphologies of the CrC coating at 300 °C, 400 °C, and 500 °C were investigated by using a high temperature tribometer, the effects of wear temperatures on the friction-wear properties of the CrC coating were discussed. The results show that the CrC coating exhibits fine dense structure, and the lattice constants of CrC coatings are dependent on processing parameters. The C and Cr elements in the coating are mutually diffused with the W, Co, and Ti in the substrate. The average COF of the coating at 300 °C, 400 °C, and 500 °C is 0.64, 0.63, and 0.40, respectively. The Cr2O3 layer formed on the CrC coating at 500 °C has excellent oxidation resistance, which improves lubrication and wear performance, the wear mechanism is abrasive wear and oxidation wear.

  6. Structural analysis of Cr aggregation in ferromagnetic semiconductor (Zn,Cr)Te

    SciTech Connect

    Kobayashi, H.; Yamawaki, K.; Nishio, Y.; Kanazawa, K.; Kuroda, S.; Mitome, M.; Bando, Y.

    2013-12-04

    The Cr aggregation in a ferromagnetic semiconductor (Zn,Cr)Te was studied by performing precise analyses using TEM and XRD of microscopic structure of the Cr-aggregated regions formed in iodine-doped Zn{sub 1−x}Cr{sub x}Te films with a relatively high Cr composition x ∼ 0.2. It was found that the Cr-aggregated regions are composed of Cr{sub 1−δ}Te nanocrystals of the hexagonal structure and these hexagonal precipitates are stacked preferentially on the (111)A plane of the zinc-blende (ZB) structure of the host ZnTe crystal with its c-axis nearly parallel to the (111){sub ZB} plane.

  7. Stratification Mechanism and Interface Characterization of (TiN), (TiC)/NiCrBSi Composite Coatings Synthesized by Laser Remelting

    NASA Astrophysics Data System (ADS)

    Liu, Rongxiang; Lei, Tingquan; Guo, Lixin

    TiC/TiN-reinforced composite coatings were fabricated on the substrate of Ti-6Al-4V alloy using laser remelting. X-ray diffraction (XRD) was used to identify the phases in the laser-clad composite coating; the interface characterization of the dilution zone-clad zone (IDC) and the dilution zone-heat-affected zone (IDH) was observed with a scanning electron microscope (SEM). The results show that the microstructure of a cross-section has stratification characterization, and consists of the clad zone (CZ), the dilution zone (DZ), the diffusion layer (DL) and the heat-affected zone (HAZ). The layer-by-layer microstructure results from the boundary layer phenomenon of viscous melt-fluid and diffusion. The kind of reinforced particle has an effect on the interface morphology, microstructure and flow characterization of the melt-fluid. The phase constitution in the clad zone consists of (Cr-Ni-Fe), TiC, Ni4B3, Ti2Ni, Cr2B and M23C6 for TiC+NiCrBSi coating, and (Cr-Ni-Fe), TiN, NiB, Cr2Ti and Ti2Ni for TiN+NiCrBSi coating. The interfaces of the IDC in the NiCrBSi-clad layer is clear and clean; those of TiC+NiCrBSi and TiN+NiCrBSi are illegible. Ti-Ni phases with acicular microstructure link dilution zone and clad zone, and two kinds of phase with acicular microstructure, are similar in composition and shape.

  8. Be/W and W/Be bilayers deposited on Si substrates with hydrogenated Fe-Cr and Fe-Cr-Al interlayers for plasma facing components

    NASA Astrophysics Data System (ADS)

    Greculeasa, S. G.; Palade, P.; Schinteie, G.; Lungu, G. A.; Porosnicu, C.; Jepu, I.; Lungu, C. P.; Kuncser, V.

    2016-12-01

    Be/W and W/Be bilayers, of interest in regard to the specific behavior of plasma facing components (PFCs) were deposited on Si substrates by thermionic vacuum arc, with Fe, Fe-Cr and Fe-Cr-Al interlayers. The interlayers, with compositions approaching the one of the reduced activation steels used in supporting PFCs, were subsequently annealed in hydrogen atmosphere. The multilayers were characterized with respect to morphologic, structural, diffusional and atomic intermixing aspects via XRD, XRR, X-ray photoemission spectroscopy and Mössbauer spectroscopy. All as-prepared samples present partially amorphous structures. A main α-Fe phase is observed, as well as (superparamagnetic) secondary Fe oxides, metallic Fe with Si, Cr, W and Be neighbors, Be-rich Fe-Be and Fe-Si phases. High amounts of tungsten and tungsten oxides were also evidenced in the Fe layer. The strong atomic intermixing of W and Be layers was indirectly supported by the unusual densities of W and Be layers and 57Fe Mössbauer spectroscopy results.

  9. Diffusion kinetics of Cr in spinel: Experimental studies and implications for 53Mn-53Cr cosmochronology

    NASA Astrophysics Data System (ADS)

    Posner, Esther S.; Ganguly, Jibamitra; Hervig, Richard

    2016-02-01

    The 53Mn-53Cr decay system, in which 53Mn decays to 53Cr (t1/2 = 3.7 Ma) has been widely used to construct 53Cr/52Cr vs. 55Mn/52Cr isochrons and thus determine relative ages of early solar system objects or events, assuming that the initial Cr isotopic ratio, (53Cr/52Cr)o, equals (53Mn/52Cr)o. With the primary objective of interpretation of these ages within a diffusion kinetic framework, we have determined the tracer diffusion coefficient of Cr in natural spinels, which are very close to the MgAl2O4 end-member composition, as a function of temperature and oxygen fugacity (f(O2)). It is found that the diffusion coefficient of Cr, D(Cr), in two stocks of spinels (referred to as cut-gems and gem-gravels) with very similar major element chemistry is consistently different, but the data in each stock yield well defined Arrhenius relations that show a difference of log D of 0.6-1.0, depending on temperature, with the D(Cr) in gem-gravel being higher than that in the cut-gem stock. The D(Cr) was found to have a positive dependence on f(O2) in the range of f(O2) of around ±2 log units relative to that of the wüstite-magnetite buffer. The difference in the D(Cr) between the two stocks and the observed D(Cr) vs. f(O2) relation has been explained in terms of a change of point defect concentration resulting from heterovalent substitution of trace elements and equilibration with the imposed f(O2) conditions, respectively. Assuming a homogeneous semi-infinite matrix, the closure temperature (Tc) of Cr diffusion in spinel has been calculated as a function of grain size, cooling rate, peak temperature (To) and f(O2). Also the dependence of D(Cr) and Tc(Cr) on the Cr# (i.e. Cr/(Cr + Al) ratio) has been accounted for using available D(Cr) vs. Cr# data in Suzuki et al. (2008). We argue, on the basis of crystal chemical considerations and available diffusion kinetic data for minerals, that the Tc for Mn should be much lower than that for Cr in spinel, olivine and orthopyroxene, and

  10. Bright nitriding of Cr-Mo-steels in plasma and gas

    SciTech Connect

    Larisch, B.; Spies, H.J.; Hoeck, K.

    1995-12-31

    Although the reduction of the white layer in special gas atmospheres directly after nitriding and bright nitriding were reported a long time ago, the white layer is mostly removed by mechanical or chemical means in industrial practice. The main reason for this is poor process control. However, new requirements such as the duplex treatment (nitriding + hardcoating), demand a more detailed examination of bright nitriding. Today, new possibilities exist for process control in gas nitriding by solid electrolyte sensors. Steel grades 17CrMoV10 and 31CrMoV9 were bright nitrided in gas and plasma. In contrast to the above experiments, in the two-step technology no white layer forms in the first step (20min) at a higher nitriding potential. By this, the formation of a soft surface layer (of iron) can be avoided. Limits of this technology--for instance in the depth of the formed nitrided case--are discussed. Reasons for the often discussed faster nitriding in plasma are explained on the basis of the experimental results. The influence of ion bombardment in plasma nitriding on the activation of the surface and the nitriding results is discussed in comparison to gas nitriding. In this context the advantages of plasma nitriding--with respect to higher chromium alloyed steels (>5%Cr), which tend to passivation--are shown.

  11. Interstitial loop transformations in FeCr

    SciTech Connect

    Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; Xu, Haixuan

    2015-03-27

    Here, we improve the Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) algorithm by integrating the Activation Relaxation Technique nouveau (ARTn), a powerful open-ended saddle-point search method, into the algorithm. We use it to investigate the reaction of 37-interstitial 1/2[1 1 1] and 1/2[View the MathML source] loops in FeCr at 10 at.% Cr. They transform into 1/2[1 1 1], 1/2[View the MathML source], [1 0 0] and [0 1 0] 74-interstitial clusters with an overall barrier of 0.85 eV. We find that Cr decoration locally inhibits the rotation of crowdions, which dictates the final loop orientation. Moreover, the final loop orientation depends on the details of the Cr decoration. Generally, a region of a given orientation is favored if Cr near its interface with a region of another orientation is able to inhibit reorientation at this interface more than the Cr present at the other interfaces. Also, we find that substitutional Cr atoms can diffuse from energetically unfavorable to energetically favorable sites within the interlocked 37-interstitial loops conformation with barriers of less than 0.35 eV.

  12. Interstitial loop transformations in FeCr

    DOE PAGES

    Béland, Laurent Karim; Osetsky, Yuri N.; Stoller, Roger E.; ...

    2015-03-27

    Here, we improve the Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) algorithm by integrating the Activation Relaxation Technique nouveau (ARTn), a powerful open-ended saddle-point search method, into the algorithm. We use it to investigate the reaction of 37-interstitial 1/2[1 1 1] and 1/2[View the MathML source] loops in FeCr at 10 at.% Cr. They transform into 1/2[1 1 1], 1/2[View the MathML source], [1 0 0] and [0 1 0] 74-interstitial clusters with an overall barrier of 0.85 eV. We find that Cr decoration locally inhibits the rotation of crowdions, which dictates the final loop orientation. Moreover, the final loop orientationmore » depends on the details of the Cr decoration. Generally, a region of a given orientation is favored if Cr near its interface with a region of another orientation is able to inhibit reorientation at this interface more than the Cr present at the other interfaces. Also, we find that substitutional Cr atoms can diffuse from energetically unfavorable to energetically favorable sites within the interlocked 37-interstitial loops conformation with barriers of less than 0.35 eV.« less

  13. Microstructure and properties of borocarburized 15CrNi6 steel after laser surface modification

    NASA Astrophysics Data System (ADS)

    Kulka, M.; Pertek, A.

    2004-09-01

    The paper presents the results of laser heat treatment (LHT) of the borided layers produced on the carburized 15CrNi6 low-carbon steel. The two-step treatment carburizing followed by boriding is termed borocarburizing. Laser tracks were arranged by CO 2 laser beam as a single track and as multiple tracks formed in the shape of helical line. The microstructure in both cases consists of the following zones: iron borides (FeB and Fe 2B) of laser modified morphology, needle-like iron borides, carburized layer with heat affected zone (martensite and alloyed cementite), carburized layer without heat treatment and the substrate (ferrite and pearlite). X-ray microanalysis of the laser modified borocarburized specimen confirmed the presence of the same two types of iron borides (FeB and Fe 2B), like those indicated in the as-borided layer. The layer after borocarburizing and LHT has a high microhardness of iron borides, reducing the hardness gradient between the diffusion layer and the substrate in comparison with only borided layer. Probably, the brittleness of this layer is lower. The improved wear resistance of this layer has been found in comparison with borided and borocarburized layers after conventional heat treatment. It is probably result of globular iron boride presence after laser surface modification.

  14. Structure and mechanical properties of polycrystalline CrN/TiN superlattices

    SciTech Connect

    Yashar, P.; Barnett, S.A.; Rechner, J.; Sproul, W.D.

    1998-09-01

    Polycrystalline CrN/TiN superlattice films were deposited on M1 tool steel using unbalanced reactive magnetron sputtering with opposed cathodes. The Cr and Ti targets were sputtered in Ar{endash}N{sub 2} mixtures with partial pressure control of the N{sub 2}. As the N{sub 2} partial pressure was increased from 0.1 to 1.1 mTorr, TiN{sub x} films went from stoichiometric B1-cubic TiN to slightly overstoichiometric TiN, while CrN{sub x} films went from cubic Cr{endash}N solid solutions to hexagonal Cr{sub 2}N to B1-cubic CrN. Since the N{sub 2} partial pressure required to form stoichiometric CrN was {approx}10 times that required to form stoichiometric TiN, nitrogen was inlet at the Cr target position to maximize the difference in N{sub 2} partial pressures. Two series of CrN/TiN superlattices, with TiN fractions of 0.4 and 0.6, were deposited with periods ranging from 2 to 60 nm. X-ray diffraction showed a very strong (111) texture with first-order satellite peaks around the (111) Bragg peak. Kinematical diffraction simulations of the superlattice x-ray patterns indicated a strong composition modulation and a significant fluctuation in {ital d}-spacing that was related to ion bombardment defects. Cross-sectional transmission electron microscope images showed a columnar film structure with well-defined superlattice layers. Nanoindentation of 2-{mu}m-thick CrN/TiN samples showed a maximum hardness of 35 GPa at a period of 2.3 nm, compared to 25 GPa for TiN and 14 GPa for CrN films. The maximum superlattice hardness was thus {approx}75{percent} larger than the rule-of-mixtures value. The hardness enhancement mechanisms are discussed. {copyright} {ital 1998 American Vacuum Society.}

  15. Etching of Cr tips for scanning tunneling microscopy of cleavable oxides.

    PubMed

    Huang, Dennis; Liu, Stephen; Zeljkovic, Ilija; Mitchell, J F; Hoffman, Jennifer E

    2017-02-01

    We report a detailed three-step roadmap for the fabrication and characterization of bulk Cr tips for spin-polarized scanning tunneling microscopy. Our strategy uniquely circumvents the need for ultra-high vacuum preparation of clean surfaces or films. First, we demonstrate the role of ex situ electrochemical etch parameters on Cr tip apex geometry, using scanning electron micrographs of over 70 etched tips. Second, we describe the suitability of the in situ cleaved surface of the layered antiferromagnet La1.4Sr1.6Mn2O7 to evaluate the spin characteristics of the Cr tip, replacing the ultra-high vacuum-prepared test samples that have been used in prior studies. Third, we outline a statistical algorithm that can effectively delineate closely spaced or irregular cleaved step edges, to maximize the accuracy of step height and spin-polarization measurements.

  16. Radiation resistance of (Ni,Fe)Cr2O4 spinels by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Van Brutzel, Laurent; Alvarez, Pierre; Chartier, Alain

    2014-05-01

    Molecular dynamics simulations are carried out to study primary radiation damage in NiCr2O4 and FeCr2O4 spinels, which are part of the corrosion layer of the vapour generators used in nuclear reactors. The radiation resistance of both spinels is evaluated by studying point defect recombination processes, threshold displacement energies, and 20 keV displacement cascades initiated with different PKA masses. Results are mainly in agreement with previous studies involving MgAl2O4 showing that radiation facilitates the transition to inverse spinel structure or NaCl structure. However, we find some differences between the two studied spinels indicating that NiCr2O4 is more sensitive to radiation.

  17. Pressure-induced normal-incommensurate and incommensurate-commensurate phase transitions in CrOCl

    PubMed Central

    Bykov, Maxim; Bykova, Elena; Dubrovinsky, Leonid; Hanfland, Michael; Liermann, Hanns-Peter; van Smaalen, Sander

    2015-01-01

    The high-pressure behavior of layered CrOCl is shown to be governed by non-bonded interactions between chlorine atoms in relation to a rigid framework composed of Cr and O atoms. The competition between optimizing intra- and interlayer Cl–Cl distances and the general trend towards denser packing defines a novel mechanism for high-pressure phase transitions of inorganic materials. CrOCl possesses an incommensurate phase for 16–51 GPa. Single-crystal x-ray diffraction in a diamond anvil cell provides an accurate description of the evolution of the incommensurate wave with pressure. It thus demonstrates a continuous increase of the amplitude up to 30 GPa, followed by a decrease of the wavelength until a lock-in transition occurs at 51 GPa. PMID:25999303

  18. Method of bonding an interconnection layer on an electrode of an electrochemical cell

    DOEpatents

    Pal, Uday B.; Isenberg, Arnold O.; Folser, George R.

    1992-01-01

    An electrochemical cell containing an air electrode (16), contacting electrolyte and electronically conductive interconnection layer (26), and a fuel electrode, has the interconnection layer (26) attached by: (A) applying a thin, closely packed, discrete layer of LaCrO.sub.3 particles (30), doped with an element selected from the group consisting of Ca, Sr, Co, Ba, Mg and their mixtures on a portion of the air electrode, and then (B) electrochemical vapor depositing a dense skeletal structure (32) between and around the doped LaCrO.sub.3 particles (30).

  19. Method of bonding an interconnection layer on an electrode of an electrochemical cell

    DOEpatents

    Pal, U.B.; Isenberg, A.O.; Folser, G.R.

    1992-01-14

    An electrochemical cell containing an air electrode, contacting electrolyte and electronically conductive interconnection layer, and a fuel electrode, has the interconnection layer attached by: (A) applying a thin, closely packed, discrete layer of LaCrO[sub 3] particles, doped with an element selected from the group consisting of Ca, Sr, Co, Ba, Mg and their mixtures on a portion of the air electrode, and then (B) electrochemical vapor depositing a dense skeletal structure between and around the doped LaCrO[sub 3] particles. 2 figs.

  20. Thermal conductivity of nitride films of Ti, Cr, and W deposited by reactive magnetron sputtering

    SciTech Connect

    Jagannadham, Kasichainula

    2015-05-15

    Nitride films of Ti, Cr, and W were deposited using reactive magnetron sputtering from metal targets in argon and nitrogen plasma. TiN films with (200) orientation were achieved on silicon (100) at the substrate temperature of 500 and 600 °C. The films were polycrystalline at lower temperature. An amorphous interface layer was observed between the TiN film and Si wafer deposited at 600 °C. TiN film deposited at 600 °C showed the nitrogen to Ti ratio to be near unity, but films deposited at lower temperature were nitrogen deficient. CrN film with (200) orientation and good stoichiometry was achieved at 600 °C on Si(111) wafer but the film deposited at 500 °C showed cubic CrN and hexagonal Cr{sub 2}N phases with smaller grain size and amorphous back ground in the x-ray diffraction pattern. An amorphous interface layer was not observed in the cubic CrN film on Si(111) deposited at 600 °C. Nitride film of tungsten deposited at 600 °C on Si(100) wafer was nitrogen deficient, contained both cubic W{sub 2}N and hexagonal WN phases with smaller grain size. Nitride films of tungsten deposited at 500 °C were nonstoichiometric and contained cubic W{sub 2}N and unreacted W phases. There was no amorphous phase formed along the interface for the tungsten nitride film deposited at 600 °C on the Si wafer. Thermal conductivity and interface thermal conductance of all the nitride films of Ti, Cr, and W were determined by transient thermoreflectance technique. The thermal conductivity of the films as function of deposition temperature, microstructure, nitrogen stoichiometry and amorphous interaction layer at the interface was determined. Tungsten nitride film containing both cubic and hexagonal phases was found to exhibit much higher thermal conductivity and interface thermal conductance. The amorphous interface layer was found to reduce effective thermal conductivity of TiN and CrN films.

  1. Enhanced wear and fatigue properties of Ti-6Al-4V alloy modified by plasma carburizing/CrN coating.

    PubMed

    Park, Y G; Wey, M Y; Hong, S I

    2007-05-01

    In this study, a newly developed duplex coating method incorporating plasma carburization and CrN coating was applied to Ti-6Al-4V and its effects on the wear resistance and fatigue life were investigated. The carburized layer with approximately150 microm in depth and CrN coating film with 7.5 microm in thickness were formed after duplex coating. Hard carbide particles such as TiC And V(4)C(3) were formed in the carburized layer. XRD diffraction pattern analysis revealed that CrN film had predominant [111] and [200] textures. The hardness (Hv) was significantly improved up to about 1,960 after duplex coating while the hardness value of original Ti-6Al-4V was 402. The threshold load for the modification and/or failure of CrN coating was measured to be 32 N using the acoustic emission technique. The wear resistance and fatigue life of duplex-coated Ti-6Al-4V improved significantly compared to those of un-treated specimen. The enhanced wear resistance can be attributed to the excellent adhesion and improved hardness of CrN coating film for the duplex-coated Ti-6Al-4V. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the surface, resulting in the enhanced fatigue life.

  2. Antiproton Production by CR on Air Nuclei

    NASA Technical Reports Server (NTRS)

    Maskalenko, I. V.; Mashnik, S. G.

    2003-01-01

    Recent measurements of the cosmic ray (CR) antiproton flux have been shown to challenge existing CR propagation models. In particular, the conventional reacceleration model designed to match secondary/primary nuclei ratios produces too few antiprotons. Recently there appear some indications that the atmospheric contribution to antiproton production is considerably underestimated, which implies that antiproton CR flux might be lower. This may be the primary reason of the discrepancy discovered in CR propagation. We use the Los Alamos version of the Quark-Gluon String Model code LAQGSM together with available data on antiproton production on nuclei to analyse the accuracy of existing parameterizations of antiproton production cross section. The LAQGSM model has been shown to reproduce well nuclear reactions and hadronic data in the range 0.01-800 GeV/nucleon.

  3. a Sexafs Study of Ultrathin cr Films

    NASA Astrophysics Data System (ADS)

    Cook, J. C.; Dowling, M.; Schwarzacher, W.; McCash, E. M.

    Three types of Cr films were grown on Pd(100) at different substrate temperatures. The film thickness was found to be the crucial parameter in determining the film structure; substrate temperature was found to make little difference to the surface EXAFS pattern observed. Films with a thickness greater than 6 monolayers (ML) of Cr were body-centered-cubic (bcc); those with a thickness less than 3 ML Cr appear to be face-centered-cubic (fcc) and those in between were initially bcc but after annealing to ~500 K produced an fcc-like SEXAFS pattern. The SEXAFS of both thin and medium films can be interpreted in terms of a Cr-Pd alloy on the surface.

  4. Fiat C.R. 20 pursuit airplane

    NASA Technical Reports Server (NTRS)

    1927-01-01

    The Fiat C.R. 20 has an all metal frame covered with fireproof fabric, except for the area near the engines, which is covered in duraluminum. It is armed with 4 machine guns and is capable of 280 KPH.

  5. Thermal Stability of NaxCrO2 for Rechargeable Sodium Batteries; Studies by High-Temperature Synchrotron X-ray Diffraction.

    PubMed

    Yabuuchi, Naoaki; Ikeuchi, Issei; Kubota, Kei; Komaba, Shinichi

    2016-11-30

    Thermal stability and phase transition processes of NaCrO2 and Na0.5CrO2 are carefully examined by high-temperature synchrotron X-ray diffraction method. O3-type NaCrO2 shows anisotropic thermal expansion on heating, which is a common character as layered materials, without phase transition in the temperature range of 27-527 °C. In contrast, for the desodiated phase, in-plane distorted P3-type layered oxide (P'3 Na0.5CrO2), phase transition occurs in the following order. Monoclinic distortion associated with Na/vacancy ordering is gradually lost on heating, and its symmetry increases and changes to a rhombohedral lattice at 207 °C. On further heating, phase segregation to two P3 layered metastable phases, which have different interlayer distances (17.0 and 13.5 Å, presumably sodium-rich and sodium-free P3 phases, respectively) are observed on heating to 287-477 °C, but oxygen loss is not observed. Oxygen loss is observed at temperatures only above 500 °C, resulting in the formation of corundum-type Cr2O3 and O3 NaCrO2 as thermodynamically stable phases. From these results, possibility of NaxCrO2 as a positive electrode material for safe rechargeable sodium batteries is also discussed.

  6. Cytotoxic and genotoxic potential of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA complex in human hepatoma (HepG2) cells.

    PubMed

    Novotnik, Breda; Ščančar, Janez; Milačič, Radmila; Filipič, Metka; Žegura, Bojana

    2016-07-01

    Chromium (Cr) and ethylenediaminetetraacetate (EDTA) are common environmental pollutants and can be present in high concentrations in surface waters at the same time. Therefore, chelation of Cr with EDTA can occur and thereby stable Cr(III)-EDTA complex is formed. Since there are no literature data on Cr(III)-EDTA toxicity, the aim of our work was to evaluate and compare Cr(III)-EDTA cytotoxic and genotoxic activity with those of Cr(VI) and Cr(III)-nitrate in human hepatoma (HepG2) cell line. First the effect of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on cell viability was studied in the concentration range from 0.04 μg mL(-1) to 25 μg mL(-1) after 24 h exposure. Further the influence of non-cytotoxic concentrations of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on DNA damage and genomic stability was determined with the comet assay and cytokinesis block micronucleus cytome assay, respectively. Cell viability was decreased only by Cr(VI) at concentrations above 1.0 μg mL(-1). Cr(VI) at ≥0.2 μg mL(-1) and Cr(III) at ≥1.0 μg mL(-1) induced DNA damage, while after Cr(III)-EDTA exposure no formation DNA strand breaks was determined. Statistically significant formation of micronuclei was induced only by Cr(VI) at ≥0.2 μg mL(-1), while no influence on the frequency of nuclear buds nor nucleoplasmic bridges was observed at any exposure. This study provides the first evidence that Cr(III)-EDTA did not induce DNA damage and had no influence on the genomic stability of HepG2 cells.

  7. Fabrication of Pd-Cr wire

    NASA Technical Reports Server (NTRS)

    Diamond, Sidney; Leach, Dennen M.

    1989-01-01

    Fabrication of Pd-13 percent Cr alloy wires is described. Melting, casting, swaging and annealing processes are discussed. Drawing to reach two diameters (0.003 inch and 0.00176 inch) of wire is described. Representative micrographs of the Pd-Cr alloy at selected stages during wire fabrication are included. The resistance of the wire was somewhat lower, by about 15 to 20 percent, than comparable wire of other alloys used for strain gages.

  8. Evolution of oxide scale on a Ni-Mo-Cr alloy at 900 deg. C

    SciTech Connect

    Ul-Hamid, A. . E-mail: anwar@kfupm.edu.sa; Mohammed, A.I.; Al-Jaroudi, S.S.; Tawancy, H.M.; Abbas, N.M.

    2007-01-15

    The cyclic oxidation behavior of a Ni-Mo-Cr alloy was studied in air at 900 deg. C for exposure periods of up to 1000 h. The morphology, microstructure and composition of the oxide scale was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Oxidation kinetics was determined by weight gain measurements. The results show that steady state oxidation was achieved within 1 h of exposure. During transient oxidation, the alloy grain boundaries intersecting the alloy surface became depleted in Ni and enriched in Mo and Cr. The scale initially formed at the surface was NiO which grew outwardly. However, a protective Cr{sub 2}O{sub 3} layer developed, rapidly retarding the rate of oxidation. Formation of NiMoO{sub 4} was also observed. The presence of Mo in the alloy facilitated the formation of a Cr{sub 2}O{sub 3} layer at an early stage of oxidation. The alloy exhibited considerable oxide spalling during prolonged exposure.

  9. Magnetization at the interface of Cr2O3 and paramagnets with large stoner susceptibility

    NASA Astrophysics Data System (ADS)

    Cao, Shi; Street, M.; Wang, Junlei; Wang, Jian; Zhang, Xiaozhe; Binek, Ch; Dowben, P. A.

    2017-03-01

    From the Cr 2p3/2 x-ray magnetic circular dichroism signal, there is clear evidence of interface polarization with overlayers of both Pd and Pt on chromia (Cr2O3). The residual boundary polarization of chomia is stronger for a Pt overlayer than in the case of a Pd overlayer. The reduction of chromia boundary magnetization with a paramagnetic metal overlayer, compared to the free surface, is interpreted as a response to the induced spin polarization in Pt and Pd. Magnetization induced in a Pt overlayer, via proximity to the chromia boundary magnetization, is evident in the polar magneto-optical Kerr measurements. These results are essential to explainations why Pt and Pd are excellent spacer layers for voltage controlled exchange bias, in the [Pd/Co] n /Pd/Cr2O3 and [Pt/Co] n /Pt/Cr2O3 perpendicular magneto-electric exchange bias systems. The findings pave the way to realize ultra-fast reversal of induced magnetization in a free moment paramagnetic layer, with possible application in voltage-controlled magnetic random access memory.

  10. Influence of boric acid coatings on the oxidation of 2. 25Cr-1Mo steel in oxygen

    SciTech Connect

    Simms, N.J. ); Little, J.A. . Dept. of Metallurgy and Materials Science)

    1989-05-01

    The oxidation of samples of 2.25Cr-1Mo steel covered with boric oxide in dry flowing oxygen has been studied at 600{sup 0}C. For all times up to 100 hours of exposure, the steel with a borate layer at the original metal-oxygen interface gains less weight than an untreated specimen. The presence of boron also modifies the grain structure of the magnetite layer formed, giving a fine equiaxed microstructure with less porosity.

  11. Modulation of active Cr(III) complexes by bath preparation to adjust Cr(III) electrodeposition

    NASA Astrophysics Data System (ADS)

    Li, Lei; Wang, Zhi; Wang, Ming-yong; Zhang, Yi

    2013-09-01

    The preparation process of the Cr(III) bath was studied based on a perspective of accelerating the formation of active Cr(III) complexes. The results of ultraviolet-visible absorption spectroscopy (UV-Vis) and electrodeposition showed that active Cr(III) complexes in the bath prepared at room temperature in several days were rare for depositing chromium. The increase of heating temperature, time, and pH value during the bath preparation promoted the formation of active Cr(III) complexes. The chromium deposition rate increased with the concentration of active Cr(III) complexes increasing. Increasing the heating temperature from 60 to 96°C, the chromium deposition rate increased from 0.40 to 0.71 μm/min. When the concentration of active Cr(III) complexes increased, the grain size of Cr coatings increased, and the carbon content of the coating decreased. It is deduced that Cr(H2O)4(OH)L2+ (L is an organic ligand, and its valence is omitted) is a primary active Cr(III) complex.

  12. Interatomic potential to study the formation of NiCr clusters in high Cr ferritic steels

    NASA Astrophysics Data System (ADS)

    Bonny, G.; Bakaev, A.; Olsson, P.; Domain, C.; Zhurkin, E. E.; Posselt, M.

    2017-02-01

    Under irradiation NiSiPCr clusters are formed in high-Cr ferritic martensitic steels as well as in FeCr model alloys. In the literature little is known about the origin and contribution to the hardening of these clusters. In this work we performed density functional theory (DFT) calculations to study the stability of small substitutional NiCr-vacancy clusters and interstitial configurations in bcc Fe. Based on DFT data and experimental considerations a ternary potential for the ferritic FeNiCr system was developed. The potential was applied to study the thermodynamic stability of NiCr clusters by means of Metropolis Monte Carlo (MMC) simulations. The results of our simulations show that Cr and Ni precipitate as separate fractions and suggest only a limited synergetic effect between Ni and Cr. Therefore our results suggest that the NiCrSiP clusters observed in experiments must be the result of other mechanisms than the synergy of Cr and Ni at thermal equilibrium.

  13. Microstructure and property of diamond-like carbon films with Al and Cr co-doping deposited using a hybrid beams system

    NASA Astrophysics Data System (ADS)

    Dai, Wei; Liu, Jingmao; Geng, Dongsen; Guo, Peng; Zheng, Jun; Wang, Qimin

    2016-12-01

    DLC films with weak carbide former Al and carbide former Cr co-doping (Al:Cr-DLC) were deposited by a hybrid beams system comprising an anode-layer linear ion beam source (LIS) and high power impulse magnetron sputtering using a gas mixture of C2H2 and Ar as the precursor. The doped Al and Cr contents were controlled via adjusting the C2H2 fraction in the gas mixture. The composition, microstructure, compressive stress, mechanical properties and tribological behaviors of the Al:Cr-DLC films were researched carefully using X-ray photoelectron spectroscopy, transmission electron microscopy, Raman spectroscopy, stress-tester, nanoindentation and ball-on-plate tribometer as function of the C2H2 fraction. The results show that the Al and Cr contents in the films increased continuously as the C2H2 fraction decreased. The doped Cr atoms preferred to bond with the carbon while the Al atoms mainly existed in metallic state. Structure modulation with alternate multilayer consisted of Al-poor DLC layer and Al-rich DLC layer was found in the films. Those periodic Al-rich DLC layers can effectively release the residual stress of the films. On the other hand, the formation of the carbide component due to Cr incorporation can help to increase the film hardness. Accordingly, the residual stress of the DLC films can be reduced without sacrificing the film hardness though co-doping Al and Cr atoms. Furthermore, it was found that the periodic Al-rich layer can greatly improve the elastic resilience of the DLC films and thus decreases the film friction coefficient and wear rate significantly. However, the existence of the carbide component would cause abrasive wear and thus deteriorate the wear performance of the films.

  14. Effect of cryogenic burnishing on surface integrity modifications of Co-Cr-Mo biomedical alloy.

    PubMed

    Yang, Shu; Dillon, Oscar W; Puleo, David A; Jawahir, Ibrahim S

    2013-01-01

    Severe plastic deformation (SPD) processes have been used to modify the surface integrity properties of many materials by generating ultrafine or even nanometer-sized grains in the surface and subsurface region. These fine grained materials created by SPD and dynamic recrystallization in a thin layer near the surface usually have higher hardness and frequently exhibit enhanced mechanical properties (wear resistance, corrosion resistance, fatigue life, etc.). Cryogenic burnishing, a SPD process, was used to improve several surface integrity parameters of a Co-Cr-Mo biomedical alloy. Application of liquid nitrogen during the burnishing process significantly suppressed the temperature rise within and outside the nitrogen application zone. Better surface finish, high hardness value, thick burnishing-influenced surface layer, and significant grain refinement were simultaneously achieved with the application of cryogenic cooling. Current results show that cryogenic burnishing can be an effective processing method for modifying the studied surface integrity properties of Co-Cr-Mo biomedical alloy.

  15. Large magnetization and high Curie temperature in highly disordered nanoscale Fe2CrAl thin films

    NASA Astrophysics Data System (ADS)

    Dulal, Rajendra P.; Dahal, Bishnu R.; Forbes, Andrew; Pegg, Ian L.; Philip, John

    2017-02-01

    We have successfully grown nanoscale Fe2CrAl thin films on polished Si/SiO2 substrates using an ultra-high vacuum deposition with a base pressure of 9×10-10 Torr. The thickness of thin films ranges from 30 to 100 nm. These films exhibit cubic crystal structure with lattice disorder and display ferromagnetic behavior. The Curie temperature is greater than 400 K, which is much higher than that reported for bulk Fe2CrAl. The magnetic moments of the films varies from 2.5 to 2.8 μB per formula unit, which is larger than the reported bulk values. Thus, the disordered nanoscale Fe2CrAl films exhibit strong Fe-Fe exchange interactions through Fe-Cr-Fe and Fe-Al-Fe layers, resulting in both a large magnetization and a high Curie temperature.

  16. Electronic band alignment and electron transport in Cr/BaTiO{sub 3}/Pt ferroelectric tunnel junctions

    SciTech Connect

    Zenkevich, A.; Minnekaev, M.; Matveyev, Yu.; Lebedinskii, Yu.; Bulakh, K.; Chouprik, A.; Baturin, A.; Maksimova, K.; Thiess, S.; Drube, W.

    2013-02-11

    Electroresistance in ferroelectric tunnel junctions is controlled by changes in the electrostatic potential profile across the junction upon polarization reversal of the ultrathin ferroelectric barrier layer. Here, hard X-ray photoemission spectroscopy is used to reconstruct the electric potential barrier profile in as-grown Cr/BaTiO{sub 3}(001)/Pt(001) heterostructures. Transport properties of Cr/BaTiO{sub 3}/Pt junctions with a sub-{mu}m Cr top electrode are interpreted in terms of tunneling electroresistance with resistance changes of a factor of {approx}30 upon polarization reversal. By fitting the I-V characteristics with the model employing an experimentally determined electric potential barrier we derive the step height changes at the BaTiO{sub 3}/Pt (Cr/BaTiO{sub 3}) interface +0.42(-0.03) eV following downward to upward polarization reversal.

  17. CoCrMo Metal-on-Metal Hip Replacements

    PubMed Central

    Liao, Yifeng; Hoffman, Emily; Wimmer, Markus; Fischer, Alfons; Jacobs, Joshua; Marks, Laurence

    2012-01-01

    After the rapid growth in the use of CoCrMo metal-on-metal hip replacements since the second generation was introduced circa 1990, metal-on-metal hip replacements have experienced a sharp decline in the last two years due to biocompatibility issues related to wear and corrosion products. Despite some excellent clinical results, the release of wear and corrosion debris and the adverse response of local tissues have been of great concern. There are many unknowns regarding how CoCrMo metal bearings interact with the human body. This perspective article is intended to outline some recent progresses in understanding wear and corrosion of metal-on-metal hip replacement both in-vivo and in-vitro. The materials, mechanical deformation, corrosion, wear-assisted corrosion, and wear products will be discussed. Possible adverse health effects caused by wear products will be briefly addressed, as well as some of the many open questions such as the detailed chemistry of corrosion, tribochemical reactions and the formation of graphitic layers. Nowadays we design almost routinely for high performance materials and lubricants for automobiles; humans are at least as important. It is worth remembering that a hip implant is often the difference between walking and leading a relatively normal life, and a wheelchair. PMID:23196425

  18. Irradiation-induced formation of a spinel phase at the FeCr/MgO interface

    DOE PAGES

    Xu, Yun; Yadav, Satyesh Kumar; Aguiar, Jeffery A.; ...

    2015-04-27

    Oxide dispersion strengthened ferritic/martensitic alloys have attracted significant attention for their potential uses in future nuclear reactors and storage vessels, as the metal/oxide interfaces act as stable high-strength sinks for point defects while also dispersing helium. Here, in order to unravel the evolution and interplay of interface structure and chemistry upon irradiation in these types of materials, an atomically sharp FeCr/MgO interface was synthesized at 500 °C and separately annealed and irradiated with Ni3+ ions at 500 °C. After annealing, a slight enrichment of Cr atoms was observed at the interface, but no other structural changes were found. However, undermore » irradiation, sufficient Cr diffuses across the interface into the MgO to form a Cr-enriched transition layer that contains spinel precipitates. First-principles calculations indicate that it is energetically favorable to incorporate Cr, but not Fe, substitutionally into MgO. Furthermore, our results indicate that irradiation can be used to form new phases and complexions at interfaces, which may have different radiation tolerance than the pristine structures.« less

  19. Irradiation-induced formation of a spinel phase at the FeCr/MgO interface

    SciTech Connect

    Xu, Yun; Yadav, Satyesh Kumar; Aguiar, Jeffery A.; Anderoglu, Osman; Baldwin, Jon Kevin; Wang, Yongqiang; Misra, Amit; Luo, Hongmei; Uberuaga, Blas P.; Li, Nan

    2015-04-27

    Oxide dispersion strengthened ferritic/martensitic alloys have attracted significant attention for their potential uses in future nuclear reactors and storage vessels, as the metal/oxide interfaces act as stable high-strength sinks for point defects while also dispersing helium. Here, in order to unravel the evolution and interplay of interface structure and chemistry upon irradiation in these types of materials, an atomically sharp FeCr/MgO interface was synthesized at 500 °C and separately annealed and irradiated with Ni3+ ions at 500 °C. After annealing, a slight enrichment of Cr atoms was observed at the interface, but no other structural changes were found. However, under irradiation, sufficient Cr diffuses across the interface into the MgO to form a Cr-enriched transition layer that contains spinel precipitates. First-principles calculations indicate that it is energetically favorable to incorporate Cr, but not Fe, substitutionally into MgO. Furthermore, our results indicate that irradiation can be used to form new phases and complexions at interfaces, which may have different radiation tolerance than the pristine structures.

  20. Investigation of structural changes in chiral magnet Cr1/3NbS2 under application of pressure

    NASA Astrophysics Data System (ADS)

    Mito, M.; Tajiri, T.; Tsuruta, K.; Deguchi, H.; Kishine, J.; Inoue, K.; Kousaka, Y.; Nakao, Y.; Akimitsu, J.

    2015-05-01

    We perform structural analysis experiments on the chiral magnet Cr1/3NbS2, in which Cr3+ ions are inserted between hexagonal NbS2 layers. The noncentrosymmetrical nature of the inserted Cr3+ appears as a distorted CrS6 octahedron. Under the application of hydrostatic pressure, the lattice shrinks significantly along the c-axis rather than the a-axis. However, at a pressure P of approximately 3-4 GPa, a kink in the rate of decrease in the lattice parameters is observed, and the slight movement of a Nb atom along the c-axis brings about a decrease in the distortion of the CrS6 octahedron. This structural change qualitatively suggests a decrease in the strength of the Dzyaloshinskii-Moriya (D-M) interaction. Under hydrostatic pressure, the magnetic ordering temperature TC decreases, and dTC/dP exhibits a slight change at around 3 GPa. A series of experiments indicates that the change in the structural symmetry of the CrS6 octahedron influences the exchange network between Cr3+ ions as well as the D-M interaction.

  1. Solute redistribution and phase stability at FeCr/TiO2–x interfaces under ion irradiation

    DOE PAGES

    Xu, Y.; Aguiar, J. A.; Yadav, S. K.; ...

    2015-02-26

    Cr diffusion in trilayer thin films of 100 nm Fe–18Cr/125 nm TiO2–x/100 nm Fe–18Cr deposited on MgO substrates at 500 °C was studied by either annealing at 500 °C or Ni3+ ion irradiation at 500 °C. Microchemistry and microstructure evolution at the metal/oxide interfaces were investigated using (high-resolution) transmission electron microscopy, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy. Diffusion of Cr into the O-deficient TiO2 layer, with negligible segregation to the FeCr/TiO2–x interface itself, was observed under both annealing and irradiation. Cr diffusion into TiO2–x was enhanced in ion-irradiated samples as compared to annealed. Irradiation-induced voids and amorphization ofmore » TiO2–x was also observed. The experimental results are rationalized using first-principles calculations that suggest an energetic preference for substituting Ti with Cr in sub-stoichiometric TiO2. Furthermore, the implications of these results on the irradiation stability of oxide-dispersed ferritic alloys are discussed.« less

  2. The role of Zr and Nb in oxidation/sulfidation behavior of Fe-Cr-Ni alloys

    SciTech Connect

    Natesan, K. ); Baxter, D.J. INCO Alloy Ltd., Hereford, England )

    1990-11-01

    05Structural Fe-Cr-Ni alloys may undergo rapid degradation at elevated temperatures unless protective surface oxide scales are formed and maintained. The ability of alloys to resist rapid degradation strongly depends on their Cr content and the chemistry of the exposure environment. Normally, 20 wt % Cr is required for service at temperatures up to 1000{degree}C; the presence of sulfur, however, inhibits formation of a protective surface oxide scale. The oxidation and sulfidation behavior of Fe-Cr-Ni alloys is examined over a wide temperature range (650 to 1000{degree}C), with particular emphasis on the effects of alloy Cr content and the radiation of reactive elements such as Nb and Zr. Both Nb and Zr are shown to promote protective oxidation behavior on the 12 wt % Cr alloy in oxidizing environments and to suppress sulfidation in mixed oxygen/sulfur environments. Additions of Nb and Zr at 3 wt % level resulted in stabilization of Cr{sub 2}O{sub 3} scale and led to a barrier layer of Nb- or Zr-rich oxide at the scale/metal interface, which acted to minimize the transport of base metal cations across the scale. Oxide scales were preformed in sulfur-free environments and subsequently exposed to oxygen/sulfur mixed-gas atmospheres. Preformed scales were found to delay the onset of breakaway corrosion. Corrosions test results obtained under isothermal and thermal cycling conditions are presented. 58 refs., 55 figs., 8 tabs.

  3. Atomic-level structural and chemical analysis of Cr-doped Bi2Se3 thin films

    NASA Astrophysics Data System (ADS)

    Ghasemi, A.; Kepaptsoglou, D.; Collins-McIntyre, L. J.; Ramasse, Q.; Hesjedal, T.; Lazarov, V. K.

    2016-05-01

    We present a study of the structure and chemical composition of the Cr-doped 3D topological insulator Bi2Se3. Single-crystalline thin films were grown by molecular beam epitaxy on Al2O3 (0001), and their structural and chemical properties determined on an atomic level by aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy. A regular quintuple layer stacking of the Bi2Se3 film is found, with the exception of the first several atomic layers in the initial growth. The spectroscopy data gives direct evidence that Cr is preferentially substituting for Bi in the Bi2Se3 host. We also show that Cr has a tendency to segregate at internal grain boundaries of the Bi2Se3 film.

  4. Infrared spectra of giant magnetoresistance Fe/Cr/Fe trilayers

    SciTech Connect

    Uran, S.; Grimsditch, M.; Fullerton, E.E.; Bader, S.D.

    1998-02-01

    Magnetic-field-induced changes in infrared transmission and reflection from Fe/Cr/Fe trilayers are reported. Changes as large as {approx}1{percent} (compared with 4{endash}5{percent} changes in resistivity) are observed around 2000cm{sup {minus}1}, and the magnitude of the effect decreases monotonically to zero at {approx}5000cm{sup {minus}1}. The field dependence mimics that of the resistivity, and saturates at the same field at which the magnetization of the two Fe layers align parallel to each other. A simple model, which estimates the frequency dependence of the resistivity and includes the frequency dependence of the skin depth, produces semiquantitative agreement with experiment. {copyright} {ital 1998} {ital The American Physical Society}

  5. Reduction of Cr(VI) to Cr(III) by wetland plants: Potential for in situ heavy metal detoxification

    SciTech Connect

    Lytle, C.M.; Qian, J.H.; Hansen, D.; Zayed, A.; Terry, N.; Lytle, F.W.; Yang, N.

    1998-10-15

    Reduction of heavy metals in situ by plants may be a useful detoxification mechanism for phytoremediation. Using X-ray spectroscopy, the authors show that Eichhornia crassipes (water hyacinth), supplied with Cr(VI) in nutrient culture, accumulated nontoxic Cr(III) in root and shoot tissues. The reduction of Cr(VI) to Cr(III) appeared to occur in the fine lateral roots. The Cr(III) was subsequently translocated to leaf tissues. Extended X-ray absorption fine structure of Cr in leaf and petiole differed when compared to Cr in roots. In roots, Cr(III) was hydrated by water, but in petiole and more so in leaf, a portion of the Cr(III) may be bound to oxalate ligands. This suggests that E. crassipes detoxified Cr(VI) upon root uptake and transported a portion of the detoxified Cr to leaf tissues. Cr-rich crystalline structures were observed on the leaf surface. The chemical species of Cr in other plants, collected from wetlands that contained Cr(VI)-contaminated wastewater, was also found to be Cr(III). The authors propose that this plant-based reduction of Cr(VI) by E. crassipes has the potential to be used for the in situ detoxification of Cr(VI)-contaminated wastestreams.

  6. Cr/Sc multilayer radiator for parametric EUV radiation in “water-window” spectral range

    NASA Astrophysics Data System (ADS)

    Uglov, S. R.; Kaplin, V. V.; Kubankin, A. S.; André, J.-M.; Le Guen, K.; Jonnard, Ph; de Rossi, S.; Meltchakov, E.; Delmotte, F.

    2016-07-01

    The results of experimental investigation of parametric radiation generated by 5.7 MeV electrons in a multilayer structure consisting of 100 Cr/Sc bi-layers deposited on a Si3N4 membrane are presented. The multilayer structure was specially created for generation of parametric radiation with photon energy in “water-window” spectral range. First test measurements of angular distributions of radiation have been done and discussed.

  7. First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

    NASA Astrophysics Data System (ADS)

    Piochaud, J. B.; Klaver, T. P. C.; Adjanor, G.; Olsson, P.; Domain, C.; Becquart, C. S.

    2014-01-01

    The influence of the local environment on vacancy and self-interstitial formation energies has been investigated in a face-centered-cubic (fcc) Fe-10Ni-20Cr model alloy by analyzing an extensive set of first-principle calculations based on density functional theory. Chemical disorder has been considered by designing special quasirandom structures and four different collinear magnetic structures have been investigated in order to determine a relevant reference state to perform point defect calculations at 0 K. Two different convergence methods have also been used to characterize the importance of the method on the results. Although our fcc Fe-10Ni-20Cr would be better represented in terms of applications by the paramagnetic state, we found that the antiferromagnetic single-layer magnetic structure was the most stable at 0 K and we chose it as a reference state to determine the point defect properties. Point defects have been introduced in this reference state, i.e., vacancies and Fe-Fe, Fe-Ni, Fe-Cr, Cr-Cr, Ni-Ni, and Ni-Cr dumbbell interstitials oriented either parallel or perpendicular to the single layer antiferromagnetic planes. Each point defect studied was introduced at different lattice sites to consider a sufficient variety of local environments and analyze its influence on the formation energy values. We have estimated the point defect formation energies with linear regressions using variables which describe the local environment surrounding the point defects. The number and the position of Ni and Cr first nearest neighbors to the point defects were found to drive the evolution of the formation energies. In particular, Ni is found to decrease and Cr to increase the vacancy formation energy of the model alloy, while the opposite trends are found for the dumbbell interstitials. This study suggested that, to a first approximation, the first nearest atoms to point defects can provide reliable estimates of point defect formation energies.

  8. 1-Quasiconformal mappings and CR mappings on Goursat groups.

    PubMed

    Wu, Qing Yan; Fu, Zun Wei

    2014-01-01

    We show that 1-quasiconformal mappings on Goursat groups are CR or anti-CR mappings. This can reduce the determination of 1-quasiconformal mappings to the determination of CR automorphisms of CR manifolds, which is a fundamental problem in the theory of several complex variables.

  9. 1-Quasiconformal Mappings and CR Mappings on Goursat Groups

    PubMed Central

    Wu, Qing Yan; Fu, Zun Wei

    2014-01-01

    We show that 1-quasiconformal mappings on Goursat groups are CR or anti-CR mappings. This can reduce the determination of 1-quasiconformal mappings to the determination of CR automorphisms of CR manifolds, which is a fundamental problem in the theory of several complex variables. PMID:24895673

  10. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al Part II: Scale Microstructures

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

  11. Comparison of the Isothermal Oxidation Behavior of As-Cast Cu-17 Percent Cr and Cu-17 Percent Cr-5 Percent Al. Part 2; Scale Microstructures

    NASA Technical Reports Server (NTRS)

    Raj, S. V.

    2008-01-01

    The isothermal oxidation kinetics of as-cast Cu-17%Cr and Cu-17%Cr-5%Al in air were studied between 773 and 1173 K under atmospheric pressure. Details of the oxidation kinetics of these alloys were discussed in Part I. This paper analyzes the microstructures of the scale and its composition in an attempt to elucidate the oxidation mechanisms in these alloys. The scales formed on Cu-17%Cr specimens oxidized between 773 and 973 K consisted of external CuO and subsurface Cu2O layers. The total thickness of these scales varied from about 10 m at 773 K to about 450 m at 973 K. In contrast, thin scales formed on Cu-17%Cr-5%Al alloys oxidized between 773 and 1173 K. The exact nature of these scales could not be determined by x-ray diffraction but energy dispersive spectroscopy analyses were used to construct a scale composition map. Phenomenological oxidation mechanisms are proposed for the two alloys.

  12. Effect of aluminizing treatment on the oxidation properties of 12Cr heat resisting steel

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Hwan; Wang, Jei-Pil; Kang, Chang-Yong

    2011-12-01

    In order to investigate the effect of aluminization on the oxidation properties of 12Cr martensitic heat resisting steel, a specimen was prepared by forging after centrifugal casting. After aluminizing treatment under various conditions, scanning electron microscopy observation, and hardness, line profile and x-ray diffraction analysis of the alloy layer were performed. The results confirmed that the thickness of the layer of Al13Fe4, with a Vickers hardness of over 880, increased with increasing aluminizing temperature and time. Moreover, it was concluded from the results of the oxidation experiment that the oxidation properties of the aluminized specimen were improved by up to approximately 30 %.

  13. Sensitivity of a global climate model to the critical Richardson number in the boundary layer parameterization

    SciTech Connect

    Zhang, Ning; Liu, Yangang; Gao, Zhiqiu; Li, Dan

    2015-04-27

    The critical bulk Richardson number (Ricr) is an important parameter in planetary boundary layer (PBL) parameterization schemes used in many climate models. This paper examines the sensitivity of a Global Climate Model, the Beijing Climate Center Atmospheric General Circulation Model, BCC_AGCM to Ricr. The results show that the simulated global average of PBL height increases nearly linearly with Ricr, with a change of about 114 m for a change of 0.5 in Ricr. The surface sensible (latent) heat flux decreases (increases) as Ricr increases. The influence of Ricr on surface air temperature and specific humidity is not significant. The increasing Ricr may affect the location of the Westerly Belt in the Southern Hemisphere. Further diagnosis reveals that changes in Ricr affect stratiform and convective precipitations differently. Increasing Ricr leads to an increase in the stratiform precipitation but a decrease in the convective precipitation. Significant changes of convective precipitation occur over the inter-tropical convergence zone, while changes of stratiform precipitation mostly appear over arid land such as North Africa and Middle East.

  14. Adsorption of H2, Cl2, and HCl molecules on α-Cr2O3(0001) surfaces: A density functional theory investigation

    NASA Astrophysics Data System (ADS)

    Nigussa, K. N.; Nielsen, K. L.; Borck, Ø.; Støvneng, J. A.

    2016-11-01

    Density functional theory calculations show that H2, Cl2, and HCl molecules chemisorb dissociatively on the Cr2O3(0001) surface, which can be terminated by Cr atoms, Chromyl groups (Cr=O), or O atoms. It is investigated that these molecules energetically prefer to adsorb dissociatively than in molecular form. Several dissociative adsorption sites have been considered for all the molecules on all the differently terminated surfaces and the corresponding adsorption energies are calculated. Dissociation energy barriers are estimated with the nudged elastic band method. Notable results from the dissociative adsorptions of Cl2 and H2 are the formation of a CrCl2 complex on the Cr terminated surface, and H2O complex on the O and the Cr=O terminated surfaces, and a H2O layer on the Cr=O terminated surface. Dissociative adsorption of HCl is less favored on the Cr=O and O terminated surfaces than on the Cr terminated surface.

  15. Increasing the structural complexity of chromium(IV) oxides by high-pressure and high-temperature reactions of CrO2.

    PubMed

    Castillo-Martínez, E; Arévalo-López, A M; Ruiz-Bustos, R; Alario-Franco, M A

    2008-10-06

    This work presents an overview of a series of increasingly complex oxides synthesized from CrO 2, under high-pressure and high-temperature conditions, having Cr (4+) in octahedral coordination. Although the emphasis is on the structure and microstructure of the compounds as obtained from X-ray diffraction and transmission electron microscopy and diffraction, attention is also given to their interesting electronic and magnetic properties. The study is complemented with an electron energy loss spectroscopic analysis of the different phases. These are the cubic perovskite SrCrO 3, the orthorhombic perovskite CaCrO 3, the solid solution Sr 1-xCa xCrO 3, the Ruddlesden-Popper-type Sr 3Cr 2O 7, the family CrSr 2RECu 2O 8 (RE = rare earth), a compositionally modulated perovskite "PbCrO 3", and the misfit layer oxide SrO 2[CrO 2] 1.85.

  16. Burning Graphene Layer-by-Layer

    NASA Astrophysics Data System (ADS)

    Ermakov, Victor A.; Alaferdov, Andrei V.; Vaz, Alfredo R.; Perim, Eric; Autreto, Pedro A. S.; Paupitz, Ricardo; Galvao, Douglas S.; Moshkalev, Stanislav A.

    2015-06-01

    Graphene, in single layer or multi-layer forms, holds great promise for future electronics and high-temperature applications. Resistance to oxidation, an important property for high-temperature applications, has not yet been extensively investigated. Controlled thinning of multi-layer graphene (MLG), e.g., by plasma or laser processing is another challenge, since the existing methods produce non-uniform thinning or introduce undesirable defects in the basal plane. We report here that heating to extremely high temperatures (exceeding 2000 K) and controllable layer-by-layer burning (thinning) can be achieved by low-power laser processing of suspended high-quality MLG in air in “cold-wall” reactor configuration. In contrast, localized laser heating of supported samples results in non-uniform graphene burning at much higher rates. Fully atomistic molecular dynamics simulations were also performed to reveal details of oxidation mechanisms leading to uniform layer-by-layer graphene gasification. The extraordinary resistance of MLG to oxidation paves the way to novel high-temperature applications as continuum light source or scaffolding material.

  17. Burning Graphene Layer-by-Layer

    PubMed Central

    Ermakov, Victor A.; Alaferdov, Andrei V.; Vaz, Alfredo R.; Perim, Eric; Autreto, Pedro A. S.; Paupitz, Ricardo; Galvao, Douglas S.; Moshkalev, Stanislav A.

    2015-01-01

    Graphene, in single layer or multi-layer forms, holds great promise for future electronics and high-temperature applications. Resistance to oxidation, an important property for high-temperature applications, has not yet been extensively investigated. Controlled thinning of multi-layer graphene (MLG), e.g., by plasma or laser processing is another challenge, since the existing methods produce non-uniform thinning or introduce undesirable defects in the basal plane. We report here that heating to extremely high temperatures (exceeding 2000 K) and controllable layer-by-layer burning (thinning) can be achieved by low-power laser processing of suspended high-quality MLG in air in “cold-wall” reactor configuration. In contrast, localized laser heating of supported samples results in non-uniform graphene burning at much higher rates. Fully atomistic molecular dynamics simulations were also performed to reveal details of oxidation mechanisms leading to uniform layer-by-layer graphene gasification. The extraordinary resistance of MLG to oxidation paves the way to novel high-temperature applications as continuum light source or scaffolding material. PMID:26100466

  18. Cross-track Infrared Sounder (CrIS) satellite observations of tropospheric ammonia

    NASA Astrophysics Data System (ADS)

    Shephard, M. W.; Cady-Pereira, K. E.

    2015-03-01

    Observations of atmospheric ammonia are important in understanding and modelling the impact of ammonia on both human health and the natural environment. We present a detailed description of a robust retrieval algorithm that demonstrates the capabilities of utilizing Cross-track Infrared Sounder (CrIS) satellite observations to globally retrieval ammonia concentrations. Initial ammonia retrieval results using both simulated and real observations show that (i) CrIS is sensitive to ammonia in the boundary layer with peak vertical sensitivity typically around ~ 850-750 hPa (~ 1.5 to 2.5 km), which can dip down close to the surface (~ 900 hPa) under ideal conditions, (ii) it has a minimum detection limit of ~ 1 ppbv (peak profile value typically at the surface), and (iii) the information content can vary significantly with maximum values of ~ 1 degree-of-freedom for signal. Comparisons of the retrieval with simulated "true" profiles show a small positive retrieval bias of 6% with a standard deviation of ~ ± 20% (ranging from ± 12 to ± 30% over the vertical profile). Note that these uncertainty estimates are considered as lower bound values as no potential systematic errors are included in the simulations. The CrIS NH3 retrieval applied over the Central Valley in CA, USA, demonstrates that CrIS correlates well with the spatial variability of the boundary layer ammonia concentrations seen by the nearby Quantum Cascade-Laser (QCL) in situ surface and the Tropospheric Emission Spectrometer (TES) satellite observations as part of the DISCOVER-AQ campaign. The CrIS and TES ammonia observations show quantitatively similar retrieved boundary layer values that are often within the uncertainty of the two observations. Also demonstrated is CrIS's ability to capture the expected spatial distribution in the ammonia concentrations, from elevated values in the Central Valley from anthropogenic agriculture emissions, to much lower values in the unpolluted or clean surrounding

  19. Study of Different Variants of Mo Enzyme crARC and the Interaction with Its Partners crCytb5-R and crCytb5-1.

    PubMed

    Chamizo-Ampudia, Alejandro; Galvan, Aurora; Fernandez, Emilio; Llamas, Angel

    2017-03-21

    The mARC (mitochondrial Amidoxime Reducing Component) proteins are recently discovered molybdenum (Mo) Cofactor containing enzymes. They are involved in the reduction of several N-hydroxylated compounds (NHC) and nitrite. Some NHC are prodrugs containing an amidoxime structure or mutagens such as 6-hydroxylaminopurine (HAP). We have studied this protein in the green alga Chlamydomonas reinhardtii (crARC). Interestingly, all the ARC proteins need the reducing power supplied by other proteins. It is known that crARC requires a cytochrome b₅ (crCytb5-1) and a cytochrome b₅ reductase (crCytb5-R) that form an electron transport chain from NADH to the substrates. Here, we have investigated NHC reduction by crARC, the interaction with its partners and the function of important conserved amino acids. Interactions among crARC, crCytb5-1 and crCytb5-R have been studied by size-exclusion chromatography. A protein complex between crARC, crCytb5-1 and crCytb5-R was identified. Twelve conserved crARC amino acids have been substituted by alanine by in vitro mutagenesis. We have determined that the amino acids D182, F210 and R276 are essential for NHC reduction activity, R276 is important and F210 is critical for the Mo Cofactor chelation. Finally, the crARC C-termini were shown to be involved in protein aggregation or oligomerization.

  20. Study of Different Variants of Mo Enzyme crARC and the Interaction with Its Partners crCytb5-R and crCytb5-1

    PubMed Central

    Chamizo-Ampudia, Alejandro; Galvan, Aurora; Fernandez, Emilio; Llamas, Angel

    2017-01-01

    The mARC (mitochondrial Amidoxime Reducing Component) proteins are recently discovered molybdenum (Mo) Cofactor containing enzymes. They are involved in the reduction of several N-hydroxylated compounds (NHC) and nitrite. Some NHC are prodrugs containing an amidoxime structure or mutagens such as 6-hydroxylaminopurine (HAP). We have studied this protein in the green alga Chlamydomonas reinhardtii (crARC). Interestingly, all the ARC proteins need the reducing power supplied by other proteins. It is known that crARC requires a cytochrome b5 (crCytb5-1) and a cytochrome b5 reductase (crCytb5-R) that form an electron transport chain from NADH to the substrates. Here, we have investigated NHC reduction by crARC, the interaction with its partners and the function of important conserved amino acids. Interactions among crARC, crCytb5-1 and crCytb5-R have been studied by size-exclusion chromatography. A protein complex between crARC, crCytb5-1 and crCytb5-R was identified. Twelve conserved crARC amino acids have been substituted by alanine by in vitro mutagenesis. We have determined that the amino acids D182, F210 and R276 are essential for NHC reduction activity, R276 is important and F210 is critical for the Mo Cofactor chelation. Finally, the crARC C-termini were shown to be involved in protein aggregation or oligomerization. PMID:28335548

  1. Local A‐Site Layering in Rare‐Earth Orthochromite Perovskites by Solution Synthesis

    PubMed Central

    Daniels, Luke M.; Kashtiban, Reza J.; Kepaptsoglou, Demie; Ramasse, Quentin M.; Sloan, Jeremy

    2016-01-01

    Abstract Cation size effects were examined in the mixed A‐site perovskites La0.5Sm0.5CrO3 and La0.5Tb0.5CrO3 prepared through both hydrothermal and solid‐state methods. Atomically resolved electron energy loss spectroscopy (EELS) in the transmission electron microscope shows that while the La and Sm cations are randomly distributed, increased cation‐radius variance in La0.5Tb0.5CrO3 results in regions of localised La and Tb layers, an atomic arrangement exclusive to the hydrothermally prepared material. Solid‐state preparation gives lower homogeneity resulting in separate nanoscale regions rich in La3+ and Tb3+. The A‐site layering in hydrothermal La0.5Tb0.5CrO3 is randomised upon annealing at high temperature, resulting in magnetic behaviour that is dependent on synthesis route. PMID:27727487

  2. Local A-Site Layering in Rare-Earth Orthochromite Perovskites by Solution Synthesis.

    PubMed

    Daniels, Luke M; Kashtiban, Reza J; Kepaptsoglou, Demie; Ramasse, Quentin M; Sloan, Jeremy; Walton, Richard I

    2016-12-19

    Cation size effects were examined in the mixed A-site perovskites La0.5 Sm0.5 CrO3 and La0.5 Tb0.5 CrO3 prepared through both hydrothermal and solid-state methods. Atomically resolved electron energy loss spectroscopy (EELS) in the transmission electron microscope shows that while the La and Sm cations are randomly distributed, increased cation-radius variance in La0.5 Tb0.5 CrO3 results in regions of localised La and Tb layers, an atomic arrangement exclusive to the hydrothermally prepared material. Solid-state preparation gives lower homogeneity resulting in separate nanoscale regions rich in La(3+) and Tb(3+) . The A-site layering in hydrothermal La0.5 Tb0.5 CrO3 is randomised upon annealing at high temperature, resulting in magnetic behaviour that is dependent on synthesis route.

  3. Real space probe of short-range interaction between Cr in a ferromagnetic semiconductor ZnCrTe.

    PubMed

    Kanazawa, Ken; Nishimura, Taku; Yoshida, Shoji; Shigekawa, Hidemi; Kuroda, Shinji

    2014-12-21

    The short-range interaction between Cr atoms was directly examined by scanning tunneling microscopy measurements on a Zn(0.95)Cr(0.05)Te film. Our measurements revealed that a Cr atom formed a localized state within the bandgap of ZnTe and this state was broadened for a pair of Cr atoms within a distance of ∼ 1 nm.

  4. Cr Stable Isotopes in Snake River Plain Aquifer Groundwater: Evidence for Natural Reduction of Dissolved Cr(VI)

    SciTech Connect

    Amanda L. Raddatz; Thomas M. Johnson; Travis L. McLing

    2011-01-01

    At Idaho National Laboratory, Cr(VI) concentrations in a groundwater plume once exceeded regulatory limits in some monitoring wells but have generally decreased over time. This study used Cr stable isotope measurements to determine if part of this decrease resulted from removal of Cr(VI) via reduction to insoluble Cr(III). Although waters in the study area contain dissolved oxygen, the basalt host rock contains abundant Fe(II) and may contain reducing microenvironments or aerobic microbes that reduce Cr(VI). Insomecontaminated locations, 53Cr/52Cr ratios are close to that of the contaminant source, indicating a lack of Cr(VI) reduction. In other locations, ratios are elevated. Part of this shift may be caused by mixing with natural background Cr(VI), which is present at low concentrations but insomelocations has elevated 53Cr/52Cr.Somecontaminated wells have 53Cr/52Cr ratios greater than the maximum attainable by mixing between the inferred contaminant and the range of natural background observed in several uncontaminated wells, suggesting that Cr(VI) reduction has occurred. Definitive proof of reduction would require additional evidence. Depth profiles of 53Cr/52Cr suggest that reduction occurs immediately below the water table, where basalts are likely least weathered and most reactive, and is weak or nonexistent at greater depth.

  5. Modelling Layer parallel stylolites

    NASA Astrophysics Data System (ADS)

    Koehn, Daniel; Pataki Rood, Daisy; Beaudoin, Nicolas

    2016-04-01

    We modeled the geometrical roughening of mainly layer-dominated stylolites in order to understand their structural evolution, to present an advanced classification of stylolite shapes and to relate this classification to chemical compaction and stylolite sealing capabilities. Our simulations show that layer-dominated stylolites can grow in three distinct stages, an initial slow nucleation, a fast layer-pinning phase and a final freezing stage if the layer dissolves completely during growth. Dissolution of the pinning layer and thus destruction of the compaction tracking capabilities is a function of the background noise in the rock and the dissolution rate of the layer itself. Low background noise needs a slower dissolving layer for pinning to be successful but produces flatter teeth than higher background noise. We present an advanced classification based on our simulations and separate stylolites into four classes: rectangular layer type, seismogram pinning type, suture/sharp peak type and simple wave-like type.

  6. Basic Ozone Layer Science

    EPA Pesticide Factsheets

    Learn about the ozone layer and how human activities deplete it. This page provides information on the chemical processes that lead to ozone layer depletion, and scientists' efforts to understand them.

  7. Calibration of CR-39 with monoenergetic protons

    NASA Astrophysics Data System (ADS)

    Xiaojiao, Duan; Xiaofei, Lan; Zhixin, Tan; Yongsheng, Huang; Shilun, Guo; Dawei, Yang; Naiyan, Wang

    2009-10-01

    Calibration of solid state nuclear track detector CR-39 was carried out with very low-energy monoenergetic protons of 20-100 keV from a Cockcroft Walton accelerator. To reduce the beam of the proton from the accelerator, a novel method was adopted by means of a high voltage pulse generator. The irradiation time of the proton beam on each CR-39 sheet was shortened to one pulse with duration of 100 ns, so that very separated proton tracks around 104 cm-2 can be irradiated and observed and measured on the surface of the CR-39 detector after etching. The variations of track diameter with etching time as well as with proton energy response curve has been carefully calibrated for the first time in this very low energy region. The calibration shows that the optical limit for the observation of etched tracks of protons in CR-39 is about or a little lower that 20 keV, above which the proton tracks can be seen clearly and the response curve can be used to distinguish protons from the other ions and determine the energy of the protons. The extension of response curve of protons from traditionally 20 to 100 keV in CR-39 is significant in retrieving information of protons produced in the studies of nuclear physics, plasma physics, ultrahigh intensity laser physics and laser acceleration.

  8. CrIS High Resolution Hyperspectral Radiances

    NASA Astrophysics Data System (ADS)

    Hepplewhite, C. L.; Strow, L. L.; Motteler, H.; Desouza-Machado, S. G.; Tobin, D. C.; Martin, G.; Gumley, L.

    2014-12-01

    The CrIS hyperspectral sounder flying on Suomi-NPPpresently has reduced spectral resolution in the mid-wave andshort-wave spectral bands due to truncation of the interferograms inorbit. CrIS has occasionally downlinked full interferograms for thesebands (0.8 cm max path, or 0.625 cm-1 point spacing) for a feworbits up to a full day. Starting Oct.1, 2014 CrIS will be commandedto download full interferograms continuously for the remainder of themission, although NOAA will not immediately produce high-spectralresolution Sensor Data Records (SDRs). Although the originalmotivation for operating in high-resolution mode was improved spectralcalibration, these new data will also improve (1) vertical sensitivityto water vapor, and (2) greatly increase the CrIS sensitivity tocarbon monoxide. This should improve (1) NWP data assimilation ofwater vapor and (2) provide long-term continuity of carbon monoxideretrievals begun with MOPITT on EOS-TERRA and AIRS on EOS-AQUA. Wehave developed a SDR algorithm to produce calibrated high-spectralresolution radiances which includes several improvements to theexisting CrIS SDR algorithm, and will present validation of thesehigh-spectral resolution radiances using a variety of techniques,including bias evaluation versus NWP model data and inter-comparisonsto AIRS and IASI using simultaneous nadir overpasses (SNOs). Theauthors are presently working to implement this algorithm for NASASuomi NPP Program production of Earth System Data Records.

  9. Structure and energetics of Cr(CO)6 and Cr(CO)5

    NASA Technical Reports Server (NTRS)

    Barnes, Leslie A.; Liu, Bowen; Lindh, Roland

    1993-01-01

    The geometric structures and energetics of Cr(CO)6 and Cr(CO)5 are determined at the modified coupled-pair functional, single and double excitation coupled-cluster (CCSD), and CCSD(T) levels of theory. For Cr(CO)6, the structure and force constants for the totally symmetric representation are in good agreement with experimental data once basis set constants are taken into account. In the largest basis set at the CCSD(T) level of theory, the total binding energy of CR(CO)6 is estimated at around 140 kcal/mol, or about 86 percent of the experimental value. In contrast, the first bond energy of Cr(CO)6 is very well described at the CCSD(T) level of theory, with the best estimated value of 38 kcal/mol being within the experimental uncertainty.

  10. Magnetic Properties of Cr-based Ternary Compound CrAlGe

    NASA Astrophysics Data System (ADS)

    Yoshinaga, Soshi; Mitsui, Yoshifuru; Umetsu, Rie Y.; Koyama, Keiichi

    Structural and magnetic properties of Cr-based compound CrAlGe were investigated. The crystal structure was found to be an orthorhombic TiSi2-type with lattice parameters a = 0.4770 nm, b = 0.8254 nm and c = 0.8725 nm at room temperature. Magnetization curve of CrAlGe showed the ferromagnetic behavior. The saturation magnetic moment, spontaneous magnetic moment and Curie temperature of CrAlGe were determined to be 0.45 μB/f.u., 0.41 μB/f.u. and TC = 80 K, respectively. For the temperature T below 30 K, the decrease in the square of the spontaneous magnetization M0(T)2 was proportional to T2. However, for 30 CrAlGe is a weak itinerant electron ferromagnet.

  11. Cr precipitation in neutron irradiated industrial purity Fe-Cr model alloys

    NASA Astrophysics Data System (ADS)

    Kuksenko, V.; Pareige, C.; Pareige, P.

    2013-01-01

    The microstructure of four neutron irradiated Fe-Cr model alloys of industrial purity (Fe-2.5%Cr, Fe-5%Cr, Fe-9%Cr and Fe-12%Cr) has been characterized by atom probe tomography (APT). Irradiation has been performed at 300 °C up to 0.6 dpa in MTR reactor. APT investigations confirmed the enhanced precipitation of α' clusters as these clusters have only been observed in supersaturated model alloys. In addition a nonexpected family of clusters has been revealed due to irradiation induced segregation of impurities: NiSiPCr-enriched clusters. They might be associated to defect clusters invisible by transmission electron microscopy (TEM). A quantitative description of these objects is presented in this paper and results are compared with TEM and SANS data of the literature obtained on the same model alloy.

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

    PubMed

    Fiol, Núria; Escudero, Carlos; Villaescusa, Isabel

    2008-07-01

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

  13. Study of magnetism in Ni-Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Kishore, G. V. K.; Kumar, Anish; Chakraborty, Gopa; Albert, S. K.; Rao, B. Purna Chandra; Bhaduri, A. K.; Jayakumar, T.

    2015-07-01

    Nickel base Ni-Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni-Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr-C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co-Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni-Cr alloy deposits on stainless steel.

  14. LaCrO{sub 3}-dispersed Cr for metallic interconnect of planar SOFC

    SciTech Connect

    Song, Rak-Hyun; Shin, Dong Ryul; Dokiya, Masayuki

    1996-12-31

    In the planar SOFC, the interconnect materials plays two roles as an electrical connection and as a gas separation plate in a cell stack. The interconnect materials must be chemically stable in reducing and oxidizing environments, and have high electronic conductivity, high thermal conductivity, matching thermal expansion with an electrolyte, high mechanical strength, good fabricability, and gas tightness. Lanthanum chromite so far has been mainly used as interconnect materials in planar SOFC. However, the ceramic materials are very weak in mechanical strength and have poor machining property as compared with metal. Also the metallic materials have high electronic conductivity and high thermal conductivity. Recently some researchers have studied metallic interconnects such as Al{sub 2}O{sub 3}/Inconel 600 cermet, Ni-20Cr coated with (LaSr)CoO{sub 3}, and Y{sub 2}O{sub 3-} or La{sub 2}O{sub 3}-dispersed Cr alloy. These alloys have still some problems because Ni-based alloys have high thermal expansion, the added Al{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and La{sub 2}O{sub 3} to metals have no electronic conductivity, and the oxide formed on the surface of Cr alloy has high volatility. To solve these problems, in this study, LaCrO{sub 3}-dispersed Cr for metallic interconnect of planar SOFC was investigated. The LaCrO{sub 3}-dispersed Cr can be one candidate of metallic interconnect because LaCrO{sub 3} possesses electronic conductivity and Cr metal has relatively low thermal expansion. The content of 25 vol.% LaCrO{sub 3} Was selected on the basis of a theoretically calculated thermal expansion. The thermal expansion, electrical and oxidation properties were examined and the results were discussed as related to SOFC requirements.

  15. Femtosecond Cr:LiSAF and Cr:LiCAF lasers pumped by tapered diode lasers.

    PubMed

    Demirbas, Umit; Schmalz, Michael; Sumpf, Bernd; Erbert, Götz; Petrich, Gale S; Kolodziejski, Leslie A; Fujimoto, James G; Kärtner, Franz X; Leitenstorfer, Alfred

    2011-10-10

    We report compact, low-cost and efficient Cr:Colquiriite lasers that are pumped by high brightness tapered laser diodes. The tapered laser diodes provided 1 to 1.2 W of output power around 675 nm, at an electrical-to-optical conversion efficiency of about 30%. Using a single tapered diode laser as the pump source, we have demonstrated output powers of 500 mW and 410 mW together with slope efficiencies of 47% and 41% from continuous wave (cw) Cr:LiSAF and Cr:LiCAF lasers, respectively. In cw mode-locked operation, sub-100-fs pulse trains with average power between 200 mW and 250 mW were obtained at repetition rates around 100 MHz. Upon pumping the Cr:Colquiriite lasers with two tapered laser diodes (one from each side of the crystal), we have observed scaling of cw powers to 850 mW in Cr:LiSAF and to 650 mW in Cr:LiCAF. From the double side pumped Cr:LiCAF laser, we have also obtained ~220 fs long pulses with 5.4 nJ of pulse energy at 77 MHz repetition rate. These are the highest energy levels reported from Cr:Colquiriite so far at these repetition rates. Our findings indicate that tapered diodes in the red spectral region are likely to become the standard pump source for Cr:Colquiriite lasers in the near future. Moreover, the simplified pumping scheme might facilitate efficient commercialization of Cr:Colquiriite systems, bearing the potential to significantly boost applications of cw and femtosecond lasers in this spectral region (750-1000 nm).

  16. Layer-by-layer cell membrane assembly

    NASA Astrophysics Data System (ADS)

    Matosevic, Sandro; Paegel, Brian M.

    2013-11-01

    Eukaryotic subcellular membrane systems, such as the nuclear envelope or endoplasmic reticulum, present a rich array of architecturally and compositionally complex supramolecular targets that are as yet inaccessible. Here we describe layer-by-layer phospholipid membrane assembly on microfluidic droplets, a route to structures with defined compositional asymmetry and lamellarity. Starting with phospholipid-stabilized water-in-oil droplets trapped in a static droplet array, lipid monolayer deposition proceeds as oil/water-phase boundaries pass over the droplets. Unilamellar vesicles assembled layer-by-layer support functional insertion both of purified and of in situ expressed membrane proteins. Synthesis and chemical probing of asymmetric unilamellar and double-bilayer vesicles demonstrate the programmability of both membrane lamellarity and lipid-leaflet composition during assembly. The immobilized vesicle arrays are a pragmatic experimental platform for biophysical studies of membranes and their associated proteins, particularly complexes that assemble and function in multilamellar contexts in vivo.

  17. Photonic layered media

    DOEpatents

    Fleming, James G.; Lin, Shawn-Yu

    2002-01-01

    A new class of structured dielectric media which exhibit significant photonic bandstructure has been invented. The new structures, called photonic layered media, are easy to fabricate using existing layer-by-layer growth techniques, and offer the ability to significantly extend our practical ability to tailor the properties of such optical materials.

  18. Effect of Sealing Treatment on Corrosion Resistance of Plasma-Sprayed NiCrAl/Cr2O3-8 wt.%TiO2 Coating

    NASA Astrophysics Data System (ADS)

    Zhang, Jingjing; Wang, Zehua; Lin, Pinghua; Lu, Wenhuan; Zhou, Zehua; Jiang, Shaoqun

    2011-03-01

    Plasma-sprayed ceramic coatings inherently contain pores and micro-cracks which is deleterious when performed in aggressive environment. Various methods were applied to the as-sprayed coatings in order to improve the corrosion resistance. In the investigation of this study, plasma-sprayed NiCrAl/Cr2O3-8 wt.%TiO2 coatings were sealed by epoxy resin and silicone resin, respectively. Coatings were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), optical microscopy (OM) and x-ray diffraction (XRD). The possible corrosion mechanism was discussed. The results of salt spray test and electrochemical measurements indicated that after the sealing treatment, the porosity of coatings decreased obviously and a compact layer was formed to protect the coating from corrosion. The silicone resin proved to be more effective than epoxy resin in enhancing the corrosion resistance of the coatings used in this research.

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

    PubMed

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

    2014-09-15

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

  20. Bioremediation of chromium by the yeast Pichia guilliermondii: toxicity and accumulation of Cr (III) and Cr (VI) and the influence of riboflavin on Cr tolerance.

    PubMed

    Ksheminska, Helena; Jaglarz, Anita; Fedorovych, Daria; Babyak, Lyubov; Yanovych, Dmytro; Kaszycki, Pawel; Koloczek, Henryk

    2003-01-01

    A comparative study has been made on the sensitivity of the yeast Pichia guilliermondii to Cr (III) and Cr (VI) as well as on the Cr uptake potential at growth-inhibitory concentrations of chromium. The strains used in the study were either isolated from natural sources or obtained from a laboratory strain collection. The results show that most of the natural strains were more tolerant to chromium and were able to grow in the presence of 5 mM Cr (III) or 0.5 mM Cr (VI), that is at concentrations which substantially inhibited the growth of laboratory strains. The cellular Cr content after treatment was similar for both strain types and ranged from 1.2-4.0 mg/g d.w. and 0.4-0.9 mg/g d.w., for Cr (III) and Cr (VI) forms, respectively, however, in one case of a natural strain it reached the value of 10 mg Cr (III)/g dry mass. Natural-source strains were grouped into four groups based on the yeasts' differential response to Cr (III) and Cr (VI). Hexavalent Cr-resistant mutants of a P. giuilliermondii laboratory strain, which revealed markedly changed capabilities of chromium accumulation, were obtained by means of UV-induced mutagenesis. Cr (VI) treatment triggered oversynthesis of riboflavin and the addition of exogenous riboflavin increased P. guilliermondii resistance to both Cr (III) and Cr (VI). Electrophoretic protein profiles revealed the induction and/or suppression of several proteins in response to toxic Cr (VI) levels.

  1. Identification and geochemical modeling of processes controlling leaching of Cr(VI) and other major elements from chromite ore processing residue

    NASA Astrophysics Data System (ADS)

    Geelhoed, Jeanine S.; Meeussen, Johannes C. L.; Hillier, Stephen; Lumsdon, David G.; Thomas, Rhodri P.; Farmer, John G.; Paterson, Edward

    2002-11-01

    Chromite ore processing residue (COPR) contains very high levels of chromium as Cr(III) and Cr(VI) and has a pH of ˜11.5 to 12. Millions of tonnes of COPR have in the past been deposited in urban areas. We have studied the factors that control leaching of Cr(VI), Ca, Al, Si, and Mg from COPR by means of batch experiments, mineralogical characterization of COPR via X-ray powder diffraction and scanning electron microscopy, and chemical equilibrium modeling. Batch experiments at a range of pH values and two liquid:solid ratios showed that mineral solubility control exists for aqueous concentrations of Cr(VI) above pH 10. Calculations indicate that the solid phases that control the solubility of Cr(VI) at pH values above 11 are Cr(VI)-substituted hydrogarnet (Ca 3Al 2(H 4O 4,CrO 4) 3) and Cr(VI)-hydrocalumite (Ca 4Al 2(OH) 12CrO 4·6 H 2O), a layered double-hydroxide clay with chromate anions held in the interlayers. In the pH range 9.5 to 11, the description of the Cr(VI) concentration in solution was strongly improved by the incorporation in the model of Cr(VI)-ettringite (Ca 6Al 2(OH) 12(CrO 4) 3·26 H 2O), which precipitates as a secondary phase when hydrocalumite dissolves. The proposed model for leaching of COPR at high pH includes Cr(VI)-bearing hydrogarnet, Cr(VI)-hydrocalumite, Cr(VI)-ettringite, brucite, calcite, Ca 2Al 2(OH) 10·3 H 2O, CaH 2SiO 4, and gehlenite hydrate (Ca 2Al 2(OH) 6SiO 8H 8·H 2O). The model accurately predicts the concentrations of Cr(VI), Ca, Al, Si, and Mg in solution in the pH range 10 to 12 as well as the pH-buffering behavior. Below pH 8, a decrease in the Cr(VI) concentration in solution is observed, which may be attributed to sorption of chromate onto freshly precipitated Al and Fe hydroxide surfaces. Sulfate and carbonate show the same type of behavior as chromate. The chemistry of COPR shows similarities with cement and high-pH municipal waste incinerator bottom ash.

  2. TiC reinforced cast Cr steels

    SciTech Connect

    Dogan, O.N.; Hawk, J.A.; Schrems, K.K.

    2006-06-01

    A new class of materials, namely TiC-reinforced cast chromium (Cr) steels, was developed for applications requiring high abrasion resistance and good fracture toughness. The research approach was to modify the carbide structure of commercial AISI 440C steel for better fracture resistance while maintaining the already high abrasion resistance. The new alloys contained 12Cr, 2.5–4.5Ti, and 1–1.5C (wt.%) and were melted in a vacuum induction furnace. Their microstructure was composed primarily of a martensitic matrix with a dispersion of TiC precipitates. Modification of TiC morphology was accomplished through changing the cooling rate during solidification. Wear rates of the TiC-reinforced Cr steels were comparable to that of AISI 440C steel, but the impact resistance was much improved.

  3. A thermodynamic model of Fe Cr spinels

    NASA Astrophysics Data System (ADS)

    Kurepin, Viktor A.

    2005-07-01

    A new thermodynamic model for multi-component spinel solid solutions has been developed which takes into account thermodynamic consequences of cation mixing in spinel sublattices. It has been applied to the evaluation of thermodynamic functions of cation mixing and thermodynamic properties of Fe3O4 FeCr2O4 spinels using intracrystalline cation distribution in magnetite, lattice parameters and activity-composition relations of magnetite chromite solid solutions. According to the model, cation distribution in binary spinels, (Fe1-x2+ Fex3+)[Fex2+Fe2-2y-x3+Cr2y]O4, and their thermodynamic properties depend strongly on Fe2+ Cr3+ cation mixing. Mixing of Fe2+ Fe3+ and Fe3+ Cr3+ can be accepted as ideal. If Fe2+, Fe3+ and Cr are denoted as 1, 3 and 4 respectively, the equation of cation distribution is -RT ln(x2/((1-x)(2-2y-x)))= ΔG13* + (1-2x)W13+y(W14-W13-W34) where ΔG13* is the difference between the Gibbs energy of inverse and normal magnetite, Wij is a Margules parameter of cation mixing and ΔG13*, J/mol =-23,000+13.4 T, W14=36 kJ/mol, W13=W34=0. The positive nonconfigurational Gibbs energy of mixing is the main reason for changing activity composition relations with temperature. According to the model, the solvus in Fe3O4 FeCr2O4 spinel has a critical temperature close to 500°C, which is consistent with mineralogical data.

  4. Short duration thermal metamorphism in CR chondrites

    NASA Astrophysics Data System (ADS)

    Briani, G.; Quirico, E.; Gounelle, M.; Paulhiac-Pison, M.; Montagnac, G.; Beck, P.; Orthous-Daunay, F.-R.; Bonal, L.; Jacquet, E.; Kearsley, A.; Russell, S. S.

    2013-12-01

    CR chondrites are considered as one of the most primitive classes of meteorites. Most of them experienced a mild aqueous alteration and show no evidence of significant effect of thermal metamorphism. We present here a search for low degree metamorphic effects in CR chondrites. We studied 15 CR chondrites using different metamorphic indicators: (1) structure and Ni content of metal grains; (2) hydration state of matrix; (3) structure and composition of organic matter. The different metamorphic indicators show that two of the analyzed CR chondrites, GRA 06100 and GRO 03116, experienced thermal metamorphism. Indeed, all of the metal grains in GRA 06100 and half of the metal grains in GRO 03116 show Ni-rich phases; the matrix of GRA 06100 is almost completely dehydrated, and the matrix of GRO 03116 is partially dehydrated; Raman spectra of organic matter in these two meteorites are clearly different from those obtained for organic matter in the other CR chondrites, which resemble Raman spectra of organic matter in unmetamorphosed, CM2 meteorites; IR spectra of insoluble organic matter extracted from GRA 06100 and GRO 03116 show lower carbonyl abundance and higher CH2/CH3 ratio with respect to organic matter of unmetamorphosed chondrites. The other CR chondrites analyzed here lack these characteristics and only show a few metal grains with Ni-rich inclusions. Our results also show that the metamorphic effects observed in GRA 06100 and GRO 03116 are different from those observed in type 3 chondrites, which experienced long-duration metamorphism of radiogenic origin. We infer that thermal processing in these two CRs extended over a short duration and was triggered by impacts.

  5. Differential Modulation of Retinal Degeneration by Ccl2 and Cx3cr1 Chemokine Signalling

    PubMed Central

    Luhmann, Ulrich F. O.; Lange, Clemens A.; Robbie, Scott; Munro, Peter M. G.; Cowing, Jill A.; Armer, Hannah E. J.; Luong, Vy; Carvalho, Livia S.; MacLaren, Robert E.; Fitzke, Frederick W.; Bainbridge, James W. B.; Ali, Robin R.

    2012-01-01

    Microglia and macrophages are recruited to sites of retinal degeneration where local cytokines and chemokines determine protective or neurotoxic microglia responses. Defining the role of Ccl2-Ccr2 and Cx3cl1-Cx3cr1 signalling for retinal pathology is of particular interest because of its potential role in age-related macular degeneration (AMD). Ccl2, Ccr2, and Cx3cr1 signalling defects impair macrophage trafficking, but have, in several conflicting studies, been reported to show different degrees of age-related retinal degeneration. Ccl2/Cx3cr1 double knockout (CCDKO) mice show an early onset retinal degeneration and have been suggested as a model for AMD. In order to understand phenotypic discrepancies in different chemokine knockout lines and to study how defects in Ccl2 and/or Cx3cr1 signalling contribute to the described early onset retinal degeneration, we defined primary and secondary pathological events in CCDKO mice. To control for genetic background variability, we compared the original phenotype with that of single Ccl2, Cx3cr1 and Ccl2/Cx3cr1 double knockout mice obtained from backcrosses of CCDKO with C57Bl/6 mice. We found that the primary pathological event in CCDKO mice develops in the inferior outer nuclear layer independently of light around postnatal day P14. RPE and vascular lesions develop secondarily with increasing penetrance with age and are clinically similar to retinal telangiectasia not to choroidal neovascularisation. Furthermore, we provide evidence that a third autosomal recessive gene causes the degeneration in CCDKO mice and in all affected re-derived lines and subsequently demonstrated co-segregation of the naturally occurring RD8 mutation in the Crb1 gene. By comparing CCDKO mice with re-derived CCl2−/−/Crb1Rd8/RD8, Cx3cr1−/−/Crb1Rd8/RD8 and CCl2−/−/Cx3cr1−/−/Crb1Rd8/RD8 mice, we observed a differential modulation of the retinal phenotype by genetic background and both chemokine signalling pathways. These findings

  6. On Some Features of Chromium Carbide Diffusion Layer Formation

    NASA Astrophysics Data System (ADS)

    Glowacki, Z.; Kaluba, W.

    1982-05-01

    The formation of chromium carbide diffusion layers on iron-carbon alloys was studied in this investigation. The investigation was carried out on graphite, plain carbon steels, gray cast iron, and white cast iron. The carbide layers were obtained by the powder pack method. To distinguish the effect of iron from the chromizing medium on the layer morphology, high purity iron and chromium powders were used as the components of the powder mixture. The samples were chromized in the temperature range of 870 to 1373 K for five to 1500 minutes. Phase composition of the layers was examined by X-ray diffraction method. To assess chromium and iron distribution in the layers, an electron micro-probe was employed. Microstructure of the layers was examined with the aid of light and electron microscopes. Both replica and thin foil methods were used in this work. The original method of thin foil preparation was used to show the M7C3 layer substructure and to define its crystallographic orientation. It was found that formation of the carbide layer began at temperatures below A1 transformation, when the samples were heated to a normal chromizing temperature. It was proved that M3C appearance in the layer depends on both chromizing temperature and amount of carbon in the alloy. The Fe : Cr ratio in the chromized medium was found to affect the microstructure and thickness of the layers strongly. The needle-shaped grains of the M7C3 layer showed particular crystallographic orientation, i.e., [0001] M7C3 crystallographic direction was perpendicular to the diffusion front. The new data on microstructure of the carbide layers were obtained by thin foil method. The growth direction of the carbide layer was defined, which allowed the suggestion of the diffusion model for the carbide layer formation.

  7. Scintillator reflective layer coextrusion

    DOEpatents

    Yun, Jae-Chul; Para, Adam

    2001-01-01

    A polymeric scintillator has a reflective layer adhered to the exterior surface thereof. The reflective layer comprises a reflective pigment and an adhesive binder. The adhesive binder includes polymeric material from which the scintillator is formed. A method of forming the polymeric scintillator having a reflective layer adhered to the exterior surface thereof is also provided. The method includes the steps of (a) extruding an inner core member from a first amount of polymeric scintillator material, and (b) coextruding an outer reflective layer on the exterior surface of the inner core member. The outer reflective layer comprises a reflective pigment and a second amount of the polymeric scintillator material.

  8. Long-term corrosion investigation of AISI 316L, Co-28Cr-6Mo, and Ti-6Al-4V alloys in simulated body solutions

    NASA Astrophysics Data System (ADS)

    Karimi, Shima; Nickchi, Tirdad; Alfantazi, Akram M.

    2012-06-01

    The long-term weight loss, ion release and surface composition of AISI 316L, the Co-28Cr-6Mo and Ti-6Al-4V alloys were investigated in phosphate buffered solutions (PBS) with various bovine serum albumin (BSA) concentrations. All the samples lost weight up to 14 weeks and then started to gain weight. This can be explained by precipitation of dissolved ions on the surface after 14 weeks of immersion. The quantities of the dissolved ions were measured in immersed solution for 8, 14 and 22 weeks by induced coupled plasma-optical emission spectrometer (ICP-OES). The amounts of Fe released from 316L, and Co and Mo released from the Co-28Cr-6Mo alloy decreased after 14 weeks of immersion in PBS and BSA solutions. This observation coincides with the weight change of the samples. The oxide layer composition and concentration of the specimens exposed to solutions for 22 weeks were identified by X-ray photoelectron spectroscopy (XPS) analysis. The XPS results revealed that chromium is the main component of the 316L and Co-28Cr-6Mo alloy. The high Cr concentration of the 316L and Co-Cr-Mo oxide layer corresponds with the slow dissolution rate of Cr compared to other alloying elements of the 316L and Co-28Cr-6Mo alloy.

  9. The Mn-53-Cr-53 System in CAIs: An Update

    NASA Technical Reports Server (NTRS)

    Papanastassiou, D. A.; Wasserburg, G. J.; Bogdanovski, O.

    2005-01-01

    High precision techniques have been developed for the measurement of Cr isotopes on the Triton mass spectrometer, at JPL. It is clear that multiple Faraday cup, simultaneous ion collection may reduce the uncertainty of isotope ratios relative to single Faraday cup ion collection, by the elimination of uncertainties from ion beam instabilities (since ion beam intensities for single cup collection are interpolated in time to calculate isotope ratios), and due to a greatly increased data collection duty cycle, for simultaneous ion collection. Efforts to measure Cr by simultaneous ion collection have not been successful in the past. Determinations on Cr-50-54Cr, by simultaneous ion collection on the Finnigan/ MAT 262 instrument at Caltech, resulted in large variations in extrinsic precision, for normal Cr, of up to 1% in Cr-53/Cr-52 (data corrected for mass fractionation, using Cr-50/Cr-52).

  10. AF Cr(VI) Minimize Roadmap: Phase 1 Results

    DTIC Science & Technology

    2010-12-01

    HC-1 WC/CoCr, Tribaloy 400, Tribaloy 800, Cr3C2/20(80Ni-20Cr) Thermal Spray (HVOF) 1.4, 1.5, 1.10, 1.15, 1.27, 1.39, 1.64 Hard Chrome LOS Plating...Landing Gear High Strength Steel HC-1 WC/CoCr, Tribaloy 400, Cr3C2/20(80Ni-20Cr) Thermal Spray (HVOF) 1.8, 1.46, 1.15, 1.16, 1.27, 1.39, 1.64 Hard...Chrome LOS Plating Engine Components Nickel Alloys (Inconel) HC-2 WC/CoCr, Tribaloy 400, Tribaloy 800, Cr3C2/20(80Ni-20Cr) Thermal Spray (HVOF) 1.4

  11. Auger electron spectroscopy study of oxidation of a PdCr alloy used for high-temperature sensors

    NASA Technical Reports Server (NTRS)

    Boyd, Darwin L.; Zeller, Mary V.; Vargas-Aburto, Carlos

    1993-01-01

    A Pd-13 wt. percent Cr solid solution is a promising high-temperature strain gage alloy. In bulk form it has a number of properties that are desirable in a resistance strain gage material, such as a linear electrical resistance versus temperature curve to 1000 C and stable electrical resistance in air at 1000 C. However, unprotected fine wire gages fabricated from this alloy perform well only to 600 C. At higher temperatures severe oxidation degrades their electrical performance. In this work Auger electron spectroscopy was used to study the oxidation chemistry of the alloy wires and ribbons. Results indicate that the oxidation is caused by a complex mechanism that is not yet fully understood. As expected, during oxidation, a layer of chromium oxide is formed. This layer, however, forms beneath a layer of metallic palladium. The results of this study have increased the understanding of the oxidation mechanism of Pd-13 wt. percent Cr.

  12. Formation of a regular domain structure in TGS-TGS + Cr crystals with a profile impurity distribution

    NASA Astrophysics Data System (ADS)

    Belugina, N. V.; Gainutdinov, R. V.; Tolstikhina, A. L.; Ivanova, E. S.; Kashevich, I. F.; Shut, V. N.; Mozzharov, S. E.

    2015-07-01

    A complex investigation of TGS-TGS + Cr crystals with a profile impurity distribution of chromium ions Cr3+ has been carried out at the macrolevel (measurement of dielectric properties by the method of nematic liquid crystals) and microlevel (domain structure according to atomic force microscopy data). It is established that periodic doped layers are formed only in individual growth pyramids in the regions where the polarization vector has a nonzero component along the normal to the growth faces rather than throughout the entire crystal volume. The domain configuration at the boundary of growth layers with different impurity compositions has been studied by piezoelectric force microscopy. The static unipolarity of layers with and without chromium impurity is approximately identical, whereas the domain-wall density in doped regions is higher than that in undoped ones by a factor of about 7.

  13. Formation of a regular domain structure in TGS–TGS + Cr crystals with a profile impurity distribution

    SciTech Connect

    Belugina, N. V. Gainutdinov, R. V.; Tolstikhina, A. L.; Ivanova, E. S.; Kashevich, I. F.; Shut, V. N.; Mozzharov, S. E.

    2015-07-15

    A complex investigation of TGS–TGS + Cr crystals with a profile impurity distribution of chromium ions Cr{sup 3+} has been carried out at the macrolevel (measurement of dielectric properties by the method of nematic liquid crystals) and microlevel (domain structure according to atomic force microscopy data). It is established that periodic doped layers are formed only in individual growth pyramids in the regions where the polarization vector has a nonzero component along the normal to the growth faces rather than throughout the entire crystal volume. The domain configuration at the boundary of growth layers with different impurity compositions has been studied by piezoelectric force microscopy. The static unipolarity of layers with and without chromium impurity is approximately identical, whereas the domain-wall density in doped regions is higher than that in undoped ones by a factor of about 7.

  14. First liquid-layer implosion experiments on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Zylstra, Alex; Olson, R.; Leeper, R.; Kline, J.; Yi, S. A.; Peterson, R.; Bradley, P.; Haines, B.; Yin, L.; Wilson, D.; Herrmann, H.; Shah, R.; Biener, J.; Braun, T.; Kozioziemski, B.; Berzak Hopkins, L.; Hamza, A.; Nikroo, A.; Meezan, N.; Biener, M.; Sater, J.; Walters, C.

    2016-10-01

    Replacing the standard ice layer in an ignition design with a liquid layer allows fielding the target with a higher central vapor pressure, leading to reduced implosion convergence ratio (CR). At lower CR, the implosions are expected to be more robust to instabilities and asymmetries than standard ignition designs. The first liquid-layer implosions on the National Ignition Facility (NIF) have been performed by wicking the liquid fuel into a supporting foam. A 3-shot series has been conducted at CR=14-16 using a HDC ablator driven by a 3-shock pulse in a near-vacuum Au hohlraum; data and inferred quantities, such as pressure, show good agreement with expectations.

  15. Microstructural and mechanical characteristics of Ni–Cr thin films

    SciTech Connect

    Petley, Vijay; Sathishkumar, S.; Thulasi Raman, K.H.; Rao, G.Mohan; Chandrasekhar, U.

    2015-06-15

    Highlights: • Ni–Cr thin films of varied composition deposited by DC magnetron co-sputtering. • Thin film with Ni–Cr: 80–20 at% composition exhibits most distinct behavior. • The films were tensile tested and exhibited no cracking till the substrate yielding. - Abstract: Ni–Cr alloy thin films have been deposited using magnetron co-sputtering technique at room temperature. Crystal structure was evaluated using GIXRD. Ni–Cr solid solution upto 40 at% of Cr exhibited fcc solid solution of Cr in Ni and beyond that it exhibited bcc solid solution of Ni in Cr. X-ray diffraction analysis shows formation of (1 1 1) fiber texture in fcc and (2 2 0) fiber texture in bcc Ni–Cr thin films. Electron microscopy in both in-plane and transverse direction of the film surface revealed the presence of columnar microstructure for films having Cr upto 40 at%. Mechanical properties of the films are evaluated using nanoindentation. The modulus values increased with increase of Cr at% till the film is fcc. With further increase in Cr at% the modulus values decreased. Ni–Cr film with 20 at% Ni exhibits reduction in modulus and is correlated to the poor crystallization of the film as reflected in XRD analysis. The Ni–Cr thin film with 80 at% Ni and 20 at% Cr exhibited the most distinct columnar structure with highest electrical resistivity, indentation hardness and elastic modulus.

  16. Effects of Cr on the interdiffusion between Ce and Fe-Cr alloys

    NASA Astrophysics Data System (ADS)

    Lo, Wei-Yang; Silva, Nicolas; Wu, Yuedong; Winmann-Smith, Robert; Yang, Yong

    2015-03-01

    Fuel cladding chemical interaction (FCCI) has been a long-standing issue for the metallic fuel with a steel cladding in a sodium-cooled fast reactor, particularly for a high burnup fuel. Although the FCCI has been largely improved by alloying the fuels with Zr or Pd elements, applying a physical diffusion barrier between fuel and cladding, and employing advanced ferritic/martensitic (F/M) claddings, there is a scientific knowledge gap in understanding the behavior of chromium and its effects on the interdiffusion between lanthanides and advanced F/M steels that contain 9-12 wt.% Cr. In this paper, we systematically studied the interdiffusion between cerium and Fe-Cr model alloys with Cr contents of 6, 9 and 12 wt.%. Following the thermal annealing at 560 °C for up to 100 h, detailed microstructural characterizations were performed to determine the interdiffusion microstructures, compositional distributions, diffusion kinetics, and phase structures in the interdiffusion zone. This study unambiguously disclosed that, as the Ce diffuses into Fe-Cr model alloys, Cr segregates and precipitates into Cr-rich σ phase consisted of Fe and Cr instead of forming a ternary phase together with Fe and Ce. The precipitation of those nano-sized σ phase particles at the Ce diffusion front would effectively slow down the interdiffusion.

  17. High temperature coarsening of Cr2Nb precipitates in Cu-8 Cr-4 Nb alloy

    NASA Technical Reports Server (NTRS)

    Anderson, Kenneth Reed

    1996-01-01

    A new high-temperature-strength, high-conductivity Cu-Cr-Nb alloy with a CrNb ratio of 2:1 was developed to achieve improved performance and durability. The Cu-8 Cr4 Nb alloy studied has demonstrated remarkable thermal and microstructural stability after long exposures at temperatures up to 0.98 T(sub m). This stability was mainly attributed to the slow coarsening kinetics of the Cr2Nb precipitates present in the alloy. At all temperatures, the microstructure consists of a bimodal and sometimes trimodal distribution of strengthening Cr2Nb precipitates, depending on precipitation condition, i.e. from liquid or solid solution, and cooling rates. These precipitates remain in the same size range, i.e. large precipitates of approximately I pm, and small precipitates less dm 300 nm, and effectively pin the grain boundaries thus retaining a fine grain size of 2.7 micro-m after 100 h at 1323 K. (A relatively small number of Cr-rich and Nb-rich particles were also present.) This grain boundary pinning and sluggish coarsening of Cr2Nb particles explain the retention of good mechanical properties after prolonged holding at very high temperatures, e.g., 75% of the original hardness after aging for 100 h at 1273 K. Application of LSW-based coarsening models indicated that the coarsening kinetics of the large precipitates are most likely governed by grain boundary diffsion and, to a lesser extent, volume diffusion mechanisms.

  18. Evaluation of the castability of a Co-Cr-Mo-W alloy varying the investing technique.

    PubMed

    Carreiro, Adriana da Fonte Porto; Ribeiro, Ricardo Faria; Mattos, Maria da Gloria Chiarello de; Rodrigues, Renata Cristina Silveira

    2005-01-01

    The purpose of this study was to compare the castability of Co-Cr-Mo-W (Remanium 2000), Ni-Cr (Durabond) and Co-Cr-Mo (Vera PDI) alloys invested with either conventional (phosphate- and silica-based) or mixed investing techniques. A 10 X 10 mm square-shaped nylon net containing 100 open squares served as a template for construction of wax patterns, which were invested with phosphate-based investment (Termocast), silica-based investment (Refrafil) and mixed investing technique (2-mm layer phosphate investment plus filling with silica investment). Forty-five cast specimens (5 per experimental condition) were obtained and sandblasted with aluminum oxide. The number of completely reproduced cast segments was counted to obtain a percentage designated "castability value", which indicated the accuracy of the alloy to reproduce mold details. Statistical analysis using two-way ANOVA and Tukey's test showed that, comparing the alloys, Remanium 2000 had statistically similar castability (p>0.05) to Vera PDI and lower than Durabond (p<0.05). Considering the mixed technique results, Remanium 2000 yielded lower castability value (p<0.05) than Durabond and Vera PDI alloys, which showed similar results to each other (p>0.05). In conclusion, the castability of the Co-Cr-Mo-W alloy (Remanium 2000) was comparable to that of the Co-Cr alloy (Vera PDI) and worse than that of the Ni-Cr alloy (Durabond). Except for Remanium 2000, the mixed investing technique considerably improved the accuracy of the alloys to reproduce cast details, compared to the phosphate-based investment. The mixed investing technique appears as a viable alternative to improve castability of base metal alloys without decreasing the surface quality of the metallic pieces.

  19. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

  20. Effect of welding thermal cycles on the oxidation resistance of 9 wt.% Cr heat resistant steels in 550 °C lead-bismuth eutectic

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Rong, Lijian; Li, Dianzhong; Lu, Shanping

    2016-12-01

    The oxidation resistance for the heat affected zone (HAZ) and base metal of 9 wt.% Cr heat resistant steel in 550 °C lead-bismuth eutectic has been investigated. The oxide film presents a three-layer structure. The outer layer is Fe3O4 while the inner layer is mainly FeCr2O4. The oxide film thickness becomes thinner and thinner in turns of the coarse grained HAZ, fine grained HAZ, inter-critical HAZ and base metal. The oxygen diffusion is the rate determining step during the oxidation process. The Cr-enriched M23C6 plays a significant role on the oxidation rate at the initial stage of oxidation. Increasing the carbon content is a useful method to improve the oxidation resistance.

  1. Morphology, deformation, and defect structures of TiCr{sub 2} in Ti-Cr alloys

    SciTech Connect

    Chen, K.C.; Allen, S.M.; Livingston, J.D.

    1992-12-31

    The morphologies and defect structures of TiCr{sub 2} in several Ti-Cr alloys have been examined by optical metallography, x-ray diffraction, and transmission electron microscopy (TEM), in order to explore the room-temperature deformability of the Laves phase TiCr{sub 2}. The morphology of the Laves phase was found to be dependent upon alloy composition and annealing temperature. Samples deformed by compression have also been studied using TEM. Comparisons of microstructures before and after deformation suggest an increase in twin, stacking fault, and dislocation density within the Laves phase, indicating some but not extensive room-temperature deformability.

  2. Enhancement of ferromagnetism by Cr doping in Ni-Mn-Cr-Sb Heusler alloys

    NASA Astrophysics Data System (ADS)

    Khan, Mahmud; Dubenko, Igor; Stadler, Shane; Jung, J.; Stoyko, S. S.; Mar, Arthur; Quetz, Abdiel; Samanta, Tapas; Ali, Naushad; Chow, K. H.

    2013-03-01

    A series of Mn rich Ni50Mn37-xCrxSb13 Heusler alloys have been investigated by dc magnetization and electrical resistivity measurements. Due to the weakening of the Ni-Mn hybridization, the martensitic transition shifts to lower temperatures with increasing Cr concentration, while the saturation magnetization at 5 K increases. The magnetoresistance and exchange bias properties are dramatically suppressed with increasing Cr concentration. The observed behaviors suggest that substitution of Cr for Mn in Ni50Mn37-xCrxSb13 Heusler alloys not only destabilizes the martensitic phase but also enhances ferromagnetism in the system. The possible mechanisms responsible for the observed behavior are discussed.

  3. Strengthening in rapidly solidified age hardened Cu-Cr and Cu-Cr-Zr alloys

    SciTech Connect

    Correia, J.B.; Davies, H.A.; Sellars, C.M.

    1997-01-01

    Cu-Cr and Cu-Cr-Zr alloy powders were produced by water atomization and consolidated by warm extrusion. Coherent Cr precipitation is associated with the peak hardness condition in these alloys. The mechanical properties obtained after aging treatments, namely the peak hardness, and the corresponding proof stress are related to the concentration of the alloying element initially in solid solution in the powders. The strengthening observed is interpreted in terms of theories of precipitation and dispersion strengthening and compared with similar analyses reported previously in the literature for these alloy systems.

  4. Magnetostriction and ferroelectric state in AgCrS₂.

    PubMed

    Streltsov, Sergey V; Poteryaev, Alexander I; Rubtsov, Alexey N

    2015-04-29

    The band structure calculations in the GGA+U approximation show the presence of additional lattice distortions in the magnetically ordered phase of AgCrS2. The magnetostriction leads to the formation of long and short Cr-Cr bonds in the case when the respective Cr ions have the same or opposite spin projections. These changes in the Cr lattice are accompanied by distortions of the CrS6 octahedra, which in turn lead to the development of spontaneous electric polarization.

  5. Effective adsorption of Cr(VI) on mesoporous Fe-functionalized Akadama clay: Optimization, selectivity, and mechanism

    NASA Astrophysics Data System (ADS)

    Ji, Min; Su, Xiao; Zhao, Yingxin; Qi, Wenfang; Wang, Yue; Chen, Guanyi; Zhang, Zhenya

    2015-07-01

    A Japanese volcanic soil, Akadama clay, was functionalized with metal salts (FeCl3, AlCl3, CaCl2, MgCl2, MnCl2) and tested for Cr(VI) removal from aqueous solution. FeCl3 was selected as the most efficient activation agent. To quantitatively investigate the independent or interactive contribution of influencing factors (solution pH, contact time, adsorbent dose, and initial concentration) to Cr(VI) adsorption onto Fe-functionalized AC (FFAC), factorial experimental design was applied. Results showed initial concentration contributed most to adsorption capacity of Cr(VI) (53.17%), followed by adsorbent dosage (45.15%), contact time (1.12%) and the interaction between adsorbent dosage and contact time (0.37%). The adsorption showed little dependence on solution pH from 2 to 8. Adsorption selectivity of Cr(VI) was evaluated through analyzing distribution coefficient, electrical double layer theory, as well as the valence and Pauling's ionic radii of co-existing anions (Cl-, SO42-, and PO43-). EDX and XPS analyses demonstrated the adsorption mechanism of Cr(VI) onto FFAC included electrostatic attraction, ligant exchange, and redox reaction. Improved treatment for tannery wastewater shows a potential application of FFAC as a cost-effective adsorbent for Cr(VI) removal.

  6. Characterization of Cr poisoning in a solid oxide fuel cell cathode using a high-energy x-ray microbeam.

    SciTech Connect

    Liu, D. J.; Almer, J.; Cruse, T.

    2010-01-01

    A key feature of planar solid oxide fuel cells (SOFCs) is the feasibility of using metallic interconnects made of high temperature ferritic stainless steels, which reduce system cost while providing excellent electric conductivity. Such interconnects, however, contain high levels of chromium, which has been found to be associated with SOFC cathode performance degradation at SOFC operating temperatures; a phenomenon known as Cr poisoning. Here, we demonstrate an accurate measurement of the phase and concentration distributions of Cr species in a degraded SOFC, as well as related properties including deviatoric strain, integrated porosity, and lattice parameter variation, using high energy microbeam X-ray diffraction and radiography. We unambiguously identify (MnCr){sub 3}O{sub 4} and Cr{sub 2}O{sub 3} as the two main contaminant phases and find that their concentrations correlate strongly with the cathode layer composition. Cr{sub 2}O{sub 3} deposition within the active cathode region reduces porosity and produces compressive residual strains, which hinders the reactant gas percolation and can cause structural breakdown of the SOFC cathode. The information obtained through this study can be used to better understand the Cr-poisoning mechanism and improve SOFC design.

  7. Chemical and electrochemical behavior of the Cr(3)/Cr(2) half cell in the NASA Redox Energy Storage System

    NASA Technical Reports Server (NTRS)

    Johnson, D. A.; Reid, M. A.

    1982-01-01

    The Cr(III) complexes in the NASA Redox Energy Storage System were isolated and identified as Cr(H2O)6(+3) and Cr(H2O)5Cl(+2) by ion exchange chromatography and visible spectrophotometry. The cell reactions during charge-discharge cycles were followed by means of visible spectrophotometry. The spectral bands were resolved into component peaks and concentrations calculated using Beer's Law. During the charge mode Cr(H2O)5Cl(+2) is reduced to Cr(H2O)5Cl(+) and during the discharge mode Cr(H2O)5Cl(+) is oxidized back to Cr(H2O)5Cl(+2). Both electrode reactions occur via a chloride-bridge inner-sphere reaction pathway. Hysteresis effects can be explained by the slow attainment of equilibrium between Cr(H2O)6(+3) and Cr(H2O)5Cl(+2).

  8. Dependence of Precipitation Behavior and Creep Strength on Cr Content in High Cr Ferritic Heat Resistant Steels

    NASA Astrophysics Data System (ADS)

    Murata, Yoshinori; Yamashita, Koji; Morinaga, Masahiko; Hara, Toru; Miki, Kazuhiro; Azuma, Tsukasa; Ishiguro, Toru; Hashizume, Ryokichi

    It is known that high temperature tensile strength increases with increasing Cr content in Cr containing heat resistant steels. Recently, however, it was found that long-term creep strength decreased with increasing Cr content in the heat resistant steels containing 8.5-12%Cr. In this study, precipitation behavior of M23C6 carbide and the Z phase after creep tests was investigated using two kinds of high Cr ferritic steels (9Cr and 10.5Cr). As a result, 10.5Cr steel exhibited larger average particle size of M23C6 than 9Cr steel irrespective of creep stress levels, but the amount of M23C6 carbide was almost the same in both steels. On the other hand, the amount of the Z phase became large in 10.5Cr steel compared with 9Cr steel. These experimental results indicate that high level of Cr content accelerates precipitation and coalescence rate of both M23C6 carbide and the Z phase, resulting in degradation of long term creep strength in 10.5 Cr steel compared to 9Cr steel.

  9. Effects of 200 keV Ar-ions irradiation on the structural and optical properties of reactively sputtered CrN films

    NASA Astrophysics Data System (ADS)

    Novaković, M.; Popović, M.; Zhang, K.; Rakočević, Z.; Bibić, N.

    2016-12-01

    Modification in structural and optical properties of chromium-nitride (CrN) films induced by argon ion irradiation and thermal annealings were investigated using various experimental techniques. CrN films deposited by d. c. reactive sputtering on Si substrate were implanted with 200 keV argon ions, at fluences of 5-20 × 1015 ions/cm2. As-implanted samples were then annealed in vacuum, for 2 h at 700 °C. Rutherford backscattering spectrometry, X-ray diffraction, cross-sectional (high-resolution) transmission electron microscopy and spectroscopic ellipsometry (SE) measurements were carried out in order to study structural and optical properties of the layers. After irradiation with 200 keV Ar ions a damaged surface layer of nanocrystalline structure was generated, which extended beyond the implantation profile, but left an undamaged bottom zone. Partial loss of columnar structure observed in implanted samples was recovered after annealing at 700 °C and CrN started to decompose to Cr2N. This layer geometry determined from transmission electron microscopy was inferred in the analysis of SE data using the combined Drude and Tauc-Lorentz model, and the variation of the optical bandgap was deduced. The results are discussed on the basis of the changes induced in the microstructure. It was found that the optical properties of the layers are strongly dependent on the defects' concentration of CrN.

  10. Piezoelectric Resonator with Two Layers

    NASA Technical Reports Server (NTRS)

    Stephanou, Philip J. (Inventor); Black, Justin P. (Inventor)

    2013-01-01

    A piezoelectric resonator device includes: a top electrode layer with a patterned structure, a top piezoelectric layer adjacent to the top layer, a middle metal layer adjacent to the top piezoelectric layer opposite the top layer, a bottom piezoelectric layer adjacent to the middle layer opposite the top piezoelectric layer, and a bottom electrode layer with a patterned structure and adjacent to the bottom piezoelectric layer opposite the middle layer. The top layer includes a first plurality of electrodes inter-digitated with a second plurality of electrodes. A first one of the electrodes in the top layer and a first one of the electrodes in the bottom layer are coupled to a first contact, and a second one of the electrodes in the top layer and a second one of the electrodes in the bottom layer are coupled to a second contact.

  11. Evaluation of (50)Cr, (52)Cr, (53)Cr, (54)Cr Neutron Cross Section Data for Energies up to 200 MeV

    SciTech Connect

    Pereslavtsev, P; Konobeyev, A; Fischer, U; Leal, Luiz C

    2011-01-01

    This work is on the evaluation of high energy general purpose neutron cross section data for the stable isotopes (50)Cr, (52)Cr, (53)Cr and (54)Cr. The GNASH and TALYS codes were applied for the nuclear reaction calculations that involve neutrons, protons, deuterons, tritons, hellions, alphas and photons in the energy range from 1 keV up to 200 MeV. The main focus of this work was on the quality of the evaluated data and their representation in ENDF files prepared in accordance with ENDF-6 format rules. Global optical model potentials were used for all particles in the calculations. The Geometry-Dependent Hybrid preequilibrium model (GDH) was included in TALYS for a better description of the complex particle emissions. The best fit of the experimental data was achieved by adjusting the nuclear model parameters. The data files include also newly evaluated resonance parameters and their covariances. Covariance data for all reaction channels were evaluated by the Unified Monte Carlo Approach. The new structure of the evaluated data files is discussed.

  12. Editing ISBD(CR): Approach, Scope, Definitions.

    ERIC Educational Resources Information Center

    Swanson, Edward

    This paper presents the background of the development of the International Standard Bibliographic Description for Serials and Other Continuing Resources, or ISBD(CR). Discussion includes: formation of a working group in 1997 to look at the existing ISBD and objectives of the project; the first official meeting of the working group in August 1998…

  13. Effect of Cr/C Ratio on Microstructure and Corrosion Performance of Cr3C2-NiCr Composite Fabricated by Laser Processing

    NASA Astrophysics Data System (ADS)

    Lou, Deyuan; Liu, Dun; He, Chunlin; Bennett, Peter; Chen, Lie; Yang, Qibiao; Fearon, Eamonn; Dearden, Geoff

    2016-01-01

    The present study focuses on the effect of different Cr/C ratios on the microstructure, microhardness, and corrosion resistance of Ni-based laser clad hardfacings, reinforced by in situ synthesized chromium carbide particles. Cr3C2-NiCr composites have been laser processed with graphite/Cr/Ni powder blends with varying Cr/C ratios. Following phase analysis (x-ray diffraction) and microstructure investigation (scanning electron microscopy; energy dispersive x-ray analysis; transmission electron microscopy), the solidification of laser melt pool is discussed, and the corrosion resistances are examined. Several different zones (planar, dendritic, eutectic and re-melt zone) were formed in these samples, and the thicknesses and shapes of these zones vary with the change of Cr/C ratio. The sizes and types of carbides and the content of reserved graphite in the composites change as the Cr/C ratio varies. With the content of carbides (especially Cr3C2) grows, the microhardness is improved. The corrosive resistance of the composites to 0.2M H2SO4 aqueous solution decreases as the Cr/C ratio reduces owing to not only the decreasing Cr content in the NiCr matrix but also the galvanic corrosion formed within the carbide and graphite containing Ni matrix.

  14. Spatially resolved quantitative magnetic order measurement in spinel CuCr{sub 2}S{sub 4} nanocrystals

    SciTech Connect

    Negi, D. S.; Loukya, B.; Datta, R.; Ramasamy, K.; Gupta, A.

    2015-05-04

    We have utilized spatially resolved high resolution electron energy loss spectroscopy to quantify the relative percentage of ferromagnetic order in the core and the surface regions of CuCr{sub 2}S{sub 4} nanoparticles with nanocube and nanocluster morphology. The organic capping layer is found to play a significant role in restoring magnetic order at the surface. The technique is based on recording the fine features of the Cr L{sub 3} absorption edge and matching them with the theoretical spectra. The nanoscale probing technique we have developed is quite versatile and can be extended to understand magnetic ordering in a number of nanodimensional magnetic materials.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  16. Effect of different alloyed layers on the high temperature oxidation behavior of newly developed Ti 2AlNb-based alloys

    NASA Astrophysics Data System (ADS)

    Wu, Hongyan; Zhang, Pingze; Zhao, Haofeng; Wang, Ling; Xie, Aigen

    2011-01-01

    The application of titanium aluminide orthorhombic alloys (O-phase alloys) as potential materials in aircraft and jet engines was limited by their poor oxidation resistance at high temperature. The Ti 2AlNb-based alloys were chromised (Cr), chromium-tungstened (Cr-W) and nickel-chromised (Ni-Cr) by the double glow plasma surface alloying process to improve their high temperature oxidation resistance. The discontinuous oxidative behavior of Cr, Cr-W and Ni-Cr alloyed layers on Ti 2AlNb-based alloy at 1093 K was explored in this study. After exposing at 1093 K, the TiO 2 layer was formed on the bare alloy and accompanied by the occurrence of crack, which promoted oxidation rate. The oxidation behavior of Ti 2AlNb-based alloys was improved by surface alloying due to the formation of protective Al 2O 3 scale or continuous and dense NiCr 2O 4 film. The Ni-Cr alloyed layer presented the best high-temperature oxidation resistance among three alloyed layers.

  17. Fast neutron detection with coincidence counting of recoil tracks in CR-39

    NASA Astrophysics Data System (ADS)

    Lengar, I.; Skvarč, J.; Ilić, R.

    2002-06-01

    Unpredictable background is often the major drawback in the assessment of low fluences of fast neutrons with solid state nuclear track detectors. The problem can be effectively solved by counting coincidence tracks in two detector foils that are in close contact during the irradiation. The detection of fast neutrons performed with a pair of CR-39 detector foils, subsequent chemical etching and evaluation of the etched tracks by an automatic track counting system was studied. After counting, only tracks produced by the same recoil nuclei in the surface layers of both detector foils were taken into account. In this way, the background due to objects that cannot be separated from tracks by an automatic counting system was drastically reduced. Emphasis was given to determining the properties of such a coincidence fast neutron detector based on utilisation of CR-39. The response of the coincidence detector was found to be 3×10 -5 tracks/neutron and is comparable with a detector based on counting tracks in a single foil of CR-39. The lower neutron detection limit was found to be 2×10 4 cm -2 with a counting area of 10 cm 2, and is two orders of magnitude lower than that obtained with a detector based on counting tracks in a single foil of CR-39.

  18. Photoelectric converters on Cr/x/Te/y/-Zn/x/Cd/1-x/S heterojunction

    NASA Astrophysics Data System (ADS)

    Konstantinova, E. M.; Stratieva, N. R.

    The layer properties of Zn(x)Cd(1-x)S(x) are are investigated, and the use of these materials in heterojunction photocells and convertors is evaluated. Results show that the calculated lattice mismatch of the semiconductor decreases with an increase of the Zn content in the solid solutions. A Cr(x)Te(y)-Zn(x)Cd(1-x)S heterojunction is fabricated and is found to have an increase in efficiency of 1% when the open-circuit voltage is raised by about 150 mV and the other parameters are held constant. The open-circuit voltage for photocells based on Cr(x)Te(y) and Zn(x)Cd(1-x)S, with x = 0.05-0.3, is measured under 80 mW/sq cm illumination, and is shown to be lower than the open circuit voltages for Cr(x)Te(y)-Zn(x) Cd(1-x)S samples. In addition, the I-V characteristics of the samples are determined. It is concluded that the wide spectral sensitivity, the high open-circuit voltage, as well as satisfactory conversion efficiencies, of solar cells based on Cr(x)Te(y)-Zn(x)Cd(1-x)S will allow the development of solar energy convertors with improved parameters.

  19. Fingerprints of surface magnetism in Cr2O3 based exchange bias heterostructures

    NASA Astrophysics Data System (ADS)

    He, Xi; Wang, Yi; Binek, Ch.

    2009-03-01

    Magnetoelectric materials experienced a recent revival as promising components of novel spintronic devices [1, 2, 3]. Since the magnetoelectric (ME) effect is relativistically small in traditional antiferromagnetic (AF) compounds like Cr2O3 (max. αzz 4ps/m) and also cross-coupling between ferroic order parameters is typically small in the modern multiferroics, it is a challenge to electrically induce sufficient magnetization required for the envisioned device applications. In exchange bias systems the bias field depends critically on the AF interface magnetization. Hence, a strong relation between the latter and the surface magnetization of the free Cr2O3 pinning layer can be expected. Our recent research indicates that there are surface magnetic phase transitions in free Cr2O3 (111) films accompanying surface structural phase transitions. Well defined AF interface magnetization is initialized through ME annealing to T=20K. Subsequently, the interface magnetization is thermally driven through phase transitions at T=120 and 210K. Their effects on the exchange bias are studied in Cr2O3 (111)/CoPt films with the help of polar Kerr and SQUID magnetometry. [1] P. Borisov et al. Phys. Rev. Lett. 94, 117203 (2005). [2] Ch. Binek, B.Doudin, J. Phys. Condens. Matter 17, L39 (2005). [3] R. Ramesh et al. 2007 Nature Materials 6 21. Financial support by NSF through Career DMR-0547887, MRSEC DMR-0820521 and the NRI.

  20. Independent safety evaluation of the CR562 (CR6) control rod test

    SciTech Connect

    Van Keuren, J.C.

    1988-10-01

    This report documents the Independent Safety Evaluation performed for the CR562 control rod. CR562 is a reference Series II control rod which has been designated as an experiment (CR-6) since post- irradiation examination has been planned as part of the surveillance program for FFTF control rods. Prior analysis as an experiment has not been required since the test operated within the Technical Specification Limits up to this time. The control rod will be operated beyond the Technical Specification fluence limit during the last 30 days of Cycle 10B. A TDD-1A has been written to support this extension, and this ISE documents the independent review. A similar procedure was used for the CR544 control rod. 9 refs.

  1. Electrochemical Atomic Layer Processing

    DTIC Science & Technology

    1994-06-25

    where an atomic layer of an element is deposited , or removed, in a surface limited reaction. The potentials used are referred to as underpotentials in...the electrochemical literature. The atomic layer deposition process is referred to as underpotential deposition (UPD). 14. SUBJECT TERMS 15, NUMBER OF...reaction. The potentials used are referred to as underpotentials in the electrochemical literature. The atomic layer deposition process is referred to as

  2. Furnace brazing type 304 stainless steel to vanadium alloy (V?5Cr?5Ti)

    NASA Astrophysics Data System (ADS)

    Steward, R. V.; Grossbeck, M. L.; Chin, B. A.; Aglan, H. A.; Gan, Y.

    2000-12-01

    In this investigation, pure copper was joined to type 304 stainless steel and V-5Cr-5Ti by brazing in a high vacuum furnace. Microstructural changes in the brazed region and surrounding substrates were examined as a function of holding time at temperatures of 20°C, 40°C and 60°C above the melting point of copper. Reaction layers, which were extremely brittle, formed between the Cu and V-5Cr-5Ti substrates. The formation of intermetallic phases at the filler metal/substrate interfaces was evaluated. Additionally, precipitates (FeCu 2 and FeCu 18) formed in the Cu rich filler region. For temperatures ⩾60°C above the melting point of Cu, extensive transverse cracking was observed. Hardness tests substantiated the hypothesis that the Cu/V-5Cr-5Ti reaction layer was extremely brittle, since micro-cracks propagated from the tips of the diamond-shaped indentations. Results of mechanical properties tests of the brazed material are also presented.

  3. Diffusional transport during the cyclic oxidation of. gamma. +. beta. , Ni-Cr-Al(Y, Zr) alloys

    SciTech Connect

    Nesbitt, J.A.; Heckel, R.W. )

    1988-02-01

    The cyclic oxidation behavior of several cast {gamma} + {beta}, Ni-Cr-Al(Y, Zr) alloys and one LPPS {gamma} + {beta}, Ni-Co-Cr-Al(Y) alloy was examined ({gamma}, fcc; {beta}, NiAl structure). Cyclic oxidation was performed by cycling between 1200{degree}C and approximately 70{degree}C. Oxide morphologies and microstructural changes during cyclic oxidation were noted. Recession of the high-Al {beta} phase was nonparabolic with time. Kirkendall porosity resulting from diffusional transport within the alloy was observed in the near-surface {gamma}-phase layer of one alloy. Concentration profiles for Ni, Cr, and Al were measured in the {gamma}-phase layer after various cyclic oxidation exposures. It was observed that cyclic oxidation results in a decreasing Al concentration at the oxide-metal interface due to a high demand for Al (a high rate of Al consumption) associated with oxide scale cracking and spalling. In addition, diffusion paths plotted on the ternary phase diagram shifted to higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption, and highest Al content, underwent breakway oxidation after 500 1-hr cycles at 1200{degree}C. Breakaway oxidation occurred when the Al concentration at the oxide-metal interface approached zero. The relationship between the Al transport in the alloy and breakaway oxidation is discussed.

  4. Initial Characterization of V-4Cr-4Ti and MHD Coatings Exposed to Flowing Li

    SciTech Connect

    Pint, Bruce A; Pawel, Steven J; Howell, Michael; Moser, Jeremy L; Garner, George Walter; Santella, Michael L; Tortorelli, Peter F; Wiffen, Frederick W; Distefano, James R

    2009-01-01

    Conduct an experiment with flowing Li in a thermal gradient to determine the compatibility of V-4Cr-4Ti and a multi-layer electrically-insulating coating needed to reduce the magneto hydrodynamic (MHD) force in the first wall of a lithium cooled blanket. A mono-metallic V-4Cr-4Ti thermal convection loop was operated in vacuum ({approx}10{sup -5}Pa) at a maximum Li temperature of 700 C for 2,355h and Li flow rate of 2-3 cm/s. Two-layer, physical vapor deposited Y{sub 2}O{sub 3}-vanadium, electrically-insulating coatings on V-4Cr-4Ti substrates as well as uncoated tensile and sheet specimens were located in the flow path in the hot and cold legs. After exposure, specimens at the top of the hot leg showed a maximum mass loss equivalent to {approx}1.3 {micro}m of uniform metal loss. Elsewhere, small mass gains were observed on the majority of specimens that also showed an increase in hardness and room temperature yield stress and a decrease in ductility consistent with interstitial uptake. Specimens that lost mass showed a decrease in yield stress and hardness. Profilometry showed no significant thickness loss from the coatings.

  5. Strain induced ferromagnetism in epitaxial Cr{sub 2}O{sub 3} thin films integrated on Si(001)

    SciTech Connect

    Punugupati, Sandhyarani Narayan, Jagdish; Hunte, Frank

    2014-09-29

    We report on the epitaxial growth and magnetic properties of antiferromagnetic and magnetoelectric (ME) Cr{sub 2}O{sub 3} thin films deposited on cubic yttria stabilized zirconia (c-YSZ)/Si(001) using pulsed laser deposition. The X-ray diffraction (2ϴ and Φ) and TEM characterizations confirm that the films were grown epitaxially. The Cr{sub 2}O{sub 3}(0001) growth on YSZ(001) occurs with twin domains. There are four domains of Cr{sub 2}O{sub 3} with in-plane rotation of 30° or 150° from each other about the [0001] growth direction. The epitaxial relation between the layers is given as [001]Si ‖ [001]YSZ ‖ [0001]Cr{sub 2}O{sub 3} and [100]Si ǁ [100]YSZ ǁ [101{sup ¯}0] Cr{sub 2}O{sub 3} or [112{sup ¯}0] Cr{sub 2}O{sub 3}. Though the bulk Cr{sub 2}O{sub 3} is an antiferromagnetic with T{sub N} = 307 K, we found that the films exhibit ferromagnetic like hysteresis loops with high saturation and finite coercive field up to 400 K. The thickness dependent magnetizations together with oxygen annealing results suggest that the ferromagnetism (FM) is due to oxygen related defects whose concentration is controlled by strain present in the films. This FM, in addition to the intrinsic magneto-electric properties of Cr{sub 2}O{sub 3}, opens the door to relevant spintronics applications.

  6. A Study of NbCr and NbCr^{-} by Anion Photoelectron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Baudhuin, Melissa A.; Boopalachandran, Praveenkumar; Rajan, Srijay S.; Leopold, Doreen G.

    2013-06-01

    We report the 488 nm photoelectron spectrum of the NbCr^{-} anion. For the ^{2}Δ ground state of neutral NbCr, the short bond length (1.894 Å) and high bond energy (D_0 3.0263(6) eV) measured by R2PI spectroscopy indicate high order multiple bonding. We find that the NbCr^{-} anion has a ^{1}Σ^{+} ground state, in which the "extra" electron occupies the (4d)δ bonding orbital, giving a 1σ^{2}1π^{4}1δ^{4}2σ^{2} valence electron configuration and a formal bond order of 6. Low-lying excited states of NbCr (assigned as two ^{2}Σ^{+} states) and NbCr^{-} (^{3}Δ) are also observed. The spectra provide the electron affinity of NbCr, energies of the ^{2}Σ^{+} and the ^{3}Δ excited states, vibrational frequencies for the NbCr and NbCr^{-} ground states and for the ^{2}Σ^{+} excited states, and (from Franck-Condon analyses) differences among the bond lengths of the observed states. These results are compared with our previous data for the Group 5/6 congeners NbMo, VCr, and VMo, and with DFT predictions. We also report results for ongoing experiments on the flow tube reactions of the Group V metals Nb and Ta with butadiene, and the vibrationally-resolved photoelectron spectra of some of the organometallic reaction product anions. S. M. Sickafoose, J. D. Langenberg, and M. D. Morse, J. Phys. Chem. A. 104, 3521-3527 (2000).

  7. Layered plasma polymer composite membranes

    DOEpatents

    Babcock, W.C.

    1994-10-11

    Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is [>=]2 and is the number of selective layers. 2 figs.

  8. Observation of the bulk spin-flop in an Fe/Cr superlattice

    NASA Astrophysics Data System (ADS)

    Bottyán, L.; Deák, L.; Dekoster, J.; Kunnen, E.; Langouche, G.; Meersschaut, J.; Major, M.; Nagy, D. L.; Rüter, H. D.; Szilágyi, E.; Temst, K.

    2002-02-01

    The layer magnetisation reorientation transition (spin-flop, SF) was studied in an artificial layer antiferromagnet (AF), namely in MgO(0 0 1)/[ 57Fe(2.6 nm)/Cr(1.3 nm)] 20 epitaxial superlattice (SL) by synchrotron Mössbauer reflectometry and Kerr effect (SMOKE). The SF occurs simultaneously in the entire SL stack (bulk SF) in an increasing field of HSF=13 mT along the easy direction parallel to the layer magnetisations. It is recognised by the kink in the SMOKE loop and by the sharp up-rise of the AF Bragg peak in the delayed Mössbauer reflectivity. The moderate value of observed HSF is compared with estimations from a spin-chain model and interpreted as due to intraplane domain-wall motion during SF.

  9. Single-crystal growth and properties of CrB, Cr 3B 4, Cr 2B 3 and CrB 2 from high-temperature aluminum solutions

    NASA Astrophysics Data System (ADS)

    Okada, Shigeru; Kudou, Kunio; Iizumi, Kiyokata; Kudaka, Katsuya; Higashi, Iwami; Lundström, Torsten

    1996-09-01

    Single crystals of CrB, Cr 3B 4, Cr 2B 3, and CrB 2 were grown from high-temperature Al solutions. The crystals were examined by X-ray diffraction and chemical analysis. The CrB, Cr 3B 4, and Cr 2B 3 single crystals were obtained as columnar and thick-platelet crystals having well-developed (010) and (100) faces with maximum dimensions of 3 to 8 mm. CrB 2 single crystals 4-8 mm in size were obtained as thick platelets having well-developed (0001) planes or as needles elongated in the <0001> direction. The Vickers microhardness and electrical resistivity of the crystals were measured, and oxidation at high temperature in air was studied.

  10. Oxygen Isotopes and Geothermometry of Secondary Minerals in CR Chondrites

    NASA Astrophysics Data System (ADS)

    Jilly, C. E.; Huss, G. R.; Nagashima, K.; Schrader, D. L.

    2014-09-01

    We report oxygen isotopes measured from secondary calcite and magnetite in QUE 99177, a weakly altered CR chondrite, and discuss implications for temperature and fluid chemistry during aqueous alteration on the CR parent body.

  11. Adsorption studies of Cr(III) and Cr(VI) on lead sulphide, copper sulphide and zinc sulphide - determination Cr(III) in the presence of Cr(VI)

    SciTech Connect

    Sarwar, M.; Masood, M.K.; Farooq, S. )

    1990-01-01

    The adsorption studies of Cr(VI) in presence of Cr(III) on the sulphide of Lead, Zinc and Copper has been studied. It has been found that in case of lead sulphide 100% adsorption of Cr(VI) took place at pH 4.0 and of Cr(III) at pH 7.0. While in case of zinc sulphide and 100% adsorption of Cr(VI) took place at pH 4.5 and of Cr(III) at pH 6.5. In case of copper sulphide 100% adsorption of Cr(VI) took place at pH 5.0 and of Cr(III) at pH 7.0. This difference in adsorption at different pH values forms the basis for the determination of these ions. The method is accurate.

  12. Distribution of C Cr associates and mechanical stability of Cr martensitic steels

    NASA Astrophysics Data System (ADS)

    Gondi, P.; Montanari, R.; Tata, M. E.

    1998-10-01

    Structural and mechanical stability of two martensitic steels with different Cr content (MANET and modified F82H) has been studied by means of internal friction (IF) and dynamic modulus ( Md) measurements, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) observations with EDS microanalysis and mechanical tests (hardness, Charpy). Following thermal treatments at 700°C, MANET samples cooled from the austenitic field at a rate of 150°C/min, exhibit Cr segregation both inside the grains and in the zones near grain boundaries. The Cr segregation induces internal stresses, which influence the mechanical properties, in particular the fracture mode, ductile-brittle transition temperature (DBTT) and upper shelf energy (USE). The material is not stable: DBTT changes depending on the time of the treatment and after 20 h at 700°C a mixed fracture mode (quasi-cleavage plus intercrystalline) is observed. Cr segregation is very weak in modified F82H steel submitted to the same treatments and a greater mechanical stability has been observed. The different behaviour of MANET and modified F82H is discussed on the basis of IF and Md results, which show that the stability of the distribution of C-Cr associates in as-quenched materials is a factor of great importance to avoid the Cr segregation.

  13. Impact behavior of 9-Cr and 12-Cr ferritic steels after low-temperature irradiation

    SciTech Connect

    Klueh, R.L.; Vitek, J.M.; Corwin, W.R.; Alexander, D.J.

    1987-01-01

    Miniature Charpy impact specimens of 9Cr-1MoVNb and 12Cr-1MoVW steels and these steels with 1 and 2% Ni were irradiated in the High-Flux Isotope Reactor (HFIR) at 50/sup 0/C to displacement damage levels of up to 9 dpa. Nickel was added to study the effect of transmutation helium. Irradiation caused an increase in the ductile-brittle transition temperature (DBTT). The 9Cr-1MoVNb steels, with and without nickel, showed a larger shift than the 12Cr-1MoVW steels, with and without nickel. The results indicated that helium also increased the DBTT. The same steels were previously irradiated at higher temperatures. From the present and past tests, the effect of irradiation temperature on the DBTT behavior can be evaluated. For the 9Cr-1MoVNb steel, there is a continuous decrease in the magnitude of the DBTT increase up to an irradiation temperature of about 400/sup 0/C, after which the shift drops rapidly to zero at about 450/sup 0/C. The DBTT of the 12Cr-1MoVW steel shows a maximum increase at an irradiation temperature of about 400/sup 0/C and less of an increase at either higher or lower irradiation temperatures.

  14. Biosorption and bioreduction of Cr(VI) by locally isolated Cr-resistant bacteria.

    PubMed

    Zakaria, Z A; Aruleswaran, N; Kaur, S; Ahmad, W A

    2007-01-01

    Cr(VI) biosorption and bioreduction ability of locally isolated Cr-resistant bacteria was investigated using the shake-flask technique. A mixture of S. epidermidis and B. cereus showed the highest minimum inhibitory concentration (MIC) level at 750 mg/L Cr(VI) followed by S. aureus and Bacillus sp. of 250 mg/L, and A. haemolyticus of 70 mg/L. From the Langmuir adsorption isotherm, the treatment of cells with heat-acid resulted in the highest amount of Cr(VI) adsorped (78.25 mg/g dry wt. for S. epidermidis) compared to heat-acetone (67.93 mg/g dry wt. Bacillus sp.), heat only (36.05 mg/g dry wt. S. epidermidis) or untreated cells (45.40 mg/g dry wt. S. epidermidis and B. cereus). FTIR analysis showed the involvement of amine groups in Cr(VI) adsorption. In the bioreduction study, A. haemolyticus was able to completely reduce Cr(VI) up to 50 mg/L.

  15. Studies with nonradioisotopic sodium chromate. II. Single- and double-label sup 52 Cr/ sup 51 Cr posttransfusion recovery estimations

    SciTech Connect

    Heaton, W.A.; Keegan, T.; Hanbury, C.M.; Holme, S.; Pleban, P. )

    1989-10-01

    A recently developed nonradioisotopic 52Cr technique was used to measure either red cell volume or posttransfusion recovery of stored red cells. The experimental method uses Zeeman electrothermal atomic absorption spectrophotometry to measure red cell chromium. Results from the 52Cr method were compared with those from 51Cr single-label and 125I-albumin/51Cr double-label procedures using 49-day AS-1 red cell concentrates drawn and prepared according to standard procedures. In the first group of five donors, red cell volume was estimated concurrently with both 52Cr-labeled fresh red cells and 125I-albumin. The latter measured plasma volume from which red cell volume was estimated on the basis of the hematocrit (125I red cell volume). 51Cr-labeled stored red cells were transfused to measure posttransfusion recoveries. The correlation between 52Cr and 125I red cell volumes was significant (r = 0.68, p less than 0.01), and, in this group, the differences were not significant (p less than 0.05). Twenty-four-hour posttransfusion recoveries of 51Cr-labeled stored red cells averaged 66 +/- 5 percent when measured with the 125I/51Cr technique and 69 +/- 8 percent when measured with the 52Cr/51Cr method. In the second group of five donors, red cell volume was estimated by the 125I-albumin technique, and the posttransfusion recovery of stored red cells was quantitated by 51Cr- and 52Cr-labeled stored cells simultaneously. In this group, posttransfusion recoveries with 125I/51Cr averaged 73 +/- 7 percent; with 125I/52Cr, they averaged 75 +/- 10 percent. Using the single-label method of calculation, recoveries averaged 76 +/- 7 and 75 +/- 10 percent for the 51Cr and 52Cr methods, respectively.

  16. Toxic effects of Cr(VI) and Cr(III) on energy metabolism of heterotrophic Euglena gracilis.

    PubMed

    Jasso-Chávez, Ricardo; Pacheco-Rosales, Angélica; Lira-Silva, Elizabeth; Gallardo-Pérez, Juan Carlos; García, Noemí; Moreno-Sánchez, Rafael

    2010-11-15

    To assess the toxic effect of Cr on energy metabolism, heterotrophic Euglena gracilis was grown in a medium that prompts high yield biomass and in the presence of different Cr(VI) or Cr(III) concentrations. The cell growth IC₅₀ value was 12 and >250μM for Cr(VI) and Cr(III), respectively; in these cells chromium was accumulated and a fraction compartmentalized into mitochondria, and synthesis of cysteine and glutathione was induced. Respiration of control isolated mitochondria was strongly inhibited by added Cr(VI) or Cr(III) with L-lactate or succinate as substrates. In turn, cellular and mitochondrial respiration, respiratory Complexes I, III and IV, glycolysis and cytosolic NAD(+)-alcohol and -lactate dehydrogenases from cells cultured with Cr(VI) were significantly lower than control, whereas AOX and external NADH dehydrogenase activities were unaltered or increased, respectively. Addition of Cr(VI) or Cr(III) to isolated mitochondria or cytosol from control- or Cr(VI)-grown cells induced inhibition of respiration, respiratory Complexes III, IV and AOX, and glycolytic pyruvate kinase; whereas Complex I, external NADH dehydrogenase, and other glycolytic enzymes were unaffected. Protein contents of mitochondrial Complexes I, III, IV and V, and ANT were diminished in Cr(VI)-grown cells. Decreased respiration and glycolysis induced by Cr(VI) resulted in lower cellular ATP content. Results suggested that Cr(VI) cytotoxicity altered gene expression (as widely documented) and hence enzyme content, and induced oxidative stress, but it was also related with direct enzyme inhibition; Cr(III) was also cytotoxic although at higher concentrations. These findings establish new paradigms for chromium toxicity: Cr(VI) direct enzyme inhibition and non-innocuous external Cr(III) toxicity.

  17. Deletion of the Complement Phagocytic Receptors CR3 and CR4 Does Not Alter Susceptibility to Experimental Cerebral Malaria

    PubMed Central

    Ramos, T.N.; Bullard, Dan C.; Barnum, S.R.

    2015-01-01

    Summary Complement receptors for C3-derived fragments (CR1-4) play critical roles in innate and adaptive immune responses. Of these receptors, CR3 and CR4 are important in binding and phagocytosis of complement-opsonized pathogens including parasites. The role of CR3 and CR4 in malaria or in cerebral malaria has received little attention and remains poorly understood in both human disease and rodent models of malaria. CR3 and CR4 are members of the β2-integrin family of adhesion molecules and are expressed on all leukocytes that participate in the development of cerebral malaria (CM), most importantly as it relates to parasite phagocytosis (monocytes/macrophages) and antigen processing and presentation (dendritic cells). Thus it is possible that these receptors might play an important role in disease development. To address this question, we examined the role of CR3-/- and CR4-/- mice in experimental cerebral malaria (ECM). We found that both CR3-/- and CR4-/- mice were fully susceptible to ECM and developed disease comparable to wild type mice. Our results indicate that CR3 and CR4 are not critical to the pathogenesis of ECM despite their role in elimination of complement-opsonized pathogens. These findings support recent studies indicating the importance of the terminal complement pathway and the membrane attack complex in ECM pathogenesis. PMID:22882618

  18. Deletion of the complement phagocytic receptors CR3 and CR4 does not alter susceptibility to experimental cerebral malaria.

    PubMed

    Ramos, T N; Bullard, D C; Barnum, S R

    2012-11-01

    Complement receptors for C3-derived fragments (CR1-4) play critical roles in innate and adaptive immune responses. Of these receptors, CR3 and CR4 are important in binding and phagocytosis of complement-opsonized pathogens including parasites. The role of CR3 and CR4 in malaria or in cerebral malaria (CM) has received little attention and remains poorly understood in both human disease and rodent models of malaria. CR3 and CR4 are members of the β(2) -integrin family of adhesion molecules and are expressed on all leucocytes that participate in the development of CM, most importantly as it relates to parasite phagocytosis (monocytes/macrophages) and antigen processing and presentation (dendritic cells). Thus, it is possible that these receptors might play an important role in disease development. To address this question, we examined the role of CR3(-/-) and CR4(-/-) in experimental cerebral malaria (ECM). We found that both CR3(-/-) and CR4(-/-) mice were fully susceptible to ECM and developed disease comparable to wild-type mice. Our results indicate that CR3 and CR4 are not critical to the pathogenesis of ECM despite their role in elimination of complement-opsonized pathogens. These findings support recent studies indicating the importance of the terminal complement pathway and the membrane attack complex in ECM pathogenesis.

  19. Reductive activation of Cr(Vi) by nitric oxide synthase.

    PubMed

    Porter, Ryan; Jáchymová, Marie; Martásek, Pavel; Kalyanaraman, B; Vásquez-Vivar, Jeannette

    2005-05-01

    Chromium(VI) is a recognized toxicant whose effects have been linked to its reduction to lower oxidation states. Although Cr(VI) is reduced by several systems, it is anticipated that its reduction by nitric oxide synthase (NOS) could have significant effects in endothelial and brain cells that express high constitutive levels of the enzyme. This possibility was examined by electron paramagnetic resonance that showed the formation of a stable Cr(V) species from NOS/Cr(VI). The formation of Cr(V) was calcium/calmodulin-independent indicating that Cr(VI) to Cr(V) reduction occurs at the flavin-containing domain of NOS. Accordingly, Cr(VI) reduction by the reductase domain of NOS and the chimera protein cytochrome-P450-reductase+tail-nNOS also generated Cr(V). Activation of tetrahydrobiopterin (BH(4))-free NOS with calcium/calmodulin diminished Cr(V) steady-state levels while increasing superoxide formation. Since SOD restored Cr(V) to control levels, this result was taken as evidence for a reaction between Cr(V) and superoxide. Supplementation of NOS with BH(4) cofactor not only failed to increase Cr(V) yields but generated superoxide and hydroxyl radical. Since the holoenzyme does not generate superoxide, this reaction indicated that Cr(V) mediates the oxidation of BH(4)-bound to the enzyme. In the presence of L-arginine, however, Cr(VI) neither enhances superoxide release nor inhibits NO formation from fully active NOS. This suggests that L-arginine protects BH(4) from Cr(V)-mediated oxidation. While Cr(V) was inactive toward NO, spin trapping experiments with 5-tert-butoxycarbonyl 5-methyl-1-pyrroline N-oxide and oxygen consumption measurements showed that Cr(V) reacts with superoxide by a one-electron-transfer mechanism to generate oxygen and Cr(IV). Thus, reduction of Cr(VI) to Cr(V) by NOS occurs in resting and fully active states. It is likely that the reaction between Cr(V) and superoxide influences the cytotoxic mechanisms of Cr(VI) in cells.

  20. Layers and Erosion and more Layers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 4 November 2003

    This image is located within a set of eroded layered rocks known as the Medusae Fossae Formation. Careful inspection of this image reveals four separate layers. Starting at the bottom of the image, as well as the bottom of the sequence of layers, is a somewhat hilly, cratered plain. Above that is a mud or lava flow with a lobate edge that is characteristic of fluid flow. Above that is a layer with a spectacular rayed crater. This layer shows linear erosional patterns that are probably caused by persistent wind abrasion, typical of rocks in this area. And finally, a more blocky unit lies on top, mostly eroded away.

    Image information: VIS instrument. Latitude 3.6, Longitude 218.6 East (141.4 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  1. Dual-phase Cr-Ta alloys for structural applications

    DOEpatents

    Liu, Chain T.; Brady, Michael P.; Zhu, Jiahong; Tortorelli, Peter F.

    2001-01-01

    Dual phase alloys of chromium containing 2 to 11 atomic percent tantalum with minor amounts of Mo, Cr, Ti, Y, La, Cr, Si and Ge are disclosed. These alloys contain two phases including Laves phase and Cr-rich solid solution in either eutectic structures or dispersed Laves phase particles in the Cr-rich solid solution matrix. The alloys have superior mechanical properties at high temperature and good oxidation resistance when heated to above 1000.degree. C. in air.

  2. Microstructure and Sliding Wear Performance of Cr7C3-(Ni,Cr)3(Al,Cr) Coating Deposited from Cr7C3 In Situ Formed Atomized Powder

    NASA Astrophysics Data System (ADS)

    Zhu, Hong-Bin; Shen, Jie; Gao, Feng; Yu, Yueguang; Li, Changhai

    2017-01-01

    This work is aimed at developing a new type of Cr7C3-(Ni,Cr)3(Al,Cr) coating for parts used in heavy-duty diesel engines. The feedstock, in which the stripe-shaped Cr7C3 was in situ formed, was firstly prepared by vacuum melting and gas atomization and then subjected by high-velocity oxy-fuel spraying to form the coatings. The carbon content, microstructure and phase constitution of the powders, as well as the sprayed coatings, were analyzed by chemical analysis, SEM and XRD. The hardness and sliding wear performance of the sprayed coatings were also tested and compared to a commercial Cr3C2-NiCr coating used on piston rings. The results showed that the content of carbon in feedstock was almost the same as designed, and that the volume content of in situ formed Cr7C3 was increased with carbon and chromium added. The major phases of the powders and sprayed coatings are Cr7C3 and Cr-alloyed Ni3Al. Only a small amount of carbon lost during the spraying process. As Cr7C3 content increased in the coatings, the microhardness at room temperature was firstly increased to about 1000Hv0.3. The microhardness of the coatings stayed almost constant, while the testing temperature was raised up to 700 °C for 0.5 h, which illustrates the potential application of the investigated coatings under high temperature conditions. The coatings containing 70 and 77 vol.% Cr7C3 showed the most promising wear resistance, lower friction coefficient and better tribological compatibility to gray cast iron counterpart than other tested Cr7C3-(Ni,Cr)3(Al,Cr) coatings and the reference Cr3C2-NiCr coating.

  3. Safety and efficacy of a novel Prunus domestica extract (Sitoprin, CR002) on testosterone-induced benign prostatic hyperplasia (BPH) in male Wistar rats.

    PubMed

    Swaroop, Anand; Bagchi, Manashi; Kumar, Pawan; Preuss, Harry G; Bagchi, Debasis

    2015-01-01

    The efficacy of a novel Prunus domestica bark extract (Sitoprin, CR002) was investigated on testosterone propionate (TP)-induced benign prostatic hyperplasia (BPH) in male Wistar rats. BPH was induced by daily subcutaneous administration of TP (3.0 mg/kg) over a period of 15 days (interim sacrifice group) and for an additional 21 days (terminal sacrifice group). We evaluated the dose-dependent efficacy (0, 50, 100 and 200 mg/kg body weight/day) of CR002 and a control group against BPH, and compared with a reference standard Prunus africana extract (CR001). Extensive clinical examinations were carried out on days 1, 7, 14, 21, 28 and 35 of treatment period to determine the onset, duration and severity of clinical signs. Clinical pathology, hematology, biochemistry and histopathology were performed on days 15 and 35, prior to necropsy. Animals were fasted overnight prior to blood collection. Prostate glands and tissues were examined. On day 36, histopathology of ventral prostrate of control rats demonstrates single layer of columnar mucin secreting epithelial cells along with a lumen occupied with eosinophilic secretion. In contrast, CR002 and CR001 groups (100 and 200 mg/kg/day) exhibited no hyperplasia and proliferation of epithelial cells. Prostate histopathology of these treated groups was comparable with control rats. The hyperplasia and hypertrophy of prostrate was reduced to single-layered cell indicating the efficacy of CR002 and CR001. Overall, results demonstrate that CR002 exhibits therapeutic efficacy/activity in TP-induced BPH in rats, which is comparable to CR001.

  4. Recovery of Cr as Cr(III) from Cr(VI)-contaminated kaolinite clay by electrokinetics coupled with a permeable reactive barrier.

    PubMed

    Suzuki, Tasuma; Kawai, Katsunori; Moribe, Mai; Niinae, Masakazu

    2014-08-15

    Zero-valent iron (Fe(0)) and magnetite (Fe3O4) were investigated as potential reductants in an electrokinetic/permeable reactive barrier hybrid system (EK/PRB) for the recovery of Cr as Cr(III) from Cr(VI)-contaminated kaolinite. For the EK/Fe(0) PRB, regardless of the pH in the anode well, the system facilitated the reduction of Cr(VI) into Cr(III), but the recovery of the Cr(III) in the PRB was low. Conversely, the reduction of Cr(VI) occurred only in the PRB for the EK/Fe3O4 PRB. However, when the anode pH was not controlled and the soil pH values correspondingly decreased gradually from the anode side, a greater fraction of Cr(VI) sorbed onto the kaolinite; as a result, a lower amount of Cr(VI) migrated to the Fe3O4 PRB. In addition, it was found that the majority of Cr(VI) migrating to the Fe3O4 PRB retained its oxidation state without being converted into Cr(III). These two adverse effects were mitigated by maintaining the soil pH values at 6.8, but at the same time, 18% of Cr(VI) penetrated through the Fe3O4 PRB. The penetration of Cr(VI) through the Fe3O4 PRB was successfully prevented by increasing the reaction time through the introduction of a cation exchange membrane between the Fe3O4 PRB and the anode well.

  5. On the interdiffusion in multilayered silicide coatings for the vanadium-based alloy V-4Cr-4Ti

    NASA Astrophysics Data System (ADS)

    Chaia, N.; Portebois, L.; Mathieu, S.; David, N.; Vilasi, M.

    2017-02-01

    To provide protection against corrosion at high temperatures, silicide diffusion coatings were developed for the V-4Cr-4Ti alloy, which can be used as the fuel cladding in next-generation sodium-cooled fast breeder reactors. The multilayered coatings were prepared by halide-activated pack cementation using MgF2 as the transport agent and pure silicon (high activity) as the master alloy. Coated pure vanadium and coated V-4Cr-4Ti alloy were studied and compared as substrates. In both cases, the growth of the silicide layers (V3Si, V5Si3, V6Si5 and VSi2) was controlled exclusively by solid-state diffusion, and the growth kinetics followed a parabolic law. Wagner's analysis was adopted to calculate the integrated diffusion coefficients for all silicides. The estimated values of the integrated diffusion coefficients range from approximately 10-9 to 10-13 cm2 s-1. Then, a diffusion-based numerical approach was used to evaluate the growth and consumption of the layers when the coated substrates were exposed at critical temperatures. The estimated lifetimes of the upper VSi2 layer were 400 h and 280 h for pure vanadium and the V-4Cr-4Ti alloy, respectively. The result from the numeric simulation was in good agreement with the layer thicknesses measured after aging the coated samples at 1150 °C under vacuum.

  6. Control of Nd and Cr concentrations in Nd,Cr : Gd 3Ga 5O 12 single crystals grown by Czochralski method

    NASA Astrophysics Data System (ADS)

    Keszei, B.; Paitz, J.; Vandlik, J.; Süveges, A.

    2001-06-01

    During the growth process of the Nd,Cr : Gd 3Ga 5O 12 (Nd,Cr : GGG) laser crystals the optimum concentrations of the dopants cannot be realized in axial direction of the crystal at a constant pulling (growth) rate as the effective segregation coefficients ( k) of Nd 3+ and Cr 3+ are not unity and not uniform ( k<1 and k>1, respectively). To solve this problem the dopant concentrations were measured in the crystals grown at different pulling rates by atomic absorption to determine the effective and equilibrium segregation coefficients and the ratio of the boundary layer thickness and diffusion coefficients. In the light of these parameters we suggest a pulling (growth) rate program as a function of the fraction of the crystallized melt leading to the smallest concentration variation of the dopants along the length axis of the crystals. The variation of Nd 3+ concentration in the crystal reduced from 35% to 19% while the laser efficiency increased by 15-20% by this method.

  7. Evaluation of hardening behaviors in ion-irradiated Fe-9Cr and Fe-20Cr alloys by nanoindentation technique

    NASA Astrophysics Data System (ADS)

    Li, Shilei; Wang, Yanli; Dai, Xianyuan; Liu, Fang; Li, Jinyu; Wang, Xitao

    2016-09-01

    The ion irradiation hardening behaviors of Fe-9 wt% Cr and Fe-20 wt% Cr model alloys were investigated by nanoindentation technique. The specimens were irradiated with 3 MeV Fe11+ ions at room temperature up to 1 and 5 dpa for Fe-9Cr alloy and 1 and 2.5 for Fe-20Cr alloy. The ratio of average hardness in the same depth of irradiated and unirradiated (Hirr. av/Hunirr. av) was used to determine the critical indentation depth hcrit to eliminate the softer substrate effect. The Nix-Gao model was used to explain the indentation size effect. Irradiation hardening is clearly observed in both Fe-9Cr alloy and Fe-20Cr alloy after ion irradiation. The differences of ISE and irradiation hardening behaviors between Fe-9Cr and Fe-20Cr alloys are considered to be due to their different microstructures and microstructural evolution under ion irradiation.

  8. Method of forming a dense, high temperature electronically conductive composite layer on a porous ceramic substrate

    DOEpatents

    Isenberg, Arnold O.

    1992-01-01

    An electrochemical device, containing a solid oxide electrolyte material and an electrically conductive composite layer, has the composite layer attached by: (A) applying a layer of LaCrO.sub.3, YCrO.sub.3 or LaMnO.sub.3 particles (32), on a portion of a porous ceramic substrate (30), (B) heating to sinter bond the particles to the substrate, (C) depositing a dense filler structure (34) between the doped particles (32), (D) shaving off the top of the particles, and (E) applying an electronically conductive layer over the particles (32) as a contact.

  9. Multiple density layered insulator

    DOEpatents

    Alger, Terry W.

    1994-01-01

    A multiple density layered insulator for use with a laser is disclosed wh provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation.

  10. Multiple density layered insulator

    DOEpatents

    Alger, T.W.

    1994-09-06

    A multiple density layered insulator for use with a laser is disclosed which provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation. 4 figs.

  11. The Atmospheric Boundary Layer

    ERIC Educational Resources Information Center

    Tennekes, Hendrik

    1974-01-01

    Discusses some important parameters of the boundary layer and effects of turbulence on the circulation and energy dissipation of the atmosphere. Indicates that boundary-layer research plays an important role in long-term forecasting and the study of air-pollution meteorology. (CC)

  12. The Cr-substitution concentration dependence of the structural, electric and magnetic behaviors for Aurivillius Bi5Ti3FeO15 multiferroic ceramics

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Bai, Wei; Yang, Jing; Xu, Wenfei; Zhang, Yuanyuan; Lin, Tie; Meng, Xiangjian; Duan, Chun-Gang; Tang, Xiaodong; Chu, Junhao

    2013-12-01

    Aurivillius Bi5Ti3FeO15 (BTFO) multiferroic ceramics with different Cr-doped concentrations have been synthesized by the conventional solid state reaction method. The influences of Cr-doping concentrations on the structural, magnetic, dielectric, and ferroelectric properties of BTFO ceramics are investigated in detail. All these sintered Cr-substituted BTFO ceramics are determined to be layered perovskite Aurivillius structure by X-ray diffraction, as well as the lattice parameters a, b, and c are in good accordance with Vegard's law along with the Cr-doping concentration. The lattice distortion a/b for Aurivillius family decreases with increasing Cr-doping concentration. Moreover, Cr-doping can promote greatly the grain growth of BTFO samples confirmed from field emission scanning electron microscopy characterization. However, no obvious signs of the improvement in ferroelectric properties are found in Cr-doped BTFO ceramics, and abnormal ferroelectric polarization versus electric field (P-E) loops are observed as Cr-doping content is beyond 0.1. Similar ɛ (tanδ) versus frequency plots to those of the BTFO sample are exhibited when Cr-doping concentration is less than 0.1. Nevertheless, obvious dielectric dispersion phenomena are shown as the Cr-doping concentration is beyond 0.1, and this dispersion behavior becomes strong with further increasing Cr-doping concentration, which are clearly indicated by the appearance of dielectric loss relaxation peaks in the measurement frequency from 102 Hz to 106 Hz. In addition, the corresponding frequency to relaxation peak shifts towards high frequencies with the Cr-doping concentration. Finally, the same magnetic orderings for all these Cr-doped BTFO ceramics as those of the BTFO one, i.e., superparamagnetic state dominated with antiferromagnetic interaction, are unambiguously found, signifying that the predicted Fe3+-O-Cr3+ 180° ferromagnetic superexchange interaction based on the Goodenough-Kanamori (G-K) rule might

  13. Long range supercurrents in ferromagnetic CrO2 using a multilayer contact structure

    NASA Astrophysics Data System (ADS)

    Anwar, M. S.; Veldhorst, M.; Brinkman, A.; Aarts, J.

    2012-01-01

    We report measurements of long ranged supercurrents through ferromagnetic and fully spin-polarized CrO2 deposited on TiO2 substrates. In earlier work, we found supercurrents in films grown on sapphire but not on TiO2. Here, we employed a special contact arrangement, consisting of a Ni/Cu sandwich between the film and the superconducting amorphous Mo70Ge30 electrodes. The distance between the contacts was almost a micrometer, and we find the critical current density to be significantly higher than found in the films deposited on sapphire. We argue this is due to spin mixing in the Ni/Cu/CrO2 layer structure, which is helpful in the generation of the odd-frequency spin triplet correlations needed to carry the supercurrent.

  14. Multiparameter characterization of subnanometre Cr/Sc multilayers based on complementary measurements

    PubMed Central

    Haase, Anton; Bajt, Saša; Hönicke, Philipp; Soltwisch, Victor; Scholze, Frank

    2016-01-01

    Cr/Sc multilayer systems can be used as near-normal incidence mirrors for the water window spectral range. It is shown that a detailed characterization of these multilayer systems with 400 bilayers of Cr and Sc, each with individual layer thicknesses <1 nm, is attainable by the combination of several analytical techniques. EUV and X-ray reflectance measurements, resonant EUV reflectance across the Sc L edge, and X-ray standing wave fluorescence measurements were used. The parameters of the multilayer model were determined via a particle-swarm optimizer and validated using a Markov chain Monte Carlo maximum-likelihood approach. For the determination of the interface roughness, diffuse scattering measurements were conducted. PMID:27980515

  15. Age- and light-dependent development of localised retinal atrophy in CCL2(-/-)CX3CR1(GFP/GFP) mice.

    PubMed

    Chen, Mei; Hombrebueno, Jose R; Luo, Chang; Penalva, Rosana; Zhao, Jiawu; Colhoun, Liza; Pandi, Sudha Pirya Soundara; Forrester, John V; Xu, Heping

    2013-01-01

    Previous studies have shown that CCL2/CX3CR1 deficient mice on C57BL/6N background (with rd8 mutation) have an early onset (6 weeks) of spontaneous retinal degeneration. In this study, we generated CCL2(-/-)CX3CR1(GFP/GFP) mice on the C57BL/6J background. Retinal degeneration was not detected in CCL2(-/-)CX3CR1(GFP/GFP) mice younger than 6 months. Patches of whitish/yellowish fundus lesions were observed in 17∼60% of 12-month, and 30∼100% of 18-month CCL2(-/-)CX3CR1(GFP/GFP) mice. Fluorescein angiography revealed no choroidal neovascularisation in these mice. Patches of retinal pigment epithelium (RPE) and photoreceptor damage were detected in 30% and 50% of 12- and 18-month CCL2(-/-)CX3CR1(GFP/GFP) mice respectively, but not in wild-type mice. All CCL2(-/-)CX3CR1(GFP/GFP) mice exposed to extra-light (∼800lux, 6 h/day, 6 months) developed patches of retinal atrophy, and only 20-25% of WT mice which underwent the same light treatment developed atrophic lesions. In addition, synaptophysin expression was detected in the outer nucler layer (ONL) of area related to photoreceptor loss in CCL2(-/-)CX3CR1(GFP/GFP) mice. Markedly increased rhodopsin but reduced cone arrestin expression was observed in retinal outer layers in aged CCL2(-/-)CX3CR1(GFP/GFP) mice. GABA expression was reduced in the inner retina of aged CCL2(-/-)CX3CR1(GFP/GFP) mice. Significantly increased Müller glial and microglial activation was observed in CCL2(-/-)CX3CR1(GFP/GFP) mice compared to age-matched WT mice. Macrophages from CCL2(-/-)CX3CR1(GFP/GFP) mice were less phagocytic, but expressed higher levels of iNOS, IL-1β, IL-12 and TNF-α under hypoxia conditions. Our results suggest that the deletions of CCL2 and CX3CR1 predispose mice to age- and light-mediated retinal damage. The CCL2/CX3CR1 deficient mouse may thus serve as a model for age-related atrophic degeneration of the RPE, including the dry type of macular degeneration, geographic atrophy.

  16. Multiple layer insulation cover

    DOEpatents

    Farrell, James J.; Donohoe, Anthony J.

    1981-11-03

    A multiple layer insulation cover for preventing heat loss in, for example, a greenhouse, is disclosed. The cover is comprised of spaced layers of thin foil covered fabric separated from each other by air spaces. The spacing is accomplished by the inflation of spaced air bladders which are integrally formed in the cover and to which the layers of the cover are secured. The bladders are inflated after the cover has been deployed in its intended use to separate the layers of the foil material. The sizes of the material layers are selected to compensate for sagging across the width of the cover so that the desired spacing is uniformly maintained when the cover has been deployed. The bladders are deflated as the cover is stored thereby expediting the storage process and reducing the amount of storage space required.

  17. Cr laser research at AlliedSignal

    SciTech Connect

    Shand, M.L.

    1994-12-31

    The Applied Physics Laboratory of AlliedSignal, Inc. has been developing Cr lasers and applications for a number of years. This operation has resulted in new laser designs and in improved engineering and packaging which are critical to acceptable performance in the field. Although most of the work has been part of military programs, AlliedSignal, with partners, has recently been offering its lasers to commercial programs as a supplier to the OEM market. This paper will present several laser systems which have recently been developed at AlliedSignal. These systems will include those based on alexandrite and Cr:LiSAF. The examples chosen will show the versatility of these laser materials.

  18. All-3 d Electron-Hole Bilayers in CrN /MgO (111 ) Multilayers for Thermoelectric Applications

    NASA Astrophysics Data System (ADS)

    Botana, Antia S.; Pardo, Victor; Pickett, Warren E.

    2017-02-01

    CrN /MgO (111 ) multilayers modeled via ab initio calculations give rise to nanoscale, scalable, spatially separated two-dimensional electron and hole gases, each confined to its own CrN interface. Because of the Cr 3 d3 configuration, both electron and hole gases are based on correlated transition-metal layers involving bands of 3 d character. Transport calculations predict each subsystem will have a large thermopower, on the order of 250 μ V /K at room temperature. These heterostructures combine a large thermoelectric efficiency with scalable nanoscale conducting sheets; for example, operating at a temperature difference of 50 K, 40 bilayers could produce a 1-V voltage with a film thickness of 100 nm.

  19. Kinetic Monte Carlo simulation of phase-precipitation versus instability behavior in short period FeCr superlattices

    NASA Astrophysics Data System (ADS)

    Rodríguez-Martínez, F. J.; Castejón-Mochón, J. F.; Castrillo, P.; Berenguer-Vidal, R.; Dopico, I.; Martin-Bragado, I.

    2017-02-01

    The structural evolution of FeCr superlattices has been studied using a quasi-atomistic Object Kinetic Monte Carlo model. Superlattices with different spatial periods have been simulated for anneal durations from few hours to several months at 500 °C. Relatively-long period superlattices stabilize into Fe-rich and Cr-rich layers with compositions close to those of bulk α and α‧ phases. In contrast, superlattices with very short periods (4, 5, 6 nm) are observed to undergo instability and, for long annealing times, evolve into three-dimensionally decomposed regions, in qualitative agreement to recent experimental observations. The instability onset is delayed as the spatial period increases, and it occurs via interface roughness. This evolution can be explained as a minimization of the free-energy associated to the α/α‧ interfaces. A comprehensive description of the evolution dynamics of FeCr-based structures is obtained with our model.

  20. Reversed Crystal-Field Splitting and Spin-Orbital Ordering in α-Sr2CrO4

    NASA Astrophysics Data System (ADS)

    Ishikawa, Takashi; Toriyama, Tatsuya; Konishi, Takehisa; Sakurai, Hiroya; Ohta, Yukinori

    2017-03-01

    The origin of successive phase transitions observed in the layered perovskite α-Sr2CrO4 is studied by the density-functional-theory-based electronic structure calculation and mean-field analysis of the proposed low-energy effective model. We find that, despite the fact that the CrO6 octahedron is elongated along the c-axis of the crystal structure, the crystal-field level of nondegenerate 3dxy orbitals of the Cr ion is lower in energy than that of doubly degenerate 3dyz and 3dxz orbitals, giving rise to the orbital degrees of freedom in the system with a 3d2 electron configuration. We show that the higher (lower) temperature phase transition is caused by the ordering of the orbital (spin) degrees of freedom.

  1. CoCrPt-SiO{sub 2} granular-type longitudinal media on Ru underlayer for sputtered tape applications

    SciTech Connect

    Lee, Hwan-Soo; Zhu Jiangang; Laughlin, David E.

    2008-04-01

    CoCrPt-SiO{sub 2} films for use as thin film tape media have been investigated. Bias sputtering and high Ar pressure were utilized to achieve desirable media properties (good in-plane orientation and enhanced grain decoupling) in these media. The in-plane orientation of the bias sputtered CoCrPt-SiO{sub 2} magnetic layer was well maintained even at a high content of SiO{sub 2} as Ru was used as an underlayer and deposited at high Ar pressure. Films of (10.0) textured CoCrPt-SiO{sub 2} on a Ru underlayer showed a large in-plane coercivity of 4000 Oe and transmission electron microscopy revealed an average grain size of about 10 nm, well decoupled by the oxide. The in-plane coercivity was a strong function of the Ru thickness.

  2. Cr-doped scandium borate laser

    DOEpatents

    Chai, Bruce H.; Lai, Shui T.; Long, Margaret N.

    1989-01-01

    A broadly wavelength-tunable laser is provided which comprises as the laser medium a single crystal of MBO.sub.3 :Cr.sup.3+, where M is selected from the group of Sc, In and Lu. The laser may be operated over a broad temperature range from cryogenic temperatures to elevated temperatures. Emission is in a spectral range from red to infrared, and the laser is useful in the fields of defense, communications, isotope separation, photochemistry, etc.

  3. Resistance switching mode transformation in SrRuO3/Cr-doped SrZrO3/Pt frameworks via a thermally activated Ti out-diffusion process.

    PubMed

    Jo, Yongcheol; Jung, Kyooho; Kim, Jongmin; Woo, Hyeonseok; Han, Jaeseok; Kim, Hyungsang; Hong, Jinpyo; Lee, Jeon-Kook; Im, Hyunsik

    2014-12-08

    This work reports on a mechanism for irreversible resistive switching (RS) transformation from bipolar to unipolar RS behavior in SrRuO3 (SRO)/Cr-doped SrZrO3 (SZO:Cr)/Pt capacitor structures prepared on a Ti/SiO2/Si substrate. Counter-clockwise bipolar RS memory current-voltage (I-V) characteristics are observed within the RS voltage window of -2.5 to +1.9 V, with good endurance and retention properties. As the bias voltage increases further beyond 4 V under a forward bias, a forming process occurs resulting in irreversible RS mode transformation from bipolar to unipolar mode. This switching mode transformation is a direct consequence of thermally activated Ti out-diffusion from a Ti adhesion layer. Transition metal Ti effectively out-diffuses through the loose Pt electrode layer at high substrate temperatures, leading to the unintended formation of a thin titanium oxide (TiO(x) where x < 2) layer between the Pt electrode and the SZO:Cr layer as well as additional Ti atoms in the SZO:Cr layer. Cross-sectional scanning electron microscopy, transmission electron microscopy and Auger electron spectroscopy depth-profile measurements provided apparent evidence of the Ti out-diffusion phenomenon. We propose that the out-diffusion-induced additional Ti atoms in the SZO:Cr layer contributes to the creation of the metallic filamentary channels.

  4. Cr Isotope Response to Ocean Anoxic Event 2

    NASA Astrophysics Data System (ADS)

    Holmden, C. E.; Jacobson, A. D.; Sageman, B. B.; Hurtgen, M.

    2015-12-01

    The element Cr offers a redox sensitive isotopic proxy with potential for tracing past oxygen levels in the oceans. We examine this potential in a marine carbonate section deposited during Cretaceous Ocean Anoxic Event 2 (OAE 2) in the Western Interior Seaway, Colorado. Redox changes are the main source of Cr isotope fractionation in Earth surface environments. Cr(VI), in the form of the chromate oxyanion, is the thermodynamically favoured species in oxygenated seawater. Reduction of Cr(VI) causes light isotopes to partition into Cr(III), which is reactive and susceptible to removal into marine sediment. Therefore, widespread ocean anoxia should correlate with positive shifts in seawater chromate Cr isotope values (δ53Cr), assuming that all Cr input fluxes remained constant during the event. We find instead that inferred seawater δ53Cr values decreased during OAE 2. The minima of the sedimentary δ53Cr excursion coincides with the peak interval of anomalously enriched concentrations of Cr and other trace metals of basaltic affinity attributed to eruption of the Caribbean Large Igneous Province (CLIP). We propose that an anoxic, hydrothermal plume enriched in Cr(III) with low δ53Cr values characteristic of igneous rocks moved from deep waters of the CLIP eruption site in the eastern Pacific into deep waters of the proto-North Atlantic through an oceanic gateway in the Central Americas. Once inside, metal-rich waters upwelled against the surrounding continental margins. CLIP volcanism delivered a submarine weathering flux of Cr to the oceans during OAE 2 that was large enough to mask the expected isotopic response of the ocean Cr cycle to increasing anoxia, particularly in the proto-North Atlantic Ocean.

  5. Nature of bonding in complexes containing "supershort" metal-metal bonds. raman and theoretical study of M2(dmp)4 [M = Cr (natural abundance Cr, 50Cr, and 54Cr) and Mo; dmp = 2,6-dimethoxyphenyl].

    PubMed

    Da Re, Ryan E; Eglin, Judith L; Carlson, Christin N; John, Kevin D; Morris, David E; Woodruff, William H; Bailey, James A; Batista, Enrique; Martin, Richard L; Cotton, F Albert; Hillard, Elizabeth A; Murillo, Carlos A; Sattelberger, Alfred P; Donohoe, Robert J

    2010-02-17

    We report an investigation of complexes of the type M(2)(dmp)(4) (M = Mo, Cr; dmp = 2,6-dimethoxyphenyl) using resonance Raman (RR) spectroscopy, Cr isotopic substitution, and density functional theory (DFT) calculations. Assignment of the Mo-Mo stretching vibration in the Mo(2) species is straightforward, as evidenced by a single resonance-enhanced band at 424 cm(-1), consistent with an essentially unmixed metal-metal stretch, and overtones of this vibration. On the other hand, the Cr(2) congener has no obvious metal-metal stretching mode near 650-700 cm(-1), where empirical predictions based on the Cr-Cr distance as well as DFT calculations suggest that this vibration should appear if unmixed. Instead, three bands are observed at 345, 363, and 387 cm(-1) that (a) have relative RR intensities that are sensitive to the Raman excitation frequency, (b) exhibit overtones and combinations in the RR spectra, and (c) shift in frequency upon isotopic substitution ((50)Cr and (54)Cr). DFT calculations are used to model the vibrational data for the Mo(2) and Cr(2) systems. Both the DFT results and empirical predictions are in good agreement with experimental observations in the Mo(2) complex, but both, while mutually consistent, differ radically from experiment in the Cr(2) complex. Our experimental and theoretical results, especially the Cr isotope shifts, clearly demonstrate that the potential energy of the Cr-Cr stretching coordinate is distributed among several normal modes having both Cr-Cr and Cr-ligand character. The general significance of these results in interpreting spectroscopic observations in terms of the nature of metal-metal multiple bonding is discussed.

  6. Approaches for quantifying energy intake and % calorie restriction (CR) during CR interventions in humans: the multicenter CALERIE study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calorie restriction (CR) is a component of most weight-loss interventions and a potential strategy to slow aging. Accurate determination of energy intake and %CR is critical when interpreting the results of CR interventions; this is best achieved using the doubly labeled water method to quantify tot...

  7. Laser powder coating by multi-thin-layer technics

    NASA Astrophysics Data System (ADS)

    Sepold, Gerd; Becker, Reinhard

    1990-10-01

    The laser beam is an interesting tool for production of thin surface layers. The energy input is locally limited thus leading to a snall heat loading of the substrate. The geometric dinensions of the coatings are small as compared to conventional thermal technics like surface melting and coating. In the following the multithin-layer technique is introduced. By this process coatings of small dimensions could be produced. Due to high processing speeds high cooling rates up to lO K/s are achieved by heat conduction into the substrate. This process results in fine microcrystalline structures of the deposit. Using NiCrBSi as coating material it will be shown how and to which extent different parameters influence structure and geometry of the coating. 2. MULTI-THIN-LAYER TECHNIQUE The multi-pass thin layer technique is in principle a powder feed process. Under an oblique angle a powder is blown by an inert gas stream into the laser beam. On their way to the surface the powder particles are partially heated. The surface itself is melted by the laser beam. So a good adherence is ensured between the molten surface and the impinging melting particles. This process can be repeated several times thus forming a coating by a multithinlayer technique see fig. 2. In principle the powder feed process is a well known " thick coating " process for conventional coatings like turbine blades dyes etc. /1/. In this however very small dimensions are desired which may be used for reasons of wear or corrosion resistance or for conductive or insolating layers in micro technics. In this work we investigated the influence of some processing parameters in order to achieve layers or traces of small geometries. 3. MULTIPLE THIN LAYER COATING OF NiCrBSi NiCrBSi had been used as a coating material to produce thin layers or traces. These alloys are hard and wear resistant materials which are usually applied by conventional powder spraying methods followed by arc- or flame-fusing of the sprayed layer

  8. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    SciTech Connect

    Bates, MK; Jia, QY; Ramaswamy, N; Allen, RJ; Mukerjee, S

    2015-03-12

    We report a Ni-Cr/C electrocatalyst with unpreeedented massactivity for the hydrogen evolution reaction (HER). in alkaline electrolyte. The HER Oietics of numerous binary and ternary Ni-alloys and composite Ni/metal-euride/C samples were evaluated in aquebus 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni-Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to munerous binary dor ternary Ni-alloys, inCluding Ni Mg materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a, sink for the H-ads, intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiO content and that the Cr2O3 appears to stabilize the composite NiO component-under HER conditions (where NiOx would typically be reduced to metallic Ni-0). Furthermore, in contrast to Pt, the Ni(O-x)/Cr2O3 catalyst appears resistant to poisoning by the anion.exchange ionomer (AEI), a serloua consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a: detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI.

  9. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    PubMed Central

    Bates, Michael K.; Jia, Qingying; Ramaswamy, Nagappan; Allen, Robert J.; Mukerjee, Sanjeev

    2015-01-01

    We report a Ni–Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni–Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to numerous binary and ternary Ni-alloys, including Ni–Mo materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a sink for the Hads intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiOx content and that the Cr2O3 appears to stabilize the composite NiOx component under HER conditions (where NiOx would typically be reduced to metallic Ni0). Furthermore, in contrast to Pt, the Ni(Ox)/Cr2O3 catalyst appears resistant to poisoning by the anion exchange ionomer (AEI), a serious consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI. PMID:26191118

  10. Observations of a Cast Cu-Cr-Zr Alloy

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2006-01-01

    Prior work has demonstrated that Cu-Cr-Nb alloys have considerable advantages over the copper alloys currently used in regeneratively cooled rocket engine liners. Observations indicated that Zr and Nb have similar chemical properties and form very similar compounds. Glazov and Zakharov et al. reported the presence of Cr2Zr in Cu-Cr-Zr alloys with up to 3.5 wt% Cr and Zr though Zeng et al. calculated that Cr2Zr could not exist in a ternary Cu-Cr-Zr alloy. A cast Cu-6.15 wt% Cr-5.25 wt% Zr alloy was examined to determine if the microstructure developed would be similar to GRCop-84 (Cu-6.65 wt% Cr-5.85 wt% Nb). It was observed that the Cu-Cr-Zr system did not form any Cr2Zr even after a thermal exposure at 875 C for 176.5 h. Instead the alloy consisted of three phases: Cu, Cu5Zr, and Cr.

  11. The Application of Layer Theory to Design: The Control Layer

    ERIC Educational Resources Information Center

    Gibbons, Andrew S.; Langton, Matthew B.

    2016-01-01

    A theory of design layers proposed by Gibbons ("An Architectural Approach to Instructional Design." Routledge, New York, 2014) asserts that each layer of an instructional design is related to a body of theory closely associated with the concerns of that particular layer. This study focuses on one layer, the control layer, examining…

  12. Magnetic phase transitions in epitaxial Fe/Cr superlattices

    SciTech Connect

    Fullerton, E.E.; Sowers, C.H.; Bader, S.D.; Riggs, K.T.; Berger, A.

    1995-12-31

    The surface spin-flop and Neel transitions are examined in Fe/Cr superlattices. The surface spin-flop, originally predicted by Mills [Phys. Rev. Lett. 20, 18 (1968)], is observed in Fe/Cr(211) superlattices with antiferromagnetic interlayer coupling and uniaxial in-plane-anisotropy. The Neel transition (T{sub N}) of Cr is observed in Fe/Cr(001) superlattices, for which the onset of antiferromagnetism is at a thickness t{sub Cr} of 42{angstrom}. The bulk value of T{sub N} is approached asymptotically as t{sub Cr} increases and is characterized by a three-dimensional shift exponent. These T{sub N} results are attributed to finite-size effects and spin-frustration near rough Fe-Cr interfaces.

  13. Compliant layer chucking surface

    DOEpatents

    Blaedel, Kenneth L.; Spence, Paul A.; Thompson, Samuel L.

    2004-12-28

    A method and apparatus are described wherein a thin layer of complaint material is deposited on the surface of a chuck to mitigate the deformation that an entrapped particle might cause in the part, such as a mask or a wafer, that is clamped to the chuck. The harder particle will embed into the softer layer as the clamping pressure is applied. The material composing the thin layer could be a metal or a polymer for vacuum or electrostatic chucks. It may be deposited in various patterns to affect an interrupted surface, such as that of a "pin" chuck, thereby reducing the probability of entrapping a particle.

  14. Concentric layer ramjet fuel

    SciTech Connect

    Burdette, G.W.; Francis, J.P.

    1988-03-08

    This patent describes a solid fuel ramjet grain comprising concentric layers of solid ramjet fuel having a perforation therethrough along the center axis of the grain. The performation is connected to a combustion after-chamber. The solid ramjet fuel layers comprises a pure hydroxyl-terminated polybutadiene hydrocarbon fuel or a mixture of a hydroxyl-terminated polybutadiene hydrocarbon fuel and from about 5 to about 60 percent by weight of an additive to increase the fuel regression rate selected from the group consisting of magnesium, boron carbide, aluminum, and zirconium such that, when buried in the operation of the ramjet, each fuel layer produces a different level of thrust.

  15. Multi-layer coatings

    DOEpatents

    Maghsoodi, Sina; Brophy, Brenor L.; Abrams, Ze'ev R.; Gonsalves, Peter R.

    2016-06-28

    Disclosed herein are coating materials and methods for applying a top-layer coating that is durable, abrasion resistant, highly transparent, hydrophobic, low-friction, moisture-sealing, anti-soiling, and self-cleaning to an existing conventional high temperature anti-reflective coating. The top coat imparts superior durability performance and new properties to the under-laying conventional high temperature anti-reflective coating without reducing the anti-reflectiveness of the coating. Methods and data for optimizing the relative thickness of the under-layer high temperature anti-reflective coating and the top-layer thickness for optimizing optical performance are also disclosed.

  16. MEANS II: Knowledge Oriented Materials Engineering of Layered Thermal Barrier Systems (NOMELT)

    DTIC Science & Technology

    2008-06-22

    metallic bond coat (BC) interlayer between the superalloy substrate and the thermally insulating ceramic top layer. The primary purpose of the BC layer...overlay coatings . An advantage of overlay coatings is that a specific composition can be placed on the superalloy surface without significant initial...deposited on a 2nd generation single crystal PWA1484 superalloy substrate. The NiCoCrAlY bond coat with nominal composition in Table 1 [19] was

  17. Effect of chromium on the formation of intermetallic phases in hot-dipped aluminide Cr-Mo steels

    NASA Astrophysics Data System (ADS)

    Cheng, Wei-Jen; Wang, Chaur-Jeng

    2013-07-01

    Cr-Mo steels with different chromium contents were coated by hot-dipping into molten baths containing pure aluminum and Al-10 wt.% Si for 180 s. The effect of chromium content in the steels on the formation of the intermetallic phases in the aluminide coatings was studied. The results show that all the aluminide coatings can be distinguished into an outer pure aluminum or Al-Si topcoat and an inner intermetallic layer. The intermetallic layers, resulting from the steels hot-dipped in pure aluminum, have the same phase constitution, an outer minor FeAl3 and an inner major Fe2Al5. In the aluminide coatings on the steels with 0 and 2.25 wt.% chromium after hot-dipping in Al-10 wt.% Si, the intermetallic layers were composed of an outer layer of τ5(H)-Al7(Fe,Cr)2Si and an inner one of FeAl3/τ1-(Al,Si)5Fe3/Fe2Al5, while a small amount of polyhedral τ5(H)-Al7(Fe,Cr)2Si and plate-shaped τ6-Al4FeSi were observed in the Al-Si topcoats. In the aluminide coatings on the steels with 5 and 9 wt.% chromium after hot-dipping in Al-10 wt.% Si, the intermetallic layers were composed of only a τ5(H)-Al7(Fe,Cr)2Si phase. A large amount of scattered granular τ5(C)-Al7(Fe,Cr)2Si and a small amount of plate-shaped τ4-Al3FeSi2 and τ6-Al4FeSi were also found in the Al-Si topcoats. When the chromium content reached 5 wt.%, the amount of steel, which dissolved when samples were hot-dipped in Al-10 wt.% Si, increased. Also, the rate of dissolving went up as chromium content went up. The increase of dissolution is because the interdiffusion between steels and Al-10 wt.% Si bath was enhanced by the formation of scattered granular τ5(C)-Al7(Fe,Cr)2Si, which was stabilized by chromium.

  18. Investigation of potential soil contamination with Cr and Ni in four metal finishing facilities at Asopos industrial area.

    PubMed

    Panagopoulos, Ioannis; Karayannis, Athanassios; Kollias, Konstantinos; Xenidis, Anthimos; Papassiopi, Nymphodora

    2015-01-08

    The objective of this work was to investigate whether previous disposal practices in four metal finishing facilities, located at Asopos river basin (East-Central Greece), have caused any potential serious contamination of soils. The study focused mainly on Cr and Ni, which are the primary elements of concern in the area. To estimate the natural geochemical levels of Cr and Ni, thirty soil samples were collected from locations that were not suspected of any contamination. In this group of samples, Cr concentration varied between 60 and 418 mg/kg, and Ni concentrations varied from 91 to 1200 mg/kg. The second group of samples consisted of more than 100 drill cores and surface soil samples, potentially affected by the disposal of effluents and/or the drainage of runoff water from the industrial facilities. According to the findings of the study, the disposal of treated effluents in absorption type sinks resulted occasionally in the contamination of a thin layer of soil just at the bottom of the sinks, but there was no indication of downward migration, since Cr and Ni concentrations in the lower soil layers were similar to those of the reference soils.

  19. X-ray photoelectron and scanning Auger electron spectroscopy study of electrodeposited ZnCr coatings on steel.

    PubMed

    Itani, H; Duchoslav, J; Arndt, M; Steck, T; Gerdenitsch, J; Faderl, J; Preis, K; Winkler, W; Stifter, D

    2012-05-01

    Zn-Cr alloyed coatings electrochemically deposited are of high interest for leading steel manufacturing companies because of their novel properties and high corrosion resistance compared with conventional Zn coatings on steel. For tuning and optimizing the properties of the electrodeposited Zn-Cr coatings, a broad range of the deposition conditions must be studied. For this reason, two different types of material were investigated in this study, one with a low electrolyte temperature and one with an elevated electrolyte pH, compared with the standard values. Because different corrosion performance and delamination behaviour of the layers were observed for the two types, advanced surface analysis was conducted to understand the origin of this behaviour and to discover differences in the formation of the coatings. The topmost surface, the shallow subsurface region, and the whole bulk down to the coating-steel interface surface were analysed in detail by X-ray photoelectron spectroscopy (XPS) and high-resolution scanning Auger electron spectroscopy to determine the elemental and the chemical composition. For better understanding of the resulting layer structure, multiple reference samples and materials were measured and their Auger and XPS spectra were fitted to the experimental data. The results showed that one coating type is composed of metallic Zn and Cr, with oxide residing only on the surface and interface, whereas the other type contains significant amounts of Zn and Cr oxides throughout the whole coating thickness.

  20. Procurement of V-Cr-Ti alloys to study minor variations on V-4Cr-4Ti

    SciTech Connect

    Grossbeck, M.L.

    1998-03-01

    The alloys V-6Cr-3Ti, V-4Cr-4Ti-Si, V-6Cr-6Ti, and V-3Cr-3Ti, were prepared by Teledyne Wah Chang Albany Corp. in 1994. Plate and sheet ranging from 0.76 mm to 6.25 mm with residual material being left in 12--20 mm thick bar were fabricated. Although the heats were prepared on a pilot plant scale using different equipment, an effort was made to keep the processing as close to Wah Chang Heat 832665, the reference fusion heat of V-4Cr-4Ti, as possible.

  1. Combustion zone durability program-B. Task VIII. Sputter deposited ceramic and metallic coatings. Executive summary. [Graded metal; metal/ceramic layered; dense surface ceramic

    SciTech Connect

    Patten, J. W.; Moss, R. W.; Hays, D. D.

    1980-11-01

    The graded metal coatings are of the CoCrAlY type modified by including high Cr surface compositions, gradients in Cr and Al composition, underlayers and graded Pt additions, and Hf substitutions for Y. The metal ceramic layered coatings consist of alternate metal (Ni, Ni-Cr, CoCrAlY or Pt) and ceramic (Al/sub 2/O/sub 3/ or ZrO/sub 2/ + Y) layers. Investigations of dense surface ceramic coatings are directed towards methods for obtaining adherent impermeable ceramic protective coatings for gas turbine hot section components. Increased coating adherence is being sought through two coating designs intended to accomodate expansion and modulus mismatches at the coating-substrate interface.

  2. Low-temperature oriented growth of vanadium dioxide films on CoCrTa metal template on Si and vertical metal-insulator transition

    SciTech Connect

    Okimura, Kunio; Mian, Md.Suruz

    2012-09-15

    The authors achieved oriented growth of vanadium dioxide (VO{sub 2}) films on CoCrTa metal template grown on an Si substrate. Low-temperature ({approx}250 Degree-Sign C) deposition of VO{sub 2} films using inductively coupled-plasma-assisted sputtering technique realized an abrupt interface between VO{sub 2} and CoCrTa layers, suppressing the oxidation and diffusion of metal components. The films revealed a metal-insulator transition with resistance change of over 2 orders of magnitude. The CoCrTa film, in which Co hexagonal crystalline grains with c-axis orientation were surrounded by segregated Cr and Ta, serves for the oriented growth of VO{sub 2} crystalline film, enabling higher orders of transition in resistance and low voltage switching, even for the vertical (out-of-plane) direction.

  3. Terby's Layered Rocks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    14 March 2004 Layered rock outcrops are common all across Mars, and the Mars rover, Opportunity, has recently investigated some layered rocks in Meridiani Planum. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rocks in northern Terby Crater, located just north of the giant Hellas Basin near 27.5oS, 285.8oW. Hundreds of layers are exposed in a deposit several kilometers thick within Terby. A history of events that shaped the northern Hellas region is recorded in these rocks, just waiting for a person or robot to investigate. The picture covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the left.

  4. Addressing Ozone Layer Depletion

    EPA Pesticide Factsheets

    Access information on EPA's efforts to address ozone layer depletion through regulations, collaborations with stakeholders, international treaties, partnerships with the private sector, and enforcement actions under Title VI of the Clean Air Act.

  5. Manufacturing and High Heat Flux Testing of Brazed Flat-Type W/CuCrZr Plasma Facing Components

    NASA Astrophysics Data System (ADS)

    Lian, Youyun; Liu, Xiang; Feng, Fan; Chen, Lei; Cheng, Zhengkui; Wang, Jin; Chen, Jiming

    2016-02-01

    Water-cooled flat-type W/CuCrZr plasma facing components with an interlayer of oxygen-free copper (OFC) have been developed by using vacuum brazing route. The OFC layer for the accommodation of thermal stresses was cast onto the surface of W at a temperature range of 1150 °C-1200 °C in a vacuum furnace. The W/OFC cast tiles were vacuum brazed to a CuCrZr heat sink at 940 °C using the silver-free filler material CuMnSiCr. The microstructure, bonding strength, and high heat flux properties of the brazed W/CuCrZr joint samples were investigated. The W/Cu joint exhibits an average tensile strength of 134 MPa, which is about the same strength as pure annealed copper. High heat flux tests were performed in the electron beam facility EMS-60. Experimental results indicated that the brazed W/CuCrZr mock-up experienced screening tests of up to 15 MW/m2 and cyclic tests of 9 MW/m2 for 1000 cycles without visible damage. supported by National Natural Science Foundation of China (No. 11205049) and the National Magnetic Confinement Fusion Science Program of China (No. 2011GB110004)

  6. InN nanorods prepared with CrN nanoislands by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Liu, Kuang-Wei; Chang, Shoou-Jinn; Young, Sheng-Joue; Hsueh, Tao-Hung; Hung, Hung; Mai, Yu-Chun; Wang, Shih-Ming; Chen, Kuan-Jen; Wu, Ya-Ling; Chen, Yue-Zhang

    2011-07-01

    The authors report the influence of CrN nanoisland inserted on growth of baseball-bat InN nanorods by plasma-assisted molecular beam epitaxy under In-rich conditions. By inserting CrN nanoislands between AlN nucleation layer and the Si (111) substrate, it was found that we could reduce strain form Si by inserting CrN nanoisland, FWHM of the x-ray rocking curve measured from InN nanorods from 3,299 reduced to 2,115 arcsec. It is due to the larger strain from lattice miss-match of the film-like InN structure; however, the strain from lattice miss-match was obvious reduced owing to CrN nanoisland inserted. The TEM images confirmed the CrN structures and In droplets dissociation from InN, by these results, we can speculate the growth mechanism of baseball-bat-like InN nanorods.

  7. Trapping of Cr by formation of ferrihydrite during the reduction of chromate ions by Fe(II)-Fe(III) hydroxysalt green rusts

    SciTech Connect

    Loyaux-Lawniczak, S.; Refait, P.; Ehrhardt, J.J.; LeComte, P.; Genin, J.M.R.

    2000-02-01

    Hexavalent chromium, a byproduct of many industrial processes, is toxic and produces mobile aqueous oxyanions, whereas Cr(III) is relatively immobile in the environment and, moreover, essential in human glucidic metabolism. For this reason, Fe(II)-Fe(III) layered double hydroxysalt green rusts, recently identified as a mineral in hydromorphic soils, were evaluated as potential Fe(II)-bearing phases for hexavalent chromium reduction. Both considered synthetic varieties, the hydroxysulfate GR(SO{sub 4}{sup 2{minus}}) and the hydroxychloride GR(Cl{sup {minus}}), proved to be very reactive; their interaction with potassium chromate solutions leads to the rapid and complete reduction of Cr(VI) into Cr(III). The Cr(III)-bearing solid phase, studied by X-ray diffraction, Moessbauer, X-ray photoelectron, and Raman spectroscopies, was determined to be a poorly ordered Cr(III)-Fe(III) oxyhydroxide, similar to the 2 the line ferrihydrite. The comparison between the experimental redox potential and pH values for a theoretical equilibrium diagram bearing Cr and Fe phases indicated that the solubility of this solid solution, which may govern the behavior of chromium in the environment, is of the same order as that of pure Cr(OH){sub 3}.

  8. Investigation of structural changes in chiral magnet Cr{sub 1∕3}NbS{sub 2} under application of pressure

    SciTech Connect

    Mito, M. Tsuruta, K.; Deguchi, H.; Tajiri, T.; Kishine, J.; Inoue, K.; Kousaka, Y.; Nakao, Y.; Akimitsu, J.

    2015-05-14

    We perform structural analysis experiments on the chiral magnet Cr{sub 1∕3}NbS{sub 2}, in which Cr{sup 3+} ions are inserted between hexagonal NbS{sub 2} layers. The noncentrosymmetrical nature of the inserted Cr{sup 3+} appears as a distorted CrS{sub 6} octahedron. Under the application of hydrostatic pressure, the lattice shrinks significantly along the c-axis rather than the a-axis. However, at a pressure P of approximately 3–4 GPa, a kink in the rate of decrease in the lattice parameters is observed, and the slight movement of a Nb atom along the c-axis brings about a decrease in the distortion of the CrS{sub 6} octahedron. This structural change qualitatively suggests a decrease in the strength of the Dzyaloshinskii-Moriya (D-M) interaction. Under hydrostatic pressure, the magnetic ordering temperature T{sub C} decreases, and dT{sub C}/dP exhibits a slight change at around 3 GPa. A series of experiments indicates that the change in the structural symmetry of the CrS{sub 6} octahedron influences the exchange network between Cr{sup 3+} ions as well as the D-M interaction.

  9. Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju

    2015-10-01

    A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

  10. Synthesis and mechanical properties of CrMoC{sub x}N{sub 1-x} coatings deposited by a hybrid coating system

    SciTech Connect

    Yun, Ji Hwan; Heo, Su Jeong; Kim, Kwang Ryul; Kim, Kwang Ho

    2008-01-15

    Quaternary CrMoC{sub x}N{sub 1-x} coatings were deposited on steel substrates (AISI D2) and Si wafers by a hybrid coating system combining an arc-ion plating technique and a dc reactive magnetron sputtering technique using Cr and Mo targets in an Ar/N{sub 2}/CH{sub 4} gaseous mixture. The carbon content of CrMoC{sub x}N{sub 1-x} coatings was linearly increased with increasing CH{sub 4}/(CH{sub 4}+N{sub 2}) gas flow rate ratio. The maximum hardness of 44 GPa was obtained from the CrMoC{sub x}N{sub 1-x} coatings containing a carbon content of x=0.33 with a residual stress of -4.4 GPa. The average friction coefficient of Cr-Mo-N coatings was 0.42, and it is decreased to 0.31 after applying CrMoC{sub x}N{sub 1-x} coatings. This result was caused by the formation of a carbon-rich transfer layer that acted as a solid lubricant to reduce contact between the coating surface and steel ball. The microstructure of the coatings was investigated by x-ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy. In this work, the microstructure and mechanical properties of the CrMoC{sub x}N{sub 1-x} coatings were systematically investigated with the instrumental analyses.

  11. Solute redistribution and phase stability at FeCr/TiO2–x interfaces under ion irradiation

    SciTech Connect

    Xu, Y.; Aguiar, J. A.; Yadav, S. K.; Anderoglu, O.; Baldwin, J. K.; Wang, Y. Q.; Valdez, James A.; Misra, A.; Luo, H. M.; Uberuaga, B. P.; Li, N.

    2015-02-26

    Cr diffusion in trilayer thin films of 100 nm Fe–18Cr/125 nm TiO2–x/100 nm Fe–18Cr deposited on MgO substrates at 500 °C was studied by either annealing at 500 °C or Ni3+ ion irradiation at 500 °C. Microchemistry and microstructure evolution at the metal/oxide interfaces were investigated using (high-resolution) transmission electron microscopy, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy. Diffusion of Cr into the O-deficient TiO2 layer, with negligible segregation to the FeCr/TiO2–x interface itself, was observed under both annealing and irradiation. Cr diffusion into TiO2–x was enhanced in ion-irradiated samples as compared to annealed. Irradiation-induced voids and amorphization of TiO2–x was also observed. The experimental results are rationalized using first-principles calculations that suggest an energetic preference for substituting Ti with Cr in sub-stoichiometric TiO2. Furthermore, the implications of these results on the irradiation stability of oxide-dispersed ferritic alloys are discussed.

  12. Temporal evolution of ion energy distribution functions and ion charge states of Cr and Cr-Al pulsed arc plasmas

    SciTech Connect

    Tanaka, Koichi; Anders, André

    2015-11-15

    To study the temporal evolution of ion energy distribution functions, charge-state-resolved ion energy distribution functions of pulsed arc plasmas from Cr and Cr-Al cathodes were recorded with high time resolution by using direct data acquisition from a combined energy and mass analyzer. The authors find increases in intensities of singly charged ions, which is evidence that charge exchange reactions took place in both Cr and Cr-Al systems. In Cr-Al plasmas, the distributions of high-charge-state ions exhibit high energy tails 50 μs after discharge ignition, but no such tails were observed at 500 μs. The energy ratios of ions of different charge states at the beginning of the pulse, when less neutral atoms were in the space in front of the cathode, suggest that ions are accelerated by an electric field. The situation is not so clear after 50 μs due to particle collisions. The initial mean ion charge state of Cr was about the same in Cr and in Cr-Al plasmas, but it decreased more rapidly in Cr-Al plasmas compared to the decay in Cr plasma. The faster decay of the mean ion charge state and ion energy caused by the addition of Al into a pure Cr cathode suggests that the mean ion charge state is determined not only by ionization processes at the cathode spot but also by inelastic collision between different elements.

  13. Tandem Solar Cells from Accessible Low Band-Gap Polymers Using an Efficient Interconnecting Layer.

    PubMed

    Bag, Santanu; Patel, Romesh J; Bunha, Ajaykumar; Grand, Caroline; Berrigan, J Daniel; Dalton, Matthew J; Leever, Benjamin J; Reynolds, John R; Durstock, Michael F

    2016-01-13

    Tandem solar cell architectures are designed to improve device photoresponse by enabling the capture of wider range of solar spectrum as compared to single-junction device. However, the practical realization of this concept in bulk-heterojunction polymer systems requires the judicious design of a transparent interconnecting layer compatible with both polymers. Moreover, the polymers selected should be readily synthesized at large scale (>1 kg) and high performance. In this work, we demonstrate a novel tandem polymer solar cell that combines low band gap poly isoindigo [P(T3-iI)-2], which is easily synthesized in kilogram quantities, with a novel Cr/MoO3 interconnecting layer. Cr/MoO3 is shown to be greater than 80% transparent above 375 nm and an efficient interconnecting layer for P(T3-iI)-2 and PCDTBT, leading to 6% power conversion efficiencies under AM 1.5G illumination. These results serve to extend the range of interconnecting layer materials for tandem cell fabrication by establishing, for the first time, that a thin, evaporated layer of Cr/MoO3 can work as an effective interconnecting layer in a tandem polymer solar cells made with scalable photoactive materials.

  14. Structured luminescence conversion layer

    DOEpatents

    Berben, Dirk; Antoniadis, Homer; Jermann, Frank; Krummacher, Benjamin Claus; Von Malm, Norwin; Zachau, Martin

    2012-12-11

    An apparatus device such as a light source is disclosed which has an OLED device and a structured luminescence conversion layer deposited on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The structured luminescence conversion layer contains regions such as color-changing and non-color-changing regions with particular shapes arranged in a particular pattern.

  15. Preparation and high-temperature oxidation behavior of plasma Cr-Ni alloying on Ti6Al4V alloy based on double glow plasma surface metallurgy technology

    NASA Astrophysics Data System (ADS)

    Wei, Dong-Bo; Zhang, Ping-Ze; Yao, Zheng-Jun; Wei, Xiang-Fei; Zhou, Jin-Tang; Chen, Xiao-Hu

    2016-12-01

    To improve the oxidation resistance of Ti6Al4V alloy, it was coated with a Cr-Ni alloy with 20, 40, 60, and 80 at.% Ni content using the double-glow plasma surface metallurgy technology. The coatings were dense, uniform, and compact, including a complete structure of deposited layer, interdiffusion layer, and sputtering-affected zone. The effect of Ni content on the isothermal oxidation behavior of coating was investigated at 750, 850, and 950 °C. The results show that the oxide scale consisted of NiO and Cr2O3. The morphology and distribution of NiO in oxide scale were affected by oxidation temperature and Ni content. When the Ni content was ≤40 at.%, the oxidation resistance of the Cr-Ni alloy coating was enhanced.

  16. Cr Isotope Variation in the Components of Unequilibrated Chondrite QUE 97008 (L3.05) and Implications for 53Mn-53Cr Dating of Unequilibrated Chondrites

    NASA Astrophysics Data System (ADS)

    Kadlag, Y.; Becker, H.

    2016-08-01

    In this study, we report Cr isotope variation in physically separated components of unequilibrated chondrite QUE 97008. Decoupling of 54Cr and 53Cr and Mn/Cr indicate the presence of at least two types of 54CR depleted and enriched carriers.

  17. Simultaneous analysis of Cr(III), Cr(VI), and chromium picolinate in foods using capillary electrophoresis-inductively coupled plasma mass spectrometry.

    PubMed

    Chen, YiQuan; Chen, JinFa; Xi, Zhiming; Yang, Guidi; Wu, Zujian; Li, JianRong; Fu, FengFu

    2015-05-01

    We herein reported a method for the simultaneous detection of trace Cr(VI), Cr(III), and chromium(III) picolinate (CrPic) in foods using CE-ICP-MS together with ultrasonic-assisted extraction. The Cr(III) (Cr(3+) ) was chelated with trans-1,2-diaminocyclohexane-N,N,N´,N´-tetraacetic acid (DCTA) to form a single charged Cr-DCTA(-) complex. Then, Cr(VI) (CrO4 (2-) ), Cr-DCTA(-) , and CrPic were separated by CE within 8 min under a separation voltage of -13 KV followed by their monitoring with ICP mass spectrometer (ICP-MS). The proposed method is simple, effective, and sensitive. It has an instrument detection limit of 0.10, 0.18, and 0.20 ngCr/mL for Cr(VI), Cr(III), and CrPic, respectively. With the help of the methods, we have successfully determined Cr(VI), Cr(III), and CrPic in nutritional supplement (CrPic yeast tablet) with an RSD (n = 5) <6% and a recovery of 93-103%. The experimental results showed that CrPic was the main speciation of chromium in the nutritional supplement, with a concentration of 1514.6 μg Cr/g.

  18. Syntheses and structural characterizations of CrSi2 nanostructures using Si substrates under CrCl2 vapor

    NASA Astrophysics Data System (ADS)

    Li, Wen; Meng, Erchao; Matsushita, Tomoji; Oda, Shingo; Ishikawa, Daisuke; Nakane, Kaito; Hu, Junhua; Guan, Shaokang; Ishida, Akihiro; Tatsuoka, Hirokazu

    2013-02-01

    Chromium disilicide (CrSi2) nanostructures were grown by the exposure of Si substrates to CrCl2 vapor at atmospheric pressure, and the growth condition dependence on the morphological and structural properties of CrSi2 was systemically investigated. The various structures of CrSi2, such as microrods, nanowire bundles along with microrods and dendritic nanowire structures, have been grown. It was found that the Si substrate temperature and the quantity of the CrCl2 source materials significantly affect the morphological and structural properties of the CrSi2 structures. The structural evolution of CrSi2 has been discussed on the basis of thermodynamic reactions, vapor deposition growth and dendritic growth phenomena. This growth process provides a simple and controllable method to grow novel nano-scaled structures of transition metal silicides for technological use.

  19. Relaxor-like dielectric response of spin liquid CuCrO{sub 2}

    SciTech Connect

    Mazumder, N. Roy, R.; Ghorai, U. K.; Saha, S.; Chattopadhyay, K. K.

    2014-04-24

    Broadband dielectric analysis (10{sup −2}-10{sup 7} Hz) of layered triangular lattice CuCrO{sub 2} is performed (123 K - 473 K) and analyzed in connection with recently observed spin frustration in this multiferroic [M. Poienar et al. Phys. Rev. B 81, 104411, (2010); M. Frontzek et al. Phys. Rev. B 84, 094448, (2011)]. Most unexpectedly, this well known delafossite has found to have nontrivial charge degrees of freedom, being characterized by a relaxor-like dielectric relaxation around 375 K with FWHM of ∼100K. The result strongly suggests the existence of intermolecular Coulomb interaction between charge disproportionation induced electric dipoles.

  20. Dry Sliding Wear Characteristics of Plasma-Nitrocarburized Co - Cr - Mo Alloy

    NASA Astrophysics Data System (ADS)

    Bayrak, Ö.; Kovaci, H.; Yildiz, F.; Yetim, A. F.; Çelik, A.

    2017-03-01

    Forged low-carbon alloy Co - 27% Cr - 6% Mo - 0.06% C is studied after 2-h plasma nitrocarburizing in a gaseous mixture of 10% CO2 + 20% N2 + 70% H2 at 400, 500 and 600°C. The surface layer and the core are studied by diffractometric analysis and scanning electron microscopy. The microhardness and the tribological characteristics of the alloy are determined. The effect of the temperature of nitrocarburizing on the wear resistance, surface roughness and friction coefficient of the alloy is considered.

  1. Effect of oxidation on tensile behavior of V-5Cr-5Ti alloy

    SciTech Connect

    Natesan, K.; Soppet, W.K.

    1995-04-01

    The objectives of this task are to (a) evaluate the oxygen uptake behavior of V-5Cr-5Ti alloy as a function of temperature and oxygen partial pressure in the exposure environment, (b) examine the microstructural characteristics of oxide scales and oxygen entrapped at the grain boundaries in the substrate alloy, (c) evaluate the influence of oxygen uptake on the tensile properties of the alloy at room and elevated temperatures, (d) evaluate oxidation kinetics of the alloy with the aluminum-enriched surface layers, and (e) determine the effect of oxygen uptake on tensile behavior of the alloy.

  2. Oxidative vaporization kinetics of Cr2O3 in oxygen from 1000 to 1300 C

    NASA Technical Reports Server (NTRS)

    Stearns, C. A.; Kohl, F. J.; Fryburg, G. C.

    1974-01-01

    Rates of oxidative vaporization of Cr2O3 on preoxidized resistively heated chromium were determined in flowing oxygen at a pressure of 0.115 Torr for temperatures from 1000 to 1300 C. Reaction controlled rates were obtained from experimental rates by a gold calibration technique, and these rates were shown to agree with those predicted by thermochemical analysis. The activation energy obtained for the oxidative vaporization reaction corresponded numerically with the thermochemical enthalpy of the reaction. A theoretical equation is given for calculating the rate from thermodynamic data using boundary-layer theory.

  3. Method of forming a plasma sprayed interconnection layer on an electrode of an electrochemical cell

    DOEpatents

    Spengler, C.J.; Folser, G.R.; Vora, S.D.; Kuo, L.; Richards, V.L.

    1995-06-20

    A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO{sub 3} particles doped with an element selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by plasma spraying doped LaCrO{sub 3} powder, preferably compensated with chromium as Cr{sub 2}O{sub 3} and/or dopant element, preferably by plasma arc spraying; and, (C) heating the doped and compensated LaCrO{sub 3} layer to about 1100 C to 1300 C to provide a dense, substantially gas-tight, substantially hydration-free, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the unselected portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell. 6 figs.

  4. Method of forming a plasma sprayed interconnection layer on an electrode of an electrochemical cell

    DOEpatents

    Spengler, Charles J.; Folser, George R.; Vora, Shailesh D.; Kuo, Lewis; Richards, Von L.

    1995-01-01

    A dense, substantially gas-tight, electrically conductive interconnection layer is formed on an air electrode structure of an electrochemical cell by (A) providing an electrode surface; (B) forming on a selected portion of the electrode surface, a layer of doped LaCrO.sub.3 particles doped with an element selected from Ca, Sr, Ba, Mg, Co, Ni, Al and mixtures thereof by plasma spraying doped LaCrO.sub.3 powder, preferably compensated with chromium as Cr.sub.2 O.sub.3 and/or dopant element, preferably by plasma arc spraying; and, (C) heating the doped and compensated LaCrO.sub.3 layer to about 1100.degree. C. to 1300.degree. C. to provide a dense, substantially gas-tight, substantially hydration-free, electrically conductive interconnection material bonded to the electrode surface. A solid electrolyte layer can be applied to the unselected portion of the air electrode, and a fuel electrode can be applied to the solid electrolyte, to provide an electrochemical cell.

  5. The structure and energetics of Cr(CO)6 and Cr(CO)5

    NASA Technical Reports Server (NTRS)

    Barnes, Leslie A.; Liu, Bowen; Lindh, Roland

    1992-01-01

    The geometric structure of Cr(CO)6 is optimized at the modified coupled pair functional (MCPF), single and double excitation coupled-cluster (CCSD) and CCSD(T) levels of theory (including a perturbational estimate for connected triple excitations), and the force constants for the totally symmetric representation are determined. The geometry of Cr(CO)5 is partially optimized at the MCPF, CCSD, and CCSD(T) levels of theory. Comparison with experimental data shows that the CCSD(T) method gives the best results for the structures and force constants, and that remaining errors are probably due to deficiencies in the one-particle basis sets used for CO. The total binding energies of Cr(CO)6 and Cr(CO)5 are also determined at the MCPF, CCSD, and CCSD(T) levels of theory. The CCSD(T) method gives a much larger total binding energy than either the MCPF or CCSD methods. An analysis of the basis set superposition error (BSSE) at the MCPF level of treatment points out limitations in the one-particle basis used. Calculations using larger basis sets reduce the BSSE, but the total binding energy of Cr(CO)6 is still significantly smaller than the experimental value, although the first CO bond dissociation energy of Cr(CO)6 is well described. An investigation of 3s3p correlation reveals only a small effect. In the largest basis set, the total CO binding energy of Cr(CO)6 is estimated to be 140 kcal/mol at the CCSD(T) level of theory, or about 86 percent of the experimental value. The remaining discrepancy between the experimental and theoretical value is probably due to limitations in the one-particle basis, rather than limitations in the correlation treatment. In particular an additional d function and an f function on each C and O are needed to obtain quantitative results. This is underscored by the fact that even using a very large primitive set (1042 primitive functions contracted to 300 basis functions), the superposition error for the total binding energy of Cr(CO)6 is 22

  6. Microstructure and properties of the Ti/Al2O3/NiCr composites fabricated by explosive compaction/cladding.

    PubMed

    Wang, Bingfeng; Xie, Fangyu; Wang, Bin; Luo, Xiaozhou

    2015-05-01

    Titanium/aluminum oxide/nickel chromium (Ti/Al2O3/NiCr) composite bar prepared by explosive compaction/cladding technique represents a new kind of sandwich-structural composites for medical application. Formation of the interfaces of Ti/Al2O3 and Al2O3/NiCr govern the properties of the composite material. The electrical resistivity and microstructure of the intermediate layer and the interfaces of the Ti/Al2O3/NiCr explosive compaction/cladding bar are investigated by means of four-point probe analysis, optical microscopy, scanning electron microscopy, electron microprobe analysis, and X-ray diffraction. The Ti/Al2O3/NiCr composite bar is characterized by the consolidated ceramic intermediate layer and the metallurgical bonding interfaces. The intermediate ceramic layer plays a role of insulation and thermal conductance in this composite. The average shear strength of the composite bar is about 9.36 MPa. The heat affected zone characterized by relatively larger sizes of grains is distinguished from the other part of the Ti tube. The intermetallics AlTi3 and Al0.9Ni4.22 are generated at the intermediate ceramic layer. Formation mechanism of the interfaces of the explosive compaction/cladding bar are described.

  7. Crystal structure and magnetic properties of Li,Cr-containing molybdates Li 3Cr(MoO 4) 3, LiCr(MoO 4) 2 and Li 1.8Cr 1.2(MoO 4) 3

    NASA Astrophysics Data System (ADS)

    Sarapulova, A.; Mikhailova, D.; Senyshyn, A.; Ehrenberg, H.

    2009-12-01

    Single crystals of LiCr(MoO 4) 2, Li 3Cr(MoO 4) 3 and Li 1.8Cr 1.2(MoO 4) 3 were grown by a flux method during the phase study of the Li 2MoO 4-Cr 2(MoO 4) 3 system at 1023 K. LiCr(MoO 4) 2 and Li 3Cr(MoO 4) 3 single phases were synthesized by solid-state reactions. Li 3Cr(MoO 4) 3 adopts the same structure type as Li 3In(MoO 4) 3 despite the difference in ionic radii of Cr 3+ and In 3+ for octahedral coordination. Li 3Cr(MoO 4) 3 is paramagnetic down to 7 K and shows a weak ferromagnetic component below this temperature. LiCr(MoO 4) 2 is isostructural with LiAl(MoO 4) 2 and orders antiferromagnetically below 20 K. The magnetic structure of LiCr(MoO 4) 2 was determined from low-temperature neutron diffraction and is based on the propagation vektor k⇒=({1}/{2},{1}/{2},0). The ordered magnetic moments were refined to 2.3(1) μ B per Cr-ion with an easy axis close to the [1 1 1¯] direction. A magnetic moment of 4.37(3) μ B per Cr-ion was calculated from the Curie constant for the paramagnetic region. The crystal structures of the hitherto unknown Li 1.8Cr 1.2(MoO 4) 3 and LiCr(MoO 4) 2 are compared and reveal a high degree of similarity: In both structures MoO 4-tetrahedra are isolated from each other and connected with CrO 6 and LiO 5 via corners. In both modifications there are Cr 2O 10 fragments of edge-sharing CrO 6-octahedra.

  8. Formation of Cr-modified silicide coatings on a Ti-Nb-Si based ultrahigh-temperature alloy by pack cementation process

    NASA Astrophysics Data System (ADS)

    Qiao, Yanqiang; Guo, Xiping

    2010-10-01

    Cr-modified silicide coatings were prepared on a Ti-Nb-Si based ultrahigh temperature alloy by Si-Cr co-deposition at 1250 °C, 1350 °C and 1400 °C for 5-20 h respectively. It was found that both coating structure and phase constituents changed significantly with increase in the co-deposition temperature and holding time. The outer layers in all coatings prepared at 1250 °C for 5-20 h consisted of (Ti,X) 5Si 3 (X represents Nb, Cr and Hf elements). (Ti,X) 5Si 4 was found as the only phase constituent in the intermediate layers in both coatings prepared at 1250 °C for 5 and 10 h, but the intermediate layers in the coatings prepared at 1250 °C for 15 and 20 h were mainly composed of (Ti,X) 5Si 3 phase that was derived from the decomposition of (Ti,X) 5Si 4 phase. In the coating prepared at 1350 °C for 5 h, single (Ti,X) 5Si 3 phase was found in its outmost layer, the same as that in the outer layers in the coatings prepared at 1250 °C; but in the coatings prepared at 1350 °C for 10-20 h, (Nb 1.95Cr 1.05)Cr 2Si 3 ternary phase was found in the outmost layers besides (Ti,X) 5Si 3 phase. In the coatings prepared at 1400 °C for 5-20 h, (Nb 1.95Cr 1.05)Cr 2Si 3 ternary phase was the single phase constituent in their outmost layers. The phase transformation (Ti,X) 5Si 4 → (Ti,X) 5Si 3 + Si occurred in the intermediate layers of the coatings prepared at 1350 and 1400 °C with prolonging co-deposition time, similar to the situation in the coatings prepared at 1250 °C for 15 and 20 h, but this transformation has been speeded up by increase in the co-deposition temperature. The transitional layers were mainly composed of (Ti,X) 5Si 3 phase in all coatings. The influence of co-deposition temperature on the diffusion ability of Cr atoms was greater than that of Si atoms in the Si-Cr co-deposition processes investigated. The growth of coatings obeyed inverse logarithmic laws at all three co-deposition temperatures. The Si-Cr co-deposition coating prepared at 1350

  9. Microstructure and properties of laser-borided 41Cr4 steel

    NASA Astrophysics Data System (ADS)

    Kulka, M.; Makuch, N.; Pertek, A.

    2013-02-01

    Laser-boriding, instead of diffusion-boriding, was applied to formation of boride layers on 41Cr4 steel. The microstructure and properties of these layers were compared to those obtained after typical diffusion-boriding. Three zones characterized the microstructure of laser-borided layer: laser-borided zone, hardened medium-carbon zone (heat affected zone) and medium-carbon substrate without heat treatment. The through-hardened laser-borided steel was also analyzed. In this case two zones characterized the microstructure: laser-borided zone and hardened medium-carbon substrate. The microstructure of laser-borided zone consisted of eutectic mixture of borides and martensite. This phase composition (especially martensite presence) was the reason for microhardness decrease at the surface in comparison with diffusion-borided steel. However, the use of laser-boriding causes the decrease in microhardness gradient between the surface and the substrate in comparison with typical diffusion-boriding process. The value of mass wear intensity factor of the hardened laser-borided layer was comparable to that obtained in case of diffusion-boriding and through-hardening. The use of laser-borided layers instead of typical diffusion-borided layers may be advantageous under conditions of high abrasive wear of mating parts. For the experimental condition used, the laser-boriding process presented worst results concerning the fatigue strength. The cracks formed on the surface during laser re-melting were the reason for relatively quick first fatigue crack. In case of elements, which require high fatigue strength, the use of modified laser processing parameters would be necessary. The better results should be obtained by increasing of tracks overlapping. Although the cohesion of laser-borided layer was sufficient, the diffusion-borided layer showed a better cohesion.

  10. Cr(VI) reduction in continuous-flow coculture bioreactor

    SciTech Connect

    Wang, Y.T.; Chirwa, E.M.; Shen, H.

    2000-04-01

    A continuous-flow coculture bioreactor with a phenol-degrading organism, Pseudomonas putida DMP-1, and a Cr(VI)-reducing species, Escherichia coli ATCC 33456, was developed for simultaneous removal of phenol and Cr(VI). Phenol was the sole energy and carbon source added to the coculture along with a basal medium and hexavalent chromium. The coculture bioreactor was operated under three liquid detention times (0.20, 0.31, and 0.52 days) with phenol and Cr(VI) loadings ranging from 2,500 to 8,200 mg/L/day and 4.5-33.2 mg/L/day, respectively. After 279 days of continuous operation, eight quasi-steady-state operation conditions were obtained with near complete removal of phenol and Cr(VI). Elevated levels of Cr(VI) and phenol were observed in the effluent under a high influent Cr(VI) concentration (16 mg/L) or a short liquid detention time (0.20 days). The system recovered from Cr(VI) toxicity after influent Cr(VI) level was reduced. Chromium mass balance analysis revealed that nearly all of the influent Cr(VI) was reduced to Cr(III) in the coculture bioreactor through biological activity. Spectra of UV-Vis and mass spectrometers suggested that phenol metabolites produced by P. putida were utilized by E. coli.

  11. Cr(VI) uptake mechanism of Bacillus cereus.

    PubMed

    Chen, Zhi; Huang, Zhipeng; Cheng, Yangjian; Pan, Danmei; Pan, Xiaohong; Yu, Meijuan; Pan, Zhiyun; Lin, Zhang; Guan, Xiong; Wu, Ziyu

    2012-04-01

    In this study, we investigated the Cr(VI) uptake mechanism in an indigenous Cr(VI)-tolerant bacterial strain -Bacillus cereus through batch and microscopic experiments. We found that both the cells and the supernatant collected from B. cereus cultivation could reduce Cr(VI). The valence state analysis revealed the complete transformation from Cr(VI) into Cr(III) by living B. cereus. Further X-ray absorption fine structure and Fourier transform infrared analyses showed that the reduced Cr(III) was coordinated with carboxyl and amido functional groups from either the cells or supernatant. Scanning electron microscopy and atomic force microscopy observation showed that noticeable Cr(III) precipitates were accumulated on bacterial surfaces. However, Cr(III) could also be detected in bacterial inner portions by using transmission electron microscopy thin section analysis coupled with energy dispersive X-ray spectroscopy. Through quantitative analysis of chromium distribution, we determined the binding ratio of Cr(III) in supernatant, cell debris and cytoplasm as 22%, 54% and 24%, respectively. Finally, we further discussed the role of bacterium-origin soluble organic molecules to the remediation of Cr(VI) pollutants.

  12. Microstructural characterization of as-cast Cr-Si alloys

    SciTech Connect

    Chad, V.M. Faria, M.I.S.T.; Coelho, G.C.; Nunes, C.A.; Suzuki, P.A.

    2008-01-15

    This work presents results of microstructural characterization of as-cast Cr-Si alloys. The alloys were prepared by arc melting pure Cr (min. 99.996%) and Si (min. 99.998%) powder mixtures under argon atmosphere in a water-cooled copper crucible with nonconsumable tungsten electrode and titanium getter. The phases were identified by scanning electron microscopy (SEM), using the back-scattered electron (BSE) image mode and X-ray diffraction (XRD). The results confirm the currently accepted Cr-Si phase diagram in terms of the invariant reactions and solid phases present in this system. Small corrections are proposed for the compositions of the liquid phase in the following reactions: (i) L {r_reversible} Cr{sub SS}+Cr{sub 3}Si, from 15 to 16 at.% Si; (ii) L+{alpha}Cr{sub 5}Si{sub 3} {r_reversible} CrSi, from 51 at.% Si to slightly above 53 at.% Si; (iii) L {r_reversible} CrSi+CrSi{sub 2}, from 56 to slightly above 57 at.% Si; (iv) L {r_reversible} CrSi{sub 2}+Si, from 82 to slightly above 85 at.% Si.

  13. In situ Formation and Electron-Spectroscopic Study of Bis(arene) V and Cr Compounds ona Graphite Surface

    DTIC Science & Technology

    2013-03-07

    free molecule. Electron transfer to the substrate was indicated by the decrease in the sample work function (/S), due to the formation of a dipole... layer or for the free molecule (Fig. 1). Hole doping is considered unlikely for the present systems. A calculation for the [CrBz2] anion (not shown...due to the clustering22,23 of unreacted TM atoms. IV. CONCLUSIONS In summary, thin bis(arene)TM layers on HOPG have been formed in situ in an UHV

  14. Removal of hexavalent chromium from aqueous solutions using micro zero-valent iron supported by bentonite layer.

    PubMed

    Daoud, Waseem; Ebadi, Taghi; Fahimifar, Ahmad

    2015-01-01

    Hexavalent chromium Cr(VI) is of particular environmental concern due to its toxicity, mobility, and challenging removal from industrial wastewater. It is a strong oxidizing agent that is carcinogenic and mutagenic and diffuses quickly through soil and aquatic environments. Moreover, it does not form insoluble compounds in aqueous solutions; therefore, separation by precipitation is not feasible. While Cr(VI) oxyanions are very mobile and toxic in the environment, trivalent Cr(III) cations are the opposite and, like many metal cations, Cr(III) forms insoluble precipitates. Thus, reducing Cr(VI)-Cr(III) simplifies its removal from effluent and also reduces its toxicity and mobility. Permeable reactive barriers (PRBs) with zero-valent iron (ZVI) have been used to remediate contaminated groundwater with metals, but using ZVI in remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation, and difficulty in separation of iron from the treated solution. Thus, the technology used in the present study is developed to address these problems by placing a layer of bentonite after the PRB layer to remove iron from the treated water. The removal rates of Cr(VI) under different values of pH were investigated, and the results indicated the highest adsorption capacity at low pH.

  15. Magnetic bubble for CR experiments in space

    NASA Astrophysics Data System (ADS)

    Spillantini, Piero

    2015-01-01

    It is proposed to equip with an intense magnetic field the innovative isotropic, high granularity, homogeneous, deep cubic calorimeter, nicknamed 'calocube', in development for CR experiments in space. A number of identical coils are arranged for constituting three mutually orthogonal magnetic torus's forming a 'magnetic bubble' wrapping the calocube. Number and shape of the coils are discussed. Magnetic field intensity, and encumbrance and mass of the coils are evaluated for a model of the system wrapping a 1 m side calocube. A reduced version, with only one magnetic torus (4 coils) wrapping a 0.8 m side calocube is evaluated and discussed.

  16. Femtosecond, Cr{sup 4+}:YAG laser

    SciTech Connect

    Nathel, H.; Sennaroglu, A.; Pollock, C.R.

    1994-08-01

    Results from both a regeneratively-initiated and self-initiated, mode-locked CR.YAG laser which is tunable from 1.51 to 1.53 {mu}m are reported. One hundred and twenty femtsosecond, nearly transform-limited pulses have been generated with peak output powers of 45 kW. The stable, high peak power pulses and room temperature operation of this laser make it a very suitable alternative to the cumbersome, cryogenic mode-locked NaCl laser commonly used in both narrow bandgap semiconductor and optical communications research.

  17. Tests on Double Layer Metalization

    NASA Technical Reports Server (NTRS)

    Woo, D. S.

    1983-01-01

    28 page report describes experiments in fabrication of integrated circuits with double-layer metalization. Double-layer metalization requires much less silicon "real estate" and allows more flexibility in placement of circuit elements than does single-layer metalization.

  18. Magnetic interactions in CoCrPt-oxide based perpendicular magnetic recording media

    SciTech Connect

    Tan, H. K.; Varghese, B.; Piramanayagam, S. N.

    2014-10-28

    First order reversal curves (FORC) method has been reported to be an efficient tool to study interaction between grains and layers of magnetic materials. Although a few studies have been carried out on perpendicular recording media in the past, a study on the effect of systematic variation of exchange interaction in granular perpendicular magnetic recording media on FORC contours has not been carried out in detail. Such a study will help to understand the use of FORC better. In this paper, we have made a systematic set of samples in order to study the variation in exchange coupling and its effect on FORC contours. The pressure during the deposition of the second ruthenium layer and the magnetic layer was varied to alter the separation between the grains and hence the exchange interaction between the grains in the CoCrPt-oxide recording layer. In addition, the thickness of Co-alloy cap layer was used as an additional tool to control the exchange interaction between the magnetic grains. The results indicated that the interaction field obtained from the FORC does not vary in a significant manner when the changes in exchange interaction are small. In comparison, the peak intensity of the FORC shows a clear trend as the exchange coupling is varied, making it a more suitable parameter to study the exchange and magnetostatic interactions in systems such as magnetic recording media.

  19. Electronic, magnetic and Fermi properties investigates on quaternary Heusler NiCoCrAl, NiCoCrGa and NiFeCrGa

    NASA Astrophysics Data System (ADS)

    Wei, Xiao-Ping; Zhang, Ya-Ling; Chu, Yan-Dong; Sun, Xiao-Wei; Sun, Ting; Guo, Peng; Deng, Jian-Bo

    2015-07-01

    Using the full-potential local-orbital minimum-basis method within the framework of density functional theory, we study the electronic, magnetic and Fermi properties of three quaternary Heusler compounds: NiCoCrAl, NiCoCrGa and NiFeCrGa. Results identify that these compounds are half-metallic ferromagnets with integer spin magnetic moment, and their spin moments follow the Slater-Pauling rule. Accordingly, the origin of gap and magnetic moment are also discussed. In addition, the Fermi surface is further plotted to explore the behavior of electronic states in the vicinity of Fermi level for these compounds. Finally, we argue the influence of tetragonal deformation on electronic and magnetic properties. Meanwhile, the possible L21 disorder is also discussed for NiCoCrAl and NiCoCrGa.

  20. EDITORIAL: Atomic layer deposition Atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Godlewski, Marek

    2012-07-01

    The growth method of atomic layer deposition (ALD) was introduced in Finland by Suntola under the name of atomic layer epitaxy (ALE). The method was originally used for deposition of thin films of sulphides (ZnS, CaS, SrS) activated with manganese or rare-earth ions. Such films were grown for applications in thin-film electroluminescence (TFEL) displays. The ALE mode of growth was also tested in the case of molecular beam epitaxy. Films grown by ALD are commonly polycrystalline or even amorphous. Thus, the name ALE has been replaced by ALD. In the 80s ALD was developed mostly in Finland and neighboring Baltic countries. Deposition of a range of different materials was demonstrated at that time, including II-VI semiconductors (e.g. CdTe, CdS) and III-V (e.g. GaAs, GaN), with possible applications in e.g. photovoltaics. The number of publications on ALD was slowly increasing, approaching about 100 each year. A real boom in interest came with the development of deposition methods of thin films of high-k dielectrics. This research was motivated by a high leakage current in field-effect transistors with SiO2-based gate dielectrics. In 2007 Intel introduced a new generation of integrated circuits (ICs) with thin films of HfO2 used as gate isolating layers. In these and subsequent ICs, films of HfO2 are deposited by the ALD method. This is due to their unique properties. The introduction of ALD to the electronics industry led to a booming interest in the ALD growth method, with the number of publications increasing rapidly to well above 1000 each year. A number of new applications were proposed, as reflected in this special issue of Semiconductor Science and Technology. The included articles cover a wide range of possible applications—in microelectronics, transparent electronics, optoelectronics, photovoltaics and spintronics. Research papers and reviews on the basics of ALD growth are also included, reflecting a growing interest in precursor chemistry and growth

  1. Kimberlitic olivines derived from the Cr-poor and Cr-rich megacryst suites

    NASA Astrophysics Data System (ADS)

    Moore, Andy; Costin, Gelu

    2016-08-01

    Reversed-zoned olivines (Fe-richer cores compared to rims), appear to be ubiquitous in kimberlites with a wide distribution. These olivines generally comprise a subordinate population relative to the dominant normally zoned olivines. However, they are notably more abundant in the megacryst-rich mid-Cretaceous Monastery and early Proterozoic Colossus kimberlites, located on the Kaapvaal and Zimbabwe cratons, respectively. The reverse-zoned olivines at these two localities define compositional fields that are closely similar to those for two olivine megacryst populations of the Cr-poor association which have been documented in the Monastery kimberlite. This points to a genetic link between megacrysts and the reversed zoned olivines. The ubiquitous, occurrence of the Fe-rich (relative to the field for rims) olivines in kimberlites with a wide geographic distribution in turn argues for an intimate link between megacrysts and the host kimberlite. Some large olivines have inclusions of rounded Cr-rich clinopyroxenes, garnets and/or spinel, characterized by fine-scale, erratic internal compositional zoning. Olivines with such chemically heterogeneous Cr-rich inclusions are not derived from disaggregated mantle peridotites, but are rather linked to the Cr-rich megacryst suite. Consequently, they cannot be used as evidence that cores of a majority of kimberlitic olivines are derived from disaggregated mantle peridotites.

  2. Investigation on Mechanical Properties of 9%Cr/CrMoV Dissimilar Steels Welded Joint

    NASA Astrophysics Data System (ADS)

    Liu, Xia; Lu, Fenggui; Yang, Renjie; Wang, Peng; Xu, Xiaojin; Huo, Xin

    2015-04-01

    Advanced 9%Cr steel with good heat resistance and CrMoV with good toughness were chosen as candidate materials to fabricate combined rotor for steam turbine operating at over 620 °C. But the great difference in base metals properties presents a challenge in achieving sound defect-free joint with optimal properties in dissimilar welded rotor. In this paper, appropriate selection of filler metal, welding parameters, and post-weld heat treatment was combined to successfully weld 1100-mm-diameter 9%Cr/CrMoV dissimilar experimental rotor through ultra-narrow gap submerge arc welding. Some properties such as hardness, low-cycle fatigue (LCF), and high-cycle fatigue (HCF) combined with microstructural characterization qualify the integrity of the weld. Microstructural analysis indicated the presence of high-temperature tempered martensite as the phase responsible for the improved properties obtained in the weld. The Coffin-Manson parameters were obtained by fitting the data in LCF test, while the conditional fatigue strength was derived from the HCF test based on S-N curve. Analysis of hardness profile showed that the lowest value occurred at heat-affected zone adjacent to base metal which represents the appropriate location of fracture for the samples after LCF and HCF tests.

  3. Temperature Dependent Electrical Transport Properties of Ni-Cr and Co-Cr Binary Alloys

    SciTech Connect

    Thakore, B. Y.; Khambholja, S. G.; Bhatt, N. K.; Jani, A. R.; Suthar, P. H.; Gajjar, P. N.

    2011-12-12

    The temperature dependent electrical transport properties viz. electrical resistivity and thermal conductivity of Ni{sub 10}Cr{sub 90} and Co{sub 20}Cr{sub 80} alloys are computed at various temperatures. The electrical resistivity has been calculated according to Faber-Ziman model combined with Ashcroft-Langreth partial structure factors. In the present work, to include the ion-electron interaction, we have used a well tested local model potential. For exchange-correlation effects, five different forms of local field correction functions due to Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al (F) and Sarkar et al (S) are used. The present results due to S function are in good agreement with the experimental data as compared to results obtained using other four functions. The S functions satisfy compressibility sum rule in long wave length limit more accurately as compared to T, IU and F functions, which may be responsible for better agreement of results, obtained using S function. Also, present result confirms the validity of present approach in determining the transport properties of alloys like Ni-Cr and Co-Cr.

  4. Increase of Structural Phase Transition Temperature with Cr doping in Cr:VO2 Thin Films

    NASA Astrophysics Data System (ADS)

    Brown, B. L.; Lee, Mark; Clem, P.; Nordquist, C. D.; Jordan, T. S.; Wolfley, S. L.; Leonhardt, D.; Custer, J. A.

    2013-03-01

    Bulk crystal VO2 has a well-known structural phase transition near Tc = 68 °C that separates a low-temperature insulating phase from a high-temperature metallic phase with several orders-of-magnitude resistance contrast between the two phases. We report electrical and optical studies of the effect of Cr doping on the Tc in Cr:VO2 thin films. Resistivity, Hall effect, and infrared reflectivity all show that Cr doping systematically increases Tc from 50 °C up to ~ 75 °C at 11% Cr with similar transition width and hysteresis from DC to infrared, but the effect appears to saturate. At the same time, there is a modest decrease in resistance contrast. We will discuss possible effects of both carrier density and scattering changes across Tc on the resistance. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  5. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.

    1996-08-01

    Alloys of Cr-Cr{sub 2}Nb with exceptionally high strength at 1200{degrees}C have been developed. However, these compositions suffer from limited ductility and toughness at room temperature. Despite improvements from processing modifications, as-fabricated defects still limit room temperature mechanical behavior. In contrast, an alloy system with only a small mismatch of the coefficients of thermal expansion of the two phases, Cr-Cr{sub 2}Zr, showed good fabricability. However, these alloys are weaker than Cr-Cr{sub 2}Nb compositions at high temperatures and have poor oxidation resistance. Silicide coatings can provide high-temperature oxidation and sulfidation protection of these alloys. Improvements in room temperature mechanical properties of Laves-phase-strengthened alloys will rely on further development based on increasing the ductility of the matrix phase by impurity control and compositional modifications.

  6. LiCaAl/sub 6/:Cr/sup 3+/

    SciTech Connect

    Payne, S.A.; Chase, L.L.; Newkirk, H.W.; Smith, L.K.; Krupke, W.F. )

    1988-11-01

    The authors report the discovery of a new laser, LiCaAIF/sub 6/:Cr/sup 3/ (Cr/sup 3+/ :LiCAF). The intrinsic (extrapolated maximum) slope efficiency was found to be 67 percent. For comparison, they also measured the intrinsic slope efficiencies of BeAl/sub 2/O/sub 4/:Cr/sup 3+/ (alexandrite), Na/sub 3/Ga/sub 2/Li/sub 3/F/sub 12/:Cr/sup 3+/, and ScBO/sub 3/:Cr/sup 3+/, and obtained values of 65,28, and 26 percent, respectively. The tuning range of LiCaAIF/sub 6/:Cr/sup 3+/ was determined to be at least 720-840 nm. The conventional spectroscopic properties, such as the absorption, emission, and emission lifetimes as a function of temperature, are reported as well.

  7. Indigenous amino acids in primitive CR meteorites

    NASA Astrophysics Data System (ADS)

    Martins, Z.; Alexander, C. M. O. D.; Orzechowska, G. E.; Fogel, M. L.; Ehrenfreund, P.

    CR chondrites are among the most primitive meteorites. In this paper, we report the first measurements of amino acids in Antarctic CR meteorites. Three CRs, Elephant Moraine (EET) 92042, Graves Nunataks (GRA) 95229, and Grosvenor Mountains (GRO) 95577, were analyzed for their amino acid content using high-performance liquid chromatography with UV fluorescence detection (HPLC-FD) and gas chromatography-mass spectrometry (GC-MS). Our data show that EET 92042 and GRA 95229 are the most amino acid-rich chondrites ever analyzed, with total amino acid concentrations ranging from 180 ppm to 249 ppm. The most abundant amino acids present in the EET 92042 and GRA 95229 meteorites are the α-amino acids glycine, isovaline, α-aminoisobutyric acid (α-AIB), and alanine, with δ13C values ranging from +31.6‰ to +50.5‰. The carbon isotope results together with racemic enantiomeric ratios determined for most amino acids strongly indicate an extraterrestrial origin for these compounds. Compared to Elephant Moraine (EET) 92042 and GRA 95229, the more aqueously altered GRO 95577 is depleted in amino acids. In both CRs and CMs, the absolute amino acid abundances appear to be related to the degree of aqueous alteration in their parent bodies. In addition, the relative abundances of α-AIB and β-alanine in the Antarctic CRs also appear to depend on the degree of aqueous alteration.

  8. Using the Scanning Electron Microscope to Study Tracks in CR-39

    NASA Astrophysics Data System (ADS)

    Sullivan, Kyle; Roberts, Samuel; McLean, James; Padalino, Steve

    2002-10-01

    CR-39 is a plastic used for high-energy charged particle detection. When particles hit the detector, they create tracks. These tracks can be enlarged with wet-chemical etching, and are useful in determining the energy and type of incident particle. To understand the etching process beyond the capabilities of an optical microscope, a scanning electron microscope investigation was undertaken. Preparation of a CR-39 sample involved exposing it to 5.5 MeV alpha particles, etching it in 6M NaOH at 80 degrees Celsius, and applying a thin conductive layer of gold-palladium. Three main areas of study were focused upon. It was found that the diameters of tracks increased linearly as a function of how long the samples were etched. A depth profile of a track was constructed by using the parallax that occurs between normal and tilted views. Techniques for scanning an entire sample were compared to optical methods used at the Laboratory for Laser Energetics. Although higher image quality can be achieved, factors, such as total scan time, decreased its appeal as a new way to scan CR-39. Research funded in part by the United States Department of Energy

  9. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting.

    PubMed

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng-Chang; Wang, Di-Yan; Yang, Jiang; Hwang, Bing-Joe; Dai, Hongjie

    2015-10-05

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2 O3 -blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2 O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2 O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm(-2) at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. The non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.

  10. A sulfur segregation study of PWA 1480, NiCrAl, and NiAl alloys

    NASA Technical Reports Server (NTRS)

    Jayne, D. T.; Smialek, J. L.

    1993-01-01

    Some nickel based superalloys show reduced oxidation resistance from the lack of an adherent oxide layer during high temperature cyclic oxidation. The segregation of sulfur to the oxide-metal interface is believed to effect oxide adhesion, since low sulfur alloys exhibit enhanced adhesion. X ray Photoelectron Spectroscopy (XPS) was combined with an in situ sample heater to measure sulfur segregation in NiCrAl, PWA 1480, and NiAl alloys. The polished samples with a 1.5 to 2.5 nm (native) oxide were heated from 650 to 1100 C with hold times up to 6 hr. The sulfur concentration was plotted as a function of temperature versus time at temperature. One NiCrAl sulfur study was performed on the same casting used by Browning to establish a base line between previous Auger Electron Spectroscopy (AES) results and the XPS results of this study. Sulfur surface segregation was similar for PWA 1480 and NiCrAl and reached a maximum of 30 at% at 800 to 850 C. Above 900 C the sulfur surface concentration decreased to about 3 at% at 1100 C. These results are contrasted to the minimal segregation observed for low sulfur hydrogen annealed materials which exhibit improved scale adhesion.

  11. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting

    DOE PAGES

    Gong, Ming; Zhou, Wu; Kenney, Michael James; ...

    2015-08-24

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20more » mA cm–2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.« less

  12. Sintered Cr/Pt and Ni/Au ohmic contacts to B12P2

    DOE PAGES

    Frye, Clint D.; Kucheyev, Sergei O.; Edgar, James H.; ...

    2015-04-09

    With this study, icosahedral boron phosphide (B12P2) is a wide-bandgap semiconductor possessing interesting properties such as high hardness, chemical inertness, and the reported ability to self-heal from irradiation by high energy electrons. Here, the authors developed Cr/Pt and Ni/Au ohmic contacts to epitaxially grown B12P2 for materials characterization and electronic device development. Cr/Pt contacts became ohmic after annealing at 700 °C for 30 s with a specific contact resistance of 2×10–4 Ω cm2, as measured by the linear transfer length method. Ni/Au contacts were ohmic prior to any annealing, and their minimum specific contact resistance was ~l–4 × 10–4 Ωmore » cm2 after annealing over the temperature range of 500–800 °C. Rutherford backscattering spectrometry revealed a strong reaction and intermixing between Cr/Pt and B12P2 at 700 °C and a reaction layer between Ni and B12P2 thinner than ~25 nm at 500 °C.« less

  13. Histopathological evaluation of pulpotomy with Er,Cr:YSGG laser vs formocresol.

    PubMed

    Toomarian, Lida; Fekrazad, Reza; Sharifi, Davood; Baghaei, Mojdeh; Rahimi, Hessam; Eslami, Behnam

    2008-10-01

    The purpose of this study was to histologically investigate whether pulpotomy with Er,Cr:YSGG laser is an acceptable alternative for formocresol. Pulpotomy of 48 dog's primary canine teeth was performed with formocresol or Er,Cr:YSGG laser. Histological evaluations on hematoxylin and eosin-stained pulp tissues were made by an optical microscope 7 or 60 days later. Statistical analysis was performed with Fisher's exact test, Mann-Whitney U test, and Student's t test. Seven days after pulpotomy, samples treated with laser had significantly favorable histological features in the following measures: continuity of odontoblastic layer (P<0.001), presence of hemorrhage (P<0.008), amount of inflammation (P<0.002), tissue necrosis (P<0.001), internal resorption (P<0.002), level of vascularization (P<0.002), and size of abscess (P<0.041). Similar results were observed 60 days after pulpotomy, except that the differences were not mostly significant due to natural exfoliation of 16 teeth. In conclusion, Er,Cr:YSGG laser system is an acceptable alternative for formocresol in pulpotomy of deciduous teeth.

  14. Assessment of root caries removal by Er,Cr:YSGG laser

    NASA Astrophysics Data System (ADS)

    Geraldo-Martins, Vinícius R.; Marques, Márcia M.

    2007-02-01

    The present study aimed to compare root caries removal by air turbine and Er,Cr:YSGG laser, and examine morphological changes after these caries removal techniques under scanning electron microscopy (SEM). Seventy two extracted human carious-free third molars were used in this study. After the in vitro root caries induction using S. mutans, the carious lesions were removed by the conventional technique, using burs (control), and by the Er,Cr:YSGG laser, using 13 different parameters, between 1 and 4,0 W. During caries removal, preparation time was recorded for all groups. The results appointed out that the conventional method was the fastest one. When only laser treatment was evaluated, the higher parameters seemed to remove caries faster then the lower ones. SEM revealed that the surfaces treated by air turbine were smooth, but with debris. The laser groups demonstrated smooth undulations, with little or absence of smear layer, and no signs of carbonization. These results suggest that caries removal by Er,Cr:YSGG laser was effective. Therefore, this equipment requires training on cavity preparation, in order to avoid damages in dental hard tissues.

  15. HVOF sprayed WC-CoCr coatings on aluminum: tensile and tribological properties

    NASA Astrophysics Data System (ADS)

    Koutsomichalis, A.; Vardavoulias, M.; Vaxevanidis, N.

    2017-02-01

    This paper provides a comprehensive assessment of the tensile and sliding wear behaviour of WC-10Co4Cr agglomerated and sintered powder deposited on aluminum by Hyper Velocity Oxy-Fuel (HVOF) process. Microstructural analysis (SEM) identified grains of tungsten carbide (WC) in the metal matrix of the cobalt-chromium (Co-Cr). A transformation of the WC in the W2C phase was observed and decomposition of WC in the metal matrix. The HVOF WC-Co-Cr coating was found to decrease tensile strength of the aluminum substrate. Transverse cracks were observed to initiate on the coating surface, increasing rapidly with the increase in tensile strain and stopped on the coating-substrate interface causing decohesion. Tribological properties were examined using the pin-on-disk method under various loads. The friction coefficient rose abruptly at the start-up phase and stabilized at almost the same sliding distance independently of the applied load. Both the friction coefficient and the wear volume were found to increase with increasing applied load. Study of the wear mechanisms revealed surface micro-cracking and fragmentation of flattened coating layers with subsequent gradual pull out of the carbide particles.

  16. Chromium (VI) and zinc (II) waste water co-treatment by forming layered double hydroxides: mechanism discussion via two different processes and application in real plating water.

    PubMed

    Zhang, Jia; Li, Yang; Zhou, Jizhi; Chen, Dan; Qian, Guangren

    2012-02-29

    Two processes, adsorption after synthesis (AAS) and adsorption during synthesis (ADS) were compared in CrO4(2-) and Zn2+/CrO4(2-) removal. Kinetic results showed that ADS was a better method than AAS, since Cr content was 0.65/0.81 mmol/g in Cr-ADS/ZnCr-ADS, but it was only 0.37/0.56 mmol/g in Cr-AAS/ZnCr-AAS. Then, a low-cost mixture was proposed to function as ADS raw materials in treating real plating waters. This mixture first got an isothermal saturation of 1.1 mmol/g in simulated CrO4(2-) water. When Zn2+ was co-treated, it was increased to 1.3 mmol/g. At the same time, a Zn2+ removal of 1.5 mmol/g was attained. Furthermore, real plating water co-treatment reached equilibrium in 6h and obtained 1.4/0.9 mmol/g for Zn2+/CrO4(2-), respectively. According to XRD analysis, this co-treatment enhancement resulted from the formation of Zn and Cr contained layered double hydroxide.

  17. Spin densities for Ni, Pt_3Cr, and Pd_3Cr

    NASA Astrophysics Data System (ADS)

    Chau, Hung T.; Lu, Z. W.; Klein, Barry M.

    1997-03-01

    Recent ab-initio calculations^1 demonstrated that the L12 ordering in Pt_3Cr is a direct consequence of spin-polarization, i.e., magnetic moment formation in the L12 structure stabilizes it over its rival DO_22 structure (which is more stable in a non magnetic calculation). Here we present calculations of the magnetic structures of Pt_3Cr and Pd_3Cr in the L12 structure. We use fcc Ni calculations as a benchmark system since its magnetic structure has been well studied experimentally and theoretically. Our LSDA-calculated Ni magnetic structure factors are in good accord with experiment as well as with previous theoretical results. Our calculated magnetic structure factors for Pt_3Cr are in fair agreement with experiment.^2 The calculated local magnetic moment at the Pt site ( ~ 0) differs somewhat from the early experimental estimate of -0.27 μB ^2 but is, however, closer to the recent circular X-ray dichroism experimental value^3 of -0.1 μ_B. We also find that the contribution of the orbital polarization to the Pt-site local moment is negligible. We will also show magnetic structure factors of Pd_3Cr in the L12 structure, for which no experimental data are yet available for comparison. Work supported by a grant from Sandia National Laboratories ^1Z. W. Lu, B. M. Klein, A. Zunger, Phys. Rev. Lett. 75, 1320 (1995). ^2S. K. Burke, et al., J. of Magn. Magn. Mat. 15, 505 (1980). ^3H. Maruyama, et al, J. of Magn. Magn. Mat. 140, 43 (1995).

  18. Boundary layer simulator improvement

    NASA Technical Reports Server (NTRS)

    Praharaj, Sarat C.; Schmitz, Craig P.; Nouri, Joseph A.

    1989-01-01

    Boundary Layer Integral Matrix Procedure (BLIMPJ) has been identified by the propulsion community as the rigorous boundary layer program in connection with the existing JANNAF reference programs. The improvements made to BLIMPJ and described herein have potential applications in the design of the future Orbit Transfer Vehicle engines. The turbulence model is validated to include the effects of wall roughness and a way is devised to treat multiple smooth-rough surfaces. A prediction of relaminarization regions is examined as is the combined effects of wall cooling and surface roughness on relaminarization. A turbulence model to represent the effects of constant condensed phase loading is given. A procedure is described for thrust decrement calculation in thick boundary layers by coupling the T-D Kinetics Program and BLIMPJ and a way is provided for thrust loss optimization. Potential experimental studies in rocket nozzles are identified along with the required instrumentation to provide accurate measurements in support of the presented new analytical models.

  19. North Polar Layers

    NASA Technical Reports Server (NTRS)

    2004-01-01

    3 December 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an exposure of finely-detailed layers in the martian north polar region. The polar ice cap, which is made up of frozen water (whereas the south polar cap is mostly frozen carbon dioxide), is underlain by a thick sequence of layers. Some have speculated that these layers may record the history of changes in martian climate during the past few hundreds of millions of years. This picture is located near 86.0oN, 30.2oW, and covers an area approximately 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

  20. MHD turbulent mixing layers

    SciTech Connect

    Esquivel, A.; Lazarian, A.; Benjamin, R.A.; Cho, J.; Leitner, S.N.

    2005-09-28

    Turbulent mixing layers have been proposed to explain observations of line ratios of highly ionized elements in the interstellar medium. We present preliminary results of numerical simulations of turbulent mixing layers in a magnetized medium. We developed a MHD code with radiative cooling. The magnetic field is expected to be a controlling factor by suppressing instabilities that lead to the turbulent mixing. Our results suggest that the difference in turbulent mixing in the unmagnetized case as compared to the case of a weak magnetic field, {beta} = Pgas/Pmag {approx} 10, is insignificant. With a more thorough exploration of parameter space, this work will provide more reliable diagnostics of turbulent mixing layers than those available today.