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Sample records for al ca ti

  1. 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.

  2. 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.

  3. 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.

  4. Plasma-sprayed CaTiSiO5 ceramic coating on Ti-6Al-4V with excellent bonding strength, stability and cellular bioactivity

    PubMed Central

    Wu, Chengtie; Ramaswamy, Yogambha; Liu, Xuanyong; Wang, Guocheng; Zreiqat, Hala

    2008-01-01

    Novel Ca-Si-Ti-based sphene (CaTiSiO5) ceramics possess excellent chemical stability and cytocompatibility. The aim of this study was to prepare sphene coating on titanium alloy (Ti-6Al-4V) for orthopaedic applications using the plasma spray method. The phase composition, surface and interface microstructure, coating thickness, surface roughness and bonding strength of the plasma-sprayed sphene coating were analysed using X-ray diffraction, scanning electron microscopy, atomic force microscopy and the standard mechanical testing of the American Society for Testing and Materials, respectively. The results indicated that sphene coating was obtained with a uniform and dense microstructure at the interface of the Ti-6Al-4V surface and the thickness and surface roughness of the coating were approximately 150 and 10 μm, respectively. Plasma-sprayed sphene coating on Ti-6Al-4V possessed a significantly improved bonding strength and chemical stability compared with plasma-sprayed hydroxyapatite (HAp) coating. Plasma-sprayed sphene coating supported human osteoblast-like cell (HOB) attachment and significantly enhanced HOB proliferation and differentiation compared with plasma-sprayed HAp coating and uncoated Ti-6Al-4V. Taken together, plasma-sprayed sphene coating on Ti-6Al-4V possessed excellent bonding strength, chemical stability and cellular bioactivity, indicating its potential application for orthopaedic implants. PMID:18664431

  5. Crystal characterization and optical spectroscopy of Ti{sup 3+}-doped CaGdAlO{sub 4} crystals

    SciTech Connect

    Kodama, N.; Yamaga, M.

    1998-01-01

    CaGdAlO{sub 4} crystals doped with Ti ions were grown using the Czochralski technique in a reducing atmosphere in order to convert the valence of Ti to trivalence. The fluorescence of the {sup 2}E{r_arrow}{sup 2}T{sub 2} transition of Ti{sup 3+} in the crystals shows a broad band with a peak at 535 nm excited with the light of 410 nm in the optical absorption band at room temperature because of a strong electron-phonon coupling of the {sup 2}E excited state. The Ti{sup 3+} fluorescence is influenced in intensity by O{sup 2{minus}} vacancies at the ligands of the Ti{sup 3+} octahedra along the c axis, which are easily produced in a reducing atmosphere. The x-ray crystal analyses and the polarization of the optical absorption and fluorescence spectra deduce the energy levels and wave functions of the ground and excited states of Ti{sup 3+} in CaGdAlO{sub 4}. The peak energy of the fluorescence band shifts to higher energy as increasing excitation energy in the absorption band. The linear dependence of the fluorescence-peak energy on the excitation energy shows that the fluorescence is inhomogeneously broadened by a random distribution of Ca{sup 2+} and Gd{sup 3+} ions in the disordered lattice.

  6. Fluoride evaporation and crystallization behavior of CaF2-CaO-Al2O3-(TiO2) slag for electroslag remelting of Ti-containing steels

    NASA Astrophysics Data System (ADS)

    Shi, Cheng-bin; Cho, Jung-wook; Zheng, Ding-li; Li, Jing

    2016-06-01

    To elucidate the behavior of slag films in an electroslag remelting process, the fluoride evaporation and crystallization of CaF2-CaO-Al2O3-(TiO2) slags were studied using the single hot thermocouple technique. The crystallization mechanism of TiO2-bearing slag was identified based on kinetic analysis. The fluoride evaporation and incubation time of crystallization in TiO2-free slag are found to considerably decrease with decreasing isothermal temperature down to 1503 K. Fish-bone and flower-like CaO crystals precipitate in TiO2-free slag melt, which is accompanied by CaF2 evaporation from slag melt above 1503 K. Below 1503 K, only near-spherical CaF2 crystals form with an incubation time of less than 1 s, and the crystallization is completed within 1 s. The addition of 8.1wt% TiO2 largely prevents the fluoride evaporation from slag melt and promotes the slag crystallization. TiO2 addition leads to the precipitation of needle-like perovskite (CaTiO3) crystals instead of CaO crystals in the slag. The crystallization of perovskite (CaTiO3) occurs by bulk nucleation and diffusion-controlled one-dimensional growth.

  7. Reoxidation of Aluminum in Fe- Al- M (M = C, Mn, and Ti) melts with CaO-Al2 O3-Fe t O (3 mass pct) slags

    NASA Astrophysics Data System (ADS)

    Lee, Kwang Ro; Suito, Hideaki

    1996-06-01

    An Fe-0.01 to 0.5 mass pct Al alloy and an Fe-0.003 to 0.71 mass pct Al-1 mass pct M (M = C, Mn, and Ti) alloy were reoxidized with the CaO-Al2O3-FetO (3 mass pct) slags at 1873 K in an Al2O3 or CaO crucible for 5 and 60 minutes. The contents of acid-insoluble Al, total O, and alloying element M in metal as well as those of M and FetO in slag were measured as a function of total Al content. On the basis of the present and previous results for Fe- Al- Te alloys, the effect of alloying elements on the degree of supersaturation with respect to the Al2O3 precipitation was studied. As a result, the supersaturation phenomenon was observed in all experiments at 5 minutes, but in the experiments at 60 minutes, it was observed only in Fe- Al and Fe- Al- Ti alloys. No supersaturation was observed in the reoxidation of Si in Fe-0.13 to 0.98 mass pct Si alloys with the CaO-SiO2-FetO (3 mass pct) slags in a CaO crucible at 5 and 60 minutes.

  8. 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.

  9. 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.

  10. Photocatalytic characteristics for the nanocrystalline TiO2 on the Ag-doped CaAl2O4:(Eu,Nd) phosphor

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Sik; Sung, Hyun-Je; Kim, Bum-Joon

    2015-04-01

    This study investigated the photocatalytic behavior of nanocrystalline TiO2 deposited on Ag-doped long-lasting phosphor (CaAl2O4:Eu2+,Nd3+). The CaAl2O4:Eu2+,Nd3+ phosphor powders were prepared via conventional sintering using CaCO3, Al2O3, Eu2O3, and Nd2O3 as raw materials according to the appropriate molar ratios. Silver nanoparticles were loaded on the phosphor by mixing with an aqueous Ag-dispersion solution. Nanocrystalline TiO2 was deposited on Ag-doped CaAl2O4:Eu2+,Nd3+ powders via low-pressure chemical vapor deposition (LPCVD). The TiO2 coated on the phosphor was actively photo-reactive under irradiation with visible light and showed much faster benzene degradation than pure TiO2, which is almost non-reactive. The coupling of TiO2 with phosphor may result in an energy band bending in the junction region, which then induces the TiO2 crystal at the interface to be photo-reactive under irradiation with visible light. In addition, the intermetallic compound of CaTiO3 that formed at the interface between TiO2 and the CaAl2O4:(Eu2+,Nd3+) phosphor results in the formation of oxygen vacancies and additional electrons that promote the photodecomposition of benzene gas. The addition of Ag nanoparticles enhanced the photocatalytic reactivity of the TiO2/CaAl2O4:Eu2+,Nd3+ phosphor. TiO2 on the Ag-doped phosphor presented a higher benzene gas decomposition rate than the TiO2 did on the phosphor without Ag-doping under both irradiation with ultraviolet and visible light.

  11. 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.

  12. 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.

  13. Symmetry-dependent interfacial reconstruction to compensate polar discontinuity at perovskite oxide interfaces (LaAlO{sub 3}/SrTiO{sub 3} and LaAlO{sub 3}/CaTiO{sub 3})

    SciTech Connect

    Lee, Joohwi; Moon, Seon Young; Kim, Jin-Sang; Choi, Jung-Hae E-mail: almacore@kist.re.kr; Choi, Jong Kwon; Park, Jaehong; Hwang, Cheol Seong; Baek, Seung-Hyub; Chang, Hye Jung E-mail: almacore@kist.re.kr

    2015-02-16

    We report the crystal symmetry-dependency of the interfacial reconstruction to relieve the polar discontinuity at the complex oxide heterointerfaces. We chose LaAlO{sub 3}/SrTiO{sub 3} and LaAlO{sub 3}/CaTiO{sub 3} interfaces as model systems, where the neutral TiO{sub 2} and the positive LaO{sup +} layers form the polar discontinuity at the interface with TiO{sub 2}-terminated (001) cubic SrTiO{sub 3} and orthorhombic CaTiO{sub 3}. Using scanning transmission electron microscopy, we observed that the interlayer distance abnormally increased at the interface. We performed the first-principles calculations to understand the detailed atomic displacement at the interfaces having no oxygen vacancy and intermixing. Our results show that cations were reconstructed in different ways depending on the crystal symmetry through the octahedral tilts and atomic displacements to compensate the polar discontinuity at the interfaces. Our results imply that the interfacial reconstructions have to be considered along with the ionic compensation (intermixing) and electronic compensation (two dimensional electron gas) to fully understand the interfacial phenomena.

  14. Impedance-based interpretations in 2-dimensional electron gas conduction formed in the LaAlO3/SrxCa1-xTiO3/SrTiO3 system

    NASA Astrophysics Data System (ADS)

    Park, Chan-Rok; Moon, Seon Young; Park, Da-Hee; Kim, Shin-Ik; Kim, Seong-Keun; Kang, Chong-Yun; Baek, Seung-Hyub; Choi, Jung-Hae; Kim, Jin-Sang; Choi, Eunsoo; Hwang, Jin-Ha

    2016-06-01

    Frequency-dependent impedance spectroscopy was applied to the 2-dimensioanl conduction transport in the LaAlO3/SrxCa1-xTiO3/SrTiO3 system. The 2-dimensional conduction modifies the electrical/dielectric responses of the LaAlO3/SrxCa1-xTiO3/SrTiO3 depending on the magnitude of the interfacial 2-dimensional resistance. The high conduction of the 2-dimensional electron gas (2DEG) layer can be described using a metallic resistor in series with two parallel RC circuits. However, the high resistance of the 2-dimensional layer drives the composite system from a finite low resistor in parallel with the surrounding dielectrics composed of LaAlO3 and SrTiO3 materials to a dielectric capacitor. This change in the resistance of the 2-dimensional layers modifies the overall impedance enabled by the presence of the interfacial layer due to SrxCa1-xTiO3, which alters the charge transport of the 2-dimensional layer from metallic to semiconducting conduction. A noticeable change is observed in the capacitance Bode plots, indicating highly amplified dielectric constants compared with the pristine SrTiO3 substrates and SrxCa1-xTiO3 with a greater Ca content.

  15. Structural characterization of Nd-doped Hf-zirconolite Ca 1-xNd xHfTi 2-xAl xO 7 ceramics

    NASA Astrophysics Data System (ADS)

    Caurant, Daniel; Loiseau, Pascal; Bardez, Isabelle

    2010-12-01

    Because of its high incorporation capacity and of the high thermal neutron capture cross-section of hafnium, Hf-zirconolite (CaHfTi 2O 7) ceramic can be envisaged as a potential waste form for minor actinides (Np, Am, Cm) and plutonium immobilization. In this work, Nd-doped Hf-zirconolite Ca 1-xNd xHfTi 2-xAl xO 7 ( x = 0; 0.01 and 0.2) ceramics have been prepared by solid state reaction. Neodymium has been used as trivalent actinide surrogate. The ceramic samples structure has been studied by X-ray diffraction and refined by the Rietveld method. This revealed that Nd 3+ ions only enter the Ca site, whereas part of Hf 4+ ions substitute titanium into Ti(1) sites and Al 3+ ions mainly occupy the Ti(2) split sites and Ti(3) sites of the zirconolite structure. Using various spectroscopic techniques (electron spin resonance, optical absorption and fluorescence), the environment of Nd 3+ cations in Hf-zirconolite has been studied and compared with that of Nd 3+ cations in Zr-zirconolite (CaZrTi 2O 7). Different local environments of Nd 3+ cations have been detected in Hf-zirconolite that can be attributed to the existence of an important disorder around Nd in the Ca site probably due to the statistical occupancy of the next nearest cationic site of neodymium (a split Ti site) by Ti 4+, Al 3+ cations and vacancies. No significant differences were observed concerning Nd 3+ cations environment and distribution in Hf- and Zr-zirconolite ceramics.

  16. 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.

  17. Effects of CaF2 vis-a-vis TiO2 as nucleating agent in SiO2-Al2O3-CaO glass-ceramics

    NASA Astrophysics Data System (ADS)

    Mukherjee, Debasis Pradip; Datta, Tanmoy; Das, Sudip Kumar

    2013-06-01

    The independent effects of CaF2 and TiO2 on the glass-ceramics based on SiO2-Al2O3-CaO system have been investigated. The crystallization behavior, microstructure, mechanical properties and chemical resistance of the glass-ceramics were studied by Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), FTIR, mechanical and chemical resistance measurements. The CaF2 containing glass ceramics are found to be much superior to that of TiO2 containing glass ceramics on the basis of sintering strength, mechanical and chemical properties.

  18. Effect of micro-alloy elements (Ti, Nb, Al and Ca) on corrosion resistance of 26%Cr-2%Mo stainless steel in chloride solutions

    SciTech Connect

    Kim, H.; Lee, Y.D.

    1999-11-01

    Ferritic stainless steels have higher corrosion and stress corrosion cracking resistance in chloride environments than austenitic stainless steels. The production mat of ferritic stainless steels is lower than austenitic stainless steels. However, the application of highly alloyed ferritic stainless steels is limited due to low toughness and intergranular corrosion attack. Corrosion resistance of 26%Cr-2%Mo ferritic steels was evaluated using polarization test in 20% NaCl solution and the ferric chloride test. In addition, TEM and SEM were employed to analyze the secondary phases around the matrix where pitting corrosion occurred. In ferric chloride test the crevice corrosion resistance of non-stabilized alloy and Ca added alloy was lower than that of stabilized alloy and the crevice corrosion resistance of stabilized alloys was independent of stabilizing element such as Ti and Nb. The pitting corrosion resistance in chloride solution depended on micro-alloying elements as well as the surface treatment such as pickling and polishing. The effect of micro-alloy element and surface treatment on corrosion properties was explained with the aid of SEM observations. Among the polished alloys, the addition of Nb was the most effective for pitting corrosion resistance but the addition of Ti or Ca decreased the corrosion resistance. The pickling increased the corrosion resistance in all alloys except alloy No. 4 (Ti + Nb + Al). Pickling effectively increased corrosion resistance of the alloy containing Ti or Ca, due to removal of pit initiation sites associated with TiN inclusions or unstable phase (i.e., CaS, TiN).

  19. Tailor-Made Core-Shell CaO/TiO2-Al2O3 Architecture as a High-Capacity and Long-Life CO2 Sorbent.

    PubMed

    Peng, Weiwei; Xu, Zuwei; Luo, Cong; Zhao, Haibo

    2015-07-01

    CaO-based sorbents are widely used for CO2 capture, steam methane reforming, and gasification enhancement, but the sorbents suffer from rapid deactivation during successive carbonation/calcination cycles. This research proposes a novel self-assembly template synthesis (SATS) method to prepare a hierarchical structure CaO-based sorbent, Ca-rich, Al2O3-supported, and TiO2-stabilized in a core-shell microarchitecture (CaO/TiO2-Al2O3). The cyclic CO2 capture performance of CaO/TiO2-Al2O3 is compared with those of pure CaO and CaO/Al2O3. CaO/TiO2-Al2O3 sorbent achieved superior and durable CO2 capture capacity of 0.52 g CO2/g sorbent after 20 cycles under the mild calcination condition and retained a high-capacity and long-life performance of 0.44 g CO2/g sorbent after 104 cycles under the severe calcination condition, much higher than those of CaO and CaO/Al2O3. The microstructure characterization of CaO/TiO2-Al2O3 confirmed that the core-shell structure of composite support effectively inhibited the reaction between active component (CaO particles) and main support (Al2O3 particles) by TiO2 addition, which contributed to its properties of high reactivity, thermal stability, mechanical strength, and resistance to agglomeration and sintering. PMID:26047026

  20. SiO2-CaO-K2O coatings on alumina and Ti6Al4V substrates for biomedical applications.

    PubMed

    Vitale-Brovarone, C; Verné, E

    2005-09-01

    Alumina and Ti6Al4V alloys are widely used for orthopedics and dental applications due to their good mechanical properties and biocompatibility. Unfortunately they can not provide a satisfactory osteointegration when implanted. In fact, both alumina and Ti6Al4V are not bioactive and thus they can only guarantee a morphological fixation with the surrounding tissues without a suitable chemical anchorage. Aiming to impart bioactive properties to these materials a coating can be proposed. At this purpose, a bioactive glass belonging to the SiO2-CaO-K2O system was selected and prepared. This glass, named SCK, possess a thermal expansion coefficient matching with the alumina (8.5x 10(- 6)/ degrees C) and Ti6Al4V (9 x 10(- 6)/ degrees C) ones and thus is a good candidate to produce coatings on both of them. Simple and low-cost enameling and glazing techniques were used to realize the coatings. Structural, morphological and compositional characterizations of the coatings were carried out by means of X-ray diffraction, optical and scanning microscopy and compositional analyses. The in vitro properties of the coatings were investigated by soaking them in a simulated body fluid (SBF) in order to study the precipitation, on their surfaces, of a biologically active layer of hydroxylapatite (HAp). PMID:16167116

  1. Giant dielectric response and low dielectric loss in Al{sub 2}O{sub 3} grafted CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

    SciTech Connect

    Rajabtabar-Darvishi, A.; Bayati, R. E-mail: mbayati@ncsu.edu; Sheikhnejad-Bishe, O.; Wang, L. D.; Li, W. L.; Sheng, J.; Fei, W. D. E-mail: mbayati@ncsu.edu

    2015-03-07

    This study sheds light on the effect of alumina on dielectric constant and dielectric loss of novel CaCu{sub 3}Ti{sub 4}O{sub 12} composite ceramics. Alumina, at several concentrations, was deposited on the surface of CaCu{sub 3}Ti{sub 4}O{sub 12} particles via sol-gel technique. The dielectric constant significantly increased for all frequencies and the dielectric loss substantially decreased for low and intermediate frequencies. These observations were attributed to the change in characteristics of grains and grain boundaries. It was found that the insulating properties of the grain boundaries are improved following the addition of Al{sub 2}O{sub 3}. The relative density of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics decreased compared to the pure CaCu{sub 3}Ti{sub 4}O{sub 12} and the grain size was greatly changed with the alumina content affecting the dielectric properties. With the addition of alumina into CaCu{sub 3}Ti{sub 4}O{sub 12}, tighter interfaces formed. The 6%- and 10%-alumina ceramics showed the minimum dielectric loss and the maximum dielectric constant, respectively. Both the dielectric constant and loss tangent decreased in the 20%-alumina ceramic due to the formation of CuO secondary phase. It was revealed that Al serves as an electron acceptor decreasing the electron concentration, if Al{sup 3+} ions substitute for Ti{sup 4+} ions, and as an electron donor increasing the electron concentration, if Al{sup 3+} ions substitute for Ca{sup 2+} ions. We established a processing-microstructure-properties paradigm which opens new avenues for novel applications of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics.

  2. Excellent stability of plasma-sprayed bioactive Ca 3ZrSi 2O 9 ceramic coating on Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Liang, Ying; Xie, Youtao; Ji, Heng; Huang, Liping; Zheng, Xuebin

    2010-05-01

    In this work, novel zirconium incorporated Ca-Si based ceramic powder Ca 3ZrSi 2O 9 was synthesized. The aim of this study was to fabricate Ca 3ZrSi 2O 9 coating onto Ti-6Al-4V substrate using atmospheric plasma-spraying technology and to evaluate its potential applications in the fields of orthopedics and dentistry. The phase composition, surface morphologies of the coating were examined by XRD and SEM, which revealed that the Ca 3ZrSi 2O 9 coating was composed of grains around 100 nm and amorphous phases. The bonding strength between the coating and the substrate was 28 ± 4 MPa, which is higher than that of traditional HA coating. The dissolution rate of the coating was assessed by monitoring the ions release and mass loss after immersion in the Tris-HCl buffer solution. The in vitro bioactivity of the coating was determined by observing the formation of apatite on its surface in simulated body fluids. It was found that the Ca 3ZrSi 2O 9 coating possessed both excellent chemical stability and good apatite-formation ability, suggesting its potential use as bone implants.

  3. Characterization of Ti6Al7Nb alloy foams surface treated in aqueous NaOH and CaCl2 solutions.

    PubMed

    Bütev, Ezgi; Esen, Ziya; Bor, Şakir

    2016-07-01

    Ti6Al7Nb alloy foams having 53-73% porosity were manufactured via evaporation of magnesium space holders. A bioactive 1µm thick sodium hydrogel titanate layer, NaxH2-xTiyO2y+1, formed after 5M NaOH treatment, was converted to crystalline sodium titanate, Na2TiyO2y+1, as a result of post-heat treatment. On the other hand, subsequent CaCl2 treatment of NaOH treated specimens induced calcium titanate formation. However, heat treatment of NaOH-CaCl2 treated specimens led to the loss of calcium and disappearance of the titanate phase. All of the aforementioned surface treatments reduced yield strengths due to the oxidation of the cell walls of the foams, while elastic moduli remained mostly unchanged. Accordingly, equiaxed dimples seen on the fracture surfaces of as-manufactured foams turned into relatively flat and featureless fracture surfaces after surface treatments. On the other hand, Ca- and Na-rich coating preserved their mechanical stabilities and did not spall during fracture. The relation between mechanical properties of foams and macro-porosity fraction were found to obey a power law. The foams with 63 and 73% porosity met the desired biocompatibility requirements with fully open pore structures and elastic moduli similar to that of bone. In vitro tests conducted in simulated body fluid (SBF) showed that NaOH-heat treated surfaces exhibit the highest bioactivity and allow the formation of Ca-P rich phases having Ca/P ratio of 1.3 to form within 5 days. Although Ca-P rich phases formed only after 15 days on NaOH-CaCl2 treated specimens, the Ca/P ratio was closer to that of apatite found in bone. PMID:26807769

  4. Observation of indium ion migration-induced resistive switching in Al/Mg0.5Ca0.5TiO3/ITO

    NASA Astrophysics Data System (ADS)

    Lin, Zong-Han; Wang, Yeong-Her

    2016-08-01

    Understanding switching mechanisms is very important for resistive random access memory (RRAM) applications. This letter reports an investigation of Al/Mg0.5Ca0.5TiO3 (MCTO)/ITO RRAM, which exhibits bipolar resistive switching behavior. The filaments that connect Al electrodes with indium tin oxide electrodes across the MCTO layer at a low-resistance state are identified. The filaments composed of In2O3 crystals are observed through energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, nanobeam diffraction, and comparisons of Joint Committee on Powder Diffraction Standards (JCPDS) cards. Finally, a switching mechanism resulting from an electrical field induced by In3+ ion migration is proposed. In3+ ion migration forms/ruptures the conductive filaments and sets/resets the RRAM device.

  5. Experimental Determination of the Phase Diagram of the CaO-SiO2-5 pctMgO-10 pctAl2O3-TiO2 System

    NASA Astrophysics Data System (ADS)

    Shi, Junjie; Sun, Lifeng; Zhang, Bo; Liu, Xuqiang; Qiu, Jiyu; Wang, Zhaoyun; Jiang, Maofa

    2016-02-01

    Ti-bearing CaO-SiO2-MgO-Al2O3-TiO2 slags are important for the smelting of vanadium-titanium bearing magnetite. In the current study, the pseudo-melting temperatures were determined by the single-hot thermocouple technique for the specified content of 5 to 25 pct TiO2 in the CaO-SiO2-5 pctMgO-10 pctAl2O3-TiO2 phase diagram system. The 1573 K to 1773 K (1300 °C to 1500 °C) liquidus lines were first calculated based on the pseudo-melting temperatures according to thermodynamic equations in the specific primary crystal field. The phase equilibria at 1573 K (1300 °C) were determined experimentally using the high-temperature equilibrium and quench method followed by X-ray fluorescence, X-ray diffraction, scanning electron microscope, and energy dispersive X-ray spectroscope analysis; the liquid phase, melilite solid solution phase (C2MS2,C2AS)ss, and perovskite phase of CaO·TiO2 were found. Therefore, the phase diagram was constructed for the specified region of the CaO-SiO2-5 pctMgO-10 pctAl2O3-TiO2 system.

  6. Crystal structure and dielectric properties of Ca(0.85)Nd(0.1)TiO(3) - LnAlO(3) ceramics.

    PubMed

    Eung, S; Dong, H; Yang, Jun-Mo; Hyung, S; Nur, I; Ohsato, Hitoshi

    2008-05-01

    The microwave dielectric properties of Ca(0.85)Nd(0.1)TiO(3) - LnAlO(3) (Ln = Sm, Gd, Dy, Er) ceramics are investigated in this paper. The structural characteristics of the specimens were evaluated by Rietveld refinement of Xray diffraction (XRD) patterns and high-resolution transmission electron microscopy (HRTEM). Solid solution limits were dependent on the ionic radius of Ln(3+) ions. With the decrease of the ionic radius of the Ln(3+) ions, the thermal stability of the resonant frequency decreases. This can be attributed to the increased level of oxygen octahedral distortion caused by the increase in the B-site bond valence in the ABO(3) perovskite structure. The dielectric constant (K) and the quality factor (Qf) of the specimens were dependent on the polarizability and grain size, respectively. PMID:18519215

  7. Crystallographic Structure of Ti-6Al-4V, Ti-HP and Ti-CP Under High Pressure

    SciTech Connect

    Halevy, I.; Zamir, G; Winterrose, M; Ghose, S; Grandini, C; Moreno-Gobbi, A

    2010-01-01

    The phase stability of a commercial purity (Ti-CP), high purity (Ti-HP) and Ti-6Al-4V alloy were investigated in a diamond anvil cell up to 32 GPa and 298 K using a polychromatic X-ray beam. The Ti-CP and Ti-HP shown the same HCP (c/a {approx} 0.632) to Hexagonal (c/a {approx} 1.63) non reversible martensitic transition at about 9 GPa. The as received Ti-6Al-4V shows a very low relative volume fraction {beta}-Ti/{alpha}-Ti. No phase changes were observed in the Ti-6Al-4V alloy in the pressure range of this study. The {alpha} phase of the Ti-6Al-4V shows monotonic volume cell pressure dependence. This volume change is reversible and non-hysteretic. The cell of the a phase recovered its original volume when the pressure was released.

  8. Effect of inflammatory conditions and H2O2 on bare and coated Ti-6Al-4V surfaces: Corrosion behavior, metal ion release and Ca-P formation under long-term immersion in DMEM

    NASA Astrophysics Data System (ADS)

    Höhn, Sarah; Virtanen, Sannakaisa

    2015-12-01

    The surface oxide film and calcium-phosphate (Ca-P) formation on Ti-6Al-4V during long-term immersion in biological environments play a decisive role for the biocompatibility of the implant. Hence, the aim of the study was to evaluate the corrosion resistance, metal ion release and Ca-P formation in DMEM under physiological conditions at pH values of 7.4 and in comparison under simulated inflammatory conditions with pH 5 and in presence of H2O2. Furthermore, the influence of the immersion conditions was investigated on different surface treatments: on bare Ti-6Al-4V, after anodization, and for TiO2 nanoparticle (NP) and hydroxyapatite (HA)-incorporated TiO2-NP coatings. In the absence of H2O2, the impedance response indicated a stable thin oxide film and Ca-P formation after 28 days or 56 days depending on the coating, while under inflammatory conditions the Ca-P formation on the surface is time-delayed and dissolution of the anodized oxide layer as well as selective etching of the β-phase and phase boundaries in case of the bare alloy occur. Electrochemical impedance spectroscopy (EIS), however, indicates a good general corrosion behavior in all cases. The quantities of Ti, Al and V released from the bare and coated Ti-6Al-4V alloy markedly increased with decreasing pH (pH ≤ 5). Although the rapid increase of metal release was observed for all samples at pH 5, the quantities were significantly higher for the bare and anodized alloy than after coating with TiO2-NP or HA.

  9. Microstructure and Microwave Dielectric Properties of (1-x)MgAl2O4-x(Ca0.8Sr0.2)TiO3 Ceramics

    NASA Astrophysics Data System (ADS)

    Huang, Yafei; Yu, Jun; Shen, Chunying; Tang, Mingliang

    2016-06-01

    The microwave dielectric properties of the (1-x)MgAl2O4-x(Ca0.8Sr0.2)TiO3 (x = 0.02 to 0.10) ceramic system synthesized by the traditional solid-state reaction method have been investigated. Spinel-structured MgAl2O4 was present together with perovskite-structured (Ca0.8Sr0.2)TiO3, and this multiphase system was verified by x-ray diffraction (XRD) and energy spectrum analyses throughout the whole compositional range. With increasing x, the temperature coefficient of resonant frequency (τ f) and permittivity (ɛ r) gradually increased. Consequently, near-zero τ f could be obtained for samples with x = 0.08. Excellent microwave dielectric properties with relative permittivity (ɛ r) of 10.92, quality factor (Q × f) of 52,563 GHz (at 12.9 GHz), and temperature coefficient of resonant frequency (τ f) of -5.6 ppm/°C were obtained for 0.92MgAl2O4-0.08(Ca0.8Sr0.2)TiO3 composite sintered at 1440°C for 3 h, making this material a promising candidate for use in global communication satellites and radar detectors.

  10. Phase Relations and Elemental Distribution Among Co-Existing Phases in the Ceramics of the Pseudobinary System CaZrTi{sub 2}O{sub 7}-LnAlO{sub 3} (Ln= Nd, Sm)

    SciTech Connect

    Mikhailenko, Natalia; Stefanovsky, Sergey

    2007-07-01

    In the ceramics in series (1-x) CaZrTi{sub 2}O{sub 7} - x NdAlO{sub 3} and (1-x) CaZrTi{sub 2}O{sub 7} - x SmAlO{sub 3} (x = 0.25, 0.5 and 0.75) produced by cold pressing and sintering at 1400, 1450 and 1500 deg. C zirconolite was found to be a major phase, perovskite was an extra phase and traces of residual baddeleyite occurred. At x = 0.75 the perovskite was major phase and zirconolite and cubic oxide of fianite or tazheranite type were extra phases. Major Nd and Sm host phase at x = 0.25 was found to be zirconolite (about 65% of total Nd{sub 2}O{sub 3} and 74% of total Sm{sub 2}O{sub 3}). With the x value increasing perovskite becomes major host phase for Nd and Sm accumulating of up to about 92% of total Nd and about 72% of total Sm. As follows from SEM/EDS data Nd and Sm contents in the zirconolite may reach {approx}1 formula unit (fu). (authors)

  11. Characteristics of heat resistant alloys Ti10Nb45Al and Ti18Nb48Al

    SciTech Connect

    Weijun Zhang; Guoliang Chen; Yandong Wang; Zuqing Sun )

    1993-05-01

    Based on a systematic study of the ternary Ti-Nb-Al system, two attractive heat resistant alloys, Ti10Nb45Al and Ti18Nb48Al, were developed, and the characteristics of these alloys were discussed: (1) After annealing at 1,200 C for 240 h and furnace cooling to room temperature, the Ti10Nb45Al alloy exhibits an [alpha][sub 2] + [gamma] lamellar microstructure, and the Ti18Nb48Al alloy shows a plate-like structure consisting of [alpha][sub 2], [gamma] and [gamma][sub 1] phases. (2) The specific strengths of Ti10Nb45Al and Ti18Nb48Al are much higher than TiAl and superalloys in the temperature range of 800 [approximately] 1,100 C. The compressive yield strengths of these alloys are on the order of 700 MPa at 800 C and 350 MPa at 1,100 C. The density of these alloys is about 4.3 g/cm[sup 3]. (3) The annealed Ti10Nb45Al and Ti18Nb48Al exhibit some ductility at room temperature, with the compressive elongation on the order of 12% and the fracture toughness as high as 16 MPa[radical]m. The ductile-brittle transformation temperatures for Ti10Nb45Al and Ti18Nb48Al are 650 C and 750 C, respectively. (4) The parabolic constant K[sub p] for oxidation of Ti10Nb45Al and Ti18Nb48Al are 0.88 and 0.29 mg[sup 2]cm[sup [minus]4]h[sup [minus]1] respectively, which are two orders of magnitude lower than that of TiAl and Ti[sub 3]Al alloys.

  12. Durability Assessment of TiAl Alloys

    NASA Technical Reports Server (NTRS)

    Draper, Susan L.; Lerch, Bradley A.

    2008-01-01

    The durability of TiAl is a prime concern for the implementation of TiAl into aerospace engines. Two durability issues, the effect of high temperature exposure on mechanical properties and impact resistance, have been investigated and the results are summarized in this paper. Exposure to elevated temperatures has been shown to be detrimental to the room temperature ductility of gamma alloys with the most likely mechanisms being the ingress of interstitials from the surface. Fluorine ion implantation has been shown to improve the oxidation resistance of gamma alloys, and ideally it could also improve the environmental embrittlement of high Nb content TiAl alloys. The effect of F ion implantation on the surface oxidation and embrittlement of a third generation, high Nb content TiAl alloy (Ti-45Al-5Nb-B-C) were investigated. Additionally, the ballistic impact resistance of a variety of gamma alloys, including Ti-48Al-2Cr- 2Nb, Ti-47Al-2Cr-2Nb, ABB-2, ABB-23, NCG359E, 95A and Ti-45Al-5Nb-B-C was accessed. Differences in the ballistic impact properties of the various alloys will be discussed, particularly with respect to their manufacturing process, microstructure, and tensile properties.

  13. Effect of surface chemistries and characteristics of Ti6Al4V on the Ca and P adsorption and ion dissolution in Hank's ethylene diamine tetra-acetic acid solution.

    PubMed

    Chang, E; Lee, T M

    2002-07-01

    This study examined the influence of chemistries and surface characteristics of Ti6Al4V on the adsorption of Ca and P species and ion dissolution behavior of the material exposed in Hank's solution with 8.0 mM ethylene diamine tetra-acetic acid at 37 degrees C. The variation of chemistries of the alloy and nano-surface characteristics (chemistries of nano-surface oxides, amphoteric OH group adsorbed on oxides, and oxide thickness) was effected by surface modification and three passivation methods (34% nitric acid passivation. 400 degrees C heated in air, and aged in 100 degrees C water). X-ray photoelectron spectroscopy and Auger electron spectroscopy were used for surface analyses. The chemistries of nano-surface oxides in a range studied should not change the capability of Ca and P adsorption. Nor is the capability affected significantly by amphoteric OH group and oxide thickness. However, passivations influence the surface oxide thickness and the early stage ion dissolution rate of the alloy. The rate-limiting step of the rate can be best explained by metal-ion transport through the oxide film, rather than hydrolysis of the film. Variation of the chemistries of titanium alloy alters the electromotive force potential of the metal, thereby affecting the corrosion and ion dissolution rate. PMID:12069333

  14. Electrophoretic deposition of porous CaO-MgO-SiO2 glass-ceramic coatings with B2O3 as additive on Ti-6Al-4V alloy.

    PubMed

    Zhang, Wei; Chen, Xianchun; Liao, Xiaoming; Huang, Zhongbing; Dan, Xiuli; Yin, Guangfu

    2011-10-01

    The sub-micron glass-ceramic powders in CaO-MgO-SiO(2) system with 10 wt% B(2)O(3) additive were synthesized by sol-gel process. Then bioactive porous CaO-MgO-SiO(2) glass-ceramic coatings on Ti-6Al-4V alloy substrates were fabricated using electrophoretic deposition (EPD) technique. After being calcined at 850°C, the above coatings with thickness of 10-150 μm were uniform and crack-free, possessing porous structure with sub-micron and micron size connected pores. Ethanol was employed as the most suitable solvent to prepare the suspension for EPD. The coating porous appearance and porosity distribution could be controlled by adjusting the suspension concentration, applied voltage and deposition time. The heat-treated coatings possessed high crystalline and was mainly composed of diopside, akermanite, merwinite, calcium silicate and calcium borate silicate. Bonelike apatite was formed on the coatings after 7 days of soaking in simulated body fluid (SBF). The bonding strength of the coatings was needed to be further improved. PMID:21858723

  15. 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)

  16. Itinerant antiferromagnetism of TiAl alloys

    NASA Astrophysics Data System (ADS)

    Petrişor, T.; Pop, I.; Giurgiu, A.; Farbaş, N.

    1986-06-01

    Magnetic susceptibility measurements of TiAl alloys are reported. Aluminium, by alloying, acts on the Néel temperature of pure titanium giving rise to a complicated phase diagram. A theoretical model, based on the itinerant antiferromagnetism model of chromium is proposed in order to explain the magnetic phase diagram of TiAl alloys. The experimental and theoretical magnetic phase diagram are in good agreement.

  17. HYDROGEN ADSORPTION ON β-TiAl (001) AND Ni/TiAl (001) SURFACES

    NASA Astrophysics Data System (ADS)

    Mubarak, A. A. Karim; Alelaimi, Mahmoud

    2014-04-01

    In this paper, we present first principles calculations of the energetic, electronic and magnetic properties of the variant termination of TiAl (001) and Ni/TiAl (001) surfaces with and without hydrogen atoms. The calculations have been performed within the density functional theory using full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) is utilized as the exchange-correlation energy. The octahedral site is the stable absorption site of H atom in the β-TiAl system. This absorption reduces the cohesive energy of β-TiAl system due to increase in the lattice constant. The surface energy for both TiAl (001) terminations is calculated. The stable adsorption site of H atoms on the variant termination of TiAl (001) surface is performed. The adsorption energy of hydrogen on Ti is more energetic than that on Al. The adsorption of H atom on both terminations of H/Ni/TiAl (001) is more preferable at the bridge site. The adsorption energies are enhanced on Ni atom due to the contraction between d-Ni bands and TiAl substrate band.

  18. Perrierite-(La), (La,Ce,Ca)4(Fe2+,Mn)(Ti,Fe3+,Al)4(Si2O7)2O8, a new mineral species from the Eifel volcanic district, Germany

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Blass, G.; Pekov, I. V.; Belakovskiy, D. I.; Van, K. V.; Rastsvetaeva, R. K.; Aksenov, S. M.

    2012-12-01

    Non-metamict perrierite-(La) discovered in the Dellen pumice quarry, near Mendig, in the Eifel volcanic district, Rheinland-Pfalz, Germany has been approved as a new mineral species (IMA no. 2010-089). The mineral was found in the late assemblage of sanidine, phlogopite, pyrophanite, zirconolite, members of the jacobsite-magnetite series, fluorcalciopyrochlore, and zircon. Perrierite-(La) occurs as isolated prismatic crystals up to 0.5 × 1 mm in size within cavities in sanidinite. The new mineral is black with brown streak; it is brittle, with the Mohs hardness of 6 and distinct cleavage parallel to (001). The calculated density is 4.791 g/cm3. The IR spectrum does not contain absorption bands that correspond to H2O and OH groups. Perrierite-(La) is biaxial (-), α = 1.94(1), β = 2.020(15), γ = 2.040(15), 2 V meas = 50(10)°, 2 V calc = 51°. The chemical composition (electron microprobe, average of seven point analyses, the Fe2+/Fe3+ ratio determined from the X-ray structural data, wt %) is as follows: 3.26 CaO, 22.92 La2O3, 19.64 Ce2O3, 0.83 Pr2O2, 2.09 Nd2O3, 0.25 MgO, 2.25 MnO, 3.16 FeO, 5.28 Fe2O3, 2.59 Al2O3, 16.13 TiO2, 0.75 Nb2O5, and 20.06 SiO2, total is 99.21. The empirical formula is (La1.70Ce1.45Nd0.15Pr0.06Ca0.70)Σ4.06(Fe{0.53/2+}Mn0.38Mg0.08)Σ0.99(Ti2.44Fe{0.80/3+}Al0.62Nb0.07)Σ3.93Si4.04O22. The simplified formula is (La,Ce,Ca)4(Fe2+,Mn)(Ti,Fe3+,Al)4(Si2O7)2O8. The crystal structure was determined by a single crystal. Perrierite-(La) is monoclinic, space group P21/ a, and the unit-cell dimensions are as follows: a =13.668(1), b = 5.6601(6), c = 11.743(1) Å, β = 113.64(1)°; V = 832.2(2) Å3, Z = 2. The strong reflections in the X-ray powder diffraction pattern are [ d, Å ( I, %) ( hkl)]: 5.19 (40) (110), 3.53 (40) (overline 3 11), 2.96 (100) (overline 3 13, 311), 2.80 (50) (020), 2.14 (50) (overline 4 22, overline 3 15, 313), 1.947 (50) (024, 223), 1.657 (40) (overline 4 07, overline 4 33, 331). The holotype specimen of perrierite-(La) is

  19. Aluminian Low-Ca Pyroxene in a Ca-Al-rich Chondrule from the Semarkona Meteorite

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    A Ca-AI-rich chondrule (labeled G7) from the Semarkona LL3.0 ordinary chondrite (OC) consists of 73 vol% glassy mesostasis, 22 vol% skeletal forsterite. 3 vol% fassaite (i.e., Al-Ti diopside), and 2 vol% Al-rich, low-Ca pyroxene. The latter phase, which contains up to 16.3 wt% A1203, is among the most AI-rich, low-Ca pyroxene grains ever reported. It is inferred that 20% of the tetrahedral sites and 13% of the octahedral sites in this grain are occupied by Al. Approximately parallel optical extinction implies that the Al-rich, low-Ca pyroxene grains are probably orthorhombic, consistent with literature data that show that A1203 stabilizes the orthoenstatite structure relative to protoenstatite at low pressure. The order of crystallization in the chondrule was forsterite, AI-rich low-Ca pyroxene, and fassaite; the residual liquid vitrified during chondrule quenching. Phase relationships indicate that, for a G7-composition liquid at equilibrium, spinel and anorthite should crystallize early and orthopyroxene should not crystallize at all. The presence of AI-rich orthopyroxene in G7 is due mainly to the kinetic failure of anorthite to crystallize; this failure was caused by quenching of the G7 precursor droplet. Aluminum preferentially enters the relatively large B tetrahedra of orthopyroxene; because only one tetrahedral size occurs in fassaite, this phase contains higher mean concentrations of Al2O3 than the Al-rich orthopyroxene (17.8 and 14.7 wt%, respectively). Chondrule G7 may have formed by remelting an amoeboid olivine inclusion that entered the OC region of the solar nebula during an episode of chondrule formation.

  20. Piezoelectric and Dielectric Properties of Multilayered BaTiO3/(Ba,Ca)TiO3/CaTiO3 Thin Films.

    PubMed

    Zhu, Xiao Na; Gao, Ting Ting; Xu, Xing; Liang, Wei Zheng; Lin, Yuan; Chen, Chonglin; Chen, Xiang Ming

    2016-08-31

    Highly oriented multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films were fabricated on Nb-doped (001) SrTiO3 (Nb:STO) substrates by pulsed laser deposition. The configurations of multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films are designed with the thickness ratio of 1:1:1 and 2:1:1 and total thickness ∼300 nm. Microstructural characterization by X-ray diffraction indicates that the as-deposited thin films are highly c-axis oriented and large in-plane strain is determined in BaTiO3 and CaTiO3 layers. Piezoresponse force microscopy (PFM) studies reveal an intense in-plane polarization component, whereas the out-of-plane shows inferior phase contrast. The optimized combination is found to be the BaTiO3-(Ba0.85Ca0.15)TiO3-CaTiO3 structure with combination ratio 2:1:1, which displays the largest domain switching amplitude under DC electric field, the largest room-temperature dielectric constant ∼646, a small dielectric loss of 0.03, and the largest dielectric tunability of ∼50% at 400 kV/cm. These results suggest that the enhanced dielectric and tunability performance are greatly associated with the large in-plane polarization component and domain switching. PMID:27514235

  1. Erase-mode recording characteristics of photochromic CaF2, SrTiO3, and CaTiO3 crystals.

    NASA Technical Reports Server (NTRS)

    Duncan, R. C., Jr.

    1972-01-01

    Erase-mode optical recording characteristics of photochromic crystal wafers of CaF2:La,Na; CaF2:Ce,Na; SrTiO3:Ni,Mo,Al; and CaTiO3:Ni,Mo have been measured. An argon laser operating at 5145 A was used for both optical recording and optical readout. Sensitometric curves of optical-density change versus logarithm of exposure are shown for a number of erase-beam intensities between 0.2 mW/sq cm and 2 W/sq cm. In this range, time-intensity reciprocity holds for the CaF2 materials but fails for the titanates, particularly at low intensities. The dependences of sensitivity, gamma, and maximum transmission contrast ratio on wafer thickness and material are discussed. Wafers of SrTiO3, CaTiO3, and CaF2 exhibiting approximately equal maximum contrast ratios have relative sensitivities approximately in the ratio 5:2:1, respectively, at an erase intensity of 1 W/sq cm.

  2. Glass-ceramic nuclear waste forms obtained by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): Study of the crystallization from the surface

    NASA Astrophysics Data System (ADS)

    Loiseau, P.; Caurant, D.

    2010-07-01

    Glass-ceramic materials containing zirconolite (nominally CaZrTi 2O 7) crystals in their bulk can be envisaged as potential waste forms for minor actinides (Np, Am, Cm) and Pu immobilization. In this study such matrices are synthesized by crystallization of SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th) as surrogates. A thin partially crystallized layer containing titanite and anorthite (nominally CaTiSiO 5 and CaAl 2Si 2O 8, respectively) growing from glass surface is also observed. The effect of the nature and concentration of surrogates on the structure, the microstructure and the composition of the crystals formed in the surface layer is presented in this paper. Titanite is the only crystalline phase able to significantly incorporate trivalent lanthanides whereas ThO 2 precipitates in the layer. The crystal growth thermal treatment duration (2-300 h) at high temperature (1050-1200 °C) is shown to strongly affect glass-ceramics microstructure. For the system studied in this paper, it appears that zirconolite is not thermodynamically stable in comparison with titanite growing form glass surface. Nevertheless, for kinetic reasons, such transformation (i.e. zirconolite disappearance to the benefit of titanite) is not expected to occur during interim storage and disposal of the glass-ceramic waste forms because their temperature will never exceed a few hundred degrees.

  3. Redistribution of Ti and Al in deuterium charged TiAl

    NASA Technical Reports Server (NTRS)

    Legzdina, D.; Robertson, I. M.; Birnbaum, H. K.

    1992-01-01

    The redistribution of titanium and aluminum in a single-phase TiAl alloy that has been exposed to a high pressure of deuterium gas at high temperature is studied. The microstructure in the as-received, uncharged condition consisted of single-phase gamma TiAl grains and a random distribution of precipitates. Precipitates were distributed throughout the matrix and along the grain boundaries. The chemistry of the precipitates varied considerably; some were rich in Al, while other were mostly Ti with some Si and Al. The dislocation density in most grains was low, although in a few grains a high dislocation density was observed. FCC deuterides with a lattice parameter of 0.45 nm form in a Ti-52.1Al-2.1Ta (at. pct) alloy after exposure to 1.38 MPa of deuterium gas at 650 C for 213 hr. The structure and lattice parameter are consistent with the formation of Ti(l)D2. The deuterides that form in this alloy are enriched in Ti and deficient in Al and Ta compared to the deuteride-free matrix. Regions of the matrix contiguous with the deuterides have a correspondingly enhanced aluminum and tantalum concentration.

  4. Redistribution of Ti and Al in deuterium charged TiAl

    SciTech Connect

    Legzdina, D.; Robertson, I.M.; Birnbaum, H.K. )

    1992-06-01

    The redistribution of titanium and aluminum in a single-phase TiAl alloy that has been exposed to a high pressure of deuterium gas at high temperature is studied. The microstructure in the as-received, uncharged condition consisted of single-phase gamma TiAl grains and a random distribution of precipitates. Precipitates were distributed throughout the matrix and along the grain boundaries. The chemistry of the precipitates varied considerably; some were rich in Al, while other were mostly Ti with some Si and Al. The dislocation density in most grains was low, although in a few grains a high dislocation density was observed. FCC deuterides with a lattice parameter of 0.45 nm form in a Ti-52.1Al-2.1Ta (at. pct) alloy after exposure to 1.38 MPa of deuterium gas at 650 C for 213 hr. The structure and lattice parameter are consistent with the formation of Ti(l)D2. The deuterides that form in this alloy are enriched in Ti and deficient in Al and Ta compared to the deuteride-free matrix. Regions of the matrix contiguous with the deuterides have a correspondingly enhanced aluminum and tantalum concentration. 10 refs.

  5. Investigation of Wear Anisotropy in a Severely Deformed Al-Al3Ti Composite

    NASA Astrophysics Data System (ADS)

    El-Hadad, Shimaa; Sato, Hisashi; Watanabe, Yoshimi

    2012-09-01

    In the current investigation, Al-Al3Ti composite was processed by equal channel angular pressing (ECAP). ECAP was carried out using routes A and BC up to eight passes of deformation. It was observed that increasing the number of ECAP passes causes fragmentation of Al3Ti platelet particles and decreases their sizes compared to their original sizes in the undeformed Al-Al3Ti specimens. Moreover, the microstructure of route A-ECAPed Al-Al3Ti composite samples showed a strong alignment of the fragmented Al3Ti particles parallel to the pressing axis. On the other hand, ECAPed Al-Al3Ti alloy specimens by route BC have a relatively homogeneous distribution of Al3Ti particles. Because of the platelet Al3Ti particle fragmentation by ECAP, all the ECAPed specimens showed small anisotropy in their wear property in spite of this observed anisotropic microstructure induced by route A-ECAP.

  6. Investigation of Wear Anisotropy in a Severely Deformed Al-Al3Ti Composite

    NASA Astrophysics Data System (ADS)

    El-Hadad, Shimaa; Sato, Hisashi; Watanabe, Yoshimi

    2012-05-01

    In the current investigation, Al-Al3Ti composite was processed by equal channel angular pressing (ECAP). ECAP was carried out using routes A and BC up to eight passes of deformation. It was observed that increasing the number of ECAP passes causes fragmentation of Al3Ti platelet particles and decreases their sizes compared to their original sizes in the undeformed Al-Al3Ti specimens. Moreover, the microstructure of route A-ECAPed Al-Al3Ti composite samples showed a strong alignment of the fragmented Al3Ti particles parallel to the pressing axis. On the other hand, ECAPed Al-Al3Ti alloy specimens by route BC have a relatively homogeneous distribution of Al3Ti particles. Because of the platelet Al3Ti particle fragmentation by ECAP, all the ECAPed specimens showed small anisotropy in their wear property in spite of this observed anisotropic microstructure induced by route A-ECAP.

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

    NASA Technical Reports Server (NTRS)

    Kimura, Makoto; El-Goresy, Ahmed; Palme, Herbert; Zinner, Ernst

    1993-01-01

    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.

  8. 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.

  9. A comparison in mechanical properties of cermets of calcium silicate with Ti-55Ni and Ti-6Al-4V alloys for hard tissues replacement.

    PubMed

    Ataollahi Oshkour, Azim; Pramanik, Sumit; Shirazi, Seyed Farid Seyed; Mehrali, Mehdi; Yau, Yat-Huang; Abu Osman, Noor Azuan

    2014-01-01

    This study investigated the impact of calcium silicate (CS) content on composition, compressive mechanical properties, and hardness of CS cermets with Ti-55Ni and Ti-6Al-4V alloys sintered at 1200°C. The powder metallurgy route was exploited to prepare the cermets. New phases of materials of Ni16Ti6Si7, CaTiO3, and Ni31Si12 appeared in cermet of Ti-55Ni with CS and in cermet of Ti-6Al-4V with CS, the new phases Ti5Si3, Ti2O, and CaTiO3, which were emerged during sintering at different CS content (wt%). The minimum shrinkage and density were observed in both groups of cermets for the 50 and 100 wt% CS content, respectively. The cermets with 40 wt% of CS had minimum compressive Young's modulus. The minimum of compressive strength and strain percentage at maximum load were revealed in cermets with 50 and 40 wt% of CS with Ti-55Ni and Ti-6Al-4V cermets, respectively. The cermets with 80 and 90 wt% of CS showed more plasticity than the pure CS. It concluded that the composition and mechanical properties of sintered cermets of Ti-55Ni and Ti-6Al-4V with CS significantly depend on the CS content in raw cermet materials. Thus, the different mechanical properties of the cermets can be used as potential materials for different hard tissues replacements. PMID:25538954

  10. Multilayer (TiN, TiAlN) ceramic coatings for nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Alat, Ece; Motta, Arthur T.; Comstock, Robert J.; Partezana, Jonna M.; Wolfe, Douglas E.

    2016-09-01

    In an attempt to develop an accident-tolerant fuel (ATF) that can delay the deleterious consequences of loss-of-coolant-accidents (LOCA), multilayer coatings were deposited onto ZIRLO® coupon substrates by cathodic arc physical vapor deposition (CA-PVD). Coatings were composed of alternating TiN (top) and Ti1-xAlxN (2-layer, 4-layer, 8-layer and 16-layer) layers. The minimum TiN top coating thickness and coating architecture were optimized for good corrosion and oxidation resistance. Corrosion tests were performed in static pure water at 360 °C and 18.7 MPa for up to 90 days. The optimized coatings showed no spallation/delamination and had a maximum of 6 mg/dm2 weight gain, which is 6 times smaller than that of a control sample of uncoated ZIRLO® which showed a weight gain of 40.2 mg/dm2. The optimized architecture features a ∼1 μm TiN top layer to prevent boehmite phase formation during corrosion and a TiN/TiAlN 8-layer architecture which provides the best corrosion performance.

  11. Biomimetic Hydroxyapatite Growth on Functionalized Surfaces of Ti-6Al-4V and Ti-Zr-Nb Alloys

    NASA Astrophysics Data System (ADS)

    Pylypchuk, Ie V.; Petranovskaya, A. L.; Gorbyk, P. P.; Korduban, A. M.; Markovsky, P. E.; Ivasishin, O. M.

    2015-08-01

    A biomimetic approach for coating titanium-containing alloys with hydroxyapatite (HA) is reported in the article. Two types of Ti-containing alloys were chosen as an object for coating: Ti-6Al-4V (recommended for orthopedic application) and a novel highly biocompatible Ti-Zr-Nb alloy, with good mechanical compatibility due to a modulus that is more close to that of human bones (E ≈ 50 GPa instead of 110 GPa in Ti-6Al-4V). Coating process was carried out in a 10×-concentrated simulated body fluid (SBF)—synthetic analog of human body plasma. The effect of oxidized and carboxylated alloy surface on formation of biomimetic hydroxyapatite has been studied. By XRD, we found influence of thermal conditions on HA crystal formation and size. SEM images and Fourier transform infrared confirmed that hydroxyapatite with different morphology, crystallinity, and Ca/P ratio formed on metallic surfaces. X-ray photoelectron spectroscopy showed that in the Ti-6AL-4V sample the observed Ca/P ratio reach 0.97, whereas in the Ti-Zr-Nb sample the observed Ca/P ratio reach 1.15.

  12. Biomimetic Hydroxyapatite Growth on Functionalized Surfaces of Ti-6Al-4V and Ti-Zr-Nb Alloys.

    PubMed

    Pylypchuk, Ie V; Petranovskaya, A L; Gorbyk, P P; Korduban, A M; Markovsky, P E; Ivasishin, O M

    2015-12-01

    A biomimetic approach for coating titanium-containing alloys with hydroxyapatite (HA) is reported in the article. Two types of Ti-containing alloys were chosen as an object for coating: Ti-6Al-4V (recommended for orthopedic application) and a novel highly biocompatible Ti-Zr-Nb alloy, with good mechanical compatibility due to a modulus that is more close to that of human bones (E ≈ 50 GPa instead of 110 GPa in Ti-6Al-4V). Coating process was carried out in a 10×-concentrated simulated body fluid (SBF)-synthetic analog of human body plasma. The effect of oxidized and carboxylated alloy surface on formation of biomimetic hydroxyapatite has been studied. By XRD, we found influence of thermal conditions on HA crystal formation and size. SEM images and Fourier transform infrared confirmed that hydroxyapatite with different morphology, crystallinity, and Ca/P ratio formed on metallic surfaces. X-ray photoelectron spectroscopy showed that in the Ti-6AL-4V sample the observed Ca/P ratio reach 0.97, whereas in the Ti-Zr-Nb sample the observed Ca/P ratio reach 1.15. PMID:26297184

  13. Adhesion of metal carbide/nitride interfaces: Al/TiC and Al/TiN

    NASA Astrophysics Data System (ADS)

    Liu, L. M.; Wang, S. Q.; Ye, H. Q.

    2003-12-01

    We employ density functional theory to investigate and compare Al/TiC and Al/TiN interfaces by electronic structures, relaxed atomic geometries and adhesions. The results show that the preferred bonding site is the interfacial Al atoms above the ceramic's metalloid atoms for both systems. The calculated adhesion energies are quantitatively in agreement with other calculated and experimental results of Al on the carbide and nitride. A detailed comparison of the adhesion energies and relaxed structures shows weaker bonding and less relaxation in the Al/nitride case, which is correlated with the lower surface energy of the ceramic. We have thoroughly characterized the electronic structure and determined that the polar covalent Al3sp-C(N)2s bonds constitute the primary interfacial bonding interaction. The larger overlapping bonding states at the Al/TiC interface reveal the reason why it exhibits relatively larger adhesion energy. Cleavage may take place preferentially at the interface, especially for the Al/TiN, which is in agreement with experimental results.

  14. Diffusion Research in BCC Ti-Al-Mo Ternary Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Tang, Bin; Xu, Guanglong; Wang, Chuanyun; Kou, Hongchao; Li, Jinshan; Cui, Yuwen

    2014-04-01

    Interdiffusion in Ti-Al-Mo β solid solution was investigated at 1523 K (1250 °C) by analyzing diffusion couples. From the concentration profiles analytically represented by error function expansion (ERFEX), the ternary interdiffusion coefficients and impurity diffusivity were extracted by the Whittle-Green and generalized Hall methods. A comparison of the diffusion in five Ti-Al-X (Co, Cr, Fe, Mo, and V) ternaries reveals Ti-Al-Mo is comparably like Ti-Al-(Cr, V) while Ti-Al-(Co, Fe) are predominantly of interstitial nature.

  15. Crystal structure of the mineral (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4}: a triclinic representative of the amphibole family

    SciTech Connect

    Rastsvetaeva, R. K. Aksenov, S. M.

    2012-05-15

    A mineral belonging to the amphibole family found at the Rothenberg paleovolcano (Eifel, Germany) was studied by single-crystal X-ray diffraction. The triclinic pseudomonoclinic unit-cell parameters are a = 5.3113(1) Angstrom-Sign , b = 18.0457(3) Angstrom-Sign ; c = 9.8684(2) Angstrom-Sign , {alpha} = 90.016(2) Degree-Sign , {beta} = 105.543(4) Degree-Sign , {gamma} = 89.985(2) Degree-Sign . The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 2.7% based on 6432 reflections with |F| > 3{sigma}(F) taking into account twinning. The mineral with the idealized formula (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4} has some symmetry and structural features that distinguish it from other minerals of this family.

  16. Effect of Al on the Wetting Behavior Between TiC x and Molten Ti-Al Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Xuyang; Lv, Xuewei; Dong, Hongbiao; Li, Chunxin; Bai, Chenguang

    2015-10-01

    The wetting behavior and the interfacial reactions between TiC x substrate and molten Ti-Al alloys with different Al contents were studied using the Sessile Drop method at 1758 K (1485 °C) in argon atmosphere. It is found that the wettability and interface reaction products depend on Al content in the molten alloy. The initial contact angles between the molten Ti-Al alloy and TiC0.78 surface reduces from 110 to 80 deg when Al content in the alloy changes from 40 to 80 wt pct. The reduction in the initial contact angle is due to the decrease of surface tension of the molten Ti-Al alloys with increasing Al contents. The segregation of Al atoms to the surface occurred at all bulk concentrations of Ti-Al alloys. Al with lower surface tension tends to segregate on the surface of liquid Ti-Al alloy. In the spreading stage, the interfacial reaction led to the decrease in the contact angle. The adhesion in Ti-Al/TiC x system can be interpreted in terms of strong chemical interactions, which is greatly affected by the diffusion of C. The equilibrium contact angle was measured less than 10 deg. Finally, the reaction sequence at the Ti-Al melt and TiC x substrate interface is proposed.

  17. Formation and Thermodynamics of Mg-Al-Ti-O Complex Inclusions in Mg-Al-Ti-Deoxidized Steel

    NASA Astrophysics Data System (ADS)

    Ren, Ying; Zhang, Lifeng; Yang, Wen; Duan, Haojian

    2014-12-01

    The formation of Mg-Al-Ti-O complex inclusions in steel was investigated by laboratory experiments and thermodynamic calculation. The composition evolutions of Mg-Al-Ti-O inclusions in steel with different contents of [Al], [Mg], and [Ti] were discussed. Mg-Al-Ti-O complex inclusion with high TiOx content was liquid at 1873 K (1600 °C), indicating MgAl2O4 spinel inclusions can be modified to low melting temperature ones by combining TiOx component. The stability diagram of Al-Mg-Ti-O system inclusions in the molten steel at 1873 K (1600 °C) was calculated, considering many kinds of oxide inclusions such as MgO, Al2O3, TiOx, MgTi2O4, MgAl2O4, Al2TiO5, and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of Al-Mg-Ti-O complex inclusions in molten steel with a large concentration range of [Al], [Mg], and [Ti].

  18. The Interface of TiB2 and Al3Ti in Molten Aluminum

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoming; Song, Jie; Vian, Wei; Ma, Haibin; Han, Qingyou

    2015-12-01

    In the grain refinement of aluminum, Al3Ti and TiB2 particles are introduced to reduce the casting grain size down to 200 micrometer level, which makes cold working possible. The particles are brought in by the addition of Al-Ti-B-type master alloys. It is generally believed that TiB2 particles are stable and nucleate α-Al grains in solidification in the presence of titanium in solution from the dissolution of Al3Ti particles in the master alloys. The titanium in solution either forms Al3Ti layers on the surface of TiB2 particles to promote the nucleation of α-Al grains or remains as solute to restrict the growth of α-Al grains in solidification. However, a consensus on a grain refinement mechanism is still to be reached due to the lack of direct observation of the three phases in castings. This paper presents finding of the TiB2/Al3Ti interfaces in an Al-Ti-B master alloy. It demonstrates a strong epitaxial growth of Al3Ti on the surface of TiB2 particles, a sign of the formation of an Al3Ti layer on the surface of TiB2 particles in grain refinement practice. The Al3Ti layer has a crystal coherency with α-Al and hence offers a substrate for heterogeneous nucleation of α-Al grains. However, the layer must be dynamic to avoid the formation of compounded Al3Ti and TiB2 particles leading to the loss of efficiency in grain refinement.

  19. Properties of TiAlN coating deposited by MPIIID on TiN substrates

    NASA Astrophysics Data System (ADS)

    El-Hossary, F. M.; Abd El-Rahman, A. M.; Raaif, M.; Ghareeb, D. A.

    2016-03-01

    Metal plasma immersion ion implantation and deposition (MPIIID) is employed to produce TiAlN hard coatings on Ti substrate. To improve the load-bearing capacity of Ti substrate, nitrogen PIII is used to prepare a bearing TiN layer on Ti-base substrate. The MPIIID process is performed using Ti50:Al50 target for different nitrogen/argon gas fractions. The effect of N2/Ar gas ratio on the microstructure, mechanical and tribological properties of TiAlN coatings has been studied. The plastic microhardness of TiAlN increases with increasing the nitrogen gas fraction to reach a maximum value of 30 GPa at 100 % N2. The plasticity index and the resistance to plastic deformation increase with increasing the nitrogen gas fraction. The wear volume loss of TiAlN coating deposited on TiN substrate decreases by a factor of 103 in comparison with pure Ti. Moreover, the friction coefficient decreases from nearly 0.8 for Ti to 0.25 for TiAlN coatings. The enhanced mechanical and tribological properties of the coating are correlated with the formation of TiAlN hard phase. This phase has random-oriented microstructure, finer grain size, high oxidation resistance and residual internal stress. Moreover, the TiN interface acts as a barrier for the motion of dislocations.

  20. Molar Volume Modeling of Ti-Al-Nb and Ti-Al-Mo Ternary Systems

    NASA Astrophysics Data System (ADS)

    Zhu, Jun; Zhang, Chuan; Cao, Weisheng; Chen, Shuanglin; Zhang, Fan; Park, Joon Sik; Yi, Seonghoon

    2015-08-01

    Molar volume modeling was performed for both Ti-Al-Nb and Ti-Al-Mo ternary systems based on the thermodynamic modeling of these two systems. Comparison between the calculated phase equilibria and the experimental data proved the accuracy of thermodynamic modeling. With the calculated density contour curves superimposed on the equilibrium phase diagram, it provides a map for alloy developers to identify the promising alloy compositions that satisfy both the phase stability and density requirements and rule out those that fail to meet the requirements.

  1. Ca-Al-rich chondrules and inclusions in ordinary chondrites

    NASA Technical Reports Server (NTRS)

    Bischoff, A.; Keil, K.

    1983-01-01

    Ca-Al-rich objects, hitherto mostly found in carbonaceous chondrites, are shown to be widespread, albeit rare, constituents of type 3 ordinary chondrites. Widespread occurrence and textural similarities of Ca-Al-rich chondrules to common, Mg-Fe-rich chondrules suggest that they formed by related processes. It is suggested in this article that Ca-Al-rich chondrules were formed by total melting and crystallization of heterogeneous, submillimeter- to submillimeter-sized dustballs made up of mixtures of high-temperature, Ca-Al-rich and lower-temperature, Na-K-rich components.

  2. Creep deformation of a two-phase TiAl/Ti[sub 3]Al lamellar alloy and the individual TiAl and Ti[sub 3]Al constituent phases

    SciTech Connect

    Bartholomeusz, M.F.; Wert, J.A. ); Qibin Yang )

    1993-08-01

    Two-phase TiAl/Ti[sub 3]Al alloys in which the constituent phases form a lamellar microstructure are reported to possess good combinations of low-temperature fracture toughness, tensile strength and fatigue resistance. However, information about the high-temperature creep properties of the two-phase TiAl/Ti[sub 3]Al alloys with lamellar microstructures (referred to as lamellar alloys in the remainder of the paper) is limited. Based on a simple rule of mixtures model of strength, it would be expected that the creep rates of the lamellar alloy would be between the creep rates of TiAl and Ti[sub 3]Al. In contrast to composite model predictions of strength, Polvani and coworkers found that the minimum creep rates of two duplex alloys, a [gamma]/[gamma][prime] nickel-base superalloy and NiAl/Ni[sub 2]AlTi, were significantly lower than the minimum creep rates of either of the constituent phases. They also reported that most dislocations in the two-phase NiAl/Ni[sub 2]AlTi alloy were contained within the semi-coherent interfacial dislocation networks between the two phases. Based on this observation they proposed that the creep rate is controlled by the rate at which dislocations moving through both phases are emitted and absorbed by the interphase dislocation networks. The greater strain hardening rate of the lamellar TiAl/Ti[sub 3]Al alloy suggests that it may exhibit lower steady-state creep rates that the individual constituent phases. The objective of the present study is to evaluate the creep properties of a TiAl/ Ti[sub 3]Al lamellar alloy and of the individual constituent phases. In this paper, the results of this investigation will be presented and compared with previously published results for this alloy system.

  3. Interfacial reactions and oxidation behavior of Al 2O 3 and Al 2O 3/Al coatings on an orthorhombic Ti 2AlNb alloy

    NASA Astrophysics Data System (ADS)

    Li, H. Q.; Wang, Q. M.; Gong, J.; Sun, C.

    2011-02-01

    The uniform and dense Al2O3 and Al2O3/Al coatings were deposited on an orthorhombic Ti2AlNb alloy by filtered arc ion plating. The interfacial reactions of the Al2O3/Ti2AlNb and Al2O3/Al/Ti2AlNb specimens after vacuum annealing at 750 °C were studied. In the Al2O3/Ti2AlNb specimens, the Al2O3 coating decomposed significantly due to reaction between the Al2O3 coating and the O-Ti2AlNb substrate. In the Al2O3/Al/Ti2AlNb specimens, a γ-TiAl layer and an Nb-rich zone came into being by interdiffusion between the Al layer and the O-Ti2AlNb substrate. The γ-TiAl layer is chemically compatible with Al2O3, with no decomposition of Al2O3 being detected. No internal oxidation or oxygen and nitrogen dissolution zone was observed in the O-Ti2AlNb alloy. The Al2O3/Al/Ti2AlNb specimens exhibited excellent oxidation resistance at 750 °C.

  4. Crystalline Al1 - x Ti x phases in the hydrogen cycled NaAlH4 + 0.02TiCl3 system

    NASA Astrophysics Data System (ADS)

    Pitt, M. P.; Vullum, P. E.; Sørby, M. H.; Emerich, H.; Paskevicius, M.; Buckley, C. E.; Gray, E. MacA.; Walmsley, J. C.; Holmestad, R.; Hauback, B. C.

    2013-03-01

    The hydrogen (H) cycled planetary milled (PM) NaAlH4 + 0.02TiCl3 system has been studied by high resolution synchrotron X-ray diffraction and transmission electron microscopy during the first 10 H cycles. After the first H absorption, we observe the formation of four nanoscopic crystalline (c-) Ti-containing phases embedded on the NaAlH4 surface, i.e. Al2Ti, Al3Ti, Al82Ti18 and Al89Ti11, with 100% of the originally added Ti atoms accounted for. Al2Ti and Al3Ti are observed morphologically as a mechanical couple on the NaAlH4 surface, with a moderately strained interface. Electron diffraction shows that the Al82Ti18 phase retains some ordering from the L12 structure type, with the observation of forbidden (100) ordering reflections in the fcc Al82Ti18 lattice. After 2 H cycles the NaAlH4 + 0.02TiCl3 system displays only two crystalline Ti-containing phases, Al3Ti and Al89Ti11. After 10 H cycles, the Al89Ti11 is completely converted to Al85Ti15. Al89Ti11, Al85Ti15 and Al3Ti do not display any ordering reflections, and they are modeled in the A1 structure type. Quantitative phase analysis indicates that the Al3Ti proportion continues to increase with further H cycles. The formation of Ti-poor Al1 - x Ti x (x < 0.25) phases in later H cycles is detrimental to hydrogenation kinetics, compared to the starting Ti-richer near-surface Al2Ti/NaAlH4 interface present during the first absorption of hydrogen.

  5. Modeling creep deformation of a two-phase TiAl/Ti[sub 3]Al alloy with a lamellar microstructure

    SciTech Connect

    Bartholomeusz, M.F. ); Wert, J.A. . Dept. of Materials Science and Engineering)

    1994-10-01

    A two-phase TiAl/Ti[sub 3]Al alloy with a lamellar microstructure has been previously shown to exhibit a lower minimum creep rate than the minimum creep rates of the constituent TiAl and Ti[sub 3]Al single-phase alloys. Fiducial-line experiments described in the present article demonstrate that the creep rates of the constituent phases within the two-phase TiAl/Ti[sub 3]Al lamellar alloy tested in compression are more than an order of magnitude lower than the creep rates of single-phase TiAl and Ti[sub 3]Al alloys tested in compression at the same stress and temperature. Additionally, the fiducial-line experiments show that no interfacial sliding of the phases in the TiAl/Ti[sub 3]Al lamellar alloy occurs during creep. The lower creep rate of the lamellar alloy is attributed to enhanced hardening of the constituent phases within the lamellar microstructure. A composite-strength model has been formulated to predict the creep rate of the lamellar alloy, taking into account the lower creep rates of the constituent phases within the lamellar microstructure. Application of the model yields a very good correlation between the predicted an experimentally observed minimum creep rates over moderate stress and temperature ranges.

  6. Cost-Effective TiAl based Materials

    NASA Technical Reports Server (NTRS)

    Moxson, V. S.; Sun, Fusheng; Draper, Susan L.; Froes, F. H.; Duz, V.

    2003-01-01

    Because of their inherent low ductility, TiAl-based materials are difficult to fabricate, especially thin gage titanium gamma aluminide (TiAl) sheet and foil. In this paper, an innovative powder metallurgy approach for producing cost-effective thin gage TiAl sheets (with 356 mm long and 235 mm wide, and a thickness of 0.74, 1.09, 1.55, and 2.34 mm, respectively) is presented. The microstructures and tensile properties at room and elevated temperatures of the thin gage TiAl are studied. Results show that these TiAl sheets have a relatively homogenous chemistry, uniform microstructure, and acceptable mechanical properties. This work demonstrates a cost-effective method for producing both flat products (sheet/foil) and complex chunky parts of TiAl for various advanced applications including aerospace and automotive industries.

  7. High temperature creep behaviour of Al-rich Ti-Al alloys

    NASA Astrophysics Data System (ADS)

    Sturm, D.; Heilmaier, M.; Saage, H.; Aguilar, J.; Schmitz, G. J.; Drevermann, A.; Palm, M.; Stein, F.; Engberding, N.; Kelm, K.; Irsen, S.

    2010-07-01

    Compared to Ti-rich γ-TiAl-based alloys Al-rich Ti-Al alloys offer an additional reduction of in density and a better oxidation resistance which are both due to the increased Al content. Polycrystalline material was manufactured by centrifugal casting. Microstructural characterization was carried out employing light-optical, scanning and transmission electron microscopy and XRD analyses. The high temperature creep of two binary alloys, namely Al60Ti40 and Al62Ti38 was comparatively assessed with compression tests at constant true stress in a temperature range between 1173 and 1323 K in air. The alloys were tested in the cast condition (containing various amounts of the metastable phases Al5Ti3 and h-Al2Ti) and after annealing at 1223 K for 200 h which produced (thermodynamically stable) lamellar γ-TiAl + r-Al2Ti microstructures. In general, already the as-cast alloys exhibit a reasonable creep resistance at 1173 K. Compared with Al60Ti40, both, the as-cast and the annealed Al62Ti38 alloy exhibit better creep resistance up to 1323 K which can be rationalized by the reduced lamella spacing. The assessment of creep tests conducted at identical stress levels and varying temperatures yielded apparent activation energies for creep of Q = 430 kJ/mol for the annealed Al60Ti40 alloy and of Q = 383 kJ/mol for the annealed Al62Ti38 material. The latter coincides well with that of Al diffusion in γ-TiAl, whereas the former can be rationalized by the instability of the microstructure containing metastable phases.

  8. Study of preparation of TiB{sub 2} by TiC in Al melts

    SciTech Connect

    Ding Haimin; Liu Xiangfa; Nie Jinfeng

    2012-01-15

    TiB{sub 2} particles are prepared by TiC in Al melts and the characteristics of them are studied. It is found that TiC particles are unstable when boron exists in Al melts with high temperature and will transform to TiB{sub 2} and Al{sub 4}C{sub 3}. Most of the synthesized TiB{sub 2} particles are regular hexagonal prisms with submicron size. The diameter of the undersurfaces of these prisms is ranging from 200 nm to 1 {mu}m and the height is ranging from 100 nm to 300 nm. It is considered that controlling the transformation from TiC to TiB{sub 2} is an effective method to prepare small and uniform TiB{sub 2} particles. - Highlights: Black-Right-Pointing-Pointer TiC can easily transform into TiB{sub 2} in Al melts. Black-Right-Pointing-Pointer TiB{sub 2} formed by TiC will grow into regular hexagonal prisms with submicron size. Black-Right-Pointing-Pointer Controlling the transformation from TiC to TiB{sub 2} is an effective method to prepare small and uniform TiB{sub 2} particles.

  9. 40Ca(α,γ)44Ti and the production of 44Ti in supernovae

    NASA Astrophysics Data System (ADS)

    Vockenhuber, C.; Ouellet, C. O.; The, L.-S.; Buchmann, L.; Caggiano, J.; Chen, A. A.; D'Auria, J. M.; Davids, B.; Fogarty, L.; Frekers, D.; Hussein, A.; Hutcheon, D. A.; Kutschera, W.; Ottewell, D.; Paul, M.; Pavan, M. M.; Pearson, J.; Ruiz, C.; Ruprecht, G.; Trinczek, M.; Wallner, A.

    2008-01-01

    The nuclide 44Ti is predicted to be produced in significant quantities in core-collapse supernovae, and indeed it has been observed in the supernova remnant Cassiopeia-A by space-based γ-ray telescopes. The main production of 44Ti takes place in the α-rich freeze-out phase deep inside the supernova. The key reactions governing the 44Ti abundance have been identified in an earlier sensitivity study. Using the recoil mass spectrometer DRAGON at the TRIUMF-ISAC facility in Vancouver, Canada, we measured the main production reaction 40Ca(α,γ)44Ti, resulting in an increased reaction rate compared to the rate derived from previous prompt γ-ray studies, which is commonly used in supernova models. The uncertainty of the 44Ti production is now dominated by the rate of reactions with short-lived nuclides around 44Ti, namely 45V(p,γ)46Cr, 44Ti(α,p)47V and 44Ti(α,γ)48Cr. The sensitivity of these reactions on the 44Ti production has been revisited.

  10. Effect of Al2O3 Addition on the Precipitated Phase Transformation in Ti-Bearing Blast Furnace Slags

    NASA Astrophysics Data System (ADS)

    Li, Zhongmin; Li, Jinfu; Sun, Yongqi; Seetharaman, Seshadri; Liu, Lili; Wang, Xidong; Zhang, Zuotai

    2016-04-01

    The present paper aims to provide a fundamental understanding on phase change of Ti-enriched crystalline phase induced by Al2O3 addition in Ti-bearing blast furnace slags with different basicities using Single Hot Thermocouple Technique and X-ray Diffraction. The results showed that an increase in the Al2O3 content led to phase change from rutile or perovskite to Mg3Al4Ti8O25 and prompted crystallization of the slags with basicity of 0.60 and 0.75, whereas only CaTiO3 was precipitated at a basicity of 0.95. Both thermodynamic and kinetic analyses were conducted to study the slag crystallization, which would throw light on phase change and enhanced crystallization. To further reveal the relationship with Al2O3 addition on slag structure and crystallization, Fourier transform infrared spectroscopy and magic angle spinning-nuclear magnetic resonance were adopted, with AlO4 tetrahedra and AlO6 octahedra observed in the slag. For slags with the basicity of 0.60 and 0.75, AlO6 octahedron, which was suggested to induce the phase change from TiO2 or CaTiO3 to Mg3Al4Ti8O25, was detected at high Al2O3 content. On the other hand, in slags with the basicity of 0.95, abundant Ca2+ may be connected to TiO6 octahedra, resulting in CaTiO3 formation.

  11. Microstructures and Mechanical Properties of Transient Liquid-Phase Diffusion-Bonded Ti3Al/TiAl Joints with TiZrCuNi Interlayer

    NASA Astrophysics Data System (ADS)

    Ren, H. S.; Xiong, H. P.; Pang, S. J.; Chen, B.; Wu, X.; Cheng, Y. Y.; Chen, B. Q.

    2016-04-01

    Transient liquid-phase diffusion bonding of Ti3Al-based alloy to TiAl intermetallics was conducted using Ti-13Zr-21Cu-9Ni (wt pct) interlayer foil. The joint microstructures were examined using a scanning electron microscope (SEM) equipped with an electron probe micro-analyzer (EPMA). The microhardness across the joint was measured and joint strengths were tested. The results show that the Ti3Al/TiAl joint mainly consists of Ti-rich phase, Ti2Al layer, α 2-Ti3Al band, and residual interlayer alloy dissolved with Al. The amount of residual interlayer at the central part of the joint is decreased with the increase of the bonding temperature, and meantime the Ti2Al and α 2-Ti3Al reaction bands close to the joined Ti3Al-based alloy become thickened gradually. Furthermore, the central part of the joint exhibits the maximum microhardness across the whole joint. The joints bonded at 1193 K (920 °C) for 600 seconds with a pressure of 2 MPa presented the maximum shear strength of 417 MPa at room temperature, and the strength of 234 MPa was maintained at 773 K (500 °C).

  12. Phase competition in ternary Ti-Ni-Al system

    NASA Astrophysics Data System (ADS)

    Wierzba, Bartek

    2016-07-01

    In this paper the reactive diffusion in Ti-Ni-Al system is discussed at 1173 K. The calculation method based on the binary approach is presented. The key kinetic parameter is Wagner integral diffusion coefficient. The experimental and simulation results of reactive diffusion between pure Ti and β-NiAl are compared at 1173 K after 100 h.

  13. Energetics of point defects in {gamma}-TiAl

    SciTech Connect

    Raju, S.; Mohandas, E.; Raghunathan, V.S.

    1996-02-15

    {gamma}TiAl has been receiving a great deal of attention in recent times owing to its industrial importance. This structural intermetallic is a candidate material for high temperature aerospace applications. Therefore, a study of point defect properties is useful in elucidating its physical metallurgy. In this brief communication, the authors discuss the vacancy and antisite defect properties of {gamma}-TiAl.

  14. 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.

  15. Effects of Al Contents on Carburization Behavior and Corrosion Resistance of TiAl Alloys

    NASA Astrophysics Data System (ADS)

    Liao, Cui Jiao; He, Yue Hui; Ming, Xing Zu

    2015-10-01

    TiAl alloys with Al contents of 30.7, 37, 46.5, and 54.2 at.% were carburized. Corrosion resistance of the untreated and the carburized TiAl alloys was comparatively analyzed. The phase and microstructure of the carburized TiAl alloys were studied by x-ray diffraction and scanning electron microscopy, respectively. Electrochemical corrosion behavior of the untreated and the carburized TiAl alloys was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. Experimental results indicate that different Al contents bring about distinct microstructure of the carburized layers. The lower Al content leads to the formation of the thicker binary carbides and the thinner Ti2AlC phase. Additionally, the lower Al content leads to higher corrosion resistance in the untreated and the carburized states.

  16. Apatite deposition and collagen coating effects in Ti-Al-V and Ti-Al-Nb alloys

    NASA Astrophysics Data System (ADS)

    Choi, Y.; Hong, S. I.

    2014-12-01

    The biomimetic deposition rate of apatite for Ti-6Al-4V was found to be greater than that for Ti-6Al-7Nb in regular 1 × Modified SBF. The coating of collagen was found to enhance the biomimetic deposition of apatite on Ti-6Al-4V and Ti-6Al-7Nb. The nucleation and growth of the apatite deposition layer was faster on collagen coated Ti alloys. An interesting observation is that the granular structure became less clear and the nodular boundary became obscure in apatite deposited on the collagen-coated Ti alloys. The ill-defined granular structure may be associated with the presence of more amorphous calcium phosphate. The morphology of apatite nodules was found to be modified by collagen coating and collagen addition.

  17. Interface enhanced functionalities in BaTiO3/CaTiO3 superlattices

    NASA Astrophysics Data System (ADS)

    Wu, Xifan

    2014-03-01

    Interface engineering of oxide thin films has led to the development of many intriguing physical properties and new functionalities, in which the oxygen rotation and tilting take an crucial role. The oxygen octahedral tilt has been considered to be a coherent motion in the oxide thin-films, based on which the tilt is often neglected in the modeling of ABO3 superlattices. However, combined with state-of-art experimental high-resolution electron microscopic image, our first-principles results clearly show that oxygen octahedral tilt should be more appropriately defined by the tilting angles of two individual pyramids. Each pyramid will tilt rather independently as a function of its local chemical environment. Considering the oxygen octahedral rotation at the same time, the new picture of oxygen octahedral tilting will induce a novel interface effect, in which an unstable structure in bulk CaTiO3 will be stabilized at the interface in BaTiO3/CaTiO3 superlattice. This novel interface effect induces large polarizations both in-plane and out-of-plane with a corresponding enhanced piezoelectricity. The above scenario successfully explains the recent experimental discoveries in BaTiO3/CaTiO3 superlattices by H. Lee's and P. Evan's groups respectively.

  18. Oxygen Octahedral Rotations in BaTiO3/CaTiO3 Superlattices

    NASA Astrophysics Data System (ADS)

    Cosgriff, Margaret; Chen, Pice; Corey, Nathaniel; Wu, Xifan; Mehta, Apurva; Tajiri, Hiroo; Lee, Ho Nyung; Evans, Paul

    2013-03-01

    Complex oxide superlattices have a wide range of electronic and magnetic properties, which are affected by the structure of the interfaces between different components of the superlattice. The magnitude, coherence, and electric field response of oxygen displacements in three different BaTiO3/CaTiO3 superlattice compositions are measured using x-ray diffraction. The displacements are greater in compositions with more consecutive CaTiO3 layers. The pattern of layer-by-layer alternating displacements is coherent over less than two superlattice unit cells. The net in-phase rotation of the oxygen octahedra gives rise to an x-ray reflection at (3/2 1/2 1). Density functional theory calculations for a 2(BaTiO3) /4(CaTiO3) composition predict a decrease in displacements of oxygen octahedra between barium and calcium layers when an electric field is applied, causing an intensity increase in this reflection. We found the intensity of this reflection for this composition increases by 1.6% when a 12.5 V pulse is applied, a weaker response than the 11% increase predicted. When a 20 V pulse is applied, the reflection intensity actually decreases by 3%, indicating a more complicated response.

  19. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V

    PubMed Central

    Mahdipoor, M.S.; Kirols, H.S.; Kevorkov, D.; Jedrzejowski, P.; Medraj, M.

    2015-01-01

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ Vn, where the speed exponent is 7–9 for Ti6Al4V and 11–13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl. PMID:26391370

  20. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Mahdipoor, M. S.; Kirols, H. S.; Kevorkov, D.; Jedrzejowski, P.; Medraj, M.

    2015-09-01

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ Vn, where the speed exponent is 7-9 for Ti6Al4V and 11-13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl.

  1. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V.

    PubMed

    Mahdipoor, M S; Kirols, H S; Kevorkov, D; Jedrzejowski, P; Medraj, M

    2015-01-01

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ V(n), where the speed exponent is 7-9 for Ti6Al4V and 11-13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl. PMID:26391370

  2. Microscopic Properties of Long-Period Ordering in Al-Rich TiAl Alloys

    NASA Astrophysics Data System (ADS)

    Hata, S.; Nakano, T.; Kuwano, N.; Itakura, M.; Matsumura, S.; Umakoshi, Y.

    2008-07-01

    The ordering mechanism of long-period superstructures (LPSs) in Al-rich TiAl alloys has been investigated by high-resolution transmission electron microscopy (HRTEM). The LPSs are classified in terms of arrangements of base clusters with different shapes and compositions formed in Ti-rich (002) layers of L10-TiAl matrix: square Ti4Al, fat rhombus Ti3Al, and lean rhombus Ti2Al type clusters. The HRTEM observations revealed that antiphase boundaries of long-range-ordered LPS domains and short-range-ordered microdomains are constructed by various space-filling arrangements of the base clusters. Such a microscopic property characterized by the base clusters and their arrangements is markedly analogous to that of the {left< {{text{1,1/2,0}}} rightrangle } * special-point ordering alloys such as Ni-Mo.

  3. A Comparison in Mechanical Properties of Cermets of Calcium Silicate with Ti-55Ni and Ti-6Al-4V Alloys for Hard Tissues Replacement

    PubMed Central

    Pramanik, Sumit; Shirazi, Seyed Farid Seyed; Mehrali, Mehdi; Yau, Yat-Huang; Abu Osman, Noor Azuan

    2014-01-01

    This study investigated the impact of calcium silicate (CS) content on composition, compressive mechanical properties, and hardness of CS cermets with Ti-55Ni and Ti-6Al-4V alloys sintered at 1200°C. The powder metallurgy route was exploited to prepare the cermets. New phases of materials of Ni16Ti6Si7, CaTiO3, and Ni31Si12 appeared in cermet of Ti-55Ni with CS and in cermet of Ti-6Al-4V with CS, the new phases Ti5Si3, Ti2O, and CaTiO3, which were emerged during sintering at different CS content (wt%). The minimum shrinkage and density were observed in both groups of cermets for the 50 and 100 wt% CS content, respectively. The cermets with 40 wt% of CS had minimum compressive Young's modulus. The minimum of compressive strength and strain percentage at maximum load were revealed in cermets with 50 and 40 wt% of CS with Ti-55Ni and Ti-6Al-4V cermets, respectively. The cermets with 80 and 90 wt% of CS showed more plasticity than the pure CS. It concluded that the composition and mechanical properties of sintered cermets of Ti-55Ni and Ti-6Al-4V with CS significantly depend on the CS content in raw cermet materials. Thus, the different mechanical properties of the cermets can be used as potential materials for different hard tissues replacements. PMID:25538954

  4. Nucleation and Precipitation Strengthening in Dilute Al-Ti and Al-Zr Alloys

    NASA Astrophysics Data System (ADS)

    Knipling, Keith E.; Dunand, David C.; Seidman, David N.

    2007-10-01

    Two conventionally solidified Al-0.2Ti alloys (with 0.18 and 0.22 at. pct Ti) exhibit no hardening after aging up to 3200 hours at 375 °C or 425 °C. This is due to the absence of Al3Ti precipitation, as confirmed by electron microscopy and electrical conductivity measurements. By contrast, an Al-0.2Zr alloy (with 0.19 at. pct Zr) displays strong age hardening at both temperatures due to precipitation of Al3Zr (L12) within Zr-enriched dendritic regions. This discrepancy between the two alloys is explained within the context of the equilibrium phase diagrams: (1) the disparity in solid and liquid solubilities of Ti in α-Al is much greater than that of Zr in α-Al; and (2) the relatively small liquid solubility of Ti in α-Al limits the amount of solute retained in solid solution during solidification, while the comparatively high solid solubility reduces the supersaturation effecting precipitation during post-solidification aging. The lattice parameter mismatch of Al3Ti (L12) with α-Al is also larger than that of Al3Zr (L12), further hindering nucleation of Al3Ti. Classical nucleation theory indicates that the minimum solute supersaturation required to overcome the elastic strain energy of Al3Ti nuclei cannot be obtained during conventional solidification of Al-Ti alloys (unlike for Al-Zr alloys), thus explaining the absence of Al3Ti precipitation and the presence of Al3Zr precipitation.

  5. Corrosion behavior of TiN, TiAlN, TiAlSiN-coated 316L stainless steel in simulated proton exchange membrane fuel cell environment

    NASA Astrophysics Data System (ADS)

    Nam, Nguyen Dang; Vaka, Mahesh; Tran Hung, Nguyen

    2014-12-01

    To gain high hardness, good thermal stability and corrosion resistance, multicomponent TiAlSiN coating has been developed using different deposition methods. In this study, the influence of Al and Si on the electrochemical properties of TiN-coated 316L stainless steel as bipolar plate (BP) materials has been investigated in simulated proton exchange membrane fuel cell environment. The deposited TiN, TiAlN and TiAlSiN possess high hardness of 23.9, 31.7, 35.0 GPa, respectively. The coating performance of the TiN coating is enhanced by Al and Si addition due to lower corrosion current density and higher Rcoating and Rct values. This result could be attributed to the formation of crystalline-refined TiN(200), which improves the surface roughness, surface resistance, corrosion performance, and decreased passive current density.

  6. Al-21Ti-23Cr high-temperature protective coating on TiAl intermetallic compounds by RF magnetron sputtering

    SciTech Connect

    Park, J.Y.; Lee, H.N.; Wee, D.M.; Park, S.W.; Oh, M.H.

    1997-12-31

    Ti-48Al specimens were coated with Al-21Ti-23Cr film at 200 W, 0.8 Pa and 573 K by RF magnetron sputtering. The oxidation behavior of the coated specimens was investigated through isothermal and cyclic oxidation tests, and the tensile deformation properties of the coated specimens were also investigated before and after oxidation. The isothermal and cyclic oxidation curves showed that the Al-21Ti-23Cr film was very effective in decreasing the oxidation rate of Ti-48Al. This excellent oxidation resistance is attributable to the formation of a protective Al{sub 2}O{sub 3} layer on the surface of the Al-21Ti-23Cr film. It was found from the results of the tensile test that the protective Al{sub 2}O{sub 3} layer on the surface of the Al-21Ti-23Cr film enabled the Ti-48Al to maintain its tensile properties in an oxidizing environment.

  7. Hydrogen sorption behavior of CaAl1.5Li0.5

    NASA Astrophysics Data System (ADS)

    Bereznitsky, Matvey; Mogilyanski, Dmitry; Jacob, Isaac

    2016-04-01

    The hydrogen sorption properties of an alloy with nominal composition CaAl1.5Li0.5 have been investigated in a pursuit for hydrogen-absorbing Li-containing intermetallics. X-ray analysis of the original alloy indicated a coexistence of three closely related Laves phases. The maximum hydrogen capacity, recorded at about 6 MPa and 300 °C, was approximately 2.5 H atoms per formula unit (f.u.). Pressure-composition (p-c) isotherm measurements were taken in the temperature range between 350 and 450 °C up to pressures of 133 kPa. Thermodynamic parameters are derived for two plateau regions in the p-c isotherms. Analysis of these parameters and supporting evidence from X-ray patterns of hydrogenated and dehydrogenated samples suggest: (a) an initial irreversible disproportionation of the original alloy and (b) subsequent reversible hydrogenations, featuring reversible disproportionations of CaAl2 and LiAl intermetallic compounds. Attempts to form additional Li-containing intermetallics, namely CaAlLi, TiMn2- x Li x (x = 0.2, 0.3, 0.4, 0.6) and TiAl2- x Li x (x = 0.3, 0.5), and to hydrogenate them, are reported in brief.

  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. Biocorrosion of TiO2 nanoparticle coating of Ti-6Al-4V in DMEM under specific in vitro conditions

    NASA Astrophysics Data System (ADS)

    Höhn, Sarah; Virtanen, Sannakaisa

    2015-02-01

    A TiO2 nanoparticle coating was prepared on a biomedical Ti-6Al-4V alloy using "spin-coating" technique with a colloidal suspension of TiO2 nanopowders with the aim to optimize the surface morphology (e.g., roughness) for improved biocompatibility. The influence of a TiO2 nanoparticle (NP) coating on the corrosion behavior, metal ion release, and biomimetic apatite formation was studied in DMEM, at 37.5 °C with a continuous supply of 5% CO2. Electrochemical impedance spectroscopy measurements indicate a formation of a new layer on the surface of the NP-coated sample upon 28 days immersion in DMEM. Scanning electron microscopy (SEM) and X-ray spectroscopy confirm that the surface of the NP-coated Ti-6Al-4V shows a complete coverage by a Ca-phosphate layer in contrast to the non-coated Ti-6Al-4V alloy. Hence, the TiO2-NP coating strongly enhances biomimetic apatite formation on the alloy surface. In addition, the TiO2-NP coating can efficiently reduce Al-release from the alloy, for which the bare Ti-6Al-4V alloy is significant for at least 28 days of immersion in DMEM.

  10. Electromigration performance improvement of Al-Si-Cu/TiN/Ti/n+Si contact

    NASA Astrophysics Data System (ADS)

    Shi, Gang; Sun, Zhen; Xu, Geng-Fu; Min, Yun-Hao; Luo, Jun-Yi; Lu, Yong; Li, Bing-Zong; Qu, Xin-Ping; Qian, Gang; Doan, My T.; Lee, Edmund

    1998-02-01

    In this study, two different processes, with and without rapid thermal annealing (RTA), have been compared for the Al-Si- Cu/TiN/Ti multilayer contact on n+ diffusions. A series of wafer level reliability (WLR) measurement performed on a test structure with two 1.08 X 1.08 micrometer2 contacts on n+ diffusion. The results show that RTA can increase contact electromigration (EM) lifetime dramatically. The XRD, AES and TEM analysis indicate that this improvement is attributed to oxygen stuffing in TiN, phase change of TiN and TiSi2 formation at the interface of Ti and Si.

  11. Impact of symmetry on the ferroelectric properties of CaTiO{sub 3} thin films

    SciTech Connect

    Biegalski, Michael D.; Qiao, Liang; Gu, Yijia; Chen, Long-Qing; Mehta, Apurva; He, Qian; Borisevich, Albina; Takamura, Yayoi

    2015-04-20

    Epitaxial strain is a powerful tool to induce functional properties such as ferroelectricity in thin films of materials that do not possess ferroelectricity in bulk form. In this work, a ferroelectric state was stabilized in thin films of the incipient ferroelectric, CaTiO{sub 3}, through the careful control of the biaxial strain state and TiO{sub 6} octahedral rotations. Detailed structural characterization was carried out by synchrotron x-ray diffraction and scanning transmission electron microscopy. CaTiO{sub 3} films grown on La{sub 0.18}Sr{sub 0.82}Al{sub 0.59}Ta{sub 0.41}O{sub 3} (LSAT) and NdGaO{sub 3} (NGO) substrates experienced a 1.1% biaxial strain state but differed in their octahedral tilt structures. A suppression of the out-of-plane rotations of the TiO{sub 6} octahedral in films grown on LSAT substrates resulted in a robust ferroelectric I4 mm phase with remnant polarization ∼5 μC/cm{sup 2} at 10 K and T{sub c} near 140 K. In contrast, films grown on NGO substrates with significant octahedral tilting showed reduced polarization and T{sub c}. These results highlight the key role played by symmetry in controlling the ferroelectric properties of perovskite oxide thin films.

  12. Impact of symmetry on the ferroelectric properties of CaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Biegalski, Michael D.; Qiao, Liang; Gu, Yijia; Mehta, Apurva; He, Qian; Takamura, Yayoi; Borisevich, Albina; Chen, Long-Qing

    2015-04-01

    Epitaxial strain is a powerful tool to induce functional properties such as ferroelectricity in thin films of materials that do not possess ferroelectricity in bulk form. In this work, a ferroelectric state was stabilized in thin films of the incipient ferroelectric, CaTiO3, through the careful control of the biaxial strain state and TiO6 octahedral rotations. Detailed structural characterization was carried out by synchrotron x-ray diffraction and scanning transmission electron microscopy. CaTiO3 films grown on La0.18Sr0.82Al0.59Ta0.41O3 (LSAT) and NdGaO3 (NGO) substrates experienced a 1.1% biaxial strain state but differed in their octahedral tilt structures. A suppression of the out-of-plane rotations of the TiO6 octahedral in films grown on LSAT substrates resulted in a robust ferroelectric I4 mm phase with remnant polarization ˜5 μC/cm2 at 10 K and Tc near 140 K. In contrast, films grown on NGO substrates with significant octahedral tilting showed reduced polarization and Tc. These results highlight the key role played by symmetry in controlling the ferroelectric properties of perovskite oxide thin films.

  13. Strain-coupled ferroelectric polarization in BaTiO3-CaTiO3 superlattices

    SciTech Connect

    Seo, Sung Seok A; Lee, Ho Nyung

    2009-01-01

    We report on growth and ferroelectric (FE) properties of superlattices (SLs) composed of the FE BaTiO{sub 3} and the paraelectric CaTiO{sub 3}. Previous theories have predicted that the polarization in (BaTiO{sub 3})n/(CaTiO{sub 3})n SLs increases as the sublayer thickness (n) increases when the same strain state is maintained. However, our BaTiO{sub 3}/CaTiO{sub 3} SLs show a varying lattice-strain state and systematic reduction in polarization with increasing n while coherently strained SLs with n = 1 and 2 show a FE polarization of ca. 8.5 {micro}C/cm{sup 2}. We suggest that the strain coupling plays a more important role in FE properties than the electrostatic interlayer coupling based on constant dielectric permittivities.

  14. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    An investigation was conducted to examine the fretting behavior of lambda-TiAl (Ti-48Al-2Cr-2Nb) in contact with a nickel-base superalloy (Inconel 718) in air at temperatures from 23 to 550 C. Fretting wear experiments were conducted with 9.4-mm-diameter hemispherical Inconel (IN) 718 pins in contact with Ti-48Al-2Cr-2Nb flats (and the reverse) at loads from 1 to 40 N and fretting frequencies from 50 to 160 Hz with slip amplitudes from 50 to 200 microns for 1 to 20 million fretting cycles. The results were similar for both combinations of pin and flat. Reference fretting wear experiments were also conducted with 9.4-mm-diameter hemispherical Ti-6Al-4V pins in contact with IN718 flats. The interfacial adhesive bonds between Ti-48Al-2Cr-2Nb and IN718 in contact were generally stronger than the cohesive bonds in the cohesively weaker Ti-48Al-2Cr-2Nb. The failed Ti-48Al-2Cr-2Nb subsequently transferred to the IN718 surface at any fretting condition. The wear scars produced on Ti-48Al-2Cr-2Nb contained metallic and oxide wear debris, scratches, plastically deformed asperities, cracks, and fracture pits. Oxide layers readily formed on the Ti-48Al-2Cr-2Nb surface at 550 C, but cracks easily occurred in the oxide layers. Factors including fretting frequency, temperature, slip amplitude, and load influenced the fretting behavior of Ti-48Al-2Cr-2Nb in contact with IN718. The wear volume loss of Ti-48Al-2Cr-2Nb generally decreased with increasing fretting frequency. The increasing rate of oxidation at elevated temperatures up to 200 C led to a drop in wear volume loss at 200 C. However, the fretting wear increased as the temperature was increased from 200 to 550 C. The highest temperatures of 450 and 550 C resulted in oxide film disruption with generation of cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. The wear volume loss generally increased as the slip amplitude increased. The wear volume loss also generally increased as the load increased

  16. Effects of water absorption of dielectric underlayers on Al-Si-Cu film properties and electromigration performance in Al-Si-Cu/Ti/TiN/Ti interconnects

    NASA Astrophysics Data System (ADS)

    Yoshida, Tomoyuki; Hashimoto, Shoji; Ohwaki, Takeshi; Mitsushima, Yasuichi; Taga, Yasunori

    1998-01-01

    The effects of underlying dielectric (phosphosilicate glass and borophosphosilicate glass) films to a humid air ambient on Al-Si-Cu film properties and electromigration (EM) performance in Al-Si-Cu/Ti/TiN/Ti layered films have been investigated as a function of the boron content and exposure time of the dielectric films. The Al(111) orientation in the layered films was found to improve drastically with increasing boron content and exposure time. The full width at half maximum value of an Al(111) x-ray rocking curve reached less than 1°. It was also found that the Al-Si-Cu surface becomes smoother and grain sizes increase as the Al(111) orientation improves. The improved Al(111) orientation was attributed to the improved Ti(002) orientation of the bottom Ti films. Further, it was demonstrate that interconnects fabricated from the improved layered film have excellent EM performance.

  17. Oxidation Behavior of Thermal Barrier Coatings with a TiAl3 Bond Coat on γ-TiAl Alloy

    NASA Astrophysics Data System (ADS)

    Wang, Jiqiang; Kong, Lingyan; Li, Tiefan; Xiong, Tianying

    2015-02-01

    The thermal barrier coatings investigated in this paper included a TiAl3 bond coat and a yttria partially stabilized zirconia (YSZ) layer. The TiAl3 bond coat was prepared by deposition of aluminum by cold spray, followed by a heat-treatment. The YSZ layer was prepared by air plasma spray. The isothermal and cyclic oxidation tests were conducted at 900 °C for 1000 h and 500 cycles to test the oxidation resistance of the thermal barrier coatings. The microstructure and composition of the γ-TiAl alloy with and without the thermal barrier coatings after oxidation were investigated. The results showed that a dense TGO layer about 5 μm had grown between the YSZ layer and the TiAl3 bond coat. The TGO had good adhesion to both the YSZ layer and the bond coat even after the TiAl3 bond coat entirely degraded into the TiAl2 phase, which decreased the inward oxygen diffusion. Thus, the thermal barrier coatings improved the oxidation resistance of γ-TiAl alloy effectively.

  18. Glass-ceramic nuclear waste forms obtained from SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 glasses containing lanthanides (Ce, Nd, Eu, Gd, Yb) and actinides (Th): study of internal crystallization

    NASA Astrophysics Data System (ADS)

    Loiseau, P.; Caurant, D.; Baffier, N.; Mazerolles, L.; Fillet, C.

    2004-10-01

    Glass-ceramic waste forms such as zirconolite (nominally CaZrTi 2O 7) based ones can be envisaged as good candidates for minor actinides or Pu immobilization. Such materials, in which the actinides (or lanthanides used as actinide surrogates) would be preferentially incorporated into zirconolite crystals homogeneously dispersed in a durable glassy matrix, can be prepared by controlled crystallization (nucleation + crystal growth) of parent glasses belonging to the SiO 2-Al 2O 3-CaO-ZrO 2-TiO 2 system. In this work we present the effects of the nature of the minor actinide surrogate (Ce, Nd, Eu, Gd, Yb, Th) on the structure, the microstructure and the composition of the zirconolite crystals formed in the bulk of the glass-ceramics. The amount of lanthanides and thorium incorporated into zirconolite crystals is discussed in relation with the capacity of the glass to accommodate these elements and of the crystals to incorporate them in the calcium and zirconium sites of their structure.

  19. Itinerant magnetism in CaMn2Al10

    NASA Astrophysics Data System (ADS)

    Simonson, Jack; Steinke, Lucia; Zellman, Shelby; Kistner-Morris, Jedediah; Puri, Akshat; Andrews, Evon; Aronson, Meigan

    2015-03-01

    We report the synthesis and basic properties of CaMn2Al10, a new itinerant magnet that is nearly isostructural with the known quantum critical compound YFe2Al10. Magnetic susceptibility measurements performed on single crystals reveal a cusp at 2 K. Electrical resistivity measurements similarly have a maximum at this temperature, and heat capacity measurements show a broad peak with total entropy of ~ 10 % R ln2. These results together with those of neutron diffraction measurements suggest that CaMn2Al10 is weakly magnetic and potentially close to a quantum critical point. Research supported by a DOD National Security Science and Engineering Fellowship via the AFOSR.

  20. Ab initio geometry optimization and ground state properties of layered ternary carbides Ti3MC2 (M = Al, Si and Ge)

    NASA Astrophysics Data System (ADS)

    Zhou, Yanchun; Sun, Zhimei; Wang, Xiaohui; Chen, Shengqi

    2001-11-01

    The crystal structures of all layered ternary carbides called '312' phases including Ti3AlC2, Ti3SiC2 and Ti3GeC2 have been fully optimized by means of ab initio total-energy calculations. The equilibrium lattice parameters, the atomic positions in the unit cell and interatomic distances have been determined. The differences between the calculated and the measured lattice constants are generally less than 1%. It is also shown that c/a of the hexagonal lattices decreases from Ti3AlC2 to Ti3GeC2. The calculated bulk moduli are 190 GPa for Ti3AlC2, 202 GPa for Ti3SiC2 and 198 GPa for Ti3GeC2, respectively, which are comparable to that of TiC. The electronic structures reveal that the Ti(1, 2) and C atoms form a strong Ti(2)-C-Ti(1)-C-Ti(2) covalent bond chain, while the bonding between Ti(2) and M (M = Al, Si, Ge) is relatively weak. The strong Ti(2)-C-Ti(1)-C-Ti(2) covalent bond chain corresponds to the high strength and modulus, while the metallic bond corresponds to the metallic conductivity of these ternaries.

  1. The effect of Al segregation on Schottky barrier height and effective work function in TiAl/TiN/HfO2 gate stacks

    NASA Astrophysics Data System (ADS)

    Kim, Geun-Myeong; Oh, Young Jun; Chang, K. J.

    2016-07-01

    We perform first-principles density functional calculations to investigate the effects of Al incorporation on the p-type Schottky barrier height ≤ft({φ\\text{p}}\\right) and the effective work function for various high-k/metal gate stacks, such as TiN/HfO2 with interface Al impurities, Ti1‑x Al x N/HfO2, and TiAl/TiN/HfO2. When Al atoms substitute for the interface Ti atoms at TiN/HfO2 interface, interface dipole fields become stronger, leading to the increase of {φ\\text{p}} and thereby the n-type shift of effective work function. In Ti1‑x Al x N/HfO2 interface, {φ\\text{p}} linearly increases with the Al content, attributed to the presence of interface Al atoms. On the other hand, in TiAl/TiN/HfO2 interface, where Al is assumed not to segregate from TiAl to TiN, {φ\\text{p}} is nearly independent of the thickness of TiAl. Our results indicate that Al impurities at the metal/dielectric interface play an important role in controlling the effective work function, and provide a clue to understanding the n-type shift of the effective work function observed in TiAl/TiN/HfO2 gate stacks fabricated by using thegate-last process.

  2. Laves phase in Ti-42Al-10Mn alloy

    SciTech Connect

    Chen, Z.; Jones, I.P.; Small, C.J.

    1996-07-01

    Mn is one of the most effective alloying additions to {gamma}-TiAl titanium aluminide for improving room temperature ductility. The purpose of this investigation as a whole is to study phase relationships in the Mn addition alloys over a wide range of temperatures and to determine the solubilities of Mn in the {gamma} and {alpha}{sub 2} phases in order to explore the potential of Mn additions to {gamma}-TiAl. The aim of this specific paper, however, is to confirm the identify of the ternary Ti{sub 3}Al{sub 3}Mn{sub 2} phase in the Ti-Al-Mn system and to show how to remove it.

  3. 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.

  4. A novel TiAl3/Al2O3 composite coating on γ-TiAl alloy and evaluating the oxidation performance

    NASA Astrophysics Data System (ADS)

    Wang, Jiqiang; Kong, Lingyan; Li, Tiefan; Xiong, Tianying

    2016-01-01

    A novel TiAl3/Al2O3 composite coating was prepared on γ-TiAl alloy. The process included two steps: (1) TiAl3/Al2O3 composite powders were prepared by high energy ball milling of pure Al and nano-TiO2 powders, followed by a heat-treatment; (2) the as-prepared composite powders were deposited on γ-TiAl substrate by cold spray. The cyclic oxidation was conducted at 900 °C to test the performance of the composite coating. The results showed that the composite coating had good crack resistance and effectively decreased the oxidation rate of the substrate.

  5. Al-TiH2 Composite Foams Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Prasada Rao, A. K.; Oh, Y. S.; Ain, W. Q.; A, Azhari; Basri, S. N.; Kim, N. J.

    2016-02-01

    The work presented here in describes the synthesis of aluminum based titanium-hydride particulate composite by casting method and its foaming behavior of magnesium alloy. Results obtained indicate that the Al-10TiH2 composite can be synthesized successfully by casting method. Further, results also reveal that closed-cell magnesium alloy foam can be synthesized by using Al-10TiH2 composite as a foaming agent.

  6. 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

  7. Shear transmission in lamellar Ti-48at.%Al

    SciTech Connect

    Wiezorek, J.M.K.; Zhang, X.D.; Clark, W.A.T.; Fraser, H.L.

    1997-12-31

    The transmission of shear across the interfaces between lamellae of {gamma}-TiAl and {alpha}{sub 2}-Ti{sub 3}Al has been studied in the case of a room temperature deformed Ti-48Al alloy containing a significant proportion of the lamellar microstructure. The mechanisms of shear transmission due to dislocation slip has been studied using transmission electron microscopy. Dislocations with Burgers vectors given by b = 1/3<11{bar 2}0> are the only products of slip transmission from the {gamma}-TiAl phase to the {alpha}{sub 2}-Ti{sub 3}Al phase, and essentially no dislocations with b = 1/2<11{bar 2}6>, i.e., c-component dislocations, have been observed. Slip transmission has been associated with impingement of certain cross-lamellar twins, formed by deformation in {gamma}-TiAl, with the {alpha}{sub 2} lamellae. Dislocation based models for the slip transmission processes are proposed.

  8. Reorientable dipolar CuCa antisite and anomalous screening in CaCu3Ti4O12

    NASA Astrophysics Data System (ADS)

    Delugas, Pietro; Alippi, Paola; Fiorentini, Vincenzo; Raineri, Vito

    2010-02-01

    Based on first-principles calculations, we show that the abundant CuCa antisite defect contributes sizably to dielectric screening in single-crystal CaCu3Ti4O12 . CuCa has a multi-minimum off-center equilibrium configuration, whereby it possesses a large and easily reorientable dipole moment. The low-temperature and frequency cut-off behavior of CuCa -induced response is consistent with experiment.

  9. Native defects and Pr impurities in orthorhombic CaTiO3 by first-principles calculations

    NASA Astrophysics Data System (ADS)

    Zhu, Ailing; Wang, Jianchuan; Zhao, Dongdong; Du, Yong

    2011-07-01

    Formation energies of native defects and Pr impurities in orthorhombic CaTiO3 are explored using the first-principles calculations. The Ca vacancy (VCa), Ti vacancy (VTi) and Ca antisite (CaTi) are found to be energetically preferable. The Ti antisite (TiCa) and O vacancy (VO) are not energetically favorable in the wide range of Fermi level. In Pr-doped CaTiO3, Pr substituting for Ca (PrCa) is likely to form under condition A in which CaTiO3 is in equilibrium with CaO and O2. Under condition B (TiO2, CaTiO3 and O2 are in equilibrium), PrTi defect is energetically preferable depending on the Fermi levels. Several native defects and the two sites of Pr impurities in CaTiO3 are coincided with several different defects in Pr-doped CaTiO3 reported in the literature. Based on the present calculations, we can elucidate that the Ca deficiency design of the traditional formula Ca1-xVCa(x/2)PrxTiO3 is not the best for efficient red photoluminescence, which is realized via the experimental measurements.

  10. Atomistic Simulations of Ti Additions to NiAl

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Garg, Anita; Ferrante, John; Amador, Carlos

    1997-01-01

    The development of more efficient engines and power plants for future supersonic transports depends on the advancement of new high-temperature materials with temperature capabilities exceeding those of Ni-based superalloys. Having theoretical modelling techniques to aid in the design of these alloys would greatly facilitate this development. The present paper discusses a successful attempt to correlate theoretical predictions of alloy properties with experimental confirmation for ternary NiAl-Ti alloys. The B.F.S. (Bozzolo-Ferrante-Smith) method for alloys is used to predict the solubility limit and site preference energies for Ti additions of 1 to 25 at.% to NiAl. The results show the solubility limit to be around 5% Ti, above which the formation of Heusler precipitates is favored. These results were confirmed by transmission electron microscopy performed on a series of NiAl-Ti alloys.

  11. Atomistic simulations of Ti additions to NiAl

    SciTech Connect

    Bozzolo, G.; Noebe, R.D.; Garg, A.; Ferrante, J.; Amador, C.

    1997-12-31

    The development of more efficient engines and power plants for future supersonic transports depend on the advancement of new high-temperature materials with temperature capabilities exceeding those of Ni-based superalloys. Having theoretical modelling techniques to aid in the design of these alloys would greatly facilitate this development. The present paper discusses a successful attempt to correlate theoretical predictions of alloy properties with experimental confirmation for ternary NiAl-Ti alloys. The B.F.S. (Bozzolo- Ferrante-Smith) method for alloys is used to predict the solubility limit and site preference energies for Ti additions of 1 to 25 at. % to NiAl. The results show the solubility limit to be around 5% Ti, above which the formation of Heusler precipitates is favored. These results were confirmed by transmission electron microscopy performed on a series of NiAl-Ti alloys.

  12. Shock Response of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Dandekar, Dattatraya P.; Spletzer, Stephen V.

    1999-06-01

    The properties of titanium alloys make them viable candidate materials for use in military ground vehicle systems. Ti-6Al-4V is an alloy that is currently used in aircraft/aerospace applications. However, to successfully make the transition to widespread use in the combat theater, the production and fabrication costs of this alloy must be reduced. Efforts to meet this goal have resulted in a new Ti-6Al-4V alloy material. This material was produced from 32% Ti sponge and 62% Ti-6Al-4V turnings. An ingot was formed by electron beam melting in a cold, water-cooled, copper hearth furnace. The motivation of this work is to characterize the shock response of the new alloy. Shock experiments were performed to obtain information pertaining to the shock, release, shock-reshock, and tensile behavior of the material.

  13. Explosive Fabrication of Intermetallics In Ti-Al System from Nano-Al and Coarse-Ti Powders

    NASA Astrophysics Data System (ADS)

    Chikhradze, Mikheil; Gigineishvili, Akaki; Cikhradze, Nikoloz

    2011-12-01

    Theoretical and experimental Investigations of shock wave consolidation processes of Ti-Al nano sized and ultra-disperse powder compositions are discussed. For theoretical calculations of the shock wave loaded materials were used the hydrodynamic theory and experimental adiabatics of Ti and Al. The normal and tangential stresses in the cylindrical steel tube (containers of Ti-Al reaction mixtures) were estimated using the partial solutions of elasticity theory. The mixtures of ultra-disperse Ti and nano sized (max≤50 nm) Al powder compositions were consolidated to full or near-full density by explosive-compaction technology. The ammonium nitride based industrial explosives were used for generation of shock waves. To form ultra-fine grained bulk TiAl intermetallides with different compositions, ultra-disperse Ti particles were mixed with nano-crystalline Al. Each reaction mixture was placed in a sealed container and explosively compacted using a normal and cylindrical detonation set-up. Explosive compaction experiments were performed in range of pressure impulse (5-20 GPA) at elevated temperatures. X-ray diffraction (XRD), structural investigations (SEM) and micro-hardness measurements were used to characterize the intermetallides phase composition and mechanical properties. The results of analysis revealing the effects of the compacting conditions and precursor particles sizes, affecting the consolidation and the properties of this new ultra high performance alloys are discussed.

  14. Mineralogical anatomy and implications of a Ti-Sc-rich ultrarefractory inclusion from Sayh al Uhaymir 290 CH3 chondrite

    NASA Astrophysics Data System (ADS)

    Zhang, Ai-Cheng; Ma, Chi; Sakamoto, Naoya; Wang, Ru-Cheng; Hsu, Wei-Biao; Yurimoto, Hisayoshi

    2015-08-01

    Titanium-rich minerals are common in Ca-Al-rich inclusions from primitive chondrites. They are important not only for testing the condensation models for a gas with a solar composition, but also for constraining the redox conditions of the early solar nebula. In this study, we report the detailed mineralogical features and its oxygen isotope compositions of a Ti-Sc-rich ultrarefractory inclusion A0031 from a CH3 chondrite Sayh al Uhaymir 290. The A0031 inclusion has a compact and layered texture with the interior consisting of panguite, Sc-rich anosovite, Ti-rich davisite, and anorthite. A few hexaferrum, perovskite, and spinel crystals are present as inclusions in these minerals. Outside of Ti-rich davisite are a layer of Al-Ti-rich diopside and two grains of enstatite. This texture strongly suggests that A0031 has a condensation origin. Panguite is its third occurrence in nature and similar in composition to the type panguite from the Allende meteorite. Sc-rich anosovite in A0031 has a chemical formula of (Ti4+,Ti3+,Mg,Sc,Al)3O5 with the pseudobrookite structure. This is the second report of Ti3O5 in nature, but is the first description of anosovite formed in the solar nebula as an ultrarefractory phase. The discovery of Sc-rich anosovite in A0031 reveals the stability of Ti3O5 in the early solar nebula and supports the prediction of previous equilibrium condensation calculations. The panguite, Sc-rich anosovite, and Ti-rich davisite in A0031 show a large variation in Ti3+/Titot. The primitive nature of A0031 implies that the variations in Ti3+/Titot among different Ti-rich minerals are primary features. We propose that the distribution of Ti3+ and Ti4+ could be controlled mainly by their various competition abilities of incorporating into these Ti-Sc-Al-rich minerals. Similarity of Ti3+/Titot value between Ti-rich davisite from A0031 and those in other carbonaceous chondrites indicates that most refractory inclusions might have formed in highly reducing nebular

  15. Synthesis of High-Temperature Self-lubricating Wear Resistant Composite Coating on Ti6Al4V Alloy by Laser Deposition

    NASA Astrophysics Data System (ADS)

    Luo, Jian; Liu, Xiu-Bo; Xiang, Zhan-Feng; Shi, Shi-Hong; Chen, Yao; Shi, Gao-Lian; Wu, Shao-Hua; Wu, Yu-Nan

    2015-05-01

    Laser deposition was adopted to prepare novel Ni-based solid solution (γ-NiCrAlTi)/ TiC/α-Ti/CaF2 high-temperature self-lubricating wear resistant composite coating on Ti6Al4V alloy. Microstructure, micro-hardness, wear behavior, and counter-body effect of the coating were investigated systematically. It can be seen that the coating mainly consists of γ-NiCrAlTi, TiC, α-Ti, and small fine CaF2 particles. Average micro-hardness of the coating is 1023 HV0.3, which is about three-factor higher than that of Ti6Al4V substrate (380 HV0.3). The friction coefficient and wear rate of the coating decrease at all test temperatures to different extents with respect to the substrate. The improvement in wear resistance is believed to be the combined effects of the γ-NiCrAlTi solid solution, the dominating anti-wear capabilities of the reinforced TiC carbides, and the self-lubricating property of CaF2.

  16. Electrodeposition of HAp coatings on Ti6Al4V alloy and its electrochemical behavior in simulated body fluid solution

    NASA Astrophysics Data System (ADS)

    Thanh Dinh, Thi Mai; Thom Nguyen, Thi; Pham, Thi Nam; Phuong Nguyen, Thu; Thu Trang Nguyen, Thi; Hoang, Thai; Grossin, David; Bertrand, Ghislaine; Drouet, Christophe

    2016-06-01

    Hydroxyapatite (HAp) coatings were prepared on Ti6Al4V substrate by electrodeposition method from electrolyte solution containing Ca(NO3)2, NH4H2PO4 and NaNO3. The results show that the HAp coatings were single phase crystals of HAp. Scanning electron microscope (SEM) images present that HAp/Ti6Al4V have flake shapes which arrange to form like-coral agglomerates. In vitro test of the Ti6Al4V and HAp/Ti6Al4V in simulated body fluid (SBF) solution was investigated with different immersion times. pH of SBF solution decreased and the mass of materials increased. SEM images prove the formation of apatite on the surface of Ti6Al4V and HAp/Ti6Al4V. The corrosion current density during immersion time of substrate is always higher than the one of HAp/Ti6Al4V because the deposited HAp can protect well for the substrate.

  17. Optical properties of refractory TiN, AlN and (Ti,Al)N coatings

    NASA Astrophysics Data System (ADS)

    Bilokur, M.; Gentle, A.; Arnold, M.; Cortie, M. B.; Smith, G. B.

    2015-12-01

    Titanium nitride is a golden-colored semiconductor with metallic optical properties. It is already widely used in room temperature spectrally-selective coatings. In contrast, aluminum nitride is a relatively wide-band gap, non-metallic material. Both nitrides have exceptional thermal stability, to over 1000 °C, but are susceptible to oxidation. We will show here that composite coatings consisting of these materials and their complex oxides have considerable potential for spectrally-selective applications, including at elevated temperatures. In particular, we examine the metastable materials produced by magnetron sputtering. The effective dielectric functions of these materials can be tuned over a wide range by manipulation of their microstructure. This provides a strategy to assemble materials with tunable dielectric functions using a 'bottom-up' approach. The results are compared to those achievable by conventional, 'top-down', planar optical stacks comprised of alternating layers of TiNx and AlN.

  18. Tensile strength and elongation of laser-welded Ti and Ti-6AL-7NB.

    PubMed

    Watanabe, Ikuya; Topham, D Scott

    2004-10-15

    This study established data demonstrating the possible laser-welded strengths of cast Ti and Ti-6Al-7Nb and compared them to those of two dental-casting alloys. Cast plates of Ti, Ti-6Al-7Nb, gold, and Co-Cr alloy were prepared. After polishing the surfaces to be welded, two plates were abutted and welded using an Nd:YAG laser at a pulse duration of 10 ms, spot diameter of 1 mm, and voltage of 200 V. Five specimens were prepared for each metal by welding either three or five spots unilaterally or bilaterally. The fracture load and percent elongation were measured at a crosshead speed of 1.0 mm/min. The bilaterally welded specimens performed significantly greater than unilaterally welded specimens in both fracture load and elongation whether they were welded with three or five spots per side. The bilaterally welded Ti and Ti-6Al-7Nb specimens were nearly as strong as their corresponding control specimens, whereas the gold and Co-Cr specimens were approximately half as strong. When a large proportion of the cross-sectional area of the joint is laser welded, the strength of the laser-welded portion of the cast Ti and Ti-6Al-7Nb may approach or equal that of the nonwelded metal frameworks. PMID:15368227

  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. Determination of fracture toughness of calcium phosphate coatings deposited onto Ti6Al4V substrate by using indentation technique

    NASA Astrophysics Data System (ADS)

    Aydin, Ibrahim; Cetinel, Hakan; Pasinli, Ahmet

    2012-09-01

    In this study, fracture toughness values of calcium phosphate (CaP) coatings deposited onto Ti6Al4V substrate were determined by using Vickers indentation method. In this new patent holding method, the activation processes were performed with NaOH and NaOH+H2O2 on the Ti6Al4V material surface. Thicknesses of CaP coatings were measured from cross-sections of the samples by using optical microscopy. Vickers indentation tests were performed by using microhardness tester. Young's modulus values of the coatings were determined by using ultra microhardness tester. As a result, fracture toughness (K1C) values of the CaP coatings produced by using two different activation processes, were calculated by using experimental study results. These were found to be 0.43 MPa m1/2 and 0.39 MPa m1/2, respectively. It was determined that the CaP coating on Ti6Al4V activated by NaOH+H2O2 had higher fracture toughness than the CaP coating on Ti6Al4V activated by NaOH.

  1. Localized TiSi and TiN phases in Si/Ti/Al/Cu Ohmic contacts to AlGaN/GaN heterostructures

    NASA Astrophysics Data System (ADS)

    Yoon, Seonno; Song, Yunwon; Lee, Seung Min; Lee, Hi-Deok; Oh, Jungwoo

    2016-05-01

    Microstructural changes in Si/Ti/Al/Cu (10/40/60/50 nm) Ohmic contacts to AlGaN/GaN heterostructure were investigated for complementary metal-oxide semiconductor compatible processes. Si/Ti/Al/Cu metallization exhibited a low specific contact resistance of 3.6 × 10-6 Ω-cm2 and contact resistance of 0.46 Ω-mm when a Si interfacial layer was used. Without a designated barrier metal, TiSix alloys that formed in the metallic region effectively suppressed Cu diffusion. The shallow TiN junction in AlGaN/GaN was attributed to TiSix in the metallic regions. Microstructural changes were detected by systematic physical characterization.

  2. Asymmetry of radiation damage properties in Al-Ti nanolayers

    SciTech Connect

    Setyawan, Wahyu; Gerboth, Matthew D.; Yao, Bo; Henager, Charles H.; Devaraj, Arun; Vemuri, Venkata Rama Ses; Thevuthasan, Suntharampillai; Shutthanandan, V.

    2014-02-01

    Molecular dynamics (MD) simulations were employed with empirical potentials to study the effects of multilayer interfaces and interface spacing in Al-Ti nanolayers. Several model interfaces derived from stacking of close-packed layers or face-centered cubic \\{100\\} layers were investigated. The simulations reveal significant and important asymmetries in defect production with $\\sim$60\\% of vacancies created in Al layers compared to Ti layers within the Al-Ti multilayer system. The asymmetry in the creation of interstitials is even more pronounced. The asymmetries cause an imbalance in the ratio of vacancies and interstitials in films of dissimilar materials leading to $>$90\\% of the surviving interstitials located in the Al layers. While in the close-packed nanolayers the interstitials migrate to the atomic layers adjacent to the interface of the Al layers, in the \\{100\\} nanolayers the interstitials migrate to the center of the Al layers and away from the interfaces. The degree of asymmetry and defect ratio imbalance increases as the layer spacing decreases in the multilayer films. Underlying physical processes are discussed including the interfacial strain fields and the individual elemental layer stopping power in nanolayered systems. In addition, experimental work was performed on low-dose (10$^{16}$ atoms/cm$^2$) helium (He) irradiation on Al/Ti nanolayers (5 nm per film), resulting in He bubble formation $\\sim$1 nm in diameter in the Ti film near the interface. The correlation between the preferential flux of displaced atoms from Ti films to Al films during the defect production that is revealed in the simulations and the morphology and location of He bubbles from the experiments is discussed.

  3. Dust depletion of Ca and Ti in QSO absorption-line systems

    NASA Astrophysics Data System (ADS)

    Guber, C. R.; Richter, P.

    2016-06-01

    Aims: To explore the role of titanium- and calcium-dust depletion in gas in and around galaxies, we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. Methods: We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope (VLT) and spectroscopically analyze 34 absorption-line systems at z ≤ 0.5 to measure column densities (or limits) for Ca ii and Ti ii. We complement our UVES data set with previously published absorption-line data on Ti/Ca for redshifts up to z ~ 3.8. Our absorber sample contains 110 absorbers including damped Lyman α systems (DLAs), sub-DLAs, and Lyman-Limit systems (LLS). We compare our Ti/Ca findings with results from the Milky Way and the Magellanic Clouds and discuss the properties of Ti/Ca absorbers in the general context of quasar absorption-line systems. Results: Our analysis indicates that there are two distinct populations of absorbers with either high or low Ti/Ca ratios with a separation at [Ti/Ca] ≈ 1. While the calcium-dust depletion in most of the absorbers appears to be severe, the titanium depletions are mild in systems with high Ti/Ca ratios. The derived trend indicates that absorbers with high Ti/Ca ratios have dust-to-gas ratios that are substantially lower than in the Milky Way. We characterize the overall nature of the absorbers by correlating Ti/Ca with other observables (e.g., metallicity, velocity-component structure) and by modeling the ionization properties of singly-ionized Ca and Ti in different environments. Conclusions: We conclude that Ca ii and Ti ii bearing absorption-line systems trace predominantly neutral gas in the disks and inner halo regions of galaxies, where the abundance of Ca and Ti reflects the local metal and dust content of the gas. Our study suggests that the Ti/Ca ratio represents a useful measure for the gas-to-dust ratio and overall metallicity in intervening absorption-line systems.

  4. Laser Processed TiN Reinforced Ti6Al4V Composite Coatings

    PubMed Central

    Balla, Vamsi Krishna; Bhat, Abhimanyu; Bose, Susmita; Bandyopadhyay, Amit

    2011-01-01

    The purpose of this first generation investigation is to evaluate fabrication, in vitro cytotoxicity, cell-materials interactions and tribological performance of TiN particle reinforced Ti6Al4V composite coatings for potential wear resistant load bearing implant applications. The microstructural analysis of the composites was performed using scanning electron microscope and phase analysis was done with X-ray diffraction. In vitro cell-materials interactions, using human fetal osteoblast cell line, have been assessed on these composite coatings and compared with Ti6Al4V alloy control samples. The tribological performance of the coatings were evaluated, in simulated body fluids, up to 1000 m sliding distance under 10N normal load. The results show that the composite coatings contain distinct TiN particles embedded in α + β phase matrix. The average top surface hardness of Ti6Al4V alloy increased from 394 ± 8 HV to 1138 ± 61 HV with 40 wt.% TiN reinforcement. Among the composite coatings, the coatings reinforced with 40 wt. % TiN exhibited the highest wear resistance of 3.74 × 10-6 mm3/Nm, which is lower than the wear rate, 1.04 × 10-5 mm3/Nm, of laser processed CoCrMo alloy tested under identical experimental conditions. In vitro biocompatibility study showed that these composite coatings were non-toxic and provides superior cell-material interactions compared to Ti6Al4V control, as a result of their high surface energy. In summary, excellent in vitro wear resistance and biocompatibility of present laser processed TiN reinforced Ti6Al4V alloy composite coatings clearly show their potential as wear resistant contact surfaces for load bearing implant applications. PMID:22301169

  5. Al{sub 2}TiO{sub 5}-Al{sub 2}O{sub 3}-TiO{sub 2} nanocomposite: Structure, mechanical property and bioactivity studies

    SciTech Connect

    Kalita, Samar Jyoti; Somani, Vikas

    2010-12-15

    Novel biomaterials are of prime importance in tissue engineering. Here, we developed novel nanostructured Al{sub 2}TiO{sub 5}-Al{sub 2}O{sub 3}-TiO{sub 2} composite as a biomaterial for bone repair. Initially, nanocrystalline Al{sub 2}O{sub 3}-TiO{sub 2} composite powder was synthesized by a sol-gel process. The powder was cold compacted and sintered at 1300-1500 {sup o}C to develop nanostructured Al{sub 2}TiO{sub 5}-Al{sub 2}O{sub 3}-TiO{sub 2} composite. Nano features were retained in the sintered structures while the grains showed irregular morphology. The grain-growth and microcracking were prominent at higher sintering temperatures. X-ray diffraction peak intensity of {beta}-Al{sub 2}TiO{sub 5} increased with increasing temperature. {beta}-Al{sub 2}TiO{sub 5} content increased from 91.67% at 1300 {sup o}C to 98.83% at 1500 {sup o}C, according to Rietveld refinement. The density of {beta}-Al{sub 2}TiO{sub 5} sintered at 1300 {sup o}C, 1400 {sup o}C and 1500 {sup o}C were computed to be 3.668 g cm{sup -3}, 3.685 g cm{sup -3} and 3.664 g cm{sup -3}, respectively. Nanocrystalline grains enhanced the flexural strength. The highest flexural strength of 43.2 MPa was achieved. Bioactivity and biomechanical properties were assessed in simulated body fluid. Electron microscopy confirmed the formation of apatite crystals on the surface of the nanocomposite. Spectroscopic analysis established the presence of Ca and P ions in the crystals. Results throw light on biocompatibility and bioactivity of {beta}-Al{sub 2}TiO{sub 5} phase, which has not been reported previously.

  6. Deformation modes and ideal strengths of ternary layered Ti{sub 2}AlC and Ti{sub 2}AlN from first-principles calculations

    SciTech Connect

    Liao Ting; Wang Jingyang; Zhou Yanchun

    2006-06-01

    Deformation and failure modes were studied for Ti{sub 2}AlC and Ti{sub 2}AlN by deforming the materials from elasticity to structural instability using the first-principles density functional calculations. We found that the TiC{sub 0.5}/TiN{sub 0.5} slabs remain structurally stable under deformations, whereas the weak Ti-Al bonds accommodate deformation by softening and breaking at large strains. The structural stability of the ternary compound is determined by the strength of Ti-Al bond, which is demonstrated to be less resistive to shear deformation than to tension. The ideal stress-strain relationships of ternary compounds are presented and compared with those of the binary materials, TiC and TiN, respectively. For Ti{sub 2}AlC and Ti{sub 2}AlN, their ideal tensile strengths are comparable to those of the binary counterparts, while the ideal shear strengths yield much smaller values. Based on electronic structure analyses, the low shear deformation resistance is well interpreted by the response of weak Ti-Al bonds to shear deformations. We propose that the low shear strengths of Ti{sub 2}AlC and Ti{sub 2}AlN originate from low slip resistance of Al atomic planes along the basal plane, and furthermore suggest that this is the mechanism for low hardness, damage tolerance, and intrinsic toughness of ternary layered carbides and nitrides.

  7. Increased photovoltaic performance by the optimized TiClI4 and AlCl3 surface treatment in dye-sensitized solar cells.

    PubMed

    Oh, Ju Hee; Kim, Dae-Hwan; Lee, Sang-Ju; Kwak, Giseop; Han, Yoon Soo

    2014-12-01

    The surface of TiO2 photoelectrodes coated on F-doped SnO2 (FTO) was modified by soaking it in a TiCl4:AlCl3 mixed aqueous solution with various molar ratios, and then calcining to produce the TiCl4:AlCl3-treated TiO2 photoelectrode (Ti:Al-TiO2/FTO). The highest power conversion efficiency (PCE) was obtained from dye-sensitized solar cells (DSSC) with Ti:Al(5:5)-TiO2/FTO, which was prepared from the mixed solution with the molar ratio of 5:5 (TiCi4:AlCl3). PCE of DSSC with Ti:Al (5:5)-TiO2/FTO was improved by ca. 19.6%, compared to that of the reference device with Ti:Al (10:0)-TiO2/FTO (i.e., TiO2-coated TiO2/FTO) due to an enhancement in both short-circuit photocurrent (J(sc)) and open-circuit voltage (V(oc)). A series of measurements such as UV-visible absorption, electrochemical impedance, open circuit voltage decay and dark current revealed that the increase in J(sc) was attributed to the improvement of electron collection efficiency by a prolonged electron lifetime, and the suppression of the charge recombination between injected electrons and I3(-) ions was found to increase the V(oc) value of the device with Ti:Al(5:5)-TiO2/FTO. PMID:25971045

  8. A comparative study on biodegradation and mechanical properties of pressureless infiltrated Ti/Ti6Al4V-Mg composites.

    PubMed

    Esen, Ziya; Bütev, Ezgi; Karakaş, M Serdar

    2016-10-01

    The mechanical response and biodegradation behavior of pressureless Mg-infiltrated Ti-Mg and Ti6Al4V-Mg composites were investigated by compression and simulated body fluid immersion tests, respectively. Prior porous preforms were surrounded uniformly with magnesium as a result of infiltration and the resultant composites were free of secondary phases and intermetallics. Although the composites' compressive strengths were superior compared to bone, both displayed elastic moduli similar to that of cortical bone and had higher ductility with respect to their starting porous forms. However, Ti-Mg composites were unable to preserve their mechanical stabilities during in-vitro tests such that they fractured in multiple locations within 15 days of immersion. The pressure generated by H2 due to rapid corrosion of magnesium caused failure of the Ti-Mg composites through sintering necks. On the other hand, the galvanic effect seen in Ti6Al4V-Mg was less severe compared to that of Ti-Mg. The degradation rate of magnesium in Ti6Al4V-Mg was slower, and the composites were observed to be mechanically stable and preserved their integrities over the entire 25-day immersion test. Both composites showed bioinert and biodegradable characteristics during immersion tests and magnesium preferentially corroded leaving porosity behind while Ti/Ti6Al4V remained as a permanent scaffold. The porosity created by degradation of magnesium was refilled by new globular agglomerates. Mg(OH)2 and CaHPO4 phases were encountered during immersion tests while MgCl2 was detected during only the first 5 days. Both composites were classified as bioactive since the precipitation of CaHPO4 phase is known to be precursor of hydroxyapatite formation, an essential requirement for an artificial material to bond to living bone. PMID:27442919

  9. Petrography and classification of Ca, Al-rich and olivine-rich inclusions in the Allende CV3 chondrite

    NASA Technical Reports Server (NTRS)

    Kormacki, A. S.; Wood, J. A.

    1984-01-01

    The results of a detailed, systematic petrographic survey of Ca, Al-rich and olivine-rich inclusions in the Allende CV3 chondrite are reported, and a new classification system based on clearly defined and readily applied petrographic criteria is presented. Most Allende inclusions are aggregates containing one or more of three distinct constituents: (1) rimmed concentric objects enriched in Al- and Ti-rich oxide minerals and various amounts of Ca-rich silicates; (2) porous, 'fine-grained' chaotic material enriched in Ca-rich silicates, especially clinopyroxenes and garnets; and (3) porous, 'fine-grained', mafic inclusion matrix, enriched in olivine, pyroxene, and feldspathoids. Two texturally distinct varieties of inclusions consist primarily of inclusion matrix: unrimmed olivine aggregates and rimmed olivine aggregates. Ca, Al-rich inclusions are classified on the basis of the size and abundance of their constituent concentric objects. Some fundamental relationships among Allende inclusions that previusly have not been emphasized are discussed.

  10. Effect of Microstructure on Reliability of Ca(TiZr)O3-Based Multilayer Ceramic Capacitors

    NASA Astrophysics Data System (ADS)

    Motoki, Tomoo; Naito, Masahiro; Sano, Harunobu; Konoike, Takehiro; Tomono, Kunisaburo

    2000-09-01

    We examined the reliability of Ca(TiZr)O3 (CTZ)-based Ni-electrode multilayer ceramic capacitors (MLCs) prepared by two different processes with particular interest in the microstructure. One process was to calcine the mixture of CaCO3 and TiO2 to prepare CaTiO3 (CT) powder and the mixture of CaCO3 and ZrO2 to prepare CaZrO3 (CZ) powder, and then mix these calcined powders and sinter them to synthesize the CTZ-based ceramics. The other was to calcine the mixture of CaCO3, TiO2 and ZrO2 powders together to prepare CTZ powder and then sinter them. These two processes of CTZ ceramic preparation resulted in a different crystallinity and distribution of the elements. We found that these factors influenced the reliability of CTZ-based MLCs.

  11. Effect of water absorption of dielectric underlayers on crystal orientation in Al-Si-Cu/Ti/TiN/Ti metallization

    NASA Astrophysics Data System (ADS)

    Yoshida, Tomoyuki; Hashimoto, Shoji; Hosokawa, Hideki; Ohwaki, Takeshi; Mitsushima, Yasuichi; Taga, Yasunori

    1997-05-01

    The influence of the exposure of underlying dielectric (phophosilicate glass and borophosphosilicate glass) films to a humid air ambient on crystallographic orientations in Al-Si-Cu/Ti/TiN/Ti layered structures has been investigated as a function of the boron content and exposure time of the dielectric films. The Al(111) orientation in the layered structures was found to improve drastically with increasing boron content and exposure time of the dielectric films. The full width at half maximum value of an Al(111) x-ray rocking curve reached less than 1°. It was also found that the Al-Si-Cu surface becomes smoother and the average grain size increases as the Al(111) orientation improves. The improved Al(111) orientation was attributed to the improved Ti(002) orientation of the bottom Ti films. The mechanism of the improved Ti(002) orientation was investigated. It was confirmed that the improved orientation is closely related with the surface concentration of the absorbed water in the dielectric films. Further, it was demonstrated that interconnects fabricated from the improved layered structure have excellent electromigration performance.

  12. High-temperature neutron diffraction and first-principles study of temperature-dependent crystal structures and atomic vibrations in Ti3AlC2, Ti2AlC, and Ti5Al2C3

    NASA Astrophysics Data System (ADS)

    Lane, Nina J.; Vogel, Sven C.; Caspi, El'ad N.; Barsoum, Michel W.

    2013-05-01

    Herein we report on the thermal expansions and temperature-dependent crystal structures of select ternary carbide Mn +1AXn (MAX) phases in the Ti-Al-C phase diagram in the 100-1000 °C temperature range. A bulk sample containing 38(±1) wt. % Ti5Al2C3 ("523"), 32(±1) wt. % Ti2AlC ("211"), 18(±1) wt. % Ti3AlC2 ("312"), and 12(±1) wt. % (Ti0.5Al0.5)Al is studied by Rietveld analysis of high-temperature neutron diffraction data. We also report on the same for a single-phase sample of Ti3AlC2 for comparison. The thermal expansions of all the MAX phases studied are higher in the c direction than in the a direction. The bulk expansion coefficients—9.3(±0.1)×10-6 K-1 for Ti5Al2C3, 9.2(±0.1) ×10-6 K-1 for Ti2AlC, and 9.0(±0.1)×10-6 K-1 for Ti3AlC2—are comparable within one standard deviation of each other. In Ti5Al2C3, the dimensions of the Ti-C octahedra for the 211-like and 312-like regions are comparable to the Ti-C octahedra in Ti2AlC and Ti3AlC2, respectively. The isotropic mean-squared atomic displacement parameters are highest for the Al atoms in all three phases, and the values predicted from first-principles phonon calculations agree well with those measured.

  13. Substitutional and Interstitial Diffusion in alpha2-Ti3Al(O)

    NASA Technical Reports Server (NTRS)

    Copland, Evan; Young, David J.; Gleeson, Brian; Jacobson, Nathan

    2007-01-01

    The reaction between Al2O3 and alpha2-Ti3Al was studied with a series of Al2O3/alpha2-Ti3Al multiphase diffusion couples annealed at 900, 1000 and 1100 C. The diffusion-paths were found to strongly depend on alpha2- Ti3Al(O) composition. For alloys with low oxygen concentrations the reaction involved the reduction of Al2O3, the formation of a gamma-TiAl reaction-layer and diffusion of Al and O into the alpha2-Ti3Al substrate. Measured concentration profiles across the interaction-zone showed "up-hill" diffusion of O in alpha2-Ti3Al(O) indicating a significant thermodynamic interaction between O and Al, Ti or both. Diffusion coefficients for the interstitial O in alpha2-Ti3Al(O) were determined independently from the interdiffusion of Ti and Al on the substitutional lattice. Diffusion coefficients are reported for alpha2-Ti3Al(O) as well as gamma-TiAl. Interpretation of the results were aided with the subsequent measurement of the activities of Al, Ti and O in alpha 2-Ti3Al(O) by Knudsen effusion-cell mass spectrometry.

  14. Fabrication of Al/Al3Ti Functionally Graded Materials by Reaction Centrifugal Mixed-Powder Method

    NASA Astrophysics Data System (ADS)

    El-Hadad, Shimaa; Sato, Hisashi; Miura-Fujiwara, Eri; Watanabe, Yoshimi

    2011-01-01

    Formation of compositional gradient in Al/Al3Ti Functionally graded materials (FGMs) fabricated by the centrifugal method (CM) depends mainly on the centrifugal force and the processing temperature. In this study, a novel centrifugal method, reaction centrifugal mixed-powder method (RCMPM), was proposed to fabricate Al/Al3Ti FGMs under fixed centrifugal force (G=80). The effects of RCMPM processing temperature on the formation of Al3Ti intermetallics, its morphology and its distribution in the fabricated Al/Al3Ti FGMs have been investigated. Fine granular Al3Ti were observed at relatively lower processing temperature while the known coarse platelet-like particles of Al3Ti could be achieved at higher casting temperatures. Moreover, Ti3Al intermetallics compound and unreacted Ti phases are also observed along with Al3Ti particles. In addition, distribution of Al3Ti intermetallics size and their volume fraction showed a significant change when the Al/Al3Ti FGMs processed at different temperatures relative to the liquidus temperature of the master alloy.

  15. Compton Profile Study of Intermetallic Ti{sub 3}Al

    SciTech Connect

    Vyas, V.; Sharma, G.; Mishra, M. C.; Sharma, B. K.; Joshi, K. B.

    2011-10-20

    The Compton scattering measurement on intermetallic alloy Ti{sub 3}Al is reported in this work. The measurement is made using 59.54 keV gamma-rays from Am{sup 241} source. Theoretical calculation of Compton profile is also performed employing CRYSTAL code within the framework of density functional theory to compare with the measurement. The theoretical profile of the alloy is also synthesized following the superposition model taking the published Compton profiles of elemental solids from the APW method. The experimental study of charge transfer in the alloys has also been done by performing the experimental Compton profile measurements on Ti and Al following the superposition model and charge transfer from Al to Ti is clearly seen on the alloy formation.

  16. Plasma torch production of Ti/Al nanoparticles

    SciTech Connect

    Phillips, Jonathan; Zea, Hugo; Cheng, Lily; Luhrs, Claudia; Courtney, Matthew

    2009-01-01

    Using the Aerosol-through-Plasma (A-T-P) technique high surface area bi-cationic (Ti-Al) oxide particles of a range of stoichiometries were produced that showed remarkable resistance to sintering. Specifically, we found that homogeneous nanoparticles with surface areas greater than 150 m{sup 2}/gm were produced at all stoichiometries. In particular, for particles with a Ti:Al ratio of 1:3 a surface area of just over 200 m{sup 2}/gm was measured using the BET method. The most significant characteristic of these particles was that their sinter resistance was far superior to that of TiAl particles produced using any other method. For example, A-T-P generated particles retained >70% of their surface area even after sintering at 1000 C for five hours. In contrast, particles made using all other methods lost virtually all of their surface area after an 800 C treatment.

  17. Microstructure and properties of (Ti, Al) N coatings on WC-Co cemented carbide

    NASA Astrophysics Data System (ADS)

    Li, Yudong; Liu, Zhen; Yang, Jing; Chen, Yigang

    2013-03-01

    (Ti, Al)N films were grown on WC-Co cemented carbides by R.F. reactive sputtering using Ti/Al composite target. The crystalline structure, morphology and composition of (Ti, Al)N coatings were investigated by X-ray diffraction (XRD), optical microscope and X-ray energy dispersive spectroscope (EDS), respectively. The mechanical properties of (Ti, Al)N coatings with the variable Al content were investigated by applying nanoindentation. With the increase of the Al content, the crystal structure of (Ti, Al)N films changed from fcc to hexagonal structure. When the ratio of Ti to Al in (Ti, Al)N coatings was approximately 4:1, and the N content was 40.67 %, the nano-hardness of (Ti, Al)N coating was highly up to 28 GPa. By adjusting the Al content, the lowest value of friction coefficients was 0.1397.

  18. Optical properties of the giant dielectric material CaCu_3Ti_4O_12 and CdCu_3Ti_4O_12 \\unboldmath

    NASA Astrophysics Data System (ADS)

    Homes, Christopher

    2002-03-01

    The cubic perovskite-related oxide CaCu_3Ti_4O_12 has one of the largest dielectric constants at room temperature ever measured, ɛ_0~= 80 000, [ɛ_0≈ ɛ_1(ω arrow 0)]; ɛ0 drops by a factor of 1000 below about 100 K to ɛ_0~= 100, but curiously no change in the crystallographic structure is observed. The substitution of Cd for Ca results in a much lower value for the dielectric constant of ɛ_0~= 500, but the same general temperature dependence. The temperature-dependent reflectance of CaCu_3Ti_4O_12 and CdCu_3Ti_4O_12 has been measured over a wide frequency range, and the real and imaginary parts of the complex dielectric function were calculated from a Kramers-Kronig analysis. The optical properties are dominated by the unscreened lattice modes. There are a total of 11 infrared-active Tu modes expected; all 11 modes are observed in the CdCu_3Ti_4O_12 material, but only 10 are found in CaCu_3Ti_4O_12; the mode at ≈ 480 cm-1 is absent. The low frequency mode at ≈ 120 cm-1 in CaCu_3Ti_4O_12 shows an anomalous increase in oscillator strength at low temperature, in violation of the f-sum rule.(C.C. Homes et al.), Science 293, 673 (2001). The same behavior is found, although to a lesser extent, in the Cd material. A normal coordinate analysis of the vibrational modes indicates that the low-frequency mode involves primarily the Ca(Cd) atoms, as well as the Cu-O sublattice. The increase in strength of this mode is an indication that this bonding is becoming more ionic, implying that there is a redistribution of charge on this sublattice at low temperature. This suggests that the electric fields responsible for the large value of ɛ0 may originate not from the TiO6 octahedra, as is often seen in ferroelectrics, but from the Ca/Cu-O sublattice. A possible mechanism for the reduction of ɛ0 at low temperature will be discussed in light of recent high-resolution structural studies.

  19. Mechanical anisotropy in sheets of {gamma}-TiAl alloys

    SciTech Connect

    Bartels, A.; Hartig, C.; Mecking, H.; Clemens, H.

    1997-12-31

    At room temperature sheets of {gamma}-TiAl exhibit a higher yield stress in the rolling direction than in the transverse direction. Around 700 C the opposite behavior is observed. The texture mainly consists of a modified cube component. The tetragonal c-axis <001> is aligned in the sheet plane transversely to the rolling direction. Taken into account this special texture and the single crystal yield surface of {gamma}-TiAl the authors conclude that around 700 C the CRSS of super-dislocations is higher than the CRSS of ordinary dislocations. At RT the relation changes to the opposite.

  20. Enhanced photocatalytic activity of CaTiO3-graphene nanocomposites for dye degradation

    NASA Astrophysics Data System (ADS)

    Xian, T.; Yang, H.; Huo, Y. S.

    2014-11-01

    Calcium titanate (CaTiO3) nanoparticles with an average size of 36 nm were synthesized by a polyacrylamide route. CaTiO3-graphene composites were fabricated by mixing CaTiO3 particles and graphene into absolute ethanol, followed by thermal drying. The prepared samples were characterized by x-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and UV-visible diffuse reflectance spectroscopy. Methyl orange (MO) was chosen as the target pollutant to evaluate the photocatalytic activity of the samples under UV irradiation. Our results show that CaTiO3-graphene composites exhibit enhanced photocatalytic activity compared to bare CaTiO3 particles. This can be explained by the effective suppression of electron-hole pair recombination due to the transfer of photogenerated electrons from the conduction band of CaTiO3 to graphene sheets. Hydroxyl (•OH) radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing an enhanced yield on the irradiated CaTiO3-graphene composites. Ethanol was used as a •OH scavenger to investigate its effect on photocatalytic efficiency as well as on •OH radical yields. Based on the experimental results, we suggest that •OH radicals are the dominant active species responsible for the dye degradation.

  1. Rate of reactions between D 2O and Ca xAl yO z

    NASA Astrophysics Data System (ADS)

    Christensen, A. Nørlund; Lehmann, M. S.

    1984-02-01

    The rate of the reaction between D 2O and the calcium aluminum oxides Ca 3Al 2O 6, Ca 5Al 6O 14, CaAl 2O 4, and CaAl 4O 7 was investigated by on-line neutron diffraction powder methods at temperatures from room temperature to 100°C. The rate of the reaction increases with increasing calcium content of the compounds and with increasing temperature for each of the compounds. The crystallographic stable hydrate Ca 3Al 2(OD) 12 is obtained from CaAl 4O 7 and CaAl 2O 4 at temperatures above 63°C, from Ca 5Al 6O 14 at temperatures above 49°C, and from Ca 3Al 2O 6 at temperatures as low as 7°C.

  2. Simulation of the aluminothermic smelting of Mo-Ti-Al and Mo-Ti-V-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Udoeva, L. Yu.; Chumarev, V. M.; Larionov, A. V.; Rylov, A. N.; Trubachev, M. V.

    2013-08-01

    Thermodynamic simulation is performed to estimate the parameters and indicators of the aluminothermic melting of Mo-Ti-Al and Mo-Ti-V-Cr-Al master alloys intended for the alloying of titanium. The simulation is carried out with the HSC 6.1 Chemistry software package and is based on approximate calculations of the thermodynamic properties of Mo, Cr, and V aluminides, which are unavailable in handbooks. A comparison of the calculated and experimental data on the compositions of the forming alloys demonstrates that the developed models are adequate to technological processes and can be applied to optimize the parameters and to predict the compositions of smelting products.

  3. Synthesis and photoluminescence of Ca-(Sn,Ti)-Si-O compounds

    SciTech Connect

    Abe, Shunsuke; Yamane, Hisanori; Yoshida, Hisashi

    2010-04-15

    The phase relation of the compounds prepared in the CaO-SnO{sub 2}-SiO{sub 2} system at 1673 K and in the CaO-TiO{sub 2}-SiO{sub 2} system at 1573 K was investigated in order to explore new Ti{sup 4+}-activated stannate phosphors. Solid solutions of Ca(Sn{sub 1-x}Ti{sub x})SiO{sub 5} and Ca{sub 3}(Sn{sub 1-y}Ti{sub y})Si{sub 2}O{sub 9} were synthesized at x = 0-1.0 and y = 0-0.10, respectively, and their crystal structures were analyzed by powder X-ray diffraction. Photoluminescence of these solid solutions was observed in a broad range of a visible light wavelength region under ultraviolet (UV) light excitation. The peaks of the emission band of Ca(Sn{sub 0.97}Ti{sub 0.03})SiO{sub 5} and Ca{sub 3}(Sn{sub 0.925}Ti{sub 0.075})Si{sub 2}O{sub 9} were at 510 nm under excitation of 252 nm and at 534 nm under excitation of 258 nm, respectively. The absorption edges estimated by the diffuse reflectance spectra were at 300 nm (4.1 eV) for CaSnSiO{sub 5} and at 270 nm (4.6 eV) for Ca{sub 3}SnSi{sub 2}O{sub 9}, suggesting that the excitation levels in Ca(Sn{sub 1-x}Ti{sub x})SiO{sub 5} were above the band gap of the host, although the levels in Ca{sub 3}(Sn{sub 1-y}Ti{sub y})Si{sub 2}O{sub 9} were within the band gap and near the conduction band edge.

  4. 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.

  5. Exploration of the nature of active Ti species in metallic Ti-doped NaAlH4.

    PubMed

    Wang, Ping; Kang, Xiang-Dong; Cheng, Hui-Ming

    2005-11-01

    Clarification of the nature of active Ti species has been a key challenge in developing Ti-doped NaAlH(4) as a potential hydrogen storage medium. Previously, it has been greatly hindered by the invisibility of Ti-containing species in conventional analysis techniques. In the present study, for the first time, the catalytically active Ti-containing species have been definitely identified by X-ray diffraction in the hydrides doped with metallic Ti. It was found that mechanical milling of a NaH/Al mixture or NaAlH(4) with metallic Ti powder resulted in the formation of nanocrystalline Ti hydrides. The variation of the preparation conditions during the doping process leads to a slight composition variation of the Ti hydrides. The catalytic enhancement arising upon doping the hydride with commercial TiH(2) was quite similar to that achieved in the hydrides doped with metallic Ti. Moreover, the cycling stability that was previously established in metallic Ti-doped hydrides was also observed in the hydrides doped with TiH(2). These results clearly demonstrate that the in situ formed Ti hydrides act as active species to catalyze the reversible dehydrogenation of NaAlH(4). The mechanism by which Ti hydrides catalyze the reversible de-/hydrogenation reactions of NaAlH(4) was discussed. PMID:16853602

  6. Bone bonding bioactivity of Ti metal and Ti-Zr-Nb-Ta alloys with Ca ions incorporated on their surfaces by simple chemical and heat treatments.

    PubMed

    Fukuda, A; Takemoto, M; Saito, T; Fujibayashi, S; Neo, M; Yamaguchi, S; Kizuki, T; Matsushita, T; Niinomi, M; Kokubo, T; Nakamura, T

    2011-03-01

    Ti15Zr4Nb4Ta and Ti29Nb13Ta4.6Zr, which do not contain the potentially cytotoxic elements V and Al, represent a new generation of alloys with improved corrosion resistance, mechanical properties, and cytocompatibility. Recently it has become possible for the apatite forming ability of these alloys to be ascertained by treatment with alkali, CaCl2, heat, and water (ACaHW). In order to confirm the actual in vivo bioactivity of commercially pure titanium (cp-Ti) and these alloys after subjecting them to ACaHW treatment at different temperatures, the bone bonding strength of implants made from these materials was evaluated. The failure load between implant and bone was measured for treated and untreated plates at 4, 8, 16, and 26 weeks after implantation in rabbit tibia. The untreated implants showed almost no bonding, whereas all treated implants showed successful bonding by 4 weeks, and the failure load subsequently increased with time. This suggests that a simple and economical ACaHW treatment could successfully be used to impart bone bonding bioactivity to Ti metal and Ti-Zr-Nb-Ta alloys in vivo. In particular, implants heat treated at 700 °C exhibited significantly greater bone bonding strength, as well as augmented in vitro apatite formation, in comparison with those treated at 600 °C. Thus, with this improved bioactive treatment process these advantageous Ti-Zr-Nb-Ta alloys can serve as useful candidates for orthopedic devices. PMID:20883837

  7. Al-Si-Cu/TiN multilayer interconnection and Al-Ge reflow sputtering technologies for quarter-micron devices

    NASA Astrophysics Data System (ADS)

    Kikkawa, Takamaro; Kikuta, Kuniko

    1993-05-01

    Issues of interconnection technologies for quarter-micron devices are the reliability of metal lines with quarter-micron feature sizes and the formation of contact-hole-plugs with high aspect ratios. This paper describes a TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure as a quarter-micron interconnection technology and aluminum-germanium (Al-Ge) reflow sputtering as a contact-hole filling technology. The TiN/Al-Si-Cu/TiN/Al-Si-Cu/TiN/Ti multilayer conductor structure could suppress stress-induced voiding and improve the electromigration mean-time to failure. These improvements are attributed to the fact that the grain boundaries for the Al-Si-Cu film and the interfaces between the Al-Si-Cu and the TiN films are strengthened by the rigid intermetallic compound, TiAl3. The Al-Ge alloy reflow sputtering is a candidate for contact- and via-hole filling technologies in terms of reducing fabrication costs. The Al-Ge reflow sputtering achieved low temperature contact hole filling at 300 degree(s)C. Contact holes with a diameter of 0.25 micrometers and aspect ratio of 4 could be filled. This is attributed to the low eutectic temperature for Al-Ge (424 degree(s)C) and the effect of thin polysilicon underlayer on the enhancement of Al-Ge reflow.

  8. Modeling creep deformation of a two-phase TiAI/Ti3Al alloy with a lamellar microstructure

    NASA Astrophysics Data System (ADS)

    Bartholomeusz, Michael F.; Wert, John A.

    1994-10-01

    A two-phase TiAl/Ti3Al alloy with a lamellar microstructure has been previously shown to exhibit a lower minimum creep rate than the minimum creep rates of the constituent TiAl and Ti3Al single-phase alloys. Fiducial-line experiments described in the present article demonstrate that the creep rates of the constituent phases within the two-phase TiAl/Ti3Al lamellar alloy tested in compression are more than an order of magnitude lower than the creep rates of single-phase TiAl and Ti3Al alloys tested in compression at the same stress and temperature. Additionally, the fiducial-line experiments show that no interfacial sliding of the phases in the TiAl/Ti3Al lamellar alloy occurs during creep. The lower creep rate of the lamellar alloy is attributed to enhanced hardening of the constituent phases within the lamellar microstructure. A composite-strength model has been formulated to predict the creep rate of the lamellar alloy, taking into account the lower creep rates of the constituent phases within the lamellar micro-structure. Application of the model yields a very good correlation between predicted and experimentally observed minimum creep rates over moderate stress and temperature ranges.

  9. The Kinetics of TiAl3 Formation in Explosively Welded Ti-Al Multilayers During Heat Treatment

    NASA Astrophysics Data System (ADS)

    Foadian, Farzad; Soltanieh, Mansour; Adeli, Mandana; Etminanbakhsh, Majid

    2016-06-01

    Metallic-intermetallic laminate (MIL) composites, including Ti/TiAl3 composite, are promising materials for many applications, namely, in the aerospace industry. One method to produce Ti/TiAl3 laminate composite is to provide close attachment between desired number of titanium and aluminum plates, so that by applying heat and/or pressure, the formation of intermetallic phases between the layers becomes possible. In this work, explosive welding was used to make a strong bond between six alternative Ti and Al layers. The welded samples were annealed at three different temperatures: 903 K, 873 K, and 843 K (630 °C, 600 °C, and 570 °C) in ambient atmosphere, and the variation of the intermetallic layer thickness was used to study the growth kinetics. Microstructural investigations were carried out on the welded and annealed samples using optical microscopy and scanning electron microscopy equipped with energy-dispersive X-ray spectrometer (EDS). X-ray diffraction (XRD) technique was used to identify the formed intermetallic phases. It was found that at each temperature, two different mechanisms govern the process: reaction controlled and diffusion controlled. The calculated values of activation energies for reaction-controlled and diffusion-controlled mechanisms are 232.1 and 17.4 kJ, respectively.

  10. TiAl Scramjet Inlet Flap Subelement Designed and Fabricated

    NASA Technical Reports Server (NTRS)

    Draper, Susan L.

    2004-01-01

    Next-generation launch vehicles are being designed with turbine-based combined cycle (TBCC) propulsion systems having very aggressive thrust/weight targets and long lives. Achievement of these goals requires advanced materials in a wide spectrum of components. TiAl has been identified as a potential backstructure material for maintainable composite panel heat exchangers (HEX) in the inlet, combustor, and nozzle section of a TBCC propulsion system. Weight reduction is the primary objective of this technology. Design tradeoff studies have assessed that a TiAl structure, utilizing a high-strength, hightemperature TiAl alloy called Gamma MET PX,1 reduce weight by 41 to 48 percent in comparison to the baseline Inconel 718 configuration for the TBCC propulsion system inlet, combustor, and nozzle. A collaborative effort between the NASA Glenn Research Center, Pratt & Whitney, Engineering Evaluation & Design, PLANSEE AG (Austria), and the Austrian Space Agency was undertaken to design, manufacture, and validate a Gamma-MET PX TiAl structure for scramjet applications. The TiAl inlet flap was designed with segmented flaps to improve manufacturability, to better control thermal distortion and thermal stresses, and to allow for maintainable HEX segments. The design philosophy was to avoid excessively complicated shapes, to minimize the number of stress concentrations, to keep the part sizes reasonable to match processing capabilities, and to avoid risky processes such as welding. The conceptual design used a standard HEX approach with a double-pass coolant concept for centrally located manifolds. The flowpath side was actively cooled, and an insulation package was placed on the external side to save weight. The inlet flap was analyzed structurally, and local high-stress regions were addressed with local reinforcements.

  11. Effect of Ca incorporation on the dielectric nonlinear behavior of (Ba, Ca)TiO3 multi layer ceramic capacitors

    NASA Astrophysics Data System (ADS)

    Yoon, Seok-Hyun; Park, Yunjung; Kim, Chang-Hoon; Kim, Doo-Young

    2014-12-01

    The difference in the dielectric nonlinearity was investigated by contrasting BaTiO3 and (Ba0.925Ca0.075)TiO3 multilayer ceramic capacitors utilizing the first order reversal curve (FORC) distribution based on the Preisach model. Ca incorporation caused a decrease of the dielectric constants in the low field but little differences in the high field region resulting in a steep ac field dependence, which became more significant with the decrease of temperature. Such behavior can be correlated with a decrease of the reversible and an increase of the irreversible FORC distribution near origin by Ca incorporation. These results suggest that Ca incorporation, which is known to cause the asymmetric off-center displacement at Ba-site, has the role of weakly pinning centers that increase the portion of irreversible domain walls that are immobile at low field but can contribute to polarization beyond a threshold field.

  12. Characteristics of Ti-Nb, Ti-Zr and Ti-Al containing hydrogenated carbon nitride films

    NASA Astrophysics Data System (ADS)

    Balaceanu, M.; Braic, V.; Braic, M.; Vladescu, A.; Zoita, C. N.; Grigorescu, C. E. A.; Grigore, E.; Ripeanu, R.

    2009-10-01

    Nanocomposite Me-C-N:H coatings (Me is TiNb, TiZr or TiAl), with relatively high non-metal/metal ratios, were prepared by cathodic arc method using TiNb, TiZr and TiAl alloy cathodes in a CH 4 + N 2 atmosphere. For comparison purposes, a-C-N:H films were also produced through evaporating a graphite cathode in a similar atmosphere. The films were characterized in terms of elemental and phase compositions, chemical bonds, texture, hardness, adhesion and friction behavior by GDOES, XPS, Raman spectroscopy and XRD techniques, surface profilometry, hardness and scratch adhesion measurements, and tribological tests. The nanocomposite films consisted of a mixture of crystalline metal carbonitride and amorphous carbon nitride. The non-metal/metal ratio in the films composition was found to range between 1.8 and 1.9. For the metal containing nanocomposites, grain size in the range 7-23 nm, depending on the metal nature, were determined. As compared with the a-C-N:H, the Me-C-N:H films exhibited a much higher hardness (up to about 39 GPa for Ti-Zr-C-N:H) and a better adhesion strength, while the coefficients of friction were somewhat higher (0.2-0.3 for Me-C-N:H and 0.1 for a-C-N:H).

  13. Structural modification of TiAlN coatings by preliminary Ti Ion bombardment of a steel substrate

    NASA Astrophysics Data System (ADS)

    Shugurov, A. R.; Akulinkin, A. A.; Panin, A. V.; Perevalova, O. B.; Sergeev, V. P.

    2016-03-01

    The TiAlN coatings deposited onto steel 12Cr18Ni9Ti substrates before and after preliminary treatment by Ti ion beams are studied by X-ray diffraction, transmission electron microscopy, atomic force microscopy, and nanoindentation. The modification of the surface layer of a substrate is shown to change the structure and the preferred orientation of the coatings. The mechanical properties of the TiAlN coatings are found to depend substantially on the ion bombardment time.

  14. Wear resistance of TiAlSiN thin coatings.

    PubMed

    Silva, F J G; Martinho, R P; Alexandre, R J D; Baptista, A P M

    2012-12-01

    In the last decades TiAIN coatings deposited by PVD techniques have been extensively investigated but, nowadays, their potential development for tribological applications is relatively low. However, new coatings are emerging based on them, trying to improve wear behavior. TiAlSiN thin coatings are now investigated, analyzing if Si introduction increases the wear resistance of PVD films. Attending to the application, several wear test configurations has been recently used by some researchers. In this work, TiAISiN thin coatings were produced by PVD Unbalanced Magnetron Sputtering technique and they were conveniently characterized using Scanning Electron Microscopy (SEM) provided with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), Electron Probe Micro-Analyzer (EPMA), Micro Hardness (MH) and Scratch Test Analysis. Properties as morphology, thickness, roughness, chemical composition and structure, hardness and film adhesion to the substrate were investigated. Concerning to wear characterization, two very different ways were chosen: micro-abrasion with ball-on-flat configuration and industrial non-standardized tests based on samples inserted in a feed channel of a selected plastic injection mould working with 30% (wt.) glass fiber reinforced polypropylene. TiAISiN coatings with a small amount of about 5% (wt.) Si showed a similar wear behavior when compared with TiAIN reported performances, denoting that Si addition does not improve the wear performance of the TiAIN coatings in these wear test conditions. PMID:23447962

  15. In-Situ TEM Observations of Strain-Induced Interface Instability in TiAl/Ti3Al Laminate Composite

    SciTech Connect

    Hsiung, L L

    2003-04-08

    The stability of interfaces in lamellar TiAl (or TiAl/Ti{sub 3}Al laminate composite) by straining at ambient temperatures has been investigated using in-situ staining techniques performed in a transmission electron microscope in order to obtain direct evidence to support the previously proposed creep mechanisms in refined lamellar TiAl based upon the interface sliding in association with the cooperative motion of interfacial dislocations. It has been reported previously that the mobility of interfacial dislocations can play a crucial role in the creep deformation behavior of refined lamellar TiAl [1,2]. Since the operation of lattice dislocations within refined {alpha}{sub 2} and {gamma} lamellae is largely restricted, the motion of interfacial dislocations becomes the major strain carrier for plasticity. Results of ex-situ TEM investigation have revealed the occurrence of interface sliding in low-stress (LS) creep regime and deformation twinning in high-stress (HS) creep regime. These results have led us to propose that interface sliding associated with a viscous glide of pre-existing interfacial dislocations is the predominant creep mechanism in LS regime and interface-activated deformation twinning in {gamma} lamellae is the predominant creep mechanism in HS regime. Stress concentration resulted from the pileup of interfacial dislocations is suggested to be the cause for the interface-activated deformation twinning. Accordingly, the creep resistance of refined lamellar TiAl is considered to depend greatly on the cooperative motion of interfacial dislocations, which in turn may solely be controlled and hindered by the interfacial segregation of solute atoms (such as W) or interfacial precipitation. Furthermore, through the in-situ TEM investigation, we also found that the lamellar interfaces could migrate directly through the cooperative motion of interfacial dislocations. That is, the {gamma}/{gamma}and {gamma}/{alpha}{sub 2} interfaces can migrate through

  16. Study on improved tribological properties by alloying copper to CP-Ti and Ti-6Al-4V alloy.

    PubMed

    Wang, Song; Ma, Zheng; Liao, Zhenhua; Song, Jian; Yang, Ke; Liu, Weiqiang

    2015-12-01

    Copper alloying to titanium and its alloys is believed to show an antibacterial performance. However, the tribological properties of Cu alloyed titanium alloys were seldom studied. Ti-5Cu and Ti-6Al-4V-5Cu alloys were fabricated in the present study in order to further study the friction and wear properties of titanium alloys with Cu additive. The microstructure, composition and hardness were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and hardness tester. The tribological behaviors were tested with ZrO2 counterface in 25% bovine serum using a ball-on-disc tribo-tester. The results revealed that precipitations of Ti2Cu intermetallic compounds appeared in both Ti-5Cu and Ti-6Al-4V-5Cu alloys. The tribological results showed an improvement in friction and wear resistance for both Ti-5Cu and Ti-6Al-4V-5Cu alloys due to the precipitation of Ti2Cu. The results also indicated that both CP-Ti and Ti-5Cu behaved better wear resistance than Ti-6Al-4V and Ti-6Al-4V-5Cu due to different wear mechanisms when articulated with hard zirconia. Both CP-Ti and Ti-5Cu revealed dominant adhesive wear with secondary abrasive wear mechanism while both Ti-6Al-4V and Ti-6Al-4V-5Cu showed severe abrasive wear and cracks with secondary adhesive wear mechanism due to different surface hardness integrated by their microstructures and material types. PMID:26354247

  17. Effectively CO2 photoreduction to CH4 by the synergistic effects of Ca and Ti on Ca-loaded TiSiMCM-41 mesoporous photocatalytic systems

    NASA Astrophysics Data System (ADS)

    Jo, Seung Won; Kwak, Byeong Sub; Kim, Kang Min; Do, Jeong Yeon; Park, No-Kuk; Ryu, Si Ok; Ryu, Ho-Jung; Baek, Jeom-In; Kang, Misook

    2015-11-01

    TixSiMCM-41 is a mesoporous photocatalyst with a tetragonal framework and high structural regularity. In this study, Ca was introduced to the TixSiMCM-41 surfaces to improve CO2 absorption. The catalytic performance of mesoporous Ca/TixSiMCM-41 was superior to that of the reported Ca/TixSiO2 nano-sized composite catalyst. The photoreduction of CO2 to CH4 improved remarkably over the Ca(10.0 wt.%)/Ti35Si65MCM-41 catalyst, producing 82.0 μmol g-1cat L-1 after an 8 h reaction. A model for the enhanced photoactivity over Ca/TixSiMCM-41 was suggested, and the results were attributed to the effective charge separation and inhibited recombination of the photogenerated electron-hole pairs over Ca/TixSiMCM-41.

  18. 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.

  19. Investigation on Tool Life and Surface Integrity when Drilling Ti-6Al-4V and Ti-5Al-4V-Mo/Fe

    NASA Astrophysics Data System (ADS)

    Rahim, Erween Abd.; Sharif, Safian

    Machinability study on the drilling of two alpha beta titanium alloy series, Ti-6Al-4V and Ti-5Al-4V-0.6Mo-0.4Fe were conducted using an uncoated carbide drill. The effect of cutting speed on tool life, tool failure mode, cutting force and surface integrity of the drilled surface were discussed. Results showed that Ti-6Al-4V exhibited a more superior machinability property when compared to the Ti-5Al-4V-Mo/Fe alloy system. The tool wear progression when drilling Ti-6Al-4V was lower than that of Ti-5Al-4V-Mo/Fe. The tool experienced similar failure mechanisms which were non uniform wear and chipping when drilling both alloys. At high cutting speed and after prolonged machining, excessive plastic deformation was observed on the subsurface layer of the drilled surface which resulted in increase in the hardness value.

  20. Anisotropic swelling and microcracking of neutron irradiated Ti3AlC2-Ti5Al2C3 materials

    DOE PAGESBeta

    Ang, Caen K.; Silva, Chinthaka M.; Shih, Chunghao Phillip; Koyanagi, Takaaki; Katoh, Yutai; Zinkle, Steven J.

    2015-12-17

    Mn + 1AXn (MAX) phase materials based on Ti–Al–C have been irradiated at 400 °C (673 K) with fission neutrons to a fluence of 2 × 1025 n/m2 (E > 0.1 MeV), corresponding to ~ 2 displacements per atom (dpa). We report preliminary results of microcracking in the Al-containing MAX phase, which contained the phases Ti3AlC2 and Ti5Al2C3. Equibiaxial ring-on-ring tests of irradiated coupons showed that samples retained 10% of pre-irradiated strength. Volumetric swelling of up to 4% was observed. Phase analysis and microscopy suggest that anisotropic lattice parameter swelling caused microcracking. Lastly, variants of titanium aluminum carbide may bemore » unsuitable materials for irradiation at light water reactor-relevant temperatures.« less

  1. Thick target measurement of the 40Ca(alpha,gamma)44Ti reaction rate

    SciTech Connect

    Sheets, S A; Burke, J T; Scielzo, N D; Phair, L; Bleuel, D; Norman, E B; Grant, P G; Hurst, A M; Tumey, S; Brown, T A; Stoyer, M

    2009-02-06

    The thick-target yield for the {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction has been measured for E{sub beam} = 4.13, 4.54, and 5.36 MeV using both an activation measurement and online {gamma}-ray spectroscopy. The results of the two measurements agree. From the measured yield a reaction rate is deduced that is smaller than statistical model calculations. This implies a smaller {sup 44}Ti production in supernova compared to recently measured {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction rates.

  2. Oxidation characteristics of Ti-14Al-21Nb ingot alloy

    NASA Technical Reports Server (NTRS)

    Sankaran, Sankara N.; Clark, Ronald K.; Unnam, Jalaiah; Wiedemann, Karl E.

    1990-01-01

    Static oxidation kinetics of Ti14Al21Nb (wt pct) ingot alloy were studied in air over the temperature interval of 649 to 1093 C in a thermogravimetric apparatus. The oxidation products were characterized by x ray diffraction, electron microprobe analysis, energy dispersive x ray analysis, and Auger electron spectroscopy. Cross-sections of the oxidized samples were also examined using light and scanning electron microscopy. The oxidation rate was substantially lower than the conventional alloys of titanium, but the kinetics displayed a complex behavior involving two or more oxidation rates depending on the temperature and duration of exposure. The primary oxide formed was TiO2, but this oxide was doped with Nb. Small amounts of Al2O3 and TiN were also present in the scale. Diffusion of oxygen into the alloy was observed and the diffusivity seemed to be dependent on the microstructure of the metal. A model was presented to explain the oxidation behavior of the alloy in terms of the reduction in the oxygen diffusivity in the oxide caused by the modification of the defect structure of TiO2 by Nb ions.

  3. Gas nitriding and subsequent oxidation of Ti-6Al-4V alloys

    PubMed Central

    2012-01-01

    Ti-6Al-4V alloys consisting of α-Ti grains and intergranular β-Ti islands were nitrided at 850°C for 1 to 12 h under a nitrogen pressure of 1 Pa. With increasing nitriding time, the Ti-N compound layer became thicker, and the α-Ti diffusion zone containing dissolved nitrogen became wider. In the Ti-N compound layer, the initially formed Ti2N became TiN as the nitriding progressed. The nitride layers were oxidized to rutile-TiO2 after oxidation at 700°C for 10 h in air. PMID:22221679

  4. Gas nitriding and subsequent oxidation of Ti-6Al-4V alloys.

    PubMed

    Lee, Dong Bok; Pohrelyuk, Iryna; Yaskiv, Oleh; Lee, Jae Chun

    2012-01-01

    Ti-6Al-4V alloys consisting of α-Ti grains and intergranular β-Ti islands were nitrided at 850°C for 1 to 12 h under a nitrogen pressure of 1 Pa. With increasing nitriding time, the Ti-N compound layer became thicker, and the α-Ti diffusion zone containing dissolved nitrogen became wider. In the Ti-N compound layer, the initially formed Ti2N became TiN as the nitriding progressed. The nitride layers were oxidized to rutile-TiO2 after oxidation at 700°C for 10 h in air. PMID:22221679

  5. An Innovative Method for Manufacturing Gamma-TiAl Foil

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Saqib, Mohammad; Alexa, Joel A.

    2003-01-01

    The manufacture and entrance into service of thin gage gamma-TiAl product has been hampered by the inherent low room temperature ductility of the material. In the present study a new approach was explored for the efficient manufacture of gamma-TiAl foil with improved ductility. The objective was to produce a very clean material (low interstitial content) with a highly refined, homogeneous microstructure placed in a fully lamellar condition. The processing route involved the use of RF plasma spray deposition of pre-alloyed powders, followed by consolidation via vacuum hot pressing and heat treatment. The approach took advantage of a deposition process which included no electrodes, no binders and high cooling rates. Results and discussion of the work performed to date are presented.

  6. Ti-O-N/Ti composite coating on Ti-6Al-4V: surface characteristics, corrosion properties and cellular responses.

    PubMed

    Cao, Xiao-Lin; Sun, Tao; Yu, Yonghao

    2015-03-01

    To enhance the corrosion resistance of Ti-6Al-4V and extend its lifetime in medical applications, Ti-O-N/Ti composite coating was synthesized on the surface via plasma immersion ion implantation and deposition (PIIID). Surface morphology and cross sectional morphology of the composite coating were characterized using atomic force microscopy and scanning electron microscopy, respectively. Although X-ray photoelectron spectroscopic analysis revealed that the Ti-O-N/Ti composite coating was composed of non-stoichiometric titanium oxide, titanium nitride and titanium oxynitride, no obvious characteristic peak corresponding to the crystalline phases of them was detected in the X-ray diffraction pattern. In accordance with Owens-Wendt equation, surface free energy of the uncoated and coated samples was calculated and compared. Moreover, the corrosion behavior of uncoated and coated samples was evaluated by means of electrochemical impedance spectroscopy measurement, and an equivalent circuit deriving from Randles model was used to fit Bode plots and describe the electrochemical processes occurring at the sample/electrolyte interface. On the basis of the equivalent circuit model, the resistance of the composite coating was 4.7 times higher than that of the passive layer on uncoated samples, indicating the enhanced corrosion resistance after PIIID treatment. Compared to uncoated Ti-6Al-V, Ti-O-N/Ti-coated samples facilitated ostoblast proliferation within 7 days of cell culture, while there was no statistically significant difference in alkaline phosphate activity between uncoated and coated samples during 21 days of cell culture. PMID:25737126

  7. 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.

  8. Transient creep behavior of {gamma}-TiAl polycrystals

    SciTech Connect

    Viguier, B.; Bonneville, J.; Spaetig, P.; Martin, J.L.

    1997-12-31

    Two types of transient creep experiments performed along stress-strain curves are described and successfully applied to {gamma}TiAl polycrystals at room temperature. They allow to determine activation volumes in good agreement with those measured through successive load relaxation tests. In addition, the combination of the latter method and the present ones provides relevant values of the plastic strain hardening coefficient. This latter parameter is found to exhibit similar values in transient as well as during constant strain rate tests.

  9. Knudsen Cell Studies of Ti-Al Thermodynamics

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Copland, Evan H.; Mehrotra, Gopal M.; Auping, Judith; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    In this paper we describe the Knudsen cell technique for measurement of thermodynamic activities in alloys. Numerous experimental details must be adhered to in order to obtain useful experimental data. These include introduction of an in-situ standard, precise temperature measurement, elimination of thermal gradients, and precise cell positioning. Our first design is discussed and some sample data on Ti-Al alloys is presented. The second modification and associated improvements are also discussed.

  10. 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).

  11. Ca(AlH4)2, CaAlH5, and CaH2+6LiBH4: Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra.

    PubMed

    Marashdeh, Ali; Frankcombe, Terry J

    2008-06-21

    The dehydrogenation enthalpies of Ca(AlH(4))(2), CaAlH(5), and CaH(2)+6LiBH(4) have been calculated using density functional theory calculations at the generalized gradient approximation level. Harmonic phonon zero point energy (ZPE) corrections have been included using Parlinski's direct method. The dehydrogenation of Ca(AlH(4))(2) is exothermic, indicating a metastable hydride. Calculations for CaAlH(5) including ZPE effects indicate that it is not stable enough for a hydrogen storage system operating near ambient conditions. The destabilized combination of LiBH(4) with CaH(2) is a promising system after ZPE-corrected enthalpy calculations. The calculations confirm that including ZPE effects in the harmonic approximation for the dehydrogenation of Ca(AlH(4))(2), CaAlH(5), and CaH(2)+6LiBH(4) has a significant effect on the calculated reaction enthalpy. The contribution of ZPE to the dehydrogenation enthalpies of Ca(AlH(4))(2) and CaAlH(5) calculated by the direct method phonon analysis was compared to that calculated by the frozen-phonon method. The crystal structure of CaAlH(5) is presented in the more useful standard setting of P2(1)c symmetry and the phonon density of states of CaAlH(5), significantly different to other common complex metal hydrides, is rationalized. PMID:18570508

  12. CaF2-Based Near-Infrared Photocatalyst Using the Multifunctional CaTiO3 Precursors as the Calcium Source.

    PubMed

    Huang, Shouqiang; Guo, Shengjuan; Wang, Qingji; Zhu, Nanwen; Lou, Ziyang; Li, Liang; Shan, Aidang; Yuan, Haiping

    2015-09-16

    Multistage formation of fluoride upconversion agents from the related-semiconductor precursors provides a promising route for the fabrication of near-infrared (NIR) photocatalysts with high photocatalytic activities. Herein, the cotton templated CaTiO3 "semiconduction" precursors (C-CaTiO3) were used to synthesize the NIR photocatalyst of Er3+/Tm3+/Yb3+-(CaTiO3/CaF2/TiO2) (C-ETYCCT), and the functions of the Ca2+ source for CaF2 and the heterostructure formations were displayed by C-CaTiO3. The generated CaF2 acted as the host material for the lanthanide ions, and the heterostructures were constructed among anatase, rutile, and the remaining CaTiO3. The induced oxygen vacancies and Ti3+ ions enabled the samples to utilize most of the upconversion luminescence for photocatalysis. The NIR driven degradation rate of methyl orange (MO) over C-ETYCCT reached 52.34%, which was 1.6 and 2.5 times higher than those of Er3+/Tm3+/Yb3+-(CaTiO3/TiO2) (C-ETYCT) and Er3+/Tm3+/Yb3+-(CaTiO3/CaF2) (C-ETYCC), respectively. The degradation rates of MO and salicylic acid over C-ETYCCT with UV-vis-NIR light irradiation were also much higher than those of other samples, which were mainly results of the contributions of its high upconversion luminescence and the efficient electron-hole pair separation. PMID:26305907

  13. Fretting Fatigue of Gamma TiAl Studied

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    Gamma titanium-aluminum alloy (g-TiAl) is an attractive new material for aerospace applications because of its low density and high specific strength in comparison to currently used titanium and nickel-base alloys. Potential applications for this material are compressor and low-pressure turbine blades. These blades are fitted into either the compressor or turbine disks via a dovetail connection. The dovetail region experiences a complex stress state due to the alternating centrifugal force and the natural high-frequency vibration of the blade. Because of the dovetail configuration and the complex stress state, fretting is often a problem in this area. Furthermore, the local stress state becomes more complex when the influence of the metal-metal contact and the edge of the contact is evaluated. Titanium and titanium-based alloys in the clean state exhibit strong adhesive bonds when in contact with themselves and other materials (refs. 1 and 2). This adhesion causes heavy surface damage and high friction in practical cases. Although the wear produced by fretting may be mild, the reduction in fatigue life can be substantial. Thus, there is the potential for fretting problems with these TiAl applications. Since TiAl is an emerging material, there has been limited information about its fretting behavior.

  14. Conditions for CET in a gamma TiAl alloy

    NASA Astrophysics Data System (ADS)

    Mooney, R. P.; Lapin, J.; Klimová, A.; McFadden, S.

    2015-06-01

    The solidification of gamma TiAl alloys is of interest to the aerospace and automotive industries. A gamma TiAl multicomponent alloy: Ti-45.5Al-4.7Nb-0.2C-0.2B (at. %) has been the focus of a study to investigate the solidification conditions that led to a Columnar to Equiaxed Transition (CET) in a directional solidification experiment where traditional Bridgman solidification was combined in series with the power down method. In this paper, a numerical modelling result (a locus plot of columnar growth rate and temperature gradient) from this experiment is superimposed onto CET maps generated using an established analytical model for CET from the literature. A parametric study is carried out over suitable ranges of nucleation undercooling and nuclei density values. The predicted CET positions are compared with the experimentally measured CET position. Reasonable agreement is found at low levels of nuclei density. The paper concludes with estimates for the solidification conditions (nuclei density and nucleation undercooling) that led to the CET.

  15. Plasticity and interfacial dislocation structures in Ti-Al

    SciTech Connect

    Parrini, L.; Heinrich, H.; Kostorz, G.

    1997-12-31

    The alloy Ti-48.6Al-1.9Cr-1.9Nb-1B with an equiaxed {gamma} microstructure, obtained by heat treatment at 1,200 C for 4 h, and with a lamellar microstructure, obtained by heat treatment at 1,380 C for 1 h, is characterized by compression tests and transmission electron microscopy. A lower activity of superdislocations and a more frequent pinning of ordinary dislocations are detected in the lamellar Ti-Al specimens in comparison with the non-lamellar ones during deformation at room temperature. The activity of superdislocations and the pinning of ordinary dislocations are responsible for the differences in yield stress and brittleness between lamellar and non-lamellar Ti-Al. A very high density of ordinary interfacial dislocations is found in the lamellar structure. These influence the activity of superdislocations and the pinning of ordinary dislocations. At high temperature a change in the deformation mechanism occurs. Above the brittle-to-ductile transition, the material is remarkably softer and the mechanical properties are insensitive to the presence of the lamellar interfaces.

  16. Diffusion of chromium and manganese in γ-TiAl

    NASA Astrophysics Data System (ADS)

    Prasad Tiwari, Gyanendra; Iijima, Yoshiaki; Lee, Chan-Gyu; Koo, Bon-Heun

    2011-02-01

    The γ-TiAl intermetallic compound with suitable alloying additions has shown considerable promise as a material for high-temperature applications. Diffusion studies in this alloy system are useful in assessment of their creep behaviour and structural stability in service conditions. Tracer diffusion coefficients of 51Cr and 54Mn in a γ-TiAl intermetallic compound containing 54.1 at. % aluminium were determined in the temperature range from 1095 to 1470 K. The temperature dependence of both the diffusing species follows a linear Arrhenius behaviour and can be expressed as D Cr = 4.4 × 10-3exp(-350 kJ mol-1/RT) m2 s-1 and D Mn = 1.2 × 10-3 ×exp(-326 kJ mol-1/RT) m2 s-1. The data are analysed on the basis of empirical correlations between the diffusion and melting parameters applicable for conventional mono-vacancy diffusion mechanism in metals. It is concluded that impurity diffusion in γ-TiAl occurs through the migration of thermal vacancies via nearest-neighbour or next-nearest neighbour jumps.

  17. TiO2 controlling photoluminescence of AWO4 (A =Ca,Sr,Ba) nanofilms

    NASA Astrophysics Data System (ADS)

    Jia, Runping; Zhang, Guoxin; Wu, Qingsheng; Ding, Yaping

    2006-07-01

    AWO4 (A =Ca,Sr,Ba) nanofilms are prepared by a self-inventive technique using collodion to disperse nanoparticles and form film, and their photoluminescence (PL) properties are controlled by a nano-TiO2 doping method. This cannot only reach the results of uniform film and PL enhancement, but also realize a PL increase/decrease shift effect. The PL behaviors of AWO4 nanofilms doped by TiO2 are in good agreement with Gaussion function relation. In addition, there is a positive correlation between the critical concentrations of TiO2 in AWO4-TiO2 nanofilm series and A's ionic potential.

  18. In situ synthesis and hardness of TiC/Ti5Si3 composites on Ti-5Al-2.5Sn substrates by gas tungsten arc welding

    NASA Astrophysics Data System (ADS)

    Yan, Wen-qing; Dai, Le; Gui, Chi-bin

    2013-03-01

    TiC/Ti5Si3 composites were fabricated on Ti-5Al-2.5Sn substrates by gas tungsten arc welding (GTAW). Identification of the phases was performed using X-ray diffraction (XRD). The microstructures were analyzed using scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectrometry (EDS) and optical microscopy (OM). The Vickers hardness was measured with a micro-hardness tester. The TiC/Ti5Si3 composites were obtained in a double-layer track, and the Vickers hardness of the track increased by two to three times compared with the Ti-5Al-2.5Sn substrate.

  19. Effect of neutron irradiation on defect evolution in Ti3SiC2 and Ti2AlC

    NASA Astrophysics Data System (ADS)

    Tallman, Darin J.; He, Lingfeng; Garcia-Diaz, Brenda L.; Hoffman, Elizabeth N.; Kohse, Gordon; Sindelar, Robert L.; Barsoum, Michel W.

    2016-01-01

    Herein we report on the characterization of defects formed in polycrystalline Ti3SiC2 and Ti2AlC samples exposed to neutron irradiation - up to 0.1 displacements per atom (dpa) at 350 ± 40 °C or 695 ± 25 °C, and up to 0.4 dpa at 350 ± 40 °C. Black spots are observed in both Ti3SiC2 and Ti2AlC after irradiation to both 0.1 and 0.4 dpa at 350 °C. After irradiation to 0.1 dpa at 695 °C, small basal dislocation loops, with a Burgers vector of b = 1/2 [0001] are observed in both materials. At 9 ± 3 and 10 ± 5 nm, the loop diameters in the Ti3SiC2 and Ti2AlC samples, respectively, were comparable. At 1 × 1023 loops/m3, the dislocation loop density in Ti2AlC was ≈1.5 orders of magnitude greater than in Ti3SiC2, at 3 × 1021 loops/m3. After irradiation at 350 °C, extensive microcracking was observed in Ti2AlC, but not in Ti3SiC2. The room temperature electrical resistivities increased as a function of neutron dose for all samples tested, and appear to saturate in the case of Ti3SiC2. The MAX phases are unequivocally more neutron radiation tolerant than the impurity phases TiC and Al2O3. Based on these results, Ti3SiC2 appears to be a more promising MAX phase candidate for high temperature nuclear applications than Ti2AlC.

  20. Effect of neutron irradiation on defect evolution in Ti3SiC2 and Ti2AlC

    DOE PAGESBeta

    Tallman, Darin J.; He, Lingfeng; Garcia-Diaz, Brenda L.; Hoffman, Elizabeth N.; Kohse, Gordon; Sindelar, Robert L.; Barsoum, Michel W.

    2015-10-23

    Here, we report on the characterization of defects formed in polycrystalline Ti3SiC2 and Ti2AlC samples exposed to neutron irradiation – up to 0.1 displacements per atom (dpa) at 350 ± 40 °C or 695 ± 25 °C, and up to 0.4 dpa at 350 ± 40 °C. Black spots are observed in both Ti3SiC2 and Ti2AlC after irradiation to both 0.1 and 0.4 dpa at 350 °C. After irradiation to 0.1 dpa at 695 °C, small basal dislocation loops, with a Burgers vector of b = 1/2 [0001] are observed in both materials. At 9 ± 3 and 10 ±more » 5 nm, the loop diameters in the Ti3SiC2 and Ti2AlC samples, respectively, were comparable. At 1 × 1023 loops/m3, the dislocation loop density in Ti2AlC was ≈1.5 orders of magnitude greater than in Ti3SiC2, at 3 x 1021 loops/m3. After irradiation at 350 °C, extensive microcracking was observed in Ti2AlC, but not in Ti3SiC2. The room temperature electrical resistivities increased as a function of neutron dose for all samples tested, and appear to saturate in the case of Ti3SiC2. The MAX phases are unequivocally more neutron radiation tolerant than the impurity phases TiC and Al2O3. Based on these results, Ti3SiC2 appears to be a more promising MAX phase candidate for high temperature nuclear applications than Ti2AlC.« less

  1. Multifunctional Ti-(Ca,Zr)-(C,N,O,P) films for load-bearing implants.

    PubMed

    Shtansky, D V; Gloushankova, N A; Bashkova, I A; Kharitonova, M A; Moizhess, T G; Sheveiko, A N; Kiryukhantsev-Korneev, F V; Petrzhik, M I; Levashov, E A

    2006-07-01

    Films of Ti-Ca-P-C-O-(N), Ti-Ca-C-O-(N) and Ti-Zr-C-O-(N) were deposited by DC magnetron sputtering or ion implantation-assisted magnetron sputtering of composite targets TiC0.5 + 10%Ca10(PO4)6(OH)2, TiC0.5 + 20%(CaO + TiO2) and TiC0.5 + 10%ZrO2 in an Ar atmosphere or reactively in a gaseous mixture of Ar + 14%N2. The microstructure, elemental and phase composition of films were studied by means of X-ray diffraction, transmission electron microscopy, scanning force microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The films were characterized in terms of their hardness, Young's modulus, elastic recovery, adhesion strength, and friction and wear both in air and under physiological solution. Particular attention was paid to the analysis of deformation and fracture for various film/substrate systems during scratch testing. The biocompatibility of the films was evaluated by both in vitro and in vivo experiments. In vitro studies involved the investigation of adhesion, spreading, and proliferation of MC3T3-E1 osteoblasts and IAR-2 epithelial cells, morphometric analysis, actin cytoskeleton, focal contacts staining, alkaline phosphatase activity and von Kossa staining of osteoblastic culture. Cell culture experiments demonstrated an increase of osteoblastic proliferation on Ca- and P-incorporated films. In vivo studies were fulfilled by subcutaneous implantation of Teflon plates coated with the tested films in mice and analysis of the population of adherent cells on their surfaces. The results obtained show that multicomponent nanostructured Ti-(Ca, Zr)-(C, N, O, P) films possess a combination of high hardness, wear resistance and adhesion strength, reduced Young's modulus, low friction coefficient and high biocompatibility. PMID:16530825

  2. Nanocrystalline TiAl compacts prepared by HDDR and hot pressing

    SciTech Connect

    Aoki, K.; Itoh, Y.; Kawamura, Y.; Inoue, A.; Masumoto, T.

    1997-12-31

    Nanocrystalline TiAl powder was formed by the modified HDDR (hydrogenation-disproportion-dehydrogenation-recombination) method utilizing ball milling in a hydrogen atmosphere. That is, TiAl compound powder decomposed into TiH{sub 2} and Al-rich TiAl powders by mechanical grinding in a hydrogen atmosphere (HD process). Dehydrogenation-recombination (realloying) resulted in the formation of nanocrystalline TiAl powder when heated to about 700 K in an argon atmosphere (DR process). Almost fully dense nanocrystalline TiAl compacts were prepared by a combination of HDDR and hot-pressing at 873 K which is lower than the usual consolidation temperature by about 300 K. The TiAl compact thus made was brittle in the as-pressed state but showed compressive ductility after annealing.

  3. Growth and characterization of TiAlN/CrAlN superlattices prepared by reactive direct current magnetron sputtering

    SciTech Connect

    Barshilia, Harish C.; Deepthi, B.; Rajam, K. S.; Bhatti, Kanwal Preet; Chaudhary, Sujeet

    2009-01-15

    TiAlN and CrAlN coatings were prepared using a reactive direct current magnetron sputtering system from TiAl and CrAl targets. Structural characterization of the coatings using x-ray diffraction (XRD) revealed the B1 NaCl structure of TiAlN and CrAlN coatings with a prominent reflection along the (111) plane. The XPS data confirmed the bonding structures of TiAlN and CrAlN single layer coatings. Subsequently, nanolayered multilayer coatings of TiAlN/CrAlN were deposited on silicon and mild steel (MS) substrates at different modulation wavelengths ({lambda}) with a total thickness of approximately 1.0 {mu}m. The modulation wavelengths were calculated from the x-ray reflectivity data using modified Bragg's law. TiAlN/CrAlN multilayer coatings were textured along (111) for {lambda}<200 A and the XRD patterns showed the formation of superlattice structure for coatings deposited at {lambda}=102 A. The x-ray reflectivity data showed reflections of fifth and seventh orders for multilayer coatings deposited at {lambda}=102 and 138 A, respectively, indicating the formation of sharp interfaces between TiAlN and CrAlN layers. The cross-sectional scanning electron microscopy image of TiAlN/CrAlN multilayer coatings indicated a noncolumnar and dense microstructure. A maximum hardness of 39 GPa was observed for TiAlN/CrAlN multilayer coatings deposited at {lambda}=93 A, which was higher than the rule-of-mixture value (30 GPa) for TiAlN and CrAlN. Study of thermal stability of the coatings in air using micro-Raman spectroscopy indicated that the TiAlN/CrAlN multilayer coatings were stable up to 900 deg. C in air. TiAlN/CrAlN multilayer coatings also exhibited improved corrosion resistance when compared to the MS substrate.

  4. Bioactivity of fluorapatite/alumina composite coatings deposited on Ti6Al4V substrates by laser cladding

    NASA Astrophysics Data System (ADS)

    Chien, C. S.; Liu, C. W.; Kuo, T. Y.; Wu, C. C.; Hong, T. F.

    2016-04-01

    Hydroxyapatite (HA) is one of the most commonly used coating materials for metal implants. However, following high-temperature deposition, HA easily decomposes into an unstable phase or forms an amorphous phase, and hence, the long-term stability of the implant is reduced. Accordingly, the present study investigates the use of fluorapatite (FA) fortified with 20 wt% alumina (α-Al2O3) as an alternative biomedical coating material. The coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding process performed with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min and 1200 W/600 mm/min, respectively. The results show that for all of the specimens, a strong metallurgical bond is formed at the interface between the coating layer and the transition layer due to melting and diffusion. The XRD analysis results reveal that the cladding layers in all of the specimens consist mainly of FA, β-TCP, CaF2, Ti and θ-Al2O3 phases. In addition, the cladding layers of the specimens prepared using laser powers of 400 and 800 W also contain CaTiO3 and CaAl2O4, while that of the specimen clad using a power of 1200 W contains TTCP and CaO. Following immersion in simulated body fluid for 14 days, all of the specimens precipitate dense bone-like apatite and exhibit excellent bioactivity. However, among all of the specimens, the specimen that is prepared with a laser power of 800 W shows the best biological activity due to the presence of residual FA, apatite-generating CaTiO3 and a rough cladding layer surface.

  5. Diffusion Bonding of Ti-6Al-4V Sheet with Ti-6Al-4V Foam for Biomedical Implant Applications

    NASA Astrophysics Data System (ADS)

    Hamilton, Brittany; Oppenheimer, Scott; Dunand, David C.; Lewis, Daniel

    2013-12-01

    Advanced metallic bone implants are designed to have a porous surface to improve osseointegration and reduce risks of loosening. An alternative approach to existing surface treatments to create a porous surface is to bond separately produced metallic foams onto the implant. To assess the feasibility of this approach, a Ti-6Al-4V foam was diffusion bonded onto bulk Ti-6Al-4V in an argon atmosphere at temperatures between 1173 K and 1223 K (900 °C and 950 °C) for times between 45 and 75 minutes. These specimens were tested in tension to determine bond quality: failures occurred in the foam, indicating a strong diffusion-bonded interface. The quality of the bond was confirmed by metallographic studies, indicating that this approach, which can also be applied to creating of sandwich with porous cores, is successful.

  6. Anomalous phonon properties in the silicide superconductors CaAlSi and SrAlSi

    NASA Astrophysics Data System (ADS)

    Kuroiwa, S.; Hasegawa, T.; Kondo, T.; Ogita, N.; Udagawa, M.; Akimitsu, J.

    2008-11-01

    Lattice-dynamical properties of CaAlSi and SrAlSi with a similar layer structure to MgB2 have been first investigated by both Raman-scattering and ab initio calculations. All Raman-active phonons with E' symmetry have been clearly observed for both compounds. Their line shapes are asymmetric but their linewidths are ˜10cm-1 , which is very narrower than that of MgB2 . In addition to the Raman-active modes, several extra peaks have been observed below 160cm-1 . These low-energy extra modes can be assigned to the out-of-plane vibrations of Al perpendicular to Al-Si basal plane. Since these peak intensities are strongly affected by the incident energy (resonance Raman process), the electronic state is important for them. Moreover, in both crystals of CaAlSi and SrAlSi, we point out the energy difference for the different propagation directions along the c axis and the c plane, in spite of the very close wave vector to the Brillouin-zone center. This energy difference cannot be explained by a usual Raman-scattering scenario at this stage.

  7. Microscopic Morphology and Microstructure of Ti-N and Ti-Ni Phase Between the Dilution Zone and the Clad Zone in Laser Remelting NiCrBSi/TiN Layer on Ti-6Al-4V Alloy Surface

    NASA Astrophysics Data System (ADS)

    Liu, Rongxiang; Guo, Lixin; Lei, Tingquan

    The microscopic morphology and microstructure of Ti-N and Ti-Ni phase between the dilution zone and the clad zone in laser remelting NiCrBSi/TiN layer on a Ti-6Al-4V alloy were characterized using TEM and SEM. The experimental results showed that during laser irradiation heating, TiN particles were partially dissolved into the melted Ni-base alloy, and the dissolved Ti and N atoms were precipitated in the form of TiN, TiN0.3. Ti exhibits height activity, it combines with Ni forming Ti2Ni, TiNi matrix intermetallic during laser remelting, faults exist in the Ti2Ni and TiNi phase, and crystal lattice of TiNi phase is superlattice. Lastly, the cause of the formation of the Ti-N and Ti-Ni phase is discussed.

  8. Compositions and morphologies of TiAlSi intermetallics in different diffusion couples

    SciTech Connect

    Gao, Tong; Liu, Guiliang; Liu, Xiangfa

    2014-09-15

    Two kinds of diffusion couples were designed to investigate the formation of ternary TiAlSi phases in Al–Si–Ti alloys. It was found that different diffusion processes result in various compositions and morphologies of TiAlSi intermetallics. The melted Al, Si and Ti atoms in the diffusion couple leads to the formation of flake-like TiAlSi phase through liquid–liquid reaction. Besides, unidirectional diffusion of Al and Si atoms into blocky TiAl{sub 3} particles or Ti powders via a liquid–solid diffusion process also results in the formation of TiAlSi, while keeping the block-like morphology. This kind of diffusion is a gradual process, driven by the concentration gradient. The reactions in the diffusion couples are helpful to understand the compositional and morphological evolutions of TiAlSi as reported in previous work. - Highlights: • Two diffusion couples were designed to investigate the formation of TiAlSi phases. • Compositions and morphologies of TiAlSi are influenced by the diffusion process. • Liquid–liquid and liquid–solid diffusions were detected. • The corresponding mechanisms were discussed.

  9. 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

    2016-04-01

    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.

  10. Mechanical and Tribological Properties of Cold-Sprayed Ti Coatings on Ti-6Al-4V Substrates

    NASA Astrophysics Data System (ADS)

    Khun, N. W.; Tan, A. W. Y.; Liu, E.

    2016-04-01

    A cold spray process was used to deposit titanium (Ti) coatings of different thicknesses on commercial Ti-6Al-4V (Ti64) substrates. The hardness of the Ti coatings was measured using a Vickers micro-indenter. It was found that the thicker Ti coatings had higher hardness probably due to the better uniformity and higher density of the coatings. The tribological results showed that the friction and wear of the Ti coatings tested against a steel ball under dry condition became lower with higher thickness probably due to the higher wear resistance of the thicker coatings associated with their higher hardness. The specific wear rates of all the Ti coatings were significantly lower than that of the Ti64 substrate as a result of the higher wear resistance of the Ti coatings associated with their cold-worked microstructures and the formation of high wear resistant oxide layers on their wear tracks during the wear testing.

  11. Surface modification of Ti{sub 3}Al for improved oxidation resistance

    SciTech Connect

    Vaidya, R.U.; Zurek, A.K.; Castro, R.; Sin, Y.W.; Subramanian, K.N.

    1993-08-01

    Ti{sub 3}Al has very attractive properties such as low density and high temperature mechanical strength for elevated temperature structural applications. Its major drawback however, is poor oxidation resistance at temperatures above 600{degrees}C. Potential use of Ti{sub 3}Al in high temperature applications depends on its protection from excessive oxidation. To this effect, Al{sub 2}O{sub 3} and Al{sub 3}Ti were selected as coating materials chemically compatible with Ti{sub 3}Al. Al{sub 2}O{sub 3} acts as a protective layer on the surface of Ti{sub 3}Al and is impervious to oxygen diffusion. Al{sub 3}Ti is resistant to high temperatures and also protects the Ti{sub 3}Al substrate by forming an oxide layer consisting primarily of Al{sub 2}O{sub 3}. In this study, Al{sub 2}O{sub 3} was plasma sprayed onto the surface of Ti{sub 3}Al, while the Al{sub 3}Ti was applied by laser melting. Effectiveness of the coatings were investigated after 10 hours of cyclic oxidation.

  12. Water droplet erosion mechanisms of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Kamkar Zahmatkesh, Niloofar

    Water impingement erosion of materials can be a life-limiting phenomenon for the components in many erosive environments. For example, aircraft body exposed to rain, steam turbine blade, and recently in gas turbine coupled with inlet fogging system. The last is the focus of this study. Inlet fogging system is the most common method used to augment gas turbine output during hot days; high ambient temperature causes strong deterioration of the engine performance. Micro-scaled droplets introduced into the inlet airflow allow the cooling of entering air as well as intercooling the compressor (overspray) and thus optimizes the output power. However, erosion damage of the compressor blades in overspray stage is one of the major concerns associated with the inlet fogging system. The main objective of this research work (CRIAQ MANU419 project) is to understand the erosion induced by water droplets on Titanium alloy to eventually optimize the erosion resistance of the Ti-based compressor blade. Therefore, characterization of the water droplet erosion damage on Ti-6Al-4V receives the major importance. The influence of base material microstructure and impact parameters were considered in erosion evaluation in present study. This work covers the characterization of the erosion damage on Ti-6Al-4V alloy in two parts: - The water droplet erosion damage through a novel experimental approach. The collected data were processed both qualitatively and quantitatively for multi-aspects damage study. - The influence of impact velocity on erosion in an attempt to represent the in-service conditions.

  13. Modulating TiO2 photocatalyst by Al doping: Density functional theory approach

    NASA Astrophysics Data System (ADS)

    Zhao, Ya Fei; Li, Can; Lu, Song; Gong, Yin Yan; Niu, Leng Yuan; Liu, Xin Juan

    2016-06-01

    In this work, systematic study of the thermal stability, crystal structure and electronic properties of Al doped TiO2 were studied by the first principles calculations. The results showed that Al atoms preferentially occupying the interstitial site under Ti-rich condition, but substituting the Ti atom under O-rich condition. In contrast to pure TiO2, the values of VBM and CBM are reduced for Al substituting Ti doped mode, but increased for Al interstitial atom doped mode. Thus, we can modulate the preparation condition and dosage concentration for preparing the optimal photocatalyst.

  14. Phase equilibria in the Ti-Al-O system at 945 C and analysis of Ti/Al{sub 2}O{sub 3} reactions

    SciTech Connect

    Kelkar, G.P.; Carim, A.H.

    1995-03-01

    Phase relations in the Ti-Al-O system were evaluated experimentally at 945 C. The tie lines were established using equilibrated samples with phase compositions determined by electron probe microanalysis. The phase relations were in agreement with previous estimates but the phase fields of {alpha}-Ti[O,Al] and Ti{sub 3}Al[O] were significantly different. The Ti{sub 3}Al[O] phase has a maximum solubility of 22 at.% O, corresponding to a nominal stoichiometry of Ti{sub 3}AlO, whereas the {alpha}-Ti[O,Al] phase, at a maximum O solubility of 33.33 at.%, has a negligible amount of Al in solution. The disagreement between these results and previous studies was attributed to the differences in experimental techniques for sample preparation and analysis. The reported layer sequences at the Ti/Al{sub 2}O{sub 3} interface were evaluated based on the ternary section and the corresponding O activity diagram. The layered interfaces were found to be stable, with the evolution of the reaction products governed by the thickness of the initial Ti layer and the partial pressure in the ambient.

  15. Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

    2010-11-01

    A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and 800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

  16. Phase stability of U-Mo-Ti alloys and interdiffusion behaviors of U-Mo-Ti/Al-Si

    SciTech Connect

    Park, Jong Man; Ryu, Ho Jin; Park, Jae Soon; Oh, Seok Jin; Kim, Chang Kyu; Kim, Yeon Soo; Hofman, Gerard L.

    2008-07-15

    As a remedy for reducing reaction between U-Mo and Al in U-Mo/Al dispersion fuel, adding an alloying element such as Zr and Ti in U-Mo has been proposed at ANL. Although ANL's work showed the potential effectiveness of these elements based on thermodynamic and metallurgical analyses, the effect of a Ti addition in U-Mo remains unproven. The out-of-pile tests of U-Mo-Ti alloys, which focused on phase stability and interdiffusion behavior against Al, are meaningful to predict their efficacy during an irradiation. At the 2006 RERTR conference, we presented our work on the interdiffusion behaviors of U-Mo-Zr/Al-Si. In this paper, we will present the results for substituting U-Mo-Zr with U-Mo-Ti. Unlike U-Mo-Zr alloys, the gamma-heat-treated U-7Mo-xTi (x=1{approx}3 wt%) exhibited a metastable {gamma}-U phase, regardless of the Ti content. In these samples, however, a small amount of second-phase precipitates with a high Ti concentration was observed. The gamma phase stability of the U-Mo-Ti alloys at 500 deg C was similar to that of the U-Mo-Zr alloys. Interdiffusion test results between U-Mo-Ti alloys and Al-Si alloys will also be presented and a comparison with the previous results with U- Mo-Zr/Al-Si will also be included. (author)

  17. Development of Ti-6Al-4V and Ti-1Al-8V-5Fe Alloys Using Low-Cost TiH2 Powder Feedstock

    SciTech Connect

    Joshi, Vineet V.; Lavender, Curt; Moxon, Vladimir; Duz, Vlad; Nyberg, Eric; Weil, K. Scott

    2012-09-25

    Thermo-mechanical processing was performed on two titanium alloy billets, a beta-titanium alloy (Ti1Al8V5Fe) and an alpha-beta titanium alloy (Ti6Al4V), which had been produced using a novel low-cost powder metallurgy process that relies on the use of TiH2 powder as a feedstock material. The thermomechanical processing was performed in the beta region of the respective alloys to form 16-mm diameter bars. The hot working followed by the heat treatment processes not only eliminated the porosity within the materials but also developed the preferred microstructures. Tensile testing and rotating beam fatigue tests were conducted on the as-rolled and heat-treated materials to evaluate their mechanical properties. The mechanical properties of these alloys matched well with those produced by the conventional ingot processing route.

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

    NASA Astrophysics Data System (ADS)

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

    1987-04-01

    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.

  19. 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.

  20. Analysis of structure and bonding strength of AlTiN coatings by cathodic ion plating

    NASA Astrophysics Data System (ADS)

    Dejun, Kong; Haoyuan, Guo

    2015-04-01

    AlTiN coating was prepared on the surface of YT14 hard alloy cutter by cathodic arc ion plating, and the surface-interface morphologies, line scans of the interface elements and valence state of chemical elements were analyzed with field emission scanning electron microscopy, energy dispersive spectrometer and X-ray photoelectron spectroscopy, respectively, and bonding strength of the coating was measured with scratching tester. The results show that the elements of Al and N mainly exist in the AlTiN coating with an AlN and AlTiN hard phase, and (the) Ti element mainly exists in the coating with a TiN hard phase, which improve wear resistance of AlTiN coating. The elements of Al, Ti and N are diffused at the coating interface, in which part of Ti atoms are replaced by Al atoms at the TiN lattice, still keep face-centered cubic structure of TiN coating to form metallurgical bonding, and bonding strength of the coating interface measured by scratching tester is 78.75 N, which is beneficial to improving service life of AlTiN coating prepared on the surface of carbide tool cutter.

  1. Tribological Properties of Ti(Al,O)/Al2O3 Composite Coating by Thermal Spraying

    NASA Astrophysics Data System (ADS)

    Salman, Asma; Gabbitas, Brian; Cao, Peng; Zhang, Deliang

    The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity air fuel (HVAF) thermally sprayed wear resistant Ti(Al,O)/Al2O3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting and dummy blocks aluminium extrusion. A feedstock of Ti(Al,O)/Al2O3 composite powder was produced from a mixture of Al and TiO2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity air-fuel (HVAF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The wear resistance of the coating was investigated by a tribometer using a spherical ended alumina pin as a counter body under dry and lubricating conditions. The results showed that composite coating has lower wear rate at high temperature than at room temperature without using lubricant. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

  2. Synthesis of γ-TiAl by Reactive Spark Plasma Sintering of Cryomilled Ti and Al Powder Blend, Part I: Influence of Processing and Microstructural Evolution

    NASA Astrophysics Data System (ADS)

    Sun, Yu; Kulkarni, Kaustubh; Sachdev, Anil K.; Lavernia, Enrique J.

    2014-06-01

    To provide insight into the influence of an electric field on the kinetics of diffusion, fully lamellar γ-TiAl was processed by a rapid, two-stage, solid-state reactive sintering via spark plasma sintering (SPS) of a cryomilled Ti, Al powder blend. Cryomilling was implemented in the current study to attain a nanostructured grain size in the Ti and Al powder blend, and thereby provide insight into the influence of grain size on the underlying diffusion kinetics. Following a two-step process involving SPS at 873 K (600 °C) for 15 minutes and 1523 K (1250 °C) for 30 minutes, a fully lamellar TiAl alloy, with submicron lamellar spacing, was successfully obtained. Microstructural refinement in the Ti and Al powders during cryomilling led to an increase in solid-state diffusion, and the underlying mechanisms are discussed in detail.

  3. Electrochemical characterization of MC3T3-E1 cells cultured on γTiAl and Ti-6Al-4V alloys.

    PubMed

    Bueno-Vera, J A; Torres-Zapata, I; Sundaram, P A; Diffoot-Carlo, N; Vega-Olivencia, C A

    2015-12-01

    Electrochemical impedance spectroscopy (EIS) was used to study the behavior of MC3T3-E1 cells cultured in an αMEM+FBS solution on two Ti-based alloys (Ti-6Al-4V and γTiAl) for 4, 7 and 14 days. EIS measurements were carried out at an open-circuit potential in a 1 mHz to 100 kHz frequency range. Results indicate a general increase in impedance on the Ti alloy surfaces with cells as a function of time. Bode plots indicate changes corresponding to the passive oxide film, adsorption of proteins and cell tissue on surfaces with the passage of time. Normal cellular activity based on the polygonal morphology, with long and fine cytoplasmic prolongations of the cells on Ti-6Al-4V and γTiAl was observed from SEM images. Similarly, mineralization nodules corresponding to cell differentiation associated with the osseogenetic process were observed confirmed by Alizarin Red S staining. Immunofluorescence analysis to detect the presence of collagen Type I showed an increase in the segregation of collagen as a function of time. The impedance values obtained from EIS testing are indicative of the corrosion protection offered to the Ti alloy substrates by the cell layer. This study shows that γTiAl has better corrosion resistance than that of Ti-6Al-4V in the αMEM+FBS environment in the presence of MC3T3-E1 cells. PMID:26145813

  4. Quantum Chemical Design of Doped Ca2MnAlO(5+δ) as Oxygen Storage Media.

    PubMed

    Ling, Chen; Zhang, Ruigang; Jia, Hongfei

    2015-07-01

    Brownmillerite Ca2MnAlO5 has an exceptional capability to robustly adsorb half-molecules of oxygen and form Ca2MnAlO5.5. To utilize this unique property to regulate oxygen-involved reactions, it is crucial to match the oxygen release-intake equilibrium with targeted reaction conditions. Here we perform a comprehensive investigation of the strategy of tuning the oxygen storage property of Ca2MnAlO5 through chemical doping. For undoped Ca2MnAlO5+δ, our first-principles calculation predicts that the equilibrium temperature at a pressure of 1 atm of O2 is 848 K, which is in excellent agreement with experimental results. Furthermore, the doping of alkaline earth ions at the Ca site, trivalent ions at the Al site, and 3d transition metal ions at the Mn site is analyzed. By the doping of 12.5% of Ga, V, and Ti, the equilibrium temperature shifts to high values by approximately 110-270 K, while by the doping of 12.5% of Fe, Sr, and Ba, the equilibrium temperature is lowered by approximately 20-210 K. The doping of these elements is thermodynamically stable, and doping other elements including Mg, Sc, Y, Cr, Co, and Ni generates metastable compounds. The doping of a higher content of Fe, however, lowers the oxygen storage capacity. Finally, on the basis of our calculated data, we prove that the formation energetics of nondilute interacting oxygen vacancy in doped Ca2MnAlO5.5 scale linearly with a simple descriptor, the oxygen p-band position relative to the Fermi level. The higher-oxygen p-band position leads to a lower vacancy formation energy and thus a lower oxygen release temperature. Understanding such a relationship between fundamental quantum chemical properties and macroscopic properties paves the road to the design and optimization of novel functional oxides. PMID:26066573

  5. Al-based metal matrix composites reinforced with nanocrystalline Al-Ti-Ni particles

    NASA Astrophysics Data System (ADS)

    Scudino, S.; Ali, F.; Surreddi, K. B.; Prashanth, K. G.; Sakaliyska, M.; Eckert, J.

    2010-07-01

    Al-based metal matrix composites containing different volume fractions of nanocrystalline Al70Ti20Ni10 reinforcing particles have been produced by powder metallurgy and the effect of the volume fraction of reinforcement on the mechanical properties of the composites has been studied. Room temperature compression tests reveal a considerable improvement of the mechanical properties as compared to pure Aluminum. The compressive strength increases from 155 MPa for pure Al to about 200 and 240 MPa for the samples with 20 and 40 vol.% of reinforcement, respectively, while retaining appreciable plastic deformation with a fracture strain ranging between 43 and 28 %.

  6. Growth and stress-induced transformation of zinc blende AlN layers in Al-AlN-TiN multilayers

    SciTech Connect

    Li, Nan; Yadav, Satyesh K.; Wang, Jian; Liu, Xiang -Yang; Misra, Amit

    2015-12-18

    We report that AlN nanolayers in sputter deposited {111}Al/AlN/TiN multilayers exhibit the metastable zinc-blende-structure (z-AlN). Based on density function theory calculations, the growth of the z-AlN is ascribed to the kinetically and energetically favored nitridation of the deposited aluminium layer. In situ nanoindentation of the as-deposited {111}Al/AlN/TiN multilayers in a high-resolution transmission electron microscope revealed the z-AlN to wurzite AlN phase transformation through collective glide of Shockley partial dislocations on every two {111} planes of the z-AlN.

  7. Growth and Stress-induced Transformation of Zinc blende AlN Layers in Al-AlN-TiN Multilayers

    PubMed Central

    Li, Nan; Yadav, Satyesh K.; Wang, Jian; Liu, Xiang-Yang; Misra, Amit

    2015-01-01

    AlN nanolayers in sputter deposited {111}Al/AlN/TiN multilayers exhibit the metastable zinc-blende-structure (z-AlN). Based on density function theory calculations, the growth of the z-AlN is ascribed to the kinetically and energetically favored nitridation of the deposited aluminium layer. In situ nanoindentation of the as-deposited {111}Al/AlN/TiN multilayers in a high-resolution transmission electron microscope revealed the z-AlN to wurzite AlN phase transformation through collective glide of Shockley partial dislocations on every two {111} planes of the z-AlN. PMID:26681109

  8. Growth and Stress-induced Transformation of Zinc blende AlN Layers in Al-AlN-TiN Multilayers.

    PubMed

    Li, Nan; Yadav, Satyesh K; Wang, Jian; Liu, Xiang-Yang; Misra, Amit

    2015-01-01

    AlN nanolayers in sputter deposited {111}Al/AlN/TiN multilayers exhibit the metastable zinc-blende-structure (z-AlN). Based on density function theory calculations, the growth of the z-AlN is ascribed to the kinetically and energetically favored nitridation of the deposited aluminium layer. In situ nanoindentation of the as-deposited {111}Al/AlN/TiN multilayers in a high-resolution transmission electron microscope revealed the z-AlN to wurzite AlN phase transformation through collective glide of Shockley partial dislocations on every two {111} planes of the z-AlN. PMID:26681109

  9. Measurement of the Ca40(α,γ)Ti44 reaction relevant for supernova nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Vockenhuber, C.; Ouellet, C. O.; The, L.-S.; Buchmann, L.; Caggiano, J.; Chen, A. A.; Crawford, H.; D'Auria, J. M.; Davids, B.; Fogarty, L.; Frekers, D.; Hussein, A.; Hutcheon, D. A.; Kutschera, W.; Laird, A. M.; Lewis, R.; O'Connor, E.; Ottewell, D.; Paul, M.; Pavan, M. M.; Pearson, J.; Ruiz, C.; Ruprecht, G.; Trinczek, M.; Wales, B.; Wallner, A.

    2007-09-01

    The short-lived nuclide Ti44 is an important nuclide for the understanding of explosive nucleosynthesis. The main production reaction, Ca40(α,γ)Ti44, has been studied in inverse kinematics with the recoil mass spectrometer DRAGON located at the TRIUMF-ISAC facility in Vancouver, Canada. The temperature range relevant for α-rich freeze-out during a core-collapse supernova has been covered entirely with a Ca40 beam of 0.60 to 1.15 MeV/nucleon. All relevant quantities for the calculation of the astrophysical reaction rate have been measured directly. Because of many previously undiscovered resonances, the reaction rate derived from the energy dependent Ti44 yield is higher than the one based on previous prompt γ-ray studies commonly used in supernova models. The presented new rate results in an increased Ti44 production in supernovae.

  10. Controllable two-scale network architecture and enhanced mechanical properties of (Ti5Si3+TiBw)/Ti6Al4V composites.

    PubMed

    Jiao, Y; Huang, L J; Duan, T B; Wei, S L; Kaveendran, B; Geng, L

    2016-01-01

    Novel Ti6Al4V alloy matrix composites with a controllable two-scale network architecture were successfully fabricated by reaction hot pressing (RHP). TiB whiskers (TiBw) were in-situ synthesized around the Ti6Al4V matrix particles, and formed the first-scale network structure (FSNS). Ti5Si3 needles (Ti5Si3) precipitated in the β phase around the equiaxed α phase, and formed the secondary-scale network structure (SSNS). This resulted in increased deformation compatibility accompanied with enhanced mechanical properties. Apart from the reinforcement distribution and the volume fraction, the ratio between Ti5Si3 and TiBw fraction were controlled. The prepared (Ti5Si3 + TiBw)/Ti6Al4V composites showed higher tensile strength and ductility than the composites with a one-scale microstructure, and superior wear resistance over the Ti6Al4V alloy under dry sliding wear conditions at room temperature. PMID:27622992

  11. The effect of Al content on the work function engineering at TiAlN/HfO2 interface

    NASA Astrophysics Data System (ADS)

    Kim, Geun-Myeong; Oh, Young Jun; Chang, Kee Joo

    2015-03-01

    In high-k/metal gate stacks of metal-oxide-semiconductor field-effect transistors, it is important to control the metal work function such that it should be close to the valence and conduction band edges of Si in p- and n-channel devices. It was reported that depositing TiAl on top of TiN/HfO2 stack in gate-last process can effectively induce the n-type shift of work function, while the work function is of p-type at TiN/HfO2 stack. In this work, we perform first-principles density functional calculations to investigate the Schottky barrier height at TiAlN/HfO2 interface. In bulk TiN, it is found that a substitutional Al is the most stable form of Al impurity. When substitutional Al atoms are introduced at TiN/HfO2 interface, the effective work function tends to decrease. At TiAlN/HfO2 interface, the n-type shift of the work function increases almost linearly with the Al content. This is attributed to the change of interface bonds by Al incorporation and the dipole field induced at the interface. On the other hand, relative thicknesses of TiAl and TiN at abrupt TiAl/TiN/HfO2 interface do not significantly affect the effective work function. The authors are supported by the National Research Foundation of Korea (2005-0093845).

  12. Optical spectroscopy and band gap analysis of hybrid improper ferroelectric Ca3Ti2O7

    NASA Astrophysics Data System (ADS)

    Cherian, Judy G.; Birol, Turan; Harms, Nathan C.; Gao, Bin; Cheong, Sang-Wook; Vanderbilt, David; Musfeldt, Janice L.

    2016-06-01

    We bring together optical absorption spectroscopy, photoconductivity, and first principles calculations to reveal the electronic structure of the room temperature ferroelectric Ca3Ti2O7. The 3.94 eV direct gap in Ca3Ti2O7 is charge transfer in nature and noticeably higher than that in CaTiO3 (3.4 eV), a finding that we attribute to dimensional confinement in the n = 2 member of the Ruddlesden-Popper series. While Sr substitution introduces disorder and broadens the gap edge slightly, oxygen deficiency reduces the gap to 3.7 eV and gives rise to a broad tail that persists to much lower energies.

  13. Wear Behavior of Low-Cost, Lightweight TiC/Ti-6Al-4V Composite Under Fretting: Effectiveness of Solid-Film Lubricant Counterparts

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Street, Kenneth W., Jr.; Sanders, Jeffrey H.; Hager, Carl H., Jr.; Zabinski, Jeffrey S.; VanderWal, Randall L.; Andrews, Rodney; Lerch, Bradley A.

    2007-01-01

    The wear behavior of low-cost, lightweight 10-wt% TiC-particulate-reinforced Ti-6Al-4V matrix composite (TiC/Ti- 6Al-4V) was examined under fretting at 296, 423, and 523 K in air. Bare 10-wt% TiC/Ti-6Al-4V hemispherical pins were used in contact with dispersed multiwalled carbon nanotubes (MWNTs), magnetron-sputtered diamondlike carbon/chromium (DLC/Cr), magnetron-sputtered graphite-like carbon/chromium (GLC/Cr), and magnetron-sputtered molybdenum disulphide/titanium (MoS2/Ti) deposited on Ti-6Al-4V, Ti-48Al-2Cr-2Nb, and nickel-based superalloy 718. When TiC/Ti-6Al-4V was brought into contact with bare Ti-6Al-4V, bare Ti-48Al-2Cr-2Nb, and bare nickel-based superalloy 718, strong adhesion, severe galling, and severe wear occurred. However, when TiC/Ti-6Al-4V was brought into contact with MWNT, DLC/Cr, GLC/Cr, and MoS2/Ti coatings, no galling occurred in the contact, and relatively minor wear was observed regardless of the coating. All the solid-film lubricants were effective from 296 to 523 K, but the effectiveness of the MWNT, DLC/Cr, GLC/Cr, and MoS2/Ti coatings decreased as temperature increased.

  14. Defect chemistry and dielectric properties of Yb{sup 3+}:CaTiO{sub 3} perovskite

    SciTech Connect

    Bassoli, M.; Buscaglia, M. T.; Bottino, C.; Buscaglia, V.; Molinari, M.; Maglia, F.; Parravicini, G.; Dapiaggi, M.

    2008-01-01

    The defect chemistry of Yb{sup 3+}:CaTiO{sub 3} solid solutions has been investigated both theoretically and experimentally. Three different incorporation mechanisms with similar solution energy were predicted for Yb{sup 3+} by atomistic simulation: (i) Ca site substitution with Ca vacancy compensation; (ii) Ti site substitution with O vacancy compensation; (iii) simultaneous substitution at both Ca and Ti sites with self-compensation. X-ray diffraction and scanning electron microscopy results strongly support the possibility to realize the above defect chemistries in CaTiO{sub 3} by changing the Ca/Ti ratio to force Yb{sup 3+} on the Ca site (Ca/Ti<1), on Ti site (Ca/Ti>1), or on both sites (Ca/Ti=1) according to the calculations. The temperature dependence of the relative dielectric constant (10{sup 2}-10{sup 5} Hz) of ceramics corresponding to predominant Yb substitution either at the Ca site or the Ti site is qualitatively similar to that of undoped CaTiO{sub 3}. The Curie-Weiss temperature is shifted to more negative values in comparison to CaTiO{sub 3}, suggesting that the compositions Ca{sub 1-3/2x}Yb{sub x}TiO{sub 3} and CaYb{sub x}Ti{sub 1-x}O{sub 3} are further driven away from the ferroelectric instability. In contrast, the dielectric properties (10{sup 2}-10{sup 5} Hz) of ceramics corresponding to Ca{sub 1-x/2}Yb{sub x}Ti{sub 1-x/2}O{sub 3} are radically different. The relative dielectric constant is increased of about one order of magnitude (2200 at 30 K), is almost independent of temperature, with a maximum variation of 20% in range of 20-300 K, and shows frequency dispersion above 150 K. The loss tangent at 20-300 K is <5% for frequencies {>=}1 kHz. The possible mechanism for the observed dielectric behavior is discussed.

  15. 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.

  16. First-Principles Investigation of Vibrational Properties of CaTiO3 Crystal

    NASA Astrophysics Data System (ADS)

    Medeiros, Subenia; Araujo, Maeva

    2014-03-01

    The structural, electronic, vibrational, and optical properties of perovskite CaTiO3 in the cubic, orthorhombic, and tetragonal phase are calculated in the framework of density functional theory (DFT) with different exchange-correlation potentials by CASTEP package. The calculated band structure shows an indirect band gap of 1.88 eV at the Γ-R points in the Brillouin zone to the cubic structure, a direct band gap of 2.41 eV at the Γ- Γ points to the orthorhombic structure, and an indirect band gap of 2.31 eV at theM - Γ points to the tetragonal phase. I have concluded that the bonding between Ca and TiO2 is mainly ionic and that the TiO2 entities bond covalently. Unlike some perovskites the CaTiO3 does not exhibit a ferroelectric phase transition down to 4.2 K. It is still known that the CaTiO3 has a static dielectric constant that extrapolates to a value greater than 300 at zero temperature, and the dielectric response is dominated by low frequency (ν ~ 90cm-1) polar optical modes in which cation motion opposes oxygen motion. Our calculated lattice parameters, elastic constants, optical properties, and vibrational frequencies are found to be in good agreement with the available theoretical and experimental values. The results for the effective mass in the electron and hole carriers are also presented in this work.

  17. Development of Laser Fabricated Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III

    2006-01-01

    Laser Engineered Net Shaping (LENS) depositions with Ti-6Al-4V gas-atomized powder were accomplished at five different temperatures, ranging from 30 to 400 C, imposed on the base plate. These base plate temperatures were employed in an effort to relieve stresses which develop during the deposition. Warpage of the base plate was monitored. Only a slight decline in warpage was observed as the base plate temperature was increased. Results indicate that substrate temperatures closer to the stress relief minimum of 480 C would relieve deposition stresses, though process parameters would likely need to be modified to compensate for the higher base plate temperature. The compositions of the as-received powder and the LENS deposited material were chemically analyzed. The oxygen content of the LENS material was 0.154 wt.% which is less than the maximum impurity limit of 0.2 percent for commercial Ti-6Al-4V alloys, but is over the limit allowed in ELI grade (0.13 percent). The level of oxygen in the commercial base plate used was only 0.0635 percent. Tensile specimens were machined from the LENS deposited material and tested in tension at room temperature. The ultimate and yield tensile stresses of the LENS material were about 1200 and 1150 MPa respectively, which is about 20 percent higher than the strengths of wrought Ti-6Al-4V. The higher strength of the LENS material was due to its fine structure and high oxygen content. The LENS deposits were not fully dense; voids were frequent at the interfaces between deposited layers. These dispersed sheets of voids were parallel to the longitudinal axis of the resulting tensile specimens. Apparently there was sufficient continuous, fully dense material longitudinally to enable the high strengths. Ductility was low in the LENS material. Percent elongation at failure in the LENS material was near 4 percent, which is less than half of what is usually expected from Ti-6Al-4V. The low ductility was caused by high oxygen levels, and the

  18. 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.

  19. Theoretical Prediction of Transition Metal Alloying Effects on the Lightweight TiAl Intermetallic

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Tang, Chenghuang; Zhan, Yongzhong

    2016-03-01

    The structural, mechanical properties and Debye temperature of doped intermetallic Ti7Al8X (X = Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W) have been investigated by employing the pseudo-potential plane-wave approach based on density functional theory, within the generalized gradient approximation (GGA) function. The calculated lattice constants of TiAl are found to be within 1 pct error, compared with the experimental values. The stability of calculated structures of Ti7Al8X at 0 GPa is measured by studying mechanical stability conditions and formation energy. All the single crystals are proved to be elastically anisotropic. The Young's modulus as a function of crystal orientations has been systematically investigated. Mechanical properties of polycrystals are computed from values of shear modulus ( G), bulk modulus ( B), Young's modulus ( E), Poisson's ratio ( υ), and microhardness parameter ( H) for Ti7Al8X. It is indicated that addition of alloying elements reduces the brittleness and microhardness of TiAl intermetallic. Debye temperature of TiAl calculated using elastic data of the present work is found to be influenced by the addition of alloying elements, which is further confirmed by the phonon dispersions of Ti8Al8, Ti7Al8Zr, and Ti7Al8Hf.

  20. Enhanced hardness in epitaxial TiAlScN alloy thin films and rocksalt TiN/(Al,Sc)N superlattices

    SciTech Connect

    Saha, Bivas; Lawrence, Samantha K.; Bahr, David F.; Schroeder, Jeremy L.; Birch, Jens; Sands, Timothy D.

    2014-10-13

    High hardness TiAlN alloys for wear-resistant coatings exhibit limited lifetimes at elevated temperatures due to a cubic-AlN to hexagonal-AlN phase transformation that leads to decreasing hardness. We enhance the hardness (up to 46 GPa) and maximum operating temperature (up to 1050 °C) of TiAlN-based coatings by alloying with scandium nitride to form both an epitaxial TiAlScN alloy film and epitaxial rocksalt TiN/(Al,Sc)N superlattices on MgO substrates. The superlattice hardness increases with decreasing period thickness, which is understood by the Orowan bowing mechanism of the confined layer slip model. These results make them worthy of additional research for industrial coating applications.

  1. Studies on synthesis of in-situ Al-TiC metal matrix composites

    NASA Astrophysics Data System (ADS)

    Rai, R. N.; Saha, S. C.; Datta, G. L.; Chakraborty, M.

    2016-03-01

    In the present research work, synthesis and characterization of in-situ Al-TiC composites reinforced with ceramic phases was carried out. The formation of undesirable TiAl3 particles could be avoided justifying the correct procedural requirement adopted while preparing Al-TiC composites. It was observed that distributions of reinforced particles were uniform along the grain boundaries. It was also observed that the average size of the TiC particles was of 0.5 μm. It was also noted that the presence of TiC particles in the composite enhances the yield strength and hardness substantially.

  2. The preparation of the Ti-Al alloys based on intermetallic phases

    NASA Astrophysics Data System (ADS)

    Kosova, N.; Sachkov, V.; Kurzina, I.; Pichugina, A.; Vladimirov, A.; Kazantseva, L.; Sachkova, A.

    2016-01-01

    This article deals with a method of obtaining materials in the Ti-Al system. Research was carried out in accordance with the phase diagram of the system state. It was established, that both single-phase and multiphase systems, containing finely dispersed intermetallic compositions of phases Ti3Al, TiAl and TiAl3, are formed. Additionally, it was found that the pure finely dispersed (coherent-scattering region (CSR) up to 100 nm) intermetallic compound TiAl3 is formed at molar ratio of Ti:Al = 1:3. Experimentally proved the possibility of produce the complex composition of alloys and intermetallic compounds and products based on them.

  3. Titanium self-diffusion and chemical diffusion in Ti{sub 3}Al

    SciTech Connect

    Ruesing, J.; Herzig, C.

    1995-08-15

    Temperature and concentration dependence of the diffusion of Ti and Al has been measured in the ordered {alpha}{sub 2}-phase Ti{sub 3}Al. Ti self-diffusion is almost independent of the Al concentration in the hyperstoichiometric {alpha}{sub 2}-phase. The absolute D*{sub Ti}-values are rather low. Obviously diffusion proceeds by the vacancy mechanism and no constitutional vacancies but Al antisite defects are formed. Chemical diffusion {tilde D} is larger than self-diffusion D*{sub Ti} due to the fact that the thermodynamic factor {Phi} is larger than unity in the {alpha}{sub 2}-phase. Al self-diffusion D*{sub Al} was deduced to be lower than D*{sub Ti} by a factor of two to three in the range of 1,273 K to 1,173 K.

  4. 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.

  5. Multilayered TiAlN films on Ti6Al4V alloy for biomedical applications by closed field unbalanced magnetron sputter ion plating process.

    PubMed

    Yi, Peiyun; Peng, Linfa; Huang, Jiaqiang

    2016-02-01

    Ti6Al4V alloy has been widely used as a suitable material for surgical implants such as artificial hip joints. In this study, a series of multilayered gradient TiAlN coatings were deposited on Ti6Al4V substrate using closed field unbalanced magnetron sputter ion plating (CFUBMSIP) process. Taguchi design of experiment approach was used to reveal the influence of depositing parameters to the film composition and performance of TiAlN coatings. The phase structure and chemical composition of the TiAlN films were characterized by X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Mechanical properties, including hardness, Young's modulus, friction coefficient, wear rate and adhesion strength were systematically evaluated. Potentiodynamic tests were conducted to evaluate the corrosion resistance of the coated samples in Ringer's solution at 37°C to simulate human body environment. Comprehensive performance of TiAlN films was evaluated by assigning different weight according to the application environment. S8, deposited by Ti target current of 8A, Al target current of 6A, bias voltage of -60V and nitrogen content with OEM (optical emission monitor) value of 45%, was found to achieve best performance in orthogonal experiments. Depositing parameters of S8 might be practically applied for commercialization of surgical implants. PMID:26652421

  6. Al-to-oxide and Ti-to-organic linkages in biogenic sediment: relationships to paleo-export production and bulk Al/Ti

    NASA Astrophysics Data System (ADS)

    Kryc, K. A.; Murray, R. W.; Murray, D. W.

    2003-06-01

    To increase our understanding of the mechanisms that control the distribution of Al and Ti within marine sediment, we performed sequential extractions targeting the chemical signatures of the loosely bound, exchangeable, carbonate, oxide, organic, opal, and residual fraction of sediment from a carbonate-dominated regime (equatorial Pacific) and from a mixed opal-terrigenous regime (West Antarctic Peninsula). We observe a systematic partitioning of Al and Ti between sediment phases that is related to bulk Al/Ti. We show that, where we can quantify an Al excess component, the dissolved Al is preferentially affiliated with the oxide fraction, resulting in Al/Ti molar ratios of 500-3000. This is interpreted as the result of surface complexation in the water column of dissolved Al onto oxyhydroxides. We also observe a previously undetected Ti excess with as much as 80% of the total Ti in the organic fraction, which is most likely a function of metal-organic colloidal removal from the water column. In samples where the excess metals are obscured by the detrital load, the Al and Ti are almost exclusively found in the residual phase. This argues for the paired removal of Al (preferentially by the oxide component) and Ti (preferentially by the organic component) from the water column by settling particulate matter. This research builds upon earlier work that shows changes in the bulk ratio of Al to Ti in carbonate sediment from the central-equatorial Pacific that coincide with changes in the sedimentary bulk accumulation rate (BAR). The ratios that are observed are as much as three times higher than typical shale values, and were interpreted as the result of scavenging of dissolved Al onto particles settling in the water column. Because this non-terrigenous Al excess accounts for up to 50% of the total sedimentary Al inventory and correlates best with BAR, the bulk Al/Ti may be a sensitive tracer of particle flux and, therefore, export production. Because we show that the

  7. On the effect of Ta on improved oxidation resistance of Ti-Al-Ta-N coatings

    SciTech Connect

    Pfeiler, M.; Scheu, C.; Hutter, H.; Schnoeller, J.; Michotte, C.; Mitterer, C.; Kathrein, M.

    2009-05-15

    Formation of protective oxide scales is the main reason for the high oxidation resistance of TiAlN based coatings. Here the authors report on further improvement in the oxidation resistance of TiAlN by Ta alloying. An industrial-scale cathodic arc evaporation facility was used to deposit Ti-Al-Ta-N coatings from powder metallurgically produced Ti{sub 38}Al{sub 57}Ta{sub 5} targets. After oxidation in ambient air, a significantly reduced oxide layer thickness in comparison to unalloyed TiAlN reference material was observed. Energy-dispersive x-ray spectroscopy line scans and secondary ion mass spectroscopy depth profiling showed that the oxide scale consists of an Al-rich top layer without detectable amount of Ta and a Ti-Ta-rich sublayer. Transmission electron microscopy investigations revealed {alpha}-Al{sub 2}O{sub 3}, rutile-type TiO{sub 2}, and anatase-type TiO{sub 2} as the scale forming oxides. Furthermore, the Ti-Ta-rich sublayer consists of a porous layer at the oxide-nitride interface but appears dense toward the Al-rich top layer. The improved oxidation resistance is explained by doping the TiO{sub 2} lattice by replacing Ti{sup 4+} with Ta{sup 5+} in the rutile lattice, which decreases the oxygen mass transport. This leads to reduced oxidation of Ti under formation of TiO{sub 2} at the oxide-nitride interface and is the reason for the excellent oxidation behavior of Ti-Al-Ta-N coatings.

  8. Drilling of intermetallic alloys gamma TiAl

    SciTech Connect

    Beranoagirre, A.; Olvera, D.; Lopez de Lacalle, L. N.; Urbicain, G.

    2011-01-17

    Due to their high strength/weight ratio and resistance to corrosion and wear, superalloys such as gamma TiAl or Inconel 718 appear as the best choice for the high mechanical/thermal demands in the vicinity of the combustion chamber of aircraft engines. There are assembled parts such as cases, disks or blisks; in the manufacturing of these components the last drilling operation could jeopardize the full work integrity adding new costs to the just very expensive parts. Therefore drilling is a high-added value step in the complete sequence. The present work is framed within the study of hole making in advanced materials used for lightweight applications in aerospace sector. Within this context, the paper presents the results from milling tests on three types of gamma TiAl alloys (extruded MoCuSi, ingot MoCuSi and TNB) to define an optimal set of cutting parameters, which will contribute to open the increase in use of these special alloys. Drilling tools made of integral hard metal were used, applying different feeds and cutting speeds. The influence of cutting speed and feed is discussed.

  9. Analysis of cast TiAl properties for engine materials

    SciTech Connect

    Nakagawa, Y.G.; Matsuda, K.; Masaki, S.; Imamura, R.; Arai, M.

    1995-12-31

    A gamma TiAl alloy, Alloy01, was developed for casting aeroengine hot parts in an effort to replace current Ni-base superalloys. To evaluate engineering applicability, many commercial size ingots of Alloy01 were melted, and cast into various component shapes. Property measurements were made on cast-size specimens and in some cases on machined from blade samples. These included tensile strength and ductility, creep and creep rupture strength, low and high cycle fatigue, fracture toughness, crack growth rate, and some physical properties. Some of the important observations were made as follows; the room temperature (RT) strength and ductility are believed to be determined by three major factors, aluminum content, oxygen content, and macro-structural elements. Among those the macrostructure (grain size, grain structures, and shrinkage porosity) was considered most important. The best ductility obtained for as-cast specimens was 0.5%, but a HIP treatment increased the ductility to more than 1%. The alloy exhibited an excellent creep and fatigue strength. A comparison of the property data with those of a superalloy indicated that the TiAl is technically qualified for some of the components without major design changes.

  10. Warm Spray Forming of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Molak, R. M.; Araki, H.; Watanabe, M.; Katanoda, H.; Ohno, N.; Kuroda, S.

    2014-01-01

    Warm spray (WS) is a modification of high-velocity oxy-fuel spraying, in which the temperature of the supersonic gas flow generated by the combustion of kerosene and oxygen is controlled by diluting the combustion flame with an inert gas such as nitrogen. The inert gas is injected into the mixing chamber placed between the combustion chamber and the powder feed ports, thus the temperature of the propellant gas can be controlled from ~700 to 2,000 K. Since WS allows for higher particle temperatures in comparison to cold spray, warm sprayed particles are more softened upon impact, thus resulting in greater deformation facilitating the formation of shear instability for bonding. Recently, the combustion pressure of WS has been increased from 1 (low-pressure warm spray) to 4 MPa (high-pressure warm spray) in order to increase the velocity of sprayed particles. Effects of spray parameters on microstructure, mechanical properties, and splats formation of Ti-6Al-4V were systematically studied. Obtained coatings were examined by analyzing the coating cross-section images, microhardness as well as oxygen content. In addition, flattening ratio of splats was calculated as a function of nitrogen flow rate. It was found that the increased particle velocity caused by the increased combustion pressure had significant beneficial effects in terms of improving density and controlling the oxygen level in the sprayed Ti-6Al-4V coatings.

  11. Impact damage and fatigue behavior of gamma TiAl

    SciTech Connect

    Harding, T.S.; Jones, J.W.; Pollock, T.M.; Steif, P.S.; Rubal, M.P.

    1997-12-31

    The relationship between impact damage and the fatigue behavior of gamma titanium aluminide has been examined. Axial fatigue specimens fabricated from cast Ti-47.9Al-2Cr-2Nb alloy and Ti-47.3Al-2.2Nb-0.5Mn-0.4W-0.4Mo-0.23Si alloy were impacted under controlled conditions with various indentor shapes to simulate manufacturing related damage in low pressure turbine blades. Damage was quantified and related to impact parameters. A measure of the ambient temperature fatigue strength in the damaged specimens was obtained by standard fatigue testing employing a step-loading approach. Fractographic studies were performed to differentiate impact damage from subsequent fatigue crack growth and to elucidate the mechanisms responsible for the dependence of fatigue strength on the severity of impact damage. A threshold-based fracture mechanics analysis of crack advance from damage zones, and its use in fatigue failure strength prediction, has been developed.

  12. 27Al and 1H Solid State NMR Studies Show Evidence of TiAl3 and TiH2 in Ti-doped NaAlH4

    SciTech Connect

    Herberg, J; Maxwell, R; Majzoub, E

    2005-05-26

    Previous X-ray Diffraction (XRD) and Nuclear Magnetic Resonance (NMR) studies on Ti-doped NaAlH{sub 4} revealed the reaction products of two heavily doped (33.3 at.%) samples that were solvent-mixed and mechanically-milled. This investigation revealed that nano-crystalline or amorphous Al{sub 2}O{sub 3} forms from the possible coordination of aluminum with oxygen atom of the furan ring system from added tetrahydrofuran (THF) in the solvent-mixed sample, and that TiAl{sub 3} forms in mechanically-milled samples. The present paper provides a more sophisticated NMR investigation of the these materials. On heavily doped (33.3 at.%) solvent-mixed samples, {sup 27}Al Magic Angle Spinning (MAS) NMR {sup 27}Al multiple quantum MAS (MQMAS) indicates the presence of an oxide layer of Al{sub 2}O{sub 3} on the surfaces of potentially bulk nanocrystalline Ti, nanocrystalline TiAl{sub 3}, and/or metallic aluminum. The {sup 1}H MAS NMR data also indicate the possible coordination of aluminum with the oxygen atom in the THF. On heavily doped samples that were mechanically milled, {sup 27}Al MAS NMR and static NMR confirms the presence of TiAl{sub 3}. In addition, the {sup 1}H MAS NMR and {sup 1}H spin-lattice relaxation (T{sub 1}) measurements are consistent with the presence of TiH{sub 2}. These results are in agreement with recent XAFS measurements indicating both Al and H within the first few coordination shells of Ti in the doped alanate.

  13. Effect of Cd substitution on the optical and transport properties of CaCu_3Ti_4O_12 boldmath

    NASA Astrophysics Data System (ADS)

    Homes, C. C.; Vogt, T.; Subramanian, M. A.; Ramirez, A. P.

    2003-03-01

    The effect of Cd doping on the transport and optical properties of CaCu_3Ti_4O_12 has been studied. At room temperature, CaCu_3Ti_4O_12 has a very high dielectric constant, \\varepsilon_0 ˜ 10^4. However, substituting Cd for Ca reduces \\varepsilon0 by nearly two orders of magnitude. Cd has a strong effect on the low frequency infrared active modes, and in addition a new mode is activated. A normal coordinate analysis has been performed to determine the nature of the vibrational modes, in particular the activated mode as well as the low frequency vibration, where an anomalous increase in the oscillator strength has been observed.(C.C. Homes et al.), Science 293, 673 (2001). It has been suggested that the large values of \\varepsilon0 may be due to a internal barrier layer capacitance effect due to twinning. The lower value for \\varepsilon0 in the Cd material may have implications for the degree of twinning and the associated changes in vibrational structure. This work was supported by the Department of Energy under contract number DE-AC02-98CH10886.

  14. Fabrication of Ag-Decorated CaTiO₃ Nanoparticles and Their Enhanced Photocatalytic Activity for Dye Degradation.

    PubMed

    Xian, T; Yang, H; Huo, Y S; Ma, J Y; Zhang, H M; Su, J Y; Feng, W J

    2016-01-01

    CaTiO₃nanoparticles of 30-40 nm in size were synthesized via a polyacrylamide gel route. Ag nanoparticles with size of 8-16 nm were deposited onto CaTiO₃particles by a photochemical reduction method to yield CaTiO₃@Ag composites. The photocatalytic activity of prepared samples was evaluated by degrading methyl orange under ultraviolet irradiation. It is demonstrated that Ag-decorated CaTiO₃ particles exhibit an enhanced photocatalytic activity compared to bare CaTiO₃ particles. After 60 min of photocatalysis, the degradation percentage of MO increases from 54% for bare CaTiO₃particles to 72% for CaTiO₃@Ag composites. This can be explained by the fact that photogenerated electrons are captured by Ag nanoparticles and photogenerated holes are therefore increasingly available to react with OH⁻/H₂O to generate hydroxyl (·OH) radicals. ·OH radicals were detected by fluorimetry using terephthalic acid as a probe molecule, revealing an enhanced yield on the irradiated CaTiO₃@Ag composites. In addition, it is found that the addition of ethanol, which acts as an ·OH scavenger, leads to a quenching of ·OH radicals and simultaneous decrease in the photocatalytic efficiency. This suggests that ·OH radicals are the dominant active species responsible for the dye degradation. PMID:27398489

  15. Microstructure and Mechanical Properties of the Ti-45Al-5Fe Intermetallic Alloy

    NASA Astrophysics Data System (ADS)

    Nazarova, T. I.; Imayev, V. M.; Imayev, R. M.

    2015-10-01

    Microstructure including changes in the phase composition and mechanical compression properties of the Ti-45Al-5Fe (at.%) intermetallic alloy manufactured by casting and subjected to homogenization annealing are investigated as functions of the temperature. The initial alloy has a homogeneous predominantly lamellar structure with relatively small size of colonies of three intermetallic phases: γ(TiAl), τ2(Al2FeTi), and α2(Ti3Al) in the approximate volume ratio 75:20:5. Compression tests have revealed the enhanced strength at room temperature and the improved hot workability at 800°C compared to those of TNM alloys of last generation.

  16. 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.

  17. Al-TiC Composites Fabricated by a Thermally Activated Reaction Process in an Al Melt Using Al-Ti-C-CuO Powder Mixtures: Part II. Microstructure Control and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Cho, Young-Hee; Lee, Jung-Moo; Kim, Su-Hyeon

    2015-03-01

    Controlling the processing parameters is important to minimize such undesirable microstructural features in Al/TiC composites as unreacted C, incomplete reaction products of Al3Ti and TiC aggregates, which originate from the pellet microstructure upon the combustion reaction of an Al-Ti-C-CuO pellet in an Al melt. In particular, the mean particle size of elemental powders is a key factor linked to the formation of TiC aggregates, which is significantly suppressed with smaller initial particles of Ti and C by mixing them homogenously by ball milling. Al-Cu-Mg alloys reinforced with up to 12 vol pct TiC are fabricated by the developed process, followed by extrusion. The composites after heat treatment exhibit high elastic modulus and an ultimate tensile strength of 93 GPa and 461 MPa, respectively, with a low coefficient of thermal expansion of 17.11 ppm/K.

  18. Alpha clustering in Ti isotopes: 40,44,48Ca + α resonant scattering

    NASA Astrophysics Data System (ADS)

    Bailey, Sam; Freer, Martin; Kokalova, Tzany; Wheldon, Carl; Smith, Robin; Walshe, Joseph; Prepolec, Lovro; Soić, Neven; Tokić, Vedrana; Marqués, Miguel; Achouri, Lynda; Delaunay, Franck; Parlog, Marian; Deshayes, Quentin; Fernández-Dominguez, Beatriz; Jacquot, Bertrand

    2016-03-01

    Measurements were made of the 4He(40,44,48Ca,α) resonant scattering reactions at 180° and up to Ec.m. ~ 11.5MeV, using the Thick Target Inverse Kinematics technique. These measurements are discussed, with a focus on assessing their usefulness for investigating α-clustering in medium mass 44,48,52Ti nuclei.

  19. Formation mechanism of CaTiO3 hollow crystals with different microstructures.

    PubMed

    Yang, Xianfeng; Fu, Junxiang; Jin, Chongjun; Chen, Jian; Liang, Chaolun; Wu, Mingmei; Zhou, Wuzong

    2010-10-13

    The crystal growth of CaTiO(3) hollow crystals with different microstructures has been investigated. In a water-free poly(ethylene glycol) 200 (PEG-200) solution, CaTiO(3) nanocubes formed first. The nanocubes underwent an oriented self-assembly into spherical particles, enhanced by the surface-adsorbed polymer molecules. Since the growth of nanocubes and their aggregation took place simultaneously, the nanocubes in the outer shells were larger than those in the cores. Disappearance of the small nanocubes in the cores of the spheres during an Ostwald ripening process led to spherical hollow crystals. Addition of a small amount of water (1.25 vol %) in the polymer solution enhanced surface recrystallization of the aggregated spheres, forming a cubic morphology. The orthorhombic distortion of the perovskite CaTiO(3) structure did not have a significant effect on the nanocube aggregation, resulting in a domain structure in the shells. Single-crystalline hollow cubes were produced with a slightly higher water content, e.g., 5 vol %. This process of (1) aggregation of nanocubes and (2) surface crystallization followed by (3) surface-to-core extension of recrystallization gives a good example of the reversed crystal growth route in ceramic materials. The proposed formation mechanism of the hollow CaTiO(3) crystals would enable us to control the microstructures of these materials and to explain the formation of many other hollow crystals. PMID:20843080

  20. High temperature superconductor step-edge Josephson junctions using Ti-Ca-Ba-Cu-O

    DOEpatents

    Ginley, David S.; Hietala, Vincent M.; Hohenwarter, Gert K. G.; Martens, Jon S.; Plut, Thomas A.; Tigges, Chris P.; Vawter, Gregory A.; Zipperian, Thomas E.

    1994-10-25

    A process for formulating non-hysteretic and hysteretic Josephson junctions using HTS materials which results in junctions having the ability to operate at high temperatures while maintaining high uniformity and quality. The non-hysteretic Josephson junction is formed by step-etching a LaAlO.sub.3 crystal substrate and then depositing a thin film of TlCaBaCuO on the substrate, covering the step, and forming a grain boundary at the step and a subsequent Josephson junction. Once the non-hysteretic junction is formed the next step to form the hysteretic Josephson junction is to add capacitance to the system. In the current embodiment, this is accomplished by adding a thin dielectric layer, LaA1O.sub.3, followed by a cap layer of a normal metal where the cap layer is formed by first depositing a thin layer of titanium (Ti) followed by a layer of gold (Au). The dielectric layer and the normal metal cap are patterned to the desired geometry.

  1. High temperature superconductor step-edge Josephson junctions using Ti-Ca-Ba-Cu-O

    DOEpatents

    Ginley, D.S.; Hietala, V.M.; Hohenwarter, G.K.G.; Martens, J.S.; Plut, T.A.; Tigges, C.P.; Vawter, G.A.; Zipperian, T.E.

    1994-10-25

    A process is disclosed for formulating non-hysteretic and hysteretic Josephson junctions using HTS materials which results in junctions having the ability to operate at high temperatures while maintaining high uniformity and quality. The non-hysteretic Josephson junction is formed by step-etching a LaAlO[sub 3] crystal substrate and then depositing a thin film of TlCaBaCuO on the substrate, covering the step, and forming a grain boundary at the step and a subsequent Josephson junction. Once the non-hysteretic junction is formed the next step to form the hysteretic Josephson junction is to add capacitance to the system. In the current embodiment, this is accomplished by adding a thin dielectric layer, LaA1O[sub 3], followed by a cap layer of a normal metal where the cap layer is formed by first depositing a thin layer of titanium (Ti) followed by a layer of gold (Au). The dielectric layer and the normal metal cap are patterned to the desired geometry. 8 figs.

  2. 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.

  3. In vitro bioactivity investigation of alkali treated Ti6Al7Nb alloy foams

    NASA Astrophysics Data System (ADS)

    Butev, Ezgi; Esen, Ziya; Bor, Sakir

    2015-02-01

    Biocompatible Ti6Al7Nb alloy foams with 70% porosity manufactured by space holder method were activated via alkali treatment using 5 M NaOH solution at 60 °C. The interconnected pore structures enabled formation of homogenous sodium rich coating on the foam surfaces by allowing penetration of alkali solution throughout the pores which had average size of 200 μm. The resulted coating layer having 500 nm thickness exhibited porous network morphology with 100 nm pore size. On the other hand, heat treatment conducted subsequent to alkali treatment at 600 °C in air transformed sodium rich coating into crystalline bioactive sodium titanate phases. Although the coatings obtained by additional heat treatment were mechanically stable and preserved their morphology, oxidation of the samples deteriorated the compressive strength significantly without affecting the elastic modulus. However, heat treated samples revealed better hydroxyapatite formation when soaked in simulated body fluid (SBF) compared to alkali treated foams. On the other hand, untreated surfaces containing bioactive TiO2 layer were observed to comprise of Ca and P rich precipitates only rather than hydroxyapatite within 15 days. The apatite formed on the treated porous surfaces was observed to have flower-like structure with Ca/P ratio around 1.5 close to that of natural bone.

  4. Tribological properties of thermally sprayed TiAl-Al2O3 composite coating

    NASA Astrophysics Data System (ADS)

    Salman, A.; Gabbitas, B.; Li, J.; Zhang, D.

    2009-08-01

    The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity oxy fuel (HVOF) thermally sprayed wear resistant TiAl/Al2O3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting. A feedstock of TiAl/Al2O3 composite powder was produced from a mixture of Al and TiO2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity oxy-fuel (HVOF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The results showed that the composite coating has lower wear rate at high temperature (700°C) than the uncoated H13 sample. At Room temperature without using lubricant there is no much significant difference between the wear rate of the coated and uncoated samples. The experimental results showed that the composite coating has great potential for high temperature application due to its lower wear rate at high temperature in comparison with the uncoated sample at the same temperature. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

  5. 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.

  6. Tribological and mechanical properties of Ti/TiAlN/TiAlCN nanoscale multilayer PVD coatings deposited on AISI H11 hot work tool steel

    NASA Astrophysics Data System (ADS)

    AL-Bukhaiti, M. A.; Al-hatab, K. A.; Tillmann, W.; Hoffmann, F.; Sprute, T.

    2014-11-01

    A new [Ti/TiAlN/TiAlCN]5 multilayer coatings were deposited onto polished substrate AISI H11 (DIN 1.2343) steel by an industrial magnetron sputtering device. The tribological performance of the coated system was investigated by a ball-on-disk tribometer against 100Cr6 steel and Al2O3 balls. The friction coefficients and specific wear rates were measured at various normal loads (2, 5, 8, and 10 N) and sliding velocities (0.2, 0.4, and 0.8 m/s) in ambient air and dry conditions. The phase structure, composition, wear tracks morphologies, hardness, and film/substrate adhesion of the coatings were characterized by light-microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), 3D-surface analyzer, nanoindentation, and scratch tests. Results showed that the deposited coatings showed low wear rates in the scale of 10-15 m3/N m, low friction coefficients against 100Cr6 and Al2O3 balls in the range of 0.25-0.37, and good hardness in the range of 17-20 GPa. Results also revealed that the friction coefficients and disc wear rates decrease and increase, respectively with the increase in normal load and sliding velocity for both coating/Al2O3 and coating/100Cr6 sliding system. Compared with the uncoated-H11 substrate, the deposited coating exhibited superior tribological and mechanical properties. The dominant wear mechanism was abrasive wear for coating/Al2O3 pair, while for coating/100Cr6 pair, a combination of mild adhesive wear, severe adhesive wear, and abrasive wear (extensive plowing) were the dominant wear mechanisms at different applied normal loads.

  7. 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.

  8. Investigation of Ti-doped NaAlH4 by solid-state NMR

    SciTech Connect

    Maxwell, R; Majzoub, E; Herberg, J

    2003-11-24

    In recent years, the development of Ti-doped NaAlH{sub 4} as a hydrogen storage material has gained attention because of its large weight percentage of hydrogen ({approx}5%) compared to traditional interstitial hydrides. The addition of transition-metal dopants, in the form of Ti-halides, such as TiCl{sub 3}, dramatically improves the kinetics of the absorption and desorption of hydrogen from NaAlH{sub 4}. However, the role that Ti plays in enhancing the absorption and desorption of H{sub 2} is still unknown. In the present study, {sup 27}Al, {sup 23}Na, and {sup 1}H MAS (Magic Angle Spinning) NMR (Nuclear Magnetic Resonance) has been performed to understand the titanium speciation in Ti-doped NaAlH{sub 4}. All experiments were performed on a sample of crushed single crystals exposed to Ti during growth, a sample of solvent-mixed 4TiCl{sub 3} + 112NaAlH{sub 4}, a reacted sample of solvent-mixed TiCl{sub 3} + {sup 3}NaAlH{sub 4} with THF, and a reacted sample of ball-milled TiCl3 + 3NaAlH{sub 4}. The {sup 27}Al MAS NMR has shown differences in compound formation between solvent-mixed TiCl{sub 3} + 3NaAlH{sub 4} with THF and the mechanically ball-milled TiCl{sub 3} + 3NaAlH{sub 4}. {sup 27}Al MAS NMR of the mechanically ball-milled mixture of fully-reacted TiCl{sub 3} + 3NaAlH{sub 4} showed spectral signatures of TiAl{sub 3} while, the solvent-mixed 4TiCl{sub 3} + 112NaAlH{sub 4}, which is totally reacted, does not show the presences of TiAl{sub 3}, but shows the existence of Al{sub 2}O{sub 3}.

  9. CaTiO(3) coating on titanium for biomaterial application--optimum thickness and tissue response.

    PubMed

    Ohtsu, Naofumi; Sato, Kenji; Yanagawa, Aya; Saito, Kesami; Imai, Yoshio; Kohgo, Takao; Yokoyama, Atsuro; Asami, Katsuhiko; Hanawa, Takao

    2007-08-01

    The objectives of this study were to determine the optimum thickness of a CaTiO(3) film for biomaterial applications and to investigate the biocompatibility and bone formation of titanium with a CaTiO(3) film. First, CaTiO(3) films of 10, 20, 30, and 50 nm in thickness were deposited on titanium substrates using radiofrequency magnetron sputtering followed by annealing at 873 K in air for 7.2 ks. The optimum thickness of the CaTiO(3) film for bone formation was determined by comparison with its performance regarding calcium phosphate formation in Hanks' balanced saline solution (HBSS). Regarding calcium phosphate formation, the performance of the specimen with a 50-nm-thick CaTiO(3) film was superior to those of specimens with other thicknesses. A titanium prism with a CaTiO(3) film of 50-nm in thickness was surgically inserted in both soft and hard rat tissues. The biocompatibility of CaTiO(3)-deposited titanium and bone formation on it was investigated by histological observations. A slight inflammatory reaction was observed around the titanium with the 50-nm-thick CaTiO(3) film, while no severe response, such as degeneration and necrosis, was observed in either soft or hard rat tissue. New bone formation on the titanium plate with the CaTiO(3) film was more active than that without the film. The 50-nm-thick CaTiO(3) film has biocompatibility and can facilitate new bone formation in vivo, and, consequently, it is an excellent surface modification method for biomaterial applications. PMID:17279562

  10. Cell interaction with modified nanotubes formed on titanium alloy Ti-6Al-4V.

    PubMed

    Moravec, Hynek; Vandrovcova, Marta; Chotova, Katerina; Fojt, Jaroslav; Pruchova, Eva; Joska, Ludek; Bacakova, Lucie

    2016-08-01

    Nanotubes with diameters ranging from 40 to 60nm were prepared by electrochemical oxidation of the Ti-6Al-4V alloy in electrolyte containing ammonium sulphate and ammonium fluoride. The nanotubes were further modified with calcium and phosphate ions or were heat treated. Polished Ti-6Al-4V alloy served as a reference sample. The spreading of human osteoblast-like cells was similar on all nanotube samples but lower than on polished samples. The number of initially adhered cells was higher on non-modified nanotubes, but the final cell number was the highest on Ca-enriched nanotubes and the lowest on heat-treated nanotubes. However, these differences were relatively small and less pronounced than the differences in the concentration of specific molecular markers of cell adhesion and differentiation, estimated by their intensity of immunofluorescence staining. The concentration of vinculin, i.e. a protein of focal adhesion plaques, was the lowest on nanotubes modified with calcium. Collagen I, an early marker of osteogenic cell differentiation, was also the lowest on samples modified with calcium and was highest on polished samples. Alkaline phosphatase, a middle marker of osteogenic differentiation, was observed in lowest concentration on nanotubes modified with phosphorus and the highest on heat-treated samples. Osteocalcin concentrations, a late marker of osteogenic cell differentiation, were similar on all tested samples, although they tended to be the highest on heat-treated samples. Thus, osteogenic differentiation can be modulated by various additional treatments of nanotube coatings on Ti-6Al-4V implants. PMID:27157757

  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. Ag- and Cu-doped multifunctional bioactive nanostructured TiCaPCON films

    NASA Astrophysics Data System (ADS)

    Shtansky, D. V.; Batenina, I. V.; Kiryukhantsev-Korneev, Ph. V.; Sheveyko, A. N.; Kuptsov, K. A.; Zhitnyak, I. Y.; Anisimova, N. Yu.; Gloushankova, N. A.

    2013-11-01

    A key property of multicomponent bioactive nanostructured Ti(C,N)-based films doped with Ca, P, and O (TiCaPCON) that can be improved further is their antibacterial effect that should be achieved without compromising the implant bioactivity and biocompatibility. The present work is focused on the study of structure, chemical, mechanical, tribological, and biological properties of Ag- and Cu-doped TiCaPCON films. The films with Ag (0.4-4 at.%) and Cu (13 at.%) contents were obtained by simultaneous sputtering of a TiC0.5-Ca3(PO4)2 target and either an Ag or a Cu target. The film structure was studied using X-ray diffraction, transmission and scanning electron microscopy, energy dispersive X-ray spectroscopy, glow discharge optical emission spectroscopy, and Raman-shift and IR spectroscopy. The films were characterized in terms of their hardness, elastic modulus, dynamic impact resistance, friction coefficient and wear rate (both in air and normal saline), surface wettability, electrochemical behavior and Ag or Cu ion release in normal saline. Particular attention was paid to the influence of inorganic bactericides (Ag and Cu ions) on the bactericidal activity against unicellular yeast fungus Saccharomyces cerevisiae and gram-positive bacteria Lactobacillus acidophilus, as well as on the attachment, spreading, actin cytoskeleton organization, focal adhesions, and early stages of osteoblastic cell differentiation. The obtained results show that the Ag-doped films are more suitable for the protection of metallic surfaces against bacterial infection compared with their Cu-doped counterpart. In particular, an excellent combination of mechanical, tribological, and biological properties makes Ag-doped TiCaPCON film with 1.2 at.% of Ag very attractive material for bioengineering and modification of load-bearing metal implant surfaces.

  13. Resistive switching characteristics in memristors with Al2O3/TiO2 and TiO2/Al2O3 bilayers

    NASA Astrophysics Data System (ADS)

    Alekseeva, Liudmila; Nabatame, Toshihide; Chikyow, Toyohiro; Petrov, Anatolii

    2016-08-01

    Differences between the resistive switching characteristics of Al2O3/TiO2 and TiO2/Al2O3 bilayer structures, fabricated by atomic layer deposition at 200 °C and post-deposition annealing, were studied in Pt bottom electrode (Pt-BE)/insulator/Pt top electrode (Pt-TE) capacitors. The Pt-BE/Al2O3/TiO2/Pt-TE capacitor exhibits stable bipolar resistive switching with an on-resistance/off-resistance ratio of ∼102 controlled by a small voltage of ±0.8 V. The forming process occurs in two steps of breaking of the Al2O3 layer and transfer of oxygen vacancies (VO) into the TiO2 layer. The capacitor showed poor endurance, particularly in the high-resistance state under vacuum conditions. This indicates that the insulating TiO2 layer without VO is not formed near the Al2O3 layer because oxygen cannot be introduced from the exterior. On the other hand, in the Pt-BE/TiO2/Al2O3/Pt-TE capacitor, multilevel resistive switching with several applied voltage-dependent nonvolatile states is observed. The switching mechanism corresponds to the Al2O3 layer’s trapped VO concentration, which is controlled by varying the applied voltage.

  14. 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.

  15. Osteoblastic behavior to zirconium coating on Ti-6Al-4V alloy

    PubMed Central

    Lee, Bo-Ah; Kim, Hae-Jin; Xuan, Yun-Ze; Park, Yeong-Joon; Chung, Hyun-Ju

    2014-01-01

    PURPOSE The purpose of this study was to assess the surface characteristics and the biocompatibility of zirconium (Zr) coating on Ti-6Al-4V alloy surface by radio frequency (RF) magnetron sputtering method. MATERIALS AND METHODS The zirconium films were developed on Ti-6Al-4V discs using RF magnetron sputtering method. Surface profile, surface composition, surface roughness and surface energy were evaluated. Electrochemical test was performed to evaluate the corrosion behavior. Cell proliferation, alkaline phosphatase (ALP) activity and gene expression of mineralized matrix markers were measured. RESULTS SEM and EDS analysis showed that zirconium deposition was performed successfully on Ti-6Al-4V alloy substrate. Ti-6Al-4V group and Zr-coating group showed no significant difference in surface roughness (P>.05). Surface energy was significantly higher in Zr-coating group than in Ti-6Al-4V group (P<.05). No difference in cell morphology was observed between Ti-6Al-4V group and Zr-coating group. Cell proliferation was higher in Zr-coating group than Ti-6Al-4V group at 1, 3 and 5 days (P<.05). Zr-coating group showed higher ALP activity level than Ti-6Al-4V group (P<.05). The mRNA expressions of bone sialoprotein (BSP) and osteocalcin (OCN) on Zr-coating group increased approximately 1.2-fold and 2.1-fold respectively, compared to that of Ti-6Al-4V group. CONCLUSION These results suggest that zirconium coating on Ti-6Al-4V alloy could enhance the early osteoblast responses. This property could make non-toxic metal coatings on Ti-6Al-4V alloy suitable for orthopedic and dental implants. PMID:25551012

  16. ALS-like skin changes in mice on a chronic low-Ca/Mg high-Al diet.

    PubMed

    Kihira, Tameko; Yoshida, Sohei; Kondo, Tomoyoshi; Yase, Yoshiro; Ono, Seiitsu

    2004-04-15

    Epidemiologic studies of endemic foci of amyotrophic lateral sclerosis (ALS) have shown low concentrations of Ca/Mg and high concentrations of Al/Mn in the drinking water and garden soil, which may play a causative role in the pathogenesis of endemic ALS. We studied the effects of chronic exposure to a low-Ca/Mg high-Al maltol diet on the skin of experimental animals. In ALS patients, atrophy of the epidermis, edematous changes with separated collagen fibrils and an accumulation of amorphous materials between collagen bundles were regarded as pathognomonic skin changes of ALS. Mice chronically fed a low-Ca/Mg high-Al maltol diet showed neuronal degeneration and loss in the spinal cords and cerebral cortices, as well as skin changes including atrophy, separation of collagen fibrils and accumulation of amorphous materials, similar to the skin changes characteristic of ALS. This is the first report of skin changes in animal models similar to those of ALS. We speculate that environmental factors such as chronic low-Ca/Mg high-Al condition play some causative role in the pathogenesis of Kii-ALS. PMID:15050431

  17. The ^40Ca( α,γ )^44Ti Reaction Using DRAGON

    NASA Astrophysics Data System (ADS)

    Ouellet, C.; Vockenhuber, C.; The, L. S.; Buchmann, L.; Caggiano, J.; Chen, A.; Crawford, H.; D'Auria, J.; Davids, B.; Frekers, D.; Hussein, A.; Hutcheon, D.; Kutschera, W.; Laird, A.; Lewis, R.; O'Connor, E.; Ottewell, D.; Paul, M.; Pavan, M.; Pearson, J.; Ruiz, C.; Ruprecht, G.; Trinczek, M.; Wales, B.; Wallner, A.

    2007-10-01

    ^44Ti is one a handful of short lived nuclei believed to be a signature of explosive nucleosynthesis, a product of α-rich freezeout following a core collapse supernova. To understand the production of 44Ti a key reaction, ^40Ca( α,γ )^44Ti, has been studied in inverse kinematics using the DRAGON recoil separator located at ISAC/TRIUMF in Vancouver B.C. The coincidence detection of the recoils and γ-rays coupled with a time of flight technique provided an accurate determination of the excitation function over a range of beam energies of 0.6 -- 1.14 MeV/u. Direct measurement of the stopping power permitted an accurate measure of the stellar reaction rate. The excitation function hints towards previously undiscovered resonances and the new rate results in increased ^44Ti production from supernovae judging from prompt γ-ray studies alone.

  18. Optical and electrical properties of polycrystalline and amorphous Al-Ti thin films

    NASA Astrophysics Data System (ADS)

    Canulescu, S.; Borca, C. N.; Rechendorff, K.; Davidsdóttir, S.; Pagh Almtoft, K.; Nielsen, L. P.; Schou, J.

    2016-04-01

    The structural, optical, and transport properties of sputter-deposited Al-Ti thin films have been investigated as a function of Ti alloying with a concentration ranging from 2% to 46%. The optical reflectivity of Al-Ti films at visible and near-infrared wavelengths decreases with increasing Ti content. X-ray absorption fine structure measurements reveal that the atomic ordering around Ti atoms increases with increasing Ti content up to 20% and then decreases as a result of a transition from a polycrystalline to amorphous structure. The transport properties of the Al-Ti films are influenced by electron scattering at the grain boundaries in the case of polycrystalline films and static defects, such as anti-site effects and vacancies in the case of the amorphous alloys. The combination of Ti having a real refractive index (n) comparable with the extinction coefficient (k) and Al with n much smaller than k allows us to explore the parameter space for the free-electron behavior in transition metal-Al alloys. The free electron model, applied for the polycrystalline Al-Ti films with Ti content up to 20%, leads to an optical reflectance at near infrared wavelengths that scales linearly with the square root of the electrical resistivity.

  19. Oxidation behaviour of a Ti2AlN MAX-phase coating

    NASA Astrophysics Data System (ADS)

    Wang, Qimin; Garkas, W.; Flores Renteria, A.; Leyens, C.; Sun, Chao; Kim, Kwangho

    2011-10-01

    In this paper, we reported the oxidation behaviour of Ti2AlN coatings on a -TiAl substrate. The coatings composed mainly of Ti2AlN MAX phase were obtained by magnetron sputtering and subsequent vacuum annealing. Isothermal oxidation tests at 700-900 °C were performed in air. The results indicated that the oxidation resistance of the -TiAl alloy can be improved by depositing a Ti2AlN layer on the alloy surface, especially at high temperatures. An Al-rich oxide scale formed on the coating surfaces during oxidation. This scale acts as diffusion barrier blocking the ingress of oxidation, and effectively protects the coated alloys from further oxidation attack.

  20. Al electrode dependent transition to bipolar resistive switching characteristics in pure TiO2 films

    NASA Astrophysics Data System (ADS)

    Do, Young Ho; Kwak, June Sik; Hong, Jin Pyo; Jung, Kyooho; Im, Hyunsik

    2008-12-01

    Stable bipolar resistive switching was demonstrated in polycrystalline TiO2 films involving two different top and bottom Al electrodes of two different structures (Al/TiO2/Pt and Pt/TiO2/Al) after a forming process. With an Al electrode, the transition to bipolar resistive switching was clearly observed, together with counterclockwise and clockwise switching directions, which depended on the position of the Al electrode. The transition from unipolar to bipolar resistive switching seems to be attributable to the redox reaction and trap/detrap at the interfaces between the Al electrode and TiO2 layer due to the migration of oxygen ions and electrons. However, current level analysis of devices reveals that the forming process method basically leads to the formation of conducting paths inside the TiO2 layers. The electrical device properties of the two different structures, the effects of compliance currents, and the operation voltages are also analyzed.

  1. The creep deformation and elevated temperature microstructural stability of a two-phase TiAl/Ti{sub 3}Al lamellar alloy

    SciTech Connect

    Bartholomeusz, M.F.; Wert, J.A.

    1995-08-01

    Enhanced work hardening of the phases in the lamellar microstructure has been cited as an explanation for the lower minimum creep rates of a two-phase TiAl/Ti{sub 3}Al lamellar alloy compared with the minimum creep rates of the individual TiAl and Ti{sub 3}Al single-phase alloys tested between 980 K and 1,130 K. This proposition is confirmed by TEM observations. Thermal and thermomechanical exposure result in the microstructural evolution, which increases the minimum creep rate ({dot {var_epsilon}}{sub min}) of the lamellar alloy. The effect of microstructural evolution on {dot {var_epsilon}}{sub min} will be discussed in the present paper.

  2. Effect of ultrasonic melt treatment on the refinement of primary Al3Ti intermetallic in an Al-0.4Ti alloy

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Eskin, Dmitry; Connolley, Thomas; Mi, Jiawei

    2016-02-01

    High intensity ultrasonic melt treatment was applied to an Al-0.4 wt% Ti alloy over three selected temperature ranges: 810 to 770 °C (above liquidus), 770 to 730 °C (across liquidus), and 730 to 690 °C (below liquidus). The size and morphology of the primary Al3Ti intermetallic particles were studied by scanning electron microscopy. It was found that the primary Al3Ti intermetallics were refined as a result of ultrasonication over all three temperature ranges and their morphology changed from typical large dendritic plates to small compact tablets. Quenching experiments before and after the ultrasonication were also carried out to capture the high-temperature stage of intermetallic formation. Based on the size and morphology observations, the mechanisms for the refinement of primary Al3Ti intermetallics at different solidification stages are discussed.

  3. In vitro behavior of silicate glass coatings on Ti6Al4V

    SciTech Connect

    Saiz, Eduardo; Goldman, Marni; Gomez-Vega, Jose M.; Tomsia, Antoni P.; Marshall, Grayson W.; Marshall, Sally J.

    2002-01-09

    The in vitro response in simulated body fluid (SBF) of silicate glass coatings on Ti6Al4V was evaluated. Glasses belonging to the SiO2-CaO-MgO-Na2O-K2O-P2O5 system were used to prepare 50-70 (mu)m thick coatings on Ti6Al4V, employing a simple enameling technique. Glasses with silica content higher than 55 wt percent can be used to prepare coatings that do not crack or delaminate and exhibit good adhesion to the alloy. It has been found that coatings with silica content lower than 60 wt percent are more susceptible to corrosion and precipitate carbonated hydroxyapatite on their surface during in vitro tests. However, these coatings have a higher thermal expansion than the metal and are under tension. After 2 months in SBF cracks grow in the coating that reach the glass/metal interface and initiate delamination. Glasses with silica content higher than 60 wt percent are more resistant to corrosion and have lower thermal expansion. These coatings do not crack but they do not precipitate apatite, even after 2 months in SBF.

  4. Interfacial reaction of intermetallic compounds of ultrasonic-assisted brazed joints between dissimilar alloys of Ti6Al4V and Al4Cu1Mg.

    PubMed

    Ma, Zhipeng; Zhao, Weiwei; Yan, Jiuchun; Li, Dacheng

    2011-09-01

    Ultrasonic-assisted brazing of Al4Cu1Mg and Ti6Al4V using Zn-based filler metal (without and with Si) has been investigated. Before brazing, the Ti6Al4V samples were pre-treated by hot-dip aluminizing and ultrasonic dipping in a molten filler metal bath in order to control the formation of intermetallic compounds between the Ti6Al4V samples and the filler metal. The results show that the TiAl(3) phase was formed in the interface between the Ti6Al4V substrate and the aluminized coating. For the Zn-based filler metal without Si, the Ti6Al4V interfacial area of the brazed joint did not change under the effect of the ultrasonic wave, and only consisted of the TiAl(3) phase. For the Zn-based filler metal with Si, the TiAl(3) phase disappeared and a Ti(7)Al(5)Si(12) phase was formed at the interfacial area of the brazed joints under the effect of the ultrasonic wave. Due to the TiAl(3) phase completely changing to a Ti(7)Al(5)Si(12) phase, the morphology of the intermetallic compounds changed from a block-like shape into a lamellar-like structure. The highest shear strength of 138MPa was obtained from the brazed joint free of the block-like TiAl(3) phase. PMID:21489846

  5. Evaluation of ARCAM Deposited Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Slattery, Kevin; Slaughter, Blake; Speorl, Emily; Good, James; Gilley, Scott; McLemore, Carole

    2008-01-01

    A wide range of Metal Additive Manufacturing (MAM) technologies are becoming available. One of the challenges in using new technologies for aerospace systems is demonstrating that the process and system has the ability to manufacture components that meet the high quality requirements on a statistically significant basis. The widest-used system for small to medium sized components is the ARCAM system manufactured in Gothenburg, Sweden. This system features a 4kW electron-beam gun, and has a chamber volume of 250mm long x 250mm wide x 250mm to 400mm tall. This paper will describe the basis for the quality and consistency requirements, the experimental and evaluation procedures used for the evaluation, and an analysis of the results for Ti-6Al-4V.

  6. Quantitative observations of dislocation mechanisms in gamma TiAl

    SciTech Connect

    Viguier, B.; Cieslar, M.; Martin, J.L.; Hemker, K.J.

    1995-08-01

    Quantitative TEM observations have been made on a series of gamma Ti{sub 47}Al{sub 51}Mn{sub 2} polycrystals that were deformed at different temperatures. Special attention has been given to determining the statistical variation of defect densities that occur at the different temperatures. The results, which are in good agreement with mechanical testing, indicate that three different mechanisms control deformation in this alloy: lattice friction and the formation of faulted dipoles at low temperatures, the pinning of ordinary dislocations at intermediate temperatures, and the bowing and looping of dislocations at high temperatures. The anomalous flow strength of this alloy has been found to be related to the intrinsic pinning of ordinary dislocations. Details of this pinning and subsequent unzipping process, which are the basis for the new local-pinning-unzipping (LPU) models, are outlined within.

  7. Crystallographic variant selection in Ti-6Al-4V

    SciTech Connect

    Stanford, N.; Bate, P.S. . E-mail: pete.bate@man.ac.uk

    2004-10-04

    Transformation textures in the two-phase alloy Ti-6Al-4V have been studied. Samples were heated into the fully {beta} phase condition and then slow cooled to allow diffusional transformation to {alpha}. This produced a microstructure of grain boundary {alpha} encircling colonies of Widmanstaetten {alpha}. Electron backscattered diffraction (EBSD) texture measurements showed that the {alpha} texture was markedly sharper than that calculated on a basis of equal variant probability, indicating that significant variant selection was occurring during diffusional transformation. Investigation of the {alpha} variants produced across prior {beta} grain boundaries has shown that the selection of variants during transformation is highly dependant on the crystallography of those boundaries. The effect of this crystallographic variant selection on the transformation texture has been modelled.

  8. Crystallization and (Al,Ti)-oxide growth in annealed TiO{sub 2}-Al{sub 2}O{sub 3} multilayers

    SciTech Connect

    Omari, M.A.; Sorbello, R.S.; Aita, C.R.

    2006-03-15

    A family of TiO{sub 2}-Al{sub 2}O{sub 3} multilayers ({lambda}=2-72 nm TiO{sub 2}/7 nm Al{sub 2}O{sub 3}) is sputter deposited on fused silica substrates, sequentially annealed at 973 and 1273 K, and analyzed by x-ray diffraction. The goal is to examine crystallization behavior upon annealing at temperatures at which thermodynamically stable mixed-cation phases should not form. The results show: (1) After the 973 K anneal, films with {lambda}=18-72 nm TiO{sub 2}/7 nm Al{sub 2}O{sub 3} weakly crystallize with a preferred (110) rutile orientation. In addition, enhancement of (200) rutile diffraction increases with increasing TiO{sub 2} layer thickness. (2) Significant crystallization occurs in films after the 1273 K anneal. In films with {lambda}=36-72 nm TiO{sub 2}/7 nm Al{sub 2}O{sub 3}, a metastable pseudobrookite phase, Al{sub 0.95}Ti{sub 2.05}O{sub 5}, crystallizes along with (110){sub r}. However, only rutile TiO{sub 2} and {alpha}-Al{sub 2}O{sub 3} crystallize in films with thinner TiO{sub 2} layers. An architecture-sensitive crystallization model is presented in which the first step common to all architectures is diffusive amorphization of TiO{sub 2} by Al{sub 2}O{sub 3} at 973 K to produce an amorphous mixed-cation solid solution, a-ATO. As the reaction interface sweeps through a TiO{sub 2} layer in architectures with thicker TiO{sub 2} layers (200){sub r} preferentially crystallizes from a-ATO because (200){sub r} planes can accommodate Al species with the least rutile lattice strain. We suggest that (200){sub r} provides crystallization sites for Al{sub 0.95}Ti{sub 2.05}O{sub 5} at 1273 K.

  9. Thermodynamically destabilized hydride formation in "bulk" Mg-AlTi multilayers for hydrogen storage.

    PubMed

    Kalisvaart, Peter; Shalchi-Amirkhiz, Babak; Zahiri, Ramin; Zahiri, Beniamin; Tan, XueHai; Danaie, Mohsen; Botton, Gianluigi; Mitlin, David

    2013-10-21

    Thermodynamic destabilization of MgH2 formation through interfacial interactions in free-standing Mg-AlTi multilayers of overall "bulk" (0.5 μm) dimensions with a hydrogen capacity of up to 5.5 wt% is demonstrated. The interfacial energies of Mg-AlTi and Mg-Ti (examined as a baseline) are calculated to be 0.81 and 0.44 J m(-2). The enhanced interfacial energy of AlTi opens the possibility of creating ultrathin alloy interlayers that provide further thermodynamic improvements in metal hydrides. PMID:23955681

  10. Microstructural Observations in a Cast Al-Si-Cu/TiC Composite

    NASA Astrophysics Data System (ADS)

    Karantzalis, A. E.; Lekatou, A.; Georgatis, E.; Poulas, V.; Mavros, H.

    2010-06-01

    A 3-5 vol.% TiC particulate Al-Si-Cu composite was prepared by diluting Al/20 vol.% TiC composite in an Al-7Si-4Cu alloy matrix. TiC particle distribution consists of isolated and clustered particles which are both located at the primary-α grain boundaries and at the areas of the last solidified liquid. Particle pushing by the solidification front is responsible for the final particle location. The solidified microstructure consists of primary and intermetallic phases formed by a sequence of possible eutectic reactions. No evidence of TiC particle degradation was observed.

  11. The Effect of Ti on Microstructural Characteristics and Reaction Mechanism in Bonding of Al-Ceramic Composite

    NASA Astrophysics Data System (ADS)

    Juan, Li; Kehong, Wang; Deku, Zhang

    2016-06-01

    The effect of Ti on microstructural characteristics and reaction mechanism in bonding of Al-Ceramic composite was studied. Ti and Al-Ceramic composite were diffusion welded at 550, 600, 700, 800, and 900 °C in a vacuum furnace. The microstructures and compositions of the interface layers were analyzed, and the mechanical properties and fracture morphology of the joints were examined. The results indicated that there was a systematic switch from Ti/Ti7Al5Si12/composite at 600 °C and Ti/TiAl3/Ti7Al5Si12/composite at 700 °C to Ti/Ti7Al5Si12/TiAl3/Ti7Al5Si12/composite at 800 °C and Ti/Ti7Al5Si12/TiAl3/composite at 900 °C. The formation of TiAl3 at 700 and 800 °C depended on Al segregation, which was an uphill diffusion driven by chemical potential. The maximum shear strength was 40.9 MPa, found in the joint welded at 700 °C. Most joints fractured between Ti7Al5Si12 and Al-Ceramic composite. In any case, Ti7Al5Si12 was favorable for Al-Ceramic composite welding, which attached to Al-Ceramic composite, reducing the differences in physiochemical properties between SiC and metal, improving the mechanical properties of the joints and increasing the surface wettability of Al-Ceramic composite.

  12. High-Temperature Sliding Wear Testing of Cathodic Arc Physical Vapor Deposition AlTiN- and AlTiON-Coated Hot Work Tool Steels

    NASA Astrophysics Data System (ADS)

    Birol, Yucel; Isler, Duygu; Urgen, Mustafa

    2011-11-01

    Thin hard coatings provide the much needed protection for steel thixoforming tools that must resist wear at high temperatures. The wear resistance of AlTiN- and AlTiON-coated hot work tool steel was investigated at 1023 K (750 °C), measured to be the cavity surface temperature shortly after the steel slurry was forced into the thixoforming die. The wear tests were repeated in exactly the same fashion with uncoated tool steel samples to identify the impact of AlTiN and AlTiON coatings on the high-temperature wear performance of X32CrMoV33 tool steel. The nature, the thickness, and the adherence of the oxide scales impact the tribological behavior. The poor adherence and limited ductility of ferrous oxides promote the failure of the oxide scale impairing the resistance to wear of the hot work tool steel at elevated temperatures. The substantial softening in the X32CrMoV33 hot work tool steel is also critical in the wear volume loss it suffers. AlTiN and AlTiON coatings, on the other hand, form a stable and protective oxide surface layer at high temperatures and therefore provide an enhanced resistance to oxidation. The latter is relatively more resistant to oxidation and is thus the better of the two coatings tested in the present work.

  13. Growth mechanism of atomic-layer-deposited TiAlC metal gate based on TiCl4 and TMA precursors

    NASA Astrophysics Data System (ADS)

    Jinjuan, Xiang; Yuqiang, Ding; Liyong, Du; Junfeng, Li; Wenwu, Wang; Chao, Zhao

    2016-03-01

    TiAlC metal gate for the metal-oxide-semiconductor field-effect-transistor (MOSFET) is grown by the atomic layer deposition method using TiCl4 and Al(CH3)3(TMA) as precursors. It is found that the major product of the TiCl4 and TMA reaction is TiAlC, and the components of C and Al are found to increase with higher growth temperature. The reaction mechanism is investigated by using x-ray photoemission spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The reaction mechanism is as follows. Ti is generated through the reduction of TiCl4 by TMA. The reductive behavior of TMA involves the formation of ethane. The Ti from the reduction of TiCl4 by TMA reacts with ethane easily forming heterogenetic TiCH2, TiCH=CH2 and TiC fragments. In addition, TMA thermally decomposes, driving Al into the TiC film and leading to TiAlC formation. With the growth temperature increasing, TMA decomposes more severely, resulting in more C and Al in the TiAlC film. Thus, the film composition can be controlled by the growth temperature to a certain extent. Project supported by the Key Technology Study for 16/14 nm Program of the Ministry of Science and Technology of China (Grant No. 2013ZX02303).

  14. Injection Seeding of Ti:Al2O3 in an unstable resonator theory and experiment

    NASA Technical Reports Server (NTRS)

    Barnes, J. C.; Wang, L. G.; Barnes, N. P.; Edwards, W. C.; Cheng, W. A.; Hess, R. V.; Lockard, G. E.; Ponsardin, P. L.

    1991-01-01

    Injection Seeding of a Ti:Al2O3 unstable resonator using both a pulsed single-mode Ti:Al2O3 laser and a continuous wave laser diode has been characterized. Results are compared with a theory which calculates injection seeding as function of seed and resonator alignment, beam profiles, and power.

  15. Preferential site occupancy of alloying elements in TiAl-based phases

    NASA Astrophysics Data System (ADS)

    Holec, David; Reddy, Rajeev K.; Klein, Thomas; Clemens, Helmut

    2016-05-01

    First principles calculations are used to study the preferential occupation of ternary alloying additions into the binary Ti-Al phases, namely, γ-TiAl, α2-Ti3Al, βo-TiAl, and B19-TiAl. While the early transition metals (TMs, group IVB, VB, and VIB elements) prefer to substitute for Ti atoms in the γ-, α2-, and B19-phases, they preferentially occupy Al sites in the βo-TiAl. Si is, in this context, an anomaly, as it prefers to sit on the Al sublattice for all four phases. B and C are shown to prefer octahedral Ti-rich interstitial positions instead of substitutional incorporation. The site preference energy is linked with the alloying-induced changes of energy of formation, hence alloying-related (de)stabilisation of the phases. We further show that the phase-stabilisation effect of early TMs on βo-phase has a different origin depending on their valency. Finally, an extensive comparison of our predictions with available theoretical and experimental data (which is, however, limited mostly to the γ-phase) shows a consistent picture.

  16. CaCu3Ti4O12: One-step internal barrier layer capacitor

    NASA Astrophysics Data System (ADS)

    Sinclair, Derek C.; Adams, Timothy B.; Morrison, Finlay D.; West, Anthony R.

    2002-03-01

    There has been much recent interest in a so-called "giant-dielectric phenomenon" displayed by an unusual cubic perovskite-type material, CaCu3Ti4O12; however, the origin of the high permittivity has been unclear [M. A. Subramanian, L. Dong, N. Duan, B. A. Reisner, and A. W. Sleight, J. Solid State Chem. 151, 323 (2000); C. C. Homes, T. Vogt, S. M. Shapiro, S. Wakimoto, and A. P. Ramirez, Science 293, 673 (2001); A. P. Ramirez, M. A. Subramanian, M. Gardel, G. Blumberg, D. Li, T. Vogt, and S. M. Shapiro, Solid State Commun. 115, 217 (2000)]. Impedance spectroscopy on CaCu3Ti4O12 ceramics demonstrates that they are electrically heterogeneous and consist of semiconducting grains with insulating grain boundaries. The giant-dielectric phenomenon is therefore attributed to a grain boundary (internal) barrier layer capacitance (IBLC) instead of an intrinsic property associated with the crystal structure. This barrier layer electrical microstructure with effective permittivity values in excess of 10 000 can be fabricated by single-step processing in air at ˜1100 °C. CaCu3Ti4O12 is an attractive option to the currently used BaTiO3-based materials which require complex, multistage processing routes to produce IBLCs of similar capacity.

  17. Thermopower of the 312 MAX phases Ti3SiC2 , Ti3GeC2 , and Ti3AlC2

    NASA Astrophysics Data System (ADS)

    Chaput, L.; Hug, G.; Pécheur, P.; Scherrer, H.

    2007-01-01

    The electronic structure and the thermoelectric tensor are calculated for the 312 MAX phases Ti3SiC2 , Ti3GeC2 , and Ti3AlC2 . The thermoelectric tensor is shown to be anisotropic in all cases. However, for Ti3SiC2 and Ti3GeC2 we find the components of the thermoelectric tensor to be negative along the z direction, Sz<0 , and positive in the basal plane, Sx>0 , whereas Sz>0 and Sx>0 over a large temperature range for Ti3AlC2 . This accounts for the different behavior experimentally observed. Moreover, the calculated thermopower as a function of temperature is in good agreement with experiments on polycrystals.

  18. 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

  19. Band gap structure modification of amorphous anodic Al oxide film by Ti-alloying

    SciTech Connect

    Canulescu, S. Schou, J.; Rechendorff, K.; Pleth Nielsen, L.; Borca, C. N.; Jones, N. C.; Hoffmann, S. V.; Bordo, K.; Ambat, R.

    2014-03-24

    The band structure of pure and Ti-alloyed anodic aluminum oxide has been examined as a function of Ti concentration varying from 2 to 20 at. %. The band gap energy of Ti-alloyed anodic Al oxide decreases with increasing Ti concentration. X-ray absorption spectroscopy reveals that Ti atoms are not located in a TiO{sub 2} unit in the oxide layer, but rather in a mixed Ti-Al oxide layer. The optical band gap energy of the anodic oxide layers was determined by vacuum ultraviolet spectroscopy in the energy range from 4.1 to 9.2 eV (300–135 nm). The results indicate that amorphous anodic Al{sub 2}O{sub 3} has a direct band gap of 7.3 eV, which is about ∼1.4 eV lower than its crystalline counterpart (single-crystal Al{sub 2}O{sub 3}). Upon Ti-alloying, extra bands appear within the band gap of amorphous Al{sub 2}O{sub 3}, mainly caused by Ti 3d orbitals localized at the Ti site.

  20. 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.

  1. ADSORPTION AND DISSOCIATION OF O2 ON Ti3Al (0001) STUDIED BY FIRST-PRINCIPLES

    NASA Astrophysics Data System (ADS)

    Wei, Li-Jing; Guo, Jian-Xin; Dai, Xiu-Hong; Wang, Ying-Long; Liu, Bao-Ting

    2015-05-01

    The adsorption and dissociation of oxygen molecule on Ti3Al (0001) surface have been investigated by density functional theory (DFT) with the generalized gradient approximation (GGA). All possible adsorption sites including nine vertical and fifteen parallel sites of O2 are considered on Ti3Al (0001) surface. It is found that all oxygen molecules dissociate except for three vertical adsorption sites after structure optimization. This indicates that oxygen molecules prefer to dissociate on the junction site between Ti and Al atoms. Oxygen atoms coming from dissociation of oxygen molecule tend to occupy the most stable adsorption sites of the Ti3Al (0001) surface. The distance of O-O is related to the surface dissociation distance of Ti3Al (0001) surface. The valence electron localization function (ELF) and projected density of states (DOS) show that the bonds of O-O are breakaway at parallel adsorption end structures.

  2. Nanoscale analysis on interfacial reactions in Al-Si-Cu alloys and Ti underlayer films

    NASA Astrophysics Data System (ADS)

    Yang, Jun-Mo; Lee, Sukjae; Park, Ju-Chul; Lee, Deok-Won; Lee, Tae-Kwon; Choi, Jin-Tae; Lee, Soun-Young; Kawasaki, Masahiro; Oikawa, Tetsuo

    2003-01-01

    Solid-phase reactions at the interface between sputtered Al-Si-Cu alloys and Ti films were investigated at the atomic scale by high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy (EDS) coupled with a field-emission (scanning) transmission electron microscope. The analysis results showed that the interface is composed of an amorphous-like Ti-Si layer, an intermediate-crystalline layer, and a Si-dissolved TiAl3 layer containing dissolved Si TiAl3 with a crystallographic relationship with the Al film. The nanometer-scaled interlayers effectively play a role as a barrier suppressing the interdiffusion reaction of Al and Ti during annealing treatment. Further, the quantitative composition of the interlayers was revealed by the analysis of the intensity profiles obtained from EDS elemental maps.

  3. In situ synthesized TiB-TiN reinforced Ti6Al4V alloy composite coatings: microstructure, tribological and in-vitro biocompatibility.

    PubMed

    Das, Mitun; Bhattacharya, Kaushik; Dittrick, Stanley A; Mandal, Chitra; Balla, Vamsi Krishna; Sampath Kumar, T S; Bandyopadhyay, Amit; Manna, Indranil

    2014-01-01

    Wear resistant TiB-TiN reinforced Ti6Al4V alloy composite coatings were deposited on Ti substrate using laser based additive manufacturing technology. Ti6Al4V alloy powder premixed with 5wt% and 15wt% of boron nitride (BN) powder was used to synthesize TiB-TiN reinforcements in situ during laser deposition. Influences of laser power, scanning speed and concentration of BN on the microstructure, mechanical, in vitro tribological and biological properties of the coatings were investigated. Microstructural analysis of the composite coatings showed that the high temperature generated due to laser interaction with Ti6Al4V alloy and BN results in situ formation of TiB and TiN phases. With increasing BN concentration, from 5wt% to 15wt%, the Young's modulus of the composite coatings, measured by nanoindentation, increased from 170±5GPa to 204±14GPa. In vitro tribological tests showed significant increase in the wear resistance with increasing BN concentration. Under identical test conditions TiB-TiN composite coatings with 15wt% BN exhibited an order of magnitude less wear rate than CoCrMo alloy-a common material for articulating surfaces of orthopedic implants. Average top surface hardness of the composite coatings increased from 543±21HV to 877±75HV with increase in the BN concentration. In vitro biocompatibility and flow cytometry study showed that these composite coatings were non-toxic, exhibit similar cell-materials interactions and biocompatibility as that of commercially pure titanium (CP-Ti) samples. In summary, excellent in vitro wear resistance, high stiffness and suitable biocompatibility make these composite coatings as a potential material for load-bearing articulating surfaces towards orthopaedic implants. PMID:24121827

  4. Effect of Helium ion irradiation on the structure, the phase stability, and the microhardness of TiN, TiAlN, and TiAlYN nanostructured coatings

    NASA Astrophysics Data System (ADS)

    Komarov, F. F.; Konstantinov, S. V.; Strel'nitskij, V. E.; Pilko, V. V.

    2016-05-01

    The radiation resistance of nanostructured TiN, TiAlN, and TiAlYN coatings is studied after 500-keV He+ ion irradiation in the fluence range 5 × 1016-3 × 1017 ions/cm2. The radiation-induced changes in the phase composition, the structure, the lattice parameters, the morphology, and the mechanical properties of coatings are investigated. Blistering is found to be absent, and the radiation fluence is shown to affect the strength properties of the thin coatings nonlinearly. A significant decrease in the grain sizes is detected upon ion irradiation, which causes an increase in the microhardness and the radiation resistance of the coatings. The TiN, TiAlN, and TiAlYN coatings are found to be radiation-resistant coatings, which do not undergo serious degradation during high-fluence ion irradiation.

  5. Commercially pure titanium (cp-Ti) versus titanium alloy (Ti6Al4V) materials as bone anchored implants - Is one truly better than the other?

    PubMed

    Shah, Furqan A; Trobos, Margarita; Thomsen, Peter; Palmquist, Anders

    2016-05-01

    Commercially pure titanium (cp-Ti) and titanium alloys (typically Ti6Al4V) display excellent corrosion resistance and biocompatibility. Although the chemical composition and topography are considered important, the mechanical properties of the material and the loading conditions in the host have, conventionally, influenced material selection for different clinical applications: predominantly Ti6Al4V in orthopaedics while cp-Ti in dentistry. This paper attempts to address three important questions: (i) To what extent do the surface properties differ when cp-Ti and Ti6Al4V materials are manufactured with the same processing technique?, (ii) Does bone tissue respond differently to the two materials, and (iii) Do bacteria responsible for causing biomaterial-associated infections respond differently to the two materials? It is concluded that: (i) Machined cp-Ti and Ti6Al4V exhibit similar surface morphology, topography, phase composition and chemistry, (ii) Under experimental conditions, cp-Ti and Ti6Al4V demonstrate similar osseointegration and biomechanical anchorage, and (iii) Experiments in vitro fail to disclose differences between cp-Ti and Ti6Al4V to harbour Staphylococcus epidermidis growth. No clinical comparative studies exist which could determine if long-term, clinical differences exist between the two types of bulk materials. It is debatable whether cp-Ti or Ti6Al4V exhibit superiority over the other, and further comparative studies, particularly in a clinical setting, are required. PMID:26952502

  6. Microstructural evolution and hardness of TiAl3 and TiAl2 phases on Ti-45Al-2Nb-2Mn-1B by plasma pack aluminizing

    NASA Astrophysics Data System (ADS)

    Rastkar, Ahmad Reza; Parseh, Pejman; Darvishnia, Naser; Hadavi, Seyed Mohammad Mehdi

    2013-07-01

    The surface of Ti-45Al-2Nb-2Mn-1B (at%) titanium aluminide was aluminized in a so called plasma pack aluminizing by packing the substrate in a mixture of aluminum copper alloy and application of an 18 kHz pulsed DC glow discharge plasma in argon gas. The plasma energy provided the necessary heat for melting and mutual diffusion of titanium and aluminum at the surface of titanium aluminide alloy in less than 1 h without any further heat treatment. The microstructure and hardness of different phases on the surface of Ti-45Al-2Nb-2Mn-1B alloy were characterized using optical and electron microscopy, X-ray diffraction (XRD), EDX analysis and Vickers microhardness tests. The thickness of the surface layers was up to 300 μm. The surface layers consisted mainly of TiAl3 and TiAl2 compounds. These compounds appeared in blocky and round shapes with different micrometer sizes in a matrix of aluminum alloy phase. The hardness of the surface layers was up to 600 HV0.1, which was higher than that of Ti-45Al-2Nb-2Mn-1B substrate (330 HV0.1).

  7. Thermodynamics, Solubility, and Diffusivity of Oxygen in Titanium and Ti-Al Alloys

    NASA Technical Reports Server (NTRS)

    Mehrotra, Gopal M.

    1992-01-01

    Titanium aluminides and titanium aluminide-based composites are attractive candidate materials for high-temperature structural applications. As these materials may be exposed to oxidizing environments durine their use at elevated temperatures, it is essential that they possess a good oxidation resistance. Previous studies have shown that the oxidation resistance of Al-rich alloys in the Ti-Al system is superior to that of the Ti-rich alloys. The scales formed on the surface of the Al-rich and Ti-rich alloys have been reported to be predominantly Al2O3 and TiO2, respectively. Since the relative stabilities of the oxides of Al and Ti at various temperatures and oxygen pressures can be assessed from their thermodynamic data, it is possible, With the help of thermodynamic calculations, to determine the compositions of the alloys which would form scales of Al2O3, TiO(x) or a ternary oxide such as TiAl2O5 during oxidation at a given temperature. The thermodynamic calculations require reliable activity data for the Ti-Al system. These data have not been determined for the entire composition and temperature range of interest. Using the data available in the literature, recently performed thermodynamic calculations and concluded that the stable oxide changed from TiO to Al2O3 in the existence region of the tial phase. In the case of titanium aluminide-based composites, another major concern is the mutual chemical compatibility of the matrix material with the reinforcement phase. Fibers of SiC, TiB2 and Al2O3 are currently being investigated for reinforcement of titanium aluminide matrices.

  8. Fracture characteristics of Ti-6Al-4V and Ti-5Al-2.5Fe with refined microstructure using hydrogen

    NASA Astrophysics Data System (ADS)

    Niinomi, M.; Gong, B.; Kobayashi, T.; Ohyabu, Y.; Toriyama, O.

    1995-05-01

    The hydrogenation behavior of Ti-6Al-4V, with the starting microstructures of coarse equiaxed α and coarse Widmanstätten α, respectively, was investigated under a hydrogen pressure of 0.1 MPa at temperatures between 843 and 1123 K. The hydrogen content was determined as a function of hydrogenation time, hydrogenation temperature, and hydrogen flow rate. The phases presented in the alloy of after hydrogenation were determined with X-ray and electron diffraction analysis in order to define the effect of Thermochemical Processing (TCP) on the microstructure of the alloy. Mechanical properties and fracture toughness of Ti-6Al-4V and Ti-5Al-2.5Fe subjected to the various TCP were then investigated. Hydrogenation of Ti-6Al-4V with the starting microstructure of coarse equiaxed α at 1023 K, just below hydrogen saturated β (denoted β″ (H)) transus temperature, produces a microstructure of a, orthohombic martensite (denoted α″ (H)) and β (H). Hydrogenation at 1123 K, above β (H) transus, results in a microstructure of α″ (H) and β (H). Microstructure refinement during TCP results mainly from decomposition of α″ (H) and ;β (H) into a fine mixture of α + β during dehydrogenation. An alternative TCP method is below β (H) transus hydrogenation (BTH), consisting of hydrogenation of the alloy below the hydrogenated β (H) transus temperature, air cooling to room temperature, and dehydrogenation at a lower temperature, which is found to improve mechanical properties significantly over a conventional TCP treatment. Compared with the untreated material, the BTH treatment increases the yield strength and increases the ultimate tensile strength significantly without decreasing the tensile elongation in the starting microstructure of coarse equiaxed α or with a little decrease in the tensile elongation in the starting microstructure of coarse Widmanstätten α, although the conventional TCP treatment results in a large decrease in elongation over the

  9. [Joint prostheses components of warm-forged and surface treated Ti-6Al-7Nb alloy].

    PubMed

    Semlitsch, M; Weber, H; Streicher, R M; Schön, R

    1991-05-01

    In 1978 development of a TiAl alloy with the inert alloying element niobium was initiated. In 1984, the optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy for implants has the same alpha/beta micro-structure and equally good mechanical properties as Ti-6Al-4V. The corrosion resistance of Ti-6Al-7Nb is better than that of pure titanium and Ti-6Al-4V, due to the very dense and stable passive layer. Since 1985, highly stressed anchoring stems of various hip prosthesis designs have been manufactured from hot-forged Ti-6Al-7Nb/Protasul-100. Polished surfaces of hip, knee or wrist joints made of Ti-6Al-7Nb intended to articulate with polyethylene are surface-treated by the application of a very hard, 3-5 microns thick titanium nitride coating (Tribosul-TiN), or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns. PMID:1859861

  10. p-Type hydrogen sensing with Al- and V-doped TiO2 nanostructures

    PubMed Central

    2013-01-01

    Doping with other elements is one of the efficient ways to modify the physical and chemical properties of TiO2 nanomaterials. In the present work, anatase TiO2 nanofilms doped with Al and V elements were fabricated through anodic oxidation of Ti6Al4V alloy and further annealing treatment. Hydrogen sensing behavior of the crystallized Ti-Al-V-O nanofilms at various working temperatures was investigated through exposure to 1,000 ppm H2. Different from n-type hydrogen sensing characteristics of undoped TiO2 nanotubes, the Al- and V-doped nanofilms presented a p-type hydrogen sensing behavior by showing increased resistance upon exposure to the hydrogen-containing atmosphere. The Ti-Al-V-O nanofilm annealed at 450°C was mainly composed of anatase phase, which was sensitive to hydrogen-containing atmosphere only at elevated temperatures. Annealing of the Ti-Al-V-O nanofilm at 550°C could increase the content of anatase phase in the oxide nanofilm and thus resulted in a good sensitivity and resistance recovery at both room temperature and elevated temperatures. The TiO2 nanofilms doped with Al and V elements shows great potential for use as a robust semiconducting hydrogen sensor. PMID:23311459

  11. Cyclic oxidation of aluminide coatings on Ti3Al+Nb

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Gedwill, Michael A.; Brindley, Pamela K.

    1990-01-01

    A number of pack aluminide coatings were produced on fiber-reinforced Ti3Al+Nb composites and were compared for their protection effect in cyclic oxidation at 982 C. It was found that pack aluminizing of Ti3Al+Nb can successfully produce an oxidation resistant TiAl3 coating which forms alpha-Al2O3 scales. These coatings offer a substantial improvement over the uncoated matrix material in 982 C cyclic oxidation. Coating cracks were found to contribute to degradation of thick coatings.

  12. 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.

  13. 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.

  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. PMID:25740001

  15. The mechanical and electronic properties of Al/TiC interfaces alloyed by Mg, Zn, Cu, Fe and Ti: First-principles study

    NASA Astrophysics Data System (ADS)

    Sun, Ting; Wu, Xiaozhi; Li, Weiguo; Wang, Rui

    2015-03-01

    The adhesion and ductility of (100) and (110) Al/TiC interfaces alloyed by Mg, Zn, Cu, Fe, and Ti have been investigated using first-principles methods. Fe and Ti can enhance the adhesion of (100) and (110) interfaces. Mg and Zn have the opposite effect. Interfacial electronic structures have been created to analyze the changes of the work of adhesion. It is found that more charge is accumulated at interfaces alloyed by Fe and Ti compared with pure Al/TiC. There is also an obvious downward shift in the Fermi energy of Fe, Ti at the interface. Furthermore, the unstable stacking fault energies of the interfaces are calculated; the results demonstrate that the preferred slip direction is the < 110> direction for (100) and (110) Al/TiC. Based on the Rice criterion of ductility, the results predict that Mg, Fe, and Ti are promising candidates for improving the ductility of Al/TiC interfaces.

  16. First-principles thermochemistry for the combustion of a TiCl4 and AlCl3 mixture.

    PubMed

    Shirley, Raphael; Liu, Yaoyao; Totton, Tim S; West, Richard H; Kraft, Markus

    2009-12-10

    AlCl(3) is added in small quantities to TiCl(4) fed to industrial reactors during the combustion synthesis of titanium dioxide nanoparticles in order to promote the rutile crystal phase. Despite the importance of this process, a detailed mechanism including AlCl(3) is still not available. This work presents the thermochemistry of many of the intermediates in the early stages of the mechanism, computed using quantum chemistry. The enthalpies of formation and thermochemical data for AlCl, AlO, AlOCl, AlOCl(2), AlO(2), AlO(2)Cl, AlOCl(3), AlO(2)Cl(2), AlO(3)ClTi, AlO(2)Cl(2)Ti, AlO(2)Cl(4)Ti, AlOCl(5)Ti, AlO(2)Cl(3)Tia (isomer-a), AlO(3)Cl(2)Ti, AlO(2)Cl(5)Ti, AlOCl(4)Ti, AlO(2)Cl(3)Tib (isomer-b), AlCl(7)Ti, AlCl(6)Ti, Al(2)Cl(6), Al(2)O(2)Cl, Al(2)O(2)Cl(3), Al(2)O(3)Cl(2), Al(2)O(2)Cl(2), Al(2)OCl(4), Al(2)O(3), and Al(2)OCl(3) were calculated using density functional theory (DFT). A full comparison between a number of methods is made for one of the important species, AlOCl, to validate the use of DFT and gauge the magnitude of errors involved with this method. Finally, equilibrium calculations are performed to try to identify which intermediates are likely to be most prevalent in the high temperature industrial process and as a first attempt to characterize the nucleation process. PMID:19888740

  17. Dilemma on the crystal structure of CaCu3Ti4O12

    NASA Astrophysics Data System (ADS)

    Sławiński, Wojciech; Przeniosło, Radosław; Wardecki, Dariusz; Sosnowska, Izabela; Hill, Adrian; Fitch, Andrew N.; Bieringer, Mario

    2014-03-01

    The crystal structure of CaCu3Ti4O12 has been studied using high resolution synchrotron radiation based x-ray powder diffraction. The observed x-ray diffraction patterns show pronounced Bragg peak asymmetries which should not be present assuming the commonly accepted cubic crystal structure of CaCu3Ti4O12 described by the space group Im-3. Several structural models are discussed. The first model assumes a coexistence of two phases with the cubic symmetry (both space group Im-3) and different lattice constants. The next models are based on subgroups of the cubic space group Im-3. The best agreement with the experimental data is found for the two-phase cubic model.

  18. The phase stability of Ca2TiO4 and related Ruddlesden-Popper phases

    NASA Astrophysics Data System (ADS)

    Ramadan, Amr H. H.; Hesselmann, Linda; De Souza, Roger A.

    2015-11-01

    The Ruddlesden-Popper phases of the Ca-Ti-O system, Can+1TinO3n+1, are investigated by means of atomistic simulations employing empirical pair potentials. The stability of the phases is examined in terms of various reaction schemes: the formation from the binary oxides, the addition of the perovskite oxide to a given phase, and the reaction between perovskite and rock-salt oxides. The energies of these reactions are compared with results previously obtained for the Ruddlesden-Popper phases of the Sr-Ti-O system. The importance of the disproportionation reaction of the various R-P phases in both Ca and Sr systems is also emphasized. The results obtained are in good agreement with experimental observations regarding both systems.

  19. Photoluminescence and energy storage traps in CaTiO{sub 3}:Pr{sup 3+}

    SciTech Connect

    Zhang, Xianmin; Cao, Chunyan; Zhang, Chenghua; Xie, Shiyao; Xu, Guangwen; Zhang, Jiahua; Wang, Xiao-jun

    2010-12-15

    Red-emitting CaTiO{sub 3}:Pr{sup 3+} phosphors are fabricated using a solid state method and structurally characterized by X-ray diffraction and field emission scanning electron microscopy. The optical properties are investigated using photoluminescence emission, excitation, photoluminescence decay curves, diffused reflectance and thermoluminescence spectra, and persistent phosphorescence decay curves. The optimal fabrication temperatures for photoluminescence and persistent phosphorescence are found at 1200-1300 {sup o}C for photoluminescence and 1400 {sup o}C for persistent phosphorescence. The energy storage traps for persistent phosphorescence in the system are analyzed based on the dependence of photoluminescence and persistent phosphorescence on sintering temperature. The distribution of energy storage traps is further characterized by thermoluminescence spectra and the parameters of the traps are calculated. Oxygen vacancies as the main trapping centers play the key role for persistent phosphorescence in CaTiO{sub 3}:Pr{sup 3+}.

  20. Thermoelectric Properties of Mn-Doped Ca5Al2Sb6

    NASA Astrophysics Data System (ADS)

    Zevalkink, Alex; Swallow, Jessica; Snyder, G. Jeffrey

    2012-05-01

    Ca5Al2Sb6 is a relatively inexpensive Zintl compound exhibiting promising thermoelectric efficiency at temperatures suitable for waste heat recovery. Motivated by our previous studies of Ca5Al2Sb6 doped with Na and Zn, this study focuses on doping with Mn2+ at the Al3+ site. While Mn is a successful p-type dopant in Ca5Al2Sb6, we find that incomplete dopant activation yields lower hole concentrations than obtained with either previously investigated dopant. High-temperature Hall effect and Seebeck coefficient measurements show a transition from nondegenerate to degenerate semiconducting behavior in Ca5Al2- x Mn x Sb6 samples ( x = 0.05, 0.1, 0.2, 0.3, 0.4) with increasing Mn content. Ultimately, no improvement in zT is achieved via Mn doping, due in part to the limited carrier concentration range achieved.

  1. Factors affecting the microstructure and mechanical properties of Ti-Al3Ti core-shell-structured particle-reinforced Al matrix composites

    NASA Astrophysics Data System (ADS)

    Guo, Baisong; Yi, Jianhong; Ni, Song; Shen, Rujuan; Song, Min

    2016-04-01

    This work studied the effects of matrix powder and sintering temperature on the microstructure and mechanical properties of in situ formed Ti-Al3Ti core-shell-structured particle-reinforced pure Al-based composites. It has been shown that both factors have significant effects on the morphology of the reinforcements and densification behaviour of the composites. Due to the strong interfacial bonding and the limitation of the crack propagation in the intermetallic shell during deformation by soft Al matrix and Ti core, the composite fabricated using fine spherical-shaped Al powder and sintered at 570 °C for 5 h has the optimal combination of the overall mechanical properties. The study provides a direction for the optimum combination of high strength and ductility of the composites by adjusting the fabrication parameters.

  2. First-principles phonon calculations of thermal expansion in Ti3SiC2 , Ti3AlC2 , and Ti3GeC2

    NASA Astrophysics Data System (ADS)

    Togo, Atsushi; Chaput, Laurent; Tanaka, Isao; Hug, Gilles

    2010-05-01

    Thermal properties of ternary carbides with composition Ti3SiC2 , Ti3AlC2 , and Ti3GeC2 were studied using the first-principles phonon calculations. The thermal expansions, the heat capacities at constant pressure, and the isothermal bulk moduli at finite temperatures were obtained under the quasiharmonic approximation. Comparisons were made with the available experimental data and excellent agreements were obtained. Phonon band structures and partial density of states were investigated. These compounds present unusual localized phonon states at low frequencies, which are due to atomiclike vibrations parallel to the basal plane of the Si, Al, or Ge elements.

  3. Spherical nanoindentation stress-strain curves of commercially pure titanium and Ti-6Al-4V

    DOE Data Explorer

    Weaver, Jordan S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Priddy, Matthew W. [Georgia Inst. of Technology, Atlanta, GA (United States); McDowell, David L. [Georgia Inst. of Technology, Atlanta, GA (United States); Kalidindi, Surya R. [Georgia Inst. of Technology, Atlanta, GA (United States)

    2016-07-27

    Spherical nanoindentation combined with electron back-scattered diffraction was employed to characterize the grain-scale elastic and plastic anisotropy of single crystal alpha-Ti for commercially pure (CP-Ti) and alloyed (Ti-64) titanium. In addition, alpha-beta Ti (single colony) grains were characterized. The data set includes the nanoindentation force, displacement, and contact stiffness, the nanoindentation stress-strain analysis, and the alpha-Ti crystal orientations. Details of the samples and experimental protocols can be found in Weaver et al. (2016) Acta Materialia doi:10.1016/j.actamat.2016.06.053.

  4. Radiation effects in multilayer ohmic contacts Au-Ti-Al-Ti-n-GaN

    SciTech Connect

    Belyaev, A. E.; Boltovets, N. S.; Ivanov, V. N.; Kapitanchuk, L. M.; Konakova, R. V. Kudryk, Ya. Ya.; Lytvyn, O. S.; Milenin, V. V.; Sheremet, V. N.; Sveshnikov, Yu. N.

    2009-07-15

    Radiation effects in the Au-Ti-Al-Ti-n-GaN multilayer metallization subjected to irradiation with {sup 60}Co {gamma}-ray photons in the dose range 4 x 10{sup 6}-2 x 10{sup 7} Gy are considered, and the effect of radiation on the initial contact structures and the structures subjected to a rapid thermal annealing (RTA) at high-temperature in the nitrogen atmosphere is studied. Irradiation does not significantly affect the properties of structures that were not subjected to the heat treatment. An RTA at 700 deg. C brings about a deterioration of the contact-layer morphology. The morphological and structural transformations in the contact metallization due to the RTA are enhanced by irradiation with {gamma}-ray photons. The combined radiation-thermal treatment is conducive to the mass transfer between contacting layers. In addition, after {gamma}-ray irradiation with the dose of 2 x 10{sup 7} Gy, the oxygen-impurity atoms appear over the entire contact's structure and are observed in a large amount in the near-contact GaN region.

  5. Component Activity Measurements in the Ti-Al-O System by Knudsen Cell Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Copland, Evan; Jacobson, Nathan S.

    2003-01-01

    Titanium-aluminides (containing (alpha)2-Ti3Al and gamma-TiAl intermetallic phases) have received continued research focus due to their potential as low-density materials for structural applications at intermediate temperatures. However their application above about 850C is hindered by poor oxidation resistance, characterized by the formation of a non-protective TiO2+Al2O3 scale and an oxygen-enriched subsurface zone. Consistent with this are measured titanium and aluminum activities in "oxygen-free" titanium-aluminides, which indicate Al2O3 is only stable for aluminum concentrations greater then 54 atom percent at 1373 K. However, the inability to form a protective Al2O3 scale is in apparent conflict with phase diagram studies, as experimental isothermal sections of the Ti-Al-O system show gamma-TiAl + alpha2-Ti3Al structures are in equilibrium only with Al2O3. The apparent resolution to this conflict lies in the inclusion of oxygen effects in the thermodynamic measurements

  6. Structural, morphological and interfacial characterization of Al-Mg/TiC composites

    SciTech Connect

    Contreras, A. . E-mail: acontrer@imp.mx; Angeles-Chavez, C.; Flores, O.; Perez, R.

    2007-08-15

    Morphological and structural characterization of Al-Mg/TiC composites obtained by infiltration process and wetting by the sessile drop technique were studied. Focusing at the interface, wetting of TiC substrates by molten Al-Mg-alloys at 900 deg. C was investigated. Electron probe microanalysis (EPMA) indicated that aluminum carbide (Al{sub 4}C{sub 3}) is formed at the interface and traces of TiAl{sub 3} in the wetting assemblies were detected. Scanning Electron Microscopy (SEM) observations show that TiC particles do not appear to be uniformly attacked to produce a continuous layer of Al{sub 4}C{sub 3} at the interface. Molten Al-Mg-alloys were infiltrated into TiC preforms with flowing argon at a temperature of 900 deg. C. In the composites no reaction phase was observed by SEM. Quantification of the Al phase in the composite was carried out by X-ray diffraction (XRD) and Rietveld analysis. Chemical mapping analyzed by SEM shows that the Al-Mg alloy surrounds TiC particles. In the composites with 20 wt.% of Mg the Al-Mg-{beta} phase was detected through XRD.

  7. The microstructure of minerals in coarse-grained Ca-Al-rich inclusions from the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Barber, D. J.; Martin, P. M.; Hutcheon, I. D.

    1984-01-01

    Transmission electron microscopy (TEM) is used to investigate the microstructure and microchemistry of minerals in Ca-Al-rich, coarse-grained inclusions (CAI) from the meteorite. The spinels contain only low to moderate dislocation densities and are characterized by a ubiquitous, fine black spotty texture that is thought to originate from a slightly nonstoichiometric composition. Whereas the Ti-Al-pyroxenes are relatively devoid of features, they contain veins of secondary phases apparently deposited in unhealed cracks. Chromite is identified in the veins, indicating transport of oxidized iron during alteration. The melilites show the greatest variety of microstructures and are the most heavily altered phase in CAI. High dislocation densities are common and the crystals exhibit considerable internal strain, suggesting that they have not been annealed.

  8. The microstructure of minerals in coarse-grained Ca-Al-rich inclusions from the Allende meteorite

    NASA Astrophysics Data System (ADS)

    Barber, D. J.; Martin, P. M.; Hutcheon, I. D.

    1984-04-01

    Transmission electron microscopy (TEM) is used to investigate the microstructure and microchemistry of minerals in Ca-Al-rich, coarse-grained inclusions (CAI) from the meteorite. The spinels contain only low to moderate dislocation densities and are characterized by a ubiquitous, fine black spotty texture that is thought to originate from a slightly nonstoichiometric composition. Whereas the Ti-Al-pyroxenes are relatively devoid of features, they contain veins of secondary phases apparently deposited in unhealed cracks. Chromite is identified in the veins, indicating transport of oxidized iron during alteration. The melilites show the greatest variety of microstructures and are the most heavily altered phase in CAI. High dislocation densities are common and the crystals exhibit considerable internal strain, suggesting that they have not been annealed.

  9. Effect of Impact Damage on the Fatigue Response of TiAl Alloy-ABB-2

    NASA Technical Reports Server (NTRS)

    Draper, S. L.; Lerch, B. A.; Pereira, J. M.; Nathal, M. V.; Nazmy, M. Y.; Staubli, M.; Clemens, D. R.

    2001-01-01

    The ability of gamma-TiAl to withstand potential foreign or domestic object damage is a technical risk to the implementation of gamma-TiAl in low pressure turbine (LPT) blade applications. In the present study, the impact resistance of TiAl alloy ABB-2 was determined and compared to the impact resistance of Ti(48)Al(2)Nb(2)Cr. Specimens were impacted with four different impact conditions with impact energies ranging from 0.22 to 6.09 J. After impacting, the impact damage was characterized by crack lengths on both the front and backside of the impact. Due to the flat nature of gamma-TiAl's S-N (stress vs. cycles to failure) curve, step fatigue tests were used to determine the fatigue strength after impacting. Impact damage increased with increasing impact energy and led to a reduction in the fatigue strength of the alloy. For similar crack lengths, the fatigue strength of impacted ABB-2 was similar to the fatigue strength of impacted Ti(48)Al(2)Nb(2)Cr, even though the tensile properties of the two alloys are significantly different. Similar to Ti(48)Al(2)Nb(2)Cr, ABB-2 showed a classical mean stress dependence on fatigue strength. The fatigue strength of impacted ABB-2 could be accurately predicted using a threshold analysis.

  10. High temperature air oxidation resistance of TiAlCr-Y coated Ti45Al8Nb between 750 °C - 950 °C

    NASA Astrophysics Data System (ADS)

    Dudziak, Tomasz; Datta, Prasanta; Du, Hailiang; Ross, Ian

    2013-12-01

    This study is concerned with air oxidation of TiAlCr-Y coated Ti45Al-8Nb (at%) alloy between 750 °C-950 °C for 500 hours. It was shown in these tests that at 750 °C, 850 °C and 950 °C, the oxidation degradation increased with temperature: at 750 °C the oxide scale consisted of TiO2/Al2O3/Cr2O3 phases, whilst at 850 °C the oxide scale consisted of TiO2/Al2O3 phases with a small amount of Cr2O3, and larger number of voids. The material exposed at 950 °C showed a significant formation of TiO2 with a small amount of Al2O3 and high number of voids; the formation of Cr2O3 at 950 °C was inhibited mainly due to the formation of volatile CrO3 or CrO2(OH)2 phase.

  11. Neutron Diffraction Study Oxygen Dissolution Alpha(sub 2)-Ti3Al

    NASA Technical Reports Server (NTRS)

    Jones, Camille Y.; Luecke, William E.; Copland, Evan

    2005-01-01

    Rietveld refinements of neutron powder diffraction data on alpha(sub 2)-Ti3Al have been performed to determine the crystal structure as a function of interstitial oxygen (O) concentration for three alloys with a Ti/Al ratio of approximately equal to 2.34 and O concentrations of 0.25%, 3.99% and 7.71%. The structures of the allows are hexagonal in space group P6(sub 3)/mmc where Ti and Al atoms populate unique sites with excess Al at the Ti site and O atoms occupy octahedral interstitial sites surrounded by six Ti sites. The length of the c-axis was found to increase linearly as the O occupancy of the interstitial sites increased; this lattice lengthening effect was much less pronounced along the alpha axis. Correspondingly, the increases in the lengths of Ti-Al and Ti-Ti bonds with a major component of their direction parallel to the c-axis were roughly an order of magnitude greater than the increases in the lengths of Ti-al and Ti-Ti bonds more closely aligned with the alpha-axis. Densities calculated form the lattice parameters and occupancy factors fall in the range (4.118 plus or minus 0.004) grams per cubic centimeter to (4.194 plus or minus 0.004) grams per cubic centimeter, and exhibit a nearly linear increase with oxygen concentration. Measured densities of (4.113 plus or minus 0.001) grams per cubic centimeter, (4.146 plus or minus 0.009) grams per cubic centimeter, and (4.191 plus or minus 0.002) grams per cubic centimeter for these alloys agree with the results of the refinements.

  12. 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.

  13. Development of Al-killed/Ti stabilized steels

    NASA Astrophysics Data System (ADS)

    Ramirez-Ledesma, A. L.; Aguilar-Mendez, M. A.; Rodriguez-Diaz, R. A.; >G Aramburo,

    2015-01-01

    Several Al-killed/Ti-stabilized low carbon steels were developed in a Mexican steel industry with the aim of obtaining an interstitial free steel for automotive applications. The steelmaking route involved the use of 100% sponge iron which was feed into an electric arc furnace, vacuum degassed, ladle treated and continuously casted. The resulting slabs were then hot rolled at 1100 °C and coiled at 650 °C. Then, the steel plates were cold rolled at room temperature and sheets annealed at 700 °C. As-cast micro structure showed the presence of α-ferrite with titanium nitrides in matrix and grain boundaries while in the ashot rolled condition, elongated grains showed the presence of titanium nitrides, titanium sulfides and titanium carbosulfides. The annealed sheets showed, additionally to the other precipitates, the presence of titanium carbides. Microstructure, texture, the Lankford ratio and mechanical properties of fully recrystallized coils fulfilled the target properties established by the automobile industry.

  14. Synthesis of Nano-Crystalline Gamma-TiAl Materials

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Vasquez, Peter

    2003-01-01

    One of the principal problems with nano-crystalline materials is producing them in quantities and sizes large enough for valid mechanical property evaluation. The purpose of this study was to explore an innovative method for producing nano-crystalline gamma-TiAl bulk materials using high energy ball milling and brief secondary processes. Nano-crystalline powder feedstock was produced using a Fritsch P4(TM) vario-planetary ball mill recently installed at NASA-LaRC. The high energy ball milling process employed tungsten carbide tooling (vials and balls) and no process control agents to minimize contamination. In a collaborative effort, two approaches were investigated, namely mechanical alloying of elemental powders and attrition milling of pre-alloyed powders. The objective was to subsequently use RF plasma spray deposition and short cycle vacuum hot pressing in order to effect consolidation while retaining nano-crystalline structure in bulk material. Results and discussion of the work performed to date are presented.

  15. Vibration characteristics of NiTi-Al MMC beam fabricated with ultrasonic welding

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Wang, Yiqing; Kuang, Xinbin; Zhang, Teng; Liu, Hongzhong; Lu, Bingheng; Xu, Minglong

    2015-12-01

    A free-vibration differential equation of the compound beam of NiTi-Al MMC (metal matrix composite) is built considering the recovery stress of NiTi foil and based on Timoshenko beam theory to predict the frequency tuning characteristics of the compound beam. The clamped-free (CF) beam is under compressive stress state due to the recovery stress in the NiTi foil, which may cause a reduction in its natural frequency. For an 80 mm CF beam with 8% NiTi (prestrain 3%) embedded in Al matrix, the natural frequency decreases by 52.1% when temperature is up to 70 °C. However the stress state of clamped-clamped (CC) beam depends on the combined effect of recovery stress and thermal expansion of NiTi. At least 20% NiTi should be embedded in Al matrix to increase the natural frequency of CC beam. Finally, the NiTi-Al MMC beam is prepared by ultrasonic welding process. A thermal modal experiment is conducted to study the vibration characteristics of the compound beam. The results show that the natural frequency of the compound beam could be tuned effectively by volume fraction of the NiTi embedded in Al foil, which is consistent with theoretical calculations.

  16. 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

  17. XPS Analysis of Ti6Al4V Oxidation Under UHV Conditions

    NASA Astrophysics Data System (ADS)

    Hierro-Oliva, M.; Gallardo-Moreno, A. M.; González-Martín, M. L.

    2014-12-01

    Oxidation of Ti6Al4V is studied by X-ray photoelectron spectroscopy (XPS). Oxide layer growth was monitored on the Ti6Al4V surface for 24 hours. The surface was previously etched with Ar+ ions under ultra-high vacuum conditions. XPS spectra show that TiO and Ti2O3, together with Al2O3, were the earliest oxides formed. Vanadium, despite being detected in its elementary form in the bulk, was not found in any of its oxidized states. TiO2, directly related to the good performance of Ti6Al4V for biomedical applications, did not contribute significantly to the passive layer at the beginning; nevertheless, it was identified after the oxidation process progressed to a more advanced stage. This behavior indicates that reoxidation of Ti6Al4V permits auto-healing of its passive layer, with the presence of TiO2, even in conditions of low oxygen availability.

  18. XPS Analysis of Ti6Al4V Oxidation Under UHV Conditions

    NASA Astrophysics Data System (ADS)

    Hierro-Oliva, M.; Gallardo-Moreno, A. M.; González-Martín, M. L.

    2014-09-01

    Oxidation of Ti6Al4V is studied by X-ray photoelectron spectroscopy (XPS). Oxide layer growth was monitored on the Ti6Al4V surface for 24 hours. The surface was previously etched with Ar+ ions under ultra-high vacuum conditions. XPS spectra show that TiO and Ti2O3, together with Al2O3, were the earliest oxides formed. Vanadium, despite being detected in its elementary form in the bulk, was not found in any of its oxidized states. TiO2, directly related to the good performance of Ti6Al4V for biomedical applications, did not contribute significantly to the passive layer at the beginning; nevertheless, it was identified after the oxidation process progressed to a more advanced stage. This behavior indicates that reoxidation of Ti6Al4V permits auto-healing of its passive layer, with the presence of TiO2, even in conditions of low oxygen availability.

  19. 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. PMID:22072595

  20. Microstructural refinement of Ti-44Al-11Nb by severe plastic deformation

    SciTech Connect

    Sastry, S.M.L.; Mahapatra, R.N.; Hasson, D.F.

    2000-03-17

    Recent studies have demonstrated that Seere Plastic Deformation (SPD) can be successfully used to produce submicrometer sized grains. Equal Channel Angular Extrusion (ECAE) has proven to be an effective technique for producing severe plastic deformation. With the objective of producing sub micron grains and determining the beneficial effects of such microstructures on mechanical properties, the authors have an ongoing study of severe plastic deformation effects in several TiAl and Ti{sub 3}Al based intermetallics. The microstructural modifications in a Ti-44Al-11Nb (all compositions are in atomic percent) alloy processed by equal channel angular extrusion are evaluated.

  1. Combustion synthesis of ceramic-metal composite materials - The TiC-Al2O3-Al system

    NASA Technical Reports Server (NTRS)

    Feng, H. J.; Moore, John J.; Wirth, D. G.

    1992-01-01

    Combustion synthesis was applied for producing ceramic-metal composites with reduced levels of porosity, by allowing an excess amount of liquid metal, generated by the exothermic reaction during synthesis, to infiltrate the pores. It is shown that this method, when applied to TiC-Al2O3 system, led to a decreased level of porosity in the resulting TiC-Al2O3-Al product, as compared with that of TiC-Al2O3 system. This in situ procedure is more efficient than the two-stage conventional processes (i.e., sintering followed by liquid metal infiltration), although there are limitations with respect to total penetration of the liquid metal and maintaining a stable propagation of the combustion reaction.

  2. Vickers hardness, indentation creep and corrosion behaviour of Al-5Ti-1B alloy with copper content

    NASA Astrophysics Data System (ADS)

    Said Gouda, El; Nassar, Amira

    2014-11-01

    The effects of 1, 3 and 5 wt.% Cu additions on structure, Vickers hardness, indentation creep and corrosion behaviour of Al-5Ti-1B ternary alloy were studied and analyzed. The Al-5Ti-1B alloy exhibited a mixture of Al3Ti and TiB2 intermetallic compounds (IMCs), and Al solid solution. Additions of 1 and 3 wt.% Cu showed the same phases, indicating a complete solubility of Cu atoms in Al matrix. In addition, the Al-5Ti-1B-5Cu alloy exhibited a precipitation of CuAl2 IMC. Furthermore, additions of Cu decreased the particle size of Al matrix. This structural behaviour increased rapidly the Vickers hardness number (HV) from 643 to 1395 MPa, increased the indentation creep resistance and improved corrosion behaviour of the Al-5Ti-1B alloy. Cu is anti-corrosion phase when completely dissolved or precipitated as IMC in Al matrix.

  3. The effect of Ti addition on oxidation behavior of FeAl intermetallic alloy

    SciTech Connect

    Li, D.; Lin, D.

    1997-12-31

    The influence of Ti addition on the high temperature oxidation behaviors of FeAl intermetallic alloys in air at 1,000 C and 1,100 C have been investigated. The oxidation kinetics of FeAl alloys were examined by the weight gain method and oxide products were examined by XRD, SEM, EDS and EPMA. The results showed that the oxidation kinetic curves of both Ti-doped and binary Fe-36.5Al alloys were described as different parabolas followed the formula: ({Delta}W/S){sup 2} = K{sub p}t. The parabolic rate constant, K{sub p} values are about 2.4 and 3.3 mg{sup 2}cm{sup {minus}4}h{sup {minus}1} for Fe-36.5Al alloy and about 1.3 and 2.0 mg{sup 2}cm{sup {minus}4}h{sup {minus}1} for Fe-36.5Al-2Ti alloy when oxidizing at 1,000 C and 1,100 C respectively. The difference between Fe-36.5Al and Fe-36.5Al-2Ti alloy is not only in the surface morphology but also in the phase components. In the surface there is only {alpha}-Al{sub 2}O{sub 3} oxide for the Fe-36.5Al alloy while there are {alpha}-Al{sub 2}O{sub 3} and TiO oxide for the Fe-36.5Al-2Ti alloy. The effects of Ti addition on the oxidation resistance of FeAl alloy were discussed based on the microstructural evidence.

  4. An ex situ study of the adsorption of calcium phosphate from solution onto TiO2(110) and Al2O3(0001)

    NASA Astrophysics Data System (ADS)

    Murphy, M.; Walczak, M. S.; Hussain, H.; Acres, M. J.; Muryn, C. A.; Thomas, A. G.; Silikas, N.; Lindsay, R.

    2016-04-01

    Ex situ atomic force microscopy and x-ray photoelectron spectroscopy are employed to characterise the adsorption of calcium phosphate from an aqueous solution of CaCl2.H2O and KH2PO4 onto rutile-TiO2(110) and α-Al2O3(0001). Prior to immersion, the substrates underwent wet chemical preparation to produce well-defined surfaces. Calcium phosphate adsorption is observed on both rutile-TiO2(110) and α-Al2O3(0001), with atomic force microscopy images indicating island-type growth. In contrast to other studies on less well-defined TiO2 and Al2O3 substrates, the induction period for calcium phosphate nucleation appears to be comparable on these two surfaces.

  5. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    NASA Astrophysics Data System (ADS)

    Ohmi, Tatsuya; Mizuma, Kiminori; Matsuura, Kiyotaka; Iguchi, Manabu

    2008-02-01

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  6. Joining of Ni-TiC FGM and Ni-Al Intermetallics by Centrifugal Combustion Synthesis

    SciTech Connect

    Ohmi, Tatsuya; Matsuura, Kiyotaka; Iguchi, Manabu; Mizuma, Kiminori

    2008-02-15

    A centrifugal combustion synthesis (CCS) process has been investigated to join a Ni-Al intermetallic compound and a Ni-TiC cermet. The cermet, a tubular graphite mold, and a green compact of reactants consisting of Al, Ni and NiO were set in a centrifugal caster. When the combustion synthesis reaction was induced in the centrifugal force field, a synthesized molten Ni-Al alloy flowed into the graphite mold and joined to the cermet. The soundness of the joint interface depended on the volume percentage of TiC phase in the cermet. A lot of defects were formed near the interface between the Ni-TiC cermet and the cast Ni-Al alloy when the volume percentage of TiC was 50% or higher. For this kind of cermet system, using a functionally graded cermet such as Ni-10 vol.%TiC/Ni-25 vol.%TiC/Ni-50 vol.%TiC overcame this difficulty. The four-point bending strength of the joined specimen consisting of the three-layered FGM cermet and cast Ni-29 mol%Al alloy was 1010 MPa which is close to the result for a Ni-29 mol%Al alloy specimen.

  7. Microstructural analysis of Al alloys dispersed with TiB2 particulate for MMC applications

    PubMed

    Wang; Brydson; Jha; Ellis

    1999-11-01

    A dispersion of TiB2 particulates in an Al alloy matrix was formed via the in-situ reaction between mixtures of K2TiF6 (K2ZrF6), KBF4 and molten aluminium. The dispersion of the ceramic phase in the aluminium matrix was also achieved in some experiments by adding exogenous TiB2 particles to the fluoride melt in contact with molten aluminium. In this work, we have examined the microstructure of the as-cast metal matrix composites using analytical electron microscopy and X-ray diffraction techniques. The phases formed as a result of the reaction between the molten fluoride flux and liquid aluminium have been identified. These were (Ti, Zr, Al)B2, Al3Ti and possibly AlB12 in the Al-matrix, and KAlF4 and KMgF3 in the solidified flux. The mechanism of formation of TiB2 and Al3Ti is explained. The role of alloying elements is also explained in the context of interfacial chemistry and dispersion. PMID:10540266

  8. Electrical characteristics of p-Si/TiO2/Al and p-Si/TiO2-Zr/Al Schottky devices

    NASA Astrophysics Data System (ADS)

    Hüdai Taşdemir, İbrahim; Vural, Özkan; Dökme, İlbilge

    2016-06-01

    Electrical devices involve different types of diode in prospective electronics is of great importance. In this study, p-type Si surface was covered with thin film of TiO2 dispersion in H2O to construct p-Si/TiO2/Al Schottky barrier diode (D1) and the other one with TiO2 dispersion doped with zirconium to construct p-Si/TiO2-Zr/Al diode (D2) by drop-casting method in the same conditions. Electrical properties of as-prepared diodes and effect of zirconium as a dopant were investigated. Current-voltage (I-V) characteristics of these devices were measured at ambient conditions. Some parameters including ideality factor (n), barrier height (ΦB0), series resistance (Rs) and interface state density (Nss) were calculated from I-V behaviours of diodes. Structural comparisons were based on SEM and EDX measurements. Experimental results indicated that electrical parameters of p-Si/TiO2/Al Schottky device were influenced by the zirconium dopant in TiO2.

  9. Wetting Behavior of Laser Synthetic Surface Micro Textures on Ti-6Al-4V for Bioapplication

    SciTech Connect

    Dahotre, Narendra B; Paital, Sameer R; Samant, Anoop N; Daniel, Claus

    2010-01-01

    Wettability at the surface of an implant material play a key role in its success as it modulate the protein adsorption and thereby influences cell attachment and tissue integration at the interface. Hence, surface engineering of implantable materials to enhance wettability to physiological fluid under in vivo conditions is an area of active research. In light of this, in the present work a laser based optical interference and direct melting techniques were used to develop synthetic micro textures on Ti-6Al-4V alloys and their effects on wettability were systematically studied. Improved wettability to simulated body fluid and distilled water was observed for the Ca-P coatings obtained by direct melting technique. This superior wettability was attributed to both the appropriate surface chemistry and three dimensional surface features obtained using this technique. To assert a better control on surface texture and wettability a three dimensional thermal model based on COMSOL sTM multiphysics was employed to predict the features obtained by laser melting technique. The effect of physical texture and wetting on biocompatibility of laser processed Ca-P coating was evaluated in the preliminary efforts on culturing of mouse MC3T3-E1 osteoblast cells.

  10. Crystal Structure and Photocatalytic Activity of Al-Doped TiO2 Nanofibers for Methylene Blue Dye Degradation.

    PubMed

    Lee, Deuk Yong; Lee, Myung-Hyun; Kim, Bae-Yeon; Cho, Nam-Ihn

    2016-05-01

    Al-TiO2 nanofibers were prepared using a sol-gel derived electrospinning by varying the Al/Ti molar ratio from 0 to 0.73 to investigate the effect of Al doping on the crystal structure and the photocatalytic activity of Al-TiO2 for methylene blue (MB) degradation. XRD results indicated that as the Al/Ti molar ratio rose, crystal structure of Al-TiO2 was changed from anatase/rutile (undoped), anatase (0.07-0.18), to amorphous phase (0.38-0.73), which was confirmed by XPS and Raman analysis. The degradation kinetic constant increased from 7.3 x 10(-4) min(-1) to 4.5 x 10(-3) min(-1) with the increase of Al/Ti molar ratios from 0 to 0.38, but decreased to 3.4 x 10(-3) min(-1) when the Al/Ti molar ratio reached 0.73. The Al-TiO2 catalyst doped with 0.38 Al/Ti molar ratio demonstrated the best MB degradation. Experimental results indicated that the Al doping in Al-TiO2 was mainly attributed to the crystal structure of TiO2 and the photocatalytic degradation of MB. PMID:27483928

  11. Dual functions of TiC nanoparticles on tribological performance of Al/graphite composites

    NASA Astrophysics Data System (ADS)

    Fallahdoost, Hamid; Nouri, Alireza; Azimi, Amin

    2016-06-01

    In this study, the effect of TiC nanoparticles as a reinforcement on the mechanical and tribological properties of Aluminum-based self lubricating composite was investigated. The microstructure, relative density, hardness, and tribological properties of Al/graphite and Al/TiC/graphite composites were examined as a function of graphite content. The tribo-surfaces of the samples were analyzed using SEM and EDS elemental mapping. The results indicated that the addition of TiC nanoparticles not only decreased the wear rate and coefficient of friction of the composites, but also facilitated the formation of a stable graphite layer at longer sliding distances and high sliding velocities by forming a durable graphite/TiC composite on the tribo-surface. Therefore, the stability of graphite layer can be considered as a possible cause for decrease in wear rate of the Al/TiC/graphite composite.

  12. Corrosion behavior of PIRAC nitrided Ti-6Al-4V surgical alloy.

    PubMed

    Starosvetsky, D; Shenhar, A; Gotman, I

    2001-02-01

    Hard titanium nitride (TiN) coatings were obtained on the surface of Ti-6Al-4V alloy using an original PIRAC nitriding method, based on annealing the samples under a low pressure of monatomic nitrogen created by selective diffusion of N from the atmosphere. PIRAC nitrided samples exhibited excellent corrosion resistance in Ringer's solution in both potentiodynamic and potentiostatic tests. The anodic current and metal ion release rate of PIRAC nitrided Ti-6Al-4V at the typical corrosion potential values were significantly lower than those of the untreated alloy. This, together with the excellent adhesion and high wear resistance of the TiN coatings, makes PIRAC nitriding an attractive surface treatment for Ti-6Al-4V alloy surgical implants. PMID:15348321

  13. Interaction of Al2O3-ZrO2 fibers with a Ti-Al matrix during pressure casting

    NASA Astrophysics Data System (ADS)

    Nourbakhsh, S.; Liang, F. L.; Margolin, H.

    1990-01-01

    Electron and optical electron microscopy, together with energy dispersive X-ray (EDX) chemical microanalysis, were employed to examine the microstructure of a pressure-cast composite consisting of a Ti-48.4 at. pct Al-1 at. pct Mn matrix reinforced with DuPont’s PRD-166 A12O3 fibers containing 20 wt pct partially stabilized ZrO2. The originally cylindrical fibers were found to have a scalloped surface, and a zone just below the surface was free of ZrO2. In addition, the fibers contained entrapped TiAl, and a small portion of the fiber periphery was covered by ZrO2 particles, which were free of the Y2O3 and HfO2 oxides present in the ZrO2 within the fibers. The matrix consisted of a mixture of TiAl and a lamellar structure of TiAl and Ti3Al and contained Zr not originally present in the matrix alloy. An analysis of the origin of this microstructure is presented.

  14. Effect of UV irradiation on the surface Gibbs energy of Ti6Al4V and thermally oxidized Ti6Al4V.

    PubMed

    Pacha-Olivenza, M A; Gallardo-Moreno, A M; Méndez-Vilas, A; Bruque, J M; González-Carrasco, J L; González-Martín, M L

    2008-04-01

    Thermal oxidation of Ti6Al4V increases the thickness, modifies the structure, and changes the amount of alloying elements of the surface titanium dioxide layer with respect to the spontaneous passive layer of Ti6Al4V. The effects on the surface properties of Ti6Al4V and thermally oxidized Ti6Al4V after different periods of UV irradiation have been studied by measurement of water, formamide, and diiodomethane contact angles. The rate of modification of the water contact angle with the irradiation time is dependent on the surface treatment, but the water adhesion work, after an initial energetic step, follows a similar trend for both. Application of the Young equation together with the van Oss approach allowed evaluation of the surface Gibbs energy of the alloys. Similar to the water adhesion work, the surface Gibbs energy dependence on the irradiation time follows a similar trend for both samples and it is due to the change of the electron-donor parameter of the acid-base component. Also, a linear relationship common for both samples has been obtained between the cosines of the water contact angle and the formamide or diiodomethane contact angle. These facts indicate that the surface modification continuously produced by the UV irradiation is similar all along the process and similar for both samples after an energetic threshold for the thermally oxidized sample. It has been also tested that the hydrophilic-hydrophobic conversion is reversible for Ti6Al4V and Ti6Al4V thermally treated. PMID:18221751

  15. Effect of V or Zr addition on the mechanical properties of the mechanically alloyed Al-8wt%Ti alloys

    SciTech Connect

    Moon, I.H.; Lee, J.H.; Lee, K.M. . Dept. of Materials Engineering); Kim, Y.D. . Div. of Metals)

    1995-01-01

    Mechanical alloying (MA) of Al-Ti alloy, being a solid state process, offers the unique advantage of producing homogeneous and fine dispersions of thermally stable Al[sub 3]Ti phase, where the formation of the fine Al[sub 3]Ti phase by the other method is restricted from the thermodynamic viewpoint. The MA Al-Ti alloys show substantially higher strength than the conventional Al alloys at the elevated temperature due to the presence of Al[sub 3]Ti as well as Al[sub 4]C[sub 3] and Al[sub 2]O[sub 3], of which the last two phases were introduced during MA process. The addition of V or Zr to Al-Ti alloy was known to decrease the lattice mismatch between the intermetallic compound and the aluminum matrix, and such decrease in lattice mismatching can influence positively the high temperature mechanical strength of the MA Al-Ti by increasing the resistance to dispersoid coarsening at the elevated temperature. In the present study, therefore, the mechanical behavior of the MA Al-Ti-V and Al-Ti-Zr alloys were investigated in order to evaluate the effect of V or Zr addition on the mechanical properties of the MA Al-8Ti alloy at high temperature.

  16. The nitriding behavior of Ti-Al alloys at 1000 C

    SciTech Connect

    Magnan, J.; Weatherly, G.C.; Cheynet, M.C.

    1999-01-01

    The nitriding behavior of a series of alloys in the binary Ti-Al system has been determined at 1000 C, under a controlled atmosphere of pure nitrogen gas, for times ranging between 7 and 100 hours. The scales and subscales were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive and wavelength dispersive X-ray analysis, electron energy loss spectroscopy, and optical microscopy. Upon formation of a surface nitride scale, the subscale became enriched in Al and resulted in the formation of a series of Al-rich intermetallic phases. This enrichment has been linked to the transport processes in the scale and subscale and a shifting of the diffusion path toward the Al-rich corner of the ternary isotherm. The formation of Al-rich intermetallic phases in the subscale was shown to result in rapid breakaway nitriding of the TiAl and TiAl{sub 2} alloys. The stoichiometry of the binary nitrides AlN and TiN was measured, as well as the composition of the ternary nitride Ti{sub 2}AlN.

  17. The structure of the alloy Ti-50Al-15Mo between 800 C and 1400 C

    SciTech Connect

    Chen, Z.; Jones, I.P.; Small, C.J.

    1997-09-01

    The alloy Ti-50Al-15Mo (at.%) has been annealed at 1400 C, 1350 C, 1200 C, 1000 C and 800 C and subsequently quenched. The resulting phases have been identified and their compositions measured. The structures of the equilibrium phases at the various temperatures have thus been inferred, along with their compositions. Of particular interest are a diffusionless transformation of {gamma}-TiAl to a D0{sub 22} structure similar to that of TiAl{sub 3} and a further ordering of the D0{sub 22} structure similar to that of TiAl{sub 3} and a further ordering of the D0{sub 22} compound to a new phase which the authors have termed {gamma}{double_prime}.

  18. Laser remelting of Ti6AL4V using high power diode laser

    NASA Astrophysics Data System (ADS)

    Amaya-Vázquez, M. R.; Sánchez-Amaya, J. M.; Boukha, Z.; El Amrani, K.; Botana, F. J.

    2012-04-01

    Titanium alloys present excellent mechanical and corrosion properties, being widely employed in different industries such as medical, aerospace, automotive, petrochemical, nuclear and power generation, etc. Ti6Al4V is the α-β alloy most employed in industry. The modification of its properties can be achieved with convectional heat treatments and/or with laser processing. Laser remelting (LR) is a technology applied to Ti6Al4V by other authors with excimer and Nd-Yag laser with pure argon shielding gas to prevent risk of oxidation. In the present contribution, laser remelting has been applied for the first time to Ti6Al4V with a high power diode laser (with pure argon as shielding gas). Results showed that remelted samples (with medium energy densities) have higher microhardness and better corrosion resistance than Ti6Al4V base metal.

  19. Mechanical properties and corrosion resistance of Ti-6Al-7Nb alloy dental castings.

    PubMed

    Kobayashi, E; Wang, T J; Doi, H; Yoneyama, T; Hamanaka, H

    1998-10-01

    With the aim of applying a novel titanium alloy, Ti-6Al-7Nb, to a dental casting material, a comprehensive research work was carried out on its characteristics, such as castability, mechanical properties and corrosion resistance in the present study. As a result, Ti-6Al-7Nb alloy exhibited sufficient castability by a dental casting method for titanium alloys and enough mechanical properties for dental application. It is also showed excellent corrosion resistance through an immersion test in 1.0% lactic acid and an anodic polarization test in 0.9% NaCl solution. From these results, it is concluded that this Ti-6Al-7Nb alloy is applicable as a dental material in place of Ti-6Al-4V alloy, which includes cytotoxic vanadium. PMID:15348689

  20. Adhesion strength of sputtered TiAlN-coated WC insert tool

    NASA Astrophysics Data System (ADS)

    Budi, Esmar; Razali, M. Mohd.; Nizam, A. R. Md.

    2013-09-01

    The adhesion strength of TiAlN coating that deposited by using DC magnetron sputtering on WC insert tool are studied. TiAlN coating are deposited on Tungsten Carbide (WC) insert tool by varying negatively substrate bias from 79 to 221 volt and nitrogen flow rate from 30 to 72 sccm. The adhesion strength are obtained by using Rockwell indentation test method with a Brale diamond at applied load of 60,100 and 150 kgf. The lateral diameter of indentation is plotted on three different applied loads and the adhesion strength of TiAlN coating was obtained from the curved slopes at 100 and 150 kgf. The lower curve slop indicated better adhesion strength. The results shows that the adhesion strength of sputterred TiAlN coating tend to increase as the negatively substrate bias and nitrogen flow rate are increased.

  1. Processing and mechanical properties of {gamma}-TiAl based alloy sheet material

    SciTech Connect

    Clemens, H.; Schretter, P.; Glatz, W.; Koeppe, C.; Bartels, A.; Behr, R.; Wanner, A.

    1995-12-31

    The status of rolling of Ti-48Al-2Cr and Ti-47Al-2Cr-0.2Si on industrial scale is described. Defect-free sheet material up to {approximately}800x300x1.5 mm has been produced with grain sizes in the range of 5--20 {micro}m. Tensile properties of Ti-48Al-2Cr sheet material after different heat treatments have been measured at room temperature and 700 C. Fracture elongations at room temperature are in the range of 2.5--5% which proves the good homogeneity of the microstructure. Crack growth characteristics and K{sub IC}-values for different microstructures were determined. The superplastic behavior with respect to grain size was investigated in the temperature range of 950--1,200 C. Initial experiments clearly demonstrate that superplastic forming methods can be applied for shaping of {gamma}-TiAl sheet materials.

  2. APFIM investigations on ordered γ-TiAl using single-layer detection method

    NASA Astrophysics Data System (ADS)

    Wesemann, J.; Frommeyer, G.; Kreuss, M.

    1995-03-01

    The defect structure in the γ-phase of an α 2/γ- Ti 51Al 46Cr 3 alloy and the site occupation of chromium has been studied using atom-probe field-ion microscopy (APFIM). Because of the difficult separation of adjacent atomic layers during conventional APFIM measurements a video-controlled field-evaporation technique was carried out. The γ-phase is hyperstoichiometric in aluminium. Many Al antistructure atoms were detected in Ti layers but no Ti antistructure atoms were found in Al layers. Chromium has a strong preference for occupying Ti sites in the ordered γ-phase (L1 0 type of superlattice). This seems to be in contrast with the results obtained by ALCHEMI (atom location by channelling-enhanced microanalysis). However, this discrepancy can be explained with the dependence of the site preference of chromium on the local Al concentration.

  3. 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.

  4. 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.

  5. Surface integrity after pickling and anodization of Ti-6Al-4V titanium alloy

    NASA Astrophysics Data System (ADS)

    Vermesse, Eric; Mabru, Catherine; Arurault, Laurent

    2013-11-01

    The surface integrity of Ti-6Al-4V titanium alloy was studied at different stages of surface treatments, especially pickling and compact anodization, through surface characteristics potentially worsening fatigue resistance.

  6. Materials Characterization of Electron Beam Melted Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Draper, Susan; Lerch, Brad; Rogers, Richard; Martin, Richard; Locci, Ivan; Garg, Anita

    2015-01-01

    An in-depth material characterization of Electron Beam Melted (EBM) Ti-6Al-4V material has been completed. Hot Isostatic Pressing (HIP) was utilized to close porosity from fabrication and also served as a material heat treatment to obtain the desired microstructure. The changes in the microstructure and chemistry from the powder to pre-HIP and post-HIP material have been analyzed. Computed tomography (CT) scans indicated porosity closure during HIP and high-density inclusions scattered throughout the specimens. The results of tensile and high cycle fatigue (HCF) testing are compared to conventional Ti-6Al-4V. The EBM Ti-6Al-4V had similar or superior mechanical properties compared to conventionally manufactured Ti-6Al-4V.

  7. Adhesion strength of sputtered TiAlN-coated WC insert tool

    SciTech Connect

    Budi, Esmar; Razali, M. Mohd.; Nizam, A. R. Md.

    2013-09-09

    The adhesion strength of TiAlN coating that deposited by using DC magnetron sputtering on WC insert tool are studied. TiAlN coating are deposited on Tungsten Carbide (WC) insert tool by varying negatively substrate bias from 79 to 221 volt and nitrogen flow rate from 30 to 72 sccm. The adhesion strength are obtained by using Rockwell indentation test method with a Brale diamond at applied load of 60,100 and 150 kgf. The lateral diameter of indentation is plotted on three different applied loads and the adhesion strength of TiAlN coating was obtained from the curved slopes at 100 and 150 kgf. The lower curve slop indicated better adhesion strength. The results shows that the adhesion strength of sputterred TiAlN coating tend to increase as the negatively substrate bias and nitrogen flow rate are increased.

  8. Relation between surface slip topography and stress corrosion cracking in Ti-8 wt % Al

    NASA Technical Reports Server (NTRS)

    Boyd, J. D.; Hoagland, R. G.

    1974-01-01

    The deformation behavior of Ti-8 wt % Al has been investigated in an inert environment (air), and an aggressive environment (salt water). Details of surface slip geometry were examined by high resolution surface replicas at various stages of deformation in both environments. Specimens aged to contain a fine dispersion of Ti3Al precipitates failed by subcritical crack growth in salt water, whereas specimens in the single phase condition showed no effects of environment on the yield or fracture characteristics. The Ti3Al precipitates produce little change in strength level or slip character compared to the single phase alloy, and there is no evidence of any effects of environment on the character of surface slip. Rather, the presence of trenches along slip bands on the surface of aged specimens suggest that the specific effect of the Ti3Al precipitates is to render the surface slip steps chemically active relative to the surrounding matrix by slip induced dissolution of the particles.

  9. Optically stimulated luminescence in K2SO4:AEu (A=Ca,Na,Al)

    NASA Astrophysics Data System (ADS)

    More, Y. K.; Patil, R. R.; Wankhede, S. P.; Kulkarni, M. S.; Kumar, Munish; Bhatt, B. C.; Moharil, S. V.

    2015-08-01

    Optically stimulated luminescence in doped K2SO4 is reported. K2SO4 was prepared by simple melt quenched process using readymade potassium sulphate. Samples were doped with Eu and AEu (A=Ca, Na and Al). Out of these samples K2SO4:Eu and K2SO4:Ca,Eu shows good OSL response to 470 nm optical stimulation. K2SO4:Eu and K2SO4:Ca,Eu have the sensitivities comparable with that of commercial phosphor Al2O3:C (Landauer).

  10. Electronic structure and magnetic properties of CoTi 1- xAl x alloys

    NASA Astrophysics Data System (ADS)

    Jezierski, A.; Borstel, G.

    1995-02-01

    The band structure of ordered CoTi, CoAl and Co 2TiAl alloys is calculated by the spin-polarized TB LMTO method. We do not observe a magnetic moment on the Co atom in CoTi and CoAl compounds with the CsCl type structure. The Co 2TiAl alloy with the L2 1 type structure is ferromagnetic with a magnetic moment on the Co atom mCo = 0.27 μB and a small opposite induced magnetic moment on the Ti atom mTi = - 0.05 μB. The electronic densities of states of the disorder CoTi 1- xAl x alloys are computed by the TB LMTO CPA method. We find that the magnetic moment has the maximum for x = 0.5 and it decreases to zero for x = 0 and x = 1.0. From the values of the density of states at the Fermi level we calculate the electronic specific heat coefficient γ. The general trend of γ is close to the experimental data.

  11. Adhesion strength and nucleation thermodynamics of four metals (Al, Cu, Ti, Zr) on AlN substrates

    NASA Astrophysics Data System (ADS)

    Tao, Yuan; Ke, Genshui; Xie, Yan; Chen, Yigang; Shi, Siqi; Guo, Haibo

    2015-12-01

    Devices based on AlN generally require adherent and strong interfaces between AlN and other materials, whereas most metals are known to be nonwetting to AlN and form relatively weak interfaces with AlN. In this study, we selected four representative metals (Al, Cu, Ti, and Zr) to study the adhesion strength of the AlN/metal interfaces. Mathematical models were constructed between the adhesion strength and enthalpy of formation of Al-metal solid solutions, the surface energies of the metals, and the lattice mismatch between the metals and AlN, based on thermodynamic parameters calculated using density functional theory. It appears that the adhesion strength is mainly determined by the lattice mismatch, and is in no linear correlation with either the Al-metal solution's formation enthalpies or the metals' surface energies. We also investigated the nucleation thermodynamics of the four metals on AlN substrates. It was found that Ti forms the strongest interface with AlN, and has the largest driving force for nucleation on AlN substrates among the four metals.

  12. POWDER METALLURGY TiAl ALLOYS: MICROSTRUCTURES AND PROPERTIES

    SciTech Connect

    Hsiung, L

    2006-12-11

    The microstructures and properties of powder metallurgy TiAl alloys fabricated by hot extrusion of gas-atomized powder at different elevated temperatures were investigated. Microstructure of the alloy fabricated at 1150 C consisted of a mixture of fine ({gamma} + {alpha}{sub 2}) equiaxed grains and coarse ordered B2 grains. Particles of ordered hexagonal {omega} phase were also observed in some B2 grains. The alloy containing B2 grains displayed a low-temperature superplastic behavior: a tensile elongation of 310% was measured when the alloy was tested at 800 C under a strain rate of 2 x 10{sup -5} s{sup -1}. Microstructure of the alloy fabricated at 1250 C consisted of a mixture of fine ({gamma} + {alpha}{sub 2}) equiaxed grains, coarse {alpha}{sub 2} grains, and lamellar ({gamma} + {alpha}{sub 2}) colonies. An observation of stacking faults associated with fine {gamma} lamellae in {alpha}{sub 2} grains reveals that the stacking fault of {alpha}{sub 2} phase plays an important role in the formation of lamellar ({gamma} + {alpha}{sub 2}) colonies. Unlike the alloy fabricated at 1150{sup o}, the alloy fabricated at 1250{sup o} displayed no low-temperature superplasticity, but a tensile elongation of 260% at 1000 C was measured. Microstructure of the alloy fabricated at 1400 C consisted of fully lamellar ({gamma} + {alpha}{sub 2}) colonies with the colony size ranging between 50 {micro}m and 100 {micro}m, in which the width of {gamma} lamella is in a range between 100 nm and 350 nm, and the width of {alpha}{sub 2} lamella is in a range between 10 nm and 50 nm. Creep behavior of the ultrafine lamellar alloy and the effects of alloying addition on the creep resistance of the fully lamellar alloy are also investigated.

  13. Metal science and engineering aspects of TiAl-based binary alloys investigations

    SciTech Connect

    Bondarev, B.I.; Elagin, D.V.; Molotkov, A.V.; Notkin, A.B.

    1995-12-31

    This paper covers structure and mechanical properties of TiAl-based alloys depending on the process of material production as well as on working and heat treatment conditions. TiAl-based binary alloys were studied. The basic types of structures which can be observed in this alloy were revealed.These structures were examined and methods of their formation were determined.The processes for manufacturing components for gas turbine and car engine applications are discussed.

  14. Corrosion protection and galvanic corrosion prevention for 7075 Al and Ti-6Al-6V-2Sn alloys. Final report

    SciTech Connect

    Clay, F.A.

    1980-07-01

    Sulfuric-acid-anodized and electroless-nickel-plated 7075 aluminum alloy panels successfully passed 96 hours of salt spray testing when galvanically coupled to duplex-annealed Ti-6Al-6V-2Sn alloy panels. Adherent paint deposits were produced on the titanium alloy and electroless nickel surfaces using a wash primer, an epoxy primer, and a urethane paint coating. A painted part survived 35 cycles of alternating salt spray and hot and freezing environments without blistering. A low chloride cutting fluid was selected for production machining of Ti-6Al-6V-2Sn, based on chemical analysis and stress-corrosion tests. A cleaning process was developed to remove both titanium and aluminum cutting fluids. Modified wedge-opening-loading specimens were used to verify that no stress-corrosion cracking problems occurred with the duplex-annealed Ti-6Al-6V-2Sn alloy because of residual titanium or aluminum cutting fluids.

  15. Effects of plasma treatment on the Ohmic characteristics of Ti/Al/Ti/Au contacts to n-AlGaN

    SciTech Connect

    Cao, X. A.; Piao, H.; LeBoeuf, S. F.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2006-08-21

    The effects of surface treatment using Cl{sub 2}/BCl{sub 3} and Ar inductive coupled plasmas on the Ohmic characteristics of Ti/Al/Ti/Au contacts to n-type Al{sub x}Ga{sub 1-x}N (x=0-0.5) were investigated. Plasma treatment significantly increased the surface conductivity of GaN and Al{sub 0.1}Ga{sub 0.9}N, leading to improved Ohmic behaviors of the contacts. However, it reduced the surface doping level in Al{sub x}Ga{sub 1-x}N (x{>=}0.3) and degraded the contact properties. Following a 900-1000 deg. C anneal, the Ti/Al/Ti/Au contacts to Al{sub x}Ga{sub 1-x}N (x=0-0.3) became truly Ohmic, with specific contact resistances of (3-7)x10{sup -5} {omega} cm{sup 2}, whereas the contact to Al{sub 0.5}Ga{sub 0.5}N remained rectifying even without the plasma treatment. X-ray photoelectron spectroscopy measurements confirmed that the Fermi level moved toward the conduction band in GaN after the plasma treatment, but it was pinned by plasma-induced deep-level states in Al{sub 0.5}Ga{sub 0.5}N. This study emphasizes the need to mitigate plasma damage introduced during the mesa etch step for AlGaN-based deep-UV emitters and detectors.

  16. 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.

  17. 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.

  18. 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

    2016-05-01

    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.

  19. Evaluation of physicochemical properties of surface modified Ti6Al4V and Ti6Al7Nb alloys used for orthopedic implants.

    PubMed

    Basiaga, Marcin; Kajzer, Wojciech; Walke, Witold; Kajzer, Anita; Kaczmarek, Marcin

    2016-11-01

    The paper presents the results of selected functional properties of TiO2 layers deposited by ALD method on the surface of Ti6Al4V and Ti6Al7Nb alloys intended for implants in bone surgery. TiO2 layer was applied at the constant temperature of the ALD process at T=200°C at a variable number of cycles, which resulted in a different layer thickness. Different process cycles of 500, 1250, and 2500 were analyzed. The application of experimental methods (AFM, SEM, wettability, potentiodynamic test, EIS, scratch test, nanohardness and layer thickness) enabled to select the optimal number of cycles, and thus the thickness of the TiO2 layer of the most favorable functional properties. The obtained results clearly showed that regardless of the type of titanium substrate, the TiO2 layer applied in a 2500cycle ALD process has the best physicochemical and electrochemical properties. These properties have major impact on biocompatibility, and therefore the quality of the final product. The information obtained can be useful for manufacturers of medical devices involved in the production of implants used in reconstructive surgery of skeletal system. PMID:27524088

  20. Nuclear structure towards N = 40 60Ca: in-beam γ-ray spectroscopy of 58,60Ti.

    PubMed

    Gade, A; Janssens, R V F; Weisshaar, D; Brown, B A; Lunderberg, E; Albers, M; Bader, V M; Baugher, T; Bazin, D; Berryman, J S; Campbell, C M; Carpenter, M P; Chiara, C J; Crawford, H L; Cromaz, M; Garg, U; Hoffman, C R; Kondev, F G; Langer, C; Lauritsen, T; Lee, I Y; Lenzi, S M; Matta, J T; Nowacki, F; Recchia, F; Sieja, K; Stroberg, S R; Tostevin, J A; Williams, S J; Wimmer, K; Zhu, S

    2014-03-21

    Excited states in the neutron-rich N = 38, 36 nuclei (60)Ti and (58)Ti were populated in nucleon-removal reactions from (61)V projectiles at 90 MeV/nucleon. The γ-ray transitions from such states in these Ti isotopes were detected with the advanced γ-ray tracking array GRETINA and were corrected event by event for large Doppler shifts (v/c ∼ 0.4) using the γ-ray interaction points deduced from online signal decomposition. The new data indicate that a steep decrease in quadrupole collectivity occurs when moving from neutron-rich N = 36, 38 Fe and Cr toward the Ti and Ca isotones. In fact, (58,60)Ti provide some of the most neutron-rich benchmarks accessible today for calculations attempting to determine the structure of the potentially doubly magic nucleus (60)Ca. PMID:24702356

  1. Thermal stability of TiAlN/CrN multilayer coatings studied by atom probe tomography.

    PubMed

    Choi, Pyuck-Pa; Povstugar, Ivan; Ahn, Jae-Pyeong; Kostka, Aleksander; Raabe, Dierk

    2011-05-01

    This study is about the microstructural evolution of TiAlN/CrN multilayers (with a Ti:Al ratio of 0.75:0.25 and average bilayer period of 9 nm) upon thermal treatment. Pulsed laser atom probe analyses were performed in conjunction with transmission electron microscopy and X-ray diffraction. The layers are found to be thermally stable up to 600 °C. At 700 °C TiAlN layers begin to decompose into Ti- and Al-rich nitride layers in the out-of-plane direction. Further increase in temperature to 1000 °C leads to a strong decomposition of the multilayer structure as well as grain coarsening. Layer dissolution and grain coarsening appear to begin at the surface. Domains of AlN and TiCrN larger than 100 nm are found, together with smaller nano-sized AlN precipitates within the TiCrN matrix. Fe and V impurities are detected in the multilayers as well, which diffuse from the steel substrate into the coating along columnar grain boundaries. PMID:21146308

  2. Tribocorrosion behavior of veneering biomedical PEEK to Ti6Al4V structures.

    PubMed

    Sampaio, Miguel; Buciumeanu, Mihaela; Henriques, Bruno; Silva, Filipe S; Souza, Júlio C M; Gomes, José R

    2016-02-01

    In dentistry, prosthetic structures must be able to support masticatory loads combined with a high biocompatibility and wear resistance in the presence of a corrosive environment. In order to improve the simultaneous wear and corrosion response of highly biocompatible prosthetic structures, a veneering poly-ether-ether-ketone (PEEK) to Ti6Al4V substrate was assessed by tribocorrosion analyses under conditions mimicking the oral environment. Samples were synthesized by hot pressing the PEEK veneer onto Ti6Al4V cylinders. The tribocorrosion tests on Ti6Al4V or PEEK/Ti6Al4V samples were performed on a reciprocating ball-on-plate tribometer at 30N normal load, 1Hz and stroke length of 3mm. The tests were carried out in artificial saliva at 37°C. Open circuit potential (OCP) was measured before, during and after reciprocating sliding tests. The worn surfaces were characterized by scanning electron microscopy. The results revealed a lower wear rate on PEEK combined with a lower coefficient of friction (COF), when compared to Ti6Al4V. In fact, PEEK protected Ti6Al4V substrate against the corrosive environment and wear avoiding the release of metallic ions to the surrounding environment. PMID:26454136

  3. Microstructure, mechanical properties, and high-temperature oxidation resistance of boronized {gamma}-TiAl(Mn)

    SciTech Connect

    Kim, S.; Yoon, Y.; Kim, H.; Park, K.

    1997-12-31

    Titanium aluminide (TiAl) based intermetallic compounds are considered as potential materials for high-performance automobile and aircraft engine components and airframe applications because of their low density (3.8 g/cm{sup 3}), high melting temperature (1,480 C), and good elevated temperature strength retention. To improve the wear and high-temperature oxidation resistance of reactively sintered {gamma}-TiAl(Mn) intermetallic compounds, they were boronized in the temperature range of 900 to 1,100 C for 5 to 11 hours with powder mixtures of B{sub 4}C and Na{sub 2}B{sub 4}O{sub 7}. It was found that the coating layer consisted of three sublayers, i.e., outer, middle, and inner sublayers. The outer, middle, and inner sublayers were identified as a mixture of TiB{sub 2} and TiO{sub 2}, a mixture of Al{sub 2}O{sub 3} and TiO{sub 2}, and Ti-rich TiAl based compounds, respectively. The coating layer significantly improved the surface hardness and the wear and high-temperature oxidation resistances. The highest surface hardness (Hv {approx} 2,720) was obtained at 900 C for 11 hours. This surface hardness is much higher than that of TiAl(Mn) (Hv {approx} 400). In addition, the specimens boronized at both 1,000 and 1,050 C for 9 hours showed an excellent high-temperature oxidation resistance. It is believed that the boronizing on the TiAl(Mn) intermetallics is very effective to improve the wear and high-temperature oxidation resistances.

  4. Investigation of reaction kinetics and interfacial phase formation in Ti3Al + Nb composites

    NASA Technical Reports Server (NTRS)

    Wawner, F. E.; Gundel, D. B.

    1992-01-01

    Titanium aluminide metal matrix composites are prominent materials systems being considered for high temperature aerospace applications. One of the major problems with this material is the reactivity between existing reinforcements and the matrix after prolonged thermal exposure. This paper presents results from an investigation of reaction kinetics between Ti-14Al-21Nb (wt pct) and SCS-6 fibers and SiC fibers with surface coatings of TiB2, TiC, TiN, W, and Si. Microstructural evaluation of the reaction layers as well as matrix regions around the fibers is presented.

  5. Supersaturated Al(Ti) solid solutions with partial L1{sub 2} ordering prepared by mechanical alloying

    SciTech Connect

    Fan, G.J.; Quan, M.X.; Hu, Z.Q.

    1995-08-01

    The authors report phase formation during mechanical alloying of Al rich Ti-Al powder blends. Their experimental results further support the idea that the synthesis of Al rich supersaturated solid solutions in the Al-Ti system occurs in the following two steps. First, the ordered L1{sub 2}-Al{sub 3}Ti intermetallic compound is formed at Al/Ti interfaces. Second, the ordered L1{sup 2}-Al{sub 3}Ti compound was partially disordered by mechanical deformation. Meanwhile, Ti or Al atoms dissolve into the partially disordered phase and a supersaturated solid solution is finally obtained. However, the disordering is not complete and the resulting alloys may exhibit partial L1{sub 2} ordering.

  6. Al-TiC Composites Fabricated by a Thermally Activated Reaction Process in an Al Melt Using Al-Ti-C-CuO Powder Mixtures. Part I: Microstructural Evolution and Reaction Mechanism

    NASA Astrophysics Data System (ADS)

    Cho, Young-Hee; Lee, Jung-Moo; Kim, Su-Hyeon

    2014-11-01

    Al matrix composites reinforced with TiC particles are fabricated by a thermally activated reaction of Al-Ti-C powder mixtures in an Al melt. In the presence of CuO, reactant mixtures in the form of a pellet added to molten Al at temperatures higher than 1093 K (820 °C) instantly reach the peak temperature over 1785 K (1512 °C), followed by combustion wave propagation with in situ synthesizing TiC with a size of approximately 1 μm. Incomplete reaction products such as unreacted C, Al3Ti, and TiC aggregates are also observed. The pellet microstructure evolution upon the combustion reaction indicates that preheating temperature, i.e., the initial melt temperature, affects both the thermodynamic and kinetic characteristics of the reaction, and thereby influences the final microstructure of the Al/TiC composites. Based on the experimental and theoretical results, a sequence of the reaction leading upto the in situ synthesis of TiC is illustrated and the corresponding mechanism for the present process is proposed.

  7. Improved hydrogen storage kinetics of nanoconfined NaAlH₄ catalyzed with TiCl₃ nanoparticles.

    PubMed

    Nielsen, Thomas K; Polanski, Marek; Zasada, Dariusz; Javadian, Payam; Besenbacher, Flemming; Bystrzycki, Jerzy; Skibsted, Jørgen; Jensen, Torben R

    2011-05-24

    Nanoparticles of NaAlH(4) have been infiltrated in nanoporous carbon aerogel with TiCl(3) nanoparticles in order to explore possible synergetic effects between nanoconfinement and a functionalized catalytic scaffold. Resorcinol formaldehyde carbon aerogels with an average pore size of 17 nm and total pore volume of 1.26 mL/g were infiltrated with TiCl(3) to obtain an aerogel doped with 3.0 wt % TiCl(3) nanoparticles. NaAlH(4) was melt-infiltrated into the functionalized carbon aerogel at 189 °C and p(H(2)) ∼ 186-199 bar. Energy-dispersive spectrometry (EDS) combined with focused ion beam (FIB) techniques revealed the presence of Na, Al, Ti, and Cl inside the aerogel scaffold material. The infiltrated NaAlH(4) was X-ray amorphous, whereas (27)Al magic-angle spinning (MAS) NMR spectroscopy confirmed the presence of nanoconfined NaAlH(4). Temperature-programmed desorption mass spectroscopy (TPD-MS) and Sieverts' measurements demonstrated significantly improved hydrogen desorption kinetics for this new nanoconfined NaAlH(4)-TiCl(3) material as compared to nanoconfined NaAlH(4) without the catalysts TiCl(3) and to bulk ball-milled samples of NaAlH(4)-TiCl(3). We find that the onset temperature for hydrogen release was close to room temperature (T(onset) = 33 °C), and the hydrogen release rate reached a maximum value at 125 °C, which demonstrates favorable synergetic effects between nanoconfinement and catalyst addition. PMID:21446760

  8. Characteristics of Ti(C, N)/TiB composite layer on Ti-6Al-4V alloy produced by laser surface melting

    NASA Astrophysics Data System (ADS)

    Zeng, Xian; Yamaguchi, Tomiko; Nishio, Kazumasa

    2016-06-01

    A Ti(C, N)/TiB reinforced titanium matrix composite layer was successfully in-situ synthesized by laser melting on Ti-6Al-4V alloy surface with Ti-BN-C mixed powder, aiming at improving the wear resistance. The microstructure, chemical composition, hardness and wear behavior were analyzed. The results showed that, the cross sectional microstructure can be clearly divided into three parts, which were the laser melted layer, heat affected zone and non-affected zone. The reinforcements in laser melted layer consisted of dendritic TiC0.3N0.7 phases and fine-structure TiB phases. The matrix in laser melted layer was in a two-phase structure, being composed of platelet α titanium and intergranular β titanium. The hardness was increased from 320 HV in the substrate to 450-550 HV in the modified layer. The wear resistance was improved that, the wear volume loss of the laser treated sample was approximately half of the as received Ti-6Al-4V alloy after 8 h wear test.

  9. Electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys for biomedical applications.

    PubMed

    Lu, Jinwen; Zhao, Yongqing; Niu, Hongzhi; Zhang, Yusheng; Du, Yuzhou; Zhang, Wei; Huo, Wangtu

    2016-05-01

    The present study is to investigate the microstructural characteristics, electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys with Fe addition for biomedical application, and Ti-6Al-4V alloy with two-phase (α+β) microstructure is also studied as a comparison. Microstructural characterization reveals that the phase and crystal structure are sensitive to the Fe content. Ti-6Al alloy displays feather-like hexagonal α phase, and Ti-6Al-1Fe exhibits coarse lath structure of hexagonal α phase and a small amount of β phase. Ti-6Al-2Fe and Ti-6Al-4Fe alloys are dominated by elongated, equiaxed α phase and retained β phase, but the size of α phase particle in Ti-6Al-4Fe alloy is much smaller than that in Ti-6Al-2Fe alloy. The corrosion resistance of these alloys is determined in SBF solution at 37 °C. It is found that the alloys spontaneously form a passive oxide film on their surface after immersion for 500 s, and then they are stable for polarizations up to 0 VSCE. In comparison with Ti-6Al and Ti-6Al-4V alloys, Ti-6Al-xFe alloys exhibit better corrosion resistance with lower anodic current densities, larger polarization resistances and higher open-circuit potentials. The passive layers show stable characteristics, and the wide frequency ranges displaying capacitive characteristics occur for high iron contents. Elasticity experiments are performed to evaluate the elasticity property at room temperature. Ti-6Al-4Fe alloy has the lowest Young's modulus (112 GPa) and exhibits the highest strength/modulus ratios as large as 8.6, which is similar to that of c.p. Ti (8.5). These characteristics of Ti-6Al-xFe alloys form the basis of a great potential to be used as biomedical implantation materials. PMID:26952395

  10. Ab initio molecular dynamics studies on effect of Zr on oxidation resistance of TiAlN coatings

    NASA Astrophysics Data System (ADS)

    Pi, Jingwu; Kong, Yi; Chen, Li; Du, Yong

    2016-08-01

    It was demonstrated experimentally that doping Zr into TiAlN coatings at room temperature will detriment its oxidation resistance. On the other hand, there are evidences that doping Zr into TiAlN at high temperature will improve coating's oxidation resistance. In the present work, we address the effect of Zr on the oxidation resistance of TiAlN by means of ab initio molecular dynamics simulations. The TiAlN and TiAlZrN (1 Zr atom replacing 1 Ti atom) surfaces covered with 4 oxygen atoms at 300 K and 1123 K were simulated. Based on the analysis of the atomic motion, bond formation after relaxation, and the charge density difference maps we find that at 300 K, the addition of Zr induces escape of Ti atoms from the surface, resulting in formation of surface vacancies and subsequently TiO2. Comparison of metal-oxygen dimers in the vacuum and above the TiAlZrN surface further shows that the addition of Zr in the TiAlN surface will change the lowest bonding energy sequence from Zrsbnd O < Tisbnd O < Alsbnd O in the vacuum to Tisbnd O < Zrsbnd O < Alsbnd O above the TiAlZrN surface. From Molecular Dynamics simulations at 1123 K, it is find that no Ti vacancies were generated in the surface. Moreover, less charge is transferred from metal to N atoms and the bond lengths between Ti and O atoms become shorter at 1123 K as compared with 300 K, suggesting that the addition of Zr atom promotes the interaction of Ti and O at TiAlZrN surface at 1123 K, leading to a more stable surface. Our simulation explains why Zr-doping at 1123 K increases TiAlN coating's oxidation resistance while at 300 K reduces its oxidation resistance.

  11. Localized moment in Mn-doped γ-TiAl alloys

    NASA Astrophysics Data System (ADS)

    Coletti, J.; Suresh Babu, V.; Pavlovic, A. S.; Seehra, Mohindar S.

    1990-12-01

    For the γ-phase Ti50-xMnxAl50 alloys (x=0, 0.06, 0.77, 1.85, and 3.30), lattice parameters by x-ray diffraction and temperature dependence (5-300 K) of the magnetic susceptibility are measured. With Mn doping, the tetragonality of the L10 unit cell of γ-TiAl decreases and a localized moment μ~=2.31μB/Mn atom appears. The results can be explained in terms of Mn substituting for Ti, although a theoretical understanding of the small magnitude of the moment is still lacking.

  12. Thermal vacancy formation and positron-vacancy interaction in Ti3Al at high temperatures

    NASA Astrophysics Data System (ADS)

    Würschum, R.; Kümmerle, E. A.; Badura-Gergen, K.; Seeger, A.; Herzig, Ch.; Schaefer, H.-E.

    1996-07-01

    In order to study the formation of thermal vacancies in the Ti-Al alloy system, high-temperature positron lifetime measurements together with a modeling of defect formation in the framework of nearest-neighbor pair bonds were performed for α2Ti3Al and compared to recent results on γTiAl [U. Brossmann, R. Würschum, K. Badura, and H.-E. Schaefer, Phys. Rev. B 49, 6457 (1994)]. Substantial increases of the positron lifetime τ were observed for Ti65.6Al34.4 and Ti77.1Al22.9 in the temperature range T≳1200 K where thermal vacancy concentrations above the detection limit of positron annihilation are expected from the model calculations for the α2 phase. Within the high-temperature increase of the positron lifetime in the α2 and the β phase single-component positron lifetime spectra were observed. This behavior is in contrast to the two-component spectra observed conventionally at intermediate positron trapping rates and is attributed to a fast detrapping and retrapping of positrons at vacancies due to a low positron-vacancy binding energy. For this case, a vacancy formation enthalpy of HFV=(1.55±0.2) eV in α2Ti65.6Al34.4 and HFV=(1.8±0.2) eV in βTi77.1Al22.9 can be derived. These results are discussed in the context of recent 44Ti tracer diffusion studies.

  13. Microstructure and tribological behaviors of Ti6Al4V alloy treated by plasma Ni alloying

    NASA Astrophysics Data System (ADS)

    Wang, Zhenxia; He, Zhiyong; Wang, Yingqin; Liu, Xiaoping; Tang, Bin

    2011-09-01

    Ni modified layer was prepared on surface of the Ti6Al4V substrate by plasma surface alloying technique. Surface morphology, micro-structure, composition distribution, phase structure, and microhardness of the Ni modified layer were analyzed. Tribological performance of the Ni modified layer and Ti6Al4V substrate was investigated by using pin-on-disc tribometer. The results indicate that roughness of the Ni modified layer was increased due to formation of the micro-convex on the modified surface. The concentration of Ni gradually decreased from the surface to interior. The maximum content of Ni atoms was nearly 90%. The modified layer was composed of TiNi, Ti2Ni and Ti phases. The maximum microhardness of the Ni modified layer was about 677 HV0.025 which was increased about two-fold of microhardness of the control Ti6Al4V substrate. Wear resistance of the Ni modified layer was improved obviously, and showed micro-abrasion wearing. The strengthened mechanism of the as-treated Ti6Al4V alloy is discussed.

  14. Corrosion behavior of cast Ti-6Al-4V alloyed with Cu.

    PubMed

    Koike, Marie; Cai, Zhuo; Oda, Yutaka; Hattori, Masayuki; Fujii, Hiroyuki; Okabe, Toru

    2005-05-01

    It has recently been found that alloying with copper improved the inherently poor grindability and wear resistance of titanium. This study characterized the corrosion behavior of cast Ti-6Al-4V alloyed with copper. Alloys (0.9 or 3.5 mass % Cu) were cast with the use of a magnesia-based investment in a centrifugal casting machine. Three specimen surfaces were tested: ground, sandblasted, and as cast. Commercially pure titanium and Ti-6Al-4V served as controls. Open-circuit potential measurement, linear polarization, and potentiodynamic cathodic polarization were performed in aerated (air + 10% CO(2)) modified Tani-Zucchi synthetic saliva at 37 degrees C. Potentiodynamic anodic polarization was conducted in the same medium deaerated by N(2) + 10% CO(2). Polarization resistance (R(p)), Tafel slopes, and corrosion current density (I(corr)) were determined. A passive region occurred for the alloy specimens with ground and sandblasted surfaces, as for CP Ti. However, no passivation was observed on the as-cast alloys or on CP Ti. There were significant differences among all metals tested for R(p) and I(corr) and significantly higher R(p) and lower I(corr) values for CP Ti compared to Ti-6Al-4V or the alloys with Cu. Alloying up to 3.5 mass % Cu to Ti-6Al-4V did not change the corrosion behavior. Specimens with ground or sandblasted surfaces were superior to specimens with as-cast surfaces. PMID:15744719

  15. Micromechanism in Self-Lubrication of TiB2/Al Composite.

    PubMed

    Zhou, Xin; Jiang, Longtao; Lei, Shengbin; Tian, Wei Quan; Wu, Gaohui

    2015-06-17

    The authors discovered the self-lubrication behavior of TiB2/Al composite and pointed out that the materials responsible for the self-lubrication behavior comes from the oxidation of TiB2. Atomic/friction force microscopy and first-principles calculations have been employed to study the self-lubrication microscopic mechanism of TiB2/Al composite. Atomic force microscopy confirms the existence of a soft film with nanometer thickness on the TiB2 surface, which was attributed to H3BO3 film. Friction measurements revealed much smaller friction force on this H3BO3 nanofilm than that on Al matrix. The detailed structure and interactions among H3BO3 molecules and between the H3BO3 sheet and substrate were explored by density functional theory based calculations. The details of adsorption of H3BO3 sheet on TiB2 and TiO2 surface were scrutinized and the potential of the relative movement between H3BO3 sheets were scanned and compared with that of graphite. The generation of H3BO3 film, the strong chemical adsorption of H3BO3 film on the surface of the composite, the strong hydrogen bonding in H3BO3 film, and small potential in the relative slide between H3BO3 sheets warrant the good self-lubricant properties of TiB2/Al metal matrix composites. PMID:26010553

  16. Fixation of bioactive calcium alkali phosphate on Ti6Al4V implant material with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Symietz, Christian; Lehmann, Erhard; Gildenhaar, Renate; Koter, Robert; Berger, Georg; Krüger, Jörg

    2011-04-01

    Bone implants made of metal, often titanium or the titanium alloy Ti6Al4V, need to be surface treated to become bioactive. This enables the formation of a firm and durable connection of the prosthesis with the living bone. We present a new method to uniformly cover Ti6Al4V with a thin layer of ceramics that imitates bone material. These calcium alkali phosphates, called GB14 and Ca10, are applied to the metal by dip coating of metal plates into an aqueous slurry containing the fine ceramic powder. The dried samples are illuminated with the 790 nm radiation of a pulsed femtosecond laser. If the laser fluence is set to a value just below the ablation threshold of the ceramic (ca. 0.4 J/cm 2) the 30 fs laser pulses penetrate the partly transparent ceramic layer of 20-40 μm thickness. The remaining laser fluence at the ceramic-metal interface is still high enough to generate a thin metal melt layer leading to the ceramic fixation on the metal. The laser processing step is only possible because Ti6Al4V has a lower ablation threshold (between 0.1 and 0.15 J/cm 2) than the ceramic material. After laser treatment in a fluence range between 0.1 and 0.4 J/cm 2, only the particles in contact with the metal withstand a post-laser treatment (ultrasonic cleaning). The non-irradiated rest of the layer is washed off. In this work, we present results of a successful ceramic fixation extending over larger areas. This is fundamental for future applications of arbitrarily shaped implants.

  17. Electrical properties of palladium-doped CaCu3Ti4O12 ceramics

    NASA Astrophysics Data System (ADS)

    Singh, Arashdeep; Md Mursalin, Sk.; Rana, P.; Sen, Shrabanee

    2015-09-01

    The effect of doping palladium (Pd) at the Cu site of CaCu3Ti4O12 powders (CCPTO) synthesized by sol-gel technique on electrical properties was studied. XRD analysis revealed the formation of CCTO and CCPTO ceramics with some minor quantities of impurities. SEM micrographs revealed that the grain size decreased with Pd doping. TEM micrographs of CCPTO powder showed the formation of irregular-shaped particles of ~40 nm. The dielectric constant and dielectric loss showed a significant enhancement with Pd doping. A significant decrease in grain-boundary resistance with Pd doping was ascertained by impedance spectroscopy study.

  18. On the electron affinities of the Ca, Sc, Ti and Y atoms

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

    1988-01-01

    For the Ca, Sc, Ti and Y atoms calculations are performed for the ground states of the neutrals and the ground and several low-lying excited states of the negative ions. Overall the computed electron affinities are in good accord with experiment. The calculations show the rapid stabilization of the 3d orbital relative to the 4p as the nuclear charge increases. The 3F(0) and 3D(0) terms are found to be close in energy in Sc(-) and in Y(-). This confirms earlier speculation that some of the peaks in the photodetachment spectra of Y(-) originate from the bound excited 3F(0) term of Y(-).

  19. Improving the osteointegration of Ti6Al4V by zeolite MFI coating.

    PubMed

    Li, Yong; Jiao, Yilai; Li, Xiaokang; Guo, Zheng

    2015-05-01

    Osteointegration is crucial for success in orthopedic implantation. In recent decades, there have been numerous studies aiming to modify titanium alloys, which are the most widely used materials in orthopedics. Zeolites are solid aluminosilicates whose application in the biomedical field has recently been explored. To this end, MFI zeolites have been developed as titanium alloy coatings and tested in vitro. Nevertheless, the effect of the MFI coating of biomaterials in vivo has not yet been addressed. The aim of the present work is to evaluate the effects of MFI-coated Ti6Al4V implants in vitro and in vivo. After surface modification, the surface was investigated using field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). No difference was observed regarding the proliferation of MC3T3-E1 cells on the Ti6Al4V (Ti) and MFI-coated Ti6Al4V (M-Ti) (p > 0.05). However, the attachment of MC3T3-E1 cells was found to be better in the M-Ti group. Additionally, ALP staining and activity assays and quantitative real-time RT-PCR indicated that MC3T3-E1 cells grown on the M-Ti displayed high levels of osteogenic differentiation markers. Moreover, Van-Gieson staining of histological sections demonstrated that the MFI coating on Ti6Al4V scaffolds significantly enhanced osteointegration and promoted bone regeneration after implantation in rabbit femoral condylar defects at 4 and 12 weeks. Therefore, this study provides a method for modifying Ti6Al4V to achieve improved osteointegration and osteogenesis. PMID:25757911

  20. Two-dimensional conductivity at LaAlO3/SrTiO 3 interfaces

    NASA Astrophysics Data System (ADS)

    Raslan, Amany

    Experiments have observed a two-dimensional electron gas at the interface of two insulating oxides: strontium titanate (SrTiO3) and lanthanum aluminate (LaAlO3). These interfaces exhibit metallic, superconducting, and magnetic behaviours, which are strongly affected by impurities. Motivated by experiments, we introduce a simple model in which impurities lie at the interface. We treat the LaAlO3 as an insulator and model the SrTiO 3 film. By solving a set of self-consistent Hartree equations for the charge density, we obtain the band structure of the SrTiO3 film. We then study the relative contributions made by the occupied bands to the two-dimensional conductivity of the LaAlO3/SrTiO 3 interface. We find that the fractional conductivity of each band depends on several parameters: the mass anisotropy, the filling, and the impurity potential.

  1. Dielectric and electromechanical properties of LiNbO3-modified (BiNa)TiO3-(BaCa)TiO3 lead-free piezoceramics

    NASA Astrophysics Data System (ADS)

    Zaman, Arif; Hussain, Ali; Malik, Rizwan Ahmed; Maqbool, Adnan; Nahm, Sahn; Kim, Myong-Ho

    2016-05-01

    The dielectric and electromechanical properties of LiNbO3-modified (1-x) [0.91Na0.5Bi0.5TiO3-0.09Ba0.70Ca0.30TiO3]-xLiNbO3 (abbreviated as (BiNa)TiO3-(BaCa)TiO3-LN) lead-free piezoceramics were investigated. The electrical properties revealed that the addition of LiNbO3 (LN) induces a phase transition from a non-ergodic relaxor to an ergodic relaxor in the (BiNa)TiO3-(BaCa)TiO3-LN system. A large electrostrain of ~0.418% with a normalized strain of ~690 pm V-1 at 6 kV mm-1 was observed at the coexistence of the non-ergodic relaxor and ergodic relaxor phases for LN 0.020, where a field-assisted reversible phase transition between metastable ferroelectric and stable ergodic relaxor phases occurs. Subsequently, a gradual enhancement in the temperature stability of the dielectric constant was observed. At 3 mol.% LN, a nearly constant temperature and a frequency-invariant permittivity of ɛ r ~ 3300 over a broad temperature range of 147 °C-306 °C was observed along with small losses from room temperature up to 400 °C.

  2. Effect of substrate temperature and gas flow ratio on the nanocomposite TiAlBN coating

    NASA Astrophysics Data System (ADS)

    Rosli, Z. M.; Kwan, W. L.; Juoi, J. M.

    2016-07-01

    Nanocomposite TiAlBN (nc-TiAlBN) coatings were successfully deposited via RF magnetron sputtering by varying the nitrogen-to-total gas flow ratio (RN), and substrate temperature (TS). All coatings were deposited on AISI 316 substrates using single Ti-Al-BN hot-pressed disc as a target. The grain size, phases, and chemical composition of the coatings were evaluated using glancing angle X-ray diffraction analysis (GAXRD) and X-ray photoelectron spectroscopy (XPS). Results showed that the grains size of the deposited nc-TiAlBN coatings were in the range of 3.5 to 5.7 nm and reached a nitride saturation state as early as 15 % RN. As the nitrogen concentration decreases, boron concentration increased from 9 at.% to 16.17 at.%. and thus, increase the TiB2 phase within the coatings. The TS, however, showed no significant effect either on the crystallographic structure, grain size, or in the chemical composition of the deposited nc-TiAlBN coating.

  3. Investigation of boron distribution in a TiAl-based alloy using particle-tracking

    SciTech Connect

    Pu, Z.; Wu, K.H.

    1996-01-01

    One of the key shortcomings of current TiAl intermetallic alloy is the inverse relationship between tensile properties and fracture/creep resistance. TiAl-based alloys with a fully lamellar structure generally display`s high fracture toughness and creep resistance, but poor ductility. Inversely, material with a duplex microstructure has very good ductility, but poor fracture toughness and creep resistance. Research efforts have focused on overcoming this deficiency. Now that it is widely accepted that the poor ductility of lamellar structures originates from the large grain size, refining the lamellar structure of TiAl-based alloys presents itself as a feasible solution. The question remains as to how to accomplish this goal. Microalloying is considered one approach for refining the fully lamellar structure. The present authors have reported that the addition of boron can effectively refine the grain size of fully lamellar structure. However, the distribution of boron in TiAl alloys and the mechanism in boron that suppresses grain growth are not yet clear. In the present paper, the distribution of boron in a Ti-rich TiAl-based alloy, as a function of the bulk boron content, annealing temperature, and thermomechanical process, is analyzed using a Particle-Tracking Autoradiography (PTA) technique.

  4. Thermal conductivity of PVD TiAlN films using pulsed photothermal reflectance technique

    NASA Astrophysics Data System (ADS)

    Ding, Xing-Zhao; Samani, M. K.; Chen, George

    2010-11-01

    In the present work, we have measured thermal-conductivity of industrial thin film TiAlN with a thickness of around 3 μm. These films are used in machining industry for cutting tools in order to increase their service life. A series of TiAlN coating with a different Al/Ti atomic ratio were deposited on Fe-304 stainless steel (AISI304) substrate by a lateral rotating cathode arc process. The samples were then coated with a 0.8 μm gold layer on top by magnetron sputtering. We present the thermal-conductivity measurement of these samples using pulsed photothermal reflectance (PPR) technique at room temperature. The thermal conductivity of the pure TiN coating is about 11.9 W/mK. A significant decrease in thermal conductivity was found with increasing Al/Ti atomic ratio. A minimum thermal conductivity of about 4.63 W/mK was obtained at the Al/Ti atomic ratio of around 0.72.

  5. Adhesion and corrosion behavior of Al-Zn and TiN/Ti/TiN coatings on a Du-0.75 wt% ti alloy. (Reannouncement with new availability information)

    SciTech Connect

    Chang, F.C.; Levy, M.; Huie, R.; Kane, M.; Buckley, P.

    1992-08-01

    Al-Zn alloy and multilayer TiN/Ti/TiN thin coatings were deposited on DU-0; 75Ti alloy specimens by a cathodic arc plasma physical vapor deposition process. The quality, soundness and adhesion of the coatings to the substrate were evaluated by automatic scratch testing, in combination with optical and scanning electron microscopy examination of the scratch morphology. The galvanic corrosion behavior of DU-0.75Ti alloy coupled to the coated alloys and aluminum alloy 7075-T6 was also investigated by electrochemical tests in a 0.5 N NaCl aqueous solution.

  6. Investigation of thermal atomic layer deposited TiAlX (X = N or C) film as metal gate

    NASA Astrophysics Data System (ADS)

    Xiang, Jinjuan; Zhang, Yanbo; Li, Tingting; Wang, Xiaolei; Gao, Jianfeng; Yin, Huaxiang; Li, Junfeng; Wang, Wenwu; Ding, Yuqiang; Xu, Chongying; Zhao, Chao

    2016-08-01

    TiAlX (X = N or C) films are developed by thermal atomic layer deposition (ALD) technique as metal gate. The TiAlX films are deposited by using four different combinations of precursors: A: TiCl4-NH3-TMA-NH3, B: TiCl4-TMA-NH3, C: TiCl4-NH3-TMA and D: TiCl4-TMA. The physical characteristics of the TiAlX films such as chemical composition, growth rate, resistivity and surface roughness are estimated by X-ray photoemission spectroscopy, scanning electron microscope, four point probe method and atomic force microscopy respectively. Additionally, the electrical characteristics of the TiAlX films are investigated by using metal-oxide-semiconductor (MOS) capacitor structure. It is shown that NH3 presence in the reaction makes the film more like TiAlN(C) while NH3 absence makes the film more like TiAlC. The TiAlC film deposited by TiCl4-TMA has effective work function close to mid-gap of Si, which is rather potential for low power FinFET device application.

  7. Effect of AL2O3 and TiO2 nanoparticles on aquatic organisms

    NASA Astrophysics Data System (ADS)

    Gosteva, I.; Morgalev, Yu; Morgaleva, T.; Morgalev, S.

    2015-11-01

    Environmental toxicity of aqueous disperse systems of nanoparticles of binary compounds of titanium dioxides (with particle size Δ50=5 nm, Δ50=50 nm, Δ50=90 nm), aluminum oxide alpha-forms (Δ50=7 nm and Δ50=70 nm) and macro forms (TiO2 Δ50=350 nm, Al2O3 A50=4000 nm) were studied using biological testing methods. The bioassay was performed using a set of test organisms representing the major trophic levels. We found the dependence of the toxic effect concentration degree of nTiO2 and nAl2O3 on the fluorescence of the bacterial biosensor "Ekolyum", the chemotactic response of ciliates Paramecium caudatum, the growth of unicellular algae Chlorella vulgaris Beijer and mortality of entomostracans Daphnia magna Straus. We revealed the selective dependence of nTiO2 and nAl2O3 toxicity on the size, concentration and chemical nature of nanoparticles. The minimal concentration causing an organism's response on nTiO2 and nAl2O3 effect depends on the type of the test- organism and the test reaction under study. We specified L(E)C50 and acute toxicity categories for all the studied nanoparticles. We determined that nTiO2 (Δ50=5 nm) belong to the category «Acute toxicity 1», nTiO2 (A50=90 nm) and nAl2O3 (Δ50=70 nm) - to the category «Acute toxicity 2», nAl2O3 (Δ50=7 nm) - to the category «Acute toxicity 3». No acute toxicity was registered for nTiO2 (Δ50=50 nm) and macro form TiO2.

  8. Structural properties of Al and TiAl3 metallic glasses — An embedded atom method study

    NASA Astrophysics Data System (ADS)

    Tahiri, M.; Trady, S.; Hasnaoui, A.; Mazroui, M.; Saadouni, K.; Sbiaai, K.

    2016-06-01

    In this paper, we investigated the structural properties of metallic glasses (MGs). We emphasized our study on monatomic Al and binary TiAl3 systems. The calculations are performed by using the molecular dynamics (MD) simulation based on semi-empirical many-body potentials derived from the embedded atom method. The structure is analyzed using the radial distribution function (RDF), the common neighbor analysis (CNA) and the coordination numbers (CNs). Our results demonstrated that it is possible to form MGs in both systems upon fast cooling from the liquid state. This is confirmed by the fact that the system energy and/or volume during the cooling stage decrease continuously with a slight change and by atomic scale analysis using the RDF, CNA and CN analyzing techniques. Furthermore, this specific study shows that under the same conditions, the icosahedral structures appeared in TiAl3 are more abundant than in pure Al. Implications of these findings are discussed.

  9. The preparation and properties of composite materials based on cubic titanium trialuminide. [64Al28Ti8Fe; 67Al25Ti8Mn

    SciTech Connect

    Morris, D.G.; Leboeuf, M. )

    1993-04-01

    Intermetallics based on Al[sub 3]Ti, particularly when alloyed to the more highly symmetric L1[sub 2] cubic crystal structure, show good strength over the temperature range from room temperature up to about 700C and good oxidation resistance. Unfortunately these materials have poor ambient temperature ductility and toughness. An obvious way to improve this low toughness is to make use of composite philosophy, namely to incorporate second phase ductile particles which could act as crack bridges and delay failure. This article describes some experiments along these lines which show in particular the major problems of reactions occurring during consolidation of powder-source materials, and of internal cracking brought about by differential thermal dilations. The potential of these methods of material preparation for bringing about improvements in toughness of these intermetallics is discussed. Gas atomized powders of two cubic titanium trialuminide alloys were used for the present experiments. These powders were of composition 64% Al, 28% Ti and 8% Fe and 67% Al, 25% Ti and 8% Mn and had mean sizes of about 50[mu]m. Small quantities of powder were mixed with selected elemental powders in the desired proportions and the mixtures were consolidated in steel cans by HIP under a pressure of 100MPa at 1,140 C for 3h followed by slow cooling. The composite materials prepared were: using the Al-Ti-Fe matrix - additions of pure Fe powder in volume proportions of 1.4%, 2.7% and 5.5%; using the Al-Ti-Mn matrix - additions of pure V, Nb or W powders in a constant volume proportion of about 3.6%.

  10. Surface Properties of the IN SITU Formed Ceramics Reinforced Composite Coatings on TI-3AL-2V Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Guo, Wei; Hu, Dakui; Luo, Hui; Zhang, Yuanbin

    2012-04-01

    The synthesis of hard composite coating on titanium alloy by laser cladding of Al/Fe/Ni+C/Si3N4 pre-placed powders has been investigated in detail. SEM result indicated that a composite coating with metallurgical joint to the substrate was formed. XRD result indicated that the composite coating mainly consisted of γ-(Fe, Ni), FeAl, Ti3Al, TiC, TiNi, TiC0.3N0.7, Ti2N, SiC, Ti5Si3 and TiNi. Compared with Ti-3Al-2V substrate, an improvement of the micro-hardness and the wear resistance was observed for this composite coating.

  11. Characterisation of Sol-Gel Synthesis of Phase Pure CaTiO3 Nano Powders after Drying

    NASA Astrophysics Data System (ADS)

    Mallik, P. K.; Biswal, G.; Patnaik, S. C.; Senapati, S. K.

    2015-02-01

    According to a few recent studies, calcium titanate (CT) is a material that is similar to hydroxyapatite in biological properties. However, calcium titanate is not currently being used in the biomedical applications as to hydroxyapatite. The objective is to prepare nano calcium titanate powders from the equimolar solution of calcium oxide, ethanol and Titanium (IV) isopropoxide via sol-gel synthesis. The phase analysis and morphology of powder particles were studied by X-ray diffraction (XRD), while the composition and size of powder particles were determined by Transmission electron microscope (TEM) attached with energy dispersive x-ray spectrometer (EDS). As results, XRD confirm the presence of phase pure crystalline CaTiO3 after drying at 100°C for 24 hours, while TEM analysis confirms about 13 nm sizes of CaTiO3 particles and some agglomerated particle of 20-30 nm. Moreover, EDS analysis indicates that the approximately stoichiometric Ca/Ti ratio 1:1 was obtained in the CaTiO3 powders. Finally, it can be concluded that described sol-gel synthesis could be novel method for the production of nano CaTiO3 particles at lower temperature compared to any other methods of production.

  12. Characterization and mechanical properties investigation of TiN-Ag films onto Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Du, Dongxing; Liu, Daoxin; Zhang, Xiaohua; Tang, Jingang; Xiang, Dinggen

    2016-03-01

    To investigate their effect on fretting fatigue (FF) resistance of a Ti-6Al-4V alloy, hard solid lubricating composite films of TiN with varying silver contents (TiN-Ag) were deposited on a Ti-6Al-4V alloy using ion-assisted magnetron sputtering. The surface morphology and structure were analyzed by atomic force microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and transmission electron microscopy. The hardness, bonding strength, and toughness of films were tested using a micro-hardness tester, scratch tester, and a repeated press-press test system that was manufactured in-house, respectively. The FF resistance of TiN-Ag composite films was studied using self-developed devices. The results show that the FF resistance of a titanium alloy can be improved by TiN-Ag composite films, which were fabricated using hard TiN coating doped with soft Ag. The FF life of Ag0.5, Ag2, Ag5, Ag10 and Ag20 composite films is 2.41, 3.18, 3.20, 2.94 and 2.87 times as great as that of the titanium alloy, respectively. This is because the composite films have the better toughness, friction lubrication, and high bonding strength. When the atomic fraction of Ag changes from 2% to 5%, the FF resistance of the composite films shows the best performance. This is attributed to the surface integrity of the composite film is sufficiently fine to prevent the initiation and early propagation of FF cracks.

  13. Structure and dielectric properties of Na0.5Bi0.5TiO3-CaTiO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Birks, E.; Dunce, M.; Ignatans, R.; Kuzmin, A.; Plaude, A.; Antonova, M.; Kundzins, K.; Sternberg, A.

    2016-02-01

    Despite wide studies of Na0.5Bi0.5TiO3, structure of this material and its connection with the observed physical properties still raise numerous questions due to mutually contradicting results obtained. Here, structure and dielectric properties of poled and unpoled Na0.5Bi0.5TiO3-CaTiO3 solid solutions are studied, projecting the obtained concentration dependence of structure and dielectric properties on pure Na0.5Bi0.5TiO3 as the end member of this material group. X-ray diffraction patterns for Na0.5Bi0.5TiO3-CaTiO3 solid solutions reveal dominating of an orthorhombic Pnma phase, even for the compositions approaching the end composition (Na0.5Bi0.5TiO3), whereas structure of pure Na0.5Bi0.5TiO3 can be considered, assuming coexistence of rhombohedral and orthorhombic phases. This allows one to avoid appearance of a large difference of rhombohedral distortions between the unpoled and poled Na0.5Bi0.5TiO3, if the rhombohedral distortion is calculated as for single R3c phase. Features of dielectric permittivity, corresponding to the observed structural phase transition, are identified. It is discussed that the rhombohedral R3c phase is responsible for appearance of the frequency-dependent shoulder of dielectric permittivity temperature dependence, characteristic for unpoled Na0.5Bi0.5TiO3.

  14. A new phase in rapidly solidified Ti[sub 3]Al-based alloys

    SciTech Connect

    Xu Rui; Xu Daming; Li Qingchun . Dept. of Materials Science and Engineering); Li Dong; Cui Yuyou; Hu Zhuangqi . State Key Lab. for RSA)

    1995-01-15

    Rapid solidification processing has been developed to improve the properties of alloys through refining microstructures, disordering and forming metastable phases. The as-melt spun Ti[sub 3]Al-based alloy with Nb additions above 5-at%, which consist of [alpha][sub 2] and [beta][sub 0] phases in a normal condition, exhibited as single [beta][sub 0] structure. Jackson et al have carried out a comparative study of I/M and RS Ti[sub 3]Al-1 Zr(at%) alloy. Their study revealed that considerable refinement of grains and anti-phase domains was achieved in the rapidly solidified material prepared by the pendant drop melt extraction process (PDME). It is suggested that rapid solidification processing can reduce the ordering of the Ti[sub 3]Al-based alloy. In the past years, it was found that the Ti[sub 3]Al-based alloy with alloying additions (mainly Nb) has been studied extensively, and some new phases such as T and O have been observed in the alloys, but less attention has been given to alloys with low Nb additions. The RS Ti[sub 3]Al-base alloys with Nb below 5-at% have been investigated systematically and a new metastable phase, ordering martensite [alpha][double prime][sub 0] (orthogonal), has been observed in these alloys.

  15. Mechanical and corrosion properties of Al/Ti film on magnesium alloy AZ31B

    NASA Astrophysics Data System (ADS)

    Zeng, Rong-Chang; Jiang, Ke; Li, Shuo-Qi; Zhang, Fen; Cui, Hong-Zhi; Han, En-Hou

    2015-03-01

    Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coatings were deposited on magnesium alloy AZ31B using magnetron sputtering (MS). The low temperature diffusion bonding behavior of the Mg/Al/Ti coating was investigated through SEM and its affiliated EDS. The phase structure and critical load of the coatings were examined by means of XRD and scratch tests, respectively. The results demonstrated that the bonding strength was significantly improved after a post heat treatment (HT) at a temperature of 210°C. The diffusion mechanism of the interfaces of Mg/Al and Al/Ti in the coating was discussed based on the analysis of formation energy of vacancies and diffusion rates. The Al/Ti dual layer enhanced the corrosion resistance of the alloy. And the HT process further increased the corrosion resistance of the coated alloy. This result implies that a post HTat a lower temperature after MS is an effective approach to enhance the bonding strength and corrosion resistance of the Al/Ti film on Mg alloys.

  16. 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.

  17. 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.

  18. Spectroscopic properties of Nd 3+ ions in nano-perovskite CaTiO 3

    NASA Astrophysics Data System (ADS)

    Lemański, K.; Gągor, A.; Kurnatowska, M.; Pązik, R.; Dereń, P. J.

    2011-10-01

    In this work, we present for the first time the spectroscopic properties of perovskite nanocrystals CaTiO 3: Nd 3+, measured at room and liquid nitrogen temperature. Samples were prepared by the sol-gel method and annealed at 700 and 1000 °C. The concentration of Nd 3+ ranged from 0.5% to 5%. Average nanocrystallite size primarily depends on the annealed temperature and is about 25 and 50 nm for 700 and 1000 °C, respectively. The absorption, emission and excitation spectra (monitored at 1078 nm) as well as the decay time profile of the emission from the 4F3/2 energy level of Nd 3+ are obtained. The increasing amount of Nd 3+ ions decreases the lifetime of the 4F3/2 level and that changes from 146 μs for 0.5% to 50 μs for 5% of Nd 3+ concentration. The strongest emission was observed at two regions: 1050-1120 nm and 865-930 nm and was assigned to the 4F3/2→ 4I11/2 and 4F3/2→ 4I9/2 transitions, respectively. The spectroscopic quality parameter of neodymium in the CaTiO 3 lattice has been calculated from the emission spectra. The influence of luminescent properties depending on the annealing temperature and concentration of neodymium ions is discussed.

  19. [Preparation and characterization of long-afterglow nanophosphors CaTiO3 : Pr].

    PubMed

    Qi, Yan; Meng, Jian-Xin; Shi, Chao-Pu; Zhang, Wen-Wen

    2007-07-01

    CaTiO3 : Pr nanophosphors were prepared with a gel-network precipitation technique using cheap inorganic precursors. The samples, being well dispersed and sphere-like with an average diameter of 100 nm, were observed with transmission electron microscope (TEM). The mechanism of coprecipitation and crystallization was discussed briefly based on TG-DTA and the X-ray diffractometer (XRD) results. The luminescent properties were investigated by the fluorescence spectrophotometer. The conditions of the preparation process were also studied systematically and the optimal conditions were concluded. The results show that the products with strongest luminescence intensity could be prepared at 1 100 degrees C for one hour, and the luminescent features of samples synthesized by the gel-network precipitation technique are similar to those by solid-state reaction, while the calcining temperature is reduced about 200 degrees C. In conclusion, uniform long-afterglow nanophosphors CaTiO3 : Pr were successfully synthesized with simple apparatus at low cost. PMID:17944396

  20. Unique local structures of Ca, Ti, Fe and Zr in natural glasses formed by meteorite impact

    NASA Astrophysics Data System (ADS)

    Yoshiasa, Akira; Tobase, Tsubasa; Okube, Maki; Wang, Ling; Isobe, Hiroshi; Mashimo, Tsutomu; Graduate School of Science; Technology Collaboration; Materials; Structures Laboratory, Tokyo Institute of Technology Collaboration

    2015-06-01

    The local structures of cation in tektite from six strewn fields, impact-related glass, and non-impact-related glass were studied by Ca, Ti, Fe and Zr K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Shock compression also causes local structural changes of gest and minor elements as well as transition of host structures. How to be left a record is peculiar by each element. The XAFS measurements were performed at the beam lines BL-NW10A and BL-9C, KEK, Japan. The comparison of XANES spectra and bonding distances between crystalline reference minerals and natural glasses was done. Based on the different valence states of iron, the degrees of oxidation states were estimated. The local structures of Ca, Ti and Zr ions are useful probe for physical conditions and formation process of glasses. Tektites experienced high quenching rates and a reduced atmospheric environment when they were ejected into outer space. Other impact-related glass, which was remained close to the crater, experienced a more complicated environment. The local structural changes of cation in the impact-related glass are rich in a variety. Analysis of local structure is help to compare their formation process and distinguish them.

  1. CaTiO3:Eu3+ red nanophosphor: low temperature synthesis and photoluminescence properties.

    PubMed

    Shivram, M; Prashantha, S C; Nagabhushana, H; Sharma, S C; Thyagarajan, K; Harikrishna, R; Nagabhushana, B M

    2014-01-01

    Nanoparticles of Eu3+ doped (1-9 mol%) CaTiO3 were prepared using low temperature (500°C) solution combustion technique using metal nitrates as precursors and urea as fuel. The powder X-ray diffraction patterns of the as-formed products show single orthorhombic phase. The crystallite size was estimated using Scherrer's method and found to be in the range 40-45 nm. The effect of Eu3+ ions on luminescence characteristics of CaTiO3 was studied and the results were discussed in detail. The phosphors exhibit bright red emission upon 398 nm excitation. The characteristic emission peaks recorded at ∼540, 593, 615, 653, 696 and 706 nm (5D0→7Fj=0,1,2,3,4,5) were attributed to Eu3+ ions. The electronic transition corresponding to 5D0→7F2 (615 nm) was stronger than the magnetic dipole transition 5D0→7F1 of Eu3+ ions (596 nm). The CIE chromaticity co-ordinates were calculated from emission spectra, the values (x,y) very close to NTSC standard value of red emission. Therefore, the present phosphors were highly useful for display applications. PMID:24211621

  2. Polarization Domain Switching of Improper Hybrid Ferroelectric (Ca,Sr)3Ti2O7 Crystals

    NASA Astrophysics Data System (ADS)

    Lim, Seong Joon; Gao, Bin; Kim, Jaewook; Huang, Fei-Ting; Cheong, Sang-Wook; RCEM Team

    The observation of switchable polarization loops at room temperature in (Ca,Sr)3Ti2O7, induced by improper hybrid ferroelectricity, has drawn much attention. Since the ferroelectric polarization directly couples with structural distortions (oxygen octahedral tilting and rotation) in hybrid improper ferroelectrics, the energy barrier for polarization switching is predicted to be large, and the observation of ferroelectric polarization loops was a surprise. Furthermore, the observed complexity of the domain wall configuration in (Ca,Sr)3Ti2O7 may complicate the domain wall motion or the domain nucleation for polarization switching. Thus, it is imperative to understand the mechanism and dynamics of polarization domain switching. Particularly, it has to be clarified if polarization switching occurs through 90° or 180° switching. Comparing piezoresponse force microscope and polarized optical microscope images before and after applying electric fields consecutively, we explored the mechanism and dynamics of polarization domain switching. This work is funded by the Gordon and Betty Moore Foundation's EPiQS Initiative through Grant GBMF4413 to the Rutgers Center for Emergent Materials.

  3. Direct Metal Deposition by Laser in TiNi-Al System for Graded Structure Fabrication

    NASA Astrophysics Data System (ADS)

    Shishkovsky, I.; Kakovkina, N.; Missemer, F.

    2016-07-01

    Intermetallic phase formation was studied in powdered TiNi-Al system under layerwise laser cladding with the aim of forming a gradient of properties due to a change in the concentration relation of Al in the NiTi powder mixture from one layer to another. The relationship between the laser cladding parameters and the intermetallic phase structures in consecutively cladded layers were determined. The structure of intermetallic compounds formed by laser synthesis was studied by optical microscopy, measurement of microhardness, SEM with EDX analysis. Microhardness doubling from 500 HV to 1000 HV was achieved due to nitinol matrix enrichment by Al, which is promising for aerospace applications.

  4. Effect of initial microstructure on the compactability of rapidly solidified Ti-rich TiAl powder

    SciTech Connect

    Nishida, M.; Chiba, A.; Morizono, Y.; Kai, T.; Sugimoto, J.

    1997-12-31

    Initial microstructure dependence of compactability at elevated temperature in rapidly solidified Ti-rich TiAl alloy powders produced by plasma rotating electrode process (PREP) has been investigated. There were two kinds of powders with respect to the microstructure. The first one had a surface relief of a martensitic phase, which was referred as M powder. The second one had a dendritic structure, which was referred as D powder. {alpha}{sub 2}+{gamma} microduplex and {alpha}{sub 2}/{gamma} lamellar structures were formed in M and D powders of the Ti-40 at%Al alloy by heat treatment at 1,273 K, respectively. The microduplex structure consisted of {gamma} precipitate in the twin related {alpha}{sub 2} matrix with the usual orientation relationship. It was difficult to compact the D powder by hot pressing at 1,273 K under 50 MPa for 14.4 ks. On the other hand, the M powder was compacted easily by hot pressing with the same condition. The twin related {alpha}{sub 2} and {alpha}{sub 2} boundary changed to random ones and the {alpha}{sub 2} and {gamma} phases lost the usual orientation relationship in the duplex structure during the hot pressing. In other words, the low energy boundaries were changed to the high energy ones suitable for grain boundary sliding. Dislocations were scarcely observed inside of both the {alpha}{sub 2} and {gamma} crystal grains. It was concluded that the grain boundary sliding was a predominant deformation mode in the M powder during the hot pressing. D and M powders in Ti-45 and 47 at%Al alloys showed the same tendency as those in Ti-40 at%Al alloy during hot pressing.

  5. Experimental and theoretical characterization of ordered MAX phases Mo{sub 2}TiAlC{sub 2} and Mo{sub 2}Ti{sub 2}AlC{sub 3}

    SciTech Connect

    Anasori, Babak; Dahlqvist, Martin; Lu, Jun; Hultman, Lars; Eklund, Per; Rosén, Johanna; Halim, Joseph; Moon, Eun Ju; Hosler, Brian C.; May, Steven J.; Barsoum, Michel W.; Caspi, El'ad N.

    2015-09-07

    Herein, we report on the phase stabilities and crystal structures of two newly discovered ordered, quaternary MAX phases—Mo{sub 2}TiAlC{sub 2} and Mo{sub 2}Ti{sub 2}AlC{sub 3}—synthesized by mixing and heating different elemental powder mixtures of mMo:(3-m)Ti:1.1Al:2C with 1.5 ≤ m ≤ 2.2 and 2Mo: 2Ti:1.1Al:2.7C to 1600 °C for 4 h under Ar flow. In general, for m ≥ 2 an ordered 312 phase, (Mo{sub 2}Ti)AlC{sub 2}, was the majority phase; for m < 2, an ordered 413 phase (Mo{sub 2}Ti{sub 2})AlC{sub 3}, was the major product. The actual chemistries determined from X-ray photoelectron spectroscopy (XPS) are Mo{sub 2}TiAlC{sub 1.7} and Mo{sub 2}Ti{sub 1.9}Al{sub 0.9}C{sub 2.5}, respectively. High resolution scanning transmission microscopy, XPS and Rietveld analysis of powder X-ray diffraction confirmed the general ordered stacking sequence to be Mo-Ti-Mo-Al-Mo-Ti-Mo for Mo{sub 2}TiAlC{sub 2} and Mo-Ti-Ti-Mo-Al-Mo-Ti-Ti-Mo for Mo{sub 2}Ti{sub 2}AlC{sub 3}, with the carbon atoms occupying the octahedral sites between the transition metal layers. Consistent with the experimental results, the theoretical calculations clearly show that M layer ordering is mostly driven by the high penalty paid in energy by having the Mo atoms surrounded by C in a face-centered configuration, i.e., in the center of the M{sub n+1}X{sub n} blocks. At 331 GPa and 367 GPa, respectively, the Young's moduli of the ordered Mo{sub 2}TiAlC{sub 2} and Mo{sub 2}Ti{sub 2}AlC{sub 3} are predicted to be higher than those calculated for their ternary end members. Like most other MAX phases, because of the high density of states at the Fermi level, the resistivity measurement over 300 to 10 K for both phases showed metallic behavior.

  6. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect.

    PubMed

    Naveed-Ul-Haq, M; Shvartsman, Vladimir V; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C

    2016-01-01

    The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 - 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 -CoFe2O4 bulk composites with similar content of the ferrite phase. PMID:27555563

  7. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

    PubMed Central

    Naveed-Ul-Haq, M.; Shvartsman, Vladimir V.; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C.

    2016-01-01

    The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 − 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 −CoFe2O4 bulk composites with similar content of the ferrite phase. PMID:27555563

  8. First-principles calculations for point defects in MAX phases Ti2AlN

    NASA Astrophysics Data System (ADS)

    Zhang, Yaowen; Yang, Shutong; Wang, Canglong

    2016-04-01

    This paper outlines general physical issues associated with performing computational numerical simulations of primary point defects in MAX phases Ti2AlN. First-principles solutions are possible due to the development of computational resources of software and hardware. The calculation accuracy is a good agreement with the experimental results. As an important application of our simulations, the results could provide a theoretical guidance for future experiments and application of Ti2AlN. For example, the N mono-vacancy is the most difficult to form. On the contrary, the mono-vacancy formation in Ti2AlN is energetically most favorable for the Al atom. The essence of the phenomena is explained by the calculated density of state (DOS).

  9. Nitric acid passivation of Ti6Al4V reduces thickness of surface oxide layer and increases trace element release.

    PubMed

    Callen, B W; Lowenberg, B F; Lugowski, S; Sodhi, R N; Davies, J E

    1995-03-01

    Passivation of Ti6Al4V and cpTi implants using methods based on the ASTM-F86 nitric acid protocol are used with the intention of reducing their surface reactivity, and consequently the corrosion potential, in the highly corrosive biologic milieu. The ASTM-F86 passivation protocol was originally developed for surgical implants made of stainless steel and chrome cobalt alloy. Using X-ray photoelectron spectroscopy (XPS) to examine the effect of nitric acid passivation on the surface oxide layer of mill-annealed Ti6Al4V and cpTi, we have found that such treatment actually reduced the oxide thickness on the alloy while having no significant effect on the pure metal. These results correlated with observations obtained using graphite furnace atomic absorption spectrophotometry (GFAAS) to detect trace element release from solid, mill-annealed, Ti6Al4V and cpTi into serum-containing culture medium. We detected significantly greater levels of Ti, Al, and V in the presence of passivated compared to nonpassivated Ti6Al4V. In contrast, nitric acid passivation did not influence Ti release from mill-annealed cpTi. These results, derived from two mill-annealed Ti-based metals, would indicate that re-examination of ASTM-F86-based passivation protocols with respect to Ti6Al4V should be considered in view of the widespread use of this alloy for biomedical devices. PMID:7615579

  10. Electrophoretic deposition of bioactive silica-calcium phosphate nanocomposite on Ti-6Al-4V orthopedic implant.

    PubMed

    Aniket; El-Ghannam, Ahmed

    2011-11-01

    Bioactive silica-calcium phosphate nanocomposite (SCPC) has been coated on Ti-6Al-4V implant employing an electrophoretic deposition (EPD) technique. The effects of composition and pH of the suspending medium on the zeta potential of three different SCPC formulations; SCPC25, SCPC50 and SCPC75 were analyzed. The average zeta potential of SCPC50 in pure ethanol was more negative than that of SCPC25 or SCPC75; however, the difference was not statistically significant. Discs of Ti-6Al-4V were passivated, coated with SCPC50 (200 nm-10 μm) and thermally treated at 600-800°C to produce a coating thickness in the range of 43.1 ± 5.7 to 30.1 ± 4.6 μm. After treatment at 600, 700, and 800°C, the adhesion strength at the SCPC50/Ti-6Al-4V interface was 42.6 ± 3.6, 44.7 ± 8.7, and 47.2 ± 4.3 MPa, respectively. SEM-EDX analyses of SCPC50-coated Ti-6Al-4V preimmersed in PBS for 7 days showed the formation of a Ca-deficient hydroxyapatite surface layer. ICP-OES analyses of the immersing solution (n = 6) showed an increase in the ionic concentration of Si from 3.3 ± 0.9 to 5.0 ± 1.2 ppm between days 1 and 4; after which no significant change in the Si concentration was measured. Bone marrow mesenchymal stem cells attached to the SCPC50-coated implants expressed significantly higher (p < 0.05) alkaline phosphatase activity (82.4 ± 25.6 nmoles p-NP/mg protein/min) than that expressed by cells attached to HA-coated or uncoated implants. Results of the study suggest that bioactive SCPC50 can efficiently be coated on Ti-6Al-4V using EPD. The SCPC50 coating has the potential to enhance bone integration with the orthopedic implant. PMID:21948397

  11. Cytocompatibility of Ti-6Al-4V and Ti-5Al-2.5Fe alloys according to three surface treatments, using human fibroblasts and osteoblasts.

    PubMed

    Bordji, K; Jouzeau, J Y; Mainard, D; Payan, E; Netter, P; Rie, K T; Stucky, T; Hage-Ali, M

    1996-05-01

    Titanium alloys are well known for their superior mechanical properties as well as for their good biocompatibility, making them desirable as surgical implant materials. However, these alloys have been proven to behave poorly in friction since wear particles were often detected in tissues and organs associated with titanium implants. In this paper, three surface treatments were investigated in order to improve the wear resistance and the hardness of Ti-6Al-4V and Ti-5Al-2.5Fe: (a) glow discharge nitrogen implantation (10(17) atoms cm-2), (b) plasma nitriding by plasma diffusion treatment (PDT) and (c) deposition of TiN layer by plasma-assisted chemical vapour deposition (PACVD) additionally to PDT. Surface characterization after the different treatments showed considerable improvement in surface hardness, especially after the two nitriding processes. Moreover, the good corrosion resistance of untreated alloys was maintained. A cell culture model using human cells was chosen to study the effect of such treatments on the cytocompatibility of these materials. The results showed that Ti-5Al-2.5Fe alloy was as cytocompatible as the Ti-6Al-4V alloy and the same surface treatment led to identical biological consequences on both alloys. Nitrogen implantation did not modify at all the cellular behaviour observed on untreated samples. After the two nitriding treatments, cell proliferation and viability appeared to be significantly reduced and the scanning electron microscopy study revealed somewhat irregular surface states. However, osteoblast phenotype expression and protein synthesis capacity were not affected. PDT and PACVD may be interesting alternatives to the physical vapour deposition technique. PMID:8718939

  12. Thermal and structural characterization of Cu-Al-Mn-X (Ti, Ni) shape memory alloys

    NASA Astrophysics Data System (ADS)

    Canbay, C. Aksu; Genc, Z. Karagoz; Sekerci, M.

    2014-05-01

    In this study, the Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys at the range of 10-12 at.% of aluminum and 4-5 at.% manganese were produced by arc melting. We have investigated the effects of the alloying elements on the transformation temperatures, and the structural and the magnetic properties of the quaternary Cu-Al-Mn-X (X = Ni, Ti) shape memory alloys. The evolution of the transformation temperatures was studied by differential scanning calorimetry with different heating and cooling rates. The characteristic transformation temperatures and the thermodynamic parameters were highly sensitive to variations in the aluminum and manganese content, and it was observed that the nickel addition into the Cu-Al-Mn system decreased the transformation temperature although Ti addition caused an increase in the transformation temperatures. The effect of the nickel and the titanium on the thermodynamic parameters such as enthalpy and entropy values was investigated. The structural changes of the samples were studied by X-ray diffraction measurements and by optical microscope observations at room temperature. It is evaluated that the element Ni has been completely soluble in the matrix, and the main phase of the Cu-Al-Mn-Ni sample is martensite, and due to the low solubility of the Ti, the Cu-Al-Mn-Ti sample has precipitates, and a martensite phase at room temperature. The magnetic properties of the Cu-Al-Mn, Cu-Al-Mn-Ni and Cu-Al-Mn-Ti samples were investigated, and the effect of the nickel and the titanium on the magnetic properties was studied.

  13. A high-temperature neutron diffraction study of Nb2AlC and TiNbAlC

    DOE PAGESBeta

    Bentzel, Grady W.; Lane, Nina J.; Vogel, Sven C.; An, Ke; Barsoum, Michel W.; Caspi, El'ad N.

    2014-12-16

    In this paper, we report on the crystal structures of Nb2AlC and TiNbAlC actual composition (Ti0.45,Nb0.55)2AlC compounds determined from Rietveld analysis of neutron diffraction patterns in the 300-1173 K temperature range. The average linear thermal expansion coefficients of a Nb2AlC sample in the a and c directions are, respectively, 7.9(5)x10-6 K-1 and 7.7(5)x10-6 K-1 on one neutron diffractometer and 7.3(3)x10-6 K-1 and 7.0(2)x10-6 K-1 on a second diffractometer. The respective values for the (Ti0.45,Nb0.55)2AlC composition - only tested on one diffractometer - are 8.5(3)x10-6 K-1 and 7.5(5)x10-6 K-1. These values are relatively low compared to other MAX phases. Like othermore » MAX phases, however, the atomic displacement parameters show that the Al atoms vibrate with higher amplitudes than the Ti and C atoms, and 1 more along the basal planes than normal to them. In addition, when the predictions of the atomic displacement parameters obtained from density functional theory are compared to the experimental results, good quantitative agreement is found for the Al atoms. In case of the Nb and C atoms, the agreement was more qualitative.« less

  14. Thermal stability of nanocrystalline (Ti,Zr)0.54Al0.46N films implanted by He+ ions

    NASA Astrophysics Data System (ADS)

    Uglov, V. V.; Abadias, G.; Rovbut, A. Y.; Zlotski, S. V.; Saladukhin, I. A.; Skuratov, V. A.; Petrovich, S.

    2015-07-01

    The influence of irradiation with He+ ions on the thermal stability of TiZrN and (Ti,Zr)0.54Al0.46N nanocrystalline films was studied. The TiZrN and (Ti,Zr)0.54Al0.46N films were prepared by reactive magnetron sputtering. XRD research showed that the TiZrN and (Ti,Zr)0.54Al0.46N films were single-phase systems (based on cubic c-(Ti,Zr)N and cubic c-(Ti,Zr,Al)N solid solutions) with nanocrystalline (grain size 30 and 21 nm, respectively) structure. The irradiation with He+ ions and thermal annealing up to 800 °C do not affect the structure and phase composition of the (Ti,Zr)0.54Al0.46N film. The prior irradiation of the (Ti,Zr)0.54Al0.46N film with He+ ions activates spinodal decomposition of the c-(Ti,Zr,Al)N solid solution after thermal annealing at 1000 °C due to redistribution of the components of the solid solution inside the grains.

  15. Microstructure Changes and Phase Growth Occurring at the Interface of the Al/Ti Explosively Welded and Annealed Joints

    NASA Astrophysics Data System (ADS)

    Fronczek, D. M.; Chulist, R.; Litynska-Dobrzynska, L.; Szulc, Z.; Zieba, P.; Wojewoda-Budka, J.

    2016-03-01

    The manuscript presents a close examination of the titanium and aluminum platters manufactured by explosive welding method. In particular, the microstructure changes of the Al/Ti wavy shape interface after annealing at 773 and 903 K were studied. Three stable TiAl3, TiAl, and Ti3Al and a metastable TiAl2 intermetallic phases have been formed in the state directly after explosive welding. The orientation map and TEM images obtained after explosive welding process showed very fine grains of aluminum mixed with intermetallics in the interface region between the peninsulas or islands. After annealing for 100 h the TiAl3 continuous layer was obtained; however, the layer achieved at 903 K was much wider than that obtained at 773 K. An examination of the growth kinetics at 903 K revealed that incubation time was less than 5 min. After this period, the growth was solely governed by chemical reaction.

  16. Synthesis and luminescent properties of CaTiO3: Pr3+ microfibers prepared by electrospinning method.

    PubMed

    Peng, Chong; Hou, Zhiyao; Zhang, Cuimiao; Li, Guogang; Lian, Hongzhou; Cheng, Ziyong; Lin, Jun

    2010-03-29

    One-dimensional Pr(3+)-doped CaTiO(3) microfibers were fabricated by a simple and cost-effective electronspinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential analysis (TG-DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), quantum efficiency (QE), and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. Under ultraviolet excitation and low-voltage electron beams (1-3 kV) excitation, the CaTiO(3):x Pr(3+) samples show the red emission at 612 nm, corresponding to (1)D(2)-(3)H(4) transition of Pr(3+). The luminescence intensity, quantum efficiency, and the lifetime have been studied as a function of the doping concentration of Pr(3+) in the CaTiO(3) samples. PMID:20389776

  17. Effect of SiC interlayer between Ti6Al4V alloy and hydroxyapatite films.

    PubMed

    Azem, Funda Ak; Birlik, Isil; Braic, Viorel; Toparli, Mustafa; Celik, Erdal; Parau, Anca; Kiss, Adrian; Titorencu, Irina; Vladescu, Alina

    2015-04-01

    Bioactive coatings are frequently used to improve the osseointegration of the metallic implants used in dentistry or orthopaedics. Among different types of bioactive coatings, hydroxyapatite (Ca10(PO4)6(OH)2) is one of the most extensively used due to its chemical similarities to the components of bones and teeth. In this article, production and characterization of hydroxyapatite films deposited on Ti6Al4V alloy prepared by magnetron sputtering were reported. Besides, SiC was deposited on substrate surface to study the interlayer effect. Obtained coatings were annealed at 600 °C for 30 and 120 min in a mixed atmosphere of N2 + H2O vapours with the heating rate of 12 °C min(-1). The effects of SiC interlayer and heat treatment parameters on the structural, mechanical and corrosion properties were investigated. After heat treatment process, the crystalline hydroxyapatite was obtained. Additionally, cell viability tests were performed. The results show that the presence of the SiC interlayer contributes a decrease in surface roughness and improves the mechanical properties and corrosion performance of the hydroxyapatite coatings. Biological properties were not affected by the presence of the SiC interlayer. PMID:25934259

  18. The behavior of internal markers in Ti-6Al-4V deformed in superplastic tension

    SciTech Connect

    Blackwell, P.L.; Bate, P.S.

    1996-11-01

    In the current work, internal markers were introduced into one of the best known superplastic materials, Ti-6 wt pct Al-4 wt pct V. Two sheets of 0.7-mm thickness were pressed into intimate contact after first cleaning the contacting surfaces and spraying a thin layer of an aqueous solution of Ca(OH){sub 2} onto one of those surfaces and allowing it to dry. The edges were joined using argon microplasma fusion welding and the assembly hot isostatically pressed at 900 C in a high purity argon atmosphere at 100 MPa for 90 minutes. Decomposition leaves particles of CaO at the interface, the remaining hydrogen and oxygen as well as any trapped atmospheric nitrogen and oxygen diffusing rapidly away from the interface into the bulk titanium. Specimens with a 35-mm parallel gage of 9.5-mm width were cut from the bonded sheet. These were tested in uniaxial tension at 920 C in air, with a layer of proprietary glaze to minimize the uptake of atmospheric elements. Extensions to strains of 0.4 and 1.0 were made at a strain rate of 10{sup {minus}4} s{sup {minus}1}. The strain rate was actually switched between values of 0.9 {times} 10{sup {minus}4} s{sup {minus}1} and 1.1 {times} 10{sup {minus}4} s{sup {minus}1}, with strain periods of 0.025 at each rate, to allow the strain rate sensitivity to be measured. The internal marker particles developed into small voids at the test temperature, even in the absence of deformation. The experimental observations are not consistent in the authors view, with grain boundary sliding having made any significant contribution to the deformation in the tensile tests.

  19. Improved tribological behavior of boron implanted Ti-6Al-4V

    SciTech Connect

    Baker, N.P.; Walter, K.C.; Nastasi, M.

    1998-03-01

    Boron implanted of Ti6Al4V has been conducted at combinations of 32 and 40 keV to supplement that done previously at 75 keV. Shallower boron depth profiles with higher B-concentrations in the Ti64 surface have been obtained by tailoring the combinations of ion energy and dose. This work used three different ion energy and dose combinations of 4 {times} 10{sup 17} B-at/cm{sup 2} at 40 keV plus 2 {times} 10{sup 17} B-at/cm{sup 2} at 32 keV, 4 {times} 10{sup 17} B-at/cm{sup 2} at 40 keV, and 4 {times} 10{sup 17} B-at/cm{sup 2} at 32 keV plus 2 {times} 10{sup 17} B-at/cm{sup 2} at 40 keV. Comparisons are made between Ti6Al4V with a shallow implanted boron depth profile, Ti6Al4V with a deeper boron depth profile and nitrogen implanted using a plasma source ion implantation process. It has been previously shown that while boron implanted Ti64 has a {approximately} 30% higher surface hardness than nitrogen implanted Ti64, the N-implantation reduced the wear coefficient of Ti64 by 25--120x, while B-implantation reduced the wear coefficient by 6.5x or less. The results show that no significant improvement is made in the wear resistance of boron implanted Ti6Al4V by increasing the concentration of boron at the surface from approximately 10% to 43%. Transmission electron microscopy (TEM) and selected area diffraction (SAD) indicated the formation of crystalline TiB in the implanted surface layer. Shallower depth profiles result in reductions of the Ti6Al4V wear coefficient by 6.5x or less which is the same result obtained earlier with the deeper boron depth profile. Surface hardness of Ti6Al4V with shallower boron depth profiles was improved approximately 10% compared to the results previously acquired with deeper boron depth profiles.

  20. Oxidation resistance of quintuple Ti-Al-Si-C-N coatings and associated mechanism

    SciTech Connect

    Wu Guizhi; Ma Shengli; Xu Kewei; Ji, Vincent; Chu, Paul K.

    2012-07-15

    The oxidation behavior of Ti-Al-Si-C-N hard coatings with different Al contents deposited on high-speed steel and Si substrates by hybrid arc-enhanced magnetron sputtering is investigated in the temperature range of 500 Degree-Sign C-1000 Degree-Sign C. The coating hardness is maintained at around 35 GPa, and the parabolic oxidation rate constant K{sub p} at 1000 Degree-Sign C decreases to 3.36 Multiplication-Sign 10{sup -10} kg{sup 2} m{sup -4} s{sup -1} when the Al concentration is increased to 30 at. %, indicating that Ti-Al-Si-C-N coatings with larger Al concentrations have better oxidation resistance. X-ray diffraction, cross-sectional scanning electron microscopy, and x-ray photoelectron spectroscopy reveal a protective surface layer consisting of Al{sub 2}O{sub 3}, TiO{sub 2}, and SiO{sub 2} that retards inward oxygen diffusion. A mechanism is proposed to elucidate the oxide formation. As a consequence of the good oxidation resistance, the Ti-Al-Si-C-N coatings have a large potential in high-speed dry cutting as well as other high temperature applications.

  1. Reactivity enhancement of oxide skins in reversible Ti-doped NaAlH{sub 4}

    SciTech Connect

    Delmelle, Renaud; Borgschulte, Andreas; Gehrig, Jeffrey C.; Züttel, Andreas

    2014-12-15

    The reversibility of hydrogen sorption in complex hydrides has only been shown unambiguously for NaAlH{sub 4} doped with transition metal compounds. Despite a multitude of investigations of the effect of the added catalyst on the hydrogen sorption kinetics of NaAlH{sub 4}, the mechanism of catalysis remains elusive so far. Following the decomposition of TiCl{sub 3}-doped NaAlH{sub 4} by in-situ X-ray photoelectron spectroscopy (XPS), we link the chemical state of the dopant with those of the hydride and decomposition products. Titanium and aluminium change their oxidation states during cycling. The change of the formal oxidation state of Al from III to zero is partly due to the chemical reaction from NaAlH{sub 4} to Al. Furthermore, aluminium oxide is formed (Al{sub 2}O{sub 3}), which coexists with titanium oxide (Ti{sub 2}O{sub 3}). The interplay of metallic and oxidized Ti with the oxide skin might explain the effectiveness of Ti and similar dopants (Ce, Zr…)

  2. Interaction behaviors at the interface between liquid Al-Si and solid Ti-6Al-4V in ultrasonic-assisted brazing in air.

    PubMed

    Chen, Xiaoguang; Yan, Jiuchun; Gao, Fei; Wei, Jinghui; Xu, Zhiwu; Fan, Guohua

    2013-01-01

    Power ultrasonic vibration (20 kHz, 6 μm) was applied to assist the interaction between a liquid Al-Si alloy and solid Ti-6Al-4V substrate in air. The interaction behaviors, including breakage of the oxide film on the Ti-6Al-4V surface, chemical dissolution of solid Ti-6Al-4V, and interfacial chemical reactions, were investigated. Experimental results showed that numerous 2-20 μm diameter-sized pits formed on the Ti-6Al-4V surface. Propagation of ultrasonic waves in the liquid Al-Si alloy resulted in ultrasonic cavitation. When this cavitation occurred at or near the liquid/solid interface, many complex effects were generated at the small zones during the bubble implosion, including micro-jets, hot spots, and acoustic streaming. The breakage behavior of oxide films on the solid Ti-6Al-4V substrate, excessive chemical dissolution of solid Ti-6Al-4V into liquid Al-Si, abnormal interfacial chemical reactions at the interface, and phase transformation between the intermetallic compounds could be wholly ascribed to these ultrasonic effects. An effective bond between Al-Si and Ti-6Al-4V can be produced by ultrasonic-assisted brazing in air. PMID:22824641

  3. Development and Evaluation of TiAl Sheet Structures for Hypersonic Applications

    NASA Technical Reports Server (NTRS)

    Draper, S. L.; Krause, D.; Lerch, B.; Locci, I. E.; Doehnert, B.; Nigam, R.; Das, G.; Sickles, P.; Tabernig, B.; Reger, N.; Rissbacher, K.

    2007-01-01

    A cooperative program between the National Aeronautics and Space Administration (NASA), the Austrian Space Agency (ASA), Pratt & Whitney, Engineering Evaluation and Design, and Plansee AG was undertaken to determine the feasibility of achieving significant weight reduction of hypersonic propulsion system structures through the utilization of TiAl. A trade study defined the weight reduction potential of TiAl technologies as 25 to 35 percent compared to the baseline Ni-base superalloy for a stiffener structure in an inlet, combustor, and nozzle section of a hypersonic scramjet engine (ref. 1). A scramjet engine inlet cowl flap was designed, along with a representative subelement, using design practices unique to TiAl. A sub-element was fabricated and tested to assess fabricability and structural performance and validate the design system. The TiAl alloy selected was Plansee's third generation alloy Gamma Met PX (Plansee AG ), a high temperature, high strength gamma-TiAl alloy with high Nb content (refs. 2 and 3). Characterization of Gamma Met PX sheet, including tensile, creep, and fatigue testing was performed. Additionally, design-specific coupons were fabricated and tested in order to improve subelement test predictions. Based on the sheet characterization and results of the coupon tests, the subelement failure location and failure load were accurately predicted.

  4. Development of porous Ti6Al4V/chitosan sponge composite scaffold for orthopedic applications.

    PubMed

    Guo, Miao; Li, Xiang

    2016-01-01

    A novel composite scaffold consisting of porous Ti6Al4V part filled with chitosan sponge was fabricated using a combination of electron beam melting and freeze-drying. The mechanical properties of porous Ti6Al4V part were examined via compressive test. The ultimate compressive strength was 85.35 ± 8.68 MPa and the compressive modulus was 2.26 ± 0.42 GPa. The microstructure of composite scaffold was characterized using scanning electron microscopy. The chitosan sponge filled in Ti6Al4V part exhibited highly porous and well-interconnected micro-pore architecture. The osteoblastic cells were seeded on scaffolds to test their seeding efficiency and biocompatibility. Significantly higher cell seeding efficiency was found on composite scaffold. The biological response of osteoblasts on composite scaffolds was superior in terms of improved cell attachment, higher proliferation, and well-spread morphology in relation to porous Ti6Al4V part. These results suggest that the Ti6Al4V/chitosan composite scaffold is potentially useful as a biomedical scaffold for orthopedic applications. PMID:26478418

  5. Diffusion of 3D-transition elements in Ti-54at%Al

    SciTech Connect

    Lee, C.G.; Iijima, Y.; Kim, S.E.; Lee, Y.T.; Kim, H.M.

    1995-12-31

    The diffusion coefficients of iron, cobalt, manganese and chromium in Ti-54at%Al alloy were measured over the temperature range from 1,000 to 1,540 K. This study used the radioactive tracers {sup 59}Fe, {sup 57}Co, {sup 54}Mn and {sup 51}Cr and employed the serial the radio-frequency sputter-microsectioning method to measure the penetration profiles of the radioisotope into the specimen. The temperature dependence of the diffusion coefficients was analyzed to be expressed by the following Arrhenius equations: D{sub Fe/TiAl} = (1.3 {times} 10{sup {minus}3}) exp ({minus}363 kJ mol{sup {minus}1}/RT) m{sup 2}/s, D{sub Co/TiAl} = (1.1 {times} 10{sup {minus}3}) exp ({minus}318 kJ mol{sup {minus}1}/RT) m{sup 2}/s, D{sub Mn/TiAl} = (1.2 {times} 10{sup {minus}3}) exp ({minus}326 kJ mol{sup {minus}1}/RT) m{sup 2}/s, D{sub Cr/TiAl} = (4.4 {times} 10{sup {minus}3}) exp ({minus}350 kJ mol{sup {minus}1}/RT) m{sup 2}/s.

  6. Fracture toughness of stoichiometric, non-stoichiometric and ternary-alloyed Al{sub 2}Ti

    SciTech Connect

    Ma, J.C.; Lukitsch, M.J.; Ambrow, C.E.; Benci, J.E.

    1997-12-31

    Polycrystalline stoichiometric Al{sub 2}Ti was produced via casting or powder metallurgy and further processed yielding material in six conditions. The fracture toughness of the six material conditions was determined from the critical load to initiate cracks with a Vickers indenter. The results show a strong dependence on material condition. Powder processed Al{sub 2}Ti exhibits the highest fracture toughness value among the material conditions studied. Polycrystalline non-stoichiometric Al{sub 2{+-}y}Ti{sub 1{+-}y} and ternary-alloyed Al{sub 2}Ti + X were prepared in as-cast and cast and annealed conditions. Each material condition exhibited a multiphase microstructure. The composition of the phases present in each alloy was analyzed with SEM/EDS. Fracture toughness values of cast and annealed stoichiometric and non-stoichiometric binary alloys are 20--30% greater than as-cast stoichiometric Al{sub 2}Ti. For the ternary alloys, the fracture toughness values show a strong dependence on the ternary element used and heat treatment condition. The fracture toughness values of three hot forged ternary alloys were also determined.

  7. New Powder Metallurgical Approach to Achieve High Fatigue Strength in Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Cao, Fei; Ravi Chandran, K. S.; Kumar, Pankaj; Sun, Pei; Zak Fang, Z.; Koopman, Mark

    2016-05-01

    Recently, manufacturing of titanium by sintering and dehydrogenation of hydride powders has generated a great deal of interest. An overarching concern regarding powder metallurgy (PM) titanium is that critical mechanical properties, especially the high-cycle fatigue strength, are lower than those of wrought titanium alloys. It is demonstrated here that PM Ti-6Al-4V alloy with mechanical properties comparable (in fatigue strength) and exceeding (in tensile properties) those of wrought Ti-6Al-4V can be produced from titanium hydride powder, through the hydrogen sintering and phase transformation process. Tensile and fatigue behavior, as well as fatigue fracture mechanisms, have been investigated under three processing conditions. It is shown that a reduction in the size of extreme-sized pores by changing the hydride particle size distribution can lead to improved fatigue strength. Further densification by pneumatic isostatic forging leads to a fatigue strength of ~550 MPa, comparable to the best of PM Ti-6Al-4V alloys prepared by other methods and approaching the fatigue strengths of wrought Ti-6Al-4V alloys. The microstructural factors that limit fatigue strength in PM titanium have been investigated, and pathways to achieve greater fatigue strengths in PM Ti-6Al-4V alloys have been identified.

  8. Treating orthopedic prosthesis with diamond-like carbon: minimizing debris in Ti6Al4V.

    PubMed

    Oliveira, Luciane Y S; Kuromoto, Neide K; Siqueira, Carlos J M

    2014-10-01

    Prostheses are subject to various forms of failing mechanisms, including wear from ordinary patient motion. Superficial treatments can improve tribological properties of the contact pair, minimizing wear and increasing prostheses lifetime. One possibility is the diamond-like carbon (DLC) coating, where Carbon is deposited with variable ratio of sp(2)/sp(3) structures, leading to an increase in surface hardness. So in this research Ti6Al4V samples were coated with DLC using sputtering process to evaluate the debris release. The Ti6Al4V and Ti6Al4V plus DLC coating surfaces were analyzed using Raman spectroscopy and instrumented indentation (hardness). The wear behavior was tested using a reciprocating linear tribometer. The wear rate was smaller in the coated samples, producing less debris than the untreated Ti6Al4V alloy. Debris morphology was also evaluated, using scanning electronic microscopy, and it was observed that debris size from the coated samples were bigger than those observed from the uncoated Ti6Al4V alloy, above the size that generally triggers biological response from the host. PMID:24948374

  9. Microstructure evolution of Ti-48Al-xNb gamma intermetallics

    NASA Astrophysics Data System (ADS)

    Li, Y. G.; Loretto, M. H.

    1994-06-01

    The microstructures of Ti-48Al alloys containing either 2 at.% or 8 at.% Nb have been studied in as-cast, as-HIPped and in heat-treated samples. The as-cast Ti-48Al-2Nb and Ti-48Al-8Nb are heterogeneous and lower Nb content has been detected in the interdentiritic gamma by EDX analysis. Depending on the heat-treatment temperature and cooling rate, the microstructure obtained vary from martensitic structure in the water quenched samples to duplex structure consisting of gamma grains and lamellar alpha(sub 2)/gamma and to fully lamellar structure in the furnace cooled samples. Nb was found to have a high solubility in both alpha and gamma phases and to expand the gamma phase region so that a fully gamma structure is obtained in the Ti-48Al-8Nb sample by annealing at 1200 C. A dense array of planar defects (antiphase boundaries, stacking faults and microtwins) was obtained in the Ti-48Al-8Nb alloy water quenched from 1400 C.

  10. Electrophoretic deposition of double-layer HA/Al composite coating on NiTi.

    PubMed

    Karimi, Esmaeil; Khalil-Allafi, Jafar; Khalili, Vida

    2016-01-01

    In order to improve the bioactivity of NiTi alloys, which are being known as the suitable materials for biomedical applications, numerous NiTi disks were electrophoretically coated by hetero-coagulated hydroxyapatite/aluminum composite coatings in three main voltages from suspensions with different Al concentrations. In this paper, the amount of Ni ions release and bioactivity of prepared samples as well as bonding strength of the coating to substrate were investigated. The surface characterization of the coating by XRD, EDX, SEM, and FTIR showed that HA particles bonded by Al particles. It caused the formation of a free crack coating on NiTi disks. Moreover, the bonding strength of HA/Al coatings to NiTi substrate were improved by two times as compared to that of the pure HA coatings. Immersing of coated samples in SBF for 1 week showed that apatite formation ability was improved on HA/Al composite coating and Ni ions release from the surface of composite coating decreased. These results induce the appropriate bioactivity and biocompatibility of the deposited HA/Al composite coatings on NiTi disks. PMID:26478383

  11. Microstructure Evolution of Cold-Sprayed Al-Si Alloy Coatings on γ-TiAl During Heat Treatment

    NASA Astrophysics Data System (ADS)

    Wang, Jiqiang; Kong, Lingyan; Li, Tiefan; Xiong, Tianying

    2015-08-01

    This paper investigated the influence of heat treatment on the microstructure of Al-Si alloy coatings on γ-TiAl alloy. The coatings were prepared by cold spraying with Al-12Si and Al-20Si alloy powders as the feedstock, and then the as-sprayed coatings were subjected to heat treatment. The microstructure, chemical composition, and phase transformation of the coatings were studied by SEM, XRD, and EPMA. The diffusing behavior of Al and Si during heat treatment was investigated. The results showed that a silicon-aluminizing coating was formed through the inward diffusion of Al/Si elements into the substrate. The obtained kinetics curve of the formation of silicon-aluminizing coating at 580 °C similarly followed parabolic law.

  12. Mode of formation of hibonite (CaAl12O19) within the U-Th skarns from the granulites of S-E Madagascar

    NASA Astrophysics Data System (ADS)

    Rakotondrazafy, Michel A. F.; Moine, B.; Cuney, M.

    1996-03-01

    In Madagascar, hibonite occurs as a rather frequent mineral within thorianite-bearing skarns which are widespread in the Pan African granulitic formations constituting the S-E part of the Island (Tranomaro area). In these skarns, leucocratic segregations made up of CO3-scapolite to meionite (Anequivalent=89 95% which implies T≥850° C), spinel and corundum were formed at stage 1 of metasomatism in a titanite-bearing matrix consisting of scapolite (Aneq=77 88) and aluminous diopside. During stage 2 of metasomatism, scapolite from the lenses were altered to anorthite+calcite while the less calcic scapolite remained stable which indicates T≈800° C. Hibonite crystallized at the expense of corundum and spinel. Expressed as mol% of the CaAl12O19/Ca(Al10TiR2+)O19/REE(Al11R2+)O19 [+Th (Al10R2+ 2)O19] end-members ( R 2+=Mg, Fe2+, Zn2+; Al=Al, Fe3+; Ti=Ti, Si), its composition varies from 26/72/2 to 50/23/27. The ideal activity of the CaAl12O19 component is about 0.25. Fluid inclusions in corundum, hibonite and anorthite are composed of nearly pure CO2. In corundum, the isochores for primary inclusions are in agreement with the P-T estimates for regional metamorphism and stage 1 metasomatism ( T≈850° C, P≈5 kbar). Inclusions with the highest density in hibonite and anorthite constrain P to about 3 3.5 kbar for T=800° C. Thermodynamic calculations indicate that, in addition to a low activity of CaAl12O19, stability of hibonite in equilibrium with anorthite and calcite implies an extremely low activity of silica (below the zircon-baddeleyite buffer). By contrast the activity of CO2 may be high, in agreement with the observed fluid compositions. These results are corroborated by a short comparison with the other granulite occurrences of hibonite in Tanzania and South India.

  13. Development of spin-gapless semiconductivity and half metallicity in Ti2MnAl by substitutions for Al

    NASA Astrophysics Data System (ADS)

    Lukashev, Pavel; Gilbert, Simeon; Staten, Bradley; Hurley, Noah; Fuglsby, Ryan; Kharel, Parashu; Huh, Yung; Valloppilly, Shah; Zhang, Wenyong; Yang, K.; Sellmyer, David J.

    In recent years, ever increasing interest in spin-based electronics has resulted in the search for a new class of materials that can provide a high degree of spin polarized electron transport. An ideal candidate would act like insulator for one spin channel and a conductor or semiconductor for the opposite spin channel (e.g., half metal (HM), spin-gapless semiconductor (SGS)). Here, we present the combined computational, theoretical, and experimental study of Ti2MnAl, a Heusler compound with potential application in the field of spintronics. We show that in the ground state this material is metallic, however it becomes a SGS when 50% of Al is substituted with In (e.g., Ti2MnAl0.5In0.5) , and a HM when 50% of Al is substituted with Sn (e.g., Ti2MnAl0.5Sn0.5) . Detailed study of the structural, electronic, and magnetic properties of these materials is presented. Financial support: DOE/BES (DE-FG02-04ER46152); NSF NNCI: 1542182; NRI; Academic and Scholarly Excellence Funds, Office of Academic Affairs, SDSU; UNI Faculty Summer Fellowship; Program for Outstanding Innovative Talents in Hohai University.

  14. Resistive Switching in Al/Al2O3/TiO2/Al/PES Flexible Device for Nonvolatile Memory Application.

    PubMed

    Lin, Chun-Chieh; Lee, Wang-Ying; Lee, Han-Tang

    2016-05-01

    Resistive switching memory devices with superior properties are possibly used in next-generation nonvolatile memory to replace the flash memory. In addition, flexible electronics has also attracted much attention because of its light-weight and flexibility. Therefore, an Al/Al2O3/TiO2/Al/PES flexible resistive switching memory is employed in this study. The resistive switching characteristics and stability of the flexible device are improved by inserting the Al2O3 film. The resistive switching of the flexible device can be repeated over hundreds of times after the bending test. A possible resistive switching model of the flexible device is also proposed. In addition, the non-volatility of the flexible device is demonstrated. Based on our research results, the proposed Al2O3/TiO2-based resistive switching memory is possibly used in next-generation flexible electronics and nonvolatile memory applications. PMID:27483828

  15. Oxide formation on NbAl{sub 3} and TiAl due to ion implantation of {sup 18}O

    SciTech Connect

    Hanrahan, R.J. Jr.; Verink, E.D. Jr.; Withrow, S.P.; Ristolainen, E.O.

    1993-12-31

    Surface modification by ion implantation of {sup 18}O ions was investigated as a technique for altering the high-temperature oxidation of aluminide intermetallic compounds and related alloys. Specimens of NbAl{sub 3} and TiAl were implanted to a dose of 1 {times} 10{sup 18} ions/cm{sup 2} at 168 keV. Doses and accelerating energies were calculated to obtain near-stoichiometric concentrations of oxygen. Use of {sup 18}O allowed the implanted oxygen profiles to be measured using secondary ion mass spectroscopy (SIMS). The near surface oxides formed were studied using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy. Specimens were also examined using x-ray diffraction and SEM. This paper presents results for specimens examined in the as-implanted state. The oxide formed due to implantation is a layer containing a mixture of Nb or Ti and amorphous Al oxides.

  16. Are new TiNbZr alloys potential substitutes of the Ti6Al4V alloy for dental applications? An electrochemical corrosion study.

    PubMed

    Ribeiro, Ana Lúcia Roselino; Hammer, Peter; Vaz, Luís Geraldo; Rocha, Luís Augusto

    2013-12-01

    The main aim of this work was to assess the electrochemical behavior of new Ti35Nb5Zr and Ti35Nb10Zr alloys in artificial saliva at 37 °C to verify if they are indicated to be used as biomaterials in dentistry as alternatives to Ti6Al4V alloys in terms of corrosion protection efficiency of the material. Electrochemical impedance spectroscopy (EIS) experiments were carried out for different periods of time (0.5-216 h) in a three-electrode cell, where the working electrode (Ti alloys) was exposed to artificial saliva at 37 °C. The near-surface region of the alloys was investigated using x-ray photoelectron spectroscopy (XPS). All alloys exhibited an increase in corrosion potential with the immersion time, indicating the growth and stabilization of the passive film. Ti35Nb5Zr and Ti6Al4V alloys had their EIS results interpreted by a double-layer circuit, while the Ti35Nb10Zr alloy was modeled by a one-layer circuit. In general, the new TiNbZr alloys showed similar behavior to that observed for the Ti6Al4V. XPS results suggest, in the case of the TiNbZr alloys, the presence of a thicker passive layer containing a lower fraction of TiO2 phase than that of Ti6Al4V. After long-term immersion, all alloys develop a calcium phosphate phase on the surface. The new TiNbZr alloys appear as potential candidates to be used as a substitute to Ti6Al4V in the manufacturing of dental implant-abutment sets. PMID:24280708

  17. First-Principles Calculations of Structural, Electronic and Optical Properties of CaTiO3 Crystal

    NASA Astrophysics Data System (ADS)

    Medeiros, Subênia; Silva, Jusciane; Albuquerque, Eudenilson; Freire, Valder

    2013-03-01

    The structural, electronic, vibrational, and optical properties of perovskite CaTiO3 in the cubic, orthorhombic, and tetragonal phase are calculated in the framework of density functional theory (DFT) with different exchange-correlation potentials by CASTEP package. The calculated band structure shows an indirect band gap of 1.88 eV at the Γ-R points in the Brillouin zone to the cubic structure, a direct band gap of 2.41 eV at the Γ - Γ points to the orthorhombic structure, and an indirect band gap of 2.31 eV at the M' Γ points to the tetragonal phase. I have concluded that the bonding between Ca and TiO2 is mainly ionic and that the TiO2 entities bond covalently. Unlike some perovskites the CaTiO3 does not exhibit a ferroelectric phase transition down to 4.2 K. It is still known that the CaTiO3 has a static dielectric constant that extrapolates to a value greater than 300 at zero temperature. Our calculated lattice parameters, elastic constants, optical properties, and vibrational frequencies are found to be in good agreement with the available theoretical and experimental values. The results for the effective mass in the electron and hole carriers are also presented in this work.

  18. Investigations on the electronic, structural, magnetic properties related to shape-memory behavior in Ti{sub 2}CoX (X=Al, Ga, In)

    SciTech Connect

    Wei, Xiao-Ping; Chu, Yan-Dong; Sun, Xiao-Wei; E, Yan; Deng, Jian-Bo; Xing, Yong-Zhong

    2015-02-15

    Highlights: • The analysis of phase stability trend is studied for Ti{sub 2}CoX(X = Al, Ga, In). • Ti{sub 2}CoGa is more suitable as shape memory alloy. • Total magnetic moments disappear with a increase of c/a ratio for all systems. • Density of states at the Fermi level are also shown. - Abstract: Using the full-potential local orbital minimum-basis method, we have performed a systematic investigations on the electronic, structural, and magnetic properties related to shape memory applications for Ti{sub 2}CoX (X=Al, Ga, In) alloys. Our results confirm that these alloys are half-metallic ferromagnets with total magnetic moment of 2μ{sub B} per formula unit in austenite phase, and undergo a martensitic transformation at low temperatures. The relative stabilities of the martensitic phases differ considerably between Ti{sub 2}CoX (X=Al, Ga, In). Details of the electronic structures suggest that the differences in hybridizations between the magnetic components are responsible for trends of phase. Quantitative estimates for the energetics and the magnetizations indicate that Ti{sub 2}CoGa is a promising candidate for shape memory applications.

  19. Ti2FeZ (Z=Al, Ga, Ge) alloys: Structural, electronic, and magnetic properties

    NASA Astrophysics Data System (ADS)

    Liping, Mao; Yongfan, Shi; yu, Han

    2014-11-01

    Using the first-principle projector augmented wave potential within the generalized gradient approximation taking into account the on-site Coulomb repulsive, we investigate the structural, electronic and magnetic properties of Ti2FeZ (Z=Al, Ga, Ge) alloys with Hg2CuTi-type structure. These alloys are found to be half-metallic ferrimagnets. The total magnetic moments of the Heusler alloys Ti2FeZ follow the μt=Zt-18 rule and agree with the Slater-Pauling curve quite well. The band gaps are mainly determined by the bonding and antibonding states created from the hybridizations of the d states between the Ti(A)-Ti(B) coupling and Fe atom.

  20. Surface modification of TiAlSiCN coatings to improve oxidation protection

    NASA Astrophysics Data System (ADS)

    Kuptsov, K. A.; Kiryukhantsev-Korneev, Ph. V.; Sheveyko, A. N.; Shtansky, D. V.

    2015-08-01

    Coatings with high thermal stability and oxidation resistance are highly anticipated for various high-temperature applications. In this work we compare three different approaches to increase the oxidation resistance of nanocomposite TiAlSiCN coatings with exceptionally high thermal stability: (i) deposition of a thin Al top-layer, (ii) Al ion implantation into their topmost surface, and (iii) deposition of a thin AlOx top-layer. The coatings were annealed in air at 1000, 1100, and 1200 °C for 1 h and their oxidation was studied using scanning electron microscopy and glow discharge optical emission spectroscopy. The obtained results demonstrate that the deposition of a thin top-layer of amorphous AlOx increases the oxidation resistance of the TiAlSiCN coatings from 1000 to 1100 °C. This decreases the gap between the high thermal stability (1300 °C) and oxidation resistance of the TiAlSiCN coatings, which is particularly important for high-speed and dry cutting applications. In contrast, the deposition of either a thin Al top-layer or Al ion implantation resulted in a negative effect. The factors affecting the rapid oxidation of such coatings at 1000 and 1100 °C are discussed.

  1. FeAl-TiC and FeAl-WC composites - melt infiltration processing, microstructure and mechanical properties

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.

    1997-04-01

    TiC-based and WC-based cermets were processed with iron aluminide, an intermetallic, as a binder by pressureless melt infiltration to near full density (> 97 % theoretical density). Phase equilibria calculations in the quaternary Fe-Al-Ti-C and Fe-Al-W-C systems at 145{degrees}C were performed to determine the solubility of the carbide phases in liquid iron aluminide. This was done by using Thermocalc{trademark} and the results show that molten Fe-40 at.% Al in equilibrium with Ti{sub 0.512}C{sub 0.488} and graphite, dissolves 4.9 at% carbon and 64 atomic ppm titanium. In the Fe-Al-W-C system, liquid Fe-40 at.% Al in equilibrium with graphite dissolves about 5 at.% carbon and 1 at.% tungsten. Due to the low values for the solubility of the carbide phases in liquid iron aluminide, liquid phase sintering of mixed powders does not yield a dense, homogeneous microstructure for carbide volume fractions greater than 0.70. Melt infiltration of molten FeAl into TiC and WC preforms serves as a successful approach to process cermets with carbide contents ranging from 70 to 90 vol. %, to greater than 97% of theoretical density. Also, the microstructures of cermets prepared by melt infiltration were very homogeneous. Typical properties such as hardness, bend strength and fracture toughness are reported. SEM observations of fracture surfaces suggest the improved fracture toughness to result from the ductility of the intermetallic phase. Preliminary experiments for the evaluation of the oxidation resistance of iron aluminide bonded cermets indicate that they are more resistant than WC-Co cermets.

  2. Local structures of Ca, Ti and Fe in meteorite fusion crusts

    NASA Astrophysics Data System (ADS)

    Tobase, T.; Yoshiasa, A.; Hiratoko, T.; Hongu, H.; Isobe, H.; Nakatsuka, A.; Arima, H.; Sugiyama, K.

    2016-05-01

    The local structures of meteorite fusion crusts were studied by Ca, Ti and Fe K-edge XANES and EXAFS spectroscopy. The surface of meteorites were melted and volatilized with extreme high temperature and large temperature gradient when meteorites were rushed into atmosphere. This study indicated that meteorite fusion crusts have unique local structures. The local structures of fusion crusts differ from tektites especially in intensity of the shoulder in the rising flank of the edge in Ca XANES spectra. It is consistent with chemical composition change by the volatilization of Si at fusion during atmospheric entry. The high estimated Fe3+/ (Fe2++Fe3+) ratio in meteorite fusion crusts indicates that meteorite fusion crusts are formed into atmospheric oxidation condition. The Ca-O distances in meteorite fusion crusts are 2.612.66 A and are extremely longer than in other natural glasses. The fusion crusts have unique local structure since they experienced extremely high temperature and short quenching time. The XAFS method is effective in distinction of meteorite fusion crusts and classification of natural glass.

  3. Electronic structure investigation of Ti3 AlC2 , Ti3 SiC2 , and Ti3 GeC2 by soft x-ray emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Magnuson, M.; Palmquist, J.-P.; Mattesini, M.; Li, S.; Ahuja, R.; Eriksson, O.; Emmerlich, J.; Wilhelmsson, O.; Eklund, P.; Högberg, H.; Hultman, L.; Jansson, U.

    2005-12-01

    The electronic structures of epitaxially grown films of Ti3AlC2 , Ti3SiC2 , and Ti3GeC2 have been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured high-resolution Ti L , C K , Al L , Si L , and Ge M emission spectra are compared with ab initio density-functional theory including core-to-valence dipole matrix elements. A qualitative agreement between experiment and theory is obtained. A weak covalent Ti-Al bond is manifested by a pronounced shoulder in the Ti L emission of Ti3AlC2 . As Al is replaced with Si or Ge, the shoulder disappears. For the buried Al and Si layers, strongly hybridized spectral shapes are detected in Ti3AlC2 and Ti3SiC2 , respectively. As a result of relaxation of the crystal structure and the increased charge-transfer from Ti to C, the Ti-C bonding is strengthened. The differences between the electronic structures are discussed in relation to the bonding in the nanolaminates and the corresponding change of materials properties.

  4. Effect of Ti doping on Ta 2O 5 stacks with Ru and Al gates

    NASA Astrophysics Data System (ADS)

    Paskaleva, A.; Tapajna, M.; Atanassova, E.; Frohlich, K.; Vincze, A.; Dobročka, E.

    2008-07-01

    The Ti-doped Ta 2O 5 thin films (<10 nm) obtained by rf sputtering are studied with respect to their composition, dielectric and electrical properties. The incorporation of Ti is performed by two methods - a surface doping, where a thin Ti layer is deposited on the top of Ta 2O 5 and a bulk doping where the Ti layer is sandwiched between two layers of Ta 2O 5. The effect of the process parameters (the method and level of doping) on the elemental distribution in-depth of the films is investigated by the time of flight secondary ion mass spectroscopy (ToF-SIMS). The Ti and Ta 2O 5 are intermixed throughout the whole thickness but the layers are very inhomogeneous. Two sub-layers exist in all the samples — a near interfacial region which is a mixture of Ta-, Ti-, Si-oxides as well as TaSiO, and an upper Ti-doped Ta 2O 5 sub-layer. For both methods of doping, Ti tends to pile-up at the Si interface. The electrical characterisation is performed on capacitors with Al- and Ru-gate electrodes. The two types of MIS structures exhibit distinctly different electrical behavior: the Ru gate provides higher dielectric permittivity while the stacks with Al electrode are better in terms of leakage currents. The specific metal-dielectric reactions and metal-induced electrically active defects for each metal electrode/high- k dielectric stack define its particular electrical behavior. It is demonstrated that the Ti doping of Ta 2O 5 is a way of remarkable improvement of leakage characteristics (the current reduction with more than four orders of magnitude as compared with undoped Ta 2O 5) of Ru-gated capacitors which originates from Ti induced suppression of the oxygen vacancy related defects.

  5. Coagulation characteristics of titanium (Ti) salt coagulant compared with aluminum (Al) and iron (Fe) salts.

    PubMed

    Zhao, Y X; Gao, B Y; Shon, H K; Cao, B C; Kim, J-H

    2011-01-30

    In this study, the performance of titanium tetrachloride (TiCl(4)) coagulation and flocculation is compared with commonly used coagulants such as aluminum sulfate (Al(2)(SO(4))(3)), polyaluminum chloride (PACl), iron chloride (FeCl(3)), and polyferric sulfate (PFS) in terms of water quality parameters and floc properties. TiCl(4) flocculation achieved higher removal of UV(254) (98%), dissolved organic carbon (DOC) (84%) and turbidity (93%) than other conventional coagulants. Charge neutralization and physical entrapment of colloids within coagulant precipitates and adsorption, seemed to play a significant role during TiCl(4) flocculation, while the main mechanism for conventional coagulants was bridge-aggregation and adsorption. The aggregated flocs after TiCl(4) flocculation showed the fastest growth rate compared to the other coagulants, with the largest floc size (801 μm) occurring within 8 min. The floc strength factor of PACl, Al(2)(SO(4))(3), PFS, FeCl(3) and TiCl(4) was 34, 30, 29, 26 and 29, respectively, while the floc recovery factor of the TiCl(4) coagulant was the lowest. Based on the results of the above study, it is concluded that the TiCl(4) flocculation can reduce the hydraulic retention time of slow and rapid mixing, however, careful handling of sludge is required due to the low recoverability of the aggregated floc. PMID:21075521

  6. Ceramics to Ti6Al4V by Ni-Based Interlayers

    NASA Astrophysics Data System (ADS)

    Valenza, F.; Artini, C.; Passerone, A.; Cirillo, P.; Muolo, M. L.

    2014-05-01

    Pure ZrB2 and ZrB2-SiC composites were joined to Ti6Al4V at 1100 °C using B-Ni50 (at.%) as a filler alloy. The brazing medium and the processing parameters were chosen on the basis of specific wetting tests which showed the good adhesion properties of the B-Ni alloy with both the ceramic and the Ti alloy; interfacial reactions were foreseen and interpreted by phase diagram analysis. A multilayer metal-ceramic interfacial structure was observed in the joints and a key role was played by Ti coming from Ti6Al4V: it worked as the active element enhancing the adhesion of the liquid to the ceramic and segregated at the interface forming TiB. A satisfactory mechanical performance was obtained for ZrB2-SiC/Ti6Al4V joints, which exhibited a room temperature shear strength of 74 MPa.

  7. Al-Ti Particulate Composite: Processing and Studies on Particle Twinning, Microstructure, and Thermal Stability

    NASA Astrophysics Data System (ADS)

    Yadav, Devinder; Bauri, Ranjit; Kauffmann, Alexander; Freudenberger, Jens

    2016-08-01

    The present investigation shows that alternate to the ceramic particles, hard metallic particles can be used as reinforcement in an aluminum matrix to achieve a good strength-ductility combination in a composite. Titanium particles were incorporated into aluminum by friction stir processing (FSP) to process an Al-Ti particulate composite. FSP led to uniform distribution of the particles in the stir zone without any particle-matrix reaction, thereby retaining the particles in their elemental state. Fracture and twinning of the Ti particles with different frequency of occurrence on the advancing and retreating sides of the stir zone was observed. Twinning of the particles was studied by focused ion beam-assisted transmission electron microscopy. The processed Al-Ti composite exhibited a significant improvement in strength and also retained appreciable amount of ductility. The thermal stability of the fine-grained structure against abnormal grain growth (AGG) was improved by the Ti particles. The AGG in the Al-Ti composite occurred at 713 K (440 °C) compared to 673 K (400 °C) in the unreinforced aluminum processed under the same conditions. On the other hand, the particle-matrix reaction occurred only at 823 K (550 °C), and hence the Ti particles were thermally more stable compared to the matrix grain structure.

  8. Al-Ti Particulate Composite: Processing and Studies on Particle Twinning, Microstructure, and Thermal Stability

    NASA Astrophysics Data System (ADS)

    Yadav, Devinder; Bauri, Ranjit; Kauffmann, Alexander; Freudenberger, Jens

    2016-06-01

    The present investigation shows that alternate to the ceramic particles, hard metallic particles can be used as reinforcement in an aluminum matrix to achieve a good strength-ductility combination in a composite. Titanium particles were incorporated into aluminum by friction stir processing (FSP) to process an Al-Ti particulate composite. FSP led to uniform distribution of the particles in the stir zone without any particle-matrix reaction, thereby retaining the particles in their elemental state. Fracture and twinning of the Ti particles with different frequency of occurrence on the advancing and retreating sides of the stir zone was observed. Twinning of the particles was studied by focused ion beam-assisted transmission electron microscopy. The processed Al-Ti composite exhibited a significant improvement in strength and also retained appreciable amount of ductility. The thermal stability of the fine-grained structure against abnormal grain growth (AGG) was improved by the Ti particles. The AGG in the Al-Ti composite occurred at 713 K (440 °C) compared to 673 K (400 °C) in the unreinforced aluminum processed under the same conditions. On the other hand, the particle-matrix reaction occurred only at 823 K (550 °C), and hence the Ti particles were thermally more stable compared to the matrix grain structure.

  9. Wetting Behavior and Reactivity Between AlTi6 Alloy and Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Homa, M.; Sobczak, N.; Sobczak, J. J.; Morgiel, J.; Seal, S.; Nowak, R.; Bruzda, G.

    2016-02-01

    Wetting behavior between molten AlTi6 alloy and nanoporous carbon substrate (carbon nanotubes paper) was investigated by a sessile drop method in vacuum at 800, 900, and 1000 °C. In order to avoid the effect of native oxide film on metal sample, an advanced capillary purification technique coupled with non-contact heating was applied. The AlTi6 drop did not wet the MWCNT paper immediately after deposition on the substrate at 800 °C, forming a contact angle of θ = 153°. The increase in temperature up to 900 °C and holding the system for 15 min also did not affect the contact angle (θ = 153 ± 1). Further heating above 930 °C at a rate of 5 °C/min caused a gradual lowering of contact angle down to ~130° and after about 10-min interaction at 1000 °C, it reached the final value of 123°. Structural investigations of solidified sessile drop AlTi6/MWCNT couple by scanning and transmission electron microscopy showed that high-temperature interaction between MWCNTs and molten AlTi6 alloy is accompanied with liquid metal infiltration of MWCNT substrate, fragmentation of MWCNTs, and formation of TiC in the form of rod-like crystallites and fine particles uniformly distributed in the metal matrix. The mechanism of MWCNT → TiC transformation in the AlTi6/MWCNT system by high-temperature liquid-assisted process is discussed.

  10. Static and reversible elastic strain effects on magnetic order of La0.7Ca0.3MnO3/SrTiO3 superlattices

    NASA Astrophysics Data System (ADS)

    Das, Sujit; Herklotz, Andreas; Jia Guo, Er; Dörr, Kathrin

    2014-04-01

    [La0.7Ca0.3MnO3(2.6 nm)/SrTiO3(6.3 nm)]15 superlattices (SLs) have been simultaneously grown by Pulsed Laser Deposition (PLD) on different oxide substrates in an attempt to obtain different residual strain states. The substrates are (100)-oriented SrTiO3 (STO), LaAlO3 (LAO), and piezoelectric 0.72Pb (Mg1.3 Nb2.3)3-0.28PbTiO3 (PMN-PT). The La0.7Ca0.3MnO3 layers show tensile strain of ɛ = 1% on LAO and stronger strain on STO and PMN-PT (ɛ = 1.7%). The magnetization has been measured and is found to be quite different for the three SLs. Reversible biaxial compression of Δɛ=-0.1% using the PMN-PT substrate helps one to estimate which part of the differences in magnetic order among the samples is induced by elastic strain. The influence of elastic strain is found to be substantial, but does not completely account for the different behavior of the samples.

  11. Photoluminescence Properties of CaAlBO4:M (M: Pb2+, Dy3+, and Sm3+)

    NASA Astrophysics Data System (ADS)

    Erdoğmuş, E.; Pekgözlü, İ.

    2014-07-01

    Pb2+, Dy3+, and Sm3+ doped CaAlBO4 materials were synthesized by the conventional solid state reaction. The synthesized phosphors were characterized by X-Ray powder diffraction. The emission and excitation spectra of these phosphors were measured at room temperature. The emission band of CaAlBO4:Pb2+ appeared as a broad band at 339 nm upon excitation with 272 nm. The second phosphor, CaAlBO4: Dy3+, emits at 477, 570, and 670 nm upon 347 nm excitation. The third phosphor, CaAlBO4:Sm3+, emits at 563, 594, 643, and 705 nm upon 236 nm excitation.

  12. Improving the osteointegration of Ti6Al4V by zeolite MFI coating

    SciTech Connect

    Li, Yong; Jiao, Yilai; Li, Xiaokang; Guo, Zheng

    2015-05-01

    Osteointegration is crucial for success in orthopedic implantation. In recent decades, there have been numerous studies aiming to modify titanium alloys, which are the most widely used materials in orthopedics. Zeolites are solid aluminosilicates whose application in the biomedical field has recently been explored. To this end, MFI zeolites have been developed as titanium alloy coatings and tested in vitro. Nevertheless, the effect of the MFI coating of biomaterials in vivo has not yet been addressed. The aim of the present work is to evaluate the effects of MFI-coated Ti6Al4V implants in vitro and in vivo. After surface modification, the surface was investigated using field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). No difference was observed regarding the proliferation of MC3T3-E1 cells on the Ti6Al4V (Ti) and MFI-coated Ti6Al4V (M−Ti) (p > 0.05). However, the attachment of MC3T3-E1 cells was found to be better in the M−Ti group. Additionally, ALP staining and activity assays and quantitative real-time RT-PCR indicated that MC3T3-E1 cells grown on the M−Ti displayed high levels of osteogenic differentiation markers. Moreover, Van-Gieson staining of histological sections demonstrated that the MFI coating on Ti6Al4V scaffolds significantly enhanced osteointegration and promoted bone regeneration after implantation in rabbit femoral condylar defects at 4 and 12 weeks. Therefore, this study provides a method for modifying Ti6Al4V to achieve improved osteointegration and osteogenesis. - Highlights: • Osteointegration is a crucial factor for orthopedic implants. • We coated MFI zeolite on Ti6Al4V substrates and investigated the effects in vitro and in vivo. • The MFI coating displayed good biocompatibility and promoted osteogenic differentiation in vitro. • The MFI coating promoted osteointegration and osteogenesis peri-implant in vivo.

  13. Influence of strain rate on the structure/property of Ti-48Al-1V

    SciTech Connect

    Gray, G.T. III.

    1990-01-01

    While the influence of strain rate on the structure/property response of pure titanium and a variety of titanium alloys has been extensively studied, the effect of strain rate on the stress-strain and deformation response of titanium aluminides remains largely unknown. In this paper, a preliminary study of the effect of strain rate and temperature on the substructure evolution and mechanical response of a (48Al-1V)TiAl alloy is presented. The compressive true stress-true strain response of Ti-48Al-1V was found to depend on both the applied strain rate, varied between 0.001 and 7500 s{sup {minus}1}, and the test temperature, varied between 25 and 700{degree}C. The rate of strain hardening in Ti-48Al-1V is seen to increase with increasing strain rate. The substructure evolution of Ti-48Al-1V was observed to depend on the applied strain rate and temperature of deformation. The substructure of Ti-48Al-1V deformed to {var epsilon} = 0.20 at 0.001 s{sup {minus}1} at 25{degree}C was seen to consist of predominately random dislocation debris and isolated grains containing a high density of stacking faults. The majority of the dislocations appear to be (111) 1/2{l angle}110{r angle} unit type ordinary dislocations which is consistent with previous observations on Ti-48Al. Increasing the rate of deformation at room temperature to 75000 s{sup {minus}1} is seen to increase the density of deformation twins and the overall random dislocation debris density. The substructure of Ti-48Al-1V deformed a at high-strain-rate at elevated temperatures was seen to be quite similar to that observed following high-rate deformation at room temperature except for an even higher incidence of twinning. The defect generation and the rate sensitivity of TiAl are discussed as a function of strain rate and contrasted to that observed in conventional titanium alloys. 34 refs., 8 figs.

  14. Intermixtures at LaAlO3/SrTiO3 interfaces

    NASA Astrophysics Data System (ADS)

    Chen, Hanghui; Kolpak, Alexie; Ismail-Beigi, Sohrab

    2010-03-01

    The intriguing transport properties observed at the LaAlO3/SrTiO3 n-type interface have precipitated numerous studies in the past few years. However, it remains uncertain whether the interface obtained experimentally is atomically sharp, and if not, what role the disorder plays in the unique behavior of this system. We use first principles density functional theory to find the energetics of cation intermixing, specifically La-Sr and Al-Ti, at the LaAlO3/SrTiO3 n-type interface. We find that an ideal interface with no intermixing is not thermodynamically stable. Ti-Al intermixing reduces the total energy while Sr-La intermixing increases the total energy. We explain the energetics and this asymmetry in terms of a simple electrostatic model, which is able to accurately describe the DFT results. We also discuss how intermixing affects the polar field in the LaAlO3, the ``polar catastrophe'', and the critical thickness of LaAlO3 needed to induce a metal-insulator transition.

  15. Microstructures and Properties of Plasma Electrolytic Oxidized Ti Alloy (Ti-6Al-4V) for Bio-implant Application

    NASA Astrophysics Data System (ADS)

    Kumari, Renu; Blawert, Carsten; Majumdar, J. Dutta

    2016-02-01

    In the present study, plasma electrolytic oxidation (PEO) of Ti6Al4V has been performed in an electrolyte containing 20 g/L of Na2SiO3, 10 g/L of Na3PO4, 2 g/L of KOH, and 5 g/L of hydroxyapatite at an optimum constant potential of 430 V for 10 minutes. Followed by PEO treatment, surface roughness was measured using non-contact optical profilometer. A detailed characterization of microstructure, composition and phase analysis was carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopic analysis, Fourier-transform infrared, and X-ray diffraction study. The mechanical properties of the surface have been evaluated by measuring nano-hardness and wear resistance. The effect of surface modification on corrosion resistance property has also been evaluated in Hank's solution. Finally, wettability and bioactivity test have been also performed. PEO developed a thick (150 μm) porous (35 pct) oxide film on the surface of Ti-6Al-4V consisting of anatase, rutile, and SiO2. The nano-hardness of the PEO-treated surface is increased to 8 ± 0.5 GPa as compared to 2 ± 0.4 GPa of the as-received Ti-6Al-4V. Wear and corrosion resistance were improved following oxidation. There is an improvement in wettability in terms of decrease in contact angle from 60 ± 1.5 to 45 ± 1 deg. Total surface energy and its polar component were also increased significantly on PEO-treated surface as compared to the as-received Ti6Al4V.

  16. Multi-step wrought processing of TiAl-based alloys

    SciTech Connect

    Fuchs, G.E.

    1997-04-01

    Wrought processing will likely be needed for fabrication of a variety of TiAl-based alloy structural components. Laboratory and development work has usually relied on one-step forging to produce test material. Attempts to scale-up TiAl-based alloy processing has indicated that multi-step wrought processing is necessary. The purpose of this study was to examine potential multi-step processing routes, such as two-step isothermal forging and extrusion + isothermal forging. The effects of processing (I/M versus P/M), intermediate recrystallization heat treatments and processing route on the tensile and creep properties of Ti-48Al-2Nb-2Cr alloys were examined. The results of the testing were then compared to samples from the same heats of materials processed by one-step routes. Finally, by evaluating the effect of processing on microstructure and properties, optimized and potentially lower cost processing routes could be identified.

  17. Selected fretting-wear-resistant coatings for Ti-6 pct Al-4 pct V alloy

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1985-01-01

    The ability of several wear-resistant coatings to reduce fretting in the Ti-6Al-4V alloy is investigated. The experimental apparatus and procedures for evaluating fretting in uncoated Ti-6Al-4V alloy and in the alloy with plasma-sprayed coatings, polymer-bonded coating, and surface treatments are described. The wear volume and wear rate for the alloys are measured and compared. It is concluded that Al2O3 with 13 percent TiO2, preoxidation and nitride surface treatments, and MoS2 sputtering result in wear-resistant surfaces; however, the polyimide coating is the most wear resistant coating in both dry and moist air, and it causes the least wear to the uncoated alloy surface.

  18. Enhanced superplasticity and strength in modified Ti-6Al-4V alloys

    SciTech Connect

    Wert, J.A.; Paton, N.E.

    1983-12-01

    Beta-stabilizing elements were added Ti-6Al-4V alloy with a view to lowering its optimum superplastic forming temperature. The alloys modified with 2 wt pct Fe, Co, and Ni produced values of flow stress, strain rate sensitivity, and total elongation at 1088 K approaching those of the base Ti-6Al-4V alloy at its standard superplastic forming temperature of 1200 K. In addition to lowering the superplastic forming temperature, the beta-stabilizing elements also increased room temperature strength levels above those normally found for Ti-6Al-4V. The addition of beta-stabilizing elements raised resistance to deformation at room temperature, while lowering it at elevated temperatures. This result is explained by considering the effects of high-diffusivity beta stabilizers on deformation processes at room and elevated temperatures. 23 references.

  19. Porous Ti6Al4V alloys with enhanced normalized fatigue strength for biomedical applications.

    PubMed

    Li, Fuping; Li, Jinshan; Kou, Hongchao; Zhou, Lian

    2016-03-01

    In this paper, porous Ti6Al4V alloys for biomedical applications were fabricated by diffusion bonding of alloy meshes. The compression-compression fatigue behavior was studied. It results that porous Ti6Al4V alloys show enhanced normalized fatigue strength which is in the range of 0.5-0.55 at 10(6)cycles. The porosity has some effect on the absolute S-N curves but minor effect on the normalized S-N curves. The relationship between strain per cycle and number of cycles shows three distinct stages and the value of strain per cycle is constant in stage II. The reasons for the higher normalized fatigue strength of porous Ti6Al4V alloys are discussed based on the fatigue crack initiation and propagation. PMID:26706555

  20. Effect of Reactive Sputtering Parameters on TiAlN Nanocoating Structure and Morphology

    SciTech Connect

    Budi, Esmar; Razali, M. Mohd.; Nizam, A. R. Md.

    2010-10-24

    The effect of substrate bias and nitrogen flow rate on the TiAlN nanocoating structure and morphology has been investigated by using reactive unbalance DC magnetron sputtering. TiAlN nanocoating was deposited on the tungsten carbide insert tool and the structure and morphology were characterized by using XRD and AFM, respectively. The substrate bias was varied between 0 to -221 V and the nitrogen flow rate was varied between 30 to 72 sccm. The results showed that the structure of TiAlN nanocoating consisted of mainly (111) and (200) plane. The structure was significatly influenced by substrate bias in promoting finer crystal size and increased crystal plane spacing while the rms roughness of nanocoating was influenced by substrate bias and nitrogen flow rate.

  1. 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.

  2. Effect of Milling Parameters on Microstructure of Ti/Al Composite Powder Produced by Discus Milling

    NASA Astrophysics Data System (ADS)

    Raynova, S.; Cao, P.; Gabbitas, B.; Zhang, D.

    The motivation of this research is to develop a process for producing Ti/Al composite powders that enable synthesis of a single-phase TiAl intermetallic bulk material, which is then used as a target for physical vapour deposition (PVD) coating. This study reports the effects of milling time, amount of process control agent (PCA) added as well as the powder-to-medium ratio on the microstructure of the Ti/Al composite powder. Optical microscopy and scanning electron microscopy (SEM) were used to evaluate the level of mixing and the resulting powder particle size. X-ray diffraction analysis and differential thermal analysis were used for determining the phase constituents and the solid state reaction temperature of the as-milled powders.

  3. Industrial Application of Thin Films (TiAl)N Deposited on Thermo-Wells

    SciTech Connect

    Velez, G.; Jaramillo, S.; Arango, Y. C.; Devia, D.; Quintero, J.; Devia, A.

    2006-12-04

    The thermo-well is formed by two layers, one layer is a ceramic and the other layer is anviloy (comprised tungsten). They are used to coat the thermocouple in the control temperature system during the Aluminum-Silicon alloy melting process. After two weeks of continuous work at 750 deg. C of temperature (the alloy temperature), a high wear in this material is observed, affecting the ceramic. (TiAl)N thin films are deposited directly on the anviloy substrates by the PAPVD (Plasma Assisted Physics Vapor Deposition) in arc pulsed technique, using a TiAl target in a mono-vaporizer system, composed by a reactor and a power controlled system. Two opposite electrodes are placed into the reactor and discharge is produced by a controlled power system. The XRD (X-ray diffraction) patterns show the presence of the (TiAl)N thin film peaks. The morphological characteristics are studied by the scanning probe microscopy (SPM)

  4. Cold Spraying of Ti2AlC MAX-Phase Coatings

    NASA Astrophysics Data System (ADS)

    Gutzmann, H.; Gärtner, F.; Höche, D.; Blawert, C.; Klassen, T.

    2013-03-01

    Cold spraying was applied to deposit Ti2AlC on different substrate materials. The study of single impacts by scanning electron microscopy indicates that bonding of the first layer is mainly attributed to the deformation and shear instabilities occurring at substrate sites. Nevertheless, as compared to the feedstock particles, the splats appear flattened by the impact. This deformation seems to be attributed not only to local, internal shear but also to internal fracture. By applying up to five passes under optimized spray parameters, Ti2AlC-coatings with thicknesses of about 110-155 μm were achieved. XRD analysis of the coating proved that the crystallographic structure of the feedstock was retained during cold spraying. The coating microstructures show rather low porosity of about <2%, but several cracks between spray layers. Successful build-up of more than one layer can probably be attributed to local deformation of the highly anisotropic Ti2AlC-phase.

  5. Electrochemical Corrosion Characteristics of Arc-Ion-Plated AlTiN Coating for Marine Application.

    PubMed

    Lee, Jung-Hyung; Kim, MyoungJun; Kim, Seong-Jong

    2016-02-01

    In this study, aluminum titanium nitride (AlTiN) coating was deposited by arc ion plating onto mirror finish STS 304 plate. The surface and cross-section of the coating was characterized by SEM and EDX analysis. Several electrochemical corrosion experiments were performed including rest potential measurement, potentiodynamic polarization experiment and Tafel analysis. The result of the experiments indicated that the AlTiN coating presented lower corrosion current density than the substrate material (STS 304) under uniform corrosion environment. It was also observed that AlTiN coating may have a risk of being attacked by localized corrosion attack such as pitting when pores or micro/nano particles in the coating are exposed to chloride ion containing corrosion environment, especially marine environment. PMID:27433658

  6. Effect of Reactive Sputtering Parameters on TiAlN Nanocoating Structure and Morphology

    NASA Astrophysics Data System (ADS)

    Budi, Esmar; Razali, M. Mohd.; Nizam, A. R. Md.

    2010-10-01

    The effect of substrate bias and nitrogen flow rate on the TiAlN nanocoating structure and morphology has been investigated by using reactive unbalance DC magnetron sputtering. TiAlN nanocoating was deposited on the tungsten carbide insert tool and the structure and morphology were characterized by using XRD and AFM, respectively. The substrate bias was varied between 0 to -221 V and the nitrogen flow rate was varied between 30 to 72 sccm. The results showed that the structure of TiAlN nanocoating consisted of mainly (111) and (200) plane. The structure was significatly influenced by substrate bias in promoting finer crystal size and increased crystal plane spacing while the rms roughness of nanocoating was influenced by substrate bias and nitrogen flow rate.

  7. Morphology Control for Al2O3 Inclusion Without Ca Treatment in High-Aluminum Steel

    NASA Astrophysics Data System (ADS)

    He, Shengping; Chen, Gujun; Guo, Yintao; Shen, Boyi; Wang, Qian

    2015-04-01

    Nozzle blockage is a major problem during continuous casting of Al-containing steel. Herein, we analyzed the thermodynamic equilibrium behavior between aluminum and oxygen in steel at 1873 K (1600 °C) and demonstrated that, the dissolved [O] initially decreases with increasing the dissolved [Al] until approximately 0.1 wt pct [Al], and after that, the dissolved [O] increases with dissolved [Al]. Thus, for high-aluminum steel with 1.0 wt pct dissolved [Al], the precipitation of Al2O3 inclusion can be avoided during cooling from deoxidation temperature to the liquidus temperature, if the actual dissolved [O] can be kept from increasing when the dissolved [Al] further increases from 0.1 to 1.0 wt pct. Hence, a method of inclusion control for high-aluminum steel without traditional Ca treatment technology was proposed based on the thermodynamic analysis. Industrial tests confirmed that low-melting point Ca-aluminate inclusions were observed typically through a slag washing with SiO2-minimized high-basicity slag during tapping, accompanied by two-step Al-adding process for production of high-aluminum steel. Moreover, there was no nozzle clogging occurred for five heats of continuous casting.

  8. 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.

  9. 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.

  10. Preparation, corrosion resistance and hemocompatibility of the superhydrophobic TiO2 coatings on biomedical Ti-6Al-4V alloys

    NASA Astrophysics Data System (ADS)

    Jiang, J. Y.; Xu, J. L.; Liu, Z. H.; Deng, L.; Sun, B.; Liu, S. D.; Wang, L.; Liu, H. Y.

    2015-08-01

    In this paper the micro-arc oxidation (MAO) technique and subsequent superhydrophobic treatment were applied to fabricate the superhydrophobic TiO2 coatings on biomedical Ti-6Al-4V alloys. The surface morphology, surface roughness, water contact angle, corrosion resistance and hemocompatibility of the MAO and superhydrophobic samples were investigated. The results showed that the single anatase TiO2 coating was formed on the surface Ti-6Al-4V alloy with rough and porous micrometer-scale structure. The low surface energy film was grafted on the surface of the TiO2 coating by self-assembling reaction during the hydrophobic treatment process, which resulted in the formation of superhydrophobic surfaces with the water contact angle of 153.39°. It was found that the corrosion resistance of the superhydrophobic samples increased by one order of magnitude compared to those of the uncoated Ti-6Al-4V alloys. The hemolysis ratio and platelets adhesion characteristics of the Ti-6Al-4V alloys were also improved greatly through the MAO treatment and subsequent superhydrophobic treatment. Especially, no platelet could be observed on the surface of the superhydrophobic samples. Therefore, the superhydrophobic TiO2 coatings of Ti-6Al-4V alloys with higher hemocompatibility would show great promise in their potential blood-contacting applications.

  11. 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

  12. Pre-Accretionary Distribution of Ca and Al Between Matrix and Chondrules in CV Chondrites

    NASA Astrophysics Data System (ADS)

    Hezel, D. C.; Palme, H.

    2007-03-01

    Ca/Al-ratios in Y-86751 (CV) chondrules are super- and in matrix sub-chondritic. The opposite is true for Allende and Efremovka. Incorporation of spinel in Allende and Efremovka chondrule precursors in a nebular setting can explain this observation.

  13. The first observation of SRS in a trigonal LiCaAlF{sub 6} crystal

    SciTech Connect

    Kaminskii, Alexandr A; Eichler, H J; Gad, G M; Ueda, Ken-ichi; Reiche, P

    2000-12-31

    The Raman parametric generation is excited for the first time in a trigonal LiCaAlF{sub 6} fluoride crystal pumped by picosecond pulses. The energy of the {chi}{sup (3)}-active vibrational mode is determined and all Stokes and anti-Stokes components of SRS are detected for this crystal in the visible region. (letters)

  14. Photoresponse dynamics in amorphous-LaAlO3/SrTiO3 interfaces

    PubMed Central

    Di Gennaro, Emiliano; Coscia, Ubaldo; Ambrosone, Giuseppina; Khare, Amit; Granozio, Fabio Miletto; di Uccio, Umberto Scotti

    2015-01-01

    The time-resolved photoconductance of amorphous and crystalline LaAlO3/SrTiO3 interfaces, both hosting an interfacial 2-dimensional electron gas, is investigated under irradiation by variable-wavelengths, visible or ultraviolet photons. Unlike bare SrTiO3 single crystals, showing relatively small photoconductance effects, both kinds of interfaces exhibit an intense and highly persistent photoconductance with extraordinarily long characteristic times. The temporal behaviour of the extra photoinduced conductance persisting after light irradiation shows a complex dependence on interface type (whether amorphous or crystalline), sample history and irradiation wavelength. The experimental results indicate that different mechanisms of photoexcitation are responsible for the photoconductance of crystalline and amorphous LaAlO3/SrTiO3 interfaces under visible light. We propose that the response of crystalline samples is mainly due to the promotion of electrons from the valence bands of both SrTiO3 and LaAlO3. This second channel is less relevant in amorphous LaAlO3/SrTiO3, where the higher density of point defects plays instead a major role. PMID:25670163

  15. Photoresponse dynamics in amorphous-LaAlO3/SrTiO3 interfaces

    NASA Astrophysics Data System (ADS)

    di Gennaro, Emiliano; Coscia, Ubaldo; Ambrosone, Giuseppina; Khare, Amit; Granozio, Fabio Miletto; di Uccio, Umberto Scotti

    2015-02-01

    The time-resolved photoconductance of amorphous and crystalline LaAlO3/SrTiO3 interfaces, both hosting an interfacial 2-dimensional electron gas, is investigated under irradiation by variable-wavelengths, visible or ultraviolet photons. Unlike bare SrTiO3 single crystals, showing relatively small photoconductance effects, both kinds of interfaces exhibit an intense and highly persistent photoconductance with extraordinarily long characteristic times. The temporal behaviour of the extra photoinduced conductance persisting after light irradiation shows a complex dependence on interface type (whether amorphous or crystalline), sample history and irradiation wavelength. The experimental results indicate that different mechanisms of photoexcitation are responsible for the photoconductance of crystalline and amorphous LaAlO3/SrTiO3 interfaces under visible light. We propose that the response of crystalline samples is mainly due to the promotion of electrons from the valence bands of both SrTiO3 and LaAlO3. This second channel is less relevant in amorphous LaAlO3/SrTiO3, where the higher density of point defects plays instead a major role.

  16. Structure of nanocrystalline arc-PVD (Ti, Al)N coatings modified with nickel

    NASA Astrophysics Data System (ADS)

    Blinkov, I. V.; Belov, D. S.; Volkhonskii, A. O.; Blinkov, V. I.; Shatalov, R. L.

    2015-05-01

    The introduction of nickel into the composition of ion-plasma vacuum-arc (Ti, Al)N coatings refines nitride-phase crystallites from 100-120 to 15-18 nm when the nickel content is varied from zero to 12 at %. The size of nitride blocks is in agreement with that of ceramic-phase grains. Some (Ti, Al)N grains grow with the nickel content up to 30-35 nm. The structure changes from columnar to equiaxed during modifying the (Ti, Al)N coatings with nickel. Nickel in a coating is in an amorphous state (detected by X-ray diffraction) when its content is no more than 12-13 at %. A further increase in its content leads to the formation of the TiNi intermetallic compound, which results in structure porosity in the deposited coating. A transition zone forms at the boundary between a (Ti, Al)N-Ni coating and the VK6-alloy substrate, which is characterized by an element concentration gradient from the coating to the substrate and vice versa.

  17. Electrical characteristics of SrTiO3/Al2O3 laminated film capacitors

    NASA Astrophysics Data System (ADS)

    Peng, Yong; Yao, Manwen; Chen, Jianwen; Xu, Kaien; Yao, Xi

    2016-07-01

    The electrical characteristics of SrTiO3/Al2O3 (160 nm up/90 nm down) laminated film capacitors using the sol-gel process have been investigated. SrTiO3 is a promising and extensively studied high-K dielectric material, but its leakage current property is poor. SrTiO3/Al2O3 laminated films can effectively suppress the demerits of pure SrTiO3 films under low electric field, but the leakage current value reaches to 0.1 A/cm2 at higher electric field (>160 MV/m). In this study, a new approach was applied to reduce the leakage current and improve the dielectric strength of SrTiO3/Al2O3 laminated films. Compared to laminated films with Au top electrodes, dielectric strength of laminated films with Al top electrodes improves from 205 MV/m to 322 MV/m, simultaneously the leakage current maintains the same order of magnitude (10-4 A/cm2) until the breakdown occurs. The above electrical characteristics are attributed to the anodic oxidation reaction in origin, which can repair the defects of laminated films at higher electric field. The anodic oxidation reactions have been confirmed by the corresponding XPS measurement and the cross sectional HRTEM analysis. This work provides a new approach to fabricate dielectrics with high dielectric strength and low leakage current.

  18. 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.

  19. The effect of APH treatment on surface bonding and osseointegration of Ti-6Al-7Nb implants: an in vitro and in vivo study.

    PubMed

    Nguyen, Thuy-Duong Thi; Moon, So-Hee; Oh, Tae-Ju; Park, Il-Song; Lee, Min-Ho; Bae, Tae-Sung

    2015-04-01

    This study investigated the effects of anodization-cyclic precalcification-heat (APH) treatment on the bonding ability of Ca-P coating to the parent metal and osseointegration of Ti-6Al-7Nb implants. Eighteen Ti-6Al-7Nb discs, 9 untreated and 9 APH-treated, were cultured with osteoblast cells in vitro, and the cellular differentiation ability was assayed at 1, 2, and 3 weeks. For in vivo testing, 28 Ti-6Al-7Nb implants (14 implants of each group) were inserted to rat tibias, and after each 4 and 6 weeks of implantation, bone bonding, and osseointegration were evaluated through removal torque and histological analysis. Osteoblast-culturing showed twice as much of the alkaline phosphatase activity on the treated surface at 3 weeks than on the untreated surface (p < 0.05). The treated implants exhibited higher removal torque values than the untreated ones (15.5 vs. 1.8 Ncm at 4 weeks and 19.7 vs. 2.6 Ncm at 6 weeks, p < 0.05). Moreover, the excellent bonding quality of coats was confirmed by the existence of cohesive fractures on the surface of removed APH implants (field emission scanning electron microscopy and histological observation). Within the limits of this study, it can be concluded that the APH treatment significantly enhanced osseointegration of the Ti-6Al-7Nb implant, with the stable bonding between the coating and the implant surface. PMID:24976109

  20. Interfacial reactions in borsic/Ti-3Al-2-1/2V composite

    NASA Technical Reports Server (NTRS)

    Rao, V. B.; Houska, C. R.; Unnam, J.; Brewer, W. D.; Tenney, D. R.

    1979-01-01

    The paper provides a detailed X-ray characterization of a borsic/Ti-3Al-2-1/2V composite, and to correlate the relative intensities of the reaction products with the mechanical properties. Based on X-ray integrated intensity data two stages of interface reactions were identified: during the first stage there is a simultaneous interdiffusion of Si, C, and Ti atoms at the filament/matrix interface resulting in the formation of Ti5Si3, TiSi and small amounts of TiSi2 and TiC. The second stage is associated with considerable TiSi2 and boride formation. It appears that the alpha-phase of Ti is more reactive in forming silicides and borides than the beta-phase. The silicide intensities and the reaction zone thicknesses are shown to be directly related to the reduction of the ultimate tensile strength by thermal degradation, and the results indicate that silicide reaction products are as detrimental to strength as the borides.

  1. Microstructure and mechanical behaviour of Ti-6Al-7Nb alloy produced by selective laser melting

    SciTech Connect

    Chlebus, Edward; Kuznicka, Bogumila Kurzynowski, Tomasz; Dybala, Bogdan

    2011-05-15

    Selective laser melting (SLM) is an advanced manufacturing technology providing alternative method of producing complex components directly from 3D computer models. The purpose of this work is to determine the influence of the SLM manufacturing strategy on mechanical properties and microstructure of the as-built Ti-Al-Nb alloy. Specimens of Ti-6Al-7Nb were produced in three versions of the specimen axis orientation with respect to its build direction. Mechanical characteristics of the alloy were determined by tensile and compression testing, as well as hardness measurements. Microstructures were characterised utilising optical microscopy, scanning electron microscopy and X-ray diffraction analysis. It was found that the as-built Ti-6Al-7Nb alloy has microstructure of {alpha}' martensite hardened by dispersive precipitates of the second phase, which results in higher tensile and compressive strengths, but lower ductility in comparison to those of an alloy manufactured by conventional methods. The layered microstructure of the material gives it a significant anisotropy of Young's modulus, moderate anisotropy of mechanical properties, but strong anisotropy of sensitivity to the build porosity. The paper develops understanding of the relationships between the strategy of layered manufacturing of the Ti-6Al-7Nb alloy and its microstructural and mechanical characteristics. This is important for future applications of the SLM technology for producing Ti-6Al-7Nb parts, e.g. the custom medical implants. - Research Highlights: {yields} The as-built SLM Ti-6Al-7Nb alloy has a layered microstructure of {alpha}' martensite. {yields} Size and orientation of the {alpha}' plates are determined by the SLM building strategy. {yields} The layered microstructure gives the alloy an anisotropy of Young's modulus. {yields} The building strategy influences anisotropy of material sensitivity to the built porosity.

  2. Lattice variations of Ti-6Al-4V alloy with hydrogen content

    SciTech Connect

    Zhu Tangkui Li, Miaoquan

    2011-07-15

    Effect of hydrogen content on the lattice parameter of Ti-6Al-4V alloy has been investigated by X-ray diffraction. The experimental results show that the solution of hydrogen in the Ti-6Al-4V alloy affects significantly on the lattice parameters of {alpha}, {beta} and {delta} phases, especially the {beta} phase. Furthermore, the critical hydrogen content of {delta} hydride formation for Ti-6Al-4V alloy is 0.385 wt.%. When the hydrogen content is lower than the critical hydrogen content, the {delta} hydride cannot precipitate and the lattice parameter ({alpha}) of {beta} phase linearly increases with the increasing of hydrogen content. When the hydrogen content is higher than the critical hydrogen content, the {delta} hydride precipitates and the lattice parameter ({alpha}) of {beta} phase varies inconspicuously with hydrogen content. In addition, the effects of lattice variations and {delta} hydride formation on microstructure are discussed. The {alpha}/{beta} interfaces of lamellar transformed {beta} phase become fuzzy with the increasing of hydrogen content because of the lattice expansion of {beta} phase. Compared with that of the Ti-6Al-4V alloy at low hydrogen content ({<=} 0.385 wt.%), the contrasts of primary {alpha} phase and transformed {beta} phase of Ti-6Al-4V alloy at high hydrogen content ({>=} 0.385 wt.%) were completely reversed due to the formation of {delta} hydride. - Research Highlights: {yields} A novel method for determining {delta} hydride in Ti-6Al-4V alloy is presented. {yields} The critical hydrogen content of {delta} hydride formation is 0.385 wt.%. {yields} The lattice parameter of {beta} phase can be expressed as follows: a=0.323(1+9.9x10{sup -2}C{sub H}) . {yields} Precipitation of {delta} hydride has a significant influence on the microstructure. {yields} The {alpha}/{beta} interfaces of transformed {beta} phase became fuzzy in the hydrogenated alloy.

  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. Directionally solidified Eu doped CaF2/Li3AlF6 eutectic scintillator for neutron detection

    NASA Astrophysics Data System (ADS)

    Kamada, Kei; Hishinuma, Kousuke; Kurosawa, Shunsuke; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

    2015-12-01

    Eu doped CaF2/Li3AlF6 eutectics were grown by μ-PD method. The directionally solidified eutectic with well-aligned 600 nm diameter Eu:CaF2 scintillator fibers surrounded with Li3AlF6 was prepared. The grown eutectics showed an emission peak at 422 nm ascribed to Eu2+ 4f-5d transition from Eu:CaF2 scintillation fiber. Li concentration in the Eu:CaF2-Li3AlF6 eutectic is around 0.038 mol/cm3,which is two times higher than that of LiCaAlF6 single crystal (0.016 mol/cm3). The light yield of Eu:CaF2-Li3AlF6 eutectic was around 7000 ph/neutron. The decay time was about 550 ns (89%) and 1450 ns (11%).

  5. Effect of interface layer on the microstructure and electromigration resistance of Al-Si-Cu alloy on TiN/Ti substrates

    NASA Astrophysics Data System (ADS)

    Olowolafe, J. O.; Kawasaki, H.; Lee, C. C.; Klein, J.; Pintchovski, F.; Jawarani, D.

    1993-05-01

    Al-Si-Cu alloy films sputter-deposited on reactively ion-sputtered TiN/Ti/SiO2 substrates were characterized and evaluated for interconnect reliability. Using x-ray diffraction techniques, both TiN and Al microstructures were analyzed and the (111) intensities of the latter correlated with the electromigration median time to fail (MTTF). The values of the MTTF increased with the Al(111) intensities for the TiN/Ti/SiO2 substrates annealed below 400 °C. A progressive decrease in both the Al(111) texture and MTTF was observed for substrates annealed above this temperature. While the improved Al(111) texture has been attributed to an improved TiN barrier textured in the (111) crystal plane (anneals below 400 °C), a TiO2 layer over the TiN barrier has been found responsible for the degradation of the Al(111) texture and the MTTF for barrier anneals above 400 °C.

  6. Initial oxidation of TiAl: An ab-initio investigation

    SciTech Connect

    Bakulin, Alexander V. Kulkova, Svetlana E.; Hu, Qing-Miao; Yang, Rui

    2014-11-14

    We present ab-initio investigation of oxygen adsorption up to two monolayer coverage on the stoichiometric TiAl(100) surface to illustrate the initial oxidation stage. The formation of band gap near the Fermi level demonstrates the transformation from metal to oxide surface with increasing oxygen coverage. The oxidation of Ti rather than Al is observed from our electronic structure calculations. The energy barriers of oxygen diffusion between different sites on surface as well as in subsurface and bulk region are derived. It is shown that the diffusion of oxygen is much easier on the surface than that into the subsurface region.

  7. Shot peening for Ti-6Al-4V alloy compressor blades

    NASA Technical Reports Server (NTRS)

    Carek, Gerald A.

    1987-01-01

    A text program was conducted to determine the effects of certain shot-peening parameters on the fatigue life of the Ti-6Al-4V alloys as well as the effect of a demarcation line on a test specimen. This demarcation line, caused by an abrupt change from untreated surface to shot-peened surface, was thought to have caused the failure of several blades in a multistage compressor at the NASA Lewis Research Center. The demarcation line had no detrimental effect upon bending fatigue specimens tested at room temperature. Procedures for shot peening Ti-6Al-4V compressor blades are recommended for future applications.

  8. Experimental and theoretical investigation of the dislocation mechanisms of microcrack nucleation in Ti3Al

    NASA Astrophysics Data System (ADS)

    Yakovenkova, L. I.; Karkina, L. E.; Elkina, O. A.

    2010-04-01

    The dislocation structure and microcracks in Ti3Al samples subjected to deformation with an indenter at room temperature are analyzed by electron microscopy. The reactions of interaction between superdislocations that carry out deformation in the basal, prismatic, and pyramidal planes (of types I and II) are considered. The types of interactions that result in the formation of dislocation barriers, i.e., microcrack nuclei, are found. The Rice-Thompson model is used to study the relation between the fracture sensitivity and the plastic-relaxation ability of the Ti3Al intermetallic compound during microcrack propagation.

  9. Isentropic Compression Driven by High-Explosive Application to TI-6AL-4V

    NASA Astrophysics Data System (ADS)

    Voltz, C.; Sollier, A.; Maillet, J.-B.; Bouyer, V.

    2009-12-01

    We report on an isentropic compression experiment of Ti-6Al-4V alloy based on the use of the release of detonation products from a high-explosive to generate a ramp wave compression in a multisteps target. VISAR and DLI measurements of the rear free surface velocities of the different steps allow computing the sound velocity of the material during its compression, which is characteristic of the EOS of the material. The experimental device is described and the sound velocity measurements are analyzed. We obtain Ti-6Al-4V strength along the compression up to 15 GPa. The results are compared with two dimensional elastic-plastic simulations.

  10. Development of Ultrafine, Lamellar Structures in Two-Phase {gamma}-TiAl Alloys

    SciTech Connect

    Maziasz, P.J., Liu, C.T.

    1997-12-31

    Processing of two-phase gamma-TiAl alloys (Ti-47Al-2Cr-2Nb or minor modifications thereof) above the alpha-transus temperature (T {sub alpha}) produced unique refined-colony/ultrafine lamellar structures in both powder- and ingot-metallurgy (P/M and I/M, respectively) alloys. These ultrafine lamellar structures consist of fine laths of the gamma and alpha {sub 2} phases, with average interlamellar spacings (lambda {sub Lambda}) of 100-200 nm and alpha {sub 2}-alpha {sub 2} spacings (lambda {sub alpha}) of 200-500 nm, and are dominated by gamma/alpha {sub 2} interfaces. This characteristic microstructure forms by extruding P/M Ti-47Al-2Cr-2Nb alloys above T {sub alpha}, and also forms with finer colony size but slightly coarser fully-lamellar structures by hot-extruding similar I/M alloys. Alloying additions of B and W refine lambda {sub L} and lambda {sub alpha} in both I/M Ti-47Al (cast and heat-treated above T {sub alpha}) or in extruded Ti-47Al-2Cr-2Nb alloys. The ultrafine lamellar structure in the P/M alloy remains stable during heat-treatment at 900 {degrees}C for 2h, but becomes unstable after 4h at 982 {degrees}C; the ultrafine lamellar structure remains relatively stable after aging for {gt}5000 h at 800 {degrees}C. Additions of B+W dramatically improve the coarsening resistance of lambda L and lambda alpha in the I/M Ti-47Al alloys aged for 168 h at 1000{degrees}C. In both the P/M and I/M Ti-47Al-2Cr-2Nb alloys, these refined-colony/ultrafine-lamellar structures correlate with high strength and good ductility at room temperature, and very good strength at high temperatures. While refining the colony size improves the room-temperature ductility, alloys with finer lambda {sub L} are stronger at both room- and high-temperatures. Additions of B+W produce finer as-processed lambda {sub L} and lambda {sub alpha} in I/M TiAl alloys, and stabilize such structures during heat-treatment or aging.

  11. Ultrafine-grained structure formation in Ti-6Al-4V alloy via warm swaging

    NASA Astrophysics Data System (ADS)

    Klimova, M.; Boeva, M.; Zherebtsov, S.; Salishchev, G.

    2014-08-01

    The influence of warm swaging on the structure and properties of Ti-6Al-4V alloy was studied. Warm swaging of the alloy in the interval 680-500°C with the total strain of ɛ=2.66 was found to be resulted in the formation of a homogeneous globular microstructure with a grain size of 0.4 μm in both longitudinal and transversal sections. Room temperature tensile strength and tensile elongation of the swaged alloy was 1315MPa and 10.5%, respectively. Ultrafine-grained Ti-6Al-4V alloy produced by swaging exhibited good workability at 600-700 °C.

  12. Fretting corrosion of CoCrMo and Ti6Al4V interfaces.

    PubMed

    Swaminathan, Viswanathan; Gilbert, Jeremy L

    2012-08-01

    Mechanically assisted corrosion (fretting corrosion, tribocorrosion etc.,) of metallic biomaterials is a primary concern for numerous implant applications, particularly in the performance of highly-loaded medical devices. While the basic underlying concepts of fretting corrosion or tribocorrosion and fretting crevice corrosion are well known, there remains a need to develop an integrated systematic method for the analysis of fretting corrosion involving metal-on-metal contacts. Such a method can provide detailed and quantitative information on the processes present and explore variations in surfaces, alloys, voltages, loadings, motion and solution conditions. This study reports on development of a fretting corrosion test system and presents elements of an in-depth theoretical fretting corrosion model that incorporates both the mechanical and the electrochemical aspects of fretting corrosion. To demonstrate the capabilities of the new system and validate the proposed model, experiments were performed to understand the effect of applied normal load on fretting corrosion performance of Ti6Al4V/Ti6Al4V, CoCrMo/Ti6Al4V, and CoCrMo/CoCrMo material couples under potentiostatic conditions with a fixed starting surface roughness. The results of this study show that fretting corrosion is affected by material couples, normal load and the motion conditions at the interface. In particular, fretting currents and coefficient of friction (COF) vary with load and are higher for Ti6Al4V/Ti6Al4V couple reaching 3 mA/cm(2) and 0.63 at about 73 MPa nominal contact stress, respectively. Ti6Al4V coupled with CoCrMo displayed lower currents (0.6 mA/cm(2)) and COF (0.3), and the fretting corrosion behavior was comparable to CoCrMo/CoCrMo couple (1.2 mA/cm(2) and 0.3, respectively). Information on the mechanical energy dissipated at the interface, the sticking behavior, and the load dependence of the inter-asperity distance calculated using the model elucidated the influence of

  13. Investigation of Aging Processes of Ti-6Al-4 V Powder Material in Laser Melting

    NASA Astrophysics Data System (ADS)

    Seyda, V.; Kaufmann, N.; Emmelmann, C.

    Laser melting of titanium material, e.g. Ti-6Al-4 V, offers great potential in manufacturing automotive components, lightweight structures and medical implants. In order to achieve required mechanical properties of laser melted components quality of powder materials is essential. Unmelted powder is recycled and reused in a subsequent process. Due to repeated recycling it is suggested that powder material changes. In this paper aging processes of Ti-6Al-4 V powder are studied. It was observed that powder particles coarsen and flowability increases. Comparing examined powder characteristics to bulk material properties it was noticed that there are significant effects of aged powder on laser melted components.

  14. Electrical characterization and modelization of CaCu3Ti4O12 polycrystalline ceramics

    NASA Astrophysics Data System (ADS)

    Cheballah, Chafe; Valdez-Nava, Zarel; Laudebat, Lionel; Guillemet-Fritsch, Sophie; Lebey, Thierry

    2015-06-01

    Since the observation almost 15 years ago of the so-called "colossal" dielectric permittivity behavior in CaCu3Ti4O12 (CCTO) ceramics, several works have been undertaken to understand its physical origin interfacial polarization being the most likelihood. In this paper, (C-V) measurements, commonly used on semiconducting materials have been used to characterize CCTO samples. Their results may be described by a head-to-tail double metal-insulating-semiconductor (MIS) structure. A comparison between experimental and numerical simulation results of such a structure shows a good agreement, whatever the frequency range. Furthermore, this model explains the non-symmetrical behavior of the electrical response of this material, a property still not taken into account by today's commonly known models. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014) - Elected submissions", edited by Adel Razek

  15. Investigations of the effect of nonmagnetic Ca substitution for magnetic Dy on spin-freezing in Dy2Ti2O7

    NASA Astrophysics Data System (ADS)

    Anand, V. K.; Tennant, D. A.; Lake, B.

    2015-11-01

    Physical properties of partially Ca substituted hole-doped Dy2Ti2O7 have been investigated by ac magnetic susceptibility {χ\\text{ac}}(T) , dc magnetic susceptibility χ (T) , isothermal magnetization M(H) and heat capacity {{C}\\text{p}}(T) measurements on Dy1.8Ca0.2Ti2O7. The spin-ice system Dy2Ti2O7 exhibits a spin-glass type freezing behavior near 16 K. Our frequency dependent {χ\\text{ac}}(T) data of Dy1.8Ca0.2Ti2O7 show that the spin-freezing behavior is significantly influenced by Ca substitution. The effect of partial nonmagnetic Ca2+ substitution for magnetic Dy3+ is similar to the previous study on nonmagnetic isovalent Y3+ substituted Dy2-x Y x Ti2O7 (for low levels of dilution), however the suppression of spin-freezing behavior is substantially stronger for Ca than Y. The Cole-Cole plot analysis reveals semicircular character and a single relaxation mode in Dy1.8Ca0.2Ti2O7 as for Dy2Ti2O7. No noticeable change in the insulating behavior of Dy2Ti2O7 results from the holes produced by 10% Ca2+ substitution for Dy3+ ions.

  16. 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.

  17. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure

    PubMed Central

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Do Kim, Keum; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-01

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization – voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization. PMID:26742878

  18. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure.

    PubMed

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Kim, Keum Do; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-01

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization - voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization. PMID:26742878

  19. Synthesis and performance of Ca-α/β-SiAlON composites from tailings

    NASA Astrophysics Data System (ADS)

    Hao, Hong-shun; Yang, Yang; Lian, Fang; Gao, Wen-yuan; Liu, Gui-shan; Hu, Zhi-qiang

    2014-05-01

    Ca-α/β-SiAlON composites were prepared using Ca-α/β-SiAlON powder synthesized from gold ore tailings, which contained abundant Si and Al elements as the major raw materials together with minor additives, through a pressure-less sintering method. The influences of sintering temperature on the phase composition and microstructure of the composites were analyzed. The scanning electron microscopy images of the composites show the interlacing of grains with elongated columnar, short columnar and plate-like morphologies. The composites sintered at 1520°C for 6 h have a flexural strength of 352 MPa, Vickers hardness of 11.2 GPa, and fracture toughness of 4.8 MPa·m1/2. The relative content of each phase in the products is I(Ca-α-SiAlON): I(β-SiAlON): I(Fe3Si) = 23:74:3, where I i stands for the diffraction peak intensity of phase i.

  20. Intermediate structures in radiation damaged titanite (CaTiSiO5): a Raman spectroscopic study.

    PubMed

    Zhang, Ming; Salje, Ekhard K H; Redfern, Simon A T; Bismayer, Ulrich; Groat, Lee A

    2013-03-20

    Effects of radiation damage and thermal annealing on the crystal structure of natural titanite (CaTiSiO(5)) were studied using Raman spectroscopy. The results show that well crystallized natural titanites generally have the P2(1)/a structure at the unit cell level, in contrast to the A2/a symmetry reported previously. Radiation caused by naturally incorporated impurities (such as U and Th) leads to structural damage and amorphization in titanite, as evidenced by a significant loss of band intensity, spectral broadening and frequency shifts. Additional bands (e.g. near 574 and 650 cm(-1)) occur in weakly or partially metamict titanite due to the formation of an intermediate phase (with the A2/a symmetry). Raman spectra of titanite thermal glasses showed features different from those of metamict titanite, especially in the Ti-O and Si-O stretching regions. The effect of thermal annealing is strongly affected by the initial degrees of damage that the sample experienced. Weakly damaged titanite samples showed that annealing leads to a structural recovery, and the spectral patterns of these recovered crystals are consistent with the P2(1)/a symmetry. Highly damaged titanite starts to recrystallize into an A2/a phase near 700-800 K, and additional structural modification occurs when annealed at 1300-1400 K, which involves significant change in broad Ti-O features. However, in terms of bandwidths, the metamict samples are far from fully recovered even on being annealed at 1300-1400 K. PMID:23407062