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Sample records for al ca cr

  1. 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.

  2. Cr Isotopes in Allende Ca-Al-rich Inclusions

    NASA Technical Reports Server (NTRS)

    Bogdanovski, O.; Papanastassiou, D. A.; Wasserburg, G. J.

    2002-01-01

    We have determined Cr isotope compositions in minerals from Allende CAI in order to address the initial 53Mn (half-life 3.7 Ma) abundance in the solar system. Additional information is contained in the original extended abstract.

  3. Progress in the material development of LiCaAlF sub 6 :Cr sup 3+ laser crystals

    SciTech Connect

    Michelle D. Shinn.; Chase, L.L.; Caird, J.A.; Payne, S.A.; Atherton, L.J.; Kway, W.L.

    1990-03-01

    High Cr{sup 3+} doping levels, up to 8 mole percent, and low losses have been obtained with the tunable solid-state laser material LiCaAlF{sub 6}:Cr{sup 3+} (Cr:LiCAF). Measurements and calculations show that high pumping and extraction efficiencies are possible with the improved material. 13 refs., 4 figs., 1 tab.

  4. Chemical zoning and diffusion of Ca, Al, Mn, and Cr in olivine of springwater pallasite

    NASA Technical Reports Server (NTRS)

    Zhou, Y.; Steele, Ian M.

    1993-01-01

    The pallasites, consisting mainly of Fe-Ni metal and olivine, are thought to represent the interior of a planetary body which slowly cooled from high temperature. Although the olivines are nearly homogeneous, ion microprobe studies revealed variations of Ca, Ti, Co, Cr, and Ni near grain edges. These variations were thought to represent diffusion in response to falling temperature of the parent body. Pallasite cooling rates have been estimated based on kamacite taenite textures but results differ by x100. In principle elemental profiles in olivine can allow estimates of cooling rate if diffusion coefficients are known; in addition, given a cooling rate, diffusion coefficients could be derived. Data are presented which show that apparent diffusion profiles can be measured for Al, Ca, Cr, and Mn which qualitatively agree with expected diffusion rates and have the potential of providing independent estimates of pallasite cooling rates.

  5. Partition coefficients for Al, Ca, Ti, Cr, and Ni in olivine obtained by melting experiment on an LL6 chondrite

    NASA Technical Reports Server (NTRS)

    Miyamoto, M.; Mikouchi, T.; Mckay, G. A.

    1994-01-01

    We report the partition coefficients for Ca, Al, Ti, Cr, and Ni in olivine obtained through a series of melting experiments on an LL6 chondrite under varying conditions of temperature and oxygen fugacity. It is necessary to examine the variation of partition coefficients up to extremely reducing conditions in order to study meteoritic olivines. For Ca, Al, and Cr, the partition coefficients tend to decrease as temperature increases, but do not change even under extremely reducing conditions.

  6. Sulfide Capacities of CaO-MgO-Al2O3-SiO2-CrO x Slags

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Wang, Yaxian; Chou, Kuo-chih; Seetharaman, Seshadri

    2016-08-01

    The sulfide capacities of CaO-MgO-Al2O3-SiO2-CrO x slags were measured by gas-slag equilibration method in the temperature range of 1823 K to 1898 K (1550 °C to 1625 °C) to reveal the effect of CrO x on the sulfide capacities of slags. Both higher basicity and temperature enhanced sulfide capacities. The CrO x additions in the range of 0 to 5 mass pct increased the sulfide capacity, but, further increase of CrO x contents to 7 pct was found to lower the sulfide capacity. Utilizing the relationship for estimating the ratio of Cr(II)/Cr(III) put forward by the present authors, the influence of Cr(II) on the sulfide capacities of the slags studied is discussed.

  7. Synthesis and characterization of phosphates in molten systems Cs 2O-P 2O 5-CaO- MIII2O 3 ( MIII—Al, Fe, Cr)

    NASA Astrophysics Data System (ADS)

    Zatovsky, Igor V.; Strutynska, Nataliya Yu.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.; Ogorodnyk, Ivan V.; Shishkin, Oleg V.

    2011-03-01

    The crystallization of complex phosphates from the melts of Cs 2O-P 2O 5-CaO- MIII2O 3 ( MIII—Al, Fe, Cr) systems have been investigated at fixed value Cs/P molar ratios equal to 0.7, 1.0 and 1.3 and Са/Р=0.2 and Ca/ МIII=1. The fields of crystallization of CsCaP 3O 9, β-Ca 2P 2O 7, Cs 2CaP 2O 7, Cs 3CaFe(P 2O 7) 2, Ca 9MIII(PO 4) 7 ( MIII—Fe, Cr), Cs 0.63Ca 9.63Fe 0.37(PO 4) 7 and CsCa 10(PO 4) 7 were determined. Obtained phosphates were investigated using powder X-ray diffraction and FTIR spectroscopy. Novel whitlockite-related phases CsCa 10(PO 4) 7 and Cs 0.63Ca 9.63Fe 0.37(PO 4) 7 have been characterized by single crystal X-ray diffraction: space group R3c, a=10.5536(5) and 10.5221(4) Å, с=37.2283(19) and 37.2405(17) Å, respectively.

  8. Cr{sup 6+}-containing phases in the system CaO-Al{sub 2}O{sub 3}-CrO{sub 4}{sup 2-}-H{sub 2}O at 23 Degree-Sign C

    SciTech Connect

    Poellmann, Herbert

    2012-01-15

    Synthesis and investigation of lamellar calcium aluminium hydroxy salts was performed to study the incorporation of chromate ions in the interlayer of lamellar calcium aluminium hydroxy salts. Different AFm-phases (calcium aluminate hydrate with alumina, ferric oxide, mono-anion phase) containing chromate were synthesized. These AFm-phases belong to the group of layered double hydroxides (LDHs). 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaCrO{sub 4}{center_dot}nH{sub 2}O and C{sub 3}A{center_dot}1/2Ca(OH){sub 2}{center_dot}1/2CaCrO{sub 4}{center_dot}12H{sub 2}O were obtained as pure phases and their different distinct interlayer water contents and properties determined. Solid solution of chromate-containing phases and tetracalcium-aluminate-hydrate (TCAH) were studied. The uptake of chromate into TCAH from solutions was proven. Chromate contents in solution decrease to <0.2 mg/l. - Graphical abstract: Chromate can be incorporated in LDH-phases with compositions like: 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}1/2CaCrO{sub 4}{center_dot}1/2Ca(OH){sub 2}{center_dot}nH{sub 2}O, 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaCrO{sub 4}{center_dot}nH{sub 2}O, 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}1/6CaCrO{sub 4}.{center_dot}5/6Ca(OH){sub 2}{center_dot}nH{sub 2}O, 3CaO{center_dot}Al{sub 2}O{sub 3}(0-x)CaCrO{sub 4}(1-x) Ca(OH){sub 2}{center_dot}12H{sub 2}O, (0CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaCrO{sub 4}{center_dot}nH{sub 2}O and C{sub 3}A{center_dot}1/2 Ca(OH){sub 2}{center_dot}1/2 CaCrO{sub 4}{center_dot}12 H{sub 2}O are given. Black-Right-Pointing-Pointer Different hydrates of Ca-Al-hydroxysalts (LDH) with chromate-anions synthesized and characterized. Black-Right-Pointing-Pointer Interlayer exchange reaction of 2OH{sup -} and CrO{sub 4}{sup 2-} investigated. Black-Right-Pointing-Pointer Thermal dehydration and change of lattice parameters are given

  9. Cross sections for He and Ne isotopes in natural Mg, Al, and Si, He isotopes in CaF2, Ar isotopes in natural Ca, and radionuclides in natural Al, Si, Ti, Cr, and stainless steel induced by 12- to 45-MeV protons

    NASA Technical Reports Server (NTRS)

    Walton, J. R.; Heymann, D.; Yaniv, A.; Edgerley, D.; Rowe, M. W.

    1976-01-01

    Stacks of thin Mg, Al, Si, Ca, CaF2, Ti, and stainless steel foils were bombarded in twelve irradiations by a variable energy cyclotron. Cross sections are reported for He and Ne in natural Mg, Al, and Si, and for He in CaF2, and for Ar in natural Ca, as determined from mass spectrometer analysis of the inert gases. In addition, cross sections of Na-22 in natural Al and Si, of V-48 in natural Ti, and of Cr-51, Mn-52, and Co-57 in stainless steel are reported. From these were deduced Cr-51 and Mn-52 cross sections in natural Cr.

  10. Thermomechanical and thermo-optical properties of the LiCaAlF sub 6 :Cr sup 3+ laser material (US)

    SciTech Connect

    Woods, B.W.; Payne, S.A.; Marion, J.E.; Hughes, R.S.; Davis, L.E. )

    1991-05-01

    Measurements of the intrinsic thermomechanical and thermo-optical properties of the new laser material LiCaAlF{sub 6}:Cr{sup 3+} (known as Cr:LiCAF) are performed. Thermal diffusivity, heat capacity, thermal expansion, elastic constants, fracture toughness, and dispersion and temperature variation of the refractive index are all characterized for this material. In addition, the magnitude of the thermal lensing induced in a flash-lamp-pumped laser rod of Cr:LiCAF is measured and compared with the results obtained for an alexandrite laser rod in the same laser head. We find that the thermal lensing of Cr:LiCAF is favorably small and that the thermomechanical properties are expected to be adequate for applications at low and medium average power.

  11. The effect of Al2O3, CaO, Cr2O3 and MgO on devitrification of silica

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, Isidor

    1988-01-01

    The effect of doping on devitrification of vitreous silica was studied at 1100, 1200, and 1300 C. Dispersion of dopants on a molecular scale was accomplished via a sol-gel technique. All dopants accelerated the devitrification of silica but to different degrees. The most active was CaO followed by MgO, Al2O3, and Cr2O3. Pure silica and silica containing Cr2O3 and Al2O3 devitrified to alpha-cristobalite only, whereas silica doped with CaO and MgO produced alpha-quartz and alpha-cristobalite. It appears that prolonged heat treatment would cause alpha-quartz to transform to alpha-cristobalite.

  12. Crystal growth and magnetic properties of Ln-Mn-Al (Ln=Gd, Yb) compounds of the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types

    SciTech Connect

    Fulfer, Bradford W.; Haldolaarachchige, Neel; Young, David P.; Chan, Julia Y.

    2012-10-15

    We report the growth and characterization of LnMn{sub 2+x}Al{sub 10-x} (Ln=Gd, Yb) crystals adopting the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types. Single crystals of LnMn{sub 2+x}Al{sub 10-x} were synthesized via the self-flux method and characterized with single crystal X-ray diffraction. We compare LnMn{sub 2+x}Al{sub 10-x} compounds adopting the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types, and outline synthesis methods to obtain each polymorph. Magnetic susceptibility measurements show paramagnetic behavior down to 3 K for both CaCr{sub 2}Al{sub 10}- and ThMn{sub 12}-type compounds, with observed magnetic moments of 1.3{mu}{sub B} for compounds adopting the CaCr{sub 2}Al{sub 10} structure type to 4.2{mu}{sub B} for those adopting the ThMn{sub 12} structure type. Compounds of both structure type exhibit metallic resistivity, with upturns at low temperature attributed to Kondo scattering. - Graphical abstract: We report the growth and characterization of LnMn{sub 2+x}Al{sub 10-x} (Ln=Gd, Yb) crystals adopting the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types. Single crystals of LnMn{sub 2+x}Al{sub 10-x} were synthesized via the self-flux method and characterized with single crystal X-ray diffraction. We compare LnMn{sub 2+x}Al{sub 10-x} compounds adopting the CaCr{sub 2}Al{sub 10} and ThMn{sub 12} structure types, and outline synthesis methods to obtain each polymorph. Magnetic susceptibility measurements show paramagnetic behavior down to 3 K for both CaCr{sub 2}Al{sub 10}- and ThMn{sub 12}-type compounds, with observed magnetic moments of 1.3{mu}{sub B} for compounds adopting the CaCr{sub 2}Al{sub 10} structure type to 4.2{mu}{sub B} for those adopting the ThMn{sub 12} structure type. Compounds of both structure type exhibit metallic resistivity, with upturns at low temperature attributed to Kondo scattering. Highlights: Black-Right-Pointing-Pointer We have grown Ln (Mn,Al){sub 12} (Ln=Gd, Yb) single crystals of the ThMn{sub 12

  13. Lunar highland rocks - Element partitioning among minerals. II - Electron microprobe analyses of Al, P, Ca, Ti, Cr, Mn and Fe in olivine

    NASA Technical Reports Server (NTRS)

    Smith, J. V.; Hansen, E. C.; Steele, I. M.

    1980-01-01

    Lunar olivines from anorthosites, granulitic impactites, and rocks in the Mg-rich plutonic trend were subjected to electron probe measurements for Al, P, Ca, Ti, Cr and Mn, which show that the FeO/MnO ratio for lunar olivines lies between 80 and 110 with little difference among the rock types. The low values of Ca in lunar olivines indicate slow cooling to subsolidus temperatures, with blocking temperatures of about 750 C for 67667 and 1000 C for 60255,73-alpha determined by the Finnerty and Boyd (1978) experiments. An important paradox is noted in the low Ti content of Fe-rich olivines from anorthosites, although both Ti and Fe tend to become enriched in liquid during fractional distillation. Except for Ca and Mn, olivine from anorthosites has lower minor element values than other rock types. Formation from a chemically distinct system is therefore implied.

  14. Ehimeite, NaCa2Mg4CrSi6Al2O22(OH)2: The first Cr-dominant amphibole from the Akaishi Mine, Higashi-Akaishi Mountain, Ehime Prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Nishio-Hamane, Daisuke; Ohnishi, Masayuki; Minakawa, Tetsuo; Yamaura, Jun-Ichi; Saito, Shohei; Kadota, Ryo

    The first Cr-dominant amphibole, ehimeite, ideally NaCa2Mg4CrSi6Al2O22(OH)2, has been found in a chromitite deposit in the Akaishi Mine, Higashi-Akaishi Mountain, Ehime Prefecture, Japan. Ehimeite occurs as prismatic crystals of up to 1.5 cm in length and 0.5 cm in width and is found in association with chromite, kämmererite (Cr-rich clinochlore), Cr-poor clinochlore, phlogopite, and uvarovite. It is transparent, emerald green to pale green in color with pale green streaks, and has a vitreous luster. Optically, it is biaxial positive with α = 1.644(2), β = 1.647(2), γ = 1.659(2), and 2Vcalc. = 53°. It has a Mohs’ hardness of 6 and densities of 3.08(3) g/cm3 (measured using heavy liquids) and 3.121 g/cm3 (calculated from powder diffraction data and the empirical formula). The empirical formula is (Na0.88K0.07)Σ0.95(Ca1.89Na0.02Mg0.09)Σ2.00(Mg4.03Cr0.62Al0.19Fe3+0.07Fe2+0.07Ti0.03)Σ5.00(Si6.14Al1.86)Σ8.00O22(OH)2 on the basis of O = 22 and OH = 2, and ehimeite mainly forms a solid solution, NaCa2Mg4(Cr, Al)Si6Al2O22(OH)2, with pargasite. It has a monoclinic unit cell with a = 9.9176(14) Å, b = 18.0009(12) Å, c = 5.2850(7) Å, β = 105.400(7)°, V = 909.6 (17) Å3, and Z = 2, and it belongs to the space group C2/m, as refined from powder XRD data. The eight strongest lines in the powder XRD pattern [d (Å), I/I0, hkl] are (3.370, 58, 150), (2.932, 43, 221), (2.697, 81, 151), (2.585, 50, 061), (2.546, 100, 202), (2.346, 42, 351), (2.156, 35, 261), and (1.514, 55, 263). The crystal structure has been refined to R1 = 0.0488 using single-crystal XRD data. It has been concluded that ehimeite in the Akaishi Mine was formed by the reaction of chromitite and the metamorphic fluid in the retrograde stage of serpentinization during the Sanbagawa metamorphism.

  15. Synthesis, characterization of double perovskite Ca{sub 2}MSbO{sub 6} (M = Dy, Fe, Cr, Al) materials via sol–gel auto-combustion and their catalytic properties

    SciTech Connect

    Feraru, S.; Samoila, P.; Borhan, A.I.; Ignat, M.; Iordan, A.R.; Palamaru, M.N.

    2013-10-15

    Double perovskite-type oxide Ca{sub 2}MSbO{sub 6} materials, where M = Dy, Fe, Cr, and Al, were prepared by using the sol–gel auto-combustion method. The role of different B-site cations on their synthesis, structures, morphologies and catalytic properties was investigated. The progress of double-perovskite type structure formation and the disappearance of the organic phases were monitored by infrared absorption spectroscopy (FTIR). Double perovskite oxide structures were evaluated using X-ray diffraction (XRD), while the microstructure of obtained compounds was studied using scanning electron microscopy (SEM). Also, BET surface areas were measured at the liquid nitrogen temperature by nitrogen adsorption. Catalytic properties of the obtained compounds were evaluated by test reaction of hydrogen peroxide decomposition. - Highlights: • Ca{sub 2}MSbO{sub 6} double perovskites were obtained by sol–gel auto-combustion method. • Ca{sub 2}MSbO{sub 6} (M = Dy, Fe, Cr and Al) as catalysts in H{sub 2}O{sub 2} decomposition • Strong relationship between particles' shape, BET area and catalytic performance • Ca{sub 2}FeSbO{sub 6} spherical grains show superior catalytic activity.

  16. Raman Structure Investigations of CaO-MgO-Al2O3-SiO2-CrO x and Its Correlation with Sulfide Capacity

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Wang, Yaxian; Wang, Qi; Chou, Kuochih

    2016-02-01

    The structures of the Cr-containing slags were analyzed by Raman spectroscopy. The results obtained show that when the Cr contents increased from 0 to 5 pct, the depolymerization degree of the silicate matrix is increased. However, increasing Cr content to 7 pct caused the depolymerization degree to decrease. The spectral results are consistent with the results of sulfide capacity measurements. And the relationship between average bridging oxygen and sulfide capacities (logCS) was discussed accordingly.

  17. Bulk modulus and specific heat of B-site doped (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B=Fe, Cr, Ru, Al, Ga)

    NASA Astrophysics Data System (ADS)

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2014-04-01

    Specific heat (Cp) thermal expansion (α) and Bulk modulus (BT) of lightly doped Rare Earth manganites (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B3+ = Fe3+,Cr3+,Ga3+,Al3+,Ru4+); (0.3Ca0.35Mn0.97Fe0.03O3 as a function of temperature (10K≤T≤ 200K) is found to be in agreement with the published data. The trend of variation of Debye temperature with B-site cationic radius is predicted probably for the first time for the B-site doped rare earth manganites.

  18. Anodic reactions in the Ca/CaCrO/sub 4/ thermal battery

    SciTech Connect

    Guidotti, R.A.; Reinhardt, F.W.

    1985-09-01

    The reaction of Ca with a CaCrO/sub 4/-(LiCl-KCl eutectic) solution at temperatures of 400/sup 0/C to 500/sup 0/C was studied to better understand the nature of the chemical reactions and electrochemical processes that occur in the Ca/CaCrO/sub 4/ thermal battery at the anode during activation and discharge. Limited tests also were conducted with a CaCrO/sub 4/-(CaCl/sub 2/-NaCl-KCl eutectic) solution at 550/sup 0/C. Ca/CaCrO/sub 4/ and CaLi/sub 2//CaCrO/sub 4/ single cells were tested to observe the relative performance differences of Ca and CaLi/sub 2/ anodes. The discharged cells were analyzed by optical microscopy, electron microprobe, Auger electron spectroscopy, and secondary-ion mass spectroscopy. These analytical data were used in conjunction with the results of chemical-reaction experiments to propose a discharge mechanism for the Ca/CaCrO/sub 4/ thermal battery, consistent with experimental observations.

  19. Anodic reactions in the Ca/CaCrO4 thermal battery

    NASA Astrophysics Data System (ADS)

    Guidotti, R. A.; Reinhardt, F. W.

    1985-09-01

    The reaction of Ca with a CaCrO4-(LiCl-KCl eutectic) solution at temperatures of 400(0)C to 500(0)C was studied to better understand the nature of the chemical reactions and electrochemical processes that occur in the Ca/CaCrO4 thermal battery at the anode during activation and discharge. Limited tests also were conducted with a CaCrO4-(CaCl2-NaCl-KCl eutectic) solution at 550(0)C. Ca/CaCrO4 and CaLi2/CaCrO4 single cells were tested to observe the relative performance differences of Ca and CaLi2 anodes. The discharged cells were analyzed by optical microscopy, electron microprobe, Auger electron spectroscopy, and secondary-ion mass spectroscopy. These analytical data were used in conjunction with the results of chemical-reaction experiments to propose a discharge mechanism for the Ca/CaCrO4 thermal battery, consistent with experimental observations.

  20. Reaction diffusion in the NiCrAl and CoCrAl systems

    NASA Technical Reports Server (NTRS)

    Levine, S. R.

    1978-01-01

    The paper assesses the effect of overlay coating and substrate composition on the kinetics of coating depletion by interdiffusion. This is accomplished by examining the constitution, kinetics and activation energies for a series of diffusion couples primarily of the NiCrAl/Ni-10Cr or CoCrAl/Ni-10Cr type annealed at temperatures in the range 1000-1205 C for times up to 500 hr. A general procedure is developed for analyzing diffusion in multicomponent multiphase systems. It is shown that by introducing the concept of beta-source strength, which can be determined from appropriate phase diagrams, the Wagner solution for consumption of a second phase in a semiinfinite couple is successfully applied to the analysis of MCrAl couples. Thus, correlation of beta-recession rate constants with couple composition, total and diffusional activation energies, and interdiffusion coefficients are determined.

  1. Melting in the system CaO-MgO-Al2O3-SiO2-FeO-Cr2O3 spanning the plagioclase-spinel lherzolite transition at 7 to 10 kbar: experiments versus thermodynamics

    NASA Astrophysics Data System (ADS)

    Keshav, S.; Tirone, M.; Gudfinnsson, G.; Presnall, D.

    2008-12-01

    Voluminous basaltic magmas erupt at mid-oceanic ridges (mid-ocean ridge basalts, MORB) as a consequence of mantle upwelling and melting beneath spreading plates. However, because the geochemistry of MORB is distinct from OIB (ocean-island basalts), both have great petrogenetic significance and carry important information about the chemical and physical properties/dynamics of the mantle. In the context of MORB, a critical yet unresolved question is how phase transitions within a polybaric melting zone affect melt productivity and thereby, possibly exert control on major and trace element composition of erupted magmas. Currently, the disagreements on these issues are fundamental, with great consequences that extend beyond petrology to global issues of potential temperatures, mantle melting, mantle heterogeneity, and mantle dynamics. Thermodynamics show that melt productivity depends critically on the transition reaction, and melting can in principle increase, decrease, or even stop at a transition. Phase equilibrium work from both systems CaO-MgO-Al2O3-SiO2-Na2O (CMASN) and CMAS-FeO (CMASF) have been used to argue that melt productivity may increase at the plagioclase-spinel (pl-sp) transition because the univariant solidus transition reaction has a positive dT/dP slope in these systems, moving to higher pressure relative to the CMAS system. However, melting models derived on the basis of MELTS and pMELTS show that the solidus has a negative slope on the pl-sp transition. If correct, this would cause suppression of melting as the mantle decompresses along a pertinent adiabat. Owing to these vast discrepancies between experiments and thermodynamics and to further clarify MORB genesis, in this work we present melting phase relations in the system CMASFCr at the plagioclase-spinel lherzolite transition from 7 to 10 kbar. Cr was chosen since recent work has shown that the addition of Cr to CMAS has an unusually large effect on Ca/Al of melt compositions at 1.1 GPa. With

  2. Creep and Toughness of Cryomilled NiAl Containing Cr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Aikin, Beverly; Salem, Jon

    2000-01-01

    NiAl-AlN + Cr composites were produced by blending cryomilled NiAl powder with approx. 10 vol % Cr flakes. In comparison to the as-consolidated matrices, hot isostatically pressed Cr-modified materials did not demonstrate any significant improvement in toughness. Hot extruded NiAl-AlN+10.5Cr, however, possessed a toughness twice that determine for the base NiAl-AlN alloy. Measurement of the 1200 to 1400 K plastic flow properties revealed that the strength of the composites was completely controlled by the properties of the NiAl-AlN matrices. This behavior could be successfully modeled by the Rule-of-Mixtures, where load is shed from the weak Cr to the strong matrix.

  3. Characterization of materials for Ca/CaCrO4 thermal batteries

    NASA Astrophysics Data System (ADS)

    Guidotti, R. A.; Reinhardt, F. W.; Poole, R. L.

    The performance of pelletized Ca/CaCrO4 thermal batteries is known to be sensitive to processing of the catholyte or DEB mix, which consists of CaCrO4 depolarized(D), KCl-LiCl eutectic electrolyte(E), and SiO2 binder(B). The chemical composition of the DEB mix affects the electrochemical behavior. Little work has been reported, however, for the characterization of DEB mixes in relation to their performance in Ca/CaCrO4 thermal batteries. Considerable variability of battery performance has also been observed when different lots of sheet calcium are used with the same DEB. The causes for this behavior remain elusive. In an effort to resolve these discrepancies in materials behavior, a study was carried out to characterize DEB powders and pellets and, to a lesser extent, sheet calcium with the primary objective of correlating observed battery performance to easily measured physical and chemical properties.

  4. Characterization of cathodic corrosion products in the Ca/CaCrO/sub 4/ thermal battery

    SciTech Connect

    Guidotti, R.A.; Reinhardt, F.W.; Venturini, E.L.; Rogers, J.W. Jr.; Cathey, W.N.

    1985-05-01

    Using thermal analysis techniques, we investigated the corrosion process resulting from the reaction of iron, nickel, and stainless steel (used as current collectors in Ca/CaCrO/sub 4/ thermal batteries) with CaCrO/sub 4/ dissolved in LiCl-KCl eutectic. The reaction product for iron was synthesized in bulk external to the battery and was characterized by chemical analysis, X-ray diffraction, Moessbauer spectroscopy, X-ray photoelectron spectroscopy, static magnetization, and electrical conductivity. This characterization provides a better understanding of the cathodic corrosion processes that occur in the Ca/CaCrO/sub 4/ thermal battery, and how the properties of the reaction layer at the catholyte-current collector interface influence battery performance.

  5. Characterization of cathodic corrosion products in the Ca/CaCrO4 thermal battery

    NASA Astrophysics Data System (ADS)

    Guidotti, R. A.; Reinhardt, F. W.; Venturini, E. L.; Rogers, J. W., Jr.; Cathey, W. N.

    1985-05-01

    Using thermal analysis techniques, the corrosion process resulting from the reaction of iron, nickel, and stainless steel (used as current collectors in Ca/CaCrO4 thermal batteries) with CaCrO4 dissolved in LiCl-KCl eutectic was investigated. The reaction product for iron was synthesized in bulk external to the battery and was characterized by chemical analysis, X-ray diffraction, Moessbauer spectroscopy, X-ray photoelectron spectroscopy, static magnetization, and electrical conductivity. This characterization provides a better understanding of the cathodic corrosion processes that occur in the Ca/CaCrO4 thermal battery, and how the properties of the reaction layer at the catholyte-current collector interface influence battery performance.

  6. Cr-Al Diffusion in Chromite Spinel at High Pressure

    NASA Astrophysics Data System (ADS)

    Suzuki, A.; Yasuda, A.; Ozawa, K.

    2005-12-01

    Compositional zoning in chromite spinel gives us important information to constrain thermal and deformation history of ultramafic-mafic rocks. For the quantitative estimation, diffusivity of elements in spinel is a critical parameter. Although the Mg-Fe2+ interdiffusion coefficient in MgAl2O4 spinel has experimentally studied by Freer & O'Reilly (1980) and Liemann & Ganguly (2002), Cr-Al interdiffusion coefficient has not been determined yet. In this study, we have experimentally determined Cr-Al interdiffusion coefficient in chromite spinel at temperatures ranging 1400-1700 °C and pressures ranging 3-7 GPa, by using diffusion couple of natural single crystals of spinel and chromite. Experiments were carried out with a multi-anvil type (MA-8 type) high-pressure apparatus at the Earthquake Research Institute, University of Tokyo. After experiments, the samples were cut perpendicular to the contact plane and analyzed with EPMA and EBSD. The elemental mapping showed that Cr, Al, Fe3+, Fe2+, and Mg diffused perpendicular to the contact plane. The Cr-Al diffusion profiles are complementary with each other and asymmetric with steeper profile in the spinel side suggesting a compositional dependence of Cr-Al diffusion in spinel. The Cr-Al interdiffusion coefficient was estimated by the Boltzmann-Matano method. The coefficient decreases with Cr# (=Cr/(Cr+Al)) of spinel, which varies more than one order of magnitude as the Cr# changes from 0.1 to 0.85 at 3 GPa and 1600 °C. It is concluded that the self-diffusion coefficient of Al is more than one order of magnitude larger than that of Cr. The Cr-Al interdiffusion coefficient is expressed by D=D0exp(-Q/RT), where D0=2.8×10-2 m2/s and Q=498 kJ/mol at Cr#=0.2. This relation is applicable up to Cr#=0.5. Extrapolation of the self-diffusion coefficient of Cr to the lower temperature shows that Cr is the slowest diffusion species in chromite spinel including oxygen. This extremely slow Cr self-diffusion is consistent with the Cr-Al

  7. Preparation of Al-Cr-Fe Coatings by Heat Treatment of Electrodeposited Cr/Al Composite Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Chen, Chang'an; Zhang, Guikai; Rao, Yongchu; Ling, Guoping

    Al-Cr-Fe coatings have been widely used in the surface engineering field of materials, due to their excellent corrosion resistance to water vapor and fused salt deposits. In this study, a new two-step approach was developed to prepare Al-Cr-Fe coatings on surfaces of SUS430 stainless steels. First, the Cr/Al composite coatings were prepared by electrodepositing Cr from aqueous solution then electrodepositing Al from AlCl3-1-ethyl-3-methyl-imidazolium chloride (AlCl3-EMIC) ionic liquid on SUS430 stainless steel substrate. In the second, heat treatment of the Cr/Al composite coatings was carried out to acquire Al-Cr-Fe coatings. Effects of the thickness of Cr/Al composite coatings, the time and temperature of heat treatment on composition and phase structure of alloy layers were studied by using scanning electron microscope (SEM), backscattered electron (BSE), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The structure transformation process and formation mechanism of Al-Cr-Fe coatings were discussed.

  8. High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

    NASA Astrophysics Data System (ADS)

    Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

    2016-04-01

    In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

  9. 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.

  10. Oxidation of Fe-Cr-Al and Fe-Cr-Al-Y Single Crystals

    NASA Astrophysics Data System (ADS)

    Grabke, H. J.; Siegers, M.; Tolpygo, V. K.

    1995-03-01

    Single crystal samples of the alloy Fe-20%Cr-5%Al with and without Y-doping were used to study the "reactive element" (RE) effect, which causes improved oxidation behaviour and formation of a protective Al2O3 layer on this alloy. The oxidation was followed by AES at 10-7 mbar O2 up to about 1000 °C. Most observations were peculiar for this low pO2 environment, but yttrium clearly favors the formation of Al-oxide and stabilizes it also under these conditions, probably by favoring its nucleation. The oxides formed are surface compounds of about monolayer thickness, not clearly related to bulk oxides. Furthermore, the morphologies of oxide scales were investigated by SEM, after oxidation at 1000°C for 100 h at 133 mbar O2. On Fe-Cr-Al the scale is strongly convoluted and tends to spalling, whereas the presence of Y leads to flat scales which are well adherent. This difference is explained by a change in growth mechanism. The tendency for separation of oxide and metal was highest for the samples with low energy metal surface, i.e. (100) and (110), the scale was better adherent on the (111) oriented surface and on the polycrystalline specimen, since in the latter cases the overall energy for scale/metal separation is higher. All observations, from the low and from the high pO2 experiments, are discussed in relation to the approximately ten mechanisms proposed in the literature for explanation of the RE effects.

  11. Ti-Cr-Al-O Thin Film Resistors

    SciTech Connect

    Jankowski, A F; Hayes, J P

    2002-03-21

    Thin films of Ti-Cr-Al-O are produced for use as an electrical resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O{sub 2}. Vertical resistivity values from 10{sup 4} to 10{sup 10} Ohm-cm are measured for Ti-Cr-Al-O films. The film resistivity can be design selected through control of the target composition and the deposition parameters. The Ti-Cr-Al-O thin film resistor is found to be thermally stable unlike other metal-oxide films.

  12. Synthesis and characterization of phosphates in molten systems Cs{sub 2}O-P{sub 2}O{sub 5}-CaO-M{sup III}{sub 2}O{sub 3} (M{sup III}-Al, Fe, Cr)

    SciTech Connect

    Zatovsky, Igor V.; Strutynska, Nataliya Yu.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.; Ogorodnyk, Ivan V.; Shishkin, Oleg V.

    2011-03-15

    The crystallization of complex phosphates from the melts of Cs{sub 2}O-P{sub 2}O{sub 5}-CaO-M{sup III}{sub 2}O{sub 3} (M{sup III}-Al, Fe, Cr) systems have been investigated at fixed value Cs/P molar ratios equal to 0.7, 1.0 and 1.3 and Sa/P=0.2 and Ca/M{sup III}=1. The fields of crystallization of CsCaP{sub 3}O{sub 9}, {beta}-Ca{sub 2}P{sub 2}O{sub 7}, Cs{sub 2}CaP{sub 2}O{sub 7}, Cs{sub 3}CaFe(P{sub 2}O{sub 7}){sub 2}, Ca{sub 9}M{sup III}(PO{sub 4}){sub 7} (M{sup III}-Fe, Cr), Cs{sub 0.63}Ca{sub 9.63}Fe{sub 0.37}(PO{sub 4}){sub 7} and CsCa{sub 10}(PO{sub 4}){sub 7} were determined. Obtained phosphates were investigated using powder X-ray diffraction and FTIR spectroscopy. Novel whitlockite-related phases CsCa{sub 10}(PO{sub 4}){sub 7} and Cs{sub 0.63}Ca{sub 9.63}Fe{sub 0.37}(PO{sub 4}){sub 7} have been characterized by single crystal X-ray diffraction: space group R3c, a=10.5536(5) and 10.5221(4) A, c=37.2283(19) and 37.2405(17) A, respectively. -- Graphical Abstract: Structural relationships between {beta}-Ca{sub 3}(PO{sub 4}){sub 2} and synthesized compounds is shown in terms aliovalent substitution of calcium atoms, which residue on three-fold axis, by other metals in {beta}-Ca{sub 3}(PO{sub 4}){sub 2} framework. Display Omitted Research highlights: {yields} Phase formation in the melts of Cs{sub 2}O-P{sub 2}O{sub 5}-CaO-M{sup III}{sub 2}O{sub 3} (M{sup III}-Al, Fe, Cr) systems were determined. {yields} The composition and structure of the compounds depend on the nature of M{sup III} and initial ratio of Cs/P. {yields} Obtained compounds have been characterized by powder X-ray diffraction and FTIR spectroscopy. {yields} Crystal structures of CsCa{sub 10}(PO{sub 4}){sub 7} and Cs{sub 0.63}Ca{sub 9.63}Fe{sub 0.37}(PO{sub 4}){sub 7} were determined by single crystal XRD.

  13. Characterization of materials for Ca/CaCrO/sub 4/ thermal batteries

    SciTech Connect

    Guidotti, R.A.; Reinhardt, F.W.; Poole, R.L.

    1982-01-01

    The performance of pelletized Ca/CaCrO/sub 4/ thermal batteries is known to be sensitive to processing of the catholyte or DEB mix, which consists of CaCrO/sub 4/ depolarizer(D), KCl-LiCl eutectic electrolyte(E), and SiO/sub 2/ binder(B). The chemical composition of the DEB mix affects the electrochemical behavior. Little work has been reported, however, for the characterization of DEB mixes in relation to their performance in Ca/CaCrO/sub 4/ thermal batteries. Considerable variability of battery performance has also been observed when different lots of sheet calcium are used with the same DEB. The causes for this behavior remain elusive. In an effort to resolve these discrepancies in materials behavior, a study was carried out to characterize DEB powders and pellets and, to a lesser extent, sheet calcium, with the primary objective of correlating observed battery performance to easily measured physical and chemical properties. A secondary objective was to examine the suitability of such techniques for process control and quality assurance during battery production. Results are presented and discussed.

  14. Development and quality assessments of commercial heat production of ATF FeCrAl tubes

    SciTech Connect

    Yamamoto, Yukinori

    2015-09-01

    Development and quality assessment of the 2nd generation ATF FeCrAl tube production with commercial manufacturers were conducted. The manufacturing partners include Sophisticated Alloys, Inc. (SAI), Butler, PA for FeCrAl alloy casting via vacuum induction melting, Oak Ridge National Laboratory (ORNL) for extrusion process to prepare the master bars/tubes to be tube-drawn, and Rhenium Alloys, Inc. (RAI), North Ridgeville, OH, for tube-drawing process. The masters bars have also been provided to Los Alamos National Laboratory (LANL) who works with Century Tubes, Inc., (CTI), San Diego, CA, as parallel tube production effort under the current program.

  15. 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.

  16. Fretting Wear of Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2001-01-01

    An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296-823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473-823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals. Keywords

  17. Experimental Studies on the Sulfide Capacities of CaO-SiO2-CrOx Slags

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Seetharaman, Seshadri

    2010-04-01

    To understand the desulfurization process during the refining of Cr-containing steel grades, this work was initiated to study the reactions between Cr-sulfur and chromium-containing slags. The sulfide capacities of CaO-SiO2-CrOx pseudo-ternary slags were measured using the traditional gas-slag equilibration technique between 1823 K and 1923 K. Sixteen different slag compositions were examined, and two different equilibrium oxygen partial pressures were used to understand the impact of the varying valence of Cr on the sulfide capacities. The results showed that log10 Cs varied linearly with the reciprocal T, and the slope was higher than the corresponding value reported for the binary CaO-SiO2 of corresponding composition. It was difficult to isolate the relative effects of the bi- and trivalent Cr in the slags because the Cr2+/Cr3+ ratio was influenced by the basicity of the slag. By using the equation developed by these authors earlier that related Cr2+/Cr3+ with basicity, oxygen partial pressure, and temperature, it was possible to obtain an approximate trend of the CrO effect on the sulfide capacities; viz. the sulfide shows a decreasing trend as Cr2+ replaces Ca2+ in the slag. With a continued increase of Cr2+ content, indications of the occurrence of a minimum point were observed; beyond which the sulfide capacities showed a slight increasing trend. The latter was attributed, based on slag-structure analysis by Gaskell et al., to the increasing extent of the polymerization reaction releasing oxygen ions for sulfide reactions.

  18. Aluminum and silicon diffusion in Fe-Cr-Al alloys

    SciTech Connect

    Heesemann, A.; Schmidtke, E.; Faupel, F.; Kolb-Telieps, A.; Kloewer, J.

    1999-02-05

    Foils of Fe-Cr-Al alloys containing about 20 wt% Cr, 5 wt% Al and additions of Si and reactive elements like Ce, La, Y, Hf, Zr or Ti are widely used as a substrate in metal-supported automotive catalytic converters. In the present paper the authors report on measurements of Al and Si diffusion in Fe-Cr-Al alloys. Due to a lack of suitable radiotracers concentration profiles were obtained by means of electron microprobe analysis. In connection with data evaluation they present numerical calculations assessing the accuracy of the Matano analysis and the thin-film solution of Fick`s 2nd law as function of the thickness of the initial diffusant layer. The results are of general interest, particularly for the evaluation of diffusion measurements involving industrial specimens with given geometry.

  19. Influence of FeCrAl Content on Microstructure and Bonding Strength of Plasma-Sprayed FeCrAl/Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Luo, Fa; Zhou, Wancheng; Zhu, Dongmei

    2016-02-01

    Low-power plasma-sprayed FeCrAl/Al2O3 composite coatings with 1.5 mm thickness have been fabricated for radar absorption applications. The effects of FeCrAl content on the coating properties were studied. The FeCrAl presents in the form of a few thin lamellae and numerous particles, demonstrating relatively even distribution in all the coatings. Results show that the micro-hardness and porosity decrease with the increase in FeCrAl content. With FeCrAl content increasing from 28 to 47 wt.%, the bonding strength of the coatings with 1.5 mm thickness increases from 10.5 to 27 MPa, and the failure modes are composed of cohesive and adhesive failure, which are ascribed to the coating microstructure and the residual stress, respectively.

  20. Spectroscopic analysis of the open 3d subshell transition metal aluminides: AlV, AlCr, and AlCo

    NASA Astrophysics Data System (ADS)

    Behm, Jane M.; Brugh, Dale J.; Morse, Michael D.

    1994-10-01

    Three open 3d subshell transition metal aluminides, AlV, AlCr, and AlCo, have been investigated by resonant two-photon ionization spectroscopy to elucidate the chemical bonding in these diatomic molecules. The open nature of the 3d subshell results in a vast number of excited electronic states in these species, allowing bond strengths to be measured by the observation of abrupt predissociation thresholds in a congested optical spectrum, giving D00(AlV)=1.489±0.010 eV, D00(AlCr)=2.272±0.009 eV, and D00(AlCo)=1.844±0.002 eV. At lower excitation energies the presence of discrete transitions has permitted determinations of the ground state symmetries and bond lengths of AlV and AlCo through rotationally resolved studies, giving r0` (AlV, Ω`=0)=2.620±0.004 Å and r0` (AlCo, Ω`=3)=2.3833±0.0005 Å. Ionization energies were also measured for all three species, yielding IE(AlV)=6.01±0.10 eV, IE(AlCr)=5.96±0.04 eV, and IE(AlCo)=6.99±0.17 eV. A discussion of these results is presented in the context of previous work on AlCu, AlNi, AlCa, and AlZn.

  1. Phase diagram and unusual magnetic excitations in distorted triangular lattice antiferromagnet α- CaCr204

    NASA Astrophysics Data System (ADS)

    Ducatman, Samuel; Perkins, Natalia

    2013-03-01

    While it is well known that the ground state of the isotropic Heisenberg model on a triangular lattice is the so called 120° structure, its appearance on the distorted triangular lattice is rather unusual. This case has been recently observed in the distorted triangular lattice antiferromagnet α-CaCr2O4 [S. Toth et al, PRB 84, 054452 (2011)] which shows the onset of the 120° long-range magnetic order below TN = 42 . 6 K . Recent neutron scattering experiments also revealed that this compound has unusual magnetic excitations with a dispersion with roton-like minima at momenta different from those corresponding to its 120°-magnetic order [S. Toth et al, PRL 109, 127203 (2012)]. Motivated by these experimental findings, we calculate a magnetic phase diagram and excitation spectrum of anisotropic Heisenberg Hamiltonian on triangular lattice. We showed that at the parameters characterizing α-CaCr2O4 compound, the ground state is indeed the 120°-structure, however, other possible magnetic orderings are very close in energy. We compute the dispersion of magnetic excitations to order 1/S and compare it with the neutron scattering data. supported by the grant NSF-DMR-0844115

  2. Hydrogen permeation characteristics of some Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Van Deventer, E. H.; Maroni, V. A.

    1983-01-01

    Hydrogen permeation data are reported for two Fe-Cr-Al alloys, Type-405 SS (Cr 14-A1 0.2) and a member of the Fecralloy family of alloys (Cr 16-A1 5). The hydrogen permeability of each alloy (in a partially oxidized condition) was measured over a period of several weeks at randomly selected temperatures (between 150 and 850°C) and upstream H 2 pressures (between 2 and 1.5 × 10 4 Pa). The permeabilities showed considerable scatter with both time and temperature and were 10 2 to 10 3 times lower than those of pure iron, even in strongly reducing environments. The exponent, n, for the relationship between upstream H 2 pressure, P, and permeability, φ, ( φ ~ Pn) was closer to 0.7 than to the expected 0.5, indicating a process limited by surface effects (e.g., surface oxide films) as opposed to bulk material effects. Comparison of these results with prior permeation measurements on other Fe-Cr-Al alloys, on Fe-Cr alloys, and on pure iron shows that the presence of a few weight percent aluminum offers the best prospects for achieving low tritium permeabilities with martensitic and ferritic steels used in fusion-reactor first wall and blanket applications.

  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 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.

  4. Cr, Mn, and Ca distributions for olivine in angritic systems: Constraints on the origins of Cr-rich and Ca-poor core olivine in angrite LEW87051

    NASA Technical Reports Server (NTRS)

    Mikouchi, T.; Mckay, G.; Le, L.

    1994-01-01

    Angrite meteorites are a type of basaltic achondrites that are noted for their very old cyrstallization ages (4.55 b.y.) and unusual chemical and mineralogical properties. In spite of great interest, only four angrites have been found. LEW87051 is the smallest one which weighs 0.6 g. It is a porphyritic rock with coarse subhedral to euhedral olivines set in a fine-grained groundmass which clearly represents a crystallized melt. The largest uncertainty about the petrogenesis of LEW87051 is the relationship between the large olivine crystals and the groundmass. Prinz et al. suggests that olivines are xenocrysts, while McKay et al. proposed a fractional cyrstallization model based on experimental studies. However, the crystals have Cr-rich and Ca-poor cores which do not match experimental olivines. Although Jurewicz and McKay tried to explaine the zoning of the rim by diffusion, some features are not explained. There also exists a definite composition boundary of Fe(2+) and MnO between the core and the rim. To clarify the origin of these olivines, we have performed experiments using LEW87051 analogs to measure the effects of oxygen fugacity on distribution coefficients of various elements in an angritic system.

  5. Bulk modulus and specific heat of B-site doped (La{sub 0.3}Pr{sub 0.7}){sub 0.65}Ca{sub 0.35}Mn{sub 1−x}B{sub x}O{sub 3} (B=Fe, Cr, Ru, Al, Ga)

    SciTech Connect

    Srivastava, Archana; Thakur, Rasna; Gaur, N. K.

    2014-04-24

    Specific heat (C{sub p}) thermal expansion (α) and Bulk modulus (B{sub T}) of lightly doped Rare Earth manganites (La{sub 0.3}Pr{sub 0.7}){sub 0.65}Ca{sub 0.35}Mn{sub 1−x}B{sub x}O{sub 3} (B{sup 3+} = Fe{sup 3+},Cr{sup 3+},Ga{sup 3+},Al{sup 3+},Ru4+); (0.3Ca{sub 0.35}Mn{sub 0.97}Fe{sub 0.03}O{sub 3} as a function of temperature (10K≤T≤ 200K) is found to be in agreement with the published data. The trend of variation of Debye temperature with B-site cationic radius is predicted probably for the first time for the B-site doped rare earth manganites.

  6. The structure of rapidly solidified Al- Fe- Cr alloys

    NASA Astrophysics Data System (ADS)

    Yearim, R.; Shechtman, D.

    1982-11-01

    Four aluminum alloys, designed for use at elevated temperatures, were studied. The alloys were supersaturated with iron and chromium, and one of them contained small amounts of Ti, V, and Zr. The starting materials were alloy powders made by the RSR (Rapid Solidification Rate) centrifugal atomization process. Extrusion bars were made from the four powders. The as-extruded microstructure and the microstructure of the alloys after annealing at 482 °C were investigated by optical and transmission electron microscopy and by X-ray diffraction. The microstructure consists of equiaxed grains of aluminum matrix and two types of precipitates, namely, Al3(Fe ,Cr) and a metastable phase, Al6(Fe,Cr). The precipitates were different in their shape, size, distribution, and location within the grains.

  7. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  8. Observations of Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report 5-(sigma) tangent column detections of Al and Fe, and strict 3-(sigma) tangent column upper limits for Ca(+) in Mercury's exosphere obtained using the HIRES spectrometer on the Keck I telescope. These are the first direct detections of Al and Fe in Mercury's exosphere. Our Ca(-) observation is consistent with that reported by The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft.

  9. 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.

  10. Magnetic properties of EuCr2Al20

    NASA Astrophysics Data System (ADS)

    Swatek, Przemysław; Kaczorowski, Dariusz

    2016-10-01

    Polycrystalline sample of EuCr2Al20 was studied by means of x-ray powder diffraction, magnetization, electrical resistivity and heat capacity measurements. The compound was found to order antiferromagnetically at TN = 4.8 K due to the magnetic moments carried on divalent of Eu ions. The experimental findings are supported by the results of ab-initio band structure calculations.

  11. Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

    1998-01-01

    A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

  12. Structure and wear behavior of AlCrSiN-based coatings

    NASA Astrophysics Data System (ADS)

    Chen, Yun; Du, Hao; Chen, Ming; Yang, Jun; Xiong, Ji; Zhao, Haibo

    2016-05-01

    AlCrN, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings have been deposited on high-polished WC-Co cemented carbide substrate and tools by mid-frequency magnetron sputtering in Ar/N2 mixtures. Al0.6Cr0.4, Al0.6Cr0.3Si0.1, and C/Mo/Nb targets were used during the deposition. The microstructure and mechanical properties of as-deposited coatings were investigated. Investigations of the wear behaviors of coated tools were also performed. The results showed that cubic structure was formed in the coatings. Broader CrAlN (1 1 1) and (2 0 0) peaks without SiNx peak were formed in the AlCrSiN/MexN coatings, which showed a nanocomposited structure. Meanwhile, according to SEM micrographs, AlCrN exhibited a columnar structure, while, AlCrSiCN, AlCrSiN/MoN, and AlCrSiN/NbN coatings showed nanocrystalline morphology. The nano-multilayered coatings performed higher hardness, H/E, and H3/E2 ratios compared with AlCrN coating. Through the Rockwell adhesion test, all the coatings exhibited adhesion strength quality HF1. After turning Inconel 718 under dry condition, the nano-multilyered coatings showed better wear resistance than AlCrN coating. Due to the molybdenum and niobium in the coating, AlCrSiN/MoN and AlCrSiN/NbN coatings showed the best wear resistance.

  13. Comparison of AlCrN and AlCrTiSiN coatings deposited on the surface of plasma nitrocarburized high carbon steels

    NASA Astrophysics Data System (ADS)

    Chen, Wanglin; Zheng, Jie; Lin, Yue; Kwon, Sikchol; Zhang, Shihong

    2015-03-01

    The AlCrN and AlCrTiSiN coatings were produced on the surface of plasma nitrocarburized T10 steels by multi-arc ion plating. The comparison of the microstructures and mechanical properties of the duplex coatings were investigated by means of X-ray diffraction, optical microscope, scanning electron microscope and transmission electron microscope, in association with mechanical property measurement. The results show that the AlCrN coatings with columnar grown are mainly composed of nanocrytalline fcc-(Cr,Al)N phases with {111} preferred orientation, whereas the superlattice and nanocomposite AlCrTiSiN coatings with planar growth mainly consist of nanocrystalline fcc-(Cr,Al)N phases with {100} perfected orientation, hcp-AlN and Si3N4 amorphous phases. The AlCrTiSiN duplex coating with the compound layer reveals higher hardness, adhesion strength, load capacity and lower friction coefficient when compared with the other duplex coatings, which is due to its superlattice and nanocomposite structure. Additionally, these improved properties are related to the appearance of the γ‧-phase which plays the nucleation sites for the coating nitrides and provides a strong supporting effect for the AlCrN and AlCrTiSiN coatings. The main wear mechanism of the duplex coatings without compound layer is spalling and chipping wear as well as tribooxidation wear, whereas the main wear mechanism of the duplex coatings with compound layer is tribooxidation wear.

  14. Synthesis of Nano Sized Cr2AlC Powders by Molten Salt Method.

    PubMed

    Xiao, Dan; Zhu, Jianfeng; Wang, Fen; Tang, Yi

    2015-09-01

    Cr2AlC powders were successfully synthesized by molten salt method using Cr, Al and C as starting materials. The effects of the process parameters and amount of Al addition on the purity of the Cr2AlC powders were also investigated in details. The formation mechanism of Cr2AlC powders was investigated by XRD and DSC. The results indicated that intermediates of Cr7C3 and Cr- Al intermetallics, such as CrAl17, Cr2Al, Cr2Al8, were formed by the reactions among the initial elements, then the intermediates gradually transformed to Cr2AlC. From the fixed composition of Cr:Al:C = 2:1.2:1, high purity Cr2AlC powders could be obtained with an inorganic salt KCl as a solvent at 1250 degrees C for 60 min under argon atmosphere which was lower than that (generally 1450 degrees C) of conventional solid state reaction.

  15. Experimental evidence of Cr magnetic moments at low temperature in Cr2A(A=Al, Ge)C.

    PubMed

    Jaouen, M; Bugnet, M; Jaouen, N; Ohresser, P; Mauchamp, V; Cabioc'h, T; Rogalev, A

    2014-04-30

    From x-ray magnetic circular dichroism experiments performed at low temperature on Cr2AlC and Cr2GeC thin films, it is evidenced that Cr atoms carry a net magnetic moment in these ternary phases. It is shown that the Cr magnetization of the Al-based compound nearly vanished at 100 K in agreement with what has been recently observed on bulk. X-ray linear dichroism measurements performed at various angles of incidence and temperatures clearly demonstrate the existence of a charge ordering along the c axis of the structure of Cr2AlC. All these experimental observations support, in part, theoretical calculations claiming that Cr dd correlations have to be considered to correctly describe the structure and properties of these Cr-based ternary phases. PMID:24721758

  16. Al/sub 2/O/sub 3/ adherence on CoCrAl alloys

    SciTech Connect

    Kingsley, L.M.

    1980-04-01

    Adherence of protective oxides on NiCrAl and CoCrAl superalloys has been promoted by a dispersion of a highly oxygen reactive element or its oxide being produced within the protection system. Two aspects of this subject are investigated here: the use of Al/sub 2/O/sub 3/ as both the dispersion and protective oxide; and the production of an HfO/sub 2/ dispersion while simultaneously aluminizing the alloy. It was found that an Al/sub 2/O/sub 3/ dispersion will act to promote the adherence of an external scale of Al/sub 2/O/sub 3/ to a degree comparable to previously tested dispersions and an HfO/sub 2/ dispersion comparable to that produced by a Rhines pack treatment is produced during aluminization.

  17. Interstitial precipitation in Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Spear, W. S.; Polonis, D. H.

    1994-06-01

    Two separate stages of precipitation have been identified during the aging of ternary Fel8Cr3Al and Fel8Cr5Al alloys at temperatures in the vicinity of 475 °C. The first stage involves the formation of interstitial precipitates resulting from C and N impurities; the second and slower stage is the formation of the Cr-rich α' phase. Transmission electron microscopy (TEM) results show that carbonitride precipitation occurs preferentially at dislocations, stacking faults, and grain boundaries, and also uniformly through the matrix. Aging for times in excess of 400 hours at 475 °C promotes coarsening of the heterogeneous precipitates and dissolution of the uniformly distributed matrix particles. A resistometric analysis shows that the kinetics of the initial stages of precipitation can be described by a (time)2/3 relation. This kinetic behavior is explained in terms of stress-assisted diffusion in the highly stressed matrix resulting from coherency strains accompanying carbonitride precipitation. Experimental values of the activation energy for the first stage reaction correlate closely with those reported for the interstitial diffusion of C and N in alpha iron.

  18. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    DOE PAGES

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explainmore » that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.« less

  19. Carbon Nanostructures Grown on Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Čaplovičová, Mária; Čaplovič, Ľubomír; Búc, Dalibor; Vinduška, Peter; Janík, Ján

    2010-11-01

    The morphology and nanostructure of carbon nanotubes (CNTs), synthesized directly on Fe-Cr-Al-based alloy substrate using an alcohol catalytic chemical vapour deposition method (ACCVD), were examined by transmission electron microscopy (TEM). The grown CNTs were entangled with chain-like, bamboo-like, and necklace-like morphologies. The CNT morphology was affected by the elemental composition of catalysts and local instability of deposition process. Straight and bended CNTs with bamboo-like nanostructure grew mainly on γ-Fe and Fe3C particles. The synthesis of necklace-like nanostructures was influenced by silicon oxide, and growth of chain-like nanostructures was supported by a catalysts consisting of Fe, Si, oxygen and trace of Cr. Most of nanotubes grew according to base growth mechanism.

  20. Normal and excess nitrogen uptake by iron-based Fe-Cr-Al alloys: the role of the Cr/Al atomic ratio

    NASA Astrophysics Data System (ADS)

    Jung, K. S.; Schacherl, R. E.; Bischoff, E.; Mittemeijer, E. J.

    2011-06-01

    Upon nitriding ferritic iron-based Fe-Cr-Al alloys, containing a total of 1.50 at. % (Cr + Al) alloying elements with varying Cr/Al atomic ratio (0.21-2.00), excess nitrogen uptake occurred, i.e. more nitrogen was incorporated in the specimens than compatible with only inner nitride formation and equilibrium nitrogen solubility of the unstrained ferrite matrix. The amount of excess nitrogen increased with decreasing Cr/Al atomic ratio. The microstructure of the nitrided zone was investigated by X-ray diffraction, electron probe microanalysis, transmission electron microscopy and electron energy loss spectroscopy. Metastable, fine platelet-type, mixed Cr1- x Al x N nitride precipitates developed in the nitrided zone for all of the investigated specimens. The degree of coherency of the nitride precipitates with the surrounding ferrite matrix is discussed in view of the anisotropy of the misfit. Analysis of nitrogen-absorption isotherms, recorded after subsequent pre- and de-nitriding treatments, allowed quantitative differentiation of different types of nitrogen taken up. The amounts of the different types of excess nitrogen as function of the Cr/Al atomic ratio are discussed in terms of the nitride/matrix misfit and the different chemical affinities of Cr and Al for N. The strikingly different nitriding behaviors of Fe-Cr-Al and Fe-Cr-Ti alloys could be explained on this basis.

  1. Zener Relaxation Peak in an Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Zheng-Cun; Cheng, He-Fa; Gong, Chen-Li; Wei, Jian-Ning; Han, Fu-Sheng

    2002-11-01

    We have studied the temperature spectra of internal friction and relative dynamic modulus of the Fe-(25 wt%)Cr-(5 wt%)Al alloy with different grain sizes. It is found that a peak appears in the internal friction versus temperature plot at about 550°C. The peak is of a stable relaxation and is reversible, which occurs not only during heating but also during cooling. Its activation energy is 2.5 (+/- 0.15) eV in terms of the Arrhenius relation. In addition, the peak is not obvious in specimens with a smaller grain size. It is suggested that the peak originates from Zener relaxation.

  2. Al, Ti, and Cr: Complex Zoning in Synthetic and Natural Nakhlite Pyroxenes

    NASA Technical Reports Server (NTRS)

    McKay, G.; Le, L.; Mikouchi, T.

    2007-01-01

    Nakhlites are olivine-bearing clinopyroxene cumulates. The cumulus pyroxenes have cores that are relatively homogeneous in Fe, Mg, and Ca, but show complex zoning of minor elements, especially Al, Ti, and Cr. Zoning patterns contain information about crystallization history parent magma compositions. But it has proven difficult to decipher this information and translate the zoning patterns into petrogenetic processes. This abstract reports results of high-precision Electron Probe MicroAnalysis (EPMA) analysis of synthetic nakhlite pyroxenes run at fO2 from IW to QFM. It compares these with concurrent analyses of natural nakhlite MIL03346 (MIL), and with standardprecision analyses of Y000593 (Y593) collected earlier. Results suggest that (1) different processes are responsible for the zoning of MIL and other more slowly-cooled nakhlites such as Y593, and (2) changes in oxidation conditions during MIL crystallization are not responsible for the unusual Cr zoning pattern

  3. RIMS analysis of Ca and Cr in genesis solar wind collectors.

    SciTech Connect

    Veryovkin, I. V.; Tripa, C. E.; Zinovev, A. V.; King, B. V.; Pellin, M. J.; Burnett, D. S.; Materials Science Division; Univ. of Newcastle; California Inst. of Tech.

    2011-01-01

    RIMS depth profiles have been measured for Cr and Ca in Genesis solar wind collector made from Si and compared to such measurements for ion-implanted Si reference material. The presence of surface contamination has been shown to be a significant factor influencing the total Ca and Cr fluence measured in the Genesis collectors. A procedure to remove the contaminant signal from these depth profiles using the reference material implanted with a minor isotope demonstrated that 36% of the measured Ca fluence in our Genesis sample comes from terrestrial contamination.

  4. Host Atom Diffusion in Ternary Fe-Cr-Al Alloys

    NASA Astrophysics Data System (ADS)

    Rohrberg, Diana; Spitzer, Karl-Heinz; Dörrer, Lars; Kulińska, Anna J.; Borchardt, Günter; Fraczkiewicz, Anna; Markus, Torsten; Jacobs, Michael H. G.; Schmid-Fetzer, Rainer

    2014-01-01

    In the Fe-rich corner of the Fe-Cr-Al ternary phase diagram, both interdiffusion experiments [1048 K to 1573 K (775 °C to 1300 °C)] and 58Fe tracer diffusion experiments [873 K to 1123 K (600 °C to 850 °C)] were performed along the Fe50Cr50-Fe50Al50 section. For the evaluation of the interdiffusion data, a theoretical model was used which directly yields the individual self-diffusion coefficients of the three constituents and the shift of the original interface of the diffusion couple through inverse modeling. The driving chemical potential gradients were derived using a phenomenological Gibbs energy function which was based on thoroughly assessed thermodynamic data. From the comparison of the individual self-diffusivities of Fe as obtained from interdiffusion profiles and independent 58Fe tracer diffusivities, the influence of the B2-A2 order-disorder transition becomes obvious, resulting in a slightly higher activation enthalpy for the bcc-B2 phase and a significantly lower activation entropy for this phase.

  5. Dipole defects in Al2O3:Mg,Cr.

    PubMed

    Blak, A R; Gobbi, V; Ayres, F

    2002-01-01

    In this work, dipole defects are investigated applying the thermally stimulated depolarisation currents (TSDC) technique. The TSDC spectra of Al2O3 doped with Mg and Cr show two bands centred at 230 K and 250 K, respectively. The maximum intensity of the bands increases linearly with the polarisation field, a typical behaviour of defects with dipole origin. An increase of the band at 250 K with gamma irradiation has been observed and a thermal decrease of the bands for heat treatments between 1000 K and 1400 K. Above this temperature the bands are partially recovered. Impurity neutron activation analysis shows that magnesium. chromium and iron content varies from 15 to 60 ppm. Optical absorption (AO) measurements show a broad band centred in 2.6 eV (21000 cm(-1)) associated with trapped holes localised on an O- ion adjacent to a cation site which is deficient in positive charge. It has been assumed that a substitutional Mg2+ ion occupies the cation site near a trapped hole on one of the six oxygen ions surrounding the magnesium impurity giving rise to the dipole responsible for the observed TSDC bands. Calculations carried out through defect simulation methods confirm that the probability of Al3+ being replaced by Mg2+ is higher than Mn2+, Co2+, Fe2+ and Cr2+. PMID:12382829

  6. 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.

  7. Process development for Ni-Cr-ThO2 and Ni-Cr-Al-ThO2 sheet

    NASA Technical Reports Server (NTRS)

    Cook, R. C.; Norris, L. F.

    1973-01-01

    A process was developed for the production of thin gauge Ni-Cr-ThO2 sheet. The process was based on the elevated temperature deposition of chromium onto a wrought Ni-2%ThO2 sheet and subsequent high temperature diffusion heat treatments to minimize chromium concentration gradients within the sheet. The mechanical properties of the alloy were found to be critically dependent on those of the Ni-2%ThO2 sheet. A similar process for the production of a Ni-Cr-Al-ThO2 alloy having improved oxidation resistance was investigated but the non-reproducible deposition of aluminum from duplex Cr/Al packs precluded successful scale-up. The mechanical properties of the Ni-Cr-Al-ThO2 alloys were generally equivalent to the best Ni-Cr-ThO2 alloy produced in the programme.

  8. Al-augite and Cr-diopside ultramafic xenoliths in basaltic rocks from western United States

    USGS Publications Warehouse

    Wilshire, H.G.; Shervais, J.W.

    1975-01-01

    Ultramafic xenoliths in basalts from the western United States are divided into Al-augite and Cr-diopside groups. The Al-augite group is characterized by Al, Ti-rich augites, comparatively Fe-rich olivine and orthopyroxene, and Al-rich spinel, the Cr-diopside group by Cr-rich clinopyroxene and spinel and by Mg-rich olivine and pyroxenes. Both groups have a wide range of subtypes, but the Al-augite group is dominated by augite-rich varieties, and the Cr-diopside group by olivine-rich lherzolites. ?? 1975.

  9. Cyclic Oxidation of FeCrAlY/Al2O3 Composites

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Draper, Susan L.; Barrett, Charles A.

    1999-01-01

    Three-ply FeCrAlY/Al2O3 composites and FeCrAlY matrix-only samples were cyclically oxidized at 1000 C and 1100 C for up to 1000 1-hr cycles. Fiber ends were exposed at the ends of the composite samples. Following cyclic oxidation, cracks running parallel to and perpendicular to the fibers were observed on the large surface of the composite. In addition, there was evidence of increased scale damage and spallation around the exposed fiber ends, particularly around the middle ply fibers. This damage was more pronounced at the higher temperature. The exposed fiber ends showed cracking between fibers in the outer plies, occasionally with Fe and Cr-rich oxides growing out of the cracks. Large gaps developed at the fiber/matrix interface around many of the fibers, especially those in the outer plies. Oxygen penetrated many of these gaps resulting in significant oxide formation at the fiber/matrix interface far within the composite sample. Around several fibers, the matrix was also internally oxidized showing Al2O3 precipitates in a radial band around the fibers. The results show that these composites have poor cyclic oxidation resistance due to the CTE mismatch and inadequate fiber/matrix bond strength at temperatures of 1000 C and above.

  10. Nanoscale Cellular Structures at Phase Boundaries of Ni-Cr-Al-Ti and Ni-Cr-Mo-Al-Ti Superalloys

    NASA Astrophysics Data System (ADS)

    Wang, Cong; Dunand, David C.

    2015-06-01

    The microstructural evolution of Ni-20 pct Cr wires was studied during pack cementation where Al and Ti, with and without prior cementation with Mo, are deposited to the surface of the Ni-Cr wires and subsequently homogenized in their volumes. Mo deposition promotes the formation of Kirkendall pores and subsequent co-deposition of Al and Ti creates a triple-layered diffusional coating on the wire surface. Subsequent homogenization drives the alloying element to distribute evenly in the wires which upon further heat treatment exhibit the γ + γ' superalloy structure. Unexpectedly, formation of cellular structures is observed at some of the boundaries between primary γ' grains and γ matrix grains. Based on additional features ( i.e., ordered but not perfectly periodic structure, confinement at γ + γ' phase boundaries as a cellular film with ~100 nm width, as well as lack of topologically close-packed phases), and considering that similar, but much larger, microstructures were reported in commercial superalloys, it is concluded that the present cellular structure solidified as a thin film, composed of eutectic γ + γ' and from which the γ' phase was subsequently etched, which was created by incipient melting of a region near the phase boundary with high solute segregation.

  11. Third element effect in the surface zone of Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Airiskallio, E.; Nurmi, E.; Heinonen, M. H.; Väyrynen, I. J.; Kokko, K.; Ropo, M.; Punkkinen, M. P. J.; Pitkänen, H.; Alatalo, M.; Kollár, J.; Johansson, B.; Vitos, L.

    2010-01-01

    The third element effect to improve the high temperature corrosion resistance of the low-Al Fe-Cr-Al alloys is suggested to involve a mechanism that boosts the recovering of the Al concentration to the required level in the Al-depleted zone beneath the oxide layer. We propose that the key factor in this mechanism is the coexistent Cr depletion that helps to maintain a sufficient Al content in the depleted zone. Several previous experiments related to our study support that conditions for such a mechanism to be functional prevail in real oxidation processes of Fe-Cr-Al alloys.

  12. Optical properties of heusler alloys Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa

    NASA Astrophysics Data System (ADS)

    Shreder, E. I.; Svyazhin, A. D.; Belozerova, K. A.

    2013-11-01

    The results of an investigation of optical properties and the calculations of the electronic structure of Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa Heusler alloys are presented. The main focus of our attention is the study of the spectral dependence of the real part (ɛ1) and imaginary part (ɛ2) of the dielectric constant in the range of wavelengths λ = 0.3-13 μm using the ellipsometric method. An anomalous behavior of the optical conductivity σ(ω) has been found in the infrared range in the Co2CrAl and Co2CrGa alloys, which differs substantially from that in the Co2FeSi and Co2FeAl alloys. The results obtained are discussed based on the calculations of the electronic structure.

  13. Al-Ca and Al-Fe metal-metal composite strength, conductivity, and microstructure relationships

    SciTech Connect

    Kim, Hyong June

    2011-01-01

    Deformation processed metal-metal composites (DMMC’s) are composites formed by mechanical working (i.e., rolling, swaging, or wire drawing) of two-phase, ductile metal mixtures. Since both the matrix and reinforcing phase are ductile metals, the composites can be heavily deformed to reduce the thickness and spacing of the two phases. Recent studies have shown that heavily drawn DMMCs can achieve anomalously high strength and outstanding combinations of strength and conductivity. In this study, Al-Fe wire composite with 0.07, 0.1, and 0.2 volume fractions of Fe filaments and Al-Ca wire composite with 0.03, 0.06, and 0.09 volume fractions of Ca filaments were produced in situ, and their mechanical properties were measured as a function of deformation true strain. The Al-Fe composites displayed limited deformation of the Fe phase even at high true strains, resulting in little strengthening effect in those composites. Al-9vol%Ca wire was deformed to a deformation true strain of 13.76. The resulting Ca second-phase filaments were deformed to thicknesses on the order of one micrometer. The ultimate tensile strength increased exponentially with increasing deformation true strain, reaching a value of 197 MPa at a true strain of 13.76. This value is 2.5 times higher than the value predicted by the rule of mixtures. A quantitative relationship between UTS and deformation true strain was determined. X-ray diffraction data on transformation of Al + Ca microstructures to Al + various Al-Ca intermetallic compounds were obtained at the Advanced Photon Source at Argonne National Laboratory. Electrical conductivity was measured over a range of true strains and post-deformation heat treatment schedules.

  14. Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system

    SciTech Connect

    Pang, Mingjun; Zhan, Yongzhong; Du, Yong

    2013-02-15

    The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.

  15. Microstructural stability of Fe-Cr-Al alloys at 450-550 °C

    NASA Astrophysics Data System (ADS)

    Ejenstam, Jesper; Thuvander, Mattias; Olsson, Pär; Rave, Fernando; Szakalos, Peter

    2015-02-01

    Iron-Chromium-Aluminium (Fe-Cr-Al) alloys have been widely investigated as candidate materials for various nuclear applications. Albeit the excellent corrosion resistance, conventional Fe-Cr-Al alloys suffer from α-α‧ phase separation and embrittlement when subjected to temperatures up to 500 °C, due to their high Cr-content. Low-Cr Fe-Cr-Al alloys are anticipated to be embrittlement resistant and provide adequate oxidation properties, yet long-term aging experiments and simulations are lacking in literature. In this study, Fe-10Cr-(4-8)Al alloys and a Fe-21Cr-5Al were thermally aged in the temperature interval of 450-550 °C for times up to 10,000 h, and the microstructures were evaluated mainly using atom probe tomography. In addition, a Kinetic Monte Carlo (KMC) model of the Fe-Cr-Al system was developed. No phase separation was observed in the Fe-10Cr-(4-8)Al alloys, and the developed KMC model yielded results in good agreement with the experimental data.

  16. The molar volume of cubic garnets in the system SiO2-Al2O3-TiO2-Fe2O3-Cr2O3-FeO-MnO-MgO-CaO-Na2O

    NASA Astrophysics Data System (ADS)

    Hamecher, E. A.; Antoshechkina, P. M.; Ghiorso, M. S.; Asimow, P. D.

    2012-12-01

    Garnet is a critical phase that controls major and trace element partitioning at pressures above ~3 GPa during partial melting of the Earth's upper mantle. A molar volume model is calibrated for cubic garnets (space group Ia3d) in the oxide system listed in the title. This model and a recent calibration of spinel molar volume (Hamecher et al., in press, CMP) will be used in calibration of thermodynamic activity-composition models of garnet and pyroxene solid solutions. The activity and molar volume models will be incorporated into the next generation MELTS (Ghiorso & Sack, 1995, CMP) model, xMELTS. A new garnet volume model calibrated with recent in situ high-P, T diffraction data is crucial for accurately modeling key mineralogical transitions in the mantle, e.g., the spinel-garnet transition and the mantle transition zone. Above 5 GPa a majorite component is an essential part of any thermodynamic model of mantle garnets, which to be useful must accurately predict garnet stability with respect to spinel, pyroxene, perovskites, and melt. Our model system contains nine independent end members: Ca3Al2Si3O12, Mg3Al2Si3O12, Fe2+3Al2Si3O12, Mg3Cr2Si3O12, Mg3Fe3+2Si3O12, Mn3Al2Si3O12, Na2(MgSi2)Si3O12, Mg3(TiMg)Si3O12, and cubic majorite component Mg3(MgSi)Si3O12. An inclusive set of end-member components is formed by linear combinations of these explicit end members. Approximately 950 published X-ray diffraction experiments performed on garnets at ambient and in situ high-P, T conditions are used to calibrate end-member equations of state and an excess volume model for this system. Optimal values of the bulk modulus and its pressure derivative are obtained by analyzing published compression and/or ultrasonic data for the end members for which such studies exist; for other end members, density functional theory results are used. For any cubic garnet in this chemical system, the model molar volume is obtained by adding excess volume terms to a linear combination of the

  17. Microstructure/Oxidation/Microhardness Correlations in Gamma-Based and Tau-Based Al-Ti-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Brady, Michael P.; Smialek, J. L.; Humphrey, D. L.

    1994-01-01

    The relationships between alloy microstructure and air oxidation kinetics and alloy microstructure and microhardness in the Al-Ti-Cr system for exposures at 800 C and 1000 C were investigated. The relevant phases were identified as tau (Ll2), gamma (LIO), r-Al2Ti, TiCrAl (laves), and Cr2AI. Protective alumina formation was associated with tau, Al-rich TiCrAl, and gamma/TiCrAl mixtures. Brittleness was associated with the TiCrAl phase and tau decomposition to A12Ti + Cr2AI. It was concluded that two-phase gamma + TiCrAl alloys offer the greatest potential for oxidation resistance and room temperature ductility in the Al-Ti-Cr system.

  18. Comparative studies on the thermal stability and corrosion resistance of CrN, CrSiN, and CrSiN/AlN coatings

    SciTech Connect

    Kim, Gwang Seok; Kim, Sung Min; Lee, Sang Yul; Lee, Bo Young

    2009-07-15

    In this work, three kinds of Cr-based nitride coatings such as monolithic CrN, CrSiN coatings, and multilayered CrSiN/AlN coating with bilayer period of 3.0 nm were deposited on both Si (100) wafer and AISI H13 steel substrates by unbalanced magnetron sputtering. Thermal stability of these coatings was evaluated by annealing the coatings at temperatures between 600 and 1000 degree sign C for 30 min in air. In addition, the corrosion behaviors of these coatings were investigated by potentiodynamic polarization tests in a deaerated 3.5 wt. % NaCl solution at 40 degree sign C. Results from annealing test show the monolithic CrN and CrSiN coatings were completely oxidized after annealed at 800 and 900 degree sign C, and their cross sectional images and atomic force microscopy showed a loose and very porous morphology due to the oxidation. Also, the hardness values of the monolithic CrN and CrSiN coatings were decreased significantly from 22 and 27 GPa to 8 and 14 GPa, respectively. However, the multilayered CrSiN/AlN coating still exhibited a dense microstructure without visible change after annealed at 1000 degree sign C, and moreover, the relatively high hardness of 25 GPa was maintained. The superior thermal stability of the CrSiN/AlN multilayer coating could be attributed to the formation of the dense and stable oxidation barrier consisted of the Al{sub 2}O{sub 3}, Cr{sub 2}O{sub 3}, and amorphous SiO{sub 2} phases near the surface region, which retard the diffusion of oxygen into the coating. In the potentiodynamic polarization test results, it was found that the significantly improved corrosion resistance of the multilayered CrSiN/AlN coating was observed in comparison with those from the monolithic CrN and CrSiN coatings, and its corrosion current density (i{sub corr}) and protective efficiency were measured to be approximately 4.21 {mu}A/cm{sup 2} and 95%, respectively.

  19. Ar + induced interfacial mixing and phase formation in the Al/Cr system

    NASA Astrophysics Data System (ADS)

    Kim, H. K.; Kim, S. O.; Song, J. H.; Kim, K. W.; Woo, J. J.; Whang, C. N.; Smith, R. J.

    1991-07-01

    Evaporated Al/Cr bilayer thin films were irradiated by 80 keV Ar + at doses in the range from 1 × 10 15 to 2 × 10 16 Ar +/cm 2 at room temperature in order to investigate the Ar + induced interfacial mixing behavior and the phase formation and transition by Ar + bombardment. Ion bombardment induces intermixing across the Al/Cr interface and mixing variance increases with increasing ion dose. Cascade and thermal spike models are found to be not adequate for the ion beam mixing mechanism at room temperature in this system. The Al 13Cr 2 phase is formed as an initial phase by ion beam mixing and then transforms into the Al 11Cr 2 or Al 4Cr phases at subsequent ion bombardment. This result is discussed in terms of the enhanced atomic mobility and the thermodynamical driving force by introducing the concept of an effective heat of formation.

  20. Evaluation of Ti-48Al-2Cr-2Nb Under Fretting Conditions

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.; Raj, Sai V.

    2001-01-01

    The fretting behavior of Ti-48Al-2Cr-2Nb (y-TiAl) in contact with the nickel-base superalloy 718 was examined in air at temperatures from 296 to 823 K (23 to 550 C). The interfacial adhesive bonds between Ti-48Al-2Cr-2Nb and superalloy 718 were generally stronger than the cohesive bonds within Ti-48Al-2Cr-2Nb. The failed Ti-48Al-2Cr-2Nb debris subsequently transferred to the superalloy 718. In reference experiments conducted with Ti-6Al-4V against superalloy 718 under identical fretting conditions, the degree of transfer was greater for Ti-6A1-4V than for Ti-48Al-2Cr-2Nb. Wear of Ti-48Al-2Cr-2Nb generally decreased with increasing fretting frequency. The increasing rate of oxidation at elevated temperatures led to a drop in wear at 473 K. However, fretting wear increased as the temperature was increased from 473 to 823 K. At 723 and 823 K, oxide film disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals.

  1. Structural disorder and magnetism in the spin-gapless semiconductor CoFeCrAl

    NASA Astrophysics Data System (ADS)

    Choudhary, Renu; Kharel, Parashu; Valloppilly, Shah R.; Jin, Yunlong; O'Connell, Andrew; Huh, Yung; Gilbert, Simeon; Kashyap, Arti; Sellmyer, D. J.; Skomski, Ralph

    2016-05-01

    Disordered CoFeCrAl and CoFeCrSi0.5Al0.5 alloys have been investigated experimentally and by first-principle calculations. The melt-spun and annealed samples all exhibit Heusler-type superlattice peaks, but the peak intensities indicate a substantial degree of B2-type chemical disorder. Si substitution reduces the degree of this disorder. Our theoretical analysis also considers several types of antisite disorder (Fe-Co, Fe-Cr, Co-Cr) in Y-ordered CoFeCrAl and partial substitution of Si for Al. The substitution transforms the spin-gapless semiconductor CoFeCrAl into a half-metallic ferrimagnet and increases the half-metallic band gap by 0.12 eV. Compared CoFeCrAl, the moment of CoFeCrSi0.5Al0.5 is predicted to increase from 2.01 μB to 2.50 μB per formula unit, in good agreement with experiment.

  2. Microstructural characterization of Al-rich Ni-Cr-Al cast alloys

    SciTech Connect

    Gonzalez-Carrasco, J.L.; Adeva, P.; Cristina, M.C.; Aballe, M. )

    1994-09-01

    Several Ni-Cr-Al alloys, with up to 30 at.% Al, were prepared in an induction furnace and cast under inert atmosphere. All alloys were homogenized for 8 h at 1,473 K under an argon atmosphere, followed by treatments at temperatures between 1,023 and 1,273 K for times up to 180 h. These alloys contain phases that are to a great extent, structurally similar. This is frequently complicated further by their particle size and their degree of order. Their characterization is not always simple and usually must be based on more than one technique. In this work the microstructural evolution was studied by means of light microscopy, scanning electron microscopy and microanalysis, and X-ray diffraction techniques. For completeness, hardness and microhardness tests were performed to evaluate the precipitation phenomenon.

  3. Microstructure evolution during annealing of TiAl/NiCoCrAl multilayer composite prepared by EB-PVD

    SciTech Connect

    Zhang, Rubing; Zhang, Deming; Chen, Guiqing; Wang, Yuesheng

    2014-07-01

    TiAl/NiCoCrAl laminate composite sheet with a thickness of 0.4–0.6 mm as well as a dimension of 150 mm × 100 mm was fabricated successfully by using electron beam physical vapor deposition (EB-PVD) method. The annealing treatment was processed at 1123 and 1323 K for 3 h in a high vacuum atmosphere, respectively. The phase composition and microstructure of TiAl/NiCoCrAl microlaminated sheet have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on the sheet characterization and results of the microstructure evolution during annealing treatment process, the diffusion mechanism of interfacial reaction in TiAl/NiCoCrAl microlaminate was investigated and discussed.

  4. Irradiation-enhanced α' precipitation in model FeCrAl alloys

    DOE PAGES

    Edmondson, Philip D.; Briggs, Samuel A.; Yamamoto, Yukinori; Howard, Richard H.; Sridharan, Kumar; Terrani, Kurt A.; Field, Kevin G.

    2016-02-17

    Model FeCrAl alloys with varying compositions (Fe(10–18)Cr(10–6)Al at.%) have been neutron irradiated at ~ 320 to damage levels of ~ 7 displacements per atom (dpa) to investigate the compositional influence on the formation of irradiation-induced Cr-rich α' precipitates using atom probe tomography. In all alloys, significant number densities of these precipitates were observed. Cluster compositions were investigated and it was found that the average cluster Cr content ranged between 51.1 and 62.5 at.% dependent on initial compositions. This is significantly lower than the Cr-content of α' in binary FeCr alloys. As a result, significant partitioning of the Al from themore » α' precipitates was also observed.« less

  5. 1100 to 1500 K Slow Plastic Compressive Behavior of NiAl-xCr Single Crystals

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Darolia, Ram

    2003-01-01

    The compressive properties of near <001> and <111> oriented NiAl-2Cr single crystals and near <011> oriented NiAl-6Cr samples have been measured between 1100 and 1500 K. The 2Cr addition produced significant solid solution strengthening in NiAl, and the <111> and <001> single crystals possessed similar strengths. The 6Cr crystals were not stronger than the 2Cr versions. At 1100 and 1200 K plastic flow in all three Cr-modified materials was highly dependent on stress with exponents > 10. The <011> oriented 6Cr alloy exhibited a stress exponent of about 8 at 1400 and 1500 K; whereas both <001> and <111> NiAl-2Cr crystals possessed stress exponents near 3 which is indicative of a viscous dislocation glide creep mechanism. While the Cottrell-Jaswon solute drag model predicted creep rates within a factor of 3 at 1500 K for <001>-oriented NiAl-2Cr; this mechanism greatly over predicted creep rates for other orientations and at 1400 K for <001> crystals.

  6. Diffusional transport during the cyclic oxidation of gamma + beta, Ni-Cr-Al(Y, Zr) alloys

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1988-01-01

    The cyclic oxidation behavior of several cast gamma + beta, Ni-Cr-Al(Y, Zr) alloys and one low-pressure plasma spraying gamma + beta, Ni-Co-Cr-Al(Y) alloy was studied. Cyclic oxidation was found to result in a decreasing Al concentration at the oxide-metal interface due to a high rate of Al consumption coupled with oxide scale cracking and spalling. Diffusion paths plotted on the ternary phase diagram showed higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption and the highest Al content underwent breakaway oxidation following 500 1-hr cycles at 1200 C.

  7. Comparison in mechanical and tribological properties of CrTiAlMoN and CrTiAlN nano-multilayer coatings deposited by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Zhang, Guojun; Jiang, Bailing

    2016-02-01

    CrTiAlN and CrTiAlMoN nano-multilayer coatings were deposited by closed field unbalanced magnetron sputtering. TiMoN and CrTiMoN nano-multilayer coatings with same Mo2N layer thickness were also prepared for comparison. The structure of these coatings is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The mechanical and tribological properties were characterized and compared by nano-indentation and ball-on-disc test. It was found that these coatings were structured by fcc metal nitride phases (including CrN, TiN, AlN and Mo2N) and the preferred orientation changed from (1 1 1) to (2 0 0) with the increase of Mo content. The TEM results showed that the coatings exhibited typical columnar structure and nano-multilayer structure with modulation periods ranged from 3.2 nm to 7.6 nm. Among these coatings, CrTiAlMoN coatings presented the highest hardness, lowest coefficient of friction (COF) and wear rate. The hardness of these nano-multilayer coatings were determined by layer interfaces: TiN/Mo2N and AlN/Mo2N layer interface showed benefit on hardness enhancement while CrN/Mo2N layer interface led to a great hardness decrement. In comparison with the other as-deposited coatings, the low COF of CrTiAlMoN coatings was not only affected by Mo addition but also related to its oxidation behaviors.

  8. 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.

  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

    2016-07-01

    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. Development of ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N.; Hoelzer, David T.; Pint, Bruce A.; Unocic, Kinga A.

    2015-09-18

    FeCrAl alloys are prime candidates for accident-tolerant fuel cladding due to their excellent oxidation resistance up to 1400 C and good mechanical properties at intermediate temperature. Former commercial oxide dispersion strengthened (ODS) FeCrAl alloys such as PM2000 exhibit significantly better tensile strength than wrought FeCrAl alloys, which would alloy for the fabrication of a very thin (~250 m) ODS FeCrAl cladding and limit the neutronic penalty from the replacement of Zr-based alloys by Fe-based alloys. Several Fe-12-Cr-5Al ODS alloys where therefore fabricated by ball milling FeCrAl powders with Y2O3 and additional oxides such as TiO2 or ZrO2. The new Fe-12Cr-5Al ODS alloys showed excellent tensile strength up to 800 C but limited ductility. Good oxidation resistance in steam at 1200 and 1400 C was observed except for one ODS FeCrAl alloy containing Ti. Rolling trials were conducted at 300, 600 C and 800 C to simulate the fabrication of thin tube cladding and a plate thickness of ~0.6mm was reached before the formation of multiple edge cracks. Hardness measurements at different stages of the rolling process, before and after annealing for 1h at 1000 C, showed that a thinner plate thickness could likely be achieved by using a multi-step approach combining warm rolling and high temperature annealing. Finally, new Fe-10-12Cr-5.5-6Al-Z gas atomized powders have been purchased to fabricate the second generation of low-Cr ODS FeCrAl alloys. The main goals are to assess the effect of O, C, N and Zr contents on the ODS FeCrAl microstructure and mechanical properties, and to optimize the fabrication process to improve the ductility of the 2nd gen ODS FeCrAl while maintaining good mechanical strength and oxidation resistance.

  11. NMR study of the ternary carbides M2 AlC (M=Ti,V,Cr)

    NASA Astrophysics Data System (ADS)

    Lue, C. S.; Lin, J. Y.; Xie, B. X.

    2006-01-01

    We have performed a systematic study of the layered ternary carbides Ti2AlC , V2AlC , and Cr2AlC using Al27 NMR spectroscopy. The quadrupole splittings, Knight shifts, as well as spin-lattice relaxation times on each material have been identified. The sign of the isotropic Knight shift varies from positive for Ti2AlC and V2AlC to negative for Cr2AlC , attributed to the enhancement of hybridization with increasing valence electron count in the transition metal. Universally long relaxation times are found for these alloys. Results provide a measure of Al-s Fermi-level density of states Ns(EF) for Ti2AlC and V2AlC . In addition, the evidence that Ns(EF) correlates with the transition metal d -electron count has been explored in the present NMR investigation.

  12. Cr-Al coatings on low carbon steel prepared by a mechanical alloying technique

    NASA Astrophysics Data System (ADS)

    Hia, A. I. J.; Sudiro, T.; Aryanto, D.; Sebayang, K.

    2016-08-01

    Four different compositions of Cr and Al coatings as Cr10o, Cr87.5Al12.5, Cr5oAl5o, and Al100 have been prepared on the surface of low carbon steel by a mechanical alloying technique. The composition of each powder was milled for 2 hour in a stainless steel crucible with a ball to powder ratio of 10:1. Hereafter, the Cr-Al powder and substrate were mechanical alloyed in air for 1 hour. Heat treatment of coated sample were carried out at 800°C in a vacuum furnace. In order to characterize the phase composition and microstructure of the coating before and after heat treatment, XRD and SEM-EDX were used. The results show that Cr, Cr-Al or Al coatings were formed on the surface of low carbon steel. After heat treatment, new phases and interdiffusion zone were formed in the coating and at the coating/steel interface, depending on the coating composition.

  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. Effect of reaction time and (Ca+Mg)/Al molar ratios on crystallinity of Ca-Mg-Al layered double Hydroxide

    NASA Astrophysics Data System (ADS)

    Heraldy, E.; Nugrahaningtyas, K. D.; Sanjaya, F. B.; Darojat, A. A.; Handayani, D. S.; Hidayat, Y.

    2016-02-01

    Ca-Mg-Al Layered Double Hydroxides (Ca-Mg-Al-LDH) compounds were successfully synthesized from brine water and AlCl3.6H2O as the starting materials by coprecipitation method. The product result was characterized by X-ray powder diffraction (XRD) and Fourier transform infrared (FT-IR). The effects of the reaction time and the molar ratios of the raw material on the crystallinity of Ca-Mg-Al-LDH were examining. Results show that increasing reaction time (30; 60 and 90 min.) could improve the crystallinity and monodispersity of layered double hydroxide compounds particles. The well-defined Ca-Mg- Al-LDH could be prepared with (Ca+Mg)/Al molar ratios 0.5.

  15. High-pressure and high-temperature synthesis and physical properties of Ca2CrO4 solid

    NASA Astrophysics Data System (ADS)

    Cao, L. P.; Jin, M. L.; Li, W. M.; Wang, X. C.; Liu, Q. Q.; Xu, Y. L.; Pan, L. Q.; Jin, C. Q.

    2016-05-01

    The bulk Ca2CrO4 samples were synthesized under high pressure and high temperature conditions using CaO and CrO2 as starting materials. The structure of the prepared Ca2CrO4 solid is characterized by X-ray diffraction with Rietveld refinement as tetragonal structure with the space group I41/acd. The CrO6 octahedrons elongate along c axis and rotate in ab plane. DC and AC magnetic susceptibility measurement results indicate spin glass behavior at low temperature. Temperature dependence of resistivity measurement results show Ca2CrO4 is an insulator at both ambient condition and high pressure.

  16. Solid state reduction of chromium (VI) pollution for Al2O3-Cr metal ceramics application

    NASA Astrophysics Data System (ADS)

    Zhu, Hekai; Fang, Minghao; Huang, Zhaohui; Liu, Yangai; Tang, Hao; Min, Xin; Wu, Xiaowen

    2016-04-01

    Reduction of chromium (VI) from Na2CrO4 through aluminothermic reaction and fabrication of metal-ceramic materials from the reduction products have been investigated in this study. Na2CrO4 could be successfully reduced into micrometer-sized Cr particles in a flowing Ar atmosphere in presence of Al powder. The conversion ratio of Na2CrO4 to metallic Cr attained 96.16% efficiency. Al2O3-Cr metal-ceramic with different Cr content (5 wt%, 10 wt%, 15 wt%, 20 wt%) were further prepared from the reduction product Al2O3-Cr composite powder, and aluminum oxide nanopowder via pressure-less sintering. The phase composition, microstructure and mechanical properties of metal-ceramic composites were characterized to ensure the potential of the Al2O3-Cr composite powder to form ceramic materials. The highest relative density and bending strength can reach 93.4% and 205 MP, respectively. The results indicated that aluminothermic reduction of chromium (VI) for metal-ceramics application is a potential approach to remove chromium (VI) pollutant from the environment.

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

    SciTech Connect

    He, Y.R.; Zheng, M.H.; Rapp, R.A.

    1995-08-01

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

  18. Sulfidation resistant coatings for coal gasification process equipment. Final technical report. [FeCrAl and CoCrAl alloys

    SciTech Connect

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

    1985-05-01

    This report presents the results of a program of research to develop and evaluate sulfidation resistant coatings for low alloy and stainless steel components of coal gasification process equipment. Furnace fused CoCrAl and FeCrAl coatings were developed for use on 304SS, and laboratory tests indicate good resistance to attack by simulated slagging gasifier atmospheres at 1000 to 1300/sup 0/F (538 to 704/sup 0/C). The CoCrAl coating exhibits the best performance and will protect 304SS at 1000 to 1600/sup 0/F (537 to 871/sup 0/C) for over 1500 hr. These coatings will protect 304SS at 1600/sup 0/F (871/sup 0/C) at the highest level of P/sub S/sub 2// for any level of P/sub O/sub 2// compared with other alloys and surface coatings. Weld parameters were studied for the deposition of FeCrAl clad layers on FeCrAl and Alloy 800 plate and on T-91 steel tube. Crack-free weld deposited layers could not be produced under any conditions for alloys with as little as 4% Al and the technical feasibility of cladding steels with weld deposited FeCrAl is considered to be poor. Similar results were obtained in tests by laser surface fusion of CoCrAl and FeCrAl coatings on 310SS and T-11 steel. The technical feasibility of aluminizing and chromizing low alloy steels by a slip pack diffusion process has been demonstrated. High quality aluminide coatings on T-11 steel resistant to CGA attack at 1000 to 1600/sup 0/F were produced. Performance was equal to or better than that of commercial pack aluminized steels. The process is considered to have the potential for a major improvement in quality and performance of large, complex components aluminized by the pack diffusion process. Development and scale up of the process is recommended. 30 refs., 63 figs., 38 tabs.

  19. Spectroscopic properties of {Cr}^{3+} in the spinel solid solution {ZnAl}_{2-x}{Cr}x{O}_4

    NASA Astrophysics Data System (ADS)

    Verger, Louisiane; Dargaud, Olivier; Rousse, Gwenaelle; Rozsályi, Emese; Juhin, Amélie; Cabaret, Delphine; Cotte, Marine; Glatzel, Pieter; Cormier, Laurent

    2016-01-01

    The evolution of the structural environment of {Cr}{^{3+}} along the solid solution {ZnAl}_{2-x}{Cr}x{O}_4 has been investigated using a multi-analytical approach. X-ray diffraction confirms that the system follows Vegard's law. Diffuse reflectance spectra show a decrease of the crystal field parameter with the Cr content, usually related to the increase of the Cr-O bond length in a point charge model. This interpretation is discussed and compared to the data obtained by first-principle calculations based on density functional theory. X-ray absorption near edge structure spectra at the Cr K-edge show a pronounced evolution in the pre-edge with the Cr content, characterised by the appearance of a third feature. Calculations enable to assign the origin of this feature to Cr neighbours. The colour change from pink to brownish pink and eventually green along the solid solution has also been quantified by calculating the L*, a*, b* and x, y coefficients in the system defined by the International Commission on Illumination.

  20. Magnetic soft modes in the distorted triangular antiferromagnet -CaCr2O4

    SciTech Connect

    Toth, Sandor; Lake, Bella; Hradil, Klaudia; Rule, K; Stone, Matthew B; Islam, A. T. M. N.

    2012-01-01

    -CaCr2O4 is a spin-3/2, distorted triangular lattice antiferromagnet with a simple 120 spin structure that masks the complex pattern of exchange interactions. The magnetic excitation spectrum has been measured using inelastic neutron scattering on powder and single crystal samples. It reveals unusual low energy modes which can be explained by linear spin-wave theory assuming nearest and next-nearest neighbor interactions. The mode softening is due to the next-nearest neighbor interactions and indicates a new magnetic phase nearby as revealed by the phase diagram constructed for this system. The extracted direct exchange interactions correlate well with the Cr3+{Cr3+ distances and are in agreement with other chromium oxide delafossite compounds.

  1. Thermodynamic analysis of chemical compatibility of several compounds with Fe-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    Chemical compatibility between Fe-19.8Cr-4.8Al (weight percent), which is the base composition for the commercial superalloy MA956, and several carbides, borides, nitrides, oxides, and silicides was analyzed from thermodynamic considerations. The effect of addition of minor alloying elements, such as Ti, Y, and Y2O3, to the Fe-Cr-Al alloy on chemical compatibility between the alloy and various compounds was also analyzed. Several chemically compatible compounds that can be potential reinforcement materials and/or interface coating materials for Fe-Cr-Al based composites were identified.

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

    SciTech Connect

    Tritremmel, Christian; Daniel, Rostislav; Mitterer, Christian; Mayrhofer, Paul H.; Lechthaler, Markus; Polcik, Peter

    2012-11-15

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

  3. Oxidation behavior of cubic phases formed by alloying Al3Ti with Cr and Mn

    NASA Technical Reports Server (NTRS)

    Parfitt, L. J.; Nic, J. P.; Mikkola, D. E.; Smialek, J. L.

    1991-01-01

    Gravimetric, SEM, and XRD data are presented which document the significant improvement obtainable in the oxidation resistance of Al3Ti-containing alloys through additions of Cr. The L1(2) Al(67)Cr(8)Ti25 alloy exhibited excellent cyclic oxidation resistance at 1473 K, with the primary oxide formed being the ideally protective alpha-Al2O3. The Al(67)Mn(8)Ti(25) alloy also tested for comparison exhibited poor cyclic oxidation resistance, with substantial occurrence of TiO2 in the protective scales. Catastrophic oxidation was also encountered in the quaternary alloy Al(67)Mn(8)Ti(22)V(3).

  4. Reduction of Cr (VI) by organic acids in the presence of Al (III).

    PubMed

    Chen, Na; Lan, Yeqing; Wang, Bo; Mao, Jingdong

    2013-09-15

    The effects of Al (III) on the reduction of Cr (VI) by three α-hydroxy acids, tartaric, malic and citric acids, were investigated through batch experiments at pH from 2.5 to 4.0 and temperatures from 25 °C to 35 °C. These reactions could be described as pseudo-zero-order with respect to Cr (VI) when the concentrations of α-hydroxy acids were greatly in excess. The transformation rates of Cr (VI) to Cr (III) in the presence of Al (III) without light were in the decreasing order of tartaric acid>malic acid>citric acid. This order suggested that the two α-hydroxyl groups in tartaric acid could play an important role in the reduction of Cr (VI) by organic acids. The possible mechanism was that the formed complex between organic acids and Al (III) significantly enhanced the reductivity of α-hydroxy acids and further led to the more complicated Cr (VI)-tartaric acid-Al (III) cyclic ester which greatly accelerated the reduction rate. The Cr (VI) reduction reaction rate increased with the decrease of pH but with the increase of Al (III) concentration, tartaric acid concentration, and temperature. As the pH decreased, the increase of [H(+)] led to an increase in {Al(III)H₂Tar₂}(+), the most active species, and thus the enhanced reduction rate.

  5. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-09-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1- x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1- x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1- x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1- x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  6. Estimation Model for Electrical Conductivity of CaF2-CaO-Al2O3 Slags

    NASA Astrophysics Data System (ADS)

    Shi, Guan-yong; Zhang, Ting-an; Dou, Zhi-he; Niu, Li-ping

    2016-09-01

    Electrical conductivity is one of the most important properties of molten slags. It has an important influence on process parameter selection of the electroslag remelting process. In the present work, a new model for estimating electrical conductivity of high-temperature slags has been proposed via calculating the conductivity by electrical conductivity of pure substances and interaction parameters between the different components in the slag has been proposed. In this model, the Arrhenius law is used to describe the relationship between electrical conductivity and temperature of slags. This model has been successfully applied to the CaF2-Al2O3, CaF2-CaO, and CaO-Al2O3, as well as CaF2-CaO-Al2O3 systems, and the calculated results are in good agreement with the measured values.

  7. 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.

  8. 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.

  9. Actinide chemistry in Allende Ca-Al-rich inclusions

    NASA Technical Reports Server (NTRS)

    Murrell, M. T.; Burnett, D. S.

    1987-01-01

    Fission track radiography is used to investigate the U and Th microscale distribution in a set of Allende-meteorite Ca-Al-rich inclusions. In the Type B inclusions, the major phases melilite and fassaite are important actinide host phases, and on the rims of Type B inclusions and throughout all other inclusions studied, perovskite is the dominant actinide host phase. Results suggest that neither alteration nor loss or gain of an actinide-rich phase appears to have been an important Th/U fractionation mechanism, and that volatility differences may be the dominant factor. Th/U and rare earth element abundance patterns for the spinel and perovskite rim suggest rim formation by volatilization of interior material, and within the constraints of the brief time scale required for this heating, several mechanisms for spinel-perovskite rim formation are possible.

  10. Structural investigations of {beta}-CaAlF{sub 5} by coupling powder XRD, NMR, EPR and spectroscopic parameter calculations

    SciTech Connect

    Body, M. . E-mail: monique.body@univ-lemans.fr; Silly, G.; Legein, C.; Buzare, J.-Y.; Calvayrac, F.; Blaha, P.

    2005-12-15

    {beta}-CaAlF{sub 5} was synthesized by solid-state reaction. The precise structure was refined from X-ray powder diffraction data in the monoclinic space group P2{sub 1}/c with lattice constants a=5.3361A, b=9.8298A, c=7.3271A, and {beta}=109.91{sup o} (Z=4). The structure exhibits isolated chains of AlF{sub 6}{sup 3-} octahedra sharing opposite corners.{sup 19}F and {sup 27}Al solid state NMR spectra were recorded using MAS and SATRAS techniques. An EPR spectrum was recorded for {beta}-CaAlF{sub 5}:Cr{sup 3+}. The experimental spectra were simulated in order to extract the NMR and EPR parameter values. Five fluorine sites and one low symmetry aluminium site were found in agreement with the refined structure. These parameters were calculated using empirical and ab-initio methods. The agreement obtained between the calculated {sup 19}F chemical shift values, {sup 27}Al quadrupolar parameters, Cr{sup 3+} EPR fine structure parameters and the experimental results demonstrates the complementarity of XRD, magnetic resonance experiments and theoretical methodologies.

  11. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    FeCrAl, 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 this 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. 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.

  12. 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.

  13. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    DOE PAGES

    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 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. Synthesis and optical properties of ZnAl2O4:Cr3+, Tb3+ powders

    NASA Astrophysics Data System (ADS)

    Thi Loan, Trinh; Thi Thuy, Nguyen; Long, Nguyen Ngoc

    2013-10-01

    ZnAl2O4:Cr3+, Tb3+ powders with different dopant contents have been synthesized by sol-gel method using the following precursors: zinc nitrate (Zn(NO3)2), aluminum nitrate (Al(NO3)3), terbium nitrate (Tb(NO3)3), chrome nitrate (Cr(NO3)3), and citric acid. The effect of the Cr3+, Tb3+ concentration and heat-treating temperature on structural and optical properties of the synthesized samples has been studied. International Workshop on Advanced Materials and Nanotechnology 2012 (IWAMN 2012).

  15. Stability comparison of several icosahedral structure units of Al-Cr alloys

    NASA Astrophysics Data System (ADS)

    Liu, Da; Wang, Renhui; Ye, Yiying

    1991-02-01

    Total energies for three types of icosahedral structure units of Al-Cr alloys have been calculated based on the embedded-atom method. The results show that the most stable structure unit is the small icosahedron with a Cr atom at its center, and the hypothetical structures based on the Mackay icosahedron and Bergman rhombic triacontahedron possess higher energies compared with those of the face-centered-cubic-solid solutions and the mechanical mixtures of pure Al and Cr crystals. These results are found to be consistent with experiment.

  16. Enthalpies of formation of CaAl4O7 and CaAl12O19 (hibonite) by high temperature, alkali borate solution calorimetry

    NASA Technical Reports Server (NTRS)

    Geiger, C. A.; Kleppa, O. J.; Grossman, L.; Mysen, B. O.; Lattimer, J. M.

    1988-01-01

    Enthalpies of formation were determined for two calcium aluminate phases, CaAl4O7 and CaAl12O19, using high-temperature alkali borate solution calorimetry. The aluminates were synthesized by multiple-cycle heating and grinding stoichiometric mixtures of CaCO3 and Al2O3, and the products were characteized by X-ray diffraction and SEM microbeam analysis. The data on impurities (CaAl4O7 was found to be about 89.00 percent pure by weight and the CaAl12O19 samples about 91.48 percent pure) were used to correct the heat of solution values of the synthetic products. The enthalpies of formation, at 1063 K, from oxides, were found to be equal to -(25.6 + or - 4.7) kJ/g.f.w. for CaAl4O7 and -(33.0 + or - 9.7) kJ/g.f.w. for CaAl12O19; the respective standard enthalpies of formation from elements, at 298 K, were estimated to be -4007 + or - 5.2 kJ/g.f.w. and -10,722 + or - 12 kJ/g.f.w.

  17. Microstructure and wear behavior of γ/Al 4C 3/TiC/CaF 2 composite coating on γ-TiAl intermetallic alloy prepared by Nd:YAG laser cladding

    NASA Astrophysics Data System (ADS)

    Liu, Xiu-Bo; Shi, Shi-Hong; Guo, Jian; Fu, Ge-Yan; Wang, Ming-Di

    2009-03-01

    As a further step in obtaining high performance elevated temperature self-lubrication anti-wear composite coatings on TiAl alloy, a novel Ni-P electroless plating method was adopted to encapsulate the as-received CaF 2 in the preparation of precursor NiCr-Cr 3C 2-CaF 2 mixed powders with an aim to decrease its mass loss and increase its compatibility with the metal matrix during a Nd:YAG laser cladding. The microstructure of the coating was examined using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) and the friction and wear behavior of the composite coatings sliding against the hardened 0.45% C steel ring was evaluated using a block-on-ring wear tester at room temperature. It was found that the coating had a unique microstructure consisting of primary dendrites TiC and block Al 4C 3 carbides reinforcement as well as fine isolated spherical CaF 2 solid lubrication particles uniformly dispersed in the NiCrAlTi ( γ) matrix. The good friction-reducing and anti-wear abilities of the laser clad composite coating was suggested to the Ni-P electroless plating and the attendant reduction of mass loss of CaF 2 and the increasing of it's wettability with the NiCrAlTi ( γ) matrix during the laser cladding process.

  18. Assessing the elastic properties and ductility of Fe-Cr-Al alloys from ab initio calculations

    NASA Astrophysics Data System (ADS)

    Nurmi, E.; Wang, G.; Kokko, K.; Vitos, L.

    2016-01-01

    Fe-Al is one of the best corrosion resistant alloys at high temperatures. The flip side of Al addition to Fe is the deterioration of the mechanical properties. This problem can be solved by adding a suitable amount of third alloying component. In the present work, we use ab initio calculations based on density functional theory to study the elastic properties of Fe?Cr?Al? alloys for Al and Cr contents up to 20 at.%. We assess the ductility as a function of chemistry by making use of the semi-empirical correlations between the elastic parameters and mechanical properties. In particular, we derive the bulk modulus to shear modulus ratio and the Cauchy pressure and monitor their trends in terms of chemical composition. The present findings are contrasted with the previously established oxidation resistance of Fe-Cr-Al alloys.

  19. Identification of electronic state in perovskite CaCr O3 by high-pressure studies

    NASA Astrophysics Data System (ADS)

    Zhou, J.-S.; Alonso, J. A.; Sanchez-Benitez, J.; Fernandez-Diaz, M. T.; Martinez-Coronado, R.; Cao, L.-P.; Li, X.; Marshall, L. G.; Jin, C.-Q.; Goodenough, J. B.

    2015-10-01

    CaCr O3 is at the crossover from localized to itinerant electronic behavior, and interpretation of its electronic state has remained controversial. It is a metal from an optical study. However, the collinear type-C antiferromagnetic spin ordering below TN≈90 K is characteristic of localized electron magnetism. We have performed many runs of high-pressure synthesis. CaCr O3 crystals can be found in some batches. We have used specific-heat measurement as a diagnostic tool to probe the electronic states near the Fermi energy. An electronic bandwidth is broadened by applying high pressure. The magnetization measurement under pressure reveals a d TN/d P <0 . The crystal structural change corresponding to the pressure-induced electron structural change has been monitored by in situ neutron diffraction under high pressure. The t22 d-electron configuration on octahedral site C r4 + is orbitally threefold degenerate. Local site distortions are argued to show that in CaCr O3 the crossover from localized to itinerant 3d electrons does not result in a charge-density wave in which segregation of the interatomic interactions results in the stabilization of molecular clusters, but in an intraatomic orbital ordering that stabilizes a half-filled localized-electron x y orbital and a 1 /4 -filled c -axis π* band. Local structural changes under pressure reveal a weakening of long-range magnetic order is associated with a smooth Mott-Hubbard transition of the x y electrons.

  20. Thermal stability and thermo-mechanical properties of magnetron sputtered Cr-Al-Y-N coatings

    SciTech Connect

    Rovere, Florian; Mayrhofer, Paul H.

    2008-01-15

    Cr{sub 1-x}Al{sub x}N coatings are promising candidates for advanced machining and high temperature applications due to their good mechanical and thermal properties. Recently the authors have shown that reactive magnetron sputtering using Cr-Al targets with Al/Cr ratios of 1.5 and Y contents of 0, 2, 4, and 8 at % results in the formation of stoichiometric (Cr{sub 1-x}Al{sub x}){sub 1-y}Y{sub y}N films with Al/Cr ratios of {approx}1.2 and YN mole fractions of 0%, 2%, 4%, and 8%, respectively. Here, the impact of Y on thermal stability, structural evolution, and thermo-mechanical properties is investigated in detail. Based on in situ stress measurements, thermal analyzing, x-ray diffraction, and transmission electron microscopy studies the authors conclude that Y effectively retards diffusional processes such as recovery, precipitation of hcp-AlN and fcc-YN, grain growth, and decomposition induced N{sub 2} release. Hence, the onset temperature of the latter shifts from {approx}1010 to 1125 deg. C and the hardness after annealing at T{sub a}=1100 deg. C increases from {approx}32 to 39 GPa with increasing YN mole fraction from 0% to 8%, respectively.

  1. Preliminary Study on Fatigue Strengths of Fretted Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2002-01-01

    The fatigue behavior (stress-life curve) of gamma titanium aluminide (Ti-48Al-2Cr-2Nb, atomic percent) was examined by conducting two tests: first, a fretting wear test with a fatigue specimen in contact with a typical nickel-based superalloy contact pad in air at temperatures of 296 and 823 K and second, a high-cycle fatigue test of the prefretted Ti-48Al-2Cr-2Nb fatigue specimen at 923 K. Reference high-cycle fatigue tests were also conducted with unfretted Ti-48Al-2Cr-2Nb specimens at 923 K. All Ti-48Al-2Cr-2Nb fatigue specimens were machined from cast slabs. The results indicate that the stress-life results for the fretted Ti-48Al-2Cr-2Nb specimens exhibited a behavior similar to those of the unfretted Ti-48Al-2Cr-2Nb specimens. The values of maximum stress and life for the fretted specimens were almost the same as those for the unfretted specimens. The resultant stress-life curve for the unfretted fatigue specimens was very flat. The flat appearance in the stress-life curve of the unfretted specimens is attributed to the presence of a high density of casting pores. The fatigue strengths of both the fretted and unfretted specimens can be significantly affected by the presence of this porosity, which can decrease the fatigue life of Ti-48Al-2Cr-2Nb. The presence of the porosity made discerning the effect of fretting damage on fatigue strength and life of the specimens difficult.

  2. Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

    1996-01-01

    A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

  3. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    DOE PAGES

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition.more » Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.« less

  4. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    SciTech Connect

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.

  5. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance L.

    2015-10-01

    The Fe-Cr-Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe-Cr-Al alloys has not been fully established. In this study, a series of Fe-Cr-Al alloys with 10-18 wt % Cr and 2.9-4.9 wt % Al were neutron irradiated at 382 °C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2<111> and a<100> were detected and quantified. Results indicate precipitation of Cr-rich α‧ is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. A structure-property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α‧ precipitates at sufficiently high chromium contents after irradiation.

  6. Structure, phase composition, and strengthening of cast Al-Ca-Mg-Sc alloys

    NASA Astrophysics Data System (ADS)

    Belov, N. A.; Naumova, E. A.; Bazlova, T. A.; Alekseeva, E. V.

    2016-02-01

    The structure and phase composition of Al-Ca-Mg-Sc alloys containing 0.3 wt % Sc, up to 10 wt % Ca, and up to 10 wt % Mg have been investigated in the cast state and state after heat treatment. It has been shown that only binary phases Al4Ca, Al3Sc, and Al3Mg2 can be in equilibrium with the aluminum solid solution. It has been found that the maximum strengthening effect caused by the precipitation of Al3Sc nanoparticles for all investigated alloys is attained after annealing at 300-350°C.

  7. Synthesis of TiB2/Fe-Cr-Al nanocomposite powder.

    PubMed

    Sachan, Ritesh; Park, Jong-Woo

    2008-10-01

    In this study, a route for synthesizing TiB2/Fe-Cr-Al nanocomposite is proposed via high energy ball milling by using directly coarse powders of TiB2, Fe, Cr and Al. Various compositions of these powder mixtures are milled up to 48 hrs to investigate the effect of composition on the crystalline refinement. The crystalline size is analyzed by an X-ray diffractometer for powder samples containing 30 to 100 wt% TiB2 (the rest of the powder consists of Fe-20 wt%Cr-5 wt%Al composition). The crystalline size after 48 hrs of ball milling decreases with increasing TiB2, and then again increases after reaching a minimum value of 18 nm at 70% TiB2. By transmission electron microscopic analysis, it is confirmed that particles of TiB2 are significantly reduced and finely dispersed in the Fe-Cr-Al matrix. The particle size of TiB2 is found around 20-25 nm, reinforced in the matrix. Considering the results of this study, the proposed mechanical milling route can be recommended as a promising way for fabrication of TiB2/Fe-Cr-Al nanocomposite powder. PMID:19198473

  8. Projectile influence on production cross section for ^48Ca-, ^50Ti-, and ^54Cr- induced fusion-evaporation reactions

    NASA Astrophysics Data System (ADS)

    Mayorov, D. A.; Werke, T. A.; Alfonso, M. C.; Bennett, M. E.; Folden, C. M., III

    2013-04-01

    Evaporation residue excitation functions for ^48Ca, ^50Ti + ^159Tb and ^48Ca, ^54Cr + ^162 Dy were measured at Texas A&M University using the vacuum spectrometer MARS. The produced residues are weakly deformed nuclei near the N = 126 shell closure. However, the production cross sections are insensitive to the associated shell stabilization to the fission barrier, an observation previously reported in literature. The ratio of maximum production cross sections between the ^48Ca/^50Ti and ^48Ca/^54Cr reactions is 47 and 7100, respectively. These substantial differences can be reproduced in theoretical calculations by inclusion of collective enhancements during de-excitation of the compound nucleus. The competition between quasifission and complete fusion further contributes to the observed separation in the excitation functions. Model-dependent estimates of the compound nucleus formation probability, PCN, yield ratios of PCN(^48Ca + ^159 Tb) / PCN(^50Ti + ^159 Tb) 2.5 and PCN(^48Ca + ^162Dy) / PCN(^54Cr + ^162Dy) 5. Heavy-ion fusion reactions with ^48Ca, ^50Ti, and ^54Cr projectiles are of interest due to modern-day efforts to synthesize superheavy elements 119 and 120 in warm fusion reactions with projectiles having Z 20.

  9. Emission properties of an amorphous AlN:Cr3+ thin-film phosphor

    NASA Astrophysics Data System (ADS)

    Caldwell, M. L.; Martin, A. L.; Dimitrova, V. I.; Van Patten, P. G.; Kordesch, M. E.; Richardson, H. H.

    2001-02-01

    Chromium-doped aluminum nitride (AlN:Cr) films were grown on p-doped silicon (111) by rf magnetron sputtering in a nitrogen atmosphere at a pressure of 10-4 Torr. Film thickness was typically 200 nm. After growth, the films were "activated" at ˜1300 K for 30 min in a nitrogen atmosphere. Films activated in this manner exhibit intense cathodoluminescence and photoluminescence emission. Spectral evidence demonstrates conclusively that the luminescent centers are Cr3+ ions.

  10. Influence of recrystallization on phase separation kinetics of oxide dispersion strengthened Fe Cr Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Pimentel, G.; Chao, J.

    2012-01-01

    The effect of different starting microstructures on the kinetics of Fe-rich ({alpha}) and Cr-rich ({alpha}') phase separation during aging of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys has been analyzed with a combination of atom probe tomography and thermoelectric power measurements. The results revealed that the high recrystallization temperature necessary to produce a coarse grained microstructure in Fe-base ODS alloys affects the randomness of Cr-atom distributions and defect density, which consequently affect the phase separation kinetics at low annealing temperatures.

  11. Ca(2+) and CaM are involved in Al(3+) pretreatment-promoted fluoride accumulation in tea plants (Camellia sinesis L.).

    PubMed

    Zhang, Xian-Chen; Gao, Hong-Jian; Wu, Hong-Hong; Yang, Tian-Yuan; Zhang, Zheng-Zhu; Mao, Jing-Dong; Wan, Xiao-Chun

    2015-11-01

    Tea plant (Camellia sinensis (L.) O. kuntze) is known to be a fluoride (F) and aluminum (Al(3+)) hyper-accumulator. Previous study showed that pre-treatment of Al(3+) caused a significant increase of F accumulation in tea plants. However, less is known about the intricate network of Al(3+) promoted F accumulation in tea plants. In this study, the involvement of endogenous Ca(2+) and CaM in Al(3+) pretreatment-promoted F accumulation in tea plants was investigated. Our results showed that Al(3+) induced the inverse change of intracellular Ca(2+) fluorescence intensity and stimulated Ca(2+) trans-membrane transport in the mature zone of tea root. Also, a link between internal Ca(2+) and CaM was found in tea roots under the presence of Al(3+). In order to investigate whether Ca(2+) and CaM were related to F accumulation promoted by Al(3+) pretreatment, Ca(2+) chelator EGTA and CaM antagonists CPZ and TFP were used. EGTA, CPZ, and TFP pretreatment inhibited Al(3+)-induced increase of Ca(2+) fluorescence intensity and CaM content in tea roots, and also significantly reduced Al(3+)-promoted F accumulation in tea plants. Taken together, our results suggested that the endogenous Ca(2+) and CaM are involved in Al(3+) pretreatment-promoted F accumulation in tea roots. PMID:26318146

  12. 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.

  13. Electrochemical deposition and microstructural characterization of AlCrFeMnNi and AlCrCuFeMnNi high entropy alloy thin films

    NASA Astrophysics Data System (ADS)

    Soare, V.; Burada, M.; Constantin, I.; Mitrică, D.; Bădiliţă, V.; Caragea, A.; Târcolea, M.

    2015-12-01

    Al-Cr-Fe-Mn-Ni and Al-Cr-Cu-Fe-Mn-Ni high entropy alloy thin films were prepared by potentiostatic electrodeposition and the microstructure of the deposits was investigated. The thin films were co-deposited in an electrolyte based on a DMF (N,N-dimethylformamide)-CH3CN (acetonitrile) organic compound. The energy dispersive spectrometry investigation (EDS) indicated that all the five respectively six elements were successfully co-deposited. The scanning electron microscopy (SEM) analysis revealed that the film consists of compact and uniform particles with particle sizes of 500 nm to 4 μm. The X-ray diffractometry (XRD) patterns indicated that the as-deposited thin films were amorphous. Body-centered-cubic (BCC) structures were identified by XRD after the films were annealed at various temperatures under inert Ar atmosphere. The alloys adhesion on the substrate was determined by the scratch-testing method, with higher values obtained for the Al-Cr-Cu-Fe-Mn-Ni alloy.

  14. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approx. 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  15. Effect of Microstructure on Creep in Directionally Solidified NiAl-31Cr-3Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, I. E.

    2001-01-01

    The 1200 to 1400 K slow strain rate characteristics of the directionally solidified (DS) eutectic Ni-33Al-31Cr-3 Mo have been determined as a function of growth rate. While differences in the light optical level microstructure were observed in alloys grown at rates ranging from 7.6 to 508 mm/h, compression testing indicated that all had essentially the same strength. The exception was Ni-33 Al-31Cr-3Mo DS at 25.4 mm/h which was slightly stronger than the other growth velocities; no microstructural reason could be found for this improvement. Comparison of the approximately 1300 K properties revealed that four different DS NiAl-34(Cr,Mo) alloys have a similar creep resistance which suggests that there is a common, but yet unknown, strengthening mechanism.

  16. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1975-01-01

    The SAP technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of the alloy Ni-17Cr-5Al-0.2 Y. SAP-NiCrAl was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. A variety of annealing treatments were applied after working to determine the recrystallization response. NiCrAlY, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl of this study exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl as has been reported for other oxide dispersion strengthened alloys. In contrast, unoxidized NiCrAlY exhibited only primary recrystallization.

  17. The role of temperature on Cr(VI) formation and reduction during heating of chromium-containing sludge in the presence of CaO.

    PubMed

    Mao, Linqiang; Gao, Bingying; Deng, Ning; Zhai, Jianping; Zhao, Yongbin; Li, Qin; Cui, Hao

    2015-11-01

    In this study, the temperature dependence of Cr(VI) formation and reduction in the presence of CaO was examined during the thermal treatment of sludge that contains chromium. thermogravimetry-differential scanning calorimetry and X-ray diffractometry were used to characterize the thermal behavior and phase transformation, respectively. Na2CO3 leaching procedure was employed to determine the amount of Cr(VI). The result showed that CaO promoted Cr(III) oxidation, however, its influence is very dependent on heating temperature, with the extent of the effect varying with temperature. From 200-400 °C, the presence of CaO facilitated formation of intermediate product Cr2O3+x containing Cr(VI) during dehydration of chromium hydrate, while Cr2O3+x would decompose as temperature over 400 °C, accompanied by part of Cr(VI) being reduced to Cr(III). From 500 to 900 °C, Cr(III) reacted with CaO to form a leachable CaCrO4 product. This product was stable and a prolonged heating time did not reduce the amount of Cr(VI) significantly. At 1000-1200 °C, part of CaCrO4 was reduced to Ca(CrO2)2 in 1h. While extended heating time above 1h resulted in the Ca(CrO2)2 being oxidized reversibly to CaCrO4 at 1200 °C. Since CaCrO4 is thermodynamically less stable over 1000 °C, MgO could induce CaCrO4 to be reduced into MgCr2O4 at around 900 °C, lower than that for the reduction from CaCrO4 into Ca(CrO2)2. It suggested that adding MgO might be a potential approach for inhibiting Cr(VI) formation during heating sludge containing chromium.

  18. The role of temperature on Cr(VI) formation and reduction during heating of chromium-containing sludge in the presence of CaO.

    PubMed

    Mao, Linqiang; Gao, Bingying; Deng, Ning; Zhai, Jianping; Zhao, Yongbin; Li, Qin; Cui, Hao

    2015-11-01

    In this study, the temperature dependence of Cr(VI) formation and reduction in the presence of CaO was examined during the thermal treatment of sludge that contains chromium. thermogravimetry-differential scanning calorimetry and X-ray diffractometry were used to characterize the thermal behavior and phase transformation, respectively. Na2CO3 leaching procedure was employed to determine the amount of Cr(VI). The result showed that CaO promoted Cr(III) oxidation, however, its influence is very dependent on heating temperature, with the extent of the effect varying with temperature. From 200-400 °C, the presence of CaO facilitated formation of intermediate product Cr2O3+x containing Cr(VI) during dehydration of chromium hydrate, while Cr2O3+x would decompose as temperature over 400 °C, accompanied by part of Cr(VI) being reduced to Cr(III). From 500 to 900 °C, Cr(III) reacted with CaO to form a leachable CaCrO4 product. This product was stable and a prolonged heating time did not reduce the amount of Cr(VI) significantly. At 1000-1200 °C, part of CaCrO4 was reduced to Ca(CrO2)2 in 1h. While extended heating time above 1h resulted in the Ca(CrO2)2 being oxidized reversibly to CaCrO4 at 1200 °C. Since CaCrO4 is thermodynamically less stable over 1000 °C, MgO could induce CaCrO4 to be reduced into MgCr2O4 at around 900 °C, lower than that for the reduction from CaCrO4 into Ca(CrO2)2. It suggested that adding MgO might be a potential approach for inhibiting Cr(VI) formation during heating sludge containing chromium. PMID:26072117

  19. Microstructure and mechanical properties of (Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N films on cemented carbide substrates

    NASA Astrophysics Data System (ADS)

    Zhao, Shi-lu; Zhang, Jun; Zhang, Zhen; Wang, Shuang-hong; Zhang, Zheng-gui

    2014-01-01

    (Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N bilayer films were deposited on cemented carbide (WC-8%Co) substrates by multi-arc ion plating (MAIP) using two Ti-Al-Zr alloy targets and one pure Cr target. To investigate the composition, morphology, and crystalline structure of the bilayer films, a number of complementary methods of elemental and structural analysis were used, namely, scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Adhesive strength and mechanical properties of the films were evaluated by scratch testing and Vickers microindentation, respectively. It is shown that the resulting films have a TiN-type face-centered cubic (FCC) structure. The films exhibit fully dense, uniform, and columnar morphology. Furthermore, as the bias voltages vary from -50 to -200 V, the microhardness (max. Hv0.01 4100) and adhesive strength (max. > 200 N) of the bilayer films are superior to those of the (Ti,Al,Zr)N and (Ti,Al,Zr,Cr)N monolayer films.

  20. New type of Schottky diode-based Cu-Al-Mn-Cr shape memory material films

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Dere, A.; Mensah-Darkwa, Kwadwo; Al-Ghamdi, Ahmed; Karagoz Genç, Z.; Gupta, R. K.; Yakuphanoglu, F.

    2016-07-01

    Cr-doped CuAlMn shape memory alloys were produced by arc melting method. The effects of Cr content on microstructure and transformation parameters of were investigated. The alloys were characterized by X-ray analysis, optical microscope observations and differential scanning calorimetry measurements. The grain size of the alloys was decreased by the addition of Cr into CuAlMn alloy system. The martensite transformation temperature was shifted both the lower temperature and higher temperature with the addition of chromium. This change was explained on the basis of the change in the thermodynamics such as enthalpy, entropy and activation energy values. The obtained results indicate that the phase transformation temperatures of the CuAlMn alloy system can be controlled by addition of Cr. We fabricated a Schottky barrier diode and observed that ideality factor and barrier height increase with increasing temperature. The diodes exhibited a thermal sensor behavior. This indicates that Schottky diode-based Cu-Al-Mn-Cr shape memory material films can be used as a sensor in high-temperature measurement applications.

  1. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Douglass, D. L.; Nasrallah, M.

    1974-01-01

    The investigation reported included a determination of the optimum composition of a Ni-Cr-Al ternary alloy with respect to oxidation resistance and minimum film-spalling tendencies. Yttrium and thorium in small amounts were added to the ternary alloy and an investigation of the oxidation mechanism and the oxide scale adherence was conducted. It was found that the oxidation mechanism of Ni-Cr-Al ternary alloys depends upon the composition of the alloy as well as the time, oxygen pressure, and temperature of oxidation.

  2. Elastic Modulus Measurement of ORNL ATF FeCrAl Alloys

    SciTech Connect

    Thompson, Zachary T.; Terrani, Kurt A.; Yamamoto, Yukinori

    2015-10-01

    Elastic modulus and Poisson’s ratio for a number of wrought FeCrAl alloys, intended for accident tolerant fuel cladding application, are determined via resonant ultrasonic spectroscopy. The results are reported as a function of temperature from room temperature to 850°C. The wrought alloys were in the fully annealed and unirradiated state. The elastic modulus for the wrought FeCrAl alloys is at least twice that of Zr-based alloys over the temperature range of this study. The Poisson’s ratio of the alloys was 0.28 on average and increased very slightly with increasing temperature.

  3. Phase Compositions of Self Reinforcement Al2O3/CaAl12O19 Composite using X-ray Diffraction Data and Rietveld Technique

    NASA Astrophysics Data System (ADS)

    Asmi, D.; Low, I. M.; O'Connor, B.

    2008-03-01

    The analysis of x-ray diffraction (XRD) patterns by the Rietveld technique was tested to the quantitatively phase compositions of self reinforcement Al2O3/CaAl12O19 composite. Room-temperature XRD patterns revealed that α-Al2O3 was the only phase presence in the CA0 sample, whereas the α-Al2O3 and CaAl12O19 phases were found for CA5, CA15, CA30, and CA50 samples. The peak intensity of CA6 in the self reinforcement Al2O3/CaAl12O19 composites increased in proportion with increase in CaAl12O19 content in contrast to α-Al2O3. The diffraction patterns for CA100 sample shows minor traces of α-Al2O3 even in relatively low peak intensity. It is suggesting that the in-situ reaction sintering of raw materials were not react completely to form 100 wt% CaAl12O19 at temperature 1650 °C. Quantitative phase compositions of self reinforcement Al2O3/CaAl12O19 composites by Rietveld analysis with XRD data has been well demonstrated. The results showed that the GOF values are relatively low and the fluctuation in the difference plots shows a reasonable fit between the observed and the calculated plot.

  4. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    SciTech Connect

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explain that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.

  5. Development of ODS FeCrAl for compatibility in fusion and fission energy applications

    DOE PAGES

    Pint, Bruce A.; Dryepondt, Sebastien N.; Unocic, Kinga A.; Hoelzer, David T.

    2014-11-15

    In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is amore » general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.« less

  6. Half-metallicity in highly L21-ordered CoFeCrAl thin films

    NASA Astrophysics Data System (ADS)

    Jin, Y.; Kharel, P.; Valloppilly, S. R.; Li, X.-Z.; Kim, D. R.; Zhao, G. J.; Chen, T. Y.; Choudhary, R.; Kashyap, A.; Skomski, R.; Sellmyer, D. J.

    2016-10-01

    The structural, magnetic, and electron-transport properties of Heusler-ordered CoFeCrAl thin films are investigated experimentally and theoretically. The films, sputtered onto MgO and having thicknesses of about 100 nm, exhibit virtually perfect single-crystalline epitaxy and a high degree of L21 chemical order. X-ray diffraction and transmission-electron microscopy show that the structure of the films is essentially of the L21 Heusler type. The films are ferrimagnetic, with a Curie temperature of about 390 K, and a net moment of 2 μB per formula unit. The room temperature resistivity is 175 μΩ cm; the carrier concentration and mobility determined from the low temperature (5 K) measurement are 1.2 × 1018 cm-3 and 33 cm2/V s, respectively. In contrast to the well-investigated Heusler alloys such as Co2(Cr1-xFex)Al, the CoFeCrAl system exhibits two main types of weak residual A2 disorder, namely, Co-Cr disorder and Fe-Cr disorder, the latter conserving half-metallicity. Point-contact Andreev reflection yields a lower bound for the spin polarization, 68% at 1.85 K, but our structural and magnetization analyses suggest that the spin polarization at the Fermi level is probably higher than 90%. The high resistivity, spin polarization, and Curie temperature are encouraging in the context of spin electronics.

  7. Development of ODS FeCrAl for Compatibility in Fusion and Fission Energy Applications

    NASA Astrophysics Data System (ADS)

    Pint, B. A.; Dryepondt, S.; Unocic, K. A.; Hoelzer, D. T.

    2014-12-01

    Oxide dispersion strengthened (ODS) FeCrAl alloys with 12-15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is a general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.

  8. Development of ODS FeCrAl for compatibility in fusion and fission energy applications

    SciTech Connect

    Pint, Bruce A.; Dryepondt, Sebastien N.; Unocic, Kinga A.; Hoelzer, David T.

    2014-11-15

    In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is a general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.

  9. Characteristics of the Energetic Igniters Through Integrating Al/NiO Nanolaminates on Cr Film Bridge

    NASA Astrophysics Data System (ADS)

    Yan, YiChao; Shi, Wei; Jiang, HongChuan; Xiong, Jie; Zhang, WanLi; Li, Yanrong

    2015-12-01

    The energetic igniters through integrating Al/NiO nanolaminates on Cr film bridges have been investigated in this study. The microstructures demonstrate well-defined geometry and sharp interfaces. The depth profiles of the X-ray photoelectron spectroscopy of Al/NiO nanolaminates annealed at 550 °C with a bilayer thickness of 250 nm show that the interdiffusion between the Al layer and NiO layer has happened and the annealing temperature cannot provide enough energy to make the diffusion process much more complete. The electrical explosion characteristics employing a capacitor discharge firing set at the optimized charging voltage of 40 V show that the flame duration time is about 700 μs, and an excellent explosion performance is obtained for (Al/NiO)n/Cr igniters with a bilayer thickness of 1000 nm.

  10. Ultracold magnetically tunable interactions without radiative-charge-transfer losses between Ca+, Sr+, Ba+, and Yb+ ions and Cr atoms

    NASA Astrophysics Data System (ADS)

    Tomza, Michał

    2015-12-01

    The Ca+, Sr+, Ba+, and Yb+ ions immersed in an ultracold gas of the Cr atoms are proposed as experimentally feasible heteronuclear systems in which ion-atom interactions at ultralow temperatures can be controlled with magnetically tunable Feshbach resonances without charge transfer and radiative losses. Ab initio techniques are applied to investigate electronic-ground-state properties of the (CaCr)+, (SrCr)+, (BaCr)+, and (YbCr)+ molecular ions. The potential energy curves, permanent electric dipole moments, and static electric dipole polarizabilities are computed. The spin-restricted open-shell coupled-cluster method restricted to single, double, and noniterative triple excitations and the multireference configuration-interaction method restricted to single and double excitations are employed. The scalar relativistic effects are included within the small-core energy-consistent pseudopotentials. The leading long-range induction and dispersion interaction coefficients are also reported. Finally, magnetic Feshbach resonances between the Ca+, Sr+, Ba+, and Yb+ ions interacting with the Cr atoms are analyzed. The present proposal opens the way towards robust quantum simulations and computations with ultracold ion-atom systems free of radiative charge-transfer losses.

  11. 30 W Cr:LiSrAlF 6 flashlamp-pumped pulsed laser.

    PubMed

    Samad, Ricardo Elgul; Baldochi, Sonia Licia; Calvo Nogueira, Gesse Eduardo; Vieira, Nilson Dias

    2007-01-01

    We report the performance of a flashlamp-pumped Cr:LiSrAlF(6) (Cr:LiSAF) laser developed and built by us. The pumping cavity incorporates filters that select the flashlamps' emission spectrum to match the absorption bands of the gain medium, allowing control of the amount of nonradiactive decay heat contribution of the optical cycle, minimizing thermal effects on the laser operation. The laser generated 2 J pulses at 15 Hz, resulting in 30 W of average power, the highest power extracted from a Cr:LiSAF rod laser to our knowledge. We were able to conclude that the laser efficiency is affected by resonator configuration changes due to thermal lens effects, and not to thermal quenching of the Cr:LiSAF luminescence. PMID:17167580

  12. 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.

  13. P- T- X controls on Ca and Na distribution between Mg-Al tourmaline and fluid

    NASA Astrophysics Data System (ADS)

    Berryman, Eleanor J.; Wunder, Bernd; Rhede, Dieter; Schettler, Georg; Franz, Gerhard; Heinrich, Wilhelm

    2016-04-01

    Ca-Na partitioning between tourmaline and a coexisting fluid is investigated in the system CaO-Na2O-B2O3-Al2O3-MgO-SiO2-H2O-Cl between 0.2-4.0 GPa and 500-700 °C. The synthesis experiments produced a mineral assemblage of tourmaline, coesite/quartz, and in some cases additional phases, typically comprising <1 wt% of the solid product. The synthesized tourmalines are solid solutions of dravite [NaMg3Al6Si6O18(BO3)3(OH)3(OH)], "oxy-uvite" (i.e. "Ca-Mg-O root name") [CaMg3Al6Si6O18(BO3)3(OH)3O], and magnesio-foitite [☐(Mg2Al)Al6Si6O18(BO3)3(OH)3(OH)]. Starting materials comprised a fluid of constant ionic strength (2.00 m) and an oxide mixture with a constant Mg/Al ratio. As a result, the number of vacancies at the X site and the Mg/Al ratio of tourmaline crystals synthesized at the same temperature vary only slightly. The major solid solution is Ca-Na exchange at the X site via the exchange vector X Ca W O[ X Na W (OH)]-1, with the exchange vector X (Ca☐)[ X Na2]-1 serving as a secondary Ca-incorporation mechanism. Tourmaline's X-site composition reflects the fluid composition, whereby the Ca (or Na) concentration in the fluid corresponds with the Ca (or Na) content in tourmaline at each pressure and temperature. At 0.2 GPa, 700 °C, Ca preferentially partitions into tourmaline, producing the most Ca-rich tourmaline crystals synthesized here. At pressures >1.0 GPa, Ca partitions preferentially into the fluid, resulting in Na-dominant tourmaline compositions. Temperature has a secondary effect on Ca-Na partitioning, with higher temperatures correlating with increased Ca incorporation in tourmaline. Based on the experimental findings, tourmaline is expected to have Ca-rich compositions when it forms in low pressure, high-temperature Ca-rich rocks, consistent with the current record of tourmaline occurrence. The bulk Mg/Al ratio and the pH of the tourmaline-forming system may also affect Ca incorporation in tourmaline, but remain to be investigated experimentally.

  14. CaFeAl mixed oxide derived heterogeneous catalysts for transesterification of soybean oil to biodiesel.

    PubMed

    Lu, Yongsheng; Zhang, Zaiwu; Xu, Yunfeng; Liu, Qiang; Qian, Guangren

    2015-08-01

    CaAl layered double oxides (LDO) were prepared by co-precipitation and calcined at 750°C, and then applied to biodiesel production by transesterification reaction between methanol and soybean oil. Compared with characteristics of CaFe/LDO and CaAl/LDO, CaFeAl/LDO had the best performance based on prominent catalytic activity and stability, and achieved over 90% biodiesel yield, which stayed stable (over 85%) even after 8 cycles of reaction. The optimal catalytic reaction condition was 12:1M-ratio of methanol/oil, reaction temperatures of 60°C, 270rpm stirring rate, 60min reaction time, and 6% weight-ratio of catalyst/oil. In addition, the CaFeAl/LDO catalyst is insoluble in both methanol and methyl esters and can be easily separated for further reaction, turning it into an excellent alternative for biodiesel synthesis.

  15. CaFeAl mixed oxide derived heterogeneous catalysts for transesterification of soybean oil to biodiesel.

    PubMed

    Lu, Yongsheng; Zhang, Zaiwu; Xu, Yunfeng; Liu, Qiang; Qian, Guangren

    2015-08-01

    CaAl layered double oxides (LDO) were prepared by co-precipitation and calcined at 750°C, and then applied to biodiesel production by transesterification reaction between methanol and soybean oil. Compared with characteristics of CaFe/LDO and CaAl/LDO, CaFeAl/LDO had the best performance based on prominent catalytic activity and stability, and achieved over 90% biodiesel yield, which stayed stable (over 85%) even after 8 cycles of reaction. The optimal catalytic reaction condition was 12:1M-ratio of methanol/oil, reaction temperatures of 60°C, 270rpm stirring rate, 60min reaction time, and 6% weight-ratio of catalyst/oil. In addition, the CaFeAl/LDO catalyst is insoluble in both methanol and methyl esters and can be easily separated for further reaction, turning it into an excellent alternative for biodiesel synthesis. PMID:25740001

  16. Internal magnetic field in the zigzag-chain family (Na,Ca)Cr2O4

    NASA Astrophysics Data System (ADS)

    Nozaki, H.; Sakurai, H.; Harada, M.; Higuchi, Y.; Brewer, J. H.; Ansaldo, E. J.; Sugiyama, J.

    2014-12-01

    In order to elucidate the magnetic nature for a novel one-dimensional zigzag chain compound, NaCr2O4, we have measured μ+SR spectra using a powder sample in the temperature range between 2 and 200 K. Weak transverse field (wTF-) μ+SR measurements indicated that the whole volume of the sample enters into an antiferromagnetic (AF) phase below TN = 125 K. The zero field (ZF-) μ+SR spectrum obtained below TN exhibits a clear oscillation with a single muon-spin precession frequency (fμ). This suggests that static AF order is formed below TN and that all the implanted muons sense the same internal magnetic field. The temperature dependence of fμ was found to be very similar to that for the intensity of the magnetic Bragg peak in neutron diffraction (ND) measurements. On the other hand, the ZF-μ+SR spectrum for the isostructural compound, β-CaCr2O4, showed a rapidly damped oscillation below TN = 21 K, supporting the formation of incommensurate AF order, as proposed by ND.

  17. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE PAGES

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; Gao, Michael C.; Tang, Zhi; Poplawsky, Jonathan D.; Liaw, Peter K.

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  18. Solute transport during the cyclic oxidation of Ni-Cr-Al alloys. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.

    1982-01-01

    Important requirements for protective coatings of Ni-Cr-Al alloys for gas turbine superalloys are resistance to oxidation accompanied by thermal cycling, resistance to thermal fatigue cracking. The resistance to oxidation accompanied by thermal cycling is discussed. The resistance to thermal fatigue cracking is also considered.

  19. Mechanical properties of aluminized CoCrAlY coatings in advanced gas turbine blades

    SciTech Connect

    Kameda, J.; Bloomer, T.E. |; Sugita, Y.; Ito, A.; Sakurai, S.

    1997-07-01

    The microstructure/composition and mechanical properties (22-950 C) in aluminized CoCrAlY coatings of advanced gas turbine blades have been examined using scanning Auger microprobe and a small punch (SP) testing method. Aluminized coatings were made of layered structure divided into four regimes: (1) Al enriched and Cr depleted region, (2) Al and Cr graded region, (3) fine grained microstructure with a mixture of Al and Cr enriched phases and (4) Ni/Co interdiffusion zone adjacent to the interface SP tests demonstrated strong dependence of the deformation and fracture behavior on the various coatings regimes. Coatings 1 and 2 showed higher microhardness and easier formation of brittle cracks in a wide temperature range, compared to coatings 3 and 4. The coating 3 had lower room temperature ductility and conversely higher elevated temperature ductility than the coating 4 due to a precipitous ductility increase above 730 C. The integrity of aluminized coatings while in-service is discussed in light of the variation in the low cycle fatigue life as well as the ductility in the layered structure.

  20. Ion irradiation testing and characterization of FeCrAl candidate alloys

    SciTech Connect

    Anderoglu, Osman; Aydogan, Eda; Maloy, Stuart Andrew; Wang, Yongqiang

    2014-10-29

    The Fuel Cycle Research and Development program’s Advanced Fuels Campaign has initiated a multifold effort aimed at facilitating development of accident tolerant fuels. This effort involves development of fuel cladding materials that will be resistant to oxidizing environments for extended period of time such as loss of coolant accident. Ferritic FeCrAl alloys are among the promising candidates due to formation of a stable Al₂O₃ oxide scale. In addition to being oxidation resistant, these promising alloys need to be radiation tolerant under LWR conditions (maximum dose of 10-15 dpa at 250 – 350°C). Thus, in addition to a number of commercially available alloys, nuclear grade FeCrAl alloys developed at ORNL were tested using high energy proton irradiations and subsequent characterization of irradiation hardening and damage microstructure. This report summarizes ion irradiation testing and characterization of three nuclear grade FeCrAl cladding materials developed at ORNL and four commercially available Kanthal series FeCrAl alloys in FY14 toward satisfying FCRD campaign goals.

  1. Influence of deposition parameters on hard Cr-Al-N coatings deposited by multi-arc ion plating

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Zhang, Shihong; Chen, Zhong; Li, Jinlong; Li, Mingxi

    2012-02-01

    The Cr-Al-N coatings were synthesized at various substrate bias voltages and nitrogen partial pressures by multi-arc ion plating (M-AIP). The relationships between deposition parameters and coating properties were investigated. Morphologies, phase structures, hardness and adhesion strength of the coatings were analyzed by SEM, XRD, XPS, nano-indenter and scratch tester. The results indicated that with the increase of substrate bias voltages, the surface macroparticles and deposition rate reduced mainly for the resputtering phenomenon. The (Cr, Al)N solid-solution phase kept unchanged, but the Cr2N and AlN phases disappeared gradually. Due to the change of phase structures and residual compressive stress, the hardness values decreased and the adhesion strength decreased initially and then increased. Similarly, with the increase of nitrogen partial pressures, the phase structures of CrAlN coatings varied from Cr + Cr2N + (Cr,Al)N to Cr2N + (Cr,Al)N. The surface macroparticles increased due to the decreasing resputtering efficiency, and the deposition rate increased initially and then decreased due to the resputtering phenomenon. With increasing nitrogen partial pressures, adhesion strength decreased initially and then increased. The microhardness increased mainly due to the increase of Cr2N contents and decrease of metal macroparticles.

  2. Study of the effects of implantation on the high Fe-Ni-Cr and Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Ribarsky, M. W.

    1985-01-01

    A theoretical study of the effects of implantation on the corrosion resistance of Fe-Ni-Cr and Ni-Cr-Al alloys was undertaken. The purpose was to elucidate the process by which corrosion scales form on alloy surfaces. The experiments dealt with Ni implanted with Al, exposed to S at high temperatures, and then analyzed using scanning electron microscopy, scanning Auger spectroscopy and X-ray fluorescence spectroscopy. Pair bonding and tight-binding models were developed to study the compositions of the alloys and as a result, a new surface ordering effect was found which may exist in certain real alloys. With these models, the behavior of alloy constituents in the presence of surface concentrations of O or S was also studied. Improvements of the models to take into account the important effects of long- and short-range ordering were considered. The diffusion kinetics of implant profiles at various temperatures were investigated, and it was found that significant non-equilibrium changes in the profiles can take place which may affect the implants' performance in the presence of surface contaminants.

  3. Mn-Cr dating of Fe- and Ca-rich olivine from 'quenched' and 'plutonic' angrite meteorites using Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    McKibbin, Seann J.; Ireland, Trevor R.; Amelin, Yuri; Holden, Peter

    2015-05-01

    Angrite meteorites are suitable for Mn-Cr relative dating (53Mn decays to 53Cr with a half life of 3.7 Myr) using Secondary Ion Mass Spectrometry (SIMS) because they contain olivine and kirschsteinite with very high 55Mn/52Cr ratios arising from very low Cr concentrations. Discrepant Mn-Cr and U-Pb time intervals between the extrusive or 'quenched' angrite D'Orbigny and some slowly cooled or 'plutonic' angrites suggests that some have been affected by secondary disturbances, but this seems to have occurred in quenched rather than in slow-cooled plutonic angrites, where such disturbance or delay of isotopic closure might be expected. Using SIMS, we investigate the Mn-Cr systematics of quenched angrites to higher precision than previously achieved by this method and extend our investigation to non-quenched (plutonic or sub-volcanic) angrites. High values of 3.54 (±0.18) × 10-6 and 3.40 (±0.19) × 10-6 (2-sigma) are found for the initial 53Mn/55Mn of the quenched angrites D'Orbigny and Sahara 99555, which are preserved by Cr-poor olivine and kirschsteinite. The previously reported initial 53Mn/55Mn value of D'Orbigny obtained from bulk-rock and mineral separates is slightly lower and was probably controlled by Cr-rich olivine. Results can be interpreted in terms of the diffusivity of Cr in this mineral. Very low Cr concentrations in Ca-rich olivine and kirschsteinite are probably charge balanced by Al; this substitutes for Si and likely diffuses at a very slow rate because Si is the slowest-diffusing cation in olivine. Diffusion in Cr-rich Mg-Fe olivine is probably controlled by cation vacancies because of deficiency in charge-balancing Al and is therefore more prone to disturbance. The higher initial 53Mn/55Mn found by SIMS for extrusive angrites is more likely to reflect closure of Cr in kirschsteinite at the time of crystallisation, simultaneous with closure of U-Pb and Hf-W isotope systematics for these meteorites obtained from pyroxenes. For the younger

  4. IBA analysis and corrosion resistance of TiAlPtN/TiAlN/TiAl multilayer films deposited over a CoCrMo using magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Canto, C. E.; Andrade, E.; de Lucio, O.; Cruz, J.; Solís, C.; Rocha, M. F.; Alemón, B.; Flores, M.; Huegel, J. C.

    2016-03-01

    The corrosion resistance and the elemental profile of multilayer coatings of TiAlPtN/TiAlN/TiAl synthesized by Physical Vapor Deposition (PVD) reactive magnetron sputtering over a CoCrMo alloy substrate in 10 periods of 30 min each were analyzed and compared to those of the substrate alone and to that of a TiAlPtN single layer coating of the same thickness. The objective of the present work was to create multilayers with different amounts of Pt to enhance the corrosion resistance of a biomedical alloy of CoCrMo. Corrosion tests were performed using Simulated Body Fluid (SBF) using potentiodynamic polarization tests at typical body temperature. The elemental composition and thickness of the coatings were evaluated with the combination of two ion beam analysis (IBA) techniques: a Rutherford Backscattering Spectroscopy (RBS) with alpha beam and a Nuclear Reaction Analysis with a deuteron beam.

  5. Microstructures, mechanical properties, and electrical resistivity of rapidly quenched Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Naohara, T.; Inoue, A.; Minemura, T.; Masumoto, T.; Kumada, K.

    1982-03-01

    By the rapid quenching technique, ductile supersaturated ferrite solid solution with high hardness and strength as well as unusual electrical properties has been found in Fe-Cr-Al ternary system. This formation range is limited to less than about 35 at. pct Cr and 23 at. pct Al. The ferrite phase has fine grains of about 10 μm in diameter. Their hardness, yield strength, and tensile fracture strength increase with increase in the amounts of chromium and aluminum, and the highest values reach about 290 DPN, 720 MPa, and 740 MPa. These alloys are so ductile that no cracks are observed even after closely contacted bending test. The good strength and ductility remain almost unchanged on tempering for one hour until heated to about 923 K where a large amount of Cr2Al compound begins to precipitate preferentially along the grain boundaries of the ferrite phase. The room-temperature resistivity increases with increasing chromium and aluminum contents and reaches as high as 1.86 μ Ώ m for Fe50Cr30Al20 alloy. Also, the temperature coefficient of resistivity in the temperature range between room temperature and 773 K decreases with increasing chromium and aluminum contents and becomes zero in the vicinity of 20 to 30 at. pct Cr and 15 at. pct Al. Thus, the present alloys may be attractive as fine gauge high-resistance and/or standard-resistance wires and plates because of the unusual electrical properties combined with high strength and good ductility.

  6. Advanced ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N; Unocic, Kinga A; Hoelzer, David T; Pint, Bruce A

    2014-09-01

    ODS FeCrAl alloys are being developed with optimum composition and properties for accident tolerant fuel cladding. Two oxide dispersion strengthened (ODS) Fe-15Cr-5Al+Y2O3 alloys were fabricated by ball milling and extrusion of gas atomized metallic powder mixed with Y2O3 powder. To assess the impact of Mo on the alloy mechanical properties, one alloy contained 1%Mo. The hardness and tensile properties of the two alloys were close and higher than the values reported for fine grain PM2000 alloy. This is likely due to the combination of a very fine grain structure and the presence of nano oxide precipitates. The nano oxide dispersion was however not sufficient to prevent grain boundary sliding at 800 C and the creep properties of the alloys were similar or only slightly superior to fine grain PM2000 alloy. Both alloys formed a protective alumina scale at 1200 C in air and steam and the mass gain curves were similar to curves generated with 12Cr-5Al+Y2O3 (+Hf or Zr) ODS alloys fabricated for a different project. To estimate the maximum temperature limit of use for the two alloys in steam, ramp tests at a rate of 5 C/min were carried out in steam. Like other ODS alloys, the two alloys showed a significant increase of the mas gains at T~ 1380 C compared with ~1480 C for wrought alloys of similar composition. The beneficial effect of Yttrium for wrought FeCrAl does not seem effective for most ODS FeCrAl alloys. Characterization of the hardness of annealed specimens revealed that the microstructure of the two alloys was not stable above 1000 C. Concurrent radiation results suggested that Cr levels <15wt% are desirable and the creep and oxidation results from the 12Cr ODS alloys indicate that a lower Cr, high strength ODS alloy with a higher maximum use temperature could be achieved.

  7. High-Temperature Thermometer Using Cr-Doped GdAlO3 Broadband Luminescence

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey; Chambers, Matthew

    2011-01-01

    A new concept has been developed for a high-temperature luminescence-based optical thermometer that both shows the desired temperature sensitivity in the upper temperature range of present state-of-the-art luminescence thermometers (above 1,300 C), while maintaining substantial stronger luminescence signal intensity that will allow these optical thermometers to operate in the presence of the high thermal background radiation typical of industrial applications. This objective is attained by using a Cr-doped GdAlO3 (Cr:GdAlO3) sensor with an orthorhombic perovskite structure, resulting in broadband luminescence that remains strong at high temperature due to the favorable electron energy level spacing of Cr:GdAlO3. The Cr:GdAlO3 temperature (and pressure) sensor can be incorporated into, or applied onto, a component s surface when a non-contact surface temperature measurement is desired, or alternatively, the temperature sensor can be attached to the end of a fiber-optic probe that can then be positioned at the location where the temperature measurement is desired. In the case of the fiber-optic probe, both the pulsed excitation and the luminescence emission travel through the fiber-optic light guide. In either case, a pulsed light source provides excitation of the luminescence, and the broadband luminescence emission is collected. Real-time temperature measurements are obtain ed using a least-squares fitting algorithm that determines the luminescence decay time, which has a known temperature dependence established by calibration. Due to the broad absorption and emission bands for Cr:GdAlO3, there is considerable flexibility in the choice of excitation wavelength and emission wavelength detection bands. The strategic choice of the GdAlO3 host is based on its high crystal field, phase stability, and distorted symmetry at the Cr3+ occupation sites. The use of the broadband emission for temperature sensing at high temperatures is a key feature of the invention and is

  8. The effect of chemical pressure on the structure and properties of A2CrOsO6 (A=Sr, Ca) ferrimagnetic double perovskite

    NASA Astrophysics Data System (ADS)

    Morrow, Ryan; Soliz, Jennifer R.; Hauser, Adam J.; Gallagher, James C.; Susner, Michael A.; Sumption, Michael D.; Aczel, Adam A.; Yan, Jiaqiang; Yang, Fengyuan; Woodward, Patrick M.

    2016-06-01

    The ordered double perovskites Sr2CrOsO6 and Ca2CrOsO6 have been synthesized and characterized with neutron powder diffraction, electrical transport measurements, and high field magnetization experiments. As reported previously Sr2CrOsO6 crystallizes with R 3 bar symmetry due to a-a-a- octahedral tilting. A decrease in the tolerance factor leads to a-a-b+ octahedral tilting and P21/n space group symmetry for Ca2CrOsO6. Both materials are found to be ferrimagnetic insulators with saturation magnetizations near 0.2 μB. Sr2CrOsO6 orders at 660 K while Ca2CrOsO6 orders at 490 K. Variable temperature magnetization measurements suggest that the magnetization of the Cr3+ and Os3+ sublattices have different temperature dependences in Sr2CrOsO6. This leads to a non-monotonic temperature evolution of the magnetic moment. Similar behavior is not seen in Ca2CrOsO6. Both compounds have similar levels of Os/Cr antisite disorder, with order parameters of η=80.2(4)% for Sr2CrOsO6 and η=76.2(5)% for Ca2CrOsO6, where η=2θ-1 and θ is the occupancy of the osmium ion on the osmium-rich Wyckoff site.

  9. Characterization of Ni-20Cr-5Al model alloy in supercritical water

    NASA Astrophysics Data System (ADS)

    Huang, Xiao; Guzonas, D.

    2014-02-01

    MCrAlY is a class of coating materials that provide corrosion and oxidation resistance to many Ni and Fe based alloys by forming dense alumina layer on the surface. In order to assess its potential as corrosion resistant coatings on components in supercritical water cooled nuclear reactors (SWCR), a Ni-20Cr-5Al model alloy is tested in SCW (500 °C and 25 MPa) for over 6000 h. The long term corrosion behavior of the samples with various surface preparations is evaluated by measuring weight change and examining surface microstructure and oxide formation. The results show that surface preparation alone can lead to changes in weight gain as great as an order of magnitude. Smooth and near stress free surface allows for more oxidation to take place in SCW, hence more weight change. Simple grinding with abrasive paper yields the least and most stable weight change while grit blasting has some effect in reducing weight gain. Comparing to other alloys tested under similar condition, Ni-20Cr-5Al has the lowest weight change. Although not detected, the formation of Al2O3 or an Al modified Cr2O3 superficial layer is likely the reason for such low weight change.

  10. Deformation and fracture of a directionally solidified NiAl-28Cr-6Mo eutectic alloy

    NASA Technical Reports Server (NTRS)

    Chen, X. F.; Johnson, D. R.; Noebe, R. D.; Oliver, B. F.

    1995-01-01

    A directionally solidified alloy based on the NiAl-(Cr, Mo) eutectic was examined by transmission and scanning electron microscopy to characterize the microstructure and room temperature deformation and fracture behavior. The microstructure consisted of a lamellar morphology with a group of zone axes (111) growth direction for both the NiAl and (Cr, Mo) phases. The interphase boundary between the eutectic phases was semicoherent and composed of a well-defined dislocation network. In addition, a fine array of coherent NiAl precipitates was dispersed throughout the (Cr, Mo) phase. The eutectic morphology was stable at 1300 K with only coarsening of the NiAl precipitates occurring after heat treatment for 1.8 ks (500 h). Fracture of the aligned eutectic is characterized primarily by a crack bridging/renucleation mechanism and is controlled by the strength of the semicoherent interface between the two phases. However, contributions to the toughness of the eutectic may arise from plastic deformation of the NiAl phase and the geometry associated with the fracture surface.

  11. Deformation and fracture of a directionally solidified NiAl-28Cr-6Mo eutectic alloy

    SciTech Connect

    Chen, X.F.; Johnson, D.R.; Noebe, R.D.; Oliver, B.F.

    1995-05-01

    A directionally solidified alloy based on the NiAl-(Cr, Mo) eutectic was examined by transmission and scanning electron microscopy to characterize the microstructure and room temperature deformation and fracture behavior. The microstructure consisted of a lamellar morphology with a group of zone axes (111) growth direction for both the NiAl and (Cr, Mo) phases. The interphase boundary between the eutectic phases was semicoherent and composed of a well-defined dislocation network. In addition, a fine array of coherent NiAl precipitates was dispersed throughout the (Cr, Mo) phase. The eutectic morphology was stable at 1300 K with only coarsening of the NiAl precipitates occurring after heat treatment for 1.8 ks (500 h). Fracture of the aligned eutectic is characterized primarily by a crack bridging/renucleation mechanism and is controlled by the strength of the semicoherent interface between the two phases. However, contributions to the toughness of the eutectic may arise from plastic deformation of the NiAl phase and the geometry associated with the fracture surface.

  12. Pressure-induced amorphous-to-amorphous configuration change in Ca-Al metallic glasses

    PubMed Central

    Lou, H. B.; Fang, Y. K.; Zeng, Q. S.; Lu, Y. H.; Wang, X. D.; Cao, Q. P.; Yang, K.; Yu, X. H.; Zheng, L.; Zhao, Y. D.; Chu, W. S.; Hu, T. D.; Wu, Z. Y.; Ahuja, R.; Jiang, J. Z.

    2012-01-01

    Pressure-induced amorphous-to-amorphous configuration changes in Ca-Al metallic glasses (MGs) were studied by performing in-situ room-temperature high-pressure x-ray diffraction up to about 40 GPa. Changes in compressibility at about 18 GPa, 15.5 GPa and 7.5 GPa during compression are detected in Ca80Al20, Ca72.7Al27.3, and Ca66.4Al33.6 MGs, respectively, whereas no clear change has been detected in the Ca50Al50 MG. The transfer of s electrons into d orbitals under pressure, reported for the pressure-induced phase transformations in pure polycrystalline Ca, is suggested to explain the observation of an amorphous-to-amorphous configuration change in this Ca-Al MG system. Results presented here show that the pressure induced amorphous-to-amorphous configuration is not limited to f electron-containing MGs. PMID:22530094

  13. Cage Structure Formation of Singly Doped Aluminum Cluster Cations Al n TM + ( TM = Ti, V, Cr)

    NASA Astrophysics Data System (ADS)

    Lang, Sandra M.; Claes, Pieterjan; Neukermans, Sven; Janssens, Ewald

    2011-09-01

    Structural information on free transition metal doped aluminum clusters, Al n TM + ( TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size ( n = 5 - 35) and temperature ( T = 145 - 300 K) dependent investigations reveal that bare Al n + clusters are inert toward argon, while Al n TM + clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum cage. The critical size, n crit , is found to be surprisingly large, namely n crit = 16 and n crit = 19 - 21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster-argon bond dissociation energies have been derived as function of cluster size from equilibrium mass spectra and are in the 0.1-0.3 eV range.

  14. Experimental study and thermodynamic modeling of the Al-Co-Cr-Ni system

    NASA Astrophysics Data System (ADS)

    Gheno, Thomas; Liu, Xuan L.; Lindwall, Greta; Liu, Zi-Kui; Gleeson, Brian

    2015-10-01

    A thermodynamic database for the Al-Co-Cr-Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β-γ equilibrium, and good agreement for three-phase β-γ-σ and β-γ-α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.

  15. Oxide scales formed on Fe-Cr-Al-based model alloys exposed to oxygen containing molten lead

    NASA Astrophysics Data System (ADS)

    Weisenburger, A.; Jianu, A.; Doyle, S.; Bruns, M.; Fetzer, R.; Heinzel, A.; DelGiacco, M.; An, W.; Müller, G.

    2013-06-01

    Based on the state of the art oxide maps concerning oxidation behavior of Fe-Cr-Al model alloys at 800 and 1000 °C in oxygen atmosphere, ten compositions, belonging to this alloy system, were designed in order to tap the borders of the alumina stability domain, during their exposure to oxygen (10-6 wt.%) containing lead, at 400, 500 and 600 °C. Eight alloys, Fe-6Cr-6Al, Fe-8Cr-6Al, Fe-10Cr-5Al, Fe-14Cr-4Al, Fe-16Cr-4Al, Fe-6Cr-8Al, Fe-10Cr-7Al and Fe-12Cr-5Al, were found to be protected against corrosion in oxygen containing lead, either by a duplex layer (Fe3O4 + (Fe1-x-yCrxAly)3O4) or by (Fe1-x-yCrxAly)3O4, depending on the temperature at which they were exposed. Two alloys namely Fe-12Cr-7Al and Fe-16Cr-6Al were found to form transient aluminas, κ-Al2O3 (at 400 and 500 °C) and θ-Al2O3 (at 600 °C), as protective oxide scale against corrosion in oxygen containing lead. An oxide map illustrating the stability domain of alumina, grown on Fe-Cr-Al alloys when exposed to molten, oxygen containing lead, was drawn. The map includes also additional points, extracted from literature and corresponding to alumina forming alloys, when exposed to HLMs, which fit very well with our findings. Chromium and aluminium contents of 12.5-17 wt.% and 6-7.5 wt.%, respectively, are high enough to obtain thin, stable and protective alumina scales on Fe-Cr-Al-based alloys exposed to oxygen containing lead at 400, 500 and 600 °C. For the temperature range and exposure times used during the current evaluation, the growth rate of the alumina scale was low. No area with detached scale was observed and no trace of α-Al2O3 was detected.

  16. The microstructure-strength relationship in a deformation processed Al-Ca composite

    SciTech Connect

    Tian, Liang; Kim, Hyongjune; Anderson, Iver; Russell, Alan

    2013-02-07

    An Al-9 vol% Ca composite was produced by powder metallurgy and deformation processing. The Al–Ca composite was extruded, swaged and wire drawn to a deformation true strain of 13.8. Both Al and Ca are face-centered cubic, so the Ca second phase deformed into continuous, nearly cylindrical filaments in the Al matrix. The formation of intermetallic compounds, filament coarsening, and spheriodization at elevated temperature was observed by scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction. Both the thickness and spacing of the Ca filaments decreased exponentially with increasing deformation. The ultimate tensile strength of the composite increased rapidly with increased deformation, especially at high deformation processing strains. The relation between deformation true strain and ultimate tensile strength is underestimated by the rule of mixtures; a modified Hall–Petch barrier strengthening model was found to fit the data better.

  17. Self-healing of defects in CaO coatings on V-5%Cr-5%Ti in liquid lithium

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1994-11-01

    In-situ electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt % dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at >360{degrees}C.

  18. Effect of surface roughness on the development of protective Al 2O 3 on Fe-10Al (at.%) alloys containing 0-10 at.% Cr

    NASA Astrophysics Data System (ADS)

    Zhang, Z. G.; Hou, P. Y.; Gesmundo, F.; Niu, Y.

    2006-11-01

    The effect of alloy surface roughness, achieved by different degrees of surface polishing, on the development of protective alumina layer on Fe-10 at.% Al alloys containing 0, 5, and 10 at.% Cr was investigated during oxidation at 1000 °C in 0.1 MPa oxygen. For alloys that are not strong Al 2O 3 formers (Fe-10Al and Fe-5Cr-10Al), the rougher surfaces increased Fe incorporation into the overall surface layer. On the Fe-10Al, more iron oxides were formed in a uniform layer of mixed aluminum- and iron-oxides since the layer was thicker. On the Fe-5Cr-10Al, more iron-rich nodules developed on an otherwise thin Al 2O 3 surface layer. These nodules nucleated preferentially along surface scratch marks but not on alloy grain boundaries. For the strong Al 2O 3-forming Fe-10Cr-10Al alloy, protective alumina surface layers were observed regardless of the surface roughness. These results indicate that the formation of a protective Al 2O 3 layer on Fe-Cr-Al surfaces is not dictated by Al diffusion to the surface. More cold-worked surfaces caused an enhanced Fe diffusion, hence produced more Fe-rich oxides during the early stage of oxidation.

  19. Ga, Ca, and 3d transition element (Cr through Zn) partitioning among spinel-lherzolite phases from the Lanzo massif, Italy: Analytical results and crystal chemistry

    SciTech Connect

    Wogelius, R.A.; Fraser, D.G.

    1994-06-01

    Ultramafic rocks exposed in Lanzo massif, Italy is a record of mantle geochemistry, melting, sub-solidus re-equilibration. Plagioclase(+ spinel)-lherzolite samples were analyzed by Scanning Proton Microscopy, other techniques. Previous work postulated partial melting events and a two-stage sub-solidus cooling history; this paper notes Ga enrichment on spinel-clinopyroxene grain boundaries, high Ga and transition element content of spinel, and pyroxene zonation in Ca and Al. Trace element levels in olivine and orthopyroxene are also presented. Zoning trends are interpreted as due to diffusion during cooling. Olivine-clinopyroxene Cr and Ca exchange as well as clinopyroxene and spinel zonation trends indicate that the massif experienced at least two sub-solidus cooling episodes, one at 20 kbar to 1000 C and one at 8 kbar <750C. Ga levels in cores of Lanzo high-Cr spinels are high (82-66 ppM) relative to other mantle spinels (66-40 ppM), indicating enrichment. Ga content of ultramafic spinels apparently increases with Cr content; this may be due to: increased Ga solubility stemming from crystal chemical effects and/or higher Ga activities in associated silicate melts. Thus, during melting, high-Cr residual spinel may tend to buffer solid-phase Ga level. These spinels are not only rich in Ga and Cr (max 26.37 el. wt %), but also in Fe (max 21.07 el. wt %), Mn (max 3400 ppM), and Zn (max 2430 ppM). These enrichments are again due to melt extraction and partitioning into spinel structure. Low Ni (min 1050 ppM) levels are due to unsuccessful competition of Ni with Cr for octahedral structural sites caused by crystal field. Comparisons of change in partitioning vs Cr content among several 3d transition elements for spinels from Lanzo, other localities allow us to separate crystal field effects from bulk chemical effects and to show that in typical assemblages, inversion of olivine-spinel partition coefficient for Ni from <1 to >1 should occur at 11% el. wt. Cr in spinel.

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

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

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

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

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

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

  3. Ca-rich Ca-Al-oxide, high-temperature-stable sorbents prepared from hydrotalcite precursors: synthesis, characterization, and CO2 capture capacity.

    PubMed

    Chang, Po-Hsueh; Chang, Yen-Po; Chen, San-Yuan; Yu, Ching-Tsung; Chyou, Yau-Pin

    2011-12-16

    We present the design and synthesis of Ca-rich Ca-Al-O oxides, with Ca(2+)/Al(3+) ratios of 1:1, 3:1, 5:1, and 7:1, which were prepared by hydrothermal decomposition of coprecipitated hydrotalcite-like Ca-Al-CO(3) precursors, for high-temperature CO(2) adsorption at 500-700 °C. In situ X-ray diffraction measurements indicate that the coprecipitated, Ca-rich, hydrotalcite-like powders with Ca(2+)/Al(3+) ratios of 5:1 and 7:1 contained Ca(OH)(2) and layered double hydroxide (LDH) phases. Upon annealing, LDH was first destroyed at approximately 200 °C to form an amorphous matrix, and then at 450-550 °C, the Ca(OH)(2) phase was converted into a CaO matrix with incorporated Al(3+) to form a homogeneous solid solution without a disrupted lattice structure. CaO nanocrystals were grown by thermal treatment of the weakly crystalline Ca-Al-O oxide matrix. Thermogravimetric analysis indicates that a CO(2) adsorption capacity of approximately 51 wt. % can be obtained from Ca-rich Ca-Al-O oxides prepared by calcination of 7:1 Ca-Al-CO(3) LDH phases at 600-700 °C. Furthermore, a relatively high CO(2) capture capability can be achieved, even with gas flows containing very low CO(2) concentrations (CO(2)/N(2) = 10 %). Approximately 95.6 % of the initial CO(2) adsorption capacity of the adsorbent is retained after 30 cycles of carbonation-calcination. TEM analysis indicates that carbonation-promoted CaCO(3) formation in the Ca-Al-O oxide matrix at 600 °C, but a subsequent desorption in N(2) at 700 °C, caused the formation CaO nanocrystals of approximately 10 nm. The CaO nanocrystals are widely distributed in the weakly crystalline Ca-Al-O oxide matrix and are present during the carbonation-calcination cycles. This demonstrates that Ca-Al-O sorbents that developed through the synthesis and calcination of Ca-rich Ca-Al LDH phases are suitable for long-term cyclic operation in severe temperature environments.

  4. Influence of Al Contents on the Microstructure, Mechanical, and Wear properties of Magnetron Sputtered CrAlN Coatings

    NASA Astrophysics Data System (ADS)

    Shah, Hetal N.; Jayaganthan, R.

    2012-09-01

    CrAlN (0 < x < 0.1) coatings were deposited on SA304 substrate by a reactive magnetron sputtering. The microstructure and composition of the as-deposited coatings were systematically characterized by field emission scanning electron microscopy/EDS and atomic force microscopy, and the phase formation by x-ray diffraction (XRD). The hardness of the coatings was investigated using nanoindentation, while wear properties were investigated using pin-on-disk tribometer. XRD study reveals that the deposited CrAlN coatings crystallized in the cubic B1 NaCl structure. The minimum and maximum hardness of the coatings are found to be 15.28 and 18.81 GPa, respectively. The COF and wear rate are found to be 0.48 and 2.25 × 10-5 mm3/N · m, which is lower than the CrN coatings deposited and characterized under the same environment (0.63 and 2.25 × 10-5 mm3/Nm).

  5. The band structure-matched and highly spin-polarized Co{sub 2}CrZ/Cu{sub 2}CrAl Heusler alloys interface

    SciTech Connect

    Ko, V.; Han, G.; Qiu, J.; Feng, Y. P.

    2009-11-16

    Here we present a lattice- and band-matched nonmagnetic L21 Heusler alloy spacer for Co{sub 2}CrZ Heusler alloys where Z=Si or Al. By first principle calculations, we find that the band structure matching is almost perfectly satisfied when they are interfaced with Cu{sub 2}CrAl. Despite the loss of half-metallicity due to interface states, our calculations show that the spin polarization at these band-matched (001) interfaces is higher than 80%. These lattice-matched Co{sub 2}CrZ/Cu{sub 2}CrAl interfaces with excellent band matching and enhanced spin scattering asymmetry are promising for all-metallic current-perpendicular-to-plane giant magnetoresistance device applications.

  6. Cr diffusion in MgAl2O4 synthetic spinels: preliminary results

    NASA Astrophysics Data System (ADS)

    Freda, C.; Celata, B.; Andreozzi, G.; Perinelli, C.; Misiti, V.

    2012-04-01

    Chromian spinel is an accessory phase common in crustal and mantle rocks, including peridotites, gabbros and basalts. Spinel, it has been identified as one of the most effective, sensible, and versatile petrogenetic indicator in mafic and ultramafic rock systems due to the strict interdependence between its physico-chemical properties (chemical composition, cation configuration etc.) and genetic conditions (temperature, pressure, and chemical characteristics of the system). In particular, studies on intra- and inter-crystalline Mg-Fe2+, Cr-Al exchange demonstrated the close relationship between spinel composition and both degree of partial melting and equilibrium temperature of spinel-peridotites. Moreover, studies focused on the chemical zoning of Mg-Fe2+ and/or Cr-Al components in spinel have been used, combined with a diffusion model, to provide quantitative information on peridotites and gabbros pressure-temperature paths and on deformation mechanisms. Although these potentials, most of the experimental studies have been performed on spinels hosting a limited content of divalent iron (sensu stricto, MgAl2O4), whereas the scarce studies on Cr-Al inter-diffusion coefficient have been performed at 3-7 GPa as pressure boundary condition. In order to contribute to the understanding of processes occurring in the lithospheric mantle, we have initiated an experimental research project aiming at determining the Cr-Al inter-diffusion in spinel at 2 GPa pressure and temperature ranging from 1100 to 1250 °C. The experiments were performed in a end-loaded piston cylinder by using a 19 mm assembly and graphite-Pt double capsules. As starting materials we used synthetic Mg-Al spinel (200-300 μm in size) and Cr2O3 powder. Microanalyses of experimental charge were performed on polished carbon-coated mounts by electronic microprobe. Line elemental analyses were made perpendicular to the contact surface between Cr2O3 powder and spinel, at interval of 2 μm. By processing these

  7. Overaluminizing of a CoNiCrAlY Coating by Inward and Outward Diffusion Treatments

    NASA Astrophysics Data System (ADS)

    Bababdani, Samira Mohseni; Nogorani, Farhad Shahriari

    2014-04-01

    Overaluminizing is a commercially accepted treatment to enhance high temperature oxidation resistance of MCrAlY overlay coatings. In the current investigation, a low pressure plasma-sprayed CoNiCrAlY coating was aluminized by two different growth modes: outward growth and inward growth. The resultant microstructures were characterized by means of scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction analysis. The results showed that the final microstructure of both types of overaluminized coatings was similar and included Al-rich NiAl and Ni-rich NiAl zones from the top to the bottom. The details of the microstructures are discussed and compared with the results of simple aluminizing of the nickel-based substrate.

  8. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    NASA Astrophysics Data System (ADS)

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-03-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description.

  9. Wear Behavior of High Velocity Arc Spraying FeNiCrAlBRE/Ni95Al Composite Coatings

    NASA Astrophysics Data System (ADS)

    Tian, H. L.; Wei, S. C.; Chen, Y. X.; Tong, H.; Liu, Y.; Xu, B. S.

    Wear-resistant FeNiCrAlBRE/Ni95Al composite coatings were deposited on carbon steel plate by high velocity arc spraying. Adhesive strength of the composite coating was improved by spraying Ni95Al cored wires as transition layer between working coating and substrate. Scanning electron microscopy and Vickers hardness testing were used to evaluate coatings structure and mechanical properties. For quantitative investigation of porosity, a computer image analyzer was used. The forming, the wear resistance and its mechanism of the coatings were studied. The results show that coating has relatively high average hardness about 550 HV0.1 and adhesive strength is 47 MPa. The worn surface characterized shallow grooves and few of debris on the coating manifested that the coating has better wear resistance under dry sliding conditions.

  10. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    PubMed Central

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-01-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description. PMID:26928759

  11. Properties of Cr:LiSrAlF[sub 6] crystals for laser operation

    SciTech Connect

    Chai, B.H.T. ); Payne, S.A.; Smith, L.K.; Beach, R.J.; Tassano, J.H.; DeLoach, L.D.; Kway, W.L.; Solarz, R.W.; Krupke, W.F. )

    1994-08-20

    We have performed several physical and optical measurements on the Cr:LiSAF (LiSrAlF[sub 6]) laser material that are relevant to its laser performance, including thermal and mechanical properties, water durabilities, and Auger upconversion constants. The expansion coefficient, Young's modulus, fracture toughness, thermal conductivity, and heat capacity are all used to determine an overall thermomechanical figure of merit for the crystal. An investigation of the water durability suggests that the cooling solution should be maintained at pH = 7 to ameliorate problems associated with water dissolution. The Auger constant was found to become much more significant at higher Cr doping, in which excited-state migration leads to a substantial increase in the upconversion rate. We propose a design for a 50-W Cr:LiSAF laser system that is based on a detailed knowledge of all the relevant material parameters.

  12. Optical and physical properties of the LiSrAlF[sub 6]:Cr laser crystal

    SciTech Connect

    Smith, L.K.; Payne, S.A.; Tassano, J.B.; DeLoach, L.D.; Kway, W.L.; Krupke, W.F.

    1993-05-18

    We have measured several of the physical and optical parameters of the LiSrAlF[sub 6]:Cr or Cr:LiSAF laser material that are important to its laser performance, including the thermomechanical properties, water durabilities and Auger upconversion constants. A thermomechanical figure-of-merit has been determined from measurements of the fracture toughness, expansion coefficient, thermal conductivity, Young's modulus, and heat capacity. Tests of water durability suggest that a neutral pH of 7 is optimum to minimize water dissolution. The Auger effect was found to be a significant factor at higher Cr concentration, where excited-state migration leads to an increase in the upconversion rate. 17 refs, 1 fig, 4 tabs.

  13. Optical and physical properties of the LiSrAlF{sub 6}:Cr laser crystal

    SciTech Connect

    Smith, L.K.; Payne, S.A.; Tassano, J.B.; DeLoach, L.D.; Kway, W.L.; Krupke, W.F.

    1993-05-18

    We have measured several of the physical and optical parameters of the LiSrAlF{sub 6}:Cr or Cr:LiSAF laser material that are important to its laser performance, including the thermomechanical properties, water durabilities and Auger upconversion constants. A thermomechanical figure-of-merit has been determined from measurements of the fracture toughness, expansion coefficient, thermal conductivity, Young`s modulus, and heat capacity. Tests of water durability suggest that a neutral pH of 7 is optimum to minimize water dissolution. The Auger effect was found to be a significant factor at higher Cr concentration, where excited-state migration leads to an increase in the upconversion rate. 17 refs, 1 fig, 4 tabs.

  14. Effect of Cr on Microstructure and Properties of a Series of AlTiCr x FeCoNiCu High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Li, Anmin; Ma, Ding; Zheng, Qifeng

    2014-04-01

    A series of AlTiCr x FeCoNiCu ( x: molar ratio, x = 0.5, 1.0, 1.5, 2.0, 2.5) high-entropy alloys (HEAs) were prepared by vacuum arc furnace. These alloys consist of α-phase, β-phase, and γ-phase. These phases are solid solutions. The structure of α-phase and γ-phase is face-centered cubic structure and that of β-phase is body-centered cubic (BCC) structure. There are four typical cast organizations in these alloys such as petal organization (α-phase), chrysanthemum organization (α-phase + β-phase), dendrite (β-phase), and inter-dendrite (γ-phase). The solidification mode of these alloys is affected by Chromium. If γ-phase is not considered, AlTiCr0.5FeCoNiCu and AlTiCrFeCoNiCu belong to hypoeutectic alloys; AlTiCr1.5FeCoNiCu, AlTiCr2.0FeCoNiCu, and AlTiCr2.5FeCoNiCu belong to hypereutectic alloys. The cast organizations of these alloys consist of pro-eutectic phase and eutectic structure (α + β). Compact eutectic structure and a certain amount of fine β-phase with uniform distribution are useful to improve the microhardness of the HEAs. More γ-phase and the microstructure with similar volume ratio values of α-phase and β-phase improve the compressive strength and toughness of these alloys. The compressive fracture of the series of AlTiCr x FeCoNiCu HEAs shows brittle characteristics, suggesting that these HEAs are brittle materials.

  15. Relative phase and physical properties of CrN/AlN multilayer: A DFT study

    NASA Astrophysics Data System (ADS)

    Cudris, E. F.; Díaz F, J. H.; Espita R, M. J.

    2016-08-01

    Using first principles total-energy calculations within the framework of density functional theory, we studied the relative stability and the structural and electronic properties of multilayer CrN/AlN in the sodium chloride (NaCl), cesium chloride (CsCl), nickel arsenide (NiAs), zinc-blende, and wurtzite structures. The calculations were carried out using the method based on pseudopotentials, employed exactly as implemented in Quantum-ESPRESSO code. Based on total energy minimization, we found that the minimum global energy of CrN/AlN is obtained for the zincblende structure. Additionally, at high pressure our calculations show the possibility of a phase transition from the zincblende to NaCl structure. For the zincblende phase, the density of states analysis reveals that the multilayer exhibits a half-metallic behavior with a magnetic moment of 3.0^p/Cr-atom. These properties come essentially from the polarization of Cr-d and N-p states that cross the Fermi level. Due to these properties, the multilayer can potentially be used in the field of spintronics or spin injectors.

  16. 1300 K Compressive Properties of Directionally Solidified Ni-33Al-33Cr-1Mo

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, S. V.; Locci, Ivan E.

    2000-01-01

    The Ni-33Al-33Cr-1Mo eutectic has been directionally solidified by a modified Bridgeman technique at growth rates ranging from 7.6 to 508 mm/h to produce grain/cellular microstructures, containing alternating plates of NiAl and Cr alloyed with Mo. The grains had sharp boundaries for slower growth rates (< 12.7 mm/h), while faster growth rates (> 25.4 mm/h) lead to cells bounded by intercellular regions. Compressive testing at 1300 K indicated that alloys DS'ed at rates between 25.4 to 254 mm/h possessed the best strengths which exceed that for the as-cast alloy.

  17. Fuel Performance Calculations for FeCrAl Cladding in BWRs

    SciTech Connect

    George, Nathan; Sweet, Ryan; Maldonado, G. Ivan; Wirth, Brian D.; Powers, Jeffrey J.; Worrall, Andrew

    2015-01-01

    This study expands upon previous neutronics analyses of the reactivity impact of alternate cladding concepts in boiling water reactor (BWR) cores and directs focus toward contrasting fuel performance characteristics of FeCrAl cladding against those of traditional Zircaloy. Using neutronics results from a modern version of the 3D nodal simulator NESTLE, linear power histories were generated and supplied to the BISON-CASL code for fuel performance evaluations. BISON-CASL (formerly Peregrine) expands on material libraries implemented in the BISON fuel performance code and the MOOSE framework by providing proprietary material data. By creating material libraries for Zircaloy and FeCrAl cladding, the thermomechanical behavior of the fuel rod (e.g., strains, centerline fuel temperature, and time to gap closure) were investigated and contrasted.

  18. Creep behavior of commercial FeCrAl foils: beneficial and detrimental effect of oxidation

    SciTech Connect

    Dryepondt, Sebastien N; Pint, Bruce A; Lara-Curzio, Edgar

    2012-01-01

    Creep tests were performed at 875 and 1050 C on commercially available FeCrAl foils (~50 m, 2 mil thickness) over a wide range of stress and duration to characterize their creep behavior. The oxide scales formed on the creep specimens were analyzed and compared to those that formed on unstressed specimens to assess the effect of stress and strain on oxide growth mechanisms. Below a specific stress threshold, creep rate and lifetime become independent of the applied load and rupture occurs due to the onset of breakaway oxidation. A creep rate model based on the strengthening of the FeCrAl foils due to load-bearing by the thermally-grown alumina scale was observed to be in good agreement with the experimental results.

  19. The Temporal Evolution of the Nanostructure of a Model Ni-Al-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2004-01-01

    The early to the later stages of precipitation of ordered gamma'-precipitates (L1(sub 2)) in Ni-5.2 Al-14.2 Cr (at.%) are studied at 873 K. Precipitates with radii as small as 0.45 nm are characterized fully by three-dimensional atom-probe (3DAP) microscopy. Contrary to what is often assumed by theory or in models, the average precipitate composition is shown to evolve with time, such that solute concentrations decrease toward an equilibrium value given by the solvus lines. Power-law time dependencies of the number density, mean radius, and supersaturations of Al and Cr are discussed in light of theoretical predictions for Ostwald ripening.

  20. Characterization and CO oxidation activity of Cu/Cr/Al{sub 2}O{sub 3} catalysts

    SciTech Connect

    Park, P.W.; Ledford, J.S.

    1998-03-01

    X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) have been used to characterize a series of Cu/Cr/Al{sub 2}O{sub 3} catalysts prepared by stepwise incipient wetness impregnation of first chromium followed by copper (designated CuCry). The copper loading was held constant at 8 wt% CuO, and chromium loadings were varied from 0 to 20 wt% Cr{sub 2}O{sub 3}. The information obtained from surface and bulk characterization has been correlated with the CO oxidation activity of the catalysts. XPS and XRD results of analogous Cry indicated that the Cr dispersion decreased and the concentration of Cr{sup 3+} species increased with increasing Cr content. The decrease in Cu dispersion of CuCry with increasing Cr content has been attributed to the formation of large crystalline CuO and CuCr{sub 2}O{sub 4}. Copper addition decreased the Cr dispersion by reacting selectively with a dispersed Cr{sup 3+} species to form CuCr{sub 2}O{sub 4} species. However, the Cu addition did not affect the Cr oxidation state distribution compared to that of Cry. For low Cr loading CuCry catalysts (Cr/Al {le} 0.027), the CO oxidation activity increased with increasing Cr content due to the formation of crystalline CuO on the Cr-modified alumina. This has been attributed to the inhibition of Cu ion diffusion into alumina lattice vacancies by highly dispersed chromium species. The CuCry catalyst of Cr/Al = 0.054 showed the highest CO oxidation activity due to the formation of CuCr{sub 2}O{sub 4} which was more active than the CuO phase. For Cr-rich catalysts (Cr/Al {ge} 0.080), the decrease in CO oxidation activity has been ascribed to the encapsulation of the active site with Cr{sub 2}O{sub 3} species.

  1. Effects of ruthenium on phase separation in a model Ni-Al-Cr-Ru superalloy

    NASA Astrophysics Data System (ADS)

    Zhou, Yang; Isheim, Dieter; Hsieh, Gillian; Noebe, Ronald D.; Seidman, David N.

    2013-04-01

    The temporal evolution of a Ni-10.0Al-8.5Cr-2.0Ru (at.%) alloy aged at 1073 K was investigated using transmission electron microscopy (TEM) and atom-probe tomography. The γ‧(L12)-precipitate morphology is spheroidal through 256 h of ageing as a result of adding Ru, which decreases the lattice parameter misfit between the γ‧(L12)- and γ(f.c.c.)-phases. The addition of Ru accelerates the compositional evolution of the γ‧(L12)- and γ(f.c.c.)-phases, which achieve their equilibrium compositions after 0.25 h. Initially, Ru accelerates the partitioning of Ni and Cr to the γ(f.c.c.)-phase, and the partitioning of Al to the γ‧(L12)-phase, but after 0.25 h, Ru, which partitions to the γ(f.c.c.)-phase, decreases the partitioning of Ni and increases the partitioning of Al and Cr. The temporal evolution of the average radius, ⟨R(t)⟩, number density, volume fraction of the γ‧(L12)-precipitates, and the supersaturations of Ni, Al, Cr, and Ru in the γ(f.c.c.)- and γ‧(L12)-phases are compared in detail with predictions of coarsening models and PrecipiCalc simulations. Based on a spline function fitting procedure of the concentration profiles between the γ‧(L12)- and γ(f.c.c.)-phases, it is demonstrated that the temporal evolution of the normalized interfacial width, δ/⟨R(t)⟩ vs. ⟨R(t)⟩, of each element, decreases with increasing ageing time: δ is the interfacial width.

  2. Effect of creep stress on microstructure of a Ni-Cr-W-Al-Ti superalloy

    SciTech Connect

    Doh, J.M.; Yoo, K.K.; Choi, J.; Hur, S.K.; Baik, H.K.

    1996-02-15

    Creep stress changes the morphology and distribution of the precipitates in the precipitation-hardened alloys. It leads to the formation of precipitate free zones (PFZs) near the grain boundaries. From the microstructural observation of the creep tested specimens of a Ni-Cr-W-Al-Ti superalloy, the relation between PFZs and the amount of plastic deformation in the creep-ruptured specimen is established and the validity of the existing model is discussed based upon the experimental results.

  3. The effect of zirconium on the cyclic oxidation of NiCrAl alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Khan, A. S.; Lowell, C. E.

    1981-01-01

    This paper examines results with cyclic oxidation tests of Ni(9-20) Cr(15-30) Al-(x)Zr alloys carried out at 1100 C and 1200 C in static air. The concentration of zirconium varies from 0 to 0.63 atomic percent. Significant aluminum penetration is found in metallographic and electron microscopic examination of oxidized surfaces. Small amounts of zirconium lead to minimal penetration, and with increased zirconium content pronounced oxide penetration is observed.

  4. Analysis of the FeCrAl Accident Tolerant Fuel Concept Benefits during BWR Station Blackout Accidents

    SciTech Connect

    Robb, Kevin R

    2015-01-01

    Iron-chromium-aluminum (FeCrAl) alloys are being considered for fuel concepts with enhanced accident tolerance. FeCrAl alloys have very slow oxidation kinetics and good strength at high temperatures. FeCrAl could be used for fuel cladding in light water reactors and/or as channel box material in boiling water reactors (BWRs). To estimate the potential safety gains afforded by the FeCrAl concept, the MELCOR code was used to analyze a range of postulated station blackout severe accident scenarios in a BWR/4 reactor employing FeCrAl. The simulations utilize the most recently known thermophysical properties and oxidation kinetics for FeCrAl. Overall, when compared to the traditional Zircaloy-based cladding and channel box, the FeCrAl concept provides a few extra hours of time for operators to take mitigating actions and/or for evacuations to take place. A coolable core geometry is retained longer, enhancing the ability to stabilize an accident. Finally, due to the slower oxidation kinetics, substantially less hydrogen is generated, and the generation is delayed in time. This decreases the amount of non-condensable gases in containment and the potential for deflagrations to inhibit the accident response.

  5. Effects of C and Cr content on high-temperature microstructures of Fe-9Al-30Mn-xC-yCr alloys

    SciTech Connect

    Chen, May-Show; Cheng, Hsin-Chung; Huang, Chiung-Fang; Chao, Chih-Yeh; Ou, Keng-Liang; Yu, Chih-Hua

    2010-02-15

    This investigation elucidated the effects of C and Cr content on the high-temperature microstructures of Fe-9Al-30Mn-xC-yCr alloys by means of optical microscopy and transmission electron microscopy. With increasing Cr content, the phase transition sequence within the {alpha} phase was found to be {alpha} + B2 {yields} {alpha} + B2 + DO{sub 3} {yields} {alpha} + DO{sub 3}. And with increasing C content, a {gamma} {yields} ({gamma} + {kappa}) phase transition was observed within the {gamma} phase. The {kappa} phase carbides ((Fe,Mn){sub 3}AlC{sub x}) had an ordered L'1{sub 2}-type structure with lattice parameter a = 0.368 nm and were formed by a spinodal decomposition during quenching. The amounts of Cr{sub 7}C{sub 3} increased with the C and Cr content. Moreover, the Al and Mn content played important roles in expanding the ({alpha} + {gamma}) region. These features have not been previously reported in the Fe-Al-Mn-C-Cr alloy system.

  6. Phosphate-sulfide assemblages and Al/Ca ratios in type-3 chondrites

    NASA Astrophysics Data System (ADS)

    Rubin, A. E.; Grossman, J. N.

    1985-09-01

    Electron microscopic examinations were carried out on various chondrites to re-examine previously reported anomalously high Al/Ca ratios. Polished thin sections of the three CV3, two CO3 and the Krymka LL3 chondrites were scanned to characterize the phosphate-sulfide inclusions. The formation of the assemblages was interpreted as proceeding in five steps, starting with the formation of metal grains with early nebular material and finishing with a reaction between schreibersite with Ca, O and Cl to form merrillite and chloropatite. The abundances of the observed assemblages were not high enough to imply Al/Ca ratios similar to whole-rocks. It is concluded that the specimens were originally examined with a broader electron beam than used to examine standard samples, and resulted in the anomalously high Al/Ca ratios.

  7. Phosphate-sulfide assemblages and Al/Ca ratios in type-3 chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, A. E.; Grossman, J. N.

    1985-01-01

    Electron microscopic examinations were carried out on various chondrites to re-examine previously reported anomalously high Al/Ca ratios. Polished thin sections of the three CV3, two CO3 and the Krymka LL3 chondrites were scanned to characterize the phosphate-sulfide inclusions. The formation of the assemblages was interpreted as proceeding in five steps, starting with the formation of metal grains with early nebular material and finishing with a reaction between schreibersite with Ca, O and Cl to form merrillite and chloropatite. The abundances of the observed assemblages were not high enough to imply Al/Ca ratios similar to whole-rocks. It is concluded that the specimens were originally examined with a broader electron beam than used to examine standard samples, and resulted in the anomalously high Al/Ca ratios.

  8. Effects of Solute Concentrations on Kinetic Pathways in Ni-Al-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Weninger, Jessica; Sudbrack, Chantal K.; Mao, Zugang; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The kinetic pathways resulting from the formation of coherent gamma'-precipitates from the gamma-matrix are studied for two Ni-Al-Cr alloys with similar gamma'-precipitate volume fractions at 873 K. The details of the phase decompositions of Ni-7.5Al-8.5Cr at.% and Ni-5.2Al-14.2Cr at.% for aging times from 1/6 to 1024 h are investigated by atom-probe tomography, and are found to differ significantly from a mean-field description of coarsening. The morphologies of the gamma'-precipitates of the alloys are similar, though the degrees of gamma'-precipitate coagulation and coalescence differ. Quantification within the framework of classical nucleation theory reveals that differences in the chemical driving forces for phase decomposition result in differences in the nucleation behavior of the two alloys. The temporal evolution of the gamma'-precipitate average radii and the gamma-matrix supersaturations follow the predictions of classical coarsening models. The compositional trajectories of the gamma-matrix phases of the alloys are found to follow approximately the equilibrium tie-lines, while the trajectories of the gamma'-precipitates do not, resulting in significant differences in the partitioning ratios of the solute elements.

  9. Structural and magnetic properties of Co 2CrAl Heusler alloys prepared by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Hakimi, M.; Kameli, P.; Salamati, H.

    2010-11-01

    Mechanical alloying has been used to produce nanocrystalline samples of Co 2CrAl Heusler alloys. The samples were characterized by using different methods. The results indicate that, it is possible to produce L2 1-Co 2CrAl powders after 15 h of ball-milling. The grain size of 15 h ball milled L2 1-Co 2CrAl Heusler phase, calculated by analyzing the XRD peak broadening using Williamson and Hall approach was 14 nm. The estimated magnetic moment per formula unit is ˜2 μ B. The obtained magnetic moment is significantly smaller than the theoretical value of 2.96 μ B for L2 1 structure. It seems that an atomic disorder from the crystalline L2 1-type ordered state and two-phase separation depresses the ferromagnetic ordering in alloy. Also, the effect of annealing on the structural and magnetic properties of ball milled powders was investigated. Two structures were identified for annealed sample, namely L2 1 and B2. The obtained value for magnetic moment of annealed sample is smaller than the as-milled sample due to the presence of disordered B2 phase and improvement of phase separation.

  10. Fe-Cr-Al containing oxide semiconductors as potential solar water-splitting materials.

    PubMed

    Sliozberg, Kirill; Stein, Helge S; Khare, Chinmay; Parkinson, Bruce A; Ludwig, Alfred; Schuhmann, Wolfgang

    2015-03-01

    A high-throughput thin film materials library for Fe-Cr-Al-O was obtained by reactive magnetron cosputtering and analyzed with automated EDX and XRD to elucidate compositional and structural properties. An automated optical scanning droplet cell was then used to perform photoelectrochemical measurements of 289 compositions on the library, including electrochemical stability, potentiodynamic photocurrents and photocurrent spectroscopy. The photocurrent onset and open circuit potentials of two semiconductor compositions (n-type semiconducting: Fe51Cr47Al2Ox, p-type semiconducting Fe36.5Cr55.5Al8Ox) are favorable for water splitting. Cathodic photocurrents are observed at 1.0 V vs RHE for the p-type material exhibiting an open circuit potential of 0.85 V vs RHE. The n-type material shows an onset of photocurrents at 0.75 V and an open circuit potential of 0.6 V. The p-type material showed a bandgap of 1.55 eV, while the n-type material showed a bandgap of 1.97 eV. PMID:25650842

  11. Fe-Cr-Al containing oxide semiconductors as potential solar water-splitting materials.

    PubMed

    Sliozberg, Kirill; Stein, Helge S; Khare, Chinmay; Parkinson, Bruce A; Ludwig, Alfred; Schuhmann, Wolfgang

    2015-03-01

    A high-throughput thin film materials library for Fe-Cr-Al-O was obtained by reactive magnetron cosputtering and analyzed with automated EDX and XRD to elucidate compositional and structural properties. An automated optical scanning droplet cell was then used to perform photoelectrochemical measurements of 289 compositions on the library, including electrochemical stability, potentiodynamic photocurrents and photocurrent spectroscopy. The photocurrent onset and open circuit potentials of two semiconductor compositions (n-type semiconducting: Fe51Cr47Al2Ox, p-type semiconducting Fe36.5Cr55.5Al8Ox) are favorable for water splitting. Cathodic photocurrents are observed at 1.0 V vs RHE for the p-type material exhibiting an open circuit potential of 0.85 V vs RHE. The n-type material shows an onset of photocurrents at 0.75 V and an open circuit potential of 0.6 V. The p-type material showed a bandgap of 1.55 eV, while the n-type material showed a bandgap of 1.97 eV.

  12. Oxidation and Hot Corrosion Behavior of Plasma-Sprayed MCrAlY-Cr2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Tiantian; Huang, Chuanbing; Lan, Hao; Du, Lingzhong; Zhang, Weigang

    2016-08-01

    The oxidation and hot corrosion behavior of two atmospheric plasma-sprayed NiCoCrAlY-Cr2O3 and CoNiCrAlY-Cr2O3 coatings, which are primarily designed for wear applications at high temperature, were investigated in this study. The two coatings were exposed to air and molten salt (75%Na2SO4-25%NaCl) environment at 800 °C under cyclic conditions. Oxidation and hot corrosion kinetic curves were obtained by thermogravimetric technique. X-ray diffraction analysis and scanning electron microscopy with energy-dispersive x-ray spectrometry were employed to characterize the coatings' microstructure, surface oxides, and composition. The results showed that both coatings provided the necessary oxidation resistance with oxidation rates of about 1.03 × 10-2 and 1.36 × 10-2 mg/cm2 h, respectively. The excellent oxidation behavior of these two coatings is attributed to formation of protective (Ni,Co)Cr2O4 spinel on the surface, while as-deposited Cr2O3 in the coatings also acted as a barrier to diffusion of oxidative and corrosive substances. The greater presence of Co in the CoNiCrAlY-Cr2O3 coating restrained internal diffusion of sulfur and slowed down the coating's degradation. Thus, the CoNiCrAlY-Cr2O3 coating was found to be more protective than the NiCoCrAlY-Cr2O3 coating under hot corrosion condition.

  13. MASS MEASUREMENT OF {sup 45}Cr AND ITS IMPACT ON THE Ca-Sc CYCLE IN X-RAY BURSTS

    SciTech Connect

    Yan, X. L.; Xu, H. S.; Litvinov, Yu. A.; Zhang, Y. H.; Tu, X. L.; Zhou, X. H.; He, J. J.; Sun, Y.; Wang, M.; Yuan, Y. J.; Xia, J. W.; Yang, J. C.; Jia, G. B.; Hu, Z. G.; Ma, X. W.; Mao, R. S.; Schatz, H.; Blaum, K.; Sun, B. H.; Audi, G.; and others

    2013-03-20

    Masses of neutron-deficient {sup 58}Ni projectile fragments have been measured at the HIRFL-CSR facility in Lanzhou, China employing the isochronous mass spectrometry technique. Masses of a series of short-lived T{sub z} = -3/2 nuclides including the {sup 45}Cr nucleus have been measured with a relative uncertainty of about 10{sup -6}-10{sup -7}. The new {sup 45}Cr mass turned out to be essential for modeling the astrophysical rp-process. In particular, we find that the formation of the predicted Ca-Sc cycle in X-ray bursts can be excluded.

  14. Formation Mechanism of CaS-Bearing Inclusions and the Rolling Deformation in Al-Killed, Low-Alloy Steel with Ca Treatment

    NASA Astrophysics Data System (ADS)

    Xu, Guang; Jiang, Zhouhua; Li, Yang

    2016-08-01

    The existing form of CaS inclusion in Ca-treated, Al-killed steel during secondary refining process was investigated with scanning electron microscopy and an energy-dispersive spectrometer (EDS). The results of 12 heats industrial tests showed that CaS has two kinds of precipitation forms. One form takes place by the direct reaction of Ca and S, and the other takes place by the reaction of CaO in calcium aluminates with dissolved Al and S in liquid steel. Thermodynamic research for different precipitation modes of CaS under different temperature was carried out. In particular, CaO-Al2O3-CaS isothermal section diagrams and component activities of calcium aluminates were calculated by the thermodynamic software FactSage. By thermodynamic calculation, a precipitation-area diagram of oxide-sulfide duplex inclusion was established by fixing the sulfur content. The quantity of CaS, which was precipitated in a reaction between [Al], [S] and (CaO), can be calculated and predicted based on the precipitation-area diagram of oxide-sulfide duplex inclusion. Electron probe microanalysis and EDS were used for observing rolling deformation of different types of CaS-bearing inclusions during the rolling process. Low modification of calcium aluminates wrapped by CaS has different degrees of harm to steel in the rolling process. A thick CaS layer can prevent some fragile calcium aluminates from being crushed during the rolling process. Some oxide-sulfide duplex inclusion contains little CaS performed better deformation during the rolling process, but when CaS in oxide-sulfide duplex inclusion becomes more, it will cause the whole inclusion to lose plastic yielding ability. The plastic deformation region of CaS-bearing inclusion in a CaO-Al2O3-CaS isothermal section diagram is confirmed.

  15. 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.

  16. Formation of α-alumina scales in the Fe-Al(Cr) diffusion coating on China low activation martensitic steel

    NASA Astrophysics Data System (ADS)

    Zhan, Qin; Zhao, Weiwei; Yang, Hongguang; Hatano, Yuji; Yuan, Xiaoming; Nozaki, Teo; Zhu, Xinxin

    2015-09-01

    To study the formation mechanism of stable α-Al2O3 scales, the oxidation behavior of Fe-Al(Cr) diffusion coating on China low activation martensitic steel has been investigated under the oxygen partial pressure ranging from 1 to 20,000 Pa at 1253 K. A single, continuous Al2O3 scale with the maximum thickness of about 2000 nm was formed on the Fe-Al(Cr) diffusion layer. The phase transformation of alumina scales on the surface of Fe-Al(Cr) layer was studied at different oxidation times ranging from 3 to 180 min. With the increase in oxygen partial pressure, the phase transformation time of α-Al2O3 is decreased. The metastable γ-Al2O3 and transition α-(Al0.948Cr0.052)2O3 phases were formed in the earlier oxidation process and finally transformed to the stable α-Al2O3 phase, which were detected by grazing incidence angle X-ray diffraction and confirmed by transmission electron microscopy. This implies that Cr shows the third element effect and serves as a template for the nucleation of the stable α-Al2O3.

  17. Fabrication and performance testing of CaO insulator coatings on V-5%Cr-5%Ti in liquid lithium

    SciTech Connect

    Park, J.H.; Dragel, G.

    1995-04-01

    Corrosion resistance of structural materials, and the magnetohydrodynamic (MHD) force and its influence on thermal hydraulics and corrosion, are major concerns in the design of liquid-metal blankets for magnetic fusion reactors (MFRs). The objective of this study is to develop in-situ stable coatings at the liquid-metal/structural-material interface, with emphasis on coatings that can be converted to an electrically insulating film to prevent adverse currents that are generated by the MHD force from passing through the structural walls. The electrical resistance of CaO coatings produced on V-5Cr-5Ti by exposure of the alloy to liquid Li that contained 0.5 - 8.5 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degree}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420{degree}C to produce a CaO coating.

  18. Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

    NASA Astrophysics Data System (ADS)

    Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

    2015-02-01

    High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

  19. Sirolimus-loaded CaP coating on Co-Cr alloy for drug-eluting stent

    PubMed Central

    Yang, Jingxin; Lee, In-Seop; Cui, Fuzhai

    2016-01-01

    To achieve polymer-free and controllable drug-eluting system, there have been many efforts to modify the surface composition and topography of metal stent. Recently, calcium phosphate is commonly applied to metallic implants as a coating material for fast fixation and firm-implant bone attachment on the account of its demonstrated bioactive and osteoconductive properties. In the present study, the release of sirolimus could be controllable because of immobilization of sirolimus during the process of biomimetic CaP coating forming. A completely new concept is the drug carrier of biomimetic CaP coating with sirolimus for an absorbable drug eluting system, which in turn can serve as a drug reservoir. We here describe the characteristic, mechanisms and drug release in vitro of new drug-eluting system in comparison to conventional system equivalent. Nano-structured calcium phosphate (CaP) coating was formed on the cobalt–chromium (Co-Cr) alloy substrate. By immersing coated sample in solution with sirolimus (rapamycin), the sirolimus could be immobilized in the newly formed CaP layer. The morphology, composition and formation process of the coating were studied with scanning electron microscopy, energy dispersive spectrometer, X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that a uniform CaP coating incorporated with sirolimus was observed on Co-Cr alloy. PMID:27252886

  20. Temperature variation of the size effect in dilute AlMg and AlCa alloys: Measurement and theory

    NASA Astrophysics Data System (ADS)

    Gilder, H. M.; Asty, M.; Audit, Ph.

    1980-12-01

    Optical-interferometric-differential-length and x-ray lattice-parameter measurements performed at low temperatures in dilute AlMg and AlCa alloys indicate that the temperature variation of the size effect corresponds to a relatively large difference between the intrinsic coefficient of thermal expansion βi of the solute atom structure and that, β, of the solvent. This result is another example of the surprising expansive properties of point defects previously described by Gilder and co-workers (high-temperature vacancy diffusion) and more recently by Ganne (low-temperature dilatometry on irradiated specimens). Specifically, in the temperature range 0.2Ca)β~-4. This, as well as the fact that the sign of the change in the coefficient of thermal expansion Δβ of the host metal caused by the introduction of the solute atom is positive for Mg and negative for Ca, indicates that solute-solvent valence effects play a minor role in determining the coefficient of thermal expansion of the dilute alloy. It is also found, to within the experimental precision, that Δβ(Mg) and Δβ(Ca) are temperature independent, suggesting a type of Matthiessen's rule for thermal expansion. A model calculation of the size effect and its temperature variation in the infinitely dilute alloy is presented. The volume-dependent forces are treated by means of a term describing the elastic energy associated with the solute-solvent volume misfit, whereas the temperature-dependent potential of Dagens et al. is used to calculate the pairwise interaction between the solvent ions and the solute ion. Good agreement with the experimental data is obtained for the size effect in both AlMg and AlCa. The calculated values of Δβ(Mg)Ci, Ci being the solute concentration, and βi(Mg) fall between the measured values in the two AlMg alloys studied. The calculation of Δβ(Ca)Ci and βi(Ca) is not possible due to a lack of elastic-constants data for pure, metallic

  1. Amorphous structure and properties in laser-clad Ni-Cr-Al coating on Al-Si alloy

    NASA Astrophysics Data System (ADS)

    Liang, Gongying; Wong, T. T.; Su, J. Y.; Woo, C. H.

    1999-09-01

    A Ni-Cr-Al coating was clad by a 5 kW CO2 laser with different laser power on Al-Si alloy. Using transmission electron microscopy, a mixing microstructure containing Ni- based amorphous structures was observed in the laser clad zones. As the uniformity of chemical composition and temperature is poor in the laser cladding, the amorphous structure with some Ni3Al crystals coexisted in the cladding. According to the morphologies of Ni-based amorphous structures, the amorphous structure existed not only in the net-like boundaries surrounding the granular structure but also in the granular structure. The microhardness of the mixture amorphous structure is between HV 600 - 800, which is lower than that of crystal phases in the coating. A differential thermal analysis showed that Ni- based amorphous structure exhibits a higher initial crystallizing temperature (about 588 degree(s)C), which is slightly higher than that of the eutectic temperature of Al- Si alloy. The wear experimental results showed that some amorphous structure exist in the laser cladding can reduce the peeling of the granular phases from matrix, and improve the its wear resistance.

  2. HIGH TEMPERATURE BRAZING ALLOY FOR JOINT Fe-Cr-Al MATERIALS AND AUSTENITIC AND FERRITIC STAINLESS STEELS

    DOEpatents

    Cost, R.C.

    1958-07-15

    A new high temperature brazing alloy is described that is particularly suitable for brazing iron-chromiumaluminum alloys. It consists of approximately 20% Cr, 6% Al, 10% Si, and from 1.5 to 5% phosphorus, the balance being iron.

  3. Electronic and magnetic properties of Cr-Mn-Ni-Al compound with LiMgPdSb-type structure

    NASA Astrophysics Data System (ADS)

    Wang, L. Y.; Wang, X. T.; Guo, R. K.; Lin, T. T.; Liu, G. D.

    2016-10-01

    We investigate the electronic and magnetic properties of Cr-Mn-Ni-Al compound with a LiMgPdSn-type structure in three different atomic arrangement configurations (AAC) by using the first-principles calculations. It was found that Cr-Mn-Ni-Al compound with type I AAC exhibits a spin-gapless semiconductive characteristic. The type II AAC is the most stable one and exhibits an especial band structure where the Fermi level slightly crosses the top of the valence bands in spin-up channel and the bottom of conductive bands in spin-down channel, which leads to the electronic transport with the spin-resolved carrier type. The Cr-Mn-Ni-Al compound shows an ordinary metallic behavior in type III AAC. The three nonequivalent atomic arrangement configurations of Cr-Mn-Ni-Al are all in ferromagnetic ground state under their equilibrium lattice parameters.

  4. Thermo-mechanical processing (TMP) of Ti-48Al-2Nb-2Cr based alloys

    SciTech Connect

    Fuchs, G.E.

    1995-02-01

    The effects of heat treatment and deformation processing on the microstructures and properties of {gamma}-TiAl based alloys produced by ingot metallurgy (I/M) and powder metallurgy (P/M) techniques were examined. The alloy selected for this work is the second generation {gamma}-TiAl based alloy -- Ti-48Al-2Nb-2Cr (at %). Homogenization of I/M samples was performed at a variety of temperatures, followed by hot working by isothermal forging. P/M samples were prepared from gas atomized powders, consolidated by both HIP and extrusion and some of the HIPed material was then hot worked by isothermal forging. The effects of processing, heat treatment and hot working on the microstructures and properties will be discussed.

  5. Effect of Ca addition on the corrosion behavior of Mg-Al-Mn alloy

    NASA Astrophysics Data System (ADS)

    Yang, Jiang; Peng, Jian; Nyberg, Eric A.; Pan, Fu-sheng

    2016-04-01

    The microstructures and corrosion resistance of magnesium-5 wt% aluminum-0.3 wt% manganese alloys (Mg-Al-Mn) with different Ca additions (0.2-4 wt%) were investigated. Results showed that with increasing Ca addition, the grain of the alloys became more refined, whereas the corrosion resistant ability of the alloys initially increased and then decreased. The alloy with 2 wt% Ca addition exhibited the best corrosion resistance, attributed to the effect of the oxide film and (Mg,Al)2Ca phases which were discontinuously distributed on the grain boundaries. These phases acted as micro-victims, they preferentially corroded to protect the α-Mg matrix. The oxide film formed on the alloy surface can hinder the solution further to protect the α-Mg matrix.

  6. Structure of multilayered Cr(Al)N/SiOx nanocomposite coatings fabricated by differential pumping co-sputtering

    NASA Astrophysics Data System (ADS)

    Kawasaki, Masahiro; Nose, Masateru; Onishi, Ichiro; Shiojiri, Makoto

    2013-11-01

    A Cr(Al)N/38 vol. % SiOx hard coating was prepared on a (001) Si substrate at 250 °C in a differential pumping co-sputtering system, which has two chambers for radio frequency (RF) sputtering and a substrate holder rotating on the chambers. The composite coating was grown by alternate sputter-depositions from CrAl and SiO2 targets with flows of N2+Ar and Ar at RF powers of 200 and 75 W, respectively, on transition layers grown on the substrate. Analytical electron microscopy reveled that the Cr(Al)N/SiOx coating had a multilayered structure of Cr(Al)N crystal layers ˜1.6 nm thick and two-dimensionally dispersed amorphous silicon oxide (a-SiOx) particles with sizes of ˜1 nm or less. The a-SiOx particles were enclosed with the Cr(Al)N layers. The coating had a low indentation hardness of ˜25 GPa at room temperature, due to a high oxide fraction of 38 vol. % and a low substrate rotational speed of 1 rpm. Faster rotation and lower oxide fraction would make a-SiOx particles smaller, resulting in the formation of Cr(Al)N crystal including the very fine a-SiOx particles with small number density. They would work as obstacles for the lattice deformation of the Cr(Al)N crystals. We have fabricated a superhard coating of Cr(Al)N/17 vol. % SiOx with a hardness of 46 GPa prepared at 12 rpm.

  7. Structure of multilayered Cr(Al)N/SiO{sub x} nanocomposite coatings fabricated by differential pumping co-sputtering

    SciTech Connect

    Kawasaki, Masahiro; Nose, Masateru; Onishi, Ichiro; Shiojiri, Makoto

    2013-11-11

    A Cr(Al)N/38 vol. % SiO{sub x} hard coating was prepared on a (001) Si substrate at 250 °C in a differential pumping co-sputtering system, which has two chambers for radio frequency (RF) sputtering and a substrate holder rotating on the chambers. The composite coating was grown by alternate sputter-depositions from CrAl and SiO{sub 2} targets with flows of N{sub 2}+Ar and Ar at RF powers of 200 and 75 W, respectively, on transition layers grown on the substrate. Analytical electron microscopy reveled that the Cr(Al)N/SiO{sub x} coating had a multilayered structure of Cr(Al)N crystal layers ∼1.6 nm thick and two-dimensionally dispersed amorphous silicon oxide (a-SiO{sub x}) particles with sizes of ∼1 nm or less. The a-SiO{sub x} particles were enclosed with the Cr(Al)N layers. The coating had a low indentation hardness of ∼25 GPa at room temperature, due to a high oxide fraction of 38 vol. % and a low substrate rotational speed of 1 rpm. Faster rotation and lower oxide fraction would make a-SiO{sub x} particles smaller, resulting in the formation of Cr(Al)N crystal including the very fine a-SiO{sub x} particles with small number density. They would work as obstacles for the lattice deformation of the Cr(Al)N crystals. We have fabricated a superhard coating of Cr(Al)N/17 vol. % SiO{sub x} with a hardness of 46 GPa prepared at 12 rpm.

  8. Structure and composition of higher-rhenium-content superalloy based on La-alloyed Ni-Al-Cr

    SciTech Connect

    Kozlov, Eduard V.; Koneva, Nina A.; Nikonenko, Elena L.; Popova, Natalya A.; Fedorischeva, Marina V.

    2015-10-27

    The paper presents the transmission and scanning electronic microscope investigations of Ni-Al-Cr superalloy alloyed with additional Re and La elements. This superalloy is obtained by a directional solidification method. It is shown that such additional elements as Re and La result in formation of new phases in Ni-Al-Cr accompanied by considerable modifications of quasi-cuboid structure in its γ’-phase.

  9. In quest of cathode materials for Ca ion batteries: the CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni).

    PubMed

    Arroyo-de Dompablo, M E; Krich, C; Nava-Avendaño, J; Palacín, M R; Bardé, F

    2016-07-20

    Basic electrochemical characteristics of CaMO3 perovskites (M = Mo, Cr, Mn, Fe, Co, and Ni) as cathode materials for Ca ion batteries are investigated using first principles calculations at the Density Functional Theory level (DFT). Calculations have been performed within the Generalized Gradient Approximation (GGA) and GGA+U methodologies, and considering cubic and orthorhombic perovskite structures for CaxMO3 (x = 0, 0.25, 0.5, 0.75 and 1). The analysis of the calculated voltage-composition profile and volume variations identifies CaMoO3 as the most promising perovskite compound. It combines good electronic conductivity, moderate crystal structure modifications, and activity in the 2-3 V region with several intermediate CaxMoO3 phases. However, we found too large barriers for Ca diffusion (around 2 eV) which are inherent to the perovskite structure. The CaMoO3 perovskite was synthesized, characterized and electrochemically tested, and results confirmed the predicted trends. PMID:27398629

  10. High hardness and superlative oxidation resistance in a pseudo-icosahehdral Cr-Al binary

    NASA Astrophysics Data System (ADS)

    Simonson, J. W.; Rosa, R.; Antonacci, A. K.; He, H.; Bender, A. D.; Pabla, J.; Adrip, W.; McNally, D. E.; Zebro, A.; Kamenov, P.; Geschwind, G.; Ghose, S.; Dooryhee, E.; Ibrahim, A.; Aronson, M. C.

    Improving the efficiency of fossil fuel plants is a practical option for decreasing carbon dioxide emissions from electrical power generation. Present limits on the operating temperatures of exposed steel components, however, restrict steam temperatures and therefore energy efficiency. Even as a new generation of creep-resistant, high strength steels retain long term structural stability to temperatures as high as ~ 973 K, the low Cr-content of these alloys hinders their oxidation resistance, necessitating the development of new corrosion resistant coatings. We report here the nearly ideal properties of potential coating material Cr55Al229, which exhibits high hardness at room temperature as well as low thermal conductivity and superlative oxidation resistance at 973 K, with an oxidation rate at least three times smaller than those of benchmark materials. These properties originate from a pseudo-icosahedral crystal structure, suggesting new criteria for future research.

  11. Cyclic Corrosion and Chlorination of an FeCrAl Alloy in the Presence of KCl

    DOE PAGES

    Israelsson, Niklas; Unocic, Kinga A.; Hellström, K.; Svensson, J-E; Johansson, L-G

    2015-05-30

    The KCl-induced corrosion of the FeCrAl alloy Kanthal® APMT in an O2 + N2 + H2O environment was studied at 600 °C. The samples were pre-oxidized prior to exposure in order to investigate the protective nature of alumina scales in the present environment. The microstructure and composition of the corroded surface was investigated in detail. Corrosion started at flaws in the pre-formed α-alumina scales, i.e. α-alumina was protective in itself. Consequently, KCl-induced corrosion started locally and, subsequently, spread laterally. An electrochemical mechanism is proposed here by which a transition metal chloride forms in the alloy and K2CrO4 forms at themore » scale/gas interface. Scale de-cohesion is attributed to the formation of a sub-scale transition metal chloride.« less

  12. Density Measurements of Low Silica CaO-SiO2-Al2O3 Slags

    NASA Astrophysics Data System (ADS)

    Muhmood, Luckman; Seetharaman, Seshadri

    2010-08-01

    Density measurements of a low-silica CaO-SiO2-Al2O3 system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose. The results obtained were in good agreement with those obtained from the model developed in the current group as well as with other results reported earlier. The density for the CaO-SiO2 and the CaO-Al2O3 binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO2 was below the 33 pct required for the orthosilicate composition, discrete {text{SiO}}4^{4 - } tetrahedral units in the silicate melt would exist along with O2- ions. The change in melt expansivity may be attributed to the ionic expansions in the order of {text{Al}}^{ 3+ } - {text{O}}^{ 2- } < {text{Ca}}^{ 2+ } - {text{O}}^{ 2- } < {text{Ca}}^{ 2+ } - {text{O}}^{ - } Structural changes in the ternary slag also could be correlated to a drastic change in the value of enthalpy of mixing.

  13. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1975-01-01

    The sintered aluminum powder (SAP) technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of a nickel alloy containing, by weight, 17% Cr, 5% Al, and 0.2% Y. The SAP-NiCrAl alloy (without the ytterbium removed by oxdation) was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. Annealing treatments were applied after working to determine the recrystallization response. The NiCrAlY alloy, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl alloy exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl alloy as has been reported for other oxide dispersion strengthened alloys. In contrast, the unoxidized NiCrAlY alloy exhibited only primary recrystallization.

  14. Effect of NiCr Clad BaF2·CaF2 Addition on Wear Performance of Plasma Sprayed Chromium Carbide-Nichrome Coating

    NASA Astrophysics Data System (ADS)

    Du, Lingzhong; Huang, Chuanbing; Zhang, Weigang; Zhang, Jingmin; Liu, Wei

    2010-03-01

    NiCr clad BaF2·CaF2 fluoride eutectic powders were added into chromium carbide-nichrome feedstock to improve the tribological properties of NiCr-Cr3C2 coating, and the structures, mechanical, and ball-on-disk sliding wear performance of the coating were characterized. The results show that NiCr cladding can effectively decrease the density and thermophysical difference between the feedstock components, while alleviate the decarburization and oxidization of the constituent phases, and form the coating with a uniform and dense microstructure. However, the addition of BaF2·CaF2 has a negative effect on mechanical properties of the coating. When the temperature reaches 500 °C, the BaF2·CaF2 eutectic is soften by the heat and smeared by the counterpart, thus the low shear stress lubricating film forms between the contact surface, that improves the tribological properties dramatically. At this temperature, the dominant wear mechanisms also change from splats spallation and abrasive wear at room temperature to plastic deformation and plawing by the counterpart. Within the temperature range from 600 to 800 °C, the friction coefficient, the wear rates of NiCr/Cr3C2-10% BaF2·CaF2 coating and its coupled Si3N4 ball are 20%, 40%, and 75% lower than those of the NiCr/Cr3C2 coating, respectively. The NiCr/Cr3C2-BaF2·CaF2 coating shows superior wear performance to the NiCr/Cr3C2 coating without lubricant additive.

  15. On the Early Stage Isothermal Oxidation of APS CoNiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Di Girolamo, G.; Alfano, M.; Pagnotta, L.; Taurino, A.; Zekonyte, J.; Wood, R. J. K.

    2012-09-01

    The aim of this study is to analyze the evolution of microstructural and room temperature mechanical properties of air plasma sprayed (APS) CoNiCrAlY coatings before and after early stage high-temperature oxidation. To this purpose, selected samples were isothermally heat treated at 1110 °C for different durations. Phase analysis and oxide scale characterization were performed using x-ray diffraction. Morphological and microstructural features of as-sprayed and oxidized CoNiCrAlY coatings were analyzed by scanning electron microscopy and energy dispersive x-ray spectroscopy. After heat treatment, a duplex oxide scale, composed of an inner α-Al2O3 layer and an outer spinel-type oxide layer, was observed on coating top-surface. The nanoindentation technique was employed to study the evolution of the mechanical properties. An increase in Young's modulus and hardness with increasing the aging time was observed, this effect was mainly addressed to the partial densification of coating microstructure.

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

    SciTech Connect

    Zheng, M.; He, Y.R.; Rapp, R.A.

    1997-12-01

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

  17. Thermodynamic Calibration of Cr-Al Exchange Equilibria for Garnet and Spinel

    NASA Astrophysics Data System (ADS)

    Hamecher, E. A.; Antoshechkina, P. M.; Ghiorso, M. S.; Asimow, P. D.

    2009-12-01

    xMELTS is a new thermodynamic model of igneous phase equilibria (Ghiorso et al., 2007, Eos 88, V31C-0608) that extends MELTS (Ghiorso and Sack, 1995, CMP 119, 197-212) and pMELTS (Ghiorso et al., 2002, G3, 10.1029/2001GC000217) to a broader range of bulk compositions and to pressure and temperature conditions spanning from the shallow crust to the top of Earth’s lower mantle. To complete xMELTS, comprehensive garnet and pyroxene solid solution models that include Cr and other minor components must be developed. Garnet is an important phase involved in partial melting of the upper mantle because it controls partitioning of major and minor elements at pressures greater than 3 GPa. Chromium is a minor but significant component of mantle rocks as its presence increases the stability of spinel relative to plagioclase at low pressure and to garnet at high pressure. Thermodynamic models incorporating Cr into garnet solid solutions have been absent from the MELTS packages, motivating simulations for Cr-free bulk compositions and preventing accurate modeling of the spinel-garnet phase transition. The extension of the garnet model to include energetics of mixing on the Y-site is the first step in a planned calibration that will also include the majorite component needed for transition zone garnets. Initially, standard state properties and phase equilibria experiments for a Cr-bearing garnet endmember were compiled. Internally consistent thermodynamic properties of the endmember species were found by examination of reversal experiments on pure systems. We used the reversal experiments of Klemme (2004, Lithos 77, 639-646) to fix the enthalpy and entropy of knorringite (Mg3Cr2Si3O12), but were unable to fit the reversals using the standard state values given by Klemme and instead re-optimized these parameters. Although a Cr-bearing garnet model is included in the PERPLEX package (Connolly, 1990, AJS 290, 666-718; Connolly and Petrini, 2002, J.Met.Pet. 20, 697-708), the Y

  18. Atomic-scale microstructure underneath nanoindentation in Al-Cr-N ceramic films

    SciTech Connect

    Zhuang, Chunqiang Li, Zhipeng; Lin, Songsheng

    2015-12-15

    In this work, Al-Cr-N ceramic films deformed by nanoindentation were peeled off from silicon substrates and their atomic-scale microstructures underneath the indenter were investigated by high resolution transmission electron microscope (HR-TEM). Dislocations were formed underneath the indenter and they accumulated along nano-grain boundaries. The accumulative dislocations triggered the crack initiation along grain boundaries, and further resulted in the crack propagation. Dislocations were also observed in nano-grains on the lateral contact area. A model was proposed to describe the variation of microstructures under nanoindentation.

  19. High-temperature relaxation in a Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Z. C.; Han, F. S.

    2003-09-01

    Two relaxational internal friction peaks were found in a (wt%)Fe-25Cr-5Al alloy. The low-temperature peak is related to Zener relaxation and the high-temperature one to grain-boundary relaxation. Their activation energy values are 2.55 (+/-0.14) eV for the Zener peak and 4.07(+/-0.15) eV for the grain-boundary relaxation peak, respectively. Grain-boundary relaxation strength remarkably increases with decreasing grain size, while the Zener peak is independent of the grain size. (

  20. Investigation on the suitability of plasma sprayed Fe Cr Al coatings as tritium permeation barrier

    NASA Astrophysics Data System (ADS)

    Fazio, C.; Stein-Fechner, K.; Serra, E.; Glasbrenner, H.; Benamati, G.

    1999-08-01

    Results on the fabrication of a tritium permeation barrier by spraying Fe-Cr-Al powders are described. The sprayed coatings were deposited at temperatures below the Ac1 temperature of the ferritic-martensitic steel substrate and no post-deposition heat treatment was applied. The aim of the investigation was the determination of the efficiency of the coatings to act as tritium permeation barrier. Metallurgical investigations as well as hydrogen isotope permeation measurements were carried out onto the produced coatings. The depositions were performed on ferritic-martensitic steels by means of three types of spray techniques: high velocity oxy fuel, air plasma spray and vacuum plasma spray.

  1. Thermophysical properties of Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy

    NASA Astrophysics Data System (ADS)

    Bykov, V. A.; Kulikova, T. V.; Vedmid', L. B.; Fishman, A. Ya.; Shunyaev, K. Yu.; Tarenkova, N. Yu.

    2014-07-01

    The thermophysical properties of the Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy in a wide range of temperatures from room temperature to 1000°C have been studied by the methods of differential scanning calorimetry, the laser flash method, and dilatometry. The obtained data on heat capacity, thermal diffusivity, and thermal expansion have been used for calculating coefficient of thermal conductivity. The sequence and temperatures of structural transformations during heating of the alloy have been established. It has been shown that the studied alloy possesses a coefficient of thermal conductivity that is 3.5-4 times smaller than that of pure titanium.

  2. EPR and optical investigations of LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor

    SciTech Connect

    Singh, Vijay; Sivaramaiah, G.; Rao, J.L.; Kim, S.H.

    2014-12-15

    Graphical abstract: The EPR spectrum of as-prepared LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor at 110 K. - Highlights: • Using the combustion synthesis, LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor has been prepared in a few minutes. • Optical investigation indicates that Cr{sup 3+} ions are present in octahedral symmetry. • The EPR signals indicate that exchange coupled Cr{sup 3+}–Cr{sup 3+} ion pairs in weakly distorted sites. - Abstract: The LaMgAl{sub 11}O{sub 19}:Cr{sup 3+} phosphor has been prepared by a low-temperature combustion synthesis method. As-prepared combustion synthesized powder was characterized using powder X-ray diffraction (XRD), diffuse reflectance (DRS), electron paramagnetic resonance (EPR) and photoluminescence (PL) studies. The X-ray diffraction pattern reveals crystalline hexagonal phases. The UV–vis diffuse reflectance spectrum exhibits three broad bands characteristic of Cr{sup 3+} ions in octahedral symmetry. The EPR spectrum exhibits several resonance signals. The signals with the effective g values at g = 4.84, 3.64 and 2.26 have been attributed to the isolated Cr{sup 3+} ions. The signal with the effective g value at g = 1.94 has been attributed to exchange coupled Cr{sup 3+}–Cr{sup 3+} ion pairs. The PL studies exhibit several bands characteristic of Cr{sup 3+} ions in octahedral symmetry.

  3. Iron-base superalloys - A phase analysis of the multicomponent system (Fe-Mn-Cr-Mo-Nb-Al-Si-C)

    NASA Technical Reports Server (NTRS)

    Gupta, H.; Nowotny, H.; Lemkey, F. D.

    1988-01-01

    In the course of studies on the iron-rich multicomponent system Fe-Mn-Cr-Mo-Nb-Al-Si-C, work was concentrated on pertinent quinary and six-component combinations namely Fe-Mn-Al-Si-C, Fe-Cr-Al-Si-C and Fe-Mn-Cr-Al-Si-C which had been elaborated at 65, 72, and 80 wt pct Fe. Manganese acts as a strong stabilizer for the cementite carbide. Chromium seems to stabilize the iron aluminide Fe2Al5 which forms in a considerable amount within an alloy of nominal composition Fe(65)Mn(15)Cr(12)Al(5)Si(2)C(1) (percent by weight). Although the Mn3AlC carbide is, like Fe3AlC, a perovskite carbide, manganese does not appear to favor the formation of the perovskite carbide. Because of the relatively low sintering temperature (700 C), for al large portion of the samples equilibria conditions are not always reached.

  4. Spin-orbit torque in Cr/CoFeAl/MgO and Ru/CoFeAl/MgO epitaxial magnetic heterostructures

    NASA Astrophysics Data System (ADS)

    Wen, Zhenchao; Kim, Junyeon; Sukegawa, Hiroaki; Hayashi, Masamitsu; Mitani, Seiji

    2016-05-01

    We study the spin-orbit torque (SOT) effective fields in Cr/CoFeAl/MgO and Ru/CoFeAl/MgO magnetic heterostructures using the adiabatic harmonic Hall measurement. High-quality perpendicular-magnetic-anisotropy CoFeAl layers were grown on Cr and Ru layers. The magnitudes of the SOT effective fields were found to significantly depend on the underlayer material (Cr or Ru) as well as their thicknesses. The damping-like longitudinal effective field (ΔHL) increases with increasing underlayer thickness for all heterostructures. In contrast, the field-like transverse effective field (ΔHT) increases with increasing Ru thickness while it is almost constant or slightly decreases with increasing Cr thickness. The sign of ΔHL observed in the Cr-underlayer devices is opposite from that in the Ru-underlayer devices while ΔHT shows the same sign with a small magnitude. The opposite directions of ΔHL indicate that the signs of spin Hall angle in Cr and Ru are opposite, which are in good agreement with theoretical predictions. These results show sizable contribution from SOT even for elements with small spin orbit coupling such as 3d Cr and 4d Ru.

  5. Electronic structure, magnetism, and antisite disorder in CoFeCrGe and CoMnCrAl quaternary Heusler alloys

    DOE PAGES

    Enamullah, .; Venkateswara, Y.; Gupta, Sachin; Varma, Manoj Raama; Singh, Prashant; Suresh, K. G.; Alam, Aftab

    2015-12-10

    In this study, we present a combined theoretical and experimental study of two quaternary Heusler alloys CoFeCrGe (CFCG) and CoMnCrAl (CMCA), promising candidates for spintronics applications. Magnetization measurement shows the saturation magnetization and transition temperature to be 3 μB, 866 K and 0.9 μB, 358 K for CFCG and CMCA respectively. The magnetization values agree fairly well with our theoretical results and also obey the Slater-Pauling rule, a prerequisite for half metallicity. A striking difference between the two systems is their structure; CFCG crystallizes in fully ordered Y-type structure while CMCA has L21 disordered structure. The antisite disorder adds amore » somewhat unique property to the second compound, which arises due to the probabilistic mutual exchange of Al positions with Cr/Mn and such an effect is possibly expected due to comparable electronegativities of Al and Cr/Mn. Ab initio simulation predicted a unique transition from half metallic ferromagnet to metallic antiferromagnet beyond a critical excess concentration of Al in the alloy.« less

  6. Electronic structure, magnetism, and antisite disorder in CoFeCrGe and CoMnCrAl quaternary Heusler alloys

    SciTech Connect

    Enamullah, .; Venkateswara, Y.; Gupta, Sachin; Varma, Manoj Raama; Singh, Prashant; Suresh, K. G.; Alam, Aftab

    2015-12-10

    In this study, we present a combined theoretical and experimental study of two quaternary Heusler alloys CoFeCrGe (CFCG) and CoMnCrAl (CMCA), promising candidates for spintronics applications. Magnetization measurement shows the saturation magnetization and transition temperature to be 3 μB, 866 K and 0.9 μB, 358 K for CFCG and CMCA respectively. The magnetization values agree fairly well with our theoretical results and also obey the Slater-Pauling rule, a prerequisite for half metallicity. A striking difference between the two systems is their structure; CFCG crystallizes in fully ordered Y-type structure while CMCA has L21 disordered structure. The antisite disorder adds a somewhat unique property to the second compound, which arises due to the probabilistic mutual exchange of Al positions with Cr/Mn and such an effect is possibly expected due to comparable electronegativities of Al and Cr/Mn. Ab initio simulation predicted a unique transition from half metallic ferromagnet to metallic antiferromagnet beyond a critical excess concentration of Al in the alloy.

  7. Chemical short-range order and the Meyer - Neldel rule for liquid alloys: AlCa and GaAlCa

    NASA Astrophysics Data System (ADS)

    You, D.; Schnyders, H. S.; Van Zytveld, J. B.

    1997-02-01

    We have measured the electrical resistivity, 0953-8984/9/7/006/img1, its specific temperature dependence, 0953-8984/9/7/006/img2, and the thermopower, S, of two series of ternary liquid alloys: 0953-8984/9/7/006/img3 and 0953-8984/9/7/006/img4. We also provide new analysis for the binary liquid alloy AlCa. We do not see the unusually large values for S that were found earlier for amorphous solid ternary alloys of the approximate composition 0953-8984/9/7/006/img5. We do find that, while chemical short-range order (CSRO) appears to occur in the liquid binary alloy 0953-8984/9/7/006/img6, CSRO is apparently destroyed by substitution of one Ga atom for one Al per complex: 0953-8984/9/7/006/img7. CSRO may exist in the liquid alloy 0953-8984/9/7/006/img8. And we find that the activated conductivities of these ternary liquid alloys (and also of liquid AlCa) are consistent with the Meyer - Neldel rule (MNR), extending the range of applicability of the MNR to systems with activation energies about an order of magnitude smaller than previously observed. These results appear to rule out two physical models as universal bases for the MNR, but are consistent with one based on a hopping conductivity whose characteristic energy is that of a polaron shift.

  8. A Study of Pack Aluminizing Process for NiCrAlY Coatings Using Response Surface Methodology

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Huang, Xiao; Liu, Rong; Yang, Qi

    2014-01-01

    Aluminizing process is widely used to provide additional Al deposition onto superalloy surface for enhanced oxidation and corrosion resistance. In this research, an aluminizing process—pack cementation process, is used to deposit Al onto the surface of NiCrAlY coatings for increasing environmental protection. The experiment is designed using Box-Behnken approach, in which three parameters, the Al content, Ni content of the pack powder, and the temperature of the process, are selected as factors; and the thickness and Al/Ni ratio of the coatings are selected as responses. The effects of the factors on the responses are analyzed and modeled empirically. It is found that these empirical models correlate well with the results from additional sets of experiment. These models can be used to produce aluminized NiCrAlY coatings with specific thicknesses and Al/Ni ratios.

  9. Effects of Ca, Cu, Al and La on pectin gel strength: implications for plant cell walls.

    PubMed

    McKenna, Brigid A; Nicholson, Timothy M; Wehr, J Bernhard; Menzies, Neal W

    2010-06-16

    Rheology of Ca-pectate gels is widely studied, but the behaviour of pectate gels formed by Cu, Al and La is largely unknown. It is well known that gel strength increases with increasing Ca concentration, and it is hypothesised that this would also be the case for other cations. Pectins are a critical component of plant cell walls, imparting various physicochemical properties. Furthermore, the mechanism of metal toxicity in plants is hypothesised to be, in the short term, related to metal interactions with cell wall pectin. This study investigated the influence of Ca, Cu, Al and La ion concentrations at pH 4 on the storage modulus as a function of frequency for metal-pectin gels prepared from pectin (1%) with a degree of esterification of 30%. Gels were formed in situ over 6d in metal chloride solution adjusted daily to pH 4. Cation concentration was varied to develop a relationship between gel strength and cation concentration. At similar levels of cation saturation, gel strength increased in the order of La<Ca < or =AlCa gels being the most swollen.

  10. Effects of Ca, Cu, Al and La on pectin gel strength: implications for plant cell walls.

    PubMed

    McKenna, Brigid A; Nicholson, Timothy M; Wehr, J Bernhard; Menzies, Neal W

    2010-06-16

    Rheology of Ca-pectate gels is widely studied, but the behaviour of pectate gels formed by Cu, Al and La is largely unknown. It is well known that gel strength increases with increasing Ca concentration, and it is hypothesised that this would also be the case for other cations. Pectins are a critical component of plant cell walls, imparting various physicochemical properties. Furthermore, the mechanism of metal toxicity in plants is hypothesised to be, in the short term, related to metal interactions with cell wall pectin. This study investigated the influence of Ca, Cu, Al and La ion concentrations at pH 4 on the storage modulus as a function of frequency for metal-pectin gels prepared from pectin (1%) with a degree of esterification of 30%. Gels were formed in situ over 6d in metal chloride solution adjusted daily to pH 4. Cation concentration was varied to develop a relationship between gel strength and cation concentration. At similar levels of cation saturation, gel strength increased in the order of La<Ca < or =AlCa gels being the most swollen. PMID:20457449

  11. Diamond growth on Fe-Cr-Al alloy by H2-plasma enhanced graphite etching

    NASA Astrophysics Data System (ADS)

    Li, Y. S.; Hirose, A.

    2007-04-01

    Without intermediate layer and surface pretreatment, adherent diamond films with high initial nucleation density have been deposited on Fe-15Cr-5Al (wt. %) alloy substrate. The deposition was performed using microwave hydrogen plasma enhanced graphite etching in a wide temperature range from 370to740°C. The high nucleation density and growth rate of diamond are primarily attributed to the unique precursors used (hydrogen plasma etched graphite) and the chemical nature of the substrate. The improvement in diamond adhesion to steel alloys is ascribed to the important role played by Al, mitigation of the catalytic function of iron by suppressing the preferential formation of loose graphite intermediate phase on steel surface.

  12. Synthesis of CORONA 5 (Ti-4.5Al-5Mo-1.5Cr)

    NASA Astrophysics Data System (ADS)

    Froes, F. H.; Highberger, W. T.

    1980-05-01

    The synthesis of CORONA 5 (Ti-4.5Al-5Mo-1.5Cr) is described from the viewpoints of alloy chemistry and microstructure. Lenticular alpha is shown to maximize fracture resistance parameters, while a globular alpha optimizes hightemperature flow characteristics. The processing and application of CORONA 5 as forging, plate, sheet and powder metallurgy products are presented. The weldability of the alloy is described and potential use of the alloy for engine applications discussed. The improved mechanical property behavior over the "workhorse" Ti-6Al-4V alloy combined with cost-effective production should result in use of CORONA 5 in many applications. Future developments for CORONA 5 are suggested both in terms of further mechanical property optimization and in light of the economics of producing the alloy.

  13. Surface Hardening and Nitride Precipitation in the Nitriding of Fe-M1-M2 Ternary Alloys Containing Al, V, or Cr

    NASA Astrophysics Data System (ADS)

    Miyamoto, Goro; Suetsugu, Shotaro; Shinbo, Kunio; Furuhara, Tadashi

    2015-11-01

    Nitride precipitation and resultant surface hardening in nitrided Fe-M1-M2 ternary alloys containing Cr, Al, or V were investigated using transmission electron microscopy and three-dimensional atom probe tomography. The (Al, Cr) and (Cr, V) mixed nitrides are formed by the co-precipitation of these elements during the nitriding of Fe-Al-Cr or Fe-Cr-V alloys. However, the precipitation of V nitrides precedes Al nitride precipitation during the nitriding of the Fe-Al-V alloy, which results in two-step hardening behavior. The addition of Cr or V to the Fe-Al alloy accelerates the precipitation kinetics of Al nitrides by promoting the nucleation of Al nitrides, which leads to substantial surface hardening.

  14. Selective substitution of Cr in CaFe{sub 4}As{sub 3} and its effect on the spin density wave.

    SciTech Connect

    Todorov, I.; Chung, D. Y.; Claus, H.; Gray, K. E.; Li, Q.; Schlueter, J.; Bakas, T.; Douvalis, A.; Gutmann, M.; Kanatzidis, M. G.; Materials Science Division; Northwestern Univ.; Univ. of Ioannina; Rutherford Appleton Lab.

    2010-08-11

    Single crystals of CaCr{sub 0.84}Fe{sub 3.16}As{sub 3}, a Cr substituted analog of CaFe{sub 4}As{sub 3}, were grown from Sn flux and characterized with single crystal neutron diffraction. CaCr{sub 0.84}Fe{sub 3.16}As{sub 3} crystallizes in the orthorhombic space group Pnma with a three-dimensional framework, where Fe, Cr, and As form a covalent channel-like network with Ca{sup 2+} cations residing in the channels. CaCr{sub 0.84}Fe{sub 3.16}As{sub 3} has a unit cell of a = 12.057(4) {angstrom}, b = 3.7374(13) {angstrom}, and c = 11.694(3) {angstrom}, as determined by room temperature single crystal neutron diffraction (R{sub 1} = 0.0747, wR{sub 2} = 0.1825). Structural data was also collected at 10 K. The single crystal neutron data showed that Cr selectively occupies a particular metal site, Fe(4). The antiferromagnetic transition associated with spin density wave (SDW) in the parent compound is preserved and shifts from 96 to 103 K with the selective Cr doping. Moessbauer, magnetic, and electrical resistivity measurements are reported.

  15. Optically stimulated luminescence in LiCaAlF6:Eu2+ phosphor.

    PubMed

    More, Y K; Wankhede, S P; Moharil, S V; Kumar, Munish; Chougaonkar, M P

    2015-09-01

    Results on optically stimulated luminescence (OSL) in LiCaAlF6:Eu(2+) are reported. Continuous wave OSL signal as recorded using blue (470 nm) stimulation was found to be ~31% that of standard phosphor lithium magnesium phosphate. The rate of OSL depletion for standard phosphor lithium magnesium phosphate is only three times less as compared with that of LiCaAlF6:Eu(2+). Strong photoluminescence (PL) in the near ultraviolet region is observed for LiCaAlF6:Eu(2+) with the characteristic Eu(2+) emission at 369 nm for 254 nm excitation. The thermoluminescence (TL) glow peak for LiCaAlF6:Eu(2+) was observed at around 180°C. The glow peak was about six times more intense compared with the dosimetric peak of the well known thermoluminescence dosimetric (TLD) phosphor LiF-TLD 100. Thus this phosphor deserves much more attention than it has received until now and may be useful as a dosimetric material in radiation dosimetry. PMID:25620581

  16. Formation Mechanism of CaS-Al2O3 Inclusions in Low Sulfur Al-Killed Steel After Calcium Treatment

    NASA Astrophysics Data System (ADS)

    Xu, Jianfei; Huang, Fuxiang; Wang, Xinhua

    2016-04-01

    The laboratory experiments of alumina inclusions modified by calcium treatment in Al-killed steel were carried out at 1873 K (1600 °C), and the inclusions in steel samples were characterized at 1, 5, and 10 minutes after calcium addition. The results show that the type of inclusions after calcium treatment was determined by the sulfur and T.O contents of steel. CaS-Al2O3 inclusions were obtained in steels with high sulfur and low T.O contents. The mass ratio between CaS and Al2O3 was determined by T.Ca and T.O contents of steel. The influence of holding time after calcium addition on the composition of inclusions was negligible. The thermodynamics for the formation of CaS-Al2O3 inclusions after calcium treatment was discussed, and a simple formation mechanism was proposed. Moreover, the CaO, Al2O3, and CaS contents in the inclusions were predicted through the sulfur, total calcium (T.Ca), and T.O contents, and it was found that the CaO content decreases with increasing S/T.O, while (pctCaS)/(pctAl2O3)1/3 increases with increasing T.Ca/T.O.

  17. Ca-,Al-rich inclusions in the unique chondrite ALH85085 - Petrology, chemistry, and isotopic compositions

    NASA Astrophysics Data System (ADS)

    Kimura, M.; El Goresy, A.; Palme, H.; Zinner, E.

    1993-05-01

    A comprehensive study is performed for the Ca-,Al-rich inclusions (CAIs) in the unique chondrite ALH85085. The ALH85085 inclusions are smaller (5-80 microns) and more refractory than their counterparts in carbonaceous chondrites. The study includes 42 inclusions for petrography and mineralogy, 15 for bulk major and minor element chemical composition, six for Mg-Al isotopic systematics, 10 for Ca isotopes, nine for Ti isotopes, and six for trace element abundances. In addition, oxygen-isotopic compositions were determined in minerals from a single inclusion. No correlation is found between mineralogy, major element chemistry, and trace element abundances. It is further shown that the high-temperature geochemical behavior of ultrarefractory trace elements is decoupled from that of the major elements Ca and Ti (Ti is correlated with the relatively volatile elements Nb and Yb) implying that perovskite is of only minor importance as carrier of ultrarefractories.

  18. Studies on the Sliding Wear Performance of Plasma Spray Ni-20Cr and Ni3Al Coatings

    NASA Astrophysics Data System (ADS)

    Kaur, Maninder; Singh, Harpreet; Singh, Balraj; Singh, Bhupinder

    2010-01-01

    Two metallic powders namely Ni-20Cr and Ni3Al were coated on AISI 309 SS steel by shrouded plasma spray process. The wear behavior of the bare, Ni-20Cr and Ni3Al-coated AISI 309 SS steel was investigated according to ASTM Standard G99-03 on a Pin-on-Disc Wear Test Rig. The wear tests were carried out at normal loads of 30 and 50 N with a sliding velocity of 1 m/s. Cumulative wear rate and coefficient of friction (μ) were calculated for all the cases. The worn-out surfaces were then examined by scanning electron microscopy analysis. Both the as-sprayed coatings exhibited typical splat morphology. The XRD analysis indicated the formation of Ni phase for the Ni-20Cr coating and Ni3Al phase for the Ni3Al coating. It has been concluded that the plasma-sprayed Ni-20Cr and Ni3Al coatings can be useful to reduce the wear rate of AISI 309 SS steel. The coatings were found to be adherent to the substrate steel during the wear tests. The plasma-sprayed Ni3Al coating has been recommended as a better choice to reduce the wear of AISI 309 SS steel, in comparison with the Ni-20Cr coating.

  19. Degradation of a TBC with HVOF-CoNiCrAlY Bond Coat

    NASA Astrophysics Data System (ADS)

    Chen, Weijie R.

    2014-06-01

    Thermal barrier coatings (TBCs) provide both thermal insulation and oxidation and corrosion protection to the substrate metal, and their durability is influenced by delamination near the interface between the ceramic topcoat and the metallic bond coat, where a layer of thermally grown oxide (TGO) forms during service exposure. In the present work, the degradation process of a TBC with an air-plasma-spray ZrO2-8 wt.%Y2O3 topcoat and a high-velocity oxy-fuel CoNiCrAlY bond coat was studied, in terms of TGO growth kinetics and aluminum depletion in the bond coat, as well as cracking behavior. The results show that the TGO growth kinetics can be described by a transient oxidation stage with δ3 = k 1 t followed by a steady-state oxidation stage with δ2 = c + k 2 t. Significant aluminum depletion was observed in the bond coat after extended thermal exposure; however, chemical failure of the bond coat did not occur even after the aluminum content near the TGO/CoNiCrAlY interface decreased to 4.5 at.%. A power-law relationship between the maximum crack length in the TBC and the TGO thickness was observed, which may serve as the basis for TBC life prediction.

  20. Deposition and Oxidation of Oxide-Dispersed CoNiCrAlY Bondcoats

    NASA Astrophysics Data System (ADS)

    Okada, Mitsutoshi; Vassen, Robert; Karger, Matthias; Sebold, Doris; Mack, Daniel; Jarligo, Maria Ophelia; Bozza, Francesco

    2014-01-01

    CoNiCrAlY powder and nano-size alumina powder were milled by a high-energy-attrition ball-mill, and an oxide-dispersed powder was produced with a mixed structure of metal and alumina in each particle. The oxide-dispersed bond coat powder was deposited by HVOF. Pores, however, were observed in the coating since the alumina was deposited without sufficient melting. Isothermal oxidation tests were carried out for the bond coat specimens at a temperature of 1373 K up to 1000 h in air. As a result, oxidation proceeded inside the coating, since oxygen penetrated through pores formed in the dispersed alumina. However, the authors find that another deposition using higher power levels led to a bond coat without pores. A commercially available oxide-dispersed CoNiCrAlY powder was also deposited by HVOF and VPS, and isothermal oxidation tests were performed. The analysis clarifies that the HVOF bond coat exhibited the thinnest thermally grown oxide than those of the VPS bond coat and conventional metallic bond coat. Furnace cycling tests were conducted using the specimens with an additional ceramic thermal-barrier coating. The specimen with the bond coat sprayed by VPS using commercial oxide-dispersed powder showed almost same number of cycles to delamination compared with the specimen with the conventional metal bond coat.

  1. On the heat capacities of M2AlC (M=Ti,V,Cr) ternary carbides

    NASA Astrophysics Data System (ADS)

    Drulis, Monika K.; Drulis, H.; Gupta, S.; Barsoum, M. W.; El-Raghy, T.

    2006-05-01

    In this paper, we report on the heat capacities cp of bulk polycrystalline samples of Ti2AlC, V2AlC, and Cr2AlC in the 3-260 K temperature range. Given the structural and chemical similarities of these compounds it is not surprising that the cp's and their temperature dependencies were quite similar. Nevertheless, at all temperatures the heat capacity of Cr2AlC was higher than the other two. The density of states at the Fermi level were 3.9, 7.5, and 14.6 (eV unit cell)-1 for Ti2AlC, V2AlC, and Cr2AlC, respectively. The results obtained are analyzed using the Debye and Einstein model approximations for cp. Good description of cp is obtained if one assumes that nine phonon modes vibrate according to the Debye model approximation whereas the remaining 3 of 12 modes expected for M2AlC formula unit fulfill an Einstein-like phonon vibration pattern. Debye temperatures θD describing acoustic phonon and Einstein temperature θE describing optical phonon contributions have been estimated for the studied compounds. The Debye temperatures are reasonably high and fall in the range of 600-700 K. A linear dependence was found between the number of d electrons along the row Ti, V, and Cr and the density of states at the Fermi level.

  2. Stepwise Depletion of Coating Elements as a Result of Hot Corrosion of NiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Rana, Nidhi; Jayaganthan, R.; Prakash, Satya

    2013-11-01

    Present investigation deals with the hot corrosion behaviour of the NiCrAlY coatings deposited by HVOF technique on Superni76 under cyclic conditions at 900 °C in the presence of Na2SO4 + 60% V2O5 salt. The weight change behaviour of the coatings was followed with time up to 200 cycles and K p value was calculated for the hot corrosion process. Surface and cross-section of the corroded samples were examined by FESEM/EDS and XRD to follow the progress of corrosion up to 200 cycles. In earlier cycles, the corrosive species oxidised top surface of the coatings. With increasing number of cycles, oxidation of the coatings occurred up to 40-μm depth. A Cr-depleted band was seen below the oxide scale. Further increase in number of cycles led to migration and oxidation of Al to form Al2O3 sublayer at coating/scale interface, thereby leading to formation of Al-depleted zone in the coating below the Al2O3 sublayer. The corrosion resistance of the NiCrAlY coatings is attributed to the formation of the continuous and dense Al2O3 sublayer at the coating/scale interface, which acts as barrier to the migration of Cr to the surface. The appearance of Al3Y after 100 and 200 cycles also contributes to the increased corrosion resistance of coatings after 100 and 200 cycles.

  3. Effect of alloying elements Al and Ca on corrosion resistance of plasma anodized Mg alloys

    NASA Astrophysics Data System (ADS)

    Anawati, Asoh, Hidetaka; Ono, Sachiko

    2016-04-01

    Plasma anodizing is a surface treatment used to form a ceramic-type oxide film on Mg alloys by the application of a high anodic voltage to create intense plasma near the metal surface. With proper selection of the process parameters, the technique can produce high quality oxide with superior adhesion, corrosion resistance, micro-hardness, wear resistance and strength. The effect of alloying element Al on plasma anodizing process of Mg alloys was studied by comparing the anodizing curves of pure Mg, AZ31, and AZ61 alloys while the effect of Ca were studied on AZ61 alloys containing 0, 1, and 2 wt% Ca. Anodizing was performed in 0.5 M Na3PO4 solution at a constant current density of 200 Am-2 at 25°C. Anodic oxide films with lava-like structure having mix composition of amorphous and crystal were formed on all of the alloys. The main crystal form of the oxide was Mg3(PO4)2 as analyzed by XRD. Alloying elements Al and Ca played role in modifying the plasma lifetime during anodization. Al tended to extend the strong plasma lifetime and therefore accelerated the film thickening. The effect of Ca on anodizing process was still unclear. The anodic film thickness and chemical composition were altered by the presence of Ca in the alloys. Electrochemical corrosion test in 0.9% NaCl solution showed that the corrosion behavior of the anodized specimens depend on the behavior of the substrate. Increasing Al and Ca content in the alloys tended to increase the corrosion resistance of the specimens. The corrosion resistance of the anodized specimens improved significantly about two orders of magnitude relative to the bare substrate.

  4. Thermochemistry of glasses and liquids in the systems CaMgSi 2O 6-CaAl 2Si 2O 8-NaAlSi 3O 8, SiO 2-CaAl 2Si 2O 8-NaAlSi 3O 8 and SiO 2-Al 2O 3-CaO-Na 2O

    NASA Astrophysics Data System (ADS)

    Navrotsky, A.; Hon, R.; Weill, D. F.; Henry, D. J.

    1980-10-01

    Enthalpies of solution in 2PbO· B 2O 3 at 712°C have been measured for glasses in the systems albite anorthite diopside, NaAlO 2-SiO 2, Ca 0.5AlO 2-SiO 2 and albite-anorthite-quartz. The systems albite-anorthite and diopside-anorthite show substantial negative enthalpies of mixing, albite-diopside shows significant positive heats of mixing. For compositions up to NaAlO2 = 0.42 (which includes the subsystem albite-silica) the system NaAlO 2-SiO 2 shows essentially zero heats of mixing. A negative ternary excess heat of mixing is found in the plagioclase-rich portion of the albite-anorthite-diopside system. The join Si 4O 8-CaAl 2Si 2O 8 shows small but significant heats of mixing. In albite-anorthite-quartz. ternary glasses, the ternary excess enthalpy of mixing is positive. Based on available heat capacity data and appropriate consideration of the glass transition, the enthalpy of the crystal-glass transition (vitrification) is a serious underestimate of the enthalpy of the crystal-liquid transition (fusion) especially when the melting point, Tf, is many hundreds of degrees higher than the glass transition temperature, Tg. On the other hand, the same heat capacity data suggest that the enthalpies of mixing in albite-anorthite-diopside liquids are calculated to be quite similar to those in the glasses. The enthalpies of mixing observed in general support the structural models proposed by TAYLOR and BROWN (1979a, b) and others for the structure of aluminosilicate glasses.

  5. Effect of electron correlation in Sr(Ca)Ru{sub 1-x}Cr{sub x}O{sub 3}: Density functional calculation

    SciTech Connect

    Hadipour, H.; Akhavan, M.

    2010-07-15

    We have investigated the electronic structure of Sr(Ca)Ru{sub 1-x}Cr{sub x}O{sub 3} using the full potential linearized augmented plane wave method by different approximation such as LSDA and LSDA+U. The LSDA calculation suggest that Cr{sup 4+}-Ru{sup 4+} hybridization is responsible for the high Curie temperature T{sub C} in SrRu{sub 1-x}Cr{sub x}O{sub 3}, but it cannot completely describe its physical behavior. Our LSDA+U DOS results for SrRu{sub 1-x}Cr{sub x}O{sub 3} clearly establishes renormalization of the intra-atomic exchange strength at the Ru sites, arising from the Cr-Ru hybridization. The antiferromagnetic coupling of Cr{sup 3+} with Ru{sup 4+,5+} lattice increases the screening, which is consistent with the low magnetic moment of the Ru ions. The more distorted Ca-based compounds as compared to the Sr-based systems shows that the hybridization mechanism is not relevant for these compounds. The bigger exchange splitting of Ru 4d and Cr 3d at the Fermi level with Ru{sup 4+,5+} and Cr{sup 3+,4+} orbital occupancies of CaRu{sub 0.75}Cr{sub 0.25}O{sub 3} in the LSDA+U calculation, compared with that of the LSDA calculation, shows that repulsion between electrons tend to keep the localized spins from overlapping. The low screening of the Ru t{sub 2g} electrons increases T{sub C} in the Ca-based systems, which is consistent with the both high Ru exchange splitting and magnetic moment. The insulating behavior of the high Cr-doped systems can be explained by considering the Ru{sup 4+}+Cr{sup 4+{yields}}Ru{sup 5+}+Cr{sup 3+} charge transfer. - Graphical Abstract: We have investigated the electronic structure of Sr(Ca)Ru{sub 1-x}Cr{sub x}O{sub 3} using different ab-initio calculation such as LSDA and LSDA+U approximation. The antiferromagnetic hybridization of Cr{sup 3+} with Ru{sup 4+,5+} lattice increases the screening, which is consistent with the low magnetic moment of the Ru ions. The LSDA+U calculation for the more distorted Cr impurity doped Ca

  6. Microstructure and Oxidation Resistance of NiCoCrAlYTa Coating by Low Pressure Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Liang, X.-H.; Zhou, K. S.; Liu, M.; Hong, R. J.; Deng, C. G.; Luo, S.; Chen, Z. K.

    The NiCoCrAlYTa coating was prepared on Ni-based single crystal super-alloys by low pressure plasma spraying (LPPS). The phases and microstructures for the coatings were characterized by X-ray diffraction and scanning electron microscopy, and the fracture toughness and micro-hardness for both coatings and substrate were also investigated. The relationship between coating properties and oxidation was analyzed. The result shows that elementary distribution of NiCoCrAlYTa coatings, which consists of γ-Ni, β-NiAl, γ'-Ni3Al, and CrCoTa phases, is much homogeneous. The composition changes with depth from the surface to substrate for the coatings. The micro-hardness of coatings is 350.8 HV0.3 and fracture toughness is 2.73 MPa m1/2. The oxidation resistance of coatings excelled than Ni-based single crystal super-alloys.

  7. Predicting diffusion paths and interface motion in gamma/gamma + beta, Ni-Cr-Al diffusion couples

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1987-01-01

    A simplified model has been developed to predict Beta recession and diffusion paths in ternary gamma/gamma + beta diffusion couples (gamma:fcc, beta: NiAl structure). The model was tested by predicting beta recession and diffusion paths for four gamma/gamma + beta, Ni-Cr-Al couples annealed for 100 hours at 1200 C. The model predicted beta recession within 20 percent of that measured for each of the couples. The model also predicted shifts in the concentration of the gamma phase at the gamma/gamma + beta interface within 2 at. pct Al and 6 at. pct Cr of that measured in each of the couples. A qualitative explanation based on simple kinetic and mass balance arguments has been given which demonstrates the necessity for diffusion in the two-phase region of certain gamma/gamma + beta, Ni-Cr-Al couples.

  8. Room and elevated temperature mechanical properties of PM TiAl alloy Ti-47Al-2Cr-2Nb

    SciTech Connect

    Liu, C.T.; Maziasz, P.J.; Schneibel, J.H.; Sikka, V.K.; Wright, J.; Walker, L.R. |; Clemens, D.R.; Nieh, T.G.

    1995-07-01

    A TiAl alloy powder with the composition Ti-47Al-2Cr-2Nb (at. %) was prepared by rotary atomization, followed by hot-extrusion and subsequent heat treatments to produce refined lamellar structures and fine duplex structures. The mechanical properties of the TiM alloy were determined at temperatures to 1000C in air, and the microstructures were characterized by TEM, SEM, and electron microprobe analyses. The alloy with the refined lamellar structure showed excellent mechanical properties at both room and elevated temperatures. It exhibited a plastic strain of 1.4% and a yield strength of 971 MPa (140.9 ksi) at room temperature. The yield strength remained approximately constant up to 800C and decreased to 577 MPa (83.7 ksi) at 1000C. The transverse fracture toughness, estimated by three-point bend testing of chevron-notched specimens at room temperature, was 22.4 MPa {radical}m. The refined lamellar structure contained long and straight alternating {alpha}{sub 2} and {gamma} platelets with an extremely fine interlamellar spacing (0.1 {mu}m) and {alpha}{sub 2}-to-{alpha}{sub 2} spacing (0.22 {mu}m). The mechanical properties of the alloy have been correlated with the unique microstructures developed by hot extrusion.

  9. CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1996-02-01

    Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. The electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5--85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400--420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance. which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes(e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {ge}360{degrees}C.

  10. Energetic igniters realized by integrating Al/CuO reactive multilayer films with Cr films

    NASA Astrophysics Data System (ADS)

    Zhu, Peng; Shen, Ruiqi; Ye, Yinghua; Zhou, Xiang; Hu, Yan

    2011-10-01

    This paper deals with the energetic igniters realized by integrating Al/CuO reactive multilayer films (RMFs) with Cr Films, which could be used in micro-ignition system. The as-deposited Al/CuO RMFs has been characterized with varied analytical techniques. Results show that distinct Al/CuO RMFs is sputter deposited in a layered geometry, and the Al/CuO RMFs gives a heat of reaction equal to 2760 J/g. The structure of igniter is similar to a capacitor, which may place an electric field across the igniter and allow the instantaneous large-current to drift through the igniter. Firing characteristics of the igniter were accomplished using constant voltage firing set. The experiment shows that the ignition delay time and total released energy of the igniter discharged in 40 V are 0.7 ms and 482.34 mJ, respectively. In addition, the explosion temperature could keep an approximately constant value of 3500 °C for 1.4 ms.

  11. Optically pumped cerium-doped LiSrAlF.sub.6 and LiCaAlF.sub.6

    DOEpatents

    Marshall, Christopher D.; Payne, Stephen A.; Krupke, William F.

    1996-01-01

    Ce.sup.3+ -doped LiSrAlF.sub.6 crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF.sub.6 with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF.sub.6 type of chemical formula, e.g. Ce-doped LiCaAlF.sub.6 and LiSrGaF.sub.6, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator.

  12. Optically pumped cerium-doped LiSrAlF{sub 6} and LiCaAlF{sub 6}

    DOEpatents

    Marshall, C.D.; Payne, S.A.; Krupke, W.F.

    1996-05-14

    Ce{sup 3+}-doped LiSrAlF{sub 6} crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF{sub 6} with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF{sub 6} type of chemical formula, e.g. Ce-doped LiCaAlF{sub 6} and LiSrGaF{sub 6}, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator. 10 figs.

  13. EBSD characterization of high-temperature phase transformations in an Al-Si coating on Cr-Mo steel

    SciTech Connect

    Cheng, Wei-Jen Wang, Chaur-Jeng

    2012-02-15

    5Cr-0.5Mo steel was coated by hot-dipping in a molten bath containing Al-10 wt.% Si. The phase transformation in the aluminide layer during diffusion at 750 Degree-Sign C in static air was analyzed by electron backscatter diffraction. The results show the aluminide layer of the as-coated specimen consisted of an outer Al-Si topcoat, a middle layer formed of scattered {tau}{sub 5(C)}-Al{sub 7}(Fe,Cr){sub 2}Si particles and minor plate-shaped {tau}{sub 4}-Al{sub 4}FeSi{sub 2} and {tau}{sub 6}-Al{sub 4}FeSi phases in the Al-Si matrix and an inner continuous {tau}{sub 5(H)}-Al{sub 7}Fe{sub 2}Si layer, respectively from the coating surface to the steel substrate. The formation of FeAl{sub 3} and Fe{sub 2}Al{sub 5} with {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates can be observed with increasing exposure time at 750 Degree-Sign C. After 5 h of exposure, the Al-Si topcoat has been consumed, and the aluminide layer consisted of Fe{sub 2}Al{sub 5} and a few {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} precipitates. The FeAl phase not only formed at the interface between Fe{sub 2}Al{sub 5} and the steel substrate, but also transformed from {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} after diffusion for 10 h. With prolonged exposure, the aluminide layer comprised only FeAl{sub 2} and FeAl. - Highlights: Black-Right-Pointing-Pointer EBSD can differentiate phases in aluminide layer with similar chemical compositions. Black-Right-Pointing-Pointer Mapping and EBSPs functions in EBSD provide a reliable phase identification. Black-Right-Pointing-Pointer A phase transformation in the aluminide layer has been described in detail. Black-Right-Pointing-Pointer 5 Fe-Al-Si and 4 Fe-Al intermetallic phases are performed during the diffusion. Black-Right-Pointing-Pointer Cubic {tau}{sub 5(C)}-Al{sub 7} (Fe,Cr){sub 2}Si and hexagonal {tau}{sub 5(H)}-Al{sub 7}(Fe,Cr){sub 2}Si are identified.

  14. Combustion Synthesis of CaAl2Si2O8:Eu2+, Dy3+ And CaSrAl2SiO7:Eu2+ Long After Glow Phosphors

    NASA Astrophysics Data System (ADS)

    Talwar, Gurjeet; Joshi, C. P.; Moharil, S. V.; Kondawar, V. K.

    2011-10-01

    CaSrAl2SiO7:Eu2+ and CaAl2Si2O8:Eu2+, Dy3+ are prepared through modified combustion technique. The photoluminescence and long after glow decay characteristics are studied. PL emission spectra of both the phosphors are obtained in blue region.

  15. Aluminum-Magnesium and Oxygen Isotope Study of Relict Ca-Al-rich Inclusions in Chondrules

    NASA Astrophysics Data System (ADS)

    Krot, Alexander N.; McKeegan, Kevin D.; Huss, Gary R.; Liffman, Kurt; Sahijpal, Sandeep; Hutcheon, Ian D.; Srinivasan, Gopalan; Bischoff, Adolph; Keil, Klaus

    2006-03-01

    Relict Ca-Al-rich inclusions (CAIs) in chondrules crystallized before their host chondrules and were subsequently partly melted together with chondrule precursors during chondrule formation. Like most CAIs, relict CAIs are 16O enriched (Δ17O<-20‰) compared to their host chondrules (Δ17O>-9‰). Hibonite in a relict CAI from the ungrouped carbonaceous chondrite Adelaide has a large excess of radiogenic 26Mg (26Mg*) from the decay of 26Al, corresponding to an initial 26Al/27Al ratio [(26Al/27Al)I] of (3.7+/-0.5)×10-5 in contrast, melilite in this CAI and plagioclase in the host chondrule show no evidence for 26Mg* [(26Al/27Al)I of <5×10-6]. Grossite in a relict CAI from the CH carbonaceous chondrite PAT 91546 has little 26Mg*, corresponding to a (26Al/27Al)I of (1.7+/-1.3)×10-6. Three other relict CAIs and their host chondrules from the ungrouped carbonaceous chondrite Acfer 094, CH chondrite Acfer 182, and H3.4 ordinary chondrite Sharps do not have detectable 26Mg* [(26Al/27Al)I<1×10-5, <(4-6)×10-6, and <1.3×10-5, respectively]. Isotopic data combined with mineralogical observations suggest that relict CAIs formed in an 16O-rich gaseous reservoir before their host chondrules, which originated in an 16O-poor gas. The Adelaide CAI was incorporated into its host chondrule after 26Al had mostly decayed, at least 2 Myr after the CAI formed, and this event reset 26Al-26Mg systematics.

  16. Structural and magnetic characterization of the complete delafossite solid solution (CuAlO₂)₁-x(CuCrO₂)x.

    PubMed

    Barton, Phillip T; Seshadri, Ram; Knöller, Andrea; Rosseinsky, Matthew J

    2012-01-11

    We have prepared the complete delafossite solid solution series between diamagnetic CuAlO(2) and the t(2g)(3)frustrated antiferromagnet CuCrO(2). The evolution with composition x in CuAl(1-x)Cr(x)O(2) of the crystal structure and magnetic properties has been studied and is reported here. The room-temperature unit cell parameters follow the Végard law and increase with x as expected. The μ(eff) is equal to the Cr(3+) spin-only S = 3/2 value throughout the entire solid solution. Θ(CW) is negative, indicating that the dominant interactions are antiferromagnetic, and its magnitude increases with Cr substitution. For dilute Cr compositions, the nearest-neighbor exchange coupling constant J(BB) was estimated by mean-field theory to be 3.0 meV. Despite the sizable Θ(CW), long-range antiferromagnetic order does not develop until x is almost 1, and is preceded by glassy behavior. The data presented here, and those on dilute Al substitution from Okuda et al, suggest that the reduction in magnetic frustration due to the presence of non-magnetic Al does not have as dominant an effect on magnetism as chemical disorder and dilution of the magnetic exchange. For all samples, the 5 K isothermal magnetization does not saturate in fields up to 5 T and minimal hysteresis is observed. The presence of antiferromagnetic interactions is clearly evident in the sub-Brillouin behavior with a reduced magnetization per Cr atom. An inspection of the scaled Curie plot reveals that significant short-range antiferromagnetic interactions occur in CuCrO(2) above its Néel temperature, consistent with its magnetic frustration. Uncompensated short-range behavior is present in the Al-substituted samples and is likely a result of chemical disorder. PMID:22133702

  17. Structure and physical properties of single crystal PrCr{sub 2}Al{sub 20} and CeM{sub 2}Al{sub 20} (M=V, Cr): A comparison of compounds adopting the CeCr{sub 2}Al{sub 20} structure type

    SciTech Connect

    Kangas, Michael J.; Schmitt, Devin C.; Sakai, Akito; Nakatsuji, Satoru; Chan, Julia Y.

    2012-12-15

    Crystal growth and full structure determination of compounds adopting the CeCr{sub 2}Al{sub 20} structure type, LnTi{sub 2}Al{sub 20} (Ln=La-Pr, Sm, and Yb), LnV{sub 2}Al{sub 20} (Ln=La-Pr, and Sm), and LnCr{sub 2}Al{sub 20} (Ln=La-Pr, Sm, and Yb), are reported. Resistivity, magnetic susceptibility, and heat capacity of flux grown single crystals of the nonmagnetic CeM{sub 2}Al{sub 20} (Ln=Ce, Yb; M=Ti, V) compounds are compared to PrCr{sub 2}Al{sub 20}. Of particular interest is PrCr{sub 2}Al{sub 20} which does not show any phase transition down to the lowest temperature of the measurement (400 mK in resistivity measurement and 1.8 K for magnetic susceptibility measurements) and exhibits Kondo behavior at low temperatures. - Graphical abstract: Crystal structure of SmV{sub 2}Al{sub 20} showing the interpenetrating diamond-like samarium network and pyrochlore-like vanadium network. Highlights: Black-Right-Pointing-Pointer Single crystals of LnM{sub 2}Al{sub 20} were grown from a molten aluminum flux. Black-Right-Pointing-Pointer Magnetic, electrical, and specific heat of single crystal LnM{sub 2}Al{sub 20} are presented. Black-Right-Pointing-Pointer PrCr{sub 2}Al{sub 20} exhibits evidence of Kondo effect.

  18. Development and property evaluation of nuclear grade wrought FeCrAl fuel cladding for light water reactors

    DOE PAGES

    Yamamoto, Yukinori; Pint, Bruce A.; Terrani, Kurt A.; Field, Kevin G.; Yang, Ying; Snead, Lance Lewis

    2015-10-19

    Development of nuclear grade, iron-based wrought FeCrAl alloys has been initiated for light water reactor (LWR) fuel cladding to serve as a substitute for zirconium-based alloys with enhanced accident tolerance. Ferritic alloys with sufficient chromium and aluminum additions can exhibit significantly improved oxidation kinetics in high-temperature steam environments when compared to zirconium-based alloys. In the first phase, a set of model FeCrAl alloys containing 10–20Cr, 3–5Al, and 0–0.12Y in weight percent, were prepared by conventional arc-melting and hot-working processes to explore the effect of composition on the properties of FeCrAlY alloys. It was found that the tensile properties were insensitivemore » to the alloy compositions studied; however, the steam oxidation resistance strongly depended on both the chromium and the aluminum contents. The second phase development focused on strengthening Fe-13Cr-5Al with minor alloying additions of molybdenum, niobium, and silicon. Combined with an optimized thermo-mechanical treatment, a thermally stable microstructure was produced with improved tensile properties at temperatures up to 741°C.« less

  19. Development and property evaluation of nuclear grade wrought FeCrAl fuel cladding for light water reactors

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Pint, B. A.; Terrani, K. A.; Field, K. G.; Yang, Y.; Snead, L. L.

    2015-12-01

    Development of nuclear grade, iron-based wrought FeCrAl alloys has been initiated for light water reactor (LWR) fuel cladding to serve as a substitute for zirconium-based alloys with enhanced accident tolerance. Ferritic alloys with sufficient chromium and aluminum additions can exhibit significantly improved oxidation kinetics in high-temperature steam environments when compared to zirconium-based alloys. In the first phase, a set of model FeCrAl alloys containing 10-20Cr, 3-5Al, and 0-0.12Y in weight percent, were prepared by conventional arc-melting and hot-working processes to explore the effect of composition on the properties of FeCrAlY alloys. It was found that the tensile properties were insensitive to the alloy compositions studied; however, the steam oxidation resistance strongly depended on both the chromium and the aluminum contents. The second phase development focused on strengthening Fe-13Cr-5Al with minor alloying additions of molybdenum, niobium, and silicon. Combined with an optimized thermo-mechanical treatment, a thermally stable microstructure was produced with improved tensile properties at temperatures up to 741 °C.

  20. Development and property evaluation of nuclear grade wrought FeCrAl fuel cladding for light water reactors

    SciTech Connect

    Yamamoto, Yukinori; Pint, Bruce A.; Terrani, Kurt A.; Field, Kevin G.; Yang, Ying; Snead, Lance Lewis

    2015-10-19

    Development of nuclear grade, iron-based wrought FeCrAl alloys has been initiated for light water reactor (LWR) fuel cladding to serve as a substitute for zirconium-based alloys with enhanced accident tolerance. Ferritic alloys with sufficient chromium and aluminum additions can exhibit significantly improved oxidation kinetics in high-temperature steam environments when compared to zirconium-based alloys. In the first phase, a set of model FeCrAl alloys containing 10–20Cr, 3–5Al, and 0–0.12Y in weight percent, were prepared by conventional arc-melting and hot-working processes to explore the effect of composition on the properties of FeCrAlY alloys. It was found that the tensile properties were insensitive to the alloy compositions studied; however, the steam oxidation resistance strongly depended on both the chromium and the aluminum contents. The second phase development focused on strengthening Fe-13Cr-5Al with minor alloying additions of molybdenum, niobium, and silicon. Combined with an optimized thermo-mechanical treatment, a thermally stable microstructure was produced with improved tensile properties at temperatures up to 741°C.

  1. A feasibility study of a diffusion barrier between Ni-Cr-Al coatings and nickel-based eutectic alloys

    NASA Technical Reports Server (NTRS)

    Young, S. G.; Zellars, G. R.

    1978-01-01

    Coating systems have been proposed for potential use on eutectic alloy components in high-temperature gas turbine engines. In a study to prevent the deterioration of such systems by diffusion, a tungsten sheet 25 microns thick was placed between eutectic alloys and an Ni-Cr-Al layer. Layered test specimens were aged at 1100 C for as long as 500 h. Without the tungsten barrier the delta phase of the eutectic deteriorated by diffusion of niobium into the Ni-Cr-Al. Insertion of the tungsten barrier stopped the diffusion of niobium from the delta phase. Chromium diffusion from the Ni-Cr-Al into the gamma/gamma-prime phase of the eutectic was greatly reduced by the barrier. However, the barrier thickness decreased with time, and tungsten diffused into both the Ni-Cr-Al and the eutectic. When the delta platelets were aligned parallel rather than perpendicular to the Ni-Cr-Al layer, diffusion into the eutectic was reduced.

  2. Microstructure of Al2O3 scales formed on NiCrAl alloys. Ph.D. Thesis - Case Western Reserve Univ.

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.

    1981-01-01

    The structure of transient scales formed on pure and Y or Zr-doped Ni-15Cr-13Al alloys oxidized for 0.1 hr at 1100 C was studied by the use of transmission electron microscopy. Crystallographically oriented scales were found on all three alloys, but especially for the Zr-doped NiCrAl. The oriented scales consisted of alpha-(Al,Cr)2O3, Ni(Al,Cr)2O4 and gamma-Al2O3. They were often found in intimate contact with each other such that the close-packed planes and directions of one oxide phase were aligned with those of another. The prominent structural features of the oriented scales were approximately equal to micrometer subgrains; voids, antiphase domain boundaries and aligned precipitates were also prevalent. Randomly oriented alpha-Al2O3 was also found and was the only oxide ever observed at the immediate oxide metal interface. These approximately 0.15 micrometer grains were populated by intragranular voids which decreased in size and number towards the oxide metal interface. A sequence of oxidation was proposed in which the composition of the growing scale changed from oriented oxides rich in Ni and Cr to oriented oxides rich in Al. At the same time the structure changed from cubic spinels to hexagonal corundums with apparent precipitates of one phase in the matrix of the other. Eventually randomly oriented pure alpha-Al2O3 formed as the stable oxide with an abrupt transition: there was no gradual loss of orientation, no gradual compositional change or no gradual decrease in precipitate density.

  3. High-pressure behaviour of Cr-Fe-Mg-Al spinels: applications to diamond geobarometry

    NASA Astrophysics Data System (ADS)

    Periotto, Benedetta; Bruschini, Enrico; Nestola, Fabrizio; Lenaz, Davide; Princivalle, Francesco; Andreozzi, Giovanni B.; Bosi, Ferdinando

    2014-05-01

    Spinels belonging to the chromite - magnesiochromite - hercynite (FeCr2O4-MgCr2O4-FeAl2O4) system are among the most common inclusions found in diamonds (Stachel and Harris 2008). In particular, although FeCr2O4 and MgCr2O4 components sum to between 85 and 88% of spinels found in diamonds, hercynite FeAl2O4 plays a not negligible role in determining their thermo-elastic properties with concentrations reaching 7-9 % (other minor end-members like MgAl2O4, MgFe2O4 and Fe2O3 rarely reach 2-3% in total, see Lenaz et al. 2009). Recent studies were focused on the determination of the diamond formation pressure by the so-called "elastic method" (see for example Nestola et al. 2011 and references therein). It was demonstrated that accurate and precise thermo-elastic parameters are fundamental to minimize the uncertainty of formation pressure. In this work we have determined the equations of state at room temperature of three synthetic spinel end-members chromite - magnesiochromite - hercynite and one natural spinel crystal extracted from a diamond (from Udachnaya mine, Siberia, Russia) by single-crystal X-ray diffraction in situ at high-pressure. A diamond-anvil cell was mounted on a STADI IV diffractometer equipped with a point detector and motorized by SINGLE software (Angel and Finger 2011). The natural crystal was investigated to test (and possibly validate) the "empirical prediction model", capable to provide bulk modulus and its first pressure derivative only knowing the composition of the spinels found in diamonds. Such prediction model could be used to obtain pressure of formation for the diamond-spinel pair through the elastic method. Details and results will be discussed. The research was funded by the ERC Starting Grant to FN (grant agreement n° 307322). References Angel R.J., Finger L.W. (2011) SINGLE A program to control single-crystal diffractometers. Journal of Applied Crystallography, 44, 247-251. Lenaz D., Logvinova A.M., Princivalle F., Sobolev N. (2009

  4. Crystal structure study of (Ca, Gd){sub 2}(Al, Ti)O{sub 4}

    SciTech Connect

    Sawada, Haruo; Marumo, Fumiyuki; Kodama, Nobuhiro

    1998-08-01

    The crystal structures of two crystals of (Ca, Gd){sub 2} (Al, Ti)O{sub 4} [tetragonal I4/mmm; Z = 4], one strongly fluorescent and the other weakly fluorescent, having minor differences in their precise compositions have been studied with single-crystal X-ray diffraction methods. The unit cell is significantly smaller for the weakly fluorescent crystal, which also shows alteration of the coordination polyhedraon around the (Ca, Gd) site, suggesting the formation of vacancies at an oxygen site.

  5. Influence of Al on Microstructure and Mechanical Behavior of Cr-Containing Transformation-Induced Plasticity Steel

    NASA Astrophysics Data System (ADS)

    Suh, Dong-Woo; Park, Seong-Jun; Han, Heung Nam; Kim, Sung-Joon

    2010-12-01

    Chromium in transformation-induced plasticity (TRIP) steel is known to have a detrimental effect on the mechanical properties by increasing the hardenability of austenite introduced during intercritical heat treatment. In this study, it is suggested that an Al addition can counterbalance the effect of Cr by encouraging ferrite formation during fast cooling and austempering. This contributes to securing the thermal stability of austenite and to retrieving the excellent mechanical properties of TRIP steel even with the addition of Cr.

  6. Letter Report Documenting Progress of Second Generation ATF FeCrAl Alloy Fabrication

    SciTech Connect

    Yamamoto, Y.; Yang, Y.; Field, K. G.; Terrani, K.; Pint, B. A.; Snead, L. L.

    2014-06-10

    Development of the 2nd generation ATF FeCrAl alloy has been initiated, and a candidate alloy was selected for trial tube fabrication through hot-extrusion and gun-drilling processes. Four alloys based on Fe-13Cr-4.5Al-0.15Y in weight percent were newly cast with minor alloying additions of Mo, Si, Nb, and C to promote solid-solution and second-phase precipitate strengthening. The alloy compositions were selected with guidance from computational thermodynamic tools. The lab-scale heats of ~ 600g were arc-melted and drop-cast, homogenized, hot-forged and -rolled, and then annealed producing plate shape samples. An alloy with Mo and Nb additions (C35MN) processed at 800°C exhibits very fine sub-grain structure with the sub-grain size of 1-3μm which exhibited more than 25% better yield and tensile strengths together with decent ductility compared to the other FeCrAl alloys at room temperature. It was found that the Nb addition was key to improving thermal stability of the fine sub-grain structure. Optimally, grains of less than 30 microns are desired, with grains up to and order of magnitude in desired produced through Nb addition. Scale-up effort of the C35MN alloy was made in collaboration with a commercial cast company who has a capability of vacuum induction melting. A 39lb columnar ingot with ~81mm diameter and ~305mm height (with hot-top) was commercially cast, homogenized, hot-extruded, and annealed providing 10mm-diameter bar-shape samples with the fine sub-grain structure. This commercial heat proved consistent with materials produced at ORNL at the lab-scale. Tubes and end caps were machined from the bar sample and provided to another work package for the ATF-1 irradiation campaign in the milestone M3FT-14OR0202251.

  7. Thermal transformation of quaternary compounds in NaF-CaF{sub 2}-AlF{sub 3} system

    SciTech Connect

    Zaitseva, Julia N.; Yakimov, Igor S.; Kirik, Sergei D.

    2009-08-15

    Details of quaternary compounds formation in the system NaF-CaF{sub 2}-AlF{sub 3} are specified. To achieve this aim, the samples of phases NaCaAlF{sub 6} and Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} have been obtained by high-temperature solid-phase synthesis. Their thermal behavior when heated up to 800 deg. C has been studied using the methods of high-temperature X-ray diffraction (XRD) and thermal analysis (TA). The system under consideration can be regarded as a quasibinary section CaF{sub 2}-NaAlF{sub 4}, where at T=745-750 deg. C invariant equilibrium is implemented with the phases CaF{sub 2}-NaCaAlF{sub 6}-Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}-(liquid melt)-(NaAlF{sub 4}). The peculiarity of the equilibrium is NaAlF{sub 4} metastability at normal pressure. Below the equilibrium temperature the quaternary phase Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} is stable and NaCaAlF{sub 6} above this temperature. The phase NaCaAlF{sub 6} fixed by rapid quenching from high temperatures and when heated up to 640 deg. C decomposes, yielding Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}. Further heating in vacuum at temperature up to 740 deg. C results in decomposition of Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} into CaF{sub 2} and Na{sub 3}AlF{sub 6}. The expected reverse transformation of Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} into NaCaAlF{sub 6} has not been observed under experimental conditions. Transformations in bulk samples reveal direct and reverse transformation of quaternary phases. Synopsis: Thermal transformation of the quaternary compounds in system (NaF-CaF{sub 2}-AlF{sub 3}) was investigated using high-temperature X-ray diffraction (XRD) and thermal analysis (TA). In the system the invariant equilibrium is implemented with the phases CaF{sub 2}-NaCaAlF{sub 6}-Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}-(liquid melt)-(NaAlF{sub 4}) at T=745-750 deg. C. - Graphical Abstract: The paper concerns of a small piece of the ternary system (NaF-CaF{sub 2}-AlF{sub 3}) which is very important for

  8. Extraordinary colossal magnetoresistance in La 0.67Ca 0.33Mn 1- xCr xO 3 ( x⩽0.3)

    NASA Astrophysics Data System (ADS)

    Sun, Young; Tong, Wei; Xu, Xiaojun; Zhang, Yuheng

    2001-06-01

    The magnetic and magnetotransport properties of La 0.67Ca 0.33Mn 1- xCr xO 3 ( x⩽0.3) perovskites have been studied. It was found that Cr doping is impotent in driving Curie temperature Tc but brings about cluster glass behaviors. Moreover, the substitution with Cr on Mn sites introduces extraordinary electrical transport and colossal magnetoresistance (CMR) behavior, characterized by double peaks. As a result, the temperature range of CMR response is greatly broadened. These results suggest that Cr doping could be a potent way in tuning CMR.

  9. Site partitioning of Cr3+ in the trichroic alexandrite BeAl2O4:Cr3+ crystal: contribution from x-ray absorption spectroscopy.

    PubMed

    Bordage, Amélie; Rossano, Stéphanie; Horn, Adolf Heinrich; Fuchs, Yves

    2012-06-01

    X-ray absorption spectroscopy measurements at the Cr K-edge of a trichroic crystal of alexandrite BeAl(2)O(4):Cr(3+) for different orientations of the crystal with respect to the polarization and direction of the x-ray incident beam have been performed. Analysis of the experimental spectra with the help of first-principles calculations of x-ray absorption spectra allowed us to estimate the proportion of chromium Cr(3+) cations among the two different octahedral sites of the alexandrite structure (70% in the C(s) site-30% in the C(i) site). The methodology presented in this work opens up new possibilities in the field of mineralogy for the study of complex minerals containing several sites potentially occupied by several transition elements or for solid solutions.

  10. Site partitioning of Cr3+ in the trichroic alexandrite BeAl2O4:Cr3+ crystal: contribution from x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Bordage, Amélie; Rossano, Stéphanie; Horn, Adolf Heinrich; Fuchs, Yves

    2012-06-01

    X-ray absorption spectroscopy measurements at the Cr K-edge of a trichroic crystal of alexandrite BeAl2O4:Cr3+ for different orientations of the crystal with respect to the polarization and direction of the x-ray incident beam have been performed. Analysis of the experimental spectra with the help of first-principles calculations of x-ray absorption spectra allowed us to estimate the proportion of chromium Cr3+ cations among the two different octahedral sites of the alexandrite structure (70% in the Cs site-30% in the Ci site). The methodology presented in this work opens up new possibilities in the field of mineralogy for the study of complex minerals containing several sites potentially occupied by several transition elements or for solid solutions.

  11. Evaluation of Pb-17Li compatibility of ODS Fe-12Cr-5Al alloys

    NASA Astrophysics Data System (ADS)

    Unocic, Kinga A.; Hoelzer, David T.

    2016-10-01

    The Dual Coolant Lead Lithium (DCLL: eutectic Pb-17Li and He) blanket concept requires improved Pb-17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3 + ZrO2 (125YZ), (3) Y2O3 + HfO2 (125YH), and (4) Y2O3 + TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb-17Li for 1000 h at 700 °C. Alloys showed promising compatibility with Pb-17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experienced the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (∼1 at.%) in Al content beneath the oxide scale was observed in all four ODS alloys, which extended 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb-17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  13. Design of alumina forming FeCrAl steels for lead or lead-bismuth cooled fast reactors

    NASA Astrophysics Data System (ADS)

    Lim, Jun; Hwang, Il Soon; Kim, Ji Hyun

    2013-10-01

    Iron-chromium-aluminum alloys containing 15-20 wt.% Cr and 4-6 wt.% Al have shown excellent corrosion resistance in the temperature range up to 600 °C or higher in liquid lead and lead-bismuth eutectic environments by the formation of protective Al2O3 layers. However, the higher Cr and Al concentrations in ferritic alloys could be problematic because of severe embrittlement in the manufacturing process as well as in service, caused by the formation of brittle phases. For this reason, efforts worldwide have so far mainly focused on the development of aluminizing surface treatments. However, aluminizing surface treatments have major disadvantages of cost, processing difficulties and reliability issues. In this study, a new FeCrAl alloy is proposed for structural materials in lead and lead-bismuth cooled nuclear applications. The alloy design relied on corrosion experiments in high temperature lead and lead-bismuth eutectic environments and computational thermodynamic calculations using the commercial software, JMatPro. The design of new alloys has focused on the optimization of Cr and Al levels for the formation of an external Al2O3 layer which can provide excellent oxidation and corrosion resistance in liquid lead alloys in the temperature range 300-600 °C while still retaining workable mechanical properties.

  14. Origin of Ca-Al-rich inclusions. II - Sputtering and collisions in the three-ph8se interstellar medium

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1981-01-01

    The theory put forward by Clayton (1977) for the formation of the Ca-Al-rich inclusions within C3 meteorites is extended to an evolutionary history in a three-phase interstellar medium. Widespread supersonic turbulence in the hot interstellar medium is maintained by supernova shock waves, giving rise to heavy sputtering of the refractory dust. Subsequent reaccumulation with varying dust/gas ratios or varying particle sizes produces isotopically fractionated Ca-Al-rich accumulates. It is thought that the Ca-Al-rich inclusions themselves are formed by the following sequence in the solar system: (1) cold accumulation of larger-than-average Ca-Al-rich particles containing supernova condensate cores into macroscopic (approximately 1 cm) Ca-Al-rich agglomerates, probably by sedimentation; and (2) fusion of the supernova condensates into macroscopic minerals by exothermic chemical reactions that begin when the accumulate has been warmed, thereby releasing energy from the unequilibrated forms accumulated from the interstellar medium.

  15. Effect of Strain Rate on Deformation Behavior of AlCoCrFeNi High-Entropy Alloy by Nanoindentation

    NASA Astrophysics Data System (ADS)

    Tian, L.; Jiao, Z. M.; Yuan, G. Z.; Ma, S. G.; Wang, Z. H.; Yang, H. J.; Zhang, Y.; Qiao, J. W.

    2016-06-01

    In this study, nanoindentation tests with continuous stiffness measurement technique were measured to investigate the deformation behavior of a high-entropy alloy AlCoCrFeNi under different indentation strain rates at room temperature. Results suggest that the creep behavior exhibits remarkable strain rate dependence. In-situ scanning images showed a conspicuous pileup around the indents, indicating that an extremely localized plastic deformation occurred during the nanoindentation. Under different strain rates, elastic modulus basically remains unchanged, while the hardness decreases with increasing indentation depth due to the indentation size effect. Furthermore, the modulus and hardness of AlCoCrFeNi HEAs are greater than that of the Al x CoCrFeNi ( x = 0.3,0.5) at the strain rate of 0.2 s-1 due to its higher negative enthalpy of mixing related to the atomic binding force, and the solid solution strengthening induced by the lattice distortion, respectively.

  16. Microwave absorption capability of microcapsules by coating FeSiAlCr with SiO2

    NASA Astrophysics Data System (ADS)

    Huang, Weirong; Zhang, Penghua; Yan, Wenjing; Zhou, Liang; Xu, Hui

    2012-10-01

    Electromagnetic wave absorption of microcapsules by coating FeSiAlCr with SiO2 is investigated. The absorption amplitude of the microcapsules is found to increase significantly in the lower frequency of microwave compared with the corpuscles of FeSiAlCr alloy. Reflection loss (RL) exceeding -10 dB can be obtained for all frequencies within 2.6-7.3 GHz, covering half of the S-band, and the whole C-band when the absorber layer thickness is 2 mm. The maximum RL can exceed -18 dB at 4.3 GHz, while the RL is only -4 dB with the corpuscles of FeSiAlCr alloy. The reason is that the microcapsules's conductance is decreased and the absorption of electromagnetic wave in the microcapsule materials is easier.

  17. Structural and magnetization behavior of highly spin polarized Co{sub 2}CrAl full Heusler alloy

    SciTech Connect

    Saha, S. N. Panda, J. Nath, T. K.

    2014-04-24

    The half metallic ferromagnet Co{sub 2}CrAl full Huesler alloy was successfully prepared by arc melting process. The electrical and magnetic properties of Co{sub 2}CrAl alloy have been studied in the temperature range of 5 – 300 K. The ferromagnetic Curie temperature T{sub c} of the same alloy has been observed at 329.8 K. The alloy shows semiconducting like electronic transport behavior throughout the studied temperature range. The origin of the semiconducting behavior of Co{sub 2}CrAl alloy can be best explained by the localization of conduction electrons and the presence of an energy gap in the electronic spectrum near the Fermi level E{sub F}.

  18. Temperature-induced structural changes in CaCl{sub 2},CaBr{sub 2}, and CrCl{sub 2}: A synchrotron x-ray powder diffraction study

    SciTech Connect

    Howard, Christopher J.; Kennedy, Brendan J.; Curfs, Caroline

    2005-12-01

    The halides CaCl{sub 2},CaBr{sub 2}, and CrCl{sub 2} all adopt, at room temperature, the same distorted rutile structure, in orthorhombic space group Pnnm, known as the calcium chloride structure. Upon heating, CaCl{sub 2} and CaBr{sub 2} each undergoes a continuous transformation to the true tetragonal rutile structure, in space group P4{sub 2}/mnm, the transition temperatures being 235 and 553 deg. C, respectively. By contrast, the structural change in CrCl{sub 2} upon heating is just further elongation of octahedra already lengthened by Jahn-Teller effects, and no phase transition occurs. The orthorhombic structure is maintained by a strong and temperature-dependent geometrical coupling of the orthorhombic strain to the order parameter, represented by the tilt angle of the CrCl{sub 6} octahedron.

  19. Microstructure of laser clad Ni- Cr- Al- Hf alloy on a γ' strengthened ni- base superalloy

    NASA Astrophysics Data System (ADS)

    Singh, Jogender; Mazumder, J.

    1988-08-01

    Alloys and coatings for alloys for improved high temperature service life under aggressive atmo-spheres are of great contemporary interest. There is a general consensus that the addition of rare earths such as Hf will provide many beneficial effects for such alloys. The laser cladding technique was used to produce Ni-Cr-AI-Hf alloys with extended solid solution of Hf. A 10 kW CO2 laser with mixed powder feed was used for laser cladding. Optical, scanning electron (SEM) and scanning transmission electron (STEM) microscopy were employed to characterize the microstructure of alloys produced during laser cladding processes. Microstructural studies revealed grain refinement, considerable in-crease in solubility of Hf in the matrix, Hf-rich precipitates, and new metastable phases. The size and morphology of γ' (Ni3Al) phase were discussed in relation to its microchemistry and the laser processing conditions. This paper will report the microstructural development in this laser clad Ni-Cr-AI-Hf alloy.

  20. Cyclic Corrosion and Chlorination of an FeCrAl Alloy in the Presence of KCl

    SciTech Connect

    Israelsson, Niklas; Unocic, Kinga A.; Hellström, K.; Svensson, J-E; Johansson, L-G

    2015-05-30

    The KCl-induced corrosion of the FeCrAl alloy Kanthal® APMT in an O2 + N2 + H2O environment was studied at 600 °C. The samples were pre-oxidized prior to exposure in order to investigate the protective nature of alumina scales in the present environment. The microstructure and composition of the corroded surface was investigated in detail. Corrosion started at flaws in the pre-formed α-alumina scales, i.e. α-alumina was protective in itself. Consequently, KCl-induced corrosion started locally and, subsequently, spread laterally. An electrochemical mechanism is proposed here by which a transition metal chloride forms in the alloy and K2CrO4 forms at the scale/gas interface. Scale de-cohesion is attributed to the formation of a sub-scale transition metal chloride.

  1. Effect of Al Enrichment by Pack Cementation of FeCr Coatings Deposited by HVOF

    NASA Astrophysics Data System (ADS)

    Bellucci, A.; Bellini, S.; Pileggi, R.; Stocchi, D.; Tuurna, S.

    2015-01-01

    A great contribution to CO2 emissions comes from coal fired power generation. Combination of carbon capture sequestering technologies with sustainable biomass conversion constitutes a decisive boost in limiting rise in global temperature. Co-firing alternative materials with pulverized coal and using oxy-fuel combustion conditions (oxy-fuel co-combustion) is a very attractive process for power industry. Materials with both high mechanical properties and high environmental resistance are required by such advanced combustion systems. One approach to improve high-temperature oxidation/corrosion resistance is to apply protective coatings. In the present work, low and high Cr content Fe-based alloys have been deposited in order to investigate the influence of Cr content on coating protective performance in oxy-fuel co-combustion conditions. Grade 91 steel has been assumed as reference substrate. Effect of Al enrichment on coating environmental resistance has also been analyzed. Activities have been performed within the framework of Macplus Project (Integrated Project co-founded by the European Commission under the 7th Framework Program in the Energy area).

  2. Growth of alumina scale on Fe-Cr-Al : a multiprobe study.

    SciTech Connect

    Veal, B. W.

    1998-06-03

    The use of local probes at specific spatial locations provides a clear picture of the scale growth. The thermal evolution of the oxide scale on 72Fe-18Cr-10Al-0.15Hf (at.%) has been investigated using a number of spectroscopic techniques. Well defined regions ({approx}70 mm in diameter) were probed by a battery of techniques as a function of oxidation at different temperatures (Between 800 C--1100 C). This study provides information about the dependence of scale evolution on fluctuations in the local composition and/or grain structure of the starting material. Results suggest that properties of the starting material, which were not investigated in this study, strongly influence the scale evolution, even to the stage of mature scales.

  3. Tensile behavior of the L(1)2 compound Al67Ti25Cr8

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Brown, S. A.

    1992-01-01

    Temperature-related variations in tensile yield strength and ductility were studied on cast, homogenized and isothermally forged Al67Ti25Cr8. Yield strength dropped discontinuously between 623 K and 773 K and then decreased gradually with increasing temperature. Below 623 K, fracture occurred prior to macroscopic yielding. Ductility decreased from 0.2 percent at 623 K to zero at 773 K, but increased again at higher temperatures. At 1073 K, an elongation of 19 percent was obtainable, and ultimate tensile strength and localized necking were observed. Fracture surfaces and deformed microstructures were examined. The 1073 K tensile specimen that exhibited 19 percent elongation showed grain boundary serrations and some evidence of recrystallization (likely dynamic) although fracture occurred predominantly via an intergranular mode.

  4. Wear and Corrosion Behavior of CoNiCrAlY Bond Coats

    NASA Astrophysics Data System (ADS)

    Rathod, W. S.; Khanna, A. S.; Rathod, R. C.; Sapate, S. G.

    2014-07-01

    The present study focusses on the wear and microstructural properties of CoNiCrAlY coatings fabricated on AISI 316L stainless steel substrate by using the (HVOF) and (CGDS) methods. A triobiological test was performed on the samples in order to understand the wear behaviour of thermally sprayed coatings. The microstructures of as-sprayed and worn out coatings were investigated by scanning electron microscopy. Coating hardness measurements were performed with nanoindentation. HVOF coating revealed lower hardness value in comparison with CGDS. Studies depicted better wear resistance of the CGDS sprayed with He, when compared to CGDS N2 and HVOF processing. Potentiodynamic polarization curves and tafel extrapolation experiments were carried at 7.5 pH value using 3.5 % NaCl as an electrolyte. Electrochemical studies depicted better corrosion resistance of the He processed coating when compared to N2 and HVOF processing.

  5. Microstructure Evolution in a New Refractory High-Entropy Alloy W-Mo-Cr-Ti-Al

    NASA Astrophysics Data System (ADS)

    Gorr, Bronislava; Azim, Maria; Christ, Hans-Juergen; Chen, Hans; Szabo, Dorothee Vinga; Kauffmann, Alexander; Heilmaier, Martin

    2016-02-01

    The microstructure of a body-centered cubic 20W-20Mo-20Cr-20Ti-20Al alloy in the as-cast condition as well as its microstructural evolution during heat treatment was investigated. Different characterization techniques, such as focused ion beam-scanning electron microscope, X-ray diffraction, and transmission electron microscope, were applied. Experimental observations were supported by thermodynamic calculations. The alloy exhibits a pronounced dendritic microstructure in the as-cast condition with the respective dendritic and interdendritic regions showing significant fluctuations of the element concentrations. Using thermodynamic calculations, it was possible to rationalize the measured element distribution in the dendritic and the interdendritic regions. Observations of the microstructure evolution reveal that during heat treatment, substantial homogenization takes place leading to the formation of a single-phase microstructure. Driving forces for the microstructural evolution were discussed from a thermodynamic point of view.

  6. Evaluation of Cyclic Oxidation and Hot Corrosion Behavior of HVOF-Sprayed WC-Co/NiCrAlY Coating

    NASA Astrophysics Data System (ADS)

    Somasundaram, B.; Kadoli, Ravikiran; Ramesh, M. R.

    2014-08-01

    Corrosion of metallic structural materials at an elevated temperature in complex multicomponent gas environments are potential problems in many fossil energy systems, especially those using coal as a feedstock. Combating these problems involves a number of approaches, one of which is the use of protective coatings. The high velocity oxy fuel (HVOF) process has been used to deposit WC-Co/NiCrAlY composite powder on two types of Fe-based alloys. Thermocyclic oxidation behavior of coated alloys was investigated in the static air as well as in molten salt (Na2SO4-60%V2O5) environment at 700 °C for 50 cycles. The thermogravimetric technique was used to approximate the kinetics of oxidation. WC-Co/NiCrAlY coatings showed a lower oxidation rate in comparison to uncoated alloys. The oxidation resistance of WC-Co/NiCrAlY coatings can be ascribed to the oxide layer of Al2O3 and Cr2O3 formed on the outermost surface. Coated alloys extend a protective oxide scale composed of oxides of Ni and Cr that are known to impart resistance to the hot corrosion in the molten salt environment.

  7. 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.

  8. 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.

  9. 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.

  10. Observations of the Minor Species Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report the first detections of Al and Fe, and strict upper limits for Ca(+) in the exosphere of Mercury, using the HIRES spectrometer at the Keck I telescope. We report observed 4-sigma tangent columns of 1.5x10(exp 7) Al atoms per square centimeter at an altitude of 1220 km (1.5 Mercury radii (R(sub M)) from planet center), and that for Fe of 1.6 x 10 per square centimeter at an altitude of 950 km (1.4 R(sub M)). The observed 3-sigma Ca(+) column was 3.9x10(exp 6) ions per square centimeter at an altitude of 1630 km (1.67 R(sub M). A simple model for zenith column abundances of the neutral species were 9.5 x 10(exp 7) Al per square centimeter, and 3.0 x 10(exp 8) Fe per square centimeter. The observations appear to be consistent with production of these species by impact vaporization with a large fraction of the ejecta in molecular form. The scale height of the Al gas is consistent with a kinetic temperature of 3000 - 9000 K while that of Fe is 10500 K. The apparent high temperature of the Fe gas would suggest that it may be produced by dissociation of molecules. A large traction of both Al and Fe appear to condense in a vapor cloud at low altitudes.

  11. Synthesis of Cr-doped CaTiSiO{sub 5} ceramic pigments by spray drying

    SciTech Connect

    Lyubenova, T. Stoyanova Matteucci, F.; Costa, A.L.; Dondi, M.; Ocana, M.

    2009-04-02

    Cr-doped CaTiSiO{sub 5} was synthesized by spray drying and conventional ceramic method in order to assess its potential as ceramic pigment. The evolution of the phase composition with thermal treatment was investigated by X-ray powder diffraction (XRPD) and thermal analyses (DTA-TGA-EGA). Powder morphology and particle size distribution were analyzed by scanning electron microscopy (SEM) and laser diffraction, respectively. The color efficiency of pigments was evaluated by optical spectroscopy (UV-vis-NIR) and colorimetric analysis (CIE Lab). Results proved that spray drying is an efficient procedure to prepare highly reactive pigment precursors. The spray-dried powders consist of hollow spherical particles with aggregate size in the 1-10 {mu}m range, developing a brown coloration. Optical spectra reveal the occurrence of Cr(III) and Cr(IV), both responsible for the brown color of this pigment. The former occupies the octahedral site of titanite, in substitution of Ti(IV), while the latter is located at the tetrahedral site, where replaces Si(IV)

  12. Effect of nitrogen pressure on the hardness and chemical states of TiAlCrN coatings

    SciTech Connect

    Sullivan, Jonathan F.; Huang Feng; Barnard, John A.; Weaver, Mark L.

    2005-01-01

    TiAlCrN coatings were reactively sputtered from a Ti{sub 0.37}Al{sub 0.51}Cr{sub 0.12} alloy target in this study with a nitrogen partial pressure ranging from 0% to 25% of the total pressure. The effects of the incorporation of nitrogen into the coatings on the hardness, elastic modulus, and chemical state of the metal atoms in the coatings were investigated. The hardness and reduced modulus of the coatings increased with increasing nitrogen partial pressures. The formation of ternary nitrides was inferred from the noticeable difference in the chemical states from those for the corresponding binary nitrides.

  13. Studies on the properties of Al2O3:Cr2O3 (50:50) thin film

    NASA Astrophysics Data System (ADS)

    Ponmudi, S.; Sivakumar, R.; Sanjeeviraja, C.

    2016-05-01

    Aluminium oxide (Al2O3) and chromium oxide (Cr2O3) thin films have received great attention of researchers because of their unique properties of corrosion/oxidation resistance and high dielectric constant. In addition, chromium aluminium oxide has been considered as a best candidate for deep-ultraviolet optical masks. In the present work, thin films of Al2O3:Cr2O3 (50:50) were deposited on pre-cleaned microscopic glass substrate by RF magnetron sputtering technique. The substrate temperature and RF power induced changes in structural, surface morphological, compositional and optical properties of the films have been studied.

  14. Infrared spectrum and d-d transition of γ-LiAlO 2:Cr 3+ ceramic

    NASA Astrophysics Data System (ADS)

    Wang, Xianlong; Du, Maolu; Cui, Ge; Ma, Jian; Huang, Yi

    2011-04-01

    The γ-LiAlO 2:Cr 3+ ceramics were successfully fabricated using multi-mode cavity microwave furnace, and the sample's infrared absorption spectrum was measured at room temperature. There are six bands in the range 1700-2900 cm -1. Using the crystal-field theory and introducing the average covalent factor model, we calculated the d-d transitions of Cr 3+ ions in γ-LiAlO 2 and firstly explained these bands in the infrared region. These calculation results are in good agreement with the optical experiment data.

  15. Optimization of the Ni-Cr-Al-Y/ZrO2-Y2O3 thermal barrier system

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1986-01-01

    The effects of bond and thermal barrier coating compositions, thicknesses, and densities on air plasma spray deposited Ni-Cr-Al-Y/ZrO2-Y2O3 life were evaluated in cyclic furnace oxidation tests at temperatures from 1110 to 1220 C. An empirical relation was developed to give life as a function of the above parameters. The thermal barrier system tested which had the longest life consisted of Ni-35.0 wt pct Cr-5.9 wt pct Al-0.95 wt pct Y bond coating and ZrO2-6.1 wt pct Y2O3 thermal barrier coating.

  16. Optimization of the NiCrAl-Y/ZrO-Y2O3 thermal barrier system

    NASA Technical Reports Server (NTRS)

    Stecura, S.

    1985-01-01

    The effects of bond and thermal barrier coating compositions, thicknesses, and densities on air plasma spray deposited Ni-Cr-Al-Y/ZrO2-Y2O3 life were evaluated in cyclic furnace oxidation tests at temperatures from 1110 to 1220 C. An empirical relation was developed to give life as a function of the above parameters. The thermal barrier system tested which had the longest life consisted of Ni-35.0 wt% Cr-5.9 wt% Al-0.95 wt% Y bond coating and ZrO2-6.1 wt% Y2O3 thermal barrier coating.

  17. Sr isotopic fractionation in Ca-Al inclusions from the Allende meteorite

    USGS Publications Warehouse

    Patchett, P.J.

    1980-01-01

    True relative Sr isotopic compositions, determined by double spiking on Ca-Al inclusions from the Allende meteorite show up to 1.5??? per mass unit mass fractionation relative to the Earth and bulk chondrites. All abnormal inclusions are light-isotope enriched. A lack of isotopically heavy Sr in inclusions would place constraints on the time, place and mechanism of origin of these objects. ?? 1980 Nature Publishing Group.

  18. 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.

  19. Crystal growth, polarized spectra, and laser performance of Yb:CaGdAlO4 crystal

    NASA Astrophysics Data System (ADS)

    Di, J. Q.; Xu, X. D.; Xia, C. T.; Zheng, L. H.; Aka, G.; Yu, H. H.; Sai, Q. L.; Guo, X. Y.; Zhu, L.

    2016-04-01

    In this paper, the crystal growth, polarized spectra, and laser performance of Yb:CaGdAlO4 crystal were reported. The segregation coefficient of Yb3+ ions was calculated to be 0.47. The cell parameters were determined to be a  =  b  =  0.3658 nm, c  =  1.1985 nm. The peak absorption cross-section was calculated to be 2.65  ×  10-20 cm2 at 979 nm and the peak stimulated emission cross-section was 2.23  ×  10-20 cm2 at 980 nm for the π polarization. The continuous-wave (CW) laser operations of uncoated Yb:CaGdAlO4 crystals with 5  ×  5  ×  3 mm3 in size were demonstrated. A maximum output power of 1.6 W at 1048 nm was obtained with a slope efficiency of 28%. The results show that Yb:CaGdAlO4 crystal is a promising laser medium.

  20. Hibonite, Ca2/Al, Ti/24O38, from the Leoville and Allende chondritic meteorites.

    NASA Technical Reports Server (NTRS)

    Keil, K.; Fuchs, L. H.

    1971-01-01

    Hibonite was discovered in light-colored, Ca-Al-Ti-rich and Si-Fe-poor, achondritic inclusions of the Leoville and Allende HL-group chondrites. Two varieties of hibonite occur: one emits a bright red-orange luminescence under electron bombardment and has high amounts of Al2O3 (87.7; 87.9) and low amounts of MgO (0.65; 0.8) and TiO2 (0.68; 0.8). The other emits a bright blue luminescence and is low in Al2O3 (78.7; 79.2) and high in MgO (3.3; 3.7) and TiO2 (6.5; 7.9) (in wt. %). The oxide CaO is about the same in both varieties. It is suggested that the change in the color of the visible luminescence results from changes in composition. The origin of hibonite which occurs in complex mineral assemblages together with anorthite, gelhenite, wollastonite, aluminous diopside, andradite, Ca-pyroxene, perovskite, spinel, taenite, chromite, and pentlandite, and in close proximity to nodules containing calcite, whewellite, forsterite and many of the aforementioned phases, is discussed. The proposition that hibonite and associated phases originated by contact metamorphism and metasomatism of calcite-dolomite bearing assemblages cannot, at this time, be completely ruled out.

  1. Polymer Coated CaAl-Layered Double Hydroxide Nanomaterials for Potential Calcium Supplement

    PubMed Central

    Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

    2014-01-01

    We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement. PMID:25490138

  2. Effects of Cr/Zn Substitutions on Dielectric Properties of CaCu{sub 3}Ti{sub 4}O{sub 12}(CCTO) Ceramics

    SciTech Connect

    Rajmi, R.; Yahya, A. K.; Deni, M. S. M.

    2010-07-07

    Effects of Zn and Cr substitutions on dielectric properties of CaCu{sub 3-x}Zn{sub x}Ti{sub 4-y}Cr{sub y}O{sub 12} ceramics are reported. Dielectric measurements at room temperature for un-substituted CaCu{sub 3-x}Zn{sub x}Ti{sub 4-y}Cr{sub y}O{sub 12}(x = 0, y = 0) between 10{sup 2}-10{sup 6} Hz showed dielectric constant of 2.7x10{sup 4} at 10{sup 2} Hz. Substitution of Zn for Cu in CaCu{sub 3-x}Zn{sub xTi{sub 4{sub -{sub yCr{sub yO{sub 1{sub 2}}}}}}}(y = 0, x = 0.10, 0.50)caused dielectric constant to drop with increasing x. Cr substitution at Ti-site in CaCu{sub 3-x}Zn{sub xTi{sub 4{sub -{sub yCr{sub yO{sub 1{sub 2}}}}}}}(x = 0, x = 0,) also caused decrease in dielectric constant. However, at x = 0.50, the dielectric constant at low frequency was enhanced compared to the un-substituted sample. Our results indicate that Cu and Ti sites play an important role in the formation of Internal Barrier Layer Capacitance (IBLC) in CCTO.

  3. Temperature Sensing Above 1000 C Using Cr-Doped GdAlO3 Spin-Allowed Broadband Luminescence

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.; Chambers, Matthew D.

    2012-01-01

    Cr-doped GdAlO3 (Cr:GdAlO3) is shown to produce remarkably high-intensity spin-allowed broadband luminescence with sufficiently long decay times to make effective luminescence-decay-time based temperature measurements above 1000 C. This phosphor is therefore an attractive alternative to the much lower luminescence intensity rare-earth-doped thermographic phosphors that are typically utilized at these elevated temperatures. In particular, Cr:GdAlO3 will be preferred over rare-earth-doped phosphors, such as Dy:YAG, at temperatures up to 1200 C for intensity-starved situations when the much lower emission intensity from rare-earth-doped phosphors is insufficient for accurate temperature measurements in the presence of significant radiation background. While transition-metal-doped phosphors such as Cr:Al2O3 (ruby) are known to exhibit high luminescence intensity at low dopant concentrations, quenching due to nonradiative decay pathways competing with the (sup 2)E to (sup 4)A(sub 2) radiative transition (R line) has typically restricted their use for temperature sensing to below 600 C. Thermal quenching of the broadband (sup 4)T(sub 2) to (sup 4)A(sub 2) radiative transition from Cr:GdAlO3, however, is delayed until much higher temperatures (above 1000 C). This spin-allowed broadband emission persists to high temperatures because the lower-lying (sup 2)E energy level acts as a reservoir to thermally populate the higher shorter-lived (sup 4)T(sub 2) energy level and because the activation energy for nonradiative crossover relaxation from the (sup 4)T(sub 2) level to the (sup 4)A(sub 2) ground state is high. The strong crystal field associated with the tight bonding of the AlO6 octahedra in the GdAlO3 perovskite structure is responsible for this behavior.

  4. Modeling of oxidation kinetics of Y-doped Fe-Cr-Al alloys

    SciTech Connect

    Liu, Z.; Gao, W.; He, Y.

    2000-04-01

    Studies using advanced analytical techniques indicated that the reactive elements (RE) segregate along the oxide grain boundaries and at the oxide-alloy interface during oxidation of {alpha}-Al{sub 2}O{sub 3} forming alloys. The segregation results in inward oxygen diffusion along the oxide grain boundaries as the predominant transport process in the oxide growth. The present work establishes a mathematical model based on the mechanisms of inward oxygen diffusion along the grain boundaries and oxide grain coarsening. This model has been used to describe the oxidation kinetics of Y-doped Fe-Cr-Al alloys. The results showed a much better agreement with the experimental data than the parabolic rate law. By using this model, the exponential number for the grain coarsening of alumina scales during oxidation was calculated to be {approximately}3. The activation energy for oxygen diffusing along the grain boundaries was 450 kJ/mol. They are also in good agreement with values reported in the literatures.

  5. Optimization of an oxide dispersion strengthened Ni-Cr-Al alloy for gas turbine engine vanes

    NASA Technical Reports Server (NTRS)

    Klarstrom, D. L.; Grierson, R.

    1975-01-01

    The investigation was carried out to determine the optimum alloy within the Ni-16Cr-Al-Y2O3 system for use as a vane material in advanced aircraft gas turbine engines. Six alloys containing nominally 4%, 5% and 6% Al with Y2O3 levels of 0.8% and 1.2% were prepared by mechanical attrition. Six small-scale, rectangular extrusions were produced from each powder lot for property evaluation. The approximate temperatures for incipient melting were found to be 1658 K (2525 F), 1644 K (2500 F) and 1630 K (2475 F) for the 4%, 5% and 6% aluminum levels, respectively. With the exception of longitudinal crystallographic texture, the eight extrusions selected for extensive evaluation either exceeded or were close to mechanical property goals. Major differences between the alloys became apparent during dynamic oxidation testing, and in particular during the 1366 K (2000 F)/500 hour Mach 1 tests carried out by NASA-Lewis. An aluminum level of 4.75% was subsequently judged to be optimum based on considerations of dynamic oxidation resistance, susceptibility to thermal fatigue cracking and melting point.

  6. The effect of zirconium on the isothermal oxidation of nominal Ni-14Cr-24Al alloys

    NASA Technical Reports Server (NTRS)

    Kahn, A. S.; Lowell, C. E.; Barrett, C. A.

    1980-01-01

    The isothermal oxidation of Ni-14Cr-24Al-xZr-type alloys was performed in still air at 1100, 1150, and 1200 C for times up to 200 hr. The zirconium content of the alloys varied from 0-0.63 atom percent (a/o). The oxidized surfaces were studied by optical microscopy, X-ray diffraction, and scanning electron microscopy. The base alloy was an alumina former with the zirconium-containing alloys also developing some ZrO2. The addition of zirconium above 0.066 a/o increased the rate of weight gain relative to the base alloy. Due to oxide penetratio, the weight gain increased with Zr content; however, the scale thickness did not increase. The Zr did increase the adherence of the oxide, particularly at 1200 C. The delta W/A vs. time data fit the parabolic model of oxidation. The specific diffusion mechanism operative could not be identified by analysis of the calculated activation energies. Measurements of the Al2O3 scale lattice constants yielded the same values for all alloys.

  7. Corrosion of NiCoCrAlY Coatings and TBC Systems Subjected to Water Vapor and Sodium Sulfate

    NASA Astrophysics Data System (ADS)

    Eriksson, Robert; Yuan, Kang; Li, Xin-Hai; Lin Peng, Ru

    2015-08-01

    Thermal barrier coating (TBC) systems are commonly used in gas turbines for protection against high-temperature degradation. Penetration of the ceramic top coat by corrosive species may cause corrosion damage on the underlying NiCoCrAlY bond coat and cause failure of the TBC system. In the current study, four oxidation/corrosion conditions were tried: (i) lab air, (ii) water vapor, (iii) sodium sulfate deposited on the specimens, and (iv) water vapor + sodium sulfate. The test was done at 750 °C in a cyclic test rig with 48 h cycles. The corrosion damage was studied on NiCoCrAlY-coated specimens, thin APS TBC specimens, and thick APS TBC specimens. Water vapor was found to have very minor influence on the oxidation, while sodium sulfate increased the TGO thickness both for NiCoCrAlY specimens and TBC-coated specimens; the influence of the TBC thickness was found to be very small. Sodium sulfate promoted thicker TGO; more Cr-rich TGO; the formation of Y oxides, and internally, Y sulfides; pore formation in the coating as well as in the substrate; and the formation of a Cr-depleted zone in the substrate.

  8. Evaluation on the Effect of Composition on Radiation Hardening and Embrittlement in Model FeCrAl Alloys

    SciTech Connect

    Field, Kevin G.; Briggs, Samuel A.; Edmondson, Philip; Hu, Xunxiang; Littrell, Kenneth C.; Howard, Richard; Parish, Chad M.; Yamamoto, Yukinori

    2015-09-18

    This report details the findings of post-radiation mechanical testing and microstructural characterization performed on a series of model and commercial FeCrAl alloys to assist with the development of a cladding technology with enhanced accident tolerance. The samples investigated include model alloys with simple ferritic grain structure and two commercial alloys with minor solute additions. These samples were irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) up to nominal doses of 7.0 dpa near or at Light Water Reactor (LWR) relevant temperatures (300-400 C). Characterization included a suite of techniques including small angle neutron scattering (SANS), atom probe tomography (APT), and transmission based electron microscopy techniques. Mechanical testing included tensile tests at room temperature on sub-sized tensile specimens. The goal of this work was to conduct detailed characterization and mechanical testing to begin establishing empirical and/or theoretical structure-property relationships for radiation-induced hardening and embrittlement in the FeCrAl alloy class. Development of such relationships will provide insight on the performance of FeCrAl alloys in an irradiation environment and will enable further development of the alloy class for applications within a LWR environment. A particular focus was made on establishing trends, including composition and radiation dose. The report highlights in detail the pertinent findings based on this work. This report shows that radiation hardening in the alloys is primarily composition dependent due to the phase separation in the high-Cr FeCrAl alloys. Other radiation induced/enhanced microstructural features were less dependent on composition and when observed at low number densities, were not a significant contributor to the observed mechanical responses. Pre-existing microstructure in the alloys was found to be important, with grain boundaries and pre-existing dislocation

  9. Structure and Tribological Properties of CrTiAlN Coatings Deposited by Multi-Arc Ion Plating

    NASA Astrophysics Data System (ADS)

    Tian, Canxin; Yang, Bing; He, Jun; Wang, Hongjun; Wang, Zesong; Wang, Guangfu; Fu, Dejun

    2011-02-01

    CrTiAlN coatings were prepared by using a home-made industrial scale multi-arc ion plating system. The coatings were found to be composites of face-center-cubic CrN and TiN. The surface roughness, microhardness, and tribological properties of the films were significantly affected by the nitrogen pressure and dc-pulsed bias voltage applied to the substrate. The CrTiAlN coatings with the smoothest surfaces were obtained at optimum conditions of nitrogen pressure of 5.0 Pa and bias voltage of -200 V. The samples were found to exhibit a hardness of 2900 HV0.05 with an average friction coefficient of 0.16 and wear rate of 1.5×10-16 m3/N·m against cemented carbide.

  10. Structure and stability of precipitates in 500 C exposed Ti-25V-15Cr-xAl alloys

    SciTech Connect

    Li, Y.G.; Blenkinsop, P.A.; Loretto, M.H.; Walker, N.A.

    1998-10-09

    The effects of thermal exposure on microstructural changes in {beta} Ti-25V-15Cr-(2-4)Al alloys (all compositions in wt%) have been investigated. Plasma melted alloys were either HIPped, extruded or forged before being exposed at 500 C for 24--1,000 h. It was found that {alpha} precipitation occurred in samples of Ti-25V-15Cr-3Al which were exposed at 550 C for 24 h. The amount of precipitation increased with exposure time and the composition of the {alpha} phase changed gradually. EDX analysis on TEM samples showed increasing Al and Ti and decreasing V and Cr in the precipitates with exposure time. In samples which were exposed at 550 C for over 100 h {alpha}{sub 2} was observed. The variation of Al from 2 to 4 wt% increased the precipitation and the kinetics of {alpha} to {alpha}{sub 2} ordering. The results are discussed in terms of the effects of Al and oxygen on {alpha}{sub 2} precipitation in {beta} TiVCrAl alloys.

  11. Strain rate sensitivity of nanoindentation creep in an AlCoCrFeNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Wang, Z. H.; Wu, R. F.; Qiao, J. W.

    2016-09-01

    Creep behaviors of an AlCoCrFeNi high-entropy alloy with the body-centered cubic structure were investigated by nanoindentation. The enhanced strain gradient induced by higher strain rate leads to decreased strain rate sensitivity during creep process. The present alloy exhibits excellent creep resistance, mainly due to its large entropy of mixing and highly distorted lattice structure.

  12. Microstructure and oxidation properties of 16Cr-5Al-ODS steel prepared by sol-gel and spark plasma sintering methods

    NASA Astrophysics Data System (ADS)

    Xia, Y. P.; Wang, X. P.; Zhuang, Z.; Sun, Q. X.; Zhang, T.; Fang, Q. F.; Hao, T.; Liu, C. S.

    2013-01-01

    The 16Cr-5Al oxide dispersion strengthened (ODS) ferritic steel was fabricated by sol-gel method in combination with hydrogen reduction, mechanical alloying (MA) and spark plasma sintering (SPS) techniques. The phase characterization, microstructure and oxidation resistance of the 16Cr-5Al-ODS steel were investigated in comparison with the Al free 16Cr-ODS steel. X-ray diffraction (XRD) patterns showed that the Al free and Al added 16Cr-ODS steels exhibited typical ferritic characteristic structure. The microstructure analysis investigated by transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS) revealed that Y-Ti-O complexes with particle size of 10-30 nm were formed in the Al free matrix and Y-Al-O complexes with particle size of 20-100 nm were formed in the Al contained high-Cr ODS steel matrix. These complexes are homogeneously distributed in the matrices. The fabricated 16Cr-5Al-ODS steel exhibited superior oxidation resistance compared with the Al free 16Cr-ODS steel and the commercial 304 stainless steel owing to the formation of continuous and dense Al2O3 film on the surface.

  13. Interdiffusion between the L1(2) trialuminides Al66Ti25Mn9 and Al67Ti25Cr8

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Whittenberger, J. D.

    1992-01-01

    Concentration-distance profiles obtained from Al66Ti25Mn9/Al67Ti25Cr8 diffusion couples are used to determine the interdiffusion coeffients in the temperature range 1373-1073 K. The couples are treated as pseudobinaries, and the diffusion coefficients are determined using the Matano approach. The results are then used to compute the activation energies for diffusion, and a comparison is made with some existing data for the activation energy for creep of Al22Ti8Fe3.

  14. Complex Formation Between Ca(II), Mg(II), Al(III) Ions and Salicylglycine

    PubMed Central

    Kilyén, Melinda; Labádi, lmre; Tombácz, Etelka; Kiss, Tamás

    2003-01-01

    For modelling the interactions of proteins/peptides with hard metal ions the complex formation of salicylglycine (SalGly) with Ca(II), Mg(ll) and AI(III) ions was studied in aqueous solution using pHpotentiometric and UV-vis spectroscopic techniques. Al(lll) ion was found to form more stable complexes with SalGiy than Ca(ll) or Mg(ll) ions. While AI(III) ion forms various 1:1 complexes of different protonation states in the pH range 2-7, Ca(ll), Mg(ll) ions seem to interact with SalGly only in the basic pH range and form mixed hydroxo species MLH-1 at pH ~ 8. According to the UV-vis spectroscopic measurements in the species MLH-1 the carboxylate-O- atom and the phenolate-O- coordinate to the metal ions. SaIGiy is able to keep Al(lll) in solution through inner and outer sphere coordination to metastable amorphous AI(OH)3 particles. Deprotonation of the peptide amide Nil does not occur in these systems. PMID:18365063

  15. Network topology for the formation of solvated electrons in binary CaO-Al2O3 composition glasses.

    PubMed

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J K Richard; Benmore, Chris J

    2013-06-18

    Glass formation in the CaO-Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO-Al2O3 glasses using combined density functional theory-reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O-Ca and O-Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al-O is stronger than that of Ca-O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71-74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass.

  16. Spectroscopic study and laser operation of Cr 4+-doped (Sr,Ca)Gd 4(SiO 4) 3O single crystals

    NASA Astrophysics Data System (ADS)

    Moncorgé, R.; Manaa, H.; Deghoul, F.; Borel, C.; Wyon, Ch.

    1995-02-01

    Cr-doped oxyapatite single crystals with formula AGd 4(SiO 4) 3O and A = Sr or Ca were grown and studied. The shape and the intensity of their optical absorption and fluorescence bands as well as the values and the temperature variations of the fluorescence lifetimes are characteristic of those of tetrahedrally coordinated Cr 4+ ions. Gain measurements show their potential wavelength tunability between about 1.2 and 1.5 μm. Room temperature laser action is demonstrated at 1.37 and 1.44 μm in the Ca- and Sr-compounds, respectively.

  17. Low-temperature heat capacities of CaAl2SiO6 glass and pyroxene and thermal expansion of CaAl2SiO6 pyroxene.

    USGS Publications Warehouse

    Haselton, H.T.; Hemingway, B.S.; Robie, R.A.

    1984-01-01

    Low-T heat capacities (5-380 K) have been measured by adiabatic calorimetry for synthetic CaAl2SiO6 glass and pyroxene. High-T unit cell parameters were measured for CaAl2SiO6 pyroxene by means of a Nonius Guinier-Lenne powder camera in order to determine the mean coefficient of thermal expansion in the T range 25-1200oC. -J.A.Z.

  18. Nqrs Data for AlCa2ClH10O8 [AlCa2ClO3·5(H2O)] (Subst. No. 0020)

    NASA Astrophysics Data System (ADS)

    Chihara, H.; Nakamura, N.

    This document is part of Subvolume A `Substances Containing Ag … C10H15' of Volume 48 `Nuclear Quadrupole Resonance Spectroscopy Data' of Landolt-Börnstein - Group III `Condensed Matter'. It contains an extract of Section `3.2 Data tables' of the Chapter `3 Nuclear quadrupole resonance data' providing the NQRS data for AlCa2ClH10O8 [AlCa2ClO3·5(H2O)] (Subst. No. 0020)

  19. Surface micromorphology of dental composites [CE-TZP]-[Al2O3] with Ca(+2) modifier.

    PubMed

    Berezina, Sofia; Il'icheva, Alla Alexandrovna; Podzorova, Lyudmila Ivanovna; Ţălu, Ştefan

    2015-09-01

    The objective of this study was to characterize the three-dimensional (3D) surface micromorphology of the ceramics produced from nanoparticles of alumina and tetragonal zirconia (t-ZrO2) with addition of Ca(+2) for sintering improvement. The 3D surface roughness of samples was studied by atomic force microscopy (AFM), fractal analysis of the 3D AFM-images, and statistical analysis of surface roughness parameters. Cube counting method, based on the linear interpolation type, applied for AFM data was used for fractal analysis. The morphology of non-modified ceramic sample was characterized by the rather big (1-2 μm) grains of α-Al2O3 phase with a habit close to hexagonal drowned in solid solution of t-ZrO2 with smooth surface. The pattern surfaces of modified composite content a little amount of elongated prismatic grains with composition close to the phase of СаСеAl3О7 as well as hexahedral α-Al2O3-grains. Fractal dimension, D, as well as height values distribution have been determined for the surfaces of the samples with and without modifying. It can be concluded that the smoothest surface is of the modified samples with Ca(+2) modifier but the most regular one is of the non-modified samples. A connection was observed between the surface morphology and the physical properties as assessed in previous works. PMID:26190812

  20. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    DOE PAGES

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010]/χ[001] ≈ 3.5. A strong power-lawmore » divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.« less

  1. Nanomechanical characterization of alumina coatings grown on FeCrAl alloy by thermal oxidation.

    PubMed

    Frutos, E; González-Carrasco, J L; Polcar, T

    2016-04-01

    This work studies the feasibility of using repetitive-nano-impact tests with a cube-corner tip and low loads for obtaining quantitative fracture toughness values in thin and brittle coatings. For this purpose, it will be assumed that the impacts are able to produce a cracking, similar to the pattern developed for the classical fracture toughness tests in bulk materials, and therefore, from the crack developed in the repetitive impacts it will be possible to evaluate the suitability of the classical indentation models (Anstins and Laugier) for measuring fracture toughness. However, the length of this crack has to be lower than 10% of the total coating thickness to avoid substrate contributions. For this reason, and in order to ensure a small plastic region localized at the origin of the crack tip, low load values (or small distance between the indenter tip and the surface) have to be used. In order to demonstrate the validity of this technique, repetitive-nano-impact will be done in a fine and dense oxide layer (α-Al2O3), which has been developed on the top of oxide dispersion strengthened (ODS) FeCrAl alloys (PM 2000) by thermal oxidation at elevated temperatures. Moreover, it will be shown how it is possible to know with each new impact the crack geometry evolution from Palmqvist crack to half-penny crack, being able to study the proper evolution of the different values of fracture toughness in terms of both indentation models and as a function of the strain rate, ε̇, decreasing. Thereby, fracture toughness values for α-Al2O3 layer decrease from ~4.40MPam , for high ϵ̇ value (10(3)s(-1)), to ~3.21MPam, for quasi-static ϵ̇ value (10(-3)s(-1)). On the other hand, ϵ̇ a new process to obtain fracture toughness values will be analysed, when the classical indentation models are not met. These values are typically found in the literature for bulk α-Al2O3, demonstrating the use of repetitive-nano-impact tests which not only provide qualitative information about

  2. Nanomechanical characterization of alumina coatings grown on FeCrAl alloy by thermal oxidation.

    PubMed

    Frutos, E; González-Carrasco, J L; Polcar, T

    2016-04-01

    This work studies the feasibility of using repetitive-nano-impact tests with a cube-corner tip and low loads for obtaining quantitative fracture toughness values in thin and brittle coatings. For this purpose, it will be assumed that the impacts are able to produce a cracking, similar to the pattern developed for the classical fracture toughness tests in bulk materials, and therefore, from the crack developed in the repetitive impacts it will be possible to evaluate the suitability of the classical indentation models (Anstins and Laugier) for measuring fracture toughness. However, the length of this crack has to be lower than 10% of the total coating thickness to avoid substrate contributions. For this reason, and in order to ensure a small plastic region localized at the origin of the crack tip, low load values (or small distance between the indenter tip and the surface) have to be used. In order to demonstrate the validity of this technique, repetitive-nano-impact will be done in a fine and dense oxide layer (α-Al2O3), which has been developed on the top of oxide dispersion strengthened (ODS) FeCrAl alloys (PM 2000) by thermal oxidation at elevated temperatures. Moreover, it will be shown how it is possible to know with each new impact the crack geometry evolution from Palmqvist crack to half-penny crack, being able to study the proper evolution of the different values of fracture toughness in terms of both indentation models and as a function of the strain rate, ε̇, decreasing. Thereby, fracture toughness values for α-Al2O3 layer decrease from ~4.40MPam , for high ϵ̇ value (10(3)s(-1)), to ~3.21MPam, for quasi-static ϵ̇ value (10(-3)s(-1)). On the other hand, ϵ̇ a new process to obtain fracture toughness values will be analysed, when the classical indentation models are not met. These values are typically found in the literature for bulk α-Al2O3, demonstrating the use of repetitive-nano-impact tests which not only provide qualitative information about

  3. A Single Molecular Probe for Multi-analyte (Cr3+, Al3+ and Fe3+) in Aqueous and Its Biological Application

    PubMed Central

    Wang, Junfeng; Li, Yingbo; Patel, Nikul G.; Zhang, Ge; Zhou, Demin; Pang, Yi

    2014-01-01

    An ESIPT based fluorescent sensor 1 was developed, which could selectively detect and differentiate trivalent metal ions Cr3+, Al3+ and Fe3+ in aqueous. The cell imaging experiments confirmed that 1 can be used for monitoring intracellular Cr3+ and Al3+ levels in living cells. PMID:25178169

  4. Characterization and oxidation behavior of NiCoCrAlY coating fabricated by electrophoretic deposition and vacuum heat treatment

    NASA Astrophysics Data System (ADS)

    Li, Zhiming; Qian, Shiqiang; Wang, Wei

    2011-03-01

    Electrophoretic deposition (EPD) was showed to be a feasible and convenient method to fabricate NiCoCrAlY coatings on nickel based supperalloys. The microstructure and composition of the NiCoCrAlY coatings after vacuum heat treatment were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Isothermal-oxidation test was performed at 1100 °C in static air for 100 h. The results show that the major phases in electrophoretic deposited and vacuum heat treated NiCoCrAlY coating are γ-Ni and γ‧-Ni3Al phases, also there is an extremely small quantity of Al2O3 in the coating. Composition fluctuations occur in the coating and a certain amount of titanium diffuse from the superalloy substrate to the top of the coating during vacuum heat treatment. The oxidation test results exhibit that the oxidation kinetics of this coating has two typical stages. The protective oxide layer is mainly formed in the initial linear growth stage and then the oxide layer hinders further oxidation of the coating in the subsequent parabolic growth stage. The coating can effectively protect the superalloy substrate from oxidation. A certain amount of rutile TiO2 is formed in the coating during oxidation and it is adverse to the oxidation resistance of the coating.

  5. Dielectric properties of CaNdAlO sub 4 at microwave frequencies

    SciTech Connect

    Konopka, J.; Wolff, I. ); Lewandowski, S.J. )

    1992-07-01

    Dielectric properties of CaNdAlO{sub 4} monocrystals, a prospective substrate material for the deposition of high-{ital T}{sub {ital c}} superconductors, were measured with high accuracy at microwave frequencies from 8 to 40 GHz in the temperature range from 10 to 300 K by measuring the resonant frequencies of a completely filled resonant cavity. The material was found to be highly anisotropic. At 300 K it exhibits the dielectric constant along {ital c} axis {epsilon}{sup {prime}}{sub {ital c}} = 17.68, while the dielectric constant in the {ital a}-{ital b} plane is {epsilon}{prime}=19.62, and loss tangent tan {delta}{sub {ital c}} {congruent} tan {delta} {congruent} 5.1{times} 10{sup {minus}4}. Both {epsilon}{sup {prime}}{sub {ital c}} and {epsilon}{prime} depend strongly on temperature and their thermal coefficients have opposite signs, apparently a unique property of CaNdAlO{sub 4}. Below 160 K microwave losses caused by electric field perpendicular to the optical {ital c} axis increase with decreasing temperature, exhibiting a maximum near 65 K followed by a minimum at 30 K. It is suggested that neodymium ions in CaNdAlO{sub 4} at lower temperatures become magnetically ordered, causing an increase of magnetic permeability {mu}{sup {prime}}{sub {ital c}} {gt} 1 and a significant increase of magnetic losses at microwave frequencies. A crystallographic phase transition below 60 K cannot also be excluded.

  6. Stability domain of alumina thermally grown on Fe-Cr-Al-based model alloys and modified surface layers exposed to oxygen-containing molten Pb

    NASA Astrophysics Data System (ADS)

    Jianu, A.; Fetzer, R.; Weisenburger, A.; Doyle, S.; Bruns, M.; Heinzel, A.; Hosemann, P.; Mueller, G.

    2016-03-01

    The paper gives experimental results concerning the morphology, composition, structure and thickness of the oxide scales grown on Fe-Cr-Al-based bulk alloys during exposure to oxygen-containing molten lead. The results are discussed and compared with former results obtained on Al-containing surface layers, modified by melting with intense pulsed electron beam and exposed to similar conditions. The present and previous results provide the alumina stability domain and also the criterion of the Al/Cr ratio for the formation of a highly protective alumina layer on the surface of Fe-Cr-Al-based alloys and on modified surface layers exposed to molten lead with 10-6 wt.% oxygen at 400-600 °C. The protective oxide scales, grown on alumina-forming Fe-Cr-Al alloys under the given experimental conditions, were transient aluminas, namely, kappa-Al2O3 and theta-Al2O3.

  7. The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Kumar, A.; Nasrallah, M.; Douglass, D. L.

    1974-01-01

    The effect of quaternary additions of 0.5% Y, 0.5 and 1.0% Th to a base alloy of Ni-10CR-5Al on the oxidation behavior and mechanism was studied during oxidation in air over the range of 1000 to 1200 C. The presence of yttrium decreased the oxidation kinetics slightly, whereas, the addition of thorium caused a slight increase. Oxide scale adherence was markedly improved by the addition of the quaternary elements. Although a number of oxides formed on yttrium containing alloys, quantitative X-ray diffraction clearly showed that the rate-controlling step was the diffusion of aluminum through short circuit paths in a thin layer of alumina that formed parabolically with time. Although the scale adherence of the yttrium containing alloy was considerably better than the base alloys, spalling did occur that was attributed to the formation of the voluminous YAG particles which grew in a mushroom-like manner, lifting the protective scale off the subrate locally. The YAG particles formed primarily at grain boundaries in the substrate in which the yttrium originally existed as YNi9.

  8. First-Principles Calculations, Experimental Study, and Thermodynamic Modeling of the Al-Co-Cr System

    PubMed Central

    Liu, Xuan L.; Gheno, Thomas; Lindahl, Bonnie B.; Lindwall, Greta; Gleeson, Brian; Liu, Zi-Kui

    2015-01-01

    The phase relations and thermodynamic properties of the condensed Al-Co-Cr ternary alloy system are investigated using first-principles calculations based on density functional theory (DFT) and phase-equilibria experiments that led to X-ray diffraction (XRD) and electron probe micro-analysis (EPMA) measurements. A thermodynamic description is developed by means of the calculations of phase diagrams (CALPHAD) method using experimental and computational data from the present work and the literature. Emphasis is placed on modeling the bcc-A2, B2, fcc-γ, and tetragonal-σ phases in the temperature range of 1173 to 1623 K. Liquid, bcc-A2 and fcc-γ phases are modeled using substitutional solution descriptions. First-principles special quasirandom structures (SQS) calculations predict a large bcc-A2 (disordered)/B2 (ordered) miscibility gap, in agreement with experiments. A partitioning model is then used for the A2/B2 phase to effectively describe the order-disorder transitions. The critically assessed thermodynamic description describes all phase equilibria data well. A2/B2 transitions are also shown to agree well with previous experimental findings. PMID:25875037

  9. Uniform corrosion of FeCrAl alloys in LWR coolant environments

    DOE PAGES

    Terrani, K. A.; Pint, B. A.; Kim, Y. -J.; Unocic, K. A.; Yang, Y.; Silva, C. M.; Meyer, III, H. M.; Rebak, R. B.

    2016-06-29

    In this study, the corrosion behavior of commercial and model FeCrAl alloys and type 310 stainless steel was examined by autoclave tests and compared to Zircaloy-4, the reference cladding materials in light water reactors. The corrosion studies were carried out in three distinct water chemistry environments found in pressurized and boiling water reactor primary coolant loop conditions for up to one year. The structure and morphology of the oxides formed on the surface of these alloys was consistent with thermodynamic predictions. Spinel-type oxides were found to be present after hydrogen water chemistry exposures, while the oxygenated water tests resulted inmore » the formation of very thin and protective hematite-type oxides. Unlike the alloys exposed to oxygenated water tests, the alloys tested in hydrogen water chemistry conditions experienced mass loss as a function of time. This mass loss was the result of net sum of mass gain due to parabolic oxidation and mass loss due to dissolution that also exhibits parabolic kinetics. Finally, the maximum thickness loss after one year of LWR water corrosion in the absence of irradiation was ~2 μm, which is inconsequential for a ~300–500 μm thick cladding.« less

  10. Uniform corrosion of FeCrAl alloys in LWR coolant environments

    NASA Astrophysics Data System (ADS)

    Terrani, K. A.; Pint, B. A.; Kim, Y.-J.; Unocic, K. A.; Yang, Y.; Silva, C. M.; Meyer, H. M.; Rebak, R. B.

    2016-10-01

    The corrosion behavior of commercial and model FeCrAl alloys and type 310 stainless steel was examined by autoclave tests and compared to Zircaloy-4, the reference cladding materials in light water reactors. The corrosion studies were carried out in three distinct water chemistry environments found in pressurized and boiling water reactor primary coolant loop conditions for up to one year. The structure and morphology of the oxides formed on the surface of these alloys was consistent with thermodynamic predictions. Spinel-type oxides were found to be present after hydrogen water chemistry exposures, while the oxygenated water tests resulted in the formation of very thin and protective hematite-type oxides. Unlike the alloys exposed to oxygenated water tests, the alloys tested in hydrogen water chemistry conditions experienced mass loss as a function of time. This mass loss was the result of net sum of mass gain due to parabolic oxidation and mass loss due to dissolution that also exhibits parabolic kinetics. The maximum thickness loss after one year of LWR water corrosion in the absence of irradiation was ∼2 μm, which is inconsequential for a ∼300-500 μm thick cladding.

  11. First-principles calculations, experimental study, and thermodynamic modeling of the Al-Co-Cr system.

    PubMed

    Liu, Xuan L; Gheno, Thomas; Lindahl, Bonnie B; Lindwall, Greta; Gleeson, Brian; Liu, Zi-Kui

    2015-01-01

    The phase relations and thermodynamic properties of the condensed Al-Co-Cr ternary alloy system are investigated using first-principles calculations based on density functional theory (DFT) and phase-equilibria experiments that led to X-ray diffraction (XRD) and electron probe micro-analysis (EPMA) measurements. A thermodynamic description is developed by means of the calculations of phase diagrams (CALPHAD) method using experimental and computational data from the present work and the literature. Emphasis is placed on modeling the bcc-A2, B2, fcc-γ, and tetragonal-σ phases in the temperature range of 1173 to 1623 K. Liquid, bcc-A2 and fcc-γ phases are modeled using substitutional solution descriptions. First-principles special quasirandom structures (SQS) calculations predict a large bcc-A2 (disordered)/B2 (ordered) miscibility gap, in agreement with experiments. A partitioning model is then used for the A2/B2 phase to effectively describe the order-disorder transitions. The critically assessed thermodynamic description describes all phase equilibria data well. A2/B2 transitions are also shown to agree well with previous experimental findings.

  12. Mechanical Properties and Microstructure of VPS and HVOF CoNiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Saeidi, S.; Voisey, K. T.; McCartney, D. G.

    2011-12-01

    In this study, high velocity oxy-fuel (HVOF) and vacuum plasma spraying (VPS) coatings were sprayed using a Praxair (CO-210-24) CoNiCrAlY powder. Free-standing coatings underwent vacuum annealing at different temperatures for times of up to 840 h. Feedstock powder, and as-sprayed and annealed coatings, were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). The hardness and Young's modulus of the as-sprayed and the annealed HVOF and VPS coatings were measured, including the determination of Young's moduli of the individual phases via nanoindentation and measurements of Young's moduli of coatings at temperatures up to 500 °C. The Eshelby inclusion model was employed to investigate the effect of microstructure on the coatings' mechanical properties. The sensitivity of the mechanical properties to microstructural details was confirmed. Young's modulus was constant up to ~200 °C, and then decreased with increasing measurement temperature. The annealing process increased Young's modulus because of a combination of decreased porosity and β volume fraction. Oxide stringers in the HVOF coating maintained its higher hardness than the VPS coating, even after annealing.

  13. On the nanometer scale phase separation of a low-supersaturation Ni-Al-Cr alloy

    NASA Astrophysics Data System (ADS)

    Booth-Morrison, Christopher; Zhou, Yang; Noebe, Ronald D.; Seidman, David N.

    2010-01-01

    The phase separation of a Ni-6.5 Al-9.5 Cr at. % alloy aged at 873 K was studied by atom-probe tomography and compared to the predictions of classical precipitation models. Phase separation in this alloy occurs in four distinct regimes: (i) quasi-stationary-state γ‧(L12)-precipitate nucleation; (ii) concomitant precipitate nucleation, growth and coagulation and coalescence; (iii) concurrent growth and coarsening, wherein coarsening occurs via both γ‧-precipitate coagulation and coalescence and by the classical evaporation-condensation mechanism; and (iv) quasi-stationary-state coarsening of γ‧-precipitates, once the equilibrium volume fraction of precipitates is achieved. The predictions of classical nucleation and growth models are not validated experimentally, likely due to the complexity of the atomistic kinetic pathways involved in precipitation. During coarsening, the temporal evolution of the γ‧-precipitate average radius, number density and the γ(fcc)-matrix and γ‧-precipitate supersaturations follow the predictions of classical models.

  14. Tribological Characterization of Plasma-Sprayed CoNiCrAlY-BN Abradable Coatings

    NASA Astrophysics Data System (ADS)

    Irissou, E.; Dadouche, A.; Lima, R. S.

    2014-01-01

    The processing conditions, microstructural and tribological characterizations of plasma-sprayed CoNiCrAlY-BN high temperature abradable coatings are reported in this manuscript. Plasma spray torch parameters were varied to produce a set of abradable coatings exhibiting a broad range of porosity levels (34-62%) and superficial Rockwell hardness values (0-78 HR15Y). Abradability tests have been performed using an abradable-seal test rig, capable of simulating operational wear at different rotor speeds and seal incursion rates (SIRs). These tests allowed determining the rubbing forces and quantifying the blade and seal wear characteristics for slow and fast SIRs. Erosion wear performance and ASTM C633 coating adhesion strength test results are also reported. For optimal abradability performance, it is shown that coating hardness needs to be lower than 70 and 50 HR15Y for slow and fast blade incursion rate conditions, respectively. It is shown that the erosion wear performance, as well as, the coating cohesive strength is a function of the coating hardness. The current results allow defining the coating specifications in terms of hardness and porosity for targeted applications.

  15. Cyclic Oxidation Behavior of Cold Sprayed CuCrAl-Coated and Uncoated GRCop-84 Substrates for Space Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Barrett, C.; Karthikeyan, J.; Garlick, R.

    2006-01-01

    A newly developed Cu-23 (wt %) Cr-5%Al (CuCrAl) alloy shown to resist hydridation and oxidation in an as-cast form is currently being considered as a protective coating for GRCop-84, which is an advanced copper alloy containing 8 (at.%) Cr and 4 (at.%) Nb. The coating was deposited on GRCop-84 substrates by the cold spray deposition technique. Cyclic oxidation tests conducted in air on both coated and uncoated substrates between 773 and 1073 K revealed that the coating remained intact and protected the substrate up to 1073 K. No significant weight loss of the coated specimens were observed at 773 and 873 K even after a cumulative cyclic time of 500 h. About a 10 percent weight loss observed at 973 and 1073 K was attributed to the excessive oxidation of the uncoated sides. In contrast, the uncoated substrate lost as much as 80 percent of its original weight under similar test conditions. It is concluded that the cold sprayed CuCrAl coating is suitable for protecting GRCop-84 substrates.

  16. Characterization of Cold Sprayed CuCrAl-Coated and Uncoated GRCop-84 Substrates for Space Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Karthikeyan, J.; Lerch, B. A.; Barrett, C.; Garlich, R.

    2007-01-01

    A newly developed Cu-23(wt.%)Cr-5%Al (CuCrAl) alloy is currently being considered as a protective coating for GRCop-84 (Cu-8(at.%)Cr-4%Nb). The coating was deposited on GRCop-84 substrates by the cold spray deposition technique. Cyclic oxidation tests conducted in air on both coated and uncoated substrates between 773 and 1073 K revealed that the coating remained intact and protected the substrate up to 1073 K. No significant weight loss of the coated specimens were observed at 773 and 873 K even after a cumulative cyclic time of 500 h. In contrast, the uncoated substrate lost as much as 80% of its original weight under similar test conditions. Low cycle fatigue tests revealed that the fatigue lives of thinly coated GRCop-84 specimens were similar to the uncoated specimens within the limits of experimental scatter. It is concluded that the cold sprayed CuCrAl coating is suitable for protecting GRCop-84 substrates.

  17. Electronic, optical, structural, and elastic properties of MAX phases and (Cr2Hf)2Al3C3

    NASA Astrophysics Data System (ADS)

    Mo, Yuxiang

    The term "MAX phase" refers to a very interesting and important class of layered ternary transition-metal carbides and nitrides with a novel combination of both metal- and ceramic-like properties that have made these materials highly regarded candidates for numerous technological and engineering applications. In the present dissertation work, the electronic structure and optical conductivities of 20 MAX phases Ti3AC2 (A = Al, Si, Ge), Ti2AC (A = Al, Ga, In, Si, Ge, Sn, P, As, S), Ti2AlN, M2AlC (M = V, Nb, Cr), and Tan+1AlC n (n = 1 to 4) are studied using the first-principles orthogonalized linear combination of atomic orbitals (OLCAO) method. It is confirmed that the N(Ef) (total density of states at the Fermi level Ef) increases as the number of valence electrons of the composing elements increases. The local feature of total density of states (TDOS) near Ef is used to predict structural stability. The calculated effective charge on each atom shows that the M (transition-metal) atoms always lose charge to the X (C or N) atoms, whereas the A-group atoms mostly gain charge but some lose charge. Bond order values are obtained and critically analyzed for all types of interatomic bonds in the 20 MAX phases. Also included in this work is the exploration [using (Cr2Hf)2Al3C3 as an example] of the possibility of incorporating more types of elements into a MAX phase while maintaining the crystallinity, instead of creating solid solution phases. The crystal structure and elastic properties of (Cr2Hf)2Al 3C3 are studied using the Vienna ab initio Simulation Package. Unlike MAX phases with a hexagonal symmetry ( P63/mmc, #194), (Cr 2Hf)2Al3C3 crystallizes in the monoclinic space group of P21/m (#11). Its structure is found to be energetically much more favorable against the allotropic segregation and solid solution phases. Calculations using a stress versus strain approach and the VRH approximation for polycrystals also show that (Cr2Hf)2Al3C3 has outstanding elastic moduli.

  18. Microstructure and mechanical properties of NiCoCrAlYTa alloy processed by press and sintering route

    SciTech Connect

    Pereira, J.C.; Zambrano, J.C.; Afonso, C.R.M.; Amigó, V.

    2015-03-15

    Nickel-based superalloys such as NiCoCrAlY are widely used in high-temperature applications, such as gas turbine components in the energy and aerospace industries, due to their strength, high elastic modulus, and high-temperature oxidation resistance. However, the processing of these alloys is complex and costly, and the alloys are currently used as a bond coat in thermal barrier coatings. In this work, the effect of cold press and sintering processing parameters on the microstructure and mechanical properties of NiCoCrAlY alloy were studied using the powder metallurgy route as a new way to obtain NiCoCrAlYTa samples from a gas atomized prealloyed powder feedstock. High mechanical strength and adequate densification up to 98% were achieved. The most suitable compaction pressure and sintering temperature were determined for NiCoCrAlYTa alloy through microstructure characterization. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy microanalysis (EDS) were performed to confirm the expected γ-Ni matrix and β-NiAl phase distribution. Additionally, the results demonstrated the unexpected presence of carbides and Ni–Y-rich zones in the microstructure due to the powder metallurgy processing parameters used. Thus, microhardness, nanoindentation and uniaxial compression tests were conducted to correlate the microstructure of the alloy samples with their mechanical properties under the different studied conditions. The results show that the compaction pressure did not significantly affect the mechanical properties of the alloy samples. In this work, the compaction pressures of 400, 700 and 1000 MPa were used. The sintering temperature of 1200 °C for NiCoCrAlYTa alloy was preferred; above this temperature, the improvement in mechanical properties is not significant due to grain coarsening, whereas a lower temperature produces a decrease in mechanical properties due to high porosity and

  19. A clear oscillation of the interlayer exchange coupling in Co2FeAl/Cr/Co2FeAl structure with MgO capping layer

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoguang; Zhang, Jianli; Sha, Lei; Zhang, Delin; Jiang, Yong

    2012-10-01

    We have studied the interlayer exchange coupling in Co2FeAl (CFA)/Cr/CFA/MgO multilayers via both experiments and numerical simulation. Magnetization measurement on the films shows a clear oscillation attenuation behavior with the thickness (0.6 nm < t < 10 nm) of the Cr spacer layer, and the oscillation period is about 2.1 nm. The numerical simulation demonstrates that the interlayer exchange coupling between CFA layers is 90° coupling having an oscillation behavior, which is in good agreement with the experiments. MgO capping layer is supposed to be a key factor for the clear periodic oscillation behavior in CFA/Cr/CFA trilayers.

  20. A NiCrAl pressure cell up to 4.6 GPa and its application to cuprate and pnictide superconductors

    NASA Astrophysics Data System (ADS)

    Fujiwara, Naoki; Uwatoko, Yoshiya; Matsumoto, Takehiko

    2013-06-01

    A NiCrAl-CuBe hybrid cell has been paid much attention because its maximum pressure goes beyond 3 GPa despite its large sample space. In the previous pressurizing trials for this pressure cell, we reached 4.0 GPa under a steady load of 15 ton. In the present trial, we have succeeded in reaching 4.6 GPa by using a short Teflon capsule as a pressure-mediation-liquid container. The pressure efficiency at 15 ton was 75 %. The maximum expansion of the inner diameter of the NiCrAl cylinder was 5 %, suggesting that 4.6 GPa is the upper limit of pressure. To keep high pressure above 4 GPa, a steady load control is needed: a pressure of 4.0 GPa under a steady load decreased to 3.7 GPa after the pressure cell was clamped and the steady load was released. The pressure cell is available to various experiments that need a large sample space. We have applied this pressure cell to nuclear magnetic resonance (NMR) measurements on cuprate and pnictide superconductors, such as Sr2Ca12Cu24O41, LaFeAsO1-xFx, and CaFe1-xCoxAsF. These compounds have superconducting layers, and Tcs of these compounds are enhanced by pressure application. We review what happens at optimal pressure in electric and/or magnetic properties on a microscopic level. Grant-in-Aid (Grant No. 23340101) from the Ministry of Education, Science and Culture, Japan.

  1. Acid precipitation and food quality: Effects of dietary Al, Ca and P on bone and liver characteristics in American black ducks and mallards

    USGS Publications Warehouse

    Sparling, D.W.

    1991-01-01

    American black ducks (Anas rubripes) and mallards (A. platyrhynchos) were fed diets varying in concentrations of aluminum (Al). calcium (Ca), and phosphorus (P) for 10 weeks to identify toxic effects of Al under conditions representative of areas with acid precipitation. Femur and liver tissues were analyzed for Al. Ca, and P concentrations and structural characteristics. At two weeks of age, both species demonstrated pronounced differences in femur Al and P concentrations and femur mass from dietary Al and interaction between Ca:P regimen and Al:Low Ca:Low P enhanced Al storage and decreased P and mass in femurs. Femur Ca was lowest in the Low Ca:Low P regimen but was not affected by dietary Al. At 10 weeks, femur and liver Al continued to vary with dietary Al. Elevated Al and reduced Ca lowered modulus of elasticity. Femur P increased with elevated dietary P in black ducks. Elevated dietary P negated some of the effects of dietary A! on femur mass in black ducks. Reduced Ca concentrations weakened bones of both species and lowered both Ca and P. An array of clinical signs including lameness, discoloration of the upper mandible, complete and greenstick fractures, and death were responses to elevated Al and Ca:P regimen. Black ducks seemed to display these signs over a wider range of diets than mallards. Diets of 1,000 mg/kg Al had toxic effects on both species, particularly when combined with diets low in Ca and P.

  2. A comparative first-principles study on electronic structures and mechanical properties of ternary intermetallic compounds Al8Cr4Y and Al8Cu4Y: Pressure and tension effects

    NASA Astrophysics Data System (ADS)

    Yang, Wenchao; Pang, Mingjun; Tan, Yong; Zhan, Yongzhong

    2016-11-01

    An investigation into the bulk properties, elastic properties and Debye temperature under pressure, and deformation mode under tension of Al8Cu4Y and Al8Cr4Y compounds was investigated by using first principles calculations based on density functional theory. The calculated lattice constants for the ternary compounds (Al8Cu4Y and Al8Cr4Y) are in good agreement with the experimental data. It can be seen from interatomic distances that the bonding between Al1 atom and Cr, Y, and Al2 atoms in Al8Cr4Y are stronger than Al8Cu4Y. The results of cohesive energy show that Al8Cr4Y should be easier to be formed and much stronger chemical bonds than Al8Cu4Y. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν can be obtained by using the Voigt-Reuss-Hill averaging scheme. From the results of elastic properties, Al8Cr4Y has the stronger mechanical behavior than Al8Cu4Y. Our calculations also show that pressure has a greater effect on mechanical behavior for both compounds. The ideal tensile strength are obtained by stress-strain relationships under [001](001) uniaxial tensile deformation, which are 15.4 and 23.4 GPa for Al8Cu4Y and Al8Cr4Y, respectively. The total and partial density of states and electron charge density under uniaxial tensile deformations for Al8Cu4Y and Al8Cr4Y compounds are also calculated and discussed in this work.

  3. Biochemical responses of the mycorrhizae in Pinus massoniana to combined effects of Al, Ca and low pH.

    PubMed

    Kong, F X; Liu, Y; Hu, W; Shen, P P; Zhou, C L; Wang, L S

    2000-02-01

    Biochemical responses of Pinus massoniana, with and without the inoculation mycorrhizal fungus Pisolithus tinctorius at the root, to artificial acid rain (pH 2.0) and various Ca/Al ratios were investigated. Some enzymes associated with the nutritive metabolism, such as acid phosphatase, alkaline phosphatase, nitrate reductase, mannitol dehydrogenase and trehalase, in the roots, stems and leaves of plant were obviously inhibited by the artificial acid rain and Al. After treatment with pH 2.0 + Ca/Al (0/1 or 1/10) artificial acid rain, the protein content in the organs was decreased. However, the activities of superoxide dismutase (SOD) and peroxidase (POD) and glutathione (GSH) concentrations were induced. It demonstrated that acid rain and Al could induce oxygen radicals in plant. Compared with the treatments with lower pH or Al, respectively, the combination of lower pH and Al concentration was more toxic to P. massoniana. Al toxicity could be ameliorated by the addition of Ca and the amelioration was the most when the ratio was 1/1 among the various Ca/Al ratio. Infection with mycorrhizal fungus P. tinctorius at the root of P. massoniana increased the ability of the plant to resist the toxicity of artificial acid rain and Al stress.

  4. Network topology for the formation of solvated electrons in binary CaO–Al2O3 composition glasses

    PubMed Central

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J. K. Richard; Benmore, Chris J.

    2013-01-01

    Glass formation in the CaO–Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO–Al2O3 glasses using combined density functional theory–reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O–Ca and O–Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al–O is stronger than that of Ca–O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71–74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass. PMID:23723350

  5. Effect of Aluminum Content on Plasma-Nitrided Al x CoCrCuFeNi High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Tang, Wei-Yeh; Yeh, Jien-Wei

    2009-06-01

    High-entropy alloys (HEAs) Al x CoCrCuFeNi with different aluminum contents ( x = 0 to 1.8) were plasma nitrided at 525 °C for 45 hours with an aim to develop wear-resistant structural parts. The nitrided layer comprises a well-nitrided dendrite phase and an un-nitrided Cu-rich interdendrite phase. Surface hardening is a result of the formation of various nitrides in the nitrided dendrite: CrN, Fe4N, and AlN. With increasing aluminum content, the hardness of the nitrided layer increases due to the increased amount of hard AlN phase and the increased volume fraction of bcc phase being harder than the fcc one. The nitrided layer thickness shows an apparent decrease with the increasing aluminum content of the alloy. The present alloy system provides a wide range of substrate hardness from Hv 170 to 560 before nitriding, which even becomes harder by around Hv 30 after nitriding. For Al0.5CoCrCuFeNi alloy having the highest surface hardness of Hv 1300, a layer thickness of 23 μm, and a substrate hardness of Hv 300, an adhesive wear test confirms its superior wear resistance as being 17 times that of the un-nitrided samples.

  6. Effects of Cr2O3 doping on the microstructure and electrical properties of (Ba,Ca)(Zr,Ti)O3 lead-free ceramics

    NASA Astrophysics Data System (ADS)

    Xia, Xiang; Jiang, Xiangping; Chen, Chao; Jiang, Xingan; Tu, Na; Chen, Yunjing

    2016-06-01

    Lead-free ceramics (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3- x wt.%Cr2O3 (BCZT- xCr) were prepared via the conventional solid-state reaction method. The microstructure and electrical properties of BCZT- xCr samples were systematically studied. XRD and Raman results showed that all samples possessed a single phased perovskite structure and were close to the morphotropic phase boundary (MPB). With the increase of the Cr content, the rhombohedral-tetragonal phase transition temperature ( T R-T) increases slightly, and the Curie temperature ( T C) shifts towards the low temperature side. XPS analysis reveals that Cr3+ and Cr5 + ions co-existed in Cr-doped BCZT ceramics, indicating the different impact on the electrical properties from Cr ions as "acceptor" or "donor". For the x = 0.1 sample, relative high piezoelectric constants d 33 (˜316 pC/N) as well as high Q m (˜554) and low tanδ (˜0.8%) were obtained. In addition, the AC conductivity was also investigated. Hopping charge was considered as the main conduction mechanism at low temperature. As the temperature increases, small polarons and oxygen vacancies conduction played important roles.

  7. 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.

  8. Dissolution Behavior of Indium in CaO-SiO2-Al2O3 Slag

    NASA Astrophysics Data System (ADS)

    Ko, Kyu Yeol; Park, Joo Hyun

    2011-12-01

    The solubility of indium in a molten CaO-SiO2-Al2O3 system was measured at 1773 K (1500 °C) to establish the dissolution mechanism of indium under a highly reducing atmosphere. The solubility of indium increases with increasing oxygen potential, whereas it decreases with increased activity of basic oxide. Therefore, a dissolution mechanism of indium can be constructed according to the following equation: {{In}}({{s}}) + 1/4{{O}}2 ({{g}}) = ({{In}}^{ + } ) + 1/2({{O}}^{2 - } ) The relationship between indium capacity and sulfide capacity shows a good correlation that is consistent with theoretical expectations. The enthalpy change of the indium dissolution reaction is negative, which indicates that the dissolution is an exothermic reaction. The heat of dissolution into high-silica melts is greater than that into low-silica melts. The solubility of indium is strongly dependent on the silica content. The activity coefficient, and thus the excess free energy of In2O, decreases linearly with increasing silica content, indicating that the In2O is believed to behave as a weak basic oxide in the current CaO-SiO2-Al2O3 ternary system under reducing conditions.

  9. Magnesium doping on brownmillerite Ca{sub 2}FeAlO{sub 5}

    SciTech Connect

    Malveiro, J.; Ramos, T.; Ferreira, L.P.; Waerenborgh, J.C.

    2007-06-15

    Ca{sub 2}FeAl{sub 1-} {sub x} Mg {sub x} O{sub 5} (x=0, 0.05 and 0.1) compounds adopting the brownmillerite-type structure were prepared by a self-combustion route using two different fuels. Characterisation was performed using X-ray powder diffraction, Moessbauer spectroscopy, magnetisation measurements, chemical analysis, scanning electron microscopy and 4-point dc conductivity measurements. Global results indicate that the solubility limit was reached for x=0.1. An antiferromagnetic behaviour was detected for all studied compositions, with magnetic ordering temperatures of 340 and 290 K for x=0 and 0.05, respectively. Mg doping increases the number of iron cations in tetrahedral sites, which induces magnetisation enhancement at low temperatures through the coupling between octahedral iron cations in different octahedral planes. The compounds exhibit semiconductor behaviour and Mg{sup 2+} doping yields a significant enhancement of the total conductivity, which can be essentially attributed to the presence of Fe{sup 4+} ions. - Graphical abstract: Ca{sub 2}FeAl{sub 1-} {sub x} Mg {sub x} O{sub 5} (x=0, 0.05, 0.1) compounds with the brownmillerite structure were prepared and characterised. The paramagnetic Moessbauer spectra presented were obtained at T=363 K (x=0); T=297 K (x=0.05) and T=353 K (x=0.1)

  10. Self-reactivated mesostructured Ca-Al-O composite for enhanced high-temperature CO2 capture and carbonation/calcination cycles performance.

    PubMed

    Chang, Po-Hsueh; Huang, Wei-Chen; Lee, Tai-Jung; Chang, Yen-Po; Chen, San-Yuan

    2015-03-25

    In this study, highly efficient high-temperature CO2 sorbents of calcium aluminate (Ca-Al-O) mesostructured composite were synthesized using presynthesized mesoporous alumina (MA) as a porous matrix to react with calcium nitrate through a microwave-assisted process. Upon annealing at 600 °C, a highly stable mesoporous structure composed of poorly crystalline Ca12Al14O33 phase and the CaO matrix was obtained. The Ca-Al-O mesostructured sorbents with a Ca(2+)/Al(3+) ratio of 5:1 exhibit an enhanced increasing CO2 absorption kinetics in the CO2 capture capacity from 37.2 wt % to 48.3 wt % without apparent degradation with increasing carbonation/calcination cycling up to 50 at 700 °C due to the strong self-reactivation effect of the mesoporous Ca-Al-O microstructure. Remarkable improvements in the CaO-CaCO3 conversion attained from the mesostructured Ca-Al-O composite can be explained using the concept combined with available mesoporous structure and Ca12Al14O33 phase content. However, a high Ca(2+)/Al(3+) =8:1 Ca-Al-O composite causes degradation because the pores become blocked and partial sintering induces CaO agglomeration. PMID:25730384

  11. Atomistic and Ab initio modeling of CaAl2O4 high-pressure polymorphs under Earth's mantle conditions

    NASA Astrophysics Data System (ADS)

    Eremin, N. N.; Grechanovsky, A. E.; Marchenko, E. I.

    2016-05-01

    Semi-empirical and ab initio theoretical investigation of crystal structure geometry, interatomic distances, phase densities and elastic properties for some CaAl2O4 phases under pressures up to 200 GPa was performed. Two independent simulation methods predicted the appearance of a still unknown super-dense CaAl2O4 modification. In this structure, the Al coordination polyhedron might be described as distorted one with seven vertices. Ca atoms were situated inside polyhedra with ten vertices and Ca-O distances from 1.96 to 2.49 Å. It became the densest modification under pressures of 170 GPa (density functional theory prediction) or 150 GPa (semi-empirical prediction). Both approaches indicated that this super-dense CaAl2O4 modification with a "stuffed α-PbO2" type structure could be a probable candidate for mutual accumulation of Ca and Al in the lower mantle. The existence of this phase can be verified experimentally using high pressure techniques.

  12. Effect of Withdrawal Rate and Gd on the Microstructures of Directionally Solidified NiAl-Cr(Mo) Hypereutectic Alloy

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Shen, Jun; Zhang, Yun-Peng; Guo, Lan-Lan

    2016-03-01

    The microstructures of Ni-31Al-32Cr-6Mo- xGd hypereutectic alloy were investigated at the withdrawal rates of 10 μm/s, 30 μm/s, and 90 μm/s. For the Gd-free hypereutectic alloy, the Cr(Mo) primary dendrites appear at the beginning of solidification when the withdrawal rate is 10 μm/s. As the solidification proceeds, the Cr(Mo) primary dendrite is eliminated, and the fully eutectic structure can be obtained in the steady-state zone. With increasing the withdrawal rate, the Cr(Mo) primary dendrites decrease gradually, and vanish at 90 μm/s. In addition, at a moderate withdrawal rate (30 μm/s), an optimum addition of Gd content (0.1 wt.%) results in the refinement of the microstructure, including the refinement of the eutectic cells and the intercellular region. Meanwhile, the new white phase ((Al x Gd1- x )2O3) appears in the boundary of the eutectic cells when the Gd content is not less than 0.1 wt.%.

  13. Direct coating adherent diamond films on Fe-based alloy substrate: the roles of Al, Cr in enhancing interfacial adhesion and promoting diamond growth.

    PubMed

    Li, X J; He, L L; Li, Y S; Yang, Q; Hirose, A

    2013-08-14

    Direct CVD deposition of dense, continuous, and adherent diamond films on conventional Fe-based alloys has long been considered impossible. The current study demonstrates that such a deposition can be realized on Al, Cr-modified Fe-based alloy substrate (FeAl or FeCrAl). To clarify the fundamental mechanism of Al, Cr in promoting diamond growth and enhancing interfacial adhesion, fine structure and chemical analysis around the diamond film-substrate interface have been comprehensively characterized by transmission electron microscopy. An intermediate graphite layer forms on those Al-free substrates such as pure Fe and FeCr, which significantly deteriorates the interfacial adhesion of diamond. In contrast, such a graphite layer is absent on the FeAl and FeCrAl substrates, whereas a very thin Al-rich amorphous oxide sublayer is always identified between the diamond film and substrate interface. These comparative results indicate that the Al-rich interfacial oxide layer acts as an effective barrier to prevent the formation of graphite phase and consequently enhance diamond growth and adhesion. The adhesion of diamond film formed on FeCrAl is especially superior to that formed on FeAl substrate. This can be further attributed to a synergetic effect including the reduced fraction of Al and the decreased substrate thermal-expansion coefficient on FeCrAl in comparison with FeAl, and a mechanical interlocking effect due to the formation of interfacial chromium carbides. Accordingly, a mechanism model is proposed to account for the different interfacial adhesion of diamond grown on the various Fe-based substrates.

  14. Superior Mechanical Properties of AlCoCrFeNiTi x High-Entropy Alloys upon Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Ma, S. G.; Chu, M. Y.; Yang, H. J.; Wang, Z. H.; Zhang, Y.; Qiao, J. W.

    2016-02-01

    High-entropy alloys with composition of AlCoCrFeNiTi x ( x: molar ratio; x = 0, 0.2, 0.4) under quasi-static and dynamic compression exhibit excellent mechanical properties. A positive strain-rate sensitivity of yield strength and the strong work-hardening behavior during plastic flows dominate upon dynamic loading in the present alloy system. The constitutive relationships are extracted to model flow behaviors by employing the Johnson-Cook constitutive model. Upon dynamic loading, the ultimate strength and fracture strain of AlCoCrFeNiTi x alloys are superior to most of bulk metallic glasses and in situ metallic glass matrix composites.

  15. Flux Pinning by Cr Nanoparticles in Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10-δ } Superconductor

    NASA Astrophysics Data System (ADS)

    Waqee-ur-Rehman, M.; Mumtaz, M.; Qasim, Irfan; Nadeem, K.

    2016-09-01

    Increase in flux pinning strength of Cu_{0.5}Tl_{0.5}Ba2Ca2Cu3O_{10-δ }(CuTl-1223) superconductor has been observed after addition of Cr nanoparticles. We have thoroughly investigated the infield response of Cr nanoparticles-added CuTl-1223 superconductor in an external applied magnetic field in the range of 0-7 T. Solid-state reaction technique has been employed to synthesize (Cr)x-CuTl-1223; x = 0-1.00 wt% nanoparticle-superconductor composites. The flux pinning mechanism has been analyzed on the basis of thermally activated flux flow model in the presence of a small current (10 μ A). The increase in activation energy and decrease in transition width of CuTl-1223 superconducting phase show the enhancement in its flux pinning strength upon the addition of Cr nanoparticles.

  16. Texture and microstructure in co-sputtered Mg-M-O (M = Mg, Al, Cr, Ti, Zr, and Y) films

    NASA Astrophysics Data System (ADS)

    Saraiva, M.; Depla, D.

    2012-05-01

    Mg-M-O solid solution films (M = Mg, Al, Cr, Ti, Zr, and Y) with various M contents are grown employing reactive co-sputtering by varying the target-to-substrate distance. It is shown that all films are biaxially aligned. When the two cathodes are equipped with the same target material (Mg), the in-plane alignment is determined by the cathode closest to the substrate, i.e., by the largest material flux. In the case of nearly equal material fluxes from the two cathodes, double in-plane orientation is observed. This is also the case for the Mg-Al-O and Mg-Cr-O films, while the Mg-Ti-O, Mg-Zr-O and Mg-Y-O films exhibit single in-plane orientation. Pole figures indicate that the grains in Mg-M-O (M different than Mg) are titled; in the Mg-Al-O, Mg-Cr-O, and Mg-Ti-O films, the grains tilt towards the Al, Cr, and Ti metal flux, respectively, while the grain tilt of the Mg-Zr-O and Mg-Y-O films is found to be towards the Mg metal flux. Furthermore, SEM cross-sectional images of the Mg-M-O films reveal columnar microstructure with columns tilted to the same direction as the grains. A mechanism which is based on the cation radius change upon the incorporation of an M atom in the MgO lattice is proposed to explain the tilting.

  17. Properties of TIMETAL 555 (Ti-5Al-5Mo-5V-3Cr-0.6Fe)

    NASA Astrophysics Data System (ADS)

    Fanning, J. C.

    2005-12-01

    TIMETAL 555 is a high-strength near-β titanium alloy that was designed for improved producibility and excellent mechanical property combinations, including deep hardenability. The nominal chemical composition of TIMETAL 555 is Ti-5wt.%Al-5wt.%Mo-5wt.%V-3wt.%Cr. This article provides a summary of the available data for this relatively new alloy.

  18. Nanostructural study of the charge ordering vs. x and T in the Cr doped Pr 0.5Ca 0.5Mn 1- xCr xO 3 manganites

    NASA Astrophysics Data System (ADS)

    Hervieu, Maryvonne; Martin, Christine; Barnabé, Antoine; Maignan, Antoine; Mahendiran, Ramanathan; Hardy, Vincent

    2001-05-01

    This paper presents the nanostructural characterisation of the Cr doping effect in Pr 0.5Ca 0.5Mn 1- xCr xO 3, x ranging from 0 to 0.1, by using electron microscopy techniques. This study carried out at room and low temperatures showed that the Pnma-type distortion of the perovskite cell is retained for 0⩽ x⩽0.1 and that the different species (Mn, Cr) can be considered as randomly distributed. Increasing the Cr content does not induce specific extended defects. At 92 K, due to charge ordering effect, an incommensurate modulated superstructure is observed, characterised by a q value decreasing with x. For x=0.05, considered as the "limit" composition of the charge ordered phase, three classes of crystallites have been observed. The impurity effect in the low temperature form is analysed and the charge ordering has been characterised, in the x=0.02 Field Cooled and Zero Field Cooled crystallites. These observations are discussed in relations with the magnetotransport and magnetic studies. They support that I-M transition in absence of external magnetic field in Pr 0.5Ca 0.5Mn 1- xCr xO 3 is brought by percolation of ferromagnetic clusters in the charge ordered antiferromagnetic background. The charge ordered antiferromagnetic background diminishes and the size of FM clusters increases with increasing x.

  19. Influence of Cr and W alloying on the fiber-matrix interfacial shear strength in cast and directionally solidified sapphire NiAl composites

    NASA Technical Reports Server (NTRS)

    Asthana, R.; Tiwari, R.; Tewari, S. N.

    1995-01-01

    Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys reinforced with sapphire fibers.

  20. 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.

  1. Effects of Tantalum on the Temporal Evolution of a Model Ni-Al-Cr Superalloy During Phase Decomposition

    NASA Technical Reports Server (NTRS)

    Booth, Morrison, Christopher; Seidman, David N.; Noebe, Ronald D.

    2009-01-01

    The effects of a 2.0 at.% addition of Ta to a model Ni-10.0Al-8.5Cr (at.%) superalloy aged at 1073 K are assessed using scanning electron microscopy and atom-probe tomography. The gamma'(Ll2)-precipitate morphology that develops as a result of gamma-(fcc)matrix phase decomposition is found to evolve from a bimodal distribution of spheroidal precipitates, to {001}-faceted cuboids and parallelepipeds aligned along the elastically soft {001}-type directions. The phase compositions and the widths of the gamma'-precipitate/gamma-matrix heterophase interfaces evolve temporally as the Ni-Al-Cr-Ta alloy undergoes quasi-stationary state coarsening after 1 h of aging. Tantalum is observed to partition preferentially to the gamma'-precipitate phase, and suppresses the mobility of Ni in the gamma-matrix sufficiently to cause an accumulation of Ni on the gamma-matrix side of the gamma'/gamma interface. Additionally, computational modeling, employing Thermo-Calc, Dictra and PrecipiCalc, is employed to elucidate the kinetic pathways that lead to phase decomposition in this concentrated Ni-Al-Cr-Ta alloy.

  2. Modeling the Constitutive Relationship of Powder Metallurgy Ti-47Al-2Nb-2Cr Alloy During Hot Deformation

    NASA Astrophysics Data System (ADS)

    Sun, Yu; Hu, Lianxi; Ren, Junshuai

    2015-03-01

    In the present work, the isothermal compression tests of PM alloy Ti-47Al-2Nb-2Cr were carried out in the temperature range of 950-1200 °C. A Gleeble 1500D thermosimulation machine was used, and samples were tested at strain rates ranging from 10-3 to 10-1 s-1. Based on the obtained flow stress curves, the hot deformation behavior was presented. The constitutive relationship of powder metallurgy (PM) Ti-47Al-2Nb-2Cr alloy was developed using an Arrhenius-type constitutive model that involves strain compensation in addition to an artificial neural network model. The accuracy and reliability of the developed models were quantified in terms of statistical parameters such as correlation coefficient and absolute value of relative error. It was found that deformation temperature and strain rate have obvious effects on the flow characteristics, and the flow stress increases with the increasing strain rate and the decreasing temperature. Moreover, the proposed models possess excellent prediction capability of flow stresses for the present alloy during hot deformation. Compared with the traditional Arrhenius-type model, the backpropagation neural network model is more accurate when presenting the isothermal compressing deformation behavior at elevated temperatures for PM Ti-47Al-2Nb-2Cr alloy.

  3. Overview of the multifaceted activities towards development and deployment of nuclear-grade FeCrAl Alloys

    SciTech Connect

    Field, Kevin G; Yamamoto, Yukinori; Pint, Bruce A; Terrani, Kurt A

    2016-01-01

    A large effort is underway under the leadership of US DOE Fuel Cycle R&D program to develop advanced FeCrAl alloys as accident tolerant fuel (ATF) cladding to replace Zr-based alloys in light water reactors. The primary motivation is the excellent oxidation resistance of these alloys in high-temperature steam environments right up to their melting point (roughly three orders of magnitude slower oxidation kinetics than zirconium). A multifaceted effort is ongoing to rapidly advance FeCrAl alloys as a mature ATF concept. The activities span the broad spectrum of alloy development, environmental testing (high-temperature high-pressure water and elevated temperature steam), detailed mechanical characterization, material property database development, neutron irradiation, thin tube production, and multiple integral fuel test campaigns. Instead of off-the-shelf commercial alloys that might not prove optimal for the LWR fuel cladding application, a large amount of effort has been placed on the alloy development to identify the most optimum composition and microstructure for this application. The development program is targeting a cladding that offers performance comparable to or better than modern Zr-based alloys under normal operating and off-normal conditions. This paper provides a comprehensive overview of the systematic effort to advance nuclear-grade FeCrAl alloys as an ATF cladding in commercial LWRs.

  4. Estimation of excess energies and activity coefficients for the penternary Ni-Cr-Co-Al-Mo system and its subsystems

    NASA Astrophysics Data System (ADS)

    Dogan, A.; Arslan, H.; Dogan, T.

    2015-06-01

    Using different prediction methods, such as the General Solution Model of Kohler and Muggianu, the excess energy and activities of molybdenum for the sections of the phase diagram for the penternary Ni-Cr-Co-Al-Mo system with mole ratios xNi/ xMo = 1, xCr/ xMo = 1, xCo/ xMo = 1, and xAl/ xMo = r = 0.5 and 1, were thermodynamically investigated at a temperature of 2000 K, whereas the excess energy and activities of Bi for the section corresponding to the ternary Bi-Ga-Sb system with mole ratio xGa/ xSb = 1/9 were thermodynamically investigated at a temperature of 1073 K. In the case of r = 0.5 and 1 in the alloys Ni-Cr-Co-Al-Mo, a positive deviation in the activity coefficient was revealed, as molybdenum content increased. Moreover, in the calculations performed in Chou's GSM model, the obtained values for excess Gibbs energies are negative in the whole concentration range of bismuth at 1073 K and exhibit the minimum of about -2.2 kJ/mol at the mole ratio xGa/ xSb = 1/9 in the alloy Bi-Ga-Sb.

  5. High Temperature Thermal Stability and Oxidation Resistance of Magnetron-sputtered Homogeneous CrAlON Coatings on 430 Steel

    NASA Astrophysics Data System (ADS)

    Kayani, A.; Wickey, K. J.; Nandasiri, M. I.; Moore, A.; Garratt, E.; AlFaify, S.; Gao, X.; Smith, R. J.; Buchanan, T. L.; Priyantha, W.; Kopczyk, M.; Gannon, P. E.; Gorokhovsky, V. I.

    2009-03-01

    The requirements of low cost and high-temperature corrosion resistance for bipolar interconnect plates in solid oxide fuel cell stacks has directed attention to the use of metal plates with oxidation resistant coatings. We have investigated the performance of steel plates with homogenous coatings of CrAlON (oxynitrides). The coatings were deposited using RF magnetron sputtering, with Ar as a sputtering gas. Oxygen in these coatings was not intentionally added. Oxygen might have come through contaminated nitrogen gas bottle, leak in the chamber or from the partial pressure of water vapors. Nitrogen was added during the growth process to get oxynitride coating. The Cr/Al composition ratio in the coatings was varied in a combinatorial approach. The coatings were subsequently annealed in air for up to 25 hours at 800° C. The composition of the coated plates and the rate of oxidation were characterized using Rutherford backscattering (RBS) and nuclear reaction analysis (NRA). From our results, we conclude that Al rich coatings are more susceptible to oxidation than Cr rich coatings.

  6. High temperature oxidation resistance of magnetron-sputtered homogeneous CrAlON coatings on 430 steel

    NASA Astrophysics Data System (ADS)

    Garratt, E.; Wickey, K. J.; Nandasiri, M. I.; Moore, A.; AlFaify, S.; Gao, X.; Kayani, A.; Smith, R. J.; Buchanan, T. L.; Priyantha, W.; Kopczyk, M.; Gannon, P. E.

    2009-11-01

    The requirements of low cost and high-temperature corrosion resistance for bipolar interconnect plates in solid oxide fuel cell stacks has directed attention to the use of metal plates with oxidation resistant coatings. We have investigated the performance of steel plates with homogenous coatings of CrAlON (oxynitrides). The coatings were deposited using RF magnetron sputtering, with Ar as a sputtering gas. Oxygen in these coatings was not intentionally added. Oxygen might have come through contaminated nitrogen gas bottle, leak in the chamber or from the partial pressure of water vapors. Nitrogen was added during the growth process to get oxynitride coating. The Cr/Al composition ratio in the coatings was varied in a combinatorial approach. The coatings were subsequently annealed in air for up to 25 hours at 800 oC. The composition of the coated plates and the rate of oxidation were characterized using Rutherford backscattering (RBS) and nuclear reaction analysis (NRA). Surface characterization was carried out using Atomic Force Microscopy (AFM) and surfaces of the coatings were found smooth on submicron scale. From our results, we conclude that Al rich coatings are more susceptible to oxidation than Cr rich coatings.

  7. Mechanical properties and permeability of hydrogen isotopes through CrNi35WTiAl alloy, containing radiogenic helium

    SciTech Connect

    Maksimkin, I.P.; Yukhimchuk, A.A.; Boitsov, I.Y.; Malkov, I.L.; Musyaev, R.K.; Baurin, A.Y.; Shevnin, E.V.; Vertey, A.V.

    2015-03-15

    The long-term contact of structural materials (SM) with tritium-containing media makes their properties in terms of kinetic permeability of hydrogen isotopes change. This change is the consequence of the defect formation in SM due to the result of {sup 3}He build-up generated by the radioactive decay of tritium dissolved in SM. This paper presents the experimental results concerning the permeability of hydrogen isotopes through CrNi35WTiAl alloy containing {sup 3}He and the impact of the presence of {sup 3}He and H on its mechanical properties. Tensile tests of cylindrical samples containing various concentrations of {sup 3}He (90, 230 and 560 appm) have been performed in inert and hydrogen atmospheres. The build-up of {sup 3}He has been made using the 'helium trick' technique. The maximal decrease in the plastic characteristics of the CrNi35WTiAl alloy occurs in samples with the highest {sup 3}He (560 appm) content at 873 K. The permeability of deuterium through the CrNi35WTiAl alloy in the initial state and that with 560 appm of {sup 3}He content was explored. The presence of this {sup 3}He concentration has shown an increase in deuterium permeability, evidently due to structural changes in the material under the impact of radiogenic helium.

  8. Thermal Stability of Microstructure and Hardness of Cold-Sprayed cBN/NiCrAl Nanocomposite Coating

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Tao; Li, Chang-Jiu

    2012-06-01

    cBN/NiCrAl nanocomposite coatings were deposited by cold spraying using mechanically alloyed composite powders. To examine their thermal stability, the nanocomposite coatings were annealed at different temperatures up to 1000 °C. The microstructure of composite coatings was characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that the nanostructure can be retained when the annealing temperature is not higher than 825 °C, which is 0.7 times of the melting point of the NiCrAl matrix. The dislocation density was significantly reduced when the annealing temperature was higher than 750 °C. The reaction between cBN particles and the NiCrAl matrix became noticeable when the annealing temperature was higher than 825 °C. The effects of grain refinement and work-hardening strengthening mechanisms were quantitatively estimated as a function of annealing temperature. The influence of annealing temperature on the contribution of different strengthening mechanisms to coating hardness was discussed.

  9. Deformation Behavior of Laser Welds in High Temperature Oxidation Resistant Fe-Cr-Al Alloys for Fuel Cladding Applications

    SciTech Connect

    Field, Kevin G; Gussev, Maxim N; Yamamoto, Yukinori; Snead, Lance Lewis

    2014-11-01

    Ferritic-structured Fe-Cr-Al alloys are being developed and show promise as oxidation resistant accident tolerant light water reactor fuel cladding. This study focuses on investigating the weldability of three model alloys in a range of Fe-(13-17.5)Cr-(3-4.4)Al in weight percent with a minor addition of yttrium using laser-welding techniques. A detailed study on the mechanical performance of bead-on-plate welds has been carried out to determine the performance of welds as a function of alloy composition. Laser welding resulted in a defect free weld devoid of cracking or inclusions for all alloys studied. Results indicated a reduction in the yield strength within the fusion zone compared to the base metal. Yield strength reduction was found to be primarily constrained to the fusion zone due to grain coarsening with a less severe reduction in the heat affected zone. No significant correlation was found between the deformation behavior/mechanical performance of welds and the level of Cr or Al in the alloy ranges studied.

  10. High-Temperature Mechanical Behavior of End-of-Life Cryomilled NiCrAlY Bond Coat Materials

    NASA Astrophysics Data System (ADS)

    Funk, M.; Ma, K.; Eberl, C.; Schoenung, J. M.; Göken, M.; Hemker, K. J.

    2011-08-01

    Previous work has demonstrated that the lifetime of atmospheric plasma sprayed thermal barrier coating (TBC) systems incorporating cryomilled NiCrAlY bond coats show superior reliability with up to 3 times longer lifetimes compared to conventional ones. These conventional and cryomilled NiCrAlY bond coats at end-of-life (after thermal cycle failure) were studied in detail in the present work with a focus on the mechanical behavior in the temperature range from room temperature to 1273 K (1000 °C). The investigations were carried out using microtensile samples and the DIC technique. It turns out that the low-temperature strength of the cryomilled NiCrAlY bond coat is inferior to that of conventional ones, which might be due to a more pronounced porosity. At higher temperatures (between 1173 K and 1273 K (900 °C and 1000 °C)), the cryomilled bond coat shows almost twice the strength of the conventional bond coat, despite having been exposed to almost 3 times as many thermal cycles. The thermal stability of the nitride dispersoids appears to compensate for the gamma prime dissolution that typically occurs at these elevated temperatures, allowing for strength retention.

  11. Development of a CuNiCrAl Bond Coat for Thermal Barrier Coatings in Rocket Combustion Chambers

    NASA Astrophysics Data System (ADS)

    Fiedler, Torben; Rösler, Joachim; Bäker, Martin

    2015-12-01

    The lifetime of rocket combustion chambers can be increased by applying thermal barrier coatings. The standard coating systems usually used in gas turbines or aero engines will fail at the bond coat/substrate interface due to the chemical difference as well as the different thermal expansion between the copper liner and the applied NiCrAlY bond coat. A new bond coat alloy for rocket engine applications was designed previously with a chemical composition and coefficient of thermal expansion more similar to the copper substrate. Since a comparable material has not been applied by thermal spraying before, coating tests have to be carried out. In this work, the new Ni-30%Cu-6%Al-5%Cr bond coat alloy is applied via high velocity oxygen fuel spraying. In a first step, the influence of different coating parameters on, e.g., porosity, amount of unmolten particles, and coating roughness is investigated and a suitable parameter set for further studies is chosen. In a second step, copper substrates are coated with the chosen parameters to test the feasibility of the process. The high-temperature behavior and adhesion is tested with laser cycling experiments. The new coatings showed good adhesion even at temperatures beyond the maximum test temperatures of the NiCrAlY bond coat in previous studies.

  12. Major soil element (Ca, Mg, K, Na, Al, Fe) distribution along the Qinghai-Tibet Railway

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Zhang, Y.; Zhang, H.; Ding, M.; Lin, X.

    2011-12-01

    The Tibetan Plateau (TP), which has been called the third polar region, is the highest plateau in the world. There are a series of special soils present in the TP, which are extremely important in soil sciences for their particularities. Soil chemical composition is one of the necessary indices of soil characteristics. The major element content of the soil, such as Ca, Mg, K, Na, not only can affect the soil pH value and soil fertility but also are the main drivers of soil geochemical processes. It is helpful to understand the TP environmental characteristics, to study the major soil element content.The Qinghai-Tibet Railway (QTR) is the highest-elevation and the longest highland railway on earth. There are nearly all types of TP soil along the QTR. Most of the areas along the QTR are in fairly pristine condition. This offers a good platform to study the natural environmental characteristics of the soil. This study selected 240 soil samples from 28 sample areas along the Qinghai-Tibet Railway, and the aluminum, iron, calcium, sodium, potassium and magnesium content in the soil were measured with ICP-AES. The results indicated: (1) Compared with the national soil background values, the Ca content in soil was higher along the QTR and Al was lower; but the Fe, Mg, K and Na contents were similar. (2) Along the whole QTR, the soil Al, Fe and Mg content showed a decreasing trend from Xining to Lhasa, the changes in K and Na values were relatively complex, and the distribution of Ca could be divided three sections. (3) The soil element contents varied with different soil types and parent materials. Most of the six elements content was minimum in soil, which derived from debris materials for ice and water, and the elements content was maximum in soil, which evolved from debris for flood, and the content of soil Ca developed from debris for lake was maximum. The amount of each element present in the Hapli-Cryic Aridosols and Calci-Cryic Aridosols was relatively higher than

  13. Influence cobalt on microstructural and hardness property of Al-Zn-Mg-Cu-Fe-Cr-Ni P/ M alloys

    NASA Astrophysics Data System (ADS)

    Naeem, Haider T.; Mohammad, Kahtan S.; Hussin, Kamarudin; Rahmat, Azim; Bashirom, Nurhuda

    2015-05-01

    In this study, influence cobalt additives on the microstructural and hardness properties of an Al-Zn-Mg-Cu-Fe-Cr-Ni PM alloy undergone the retrogression and re-aging treatment were carried out. Green compacts pressed at 370 MPa were then sintered at temperature 650°C in argon atmosphere for two hours. The sintered compacts subjected to a homogenizing treated at 470°C for 1.5 hours then aged at 120°C for 24 hours and retrogressed at 180°C for 30 minutes, and then re-aged at 120°C for 24 hours. Microstructural results of the Al-Zn-Mg-Cu-Fe-Cr-Ni-Co alloys introduced an intermetallics compound in the matrix of alloy, identified as the Al5Co2, Al70Co20Ni10 and Al4Ni3 phases besides to the MgZn2 and Mg2Zn11 phases which produced of the precipitation hardening during heat treatment. These compounds with precipitates provided strengthening of dispersion that led to improved Vickers's hardness and dinsifications properties of the alloy. The highest Vickers hardness of aluminum alloy containing cobalt was gotten after applying the retrogression and re-aging treatment.

  14. Hot Corrosion Behavior of Low-Pressure Cold-Sprayed CoNiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, L. W.; Ning, X. J.; Lu, L.; Wang, Q. S.; Wang, L.

    2016-02-01

    CoNiCrAlY coatings were deposited by low-pressure cold spraying and pre-oxidized in a vacuum environment, and its hot corrosion behavior in pure Na2SO4 and 75 wt.% Na2SO4 + 25 wt.% NaCl salts was investigated. The pre-oxidation treatment resulted in the formation of a dense and continuous α-Al2O3 scale on the coating surface. After being corroded for 150 h at 900 °C, the pre-oxidized coating exhibited better corrosion resistance to both salts than the as-sprayed coating. The presence of preformed Al2O3 scale reduced the consumption rate of aluminum, by delaying the formation of internal oxides and sulfides and promoting the formation of a denser and more adherent Al2O3 scale. Moreover, we investigated the corrosion mechanism of cold-sprayed CoNiCrAlY coatings in the two salts and discussed the effect of the pre-oxidation treatment.

  15. Preliminary Results on FeCrAl Alloys in the As-received and Welded State Designed to Have Enhanced Weldability and Radiation Tolerance

    SciTech Connect

    Field, Kevin G.; Gussev, Maxim N.; Hu, Xunxiang; Yamamoto, Yukinori

    2015-09-30

    The present report summarizes and discusses the recent results on developing a modern, nuclear grade FeCrAl alloy designed to have enhanced radiation tolerance and weldability. The alloys used for these investigations are modern FeCrAl alloys based on a Fe-13Cr-5Al-2Mo-0.2Si-0.05Y alloy (in wt.%, designated C35M). Development efforts have focused on assessing the influence of chemistry and microstructure on the fabricability and performance of these newly developed alloys. Specific focus was made to assess the weldability, thermal stability, and radiation tolerance.

  16. Refinement of Eutectic Si in High Purity Al-5Si Alloys with Combined Ca and P Additions

    NASA Astrophysics Data System (ADS)

    Ludwig, Thomas Hartmut; Li, Jiehua; Schaffer, Paul Louis; Schumacher, Peter; Arnberg, Lars

    2015-01-01

    The effects of combined additions of Ca and P on the eutectic Si in a series of high purity Al-5 wt pct Si alloys have been investigated with the entrained droplet technique and complementary sets of conventional castings. Differential scanning calorimetry (DSC) and thermal analysis were used to investigate the eutectic droplet undercooling and the recalescence undercooling, respectively. Optical microscopy, SEM, EPMA, and TEM were employed to characterize the resultant microstructures. It was found that 250 ppm Ca addition to Al-5Si wt pct alloys with higher P contents leads to a significant increase of the eutectic droplet undercooling. For low or moderate cooling rates, the TEM results underline that Ca additions do not promote Si twinning. Thus, a higher twin density cannot be expected in Ca containing Al-Si alloys after, e.g., sand casting. Consequently, a refinement of the eutectic Si from coarse flake-like to fine plate-like structure, rather than a modification of the eutectic Si to a fibrous morphology, was achieved. This strongly indicates that the main purpose of Ca additions is to counteract the coarsening effect of the eutectic Si imposed by higher P concentrations. Significant multiple Si twinning was observed in melt-spun condition; however, this can be attributed to the higher cooling rate. After DSC heating (slow cooling), most of Si twins disappeared. Thus, the well-accepted impurity-induced twinning mechanism may be not valid in the case of Ca addition. The possible refinement mechanisms were discussed in terms of nucleation and growth of eutectic Si. We propose that the pre-eutectic Al2Si2Ca phase and preferential formation of Ca3P2 deactivate impurity particles, most likely AlP, poisoning the nucleation sites for eutectic Si.

  17. Interaction of an aluminum atom with an alkaline earth atom: Spectroscopic and ab initio investigations of AlCa

    NASA Astrophysics Data System (ADS)

    Behm, Jane M.; Morse, Michael D.; Boldyrev, Alexander I.; Simons, Jack

    1994-10-01

    A spectroscopic analysis of diatomic AlCa generated by laser vaporization of a 2:1 Al:Ca metal alloy followed by supersonic expansion has been completed using resonant two-photon ionization spectroscopy. Four excited electronic states have been identified and investigated in the energy region from 13 500 to 17 900 cm-1. These are the [13.5] 2Πr, the [15.8] 2Σ, the [17.0] 2Δ3/2(?), and the [17.6] 2Δ3/2 states. From rotational analysis excited state bond lengths have been measured for three of the four excited states, and the ground state has been unambiguously determined as a 2Πr state with a weighted least squares value of the ground state bond length of r0` = 3.1479± 0.0010 Å. The ionization energy of the molecule has also been directly determined as 5.072±0.028 eV. Ab initio calculations for the potential energy curves of seven low-lying states of AlCa [X 2Πr, 2Σ+, 4Σ-, 4Πr, 2Πr(2), 2Δ, and 2Σ-] and for the X 1Σ+ ground electronic state of AlCa+ have been carried out. In agreement with experiment, 2Πr is calculated to be the ground electronic state of the neutral molecule. The dissociation energies of AlCa (X 2Πr) into Al(3s23p1,2P0)+Ca(4s2,1S) and for AlCa+ (X 1Σ+) into Al+(3s2,1S)+Ca(4s2,1S) are calculated to be 0.47 and 1.50 eV, respectively. The excited 2Σ+, 4Σ-, 4Πr, 2Πr(2), 2Δ, and 2Σ- states are calculated to lie 0.2, 0.7, 0.7, 1.1, 1.1, and 1.1 eV above X 2Πr, respectively, and the vertical and adiabatic ionization energies of AlCa have been calculated to be 5.03 and 4.97 eV, respectively.

  18. Enthalpies of formation of CaAl sub 4 O sub 7 and CaAl sub 12 O sub 19 (hibonite) by high temperature, alkali borate solution calorimetry

    SciTech Connect

    Geiger, C.A.; Kleppa, O.J.; Mysen, B.O.; Lattimer, J.M.; Grossman, L. )

    1988-06-01

    The enthalpies of formation of CaAl{sub 4}O{sub 7} and CaAl{sub 12}O{sub 19} (hibonite), by alkali borate solution calorimetry at 1063 K are discussed. Using these experimental enthalpy data for CaAl{sub 4}O{sub 7} and estimated values for CaAl{sub 12}O{sub 19}, the standard enthalpies of formation of these compounds from the elements at 298 K are derived. Comparison with high-temperature galvanic cell data for the Gibbs energy of formation of CaAl{sub 12}O{sub 19} allows a calculation of the standard entropy of hibonite. This value is only about 2% larger than the oxide sum. Hence it is inferred that the standard entropy of hibonite at 298 K is probably only slightly larger than oxide sum value of 343.7 J/K g.f.w. The present data were used to extrapolate Kumar and Kay's (1985) data for the Gibbs energies of formation of hibonite and CaAl{sub 4}O{sub 7} to the temperature range 1500-1700 K. These data were then used in equilibrium thermodynamic calculations of the condensation of a gas of solar composition. Contrary to calculations of Kornacki and Fegley (1984), who used thermodynamic data of Allibert et al. (1981) for calcium aluminates, the authors results show no stability field for CaAl{sub 4}O{sub 7} in a gas of solar composition at 10{sup {minus}3} to 10{sup {minus}5} atm total pressure. At 10{sup {minus}3} atm pressure, hibonite forms by reaction of corundum with the gas at 1725 K, begins to react with the gas to form gehlenite at 1607 K and disappears completely in a reaction to form spinel at 1494 K. The absence of CaAl{sub 4}O{sub 7}, from hibonite-, spinel-rich inclusions in carbonaceous chondrites cannot be used as an argument against a condensation origin for these objects.

  19. Weathering and precipitation after meteorite impact of Ni, Cr, Fe, Ca and Mn in K-T boundary clays from Stevns Klint

    NASA Astrophysics Data System (ADS)

    Miyano, Yumiko; Yoshiasa, Akira; Tobase, Tsubasa; Isobe, Hiroshi; Hongu, Hidetomo; Okube, Maki; Nakatsuka, Akihiko; Sugiyama, Kazumasa

    2016-05-01

    Ni, Cr, Fe, Ca and Mn K-edge XANES and EXAFS spectra were measured on K-T boundary clays from Stevns Klint in Denmark. According to XANES spectra and EXAFS analyses, the local structures of Ni, Cr and Fe in K-T boundary clays is similar to Ni(OH)2, Cr2O3 and FeOOH, respectively. It is assumed that the Ni, Cr and Fe elements in impact related glasses is changing into stable hydrate and oxide by the weathering and diagenesis at the surface of the Earth. Ca in K-T boundary clays maintains the diopside-like structure. Local structure of Ca in K-T clays seems to keep information on the condition at meteorite impact. Mn has a local structure like MnCO3 with divalent state. It is assumed that the origin on low abundant of Mn in the Fe-group element in K-T clays was the consumption by life activity and the diffusion to other parts.

  20. Growth and spectral characters of Nd:CaGdAlO4 crystal

    NASA Astrophysics Data System (ADS)

    Di, Juqing; Sun, Xiaohui; Xu, Xiaodong; Xia, Changtai; Sai, Qinglin; Yu, Haohai; Wang, Yicheng; Zhu, Liu; Gao, Yuan; Guo, Xueyi

    2016-04-01

    In this paper, crystal growth and polarized spectra of Nd:CaGdAlO4 (Nd:CALGO) crystal were reported. The maximal absorption cross-sections are 6.8 and 7.5 × 10-20 cm2 for π-polarization and σ-polarization, and the emission cross-sections are 12.5 × 10-20 cm2 with full width at half maximum (FWHM) of 18 and 11 nm, respectively. The Judd-Ofelt (JO) theory was used to calculate the spectral parameters and the effective intensity parameters Ω2, Ω4 and Ω6 were 0.8 × 10-20 cm2, 7.5 × 10-20 cm2 and 5.8 × 10-20 cm2, respectively. The lifetime was 123 μs. The results show that Nd:CALGO crystal is a promising medium for laser output.

  1. Photoluminescence and thermoluminescence studies of CaAl2O4:Dy(3+) phosphor.

    PubMed

    Ziyauddin, Mohammad; Tigga, Shalinta; Brahme, Nameeta; Bisen, D P

    2016-02-01

    Calcium aluminate phosphors activated by Dy(3+) have been prepared by a combustion method at a temperature of 600°C. Photoluminescence (PL) and thermoluminescence (TL) properties of gamma-irradiated Dy-doped calcium aluminate were investigated. The PL spectrum shows a broad peak around 488 nm and 573 nm, under 347 nm excitation. Thermoluminescence studies were performed for different concentrations of Dy. Optimum intensity of photoluminescence was found for 0.02 mol% concentration of Dy. It was found that initially the peak TL intensity increases with increasing concentration of Dy in the CaAl2O4 host, attains a maximum value for 0.05 mol% concentration and decreases with further increase in the doping concentration due to concentration quenching.

  2. Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

    NASA Astrophysics Data System (ADS)

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2016-05-01

    Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

  3. Fabrication and luminescent properties of Al2O3:Cr3 + microspheres via a microwave solvothermal route followed by heat treatment

    NASA Astrophysics Data System (ADS)

    Zhu, Zhenfeng; Liu, Dianguang; Liu, Hui; Du, Juan; Yu, Hongguang; Deng, Jie

    2012-06-01

    AlOOH:Cr3 + powders were synthesized via a microwave solvothermal route at 433 K for 30 min and were used as the precursor and template for the preparation of γ-Al2O3:Cr3 + by thermal transformation at 773 K for 2 h in air. The obtained γ-Al2O3 based powders were microspheres with an average diameter about 1.9 μm. Photoluminescence (PL) spectra showed that the Al2O3:Cr3 + particles presented a symmetric broad R band at 696 nm without appreciable splitting when excited at 462 nm. It is shown that the 0.04 mol% of doping concentration of Cr3 + ions in γ-Al2O3:Cr3 + is optimum. According to Dexter's theory, the critical distance between Cr3 + ions for energy transfer was determined to be 47.54 Å. Based on the corresponding PL spectrum, full width at half maximum (FWHM) of Al2O3:Cr3 + (0.04 mol%) was calculated to be 3.35 nm.

  4. Effects of Cr doping in La0.67Ca0.33MnO3: Magnetization, resistivity, and thermopower

    NASA Astrophysics Data System (ADS)

    Sun, Young; Xu, Xiaojun; Zhang, Yuheng

    2001-02-01

    The effects of Cr substitution on Mn sites in the colossal magnetoresistance (CMR) compound La0.67Ca0.33MnO3 have been studied by preparing the series La0.67Ca0.33Mn1- xCrxO3 (x<=0.3). A careful study in the magnetic and electrical transport properties has been carried out by the measurements of magnetization, resistivity, magnetoresistance, and thermopower. It was found that Cr is impotent in lowering TC when x<=0.2. An extraordinary magnetotransport behavior, characterized by double bumps, was observed around x=0.1. As a result, the temperature range of CMR is greatly broadened. The analysis of resistivity and thermopower data in the paramagnetic state enable us to identify the polaronic transport mechanism. Morever, it is found that the polaron activation energy as well as polaron binding energy are almost constant within a broad Cr content. We suggest these peculiar effects of Cr doping could be the consequence of the possible double exchange interaction between Mn3+ and Cr3+.

  5. Calotropis procera mediated combustion synthesis of ZnAl2O4:Cr3+ nanophosphors: Structural and luminescence studies

    NASA Astrophysics Data System (ADS)

    Ravikumar, B. S.; Nagabhushana, H.; Sharma, S. C.; Vidya, Y. S.; Anantharaju, K. S.

    2015-02-01

    ZnAl2O4:Cr3+ nanophosphors were synthesized for the first time by a simple and environment friendly route using Calotropis procera milk latex as fuel. The structural and surface morphological studies were carried out using powder X-ray diffraction (PXRD), scanning electron microscopy and transmission electron microscopy techniques. The photoluminescence (PL) properties of ZnAl2O4:Cr3+ as a function of dopant concentration and calcination temperature was studied in detail. The PXRD patterns and Rietveld confinement confirmed the cubic crystal system with space group Fd-3m. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 16-26 nm. The PL spectrum shows an intense peak at ∼688 and ∼699 nm assigned to spin - forbidden 2Eg → 4A2g transition of Cr3+ ions. The PL measurements for two excitations (∼410 and 527 nm) and with respect to calcination temperature indicated no significant change in the shape and position of emission peak except PL intensity. The CIE chromaticity coordinates lies well within the white region. Thermoluminescence (TL) studies revealed well resolved glow peak at ∼212 °C with a small shoulder at 188 and 233 °C. The glow peak intensity at ∼212 °C increases linearly with γ-dose which suggest ZnAl2O4:Cr3+ is suitable candidate for radiation dosimetric applications. The activation energy (E in eV), order of kinetics (b) and Frequency factor (s) were estimated using glow peak shape method.

  6. Calotropis procera mediated combustion synthesis of ZnAl2O4:Cr(3+) nanophosphors: structural and luminescence studies.

    PubMed

    Ravikumar, B S; Nagabhushana, H; Sharma, S C; Vidya, Y S; Anantharaju, K S

    2015-02-01

    ZnAl2O4:Cr(3+) nanophosphors were synthesized for the first time by a simple and environment friendly route using Calotropis procera milk latex as fuel. The structural and surface morphological studies were carried out using powder X-ray diffraction (PXRD), scanning electron microscopy and transmission electron microscopy techniques. The photoluminescence (PL) properties of ZnAl2O4:Cr(3+) as a function of dopant concentration and calcination temperature was studied in detail. The PXRD patterns and Rietveld confinement confirmed the cubic crystal system with space group Fd-3m. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 16-26 nm. The PL spectrum shows an intense peak at ∼688 and ∼699 nm assigned to spin-forbidden (2)Eg→(4)A2g transition of Cr(3+) ions. The PL measurements for two excitations (∼410 and 527 nm) and with respect to calcination temperature indicated no significant change in the shape and position of emission peak except PL intensity. The CIE chromaticity coordinates lies well within the white region. Thermoluminescence (TL) studies revealed well resolved glow peak at ∼212°C with a small shoulder at 188 and 233°C. The glow peak intensity at ∼212°C increases linearly with γ-dose which suggest ZnAl2O4:Cr(3+) is suitable candidate for radiation dosimetric applications. The activation energy (E in eV), order of kinetics (b) and Frequency factor (s) were estimated using glow peak shape method. PMID:25459629

  7. Development of thermally-sprayed Al-Cu-Fe-Cr quasicrystal coating

    NASA Astrophysics Data System (ADS)

    Setiamarga, Budi Hartono

    A class of quasicrystal alloys that has drawn a lot of attention is aluminum based quasicrystal alloys because they are hard, light weight, wear resistant, and have a non-stick property. Quasicrystalline materials in the form of coatings produced by thermal spray techniques have been developed to utilize their properties. The goal of this research has been to develop the knowledge necessary to produce good thermally sprayed Al-Cu-Fe-Cr quasicrystal coatings. Boron has been found to improve ductility, reduce porosity and increase hardness when added to other thermally sprayed powders, therefore, as part of this research, quasicrystal coatings containing boron will also be produced and evaluated. The first phase of this research utilized a fine QC-1 quasicrystal powder of Alsb{70.5}Cusb{10.1}Fesb{8.8}Crsb{10.6}. The addition of boron was done using mechanical mixing. The addition of boron in fused QC-1 powders shows that boron can reduce porosity and increase hardness. Due to difficulties with thermal spraying the fine QC-1 powder and evaporation of aluminum, a coarser QC-2 powder with similar composition to QC-1 powder was produced. QC-2 and boron modified QC-2 coatings have similar hardness and levels of porosity, around 11%, although boron modified QC-2 coatings proved to be more wear resistant than plain QC-2 coatings. Both coatings demonstrated a weak coating-substrate interface bonding. Laser heat treatment was used to reduce the porosity and strengthen the coating-substrate interface bonding. Laser treatment of QC-2 quasicrystal coatings resulted in harder and lower porosity coatings with better coating-substrate interface bonding. Unfortunately, hot-cracks in the coatings were also produced. Hot-cracks are undesireable because they decrease the coating's corrosion resistance. Thermal spraying using High Velocity Oxygen Fuel (HVOF) technique was done. It was used on QC-2 powder and QC-3 powder of composition Alsb{68.6}Cusb{10.8}Fesb{8.9}Crsb{9.7}Bsb{2.0}. This

  8. Ultrasonically-enhanced mechanochemical synthesis of CaAl-layered double hydroxides intercalated by a variety of inorganic anions.

    PubMed

    Szabados, Márton; Mészáros, Rebeka; Erdei, Szabolcs; Kónya, Zoltán; Kukovecz, Ákos; Sipos, Pál; Pálinkó, István

    2016-07-01

    CaAl-layered double hydroxides (CaAl-LDHs) were synthesised with various interlayer anions (CO3(2-), F(-), Cl(-), Br(-) and I(-)) by mechanochemical pre-treatment followed by ultrasonic irradiation in aqueous media. The parameters of the syntheses (duration of pre-milling and sonication, quality of the aqueous media, temperature) were altered in order to optimise the procedure and to understand the formation of LDH and other secondary products. The products were characterised by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The optimisation resulted in close-to-phase-pure CaAl-LDHs, not only with carbonate and chloride interlayer anions, but the hard-to-intercalate bromide and iodide as well.

  9. Effect of Rhenium Addition on Wear Behavior of Cr-Al2O3 Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Chmielewski, Marcin; Piątkowska, Anna

    2015-05-01

    Materials for applications in the automotive industry are required to be strong, stiff, hard, light weight, and wear resistant, which is very difficult to achieve in the case of conventional materials. To meet all these diverse requirements, it is necessary to combine various types of materials (such as metals and ceramics). In the present study, the chromium and chromium-rhenium matrices were reinforced with aluminum oxide to obtain composite materials with improved wear resistance. The composites were fabricated by a powder metallurgy method. The effects of the rhenium addition and volume fraction of aluminum oxide on the wear rate and the friction coefficient of the composites at room temperature were examined in a ball-on-surface apparatus under dry conditions. The worn surfaces and debris were studied by scanning electron microscopy. The final values of the friction coefficient were 0.9 and 0.8 for the Cr-25%Al2O3 and Cr-40%Al2O3 composites, respectively. Alloying Cr matrix with Re improved wear resistance of composite but, at the same time, it caused an increase in its coefficient of friction.

  10. The influence of cooling rate and Fe/Cr content on the evolution of Fe-rich compounds in a secondary Al-Si-Cu diecasting alloy

    NASA Astrophysics Data System (ADS)

    Fabrizi, A.; Timelli, G.

    2016-03-01

    This study investigates the morphological evolution of primary α-Al(Fe,Mn,Cr)Si phase in a secondary Al-Si-Cu alloy with respect to the initial Fe and Cr contents as well as to the cooling rate. The solidification experiments have been designed in order to cover a wide range of cooling rates, and the Fe and Cr contents have been varied over two levels. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes occurring at different experimental conditions. The morphological evolution of the α-Fe phase has been also analysed by observing deep etched samples. By changing the cooling rate, α-Al15(Fe,Mn,Cr)3Si2 dodecahedron crystals, as well as Chinese- script, branched structures and dendrites form, while primary coarse β-Al5(Fe,Mn)Si needles appear in the alloy with the highest Fe content at low cooling rates.

  11. Microstructural Characterization and Strengthening-Toughening Mechanism of Plasma-Sprayed Al2O3-Cr2O3 Composite Coatings

    NASA Astrophysics Data System (ADS)

    Yang, Kai; Feng, Jingwei; Zhou, Xiaming; Tao, Shunyan

    2012-09-01

    In this study, Al2O3, Cr2O3, and Al2O3-Cr2O3 coatings were fabricated by plasma spraying. X-ray diffraction was employed to determine the phase composition of powders and coatings. The morphologies and microstructures of the coatings were characterized using electron probe microanalyzer and transmission electron microscopy. Vickers hardness, fracture toughness, and bending strength of the coatings were measured. Al2O3-Cr2O3 composite coatings show better comprehensive mechanical properties than the individual Al2O3 and Cr2O3 coatings, which are attributed to the former's larger intersplat adhesion or interlamellar cohesion and lower porosity. Solid solution strengthens the phase interfaces and grain boundaries, which is beneficial to improve the mechanical performance of the composite coatings.

  12. Interdiffusion in Ni-rich, Ni-Cr-Al alloys at 1100 and 1200 C. I - Diffusion paths and microstructures. II - Diffusion coefficients and predicted concentration profiles

    NASA Technical Reports Server (NTRS)

    Nesbitt, J. A.; Heckel, R. W.

    1987-01-01

    Interdiffusion in Ni-rich Ni-Cr-Al alloys is investigated experimentally after annealing at 1100 and 1200 C using gamma/gamma, gamma/gamma+beta, gamma/gamma+gamma prime, and gamma/gamma+alpha diffusion couples. The amount and location of Kirkendall porosity suggests that Al diffuses more rapidly than Cr which diffuses more rapidly than Ni in the gamma phase of Ni-Cr-Al alloys. The location and extent of maxima and minima in the concentration profiles of the diffusion couples indicate that both cross-term diffusion coefficients are positive. Measurements are also presented of the ternary interdiffusion coefficients of the gamma phase in the Ni-Cr-Al system. It is shown that the interdiffusion coefficients can be accurately predicted by using a ternary finite-difference interdiffusion model.

  13. The effect of sulfur and zirconium Co-doping on the oxidation of NiCrAl

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1987-01-01

    The adhesion behavior of Al2O3 scales formed on NiCrAl+Zr alloys was examined as a function of both sulfur and zirconium doping levels. In general, very high levels of zirconium were required to counteract the detrimental effects of sulfur. A sulfur-zirconium adherence map was constructed, as determined from the oxidation and spalling behavior in 1100 C cyclic tests. For low sulfur alloys, the amount of zirconium required for adherence at any given sulfur level can be described by Zr greater than 600 S sup 0.2 (in ppma). These results underscore the importance of sulfur to adhesion mechanisms and suggests that sulfur gettering is a first order effect of reactive element additions to MCrAl alloys.

  14. The effect of sulfur and zirconium co-doping on the oxidation of NiCrAl

    NASA Technical Reports Server (NTRS)

    Smialek, James L.

    1988-01-01

    The adhesion behavior of Al2O3 scales formed on NiCrAl+Zr alloys was examined as a function of both sulfur and zirconium doping levels. In general, very high levels of zirconium were required to counteract the detrimental effects of sulfur. A sulfur-zirconium adherence map was constructed, as determined from the oxidation and spalling behavior in 1100 C cyclic tests. For low sulfur alloys (less than 500 ppma), the amount of zirconium required for adherence at any given sulfur level can be described by Zr greater than 600 S(0.2) (in ppma). These results underscore the importance of sulfur to adhesion mechanisms and suggest that sulfur gettering is a first order effect of reactive element additions to MCrAl alloys.

  15. Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

    NASA Astrophysics Data System (ADS)

    Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Karim, Saniah Ab; Zaman, Rosyaini Afindi; Ain, Mohd Fadzil; Ahmad, Zainal Arifin; Mohamed, Julie Juliewatty

    2016-07-01

    (1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al2O3 was reduced both dielectric loss and permittivity at least for an order of magnitude.

  16. Free-electron-like Hall effect and deviations from free-electron behavior in Ca-Al amorphous alloys

    NASA Astrophysics Data System (ADS)

    Mayeya, F. M.; Hickey, B. J.; Howson, M. A.

    1995-06-01

    The Hall coefficients of Ca-Al amorphous alloys have been measured at 4.2 K over a wide range of compositions. It is shown that the magnitude of the Hall coefficients are close to the nearly-free-electron (NFE) prediction for low Ca concentrations but deviate significantly from the NFE values for Ca concentration greater than 45 at. %. The deviations from the free-electron values have previously been attributed to the effects of s-d hybridization, while a reduction in magnitude by Au doping has been argued to result from the side-jump effect.

  17. The Role of Rhenium on the Temporal Evolution of the Nanostructure of a Model Ni-Al-Cr-Re Superalloy

    NASA Technical Reports Server (NTRS)

    Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2004-01-01

    Rhenium (2 at.%) additions to a model Ni-8.5 at.% Cr-10 at.% Al alloy are studied with respect to its effects on the temporal evolution of the nanostructure and the partitioning behavior of the four elements between the gamma (fcc) and gamma' (L1(sub 2)) phases. Chemical evolution of this quaternary alloy aged at 1073 K from 0.25 to 264 h, is investigated by three-dimensional atom-probe (3DAP) microscopy. The morphology of gamma'-precipitates remains spheroidal, even at an aging time of 264 h. The results demonstrate that Re slows the coarsening of gamma'-precipitates, in comparison to the ternary Ni-10 at.% A1-8.5 at.% Cr alloy at 1073 K.

  18. Using CrAlN multilayer coatings to improve oxidation resistance of steel interconnects for solid oxide fuel cell stacks

    NASA Astrophysics Data System (ADS)

    Smith, R. J.; Tripp, C.; Knospe, A.; Ramana, C. V.; Kayani, A.; Gorokhovsky, Vladimir; Shutthanandan, V.; Gelles, D. S.

    2004-06-01

    The requirements of low-cost and high-temperature corrosion resistance for bipolar interconnect plates in solid oxide fuel cell stacks has directed attention to the use of metal plates with oxidation resistant coatings. The performance of steel plates with multilayer coatings, consisting of CrN for electrical conductivity and CrAlN for oxidation resistance, was investigated. The coatings were deposited using large area filtered arc deposition technology, and subsequently annealed in air for up to 25 hours at 800 °C. The composition, structure, and morphology of the coated plates were characterized using Rutherford backscattering, nuclear reaction analysis, atomic force microscopy, and transmission electron microscopy techniques. By altering the architecture of the layers within the coatings, the rate of oxidation was reduced by more than an order of magnitude. Electrical resistance was measured at room temperature.

  19. Electrical transport, thermal transport, and elastic properties of M2 AlC ( M=Ti , Cr, Nb, and V)

    NASA Astrophysics Data System (ADS)

    Hettinger, J. D.; Lofland, S. E.; Finkel, P.; Meehan, T.; Palma, J.; Harrell, K.; Gupta, S.; Ganguly, A.; El-Raghy, T.; Barsoum, M. W.

    2005-09-01

    In this paper we report on a systematic investigation, in the 5to300K temperature regime, of the electronic, magnetotransport, thermoelectric, thermal, and elastic properties of four M2AlC phases: Ti2AlC , V2AlC , Cr2AlC , and Nb2AlC . The electrical conductivity, Hall coefficient, and magnetoresistances are analyzed within a two-band framework assuming a temperature-independent charge carrier concentration. As with other MAX -phase materials, these ternaries are nearly compensated, viz. the densities and mobilities of electrons and holes are almost equal. There is little correlation between the Seebeck and Hall coefficients. With Young’s and shear moduli in the 270GPa and 120GPa range, respectively, the phases studied herein are reasonably stiff. With room temperature thermal conductivities in the 25W/mK range ( 45W/mK for V2AlC ) they are also good thermal conductors.

  20. The Effect of Ballistic Impacts on the High Cycle Fatigue Properties of Ti-48Al-2Nb-2Cr (at.%)

    NASA Technical Reports Server (NTRS)

    Draper, S. L.; Lerch, B. A.; Pereira, J. M.; Nathal, M. V.; Austin, C. M.; Erdman, O.

    2000-01-01

    The ability of gamma - TiAl to withstand potential foreign and/or domestic object damage is a technical risk to the implementation of gamma - TiAl in low pressure turbine (LPT) blade applications. The overall purpose of the present study was to determine the influence of ballistic impact damage on the high cycle fatigue strength of gamma - TiAl simulated LPT blades. Impact and specimen variables included ballistic impact energy, projectile hardness, impact temperature, impact location, and leading edge thickness. The level of damage induced by the ballistic impacting was studied and quantified on both the impact (front) and backside of the specimens. Multiple linear regression was used to model the cracking and fatigue response as a function of the impact variables. Of the impact variables studied, impact energy had the largest influence on the response of gamma - TiAl to ballistic impacting. Backside crack length was the best predictor of remnant fatigue strength for low energy impacts (<0.74J) whereas Hertzian crack length (impact side damage) was the best predictor for higher energy impacts. The impacted gamma - TiAl samples displayed a classical mean stress dependence on the fatigue strength. For the fatigue design stresses of a 6th stage LPT blade in a GE90 engine, a Ti-48Al-2Nb-2Cr LPT blade would survive an impact of normal service conditions.

  1. Comparison of the transformation temperature, microstructure and magnetic properties of Co-Ni-Al and Co-Ni-Al-Cr shape memory alloys

    NASA Astrophysics Data System (ADS)

    Dağdelen, Fethi; Malkoç, Türkan; Kök, Mediha; Ercan, Ercan

    2016-06-01

    In this study, two-phase Co-Ni-Al shape memory alloys that have drawn attention recently due to their technological applications were investigated. Co-Ni-Al and Co-Ni-Al-Cr alloys were produced by melting method in an arc-melter furnace and physical properties between alloys were compared. At the end of experimental measurements it was observed that chromium addition did not change the crystal structure of the Co-Ni-Al alloy, but decreased the martensitic transformation temperature, the most significant property of shape memory alloys. Moreover, there was no significant change in the microstructure of the Co-Ni-Al alloy with chromium addition, and the presence of the two phases determined by X-ray analysis was also determined by optical microscopy. There was no significant change in micro hardness values of the alloys, while important changes in the magnetic properties were determined. It was observed that the Curie temperature decreased by approximately 500 {}^{circ}C with chromium addition and a considerable decrease in the magnetic saturation value was also determined.

  2. Influence of composition and microstructure on the corrosion behavior of different Fe-Cr-Al alloys in molten LBE

    NASA Astrophysics Data System (ADS)

    Del Giacco, M.; Weisenburger, A.; Jianu, A.; Lang, F.; Mueller, G.

    2012-02-01

    Corrosion tests in molten Lead Bismuth Eutectic (LBE) are performed on materials aimed for high temperature applications. The experiments include tests with oxygen content in solution of 10 -6-10 -8 wt.% at temperature of 500, 600 and 750 °C for 1000 h duration. The materials under investigation are Fe-Cr-Al Kanthal like alloys, namely: Kanthal - D, AF, APM and Alkrothal. The mentioned group of alloys is discussed as alternative solution for thermally high loaded parts, e.g. spacer grids, of future accelerator driven systems (ADSs) and nuclear fast reactors cooled by molten LBE. The experimental campaign highlighted the central role of temperature, oxygen content, composition (Cr and Al content) and, in some cases, microstructure for the corrosion behavior. Up to 600 °C, Kanthal alloys generally show good compatibility with LBE due to the formation of thin and protective Al 2O 3 scale. Even at 750 °C these alloys show the favorable alumina scale formation when the oxygen concentration in LBE is 10 -6 wt.%; also at 750 °C but at lower oxygen concentration of 10 -8 wt.%, dissolution attack affects Kanthal alloys except the Kanthal Alkrothal.

  3. Cage structure formation of singly doped aluminum cluster cations Al(n)TM+ (TM = Ti, V, Cr).

    PubMed

    Lang, Sandra M; Claes, Pieterjan; Neukermans, Sven; Janssens, Ewald

    2011-09-01

    Structural information on free transition metal doped aluminum clusters, Al(n)TM(+) (TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size (n = 5-35) and temperature (T = 145-300 K) dependent investigations reveal that bare Al(n)(+) clusters are inert toward argon, while Al(n)TM(+) clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum cage. The critical size, n(crit), is found to be surprisingly large, namely n(crit) = 16 and n(crit) = 19-21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster-argon bond dissociation energies have been derived as function of cluster size from equilibrium mass spectra and are in the 0.1-0.3 eV range.

  4. A magnetron sputtered microcrystalline β-NiAl coating for SC superalloys. Part I. Characterization and comparison of isothermal oxidation behavior at 1100 °C with a NiCrAlY coating

    NASA Astrophysics Data System (ADS)

    Hou, Shaojun; Zhu, Shenglong; Zhang, Tao; Wang, Fuhui

    2015-01-01

    A microcrystalline β-NiAl coating was prepared on a single-crystal (SC) superalloy substrate via magnetron sputtering and subsequent vacuum annealing. The grain sizes of the coating ranged from about 300 nm to 1 μm. A reference NiCrAlY coating, which was mainly comprised of γ‧-Ni3Al and α-Cr, was prepared by means of vacuum arc evaporation (VAE). Isothermal oxidation tests were carried out at 1100 °C in air for 50 h. Both coatings formed thin and adherent α-Al2O3 scales during tests, while the oxide scales on the bare superalloy primarily consisted of spinel (Ni,Co)Al2O4 with underlying α-Al2O3 scale. The parabolic rate constant of the NiAl-coated specimens was about one order of magnitude lower than that of the NiCrAlY coated specimens. After oxidation tests, only a small amount of γ‧ phase was detected at some columnar boundaries of the β-NiAl coating, and about 2/3 parts of the NiCrAlY coating transformed into γ phase which resolved the α-Cr precipitations, while an Al-depleted zone in thickness of about 10 μm formed beneath the TGO of the bare superalloy. Inter-diffusion zones and secondary reaction zones were observed on the specimens coated by either β-NiAl or NiCrAlY. The oxidation mechanism and microstructure evolvement of the specimens during high temperature exposures were discussed.

  5. Profiling the third-body wear damage produced in CoCr surfaces by bone cement, CoCr, and Ti6Al4V debris: a 10-cycle metal-on-metal simulator test.

    PubMed

    Halim, Thomas; Burgett, Michelle; Donaldson, Thomas K; Savisaar, Christina; Bowsher, John; Clarke, Ian C

    2014-07-01

    Particles of bone cement (polymethyl methacrylate), CoCr and Ti6Al4V were compared for their abrasion potential against CoCr substrates. This appears to be the first study utilizing CoCr and Ti6Al4V particulates to abrade CoCr bearings and the first study profiling the morphology of third-body abrasive wear scratches in a hip simulator. The 5 mg debris allotments (median size range 140-300 µm) were added to cups mounted both inverted and anatomically with metal-on-metal (MOM) bearings in a 10-cycle, hip simulator test. Surface abrasion was characterized by roughness indices and scratch profiles. Compared to third-body abrasion with metal debris, polymethyl methacrylate debris had minimal effect on the CoCr surfaces. In all, 10 cycles of abrasion with metal debris demonstrated that roughness indices (Ra, PV) increased approximately 20-fold from the unworn condition. The scratch profiles ranged 20-108 µm wide and 0.5-2.8 µm deep. The scratch aspect ratio (W/PV) averaged 0.03, and this very low ratio indicated that the 140 µm CoCr beads had plastically deformed to create wide but shallow scratches. There was no evidence of transfer of CoCr beads to CoCr bearings. The Ti64 particles produced similar scratch morphology with the same aspect ratio as the CoCr particulates. However, the titanium particulates also showed a unique ability to flatten and adhere to the CoCr, forming smears and islands of contaminating metal on the CoCr bearings. The morphology of scratches and metal transfer produced by these large metal particulates in the simulator appeared identical to those reported on retrieved metal-on-metal bearings.

  6. Evaluating controlling factors to Al(i)/(Ca + Mg) molar ratio in acidic soil water, southern and southwestern China: multivariate approach.

    PubMed

    Guo, Jing-Heng; Zhang, Xiao-Shan; Vogt, Rolf D; Xiao, Jin-Song; Zhao, Da-Wei; Xiang, Ren-Jun; Luo, Jia-Hai

    2007-06-01

    Al(i)/(Ca + Mg) molar ratio in soil water has been used as an indicator to the effects of acid deposition on terrestrial ecosystems. However, the main factors controlling this ratio have not been well documented in southern and southwestern China. In this study, we presented the variation in inorganic aluminum (Al(i)) and Al(i)/(Ca + Mg) molar ratio in different sites and soil horizons based on two to three years monitoring data, and evaluated the main factors controlling Al(i)/(Ca + Mg) molar ratio using principle component analysis (PCA) and partial least square (PLS) regression. Monitoring data showed although Al(i)/(Ca + Mg) molar ratios in most soil water were lower than assumed critical 1.0, higher molar ratios were found in some soil water at TSP and LXH site. Besides acid loading, both soil properties and soil water chemistry affected the value of Al(i)/(Ca + Mg) molar ratio in soil water. Partial least square (PLS) indicated that they had different relative importance in different soil horizons. In A-horizon, soil aluminum saturation (AlS) had higher influence on Al(i)/(Ca + Mg) molar ratio than soil water chemistry did; higher soil aluminum saturation (AlS) led to higher Al(i)/(Ca + Mg) molar ratio in soil water. In the deeper horizons (i.e., B(1)-, B(2)- and BC-horizon), inorganic aluminum (Al(i)) in soil water had more and more important role in regulating Al(i)/(Ca + Mg) molar ratio. On regional scale, soil aluminum saturation (AlS) as well as cation exchange capacity (CEC) was the dominant factor controlling Al(i)/(Ca + Mg) molar ratio. This should be paid enough attention on when making regional acid rain control policy in China.

  7. Evaluating controlling factors to Al(i)/(Ca + Mg) molar ratio in acidic soil water, southern and southwestern China: multivariate approach.

    PubMed

    Guo, Jing-Heng; Zhang, Xiao-Shan; Vogt, Rolf D; Xiao, Jin-Song; Zhao, Da-Wei; Xiang, Ren-Jun; Luo, Jia-Hai

    2007-06-01

    Al(i)/(Ca + Mg) molar ratio in soil water has been used as an indicator to the effects of acid deposition on terrestrial ecosystems. However, the main factors controlling this ratio have not been well documented in southern and southwestern China. In this study, we presented the variation in inorganic aluminum (Al(i)) and Al(i)/(Ca + Mg) molar ratio in different sites and soil horizons based on two to three years monitoring data, and evaluated the main factors controlling Al(i)/(Ca + Mg) molar ratio using principle component analysis (PCA) and partial least square (PLS) regression. Monitoring data showed although Al(i)/(Ca + Mg) molar ratios in most soil water were lower than assumed critical 1.0, higher molar ratios were found in some soil water at TSP and LXH site. Besides acid loading, both soil properties and soil water chemistry affected the value of Al(i)/(Ca + Mg) molar ratio in soil water. Partial least square (PLS) indicated that they had different relative importance in different soil horizons. In A-horizon, soil aluminum saturation (AlS) had higher influence on Al(i)/(Ca + Mg) molar ratio than soil water chemistry did; higher soil aluminum saturation (AlS) led to higher Al(i)/(Ca + Mg) molar ratio in soil water. In the deeper horizons (i.e., B(1)-, B(2)- and BC-horizon), inorganic aluminum (Al(i)) in soil water had more and more important role in regulating Al(i)/(Ca + Mg) molar ratio. On regional scale, soil aluminum saturation (AlS) as well as cation exchange capacity (CEC) was the dominant factor controlling Al(i)/(Ca + Mg) molar ratio. This should be paid enough attention on when making regional acid rain control policy in China. PMID:17057971

  8. The Molar Volume of FeO-MgO-Fe2O3-Cr2O3-Al2O3-TiO2 Spinels

    NASA Astrophysics Data System (ADS)

    Hamecher, E. A.; Antoshechkina, P. M.; Ghiorso, M. S.; Asimow, P. D.

    2011-12-01

    will include some minor components, including Ti4+ and Cr3+. Because most constraints on the activity of garnet and pyroxene at high-P are derived from experiments with coexisting spinel, we must be confident in the ability of our spinel model to realistically reproduce thermodynamic behavior over all applicable compositions. Additionally, producing a spinel molar volume model calibrated with recent in situ high-P, T diffraction data is crucial to our ability to accurately model the spinel-garnet transition in Earth's upper mantle. For example, we recently calibrated Cr-Al exchange equilibria for garnet and spinel. When this new calibration is used with the current MELTS model, a region of garnet-spinel coexistence in lherzolites is predicted with width in pressure comparable to experimental constraints. The transition occurs, however, at the unexpectedly low pressure of ~1.7 GPa. The improved model of spinel molar volume presented here, along with a new garnet molar volume model in the system FeO-MgO-CaO-Fe2O3-Cr2O3-Al2O3-TiO2-Na2O-SiO2 currently being calibrated, will enable coupled recalibration of the garnet and pyroxene models to match both the absolute pressure and width of this key transition in mantle lithology.

  9. The shock Hugoniot of the intermetallic alloy Ti-46.5Al-2Nb-2Cr

    SciTech Connect

    Millett, Jeremy; Gray, George T. Rusty III; Bourne, Neil

    2000-09-15

    Plate impact experiments were conducted on a {gamma}-titanium aluminide (TiAl) based ordered intermetallic alloy. Stress measurements were recorded using manganin stress gauges supported on the back of TiAl targets using polymethylmethacrylate windows. The Hugoniot in stress-particle velocity space for this TiAl alloy was deduced using impedance matching techniques. The results in this study are compared to the known Hugoniot data of the common alpha-beta engineering Ti-based alloy Ti-6Al-4V. The results of the current study on the intermetallic alloy TiAl support that TiAl possesses a significantly higher stress for a given particle velocity than the two-phase Ti-6Al-4V alloy. (c) 2000 American Institute of Physics.

  10. Comparative study of the absorption spectrum of Li 2CaSiO 4:Cr 4+: First-principles fully relativistic and crystal field calculations

    NASA Astrophysics Data System (ADS)

    Brik, M. G.; Ogasawara, K.

    2007-11-01

    Systematic analysis of the energy level scheme and ground state absorption of the Cr4+ ion in Li2CaSiO4 crystal was performed using the exchange charge model of the crystal field [B.Z. Malkin, in: A.A. Kaplyanskii, B.M. Macfarlane (Eds.), Spectroscopy of Solids Containing Rare-earth Ions, North-Holland, Amsterdam, 1987, pp. 33-50] and recently developed first-principles approach to the analysis of the absorption spectra of impurity ions in crystals based on the discrete variational multielectron (DVME) method [K. Ogasawara, T. Iwata, Y. Koyama, T. Ishii, I. Tanaka, H. Adachi, Phys. Rev. B 64 (2001) 115413]. Using the former method, the values of parameters of crystal field acting on the Cr4+ ion valence electrons were calculated using the Li2CaSiO4 crystal structure data. Energy levels of the Cr4+ ion obtained after diagonalizing the crystal field Hamiltonian are in good agreement with those obtained from the experimental spectra. The latter method is based on the numerical solution of the Dirac equation; therefore, all relativistic effects are automatically considered. As a result, energy level scheme of Cr4+ and its absorption spectra in both polarizations were calculated, assigned and compared with experimental data; energy of the lowest charge transfer transition was evaluated and compared with theoretical predictions for the CrO44- complex available in the literature. The main features of the experimental spectra shape are reproduced well by the calculations. By performing analysis of the molecular orbitals (MO) population, it was shown that the covalent effects play an important role in formation of the spectral properties of Cr4+ ion in the considered crystal.

  11. Effect of scanning speeds on microstructure and wear behavior of laser-processed NiCr-Cr3C2-MoS2-CeO2 on 38CrMoAl steel

    NASA Astrophysics Data System (ADS)

    Sun, Guifang; Tong, Zhaopeng; Fang, Xiaoyu; Liu, Xiaojun; Ni, Zhonghua; Zhang, Wei

    2016-03-01

    Self-lubricating wear-resistant NiCr-Cr3C2-MoS2-CeO2 layers were fabricated on 38CrMoAl extruder screws by laser processing. The effect of scanning speeds on microstructure, phases, microhardness, and wear behavior was investigated. The obtained results indicate that the laser-processed layers had fine and nonuniform microstructures with undissolved MoS2 particles distributed on the matrix. With an increase of the laser-scanning speeds, the microstructures changed from hypoeutectic to hypereutectic, volume fraction of martensite increased, microhardness increased, and thickness and friction coefficients of the layers decreased. Wear resistance of the optimized layer was increased by 29.76 times compared with that of the substrate. The undissolved MoS2 was separated from the matrix on loading. In addition to the grain-refining and solution-strengthening effects, oxide films formed on the surface of the layers shielded them and enhanced their wear resistance. The crack or fracture behavior of the laser-processed layers on loading was determined by its toughness, which also had an important effect on the wear behavior of the processed layers.

  12. TEMPORAL EVOLUTION OF SUB-NANOMETER COMPOSITIONAL PROFILES ACROSS THE GAMMA/GAMMA' INTERFACE IN A MODEL Ni-Al-Cr SUPERALLOY

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Noebe, Ronald D.; Seidman, David N.

    2005-01-01

    Early-stage phase separation in a Ni-5.2 Al-14.2 Cr at.% superalloy, isothermally decomposing at 873 K, is investigated with atom-probe tomography. Sub-nanometer scale compositional profiles across the gamma/gamma'(L12) interfaces demonstrate that both the gamma-matrix and the gamma'-precipitate compositions evolve with time. Observed chemical gradients of Al depletion and Cr enrichment adjacent to the gamma'-precipitates are transient, consistent with well-established model predictions for diffusion-limited growth, and mark the first detailed observation of this phenomenon. Furthermore, it is shown that Cr atoms are kinetically trapped in the growing precipitates.

  13. Compression, bend, and tension studies on forged Al67Ti25Cr8 and Al66Ti25Mn(g) L1(2) compounds

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Brown, S. A.; Whittenberger, J. D.

    1991-01-01

    Cast, homogenized, and isothermally forged aluminum-rich L1(2) compounds Al67Ti25Cr8 and Al66Ti25Mn(g) were tested in compression as a function of temperature and as a function of strain rate at elevated temperatures (1000 K and 1100 K). Three-point bend specimens were tested as a function of temperature in the range 300 K to 873 K. Strain gages glued on the tensile side of the ambient and 473 K specimens enabled direct strain measurements. A number of 'buttonhead' tensile specimens were electro-discharge machined, fine polished, and tested between ambient and 1073 K for yield strength and ductility as a function of temperature. Scanning electron microscope (SEM) examination of fracture surfaces from both the bend and tensile specimens revealed a gradual transition from transgranular cleavage to intergranular failure with increasing temperature.

  14. Influence of shock loading on the structure/property response of Ti-48Al-2Cr-2Nb and Ti-24Al-11Nb

    SciTech Connect

    Gray, R.T. III

    1994-02-01

    Intermetallics are receiving increasing attention for applications requiring high-leverage materials possessing potentially high pay-offs such as in gas-turbine engines. While the quasi-static deformation response of a broad range of intermetallics is receiving intense scientific and engineering study, increased utilization of intermetallics under dynamic loading requires an understanding of their high-rate/shock-wave behavior. In this paper the influence of shock loading on structure/property behavior of Ti-48Al-2Cr-2Nb and Ti-24Al-11Nb is presented. The reload constitutive response of both shock-loaded intermetallics supports the dynamic deformation of both intermetallics being controlled by a Peierls mechanism. Defect generation and storage in intermetallics is compared and contrasted to that typical to conventional disordered metals and alloys.

  15. Very Long Term Oxidation of Ti-48Al-2Cr-2Nb at 704 C In Air

    NASA Technical Reports Server (NTRS)

    Locci, I. E.; Brady, M. P.; MacKay, R. A.; Smith, J. W.

    1997-01-01

    Introduction Titanium aluminides are of great interest for intermediate-temperature (600 C - 850 C) aerospace and power generation applications because of their high specific properties. Replacement of conventional superalloys by titanium aluminides offers the potential of significant weight savings. Extensive development efforts over the past IO years have led to the identification of y (TiAl) + alpha(sub 2) (Ti3Al) alloys, such as the G.E. alloy Ti48Al-2Cr-2Nb (all composition in at. %), which offer a balance of room temperature mechanical properties and high-temperature strength retention. The two phase gamma + alpha(sub 2) class of titanium aluminides also offers superior oxidation and embrittlement resistance compared to the alpha(sub 2) and orthorhombic classes of titanium aluminides. However, environmental durability is still a major concern. Significant progress has recently been made in understanding the fundamental aspects of the oxidation behavior of binary gamma + alpha(sub 2) Ti-Al alloys. However, most of this work has concentrated on short term (less than 1000 hours), high temperature (900 C - 1000 C) exposures. Also little data are available in the literature regarding the oxidation behavior of the quaternary and higher order gamma + alpha(sub 2) engineering alloys. This is especially true for the very long-term, low temperature conditions likely to be experienced during engineering applications. The present work addresses this regime to fill this gap by characterizing the oxidation behavior of Ti48Al-2Cr-2Nb for periods up to 9000 h at 704 C in air.

  16. In-situ XAFS study for calcination process of Cr catalyst supported on γ-Al2O3 and SiO2

    NASA Astrophysics Data System (ADS)

    Watanabe, T.; Ikeda, K.; Katayama, M.; Inada, Y.

    2016-05-01

    The catalytic performance is largely affected by the oxidation state of supported Cr species, and its control changes the activity of Cr catalysts and the selectivity of products. In this study, the calcination process of the supported Cr catalysts on γ-Al2O3 and SiO2 was investigated by in-situ XAFS spectroscopy. The hydrate species was first supported by the impregnation method and was converted to CrO3 via Cr2O3 during the calcination process on both supporting materials. It was found that the temperature to complete the oxidation from Cr2O3 to CrO3 on SiO2 was higher than that on γ-Al2O3. The similarity of the interatomic distance between the surface oxygen atoms of the intermediate Cr2O3 species to that of SiO2 contributes to the stabilization of Cr2O3 on SiO2 during the calcination process.

  17. The - interaction: A study of early stages of phase separation in a Fe-20%Cr-6%Al-0.5%Ti alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Russell, Kaye F; Chao, J.; Lopez, F

    2011-01-01

    The temporal evolution of the microstructure resulting from phase separation into Fe-rich ({alpha}), Cr-rich ({alpha}{prime}), and Fe(Ti,Al) ({beta}{prime}) phases of a Fe-20Cr-6Al-0.5Ti alloy has been analyzed by thermoelectric power measurements (TEP). The early stages of decomposition and the evolution of the three-dimensional microstructure have been analyzed by atom probe tomography (APT). The roles of Cr, Al, and Ti during the decomposition process have been investigated in terms of solute partitioning between the phases. Analysis of proximity histograms revealed that significant Al and Ti partitioning occurs, which is consistent with theoretical calculations. The results indicate that as the {alpha}-{alpha}{prime} phase separation proceeds, Al and Ti are rejected into the {alpha} phase, which causes the {beta}{prime} phase to nucleate on the surface of the {alpha}{prime} phase.

  18. Tululite, Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36: a new Ca zincate-aluminate from combustion metamorphic marbles, central Jordan

    NASA Astrophysics Data System (ADS)

    Khoury, Hani N.; Sokol, Ella V.; Kokh, Svetlana N.; Seryotkin, Yurii V.; Nigmatulina, Elena N.; Goryainov, Sergei V.; Belogub, Elena V.; Clark, Ian D.

    2016-02-01

    Tululite (Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36 (the hypothetical end-member formula Ca14{Fe3+O6}[SiO4][Zn5Al9]O26) (IMA2014-065) is a new natural Ca zincate-aluminate, identified in medium-temperature (800-850 °C) combustion metamorphic (CM) spurrite-fluorellestadite marbles from central Jordan. The type locality (Tulul Al Hammam area) is situated in the northern part of the Siwaqa complex, the largest area of the "Mottled Zone" Formation in the Dead Sea region. The marbles originated from bitumen-rich chalky marine sediments of the Maastrichtian-Paleogene Muwaqqar Chalk Marl Formation, which have low clay content (and, consequently, low Al) and high Zn, Cd, and U enrichments. The bulk CM rocks derived from the low-Al protolith have unusually high (Zn + Cd)/Al ratios ( 0.2) and, as a result, a mineralogy with negligibly small percentages of Ca aluminates having low Ca:Al molar ratios (minerals of mayenite supergroup, Ca:Al = 6:7) common to most of calcareous CM rocks in the Mottled Zone. Instead, the mineral assemblage of the Zn-rich marbles contains tululite, with high Ca:Al = 2.55 molar ratios and Zn substituting for a large portion of Al (Zn:Al = 1.1). Tululite occurs in thin clusters as irregular grains with indented outlines (20-100 μm in size), having typical open-work textures associated with rock-forming calcite, fluorellestadite, spurrite, and accessory Zn-rich periclase, lime-monteponite solid solutions, calcium uranates, and zincite. Marbles also bear brownmillerite, dorrite, fluormayenite, high-fluorine Ca aluminate, and lakargiite. Secondary phases are brucite, gel-like calcium silicate hydrates and calcium silicate aluminate hydrates, including Zn- and U-bearing and Cd-rich compounds, Si-bearing hydrated compounds after calcium uranates, and basic Cd chlorides. The empirical formula of the holotype tululite (a mean of 32 analyses) is (Ca13.29Cd0.75)Σ14.04(Al5.46Zn5.20Fe3+ 2.23Si0.95Mn3+ 1.01Mg0.78P0.41)Σ16.04O36. Tululite is cubic, space

  19. Oxidation behavior of Mn and Mo alloyed Fe-16Ni-(5-8)Cr-3. 2Si-1. 0Al

    SciTech Connect

    Rawers, J.C.; Oh, J.M.; Dunning, J. )

    1990-02-01

    Oxidation tests were conducted on a master alloy, Fe-16Ni-(5-8)Cr-3Si-1Al, to which (0-4) wt/o pct Mn and/or Mo were added. Tests were conducted at temperatures ranging from 1,073-1,273 K for times up to 1,000 hr. Additions of Mn resulted in formation of a dual oxide structure and decreased oxidation protection. Addition of Mo significantly improved oxidation protection by formation of an intermetallic Fe(Mo)Si precipitate that eventually formed a protective SiO{sub 2} oxide sublayer. The oxidation protection was related to the alloy components and concentration.

  20. Atomic disorder and the magnetic, electrical, and optical properties of a Co{sub 2}CrAl Heusler alloy

    SciTech Connect

    Svyazhin, A. D. Shreder, E. I.; Voronin, V. I.; Berger, I. F.; Danilov, S. E.

    2013-03-15

    Two Co{sub 2}CrAl alloy samples subjected to different heat treatment regimes are studied. An exact distribution of atoms over the sublattices in the samples is determined by X-ray diffraction and neutron diffraction methods. These data are used to perform ab initio density of states calculations and to calculate the magnetic moments of the samples in a coherent potential approximation. The calculated magnetic moments are compared to the experimental values. The effect of atomic ordering on the electronic structure near the Fermi level is analyzed using optical methods. The possible causes of the detected temperature dependence of the electrical resistivity, unusual for metallic alloys, are discussed.

  1. Effects of a Tantalum Addition on the Morphological and Compositional Evolutions of a Model Ni-AL-Cr Superalloy

    NASA Technical Reports Server (NTRS)

    Booth-Morrison, Christopher; Seidman, David N.; Noebe, Ronald D.

    2008-01-01

    The effects of a 2.0 at.% addition of Ta to a model Ni-Al-Cr superalloy aged at 1073 K are assessed using scanning electron microscopy and atom-probe tomography. The addition of Ta results in appreciable strengthening, and the morphology is found to evolve from a bimodal distribution of spheroidal precipitates, to cuboidal precipitates aligned along the elastically soft <001>-type directions. Tantalum is observed to partition preferentially to the gamma -precipitate phase and decreases the mobility of Ni in the gamma- matrix sufficiently to cause an accumulation of Ni on the gamma-matrix side of the gamma -precipitate/gamma-matrix heterophase interface.

  2. Tensile deformation damage in SiC reinforced Ti-15V-3Cr-3Al-3Sn

    NASA Technical Reports Server (NTRS)

    Lerch, Bradley A.; Saltsman, James F.

    1991-01-01

    The damage mechanisms of a laminated, continuous SiC fiber reinforced Ti-15V-3Cr-3Al-3Sn (Ti-15-3) composite were investigated. Specimens consisting of unidirectional as well as cross-ply laminates were pulled in tension to failure at room temperature and 427 C and subsequently examined metallographically. Selected specimens were interrupted at various strain increments and examined to document the development of damage. When possible, a micromechanical stress analysis was performed to aid in the explanation of the observed damage. The analyses provide average constituent microstresses and laminate stresses and strains. It was found that the damage states were dependent upon the fiber architecture.

  3. The role of formation of continues thermally grown oxide layer on the nanostructured NiCrAlY bond coat during thermal exposure in air

    NASA Astrophysics Data System (ADS)

    Daroonparvar, Mohammadreza; Hussain, Mohammad Sakhawat; Yajid, Muhammad Azizi Mat

    2012-11-01

    In recent years, the life expectancy of thermal barrier coatings is expected to be improved by applying the nanostructured NiCrAlY bond coat. The present paper reviews the main technique used in the synthesis of nano-crystalline NiCrAlY powders using a planetary ball mill and investigates the microstructural evolution of thermally grown oxide (TGO) layer on the conventional and nanostructured atmospheric plasma sprayed (APS) NiCrAlY coatings in thermal barrier coating (TBC) systems during oxidation. Microstructural characterization showed that the growth of Ni(Cr,Al)2O4 (as spinel) and NiO on the surface of Al2O3 layer (as pure TGO) in nano TBC system was much lower compared to that of normal TBC system during thermal exposure at 1150 °C. These two oxides play a detrimental role in causing crack nucleation and growth, reducing the life of the TBC in air. This microstructure optimization of TGO layer is primarily associated with the formation of a continuous, dense, uniform Al2O3 layer (at first 24 h of isothermal oxidation at 1000 °C) over the nanostructured NiCrAlY coating.

  4. Effect of Powder Structure on Microstructure of the Oxide Scales Formed on Cold-Sprayed NiCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Li, Chang-Jiu; Yang, Guan-Jun; Li, Cheng-Xin

    Commercially available, gas-atomized NiCrAlY powder was milled in Ar atmosphere to prepare nanostructured powder. The NiCrAlY coatings in the conventional microstructure and the nanostructure were subsequently deposited by cold spraying using the as-atomized powder and milled powder. The influence of the powder structure on the microstructure of cold-sprayed coating was investigated. It was found that dense NiCrAlY coatings can be cold-sprayed using two powders. Isothermal oxidation was performed at 1000°C in air for up to 500 hours. The results showed that the growth rate of the oxide on the nanostructured NiCrAlY coating was almost comparable to that of the conventional NiCrAlY coating. A uniform Al2O3 layer was formed on the surface of the nanostructured coating surface. Moreover, a dual-subscale oxide was formed on conventional coating composing of an inner Al2O3 oxide and an external mixed oxide.

  5. Characterization of Oxide Scales Formed on High-Velocity Oxyfuel-Sprayed Ni-Co-Cr-Al-Y + ReTa Coatings

    NASA Astrophysics Data System (ADS)

    Lee, D. B.; Ko, J. H.; Yi, J. H.

    2005-09-01

    A high-velocity oxyfuel-sprayed 30 wt.% Ni-20 wt.% Co-30 wt.% Cr-10 wt.% Al-2 wt.% Y-4 wt.% Re-4 wt.% Ta coating was oxidized between 1000 and 1200 °C for up to 200 h in air, and the oxide scales were examined. The dense, sprayed coating consisted mainly of Cr3Ni2, Ni3Al, Ni3Ta, Ni, NiO, Al5Y3O12, and Cr2O3. Intermetallics and some oxides formed during spraying. During oxidation, mainly αAl2O3, along with some Al5Y3O12, CoAl2O4, CoCr2O4, Ta2O5, and Ta2O2.2 formed on the coating. The preferential oxidation of Al to form the Al-rich scales resulted in the formation of an Al-depleted region beneath the scales. Rhenium, being the most noble element, was distributed throughout the oxide scale and the coating, without forming any independent oxides.

  6. Mechanical, tribological, and electrochemical behavior of Cr 1- xAl xN coatings deposited by r.f. reactive magnetron co-sputtering method

    NASA Astrophysics Data System (ADS)

    Sanchéz, J. E.; Sanchéz, O. M.; Ipaz, L.; Aperador, W.; Caicedo, J. C.; Amaya, C.; Landaverde, M. A. Hernández; Beltran, F. Espinoza; Muñoz-Saldaña, J.; Zambrano, G.

    2010-02-01

    Chromium aluminum nitride (Cr 1- xAl xN) coatings were deposited onto AISI H13 steel and silicon substrates by r.f. reactive magnetron co-sputtering in (Ar/N 2) gas mixture from chromium and aluminum targets. Properties of deposited Cr 1- xAl xN coatings such as compositional, structural, morphological, electrochemical, mechanical and tribological, were investigated as functions of aluminum content. X-ray diffraction patterns of Cr 1- xAl xN coatings with different atomic concentrations of aluminum (0.51 < x < 0.69) showed the presence and evolution of (1 1 1), (2 0 0), and (1 0 2) crystallographic orientations associated to the Cr 1- xAl xN cubic and w-AlN phases, respectively. The rate of corrosion of the steel coated with Cr 1- xAl xN varied with the applied power; however, always being clearly lower when compared to the uncoated substrate. The behavior of the protective effect of the Cr 1- xAl xN coatings is based on the substitution of Cr for Al, when the power applied to the aluminum target increases. The mechanical properties were also sensitive to the power applied, leading to a maximum in hardness and a reduced elastic modulus of 30 and 303 GPa at 350 W and a monotonic decrease to 11 and 212 GPa at 450 W, respectively. Finally, the friction coefficient measured by pin-on disk revealed values between 0.45 and 0.70 in humid atmosphere.

  7. Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls MNi(CO)3- (M = Mg, Ca, Al)

    NASA Astrophysics Data System (ADS)

    Xie, Hua; Zou, Jinghan; Yuan, Qinqin; Fan, Hongjun; Tang, Zichao; Jiang, Ling

    2016-03-01

    The heteronuclear metal carbonyl anions MNi(CO)3- (M = Mg, Ca, Al) have been investigated using photoelectron velocity-map imaging spectroscopy. Electron affinities of neutral MNi(CO)3 (M = Mg, Ca, Al) are measured from the photoelectron spectra to be 1.064 ± 0.063, 1.050 ± 0.064, and 1.541 ± 0.040 eV, respectively. The C-O stretching mode in these three clusters is observed and the vibrational frequency is determined to be 2049, 2000, and 2041 cm-1 for MgNi(CO)3, CaNi(CO)3, and AlNi(CO)3, respectively. Density functional theory calculations are carried out to elucidate the geometric and electronic structures and to aid the experimental assignments. It has been found that three terminal carbonyls are preferentially bonded to the nickel atom in these heterobinuclear nickel carbonyls MNi(CO)3-1/0, resulting in the formation of the Ni(CO)3 motif. Ni remains the 18-electron configuration for MgNi(CO)3 and CaNi(CO)3 neutrals, but not for AlNi(CO)3. This is different from the homobinuclear nickel carbonyl Ni-Ni(CO)3 with the involvement of three bridging ligands. Present findings would be helpful for understanding CO adsorption on alloy surfaces.

  8. Temperature-dependent phase-specific deformation mechanisms in a directionally solidified NiAl-Cr(Mo) lamellar composite

    SciTech Connect

    Yu, Dunji; An, Ke; Chen, Xu; Bei, Hongbin

    2015-10-09

    Phase-specific thermal expansion and mechanical deformation behaviors of a directionally solidified NiAl–Cr(Mo) lamellar in situ composite were investigated by using real-time in situ neutron diffraction during compression at elevated temperatures up to 800 °C. Tensile and compressive thermal residual stresses were found to exist in the NiAl phase and Crss (solid solution) phase, respectively. Then, based on the evolution of lattice spacings and phase stresses, the phase-specific deformation behavior was analyzed qualitatively and quantitatively. Moreover, estimates of phase stresses were derived by Hooke's law on the basis of a simple method for the determination of stress-free lattice spacing in in situ composites. During compressive loading, the NiAl phase yields earlier than the Crss phase. The Crss phase carries much higher stress than the NiAl phase, and displays consistent strain hardening at all temperatures. The NiAl phase exhibits strain hardening at relatively low temperatures and softening at high temperatures. During unloading, the NiAl phase yields in tension whereas the Crss phase unloads elastically. Additionally, post-test microstructural observations show phase-through cracks at room temperature, micro cracks along phase interfaces at 600 °C and intact lamellae kinks at 800 °C, which is due to the increasing deformability of both phases as temperature rises.

  9. Temperature-dependent phase-specific deformation mechanisms in a directionally solidified NiAl-Cr(Mo) lamellar composite

    DOE PAGES

    Yu, Dunji; An, Ke; Chen, Xu; Bei, Hongbin

    2015-10-09

    Phase-specific thermal expansion and mechanical deformation behaviors of a directionally solidified NiAl–Cr(Mo) lamellar in situ composite were investigated by using real-time in situ neutron diffraction during compression at elevated temperatures up to 800 °C. Tensile and compressive thermal residual stresses were found to exist in the NiAl phase and Crss (solid solution) phase, respectively. Then, based on the evolution of lattice spacings and phase stresses, the phase-specific deformation behavior was analyzed qualitatively and quantitatively. Moreover, estimates of phase stresses were derived by Hooke's law on the basis of a simple method for the determination of stress-free lattice spacing in inmore » situ composites. During compressive loading, the NiAl phase yields earlier than the Crss phase. The Crss phase carries much higher stress than the NiAl phase, and displays consistent strain hardening at all temperatures. The NiAl phase exhibits strain hardening at relatively low temperatures and softening at high temperatures. During unloading, the NiAl phase yields in tension whereas the Crss phase unloads elastically. Additionally, post-test microstructural observations show phase-through cracks at room temperature, micro cracks along phase interfaces at 600 °C and intact lamellae kinks at 800 °C, which is due to the increasing deformability of both phases as temperature rises.« less

  10. Positron annihilation studies of the Al-Ca-Zn superplastic alloy: thermal and thermomechanical contribution

    SciTech Connect

    Ayciriex, M.D. ); Romero, R.; Somoza, A. ); Silvetti, S.P.; Villagra, O. )

    1993-06-15

    Positron annihilation spectroscopy (PAS) is an established method for the study of electronic structure and defect properties in metals and alloys. The application of this technique to the study of positron trapping in grain boundaries and related phenomena, however, is relatively scarce. The physical basis for the application of PAS to the study of grain boundaries is the fact that grain boundaries are regions of low atomic density which result in attractive sites to the trap positions. The superplastic alloys are particularly suitable materials to be studied with PAS; they have a fine-grained structure, and therefore a high density of grain boundaries. Moreover, in the annealed condition, they have a low density of other types of defects capable of trapping positrons, such as dislocations. This type of polycrystalline material can undergo extremely high deformations (up to hundreds and thousands percent) in a certain temperature-strain rate range without macroscopic failure. This paper is part of a whole study of the thermal and thermomechanical effects on the positron lifetime parameters and their relation with microstructural changes and the phenomenon of structural superplasticity in a Al-Ca-Zn alloy.

  11. Experimentally Produced Spinel Rims on Ca-Al-Rich Inclusion Bulk Compositions

    NASA Technical Reports Server (NTRS)

    Paque, Julie M.; Le, L.; Lofgren, G. E.

    1998-01-01

    Most Ca-Al-rich inclusions (CAls) from Allende are surrounded by a series of mineralogically distinct rim layers. Proposed modes of formation for these layers include flash heating, evaporation, and condensation. The innermost of these rim layers is generally spinel (SP), in some cases intergrown with perovskite (PV), and commonly containing varying amounts of secondary iron increasing towards the edge of the CAI. The SP or SP+PV rim is not always contiguous with the other rim layers, indicating that it is probably the result of a separate event. We have produced continuous SP rims on synthetic analogs representing Type A/B1, average Type B, and Type B2 bulk compositions by reheating a solid glass experimental charge to subliquidus crystallization temperatures. This experimental result is consistent with the formation of chondrules; and CAIs by more than one sequence of heating and cooling. Previous work indicated that prior crystallization events produced observable effects in the texture and chemistry of the final run product. Information on the nature of the heating/cooling cycles experienced by CAls and chondrules is important in modeling the environment of their formation. Additional information is contained in the original extended abstract.

  12. Carbides in iron-rich Fe-Mn-Cr-Mo-Al-Si-C systems

    NASA Technical Reports Server (NTRS)

    Lemkey, F. D.; Gupta, H.; Nowotny, H.; Wayne, S. F.

    1984-01-01

    The optimization of high carbon iron-base superalloy properties with duplex microstructure gamma + M7C3 carbide requires analysis in the context of a seven-component system. Data are first provided here for the Fe-Mn-Cr-Mo-C quinary system, at 30 at. pct carbon. A characterization of competing carbides, according to a pseudoternary phase diagram at 35 wt pct iron, is made from isothermal sections. It is noted that while M7C3 and M3C carbides' occurrences are respectively favored at the Cr and Mn corners, the M2C carbide and molybdenum cementite are predominant with increasing amounts of Mo. Lattice parameters are reported for the various carbides.

  13. Discharge properties of Mg-Al-Mn-Ca and Mg-Al-Mn alloys as anode materials for primary magnesium-air batteries

    NASA Astrophysics Data System (ADS)

    Yuasa, Motohiro; Huang, Xinsheng; Suzuki, Kazutaka; Mabuchi, Mamoru; Chino, Yasumasa

    2015-11-01

    The discharge behaviors of rolled Mg-6 mass%Al-0.3 mass%Mn-2 mass%Ca (AMX602) and Mg-6 mass%Al-0.3 mass%Mn (AM60) alloys used as anodes for Magnesium-air batteries were investigated. The AMX602 alloy exhibited superior discharge properties compared to the AM60 alloy, especially at low current density. The discharge products of the AMX602 alloy were dense and thin, and many cracks were observed at all current densities. In addition, the discharge products were detached at some sites. These sites often corresponded to the positions of Al2Ca particles. The comparison of the discharge and corrosion tests indicated that the dense and thin discharge products of AMX602 were easily cracked by dissolution of the Mg matrix around Al2Ca particles, and the cracks promoted the penetration of the electrolyte into the discharge products, retaining the discharge activity. In contrast, concerning the AM60 alloy, thick discharge products were formed on the surface during discharge, and cracking of the discharge products hardly occurred, degrading the discharge properties. Localized and deeply corroded pits that could result from the detachment of metal pieces from the anode during discharge were partly observed in the AM60 alloy. It is suggested that these detached metal pieces are another reason for the low discharge properties of the AM60 alloy.

  14. Compositional Pathways and Capillary Effects during Early-stage Isothermal Precipitation in a Nondilute Ni-Al-Cr Alloy

    NASA Technical Reports Server (NTRS)

    Sudbrack, Chantal K.; Noebe, Ronald D.; Seidman, David N.

    2006-01-01

    For a Ni-5.2 Al-14.2 Cr at.% alloy with moderate solute supersaturations, the compositional pathways, as measured with atom-probe tomography, during early to later stage y'(LI2)-precipitation (R = 0.45-10 nm), aged at 873 K, are discussed in light of a multi-component coarsening model. Employing nondilute thermodynamics, detailed model analyses during quasistationary coarsening of the experimental data establish that the y/y' interfacial free-energy is 22- 23+/-7 mJ/sq m. Additionally, solute diffusivities are significantly slower than model estimates. Strong quantitative evidence indicates that an observed y'-supersaturation of Al results from the Gibbs-Thomson effect, providing the first experimental verification of this phenomenon. The Gibbs-Thomson relationship, for a ternary system, as well as differences in measured phase equilibria with CALPHAD assessments, are considered in great detail.

  15. Diamond growth on Fe-Cr-Al alloy by H{sub 2}-plasma enhanced graphite etching

    SciTech Connect

    Li, Y. S.; Hirose, A.

    2007-04-01

    Without intermediate layer and surface pretreatment, adherent diamond films with high initial nucleation density have been deposited on Fe-15Cr-5Al (wt. %) alloy substrate. The deposition was performed using microwave hydrogen plasma enhanced graphite etching in a wide temperature range from 370 to 740 degree sign C. The high nucleation density and growth rate of diamond are primarily attributed to the unique precursors used (hydrogen plasma etched graphite) and the chemical nature of the substrate. The improvement in diamond adhesion to steel alloys is ascribed to the important role played by Al, mitigation of the catalytic function of iron by suppressing the preferential formation of loose graphite intermediate phase on steel surface.

  16. Effect of Y2O3 content on the oxidation behavior of Fe-Cr-Al-based ODS alloys

    NASA Astrophysics Data System (ADS)

    Ul-Hamid, Anwar

    2003-02-01

    A study was conducted to investigate the cyclic oxidation behavior of two oxide dispersion strengthened (ODS) Fe-Cr-Al based alloys containing 0.17 wt.% and 0.7 wt.% Y2O3. The alloys were oxidized in air for 100 h at 1200°C based on a 24 h cycle period. X-ray diffraction (XRD) and analytical transmission electron microscopy (TEM) were used to characterize the structure, morphology, and composition of the oxide scales. Both alloys formed highly adherent and continuous layers of α-Al2O3 exhibiting a morphology indicative of inward scale growth. The role of Y2O3 was to promote adherence by segregating to the grain boundaries within the oxide. Concurrently, Y2O3 generated micro-porosity resulting in a scale of comparatively higher thickness in the alloy with 0.7 wt.% Y2O3.

  17. Development and Evaluation of Directionally-Solidified NiAl/(CR,MO)-Based Eutectic Alloys for Airfoil Applications

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Locci, I. E.; Whittenberger, J. D.

    2001-01-01

    The results of recent efforts to develop directionally-solidified alloys based on the Ni-33Al-31Cr-3Mo eutectic composition are discussed. These developmental efforts included studying the effects of macroalloying and growth rates on microstructure formation as well as the elevated temperature compressive and tensile properties of these alloys. These observations revealed that contrary to conventional opinion, the cellular microstructure was stronger and tougher than the planar eutectic microstructure due to a microstructural refinement of the cell size and interlamellar spacing. The high temperature strengths of these alloys are compared with those of commercial superalloys and advanced NiAl single crystals. The implications of this research on airfoil manufacturing and applications are discussed.

  18. A first-principles study of the tetragonal and hexagonal R 2Al (R = Cr, Zr, Nb, Hf, Ta) phases

    NASA Astrophysics Data System (ADS)

    Shang, Xiu; Shen, Jiang; Tian, Fuyang

    2016-10-01

    The crystal structures, elastic moduli, electronic structure, and phonon dispersion of the tetragonal R 2Al (R = Cr, Zr, Nb, Hf, Ta) intermetallic compounds are investigated by using the first-principles method. The space group number is 139 for tetragonal Cr2Al, 136 for tetragonal Nb2Al and Ta2Al, and the space group numbers are 140 and 194 for tetragonal and hexagonal Zr2Al and Hf2Al, respectively. The results of elastic constants and phonon dispersion indicate that the present intermetallic compounds are thermodynamically stable. The stability of hexagonal Zr2Al and Hf2Al is analyzed via the electronic density of state, compared to the tetragonal Zr2Al and Hf2Al compounds. For the R2Al intermetallic compounds, the less ductility and strong anisotropy are predicted. The more negative formation enthalpy and thermodynamic stability of R2Al (R = Nb, Zr, Hf) shed light on the Nb2Al, Zr2Al, Hf2Al phases found experimentally in refractory high entropy alloys.

  19. Microstructure and Fatigue Behavior of Friction Stir-welded Noncombustive Mg-9Al-Zn-Ca Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Li, Z. Y.; Nakata, K.; Feng, J. C.; Huang, Y. X.; Liao, J. S.

    2016-06-01

    Microstructure and fatigue behavior of friction stir-welded noncombustive Mg-9Al-Zn-Ca magnesium alloy were investigated. The as-received hot-extruded material consisted of equiaxed α-Mg grains with β-Mg17Al12 and Al2Ca compounds distributed along the grain boundaries. Friction stir welding produced much refined α-Mg grains accompanied by the dissolution of the eutectic β-Mg17Al12 phase, while Al2Ca phase was dispersed homogenously into the Mg matrix. Friction stir welding produced slightly increased hardness and tensile strength in the defect-free welds compared with the base material due to microstructural refinement and uniform distribution of intermetallic compounds. The load-controlled uniaxial tensile high-cycle fatigue tests indicated that fatigue strength of 90 MPa was obtained for the friction stir-welded joint with fatigue crack initiated basically near the specimen's surface and at the retreating side of the joint. Crack propagation was characterized by cleavage and fatigue striations.

  20. Constraints on Titanite Acitvity in the System CaTiSiO4O-CaAlSiO4F: Implications for Thermobarometry in Metamorphic Rocks

    NASA Astrophysics Data System (ADS)

    Tropper, P.; Manning, C. E.; Essene, E. J.

    2006-12-01

    Titanite is a common accessory mineral that could be used reliably in phase equilibrium calculations, if activity-composition relations in Al-F titanites were known. Troitzsch and Ellis (2001, CMP, 142, 543) and Tropper et al. (2002, JPet., 43, 1787) gave non-ideal mixing models along the join CaTiSiO4O- CaAlSiO4F. Tropper et al. (2002) derived a negative interaction parameter W, whereas Troitzsch and Ellis (2001) derived a regular model with both positive and negative W, but favored positive values. These differences strongly influence calculated CaTiSiO4O activity (attn). Although more experiments are needed, our result that γttn<1 at high T indicates a large degree of non-ideal behavior, even at >900°C, which in turn will affect thermobarometry. Comparing available activity models shows that at these T, attn is substantially underestimated by the fully ionic model used by Manning and Bohlen (1991, CMP, 109, 1), in which attn = XCaXTiXSi(XO)5. This model assumes independent mixing of Al for Ti and random mixing of F and O on all O sites. However, F substitutes only in one O site (O1; Oberti et al., 1991, EJM, 3, 777). A fully ionic model should therefore be recast as attn = XCaXTiXSiXO, where XO indicates the mole fraction of O on the (O1) site. The substitution of F on the O1 site is coupled with Al, so it is called the ideal coupled model. Unlike the regular model, the prefered ionic model departs strongly from ideality at ≤600°C, consistent with independent constraints. However, experimentally determined attn is approximated by an ideal molecular model (XTi) at ≥900°C, so this model is recommended for thermobarometry in high- T metamorphic rocks until more data are available. Recalculation of the P recorded by the three eclogites from Manning and Bohlen (1991) using the different activity models discussed here yields differences that may be as high as 2.0 GPa.

  1. Infrared study of the vibrational behavior of CrO 42- guest ions matrix-isolated in metal (II) sulfates (Me=Ca, Sr, Ba, Pb)

    NASA Astrophysics Data System (ADS)

    Stoilova, D.; Georgiev, M.; Marinova, D.

    2005-03-01

    Infrared spectra of matrix-isolated CrO 42- guest ions in host sulfate matrices - CaSO 4·2H 2O, SrSO 4, BaSO 4 and PbSO 4 are reported and discussed with respect to the Cr-O stretching and O-Cr-O bending modes. An adequate measure for the CrO 42- guest ion distortion is the site group splitting Δ νas and Δ νmax (the difference between the highest and the lowest wavenumbered components of the stretching and bending modes). When the smaller SO 42- ions are replaced by the larger CrO 42- ions the mean frequencies of the asymmetric stretching and bending modes ( ν and ν) as well as the frequencies of ν1 of the CrO 42- guest ions are shifted to higher wavenumbers as compared to those in the respective neat chromates due to the larger repulsion potential at the host lattice sites (smaller values of the unit-cell volumes of the neat sulfates than those of the neat chromates). The CrO 42- guest ions exhibit three bands corresponding to the ν3 modes as deduced from the site group analysis ( C2 site symmetry in CaSO 4·2H 2O and Cs site symmetry in SrSO 4, BaSO 4 and PbSO 4). However, the bending modes ν4 and ν2 of the CrO 42- guest ions in SrSO 4, BaSO 4 and PbSO 4 show an effectively higher local symmetry than the 'rigorous' crystallographic one (two bands for ν4 and one band for ν2 instead of a triplet and a doublet expected, respectively). Such different apparent site symmetries observed in various spectral regions may be attributed to the different influence of energetic and geometrical distortions of the polyatomic entities at particular site on various modes.

  2. Structure, microstructure and magnetic properties of Sr{sub 1-x}Ca{sub x}CrO{sub 3} (0{<=}x{<=}1)

    SciTech Connect

    Castillo-Martinez, E.; Duran, A.; Alario-Franco, M.A.

    2008-04-15

    The effect of the calcium concentration on the structural, microstructural and magnetic properties of Sr{sub (1-x)}Ca{sub x}CrO{sub 3} with 0{<=}x{<=}1 has been studied. The compounds were prepared using high pressure and high temperature synthesis. X-ray diffraction shows that the samples evolve from the cubic Pm-3m space group for x=0-0.2 to tetragonal I4/mcm for x=0.4-0.5, then to the orthorhombic Pbnm space group for x=0.6, 0.8 and 1.0. Electron diffraction and high-resolution transmission electron microscopy confirmed the respective cells for the end compositions: a{sub p}xa{sub p}xa{sub p} (Pm-3m) for SrCrO{sub 3}; and the {radical}(2)a{sub p}x{radical}(2)a{sub p}x2a{sub p} (Pbnm) for CaCrO{sub 3}. For intermediate compositions some extra spots appear in the electron diffraction patterns while the electron micrographs indicate the presence of microdomains. Magnetic measurements show Curie-Weiss behaviour at high temperature for all the samples. A sharp antiferromagnetic (AFM) transition at about 91.5 K appears for x=0.8-1 together with a weak ferromagnetic ordering below T{sub N}. - Graphical abstract: HRTEM image of a crystal of Sr{sub 0.5}Ca{sub 0.5}CrO{sub 3} showing a random distribution of 2a{sub p}{approx}7.6 A all along the crystal that lacks long range order. Inset shows the FFT of the area of the image and of a tenth of that area showing the influence of the coherence length.

  3. Laser surface alloying of FeCoCrAlNi high-entropy alloy on 304 stainless steel to enhance corrosion and cavitation erosion resistance

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Wu, C. L.; Zhang, C. H.; Guan, M.; Tan, J. Z.

    2016-10-01

    FeCoCrAlNi high-entropy alloy coating was synthesized with premixed high-purity Co, Cr, Al and Ni powders on 304 stainless steel by laser surface alloying, aiming at improving corrosion and cavitation erosion resistance. Phase constituents, microstructure and microhardness were investigated using XRD, SEM, and microhardness tester, respectively. The cavitation erosion and electrochemical corrosion behavior of FeCoCrAlNi coating in 3.5% NaCl solution were also evaluated using an ultrasonic vibrator and potentiodynamic polarization measurement. Experimental results showed that with appropriate laser processing parameters, FeCoCrAlNi coating with good metallurgical bonding to the substrate could be achieved. FeCoCrAlNi coating was composed of a single BCC solid solution. The formation of simple solid solutions in HEAs was the combined effect of mixing entropy (ΔSmix), mixing enthalpy (ΔHmix), atom-size difference (δ) and valence electron concentration (VEC), and the effect of ΔSmix was much larger than that of the other factors. The microhardness of the FeCoCrAlNi coating was ~3 times that of the 304 stainless steel. Both the corrosion and cavitation erosion resistance of the coating were improved. The cavitation erosion resistance for FeCoCrAlNi HEA coating was ~7.6 times that of 304 stainless steel. The corrosion resistance was also improved as reflected by a reduction in the current density of one order of magnitude as compared with 304 stainless steel.

  4. Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Ma, Shengguo; Gao, Michael C.; Zhang, Chuan; Zhang, Teng; Yang, Huijun; Wang, Zhihua; Qiao, Junwei

    2016-07-01

    In order to understand the environmental effect on the mechanical behavior of high-entropy alloys, the tribological properties of AlCrCuFeNi2 are studied systematically in dry, simulated rainwater, and deionized water conditions against the Si3N4 ceramic ball at a series of different normal loads. The present study shows that both the friction and wear rate in simulated rainwater are the lowest. The simulated rainwater plays a significant role in the tribological behavior with the effect of forming passive film, lubricating, cooling, cleaning, and corrosion. The wear mechanism in simulated rainwater is mainly adhesive wear accompanied by abrasive wear as well as corrosive wear. In contrast, those in dry condition and deionized water are abrasive wear, adhesive wear, and surface plastic deformation. Oxidation contributes to the wear behavior in dry condition but is prevented in liquid condition. In addition, the phase diagram of Al x CrCuFeNi2 is predicted using CALPHAD modeling, which is in good agreement with the literature report and the present study.

  5. CrAlN coating to enhance the power loss and magnetostriction in grain oriented electrical steel

    NASA Astrophysics Data System (ADS)

    Goel, Vishu; Anderson, Philip; Hall, Jeremy; Robinson, Fiona; Bohm, Siva

    2016-05-01

    Grain oriented electrical steels (GOES) are coated with aluminium orthophosphate on top of a forsterite (Mg2SiO4) layer to provide stress and insulation resistance to reduce the power loss and magnetostriction. In this work Chromium Aluminium Nitride (CrAlN) was coated on GOES samples with electron beam physical vapour deposition and was tested in the single strip and magnetostriction tester to measure the power loss and magnetostriction before and after coating. Power loss was reduced by 2% after coating and 6 % post annealing at 800 °C. For applied compressive stress of 6 MPa, the magnetostrictive strain was zero with the CrAlN coating as compared to 22 and 24 μɛ for fully finished GOES and GOES without phosphate coating. The thickness of the coating was found to be 1.9 ± 0.2 μm estimated with Glow Discharge Optical Emission Spectroscopy (GDOES). The magnetic domain imaging showed domain narrowing after coating. The reduction in power loss and magnetostriction was due to the large residual compressive stress and Young's modulus (270 GPa) of the coating.

  6. High temperature tensile and creep behaviour of low pressure plasma-sprayed Ni-Co-Cr-Al-Y coating alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1986-01-01

    The high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical Ni-Co-Cr-Al-Y alloy has been studied. From room temperature to 800 K, the Ni-Co-Cr-Al-Y alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 + or - 20 kJ/mol, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 + or - 20 kJ/mol.

  7. A study of early corrosion behaviors of FeCrAl alloys in liquid lead-bismuth eutectic environments

    NASA Astrophysics Data System (ADS)

    Lim, Jun; Nam, Hyo On; Hwang, Il Soon; Kim, Ji Hyun

    2010-12-01

    Lead and lead-bismuth eutectic (LBE) alloy have been increasingly receiving attention as heavy liquid metal coolants (HLMC) for future nuclear energy systems. The compatibility of structural materials and components with lead-bismuth eutectic liquid at high temperature is one of key issues for the commercialization of lead fast reactors. In the present study, the corrosion behaviors of iron-based alumina-forming alloys (Kanthal-AF®, PM2000, MA956) were investigated by exposing to stagnant LBE environments at 500 °C and 550 °C for up to 500 h. After exposures, the thickness and chemistry of the oxide layer on the specimens were analyzed by scanning electron microscopy, scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. As a result, the oxide characteristics and the corrosion resistance were compared. In this study, it was shown that the corrosion resistance of FeCrAl ODS steels (PM2000, MA956) are superior to that of FeCrAl ferritic steel (Kanthal-AF®) in higher temperature LBE.

  8. Deformation behavior of laser welds in high temperature oxidation resistant Fe-Cr-Al alloys for fuel cladding applications

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Gussev, Maxim N.; Yamamoto, Yukinori; Snead, Lance L.

    2014-11-01

    Ferritic-structured Fe-Cr-Al alloys are being developed and show promise as oxidation resistant accident tolerant light water reactor fuel cladding. This study focuses on investigating the weldability and post-weld mechanical behavior of three model alloys in a range of Fe-(13-17.5)Cr-(3-4.4)Al (wt.%) with a minor addition of yttrium using modern laser-welding techniques. A detailed study on the mechanical performance of bead-on-plate welds using sub-sized, flat dog-bone tensile specimens and digital image correlation (DIC) has been carried out to determine the performance of welds as a function of alloy composition. Results indicated a reduction in the yield strength within the fusion zone compared to the base metal. Yield strength reduction was found to be primarily constrained to the fusion zone due to grain coarsening with a less severe reduction in the heat affected zone. For all proposed alloys, laser welding resulted in a defect free weld devoid of cracking or inclusions.

  9. The Flow Behavior and Microstructural Evolution of Ti-5Al-5Mo-5V-3Cr during Subtransus Isothermal Forging

    NASA Astrophysics Data System (ADS)

    Jones, N. G.; Dashwood, R. J.; Dye, D.; Jackson, M.

    2009-08-01

    High-strength metastable β alloys, for example, Ti-5Al-5Mo-5V-3Cr, have replaced steel as the material of choice for large components, such as the main truck beam on the latest generation of airframes. The production of these components is carried out by hot near-net-shape forging, during which process variable control is essential to achieve the desired microstructural condition and subsequent mechanical properties. The flow behavior and microstructural evolution during subtransus isothermal forging of Ti-5Al-5Mo-5V-3Cr has been investigated for two different starting microstructures and analysis has incorporated previously published results. The flow behavior, irrespective of initial microstructural condition, is found to be very similar at strains ≥0.35. It is thought that this is due to a common microstructural state being reached, where dynamic recovery of the β phase is the dominating deformation mechanism. At strains <0.35, the flow behavior is believed to be dominated by the morphology and volume fraction of the α phase. Small globular α particles are thought to have little effect on the flow behavior, while the observed flow softening is directly linked to the fragmentation of acicular α precipitates.

  10. Autogenous gas tungsten arc weldability of cast alloy Ti-48Al-2Cr-2Nb (Atomic percent) versus extruded alloy Ti-46Al-2Cr-2Nb-0.9Mo (Atomic percent)

    NASA Astrophysics Data System (ADS)

    Bharani, D. J.; Acoff, V. L.

    1998-03-01

    This study examines procedures for consistently producing sound (crack and void free) welds using the autogenous (without filler metal) gas tungsten arc (GTA) welding process. Cast alloy Ti-48Al-2Cr-2Nb (at. pct) and extruded alloy Ti-46Al-2Cr-2Nb-0.9Mo (at. pct) have been examined to determine if sound welds can be produced using autogenous GTA welding without any preheat. Experimentation consisted of GTA spot welding samples of gamma titanium aluminide at weld current levels of 45, 55, 65, and 75 A for a duration of 3 seconds. For the cast alloy, current levels of 45, 55, and 65 A for 3 seconds produced similar fusion zone microstructures, which consisted of a dendritic solidification structure. The fusion zone microstructure of the 75A for 3 seconds current level differed significantly from the lower current levels. It also consisted of a dendritic solidification structure; however, the morphology was quite different. For the extruded alloy, current levels of 45 and 55 A for 3 seconds produced fusion zone microstructures similar to the lower current level samples of the cast γ-TiAl, which consisted of a dendritic solidification structure. The fusion zone microstructures of the 65 and 75 A samples were similar to each other, but they had a dendritic solidification structure of a different morphology than that of the 45 and 55 A samples. For both alloys at all current levels, microhardness profiles showed an increase in hardness from the base metal to the fusion zone. There were no significant differences in the average fusion zone hardness as a function of increasing current level. However, nanoindentation testing did show that certain phases and microconstituents in the fusion zone did have significant variations in hardness in relation to the enrichment and depletion of chromium.

  11. Antiferromagnetism in CaAl2Si2-type CaMn2As2 and SrMn2As2 single crystals

    NASA Astrophysics Data System (ADS)

    Sangeetha, N. S.; Pandey, Abhishek; Benson, Zackery A.; Johnston, D. C.

    Magnetic susceptibility versus temperature χ (T) measurements of CaMn2As2 and SrMn2As2 crystals show clear antiferromagnetic (AFM) transitions at TN ~ 65 K and 120 K,1 respectively. The anisotropic behaviors in χ (T <=TN) suggest that both compounds are noncollinear antiferromagnets which may result either from an intrinsic noncollinear structure or from multiple collinear AFM domains that are not aligned collinearly.2 The χ (T) data at T >TN reveal that both compounds exhibit strong short-range AFM ordering, evidently associated with quasi-two-dimensional spin lattices. The electrical resistivities show insulating ground states with activation energies of ~ 63 meV in CaMn2As2 and 44 meV in SrMn2As2 . The experimental results thus reveal that both (Ca , Sr) Mn2As2 materials are AFM insulators at low temperatures and in analogy with the high Tc cuprates, may be potential parent compounds for CaAl2Si2-type superconductors. Work was supported by the USDOE under Contract No. DE-AC02-07CH11358.

  12. Effects of v- or Cr-DOPING on Phase Formation, Electric Properties and Superconductivity of the 3212-TYPE Phase Pb2Sr2(Ca0.5Y0.5)Cu3Oz

    NASA Astrophysics Data System (ADS)

    Chen, Z. Y.; Qian, Y. T.; Luo, H. M.; Qu, B.; Sheng, Z. Z.; Wang, L. M.

    The effects of vanadium or chromium on the formation, electric properties and superconductivity of Pb-3212 phase (Pb2Cu)Sr2(Ca0.5Y0.5)Cu2Oz are studied. The sites of V or Cr in PbO-CuOδ-PbO structure unit for Pb-3212 phase is also investigated. Compared with the effects of Cr-doping, V can totally substitute Ca to form a new compound Pb2Sr2(V0.5Y0.5)Cu3Oz, and V has relatively greater substitution amount in (Pb2-xMx)Sr2(Ca0.5Y0.5)Cu3Oz (M = Cr or V). Moreover, the resistivity and superconductivity of the above samples decrease with increasing V or Cr amount. Among them, the effects of V is greater, and its location (in Pb or Ca site) also affects greatly the superconductivity.

  13. Microvascular response of striated muscle to common arthroplasty-alloys: A comparative in vivo study with CoCrMo, Ti-6Al-4V, and Ti-6Al-7Nb.

    PubMed

    Kraft, Clayton N; Burian, Björn; Diedrich, Oliver; Gessmann, Jan; Wimmer, Markus A; Pennekamp, Peter H

    2005-10-01

    The impairment of skeletal muscle microcirculation by a biomaterial may have profound consequences. Due to excellent physical and corrosion characteristics, CoCrMo-, Ti-6Al-4V-, and Ti-6Al-7Nb-alloys are commonly used in orthopedic surgery. Yet concern has been raised with regard to the implications of inevitable corrosion product of these metals on the surrounding biologic environment, particularly in the case of CoCrMo. We, therefore, studied in vivo nutritive perfusion and leukocytic response of striated muscle to these alloys, thereby drawing conclusions on their inflammatory potential. In 28 hamsters, utilizing the dorsal skinfold chamber preparation and intravital microscopy, we could demonstrate that the implant material CoCrMo has a marked impact on local microvascular parameters. While the Ti-alloys Ti-6Al-4V and Ti-6Al-7Nb induced only a transient and moderate inflammatory response, the implantation of a CoCrMo sample led to a distinct and persistent activation of leukocytes combined with disruption of the microvascular endothelial integrity and marked leukocyte extravasation. Animals with Ti-alloys showed a clear tendency of recuperation, while in all but one CoCrMo-treated animals, a breakdown of microcirculation prior to the scheduled end of the experiment was observed. Overall, the alloy Ti-6Al-7Nb was tolerated slightly better than Ti-6Al-4V under the chosen test conditions, though this discrepancy was not statistically significant. Conclusively, the commonly used biomaterials Ti-6Al-7Nb and Ti-6Al-4V induce a considerably lower inflammatory response in the skeletal muscle microvascular system, compared to a CoCrMo-alloy. With a minimum of adverse host reaction, our results indicate that for this particular model Ti-alloys are better tolerated than CoCrMo implant materials.

  14. Electrochemical Corrosion of HVOF-Sprayed NiCoCrAlY Coatings in CO2-Saturated Brine

    NASA Astrophysics Data System (ADS)

    Ruiz-Luna, H.; Porcayo-Calderon, J.; Alvarado-Orozco, J. M.; García-Herrera, J. E.; Martinez-Gomez, L.; Trápaga-Martínez, L. G.; Muñoz-Saldaña, J.

    2016-08-01

    The effect of pre-oxidation treatment and surface preparation of optimized NiCoCrAlY coatings deposited by high-velocity oxygen fuel (HVOF) spraying and exposed to a low-temperature corrosive environment is reported herein. Coatings with two surface finish conditions (as-sprayed and ground) were heat treated under two different oxygen partial pressures (air and argon). The electrochemical corrosion behavior was evaluated in CO2-saturated brine via potentiodynamic polarization, polarization resistance, and electrochemical impedance measurements. The results show that the grinding process and pre-oxidation treatment in argon enhanced growth and formation of α-Al2O3 scale. The potentiodynamic polarization results show that both pre-oxidation and surface treatment had a positive influence on the corrosion resistance of the coating. The reduction of the porosity and the formation of a dense, uniform, and adherent oxide scale through pre-oxidation treatment led to an increase of the corrosion resistance due to a decrease in active sites and blocking of diffusion of reactive species into the coating. However, according to the results, complete transformation from metastable alumina phases to α-Al2O3 in addition to formation and growth of dense α-Al2O3 is required to ensure full protection of the coating and base material over long periods.

  15. Electrochemical Corrosion of HVOF-Sprayed NiCoCrAlY Coatings in CO2-Saturated Brine

    NASA Astrophysics Data System (ADS)

    Ruiz-Luna, H.; Porcayo-Calderon, J.; Alvarado-Orozco, J. M.; García-Herrera, J. E.; Martinez-Gomez, L.; Trápaga-Martínez, L. G.; Muñoz-Saldaña, J.

    2016-10-01

    The effect of pre-oxidation treatment and surface preparation of optimized NiCoCrAlY coatings deposited by high-velocity oxygen fuel (HVOF) spraying and exposed to a low-temperature corrosive environment is reported herein. Coatings with two surface finish conditions (as-sprayed and ground) were heat treated under two different oxygen partial pressures (air and argon). The electrochemical corrosion behavior was evaluated in CO2-saturated brine via potentiodynamic polarization, polarization resistance, and electrochemical impedance measurements. The results show that the grinding process and pre-oxidation treatment in argon enhanced growth and formation of α-Al2O3 scale. The potentiodynamic polarization results show that both pre-oxidation and surface treatment had a positive influence on the corrosion resistance of the coating. The reduction of the porosity and the formation of a dense, uniform, and adherent oxide scale through pre-oxidation treatment led to an increase of the corrosion resistance due to a decrease in active sites and blocking of diffusion of reactive species into the coating. However, according to the results, complete transformation from metastable alumina phases to α-Al2O3 in addition to formation and growth of dense α-Al2O3 is required to ensure full protection of the coating and base material over long periods.

  16. Phase equilibria and elements partitioning in zirconolite-rich region of Ca-Zr-Ti-Al-Gd-Si-O system

    SciTech Connect

    Knyazev, O.A.; Stefanovsky, S.V.; Ioudintsev, S.V.; Nikonov, B.S.; Omelianenko, B.I.; Mokhov, A.V.; Yakushev, A.I.

    1997-12-31

    Zirconolite-rich ceramics were produced by the cold crucible melting technique in an air atmosphere, at 1550 {+-} 50 C and 1 atm. Four samples with overall composition (in wt.%): 4.9-14.3 CaO; 19.0-41.3 ZrO{sub 2}; 24.1-42.6 TiO{sub 2}; 1.3-11.3 Al{sub 2}O{sub 3}; 6.8-30.0 Gd{sub 2}O{sub 3}; and 1.1-8.5 SiO{sub 2} have been studied. Total phases in the ceramics consist of major zirconolite and minor rutile, perovskite, zirconia, aluminium titanate, and glass. The Gd{sub 2}O{sub 3} content in zirconolite reaches up to 31.4 wt.% corresponding to the formula: (Ca{sub 0.4},Gd{sub 0.7})Zr{sub 1.0}(Ti{sub 1.4},Al{sub 0.5})O{sub 7.0}. The data on the phase composition agree well with coupled Gd incorporation into the mineral structure: Ca(II) + Ti(IV) = Gd(III) + Al(III), and 2Gd(III) = Ca(II) + Zr(IV). The highest Gd contents observed in the other phases are 25.4% for zirconia, 12.6% in glass, 8.8% in perovskite, and 1.4% for rutile. The rest of the elements` distribution in the samples are analyzed.

  17. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-05-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe- x ( x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δ χ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe- x ( x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  18. Charge-compensation effect of Al on luminescence properties of M2(Si, Al)5N8:Ce3+ (M = Ca, Sr, Ba)

    NASA Astrophysics Data System (ADS)

    Kuramoto, Daiki; Horikawa, Takashi; Hanzawa, Hiromasa; Machida, Ken-ichi

    2013-09-01

    The charge-compensated materials, M2AlxSi5-xN8:Ce3+ (M = Ca, Sr, Ba), were synthesized from appropriate mixtures of MSi, MAlSi, (MSiHy, MAlSiHy), Si3N4 and CeF3 by a direct nitriding process in a N2 gas and the luminescence properties were characterized. The resultant phosphors showed green emission suitable for LED illumination by optimizing the mixing ratio of metal elements. These phosphors were effectively excited by violet or blue light (400-430 nm) and the emission bands were observed at various wavelength regions for Ca: 489-528 nm, Sr: 511-520 nm, and Ba: 508-514 nm. Although the emission intensity of Ca2(Si, Al)5N8:Ce3+ was decreased with increasing amount of Al, those of Sr- and Ba-analogues were maximized at x = 0.5 of Al content in M2Si5-xAlxN8:Ce3+.

  19. AlSiTiN and AlSiCrN multilayer coatings: Effects of structure and surface composition on tribological behavior under dry and lubricated conditions

    NASA Astrophysics Data System (ADS)

    Faga, Maria Giulia; Gautier, Giovanna; Cartasegna, Federico; Priarone, Paolo C.; Settineri, Luca

    2016-03-01

    Nanocomposite coatings have been widely studied over the last years because of their high potential in several applications. The increased interest for these coatings prompted the authors to study the tribological properties of two nanocomposites under dry and lubricated conditions (applying typical MQL media), in order to assess the influence of the surface and bulk properties on friction evolution. To this purpose, multilayer and nanocomposite AlSiTiN and AlSiCrN coatings were deposited onto tungsten carbide-cobalt (WC-Co) samples. Uncoated WC-Co materials were used as reference. Coatings were analyzed in terms of hardness and adhesion. The structure of the samples was assessed by X-ray diffraction (XRD), while the surface composition was studied by XPS analysis. Friction tests were carried out under both dry and lubricated conditions using an inox ball as counterpart. Both coatings showed high hardness and good adhesion to the substrate. As far as the friction properties are concerned, in dry conditions the surface properties affect the sliding contact at the early beginning, while bulk structure and tribolayer formation determine the main behavior. Only AlSiTiN coating shows a low and stable coefficient of friction (COF) under dry condition, while the use of MQL media results in a rapid stabilization of the COF for all the materials.

  20. LiCaAlF6 scintillators in neutron and gamma radiation fields

    NASA Astrophysics Data System (ADS)

    Viererbl, L.; Klupák, V.; Vinš, M.; Koleška, M.; Šoltés, J.; Yoshikawa, A.; Nikl, M.

    2016-09-01

    Intentionally doped LiCaAlF6 (LiCAF) single crystals are prospective scintillators, especially for thermal neutron detection through the 6Li(n,t)4He nuclear reaction. Four different LiCAF scintillator samples were tested in various neutron and gamma fields. Two of the tested samples were LiCAF:Eu and LiCAF:Eu,Na single crystals, and another two samples were made of LiCAF:Eu micro crystals dispersed in transparent rubber, with different rubber dimensions. All LiCAF samples contain lithium enriched to6Li. A plutonium-beryllium source was used as a neutron source. The neutron spectrum was modified by moderator and filter to get different ratios between thermal, epithermal and fast neutron fluence rates. The MCNP code was used for calculations of the fluence rates for different configurations. Radionuclides 137Cs and 60Co were applied as gamma radiation sources. The light signal from the scintillator was evaluated with a photomultiplier and a multichannel analyzer. The purpose of this work was to study the characteristics of LiCAF scintillators, especially the ability to discriminate signals from neutron and gamma radiation, which is the basic scintillator condition for neutron detection in mixed neutron-gamma radiation fields. Generally, the discrimination can be done by the pulse height and/or the pulse shape of the evaluated signals. Both methods can be used for a LiCAF scintillator. However, only the pulse height discrimination method is discussed in this paper. The possibility of fast neutron detection with LiCAF scintillators was also tested.

  1. 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.

  2. 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. PMID:25746277

  3. Crustal structure of and boundary between the AlCaPa and Tisza terrains in the Pannonian basin

    NASA Astrophysics Data System (ADS)

    Hetényi, György; Ren, Yong; Dando, Ben; Stuart, Graham W.; Houseman, Gregory A.

    2014-05-01

    The evolution of the Pannonian Basin is strongly linked to that of the surrounding Alpine, Carpathian and Dinaric orogens. The eastward extrusion of Alpine-type basement that accompanied lithospheric thinning must have been accompanied by mantle downwelling and/or subduction along the Carpathians but the motive forces for these movements are debated. The internal structure of the crust within the basin is mostly covered by relatively recent sedimentary infill whose variable thickness further complicates seismic imaging. Palaeomagnetic and geological data have, however, shown that two tectonic terrains of distinct origin: AlCaPa and Tisza, occupy the basin's NW and SE part respectively. The two units have undergone different amounts of extension during opposite orientation rotations (counter-clockwise and clockwise, respectively). The boundary between these two units, known as the Mid-Hungarian Zone, is recognized as a major sinistral shear zone, geophysically clearly marked across the basin by a trough in Bouguer gravity. The Carpathian Basins Project deployed 49 broadband seismological stations perpendicular to the boundary between the AlCaPa and Tisza units. A NW-SE oriented swath of three lines covers a 450 km long and 75 km wide area. We use these and 4 permanent stations to image the crustal structure of and the boundary between AlCaPa and Tisza using the receiver function technique. The measured Moho depths show no significant change in crustal thickness between the two terrains, but the Moho is not or very weakly imaged along a ca. 40 km wide strip centred on the MHZ. Our Moho depths elsewhere in the basin agree with earlier controlled-source seismic results and recent shear-wave velocity models deduced from ambient noise analysis. The lack of a sharp Moho image beneath the MHZ implies that the crust-mantle boundary between AlCaPa and Tisza is not a sharp transition but rather a gradual increase in velocity with depth. The distinct low in gravity anomalies

  4. Teaching the Modes of Ca[superscript 2+] Transport between the Plasma Membrane and Endoplasmic Reticulum Using a Classic Paper by Kwan et al.

    ERIC Educational Resources Information Center

    Liang, Willmann

    2009-01-01

    This teaching article uses the report by Kwan et al., "Effects of methacholine, thapsigargin, and La[superscript 3+] on plasmalemmal and intracellular Ca[superscript 2+] transport in lacrimal acinar cells," where the effects of Ca[superscript 2+]-mobilizing agents in regulating Ca[superscript 2+] fluxes were examined under various conditions.…

  5. The effect of substrate bias voltages on impact resistance of CrAlN coatings deposited by modified ion beam enhanced magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Chunyan, Yu; Linhai, Tian; Yinghui, Wei; Shebin, Wang; Tianbao, Li; Bingshe, Xu

    2009-01-01

    CrAlN coatings were deposited on silicon and AISI H13 steel substrates using a modified ion beam enhanced magnetron sputtering system. The effect of substrate negative bias voltages on the impact property of the CrAlN coatings was studied. The X-ray diffraction (XRD) data show that all CrAlN coatings were crystallized in the cubic NaCl B1 structure, with the (1 1 1), (2 0 0) (2 2 0) and (2 2 2) diffraction peaks observed. Two-dimensional surface morphologies of CrAlN coatings were investigated by atomic force microscope (AFM). The results show that with increasing substrate bias voltage the coatings became more compact and denser, and the microhardness and fracture toughness of the coatings increased correspondingly. In the dynamic impact resistance tests, the CrAlN coatings displayed better impact resistance with the increase of bias voltage, due to the reduced emergence and propagation of the cracks in coatings with a very dense structure and the increase of hardness and fracture toughness in coatings.

  6. Internal nitridation of nickel-base alloys. Part 1: Behavior of binary and ternary alloys of the Ni-Cr-Al-Ti system

    SciTech Connect

    Krupp, U.; Christ, H.J.

    1999-10-01

    The internal-nitriding behavior of several model alloys of the Ni-Cr-Al-Ti system in an oxygen-free nitrogen atmosphere at 800--1100 C was studied. Thermogravimetry as well as various metallographic techniques (SEM and TEM) were used. It was shown that both the nitrogen solubility and the nitrogen diffusion coefficient are strongly affected by the Cr content of the Ni alloy. Hence, in Ni-Cr-Ti alloys a higher chromium content leads to an increased depth of the internal precipitation of TiN. Nitridation of the alloying element Cr takes place only at high concentrations of Cr. In general, the nitridation rate was found to obey Wagner`s parabolic rate law of internal oxidation. Changes in the parabolic rate constant with alloy composition can be understood by means of thermodynamic calculations in combination with microstructural observations.

  7. CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1995-09-01

    Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. Electrical resistance of CaO coatings that were produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li containing 0.5-85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {>=}360{degrees}C.

  8. Synthesis and Luminescence Characteristics of Cr3+ doped Y3Al5O12 Phosphors

    SciTech Connect

    Smith, Brenda A.; Dabestani, Reza T.; Lewis, Linda A.; Thompson, Cyril V.; Collins, Case T.; Aytug, Tolga

    2015-10-01

    Luminescence performance of yttrium aluminum garnet (Y3Al5O12) phosphors as a function of Cr3+ concentration has been investigated via two different wet-chemical synthesis techniques, direct- (DP) and hydrothermal-precipitation (HP). Using either of these methods, the red-emitting phosphor [Y3Al5-xCrxO12 (YAG: Cr3+)] showed similar photoluminescence (PL) intensities once the dopant concentration was optimized. Specifically, the YAG: Cr3+ PL emission intensity reached a maximum at Cr3+ concentrations of x = 0.02 (0.4 at.%) and x = 0.13 (2.6 at.%) for DP and HP processed samples, respectively. The results indicated the strong influence of the processing method on the optimized YAG: Cr3+ performance, where a more effective energy transfer rate between a pair of Cr3+ activators at low concentration levels was observed by using the DP synthesis technique. Development of a highly efficient phosphor, using a facile synthesis approach, could significantly benefit consumer and industrial applications by improving the operational efficiency of a wide range of practical devices.

  9. Widmannstätten laths in Ti48Al2Cr2Nb alloy by undercooled solidification

    SciTech Connect

    Liu, Yi; Hu, Rui Yang, Guang; Kou, Hongchao; Zhang, Tiebang; Wang, Jun; Li, Jinshan

    2015-09-15

    Widmannstätten laths in Ti48Al2Cr2Nb alloy were obtained by containerless electromagnetic levitation during undercooled solidification rather than heat treatments in most cases. The nucleation of γ{sub Widmannstätten} is confirmed by the thermal history of the second recalescence behaviour. High dislocation density, stacking faults and dislocation slip are observed by transmission electron microscopy. By quantitative analysis of the transformation energy, the driving force for γ{sub Widmannstätten} in the solid state phase transformation is calculated, compared with that of heat treatments. Meanwhile, the proper undercoolings (ΔT = 257–300 K), post-solidification cooling rates (11.1–29.1 K/s), the fine lamellar colony sizes (306–467 μm) and proper undercoolings in the solid state phase transformation are in favour of promoting the formation of Widmannstätten laths at moderate undercoolings. - Graphical abstract: Display Omitted - Highlights: • Widmannstätten laths were observed in undercooled TiAl alloy. • The influencing factors were discussed in undercooled TiAl alloy. • An analysis of the nucleation of γ{sub Widmannstätten} is carried out.

  10. Study of new sheep bone and Zn/Ca ratio around TiAlV screw: PIXE RBS analysis

    NASA Astrophysics Data System (ADS)

    Guibert, G.; Munnik, F.; Langhoff, J. D.; Von Rechenberg, B.; Buffat, Ph. A.; Laub, D.; Faber, L.; Ducret, F.; Gerber, I.; Mikhailov, S.

    2008-03-01

    This study reports on in vivo particle induced X-ray emission (PIXE) measurements combined with Rutherford backscattering spectroscopy (RBS) analyses of new remodeled sheep bone formed around TiAlV screws. The implants (screws) were anodized by a modified TiMax™ process. The interface between the implant and the bone was carefully investigated. [Zn]/[Ca] in-depth composition profiles as well as Ca, Fe elemental maps were recorded. The thickness of new bone formed around the screw reached 300-400 μm. Osteon and Osteoid phases were identified in the new bone. A higher [Zn]/[Ca] ratio was observed in the new bone as compared to the mature bone. Blood vessels were observed in the bone in close contact with the screw. This study shows the potential of ion beam analysis for biological and biomedical characterization.

  11. Production of radon and thorium isotopes near N=126 shell closure in 48Ca and 54Cr induced fusion reactions on 162Dy

    NASA Astrophysics Data System (ADS)

    Mayorov, Dmitriy; Werke, Tyler; Alfonso, Marisa; Folden, Charles

    2012-03-01

    Production of spherical evaporation residues (EVRs) near N=126 shell in 48Ca and 54Cr induced reactions on a 162Dy target was investigated at the Texas A&M University Cyclotron Institute using the vacuum separator MARS. For the 54Cr+162Dy reaction, only upper limits for the 4n exit-channel cross section were measured; this can be attributed to a sizably increased fissility of the 216Th compound nucleus relative to 210Rn formed in the 48Ca bombardment. A factor of > 7300 separates the production cross sections of the 4n EVRs from each reaction. A semi-empirical estimate of the lower limit on the fusion probability, PCN, ratio between the two heavy ion projectiles is PCN(48Ca+162Dy)/PCN(54Cr+162Dy) > 1.2. Investigation of spherical nuclei produced by heavy ion fusion reactions is of current interest due to efforts to synthesize superheavy nuclei near Z=120, N=184 nucleon shells. EVRs produced near the N=126 shell closure have previously revealed surprisingly low survival probabilities despite stabilization from shell effects. Similarly, enhancement of the fission channel in the de-excitation cascade of 210Rn and 216Th is observed in this work and this result can be well modeled by the inclusion of collective effects into the statistical decay of excited nuclei calculations. These results suggest that cross sections for production of superheavy nuclei near predicted Z=120, N=184 closed shells may be small regardless of the anticipated strong shell effects.

  12. Synthesis and hydration behavior of calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cement

    SciTech Connect

    Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye; Choi, Sung-Woo; Hong, Seong-Hyeon

    2014-02-15

    Calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca{sub 7}ZrAl{sub 6}O{sub 18} was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO{sub 3} coexisted with Ca{sub 7}ZrAl{sub 6}O{sub 18} even at higher temperature (1400 °C). Unexpectedly, Ca{sub 7}ZrAl{sub 6}O{sub 18} synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape. The hydration behavior of Ca{sub 7}ZrAl{sub 6}O{sub 18} was similar to that of Ca{sub 3}Al{sub 2}O{sub 6} (C3A), but the hydration products were Ca{sub 3}Al{sub 2}O{sub 6}·6H{sub 2}O (C3AH6) and several intermediate products. Thus, Zr (or ZrO{sub 2}) stabilized the intermediate hydration products of C3A.

  13. Rub tolerance evaluation of two sintered NiCrAl gas path seal materials. [wear tests of gas turbine engine seals

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1978-01-01

    Two strength level variations of sintered NiCrAl (about 40 percent dense), candidate high pressure turbine seal materials, were subject to rub tolerance testing against AM 355 steel blade tips. The high strength material (17 N/sq mm tensile strength) showed frictional and radial loads that were 20 to 50 percent higher than those measured for the low strength material (15.5 N/ sq mm tensile strength). Measured wear to the AM 355 blade tips was not significantly different for the two sintered NiCrAl seal materials. Wear of the sintered NiCrAl was characterized by material removal to a depth greater than the depth to which blade tips were driven into the seal, indicating self-erosion effects.

  14. Experimental Plan and Irradiation Target Design for FeCrAl Embrittlement Screening Tests Conducted Using the High Flux Isotope Reactor

    SciTech Connect

    Field, Kevin G.; Howard, Richard H.; Yamamoto, Yukinori

    2015-06-26

    The objective of the FeCrAl embrittlement screening tests being conducted through the use of Oak Ridge National Laboratories (ORNL) High Flux Isotope Reactor is to provide data on the radiation-induced changes in the mechanical properties including radiation-induced hardening and embrittlement through systematic testing and analysis. Data developed on the mechanical properties will be supported by extensive microstructural evaluations to assist in the development of structure-property relationships and provide a sound, fundamental understanding of the performance of FeCrAl alloys in intense neutron radiation fields. Data and analysis developed as part of this effort will be used to assist in the determination of FeCrAl alloys as a viable material for commercial light water reactor (LWR) applications with a primary focus as an accident tolerant cladding.

  15. Half-metallicity at the Heusler alloy Co(2)Cr(0.5)Fe(0.5)Al(001) surface and its interface with GaAs(001).

    PubMed

    Zarei, Sareh; Javad Hashemifar, S; Akbarzadeh, Hadi; Hafari, Zohre

    2009-02-01

    Electronic and magnetic properties of the Heusler alloy Co(2)Cr(0.5)Fe(0.5)Al(001) surfaces and its interfaces with GaAs(001) are studied within the framework of density functional theory by using the plane-wave pseudopotential approach. The phase diagram obtained by ab initio atomistic thermodynamics shows that the CrAl surface is the most stable (001) termination of this Heusler alloy. We discuss that, at the ideal surfaces and interfaces with GaAs, half-metallicity of the alloy is lost, although the CrAl surface keeps high spin polarization. The energy band profile of the stable interface is investigated and a negative p Schottky barrier of -0.78 eV is obtained for this system.

  16. On the field evaporation behavior of a model Ni-Al-Cr superalloy studied by picosecond pulsed-laser atom-probe tomography.

    PubMed

    Zhou, Yang; Booth-Morrison, Christopher; Seidman, David N

    2008-12-01

    The effects of varying the pulse energy of a picosecond laser used in the pulsed-laser atom-probe (PLAP) tomography of an as-quenched Ni-6.5 Al-9.5 Cr at.% alloy are assessed based on the quality of the mass spectra and the compositional accuracy of the technique. Compared to pulsed-voltage atom-probe tomography, PLAP tomography improves mass resolving power, decreases noise levels, and improves compositional accuracy. Experimental evidence suggests that Ni2+, Al2+, and Cr2+ ions are formed primarily by a thermally activated evaporation process, and not by post-ionization of the ions in the 1+ charge state. An analysis of the detected noise levels reveals that for properly chosen instrument parameters, there is no significant steady-state heating of the Ni-6.5 Al-9.5 Cr at.% tips during PLAP tomography. PMID:18986610

  17. CrAs(0 0 1)/AlAs(0 0 1) heterogeneous junction as a spin current diode predicted by first-principles calculations

    NASA Astrophysics Data System (ADS)

    Min, Y.; Yao, K. L.; Liu, Z. L.; Cheng, H. G.; Zhu, S. C.; Gao, G. Y.

    2009-02-01

    We report on first-principles calculations of spin-dependent quantum transport in a CrAs(0 0 1)/AlAs(0 0 1) heterogeneous junction and predict a strong diode effect of charge and spin current. The minority spin current is absolutely inhibited when the bias voltage is applied to the terminals of both CrAs and AlAs. The majority spin current is inhibited when the bias voltage is applied to the terminal of CrAs and "relaxed" when the bias voltage is applied to the terminal of AlAs. The charge and spin current diode are promising for reprogrammable logic applications in the field of spintronics.

  18. Tribological Properties of CrAlN and TiN Coatings Tested in Nano- and Micro-scale Laboratory Wear Tests

    NASA Astrophysics Data System (ADS)

    Hong, Ling; Bian, Guangdong; Hu, Shugen; Wang, Linlin; Dacosta, Herbert

    2015-07-01

    We investigated the tribological properties of CrAlN and TiN coatings produced by electron beam plasma-assisted physical vapor deposition by nano- and micro-scale wear tests. For comparison, we also conducted nano-indentation, nano-scanning wear tests, and pin-on-disk tribotests on uncoated M2 steel. The results indicate that, after nano-scale sliding tests against diamond indenter and pin-on-disk tests against ceramic alumina counterface pins, the CrAlN coating presents superior abrasive wear resistance compared to the TiN-coated and uncoated M2 steel samples. Against aluminum counterface, aluminum is more prone to attach on the CrAlN coating surface compared to TiN coating, but no apparent adhesive wear was observed, which has occurred on the TiN coating.

  19. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  20. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.