WorldWideScience

Sample records for ca sc ti

  1. No-Core Shell Model for 48-Ca, 48-Sc and 48-Ti

    Energy Technology Data Exchange (ETDEWEB)

    Popescu, S; Stoica, S; Vary, J P; Navratil, P

    2004-10-26

    The authors report the first no-core shell model results for {sup 48}Ca, {sup 48}Sc and {sup 48}Ti with derived and modified two-body Hamiltonians. We use an oscillator basis with a limited {bar h}{Omega} range around 40/A{sup 1/3} = 11 MeV and a limited model space up to 1 {bar h}{Omega}. No single-particle energies are used. They find that the charge dependence of the bulk binding energy of eight A = 48 nuclei is reasonably described with an effective Hamiltonian derived from the CD-Bonn interaction while there is an overall underbinding by about 0.4 MeV/nucleon. However, resulting spectra exhibit deficiencies that are anticipated due to: (1) basis space limitations and/or the absence of effective many-body interactions; and, (2) the absence of genuine three-nucleon interactions. They introduce phenomenological modifications to obtain fits to total binding and low-lying spectra. The resulting no-core shell model opens a path for applications to experiments such as the double-beta ({beta}{beta}) decay process.

  2. On 3d bonding in the transition metal trimers - The electronic structure of equilateral triangle Ca3, Sc3, Sc3(+), and Ti3(+)

    Science.gov (United States)

    Walch, S. P.; Bauschlicher, C. W., Jr.

    1985-01-01

    It is pointed out that transition metals and transition metal (TM) compounds are currently of considerable interest because of their relevance to catalysis and to materials science problems such as hydrogen embrittlement and crack propagation in metals. The present paper is concerned with complete active space Self-Consistent Field (SCF) externally contracted configuration interaction (CASSCF/CCI) calculations for the low-lying states of Sc3 and Sc3(+). A comparison is conducted regarding the bonding in the Ca3, Sc3, and Cu3 molecules. This comparison makes it possible to predict general trends for the TM trimers. Attention is given to the qualitative features of the bonding in the TM trimers, the basis sets and other technical details of the calculations, the calculated results for Sc3 and Sc3(+), and conclusions from this work.

  3. Particle-hole configurations and energy spectra of sup 4 sup 2 Ca, sup 4 sup 2 Sc and sup 4 sup 2 Ti nuclei

    CERN Document Server

    Kim, M W

    1996-01-01

    Shell-model calculations are performed to investigate the level structure in sup 4 sup 2 Ca, sup 4 sup 2 Sc and sup 4 sup 2 Ti nuclei. The shell model states are expressed for two-particle, particle-hole and three-particle one-hole configurations in terms of coupled two-particle states. We have used the modified surface-delta interaction, pairing and Coulomb interaction in this calculation. The configurations considered are 1f sub 7 sub / sub 2 , 2p sub 3 sub / sub 2 and 1d sub 3 sub / sub 2 Single-particle energies and parameters of the interaction are determined by least-squares fitting procedure. The resulting two-body matrix elements are applied to calculate the energy spectra of two-particle states and three-particle one-hole states in sup 4 sup 2 Ca, sup 4 sup 2 Sc and sup 4 sup 2 Ti nuclei.

  4. The Feasibility of direct measurement of the {sup 44}Ti(α, p){sup 47}V and {sup 40}Ca(α, p){sup 43}Sc reactions in forward kinematics at astrophysically relevant temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Al-Abdullah, T. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Dresden (Germany); The Hashemite University, Physics Department, P.O. Box 150459, Zarqa (Jordan); Akhmadaliev, S.; Bemmerer, D.; Sobiella, M. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Dresden (Germany); Ayranov, M. [Directorate-General for Energy, European Commission, Luxembourg (Luxembourg); Dressler, R.; Schumann, D.; Stowasser, T. [Paul Scherrer Institute, Laboratory of Radiochemistry and Environmental Chemistry, Villigen PSI (Switzerland); Elekes, Z. [Institute for Nuclear Research of the Hungarian Academy of Sciences (MTA ATOMKI), Debrecen (Hungary); Kivel, N. [Paul Scherrer Institute, Nuclear Energy and Safety, Hot Laboratory Division, Villigen PSI (Switzerland); Schmidt, K.; Takacs, M.P. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Dresden (Germany); Technische Universitaet Dresden, Institute of Nuclear and Particle Physics, Dresden (Germany); Zuber, K. [Technische Universitaet Dresden, Institute of Nuclear and Particle Physics, Dresden (Germany)

    2014-09-15

    Understanding the synthesis of radioactive {sup 44}Ti in the α-rich freeze-out following core-collapse supernovae may help to better interpret such explosive events. The γ-ray lines from the decay of {sup 44}Ti have been observed by space-based γ-ray telescopes from two supernova remnants. It is believed that the {sup 44}Ti(α, p){sup 47}V reaction dominates the destruction of {sup 44}Ti, while the {sup 40}Ca(α, p){sup 43}Sc reaction removes fuel from the main {sup 44}Ti production reaction {sup 40}Ca(α, γ){sup 44}Ti. Here we report on a possible technique to determine both reaction rates at astrophysically relevant energies in forward kinematics. The first reaction will be performed using a 1-10 MBq {sup 44}Ti target. Two important concerns are considered to make this study possible: The amount of stable Ti in the radioactive target, which will be prepared via spallation reactions at Paul Scherrer Institute (PSI), and the degree of radioactive contaminations in the experimental setup due to sputtered {sup 44}Ti atoms after intensive irradiations. Several online and offline measurements in parallel with Monte Carlo simulations were performed to investigate these issues. (orig.)

  5. Photoionization study of Ne-like K9+, Ca10+, Sc11+, Ti12+, V13+, Cr14+, Mn15+, and Fe16+ ions using the screening constant by unit nuclear charge method

    Science.gov (United States)

    Goyal, Arun; Khatri, Indu; Sow, Malick; Sakho, Ibrahima; Aggarwal, Sunny; Singh, A. K.; Mohan, Man

    2016-08-01

    Photoionization of the 2s22p6 (1S0) ground state of the Ne-like (Z=19-29) ions is presented in this paper. Resonance energies and total natural width of the 2s2p6np 1P series of the Ne-like K9+, Ca10+, Sc11+, Ti12+, V13+, Cr14+, Mn15+, and Fe16+are reported. All the calculations are made using the Screening constant by unit nuclear charge (SCUNC) formalism. New data for Ne-like K9+, Sc11+, Ti12+, V13+, Cr14+, and Mn15+ions are tabulated. Good agreements are found with available literature data.

  6. Synthesis and Isolation of the Titanium-Scandium Endohedral Fullerenes-Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 and Sc2 TiC2 @Ih -C80 : Metal Size Tuning of the Ti(IV) /Ti(III) Redox Potentials.

    Science.gov (United States)

    Junghans, Katrin; Ghiassi, Kamran B; Samoylova, Nataliya A; Deng, Qingming; Rosenkranz, Marco; Olmstead, Marilyn M; Balch, Alan L; Popov, Alexey A

    2016-09-01

    The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc-Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4 C2 @C80 (the most abundant EMF from this synthesis), Sc3 C2 @C80 , isomers of Sc2 C2 @C82 , and the family Sc2 C2 n (2 n=74, 76, 82, 86, 90, etc.), as well as Sc3 CH@C80 . The Sc-Ti/CH4 system produces the mixed-metal Sc2 TiC@C2 n (2 n=68, 78, 80) and Sc2 TiC2 @C2 n (2 n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc2 TiC@Ih -C80 , Sc2 TiC@D5h -C80 , and Sc2 TiC2 @Ih -C80 , were characterized by NMR spectroscopy. The structure of Sc2 TiC@Ih -C80 was also determined by single-crystal X-ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2 TiC- and Sc2 TiC2 -containing clusterfullerenes have Ti-localized LUMOs. Encapsulation of the redox-active Ti ion inside the fullerene cage enables analysis of the cluster-cage strain in the endohedral fullerenes through electrochemical measurements. PMID:27459520

  7. Structural, elastic and thermodynamic properties of Ti2SC

    Indian Academy of Sciences (India)

    Hongzhi Fu; Wenfang Liu; Tao Gao

    2011-12-01

    The structural parameters, elastic constants and thermodynamic properties of Ti2SC were investigated under pressure and temperature by using first-principles plane-wave pseudopotential density functional theory within the generalized gradient approximation. The obtained results are in agreement with the available experimental data. The bulk moduli along the - and -axes, $B_{a}$ and $B_{c}$, almost linearly increase with pressure, and the former is always smaller than the latter. The ratio of $B_{c}/B_{a}$ has a trend of gradual increase as the pressure increases. It is found that the elastic constants, anisotropy and Debye temperature of Ti2SC increase with pressure, while axial compressibility along the - and -axes decreases with pressure. The thermal properties including the equation of state, the Grüneisen parameter , the anisotropies $\\Delta_{p}, \\Delta_{S1}$ and $\\Delta_{S2}$, and the heat capacity are estimated at various pressures and temperatures.

  8. Synthesis and Isolation of the Titanium–Scandium Endohedral Fullerenes—Sc2TiC@Ih-C80, Sc2TiC@D5h-C80 and Sc2TiC2@Ih-C80 : Metal Size Tuning of the TiIV/TiIII Redox Potentials

    Science.gov (United States)

    Junghans, Katrin; Ghiassi, Kamran B.; Samoylova, Nataliya A.; Deng, Qingming; Rosenkranz, Marco; Olmstead, Marilyn M.; Balch, Alan L.; Popov, Alexey A.

    2016-01-01

    The formation of endohedral metallofullerenes (EMFs) in an electric arc is reported for the mixed-metal Sc–Ti system utilizing methane as a reactive gas. Comparison of these results with those from the Sc/CH4 and Ti/CH4 systems as well as syntheses without methane revealed a strong mutual influence of all key components on the product distribution. Whereas a methane atmosphere alone suppresses the formation of empty cage fullerenes, the Ti/CH4 system forms mainly empty cage fullerenes. In contrast, the main fullerene products in the Sc/CH4 system are Sc4C2@C80 (the most abundant EMF from this synthesis), Sc3C2@C80, isomers of Sc2C2@C82, and the family Sc2C2n (2n=74, 76, 82, 86, 90, etc.), as well as Sc3CH@C80. The Sc–Ti/CH4 system produces the mixed-metal Sc2TiC@C2n (2n=68, 78, 80) and Sc2TiC2@C2n (2n=80) clusterfullerene families. The molecular structures of the new, transition-metal-containing endohedral fullerenes, Sc2TiC@Ih-C80, Sc2TiC@D5h-C80, and Sc2TiC2@Ih-C80, were characterized by NMR spectroscopy. The structure of Sc2TiC@Ih-C80 was also determined by single-crystal X-ray diffraction, which demonstrated the presence of a short Ti=C double bond. Both Sc2TiC- and Sc2TiC2-containing clusterfullerenes have Ti-localized LUMOs. Encapsulation of the redox-active Ti ion inside the fullerene cage enables analysis of the cluster–cage strain in the endohedral fullerenes through electrochemical measurements. PMID:27459520

  9. Magnetic properties of Sc{sub x}Ti{sub 1-x}Fe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kessler, M. [Lab. de Cristallographie, CNRS, 38 - Grenoble (France); Deportes, J. [Lab. Louis Neel, CNRS, 38 - Grenoble (France); Ouladdiaf, B. [Institut Laue-Langevin, 38 - Grenoble (France); Sayetat, F. [Lab. de Cristallographie, CNRS, 38 - Grenoble (France)

    1995-02-09

    The magnetic properties and their thermal dependences of Sc{sub 0.1}Ti{sub 0.9}Fe{sub 1.96}, Sc{sub 0.1}Ti{sub 0.9}Fe{sub 2} and Sc{sub 0.1}Ti{sub 0.9}Fe{sub 2.04} are compared with those of TiFe{sub 2}. The substitution changes the iron-iron distances. Consequently, the Fe atoms on the 6h site show in addition to the antiferromagnetic component a small ferromagnetic one, and a weak magnetic moment appears on the 2a site. ((orig.)).

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

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Bivas [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Lawrence, Samantha K.; Bahr, David F. [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Schroeder, Jeremy L.; Birch, Jens [Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Sands, Timothy D. [School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    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.

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

    Science.gov (United States)

    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

  12. Naked (C5Me5)(2)M cations (M = Sc, Ti, and V) and their fluoroarene complexes

    NARCIS (Netherlands)

    Bouwkamp, MW; Budzelaar, PHM; Gercama, J; Morales, ID; de Wolf, J; Meetsma, A; Troyanov, SI; Teuben, JH; Hessen, B; Budzelaar, Peter H.M.; Hierro Morales, Isabel Del; Troyanov, Sergei I.

    2005-01-01

    The ionic metallocene complexes [Cp*M-2][BPh4] (CP* = C5Me5) of the trivalent 3d metals Sc, Ti, and V were synthesized and structurally characterized. For M Sc, the anion interacts weakly with the metal center through one of the phenyl groups, but for M = Ti and V, the cations are naked. They each c

  13. Structural, electronic and elastic properties of M2SC (M = Ti, Zr, Hf) compounds

    International Nuclear Information System (INIS)

    Using ab initio calculations, we have studied the structural, electronic and elastic properties of M2SC, with M = Ti, Zr and Hf. Geometrical optimization of the unit cell are in good agreement with the available experimental data. The band structures show that all three materials are conducting. The analysis of the site and momentum projected densities shows that the bonding is achieved through a hybridization of M-atom d states with S and C-atom p states. The Md-Sp bonds are lower in energy and are stiffer than Md-Cp bonds. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli, Young's moduli and Poisson's ratio for ideal polycrystalline M2SC aggregates. We estimated the Debye temperature of M2SC from the average sound velocity. This is a quantitative theoretical prediction of the elastic properties of Ti2SC, Zr2SC, and Hf2SC compounds, and it still awaits experimental confirmation

  14. Electronic structure of new mixed Ti13MC13 nanocrystallites (M = Sc, V, ..., Cu)

    International Nuclear Information System (INIS)

    The electron structure of the series of new Ti13MC13 metal-carbon molecular nanocrystallites is studied through the ab initio self-consistent discrete variation method. The third order metals (Sc, V, ..., Cu) are considered as the M-elements. The regularities of forming the electron structure, chemical bonds, charge distributions and atomic magnetic moments in the Ti13MC13 in dependence on the M-atom type and its position in the source Ti14C13 nanocrystallite are forecasted. The obtained results are compared with the electron states calculations of the 3d-admixtures in the crystalline titanium carbide

  15. The first principle study of Ni2ScGa and Ni2TiGa

    International Nuclear Information System (INIS)

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni2TiGa and Ni2ScGa alloys in the cubic L21 structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C11, C12 and C44. We calculated elastic constants in L21 structure for Ni2TiGa and Ni2ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni2TiGa, Ni 3d states and Sc 3d states for Ni2ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni2TiGa, 0.76 states/eV Cell for Ni2ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L21 phase is unstable since the phonon calculations have imagine modes

  16. Strength of the $E_{\\text{p}}$=1.842 MeV resonance in the $^{40}$Ca(p,$\\gamma$)$^{41}$Sc reaction revisited

    CERN Document Server

    Schmidt, Konrad; Anders, Michael; Bemmerer, Daniel; Caciolli, Antonio; Dietz, Mirco; Elekes, Zoltán; Junghans, Arnd R; Menzel, Marie-Luise; Schwengner, Ronald; Wagner, Andreas; Zuber, Kai

    2014-01-01

    The strength of the $E_{\\rm p} = 1.842$ MeV resonance in the $^{40}$Ca(p,$\\gamma$)$^{41}$Sc reaction is determined with two different methods: First, by an absolute strength measurement using calcium hydroxide targets, and second, relative to the well-determined strength of the resonance triplet at $E_\\alpha$ = 4.5 MeV in the $^{40}$Ca($\\alpha$,$\\gamma$)$^{44}$Ti reaction. The present new value of $\\omega\\gamma=(0.192\\pm0.017)$ eV is 37% (equivalent to $3.5\\sigma$) higher than the evaluated literature value. In addition, the ratio of the strengths of the 1.842 MeV $^{40}$Ca(p,$\\gamma$)$^{41}$Sc and 4.5 MeV $^{40}$Ca($\\alpha$,$\\gamma$)$^{44}$Ti resonances has been determined to be $0.0229\\pm0.0018$. The newly corrected strength of the 1.842-MeV resonance can be used in the future as a normalization point for experiments with calcium targets.

  17. Influence of Sc on high temperature strengthening behavior of Ti-6Al-4V alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Vacuum arc melting technique was used to prepare Ti-6Al-4V alloy containing Sc (0.3% and 0.5%, mass fraction). The ingots were melted twice by vacuum self-consumable electrode arc furnace. Forging of ingots was started in β-phase region and finished in high (α+β)-phase region. Annealing after forging was performed in low (α+β)-phase region for 30 min. Isothermal high temperature compression tests were conducted using thermal simulation machine under Ar atmosphere at 850 ℃ and 1 000 ℃, and the strain rate were 0.001, 0.01, 0.1 and 1.0 s-1. Optical microscope(OM), scanning electron microscopy(SEM), energy dispersive spectrum(EDS) and transmission electron microscope(TEM) were used to study the microstructure evolution during high temperature deformation. The results show that, the peak stress value of alloys increases with increasing Sc content after deformation at 850 ℃,however, there is no obvious strengthening of Sc when the alloys are deformed at 1 000 ℃. Sc exists as Sc2O3 forms by internal oxidation during forging procedure, only minor Sc solutes in matrix. At 850 ℃, the interaction between dislocation and participated particles and twinning mechanism controls the deformation procedure accompanied recrystallization. At 1 000 ℃, the deformation of alloys containing Sc is mainly controlled by twinning, while the deformation of alloy without Sc is not only controlled by twinning,but also the interaction between dislocation and precipitated particles inside the twinning lamellar.

  18. Apparent vanishing of ferroelectricity in nanostructured BiScO3PbTiO3

    OpenAIRE

    Amorín, H.; R. Jiménez; Ricote, J.; Hungría, T; de Castro, A.; Algueró, M.

    2010-01-01

    Abstract Nanostructured ceramics of high-temperature piezoelectric 0.375BiScO 3 -0.625PbTiO 3 were prepared by spark plasma sintering of nanocrystalline powders obtained by mechanosynthesis. The macroscopic electrical properties were characterized on dense ceramics with decreasing average grain size down to 28 nm. Results indicate that the electric field is screened by the electrically insulating grain boundaries at the nanoscale, which needs to be considered when discussing size effects i...

  19. Experimental Investigation of Electrical Conductivity and Permittivity of SC-TiO 2 -EG Nanofluids.

    Science.gov (United States)

    Fal, Jacek; Barylyak, Adriana; Besaha, Khrystyna; Bobitski, Yaroslav V; Cholewa, Marian; Zawlik, Izabela; Szmuc, Kamil; Cebulski, Józef; Żyła, Gaweł

    2016-12-01

    The paper presents experimental studies of dielectric properties of nanofluids based on ethylene glycol and SC-TiO2 nanoparticles with average size of 15-40 nm with various mass concentrations. The dielectric permittivity both real part and imaginary part as a function of temperature and frequency were measured. Also, dependence ac conductivity on frequency, temperature, and mass concentration were investigated. Based on the curves of ac conductivity, dc conductivity was calculated, and 400 % enhancement in dc conductivity was exposed.

  20. First-principles investigation on the elastic stability and thermodynamic properties of Ti2SC

    Institute of Scientific and Technical Information of China (English)

    Yang Ze-Jin; Guo Yun-Dong; Linghu Rong-Feng; Cheng Xin-Lu; Yang Xiang-Dong

    2012-01-01

    Using Vanderbilt-type plane-wave ultrasoft pseudopotentials within the generalized gradient approximation(GGA)in the frame of density functional theory(DFT),we have investigated the crystal structures,elastic,and thermodynamic properties for Ti2SC under high temperature and high pressure.The calculated pressure dependence of the lattice volume is in excellent agreement with the experimental results.The calculated structural parameter of the Ti atom experienced a subtle increase with applied pressures and the increase suspended under higher pressures.The elastic constants calculations demonstrated that the crystal lattice is still stable up to 200 CPa.Investigations on the elastic properties show that the c axis is stiffer than the a axis,which is consistent with the larger longitudinal elastic constants(C3s,C11)relative to transverse ones(C44,C12,C13).Study on Poisson's ratio confirmed that the higher ionic or weaker covalent contribution in intra-atomic bonding for Ti2SC should be assumed and the nature of ionic increased with pressure.The ratio(B/G)of bulk(B)and shear(G)moduli as well as B/C44 demonstrated the brittleness of Ti2SC at ambient conditions and the brittleness decreased with pressure.Moreover,the isothermal and adiabatic bulk moduli displayed opposite temperature dependence under different pressures.Again,we observed that the Debye temperature and Griineisen parameter show weak temperature dependence relative to the thernal expansion coefficient,entropy,and heat capacity,from which the pressure effects are clearly seen.

  1. Microstructural and high temperature deformation characterization of Ti-45Al-3Nb-(Cr, Mn, Mo, Sc) alloy

    International Nuclear Information System (INIS)

    Research highlights: → Complex microalloying increased remarkably the high temperature strength of Ti-45Al-3Nb alloy. → Strength increase was attributed to microstructural refinement, dispersive and solution strengthening effects. → The ductility of Ti45Al3Nb was remarkably enhanced owing to improvement of inhomogeneous distribution of electron cloud. - Abstract: The effect of complex microalloying by combinative additions of Nb, Sc, Mn, Cr and Mo to the directionally solidified Ti-45Al alloys on microstructures and mechanical properties has been examined in the present study. It is shown that a respective microstructure of fully lamellar for Ti-45Al-3Nb and Ti-45Al-3Nb-0.5Sc and basket weave type for Ti-45Al-3Nb-2Cr-2Mo-1Mn-0.5Sc were observed. The high temperature strength of Ti-45Al-3Nb alloy is improved via dispersive strengthening effect of fine Ti3(Al,Sc) dispersoids and solution strengthening effect from the other alloying elements. Enhanced ductility of Ti-45Al-3Nb alloy was achieved by Cr, Mn and Mo combinative additions.

  2. Scandium(III) complexes of monophosphorus acid DOTA analogues: a thermodynamic and radiolabelling study with (44)Sc from cyclotron and from a (44)Ti/(44)Sc generator.

    Science.gov (United States)

    Kerdjoudj, R; Pniok, M; Alliot, C; Kubíček, V; Havlíčková, J; Rösch, F; Hermann, P; Huclier-Markai, S

    2016-01-28

    The complexation ability of DOTA analogs bearing one methylenephosphonic (DO3AP) or methylenephosphinic (DO3AP(PrA) and DO3AP(ABn)) acid pendant arm toward scandium was evaluated. Stability constants of their scandium(iii) complexes were determined by potentiometry combined with (45)Sc NMR spectroscopy. The stability constants of the monophosphinate analogues are somewhat lower than that of the Sc-DOTA complex. The phosphorus acid moiety interacts with trivalent scandium even in very acidic solutions forming out-of-cage complexes; the strong affinity of the phosphonate group to Sc(iii) precludes stability constant determination of the Sc-DO3AP complex. These results were compared with those obtained by the free-ion selective radiotracer extraction (FISRE) method which is suitable for trace concentrations. FISRE underestimated the stability constants but their relative order was preserved. Nonetheless, as this method is experimentally simple, it is suitable for a quick relative comparison of stability constant values under trace concentrations. Radiolabelling of the ligands with (44)Sc was performed using the radioisotope from two sources, a (44)Ti/(44)Sc generator and (44m)Sc/(44)Sc from a cyclotron. The best radiolabelling conditions for the ligands were pH = 4, 70 °C and 20 min which were, however, not superior to those of the parent DOTA. Nonetheless, in vitro behaviour of the Sc(iii) complexes in the presence of hydroxyapatite and rat serum showed sufficient stability of (44)Sc complexes of these ligands for in vivo applications. PET images and ex vivo biodistribution of the (44)Sc-DO3AP complex performed on healthy Wistar male rats showed no specific bone uptake and rapid clearance through urine. PMID:26675416

  3. Influence of Sc3+ doping in B-site on electrochemical performance of Li4Ti5O12 anode materials for lithium-ion battery

    Science.gov (United States)

    Zhang, Yaoyao; Zhang, Chunming; Lin, Ye; Xiong, Ding-Bang; Wang, Dan; Wu, Xiaoyan; He, Dannong

    2014-03-01

    Anode materials Li4Ti5O12 (LTO) and Sc-doped Li4Ti4.95Sc0.05O12-δ (LTSO) for lithium-ion batteries are both successfully synthesized by the modified sol-gel method with ethylene diamine tetraacetic acid (EDTA) and citric acid (CA) as a bi-components chelating agent. The samples are characterized by XRD, BET, XPS, EDX and SEM. The dopant Sc totally enters into the 16d sites of the spinel structure of LTO, and then further affects its morphology and property. The LTSO powder exhibits a 3D network morphology and its grain size is about 200 nm. The LTSO electrode material exhibits an excellent initial discharge capacities of 174 and 94 mAh g-1 at 1 C and 40 C, respectively. The reversible capacities of LTSO at different current rates remain nearly 100% after 50 cycles, which are compared with the capacities of the second cycles. Sc3+ doping can greatly improve the electronic conductivity of LTO which is demonstrated by electrochemical impedance spectroscopy. Cyclic voltammetry measurements also reveal that LTSO has small polarization resistance due to the high electrical conductivity and Li-ion apparent diffusion rate.

  4. Doping of BiScO3-PbTiO3 Ceramics for Enhanced Properties

    Science.gov (United States)

    Sehirlioglu, Alp; Sayir, Ali; Dynys, Fred

    2008-01-01

    High-temperature piezoelectrics are a key technology for aeronautics and aerospace applications such as fuel modulation to increase the engine efficiency and decrease emissions. The principal challenge for the insertion of piezoelectric materials is the limitation on upper use temperature which is due to low Curie-Temperature (T(sub c) and increasing electrical conductivity. BiScO3 -PbTiO3 (BS-PT) system is a promising candidate for improving the operating temperature for piezoelectric actuators due to its high TC (>400 C). Effects of Zr and Mn doping of the BS-PT ceramics have been studied and all electrical and electromechanical properties for Sc-deficient and Ti-deficient BS- PT ceramics are reported as a function of electrical field and temperature. Donor doping with Zr and Mn (in Sc deficient compositions) increased the DC-resistivity and decreased tan at all temperatures. Resulting ceramics exhibited saturated hysteresis loops with low losses and showed no dependence on the applied field (above twice the coercive field) and measurement frequency.

  5. Origin of colossal dielectric response of CaCu3Ti4O12 studied by using CaTiO3/CaCu3Ti4O12/CaTiO3 multilayer thin films

    Science.gov (United States)

    Mitsugi, Masakazu; Asanuma, Shutaro; Uesu, Yoshiaki; Fukunaga, Mamoru; Kobayashi, Wataru; Terasaki, Ichiro

    2007-06-01

    To elucidate the origin of the colossal dielectric response (CDR) of CaCu3Ti4O12 (CCTO), multilayer thin films of CCTO interposed in insulating CaTiO3 (CTO) were synthesized using a pulsed laser deposition technique. The capacitance C of CTO/CCTO/CTO films with different layer thicknesses is measured. After removing the capacitance of CTO by extrapolating C to zero CTO thickness, the real part of dielectric constant of CCTO is estimated to be 329-435, which is much smaller than the reported value for CCTO thin films. This fact indicates that the CDR of CCTO is extrinsic and originates from an internal barrier layer capacitor.

  6. Computational investigation on MB n (M = Li-Cs, Be-Ba, Sc-La and Ti; n = 28 and 38).

    Science.gov (United States)

    Xu, Qianhui; Liu, Chang; Yang, Le; Jin, Peng; Tang, Chengchun; Chen, Zhongfang

    2016-08-01

    Differing from the weakly antiaromatic B80 buckyball, the medium-sized C 1-B28 and D 2h -B38, as well as their mono- to tetra-anions, are highly aromatic, as indicated by the negative nucleus-independent chemical shifts (NICSs) at their cage centers. The interior cavities and high aromaticity of the B28 and B38 cages render them very promising hosts to accommodate diverse metal atoms. Accordingly, we carried out systematic density functional theory (DFT) computations on the structures, stabilities and electronic properties of metalloborofullerenes MB n (M = Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La and Ti; n = 28 and 38). Among them, besides the recently reported M@B38(M = Sc, Y and Ti) [Lu et al. (2015) Phys Chem Chem Phys 17:20897-20902], Ti@B28 and M@B38 (M = Ca and La) also favor endohedral structures with large binding energies, and are suggested promising targets for experimental applications. Note that Ti@B28 is the first endohedral derivative based on the new B28 fullerene, and La@B38 features the largest metal size inside a B38 cage thus far. These endohedral derivatives, as exemplified by Ca@B38, may exhibit σ and π double aromaticity over the whole cage surface, indicating their considerable stability. In contrast, the other metals prefer to reside at the exterior cage surface, due mainly to the mismatch of their sizes with the boron cages, though the size match is not the only factor to determine their doping form. Furthermore, the infrared absorption spectra and (11)B nuclear magnetic resonance spectra of the three new M@B n complexes were computed to assist future experimental characterization. Graphical Abstract Putting more metals into medium-sized boron cages! PMID:27424298

  7. Thermoelastic properties of ScB2, TiB2, YB4 and HoB4

    DEFF Research Database (Denmark)

    Waskowska, A.; Gerward, L.; Staun Olsen, J.;

    2011-01-01

    High-pressure X-ray diffraction in ScB2, TiB2, YB4 and HoB4 powders and single crystals has been studied using synchrotron radiation as well as conventional X-rays. The experimental results are supported by calculations using density functional theory. ScB2, YB4 and HoB4 are hard materials (bulk ...

  8. Interface interaction and wetting of Sc2O3 exposed to Cu-Al and Cu-Ti melts

    International Nuclear Information System (INIS)

    Scandia is a thermodynamically stable oxide and could be used as a structural material for a crucible in order to avoid a melt contamination. In the present study wetting experiments of Cu-Al and Cu-Ti melts on Scandia substrate were preformed at 1423 K by a sessile drop method. It was established that Al and Ti additions lead to the improved wetting and that the final contact angle decreases with increasing the additives concentration. For Al containing melts, the contact angle changes gradually with time, and a relatively thick interaction layer, which consists of Al2O3, Sc2O3, and metallic channels, was formed at the Sc2O3/Cu-Al interface. For Ti containing melts, the final contact angle is achieved already during heating, and an extremely thin layer based on a Ti-Sc-O compound was detected by AES at the Sc2O3/Cu-Ti interface. The results of a thermodynamic analysis, which takes into account the formation free energy of the oxides, involved in the systems, and the thermodynamic properties of the liquid solutions are in a good agreement with the experimental observations. (orig.)

  9. Biological properties of nanostructured Ti incorporated with Ca, P and Ag by electrochemical method

    Energy Technology Data Exchange (ETDEWEB)

    Li, Baoe; Hao, Jingzu; Min, Yang [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Xin, Shigang [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Guo, Litong [School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou 221116 (China); He, Fei [National Key Laboratory of C1 Chemical Industry, Tianjin University, Tianjin 300072 (China); Liang, Chunyong; Wang, Hongshui [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Li, Haipeng, E-mail: lhpcx@163.com [School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130 (China)

    2015-06-01

    TiO{sub 2} nanotube arrays were synthesized on Ti surface by anodic oxidation. The elements of Ca and P were simultaneously incorporated during nanotubes growth in SBF electrolyte, and then Ag was introduced to nanotube arrays by cathodic deposition, which endowed the good osseointegration and antibacterial property of Ti. The bioactivity of the Ti surface was evaluated by simulated body fluid soaking test. The biocompatibility was investigated by in vitro cell culture test. And the antibacterial effect against Staphylococcus aureus was examined by the bacterial counting method. The results showed that the incorporation of Ca, P and Ag elements had no significant influence on the formation of nanotube arrays on Ti surface during electrochemical treatment. Compared to the polished or nanotubular Ti surface, TiO{sub 2} nanotube arrays incorporated with Ca, P and Ag increased the formation of bone-like apatite in simulated body fluid, enhanced cell adhesion and proliferation, and inhibited the bacterial growth. Based on these results, it can be concluded that the nanostructured Ti incorporated with Ca, P and Ag by electrochemical method has promising applications as implant material. - Highlights: • Nanotube arrays were prepared on Ti surface by anodic oxidation. • Ca, P and Ag were incorporated to nanotube arrays by electrochemical method. • Ca, P and Ag endowed Ti with good osseointegration and antibacterial property. • The beneficial effect of electrochemical treatment on Ti implant was demonstrated.

  10. The first principle study of Ni{sub 2}ScGa and Ni{sub 2}TiGa

    Energy Technology Data Exchange (ETDEWEB)

    Özduran, Mustafa [Ahi Evran Üniversitesi Fen Edebiyat Fakültesi Fizik Bölümü, Kırşehir (Turkey); Turgut, Kemal [Yüksek Lisans Öğrencisi, Kırşehir (Turkey); Arikan, Nihat [Ahi Evran Üniversitesi Eğitim Fakültesi İlköğretim Bölümü, Kırşehir (Turkey); İyigör, Ahmet; Candan, Abdullah [Ahi Evran Üniversitesi Merkezi Araştırma Laboratuvarı, Kırşehir (Turkey)

    2014-10-06

    We computed the electronic structure, elastic moduli, vibrational properties, and Ni{sub 2}TiGa and Ni{sub 2}ScGa alloys in the cubic L2{sub 1} structure. The obtained equilibrium lattice constants of these alloys are in good agreement with available data. In cubic systems, there are three independent elastic constants, namely C{sub 11}, C{sub 12} and C{sub 44}. We calculated elastic constants in L2{sub 1} structure for Ni{sub 2}TiGa and Ni{sub 2}ScGa using the energy-strain method. The electronic band structure, total and partial density of states for these alloys were investigated within density functional theory using the plane-wave pseudopotential method implemented in Quantum-Espresso program package. From band structure, total and projected density of states, we observed metallic characters of these compounds. The electronic calculation indicate that the predominant contributions of the density of states at Fermi level come from the Ni 3d states and Sc 3d states for Ni{sub 2}TiGa, Ni 3d states and Sc 3d states for Ni{sub 2}ScGa. The computed density of states at Fermi energy are 2.22 states/eV Cell for Ni{sub 2}TiGa, 0.76 states/eV Cell for Ni{sub 2}ScGa. The vibrational properties were obtained using a linear response in the framework at the density functional perturbation theory. For the alloys, the results show that the L2{sub 1} phase is unstable since the phonon calculations have imagine modes.

  11. Cross-plane thermal conductivity of (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices

    Science.gov (United States)

    Saha, Bivas; Koh, Yee Rui; Comparan, Jonathan; Sadasivam, Sridhar; Schroeder, Jeremy L.; Garbrecht, Magnus; Mohammed, Amr; Birch, Jens; Fisher, Timothy; Shakouri, Ali; Sands, Timothy D.

    2016-01-01

    Reduction of cross-plane thermal conductivity and understanding of the mechanisms of heat transport in nanostructured metal/semiconductor superlattices are crucial for their potential applications in thermoelectric and thermionic energy conversion devices, thermal management systems, and thermal barrier coatings. We have developed epitaxial (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices with periodicity ranging from 1 nm to 240 nm that show significantly lower thermal conductivity compared to the parent TiN/(Al,Sc)N superlattice system. The (Ti,W)N/(Al,Sc)N superlattices grow with [001] orientation on the MgO(001) substrates with well-defined coherent layers and are nominally single crystalline with low densities of extended defects. Cross-plane thermal conductivity (measured by time-domain thermoreflectance) decreases with an increase in the superlattice interface density in a manner that is consistent with incoherent phonon boundary scattering. Thermal conductivity values saturate at 1.7 W m-1K-1 for short superlattice periods possibly due to a delicate balance between long-wavelength coherent phonon modes and incoherent phonon scattering from heavy tungsten atomic sites and superlattice interfaces. First-principles density functional perturbation theory based calculations are performed to model the vibrational spectrum of the individual component materials, and transport models are used to explain the interface thermal conductance across the (Ti,W)N/(Al,Sc)N interfaces as a function of periodicity. The long-wavelength coherent phonon modes are expected to play a dominant role in the thermal transport properties of the short-period superlattices. Our analysis of the thermal transport properties of (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices addresses fundamental questions about heat transport in multilayer materials.

  12. Metal-insulator transitions in LaTiO3 / CaTiO3 superlattices

    Science.gov (United States)

    Seo, Sung Seok A.; Lee, Ho Nyung

    2010-03-01

    Strongly correlated electrons at an interface of complex oxide heterostructures often show interesting behaviors that require an introduction of new physical concepts. For example, the metallic transport behavior found in the superlattices of a Mott insulator LaTiO3 and a band insulator SrTiO3 (STO) has established the concept of interfacial electronic reconstruction. In this work, we have studied the transport property of a new type of Mott/band insulator LaTiO3/CaTiO3 (LTO/CTO) superlattices grown by pulsed laser deposition (PLD). In order to rule out concerns about the PLD plume-triggered oxygen vacancies generated in STO substrates, which might influence transport measurement, and to investigate the effect of epitaxial strain, we have used insulating NdGaO3 substrates. While both LTO and CTO single films are highly insulating, we have observed intriguing metal-insulator transitions (MIT) in the LTO/CTO superlattices depending on the global LTO/CTO thickness ratio and temperature. (Note that LTO/STO superlattices are metallic at all temperatures (2-300 K)). In this talk, we will discuss the origin of the MIT in the scheme of self compensation mechanism of d-electrons at the hetero-interface between LTO and CTO.

  13. Hydrogen Storage Properties of Ti1.2Fe+xCa Hydrogen Storage Alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The hydrogen storage properties of Ti1.2Fe+xCa (x=1%, 3% and 5% in mass fraction) alloys was investigated. Results show that the modified alloys can be activated without any thermal treatment at room temperature due to the addition of Ca and excess Ti in the alloys. Hydrogen storage properties of these modified alloys vary with Ca amount and reaction temperature. In addition, the influence mechanism of the addition of Ca and excessive Ti on the activation behavior and hydrogen storage capacity of the alloys was discussed.

  14. Anodic-hydrothermal preparation of prism-shaped CaTiO3 structure on titanium surface

    International Nuclear Information System (INIS)

    The prism-shaped perovskite structure of CaTiO3 on titanium surface was fabricated by an anodic-hydrothermal method. Firstly, the TiO2 film was formed on Ti substrate by electrochemical anodization. Secondly, the anodized TiO2/Ti substrate was used as a template for the hydrothermal synthesis of CaTiO3 coating. The samples were characterized with X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectrum. The experimental results show that anodic TiO2 substrate and alkali environment are key factors for the formation of prism-shaped CaTiO3, and the NaOH concentrations plays an important role in determining the size and shape of CaTiO3 structures. Meanwhile, the CaTiO3 surfaces possess the better deposition ability of Ca and P in vitro.

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

    CERN Document Server

    Guber, C R

    2016-01-01

    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. We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope and spectroscopically analyze 34 absorption-line systems at z<=0.5 to measure column densities (or limits) for CaII and TiII. 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 (DLAs, sub-DLAs & LLSs). 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.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 appe...

  16. Kinetics of Photocatalytic Degradation of Methylene Blue Over CaTiO3

    Institute of Scientific and Technical Information of China (English)

    HAN Chong; YANG He; XUE Xiangxin

    2015-01-01

    Kinetics of photocatalytic degradation of methylene blue (MB) over CaTiO3 was studied. Effects of the solution pH, the MB concentration, the CaTiO3 dosage, and the type of light source on photocatalytic degradation rate of MB over CaTiO3 were investigated in detail. The results show that photocatalytic degradation of MB over CaTiO3 followed the first-order reaction. The apparent rate constant (kobs) of MB signiifcantly increased with increasing solution pH while it greatly decreased with increasing MB concentration. Thekobs of MB increased with increasing CaTiO3 dosage from 0.05 to 0.1 g, whereas it slightly decreased with increasing CaTiO3 dosage in the range of 0.1-0.4 g. Thekobs of MB under UV-visible light irradiation was larger by factors of 2.2 than that under visible light irradiation. Thekobs of MB was (4.8±0.3)×10-1 h-1 under optimal conditions with the solution pH of 11, the MB concentration of 1 ppm, the CaTiO3 dosage of 0.1 g, and UV-visible light irradiation.

  17. Surface rumpling of cubic CaTiO3 from density functional theory

    Institute of Scientific and Technical Information of China (English)

    Yang Kun; Wang Chun-Lei; Li Ji-Chao; Zhang Chao; Wu Qing-Zao; Zhang Yan-Fei; Yin Na; Liu Xue-Yan

    2006-01-01

    In this paper, the structure of cubic CaTiO3 (001) surfaces with CaO and TiO2 terminations has been studied from density functional calculations. It has been found that the Ca atom has the largest relaxation for both kinds of terminations, and the rumpling of the CaO-terminated surface is much larger than that of TiO2-terminated surface.Also we have found that the metal atom relaxes much more prominently than the O atom does in each layer. The CaO-terminated surface is slightly more energetically favourable than the TiO2-terminated surface from the analysis of the calculated surface energy.

  18. Dielectric properties of CaCu2.9Co0.1Ti4O12 and CaCu3Ti3.9Co0.1O12 ceramics synthesized by semi-wet route

    Indian Academy of Sciences (India)

    K D Mandal; Alok Kumar Rai; Laxman Singh; Om Parkash

    2012-06-01

    The effect of Co+2 doping on Cu+2 and Ti+4 sites in calcium copper titanate, CaCu3Ti4O12, has been examined. The doped compositions, CaCu3−CoTi4O12 and CaCu3Ti4−CoO12 ( = 0.10) ceramics, were prepared by novel semi-wet route. In this method, calcium, copper and cobalt salts were taken in solution form and TiO2 was used in solid form. XRD analysis confirmed the formation of single-phase materials. Structure of CaCu3Ti4O12 does not change on doping with cobalt either on Cu-site or Ti-site and it remains cubic. Scanning electron micrographs (SEM) show average grain size of CaCu2.9Co0.1Ti4O12 to be larger than CaCu3Ti3.9Co0.1O12 ceramic. Energy dispersive X-ray spectroscopy (EDX) studies confined the purity of parent and Co-doped CaCu3Ti4O12 ceramics. Dielectric constant (r) and dielectric loss (tan ) of CaCu2.9Co0.1Ti4O12 is comparatively higher than that of CaCu3Ti3.9Co0.1O12 ceramic at all measured frequencies and temperatures.

  19. Spectral variations of Ca3Sc2Si3O12:Ce phosphors via substitution and energy transfer

    Institute of Scientific and Technical Information of China (English)

    LIU Yuanhong; ZHUANG Weidong; LIU Ronghui; HU Yunsheng; HE Huaqiang; ZHANG Shusheng; GAO Wei

    2012-01-01

    The luminescence intensity of emission peak at around 525 nm decreased in the Ce3+ and Er3+ co-doped Ca3Sc2Si3O12 phosphors.Mg2+ ion,which was likely incorporated into the Sc3+ position of the host crystal,was co-doped to adjust the crystal field and compensate for the excess positive charge due to the doping of Ce3+.The green emission belonged to the 5d→4f transition of Ce3+ moved toward longer wavelength by addition of Mg2+ in Ce3+ and Er3+ co-doped Ca3Sc2Si3O12 phosphor,which could increase the brightness of the phosphor.However,the position of weakening of luminescence intensity at around 525 nm remained basically unchanged by increasing the amount of Mg2+.The results showed that the weakening of luminescence intensity at around 525 nm caused by the absorption of Er3+,which had littleinfluence on the environment of the crystal field.

  20. Reactivity of first-row transition metal monocations (Sc+, Ti+, V+, Zn+) with methyl fluoride: a computational study.

    Science.gov (United States)

    Redondo, Pilar; Varela-Álvarez, Adrián; Rayón, Víctor Manuel; Largo, Antonio; Sordo, José Ángel; Barrientos, Carmen

    2013-04-11

    The gas-phase reactivity of methyl fluoride with selected first-row transition metal monocations (Sc(+), Ti(+), V(+), and Zn(+)) has been theoretically investigated. Our thermochemical and kinetics study shows that early transition-metal cations exhibit a much more active chemistry than the latest transition metal monocation Zn(+). The strong C-F bond in methyl fluorine can be activated by scandium, titanium, and vanadium monocations yielding the metal fluorine cation, MF(+). However, the rate efficiencies vary dramatically along the period 0.73 (Sc), 0.91 (Ti), and 0.028 (V) in agreement with the experimental observation. The kinetics results show the relative importance of the entrance and exit channels, apart from the "inner" bottleneck, to control the global rate constant of these reactions. At the mPW1K/QZVPP level our computed kglobal (at 295 K), 1.99 × 10(-9) cm(3) molecule(-1) s(-1) (Sc(+)), 1.29 × 10(-9) cm(3) molecule(-1) s(-1) (Ti(+)), and 3.46 × 10(-10) cm(3) molecule(-1) s(-1) (V(+)) are in good agreement with the experimental data at the same temperature. For the reaction of Zn(+) and CH3F our predicted value for kouter, at 295 K, 3.79 × 10(-9) cm(3) molecule(-1) s(-1), is in accordance with the capture rate constant. Our study suggests that consideration of the lowest excited states for Ti(+) and V(+) is mandatory to reach agreement between calculations and experimental measurements.

  1. Enhancing the photoluminescence intensity of CaTiO3:Eu3+ red phosphors with magnesium

    Institute of Scientific and Technical Information of China (English)

    张杰强; 范艳伟; 陈朝阳; 王军华; 赵鹏君; 郝斌

    2015-01-01

    Red phosphors MgxCa1–xTiO3:Eu3+ (0Ca0.6TiO3:0.03Eu3+ was 4.26 times of that of phosphor CaTiO3:0.03Eu3+. Based on these results, it implied that the PL intensity of phosphorCaTiO3:0.03Eu3+ could be significantly enhanced by introducing Mg2+ into CaTiO3 host lattices and the phosphor Mg0.4Ca0.6TiO3:0.03Eu3+ might be the promising red-emitting phosphor in making tricolor phosphor converted white-LEDs.

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

    Science.gov (United States)

    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.

  3. Wear Behavior of Cold Pressed and Sintered Al2O3/TiC/CaF2Al2O3/TiC Laminated Ceramic Composite

    Institute of Scientific and Technical Information of China (English)

    Xuefeng YANG; Jian CHENG; Peilong SONG; Shouren WANG; Liying YANG; Yanjun WANG; Ken MAO

    2013-01-01

    A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance,such as low friction coefficient and low wear rate.Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure.Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear.Al2O3/TiC ceramic was also cold pressed and sintered for comparison.Friction analysis of the two ceramics was then conducted via a wear-and-tear machine.Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum,respectively.Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite.Under the friction load,the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits.This process formed a smooth,self-lubricating film,which led to better anti-wear properties.Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.

  4. Mixed interface and charge neutrality in the oxide heterostructure DyScO3/SrTiO3

    International Nuclear Information System (INIS)

    Oxide interfaces have attracted considerable attention in recent years due to the emerging novel behavior, which does not exist in the corresponding parent bulk compounds, e.g. joining two simple band insulators LaAlO3 and SrTiO3 with different polarity can induce new properties ranging from conductivity to magnetism, even to superconductivity. The electrostatic potential diverges due to the polar discontinuity at the interface. But intermixing at the interface, defects, or formation of a polarization in the substrate can help to avoid the divergence of the electrostatic potential. We carried out density functional theory calculations based on the full-potential linearized augmented planewave (FLAPW) method as implemented in the FLEUR code (www.flapw.de) for studying sharp and intermixed DyScO3/SrTiO3 interfaces. DyScO3 layers induce the same polarity as the lanthanum aluminate. Experimental evidence for intermixing was reported for this system. We investigated both scenarios avoiding the polar catastrophe, either by forming a mixed layer at the interface or by formation of a polarization in the SrTiO3 substrate.

  5. A simple solvothermal process to synthesize CaTiO3 microspheres and its photocatalytic properties

    International Nuclear Information System (INIS)

    Highlights: • This paper presents a facile hydrothermal route to self-assemble CaTiO3 nanosheets into microspheres without any surfactants or template and discusses the photocatalytic performance of the large-scale structure. • The growth mechanism for spherical CaTiO3 is proposed to be a self assembly-nanosheets building units further oriented growth mechanism. • The molar ratio of water/ethanol is crucial for the formation of spherical CaTiO3. In addition, CaTiO3 microspheres were stable during the photocatalytic reaction and more convenient to store and handle as a micrometre-scale structure. • The present work not only helps understanding of the growth behavior of 3D CaTiO3 microspheres in a solution synthetic system, but also provides an efficient approach to enhance the photocatalytic properties of CaTiO3 catalysts by the controllable design of desirable structure and morphology. - Abstract: Novel CaTiO3 microspheres composed of nanosheets have been successfully prepared via a very simple solvothermal process in ethanol aqueous solution without any template or surfactant. The microstructure and morphology are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The effects of the reaction time, reaction temperature, and molar ratio of ethanol/water on the formation of the spherical structure have been investigated. CaTiO3 microspheres assembled by nanosheet units have been obtained by controlling the molar ratio of water/ethanol. The growth mechanism has been proposed based on the results of time-dependent experiments. It is proposed that amorphous particles transformed to nanosheets, and nanosheets self assembly into solid microspheres, then nanosheets building units further oriented growth along [1 1 0] direction result in the formation of nanosheets building units, and finally form the microsphere composed of nanosheets. CaTiO3

  6. Sodium scandium diphosphate, NaScP2O7, isotypic with α-NaTi(IIIP2O7

    Directory of Open Access Journals (Sweden)

    Zdirad Žák

    2009-12-01

    Full Text Available Crystals of the title compound, NaScP2O7, were grown by a flux method. The crystal structure is isotypic with those of α-NaTiP2O7, NaYbP2O7 and NaLuP2O7, and is closely related to that of NaYP2O7. The structural set-up consists of a three-dimensional framework of P2O7 units that are corner-shared by ScO6 octahedra, forming tunnels running parallel to [010]. The Na atoms are situated in the tunnels and are surrounded by nine O atoms in a distorted environment.

  7. A new approach to targetry and cyclotron production of 45Ti by proton irradiation of 45Sc

    Directory of Open Access Journals (Sweden)

    Fazaeli Yousef

    2014-01-01

    Full Text Available Titanium-45 with a half-life of 3.09 hours decays by emission of positrons (85% and the electron capture process (15%. These properties make this radionuclide useful in the diagnosis of tumors by positron emission tomography. In this study, after having considered the excitation functions for the 45Sc(p, n45Ti reaction using TALYS and ALICE/ASH codes and after the comparison with other experimental data, 45Ti was produced by dint of the pressing method and a newly designed and manufactured shuttle and capsule, resulting in an experimental yield of 403.3 MBq/mAh. Essential target thickness and physical yield were calculated. The scandium oxide target was irradiated at a 20 mA current and a 21 MeV proton beam energy for 1 hour.

  8. First-principles study of hydrogen storage on Ti (Sc)-decorated boron-carbon-nitride sheet

    Energy Technology Data Exchange (ETDEWEB)

    Song Nahong [College of Computer and Information Engineering, Henan University of Economics and Law, Zhengzhou 450002 (China); Wang Yusheng [College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou, Henan 450011 (China); Center of Clean Energy and Quantum Structures, School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450052 (China); Sun Qiang [Center of Clean Energy and Quantum Structures, School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450052 (China); Jia Yu, E-mail: xxwysheng@163.com [Center of Clean Energy and Quantum Structures, School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan 450052 (China)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer The gravimetric densities of H{sub 2} are 7.6 wt% and 7.8 wt%, respectively. Black-Right-Pointing-Pointer The average adsorption energy of hydrogen molecule is in the range of 0.4-0.56 eV/H{sub 2} (0.13-0.27 eV/H{sub 2}). Black-Right-Pointing-Pointer It can operate under ambient thermodynamic conditions. - Abstract: Ab initio first-principles calculations are carried out to investigate Ti (Sc)-decorated two-dimensional boron-carbon-nitride (BC{sub 2}N) sheets for their application as hydrogen storage materials. The results show that with four H{sub 2} molecules attached to per metal atom the Ti (Sc)-decorated BC{sub 2}N can store up to 7.6 wt% (7.8 wt%) of hydrogen in molecular form. The Kubas interaction and the polarization mechanism lead to the adsorption energy within the range of 0.4-0.56 eV/H{sub 2} (0.13-0.27 eV/H{sub 2}), which is suitable for ambient temperature hydrogen storage.

  9. Structure of 55Ti and 49Ca from relativistic one-neutron knockout

    CERN Document Server

    Maierbeck, P; Krücken, R; Kröll, T; Alvarez-Pol, H; Aksouh, F; Aumann, T; Behr, K; Benjamim, E A; Benlliure, J; Bildstein, V; Böhmer, M; Boretzky, K; García-Borge, M J; Brünle, A; Bürger, A; Caamaño, M; Casarejos, E; Chatillon, A; Chulkov, L V; Cortina-Gil, D; Enders, J; Eppinger, K; Fästermann, T; Friese, J; Fabbietti, L; Gascón, M; Geissel, H; Gerl, J; Górska, M; Hansen, P G; Jonson, B; Kanungo, R; Kiselev, O; Kojouharov, I; Klimkiewicz, A; Kurtukian, T; Kurz, N; Larsson, K; Bleis, T Le; Mahata, K; Maier, L; Nilsson, T; Nociforo, C; Nyman, G; Pascual-Izarra, C; Perea, A; Pérez, D; Prochazka, A; Rodriguez-Tajes, C; Rossi, D; Schaffner, H; Schrieder, G; Schwertel, S; Simon, H; Sitár, B; Stanoiu, M; Sümmerer, K; Tengblad, O; Weick, H; Winkler, S; Brown, B A; Otsuka, T; Tostevin, J; Rae, W D M

    2008-01-01

    Results are presented from a one-neutron knockout reaction at relativistic energies on 50Ca and 56Ti using the GSI FRS as a two-stage magnetic spectrometer and the Miniball array for gamma-ray detection. Inclusive and exclusive longitudinal momentum distributions and cross-sections were measured enabling the determination of the orbital angular momentum of the populated states. First-time observation of the 3.35(15) MeV nu f7/2-hole state in 49Ca and the 955(6) keV nu p3/2-hole state in 55Ti is reported. The measured data clearly indicates that the ground state of 55Ti is a 1/2- state, in agreement with shell-model calculations using the GXPF1A interaction that predict a sizable N=34 gap in 54Ca.

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

    Science.gov (United States)

    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.

  11. Enhanced Efficiency of Dye-Sensitized Solar Cells by Trace Amount Ca-Doping in TiO2 Photoelectrodes

    Directory of Open Access Journals (Sweden)

    Mengmei Pan

    2015-01-01

    Full Text Available Trace amount Ca-doped TiO2 films were synthesized by the hydrothermal method and applied as photoanodes of dye-sensitized solar cells (DSSCs. To prepare Ca-doped TiO2 film electrodes, several milliliters of Ca(NO32 solution was added in TiO2 solution during the hydrolysis process. The improvements of DSSCs were confirmed by photocurrent density-voltage (J-V characteristics, electrochemical impedance spectroscopy (EIS measurements. Owing to the doping effect of Ca, the Ca-doped TiO2 thin film shows power conversion efficiency of 7.45% for 50 ppm Ca-doped TiO2 electrode, which is higher than that of the undoped TiO2 film (6.78% and the short-circuit photocurrent density (Jsc increases from 13.68 to 15.42 mA·cm−2. The energy conversion efficiency and short-circuit current density (Jsc of DSSCs were increased due to the faster electron transport in the Ca-doped TiO2 film. When Ca was incorporated into TiO2 films, the electrons transport faster and the charge collection efficiency ηcc is higher than that in the undoped TiO2 films.

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

    Science.gov (United States)

    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.

  13. Strong irradiation tolerance to amorphization in delta-Sc{sub 4}Ti{sub 3}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J., E-mail: zhangjian@xmu.edu.cn [School of Energy, Xiamen University, Xiamen, Fujian 361005 (China); Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Patel, M.K. [Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996 (United States); Wang, Y.Q.; Tang, M. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Won, J. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon 305-806 (Korea, Republic of); Valdez, J.A. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Sickafus, K.E. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996 (United States)

    2015-04-15

    Polycrystalline delta-phase Sc{sub 4}Ti{sub 3}O{sub 12} was irradiated under two separate conditions, with 200 keV Ne{sup +} or 600 keV Kr{sup 3+} at cryogenic temperature (∼77 K) to examine its radiation tolerance to amorphization. Irradiated samples were characterized using grazing incidence X-ray diffraction and cross-sectional transmission electron microscopy. An order-to-disorder (O–D) structural transformation was observed under both ion beam irradiation conditions, but the threshold irradiation doses to produce the O–D transformation differ significantly. The order to disorder phase transformation was completed by a fluence of 2 × 10{sup 19} Ne/m{sup 2} (or a peak dose of ∼0.7 dpa) with Ne irradiation, while it was not accomplished until a fluence of 5 × 10{sup 20} Kr/m{sup 2} (or a peak dose of ∼93 dpa) with Kr irradiation. This observation was interpreted in terms of greater probability of defect survivability in dilute Ne versus dense Kr ion cascades. More interesting aspect in this study, in the basis of so-called “chemical effects”, Ti-bearing oxide Sc{sub 4}Ti{sub 3}O{sub 12} should be readily amorphous when exposed to ion irradiation, but no amorphization was observed even after 93 displacements per atom in Kr irradiation. These observations exhibit that the temperature–composition (T–C) phase diagram is a good indicator for radiation tolerance, especially for amorphization.

  14. Vacancy induced metallicity at the CaHfO3/SrTiO3 interface

    KAUST Repository

    Nazir, Safdar

    2011-03-31

    Density functional theory is used to study the electronic properties of the oxide heterointerfaceCaHfO3/SrTiO3. Structural relaxation is carried out with and without O vacancies. As compared to related interfaces, strongly reduced octahedral distortions are found. Stoichiometric interfaces between the wide band gap insulatorsCaHfO3 and SrTiO3 turn out to exhibit an insulating state. However, interface metallicity is introduced by O vacancies, in agreement with experiment. The reduced octahedral distortions and necessity of O deficiency indicate a less complicated mechanism for the creation of the interfacial electron gas.

  15. New Infrared Properties of the Tetragonal CaTiO3

    Institute of Scientific and Technical Information of China (English)

    YI Lin; DUAN Yi-Feng

    2005-01-01

    @@ First-principle calculations are performed to study the infrared optical and electronic properties of the tetragonal CaTiO3.We find that dielectric function and reflectivity exhibit a new single-peak infrared spectrum.It is shown that strong orbital hybridization can form the dipole distribution of covalent bonds (Ti-O1 and Ti-O2)and can result in anomalous optical behaviour.The tetragonal structure that determines the dipole configuration and leads to the optical dipole-dipole transition forbidden is therefore realized to be vital to cause such optical phenomena with the insulator feature.

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

    Science.gov (United States)

    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.

  17. Biomimetic Ca-P coating on pre-calcified Ti plates by electrodeposition method

    International Nuclear Information System (INIS)

    A new electrodeposition method was presented for Ca-P coating on pre-calcified titanium (PTi) plates at room temperature. The biomimetic coating morphology was investigated by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) results indicated that the functional TiOx layer with groups of -Ca and -OH was formed on PTi surface after pre-calcified chemical treatment. The TiOx layer showed a lower water contact angle and lower surface energy than those of pure titanium surfaces, and the PTi surface natures are benefited by coupling biomimetic Ca-P layer with bioactivity in the electrodeposition process. Moreover, the crystallization of Ca-P precipitate and the bond strength of coating to PTi substrates were improved significantly by post-treatments. Our results suggest this new coating process and its subsequent application to biomedical implant devices.

  18. Structural and electrical properties of nonstoichiometric semiconducting pyrochlores in Ca-Ce-Ti-Nb-O system

    International Nuclear Information System (INIS)

    Research highlights: → Nonstoichiometric semiconducting pyrochlores, CaCexTiNbO7-δ (x = 0.5-1.0) system have been synthesized by the conventional solid state route. → CaCe0.7TiNbO6.55, crystallizes into a pure cubic pyrochlore structure by accommodating smaller Ti ions on the A site. → The impedance analysis indicates relaxor behavior of these compounds due to disorder in the system. - Abstract: A series of quaternary nonstoichiometric cubic pyrochlores with varying cerium content in Ca-Ce-Ti-Nb-O system has been synthesized through solid state route. The powder X-ray diffraction and Rietveld analysis indicate that smaller Ti cation occupies the A site by displacing the A and O' ions causing displacive disorder in the cubic pyrochlore structure. The electrical conductivity measurements reveal that they exhibit semiconductor behavior in a broad temperature range (30-600 deg. C) and the conductivity increases with increase in Ce content. The X-ray photoelectron spectroscopy (XPS) analysis corroborates the presence of Ce in 3+ state. The impedance analysis reveals two types of conduction processes from the frequency dependent conductivity plots, i.e. low frequency conduction due to short range hopping and high frequency conduction due to the localized reorientation hopping mechanism. The relaxational properties indicate that hopping frequency is dependent on cerium concentration and is a measure of degree of disorder in the system.

  19. Magnetic ground state of Ti{sub 1-x}Sc{sub x}Fe{sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Saoudi, M.; Deportes, J.; Ouladdiaf, B. E-mail: ouladdiaf@ill.fr

    2001-06-01

    The magnetic ground states of the Laves phases Ti{sub 1-x}Sc{sub x}Fe{sub 2} system have been investigated by means of powder neutron diffraction and magnetisation techniques. For x=0.23, a transition is observed from a collinear ferromagnet along the c-axis to a canted one at T{sub f}=200 K. For x=0.27, 0.3, 0.33, an additional first-order transition is observed at T{sub t1}{approx}120 K accompanied by a large magnetovolume anomaly associated to a jump of the magnetic moment of the Fe atoms at the 2a site. The magnetic moment instability in a frustrated lattice should be considered to interpret this transition, although most of the other magnetic states can be discussed within Moriya's theory for itinerant electron systems with competing ferromagnetic and antiferromagnetic spin fluctuations.

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

    Energy Technology Data Exchange (ETDEWEB)

    Shtansky, D.V., E-mail: shtansky@shs.misis.ru [National University of Science and Technology “MISIS”, Leninsky prospekt 4, Moscow 119049 (Russian Federation); Batenina, I.V.; Kiryukhantsev-Korneev, Ph.V.; Sheveyko, A.N.; Kuptsov, K.A. [National University of Science and Technology “MISIS”, Leninsky prospekt 4, Moscow 119049 (Russian Federation); Zhitnyak, I.Y.; Anisimova, N.Yu.; Gloushankova, N.A. [N.N. Blokhin Russian Cancer Research Center of RAMS, Kashirskoe shosse 24, Moscow 115478 (Russian Federation)

    2013-11-15

    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 TiC{sub 0.5}–Ca{sub 3}(PO{sub 4}){sub 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.

  1. Microstructure and transformation behavior of Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} high temperature shape-memory alloy with Sc micro-addition

    Energy Technology Data Exchange (ETDEWEB)

    Ramaiah, K.V., E-mail: kvramaiah@nal.res.in [Materials Science Division, CSIR-National Aerospace Laboratories, Bangalore 560 017 (India); Saikrishna, C.N. [Materials Science Division, CSIR-National Aerospace Laboratories, Bangalore 560 017 (India); Gouthama [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208 016 (India); Bhaumik, S.K. [Materials Science Division, CSIR-National Aerospace Laboratories, Bangalore 560 017 (India)

    2015-08-15

    NiTiPd shape-memory alloys (SMAs) are potential functional materials for use as solid-state actuators in the temperature range 100–250 °C. The present study investigates the effect of 1.0 at.% Sc micro-addition to Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} alloy, Sc replacing either Ti or Ni. Results show that all the three alloys studied have stable transformation behavior on stress-free thermal cycling and hence, are suitable for cyclic actuation applications. However, the addition of Sc to NiTiPd alloy leads to decrease of transformation temperatures, the magnitude of decrease being greater for the alloy with Sc replacing Ni. The martensite finish (M{sub f}) temperature of 181 °C for the NiTiPd alloy decreased to 139 °C for Sc replacing Ti and 83 °C for Sc replacing Ni. Also, the indentation modulus of NiTiPdSc (Sc replacing Ni) alloy is found to be significantly low compared to the other alloys. Analysis indicates that the observed differences in the alloy properties are related to the solubility of Sc in the NiTiPd matrix. While the quaternary NiTiPdSc alloy, Sc replacing Ti, has a single phase microstructure, the alloy with Sc replacing Ni shows the presence of Sc-rich and TiPd-type second phases in the microstructure. TEM examination revealed that the TiPd-type phase has a distinct rod-like morphology (30–50 nm) arranged in a grid-like structure. The transformation and indentation behavior of the alloys is elucidated using thermodynamic calculations of frictional energy and an electronic structure based analysis. - Highlights: • TEM of Ni{sub 23.7}Ti{sub 50.3}Pd{sub 25}Sc{sub 1} showed distinct grid of TiPd-type phase nanorods < 50 nm. • Stress-free thermal cycling of all the three alloys showed stable transformation behavior. • Ni{sub 24.7}Ti{sub 49.3}Pd{sub 25}Sc{sub 1} and Ni{sub 23.7}Ti{sub 50.3}Pd{sub 25}Sc{sub 1} showed single and multiphase structures. • Sc micro-addition (1 at.%) to Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} alloy decreased TTs

  2. Magnetism and electronic structure of (001)- and (111)-oriented LaTiO{sub 3} bilayers sandwiched in LaScO{sub 3} barriers

    Energy Technology Data Exchange (ETDEWEB)

    Weng, Yakui; Dong, Shuai, E-mail: sdong@seu.edu.cn [Department of Physics and Jiangsu Key Laboratory of Advanced Metallic Materials, Southeast University, Nanjing 211189 (China)

    2015-05-07

    In this study, the magnetism and electronic structure of LaTiO{sub 3} bilayers along both the (001) and (111) orientations are calculated using the density functional theory. The band insulator LaScO{sub 3} is chosen as the barrier layer and substrate to obtain the isolating LaTiO{sub 3} bilayer. For both the (001)- and (111)-oriented cases, LaTiO{sub 3} demonstrates the G-type antiferromagnetism as the ground state, similar to the bulk material. However, the electronic structure is significantly changed. The occupied bands of Ti are much narrower in the (111) case, giving a nearly flat band. As a result, the exchange coupling between nearest-neighbor Ti ions is reformed in these superlattices, which will affect the Néel temperature significantly.

  3. Surface structures and osteoblast response of hydrothermally produced CaTiO{sub 3} thin film on Ti-13Nb-13Zr alloy

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin-Woo, E-mail: jinwoo@knu.ac.kr [Department of Periodontology, School of Dentistry, Kyungpook National University, 188-1, Samduk 2Ga, Jung-Gu, Daegu 700-412 (Korea, Republic of); Tustusmi, Yusuke [Department of Metals, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental Univeristy, Tokyo 101-0062 (Japan); Lee, Chong Soo; Park, Chan Hee [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Kim, Youn-Jeong; Jang, Je-Hee [Department of Periodontology, School of Dentistry, Kyungpook National University, 188-1, Samduk 2Ga, Jung-Gu, Daegu 700-412 (Korea, Republic of); Khang, Dongwoo; Im, Yeon-Min [School of Materials Science and Engineering, Gyeongsang National University, Jinju 600-701 (Korea, Republic of); Doi, Hisashi; Nomura, Naoyuki; Hanawa, Takao [Department of Metals, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental Univeristy, Tokyo 101-0062 (Japan)

    2011-06-15

    This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating calcium ions (Ca) obtained by hydrothermal treatment with or without post heat-treatment in the Ti-13Nb-13Zr alloy. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. In vitro biocompatibility of the Ca-containing surfaces was assessed in comparison with untreated surfaces using a pre-osteoblast cell line. Hydrothermal treatment produced a crystalline CaTiO{sub 3} layer. Post heat-treatment at 400 deg. C for 2 h in air significantly decreased water contact angles in the CaTiO{sub 3} layer (p < 0.001). The Ca-incorporated alloy surfaces displayed markedly increased cell viability and ALP activity compared with untreated surfaces (p < 0.001), and also an upregulated expression of various integrin genes ({alpha}1, {alpha}2, {alpha}5, {alpha}v, {beta}1 and {beta}3) at an early incubation time-point. Post heat-treatment further increased attachment and ALP activity in cells grown on Ca-incorporated Ti-13Nb-13Zr alloy surfaces. The results indicate that the Ca-incorporated oxide layer produced by hydrothermal treatment and a simple post heat-treatment may be effective in improving bone healing in Ti-13Nb-13Zr alloy implants by enhancing the viability and differentiation of osteoblastic cells.

  4. Formation of CaO·TiO2-MgO·Al2O3 dual phase inclusion in Ti stabilized stainless steel

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The formation of CaO.TiO2-MgO.Al2O3 dual phase inclusion in 321 stainless steel was investigated in the laboratory. The result indicated that the condition for the formation of CaO.TiO2-MgO.Al2O3 in 321 steel is [Ca]>0.001wt%, [Ti]>0.1wt%, and[Al]>0.01wt%. The mechanism is the following: Al2O3 inclusion turns into CaO-Al2O3 after Ca-Si wire is fed into the molten steel;[Mg] is then obtained by reducing MgO in slag or crucible wall by [Al] and [Ti]; finally CaO-Al2O3 inclusion is changed into CaO.TiO2-MgO-Al2O3 by the reaction with [Mg], [Ti], and [O] in the molten steel simultaneously.

  5. Surface structures and osteoblast response of hydrothermally produced CaTiO3 thin film on Ti-13Nb-13Zr alloy

    International Nuclear Information System (INIS)

    This study investigated the surface characteristics and in vitro biocompatibility of a titanium (Ti) oxide layer incorporating calcium ions (Ca) obtained by hydrothermal treatment with or without post heat-treatment in the Ti-13Nb-13Zr alloy. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. In vitro biocompatibility of the Ca-containing surfaces was assessed in comparison with untreated surfaces using a pre-osteoblast cell line. Hydrothermal treatment produced a crystalline CaTiO3 layer. Post heat-treatment at 400 deg. C for 2 h in air significantly decreased water contact angles in the CaTiO3 layer (p < 0.001). The Ca-incorporated alloy surfaces displayed markedly increased cell viability and ALP activity compared with untreated surfaces (p < 0.001), and also an upregulated expression of various integrin genes (α1, α2, α5, αv, β1 and β3) at an early incubation time-point. Post heat-treatment further increased attachment and ALP activity in cells grown on Ca-incorporated Ti-13Nb-13Zr alloy surfaces. The results indicate that the Ca-incorporated oxide layer produced by hydrothermal treatment and a simple post heat-treatment may be effective in improving bone healing in Ti-13Nb-13Zr alloy implants by enhancing the viability and differentiation of osteoblastic cells.

  6. Structural and dielectric behavior of pulsed laser ablated Sr 0.6Ca 0.4TiO 3 thin film and asymmetric multilayer of SrTiO 3 and CaTiO 3

    Science.gov (United States)

    Chakraborty, Pradip; Choudhury, Palash Roy; Krupanidhi, S. B.

    2011-12-01

    Homogeneous thin films of Sr 0.6Ca 0.4TiO 3 (SCT40) and asymmetric multilayer of SrTiO 3 (STO) and CaTiO 3 (CTO) were fabricated on Pt/Ti/SiO 2/Si substrates by using pulsed laser deposition technique. The electrical behavior of films was observed within a temperature range of 153 K-373 K. A feeble dielectric peak of SCT40 thin film at 273 K is justified as paraelectric to antiferroelectric phase transition. Moreover, the Curie-Weiss temperature, determined from the ɛ'( T) data above the transition temperature is found to be negative. Using Landau theory, the negative Curie-Weiss temperature is interpreted in terms of an antiferroelectric transition. The asymmetric multilayer exhibits a broad dielectric peak at 273 K, and is attributed to interdiffusion at several interfaces of multilayer. The average dielectric constants for homogeneous Sr 0.6Ca 0.4TiO 3 films (˜650) and asymmetric multilayered films (˜350) at room temperature are recognized as a consequence of grain size effect. Small frequency dispersion in the real part of the dielectric constants and relatively low dielectric losses for both cases ensure high quality of the films applicable for next generation integrated devices.

  7. Improved persistent luminescence of CaTiO{sub 3}:Pr by fluorine substitution and thermochemical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Songhak, E-mail: songhak.yoon@empa.ch [Laboratory for Solid State Chemistry and Catalysis, Empa – Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Otal, Eugenio H.; Maegli, Alexandra E.; Karvonen, Lassi; Matam, Santhosh K. [Laboratory for Solid State Chemistry and Catalysis, Empa – Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Ebbinghaus, Stefan G. [Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120 Halle/Saale (Germany); Walfort, Bernhard [LumiNova AG, Speicherstrasse 60A, CH-9053 Teufen (Switzerland); Hagemann, Hans [Department of Physical Chemistry, University of Geneva, Quai E. Ansermet 30, CH-1211 Geneva 4 (Switzerland); Pokrant, Simone [Laboratory for Solid State Chemistry and Catalysis, Empa – Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Weidenkaff, Anke [Laboratory for Solid State Chemistry and Catalysis, Empa – Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Institute for Materials Science, University of Stuttgart, Heisenbergstrasse 3, 70569 Stuttgart (Germany)

    2014-11-15

    Highlights: • Synthesis of fluorine-substituted CaTiO{sub 3}:Pr phosphors. • Rietveld refinement of CaTi(O,F){sub 3}:Pr phosphors. • Afterglow intensity improvement of ca. 450% compared to CaTiO{sub 3}:Pr. - Abstract: Fluorine-substituted CaTiO{sub 3}:Pr phosphors were prepared by a solid-state reaction. Rietveld refinements of powder X-ray diffraction patterns revealed that increasing fluorine-substitution leads to the gradual shrinkage of the unit-cell. Enhanced afterglow intensities were observed with fluorine-substitution. Furthermore, the effect of annealing atmosphere was investigated by thermochemical treatment in different atmospheres (Ar, air and NH{sub 3}). UV–Vis diffuse reflectance spectra and photoluminescence excitation spectra revealed that Pr{sup 4+} in the pristine CaTi(O,F){sub 3}:Pr phosphor was partially reduced to Pr{sup 3+} under NH{sub 3} flow leading to an intensity improvement of ca. 450% compared to CaTiO{sub 3}:Pr. The substantial improvement of afterglow intensity by fluorine substitution and annealing in NH{sub 3} is considered to be connected with the generation of oxygen vacancies and the partial reduction of Pr{sup 4+} to Pr{sup 3+}.

  8. Correlated rattling-ion origins of dielectric properties in reentrant dipole glasses BaTiO{sub 3}-BiScO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Krayzman, Victor; Levin, Igor, E-mail: igor.levin@nist.gov; Woicik, Joseph C. [Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Bridges, Frank [Department of Physics, University of California, Santa Cruz, California 95064 (United States)

    2015-11-09

    The local structure of the pseudo-cubic solid solution 0.6BaTiO{sub 3}-0.4BiScO{sub 3}, which exhibits reentrant dipole-glass behavior, has been determined using the Reverse Monte Carlo method to simultaneously fit (1) neutron and X-ray total scattering data (including the corresponding real-space pair-distribution functions), (2) Bi and Sc extended X-ray absorption fine structure, and (3) patterns of diffuse scattering in electron diffraction. These structural refinements revealed the multi-site probability density distributions for both Bi (14-sites) and Ti (8 sites), whereas Ba and Sc featured normal unimodal distributions. Bi atoms are displaced along both the 〈111〉 and 〈100〉 directions, while Ti atoms are shifted along 〈111〉. Correlated dynamic hopping of Bi and Ti over their corresponding split sites combined with chemical disorder is proposed as the origin of the strong frequency dispersion observed in dielectric measurements. The existence of split sites also explains the reentrant dipole-glass behavior reported for this system.

  9. First principles study of the electron structures of CaCu3Mn4O12 and CaCu3Ti4O12

    International Nuclear Information System (INIS)

    The electronic structures of CaCu3Mn4O12 and CaCu3Ti4O12 are investigated from HF SCF LCAO calculation. In CaCu3Mn4O12, the band and the density of states show a spin asymmetric ferrimagnetic character with a small energy gap. The Mn spin is anti-aligned with the Cu spin, and the total spin moment is 9 μ B. Our calculation correctly reproduces the observed antiferromagnetic insulating character of CaCu3Ti4O12. The gap in the band structure, which is 2.15 eV, reasonably agrees with the experimental value 1.5 eV. The electron density populations at different planes show clearly that the electron density has symmetric character. A tilted Mn(Ti) orbital implies a typical tilted three-dimensional network of MnO6 (TiO6) octahedra due to doping of the Jahn-Teller ion Cu. There is no covalency between Ca, Cu and Mn(Ti) atoms. In contrast, there are stronger bonds and somewhat likely covalency between Cu and O atoms, and also between Mn(Ti) and O atoms

  10. Cyclotron production of {sup 44}Sc for clinical application

    Energy Technology Data Exchange (ETDEWEB)

    Krajewski, S.; Bilewicz, A. [Institute of Nuclear Chemistry and Technology, Warsaw (Poland); Cydzik, I. [Institute of Nuclear Chemistry and Technology, Warsaw (Poland); European Commission Joint Research Center, Ispra (Italy). Inst. for Health and Consumer Protection; Warsaw Univ. (Poland). Heavy Ion Lab.; Abbas, K. [European Commission Joint Research Center, Ispra (Italy). Institute for Transuranium Elements; Bulgheroni, A.; Simonelli, F.; Holzwarth, U. [European Commission Joint Research Center, Ispra (Italy). Inst. for Health and Consumer Protection

    2013-08-01

    {sup 44} is a promising {beta}{sup +}-emitter for molecular imaging with intermediate half-life of 4 h. Due to the chemical similarity of Sc{sup 3+} to the Lu{sup 3+} and Y{sup 3+} cations, {sup 44}Sc-DOTA bioconjugates are expected to demonstrate similar properties in vivo as the {sup 177}Lu- and {sup 90}Y-bioconjugates, what is important in planning the radionuclide therapy. {sup 44}Sc can be obtained from the {sup 44}Ti/{sup 44}Sc generator. An alternative method for {sup 44}Sc production can be the irradiation of {sup 44}Ca target at small cyclotrons. The aim of our work was to optimize the parameters of {sup 44}CaCO{sub 3} irradiation and to develop a simple procedure for {sup 44}Sc separation from the calcium target. For optimization study, {sup 44}CaCO{sub 3} targets were irradiated by protons in the energy range of 5.6-17.5 MeV with 9 MeV being found to be the best energy for {sup 44}Ca irradiations. A simple and fast separation procedure of {sup 44}Sc from calcium target was developed using chelating resin Chelex 100. DOTATATE conjugate was successfully radiolabelled with high yield at elevated temperature using the produced {sup 44}Sc. While {sup 44}CaCO{sub 3} is relatively expensive, the cost of {sup 44}Sc-DOTATATE production can be reduced by target recovery. Due to low proton energy required to produce GBq activity level of {sup 44}Sc, the availability of {sup 44}Sc radioisotope could be enhanced to open new opportunities for applications in medical imaging. (orig.)

  11. Domains and ferroelectric switching pathways in Ca3Ti2O7 from first principles

    Science.gov (United States)

    Nowadnick, Elizabeth A.; Fennie, Craig J.

    2016-09-01

    Hybrid improper ferroelectricity, where an electrical polarization can be induced via a trilinear coupling to two nonpolar structural distortions of different symmetries, recently was demonstrated experimentally in the n =2 Ruddlesden-Popper compound Ca3Ti2O7 . In this paper we use group theoretic methods and first-principles calculations to identify possible ferroelectric switching pathways in Ca3Ti2O7 . We identify low-energy paths that reverse the polarization direction by switching via an orthorhombic twin domain or via an antipolar structure. We also introduce a chemically intuitive set of local order parameters to give insight into how these paths are relevant to ferroelectric switching nucleated at domain walls. Our findings suggest that switching may proceed via more than one mechanism in this material.

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

    Science.gov (United States)

    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.

  13. Synthesis and characterization of CTO (CaTiO{sub 3})

    Energy Technology Data Exchange (ETDEWEB)

    Silva, M.A.S.; Fernandes, T.S. M.; Santiago, A.A.X.; Sombra, A.S.B., E-mail: marceloassilva@yahoo.com.br [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil); Sales, J.C. [Universidade Estadual Vale do Acarau (UVA), Sobral, CE (Brazil)

    2011-07-01

    The objective of this work is to study the ceramic material CTO (CaTiO{sub 3}) by X-Ray Diffraction. The composites of CTO are widely used in dielectric resonators in communication systems. The CTO was prepared by solid state method in a planetary high energy ball milling (Fritsch Pulverisette 5). Stoichiometric quantities of CaCO{sub 3} (Aldrich 99%) and TiO{sub 2} (Merck 99%) were dry milled during 4h with a rotational speed of 370 rpm and then calcined at 1000 deg C for 3h. After, the CTO was studied by X-ray diffraction (XRD). The refinement showed that the CTO was formed with 100% mass, the graph of Williamson-Hall showed a homogeneous sample, with a contraction in the crystal lattice and a reasonably small particle size. (author)

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

    Directory of Open Access Journals (Sweden)

    Bailey Sam

    2016-01-01

    Full Text Available 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.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Biegalski, Michael D.; Qiao, Liang [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Gu, Yijia; Chen, Long-Qing [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16801 (United States); Mehta, Apurva [Stanford Synchrotron Lightsource SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); He, Qian; Borisevich, Albina [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Takamura, Yayoi, E-mail: ytakamura@ucdavis.edu [Department of Chemical Engineering and Materials Science, University of California Davis, Davis, California 95616 (United States)

    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.

  17. Hibonite, Ca2/Al, Ti/24O38, from the Leoville and Allende chondritic meteorites.

    Science.gov (United States)

    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.

  18. Surface chemical changes of CaTiO3:Pr3+ upon electron beam irradiation

    International Nuclear Information System (INIS)

    Surface chemical changes of CaTiO3:Pr3+ phosphor material and their effect on the red emission intensity of the 1D2→3H4 transition of Pr3+, upon electron beam irradiation are presented. Red emission at 613 nm was obtained upon probing the surface with a 2 keV electron beam. The surface chemical changes and Pr3+ red emission were monitored using an Auger Electron Spectroscopy (AES) and Cathodoluminescence (CL) spectrometer, respectively. The CL intensity decreased with a decrease in O on the surface at 1×10−8 Torr base pressure and decreased with an increase in O on the surface at 1×10−6 Torr O2. The X-ray Photoelectron Spectroscopy (XPS) revealed that CL degradation at 1×10−6 Torr O2 is due to the formation of CaO and CaOx as well as TiO2/Ti2O3 non-luminescent species on the surface.

  19. (Zn, Ca) Solid-Solution Behavior and Its Effect on Luminescence Properties in Ca1- xZnx TiO3: 0.002Pr3+ Phosphors

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Nominal composition of Ca1 - xZnxTiO3: 0. 002Pr3 + ( x = 0. 000 ~ 0. 200) phosphors were prepared by conventional solid reaction route. XRD and PL measurements were used to investigate the solid-solution structure and luminescence properties of Zn-doped Ca1- xZnxTiO3:0. 002Pr3 + phosphors. The effect of solid-solution structure formed by substitution between Ca2 + and Zn2 + ions on the luminescent properties was analyzed. The results reveal that, with the increase of Zn substitution content below 0.010, lattice parameters and the intensity of excitation peak at both 260 and 330 nm as well as the corresponding 610 nm emission intensity are monotonously decreased quickly in a similar tendency. Also, the evolution of luminescence intensity and crystal cell parameters against Zn doping concentration are in good agreement.Above results are closely related with the structure change within Ca1- xZnxTiO3:0. 002Pr3 + solid-solution phase formed by the Zn ions substitution for the Ca sites. Present study reveals that the solid-solution structure formed by substitution between Ca2 + and Zn2 + ions has significant effect on the luminescence properties of single phase Ca1- xZnxTiO3:0.002Pr3 +phosphors.

  20. Growth of Araucaria angustifolia in the Embrapa/Epagri forest reserve, Caçador, SC, Brazil Crescimento de Araucaria angustifolia na Reserva Florestal Embrapa/ Epagri, Caçador, SC

    Directory of Open Access Journals (Sweden)

    Patricia Póvoa de Mattos

    2010-06-01

    Full Text Available Araucaria Forest is one of most threatened phyto-physiognomies in the Atlantic Forest domain,
    presenting great ecological-economical importance. Nevertheless, there are still lacks of knowledge concerning growth and dynamic of important species, as Araucaria angustifolia. The objective of this work was to recover  the past growth of Araucaria angustifolia, native from Caçador, SC, Brazil, by measuring growth rings and to estimate the average periodic diametric increment. The growth rings were counted and measured, using a stereoscope microscope, in increment cores of 0.5 cm collected from 32 adult trees. The measurements were done with LINTAB measuring table, with 0.01 mm of precision. The samples sizes were irregular, varying from 4.2 to 20.2 cm long. The trees presented average diameter breast height (DBH of 76.3 cm, varying from 10.7 to 141.3 cm. The periodic diameter increment from the last 10 years was 0.4 cm, varying from 0.11 to 1.15 cm. It was observed differences among trees, but there was a tendency of reduction of growth rhythm in larger trees, being more
    evident in trees with more than 110 cm of DBH.A Floresta Ombrófila Mista (FOM é uma das fitofisionomias mais ameaçadas da área de domínio da
    Mata Atlântica, apresentando grande importância ecológico-econômica. Apesar disso, ainda existem lacunas de conhecimento sobre a produtividade primária, o crescimento e a dinâmica de espécies importantes, como a Araucaria angustifolia. O presente trabalho tem por objetivo estudar o crescimento anual de Araucaria angustifolia, nativa do Município de Caçador, SC, pela medição dos anéis de crescimento. A contagem e medição dos anéis de crescimento foram feitas com o auxílio de um microscópio estereoscópico, em baguetas de 0,5 cm de diâmetro, coletadas de 32 árvores adultas. As medições foram feitas com o medidor de anéis de crescimento LINTAB, com precisão de 0,01 mm. O comprimento das amostras

  1. Synthesis of CaTiO3 from calcium titanyl oxalate hexahydrate (CTO) as precursor employing microwave heating technique

    Indian Academy of Sciences (India)

    B M Patil; R S Srinivasa; S R Dharwadkar

    2007-06-01

    Calcium titanate, CaTiO3, an important microwave dielectric material and one of major phases in synroc (synthetic rock), a titanate ceramic with potential application for fixation of high level nuclear waste was synthesized from calcium titanyl oxalate [CaTiO (C2O4)2.6H2O] (CTO) by employing microwave heating technique. CTO heated in microwave heating system in air at 500°C for 1 h gave a perovskite, CaTiO3. The product obtained by heating of CTO in the same system at 700°C for the same duration was however, much more crystalline. CaTiO3 obtained by the present method was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET surface area measurement.

  2. Anomalous Optical and Electronic Properties of CaTiO3 Perovskites

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    With the help of the first-principles full potential linearized augmented plane wave method, absorption coefficients, reflectivity, dielectric behavior and electronic properties, including electronic energy bands, density of states and charge density distributions, are studied for the tetragonal and cubic CaTiO3. By considering the thermal expansion effects, an approximate method is proposed for the study of the stability of ground state and a tendency of phase transition, based on the minimum free energy principle. Subsequently, numerical calculations are carried out by using the first-principles perturbation method. We demonstrate that the high-temperature phase is cubic. It is shown that optical spectra in tetragonal phase exhibit single-peak feature and differ from multi-peak character in cubic. We find that strong orbital hybridization results in the co-valent bonds between Ti 3d and O 2p electrons and forms two-type dipoles (Ti-O1 and Ti-O2) in tetragonal, while the Ti-O dipoles are identical in cubic. It is argued that crystal structure determines the dipole distributions and leads to some electron states among which the dipole-dipole transition forbidden is a key, causing such anomalous optical phenomena with the insulator characteristics. The predicted charge density distribution and the tendency of phase transition from tetragonal to cubic are in good agreement with experimental observations.

  3. New low loss A{sub 9}B{sub 9}O{sub 31} (A = La; B = Ti, Mg, Sc, Fe, Al, Ga) ceramics for microwave applications

    Energy Technology Data Exchange (ETDEWEB)

    Muhammad, Raz [Materials Research Laboratory, Department of Physics, University of Peshawar, 25120 (Pakistan); Iqbal, Yaseen, E-mail: dryaseeniqbal@yahoo.co.uk [Materials Research Laboratory, Department of Physics, University of Peshawar, 25120 (Pakistan); Reaney, Ian M. [Department of Materials Science and Engineering, University of Sheffield, S1 3JD (United Kingdom)

    2015-10-15

    A{sub n}B{sub n}O{sub 3n+2} (n = 4.5) type layered perovskite ceramics with general formula A{sub 9}B{sub 9}O{sub 31} (A = La; B = Ti, Mg, Sc, Fe, Al, Ga) were prepared via a mixed oxide solid state sintering route. X-ray diffraction analysis revealed single phase La{sub 9}(TiB){sub 9}O{sub 31} (B = Ti, Mg, Sc, Fe, Al, Ga) solid solutions with orthorhombic (Pnma) symmetry when sintered at 1500–1650 °C for 4–12 h. The temperature coefficient of resonance frequency (τ{sub f}) was influenced by the polarizability of B-site cations while relative permittivity (ε{sub r}) and quality factor (Q × f{sub o}) were dependent on the relative density. The samples investigated in the present study exhibited reasonable ε{sub r} (39–48.3), high Q × f{sub o} (11823–19070 GHz) and near zero τ{sub f} (−1.28 to −22.16 ppm/°C). These ceramics might be potential candidates for microwave devices. - Highlights: • New A{sub 9}B{sub 9}O{sub 31} (A = La; B = Ti, Mg, Sc, Fe, Al, Ga) type compounds were processed. • All the compositions formed single phase ceramics with orthorhombic (Pnma) symmetry. • The dielectric properties were strongly influenced by the processing condition. • The best dielectric properties achieved were ε{sub r} = 42, Q{sub f} = 17216 GHz and τ{sub f} ∼ −1.3 ppm/°C. • Sc- and Fe-based compounds meet the bench mark for MW applications.

  4. Cr4 + :Gd3Sc2Ga3O12 passive Q-switch for the Cr3 + :LiCaAlF6 laser

    Science.gov (United States)

    Kuo, Yen-Kuang; Yang, Yang; Birnbaum, Milton

    1994-05-01

    A Cr4+:Gd3Sc2Ga3O12 (Cr4+:GSGG) broad-band saturable absorber has been demonstrated to be an excellent passive Q-switch for the flashlamp-pumped tunable Cr3+:LiCaAlF6 (Cr:LiCAF) laser at room temperature. A single Q-switched laser output pulse of 11 mJ in energy and 37 ns in duration at 778 nm was obtained in a nonoptimized laser.

  5. Thermoelastic properties of ScB{sub 2}, TiB{sub 2}, YB{sub 4} and HoB{sub 4}: Experimental and theoretical studies

    Energy Technology Data Exchange (ETDEWEB)

    Waskowska, A. [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland); Gerward, L., E-mail: gerward@fysik.dtu.dk [Department of Physics, Technical University of Denmark, Lyngby (Denmark); Staun Olsen, J. [Niels Bohr Institute, Oersted Laboratory, University of Copenhagen, Copenhagen (Denmark); Ramesh Babu, K.; Vaitheeswaran, G. [ACRHEM, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad 500 046, Andhra Pradesh (India); Kanchana, V. [Department of Physics, IIT Hyderabad, Ordnance Factory Estate, Yeddumailaram 502 205, Andhra Pradesh (India); Svane, A. [Department of Physics and Astronomy, Aarhus University, Aarhus (Denmark); Filipov, V.B.; Levchenko, G.; Lyaschenko, A. [Institute for Problems of Materials Science, Academy of Sciences of Ukraine, Kiev (Ukraine)

    2011-07-15

    High-pressure X-ray diffraction in ScB{sub 2}, TiB{sub 2}, YB{sub 4} and HoB{sub 4} powders and single crystals has been studied using synchrotron radiation as well as conventional X-rays. The experimental results are supported by calculations using density functional theory. ScB{sub 2}, YB{sub 4} and HoB{sub 4} are hard materials (bulk modulus 180-200 GPa), while TiB{sub 2} may be classified as superhard (bulk modulus about 260 GPa). We report here first experimental and theoretical determinations of the bulk modulus for HoB{sub 4} (195(5) and 198.2 GPa, respectively), and first experimental values of the bulk modulus for ScB{sub 2} (196(2) GPa) and YB{sub 4} (185(4) GPa). No pressure-induced phase transformations are observed in any of the above borides up to about 20 GPa. A continuous temperature-driven orthorhombic distortion is observed for HoB{sub 4} below 285 K. Values of the thermal expansion coefficient are reported for ScB{sub 2} and HoB{sub 4} at 293, 200 and 100 K. The thermoelastic behavior is explained in terms of bonding characteristics.

  6. Quantum criticality in CaRuO{sub 3} - Influence of Ti substitution

    Energy Technology Data Exchange (ETDEWEB)

    Baran, A. [Faculty of Manufacturing Technologies, Technical University of Kosice, Presov (Slovakia); Zorkovska, A. [Institute of Geotechnics Slovak Academy of Science, Kosice (Slovakia); Kajnakova, M.; Feher, A. [Centre of Low Temperature Physics, P. J. Safarik University and Slovak Academy of Science, Kosice (Slovakia); Sebek, J.; Santava, E. [Institute of Physics Academy of Science of Czech Republic, Prague (Czech Republic); Bradaric, I. [Condensed Matter Physics Laboratory, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade (Serbia)

    2012-08-15

    Thermodynamic and transport properties of the CaRu{sub 1-x}Ti{sub x}O{sub 3} system with x = 0, 0.03, 0.07, 0.10, and 0.15 in magnetic field up to 9 T have been studied. The unconventional temperature dependences of magnetic susceptibility, specific heat, and electrical resistivity observed for CaRuO{sub 3} are typical for non-Fermi liquids and they support the assumption about the proximity of the system to the quantum critical point. The analysis of the experimental results suggests the electronic phase separation in CaRuO{sub 3} into ferromagnetic itinerant regions coexisting with strongly correlated ones. Substitution by titanium seems to push the system towards ferromagnetism, and drives it away from the quantum criticality. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. A simple solvothermal process to synthesize CaTiO{sub 3} microspheres and its photocatalytic properties

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Weixia [State Key Lab of Silicon Materials & School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Department of Material Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen, 333001 (China); Song, Bin, E-mail: bzsong@zju.edu.cn [Department of Physics, Zhejiang University, Hangzhou, 310027 (China); Meng, Weijie; Zhao, Gaoling; Han, Gaorong [State Key Lab of Silicon Materials & School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2015-09-15

    Highlights: • This paper presents a facile hydrothermal route to self-assemble CaTiO{sub 3} nanosheets into microspheres without any surfactants or template and discusses the photocatalytic performance of the large-scale structure. • The growth mechanism for spherical CaTiO{sub 3} is proposed to be a self assembly-nanosheets building units further oriented growth mechanism. • The molar ratio of water/ethanol is crucial for the formation of spherical CaTiO{sub 3}. In addition, CaTiO{sub 3} microspheres were stable during the photocatalytic reaction and more convenient to store and handle as a micrometre-scale structure. • The present work not only helps understanding of the growth behavior of 3D CaTiO{sub 3} microspheres in a solution synthetic system, but also provides an efficient approach to enhance the photocatalytic properties of CaTiO{sub 3} catalysts by the controllable design of desirable structure and morphology. - Abstract: Novel CaTiO{sub 3} microspheres composed of nanosheets have been successfully prepared via a very simple solvothermal process in ethanol aqueous solution without any template or surfactant. The microstructure and morphology are characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy. The effects of the reaction time, reaction temperature, and molar ratio of ethanol/water on the formation of the spherical structure have been investigated. CaTiO{sub 3} microspheres assembled by nanosheet units have been obtained by controlling the molar ratio of water/ethanol. The growth mechanism has been proposed based on the results of time-dependent experiments. It is proposed that amorphous particles transformed to nanosheets, and nanosheets self assembly into solid microspheres, then nanosheets building units further oriented growth along [1 1 0] direction result in the formation of nanosheets building units, and finally form the

  8. Experimental results for studies of the 40Ca(α,γ)44Ti reaction rates

    Science.gov (United States)

    Robertson, Daniel; Becker, Hans-Werner; Bowers, Matt; Collon, Philippe; Goerres, Joachim; Lu, Wenting; Schmitt, Chris; Wiescher, Michael

    2011-10-01

    Observational studies of galactic γ emitters such as 44Ti have highlighted their use in nucleosynthesis studies of massive stars in their late stage stellar evolution and final explosive demise in core collapse supernova events. Models used in the simulation of such γ emitters rely heavily upon reliable reaction rates for both the creation and annihilation of these isotopes over large temperature ranges. The production of 44Ti mainly through the 40Ca(α,γ)44Ti reaction is thought to take place primarily in the α-rich freeze out phase of a core collapse supernova. However, current supernova models predict lower 44Ti to 56Ni ratios than observed, creating a need for more information about its production mechanism. A number of previous studies include prompt γ-ray measurements, recoil mass separator experiments and the use of AMS, all giving greatly different reaction rates. Aiding in the refinement of these needed rates, the results of experiments at the DTL, Bochum and NSL, Notre Dame will be presented against the backdrop of these previous measurements. Work supported by grant # 0758100 and # 0822648.

  9. Solid state reaction synthesis and photoluminescence properties of Dy{sup 3+} doped Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12} phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Long, Qiang; Wang, Chuang; Li, Yanyan; Ding, Jianyan; Wang, Xicheng; Wang, Yuhua, E-mail: wyh@lzu.edu.cn

    2015-11-15

    Highlights: • Ca{sub 3−x}Sc{sub 2}Si{sub 3}O{sub 12}:xDy{sup 3+} (0.01 ≤ x ≤ 0.03) was successfully synthesized under a reducing atmosphere. • The thermal stability of the Ca{sub 2.975}Sc{sub 2}Si{sub 3}O{sub 12}:0.025Dy{sup 3+} is superior to commercial phosphors in theory and experiment. • The optimal chromaticity coordinates of Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} is (x = 0.3425, y = 0.3343) upon 350 nm excitation. - Abstract: The white emission phosphor Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} was synthesized by the solid-state reaction. Phase analysis and characteristic luminescence properties are investigated by X-ray diffraction and photoluminescence spectra measurement. Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} phosphor shows strong absorption in 350–410 nm region and exhibits white emission with CIE chromaticity coordinates of (0.3425, 0.3343). Its emission intensity at 250 °C remained 74% of that measured at room temperature. Moreover, the activation energy is also calculated through the Arrhenius equation. The result shows that the thermostability of Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} is superior than that of commercial phosphor Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Ce{sup 3+}. The outstanding luminescent properties indicate that Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Dy{sup 3+} could be a potential white light emission phosphor.

  10. New Measurements of the Astrophysically Important ^44Ti Radionuclide Through the ^40Ca(α,γ)^44Ti Reaction

    Science.gov (United States)

    Robertson, Daniel; Becker, Hans-Werner; Collon, Philippe; Goerres, Joachim; Wiescher, Michael

    2010-11-01

    The relatively short-lived radionuclide ^44Ti (t1/2=58.9 ± 0.3 yrs), is of considerable importance in the study of nucleosynthesis in explosive stellar environments. It's production predominantly through the ^40Ca(α,γ)^44Ti reaction, takes place during α-rich freeze-out, in the inner most layers of a core-collapse supernova. A number of experimental studies have been previously performed to determine the stellar reaction rate. These studies included prompt γ-ray measurements from in-beam experiments, atom counting techniques utilizing accelerator mass spectrometry (AMS) and multi energy step measurements at the DRAGON recoil mass separator. The resulting calculated reaction rates show drastic disagreement. New results from experiments at the DTL, Bochum and NSL, Notre Dame, used both gamma spectroscopy and AMS techniques to measure the reaction, and investigate the discrepancies in both the experimental and predicted results. Final results of the experiments and their impact on the reaction rate will be discussed.

  11. PHOTOCATALYTIC ACTIVITY OF TiO2 NANO SUPPORTED ON MEMBRANE CELLULOSE ACETATE/NATA DE COCO (CA/NDC IN PHOTODEGRADATION OF METHYLENE BLUE

    Directory of Open Access Journals (Sweden)

    Roro Ernia Prawithasari

    2015-12-01

    Full Text Available Study of synthesis and effectiveness of membrane catalyst of cellulose acetate/nata de coco-TiO2 nano (CA/NDC-TiO2 nano in photodegradation of methylene blue in batch system has been investigated. TiO2nanoparticles were synthesized by hydrothermal method followed by calcination at 450oC. Scanning Electron Microscopy (SEM images indicate nano TiO2 has been successfully synthesized with average particle diameter as 88,63±4,37 nm. X-ray diffraction pattern (XRD of nano TiO2 shows some characteristic peaks of anatase TiO2 were still existed. Membrane photocatalyst of CA/NDC- nano TiO2 was prepared via phase inversion method by mixing TiO2 nanoparticles with CA casting solution. Thermogravimetric analysis shows three decomposition steps of CA/NDC-nano membrane as well as CA/NDC membrane. Photodegradation of methylene blue was conducted with nano-TiO2 particles and CA/NDC-TiO2 membrane for 50 minutes in batch system. The absorbance changes were measured by spectrophotometer at wavelength of 664.6 nm. The result shows the photodegradation rections tended to follow second order reaction. According to the rate constant value, k, the photocatalytic effectivity using CA-NDC/nano TiO2 membrane and nano TiO2photocatalysts in metilen blue photodegradation, statistically were not significantly different.

  12. Spectroscopic study of 44Ti by reactions 40Ca(α,γ)44Ti, 40Ca(7Li,p2nγ)44Ti and 42Ca(α,2nγ)44Ti

    International Nuclear Information System (INIS)

    The first reaction allowed to populate states of excitation energies between 9.2 and 9.8 MeV and to measure their γ-decays to low-lying states in 44Ti. Moreover this reaction helps in measuring the mean lifetime of 12 states by using the Doppler shift attenuation method. The second reaction was used to find the levels predicted by the shell model and among them the highest spin allowed Jsup(π)=12+. The third reaction helps in measuring the mean lifetime tau=3.0+-0.6 ns of the Jsup(π)=(12+) state at Esub(x)=8.040 MeV. In this measurement the delayed coincidence technique with a pulsed beam was used. A confrontation of the experimental and theoretical studies on the 44Ti nucleus is presented in this work

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

    Science.gov (United States)

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

    2013-04-01

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

  14. Sol–gel synthesis and photoluminescence of CaTi1–ZrO3 : Pr3+ phosphors

    Indian Academy of Sciences (India)

    Lixia Lin; Bing Yan

    2010-02-01

    CaTi1–ZrO3 : Pr3+ phosphors have been synthesized by sol–gel and solid state methods, with = 1/300, 2/300, 3/300, 4/300, 5/300, 6/300, 7/300, respectively. Powder X-ray diffraction (XRD), UV-visible absorption spectra, photoluminescent spectra (PL), and scanning electron microscopy (SEM) images are used to characterize the powder samples. The inverse absorption at 610 nm appearing in the UV-visible absorption spectra is due to the ${}^{1}D_{2} \\rightarrow {}^{3}H_{4}$ characteristic emission of Pr3+. Changes in the emission spectra at 610 nm were agreed with those in UV-visible absorption spectra. The strongest red excitation obtained from CaTi1–ZrO3 : Pr3+ ( = 4/300) and CaTi1–ZrO3 : Pr3+ ( = 5/300) possesses the strongest emission at 610 nm, similar to the intensities of Ca(Ti1–Zr)O3 : Pr3+ ( = 3/300, 4/300, 6/300), which may be corresponded to the cell parameters of CaTi1–ZrO3 : Pr3+.

  15. Natural CaO-TiO2-SiO2 based ceramics

    Directory of Open Access Journals (Sweden)

    Jelena Pantić

    2011-06-01

    Full Text Available Lešnica river deposits consist of a large number of minerals of different grain sizes including sphene. Since it is very difficult to obtain pure monophase titanite by different synthetic routes (sol-gel, coprecipitation, combustion, spray pyrolysis and hydrothermal method, the aim of this work was to study the structure of the sphene from the Lešnica river deposits and possibility of using it as a natural precursor for CaO-TiO2-SiO2 based ceramics. The sphene from Lešnica was analyzed by different methods: tristimulus colorimetry, infrared spectroscopy, electron microprobe and X-ray single crystal diffraction. It was confirmed that Al, Fe, Mn and P are present in the sphene structure and proposed that corresponding structural formula could be: (Ca2+1.008 Mn2+0.0021.010(Ti4+0.901 Fe3+0.033 Al3+0.060 P5+0.0010.995 Si4+1.024 O2-5.

  16. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

    Science.gov (United States)

    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

  17. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect.

    Science.gov (United States)

    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

  18. A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

    Science.gov (United States)

    Naveed-Ul-Haq, M.; Shvartsman, Vladimir V.; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C.

    2016-08-01

    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.

  19. Sodium scandium diphosphate, NaScP2O7, isotypic with α-NaTi(III)P2O7

    OpenAIRE

    Zdirad Žák; Jan Cempírek; Radek Škoda

    2009-01-01

    Crystals of the title compound, NaScP2O7, were grown by a flux method. The crystal structure is isotypic with those of α-NaTiP2O7, NaYbP2O7 and NaLuP2O7, and is closely related to that of NaYP2O7. The structural set-up consists of a three-dimensional framework of P2O7 units that are corner-shared by ScO6 octahedra, forming tunnels running parallel to [010]. The Na atoms are situated in the tunnels and are surrounded by nine O atoms in a distorted environment.

  20. Improved photoluminescence of green-emitting phosphor Ca_3Sc_2Si_3O_(12):Ce~(3+) for white light emitting diodes

    Institute of Scientific and Technical Information of China (English)

    刘元红; 庄卫东; 胡运生; 高文贵

    2010-01-01

    Ca3Sc2Si3O12:Ce3+ phosphors with single-phase were successfully synthesized by a gel-combustion method.Annealing atmosphere greatly affected the luminescent properties of the phosphor.The intensity of absorption band at 450 nm was greatly increased with a reducing atmosphere,which was very suitable as a color converter in white LED.The absorption at 243 and 311 nm was gradually enhanced with a stronger reducing atmosphere and a new absorption peak at 362 nm appeared in N2+H2 mixing gas.The emission intensit...

  1. Partial conductivities in perovskites CaZr1- x Sc x O3-α ( x = 0.03-0.20) in an oxidation atmosphere

    Science.gov (United States)

    Gorelov, V. P.; Balakireva, V. B.; Kuz'min, A. V.

    2016-01-01

    Partial (ionic, proton, and hole) conductivities of oxides CaZr1- x Sc x O3-α( x = 0.03-0.20) with the perovskite structure in air atmosphere have been studied as functions of temperature in the range of 600-900°C and partial water-vapor pressure in the range of {P_{{H_2}O}}= 40-2500 Pa. The influence of the humidity of the atmosphere on the relative change in the concentration of oxygen vacancies as a function of temperature has been estimated.

  2. Ab-initio Study of Structural Phase Transitions, Electronic and Optical Properties of the Double Perovskite A2ScSbO6 (A=Sr,Ca)

    OpenAIRE

    Ray, Rajyavardhan; Himanshu, A. K.; Bandyopadhyay, S K; Sen, Pintu; Kumar, Uday; Sinha, T. P.

    2013-01-01

    First principles study of the electronic structures and optical properties of recently synthesized double perovskite $A_2ScSbO_6$ $(A=Sr, Ca)$ have been performed within the framework of density functional theory using WIEN2k. With increasing temperature, the $Sr$ compound has three phase transitions at ${\\rm 400K}$, ${\\rm 550K}$ and ${\\rm 650K}$ approximately, leading to the following sequence of phases: $P21/n \\rightarrow I2/m \\rightarrow I4/m \\rightarrow Fm\\bar{3}m$. Starting from the mono...

  3. Study of the synthesis of TiO2 layers on macroporous ceramic supports in supercritical (SC) CO2 for processing radioactive aqueous effluents in dynamic mode

    International Nuclear Information System (INIS)

    Public and military nuclear industry generates a significant amount of radioactive liquid waste which must be treated before being released into the environment. Decontamination methods alternative to the industrial techniques (evaporation, chemical treatment) are being developed, such as column treatments or coupled filtration/sorption processes. Current researches mainly focus on the development and shaping of specific sorbents. In this context, the objectives of this thesis were first to study the synthesis of TiO2 layers on macroporous ceramic supports in supercritical (SC) CO2 and then to evaluate their potential for radionuclide extraction in these alternative processes. A robust synthesis method has been developed, based on the thermal decomposition of titanium isopropoxide in SC CO2 in the temperature range between 150 C and 350 C. Nano-structured TiO2 films were formed on the macroporous supports (ceramic foams, tubular α-alumina supports) with good adhesion, already at 150 C. The effect of the synthesis temperature on sorbents physico-chemical characteristics and sorption properties has been studied with TiO2 powders prepared under the same conditions as the supported films. The best sorption performance were observed for the powder prepared at 150 C, owing to its higher density of surface sites in comparison with powders prepared at either 250 C or 350 C. Consequently, this synthesis temperature (150 C) was selected for a detailed study of the composite sorbents (TiO2/support), in order to assess their sorption performance in continuous treatment processes. The sorption experiments have shown that a column of alumina macroporous foam (Φpore = 400μm) coated with TiO2 was suitable for processing effluents in dynamic mode with high throughputs. Both macro-pore sizes and column height were revealed as important parameters to be controlled. For the coupled filtration/sorption treatment, TiO2 membranes exhibit good mechanical strength and are able to

  4. Non-stoichiometry of Li2TiO3 under hydrogen atmosphere condition

    International Nuclear Information System (INIS)

    Li2TiO3 is one of the most promising candidates for solid breeder materials. In order to control the grain growth at the time of high temperature use, the development of Li2TiO3 which has oxide additive is needed. In the present paper, the structure and the non-stoichiometry of Li2TiO3 added with some different oxides have been extensively investigated by means of thermogravimetry and X-ray diffractometry (XRD). In the case of the Li2TiO3 samples used in this study, Li2TiO3 powder and oxide powder (CaO, ZrO2, Sc2O3) in small quantity were mixed in the following molecular ratio: CaO/Li2TiO3 = 0.20%, ZrO2/Li2TiO3 = 0.44% or Sc2O3/Li2TiO3 0.40%. These samples are designated as Ca-Li2TiO3, Zr-Li2TiO3, and Sc-Li2TiO3, respectively. Ca-Li2TiO3 and Zr-Li2TiO3 exist as double phases, and Sc-Li2TiO3 exists as a single phase. In thermogravimetry, Ca-Li2TiO3 has fewer oxygen defects than the other kinds of Li2TiO3 in the hydrogen atmosphere. The overall results suggest that the oxide additives are able to control not only the growth of the grain size but also the amount of oxygen defects

  5. Density functional theory study of Mo-doped M@(BN)48 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) clusters

    Science.gov (United States)

    Liang, Wenjuan; Jia, Jianfeng; Lv, Jin; Wu, Haishun

    2016-03-01

    The structure and magnetic properties of Mo-doped M@(BN)48 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) clusters were calculated at BPW91/LanL2DZ level. The magnetic nature of the clusters M@(BN)48 significantly changed when doping with Mo atom, except for Co@(BN)48. Only the magnetic moment for the CrMo@(BN)48 cluster was decreased to zero. Thus, M@(BN)48 clusters can be selected as the model system to detect Mo atom by the change of the magnetic moment.

  6. First-Principles Calculations of Structural, Electronic and Optical Properties of CaTiO3 Crystal

    Science.gov (United States)

    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.

  7. Influence of titanium precursor on photoluminescent emission of micro-cube-shaped CaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mazzo, Tatiana Martelli, E-mail: tatimazzo@gmail.com [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Avenida Almameda Saldanha da Gama, 89, Ponta da Praia, CEP 11030-400 Santos, SP (Brazil); Santilli do Nascimento Libanori, Gabriela [Departamento de Ciências do Mar, Universidade Federal de São Paulo, Avenida Almameda Saldanha da Gama, 89, Ponta da Praia, CEP 11030-400 Santos, SP (Brazil); Moreira, Mario Lucio [Instituto de Física e Matemática, Universidade Federal de Pelotas, P.O. Box 354, Campus do Capão do Leão, 96001-970 Pelotas, RS (Brazil); Avansi Jr, Waldir [Departamento de Física, Universidade Federal de São Carlos, Jardim Guanabara, 13565-905 São Carlos, SP (Brazil); Mastelaro, Valmor Roberto [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, Arnold Schimidt, 13566-590 São Carlos, SP (Brazil); Varela, José Arana; Longo, Elson [INCTMN/LIEC, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, R. Francisco Degni, 55, Bairro Quitandinha, 14801-907 Araraquara, SP (Brazil)

    2015-09-15

    For this research, we studied the influence of titanium tetrachloride (TC) and titanium tetraisopropoxide (TTP) precursors on CaTiO{sub 3} (CTO) synthesis by employing a microwave-assisted hydrothermal (MAH) method regarding their respective short-, medium- and long-range features to determine if the use of different titanium precursors enhances the structural evolution of the material. The growth mechanism for the formation of the micro-cube-shaped CTO is proposed to obtain nanoparticle aggregation of self-assembly nanoplates. The disorder coupled to the oxygen vacancies of [TiO{sub 5}]–[TiO{sub 6}] in complex clusters in the CTO 1 powder and twists in bonding between the [TiO{sub 6}]–[TiO{sub 6}] complex clusters in the CTO 2 powder were mainly responsible for photoluminescent (PL) emission. - Highlights: • Different titanium precursors enhance the structural evolution of the material. • [TiO{sub 5}]–[TiO{sub 6}] and twists in bonding [TiO{sub 6}]–[TiO{sub 6}] were responsible for PL emission. • Micro-cube shaped was formed by nanoparticle aggregation of self-assembly nanoplates.

  8. Preparation of TiFe based alloys melted by CaO crucible and its hydrogen storage properties

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chong-he, E-mail: chli@staff.shu.edu.cn [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Shanghai Special Casting Engineering Technology Research Center, Shanghai 201605 (China); He, Jin; Zhang, Zhao; Yang, Bo; Leng, Hai-yan [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Lu, Xiong-gang, E-mail: luxg@staff.shu.edu.cn [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Shanghai Special Casting Engineering Technology Research Center, Shanghai 201605 (China); Li, Zhi-lin; Wu, Zhu [Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Wang, Hong-bin [Shanghai Key Laboratory of Modern Metallurgy and Materials Processing, Shanghai University, Shanghai 200072 (China); Shanghai Special Casting Engineering Technology Research Center, Shanghai 201605 (China)

    2015-01-05

    Highlights: • The home-made CaO crucible was used to prepare the TiFe based alloys. • The compositions as well as the content of oxygen can be effectively controlled. • The microstructure of the alloy melted by CaO crucible is dendrite. • The samples performed a good hydrogen storage performance. • The CaO crucible may be the promising candidate for melting the TiFe based alloys. - Abstract: The carbon contamination of alloys prepared by the electro graphite crucible is impossible to avoid due to the inherit reaction between the melt and the crucible. In this study, the TiFe-based alloy is prepared by VIM process using CaO crucible as well as the electro graphite crucible. The samples are examined by means of Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive Spectrometer (EDS), and the PCT curves are also measured. It is resulted that, the oxygen content of alloys melted by CaO crucible is almost equal to the one melted by graphite crucible and without the carbon contamination, meanwhile the carbon content of alloys obtained by the electro graphite crucible is 1860 ppm, which exceeds the tolerance of the commercial alloy (1000 ppm). The microstructure of the alloy melted by CaO crucible is dendrite, while it is composed of the equiaxed crystal with the lamellar structure and the spherical TiC particles distributed along grain boundaries or within the grain when melted by the graphite crucible; the interfacial reaction of the electro graphite crucible with TiFe alloy melt is serious and the interaction layer is formed up to 200 μm in thickness, the carbon in TiFe-based alloys forms TiC. The hydrogen desorption plateau pressure of alloys melted by CaO crucible is (0.11–0.4) × 10{sup 5} Pa, and that by the graphite crucible is (0.6–1) × 10{sup 5} Pa. This may imply that the CaO crucible may be the promising candidate for melting the high performance TiFe based hydrogen storage alloys.

  9. Solid state synthesis and structural refinement of polycrystalline LaCa1-TiO3 ceramic powder

    Indian Academy of Sciences (India)

    O P Shrivastava; Narendra Kumar; I B Sharma

    2004-04-01

    Perovskite structure based ceramic precursors have a characteristic property of substitution in the ``A" site of the ABO3 structure. This makes them a potential material for nuclear waste management in synthetic rock (SYNROC) technology. In order to simulate the mechanism of rare earth fixation in perovskite, La Ca1-TiO3 (where = 0.05) has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and La as starting materials. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The ceramic phase has been characterized by its powder diffraction pattern. Step analysis data has been used to determine the structure of solid solution of lanthanum substituted calcium titanate. The SEM and EDAX analyses also confirm that the CaTiO3 can act as a host for lanthanum. X-ray data has been interpreted using CRYSFIRE and POWDERCELL softwares. The ℎ, , values for different lattice planes have been generated from the experimental data. The lanthanum substituted perovskite crystallizes in orthorhombic symmetry with space group (#62). Following unit cell parameters have been calculated: = 5.410, = 7.631, = 5.382. The calculated and observed values of corresponding intensities, 2, and density show good agreement. GSAS based calculation for bond distances Ti–O, Ca–O, La–O and bond angles Ti–O–Ca, Ca–O–Ca, La–O–Ti have been reported.

  10. Fluorescence properties of novel near-infrared phosphor CaSc{sub 2}O{sub 4}:Ce{sup 3+}, Nd{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Meng, J.X., E-mail: tmjx@jnu.edu.c [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Zhang, F.J.; Peng, W.F.; Wan, W.J.; Xiao, Q.L.; Chen, Q.Q.; Cao, L.W. [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Wang, Z.L. [School of Chemistry and Biotechnology, Yunnan Nationalities University, Kunming 650031 (China)

    2010-10-15

    Research highlights: Novel near-infrared (NIR) phosphor, CaSc{sub 2}O{sub 4}:Ce{sup 3+}, Nd{sup 3+}, was synthesized. The phosphor gives strong Nd{sup 3+} characteristic NIR emissions in the range of 880-930 nm. The NIR emission intensity gets a 200 times enhancement benefited from the efficient energy transfer from a co-doped Ce{sup 3+}. The energy transfer mechanism was also briefly based on detailed investigation on spectrum and fluorescence lifetime. - Abstract: Novel near-infrared (NIR) phosphor, CaSc{sub 2}O{sub 4}:Ce{sup 3+}, Nd{sup 3+}, was synthesized by co-precipitation method followed by firing at 1300 {sup o}C in reduced atmosphere. When irradiated with blue light, the phosphor gives strong Nd{sup 3+} characteristic NIR emissions in the range of 880-930 nm. The NIR emission intensity gets a 200 times enhancement by co-doping of Ce{sup 3+}. Detailed investigation on spectrum and fluorescence lifetimes indicated the NIR luminescence enhancement is obtained from an energy transfer process. The process initiates with efficient absorption of blue light by Ce{sup 3+} ions via an allowed 4f-5d transition, follow by efficient energy transfer from Ce{sup 3+} to Nd{sup 3+}, and emitting strong Nd{sup 3+} characteristic fluorescence.

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

    Science.gov (United States)

    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.

  12. Microwave dielectric properties of layered Mg0.93Ca0.07TiO3-(Ca0.3Li0.14Sm0.42)TiO3 ceramics

    International Nuclear Information System (INIS)

    Microwave dielectric properties of the layered functionally graded materials (FGMs) ceramics with Mg0.93Ca0.07TiO3 (MCT) and (Ca0.3Li0.14Sm0.42)TiO3 (CLST) were investigated as a function of sintering times at 1350 deg. C. The stable and uniform interfaces of the FGMs specimens were confirmed by X-ray diffraction and SEM photographs study. As a sintering time increased, Qf values of the FGMs specimens were decreased, whereas dielectric constants of the specimens did not changed remarkably. The change of Qf values could be attributed to the compositional inhomogeneity at the interfacial region resulted from the active ionic diffusion. From the EPMA work, active diffusion of Mg2+ (r=0.72 Angst) and Ti4+ (r=0.605 Angst) was detected in the interface of FGMs specimens with an increase of sintering time

  13. Anomalous current-voltage behavior of CaCu3Ti4O12 ceramics

    International Nuclear Information System (INIS)

    This letter reports on an investigation of dc current-voltage measured in CaCu3Ti4O12 ceramics. The experimental results show unusual I-V behaviors associated with the electrically inhomogeneous nature of the grains (mixture of semiconducting and insulating regions) and dependence on delay time. The data strongly suggest that both the localization of current in the conductive region and local Joule self-heating effects are essential elements to explain the abrupt drop in the electric field. In addition, the hysteresis behavior recorded during the I-V measurements shows strong dependence on delay time, i.e., the time needed for the polarization phenomena to occur

  14. Microwave synthesis and sintering characteristics of CaCu3Ti4O12

    Indian Academy of Sciences (India)

    P Thomas; L N Sathapathy; K Dwarakanath; K B R Varma

    2007-12-01

    CaCu3Ti4O12 (CCTO) was synthesized and sintered by microwave processing at 2.45 GHz, 1.1 kW. The optimum calcination temperature using microwave heating was determined to be 950°C for 20 min to obtain cubic CCTO powders. The microwave processed powders were sintered to 94% density at 1000°C/60 min. The microstructural studies carried out on these ceramics revealed the grain size to be in the range 1–7 m. The dielectric constants for the microwave sintered (1000°C/60 min) ceramics were found to vary from 11000–7700 in the 100 Hz–100 kHz frequency range. Interestingly the dielectric loss had lower values than those sintered by conventional sintering routes and decreases with increase in frequency.

  15. Chemical solution deposition of CaCu3Ti4O12 thin film

    Indian Academy of Sciences (India)

    Viswanathan S Saji; Han Cheol Choe

    2010-06-01

    CaCu3Ti4O12 (CCTO) thin film was successfully deposited on boron doped silica substrate by chemical solution deposition and rapid thermal processing. The phase and microstructure of the deposited films were studied as a function of sintering temperature, employing X-ray diffractometry and scanning electron microscopy. Dielectric properties of the films were measured at room temperature using impedance spectroscopy. Polycrystalline pure phase CCTO thin films with (220) preferential orientation was obtained at a sintering temperature of 750°C. There was a bimodal size distribution of grains. The dielectric constant and loss factor at 1 kHz obtained for a film sintered at 750°C was ∼ 2000 and tan ∼ 0.05.

  16. Investigations of the effect of nonmagnetic Ca substitution for magnetic Dy on spin-freezing in Dy2Ti2O7

    Science.gov (United States)

    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.

  17. Inelastic neutron scattering and lattice dynamics of NaNbO3 and Sr0.70Ca0.30TiO3

    Indian Academy of Sciences (India)

    S K Mishra; R Mittal; N Choudhury; S L Chaplot; D Pandey

    2008-11-01

    NaNbO3 and (Sr,Ca)TiO3 exhibit an unusual complex sequence of temperature- and pressure-driven structural phase transitions. We have carried out lattice dynamical studies to understand the phonon modes responsible for these phase transitions. Inelastic neutron scattering measurements using powder samples were carried out at the Dhruva reactor, which provide the phonon density of states. Lattice dynamical models have been developed for SrTiO3 and CaTiO3 which have been fruitfully employed to study the phonon spectra and vibrational properties of the solid solution (Sr,Ca)TiO3.

  18. High tunability of the soft mode in strained SrTiO{sub 3}/DyScO{sub 3} multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kadlec, C; Kadlec, F; Nemec, H; Kuzel, P [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Schubert, J; Panaitov, G [Institute of Bio and Nanosystems, Research Center Juelich, D-52425 Juelich (Germany)], E-mail: kuzelp@fzu.cz

    2009-03-18

    SrTiO{sub 3}/DyScO{sub 3} epitaxial multilayers with variable number and thickness (10-100 nm) of bilayers deposited on DyScO{sub 3} substrates were investigated by means of time-domain terahertz spectroscopy at room temperature. A tensile strain develops in the SrTiO{sub 3} films and shifts the eigenfrequency of the ferroelectric soft mode down by {approx}25-45 cm{sup -1} with respect to the value found for single crystals. In all films the soft mode strongly hardens upon the electrical bias and a linear coupling to a silent excitation of relaxation type at 10 cm{sup -1} is observed. We show that the change in the THz and sub-THz response of the layers with an increasing field is determined solely by the soft mode eigenfrequency and we propose a phenomenological model describing the origin of the tunability and the peculiar properties of the ferroelectric soft mode in the terahertz spectral range.

  19. Improvement in antibacterial properties of Ti by electrodeposition of biomimetic Ca-P apatite coat on anodized titania

    Energy Technology Data Exchange (ETDEWEB)

    Gad El-Rab, Sanaa M.F. [Biotechnology Department, Faculty of Science, Taif University, Taif (Saudi Arabia); Botany Department, Faculty of Science, Asuit University, Asuit (Egypt); Fadl-allah, Sahar A., E-mail: Sahar.fadlallah@yahoo.com [Materials and Corrosion Lab (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Chemistry Department, Faculty of Science, Cairo University, Cairo (Egypt); Montser, A.A. [Materials and Corrosion Lab (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Chemistry Department, Faculty of Science, South-Valley University (Egypt)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Ca-P coating on titania titanium surface was directly fabricated successfully by electrochemical deposition. Black-Right-Pointing-Pointer Treatment the titanium surface by TiO{sub 2} could improve the adhesion strength between the Ca-P coating and the surface. Black-Right-Pointing-Pointer Anodization treatment in phosphoric acid is benefit to inhibit the oral bacteria. Black-Right-Pointing-Pointer According to the electrochemical corrosion test, corrosion resistance of Ti was improved by both anodization and electrodeposition of the Ca-P/titania coating. Black-Right-Pointing-Pointer Ca-P/titania sample is believed to be a functional biomaterial which combines antibacterial activity and good corrosion resistance in bioenvironment. - Abstract: Titanium metal (Ti) with antibacterial function was successfully developed in the present study by electrodeposition of biomimetic Ca-P coat in simple supersaturated calcium and phosphate solution (SCPS). The electrochemical behavior and corrosion resistance of Ca-P deposited on anodized titanium (AT) have been investigated in SCPS by using electrochemical impedance spectroscopy (EIS). The plate-counting method was used to evaluate the antibacterial performance against Staphylococcus aureus (ATCC6538). In vitro antibacterial activity study indicated a significantly reduced number of bacteria S. aureus on Ca-P/AT plate surface when compared with that on Ti or AT surfaces and the corresponding antibacterial mechanism is discussed. The morphology and chemical structure of different titanium samples were systematically investigated by scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX). The study confirmed that the antibacterial properties of the samples were related to chemical composition of sample surface.

  20. 1 Hz linewidth Ti:sapphire laser as local oscillator for 40Ca+ optical clocks

    Science.gov (United States)

    Bian, Wu; Huang, Yao; Guan, Hua; Liu, Peiliang; Ma, Longsheng; Gao, Kelin

    2016-06-01

    A Ti:sapphire laser at 729 nm is frequency stabilized to an ultra-stable ultra-low thermal expansion coefficient (ULE) cavity by means of Pound-Drever-Hall method. An acousto-optic modulator is used as the fast frequency feedback component. 1 Hz linewidth and 2 × 10-15 frequency stability at 1-100 s are characterized by optical beating with a separated Fabry-Perot cavity stabilized diode laser. Compared to the universal method that the error signal feedback to inject current of a diode laser, this scheme is demonstrated to be simple and also effective for linewidth narrowing. The temperature of zero coefficient of the thermal expansion of the ULE cavity is measured with the help of a femto-second frequency comb. And the performance of the laser is well defined by locking it to the unperturbed clock transition line-center of 4 S1/2-3 D5/2 clock transition of a single laser cooled 40Ca+ ion. A Fourier-transform limited resonance of 6 Hz (Δv/v = 1.5 × 10-14) is observed. This laser is also used as the local oscillator for the comparison experiment of two 40Ca+ ion optical clocks and improves the stability of comparison for an order of magnitude better than the previous results.

  1. 1 Hz linewidth Ti:sapphire laser as local oscillator for (40)Ca(+) optical clocks.

    Science.gov (United States)

    Bian, Wu; Huang, Yao; Guan, Hua; Liu, Peiliang; Ma, Longsheng; Gao, Kelin

    2016-06-01

    A Ti:sapphire laser at 729 nm is frequency stabilized to an ultra-stable ultra-low thermal expansion coefficient (ULE) cavity by means of Pound-Drever-Hall method. An acousto-optic modulator is used as the fast frequency feedback component. 1 Hz linewidth and 2 × 10(-15) frequency stability at 1-100 s are characterized by optical beating with a separated Fabry-Perot cavity stabilized diode laser. Compared to the universal method that the error signal feedback to inject current of a diode laser, this scheme is demonstrated to be simple and also effective for linewidth narrowing. The temperature of zero coefficient of the thermal expansion of the ULE cavity is measured with the help of a femto-second frequency comb. And the performance of the laser is well defined by locking it to the unperturbed clock transition line-center of 4 S1/2-3 D5/2 clock transition of a single laser cooled (40)Ca(+) ion. A Fourier-transform limited resonance of 6 Hz (Δv/v = 1.5 × 10(-14)) is observed. This laser is also used as the local oscillator for the comparison experiment of two (40)Ca(+) ion optical clocks and improves the stability of comparison for an order of magnitude better than the previous results.

  2. Reaction rate sensitivity of 44Ti production in massive stars and implications of a thick target yield measurement of 40Ca(alpha,gamma)44Ti

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-02-16

    We evaluate two dominant nuclear reaction rates and their uncertainties that affect {sup 44}Ti production in explosive nucleosynthesis. Experimentally we develop thick-target yields for the {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction at E{sub {alpha}} = 4.13, 4.54, and 5.36 MeV using {gamma}-ray spectroscopy. At the highest beam energy, we also performed an activation measurement which agrees with the thick target result. From the measured yields a stellar reaction rate was developed that is smaller than current statistical-model calculations and recent experimental results, which would suggest lower {sup 44}Ti production in scenarios for the {alpha}-rich freeze out. Special attention has been paid to assessing realistic uncertainties of stellar reaction rates produced from a combination of experimental and theoretical cross sections. With such methods, we also develop a re-evaluation of the {sup 44}Ti({alpha},p){sup 47}V reaction rate. Using these two rates we carry out a sensitivity survey of {sup 44}Ti synthesis in eight expansions representing peak temperature and density conditions drawn from a suite of recent supernova explosion models. Our results suggest that the current uncertainty in these two reaction rates could lead to as large an uncertainty in {sup 44}Ti synthesis as that produced by different treatments of stellar physics.

  3. Study of new sheep bone and Zn/Ca ratio around TiAlV screw: PIXE-RBS analysis

    International Nuclear Information System (INIS)

    This study reports on in vivo particle induced X-ray emission (PIXE) measurements combined with Rutherford backscattering spectroscopy (RBS) analyses of new remodeled sheep bone formed around TiAlV screws. The implants (screws) were anodized by a modified TiMaxTM process. The interface between the implant and the bone was carefully investigated. [Zn]/[Ca] in-depth composition profiles as well as Ca, Fe elemental maps were recorded. The thickness of new bone formed around the screw reached 300-400 μm. Osteon and Osteoid phases were identified in the new bone. A higher [Zn]/[Ca] ratio was observed in the new bone as compared to the mature bone. Blood vessels were observed in the bone in close contact with the screw. This study shows the potential of ion beam analysis for biological and biomedical characterization

  4. First Principles Study of Dopant Site Selectivity in Ordered Perovskite CaCu3Ti4O12

    Institute of Scientific and Technical Information of China (English)

    XU Li-Chun; WANG Ru-Zhi; DENG Yang; YAN Hui

    2011-01-01

    We investigate the dopant site selectivity of CaCu3Ti4O12(CCTO) using the first principles calculations. Our results show that, for four cases of possible occupancy by La atom, lattice expansions and formation enthalpies with different dopant quantities indicate that doped La cations are preferentially substituted for Ca sites in CaCu3Ti4O12, which is excellent in agreement with the experimental observation(Choi et al. Adv. Mater. 21 (2009) 885).Furthermore, more interesting information of doping is also explored by the analysis of density of states and it is found that La substituting for Cu may advance the electron conduction in CCTO. It supplies a potential solution for limitations of CCTO devices by exploring the effect when La substitutes for Cu sites in the CCTO crystal.

  5. Influence of Ti{sup 4+} on the magnetic state of CaRu{sub 1-x}Ti{sub x}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Zorkovska, A. [Centre of Low Temperature Physics of the Faculty of Science UPJS and Institute of Experimental Physics SAS, 04154 Kosice (Slovakia)]. E-mail: anna.zorkovska@upjs.sk; Baran, A. [Centre of Low Temperature Physics of the Faculty of Science UPJS and Institute of Experimental Physics SAS, 04154 Kosice (Slovakia); Bradaric, I. [' Vinca' Institute of Nuclear Sciences, 11001 Belgrade (Serbia and Montenegro); Savic, I. [Faculty of Physics, University of Belgrade, 11000 Belgrade (Serbia and Montenegro); Sebek, J. [Institute of Physics AS CR, 18221 Prague (Czech Republic); Santava, E. [Institute of Physics AS CR, 18221 Prague (Czech Republic); Svoboda, P. [Faculty of Mathematics and Physics, Charles University, DES, 12116 Prague (Czech Republic); Marincev, D. [Department of Physics, Military Academy, 11000 Belgrade (Serbia and Montenegro); Kohout, S. [Physik Inst. der Universitaet Zuerich, CH 80-57 Zurich (Switzerland); Keller, H. [Physik Inst. der Universitaet Zuerich, CH 80-57 Zurich (Switzerland); Feher, A. [Centre of Low Temperature Physics of the Faculty of Science UPJS and Institute of Experimental Physics SAS, 04154 Kosice (Slovakia)

    2007-09-15

    In order to shed more light on the character of magnetic correlations at low temperatures in CaRuO{sub 3}, the delicate effect of substituting nonmagnetic Ti{sup 4+} for Ru{sup 4+} in low concentrations (0.5-15%) has been investigated by magnetization, AC-susceptibility and specific heat measurements. Despite the clear features in magnetic measurement data at 34K no specific heat anomaly has been observed, nevertheless, two temperature regions with different magnetic characters have been identified. In pure CaRuO{sub 3} significant low-temperature upturn of C/T is visible below 15K. This feature is suppressed by Ti substitution.

  6. Linking large piezoelectric coefficients to highly flexible polarization of lead free BaTiO3-CaTiO3-BaZrO3 ceramics

    Science.gov (United States)

    Benabdallah, F.; Simon, A.; Khemakhem, H.; Elissalde, C.; Maglione, M.

    2011-06-01

    We report a large d31 piezoelectric coefficient and corresponding electromechanical coupling factor, Kp, of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCTZ50) and 0.68Ba(Zr0.2Ti0.8)O3-0.32(Ba0.7Ca0.3)TiO3 (BCTZ32) lead-free piezoceramics. The piezoelectric coefficient, d31, reaches a high value of 200 pC/N for BCTZ50 at room temperature which is comparable to the one of the soft PZT. This confirms the previously reported d33 for the same material. A useful way to achieve such performances at the expense of a smaller thermal budget is suggested, enabling better control of the ceramics composition and microstructure. Based on pyroelectric and ferroelectric hysteresis loops measurements, we show that such outstanding properties are likely due to the high flexibility of polarization under thermal and electric stresses.

  7. Crystal field analysis of the absorption spectra and electron phonon interaction in Ca3Sc2Ge3O12:Ni2+

    Science.gov (United States)

    Brik, M. G.

    2006-04-01

    Exchange charge model of crystal field [B.Z. Malkin, in: A.A. Kaplyanskii, B.M. Macfarlane (Eds.), Spectroscopy of Solids Containing Rare-earth Ions, North-Holland, Amsterdam, 1987, pp. 33 50.] was used to analyze the energy level schemes of Ni2+ ion at both possible positions (octahedral and tetrahedral) in Ca3Sc2Ge3O12. The crystal field parameters were calculated from the crystal structure data; the crystal field Hamiltonian was diagonalised in the complete basis consisting of 25 wave functions of all LS terms of the Ni2+ ion. Results of calculations are in a good agreement with experimental data. From the experimental spectra available in the literature, the Huang Rhys parameter S=3.5 and effective phonon energy ℏω=200cm were evaluated for the octahedral Ni2+ ion.

  8. Investigation of various reactions for the direct synthesis of TiCr2 intermetallic compound from the TiO2–Cr2O3–Ca system

    International Nuclear Information System (INIS)

    Highlights: ► A new processing route was applied for the synthesis of TiCr2 intermetallic powder directly by the Calciothermic co-reduction of TiO2–Cr2O3 oxides. ► Various reactions in the TiO2–Cr2O3–Ca system are investigated. ► According to EDS analyses the formation of TiCr2 compound is a mutual diffusion process that needs time for its formation. ► After activation the obtained intermetallic powder showed capability for hydrogen storage. - Abstract: A new processing route was applied for the synthesis of TiCr2 intermetallic powder directly by the Calciothermic co-reduction of TiO2–Cr2O3 oxides. Differential thermal analysis (DTA) and X-ray diffraction (XRD) were used to determine the various reactions. According to DTA results heating the mixture up to about 675 °C resulted in an endothermic peak. This endothermic peak indicates the formation of a solid solution formation by the reaction of TiO2 with Cr2O3. As the temperature increased to about 950 °C the Ca started to melt (at approximately 847 °C) resulting to an exothermic peak due to the reaction of Ca with Cr2O3 forming Cr metal. The formation of CaTiO3 formed by the reaction of CaO with TiO2 decreased the amount of TiO2 in the mixture of starting materials. When the mixture was heated up to 1058 °C, Ca reacted with TiO2 forming Ti as indicated by an exothermic reaction forming Ti. Finally, when the holding time at 1200 °C and the amount of Ca were increased, the TiCr2 intermetallic was formed while the CaTiO3 compound was gradually disintegrated into CaO and Ti and the amount of oxygen content in samples was decreased. The obtained intermetallic powder showed the capability of hydrogen storage after being activated.

  9. Judd–Ofelt and energy-transfer analysis of Er{sup 3+} doped in CaSc{sub 2}O{sub 4} ceramic samples

    Energy Technology Data Exchange (ETDEWEB)

    Georgescu, Şerban [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Ştefan, Angela [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); University of Bucharest, Faculty of Physics, 405 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Toma, Octavian, E-mail: octavian.toma@inflpr.ro [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania)

    2015-11-15

    A Judd–Ofelt analysis of Er{sup 3+} in CaSc{sub 2}O{sub 4} ceramic samples is performed. The Judd–Ofelt parameters are found (Ω{sub 2}=3.88×10{sup −20} cm{sup 2}, Ω{sub 4}=1.83×10{sup −20} cm{sup 2}, Ω{sub 6}=0.83×10{sup −20} cm{sup 2}) and the radiative lifetimes of Er{sup 3+} energy levels and the branching ratios of Er{sup 3+} transitions are calculated. The luminescence lifetimes of metastable energy levels are obtained experimentally and the quantum efficiencies of these levels are calculated. The luminescence kinetics of the thermalized levels ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) at various Er{sup 3+} concentrations is used to characterize the cross-relaxation processes that influence these green-emitting levels. The decays of these levels are well described by the Inokuti–Hirayama model for dipole–dipole interaction. The C{sub DA} microparameter was found to be 6.7×10{sup −39} cm{sup 6} s{sup −1}. - Highlights: • Judd–Ofelt analysis is performed on light-scattering ceramic Er:CaSc{sub 2}O{sub 4}. • Quantum efficiencies of ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) and {sup 4}I{sub 11/2} levels of Er{sup 3+} are estimated. • Energy-transfer microparameter for cross-relaxation of ({sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}) is obtained.

  10. Effects of Ti-Based Additives on the Hydrogen Storage Properties of a LiBH4/CaH2 Destabilized System

    Directory of Open Access Journals (Sweden)

    Hongwei Yang

    2010-01-01

    Full Text Available The hydrogen storage properties of a destabilized LiBH4/CaH2 system ball-milled with TiCl3, TiF3, and TiO2 additives have been investigated. It is found that the system with TiCl3 additive has a lower dehydrogenation temperature than the ones with other additives. Further study shows that a higher amount of TiCl3 is more effective in reducing the desorption temperature of the LiBH4/CaH2 system, since it leads to a lower activation energy of dehydrogenation. The activations energies for mixtures containing 4, 10, and 25 mol% of TiCl3 are 141, 126, and 110 kJ/mol, respectively. However, the benefits of higher amounts of TiCl3 are offset by a larger reduction in hydrogen capacity of the mixtures.

  11. Fe-moment instability in Ti{sub 1-x}Sc{sub x}Fe{sub 2} Laves-phase compounds

    Energy Technology Data Exchange (ETDEWEB)

    Ouladdiaf, B. [Institut Laue-Langevin, BP 156, 38042 GRENOBLE Cedex 09 (France); Deportes, J. [Lab. Louis Neel, CNRS, BP 166, 38042 GRENOBLE Cedex 09 (France); Saoudi, M. [Centre Universitaire de Guelma, GUELMA 24 000 (Algeria)

    2002-07-01

    The magnetic properties of the pseudo-binary Laves-phase compounds Ti{sub 1-x}Sc{sub x}Fe{sub 2} were investigated by means of magnetisation and high-resolution powder neutron diffraction techniques. For x<0.2 a transition from an antiferromagnetic state to a canted one with a ferromagnetic component in the basal plane is observed, while for 0.2

  12. Large Electric-Field Modulation of Magnetic Properties in Fe Films on BiScO3-PbTiO3 Ceramics

    Directory of Open Access Journals (Sweden)

    Jing Wang

    2010-01-01

    Full Text Available Based on the magneto-optical Kerr effect, we report the electric-field modulation of the magnetic properties in Fe/BiScO3-PbTiO3 (BSPT film-on-ceramic substrate structure. The Fe films are directly grown on the fully-poled BSPT ceramic substrates by magnetron sputtering. An electric field applied parallel to the prepolarization direction of the piezoelectric BSPT can induce a reversible increase in the coercive field Hc of about 30%, whereas an electric field antiparallel to the prepolarization direction can cause a persistent, tremendous decrease (as large as 97% in Hc, and a small reversal electric field can resume it back. The strain induced by the inverse piezoelectric effect is the primary mechanism behind. This large modulation of the coercive field by the electric field could inspire further exploration of electric-field-controlled magnetic switching in multiferroic heterostructures.

  13. Synthesis and electrical characterization of Ca2Nd4Ti6O20 ceramics

    Directory of Open Access Journals (Sweden)

    Muhammad Raz

    2016-03-01

    Full Text Available Ca2Nd4Ti6O20, a layered perov skite structured material was synthesized via a chemical (citrate sol-gel route for the first time using nitrates and alkoxide precursors. Phase analysis of a sample sintered at 1625 °C revealed the formation of an orthorhombic (Pbn21 symmetry. The microstructure of the sample after sintering comprised rod-shaped grains of a size of 1.5 to 6.5µm. The room temperature dielectric constant of the sintered sample was 38 at 100 kHz. The remnant polarization (Pr and the coercive field (Ec were about 400 μC/cm2 and 8.4 kV/cm, respectively. Impedance spectroscopy revealed that the capacitance (13.7 pF and activation energy (1.39 eV of the grain boundary was greater than the capacitance (5.7 pF and activation energy (1.13 eV of the grain.

  14. Electronic stopping powers for Be, Ca and Ti in SiC

    International Nuclear Information System (INIS)

    Energy loss of ions in matter is fundamental to many applications dependent on the transport of ions in matter. In spite of a long history of studies, the electronic stopping power is not adequately described over all ranges of ions, energies and targets, particularly in the case of heavy ions or compound targets. In this study, stopping powers for Be, Ca and Ti in SiC have been determined using a time-of-flight energy elastic recoil detection analysis (ToF-E ERDA) set-up. In transmission geometry, the energy loss of heavy ions in a self-supporting SiC foil was measured over a continuous range of energies using the ToF data that was tagged by a Si detector with and without the stopping foil. By essentially calibrating the Si detector for each channel over the measured energy region based on TOF spectrometry, measurement uncertainties of less than 4% are achieved. In comparing with the experimental data, both the SRIM (stopping and range of ions in matter) code and the binary theory provide reasonable predictions

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

    Science.gov (United States)

    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.

  16. Fusion and quasifission dynamics in the reactions $^{48}$Ca+$^{249}$Bk and $^{50}$Ti+$^{249}$Bk using TDHF

    CERN Document Server

    Umar, A S; Simenel, C

    2016-01-01

    Background: Synthesis of superheavy elements (SHE) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHE have been recently produced with doubly-magic $^{48}$Ca beams. However, SHE synthesis experiments with single-magic $^{50}$Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for $Z=117,119$ superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in $^{48}$Ca,$^{50}$Ti+$^{249}$Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles. Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment. Results: Nucleu...

  17. Preparation, characterization and activity evaluation of CaZrTi{sub 2}O{sub 7} photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Chen Shifu, E-mail: chshifu@chnu.edu.cn [Department of Chemistry, Huaibei Normal University, Anhui, Huaibei 235000 (China); Ji Mingsong; Yuang Yunguang; Liu Wei [Department of Chemistry, Huaibei Normal University, Anhui, Huaibei 235000 (China)

    2012-06-15

    CaZrTi{sub 2}O{sub 7} photocatalyst sample was prepared by a polymerizable complex method. The photocatalyst was characterized by X-ray powder diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, photoluminescence emission spectroscopy, Brunauer-Emmett-Teller analysis, N{sub 2} adsorption measurements, and terephthalic acid probed fluorescence technique. The photocatalytic activity of the sample was evaluated by photocatalytic oxidation of methyl orange and photocatalytic reduction of Cr{sub 2}O{sub 7}{sup 2-} and nitrobenzene. The results showed that when the reaction solution was illuminated by UV light for 50 min, the photooxidation efficiency of methyl orange and the photoreduction efficiency of Cr{sub 2}O{sub 7}{sup 2-} were 83.1% and 87.9%, respectively. When methanol was used as the holes scavengers and the illumination time was 10 h in the photocatalytic reduction experiment of nitrobenzene, the production efficiency of aniline was 70.3%. The effect of the heat treatment conditions on the photocatalytic activity was also investigated. The optimum preparation condition for CaZrTi{sub 2}O{sub 7} sample is 800 Degree-Sign C for 12 h. The mechanisms of influence on the photocatalytic activity of the sample were also discussed with the valance band theory. - Highlights: Black-Right-Pointing-Pointer CaZrTi{sub 2}O{sub 7} photocatalyst was prepared by a polymerizable complex method. Black-Right-Pointing-Pointer The heat treatment has a significant influence on the photocatalytic activity. Black-Right-Pointing-Pointer The optimal heat treatment condition is approximately 800 Degree-Sign C for 12 h. Black-Right-Pointing-Pointer The CaZrTi{sub 2}O{sub 7} has the band bap of about 2.89 eV with particle size of about 80 nm.

  18. Influence of glass additives on the microwave dielectric properties of Ca5Nb2TiO12 ceramics

    International Nuclear Information System (INIS)

    Investigation was made to correlate the effect of composition and concentration of glass content on the sintering temperature and microwave dielectric properties of polycrystalline Ca5Nb2TiO12 ceramics. Glass systems, such as B2O3, SiO2, B2O3-SiO2, ZnO-B2O3, Al2O3-SiO2, Al2O3-B2O3-SiO2, BaO-B2O3-SiO2, MgO-B2O3-SiO2, ZnO-B2O3-SiO2, PbO-B2O3-SiO2, and 2MgO-Al2O3-5SiO2 were added to calcined Ca5Nb2TiO12 powder in different weight percentages. The structure and microstructure of the sintered ceramics were studied using powder X-ray diffraction and scanning electron microscopic methods. The specimens were characterized in the microwave frequency range (3-6 GHz). The study revealed that alumina and silica based glasses were more effective in improving the dielectric properties of Ca5Nb2TiO12 ceramics, whereas borate glasses are more suited for lowering the sintering temperature

  19. Photoluminescence properties of CaTiO{sub 3}:Eu{sup 3+} nanophosphor obtained by the polymeric precursor method

    Energy Technology Data Exchange (ETDEWEB)

    Mazzo, Tatiana Martelli, E-mail: tatimazzo@gmail.com [INCTMN, LIEC, Departamento de Química, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, SP (Brazil); Mendonça da Rocha Oliveira, Lucas [INCTMN, LIEC, Departamento de Química, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, SP (Brazil); Macario, Leilane Roberta [INCTMN, LIEC, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, 14800-900 Araraquara, SP (Brazil); Avansi, Waldir [Departamento de Física, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, SP (Brazil); Silveira André, Rafaela da; Viana Rosa, Ieda Lucia [INCTMN, LIEC, Departamento de Química, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, SP (Brazil); Varela, José Arana; Longo, Elson [INCTMN, LIEC, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, 14800-900 Araraquara, SP (Brazil)

    2014-05-01

    Europium-doped calcium titanate nanophosphors were synthesized by the polymeric precursor method (PPM) at different temperatures. X-ray absorption near edge structure (XANES) spectroscopy reveals that the introduction of Eu{sup 3+} ions into the CaTiO{sub 3} network induces to significant changes in the local order–disorder relationship around both [TiO{sub 6}] and [CaO{sub 12}] complex clusters. The X-ray diffraction (XRD) and FT-Raman reveals that the presence of the Eu{sup 3+} ions favors the structural organization at long and short ranges, which produces a faster crystallization of the CT orthorhombic phase. The increase of the annealed temperature and the Eu{sup 3+} concentration for CT:Eu{sup 3+} powders induces to a decrease in the CT:Eu{sup 3+} nanoparticle sizes. - Graphical abstract: Display Omitted - Highlights: • Eu{sup 3+} induces changes in the order–disorder around both [TiO{sub 6}] and [CaO{sub 12}] clusters. • Eu{sup 3+} favors the organization and the crystallization of the CT orthorhombic phase. • The increase of the annealed temperature induces a decrease in the nanoparticle size. • The increase of the Eu{sup 3+} concentration induces a decrease in the nanoparticle size. • Photoluminescence spectra show Eu{sup 3+} emission lines ascribed to Eu{sup 3+} transitions.

  20. Extremely large anisotropic transport caused by electronic phase separation in Ti-doped Ca3Ru2O7

    Science.gov (United States)

    Peng, Jin; Liu, J. Y.; Gu, Xiaomin; Zhou, Guotai; Wang, Wei; Hu, J.; Zhang, F. M.; Wu, X. S.

    2016-06-01

    In this paper, we reported an extremely large out-of-plane/in-plane anisotropic transport ({ρc}/{ρab} ~ 109) in double layer ruthenates. The mechanism that may be responsible for this phenomenon is also explored here. Distinct from previously well studied layered materials which show large out-of-plane/in-plane electronic anisotropy (103–106), the Ti-doped Ca3Ru2O7 single crystals not only form quasi-2D layered structure, but also show phase separation within the layers. We found that Ti doping in Ca3Ru2O7 induced electronic phase separation between the insulating phase and weak localized phase. The ratio of these two phases is very sensitive to the Ti concentration. At typical concentration, the weak localized phase may form a channel on the background of the insulating phase within the ab plane. However, the small volume of weak localized phase makes it less likely to overlap in different layers. This results in a much larger electronic anisotropy ratio than pristine compound Ca3Ru2O7. This new mechanism provides a route for further increase electronic anisotropy, which will remarkably reduce current leak and power consumption in electronic devices.

  1. New perovskite-related oxides having high dielectric constant: Ln2Ba2CaZn2Ti3O14 (Ln = La and Pr)

    Indian Academy of Sciences (India)

    Pika Jha; Ashok K Ganguli

    2003-10-01

    Two new oxides, La2Ba2CaZn2Ti3O14 and Pr2Ba2CaZn2Ti3O14, have been synthesized by the ceramic route at 1100°C. These oxides crystallize in the disordered cubic structure with an `a’ lattice parameter of 3.9728 (2) and 3.9448 (5) respectively. These oxides show high dielectric constant (70 and 57) and low loss (0.003 and 0.013 at 100 kHz) for La2Ba2CaZn2Ti)3O14 and Pr2Ba2CaZn2Ti3O14 respectively. The dielectric constant is highly stable with frequency and temperature.

  2. Interplay of the strain and microstructure in ferroelectric epitaxial CaTiO3 Films

    Science.gov (United States)

    He, Qian; Liang, Qiao; Biegalski, Michael; Borisevich, Albina

    2014-03-01

    CaTiO3 (CTO) was predicted to become ferroelectric under lattice strain. However, other factors such as oxygen octahedral tilts or microstructural details can play a role. In this work, two 20 nm CTO films were grown on LSAT and NGO by PLD. They both show ferroelectricity, with Tc near 140 K on LSAT and near 70 K on NGO, and the remnant polarization at 10K of 5 and 2 μC/cm, respectively. This is surprising given that the strain of CTO on both substrates is similar. AC-STEM shows two major differences in microstructure between two CTO films: Firstly, the first few nm of CTO on NGO show perfect epitaxial growth, and after that grains start to develop, but the c-axis of CTO remains aligned with the c-axis of NGO, suggesting the presence of 180° grain boundaries only. However for CTO/LSAT, grains begin to develop at the interface and their c-axes have two possible orientations, resulting in both 180° and 90° grain boundaries. These grain boundaries are either dislocations or ferroelastic twins. Secondly, the octahedral tilt behavior at the film/substrate interface is different: CTO/LSAT has a 5-6 unit cell transition region from the untilted LSAT to the tilted CTO, which is not the case in CTO/NGO. The connection between the microstructure, substrate strain and connections to the ferroelectric properties will be discussed in detail. Research at ORNL supported by the MSE Division, BES, U.S. DOE, and through a user project supported by ORNL's CNMS, which is also sponsored by BES, U.S. DOE.

  3. Photocatalytic reduction of CO{sub 2} with H{sub 2}O using perovskite Ca{sub x}Ti{sub y}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kwak, Byeong Sub; Kang, Misook, E-mail: mskang@ynu.ac.kr

    2015-05-15

    Highlights: • Ca{sub x}Ti{sub y}O{sub 3} was synthesized using a hydrothermal method. • The photocatalytic activity was measured by the reduction of CO{sub 2} to CH{sub 4}. • The yield of methane production was 17 μmol/g{sub cat} using Ca{sub 1.00}-Ti{sub 1.00}. - Abstract: This study is focused on the photoreduction of CO{sub 2} into CH{sub 4} using Ca{sub x}Ti{sub y}O{sub 3} perovskite nanoparticles. Ca{sub x}Ti{sub y}O{sub 3} nanoparticles were successfully synthesized by a hydrothermal method. The structure and property of Ca{sub x}Ti{sub y}O{sub 3} were characterized using XRD, UV–vis, PL, and BET techniques. The photoreduction of CO{sub 2} was performed with UV-lamp (6 W cm{sup −2}) irradiation. The gas products were analyzed in a gas chromatograph equipped with FID and TCD detectors. The methane formation rate from CO{sub 2} and H{sub 2}O was 17 μmol/g for 7 h using 0.2 g of Ca{sub 1.00}Ti{sub 1.00}O{sub 3}.

  4. Judd–Ofelt analysis of Tm{sup 3+} doped in CaSc{sub 2}O{sub 4} ceramic samples

    Energy Technology Data Exchange (ETDEWEB)

    Georgescu, Şerban [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Ştefan, Angela [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); University of Bucharest, Faculty of Physics, 405 Atomistilor Street, 077125 Măgurele-Ilfov (Romania); Voiculescu, Ana-Maria [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania); Toma, Octavian, E-mail: octavian.toma@inflpr.ro [National Institute for Laser, Plasma and Radiation Physics, 409 Atomiştilor Street, 077125 Măgurele-Ilfov (Romania)

    2015-10-15

    The Judd–Ofelt analysis is applied to light-scattering ceramic CaSc{sub 2}O{sub 4} doped with Tm{sup 3+}. The calibration of the Judd–Ofelt parameters is performed by two approaches: (i) using the known magnetic-dipole contribution to the transition intensity of {sup 3}H{sub 6}→{sup 3}H{sub 5}; (ii) using the radiative lifetime of an energy level supposed to decay mainly radiatively ({sup 1}G{sub 4} or {sup 3}F{sub 4}). The following results were obtained: Ω{sub 2}=1.55×10{sup −20} cm{sup 2}; Ω{sub 4}=1.71×10{sup −20} cm{sup 2}; Ω{sub 6}=0.98×10{sup −20} cm{sup 2}, using the first approach; Ω{sub 2}=1.70×10{sup −20} cm{sup 2}, Ω{sub 4}=1.84×10{sup −20} cm{sup 2}, Ω{sub 6}=1.13×10{sup −20} cm{sup 2} (calibration using {sup 1}G{sub 4}); Ω{sub 2}=1.57×10{sup −20} cm{sup 2}, Ω{sub 4}=1.70×10{sup −20} cm{sup 2}, Ω{sub 6}=1.04×10{sup −20} cm{sup 2} (calibration using {sup 3}F{sub 4}). The obtained Judd–Ofelt parameters are used to calculate the radiative lifetimes and quantum efficiencies of several Tm{sup 3+} levels, spontaneous emission probabilities and branching ratios of various Tm{sup 3+} transitions. A fairly good agreement was obtained between the results of these methods. - Highlights: • Judd–Ofelt (JO) analysis of ceramic Tm:CaSc{sub 2}O{sub 4} is presented. • Two calibration methods are developed for the JO parameters of Tm{sup 3+} in ceramic media. • The calibration methods yield close results. • Radiative lifetimes, branching ratios, and quantum efficiencies are obtained.

  5. Analysis of the normal optical, Michel and molecular potentials on the $^{40}$Ca($^6$Li, d)$^{44}$ Ti reaction

    Indian Academy of Sciences (India)

    MAZUMDER UTTAM K; SOMADDER ANOCK; HOQUE ENAMUL; HAQUE YASMEEN; DAS SUSANTA K; SEN GUPTA H M

    2016-06-01

    Full finite-range (FFR) distorted-wave Born approximation (DWBA) method has been applied to analyse the angular distributions of cross-sections of the $^{40}$Ca($^{6}$Li, d)$^{44}$Ti reaction at 28 MeV incident energy for the 22 transitions involving both the bound and unbound states of $^{44}$Ti byusing the normal optical, Michel and molecular potentials. The extracted spectroscopic factors for the three optical potentials are compared with those of some previous studies of zero-range (ZR) calculations of the$^{40}$Ca($^{6}$Li, d)$^{44}$Ti reaction using the normal optical potential. The $\\chi^{2}$ values of all the levels are obtained for the three optical potentials to estimate the quality of the fits. Molecular and Michel potentials have been used for the first time to analyse the four-nucleon transfer reaction and it seems that the molecular potential fits the experimental data more satisfactorily for some of the states than the normal optical and Michel potentials.

  6. Preparation and properties of CaTiO3 ∶ Zn nanoparticles based on sol-gel method%CaTiO3∶Zn纳米粉体的溶胶凝胶法制备及性能研究

    Institute of Scientific and Technical Information of China (English)

    黄万群; 张启龙; 杨辉; 申乾宏

    2012-01-01

    采用溶胶凝胶法制备了CaTiO3∶Zn纳米粉体,研究了所制粉体的微观结构及性能.结果表明,所制粉体粒径约50 nm,主晶相为CaTiO3,Zn以Zn2TiO4形式存在于晶相中.1 150℃下烧结所得CaTiO3∶Zn纳米粉体性能较优:比固相法的烧结温度降低约250℃,相对介电常数εr=155,品质因数Q·f提高至6 633 GHz.%Nano-sized CaTiO3:Zn particles were successfully synthesized through sol-gel technique. The microstructure and other properties of the prepared nano particles were investigated. The average particle size of the CaTiO3: Zn powders calculated from TEM micrograph is about 50 nm. CaTiO3 is formed as the 'major phase, and the added Zn exists as Zn2TiO4 phase. The CaTiO3:Zn ceramics can be well sintered at 1 150 ℃, about 250 ℃ lower than those of ceramics obtained by conventional solid state method. The sintered CaTiO3:Zn ceramics possess a εr of 155, and a Q '/value of 6633 GHz which is greatly improved.

  7. Research Progress of CaTiO3-LaAlO3 Microwave Dielectric Ceramics%CaTiO3-LaAlO3微波介质陶瓷的研究进展

    Institute of Scientific and Technical Information of China (English)

    王利青; 刘亚云

    2014-01-01

    从发展历程、晶体结构、制备及反应过程、介电性能等方面介绍了具有中等介电常数的CaTiO3-LaAlO3微波介质陶瓷的研究进展,讨论了目前该体系微波介质陶瓷存在的问题,并指出了以后的发展方向.

  8. Validação dos sistemas de alerta Machardy e Colpam 40® para previsão da requeima do tomateiro em Caçador, SC Validation of the warning systems MacHardy and Colpam 40® to forecast late blight in tomato from Caçador municipality, Santa Catarina state (SC) Brazil

    OpenAIRE

    Walter Ferreira Becker

    2010-01-01

    Foram validados dois sistemas de alerta na requeima do tomateiro, no município de Caçador-SC em dois ciclos de cultivo. No primeiro ciclo, os métodos de MacHardy modificado e Colpam 40®, este com valor de severidade acumulado da doença (VS) igual a 10, como alerta para a pulverização de fungicidas de contato e comparados ao sistema convencional de calendário no híbrido Carmen e na cultivar Santa Clara. Em relação ao convencional, a indicação de pulverizações pelos sistemas de alerta permitiu ...

  9. Study of the electronic structure and half-metallicity of CaMnO3/BaTiO3 superlattice

    Science.gov (United States)

    Wang, Kai; Jiang, Wei; Chen, Jun-Nan; Huang, Jian-Qi

    2016-09-01

    In this paper, the electronic structure, magnetic properties and half-metallicity of the CaMnO3/BaTiO3 superlattice are investigated by employing the first-principle calculation based on density functional theory within the GGA or GGA + U exchange-correlation functional. The CaMnO3/BaTiO3 superlattice is constructed by the cubic CaMnO3 and the tetragonal ferroelectric BaTiO3 growing alternately along (0 0 1) direction. The cubic CaMnO3 presents a robust half-metallicity and a metastable ferromagnetic phase. Its magnetic moment is an integral number of 3.000 μB per unit cell. However, the CaMnO3/BaTiO3 superlattice has a stable ferromagnetic phase, for which the magnetic moment is 12.000 μB per unit cell. It also retains the robust half-metallicity which mainly results from the strong hybridization between Mn and O atoms. The results show that the constructed CaMnO3/BaTiO3 superlattice exhibits superior magnetoelectric properties. It may provide a theoretical reference for the design and preparation of new multiferroic materials.

  10. Preparation and characterizations of Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} by complex polymerization method (CPM)

    Energy Technology Data Exchange (ETDEWEB)

    Motta, F.V. [Laboratorio Interdisciplinar de Eletroquimica e Ceramica, CMDMC, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil)], E-mail: fabiana@liec.ufscar.br; Marques, A.P.A. [Laboratorio de Analise Termica e Materiais, Departamento de Quimica, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Escote, M.T. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil); Melo, D.M.A. [Laboratorio de Analise Termica e Materiais, Departamento de Quimica, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Ferreira, A.G. [Laboratorio de Ressonancia Magnetica Nuclear, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil); Longo, E. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil); Leite, E.R. [Laboratorio Interdisciplinar de Eletroquimica e Ceramica, CMDMC, Departamento de Quimica, Universidade Federal de Sao Carlos, 13565-905 Sao Carlos, SP (Brazil); Varela, J.A. [CMDMC, LIEC, Instituto de Quimica, Universidade Estadual Paulista, 14801-907 Araraquara, SP (Brazil)

    2008-10-06

    Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} (BCT) was prepared by the complex polymerization method (CPM) using Ba{sub 0.8}Ca{sub 0.2}CO{sub 3} and [Ti[OCH(CH{sub 3}){sub 2}]{sub 4} as starting materials. The powders were crystallized at several temperatures from 400 to 1200 deg. C using different times (from 1 to 8 h). The phase evolution and the physical properties were characterized by X-ray diffraction, Raman and IR spectroscopy. Such results indicate that the precursor Ba{sub 0.8}Ca{sub 0.2}CO{sub 3} used in the synthesis of Ba{sub 0.8}Ca{sub 0.2}TiO{sub 3} promotes an effective complexation of the ions Ca{sup 2+} in the matrix of BaTiO{sub 3}. After heat treatment for 2 h at 600 deg. C the phase BCT was obtained with absence of the CaTiO{sub 3} or BaCO{sub 3} phases. The CPM is an efficient method in the synthesis of the BCT, using small reaction time and low temperature and cost for the preparation of these powders.

  11. Field induced domain switching as the origin of anomalous lattice strain along non-polar direction in rhombohedral BiScO{sub 3}-PbTiO{sub 3} close to the morphotropic phase boundary

    Energy Technology Data Exchange (ETDEWEB)

    Lalitha, K. V.; Ranjan, Rajeev, E-mail: rajeev@materials.iisc.ernt.in [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Fancher, Chris M.; Jones, Jacob L. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2015-08-03

    The lattice strain and domain switching behavior of xBiScO{sub 3}–(1-x)PbTiO{sub 3} (x = 0.40) was investigated as a function of cyclic field and grain orientation by in situ X-ray diffraction during application of electric fields. The electric field induced 200 lattice strain was measured to be five times larger than the 111 lattice strain in pseudorhombohedral xBiScO{sub 3}–(1-x)PbTiO{sub 3} (x = 0.40). It is shown that the anomalous 200 lattice strain is not an intrinsic phenomenon, but arises primarily due to stress associated with the reorientation of the 111 domains in dense polycrystalline ceramic.

  12. Polyimide/nanosized CaCu3Ti4O12 functional hybrid films with high dielectric permittivity

    Science.gov (United States)

    Yang, Yang; Zhu, Ben-Peng; Lu, Zhi-Hong; Wang, Zi-Yu; Fei, Chun-Long; Yin, Di; Xiong, Rui; Shi, Jing; Chi, Qing-Guo; Lei, Qing-Quan

    2013-01-01

    This work reports the high dielectric permittivity of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanoparticles. The dielectric behavior has been investigated over a frequency of 100 Hz-1 MHz. High dielectric permittivity (ɛ = 171) and low dielectric loss (tan δ = 0.45) at 100 Hz have been observed near the percolation threshold. The experimental results fit well with the Percolation theory. We suggest that the high dielectric permittivity originates from the large interface area and the remarkable Maxwell-Wagner-Sillars effect at percolation in which nomadic charge carriers are blocked at internal interfaces between CCTO nanoparticles and the polyimide matrix.

  13. Magnetic phase separation in double layer ruthenates Ca3(Ru1−x Ti x )2O7

    OpenAIRE

    Jin Peng; Liu, J. Y.; J. Hu; Mao, Z. Q.; F. M. Zhang; Wu, X S

    2016-01-01

    A phase transition from metallic AFM-b antiferromagnetic state to Mott insulating G-type antiferromagnetic (G-AFM) state was found in Ca3(Ru1−x Ti x )2O7 at about x = 0.03 in our previous work. In the present, we focused on the study of the magnetic transition near the critical composition through detailed magnetization measurements. There is no intermediate magnetic phases between the AFM-b and G-AFM states, which is in contrasted to manganites where a similar magnetic phase transition takes...

  14. Efficient Solar Energy Conversion Using CaCu3Ti4O12 Photoanode for Photocatalysis and Photoelectrocatalysis

    OpenAIRE

    H. S. Kushwaha; Niyaz A Madhar; B. Ilahi; Thomas, P; Aditi Halder; Rahul Vaish

    2016-01-01

    A highly efficient third generation catalyst, CaCu3Ti4O12 (CCTO) shows excellent photoelectrochemical (PEC) and photocatalytic ability. As only 4% part of the solar spectrum covers UV light, thus it is highly desirable to develop visible light active photocatalyst materials like CCTO for effective solar energy conversion. A direct band transition with a narrow band gap (1.5 eV) was observed. Under light irradiation, high photocurrent density was found to be 0.96 mA/cm2, indicating the visible...

  15. Large change in dielectric constant of CaCu3Ti4O12 under violet laser

    Science.gov (United States)

    Masingboon, C.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-03-01

    This work reports the influence of light illumination on the dielectric constant of CaCu3Ti4O12 (CCTO) polycrystals which exhibit giant dielectric constant. When the CCTO samples were exposed to 405-nm laser light, the enhancement in capacitance as high as 22% was observed for the first time, suggesting application of light-sensitive capacitance devices. To understand this change better microscopically, we also performed electronic-structure measurements using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. All these measurements suggest that this large change is driven by oxygen vacancy induced by the irradiation.

  16. Anomalous change in dielectric constant of CaCu3Ti4O12 under violet-to-ultraviolet irradiation

    Science.gov (United States)

    Masingboon, C.; Eknapakul, T.; Suwanwong, S.; Buaphet, P.; Nakajima, H.; Mo, S.-K.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-05-01

    The influence of light illumination on the dielectric constant of CaCu3Ti4O12 (CCTO) polycrystals is studied in this work. When exposed to 405-nm laser light, a reversible enhancement in the room temperature capacitance as high as 22% was observed, suggesting application of light-sensitive capacitance devices. To uncover the microscopic mechanisms mediating this change, we performed electronic structure measurements, using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. Together, these results suggest that the large capacitance enhancement is driven by oxygen vacancies induced by the irradiation.

  17. Tuning of Photoluminescence by Cation Nanosegregation in the (CaMg) x (NaSc) 1–x Si 2 O 6 Solid Solution

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Zhiguo; Liu, Guokui; Wen, Jianguo; Mei, Zhigang; Balasubramanian, Mahalingam; Molokeev, Maxim S.; Peng, Licong; Gu, Lin; Miller, Dean J.; Liu, Quanlin; Poeppelmeier, Kenneth R.

    2016-02-03

    Controlled photoluminescence tuning is important for the optimization and modification of phosphor materials. Herein we report an isostructural solid solution of (CaMg)x(NaSc)1-xSi2O6 (0 < x < 1) in which cation nanosegregation leads to the presence of two dilute Eu2+ centers. The distinct nanodomains of isostructural (CaMg)Si2O6 and (NaSc)Si2O6 contain a proportional number of Eu2+ ions with unique, independent spectroscopic signatures. Density functional theory calculations provided a theoretical understanding of the nanosegregation and indicated that the homogeneous solid solution is energetically unstable. It is shown that nanosegregation allows predictive control of color rendering and therefore provides a new method of phosphor development.

  18. Ab-initio study of the magnetism, structure and spin dependent electronic states of Ti substituted MO (M = Mg, Ca, Sr)

    Energy Technology Data Exchange (ETDEWEB)

    Jaiganesh, G., E-mail: jaiganesh@igcar.gov.in; Jaya, S. Mathi [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam - 603102 (India)

    2015-06-24

    The magnetism, structure and spin polarized electronic structure of Ti substituted MO (M = Mg, Ca, Sr) are studied using the ab-initio techniques within the framework of the density functional theory. Appropriately constructed supercell along with the full structural optimization of these cells is used for studying the influence of Ti substitution on the magnetism and electronic structure of these compounds. We find from our calculations that the Ti substituted MO compounds energetically favor magnetically ordered state. The Ti concentration is found to be important in deciding the magnetic order and we have observed antiferromagnetic order for the Ti concentration of 0.25. The Ti substituted MO compounds are thus an interesting class of materials that deserve further studies.

  19. N = 3 - 3 Transitions of Ne-like Ions in the Iron Group, Especially Ca(10+) and Ti(12+)

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Y; Encarnacion, J L; Trabert, E

    2008-10-09

    The Ti XIII 2s{sup 2}2p{sup 5}3l-3l{prime} and 2s2p{sup 6}3l-3l{prime} transitions that have been discussed previously on the basis of beam-foil spectra and laser-produced plasmas in comparison to semi-empirically scaled computations have now been treated by accurate ab initio Multi-reference Moller-Plesset calculations. While most 2s{sup 2}2p{sup 5}3l-3l{prime} line identifications are supported by the new calculations, the 2s2p{sup 6}3l-3l{prime} transition arrays are revised. Theoretical level positions are given for all elements from Ca through Fe. The quality of the calculation is demonstrated on the beam-foil spectra of Ca.

  20. Luminescence and energy transfer in Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Ce{sup 3+},Mn{sup 2+} white LED phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yongfu [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Zhang, Xia; Hao, Zhendong; Luo, Yongshi [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Wang, Xiaojun [Department of Physics, Georgia Southern University, Statesboro, GA 30460 (United States); Ma, Li, E-mail: lma@georgiasouthern.edu [Department of Physics, Georgia Southern University, Statesboro, GA 30460 (United States); Zhang, Jiahua, E-mail: zhangjh@ciomp.ac.cn [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2013-01-15

    Expanded emission spectra ranging from green to red are reported in Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12} (CSS):Ce{sup 3+},Mn{sup 2+} silicate garnets. Mn{sup 2+} may occupy Ca{sup 2+} site (Mn{sup 2+}(I)) to generate a yellow emission band at 574 nm or Sc{sup 3+} site (Mn{sup 2+}(II)) with red emission band at 680 nm. Efficient energy transfers from the green emitting Ce{sup 3+} to both Mn{sup 2+}(I) and Mn{sup 2+}(II) occur upon blue excitation into Ce{sup 3+}. Concentration dependence of Mn{sup 2+} emission is analyzed based on Ce{sup 3+}-Mn{sup 2+} energy transfer, steady state rate equations, and fluorescence lifetimes. Energy transfer efficiency ({eta}{sub T}) and rate (W) are calculated with values as high as 45% and 14.01 Multiplication-Sign 10{sup 6} s{sup -1}, respectively. - Highlights: Black-Right-Pointing-Pointer Mn{sup 2+} can occupy Ca{sup 2+} site to generate a yellow emission band at 574 nm in Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12} (CSS). Black-Right-Pointing-Pointer Mn{sup 2+} can also occupy Sc{sup 3+} site to generate a red emission band at 680 nm in CSS. Black-Right-Pointing-Pointer Remarkable energy transfers (ETs) from Ce{sup 3+} to Mn{sup 2+} occur upon blue excitation into Ce{sup 3+} in CSS. Black-Right-Pointing-Pointer Full color emissions are obtained based on Ce{sup 3+}-Mn{sup 2+} ETs in CSS:Ce{sup 3+},Mn{sup 2+}.

  1. First measurement of the nonlinear coefficient for Gd1-xLux Ca4O(BO3)3 and Gd1-xScxCa4O(BO3)3 crystals

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Mortensen, Jesper Liltorp; Germershausen, Sven;

    2007-01-01

    The effective nonlinear coefficient and temperature acceptance bandwidth of three Lu and Sc co-doped GdCa4O(B03)3 type nonlinear crystals were measured. NCPM for SHG in to the blue-UV spectral region can be obtained by controlling the co-dopant concentration. Measurements were based on intra-cavi...

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

    Science.gov (United States)

    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.

  3. Phase evolution studies in CaZrTi2O7-RE2Ti2O7 (RE = Nd3+, Sm3+) system: Futuristic ceramic host matrices for nuclear waste immobilization

    Science.gov (United States)

    Jafar, M.; Achary, S. N.; Tyagi, A. K.

    2014-04-01

    Series of compositions with general stoichiometry as Ca1-xZr1-xRE2xTi2O7 (RE = Nd3+, Sm3+) were prepared by solid state reaction and characterized by powder x-ray diffraction technique to unravel the phase fields in the title systems. The phase fields in CaZrTi2O7-Nd2Ti2O7 and CaZrTi2O7-Sm2Ti2O7 systems differed significantly at the rareearth rich regions. The common phase fields like zirconolite-2M, zirconolite-4M, cubic perovskite are observed at the zirconolite rich regions of both systems. Depending on the structure of RE2Ti2O7 phase, the cubic pyrochlore or monoclinic RE2Ti2O7 phases are observed in the studied system. The observed phase fields in these two systems indicate ionic radius of the rare-earth ion has a dominating role in the phase relations. Further details of the phases and their homogeneity are explained in the text of the manuscript.

  4. Investigation of the Size Effect on the Giant Dielectric Constant of CaCu3Ti4O12 Ceramic

    Institute of Scientific and Technical Information of China (English)

    陈恺; 李伟; 刘云飞; 包鹏; 吕笑梅; 朱劲松

    2004-01-01

    Cubic perovskite-related ceramic CaCu3Ti4O12 has a very high dielectric constant larger than 10000 in the kilohertz frequency region. It is almost constant in the 100-600 K region. The ceramic compounds were prepared by conventional solid-state reaction at different sintering temperatures 1040 ℃(C04), 1060 ℃(C06), 1080 ℃(C08),and 1100 ℃(C10). Impedance spectroscopy on Ca Cus Ti4O12 ceramics demonstrates that they are electrically heterogeneous and consist of semi-conducting grains with insulating grain boundaries. It is shown that C06 is the most suitable one for device applications. Surface observation and analysis of the grain-boundary-grained structure were carried out by using scanning electron microscopy, which confirms that the samples have clearly different crystal grain sizes and C06 has a larger grain size of about 20 μm. Compared to the dielectric relaxation spectroscopy, the mechanical relaxation spectroscopy on C06 was performed and a mechanical loss peak was found, which was attributed to the thermally activated behaviour being immanent in the grains.

  5. Synthesis and characterization of CCTO (CaCu{sub 3}Ti{sub 4}O{sub 12})

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, T.S.M.; Silva, M.A.S. da; Simao, S.H.C.; Silva, C.C.; Sombra, A.S.B., E-mail: supersainara@yahoo.com.br [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil); Sales, J.C. [Universidade Estadual Vale do Acarau (UVA), Sobral, CE (Brazil)

    2011-07-01

    The objective of this work is to study the ceramic material CCTO (CaCu{sub 3}Ti{sub 4}O{sub 12}) by X-Ray Diffraction. The CCTO is a material with a giant dielectric constant at room temperature and good temperature stability over a wide temperature and frequency ranges. The preparation method has a great influence on the structure and dielectric properties of this material. The CCTO was prepared by solid state method in a planetary high energy ball milling (Fritsch Pulverisette 5). Stoichiometric quantities of CaCO{sub 3} (Aldrich 99%), TiO{sub 2} (Merck 99%) and CuO (Analar 98%) were dry milled during 30h with a rotational speed of 370 rpm and then calcined at 1050 deg C for 12h. After, the CCTO was studied by X-ray diffraction (XRD). The refinement showed that the CCTO was formed with 100% mass, the graph of Williamson-Hall showed a homogeneous sample, with a contraction in the crystal lattice and a reasonably small particle size. (author)

  6. Improved structure stability, optical and magnetic properties of Ca and Ti co-substituted BiFeO3 nanoparticles

    Science.gov (United States)

    Kumar, Vijay; Singh, Satyendra

    2016-11-01

    We report the optical and magnetic properties of single-crystalline Ca and Ti co-substituted bismuth ferrite, Bi1-xCaxFe1-xTixO3, nanoparticles, synthesized by a facile sol-gel methodology in the compositional range wherein 0 ≤ x ≤ 0.25. X-ray diffraction (XRD) and transmission electron microscopy (TEM) investigations show that all samples possess a rhombohedrally distorted perovskite structure with space group R3c. Ca and Ti co-substitution controls the formation of secondary phases and improved the stability of perovskite phase of BiFeO3. The average particle size was estimated by Williamson Hall plot, confirmed by TEM, and found to be about 59, 50, 46, 41, 40 and 38 nm of Bi1-xCaxFe1-xTixO3 for x = 0, 0.05, 0.10, 0.15, 0.20 and 0.25, respectively. The UV-vis absorption study reveal the strong absorption of visible light with a small optical band gap (1.77-2.25 eV) for 0 ≤ x ≤ 0.25 indicates a possibility of utilizing for photocatalytic activities. The magnetic study at room-temperature displays the improved magnetization and coercive field in Bi1-xCaxFe1-xTixO3 nanoparticles due to the release of the latent magnetization locked within the toroidal spin structure of BiFeO3.

  7. Spin Dependent Hopping in Ti Doped La0.67Ca0.33MnO3

    Institute of Scientific and Technical Information of China (English)

    黄宝歆; 刘宜华; 张汝贞; 原晓波; 王成建; 梅良模

    2004-01-01

    A systematic investigation of the magnetic and transport properties of Ti doped La0.67Ca0.33MnO3 was reported. The Ti substitution for Mn ions results in a reduction in ferromagnetism and conductivity. The metal-insulator transition temperature is close to Curie temperature which decreases from 274 to 82 K as x increases from 0 to 0.17. The most important effect of Ti doping is to introduce spin clusters in the samples due to the distortion of local lattice and the inhomogeneous magnetic structure induced primarily by the random distribution of Mn ions. A maximum magnetoresistance ratio as large as 90% in 1 T at 122 K was obtained for the sample with x=0.055, which is four times larger than that obtained for LCMO sample at 272 K. There is a remarkable field-history dependent MR in the cooling process for the doped samples while such phenomenon disappears in the warming run. The resistivity follows well the variable range hopping behavior in paramagnetic state. Both the size effect and spin dependent hopping of carriers between the spin clusters should be considered in this system.

  8. AC Dielectric Properties and Positron Annihilation Study on Co and Ti Substitution Effect on Ca-Sr M-Hexaferrites

    Science.gov (United States)

    Mahmoud, K. R.; Eraky, M. R.

    2016-06-01

    The dependence of AC conductivity σ AC, dielectric constant έ, and dielectric loss tangent tan δ on frequency and composition have been investigated at room temperature for polycrystalline Ca0.5Sr0.5Co x Ti x Fe12 - 2 x O19 (where 0.0 ≤ x ≤ 0.8) hexaferrites. It was found that the parameters σ AC, ɛ ', and tan δ have maximum values at x = 0.4 of the Co and Ti substitution. The behavior of σ AC, ɛ ', and tan δ with frequency and composition was explained on the basis of the hopping conduction mechanism and the Koops model. Positron annihilation lifetime spectroscopy (PALS) was used to investigate the defects and changes in electron density for hexaferrite samples. The PAL parameters ( τ 1, I 1, τ 2, I 2, and mean lifetime) show that altering the doping percentage of the Co and Ti ions affects the size and concentration of defects. The results reveal that there are some large voids in the studied samples. The obtained results indicate the high sensitivity of the PALS technique to the enhanced structure changes with changing composition of the investigated samples and correlate the results with the measured electrical parameters.

  9. Dielectric properties, impedance analysis and modulus behavior of CaTiO3 ceramic prepared by solid state reaction

    International Nuclear Information System (INIS)

    Highlights: •A single phase orthorhombic CaTiO3 structure with sub-micron grains is produced. •The frequency exponent ‘s’ is temperature dependent and explained by CBH model. •The dielectric constant and loss tangent are frequency and temperature dependent. •The modulus plot reveals the presence of thermally activated dielectric relaxation. •Cole-cole plot reveals two primary relaxation processes exist in the sample. -- Abstract: Calcium titanate (CaTiO3) with the general formula for perovskites, ABO3, is of technological importance, particularly with regard to dielectric properties. In this work, CaTiO3 ceramic material was prepared by the conventional solid state reaction method. The dielectric properties, impedance characteristics and modulus behavior of the CaTiO3 ceramic material sintered at 1240 °C were investigated in the frequency range of 10−2–106 Hz and temperature range of 100–250 °C. The XRD analysis of the sintered CaTiO3 shows that it is an orthorhombic structure with lattice parameters a = 5.4398 Å, b = 7.6417 Å, and c = 5.3830 Å. The FESEM micrograph shows a significant difference in grain size distribution ranging from 0.26 to 2.32 μm. The AC conductivity, σAC, is found to increase with increasing temperature within the frequency range of 10−2–106 Hz confirming the hopping of electrons to be the conduction mechanism. Due to the decreasing values of the frequency exponent s with increasing temperature, the results of the σAC are discussed using the correlated barrier height (CBH) model. For dielectric studies, the dielectric constant, ε′ is found to decrease with increasing frequency. In the whole temperature range of 100–250 °C, high and low frequency plateau are observed. Each converges at high frequency (>105 Hz) for all the temperatures. The frequency dependence of loss tangent, tan δ, decreases with rise in temperature, with the loss tangent peak shifting to higher frequency. Due to its dielectric

  10. Dielectric properties, impedance analysis and modulus behavior of CaTiO{sub 3} ceramic prepared by solid state reaction

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Y.J., E-mail: yjeng_86@hotmail.com [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hassan, J., E-mail: jumiah@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hashim, M., E-mail: mansor@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

    2013-09-15

    Highlights: •A single phase orthorhombic CaTiO{sub 3} structure with sub-micron grains is produced. •The frequency exponent ‘s’ is temperature dependent and explained by CBH model. •The dielectric constant and loss tangent are frequency and temperature dependent. •The modulus plot reveals the presence of thermally activated dielectric relaxation. •Cole-cole plot reveals two primary relaxation processes exist in the sample. -- Abstract: Calcium titanate (CaTiO{sub 3}) with the general formula for perovskites, ABO{sub 3}, is of technological importance, particularly with regard to dielectric properties. In this work, CaTiO{sub 3} ceramic material was prepared by the conventional solid state reaction method. The dielectric properties, impedance characteristics and modulus behavior of the CaTiO{sub 3} ceramic material sintered at 1240 °C were investigated in the frequency range of 10{sup −2}–10{sup 6} Hz and temperature range of 100–250 °C. The XRD analysis of the sintered CaTiO{sub 3} shows that it is an orthorhombic structure with lattice parameters a = 5.4398 Å, b = 7.6417 Å, and c = 5.3830 Å. The FESEM micrograph shows a significant difference in grain size distribution ranging from 0.26 to 2.32 μm. The AC conductivity, σ{sub AC}, is found to increase with increasing temperature within the frequency range of 10{sup −2}–10{sup 6} Hz confirming the hopping of electrons to be the conduction mechanism. Due to the decreasing values of the frequency exponent s with increasing temperature, the results of the σ{sub AC} are discussed using the correlated barrier height (CBH) model. For dielectric studies, the dielectric constant, ε′ is found to decrease with increasing frequency. In the whole temperature range of 100–250 °C, high and low frequency plateau are observed. Each converges at high frequency (>10{sup 5} Hz) for all the temperatures. The frequency dependence of loss tangent, tan δ, decreases with rise in temperature, with the

  11. Probing charge transfer in a novel class of luminescent perovskite-based heterostructures composed of quantum dots bound to RE-activated CaTiO3 phosphors

    Science.gov (United States)

    Lewis, Crystal S.; Liu, Haiqing; Han, Jinkyu; Wang, Lei; Yue, Shiyu; Brennan, Nicholas A.; Wong, Stanislaus S.

    2016-01-01

    We report on the synthesis and structural characterization of novel semiconducting heterostructures composed of cadmium selenide (CdSe) quantum dots (QDs) attached onto the surfaces of novel high-surface area, porous rare-earth-ion doped alkaline earth titanate micron-scale spherical motifs, i.e. both Eu-doped and Pr-doped CaTiO3, composed of constituent, component nanoparticles. These unique metal oxide perovskite building blocks were created by a multi-pronged synthetic strategy involving molten salt and hydrothermal protocols. Subsequently, optical characterization of these heterostructures indicated a clear behavioral dependence of charge transfer in these systems upon a number of parameters such as the nature of the dopant, the reaction temperature, and particle size. Specifically, 2.7 nm diameter ligand-functionalized CdSe QDs were anchored onto sub-micron sized CaTiO3-based spherical assemblies, prepared by molten salt protocols. We found that both the Pr- and Eu-doped CaTiO3 displayed pronounced PL emissions, with maximum intensities observed using optimized lanthanide concentrations of 0.2 mol% and 6 mol%, respectively. Analogous experiments were performed on Eu-doped BaTiO3 and SrTiO3 motifs, but CaTiO3 still performed as the most effective host material amongst the three perovskite systems tested. Moreover, the ligand-capped CdSe QD-doped CaTiO3 heterostructures exhibited effective charge transfer between the two individual constituent nanoscale components, an assertion corroborated by the corresponding quenching of their measured PL signals.We report on the synthesis and structural characterization of novel semiconducting heterostructures composed of cadmium selenide (CdSe) quantum dots (QDs) attached onto the surfaces of novel high-surface area, porous rare-earth-ion doped alkaline earth titanate micron-scale spherical motifs, i.e. both Eu-doped and Pr-doped CaTiO3, composed of constituent, component nanoparticles. These unique metal oxide perovskite

  12. Electrical and microstructural properties of CaTiO3-doped K1/2Na1/2NbO3-lead free ceramics

    Indian Academy of Sciences (India)

    L Ramajo; R Parra; M A Ramírez; M S Castro

    2011-10-01

    Microstructure, electrical properties and dielectric behaviour of K1/2Na1/2NbO3 (KNN) and CaTiO3- modified K1/2Na1/2NbO3 (CTO-KNN) systems, were investigated. Discs doped with 0 to 0.55% mol of CaTiO3 (CTO) were sintered at 1125°C for 2 h. Although minority phases were found in doped samples, CaTiO3 was not detected. It was also observed that CTO changed the microstructure and grain size of KNN drastically. Also, the Curie temperature and permittivity values decreased. Addition of CTO between 0.15 and 0.45 mol% decreases the density and dielectric values. Samples prepared with higher content of CTO than 0.45 mol% showed better electrical properties.

  13. Ferroelectric phase transitions studies in 0.5Ba(Zr0.2Ti0.8) O3-0.5(Ba0.7Ca0.3)TiO3 ceramics

    OpenAIRE

    J.P.B. Silva; Queirós, E. C.; Tavares, P. B.; Sekhar, K C; Kamakshi, Koppole; Moreira, J. A.; Almeida, A; Pereira, M.; Gomes, M. J. M.

    2015-01-01

    The ferroelectric phase transitions in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT 50/50) ceramics,fabricatedbyasolidstatereaction,werestudiedbyusing X-Ray diffraction, Raman spectroscopy, and measuring electric polarization, dielectric permittivity and pyroelectric current. Xraydiffraction(XRD)confirmsthecoexistenceoftetragonal(T) andrhombohedral(R)phasesatroomtemperature.Thetemperature dependence of the Raman modes frequency reveals the existenceoftwophasetransitionscorrespondingtotherhom...

  14. Ion-microprobe measurements of Mg, Ca, Ti and Fe isotopic ratios and trace element abundance in hibonite-bearing inclusions in primitive meteorites

    International Nuclear Information System (INIS)

    This thesis reports the isotopic abundances of Mg, Ca, and Ti and rare earth element (REE) abundances in 19 hibonite-bearing inclusions from primative meteorites. The isotopic ratios of Fe were measured in one of the samples, Lance HH-1. These measurements were made by means of secondary ion mass spectrometry (CAMECA IMS-3f). The novel hardware and software developments that made this work possible are described in detail. The samples were studied in thin section in order to investigate the relationship between the inclusions and their mineralogical environments. Inclusions from a number of different meteorites, specifically, Mighei, Murray, Murchison, Lance, Efremovka, Vigarano, Qingzhen, Dhajala, and Semarkona, were studied. The isotopes of Ca and Ti show large and correlated abundance anomalies in their most neutron-rich isotopes, 48Ca and 50Ti. The largest anomalies among the samples studied here are in the Murray inclusion MY-F6, with a 4.6% deficit in 48Ca and a 5.2% deficit in 50Ti, and Lance HH-1, with 3.3% and 6.0% deficits in 48Ca and 50Ti respectively. Correlated excesses of 48Ca and 50Ti, up to 2.4% and 1.4% respectively, are found in some other samples studied here. The fact that there is a correlation of isotopic anomalies in two different elements is clear evidence for a nucleosynthetic origin of these effects. Various possibilities for the origin of these isotopic anomalies are discussed and it is shown that a Cosmic Chemical Memory-like model of the incomplete mixing of dust grains from one or several supernovae is sufficient to explain the data. Magnesium isotopes show excesses of 26Mg, attributable to the in-situ decay of 26Al, in 7 of these inclusions

  15. Structure and Characteristics of Oxide Films Containing Ca and P on Ti Substrate

    Institute of Scientific and Technical Information of China (English)

    Fu LIU; Fuping WANG; Tadao Shimizu; Kaoru Igarashi; Liancheng ZHAO

    2005-01-01

    The ceramic coating was formed by using microarc oxidation (MAO) in the electrolytic solution ofβ-Glycerophosphate sodium salt pentahydrate (β-GP) and calcium acetate (CA). The microstructure, phase structure and phase composition were investigated with scanning electron microscopy (SEM), atomic force microscope (AFM), energy dispersive X-ray microanalyser (EDX), X-ray photoelectron spectroscopy (XPS), electron probe micro analyzer (EPMA) and X-ray diffraction (XRD). Investigation of the chemical composition of the coating with EDX revealed that Ca and P of high concentration existed in oxide films. XRD patterns indicated that the oxide film was composed of only anatase at low voltage discharge, and that rutile peaks appear in addition to anatase peak with increasing MAO voltage. Despite the existence of Ca and P, compounds concerning Ca and P were not detected in the oxide film.

  16. Metalloporphyrins with all the pyrrole nitrogens replaced with phosphorus atoms, MP(P)4 (M = Sc, Ti, Fe, Ni, Cu, Zn)

    International Nuclear Information System (INIS)

    Highlights: • First systematic DFT study of the MP(P)4 compounds with increasing number of d-electrons. • Complete substitution of pyrrole nitrogens by P-atoms does not change the ground spin state. • Complete substitution of pyrrole nitrogens by P-atoms results in a bowl-like shape. • Significant stabilization of the MP(P)4 LUMOs compared to the MP counterparts. • MP(P)4 HOMO/LUMO gaps are smaller than the MP HOMO/LUMO gaps. - Abstract: We performed first systematic DFT study of the structures and electronic features (frontier orbitals energies, HOMO/LUMO and optical gaps, IPs and EAs) of the MP(P)4 compounds, with increasing number of d-electrons: 3d14s2 (Sc) → 3d24s2 (Ti) → 3d64s2 (Fe) → 3d84s2 (Ni) → 3d104s1 (Cu) → 3d104s2 (Zn). We performed systematic comparison with the tetrapyrrole MP counterparts. Complete substitution of the pyrrole nitrogens by P-atoms does not change the calculated ground spin state of the compound. All the MP(P)4 species adopt a bowl-like shape, compared to generally planar or slightly distorted shapes of their MP counterparts. Significant positive charge accumulates on P-atoms in MP(P)4. Positive charges on the metals in MP(P)4 are noticeably lower than in the MP counterparts. The calculated MP(P)4 HOMO/LUMO gaps and optical gaps are noticeably smaller than the corresponding gaps in their MP counterparts, which is explained by stabilization of the MP(P)4 LUMOs

  17. Metalloporphyrins with all the pyrrole nitrogens replaced with phosphorus atoms, MP(P){sub 4} (M = Sc, Ti, Fe, Ni, Cu, Zn)

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, Aleksey E., E-mail: aleksey73kuznets@gmail.com

    2015-02-02

    Highlights: • First systematic DFT study of the MP(P){sub 4} compounds with increasing number of d-electrons. • Complete substitution of pyrrole nitrogens by P-atoms does not change the ground spin state. • Complete substitution of pyrrole nitrogens by P-atoms results in a bowl-like shape. • Significant stabilization of the MP(P){sub 4} LUMOs compared to the MP counterparts. • MP(P){sub 4} HOMO/LUMO gaps are smaller than the MP HOMO/LUMO gaps. - Abstract: We performed first systematic DFT study of the structures and electronic features (frontier orbitals energies, HOMO/LUMO and optical gaps, IPs and EAs) of the MP(P){sub 4} compounds, with increasing number of d-electrons: 3d{sup 1}4s{sup 2} (Sc) → 3d{sup 2}4s{sup 2} (Ti) → 3d{sup 6}4s{sup 2} (Fe) → 3d{sup 8}4s{sup 2} (Ni) → 3d{sup 10}4s{sup 1} (Cu) → 3d{sup 10}4s{sup 2} (Zn). We performed systematic comparison with the tetrapyrrole MP counterparts. Complete substitution of the pyrrole nitrogens by P-atoms does not change the calculated ground spin state of the compound. All the MP(P){sub 4} species adopt a bowl-like shape, compared to generally planar or slightly distorted shapes of their MP counterparts. Significant positive charge accumulates on P-atoms in MP(P){sub 4}. Positive charges on the metals in MP(P){sub 4} are noticeably lower than in the MP counterparts. The calculated MP(P){sub 4} HOMO/LUMO gaps and optical gaps are noticeably smaller than the corresponding gaps in their MP counterparts, which is explained by stabilization of the MP(P){sub 4} LUMOs.

  18. Synthesis, Characterization and Properties of Ca5A2TiO12 (A=Nb, Ta) Ceramic Dielectric Materials for Applications in Microwave Telecommunication Systems

    Science.gov (United States)

    Bijumon, Pazhoor Varghese; Mohanan, Pezholil; Sebastian, Mailadil Thomas

    2002-06-01

    Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Qu× f> 30000 GHz) and small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator applications in microwave integrated circuits.

  19. In vitro degradation, cytocompatibility and hemolysis tests of CaF2 doped TiO2-SiO2 composite coating on AZ31 alloy

    Science.gov (United States)

    Li, Bing; Chen, Yun; Huang, Wei; Yang, Wenzhong; Yin, Xiaoshuang; Liu, Ying

    2016-09-01

    In this study, a CaF2 doped TiO2-SiO2 composite coating was successfully coated onto AZ31 alloy by sol-gel method. Electrochemical tests, in vitro degradation, direct cellular experiment and hemolysis tests were conducted and the results showed that the CaF2 doped TiO2-SiO2 composite coating can not only improve the corrosion resistance, but also enhance the biocompatibility of AZ31 alloy. XRD, SEM and EDX were also performed to characterize the crystalline structures, morphologies and chemical compositions of the coatings.

  20. Influence of Compositions on the Dielectric Properties of CaBi4Ti4O15 Ceramics%组分影响CaBi4Ti4O15介电性能的研究

    Institute of Scientific and Technical Information of China (English)

    郑夏莲; 黄新友; 高春华

    2006-01-01

    采用正交设计试验法研究了配方对CaBi4Ti4O15(CBT)铁电陶瓷介电性能的影响,得到了影响CBT陶瓷介电性能的主次因素以及各因素水平影响其性能的趋势,进而得到了综合性能佳的CBT陶瓷.探讨了各组分对CBT陶瓷介电性能影响的机理,为CBT陶瓷材料的改性研究提供了依据.

  1. Photocatalytic characteristics for the nanocrystalline TiO{sub 2} on the Ag-doped CaAl{sub 2}O{sub 4}:(Eu,Nd) phosphor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jung-Sik, E-mail: jskim@uos.ac.kr; Sung, Hyun-Je; Kim, Bum-Joon

    2015-04-15

    Highlights: • The photocatalytic reactivity of the TiO{sub 2}-coated on the Ag-doped long-lasting phosphor (CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+}). • The photodecomposition of benzene gas under visible light irradiation. • The TiO{sub 2}-coated on the Ag-doped long-lasting phosphor showed much higher photocatalytic reactivity. • The light emitted from the long-lasting phosphors contributed to the photo generation of TiO{sub 2}. - Abstract: This study investigated the photocatalytic behavior of nanocrystalline TiO{sub 2} deposited on Ag-doped long-lasting phosphor (CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+}). The CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+} phosphor powders were prepared via conventional sintering using CaCO{sub 3}, Al{sub 2}O{sub 3}, Eu{sub 2}O{sub 3}, and Nd{sub 2}O{sub 3} 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 TiO{sub 2} was deposited on Ag-doped CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+} powders via low-pressure chemical vapor deposition (LPCVD). The TiO{sub 2} coated on the phosphor was actively photo-reactive under irradiation with visible light and showed much faster benzene degradation than pure TiO{sub 2}, which is almost non-reactive. The coupling of TiO{sub 2} with phosphor may result in an energy band bending in the junction region, which then induces the TiO{sub 2} crystal at the interface to be photo-reactive under irradiation with visible light. In addition, the intermetallic compound of CaTiO{sub 3} that formed at the interface between TiO{sub 2} and the CaAl{sub 2}O{sub 4}:(Eu{sup 2+},Nd{sup 3+}) 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 TiO{sub 2}/CaAl{sub 2}O{sub 4}:Eu{sup 2+},Nd{sup 3+} phosphor. TiO{sub 2} on the Ag

  2. Electromagnetic behavior of radar absorbing materials based on Ca hexaferrite modified with Co-Ti ions and doped with La

    Directory of Open Access Journals (Sweden)

    Valdirene Aparecida da Silva

    2009-06-01

    Full Text Available Radar Absorbing Materials (RAM are compounds that absorb incidental electromagnetic radiation in tuned frequencies and dissipate it as heat. Its preparation involves the adequate processing of polymeric matrices filled with compounds that act as radar absorbing centers in the microwave range. This work shows the electromagnetic evaluation of RAM based on CoTi and La doped Ca hexaferrite. Vibrating Sample Magnetization analyses show that ion substitution promoted low values for the parameters of saturation magnetization (123.65 Am2/kg and coercive field (0.07 T indicating ferrite softening. RAM samples obtained using different hexaferrite concentrations (40-80 per cent, w/w show variations in complex permeability and permittivity parameters and also in the performance of incidental radiation attenuation. Microwave attenuation values between 40 and 98 per cent were obtained.

  3. High temperature crystallographic and thermodynamic investigations on synthetic calzirtite (Ca2Zr5Ti2O16)

    International Nuclear Information System (INIS)

    Immobilization of actinides in the high level waste (HLW) produced from nuclear reactors in durable host matrix is one of the important concerns in nuclear power technology. Rock analogue (SYNROC) ceramic composites of titanates and zirconates namely zirconolite, calzirtite etc. have been proposed as alternate host matrix for disposal of long lived fission products. These minerals have ability to incorporate or immobilize a wider variety of ions simultaneously without further segregation to any other phases and are stable in geothermal conditions. Knowledge of thermodynamic stability of these minerals is important for their deployment as host matrix for actinide waste disposal. In this work crystal structure and thermodynamic parameters of a mineral analogous titanate termed as calzirtite (Ca2Zr5Ti2O16) has been determined

  4. Dielectric properties of poly(vinylidene fluoride/CaCu3Ti4O12 nanocrystal composite thick films

    Directory of Open Access Journals (Sweden)

    2010-10-01

    Full Text Available The poly(vinylidene fluoride/CaCu3Ti4O12 (CCTO nanocrystal composite films (thickness ≈85 µm with relatively high dielectric permittivity (90 at 100 Hz were prepared by the solution casting followed by spin coating technique. The structural, the microstructural and the dielectric properties of the composites were studied using X-ray diffraction, Scanning Electron Microscope, and Impedance analyzer respectively. The effective dielectric permittivity (εeff of the composite increased with increase in the volume fraction of CCTO at all the frequencies (100 Hz to 1 MHz under investigation. The room temperature dielectric permittivity which is around 90 at 100 Hz, has increased to about 290 at 125°C (100 Hz. These results may be exploited in the development of high energy density capacitors.

  5. PDMS-SiO2-TiO2-CaO hybrid materials - Cytocompatibility and nanoscale surface features.

    Science.gov (United States)

    Almeida, J Carlos; Wacha, András; Gomes, Pedro S; Fernandes, M Helena R; Fernandes, M Helena Vaz; Salvado, Isabel M Miranda

    2016-07-01

    Two PDMS-SiO2-TiO2-CaO porous hybrid materials were prepared using the same base composition, precursors, and solvents, but following two different sol-gel procedures, based on the authors' previous works where for the first time, in this hybrid system, calcium acetate was used as calcium source. The two different procedures resulted in monolithic materials with different structures, microstructures, and surface wettability. Even though both are highly hydrophobic (contact angles of 127.2° and 150.6°), and present different filling regimes due to different surface topographies, they have demonstrated to be cytocompatible when tested with human osteoblastic cells, against the accepted idea that high-hydrophobic surfaces are not suitable to cell adhesion and proliferation. At the nanoscale, the existence of hydrophilic silica domains containing calcium, where water molecules are physisorbed, is assumed to support this capability, as discussed. PMID:27127030

  6. Preparation of high dielectric constant thin films of CaCu3Ti4O12 by sol–gel

    Indian Academy of Sciences (India)

    Deepam Maurya; Devendra P Singh; D C Agrawal; Y N Mohapatra

    2008-02-01

    Preparation of sol–gel derived CaCu3Ti4O12 (CCTO) thin films using two different sols and their characterization including their dielectric response are reported. The properties of CCTO films depend heavily on solvents used to prepare the sols. Dielectric constant as high as ∼900 at 100 kHz could be obtained when acetic acid was used to prepare the sol; in contrast, use of hexanoic acid in the sol yielded films with a much lower dielectric constant. The variation in grain and grain boundary conductivities with temperature has been measured. Activation energies of 0.08 eV and 0.68 eV have been found for grain and grain boundary conduction, respectively.

  7. Low-Temperature Sintering and Electromagnetic Properties of NiCuZn/CaTiO3 Composites

    Science.gov (United States)

    Yang, Haibo; Yang, Yanyan; Lin, Ying; Zhu, Jianfeng; Wang, Fen

    2012-04-01

    Dense CaTiO3/Ni0.37Cu0.20Zn0.43Fe1.92O3.88 (CTO/NiCuZn) composites were prepared by the conventional solid-state reaction method and sintered at 950°C. The phase compositions and surface morphologies of the composites were investigated using x-ray diffraction and scanning electron microscopy, respectively. The dielectric and magnetic properties of the composites were also investigated. The results show that the CTO/NiCuZn composites possess high dielectric constants and permeabilities, which can be used in high-frequency communications for capacitor-inductor integrating devices such as electromagnetic interference filters and antennas. With increasing NiCuZn concentration, the permeabilities of the CTO/NiCuZn composites increase, while the dielectric constants and cutoff frequencies decrease.

  8. Thermoelastic properties of ScB2, TiB2, YB4 and HoB4: Experimental and theoretical studies

    DEFF Research Database (Denmark)

    Waśkowska, A.; Gerward, Leif; Staun Olsen, J.;

    2011-01-01

    modulus 180–200 GPa), while TiB2 may be classified as superhard (bulk modulus about 260 GPa). We report here first experimental and theoretical determinations of the bulk modulus for HoB4 (195(5) and 198.2 GPa, respectively), and first experimental values of the bulk modulus for ScB2 (196(2) GPa) and YB4...... (185(4) GPa). No pressure-induced phase transformations are observed in any of the above borides up to about 20 GPa. A continuous temperature-driven orthorhombic distortion is observed for HoB4 below 285 K. Values of the thermal expansion coefficient are reported for ScB2 and HoB4 at 293, 200 and 100 K...

  9. Characterization of microstructures evolution on electrical responses of CaCu3Ti4O12 ceramics

    Directory of Open Access Journals (Sweden)

    Mohd Fariz Ab Rahman

    2016-07-01

    Full Text Available CaCu3Ti4O12 (CCTO ceramics was prepared by solid state method. The raw materials of CaCO3, CuO, and TiO2 were ball milled for 1 h. The mixed powders were calcined at 900 °C for 12 h. The phase formations of calcined powders were analyzed by using X-ray Diffraction (XRD. The calcined powders were pressed into pellet shape at 300 MPa and then were sintered at 1020, 1030 and 1040 °C for 10 h, respectively. The sintered samples were subjected to XRD, Scanning Electron Microscopy (SEM and Impedance Analyzer for phase formation, microstructural and dielectric measurement analysis respectively. XRD analysis shows the presence of CCTO and secondary phases for the calcined powders. The samples sintered at 1020 and 1040 °C show the formation of CCTO phase with trace of secondary phases while complete formation of CCTO single phase was obtained for the sample sintered at 1030 °C. SEM analysis shows the phenomena of abnormal grain growth for the samples sintered at 1020 and 1040 °C while fine grain was observed for the sample sintered at 1030 °C. Sample sintered at 1040 °C was the densest sample while the sample sintered at 1020 °C had the highest percent of porosity. The highest dielectric constant (∼3748 was achieved for samples sintered at 1040 °C while the lowest dielectric loss (∼0.025 was obtained for the samples sintered at 1020 °C. These results indicate that sintering temperatures effectively changed the properties of CCTO.

  10. Structural, dielectric and electrical properties of CaBa4SmTi3Nb7O30 ferroelectric ceramic

    Indian Academy of Sciences (India)

    Prasun Ganguly; A K Jha

    2011-07-01

    The polycrystalline sample of CaBa4SmTi3Nb7O30, a member of tungsten bronze family, was prepared by solid-state reaction method. X-ray diffraction analysis shows the formation of single-phase compound with an orthorhombic structure at room temperature. Scanning electron micrograph of the material shows uniform distribution of grains. Detailed studies of dielectric properties of the compound as a function of temperature at different frequencies suggest that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 198°C, and exhibits non-relaxor kind of diffuse phase transition. The ferroelectric nature of the compound has been confirmed by recording polarization–electric field hysteresis loop. Piezoelectric and pyroelectric studies of the compound have been discussed in this paper. Electrical properties of the material have been analyzed using complex impedance technique. The Nyquist plots manifest the contribution of grain boundaries (at higher temperature), in addition to granular contribution (at all temperatures) to the overall impedance. The temperature dependence of dc conductivity suggests that the compound has negative temperature coefficient of resistance (NTCR) behaviour. The frequency dependence of ac conductivity is found to obey Jonscher’s universal power law. The observed properties have been compared with calcium free Ba5SmTi3Nb7O30 compound.

  11. Structural and Dielectric Properties of Dy-doped( Ba, Sr, Ca) TiO3 Thick Films

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Preparation and electrocatalytic activities of Pt-TiO2 nanotubes (Ba0.57Sr0.33Ca0.10)TiO3 powders, prepared by the sol-gel method, were doped MnCO3 as acceptor and Dy2O3 as donor. This powder was mixed with an organic vehicle and BSCT thick films were fabricated by the screen-printing techniques on alumina substrate. The structural and dielectric properties of BSCT thick films were investigated with variation of Dy2O3 amount. As a result of the differential thermal analysis (DTA), exothermic peak was observed at around 670℃ due to the formation of the polycrystalline perovskite phase. All the BSCT thick films showed the XRD patterns of a typical polycrystalline perovskite structure. The average grain size of BSCT thick films decreased with increasing amount of Dy2O3. The relative dielectric constant and dielectric loss of the BSCT thick film doped Dy2O3 0. 1mol% were 4637.4 and 1.6% at 1kHz, respectively.

  12. Electrical and Pyroelectric Properties of Sol-Gel Derived (Pb, Ca)TiO3 Thin Films with Various Orientations

    Institute of Scientific and Technical Information of China (English)

    唐新桂; 丁爱丽; 王丽华

    2003-01-01

    (Pb0.76Ca0.24)TiO3(PCT)thin films with various orientations were grown on Pt/Ti/SiO2/Si substrates by using a sol-gel process and by controlling the temperature of heat-treatment.The PCT thin films with(100)and random orientation showed well-saturated hysteresis loops at an applied field of 800kV/cm,with remanent polarization and coercive electric field of 23.6 μC/cm2 and 225 k V/cm,17.8 μC/cm2 and 195 k V/cm,respectively.For highly(100)-and random-oriented PCT films,the dielectric constant and dielectric loss values of these films are 121 and 0.016,121 and 0.024 at 1 kHz,respectively.The pyroelectric coefficients p of the PCT thin films are measured by a dynamic technique.At room temperature,the p values and figures of merits of the highly(100)-and random-oriented PCT films are 185μC/m2K and 1.79 × 10-5Pa-0.5,176μC/m2K and 1.39 × 10-5Pa-0.5,respectively.

  13. X-ray diffraction and Raman spectroscopic investigations on CaZrTi2O7sbnd Y2Ti2O7 system: Delineation of phase fields consisting of potential ceramic host materials

    Science.gov (United States)

    Jafar, M.; Achary, S. N.; Salke, Niliesh P.; Sahu, A. K.; Rao, Rekha; Tyagi, A. K.

    2016-07-01

    Phase evolution from CaZrTi2O7 (zirconolite) to Y2Ti2O7 (pyrochlore) have been delineated by systematic characterization of a series of sample with composition as Ca1-xZr1-xY2xTi2O7 (0.00 ≤ x ≤ 1.00) by powder XRD, Raman spectroscopy, SEM and EDS analyses. Comparative analyses of XRD and Raman spectra revealed sequential evolution of phases with increasing concentration of Y3+ in the compositions. From the XRD studies, three distinct phase fields, namely two layer (2M) and four layer (4M) zirconolite-types and cubic pyrochlore-type are observed in between zirconolite (CaZrTi2O7) and Y2Ti2O7. 4M-zirconolite phase is observed in a narrow range of composition, viz. 0.35 ≤ x ≤ 0.40 while cubic pyrochlore type phase is observed in the compositions with x ≥ 1.20. The unit cell volume of different phases shows a non-linear increasing trend with Y3+ ion concentration which has been attributed to the distribution of cations in different structure and change in their coordination number.

  14. Spectroscopic and photoluminescence characterization of Dy(3+) in Sr0.5Ca0.5TiO3 phosphor.

    Science.gov (United States)

    Vidyadharan, Viji; Sreeja, E; Jose, Saritha K; Joseph, Cyriac; Unnikrishnan, N V; Biju, P R

    2016-02-01

    The spectroscopic and photoluminescence characteristics of trivalent dysprosium (Dy(3+))-doped Sr0.5Ca0.5TiO3 phosphor materials synthesized via solid-state reaction method were studied. The X-ray diffraction profile confirmed the orthorhombic perovskite structure of the prepared samples. Judd-Ofelt analysis was carried out to obtain the intensity parameters and predicted radiative properties of Sr0.5Ca0.5TiO3:2wt%Dy(3+). The photoluminescence spectrum of Dy(3+)-doped Sr0.5Ca0.5TiO3 showed three emission peaks at 481, 574 and 638 nm corresponding to (4)F9/2 →(6)H15/2, (4)F9/2 →(6)H13/2 and (4)F9/2 →(6)H11/2 transitions respectively. The variation of luminescence intensity with different excitation wavelengths and Dy(3+) concentrations is discussed. The decay profiles of (4)F9/2 excited levels of Dy(3+) ions show bi-exponential behaviour and also a decrease in average lifetime with increase in Dy(3+) concentration. Yellow to blue luminescence intensity ratio, CIE chromaticity co-ordinates and correlated color temperature were also calculated for different concentrations of Dy(3+)-doped Sr0.5Ca0.5TiO3 phosphor at different λex. PMID:26032295

  15. Raman scattering and x-ray diffraction studies of polycrystalline CaCu3Ti4O12 under high-pressure

    DEFF Research Database (Denmark)

    Valim, D.; Filho, A. G. S.; Freire, P. T. C.;

    2004-01-01

    We report Raman scattering and x-ray diffraction studies of polycrystalline CaCu3Ti4O12 (CCTO) under high pressures. The pressure dependence of several Raman modes was investigated. No anomalies have been observed on the phonon spectra thereby indicating that the T-h (Im (3) over bar) structure r...

  16. Effects of Fuel to Synthesis of CaTiO3 by Solution Combustion Synthesis for High-Level Nuclear Waste Ceramics.

    Science.gov (United States)

    Jung, Choong-Hwan; Kim, Yeon-Ku; Han, Young-Min; Lee, Sang-Jin

    2016-02-01

    A solution combustion process for the synthesis of perovskite (CaTiO3) powders is described. Perovskite is one of the crystalline host matrics for the disposal of high-level radioactive wastes (HLW) because it immobilizes Sr and Lns elements by forming solid solutions. Solution combustion synthesis, which is a self-sustaining oxi-reduction reaction between nitrate and organic fuel, the exothermic reaction, and the heat evolved convert the precursors into their corresponding oxide products above 1100 degrees C in air. To investigate the effects of amino acid on the combustion reaction, various types of fuels were used; a glycine, amine and carboxylic ligand mixture. Sr, La and Gd-nitrate with equivalent amounts of up to 20% of CaTiO3 were mixed with Ca and Ti nitrate and amino acid. X-ray diffraction analysis, SEM and TEM were conducted to confirm the formed phases and morphologies. While powders with an uncontrolled shape are obtained through a general oxide-route process, Ca(Sr, Lns)TiO3 powders with micro-sized soft agglomerates consisting of nano-sized primary particles can be prepared using this method. PMID:27433645

  17. Effects of Fuel to Synthesis of CaTiO3 by Solution Combustion Synthesis for High-Level Nuclear Waste Ceramics.

    Science.gov (United States)

    Jung, Choong-Hwan; Kim, Yeon-Ku; Han, Young-Min; Lee, Sang-Jin

    2016-02-01

    A solution combustion process for the synthesis of perovskite (CaTiO3) powders is described. Perovskite is one of the crystalline host matrics for the disposal of high-level radioactive wastes (HLW) because it immobilizes Sr and Lns elements by forming solid solutions. Solution combustion synthesis, which is a self-sustaining oxi-reduction reaction between nitrate and organic fuel, the exothermic reaction, and the heat evolved convert the precursors into their corresponding oxide products above 1100 degrees C in air. To investigate the effects of amino acid on the combustion reaction, various types of fuels were used; a glycine, amine and carboxylic ligand mixture. Sr, La and Gd-nitrate with equivalent amounts of up to 20% of CaTiO3 were mixed with Ca and Ti nitrate and amino acid. X-ray diffraction analysis, SEM and TEM were conducted to confirm the formed phases and morphologies. While powders with an uncontrolled shape are obtained through a general oxide-route process, Ca(Sr, Lns)TiO3 powders with micro-sized soft agglomerates consisting of nano-sized primary particles can be prepared using this method.

  18. Symmetry-dependent interfacial reconstruction to compensate polar discontinuity at perovskite oxide interfaces (LaAlO3/SrTiO3 and LaAlO3/CaTiO3)

    International Nuclear Information System (INIS)

    We report the crystal symmetry-dependency of the interfacial reconstruction to relieve the polar discontinuity at the complex oxide heterointerfaces. We chose LaAlO3/SrTiO3 and LaAlO3/CaTiO3 interfaces as model systems, where the neutral TiO2 and the positive LaO+ layers form the polar discontinuity at the interface with TiO2-terminated (001) cubic SrTiO3 and orthorhombic CaTiO3. 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

  19. Synthesis of hierarchically porous structured CaCO3 and TiO2 replicas by sol-gel method using lotus root as template.

    Science.gov (United States)

    Chen, Jui-Yi; Yang, Ching-Yu; Chen, Po-Yu

    2016-10-01

    Intensive attention has been put in mimicking the morphologies in nature owing to their uniqueness, complexity, and diversity. One of the effective approaches to mimic bio-morphologies is through biotemplating - the technique of using biological structures as template to reproduce intricate structure in other forms of materials. This work presents a facile sol-gel technique that can be widely used to convert various carbon-rich bio-structures into different materials. Lotus root, a biomorphic template with high porosity at varying length scales, was selected as the example to demonstrate this approach. The experiment was conducted by infiltrating precursors - titanium (IV) n-butoxide (TnBT) and acetic acid calcium solution - into the lotus root template under vacuum system, followed by calcination. After the treatment, the replicas were calcite CaCO3 and anatase TiO2. In both CaCO3 and TiO2 replicas, the intact structure of the template was preserved. In spite of the overall similarity of the CaCO3 and TiO2 lotus root replicas, some respective differences were found. TiO2 replica was covered with nanowire bundles of 100-200nm in diameter, formed by preferable crystallization of particles, while CaCO3 replica presented the gradient-distributed pores of 10-100μm, which greatly resembled the microstructure of lotus root template. In the BET result, TiO2 replica was mesoporous structure with pores centralizing in 3-4nm. On the other hand, CaCO3 replica had pores in a wider distribution ranging from micro to macro scale. In addition, the surface area was greatly enhanced in both cases. The synthesized materials with hierarchical biomorphic structures may have great potential for purification applications due to their large specific surface area, photocatalytic property, and high adsorption rate. PMID:27287102

  20. Radiolabeling of DOTATOC with the long-lived positron emitter {sup 44}Sc

    Energy Technology Data Exchange (ETDEWEB)

    Pruszynski, Marek; Majkowska-Pilip, Agnieszka [Centre of Radiochemistry and Nuclear Chemistry, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warszawa (Poland); Loktionova, Natalia S.; Eppard, Elisabeth [Institute of Nuclear Chemistry, Johannes Gutenberg-University of Mainz, Fritz-Strassmann-Weg 2, D-55128 Mainz (Germany); Roesch, Frank, E-mail: frank.roesch@uni-mainz.de [Institute of Nuclear Chemistry, Johannes Gutenberg-University of Mainz, Fritz-Strassmann-Weg 2, D-55128 Mainz (Germany)

    2012-06-15

    The positron-emitting radionuclide {sup 44}Sc with a half-life of 3.97 h and a {beta}{sup +} branching of 94.3% is of potential interest for clinical PET. As so far it is available from a {sup 44}Ti/{sup 44}Sc generator in Mainz, where long-lived {sup 44}Ti decays to no-carrier-added (nca) {sup 44}Sc. The {sup 44}Sc is a trivalent metal cation and should be suitable for complexation with many well established bifunctional chelators conjugated to peptides or other molecular targeting vectors. Thus, the aim of this work was to investigate the potential of {sup 44}Sc for labeling of DOTA-conjugated peptides. DOTA-D-Phe{sup 1}-Tyr{sup 3}-octreotide (DOTATOC) was used as a model molecule to study and optimize labeling procedure. Reaction parameters such as buffer conditions, concentration of peptide, pH range, reaction temperature and time were optimized. Addition of 21 nmol of DOTATOC to {sup 44}Sc in ammonium acetate buffer pH 4.0 provided labeling yields >98% within 25 min of heating in an oil-bath at 95 Degree-Sign C. This time can be reduced to 3 min only by applying microwave supported heating. {sup 44}Sc-DOTATOC was found to be stable in 0.9% NaCl, PBS pH 7.4, fetal calf and human serums, and also in the presence of competing metal cations (Fe{sup 3+}, Ca{sup 2+}, Cu{sup 2+}, Mg{sup 2+}), as well as other ligand competitors, like EDTA and DTPA, even after almost 25 h incubation at 37 Degree-Sign C. Present study shows that nca {sup 44}Sc forms stable complexes with the macrocyclic ligand DOTA and that {sup 44}Sc-DOTATOC and analog targeting vectors may be synthesized for further preclinical and clinical investigations. - Highlights: Black-Right-Pointing-Pointer Labeling of somatostatin analouges with positron emitter {sup 44}Sc was tested. Black-Right-Pointing-Pointer DOTATOC was labeled with {sup 44}Sc isotope. Black-Right-Pointing-Pointer Optimal conditions for {sup 44}Sc-DOTATOC synthesis were found. Black-Right-Pointing-Pointer Stability of {sup 44}Sc

  1. Dielectric behaviour of CaCu3Ti4O12-epoxy composites

    Directory of Open Access Journals (Sweden)

    Leandro Alfredo Ramajo

    2008-03-01

    Full Text Available The dielectric behavior of composite materials (epoxy resin - barium titanate and epoxy - CCTO was analysed as a function of ceramic amount. Composites were prepared by mixing the components and pouring them into suitable moulds. In some compositions, the matrix was reduced by tetrahydrofuran (THF incorporation. Samples containing various amounts of ceramic filler were examined by TG/DTA and scanning electron microscopy analysis. Dielectric measurements were performed from 20 Hz to 1 MHz and 30 to 120 °C. It was demonstrated that the epoxy - CCTO composites possessed higher permittivity than classic epoxy - BaTiO3 composites. However, the low resin permittivity prevailed in the composite dielectric performance.

  2. The optically stimulated luminescence (OSL) properties of LiF:Mg,Ti, Li2B4O7:Cu, CaSO4:Tm, and CaF2:Mn thermoluminescent (TL) materials

    International Nuclear Information System (INIS)

    This paper reports on an investigation into the optically stimulated luminescence (OSL) properties of several known thermoluminescent materials, namely LiF:Mg,Ti, Li2B4O7:Cu, CaSO4:Tm, and CaF2:Mn. Samples were irradiated to air doses of 15 mGy, 150 mGy and 1.5 Gy and analyzed using a commercially available OSL reader system to determine their luminescence response to continuous blue and infrared light (IR) excitation, centered at 470 nm and 830 nm wavelengths, respectively. CaF2:Mn did not show an OSL response with either IR or blue light stimulation. Li2B4O7:Cu and LiF:Mg,Ti demonstrated relatively weak OSL signals only under blue light excitation. CaSO4:Tm exhibited OSL under both IR and blue light stimulation at sensitivities roughly one order of magnitude less than the OSL response of α-Al2O3:C under the same conditions. - Highlights: • Optically stimulated luminescence (OSL) properties of several known thermoluminescent materials were investigated. • CaF2:Mn did not show an OSL response with either IR or blue light stimulation. • Li2B4O7:Cu and LiF:Mg,Ti demonstrated very weak OSL signals only under blue light excitation. • CaSO4:Tm exhibited OSL under both IR and blue light stimulation. • OSL properties of CaSO4:Tm indicated an optimal OSL readout regime

  3. Hydrothermal growth of TiO2-CaP nano-films on a Ti–Nb-based alloy in concentrated calcium phosphate solutions

    International Nuclear Information System (INIS)

    The Ti–Nb-based TLM alloy (Ti–25Nb–3Zr–2Sn–3Mo) was subjected to hydrothermal treatment in the concentrated Ca3(PO4)2, CaHPO4, and Ca(H2PO4)2 solutions for the purpose of calcification. The treated samples are covered by films consisting of Ca-rich nano-crystallites (100–500 nm) and small nano-grains. XPS and XRD analyses reveal the formation of hydroxyapatite, TiO2, and Nb2O5 at the sample surface. The sample hydrothermally treated in CaHPO4 solution exhibits bioactivity by inducing the formation of apatite layer after soaking test in the simulated body fluid for 15 days. The work would provide a good bioactive surface modification method for Ti–Nb alloy implants with complex shapes and even pores

  4. A structure energy model for C2/c pyroxenes in the system Na-Mg-Ca-Mn-Fe-Al-Cr-Ti-Si-O

    International Nuclear Information System (INIS)

    The structure of C2/c pyroxenes in the Na-Mg-Ca-Fe-Al-Cr-Ti-Si-O system can be accurately simulated by the calculation of all interionic distances in the asymmetric unit, followed by a DLS treatment that optimizes cell parameters and atomic fractional coordinates. The precise structural simulation allows an accurate treatment of the static bulk lattice energy of the phase through two-body interaction potential calculations extended to all atoms within the asymmetric unit. The parametrization of the repulsive energy is achieved with the Huggins Mayer formulation that assumes the hardness factor of substances to be constant for all salts in the family and the repulsive factors of components to be variable from salt to salt. The linear relationship observed between repulsive factors of components and ionic radii of substituting ions on sites allows a rough estimate of lattice energy (hence of enthalpy, through the Born-Haber treatment) of unknown components. The structure-energy model developed for C2/c pyroxenes in the quadrilateral can be extended to the Na-Mg-Ca-Mn-Fe-Al-Cr-Ti-Si-O system when the molar abundances of minor components CaAl2SiO6, NaAlSi2O6, NaCrSi2O6, CaMnSi2O6, CaTiAl2O6 are limited to X ≤ 0.1 and the molar abundance of CaTiAl2O6 is restricted to X ≤ 0.05. The precision of the results rests on the precision of the enthalpy values selected at Tr, Pr reference conditions, as the uncertainty involved in the static lattice energy calculations is virtually negligible. Once new experimental data are available for the end-member components of interest, the model can be easily recast to obey the new limiting conditions

  5. Effect of structural transition on magnetic and optical properties of Ca and Ti co-substituted BiFeO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pawan; Kar, Manoranjan, E-mail: mano@iitp.ac.in

    2014-01-25

    Highlights: • Secondary phase formation has been controlled for Bi{sub 0.9}Ca{sub 0.1}Fe{sub 0.9}Ti{sub 0.1}O{sub 3} • Co-substitution of Ca and Ti at Bi and Fe sites significantly increases M{sub S} and H{sub C} • Compositional driven structural transition from rhombohedral to orthorhombic symmetry. • The leakage current has reduced significantly for Ca{sup 2+} and Ti{sup 4+} co-substituted BiFeO{sub 3}. • Small band gap of co-substituted BiFeO{sub 3} may be useful for optoelectronic devices. -- Abstract: Bi{sub 1−x}Ca{sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} ceramics with x = 0.0, 0.05, 0.075, 0.10, 0.125, 0.15 and 0.2 nanoparticles were prepared by the tartaric acid modified sol–gel technique. The co-substitution of Ca and Ti in certain proportion controls the formation of secondary phases. Structural phase analysis by XRD suggested that pure bismuth ferrite stabilized in rhombohedral crystal symmetry (space group R3c) and orthorhombic (Pbnm) phase fraction was observed in co-substituted samples which increase with the increase in substitution percentage. The changes in the phonon frequencies (A{sub 1}) and line widths in Raman spectra reveal the lattice distortion in co-substituted samples which are in agreement with our XRD analysis. The improved magnetization and coercive field in co-substituted samples occurs due to the suppression of cycloid spin structure which could be explained in terms of field induced spin reorientation and weak ferromagnetism. The Ti{sup 4+} substitution at Fe site in BiFeO{sub 3} significantly reduced the oxygen vacancies and hence the associated leakage current, which leads to the increase of dielectric constant as well as frequency independent region for ∊{sub r} and tan δ (maximum in Bi{sub 0.85}Ca{sub 0.15}Fe{sub 0.85}Ti{sub 0.15}O{sub 3}). The significant decrease in dielectric loss with the increase in substitution percentage leads to the decrease in the room temperature bulk conductivity and thus enhanced

  6. Alguns aspectos epidemiológicos da mancha bacteriana (Xanthomonas spp. do tomateiro na região de Caçador/SC Some epidemiological aspects of bacterial spot (Xanthomonas spp. of tomato in Caçador/SC, Brazil

    Directory of Open Access Journals (Sweden)

    Leandro Luiz Marcuzzo

    2009-06-01

    Full Text Available Objetivando explorar alguns aspectos da epidemiologia da de orvalho e um período médio de 13 horas continuas de umidade mancha bacteriana do tomateiro, incitada por Xanthomonas spp., relativa e"90%. A população bacteriana epifítica oscilou nas 10 em Caçador/SC, um ensaio a campo foi conduzido com plantas semanas após o plantio, conforme as condições climáticas, no inoculadas antes do transplantio. A cada sete dias e durante 19 entanto após o inicio dos sintomas manteve-se estável. O semanas foi monitorada a população bacteriana epifítica, as progresso da doença foi representado pelo modelo logístico y = condições climáticas e a severidade na planta. Constatou-se que o 0.99964/(1+exp(10.35989-0.69762*x e devido a pratica de inicio da epidemia teve concomitância com início da maturação apenas 1 colheita semanal, a severidade em frutos foi alta, fisiológica dos frutos do primeiro cacho, sendo que 77 dias antes atingindo 30,22% com produtividade total de117,88 ton.ha-1. Este do início da colheita não houve sintomas nas folhas. Observou-se, estudo epidemiológico servirá de um indicativo para determinação que mesmo em condição de estiagem, houve acréscimo da doença do inicio da epidemia e será usado na validação de um sistema de devido ao constante molhamento foliar decorrente da formação previsão para a mancha bacteriana do tomateiro.Aiming to explore some epidemiological aspects of bacterial spot of tomato incited by Xanthomonas spp., a field experiment was carried out in Caçador, SC. Tomato plants were inoculated with a bacterial suspension before transplanting. At seven-day intervals the bacterial population on leaf surface and disease severity were monitored during 19 weeks. Daily weather records were registered during the crop season. It was observed that epidemic onset coincided with physiological maturation of the first fruit clusters. Leaves were symptomless until 77 days before harvest. It was

  7. Solid-state reaction mechanism and microwave dielectric properties of CaTiO{sub 3}–LaAlO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Juan [Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science & Engineering, Hubei University, Wuhan 430062 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062 (China); Fang, Danhua; Lu, Chao; Dou, Zhanming; Wang, Gan; Zhang, Fan [Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science & Engineering, Hubei University, Wuhan 430062 (China); Zhang, Tianjin, E-mail: zhangtj@hubu.edu.cn [Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science & Engineering, Hubei University, Wuhan 430062 (China); Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062 (China)

    2015-07-25

    Highlights: • CaTiO{sub 3}–LaAlO{sub 3} perovskite ceramics were prepared by four sintering reaction routes. • The solid-state reaction mechanism was investigated by XRD and TG/DSC techniques. • Sintering routes had more influence on the parameters of Q × f and τ{sub f} than on ε{sub r}. - Abstract: 0.675CaTiO{sub 3}–0.325LaAlO{sub 3} perovskite ceramics were prepared by a conventional sintering process through four reaction routes. The solid-state reaction mechanisms were investigated by X-ray diffraction and thermogravimetric/differential scanning calorimetric analysis techniques. The results show that interactions occurred between mixtures of CaCO{sub 3} and TiO{sub 2} as well as La{sub 2}O{sub 3} and Al{sub 2}O{sub 3}, and they can influence the sintering behavior of the mixtures. Prior to the formation of solid solutions, the perovskite phases CaTiO{sub 3} and LaAlO{sub 3} were formed regardless of the combination of oxide powders used as reagents. From the powder mixtures which were calcined at 1200 °C, a Ca-rich Ca{sub 9}Al{sub 6}O{sub 18} phase was present at 1400 °C if free La{sub 2}O{sub 3} and Al{sub 2}O{sub 3} used in the reaction mixtures. Ca-rich phases were also formed at higher temperature (1450 °C) if LaAlO{sub 3} was present. The densities of the ceramics obtained by the four routes were different at specific sintering temperatures, and the highest density was obtained for the reaction route two. Results indicated that the preparation pathways had more influence on Q × f and temperature coefficient of the resonant frequency (τ{sub f}) than on the dielectric constants (ε{sub r}), and Q × f decreased and τ{sub f} increased rapidly when the secondary phase presented. Route four is considered as an optimal pathway for the preparation of 0.675CaTiO{sub 3}–0.325LaAlO{sub 3} ceramics.

  8. Theoretical study of phase stability and elastic properties of T0.75Y0.75B14 (T  =  Sc, Ti, V, Y, Zr, Nb, Si)

    International Nuclear Information System (INIS)

    In this study the phase stability, elastic properties, and plastic behaviour of icosahedral transition metal borides T 0.75Y0.75B14 (T  =  Sc, Ti, V, Y, Zr, Nb, Si) have been investigated using density functional theory. Phase stability critically depends on the charge transferred by T and Y to the B icosahedra. For the metal sublattice occupancy investigated here, the minimum energy of formation is identified at an effective B icosahedra charge of  −1.8  ±  0.1. This charge corridor encompasses the highest phase stability among all the reported icosahedral transition metal boride systems so far. This data provides guidance for future experimental efforts: from a wear-resistance point of view, Sc0.75Y0.75B14, Ti0.75Y0.75B14, and Zr0.75Y0.75B14 exhibit a rather unique and attractive combination of large Young’s modulus values ranging from 488 to 514 GPa with the highest phase stability for icosahedral transition metals borides reported so far. (paper)

  9. Non-stoichiometry of Li{sub 2}TiO{sub 3} under hydrogen atmosphere condition

    Energy Technology Data Exchange (ETDEWEB)

    Hoshino, Tsuyoshi [Naka Research Establishment (Oarai site), Japan Atomic Energy Research Institute, 3607, Narita-cho, Oarai-machi, Higashi ibaraki-gun, Ibaraki-ken 311-1394 (Japan)]. E-mail: hoshino@sky.biglobe.ne.jp; Tsuchiya, Kunihiko [Naka Research Establishment (Oarai site), Japan Atomic Energy Research Institute, 3607, Narita-cho, Oarai-machi, Higashi ibaraki-gun, Ibaraki-ken 311-1394 (Japan); Hayashi, Kimio [Naka Research Establishment (Oarai site), Japan Atomic Energy Research Institute, 3607, Narita-cho, Oarai-machi, Higashi ibaraki-gun, Ibaraki-ken 311-1394 (Japan); Terai, Takayuki [Nuclear Engineering Research Laboratory, School of Engineering, The University of Tokyo, 2-22 Shirakata-Shirane, Ibaraki 319-1106 (Japan); Tanaka, Satoru [Department of Quantum Engineering and Systems Science, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Takahashi, Yoichi [Department of Applied Chemistry, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2005-11-15

    Li{sub 2}TiO{sub 3} is one of the most promising candidates for solid breeder materials. In order to control the grain growth at the time of high temperature use, the development of Li{sub 2}TiO{sub 3} which has oxide additive is needed. In the present paper, the structure and the non-stoichiometry of Li{sub 2}TiO{sub 3} added with some different oxides have been extensively investigated by means of thermogravimetry and X-ray diffractometry (XRD). In the case of the Li{sub 2}TiO{sub 3} samples used in this study, Li{sub 2}TiO{sub 3} powder and oxide powder (CaO, ZrO{sub 2}, Sc{sub 2}O{sub 3}) in small quantity were mixed in the following molecular ratio: CaO/Li{sub 2}TiO{sub 3} = 0.20%, ZrO{sub 2}/Li{sub 2}TiO{sub 3} = 0.44% or Sc{sub 2}O{sub 3}/Li{sub 2}TiO{sub 3} 0.40%. These samples are designated as Ca-Li{sub 2}TiO{sub 3}, Zr-Li{sub 2}TiO{sub 3}, and Sc-Li{sub 2}TiO{sub 3}, respectively. Ca-Li{sub 2}TiO{sub 3} and Zr-Li{sub 2}TiO{sub 3} exist as double phases, and Sc-Li{sub 2}TiO{sub 3} exists as a single phase. In thermogravimetry, Ca-Li{sub 2}TiO{sub 3} has fewer oxygen defects than the other kinds of Li{sub 2}TiO{sub 3} in the hydrogen atmosphere. The overall results suggest that the oxide additives are able to control not only the growth of the grain size but also the amount of oxygen defects.

  10. Development of methods for the selective separation of Sc for use in nuclear medicine

    International Nuclear Information System (INIS)

    Full text of publication follows. Scandium radioisotopes are increasingly finding application in PET imaging or targeted therapy [Ref.1]. They can be produced in a no-carrier-added form through various charged particle reactions using Ti or Ca targets [Refs.1,2]. In order to provide Sc of sufficient quantity and quality, fast and reliable methods for its production are needed, including, depending on the production route, the quantitative recovery of the target material. Extraction chromatographic resins allow an easy adjustment of selectivity, show fast kinetics and high capacity and are thus well suited for fast and selective separations [Ref.3]. The aim of the presented project is the development of methods for the separation of Sc radionuclides from irradiated targets. The development of the methods includes the determination of k' values of Sc, Ca, Ti and other potentially interfering elements and impurities for varying Resins, notably TRU and DGA resin, acids and pH values and the influence of macro amounts of Ti and Ca on the extraction of Sc. Elution studies were performed in order to evaluate best suited rinsing/elution conditions and volumes. Based on the obtained results, methods for the separation of Sc and its purification, from irradiated targets were developed and tested on simulated Ti and Ca targets. In order to further improve the separation new extraction chromatographic resins based on the coated nano-tubes were prepared and tested. The recovery of the target materials will also be addressed. References: [1] K. L. Kolsky, V. Joshi, L. F. Mausner and S. C. Srivastava; Radiochemical Purification of No-carrier- added Scandium-47 for Radioimmunotherapy, Appl. Radiat. Isot. Vol. 49, No. 12, pp. 1541-1549, 1998; [2] Sadeghi, Mahdi; Enferadi, Milad; Aref, Morteza; Jafari, Hoda, Nuclear data for the cyclotron production of 66Ga, 86Y, 76Br, 64Cu and 43Sc in PET imaging, Nukleonika, Volume 55, Issue 3, 293-302 (2010); [3] Horwitz, E.P., McAlister, D

  11. Evaluation of the effect of the stoichiometric ratio of Ca/Cu on the electrical and microstructural properties of the CaCu3Ti4O12 polycrystalline system

    Science.gov (United States)

    Ramírez, M. A.; Bueno, P. R.; Tararam, R.; Cavalheiro, A. A.; Longo, E.; Varela, J. A.

    2009-09-01

    The structural, microstructural, non-ohmic and dielectric properties of perovskite-type CaCu3Ti4O12 (CCTO) with Ca/Cu stoichiometries of 1/3, 1/1 and 3/1 are discussed. The 1/3 Ca/Cu ratio system presents very high dielectric permittivity (~9000 at 10 kHz) and a low non-ohmic property (α = 9), whereas the 1/1 Ca/Cu ratio system shows the opposite effect, i.e. the dielectric permittivity decreases (2740 at 10 kHz) and the non-ohmic property increases (α = 42), indicating that these properties are not directly correlated. The results of this work reinforce the idea that the greatest contribution to the very high permittivity is caused by the presence of planar defects inside the CCTO grains, generating internal nanometric domains associated with stacking faults, according to the nanoscale barrier layer capacitance model proposed very recently in the literature [1]. The non-ohmic property is related to the presence and distribution of phases such as CaTiO3 (CTO) and CuO, segregated or precipitated at the grain boundary, which generate large numbers of electrically active interfaces.

  12. Consequences of embedding Ti4+ 3d0 centers in Pr0.50Ca0.50MnO3 : Phase competition in Pr0.50Ca0.50Mn1-xTixO3

    Science.gov (United States)

    García-Muñoz, J. L.; Frontera, C.; Beran, P.; Bellido, N.; Hernández-Velasco, J.; Ritter, C.

    2010-01-01

    We have studied the structural and magnetic phase coexistence/competition derived from the partial random substitution of 3d0 nonmagnetic Ti4+ ions for Mn in Pr0.50Ca0.50MnO3 , and their evolution with the doping level in Pr0.50Ca0.50Mn1-xTixO3 ( x=0 , 0.01, 0.03, and 0.05) manganites. Combining high-resolution synchrotron, neutron powder-diffraction, and muon techniques we describe with great detail the coexistence of two different structural phases below ≈240K (charge-order transition temperature, TCO ) with different cell distortion, antiferromagnetic order, and strain characteristics. The evolution of all these features with Ti substitution level is thoroughly described. Ti4+ (3d0) ions do not favor the stabilization of ferromagnetic/metallic (FM/M) islands/regions in the antiferromagnetic/insulating (AFM/I) orbital-ordered matrix. The absence of short- and long-range ferromagnetism in zero field has been confirmed by different techniques. The proportion of microdomains exhibiting pseudo-(CE)-type magnetic order (CE: charge exchange) increases with the Ti content at expenses of the CE-type regions. Differences in the stability of competing phases against magnetic field have been found by neutron-diffraction measurements under application of external fields. The phase coexistence exhibits strong anisotropic strain effects that have been thoroughly analyzed as a function of the Ti content x . We have found very remarkable changes in the strain characteristics of the AFM segregated phases on going from 1% to 5% Ti. Large anisotropic strains develop mainly in the minority phase of the material. The magnitude of strains is discussed in comparison with anisotropic strain values recently determined in the case of substitutions (such as Co) that favor FM/M domains.

  13. Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

    Science.gov (United States)

    Yang, Yang; Wang, Ziyu; Ding, Yi; Lu, Zhihong; Sun, Haoliang; Li, Ya; Wei, Jianhong; Xiong, Rui; Shi, Jing; Liu, Zhengyou; Lei, Qingquan

    2013-11-01

    This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz-1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

  14. Preparation and Characterization of Nanostructured CaCu2.90Zn0.10Ti4O12 Ceramic

    Directory of Open Access Journals (Sweden)

    Laxman Singh

    2011-12-01

    Full Text Available Nanostructure CaCu2.90Zn0.10Ti4O12 (CCZTO electronic ceramic was synthesized by semi‐wet route. The objective of this route is to enable the calcination and sintering processes to go for completion in shorter time and at lower temperature.The samples were characterized by XRD, TEM, SEM and EDX analyses. The crystallite size of the CCZTO ceramic, obtained by XRD using Debye Scherrer formula, range from 38‐74nm which is in good agreement with the particle size observed by TEM analysis. It was observed clearly that the grain size significantly increased with an increase in sintering duration. Dielectric measurements were carried out by LCR meter in the temperature range, 300‐ 500K, at few selected frequencies. It was also observed that the dielectric constant and dielectric loss of CCZTO are temperature independent in higher frequency whereas temperature dependent in low frequency region. The ceramics exhibit high dielectric constant of 1.35 x 104 at 1 kHz.

  15. Phase developments and dielectric responses of barium substituted four-layer CaBi4Ti4O15 Aurivillius

    Indian Academy of Sciences (India)

    Huiling Du; Xiang Shi; Huilu Li

    2011-10-01

    In this paper, mixed Ca–Ba oxide Ca1−BaBi4Ti4O15 (CBBT) ceramics, fabricated by the improved traditional ceramics process were investigated by doping concentrations of Ba ion up to = 0.9 (in steps of 0.1). At room temperature, an orthorhombic crystal system was confirmed using XRD, and their parameter was obtained using the Rietveld method. Dielectric properties and phase transitions were studied and are explained in terms of lattice response of these ceramics. A shift in ferroelectric–paraelectric phase transition (C) to lower temperatures and a corresponding decrease in permittivity peak with increasing concentration of Ba2+ are also observed. The ferroelectric–paraelectric phase transition of CBBT compounds is of normal type in nature, differing from the relaxor characteristic of BBT. The decrease of orthorhombicity in the lattice structure by the larger Ba2+ ion incorporation, indicating an approach of and , results in lower Curie temperature. Appearance of anomalous loss peaks of Ba-rich compounds at 530°C reveals a phase transition development trend from ferroelectric orthorhombic structure to the paraelectric orthorhombic structure. Relationship of polarization with lattice response is discussed.

  16. Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2013-11-01

    Full Text Available This work reports the excellent dielectric properties of polyimide (PI embedded with CaCu3Ti4O12 (CCTO nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz–1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67 is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

  17. Role of Relaxation on the Giant Permittivity and Electrical Properties of CaCu3Ti4O12 Ceramics

    Science.gov (United States)

    Zhao, Xuetong; Ren, Lulu; Liao, Ruijin; Li, Jianying; Yang, Lijun; Wang, Feipeng

    2016-06-01

    CaCu3Ti4O12 (CCTO) ceramics were synthesized under various sintering conditions to investigate the role of relaxation on permittivity and electrical properties. Two relaxation processes that respectively related to grain and to domain boundary at a temperature as low as 223 K were fitted according to the Cole-Cole theory. The results indicate that both relaxations largely account for the giant permittivity of CCTO ceramics. Moreover, the relaxation behaviors of grain and of the grain boundary can be processed via impedance plots that vary from 113 K to 473 K. It is shown that longer sintering duration leads to lower resistance of grain and of grain boundary: e.g., from 3200 Ω to 810 Ω and 1.76 MΩ to 0.48 MΩ, respectively. The activation energy related to grain-boundary relaxation drops from 1.14 eV to 0.80 eV, while the value of grain stays unchanged at about 0.11 eV. The Schottky barrier of the CCTO sample decreases from 0.65 eV to 0.57 eV. It is also proposed that the nonlinearity of current-voltage property for CCTO ceramics may be strongly related to the relaxation processes of grain boundaries.

  18. Effect of microwave-assisted sintering on dielectric properties of CaCu3Ti4O12 ceramic

    Science.gov (United States)

    Rani, Suman; Ahlawat, Neetu; Punia, R.; Kundu, R. S.; Ahlawat, N.

    2016-05-01

    In this present work, CaCu3Ti4O12 (CCTO) was synthesized by conventional solid-state reaction technique. The synthesis process was carried out in two phases; by conventional process (calcination and sintering at 1080°C for 10 hours) and phase II involves the micro assisted pre sintering of conventionally calcined CCTO for very short soaking time of 30 min at 1080°C in a microwave furnace followed by sintering at 1080°C for 10 hours in conventional furnace. X-ray diffraction (XRD) patterns confirmed the formation of single phase ceramic. Dielectric properties were studied over the frequency range from 50Hz -5MHz at temperatures (273K-343K). It was observed that pre- microwave sintering enhance the dielectric constant values from 10900 to 11893 and respectively reduces the dielectric loss values from 0.49 to 0.34 at room temperature(1 KHz). CCTO ceramics which are found desirable for many technological applications. The effect is more pronounced at low frequencies of applied electric field.

  19. Synthesis and microwave dielectric properties of Ca substituted SrLa4Ti4.93Zr0.07O17 ceramics

    Indian Academy of Sciences (India)

    Abdul Manan; Ibrahim Qazi

    2014-05-01

    Microwave dielectric ceramics in Sr1-CaLa4Ti4.93Zr0.07O17 (0 ≤ ≤ 0.5) composition series were processed via a solid-state sintering rout. X-ray diffraction revealed single phase ceramics. Ca substitutions for Sr tuned f towards zero with increased uo values. In the present study, r∼ 55, uo ∼ 11960 GHz and ∼ 5.2 ppm/°C were achieved for the composition with = 0.3.

  20. Raman tensor and domain structure study of single-crystal-like epitaxial films of CaCu3Ti4O12 grown by pulsed laser deposition

    Science.gov (United States)

    Ahlawat, Anju; Mishra, Dileep K.; Sathe, V. G.; Kumar, Ravi; Sharma, T. K.

    2013-01-01

    The local domain structure of a strain free, 150 nm thick, epitaxially grown single crystalline thin film of CaCu3Ti4O12 is probed by polarized Raman spectroscopy. The polarization dependence of the Raman intensities of the observed bands as a function of varying angle between the domain axes and the polarization vector of the scattered laser photon is measured. Theoretical formulations involving the Raman tensor are presented, which enable determination of the domain structure from the observed polarized Raman spectra, and a single-crystal-like domain structure is found. The Raman tensor elements and domain orientation direction were determined by fitting the observed Raman intensities with theoretical calculations and by carrying out Raman mapping of the film. Our data show an absence of twin domain structure and twin domain boundaries in the single-crystal-like epitaxial thin films of CaCu3Ti4O12.

  1. Observation of coherent phonons in Ca-doped SrTiO{sub 3}: Doping-induced ferroelectric phase transition and ultraviolet-illumination effect

    Energy Technology Data Exchange (ETDEWEB)

    Koyama, Y; Okamura, H; Kohmoto, T [Graduate School of Science, Kobe University, Kobe 657-8501 (Japan); Moriyasu, T [Graduate School of Science and Technology, Kobe University, Kobe 657-8501 (Japan); Yamada, Y [Institute for Chemical Research, Kyoto University, Kyoto 611-0011 (Japan); Tanaka, K, E-mail: kohmoto@kobe-u.ac.j [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)

    2009-02-01

    Photo-induced effect in Ca-doped SrTiO{sub 3} was investigated by observing coherent phonons. Coherent phonons of soft modes were studied by using ultrafast polarization spectroscopy. Under an ultraviolet (UV) illumination, a shift of the ferroelectric phase transition point at 28 K toward the lower temperature side was observed, and a decrease of phonon frequencies after the UV illumination was found.

  2. CaCu3Ti4O12 thin films on conductive oxide electrode: A comparative study between chemical and physical vapor deposition routes

    International Nuclear Information System (INIS)

    Highlights: ► Dielectrics growth and characterization is one of the most hot topics of materials science and microelectronics. ► CaCu3Ti4O12 perovskite, recently, demonstrated to possess peculiar dielectric properties (Science, 2001, 293, 673–676). ► To date no deep discussion on the growth processes, properties and perspective of CCTO thin films has been proposed. ► Our paper is an effective example of interdisciplinarity, since the comparison between PLD and MOCVD has been addressed. ► Great attention has been paid to CaCu3Ti4O12 film/substrate interfaces since dielectric properties are strongly affected. - Abstract: Metal Organic Chemical Vapor Deposition (MOCVD) and Pulsed Laser Deposition (PLD) techniques have been used for the growth of CaCu3Ti4O12 (CCTO) thin films on La0.9Sr1.1NiO4/LaAlO3 (LSNO/LAO) stack. (1 0 0) oriented CCTO films have been formed through both deposition routes and film complete structural and morphological characterizations have been carried out using several techniques (X-ray diffraction, scanning electron microscopy, energy-filtered transmission electron microscopy). The comparative study demonstrated some differences at the CCTO/LSNO interfaces depending on the adopted deposition technique. Chemical/structural modification of the LSNO electrode probably occurred as a function of the different oxygen partial pressure used in the PLD and MOCVD processes.

  3. Improvement in the microwave dielectric properties of SrCa4Nb4TiO17 ceramics by Ba substitution

    Indian Academy of Sciences (India)

    Abdul Manan; Yaseen Iqbal

    2014-10-01

    Microwave dielectric ceramics in the Sr1–BaCa4Nb4TiO17 (0 ≤ ≤ 0.75) composition series were fabricated via a solid-state mixed oxide route. All the compositions formed single phase in Sr1–BaCa4Nb4TiO17 (0 ≤ ≤ 0.75) solid solutions within the detection limit of in-house X-ray diffraction (XRD). The sintered microstructure of these ceramics comprised densely packed elongated and plate-like grains. The dielectric properties varied linearly with . Relative permittivity (r) increased from 47.2 to 54.5, unloaded quality factor multiplying the resonant frequency (u o) decreased from 11,984 to 9345 GHz and temperature coefficient of resonant frequency (f) increased from –78.6 to 20 ppm/°C with an increase in x from 0 to 0.75. In the present study, r ≈ 51.6, u o ≈ 10,160 GHz (5.37 GHz) and f ≈ –13.5 ppm/°C were achieved for Sr0.5Ba0.5Ca4Nb4TiO17 ( = 0.5) ceramics.

  4. Hybrid improper ferroelectricity in Ruddlesden-Popper Ca{sub 3}(Ti,Mn){sub 2}O{sub 7} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, X. Q., E-mail: xqliu@zju.edu.cn, E-mail: xmchen59@zju.edu.cn; Wu, J. W.; Shi, X. X.; Zhao, H. J.; Zhou, H. Y.; Chen, X. M., E-mail: xqliu@zju.edu.cn, E-mail: xmchen59@zju.edu.cn [Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027 (China); Qiu, R. H.; Zhang, W. Q. [Department of Physics, Shanghai University, 99 Shangda Road, Shanghai 200444 (China)

    2015-05-18

    The hybrid improper ferroelectricity (HIF) has been proposed as a promising way to create multiferroic materials with strong magnetoelectric coupling by the first-principle calculation, and the experimental evidences of HIF in Ruddlesden-Poper Ca{sub 3}(Ti{sub 1−x}Mn{sub x}){sub 2}O{sub 7} (x = 0, 0.05, 0.1, and 0.15) ceramics have been shown in the present work. The room temperature ferroelectric hysteresis loops are observed in these ceramics, and a polar orthorhombic structure with two oxygen tilting modes has been confirmed by the X-ray powder diffraction. A first-order phase transition around 1100 K in Ca{sub 3}Ti{sub 2}O{sub 7} was evidenced, and the temperatures of phase transitions decrease linearly with increasing of the contents of Mn{sup 4+} ions. Based on the result of first-principle calculations, the polarization should be reversed by switching through the mediated Amam phase in Ca{sub 3}Ti{sub 2}O{sub 7} ceramics.

  5. Study on the influence of rutile nano-TiO2 on performance of CaSO4 whisker/PP-R resin composite%金红石型纳米TiO2对CaSO4晶须/PP-R树脂复合材料性能的影响

    Institute of Scientific and Technical Information of China (English)

    邹敏; 王琪琳

    2009-01-01

    以金红石型纳米TiO2为添加剂改善了CaSO4晶须/PP-R树脂复合材料的各项性能,并研究了金红石型纳米TiO2对PP-R树脂的力学性能、耐热性能和紫外老化性能的影响.研究结果表明:由于纳米TiO2和CaSO4晶须的协同作用,添加纳米TiO2后可进一步提高CaSO4晶须/PP-R树脂复合材料的力学性能和耐热性能;金红石纳米TiO2的加入可以大幅度提高PP-R树脂的耐紫外老化性能,添加5%纳米TiO2后的CaSO4晶须/PP-R树脂复合材料经紫外辐射72 d后,其拉伸强度仅下降了0.36MPa,冲击强度仅下降了0.36kJ·m-2,熔融温度仅下降了5.4℃;而未添加纳米TiO2的CaSO4晶须/PP-R树脂复合材料的拉伸强度下降了1.96MPa,冲击强度下降了1.47kJ·m-2,熔融温度下降了18.6℃.%The performances of CaSO4 whisker/PP-R resin composites, such as the mechanics performance, heat performance and ultraviolet aging performance, had been improved by adding rutile nanometer titanium dioxide. The results showed that adding the rutile nano-TiO2 can improve the performances of CaSO4 whisker/PP-R resin composite farther than adding CaSO4 whisker only because of the cooperation of two stuffs. The results also showed the ultraviolet aging performance of CaSO4 whisker/PP-R resin composite adding 5% can be improved greatly. The rutile nano-TiO2/CaSO4 whisker/PP-R resin composite radiated by UV after 72days, it's tensile strength was 0. 36MPa, Intensity of impact was 0. 36KJ·m-2 and it' s softening point was 5. 4℃. But the CaSO4 whisker/PP-R resin composite radiated by UV after 72days, it's tensile strength was 1.96MPa, Intensity of impact was 1.46KJ·m-2 and it's softening point cut was 18. 6℃.

  6. Morphotropic phase boundary of heterovalent perovskite solid solutions: Experimental and theoretical investigation of PbSc1/2Nb1/2O3-PbTiO3

    International Nuclear Information System (INIS)

    X-ray and neutron diffraction techniques are combined with first-principles-based simulations to derive and understand the structural properties of Pb(Sc,Nb,Ti)O3 (PSN-PT) near its morphotropic phase boundary (MPB). An analysis of our measurements yields, at room and low temperatures, an overall tetragonal T--monoclinic MC--monoclinic MB--rhombohedral R path (when adopting the notations of Vanderbilt and Cohen, Phys. Rev. B 63, 94108 (2001) for the monoclinic phases) as the Ti composition decreases across the MPB. A composition- and temperature-dependent significant mixing between some of these phases is also measured and reported here. The overall T-MC-MB-R path, which has also been proposed for Pb(Mg,Nb,Ti)O3 [A. K. Singh and D. Pandey, Phys. Rev. B 67, 64102 (2003)] is rather complex since it involves a change in the polarization path: this polarization first rotates in a (100) plane for the T-MC part of the path and then in a (1-10) plane for the MB-R part of the path. Moreover, a comparison between these measurements and first-principles-based calculations raises the possibility that this complex path, and the associated MC and MB phases, can only occur if the samples exhibit a deviation from a perfectly homogeneous and disordered situation, e.g. possess nanoscale chemically-ordered regions. If not, homogeneously disordered PSN-PT is predicted to exhibit at low temperature the same polarization path as Pb(Zr,Ti)O3, that is T-monoclinic MA-R which involves a 'single' polarization rotation in a (1-10) plane. Nanoscale inhomogeneity may thus play a key role on the macroscopic properties of PSN-PT, in particular, and of other heterovalent complex solid solutions, in general, near their MPB

  7. Density functional study of the stability and magnetic behaviour of Au{sub n}TM{sup +} clusters (TM=Au,Sc,Ti,V,Cr,Mn,Fe; 1{<=}n{<=}9)

    Energy Technology Data Exchange (ETDEWEB)

    Torres, M.B. [Dpto. de Matematicas y Computacion, Univ. de Burgos, Avda. de Cantabria s/n, 09006-Burgos (Spain); Fernandez, E.M.; Balbas, L.C. [Dpto. de Fisica Teorica, Univ. de Valladolid, Prado de la Magdalena s/n, 47011-Valladolid (Spain)

    2005-03-01

    We study the element- and size-dependent electron stability of Au{sub n}TM{sup +} clusters (TM=Sc,Ti,V,Cr,Mn,Fe,Au; 1{<=}n{<=}9) by means of first-principles density functional calculations. The interplay between the cluster atomic arrangements and their electronic and magnetic structure is investigated for the few lower energy isomeric-states in dependence of the TM-atom and its environment in the cluster. We explain the experimental magic-numbers, observed recently, as well as the trend of the impurity local magnetic moment in dependence with the size of the cluster and the position of the impurity in the host. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Shape Memory Characteristics of Ti(sub 49.5)Ni(sub 25)Pd(sub 25)Sc(sub 0.5) High-Temperature Shape Memory Alloy After Severe Plastic Deformation

    Science.gov (United States)

    Atli, K. C.; Karaman, I.; Noebe, R. D.; Garg, A.; Chumlyakov, Y. I.; Kireeva, I. V.

    2011-01-01

    A Ti(49.5)Ni25Pd25Sc(0.5) high-temperature shape memory alloy is thermomechanically processed to obtain enhanced shape-memory characteristics: in particular, dimensional stability upon repeated thermal cycles under constant loads. This is accomplished using severe plastic deformation via equal channel angular extrusion (ECAE) and post-processing annealing heat treatments. The results of the thermomechanical experiments reveal that the processed materials display enhanced shape memory response, exhibiting higher recoverable transformation and reduced irrecoverable strain levels upon thermal cycling compared with the unprocessed material. This improvement is attributed to the increased strength and resistance of the material against defect generation upon phase transformation as a result of the microstructural refinement due to the ECAE process, as supported by the electron microscopy observations.

  9. Morphotropic phase boundaries in (BiScO3)1-x(PbTiO3)x (0.60

    International Nuclear Information System (INIS)

    We have performed a structural study of the morphotropic phase boundary system (1-x)BiScO3-xPbTiO3 in which both A and B sites of the perovskite are randomly occupied. A MA monoclinic phase coexisting with a tetragonal phase has been evidenced for concentration 0.60< x<0.70. No evidence of local cations ordering nor chemical inhomogeneity has been found. Taking into account data of Eitel et al. [Jpn. J. Appl. Phys., Part 1 40, 5999 (2001); Jpn. J. Appl. Phys. 41, 2099 (2002)] and our results, a global phase diagram has been drawn. This phase diagram reveals some similarities with that of lead zirconate titanate. The results are discussed in relation with previous works in morphotropic phase boundary systems

  10. In vivo behavior of bioactive phosphate glass-ceramics from the system P2O5-Na2O-CaO containing TiO2.

    Science.gov (United States)

    Monem, Ahmed Soltan; ElBatal, Hatem A; Khalil, Elsayed M A; Azooz, Moenis A; Hamdy, Yousry M

    2008-03-01

    Soda lime phosphate bioglass-ceramics with incorporation of small additions of TiO2 were prepared in the metaphosphate and pyrophosphate region, using an appropriate two-step heat treatment of controlled crystallization defined by differential thermal analysis results. Identification and quantification of crystalline phases precipitated from the soda lime phosphate glasses were performed using X-ray diffraction analysis. Calcium pyrophosphate (beta-Ca2P2O7), sodium metaphosphate (NaPO3), calcium metaphosphate (beta-Ca(PO3)2), sodium pyrophosphate (Na4P2O7), sodium calcium phosphate (Na4Ca(PO3)6) and sodium titanium phosphate (Na5Ti(PO4)3) phases were detected in the prepared glass-ceramics. The degradation of the prepared glass-ceramics were carried out for different periods of time in simulated body fluid at 37 degrees C using granules in the range of (0.300-0.600 mm). The released ions were estimated by atomic absorption spectroscopy and the surface textures were measured by scanning electron microscopy. Evaluation of in vivo bioactivity of the prepared glass-ceramics was carried through implanting the samples in the rabbit femurs. The results showed that the addition of 0.5 TiO2 mol% enhanced the bioactivity while further increase of the TiO2 content decreased the bioactivity. The effect of titanium dioxide on the bioactivity was interpreted on the basis of its action on the crystallization process of the glass-ceramics. PMID:17701314

  11. Improved tribo-mechanical behavior of CaP-containing TiO2 layers produced on titanium by shot blasting and micro-arc oxidation.

    Science.gov (United States)

    Szesz, Eduardo M; de Souza, Gelson B; de Lima, Gabriel G; da Silva, Bruno A; Kuromoto, Neide K; Lepienski, Carlos M

    2014-10-01

    The combination of shot blasting (SB) and micro-arc oxidation (or anodic oxidation--AO) in titanium surfaces was shown to provide enhanced conditions for cell differentiation and osseointegration than those provided by SB or AO alone. This study associated both methods aiming to attain titania layers on Ti with adequate tribo-mechanical features for bone implants. SB was performed using alumina particles, and titania layers were grown by AO using a CaP-based electrolyte. Mechanical properties and scratch resistance were characterized at nanoscale by instrumented indentation and nanoscratch, and correlated with morphological and microstructural changes (XRD, SEM, EDS, AFM, and profilometry). Analytical methods were employed to correct roughness and substrate effects on the indentation results. CaP-containing TiO2 layers were produced on AO and SB + AO. The latter presented small pore size and inhomogeneous layer thickness and Ca/P ratios, caused by the non-uniform surface straining by SB that affects the oxide growth kinetics in the electrochemical process. Elastic modulus of SB + AO layer (37 GPa) were lower than the AO one (45 GPa); both of them were smaller than bulk Ti (130 GPa) and close to bone values. The hardness profiles of AO and SB + AO were similar to the substrate ones. Because of the improved load bearing capacity and unique layer features, the critical load to remove the SB + AO titania coating in scratch tests was three times as much or higher than in AO. Results indicate improved mechanical biocompatibility and tribological strength of anodic titania layers grown on sand blasted Ti surfaces. PMID:24845307

  12. Energy dependence of thermoluminescent response of CaSO{sub 4}:Dy, LiF:Mg and micro LiF:Mg,Ti in clinical beams of electrons by using different simulator objects; Dependencia energetica da resposta TL de dosimetros de CaSO{sub 4}:Dy, LiF:Mg e microLiF:Mg,Ti em feixes clinicos de eletrons utilizando diferentes objetos simuladores

    Energy Technology Data Exchange (ETDEWEB)

    Bravim, Amanda; Campos, Leticia Lucente, E-mail: abravin@ipen.b, E-mail: rsakuraba@einstein.b, E-mail: lcrodri@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Sakuraba, Roberto K.; Cruz, Jose Carlos da, E-mail: rsakuraba@einstein.b, E-mail: josecarlosc@einstein.b [Hospital Israelita Albert Einstein (HIAE), Sao Paulo, SP (Brazil)

    2011-10-26

    Yet not so widely applied in radiotherapy, the calcium sulfate doped with dysprosium (CaSO{sub 4}:Dy) is used in radioprotection and studies has been demonstrated its great potential for the dosimetry in radiotherapy. This work evaluates the energy dependence of the thermoluminescent answer of the CaSO{sub 4}:D, LiF:Mg,Ti (TLD-100) and micro LiF:Mg,Ti in clinical beams of electrons by using water simulators, PMMA and solid water

  13. Influence of CaZrO3 on dielectric properties and microstructures of BaTiO3-based X8R ceramics

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The influences of CaZrO3 on the dielectric properties and microstructures of BaTiO3 (BT)-based ceramics have been investigated. The experiment results showed that the dielectric constant at room temperature increased with the addition of CaZrO3 in the range of 0―3.0 mol%, which could be explained by the growth of BT grains. XRD analysis revealed that the tetragonality declined as CaZrO3 concentration in-creased. XRD patterns of BT ceramics with different amounts of CaZrO3 doping were analyzed by a recently developed procedure-materials analysis using diffrac-tion (MAUD), which was based on the Rietveld method combined with Fourier analysis. The results depicted that the high temperature peak of tempera-ture-capacitance characteristics (TCC) was largely dependent on the micro-strain of samples. Furthermore, more CaZrO3 doping resulted in lower porosity and higher density. It was revealed that proper usage of CaZrO3 could improve the di-electric properties significantly, which was benefit to develop X8R multi-layer ce-ramic capacitors.

  14. Influence of CaZrO3 on dielectric properties and microstructures of BaTiO3-based X8R ceramics

    Institute of Scientific and Technical Information of China (English)

    TANG Bin; ZHANG ShuRen; YUAN Ying; ZHOU XiaoHua; LIANG YiShuai

    2008-01-01

    The influences of CaZrO3 on the dielectric properties and microstructures of BaTiO3 (BT)-based ceramics have been investigated. The experiment results showed that the dielectric constant at room temperature increased with the addition of CaZrO3 in the range of 0-3.0 mol%, which could be explained by the growth of BT grains. XRD analysis revealed that the tetragonality declined as CaZrO3 concentration in- creased. XRD patterns of BT ceramics with different amounts of CaZrO3 doping were analyzed by a recently developed procedure-materials analysis using diffrac- tion (MAUD), which was based on the Rietveld method combined with Fourier analysis. The results depicted that the high temperature peak of tempera- ture-capacitance characteristics (TCC) was largely dependent on the micro-strain of samples. Furthermore, more CaZrO3 doping resulted in lower porosity and higher density. It was revealed that proper usage of CaZrO3 could improve the di- electric properties significantly, which was benefit to develop X8R multi-layer ce- ramic capacitors.

  15. Observation of rotation of polarization in thin films of Pb(Sc1/2Nb1/2)O3-PbTiO3 via a monoclinic phase

    International Nuclear Information System (INIS)

    Using a simple methodology based on the classical Bragg-Brentano X-ray geometry we have evidenced at room temperature a pseudo-cubic phase and a monoclinic (Pm) phase in thin films of PbSc1/2Nb1/2O3 (PSN) and (PbSc1/2Nb1/2O3)0.57-(PbTiO3)0.43 (PSN-PT) respectively, the latter compound corresponding to a morphotropic phase boundary (MPB) composition. Depending on the substrate and the thickness, different domains configuration are obtained. Competition between epitaxial and thermal stress induces a complex structural evolution with temperature which is different from that of ceramic samples. Indeed PSN films transform from a pseudo-cubic (triclinic) phase towards a cubic phase whereas in PSN-PT, a succession of transformations from a pure Pm phase toward a tetragonal (possibly non polar) phase is observed, a cubic phase never being reached up to 950 K. (author)

  16. Preparation and Characterization of Red Luminescent Ca0.8Zn0.2TiO3: Pr3+, Na+ Nanophosphor

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nanophosphor with the nominal composition of Ca0.8Zn0.2TiO3∶Pr3+, Na+ (CZTOPN) was synthesized at relatively low temperature by the sol-gel method. Metal ions were dispersed by citric acid in ethylene glycol solvent and then react with Ti(OC4H9)4 to form sol and gel. The decomposition process of the precursor, and crystallization and particle size of CZTOPN were examined by thermal analysis (TG-DSC), powder X-ray diffraction (XRD), and scan election microscopy (SEM). Results of TG-DSC and XRD reveal that the composition of Ca0.8Zn0.2TiO3∶Pr3+, Na+ changes with the sintering temperature. SEM data indicate that the diameter of particles is under 50 nm even if the sintering temperature increases to 1000 ℃. In contrast to a solid state reaction, the excitation spectra of samples synthesized by the sol-gel method shift blue about 10 nm and the emission intensity at 617 nm increases significantly.

  17. Static and reversible elastic strain effects on magnetic order of La0.7Ca0.3MnO3/SrTiO3 superlattices

    Science.gov (United States)

    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.

  18. Sc-47 production from titanium targets using electron linacs

    International Nuclear Information System (INIS)

    In this work we have studied the feasibility of photonuclear production of 47Sc from 48Ti via 48Ti(γ,p)47Sc reaction. Photon flux distribution for electron beams of different energies incident on tungsten converter was calculated using MCNPX radiation transport code. 47Sc production rate dependence on electron beam energy was found and 47Sc yields were estimated. It was shown that irradiating a natural Ti target results in numerous scandium isotopes which can reduce the specific activity of 47Sc. Irradiating enriched 48Ti targets with a 22 MeV 1 mA beam will result in hundreds of MBq/g activity of 47Sc and no other isotopes of scandium. Decreasing the size of the target will result in much higher average photon flux through the target and tens of GBq/g levels of specific activity of 47Sc. Increasing the beam energy will also result in higher yields, but as soon as the electron energy exceeds the 48Ti(γ,np)46Sc reaction threshold, 46Sc starts being produced and its fraction in total scandium atoms grows as beam energy increases. The results of the simulations were benchmarked by irradiating natural titanium foil with 22 MeV electron beam incident on the tungsten converter. Measured 47Sc activities were found to be in very good agreement with the predictions. - Highlights: • Optimum irradiation conditions of titanium targets were found. • MCNPX simulation and experimental results of Sc-47 yield are presented. • We demonstrated the feasibility of photonuclear production of Sc-47 from Ti-48

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

    Science.gov (United States)

    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

  20. Hydrothermal growth of TiO{sub 2}-CaP nano-films on a Ti–Nb-based alloy in concentrated calcium phosphate solutions

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongwei, E-mail: lihw74@foxmail.com [Chang’an University, School of Materials Science and Engineering (China); Fu, Tao, E-mail: taofu@mail.xjtu.edu.cn [Xi’an Jiaotong University, Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology (China); Li, Wen [Chang’an University, School of Materials Science and Engineering (China); Alajmi, Zafer; Sun, Jiamao [Xi’an Jiaotong University, Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology (China)

    2016-01-15

    The Ti–Nb-based TLM alloy (Ti–25Nb–3Zr–2Sn–3Mo) was subjected to hydrothermal treatment in the concentrated Ca{sub 3}(PO{sub 4}){sub 2}, CaHPO{sub 4}, and Ca(H{sub 2}PO{sub 4}){sub 2} solutions for the purpose of calcification. The treated samples are covered by films consisting of Ca-rich nano-crystallites (100–500 nm) and small nano-grains. XPS and XRD analyses reveal the formation of hydroxyapatite, TiO{sub 2}, and Nb{sub 2}O{sub 5} at the sample surface. The sample hydrothermally treated in CaHPO{sub 4} solution exhibits bioactivity by inducing the formation of apatite layer after soaking test in the simulated body fluid for 15 days. The work would provide a good bioactive surface modification method for Ti–Nb alloy implants with complex shapes and even pores.

  1. High-pressure investigation of CaTiO3 up to 60 GPa using x-ray diffraction and Raman spectroscopy

    Science.gov (United States)

    Guennou, Mael; Bouvier, Pierre; Krikler, Benjamin; Kreisel, Jens; Haumont, Raphaël; Garbarino, Gaston

    2010-10-01

    In this work, we investigate calcium titanate [CaTiO3(CTO)] using x-ray diffraction and Raman spectroscopy up to 60 GPa and 55 GPa, respectively. Both experiments show that the orthorhombic Pnma structure remains stable up to the highest pressures measured, in contradiction to ab initio predictions. A fit of the compression data with a second-order Birch-Murnaghan equation of state yields a bulk modulus K0 of 181.0(6) GPa. The orthorhombic distortion is found to increase slightly with pressure, in agreement with previous experiments at lower pressures and the general rules for the evolution of perovskites under pressure. High-pressure polarized Raman spectra also enable us to clarify the Raman mode assignment of CTO and identify the modes corresponding to rigid rotation of the octahedra, A -cation shifts, and Ti-O bond stretching. The Raman signature is then discussed in terms of compression mechanisms.

  2. Sorption properties and reversibility of Ti(IV) and Nb(V)-fluoride doped-Ca(BH{sub 4}){sub 2}-MgH{sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Bonatto Minella, Christian, E-mail: christian.minella@kit.edu [Institute for Metallic Materials, IFW Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany); Technische Universität Dresden, D-01062 Dresden (Germany); Garroni, Sebastiano [Dipartimento di Chimica e Farmacia, Universitá di Sassari and INSTM, Via Vienna 2, I-07100 Sassari (Italy); Pistidda, Claudio [Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH, Max Planck Str. 1, D-21502 Geesthacht (Germany); Baró, Maria Dolors [Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Gutfleisch, Oliver [Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt (Germany); Klassen, Thomas; Dornheim, Martin [Institute of Materials Research, Materials Technology, Helmholtz-Zentrum Geesthacht, Zentrum für Material- und Küstenforschung GmbH, Max Planck Str. 1, D-21502 Geesthacht (Germany)

    2015-02-15

    Highlights: • Faster desorption reaction for doped materials vs. the pure composite system. • Kinetic improvement concerning re-hydrogenation reaction showed by the addition of NbF{sub 5}. • Full characterization of the de-hydrogenation reaction pathway by means of both SR-PXD and {sup 11}B{"1H} MAS-NMR. • Study of the evolution of the chemical state of the additives upon both milling and sorption reactions. - Abstract: In the last decade, alkaline and alkaline earth metal tetrahydroborates have been the focuses of the research due to their high gravimetric and volumetric hydrogen densities. Among them, Ca(BH{sub 4}){sub 2} and the Ca(BH{sub 4}){sub 2} + MgH{sub 2} reactive hydride composites (RHC), were calculated to have the ideal thermodynamic properties which fall within the optimal range for mobile applications. In this study, the addition of NbF{sub 5} or TiF{sub 4} to the Ca(BH{sub 4}){sub 2} + MgH{sub 2} reactive hydride composite system was attempted aiming to obtain a full reversible system with the simultaneous suppression of CaB{sub 12}H{sub 12}. Structural characterization of the specimens was performed by means of in-situ Synchrotron Radiation Powder X-ray diffraction (SR-PXD) and {sup 11}B{"1H} Solid State Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). The evolution of the chemical state of the Nb- and Ti-based additives was monitored by X-ray Absorption Near Edge Structure (XANES). The addition of NbF{sub 5} or TiF{sub 4} to the Ca(BH{sub 4}){sub 2} + MgH{sub 2} system have not suppressed completely the formation of CaB{sub 12}H{sub 12} and only a slight improvement concerning the reversible reaction was displayed just in the case of Nb-doped composite material.

  3. Fusion and quasifission dynamics in the reactions 48Ca+249Bk and 50Ti+249Bk using a time-dependent Hartree-Fock approach

    Science.gov (United States)

    Umar, A. S.; Oberacker, V. E.; Simenel, C.

    2016-08-01

    Background: Synthesis of superheavy elements (SHEs) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHEs have been recently produced with doubly-magic 48Ca beams. However, SHE synthesis experiments with single-magic 50Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for Z =117 ,119 superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in 48Ca,50Ti+249Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles. Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment. Results: Nucleus-nucleus potentials, nuclear contact times, masses and charges of the fragments, as well as their kinetic and excitation energies strongly depend on the orientation of the prolate 249Bk nucleus. Long contact times associated with fusion are observed in collisions of both projectiles with the side of the 249Bk nucleus, but not on collisions with its tip. The energy and impact parameter dependencies of the fragment properties, as well as their mass-angle and mass-total kinetic energy correlations are investigated. Conclusions: Entrance channel reaction dynamics are similar with both 48Ca and 50Ti projectiles. Both are expected to lead to the formation of a compound nucleus by fusion if they have enough energy to get in contact with the side of the 249Bk target.

  4. Dielectric behaviour of Hf-doped CaCu3Ti4O12 ceramics obtained by conventional synthesis and reactive sintering

    OpenAIRE

    Rubia López, Miguel Ángel de la; Leret Molto, Pilar; Campo García, Ángel Adolfo del; Alonso, Roberto Emilio; López García, Alberto Raúl; Fernández Lozano, José Francisco; Frutos Vaquerizo, José de

    2012-01-01

    CaCu3(Ti4xHfx)O12 ceramics (JC = 0.04, 0.1 and 0.2) were prepared by conventional synthesis (CS) and through reactive sintering (RS), in which synthesis and sintering of the material take place in one single step. The microstructure and the dielectric properties of Hf-doped CCTO (CCTOHf) have been studied by XRD, FE-SEM, AFM, Raman and impedance spectroscopy (IS) in order to correlate the structure, microstructure and the electrical properties. Samples prepared by reactive sintering show s...

  5. Effect of hafnium substitution on the dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Late, Ravikiran, E-mail: ravikiranlate5887@gmail.com; Rai, Hari Mohan; Saxena, Shailendra K.; Kumar, Rajesh; Sagdeo, P. R. [Material Research Laboratory, Discipline of Physics & MSE, Indian Institute of Technology, Indore-452017 (India)

    2015-06-24

    CaCu{sub 3}Ti{sub 4-x}Hf{sub x}O{sub 12} (x = 0, 0.04, 0.08 and 0.12 i.e. 0, 1, 2 and 3 atomic %) has been prepared by conventional solid state reaction method. The structural, dielectric and optical properties of the prepared samples were studied using x-ray diffraction, impedance analyzer and diffuse reflectance spectroscopy. With increasing Hf concentration dielectric permittivity decreases whereas the dielectric loss slightly increases and optical band gap almost remain constant. The results are explained on the basis of increase in the structural disorder and porosity of the sample with Hf doping.

  6. Detection of heterogeneities in single-crystal CaCu{sub 3}Ti{sub 4}O{sub 12} using conductive atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fiorenza, Patrick; Lo Nigro, Raffaella; Raineri, Vito [Istituto per la Microelettronica e Microsistemi, Consiglio Nazionale delle Ricerche, Stradale Primosole 50, 95121 Catania (Italy); Krohns, Stephan; Lunkenheimer, Peter; Loidl, Alois [Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg (Germany); Ebbinghaus, Stefan G [Solid State Chemistry, Martin-Luther University Halle-Wittemberg, 06120 Halle (Germany); Ferrarelli, Matthew C; Sinclair, Derek C; West, Anthony R, E-mail: patrick.fiorenza@imm.cnr.it [Department of Engineering Materials, Sir Robert Hadfield Building, University of Sheffield, Mappin Street, Sheffield, S1 3JD (United Kingdom)

    2010-02-15

    This paper reports on a conductive atomic force microscopy (C-AFM) investigation to provide local electrical characterization in a single crystal of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO). The microstructure and dielectric properties were studied and provide evidence for an insulating secondary phase embedded within the semiconducting CCTO matrix. Such insulating electrical heterogeneities cannot be observed with macroscopic measurements such as conventional Impedance Spectroscopy and this study reveals C-AFM to be a powerful tool to assess the electrical homogeneity of semiconducting single crystals such as CCTO.

  7. Relativistic fine structure oscillator strengths for Li-like ions: C IV - Si XII, S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, and Ni XXVI

    OpenAIRE

    Nahar, Sultana N.

    2002-01-01

    Ab initio calculations including relativistic effects employing the Breit-Pauli R-matrix (BPRM) method are reported for fine structure energy levels and oscillator strengths upto n = 10 and 0.leq. l .leq.9 for 15 Li-like ions: C IV, N V, O VI, F VII, Ne VIII, Na IX, Mg X, Al XI, Si XII, S XIV, Ar XVI, Ca XIII, Ti XX, Cr XXII, and Ni XXVI. About one hundred bound fine structure energy levels of total angular momenta, 1/2 .leq. J .leq. 17/2 of even and odd parities, total orbital angular moment...

  8. Anomalous change in dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} under violet-to-ultraviolet irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Masingboon, C. [School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Faculty of Science and Engineering, Kasetsart University, Chalermphrakiat Sakon Nakhon Province Campus, Sakon Nakhon 47000 (Thailand); Eknapakul, T.; Suwanwong, S.; Buaphet, P. [School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Nakajima, H. [Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); Mo, S.-K. [Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, California 94720 (United States); Thongbai, P. [Department of Physics, Khon Kaen University, Khon Kaen 40000 (Thailand); King, P. D. C. [SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS (United Kingdom); Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853 (United States); Maensiri, S.; Meevasana, W. [School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Thailand Center of Excellence in Physics, CHE, Bangkok 10400 (Thailand); NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand)

    2013-05-20

    The influence of light illumination on the dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) polycrystals is studied in this work. When exposed to 405-nm laser light, a reversible enhancement in the room temperature capacitance as high as 22% was observed, suggesting application of light-sensitive capacitance devices. To uncover the microscopic mechanisms mediating this change, we performed electronic structure measurements, using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. Together, these results suggest that the large capacitance enhancement is driven by oxygen vacancies induced by the irradiation.

  9. Mn掺杂改性高温无铅压电陶瓷CaBi4Ti4O15的研究

    Institute of Scientific and Technical Information of China (English)

    初瑞清; 徐志军

    2007-01-01

    用固相合成法制备Mn掺杂改性的CaBi4Ti4O15(CBT)高温无铅压电陶瓷。分析表明,利用固相合成法制备Mn掺杂CBT的温度为850℃,制备Mn掺杂改性CBT陶瓷的烧结温度随锰含量的增加降低,压电常数影响不大。

  10. Fermi Level Unpinning and Schottky Barrier Modification by Ti,Sc and V Incorporation at NiSi2/Si Interface

    Institute of Scientific and Technical Information of China (English)

    GENG Li; MAGYARI-KOPE Blanka; ZHANG Zhi-Yong; NISHI Yoshio

    2009-01-01

    A new method is proposed to modify the Schottky barrier height (SBH) for nickel silicide/Si contact.Chemical and electrical properties for NiSi2/Si interface with titanium,scandium and vanadium incorporation are investigated by first-principles calculations. The metal/semiconductor interface states within the gap region are greatly decreased,which is related to the diminutions of junction leakage when Ti-eap is experimentally used in nickel silicide/Si contact process.It leads to an unpinning metal/semiconductor interface.The SBH obeys the SchottkyMort theory. Compared to Ti substitution,the SBH for electrons is reduced for scandium and increases for vanadium.

  11. Enhanced electrical and magnetic properties in La0.7Sr0.3MnO3 thin films deposited on CaTiO3-buffered silicon substrates

    Directory of Open Access Journals (Sweden)

    C. Adamo

    2015-06-01

    Full Text Available We investigate the suitability of an epitaxial CaTiO3 buffer layer deposited onto (100 Si by reactive molecular-beam epitaxy (MBE for the epitaxial integration of the colossal magnetoresistive material La0.7Sr0.3MnO3 with silicon. The magnetic and electrical properties of La0.7Sr0.3MnO3 films deposited by MBE on CaTiO3-buffered silicon (CaTiO3/Si are compared with those deposited on SrTiO3-buffered silicon (SrTiO3/Si. In addition to possessing a higher Curie temperature and a higher metal-to-insulator transition temperature, the electrical resistivity and 1/f noise level at 300 K are reduced by a factor of two in the heterostructure with the CaTiO3 buffer layer. These results are relevant to device applications of La0.7Sr0.3MnO3 thin films on silicon substrates.

  12. Fe4+ content and ordering of anion vacancies in partially reduced AFexTi1-xO3-y (A = Ca, Sr; x≤0.6) perovskites. An 57Fe Moessbauer spectroscopy study

    International Nuclear Information System (INIS)

    CaFexTi1-xO3-y (0.05≤x≤0.60) and SrFexTi1-xO3-y (0.20≤x≤0.60) perovskites were prepared by solid state reaction and subjected to different heat treatments in different atmospheres. Moessbauer spectroscopy of the CaFexTi1-xO3-y could detect Fe4+ in all the samples, even in those heated at 1000 deg. C in Ar atmosphere for 10 hours. Fe3+ coordinated by six, five and four anions were also identified and the estimated hyperfine parameters were consistent with those previously reported for the CaFexTi1-xO3-x/2 oxides where all the Fe cations were present as Fe3+. The Fe4+/Fe3+ ratios estimated from Moessbauer data are in agreement with coulometric titration data. The absence of tetracoordinated Fe3+ in SrFexTi1-xO3-y suggests that in contrast to CaFexTi1-xO3-y no ordering of anion vacancies takes place even for x=0.60 and explains the differences in the Fe concentration dependence of the electric transport properties of these materials. (author)

  13. Enhanced electrical and magnetic properties in La{sub 0.7}Sr{sub 0.3}MnO{sub 3} thin films deposited on CaTiO{sub 3}-buffered silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Adamo, C. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Méchin, L.; Guillet, B.; Wu, S.; Routoure, J.-M. [Groupe de Recherche en Informatique, Image, Automatique et Instrumentation de Caen, (GREYC-UMR 6072), CNRS-ENSICAEN—Université de Caen Basse-Normandie, 6 Boulevard Maréchal Juin, 14050 Caen Cedex (France); Heeg, T. [Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501 (United States); Katz, M.; Pan, X. Q. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Mercone, S. [Laboratoire de Sciences des Procédés et des Matériaux, UPR3407, CNRS, Institut Galilee, Universite Paris-Nord, Villetaneuse (France); Schubert, J.; Zander, W. [Peter Grünberg Institute (PGI9-IT), JARA-Fundamentals of Future Information Technology, Research Centre Jülich, Jülich D-52425 (Germany); Misra, R. [Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Schiffer, P. [Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); and others

    2015-06-01

    We investigate the suitability of an epitaxial CaTiO{sub 3} buffer layer deposited onto (100) Si by reactive molecular-beam epitaxy (MBE) for the epitaxial integration of the colossal magnetoresistive material La{sub 0.7}Sr{sub 0.3}MnO{sub 3} with silicon. The magnetic and electrical properties of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} films deposited by MBE on CaTiO{sub 3}-buffered silicon (CaTiO{sub 3}/Si) are compared with those deposited on SrTiO{sub 3}-buffered silicon (SrTiO{sub 3}/Si). In addition to possessing a higher Curie temperature and a higher metal-to-insulator transition temperature, the electrical resistivity and 1/f noise level at 300 K are reduced by a factor of two in the heterostructure with the CaTiO{sub 3} buffer layer. These results are relevant to device applications of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} thin films on silicon substrates.

  14. Microwave Dielectric Properties of (1-x) CaTiO3-xLaAlO3 Ceramics%(1-x)CaTiO3-xLaAlO3陶瓷的微波介电性能研究

    Institute of Scientific and Technical Information of China (English)

    赵小玻; 高勇; 侯立红; 宋涛; 王营营; 张萍萍; 车松蔚; 鲍晓芸

    2014-01-01

    通过传统的固相反应法制备了(1-x)CaTiO3-xLaAlO3陶瓷,系统地研究了LaAlO3含量的变化对陶瓷的晶体结构、微观结构和微波介电性能的影响.结果表明,LaAlO3含量的增加导致(1-x)CaTiO3-xLaAlO3陶瓷的晶格结构发生畸变,使得陶瓷的介电常数下降、Q·f值增加,并使其谐振频率温度系数向负值处发生偏移.LaAlO3的含量为x=0.33时,(1-x)CaTiO3-xLaAlO3陶瓷的烧结温度为1460℃,展示了良好的微波介电性能:εr=45.3、Q·f=36218 GHz、τf=-0.5 ppm/℃.

  15. Giant dielectric behavior and electrical properties of Ca{sub 1-3x/2}Lu{sub x}Cu{sub 3}Ti{sub 4}O{sub 12} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Boonlakhorn, Jakkree [Khon Kaen University, Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen (Thailand); Kidkhunthod, Pinit [Synchrotron Light Research Institute (Public Organization), Nakhon Ratchasima (Thailand); Putasaeng, Bundit; Yamwong, Teerapon [Thailand Science Park, National Metal and Materials Technology Center (MTEC), Pathumthani (Thailand); Thongbai, Prasit [Khon Kaen University, Materials Science and Nanotechnology Program, Faculty of Science, Khon Kaen (Thailand); Khon Kaen University, Department of Physics, Faculty of Science, Khon Kaen (Thailand); Maensiri, Santi [Suranaree University of Technology, Institute of Science, School of Physics, Nakhon Ratchasima (Thailand)

    2015-07-15

    Giant dielectric behavior and electrical properties of Ca{sub 1-3x/2}Lu{sub x}Cu{sub 3}Ti{sub 4}O{sub 12} ceramics were studied by focusing on the influences of Lu{sup 3+} doping on their microstructure and electrical properties. The mean grain size of CaCu{sub 3}Ti{sub 4}O{sub 12} was greatly reduced as the dopant content was increased to 15 at.% (x = 0.15), which was ascribed to the effect of solute drag. X-ray absorption near-edge structure confirmed the presence of Ti{sup 3+} ions in Ca{sub 1-3x/2}Lu{sub x} Cu{sub 3}Ti{sub 4}O{sub 12} ceramics. The ratio of Ti{sup 3+}/Ti{sup 4+} in CaCu{sub 3}Ti{sub 4}O{sub 12} was reduced by Lu{sup 3+} doping. Dielectric permittivity (ε') decreased with increasing Lu{sup 3+} content, which was ascribed to reduce grain boundary capacitance caused by the presence of Lu{sup 3+}. Activation energies for conduction in the grain interiors and at the grain boundaries were slightly changed with Lu{sup 3+} content. Interestingly, improved dielectric properties with ε' ∝3.56 x 10{sup 4} and tan δ ∝0.059 at 1 kHz in the Ca{sub 0.925}Lu{sub 0.05}Cu{sub 3}Ti{sub 4}O{sub 12} ceramic were achieved. (orig.)

  16. A sol-gel route to prepare Ti-Ca-Ba-Cu-O superconductor with Tc above 120

    International Nuclear Information System (INIS)

    This paper reports on the preparation of Tl-Ca-Ba-Cu-O superconductor with Tc above 120 K from Ca-Ba-Cu-O precursor mixed with thallium oxide. The Ca-Ba-Cu-O precursor was prepared by sol-gel method from the proper complexation and polymerization of the metal nitrates by citric acid and ethylene diamine. The homogeneity and small particle size make the sol-gel precursor a potential candidate for Tl-Ca-Ba-Cu-P film preparation by screen-printing or spin-coating and thallium vapor diffusion

  17. Estudo da regeneração natural, banco de sementes e chuva de sementes na reserva genética florestal de Caçador, SC.

    Directory of Open Access Journals (Sweden)

    Silvana Lucia Caldato

    2009-09-01

    Full Text Available Normal 0 21 false false false MicrosoftInternetExplorer4 Este estudo foi realizado na Reserva Genética Florestal de Caçador, no Estado de Santa Catarina no período de agosto de 1995 a janeiro de 1996. Para o estudo da regeneração natural foram instaladas 10 parcelas de 250 m² (10m x 25m. No interior das mesmas foram coletados a camada de solo juntamente com a serapilheira em até 3cm de profundidade em 40 pontos amostrais de 0,5m x 0,5m para a análise do banco de sementes no solo, e instalados 20 coletores com área de 0,5 m x 0,5 m para a avaliação da chuva de sementes. Os resultados mostram que apesar da Araucaria angustifolia ser a espécie dominante no estrato superior da floresta não apresenta indivíduos na regeneração natural e a Mimosa scabrella foi a espécie arbórea mais importante presente no banco de sementes no solo. As relações entre os três parâmetros avaliados evidenciam uma distribuição irregular das espécies na área de estudo.

  18. Assessment of CaSO4:Dy and LiF:Mg,Ti thermoluminescent dosimeters performance in the dosimetry of clinical electron beams

    International Nuclear Information System (INIS)

    The assessment of the performance of CaS04:Dy thermoluminescent detectors produced by IPEN in the dosimetry of clinical electron beams aims to propose an alternative to the LiF:Mg,Ti commercial dosimeters (TLD-100) largely applied in radiation therapy. The two types of thermoluminescent dosimeters were characterised with the use of PMMA, RMI-457 type solid water and water phantoms in radiation fields of 4, 6, 9, 12 and 16 MeV electrons of nominal energies in which the dose-response curves were obtained and the surface and depth doses were determined. The thermoluminescent response dependency with the electron nominal energies and the applied phantom were studied. The CaS04:Dy presented the same behaviour than the LiF:Mg,Ti in such a way that its application as an alternative to the TLD-100 pellets in the radiation therapy dosimetry of electron beams is viable and presents the significantly higher sensitivity to the electron radiation as its main advantage. (author)

  19. Influence of CaCO3, Al2O3, and TiO2 microfillers on physico-mechanical properties of Luffa cylindrica/polyester composites

    Directory of Open Access Journals (Sweden)

    Vinay Kumar Patel

    2016-06-01

    Full Text Available The development of natural fibre reinforced polymer composites has gained popularity in many applications due to their environment friendly characteristics over the synthetic fibre based polymer composites. This paper describes the fabrication and physical, mechanical, three-body abrasive wear and water absorption behaviour of Luffa fibre reinforced polyester composites with and without addition of micro-fillers of Al2O3, CaCO3 and TiO2. The ranking of the composite materials has been made by using Technique for order preference by similarity to ideal solution (TOPSIS method with output parameters of their physical, mechanical and abrasive wear and water absorption attributes. The addition of microfillers has enhanced greatly the physical and mechanical properties of Luffa-fibre based composites. The addition of microfillers has influenced the physico-mechanical properties of Luffa-fibre based polyester composites in descending order of CaCO3, Al2O3, and TiO2.

  20. Analysis of Fe, Ca, Ti, Ba, Ce, Zr and La element in the Sea sediment at Muria peninsula by X RF method

    International Nuclear Information System (INIS)

    he analysis of metals (Fe, Ca, Ti, Ba, Ce, Zr and La) in the sea sediment environmental samples at Muria peninsula has been carried out with X-Ray Fluorescence (XRF) method. The aim of this analysis is to know the distribution metals which accommodate the recent environmental data in supporting the license of site and Environmental Impact Assessment (EIA) for the Nuclear Power Plants (NPP). Samples taken preparation and analysis based on the procedures of environmental analysis. The result analysis that contents of mayor elements in 7 sea sediment location of sampling were Ca, Ti and Fe with concentration are (6.74 – 11.69 ) %; (0.74 – 6.89 ) % and (0.45 -1.94 ) % successively; while minor elements were Ba, Ce, Zr and La with concentration are 451.4 – 1331.6 ) mg/kg; (201.8 – 427.3) mg/kg; (192.3 – 338.5) mg/kg dan (171.7 – 298.4) mg/kg. The statistic test result shows that sampling location there is a significant difference all of element with the level significant of 95 %. (author)

  1. Extremely large electronic anisotropy caused by electronic phase separation in Ca3(Ru0.97Ti0.03)2O7 single crystal

    Science.gov (United States)

    Peng, Jing; Wu, Xiaoshan; Mao, Zhiqiang

    2015-03-01

    Bilayered ruthenate Ca3 Ru2O7 exhibits rich electronic and magnetic properties. It orders at 56K, with FM bilayers antiferromagnetically coupled along c-axis (AFM-a). The AFM transition is closely followed by a first-order metal-insulator (MI) transition at 48K where spin directions switch to the b-axis (AFM-b). While this MI transition is accompanied by the opening of anisotropic charge gap; small Fermi pockets survive from the MI transition, thus resulting in quasi-2D metallic transport behavior for Tinsulating state with a nearest-neighbor AFM order via Ti doping. Ca3(Ru0 . 97 Ti0 . 03) 2O7 is close to the critical composition for the AFM-b-to-G-AFM phase transition. Our recent studies show the sample with this composition is characterized by an electronic phase separation between the insulating G-AFM phase (major) and the localized AFM-b phase (minor). The minor AFM-b phase forms a conducting path through electronic percolation within the ab-plane, but not along the c-axis, thus resulting in extremely large electronic anisotropy with ρab /ρc ~109 , which may be the largest among bulk materials.

  2. Impedance spectroscopy studies on lead free (Ba0.85Ca0.15(Ti0.9Zr0.1O3 ceramics

    Directory of Open Access Journals (Sweden)

    Ahcène Chaouchi

    2012-12-01

    Full Text Available The AC complex impedance spectroscopy technique has been used to obtain the electrical parameters of polycrystalline sample of (Ba0.85Ca0.15(Ti0.9Zr0.1O3 in a wide frequency range at different temperatures. This sample was prepared by a high temperature solid-state reaction technique and single phase formation was confirmed by X-ray diffraction technique. This study was carried out by the means of simultaneous analysis of impedance, modulus, and electrical conductivity. The Cole-Cole (Nyquist plots suggest that the grains and grain boundaries are responsible in the conduction mechanism of the material at high temperature. The ColeCole (Nyquist plot studies revealed the presence of grain and grain boundary effect at 485 °C. On the other hand, it showed only the presence of grain boundary component of the resistivity at 535 °C. Complex impedance analysis indicated the presence of non-Debye type dielectric relaxation. The bulk resistance of the material decreases with rise in temperature similar to a semiconductor, and the Cole-Cole (Nyquist plot showed the negative temperature coefficient of resistance (NTCR character of (Ba0.85Ca0.15(Ti0.9Zr0.1O3. The value of activation energy is found to be 0.7433 eV, which suggests that the conduction may be the result of defect and charge carriers present in the materials.

  3. Comparative Study Between GGA and LDA Approximation Using First- Principles Calculations of Structural, Electronic, Optical and Vibrational Properties of CaTiO3 Crystal

    Science.gov (United States)

    Medeiros, Subenia; Araujo, Maeva

    2015-03-01

    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. 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.

  4. Magnetic behavior of La2/3Ca1/3MnO3 / BaTiO3 bilayers

    Science.gov (United States)

    Ordonez, John E.; Gomez, Maria E.; Lopera, Wilson; Marin, Lorena; Pardo, Jose A.; Morellon, Luis; Algarabel, Pedro; Prieto, Pedro

    2013-03-01

    We have grown ferroelectric BaTiO3(BTO) and ferromagnetic La2/3Ca1/3MnO3 (LCMO) onto (001) SrTiO3 and Nb:SrTiO3 by pulsed laser deposition (PLD) at pure oxygen atmosphere, and a substrate temperature of 820° C, seeking for a multiferroic behavior in this structure. From x-ray diffraction (XRD) we found lattice parameter aBTO=4.068 Å, and aLCMO=3.804 Å, for each individual layer. In the BTO/LCMO bilayer, (002)-Bragg peak for BTO maintain its position whereas (002) LCMO peak shift to lower Bragg angle indicating a strained LCMO film. Magnetization measurements reveal an increase in the Curie temperature from 170 K to 220 K for the bilayer when LCMO (t = 47 nm) is deposited on BTO (t=52 nm) film, while depositing the BTO (50 nm) above LCMO (48 nm) the Curie temperature remains at values close to that obtained for a LCMO single layer (~175 K), deposited under identical growth parameters This work has been supported by Instituto de Nanociencias de Aragón, Zaragoza, Spain, ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' COLCIENCIAS-CENM Contract RC 275-2011 and Research Project COLCIENCIAS-UNIVALLE.

  5. 稀土发光材料Mg0.2Ca0.8TiO3:Pr的合成与表征%Synthesis and characterization of rare earth luminescent materials Mg0.2Ca0.8TiO3:Pr

    Institute of Scientific and Technical Information of China (English)

    王晓楠; 左斌

    2012-01-01

    应用溶胶凝胶法制备了不同Pr^3+摩尔浓度下的Mg0.2Ca0.8TiO3:Pr纳米粉体,并通过XRD,TG,TEM,发射光谱和激发光谱等测试手段来表征Mg0.2Ca0.8TiO3:Pr的结构、形貌和荧光性质.X射线衍射结果表明:样品为正方晶格结构,其晶粒尺寸随着热处理温度的提高而逐渐增大,Pr离子浓度的提高不会影响晶体结构.发射光谱与激发光谱的强度都随着温度的升高而增强,而Pr^3+摩尔浓度的提高对发射光谱和激发光谱的影响不大.余辉性能测试表明Mg0.2Ca0.8TiO3:Pr的余辉时间可达30ms.%Mg0.2Ca0.8TiO3:Pr Pr nano powder with different Pr^3+ concentration and its structure, morphology and fluorescence property were characterized were prepared by sol-gel method, through the XRD, TG, TEM, emission and excitation spectra and other means. X ray diffraction results show that the sample is affirmative,lattice structure, its grain size increases with the heat treatment temperature increasing, and the increase of Pr ion concentration will not affect the crystal structure. The intensity of emission and excitation spectra grows with the temperature increasing, and Pr^3 + molar concentration increasing has little effect on the emission and excitation spectra. Afterglow performance test shows that the afterglow time of Mg0.2Ca0.8TiO3:Pr can reach to 30ms.

  6. {sup 48}Ti(n,xnpa{gamma}) reaction cross sections using spallation neutrons for E{sub n} = 1 to 20 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D; Mitchell, G E; Garrett, P E; Agvaanluvsan, U; Becker, J A; Bernstein, L A; Cooper, J R; Hoffman, R D; Younes, W; Devlin, N; Fotiades, N; Nelson, R O

    2005-01-06

    {gamma}-ray excitation functions have been measured for the interaction of fast neutrons with {sup 48}Ti (neutron energy from 1 MeV to 250 MeV). The Los Alamos National Laboratory spallation neutron source, at the LANSCE/WNR facility, provided a ''white'' neutron beam which is produced by bombarding a natural W target with a pulsed proton beam. The prompt-reaction {gamma} rays were measured with the large-scale Compton-suppressed Ge spectrometer, GEANIE. Neutron energies were determined by the time-of-flight technique. Excitation functions were converted to partial {gamma}-ray cross sections, taking into account the dead-time correction, the target thickness, the detector efficiency, and neutron flux (monitored with an in-line fission chamber). The data analysis is presented here for neutron energies between 1 to 20 MeV. Partial {gamma}-ray cross sections for transitions in {sup 47,48}Ti, {sup 48}Sc, and {sup 45}Ca have been determined. These results are compared to Hauser-Feshbach predictions calculated using the STAPRE code, which includes compound nuclear and pre-equilibrium emission. The partial cross sections for {gamma} rays, whose discrete {gamma}-ray cascade path leads to the ground state in {sup 48}Ti, {sup 47}Ti, {sup 48}Sc, and {sup 45}Ca have been summed to obtain estimates of the lower limits for reaction cross sections. Partial cross sections for unobserved {gamma}-rays are predicted from the STAPRE code. These lower limits are combined with Hauser-Feshbach calculations to deduce {sup 48}Ti(n,n'){sup 48}Ti, {sup 48}Ti(n,2n){sup 47}Ti, {sup 48}Ti(n,p){sup 48}Sc, and {sup 48}Ti(n,{alpha}){sup 45}Ca reaction channel cross sections.

  7. Induction of Chronic Inflammation and Altered Levels of DNA Hydroxymethylation in Somatic and Germinal Tissues of CBA/CaJ Mice Exposed to (48)Ti Ions.

    Science.gov (United States)

    Rithidech, Kanokporn Noy; Jangiam, Witawat; Tungjai, Montree; Gordon, Chris; Honikel, Louise; Whorton, Elbert B

    2016-01-01

    Although the lung is one of the target organs at risk for cancer induction from exposure to heavy ions found in space, information is insufficient on cellular/molecular responses linked to increased cancer risk. Knowledge of such events may aid in the development of new preventive measures. Furthermore, although it is known that germinal cells are sensitive to X- or γ-rays, there is little information on the effects of heavy ions on germinal cells. Our goal was to investigate in vivo effects of 1 GeV/n (48)Ti ions (one of the important heavy ions found in the space environment) on somatic (lung) and germinal (testis) tissues collected at various times after a whole body irradiation of CBA/CaJ mice (0, 0.1, 0.25, or 0.5 Gy, delivered at 1 cGy/min). We hypothesized that (48)Ti-ion-exposure induced damage in both tissues. Lung tissue was collected from each mouse from each treatment group at 1 week, 1 month, and 6 months postirradiation. For the testis, we collected samples at 6 months postirradiation. Hence, only late-occurring effects of (48)Ti ions in the testis were studied. There were five mice per treatment group at each harvest time. We investigated inflammatory responses after exposure to (48)Ti ions by measuring the levels of activated nuclear factor kappa B and selected pro-inflammatory cytokines in both tissues of the same mouse. These measurements were coupled with the quantitation of the levels of global 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC). Our data clearly showed the induction of chronic inflammation in both tissues of exposed mice. A dose-dependent reduction in global 5hmC was found in the lung at all time-points and in testes collected at 6 months postirradiation. In contrast, significant increases in global 5mC were found only in lung and testes collected at 6 months postirradiation from mice exposed to 0.5 Gy of 1 GeV/n (48)Ti ions. Overall, our data showed that (48)Ti ions may create health risks in both

  8. Enhancement of luminescence intensity and spectroscopic analysis of Eu3+-activated and Li+ charge-compensated CaTiO3 color tunable phosphors for solid-state lighting

    Science.gov (United States)

    Singh, Dhananjay Kr.; Baitha, Pankaj Kr.; Manam, J.

    2016-07-01

    The present work explores a well-crystallized perovskite calcium titanate (CaTiO3) doped with trivalent europium (Eu3+) and co-doped with lithium ion (Li+) successfully synthesized by a conventional solid-state reaction method, and the impact of single dopant and co-dopant on the photoluminescence performances of the sample has been investigated by emission, excitation and diffuse reflectance spectra at the room temperature. Photoluminescence spectra of Li+-doped CaTiO3:Eu3+ nanophosphor revealed at intense pink emission peak for Ca(0.85- y)Li y TiO3:0.15Eu3+ nanophosphor around wavelength 619 nm in the visible region upon the excitation of near-UV light at wavelength 397 nm due to 5 D 0 → 7 F 2 transition in Eu3+. The incorporation of Li+ ion on CaTiO3:Eu3+ nanophosphors enhanced the emission probability from higher 5 D 0 state to lower 7 F j state, and its PL intensity is found to be three times greater than the intensity of CaTiO3:Eu3+ nanophosphor. The spectral characteristics and the Eu-O ligand behavior were confirmed in light of Judd-Ofelt theory from the Emission spectra rather than absorption spectra. Their crystal structure was confirmed by X-ray diffraction (XRD) which is in good agreement with pure orthorhombic phase with space group Pbnm, and it also indicated that the incorporation of the dopant/co-dopant did not affect the crystal structure. The experimental observation reveals that the developed phosphor material Li+-co-doped CaTiO3:Eu3+ can be used in solid-state lighting devices.

  9. Bioactivity studies on TiO₂-bearing Na₂O-CaO-SiO₂-B₂O₃ glasses.

    Science.gov (United States)

    Jagan Mohini, G; Sahaya Baskaran, G; Ravi Kumar, V; Piasecki, M; Veeraiah, N

    2015-12-01

    Soda lime silica borate glasses mixed with different concentrations of TiO2 are synthesized by the melt-quenching technique. As a part of study on bioactivity of these glasses, the samples were immersed in simulated body fluid (SBF) solution for prolonged times (~21 days) during which weight loss along with pH measurements is carried out at specific intervals of time. The XRD and SEM analyses of post-immersed samples confirm the formation of crystalline hydroxyapatite layer (HA) on the surface of the samples. To assess the role of TiO2 on the formation of HA layer and degradability of the samples the spectroscopic studies viz. optical absorption and IR spectral studies on post- and pre-immersed samples have been carried out. The analysis of the results of degradability together with spectroscopic studies as a function of TiO2 concentration indicated that about 6.0 mol% of TiO2 is the optimal concentration for achieving better bioactivity of these glasses. The presence of the maximal concentration octahedral titanium ions in this glass that facilitates the formation of HA layer is found to be the reason for such a higher bioactivity. PMID:26354260

  10. The 'Porky' Inclusion from the Axtell Carbonaceous Chondrite: A Hercynite-bearing Condensate with Large 48Ca and 50Ti Excesses

    Science.gov (United States)

    Caillet, C.; Zinner, E.

    1995-09-01

    Only a few hercynite-rich refractory inclusions have been identified to date [1,2]. Porky (450 micrometers long) is an unusual CAI with texturally distinct regions and dominant intergrown oxide mineral phases [3]. The core is a symplectitic vermicular intergrowth of ubiquitous ferroan spinel and ilmenite. Inwards branching of ilmenite crystals and projecting fan-shaped hibonite from the borders suggest crystallization from a fast cooling melt. Three marginal regions are mineralogically identical to the core: two fine-grained areas with acicular corroded crystals contrast with an altered spinel area. The inclusion is entirely rimmed by yellow luminescing Al-diopside. Hibonite exhibits pale orange luminescence. Broad beam analyses reveal high FeO (22.5 wt %) and low CaO/Al2O3 (0.024) for the whole CAI [3]. Si, Al and Ti concentrations are very similar to those of CM inclusions. There are no significant chemical differences between the coarse-grained core and the fine-grained regions. Hibonite shows widely varying concentrations (in wt %) of TiO2 (1.5-6.8), MgO (1.2-3.6) and FeO (0.7-4.7). Spinel contains much FeO (20.5-27). Hercynite close to the border of the inclusion next to hibonite has high MgO (11 wt%) and small amounts of Cr2O3 (0.15-1.55) and V2O3 (0.1-0.3), implying a melt origin. The Al-rich, Si-poor composition indicates that Porky experienced higher temperatures than CV3 inclusions. The presence of Fe-rich mineral phases, the lack of metal grains, the relatively high NiO concentration (average = 0.25), and the orange luminescence of hibonite indicate formation or re-equilibration in an oxidizing environment. Trace element patterns are basically volatility-fractionated and mostly ultrarefractory-depleted but vary from a Group II pattern in hercynite (to a lesser extent in hibonite and diopside) to extreme excesses of the less refractory elements Nb, Eu, Tm and Yb in a fine-grained region (Fig. 1). These patterns indicate condensation from a UR-depleted gas

  11. Charged FeC{sub n} clusters: A comparison with TMC{sub n}{sup +}/TMC{sub n}{sup -} (TM = Sc, Ti, V, Co and Zn, n = 1-8) systems

    Energy Technology Data Exchange (ETDEWEB)

    Redondo, Pilar, E-mail: predondo@qf.uva.es [Computacional Chemistry Group, Departamento de Quimica Fisica y Quimica Inorganica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid (Spain); Largo, Laura; Barrientos, Carmen [Computacional Chemistry Group, Departamento de Quimica Fisica y Quimica Inorganica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid (Spain)

    2009-10-16

    The electronic and geometrical structures of the ground and excited states for the linear, fan and cyclic isomers of FeC{sub n}{sup +}andFeC{sub n}{sup -} (n = 1-8) compounds are calculated using the B3LYP method. A comparison of these results with the previously obtained for TMC{sub n}{sup +}/TMC{sub n}{sup -} (TM = Sc, Ti, V, Co and Zn) systems, is carried out. Quartet and sextet states are found the most stables for FeC{sub n}{sup +} clusters. Linear FeC{sub n}{sup -} clusters prefer doublet and quartet ground states, whereas for cyclic and fan isomers the most stables are quartet and sextet ones. n-odd linear, fan, and cyclic FeC{sub n}{sup +} isomers are more stable than adjacent n-even ones. For FeC{sub n}{sup -} clusters the opposite trend is found for linear and fan structures, whereas for cyclic isomers the relative stability decreases along the series. In general linear isomers are the most stable conformations for FeC{sub n}{sup +}/FeC{sub n}{sup -} clusters. Systematic trends of different properties are analyzed for TMC{sub n}{sup +}/TMC{sub n}{sup -} clusters.

  12. Ferroelectric, piezoelectric, and dielectric properties of BiScO3-PbTiO3-Pb(Cd1/3Nb2/3)O3 ternary high temperature piezoelectric ceramics

    Science.gov (United States)

    Zhao, Tian-Long; Chen, Jianguo; Wang, Chun-Ming; Yu, Yang; Dong, Shuxiang

    2013-07-01

    (0.95-x)BiScO3-xPbTiO3-0.05Pb(Cd1/3Nb2/3)O3 (BS-xPT-PCN) high temperature piezoelectric ceramics near the morphotropic phase boundary (MPB) have been synthesized by traditional solid-state reaction methods. The microstructural morphology, phase structure, and electrical properties of BS-xPT-PCN ceramics were investigated in detail. X-ray diffraction analysis indicated BS-xPT-PCN ceramics have a pure perovskite structure. The coexistence of rhombohedral and tetragonal phases at MPB composition enhanced the polarizability by the coupling between two dynamically equivalent energy states, resulting in the improved piezoelectric and ferroelectric properties at MPB vicinity. The BS-xPT-PCN (x = 0.60) ceramics possess the optimal piezoelectric and ferroelectric properties with d33 = 505pC/N, kp = 55.9%, kt = 36.5%, strain = 0.23% (under the electric field 37.5 kV/cm), and Pr = 39.7 μC/cm2. High temperature dielectric behaviors showed diffuse phase transition in BS-xPT-PCN ceramics. The Curie temperature Tc was found to increase from 371 °C to 414 °C with x increasing from 0.58 to 0.62. All these results together with the good thermal stabilities make the BS-xPT-PCN ceramics promising candidates for high temperature piezoelectric applications.

  13. Ca,Sr)(Zr,Ti)O3系抗还原高频介质瓷料的研究%Study on (Ca,Sr)(Zr,Ti)O3 system anti-reduction high frequency dielectric ceramics

    Institute of Scientific and Technical Information of China (English)

    张火光; 付振晓; 宋永生; 莫方策

    2015-01-01

    采用固相合成法制备了(Ca, Sr)(Zr, Ti)O3(简称CSZT)系电容器陶瓷材料,研究了主晶相组分对所制材料介电性能的影响。结果表明:通过调整主晶相CSZT中各组分的配比,再加入适量的烧结助剂,能得到一种可在还原气氛中烧结的高频介质瓷料,该瓷料可与镍内电极共烧,其相对介电常数约为89,介质损耗(tanδ)小于5×10–4,绝缘电阻达到1012Ω,介电常数温度系数为–1037×10–6/℃。%(Ca,Sr)(Zr, Ti)O3(CSZT)dielectric ceramics were prepared by solid state method and the influences of the composition of the main crystal phase on the dielectric properties of prepared CSZT ceramics were studied. The results show that the reduction-resistant ceramics can be gotten by changing the composition of CSZT and adding appropriate amount of sintering additives. The obtained high-frequency dielectric materials can be co-fired with nickel electrode at reducing atmosphere. The dielectric properties are as follows: relative permittivity is about 89, dielectric loss (tanδ) is less than 5×10–4, insulation resistance is up to 1012Ω, temperature coefficient of dielectric constant is about –1037×10–6/℃.

  14. Effects of calcining process and CeO2 on properties of (1-x)LaAlO3-xCaTiO3 microwave dielectric ceramics%预烧工艺和CeO2添加剂对(1-x)LaAlO3-xCaTiO3微波介质陶瓷性能的影响

    Institute of Scientific and Technical Information of China (English)

    薛田良; 付云侠; 夏俊芳

    2012-01-01

    利用常规固相法制备了[(1-x)LaAlO3-xCaTiO3]+yCeO2陶瓷(y为CeO2的质量分数),研究了预烧工艺和CeO2添加剂对所制陶瓷微波介电性能的影响.结果表明,LaAlO3与CaTiO3一次预烧能获得较好的微波介电性能,CeO2添加剂能有效提高材料的烧结性能和微波介电性能.(0.4LaAlO3-0.6CaTiO3)+0.2%CeO2陶瓷经1 450℃烧结5h后能获得最佳微波介电性能:εr=43.1、Q·f=29 700 GHz、τf=-2.4×10-6/℃.%[(l-x)LaA1O3-xCaTi03]+yCe02 ceramics(y was mass fraction of CeO2) were prepared by the solid-state reaction. The effects of calcining process and CeO2 addition on microwave dielectric properties of the [(l-x)LaA103-xCaTi03]+yCe02 ceramics were investigated. It shows that more excellent microwave dielectric properties are obtained when LaAlO3 and CaTiO3 are calcined together, and CeO2 addition can improve effectively the sinterablity and microwave dielectric properties of [(l-x)LaA103-xCaTi03]+yCe02 ceramics. (0.4LaAlO3-0.6CaTiO3)+0.2%CeO2 ceramics sintered at 1 450 ℃ for 5 h has best microwave dielectric properties with er of 43.1, Q ·f o f29 700 GHz and tfof-2.4× 10-6/ ℃.

  15. Phase evolution studies in CaZrTi{sub 2}O{sub 7}−RE{sub 2}Ti{sub 2}O{sub 7} (RE = Nd{sup 3+}, Sm{sup 3+}) system: Futuristic ceramic host matrices for nuclear waste immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Jafar, M., E-mail: sachary@barc.gov.in; Achary, S. N., E-mail: sachary@barc.gov.in; Tyagi, A. K., E-mail: sachary@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

    2014-04-24

    Series of compositions with general stoichiometry as Ca{sub 1−x}Zr{sub 1−x}RE{sub 2x}Ti{sub 2}O{sub 7} (RE = Nd{sup 3+}, Sm{sup 3+}) were prepared by solid state reaction and characterized by powder x-ray diffraction technique to unravel the phase fields in the title systems. The phase fields in CaZrTi{sub 2}O{sub 7−}Nd{sub 2}Ti{sub 2}O{sub 7} and CaZrTi{sub 2}O{sub 7−}Sm{sub 2}Ti{sub 2}O{sub 7} systems differed significantly at the rareearth rich regions. The common phase fields like zirconolite-2M, zirconolite-4M, cubic perovskite are observed at the zirconolite rich regions of both systems. Depending on the structure of RE{sub 2}Ti{sub 2}O{sub 7} phase, the cubic pyrochlore or monoclinic RE{sub 2}Ti{sub 2}O{sub 7} phases are observed in the studied system. The observed phase fields in these two systems indicate ionic radius of the rare-earth ion has a dominating role in the phase relations. Further details of the phases and their homogeneity are explained in the text of the manuscript.

  16. Crystal structure and luminescence properties of Lu{sup 3+} and Mg{sup 2+} incorporated silicate garnet [Ca{sub 3-(x+0.06)}Lu{sub x}Ce{sub 0.06}](Sc{sub 2-y}Mg{sub y})Si{sub 3}O{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yongfu [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Eastern South Lake Road, Changchun 130033 (China); Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Zhang Xia; Hao Zhendong; Luo Yongshi [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Eastern South Lake Road, Changchun 130033 (China); Wang Xiaojun [Department of Physics, Georgia Southern University, Statesboro, GA 30460 (United States); Zhang Jiahua, E-mail: zhangjh@ciomp.ac.cn [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Eastern South Lake Road, Changchun 130033 (China)

    2012-05-15

    The yellow-emitting phosphor [Ca{sub 3-(x+0.06)}Lu{sub x}Ce{sub 0.06}](Sc{sub 2-y}Mg{sub y})Si{sub 3}O{sub 12} obtained from Lu{sup 3+} and Mg{sup 2+} co-modified green-emitting silicate garnet Ca{sub 3}Sc{sub 2}Si{sub 3}O{sub 12}:Ce{sup 3+} (CSS:Ce{sup 3+}) exhibits promising applications for white LEDs. In this paper, we discuss the effect of charge balance on the garnet structure formation. The changes of bond length and covalence caused by the replacement of Lu{sup 3+} and Mg{sup 2+} for Ca{sup 2+} and Sc{sup 3+} are analyzed. The shift of the Ce{sup 3+} emission and excitation can be attributed to the combined results from crystal field splitting effect and centroid shift of Ce{sup 3+} 5d levels. Thermal stability is analyzed according to configurational coordinate diagram. - Highlights: Black-Right-Pointing-Pointer Charge balance plays an important role on the garnet structure formation. Black-Right-Pointing-Pointer Bond lengths and polarizability affect the position of Ce{sup 3+} emission and excitation. Black-Right-Pointing-Pointer Thermal quenching is analyzed based on configurational coordinate diagram. Black-Right-Pointing-Pointer Our results provide an optimization method for phosphors used for white LEDs.

  17. Experimental and numerical investigation of a ceramic dielectric resonator (DRA): CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO)

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, A.F.L. [Departamento de Fisica, Universidade do Aveiro, 3800-193 Aveiro (Portugal); Mestrado em Ciencias Fisicas Aplicadas, Universidade Estadual do Ceara, Campus do Itaperi 1700, CEP 60740-903 Fortaleza, Ceara (Brazil); Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil); Silva, R.R. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil); Rocha, H.H.B. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil); Departamento de Engenharia de Teleinformatica (DETI), Universidade Federal do Ceara, Caixa Postal 6007, CEP 60.755-640 Fortaleza, Ceara (Brazil); Fechine, P.B.A. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil); Departamento de Quimica Analitica e Fisico-Quimica, Universidade Federal do Ceara - UFC, Campus do Pici, CP 12100, CEP 60451-970 Fortaleza - CE (Brazil); Cavalcanti, F.S.A. [Mestrado em Ciencias Fisicas Aplicadas, Universidade Estadual do Ceara, Campus do Itaperi 1700, CEP 60740-903 Fortaleza, Ceara (Brazil); Valente, M.A. [Departamento de Fisica, Universidade do Aveiro, 3800-193 Aveiro (Portugal); Freire, F.N.A.; Sohn, R.S.T.M. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760 Fortaleza, Ceara (Brazil)] (and others)

    2008-03-01

    In this study, the CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramic phase was synthesized by microwave heating in a much shorter time compared to the conventional heating methods. The results indicate that microwave processing is a promising method for preparing CCTO ceramics. CCTO was prepared using a domestic microwave oven operated at 2.45 GHz with 800 W. After a few minutes of microwave irradiation the formation of CCTO was confirmed by X-ray powder diffraction. The CCTO ceramic was studied in the medium-frequency (MF) range (100 Hz-1 MHz) and in the microwave range of frequencies. The experimental and theoretical characteristics of the dielectric resonator antenna are investigated.

  18. Intermediate temperature ionic conductivity of Sm1.92Ca0.08Ti2O7–δ pyrochlore

    DEFF Research Database (Denmark)

    Eurenius, Karinh E. J.; Bentzer, Henrik Karnøe; Bonanos, Nikolaos;

    2011-01-01

    The results of concentration cell electromotive force methods (EMF) and electrochemical impedance spectroscopy measurements on the pyrochlore system Sm1.92Ca0.08Ti2O7–δ are presented. The data have been used to estimate total and partial conductivities and determine transport numbers for protons...... and oxide ions under various conditions. The EMF techniques employed include corrections for electrode polarisation resistance. The measurements were performed using wet and dry atmospheres in a wide range using mixtures of H2, N2, O2, and H2O in the temperature region where proton conductivity was expected...... (500–300 °C). The impedance measurements revealed the conductivity to be mainly ionic under all conditions, with the highest total conductivity measured being 0.045 S/m under wet oxygen at 500 °C. Both bulk and grain boundary conductivity was predominantly ionic, but electronic conductivity appeared...

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

    Science.gov (United States)

    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.

  20. Dielectric behaviour of (Ba0.77Ca0.23(Ti0.98Dy0.02O3 ceramics

    Directory of Open Access Journals (Sweden)

    Abdul Moquim

    2015-06-01

    Full Text Available In this study, BaTiO3 is modified with Ca2+ and in addition doped with Dy3+ at the B site lattice. The main idea is to search for new lead-free ferroelectric material and improve their properties. For this purpose, the barium calcium titanate (BCT as a host and the rare earth element Dy3+ as an activator were used to fabricate a multifunctional material. The obtained ceramics was found to be homogeneous, dense and a single phase material with no evidence of secondary phases. The dielectric study showed that TC increases with the addition of dopants and the obtained ceramics behaves like a relaxor ferroelectric. Some important structural parameters and dielectric properties of dysprosium modified barium (calcium titanate ceramics are presented.

  1. CaCu3Ti4O12 particles and MWCNT-filled microwave absorber with improved microwave absorption by FSS incorporation

    Science.gov (United States)

    Qing, Yuchang; Yang, Zhaoning; Wen, Qinlong; Luo, Fa

    2016-07-01

    Multi-walled carbon nanotube (MWCNTs)- and CaCu3Ti4O12 (CCTO) particle-filled epoxy microwave absorbing coatings were prepared, and their electromagnetic properties and reflection loss (RL) were investigated in the frequency range 8.2-12.4 GHz. The microstructures of these coatings exhibit a uniform dispersion of MWCNTs and CCTO particles in the matrix. The value and frequency dependency of complex permittivity of such coatings enhanced with increasing MWCNT content. Frequency-selective surface was used to improve their microwave absorption (both the operating bandwidth and minimum RL) without increasing the absorber thickness. Such absorber showed high microwave absorbing performance, and the bandwidth of the RL below -8 dB (more than 84.1 % absorption) can be obtained in the whole X-band with a thickness of 1.5 mm.

  2. Large photoconductivity of La0.7Ca0.3MnO3-δ/SrTiO3 heterostructures

    International Nuclear Information System (INIS)

    The electric resistivity of stoichiometric and oxygen-deficient epitaxial 10-nm-thick La0.7Ca0.3MnO3 thin films on SrTiO3 under photoexcitation has been investigated systematically. In contrast to the as-prepared film, the oxygen-deficient one exhibits a pronounced photoinduced decrease of the resistivity of up to five orders of magnitude at low temperatures. A detailed analysis of the resistivity as a function of illumination intensity and wavelength (visible to ultraviolet range) is presented for the bare substrate as well as for the film/substrate heterostructure. The roles of carrier generation in the film and carrier injection from the substrate, which both contribute to the observed effects, are discussed.

  3. Fabrication, Sintering and Electrical Properties of (Ca0.61,Nd0.26)TiO3 Nanoparticles Doped with Li-Cu-B

    Institute of Scientific and Technical Information of China (English)

    Fei Wu; Qilong Zhang; Hui Yang

    2011-01-01

    A sol-gel processing was used to synthesize (Ca0.61,Nd0.26)TiO3 (CNT) nanoparticles doped with Li-Cu-B at low temperature. Orthorhombic perovskite structure phase with a small amount of Li3BO3 secondary phase was formed by calcining the xerogels at 300℃, and monodisperse CNT nano-powders with the grain size of 10-15 nm could be obtained. By using these nanocrystalline CNT powders, dense CNT ceramics could be achieved at the low sintering temperature of 1100℃ due to the effect of the small size nanoparticles and liquid phase Li3BO3. And the dielectric properties with dielectric constant (εr= 89.52), quality value factors with frequency (Q×f=17148 GHz) and the temperature coefficient of resonant frequency (Tf) value of +239× 10-6/℃ were achieved.

  4. Microwave dielectric properties of xCaTiO3-(1-x)LaAlO3 ceramics%xCaTiO3-(1-x)LaAlO3陶瓷微波介电性能的研究

    Institute of Scientific and Technical Information of China (English)

    方丹华; 江娟; 窦占明; 陆超; 章天金

    2015-01-01

    xCaTiO3-(1-x)LaAlO3 ceramics(CTLA,0.55≤x≤0.69)were prepared by traditional solid state process .The crystal structure,microstructure and microwave dielectric properties of the prepared CTLA ceramics were investigated .The results showed that the CTLA ceramics sintered at 1 400℃exhibited excellent microwave properties:the dielectric permittivity within the range from 35 to 47,Q × f≥35 000 GHz .The temperature coefficient of resonance frequency being near to zero with the increase of LaAlO 3 molar concentration.At x=0.67 the optimal microwave properties were obtained:εr=45,Q×f=36 684 GHz,τf=6.02×10-6/℃.%采用传统固相反应法制备xCaTiO3-(1-x)LaAlO3(0.55≤x≤0.69)(CTLA)陶瓷,研究CTLA陶瓷的物相,微观结构及微波介电性能.结果表明,烧结温度在1400℃时,陶瓷的微波性能最佳,介电常数在35~47之间,Q×f≥35000 GHz .随着CaTiO3含量的增大,频率温度系数趋零,当x=0.67时,陶瓷具有最佳的微波性能:εr=45,Q×f=36684 GHz,τf=6.02×10-6/℃.①

  5. Study of the nuclear matter distribution and isoscalar transition rates of 48Ca, 50Ti and 52Cr by scattering of 104 MeV alpha-particles

    International Nuclear Information System (INIS)

    The differential cross-sections for elastic and inelastic scattering of 104 MeV α-particles on 50Ti and 52Cr have been measured for scattering angles in the range 20 0. Additionally using previously measured data for 48Ca, the cross-sections of the N = 28 isotopic sequence 48Ca-50Ti-52Cr were analyzed on the basis of the generalized optical model. Study of the angular distribution of the elastic scattering, using modified phenomenological and microscopic methods, leads to well defined and consistent values for moments of the potentials and of the matter distributions. In particular, the Fourier-Bessel method leads to a nearly model-independent determination of the differences in isotonic radii and also to a realistic determination of error bars. For the analysis of the inelastic scattering a new method is introduced, which strongly reduces the model dependence which arises when simple analytic expressions are used for the form factors (the form of the coupling potentials). For this purpose the Fourier-Bessel method has been extended to the analysis of inelastic scattering using the collective vibrational model. Using the identities between the integral moments of a folded potential and of the underlying nuclear matter distribution, isoscalar transition rates have been derived. The extracted values are confirmed by an explicit folding model analysis. Furthermore, the folding model calculations show that the density dependence of the effective interaction between α-particle and target nucleons must be taken into account also in the analysis of inelastic scattering. (orig.)

  6. Effects of rare earth ionic doping on microstructures and electrical properties of CaCu3Ti4O12 ceramics

    International Nuclear Information System (INIS)

    Graphical abstract: The dielectric constant decreases monotonically with reduced RE doping ion radius and is more frequency independent compared with that of pure CCTO sample. - Highlights: • The mean grain sizes decrease monotonically with reduced RE doping ionic radius. • Doping gives rise to the monotonic decrease of ϵr with reduced RE ionic radius. • The nonlinear coefficient and breakdown field increase with RE ionic doping. • α of all the samples is associated with the potential barrier width rather than Φb. - Abstract: Ca1–xRxCu3Ti4O12(R = La, Nd, Eu, Gd, Er; x = 0 and 0.005) ceramics were prepared by the conventional solid-state method. The influences of rare earth (RE) ion doping on the microstructure, dielectric and electrical properties of CaCu3Ti4O12 (CCTO) ceramics were investigated systematically. Single-phase formation is confirmed by XRD analyses. The mean grain size decreases monotonically with reduced RE ion radius. The EDS results reveal that RE ionic doping reduces Cu-rich phase segregation at the grain boundaries (GBs). Doping gives rise to the monotonic decrease of dielectric constant with reduced RE ionic radius but significantly improves stability with frequency. The lower dielectric loss of doped samples is obtained due to the increase of GB resistance. In addition, the nonlinear coefficient and breakdown field increase with RE ionic doping. Both the fine grains and the enhancement of potential barrier at GBs are responsible for the improvement of the nonlinear current–voltage properties in doped CCTO samples

  7. A miniaturized Microwave Bandpass Filter Based on Modified (Mg0.95Ca0.05TiO3 Substrate

    Directory of Open Access Journals (Sweden)

    Hu Mingzhe

    2016-01-01

    Full Text Available A microwave miniaturized bandpass filter using (Mg0.95Ca0.05TiO3 (abbreviated as 95MCT hereafter ceramic substrate is investigated in the present paper. The paper studies the sintering and microwave dielectric properties of Al2O3, La2O3 and SiO2 co-doped 95MCT. The XRD pattern shows that a secondary phase MgTi2O5 is easily segregated in 95MCT ceramic, however, through co-doping it can be effectively suppressed, and the microwave dielectric properties, especially, the Qf value can be significantly improved. Through optimizing the co-doping ratio of Al2O3, La2O3 and SiO2, the sintering temperature of 95MCT ceramic can be lowered by 80°C, and the microwave dielectric properties can reach Qf=61856GHz and εr=19.84, which indicates the modified 95MCT ceramic have a great potential application in microwave communication devices. Based on this, we also designed a miniaturized microwave bandpass filter (BPF on modified 95MCT substrate. Through a full wave electromagnetic structure simulation, the results show that the center frequency of the BPF is 2.45GHz and the relative bandwidth is 4.09% with the insertion loss of less than 0.2dB in the whole bandpass.

  8. High efficiency angular non-critical phase matching for Ti:sapphire laser realized on LaCa4O(BO3)3 single crystals

    International Nuclear Information System (INIS)

    Angular non-critical phase-matching (A-NCPM) second harmonic generation (SHG) for a Ti:sapphire laser was realized on LaCa4O(BO3)3 (LaCOB) single crystals, grown by the Czochralski pulling method. Properties including the wavelength, bandwidth, effective nonlinear optical (NLO) coefficient (deff), and acceptance angle were evaluated. At ambient temperature of 20 °C, the type-I NCPM (808 nm wavelength) was obtained along the y axis of LaCOB crystals, where the effective nonlinear optical coefficient (deff), PM waveband, and angular acceptance were found to be of the order of 0.59 pm/V, 803∼818 nm and 50.6 mrad cm1/2 (ΔϕL), respectively. Moreover, high single-pass SHG conversion efficiency (44.6%) was achieved for 24.8 mm long Y-cut samples at 808 nm, using a mode-locked Ti:sapphire fundamental laser. (letter)

  9. Crystal micromorphologies and forming voltage effect on resistance switching behaviors in Ti/Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7}/Pt devices

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yuchen; Song, Liwei; Hua, Lifang; Cai, Wenhui; Chen, Wei [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China); Zhao, Xu, E-mail: xzhao@hebtu.edu.cn [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050024 (China)

    2015-10-15

    Two Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7} (PSCMO)-based devices (Ti/PSCMO-1/Pt and Ti/PSCMO-2/Pt) have been prepared by pulsed laser deposition, and the micromorphology of the films can be controlled through the different deposition condition. PSCMO-1 film with a smaller grain size grows with a near-random arrangement, whereas columnar grains with a larger grain size appear in the Ti/PSCMO-2/Pt device. The I–V curves in Ti/PSCMO-2/Pt device show the higher resistance ratio and larger hysteresis than that in the Ti/PSCMO-1/Pt device without forming process. The electron transport property in the PSCMO-2 film shows the higher resistance and metal behavior in room temperature. By fitting the I–V curves, we found that the conduction process in Ti/PSCMO-1/Pt device is dominated by Schottky barrier mechanism, but the conduction behavior in Ti/PSCMO-2/Pt device are dominated by trap-charged space-charge-limited current (SCLC) mechanism. Interesting, after a forming process, the Ti/PSCMO-1/Pt device also displays the higher resistance ratio and larger hysteresis, which can be explained by SCLC mechanism. Our results suggest that the crystal micromorphology and grain size may play a critical role in oxygen vacancy movement, and result in the transformation of resistance switching along with a higher resistance ratio and larger hysteresis in the Ti/PSCMO-2/Pt device. - Highlights: • Two different Pr(Sr{sub 0.1}Ca{sub 0.9}){sub 2}Mn{sub 2}O{sub 7}-based devices have been prepared. • The device with larger grain and columnar arrangement shows higher resistance ratio. • Crystal morphologies and grain size play critical role in oxygen vacancy movement.

  10. Raman spectra of the solid-solution between Rb sub 2 La sub 2 Ti sub 3 O sub 1 sub 0 and RbCa sub 2 Nb sub 3 O sub 1 sub 0

    CERN Document Server

    Kim, H J; Yun, H S

    2001-01-01

    A site preference of niobium atom in Rb sub 2 sub - sub x La sub 2 Ti sub 3 sub - sub x Nb sub x O sub 1 sub 0 (0.0<=x<=1.0) and RbLa sub 2 sub - sub x Ca sub x Ti sub 2 sub - sub x Nb sub 1 sub + sub x O sub 1 sub 0 (0.0<=x<= 2.0), which are the solid-solutions between Rb sub 2 La sub 2 Ti sub 3 O sub 1 sub 0 are RbCa sub 2 Nb sub 3 O sub 1 sub 0 , has been investigated by Raman spectroscopy. The Raman spectra of Rb sub 2 sub - sub x La sub 2 Ti sub 3 sub - sub x Nb sub x O sub 1 sub 0 (0.0<=x<=1.0) gave an evidence that niobium atoms substituted for titanium atoms preferably occupy the highly distorted outer octahedral sites rather than the central ones in triple-octahedral perovskite layers. In contrast, the Raman spectra of RbLa sub 2 sub - sub x Ca sub x Ti sub 2 sub - sub x Nb sub 1 sub + sub x O sub 1 sub 0 (0.0<=x<= 2.0) showed no clear information for the cationic arrangement in perovskite slabs. This difference indicated that a site preference of niobium atoms is observed onl...

  11. Lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 nanowires for energy harvesting.

    Science.gov (United States)

    Zhou, Zhi; Bowland, Christopher C; Malakooti, Mohammad H; Tang, Haixiong; Sodano, Henry A

    2016-03-01

    Lead-free piezoelectric nanowires (NWs) show strong potential in sensing and energy harvesting applications due to their flexibility and ability to convert mechanical energy to electric energy. Currently, most lead-free piezoelectric NWs are produced through low yield synthesis methods and result in low electromechanical coupling, which limit their efficiency as energy harvesters. In order to alleviate these issues, a scalable method is developed to synthesize perovskite type 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) NWs with high piezoelectric coupling coefficient. The piezoelectric coupling coefficient of the BZT-BCT NWs is measured by a refined piezoresponse force microscopy (PFM) testing method and shows the highest reported coupling coefficient for lead-free piezoelectric nanowires of 90 ± 5 pm V(-1). Flexible nanocomposites utilizing dispersed BZT-BCT NWs are fabricated to demonstrate an energy harvesting application with an open circuit voltage of up to 6.25 V and a power density of up to 2.25 μW cm(-3). The high electromechanical coupling coefficient and high power density demonstrated with these lead-free NWs produced via a scalable synthesis method shows the potential for high performance NW-based devices. PMID:26868967

  12. Phase transition behaviours near the triple point for Pb-free (1 - x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 piezoceramics

    Science.gov (United States)

    Gao, Jinghui; Dai, Ye; Hu, Xinghao; Ke, Xiaoqin; Zhong, Lisheng; Li, Shengtao; Zhang, Lixue; Wang, Yu; Wang, Dong; Wang, Yan; Liu, Yongbin; Xiao, Hu; Ren, Xiaobing

    2016-08-01

    The reason for the large electromechanical response in Pb-free piezoceramic Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BZT-BCT) still remains controversial, and a central issue is whether or not the multi-phase-coexisting point (triple point) in the phase diagram is a thermodynamic tricritical point. In this letter, we study the phase transition behaviour for the ferro-para transitions of BZT-BCT specimens in the vicinity of a triple point. Our results show that latent heat and thermal hysteresis approach zero, while the permittivity peak value is maximized close to the triple-point composition, which suggests that the triple point exhibits nearly tricritical transition behaviours in the BZT-BCT system. Further, the TEM result shows that the domain width is minimized with composition approaching the triple point, which indicates a reduction of the domain wall energy possibly relevant to the tricriticality of the triple point. A sixth-order Landau energy modeling shows that the triple tricritical point provides a free-energy state of near-vanishing polarization anisotropy and thus enhances the piezoelectric response for such a material system.

  13. Resistive switching in ferroelectric lead-free 0.5Ba (Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 thin films

    Science.gov (United States)

    Silva, J. P. B.; Kamakshi, K.; Sekhar, K. C.; Queirós, E. C.; Agostinho Moreira, J.; Almeida, A.; Pereira, M.; Tavares, P. B.; Gomes, M. J. M.

    2016-08-01

    In this work, resistive switching in pulsed laser deposited ferroelectric lead-free 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (0.5BZT–0.5BCT) thin films was investigated. This study reveals that films grown at 5.5 J cm‑2 have shown optimal ferroelectric and resistive switching response, which are attributed to high tetragonality, large grain size and less defect concentration. Au/0.5BZT–0.5BCT/Pt capacitors show the electroforming free resistive switching that is explained based on the polarization modulation of the Schottky-like barrier at the 0.5BZT–0.5BCT/Au interface. The polarization induced resistive switching is evidenced by its disappearance as the temperature increases to the Curie temperature. The capacitor based on film grown at 5.5 J cm‑2 shows resistive switching characterized by high switching ratio of 106 at a low set/reset voltage  ≈1 V, and by a stable memory window, which are highly required for memory applications.

  14. Synthesis of photocatalytic La(1-x)AxTiO3.5-δ(A=Ba, Sr, Ca) nano perovskites and their application for photocatalytic oxidation of congo red dye in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    M Bradha; T Vijayaraghavan; SP Suriyaraj; R Selvakumar; Anuradha M Ashok

    2015-01-01

    A-site substituted La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites were prepared by sol-gel method and characterized using thermogravimetry/differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectros-copy and transmission electron microscopy (TEM). XRD analysis showed that the La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites derived after calcination at 800 ºC were in single phase with orthorhombic structure. The particle size of all nano perovskites was found to be~20 nm. The synthesized nano perovskites were tested for the photocatalytic decomposition of an azo dye, Congo red. The sequential behavior of La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nanoperovskites for photocatalytic decomposition of congo red in aque-ous solution by visible light at room temperature was studied at various time intervals and the efficiency of degradation of the nanop-erovskites was compared. Among all the A-site substituted La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites, Ba substituted com-pound showed the highest dye degradation.

  15. Effect of nanoporous TiO2 coating and anodized Ca2+ modification of titanium surfaces on early microbial biofilm formation

    Directory of Open Access Journals (Sweden)

    Wennerberg Ann

    2011-03-01

    Full Text Available Abstract Background The soft tissue around dental implants forms a barrier between the oral environment and the peri-implant bone and a crucial factor for long-term success of therapy is development of a good abutment/soft-tissue seal. Sol-gel derived nanoporous TiO2 coatings have been shown to enhance soft-tissue attachment but their effect on adhesion and biofilm formation by oral bacteria is unknown. Methods We have investigated how the properties of surfaces that may be used on abutments: turned titanium, sol-gel nanoporous TiO2 coated surfaces and anodized Ca2+ modified surfaces, affect biofilm formation by two early colonizers of the oral cavity: Streptococcus sanguinis and Actinomyces naeslundii. The bacteria were detected using 16S rRNA fluorescence in situ hybridization together with confocal laser scanning microscopy. Results Interferometry and atomic force microscopy revealed all the surfaces to be smooth (Sa ≤ 0.22 μm. Incubation with a consortium of S. sanguinis and A. naeslundii showed no differences in adhesion between the surfaces over 2 hours. After 14 hours, the level of biofilm growth was low and again, no differences between the surfaces were seen. The presence of saliva increased the biofilm biovolume of S. sanguinis and A. naeslundii ten-fold compared to when saliva was absent and this was due to increased adhesion rather than biofilm growth. Conclusions Nano-topographical modification of smooth titanium surfaces had no effect on adhesion or early biofilm formation by S. sanguinis and A. naeslundii as compared to turned surfaces or those treated with anodic oxidation in the presence of Ca2+. The presence of saliva led to a significantly greater biofilm biovolume but no significant differences were seen between the test surfaces. These data thus suggest that modification with sol-gel derived nanoporous TiO2, which has been shown to improve osseointegration and soft-tissue healing in vivo, does not cause greater biofilm

  16. Enhancing CaP biomimetic growth on TiO2 cuboids nanoparticles via highly reactive facets.

    Science.gov (United States)

    Ruso, Juan M; Verdinelli, Valeria; Hassan, Natalia; Pieroni, Olga; Messina, Paula V

    2013-02-19

    Pure decahedral anatase TiO(2) particles with high content of reactive {001} facets were obtained from titanium(IV) tetrachloride (TiCl(4)) using a microemulsions droplet system at specific conditions as chemical microreactor. The product was systematically characterized by X-ray diffraction, field-emission scanning and transmission electron microscopy (FE-SEM, TEM), N(2) adsorption-desorption isotherms, FT-IR and UV-vis spectroscopy, and photoluminescence studies. The obtained cuboids around 90 nm in size have a uniform and dense surface morphology with a BET specific surface area of 11.91 m(2) g(-1) and a band gap energy (3.18 eV) slightly inferior to the anatase dominated by the less-reactive {101} surface (3.20 eV). The presence of reactive facets on titania anatase favors the biomimetic growth of amorphous tricalcium phosphate after the first day of immersion in simulated human plasma. The results presented here can facilitate and improve the integration of anchored implants and enhance the biological responses to the soft tissues.

  17. Effects of LiF on microwave dielectric properties of 0.25Ca0.8Sr0.2TiO3–0.75Li0.5Nd0.5TiO3 ceramics

    Indian Academy of Sciences (India)

    Fei Liu; Changlai Yuan; Xinyu Liu; Jing Jing Qu

    2015-09-01

    The effects of LiF addition on sinterability, microstructure and microwave dielectric properties of 0.25Ca0.8Sr0.2TiO3–0.75Li0.5Nd0.5TiO3 ceramics were investigated. The LiF addition enhanced the sintering temperature of 0.25Ca0.8Sr0.2TiO3–0.75Li0.5Nd0.5TiO3 ceramics from 1200 to 1300°C, because the LiF addition could compensate the evaporation of Li during the sintering process. It was found that the bulk density and dielectric constant (r) gradually decreased, the quality factor (f) greatly increased and the temperature coefficient of resonant frequency (f) shifted to a near-zero value with the increase in LiF addition. Obviously, excess Li addition could efficiently improve the microwave dielectric properties. In addition, 0.25Ca0.8Sr0.2 TiO3–0.75Li0.5Nd0.5TiO3 + 4.0 wt% LiF ceramics sintered at 1350°C for 4 h exhibited good microwave dielectric properties of r ∼ 123.4, f ∼ 2209 GHz (at 2.43 GHz) and f ∼ 12.3 ppm °C–1.

  18. Ferroelectric, piezoelectric, and dielectric properties of BiScO{sub 3}-PbTiO{sub 3}-Pb(Cd{sub 1/3}Nb{sub 2/3})O{sub 3} ternary high temperature piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Tianlong [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Chen Jianguo; Dong Shuxiang [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Wang Chunming [School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Yu Yang [Faculty of Physics and Electronic Technology, Hubei University, Wuhan 430062 (China)

    2013-07-14

    (0.95-x)BiScO{sub 3}-xPbTiO{sub 3}-0.05Pb(Cd{sub 1/3}Nb{sub 2/3})O{sub 3} (BS-xPT-PCN) high temperature piezoelectric ceramics near the morphotropic phase boundary (MPB) have been synthesized by traditional solid-state reaction methods. The microstructural morphology, phase structure, and electrical properties of BS-xPT-PCN ceramics were investigated in detail. X-ray diffraction analysis indicated BS-xPT-PCN ceramics have a pure perovskite structure. The coexistence of rhombohedral and tetragonal phases at MPB composition enhanced the polarizability by the coupling between two dynamically equivalent energy states, resulting in the improved piezoelectric and ferroelectric properties at MPB vicinity. The BS-xPT-PCN (x = 0.60) ceramics possess the optimal piezoelectric and ferroelectric properties with d{sub 33} = 505pC/N, k{sub p} = 55.9%, k{sub t} = 36.5%, strain = 0.23% (under the electric field 37.5 kV/cm), and P{sub r} = 39.7 {mu}C/cm{sup 2}. High temperature dielectric behaviors showed diffuse phase transition in BS-xPT-PCN ceramics. The Curie temperature T{sub c} was found to increase from 371 Degree-Sign C to 414 Degree-Sign C with x increasing from 0.58 to 0.62. All these results together with the good thermal stabilities make the BS-xPT-PCN ceramics promising candidates for high temperature piezoelectric applications.

  19. Investigating the addition of SiO₂-CaO-ZnO-Na₂O-TiO₂ bioactive glass to hydroxyapatite: Characterization, mechanical properties and bioactivity.

    Science.gov (United States)

    Yatongchai, Chokchai; Placek, Lana M; Curran, Declan J; Towler, Mark R; Wren, Anthony W

    2015-11-01

    Hydroxyapatite (Ca10(PO4)6(OH)2) is widely investigated as an implantable material for hard tissue restoration due to its osteoconductive properties. However, hydroxyapatite in bulk form is limited as its mechanical properties are insufficient for load-bearing orthopedic applications. Attempts have been made to improve the mechanical properties of hydroxyapatite, by incorporating ceramic fillers, but the resultant composite materials require high sintering temperatures to facilitate densification, leading to the decomposition of hydroxyapatite into tricalcium phosphate, tetra-calcium phosphate and CaO phases. One method of improving the properties of hydroxyapatite is to incorporate bioactive glass particles as a second phase. These typically have lower softening points which could possibly facilitate sintering at lower temperatures. In this work, a bioactive glass (SiO2-CaO-ZnO-Na2O-TiO2) is incorporated (10, 20 and 30 wt%) into hydroxyapatite as a reinforcing phase. X-ray diffraction confirmed that no additional phases (other than hydroxyapatite) were formed at a sintering temperature of 560 ℃ with up to 30 wt% glass addition. The addition of the glass phase increased the % crystallinity and the relative density of the composites. The biaxial flexural strength increased to 36 MPa with glass addition, and there was no significant change in hardness as a function of maturation. The pH of the incubation media increased to pH 10 or 11 through glass addition, and ion release profiles determined that Si, Na and P were released from the composites. Calcium phosphate precipitation was encouraged in simulated body fluid with the incorporation of the bioactive glass phase, and cell culture testing in MC-3T3 osteoblasts determined that the composite materials did not significantly reduce cell viability.

  20. Assessment of CaSO{sub 4}:Dy and LiF:Mg,Ti thermoluminescent dosimeters performance in the dosimetry of clinical electron beams; Avaliacao do desempenho dos detectores termoluminesncetes de CaSO{sub 4}:Dy e LiF:Mg,Ti na dosimetria de feixes clinicos de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, Maira Goes

    2008-07-01

    The assessment of the performance of CaS0{sub 4}:Dy thermoluminescent detectors produced by IPEN in the dosimetry of clinical electron beams aims to propose an alternative to the LiF:Mg,Ti commercial dosimeters (TLD-100) largely applied in radiation therapy. The two types of thermoluminescent dosimeters were characterised with the use of PMMA, RMI-457 type solid water and water phantoms in radiation fields of 4, 6, 9, 12 and 16 MeV electrons of nominal energies in which the dose-response curves were obtained and the surface and depth doses were determined. The thermoluminescent response dependency with the electron nominal energies and the applied phantom were studied. The CaS0{sub 4}:Dy presented the same behaviour than the LiF:Mg,Ti in such a way that its application as an alternative to the TLD-100 pellets in the radiation therapy dosimetry of electron beams is viable and presents the significantly higher sensitivity to the electron radiation as its main advantage. (author)

  1. xCaTiO3-(1-x)LaAlO3微波介质陶瓷介电性能研究%Study on Dielectric Properties ofxCaTiO3-(1-x)LaAlO3 Microwave Dielectric Ceramic

    Institute of Scientific and Technical Information of China (English)

    王孝国; 宋永生; 莫方策; 周永响

    2016-01-01

    采用固相法制备了xCaTiO3-(1-x)LaAlO3(CTLA 钛酸钙-铝酸镧)复合陶瓷,研究CTLA系统陶瓷材料中x变化、工艺条件和添加剂变化与介电性能的关系。结果表明:当0.67x≤0.75,1230℃下预烧,成品添加质量分数0.5% MnO2,粉体粒度D50研磨至1.5μm时,1400℃烧结成瓷,主晶相xCaTiO3-(1-x)LaAlO3形成完全互溶钙钛矿型固溶体。可获得具有理想的微波介电性能(40≤εr≤50,Qf≥40000,τf在-20×10-6~20×10-6/℃范围内可调),不含Pb、Cd等有害杂质的高Q中介电常数微波介质陶瓷。

  2. Ultrasensitive photoelectrochemical immunoassay for CA19-9 detection based on CdSe@ZnS quantum dots sensitized TiO2NWs/Au hybrid structure amplified by quenching effect of Ab2@V(2+) conjugates.

    Science.gov (United States)

    Zhu, Hua; Fan, Gao-Chao; Abdel-Halim, E S; Zhang, Jian-Rong; Zhu, Jun-Jie

    2016-03-15

    A novel, enhanced photoelectrochemical immunoassay was established for sensitive and specific detection of carbohydrate antigen 19-9 (CA19-9, Ag). In this protocol, TiO2 nanowires (TiO2NWs) were first decorated with Au nanoparticles to form TiO2NWs/Au hybrid structure, and then coated with CdSe@ZnS quantum dots (QDs) via the layer-by-layer method, producing TiO2NWs/Au/CdSe@ZnS sensitized structure, which was employed as the photoelectrochemical matrix to immobilize capture CA19-9 antibodies (Ab1); whereas, bipyridinium (V(2+)) molecules were labeled on signal CA19-9 antibodies (Ab2) to form Ab2@V(2+) conjugates, which were used as signal amplification elements. The TiO2NWs/Au/CdSe@ZnS sensitized structure could adequately absorb light energy and dramatically depress electron-hole recombination, resulting in evidently enhanced photocurrent intensity of the immunosensing electrode. While target Ag were detected, the Ab2@V(2+) conjugates could significantly decrease the photocurrent detection signal because of strong electron-withdrawing property of V(2+) coupled with evident steric hindrance of Ab2. Thanks to synergy effect of TiO2NWs/Au/CdSe@ZnS sensitized structure and quenching effect of Ab2@V(2+) conjugates, the well-established photoelectrochemical immunoassay exhibited a low detection limit of 0.0039 U/mL with a wide linear range from 0.01 U/mL to 200 U/mL for target Ag detection. This proposed photoelectrochemical protocol also showed good reproducibility, specificity and stability, and might be applied to detect other important biomarkers.

  3. Effect of (Ca0.8Sr0.2)0.6La0.267TiO3 on Phase, Microstructure, and Microwave Dielectric Properties of Mg0.95Zn0.05TiO3 Synthesized by Polymeric Precursor Method

    Science.gov (United States)

    Naeem, Abdul; Ullah, Asad; Mahmood, Tahira; Iqbal, Yaseen; Mahmood, Asad; Hamayun, Muhammad

    2016-08-01

    A number of compounds in the (1 - x)Mg0.95Zn0.05TiO3- x(Ca0.8Sr0.2)0.6 La0.267TiO3 ( x = 0 to 0.25) composition series have been obtained via a polymeric precursor route to investigate the effect of increasing (Ca0.8Sr0.2)0.6La0.267TiO3 proportion on the phase, microstructure, and microwave dielectric properties of the sintered ceramics. Composite powders having nanometric particles were obtained by calcining the precursors at 700°C. Refinement results revealed that these samples comprised a mixture of Mg0.95Zn0.05TiO3 and (Ca0.8Sr0.2)0.6La0.267TiO3 ceramics. A combination of optimum microwave dielectric properties, i.e., dielectric constant of 25.17, quality factor of 58,754 GHz, and temperature coefficient of resonant frequency of -5.8 ppm/°C, was achieved for the x = 0.2 composition sintered at 1200°C.

  4. High-Temperature Monoclinic Cc Phase with Reduced c/a Ratio in Bi-based Perovskite Compound Bi2ZnTi1-xMnxO6.

    Science.gov (United States)

    Yu, Runze; Matsuda, Narumi; Tominaga, Ken; Shimizu, Keisuke; Hojo, Hajime; Sakai, Yuki; Yamamoto, Hajime; Oka, Kengo; Azuma, Masaki

    2016-06-20

    Monoclinic phases with Cm, Pm, and Cc space groups are indispensable to understand the high performance of electromechanical properties at the morphotropic phase boundary (MPB) of lead-based perovskite oxides Pb(ZrxTi1-x)O3 (PZT), [Pb(Mg1/3Nb2/3)O3]1-x-(PbTiO3)x (PMN-PT), and [Pb(Zn1/3Nb2/3)O3]1-x-(PbTiO3)x (PZN-PT). Here, a nearly single monoclinic phase with space group Cc was observed in the Bi-based lead-free perovskite compound Bi2ZnTi1-xMnxO6 at x = 0.4. This phase was the same as the low-temperature phase of the MPB composition of PZT but existed at a much higher temperature. Despite the reduced pseudo c/a ratio of 1.065, which is the same as that of PbTiO3 at room temperature, ionic model calculation based on the Rietveld refinement data indicated the polarization of Bi2ZnTi0.6Mn0.4O6 is 95.8 μC/cm(2). The tilting and significant anisotropic distortion of the octahedron were found to cause the c/a ratio to reduce. Accordingly, the effective piezoelectric constant d33 of Bi2ZnTi0.6Mn0.4O6 thin film was found to be 12 pm/V. PMID:27254112

  5. Investigation on microwave dielectric properties and microstructures of (1−x) LaAlO{sub 3}-xCa{sub 0.2}Sr{sub 0.8}TiO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liangzhu, E-mail: huixinglin@mail.sic.ac.cn [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Lin, Huixing; Zhao, XiangYu; Yao, Xiaogang; Jiang, Shaohu; He, Fei; Li, Botao; Luo, Lan [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 215 Chengbei Road, Jiading, Shanghai 201800 (China)

    2015-11-15

    The structural, microstructural and microwave dielectric properties of (1−x) LaAlO{sub 3}-xCa{sub 0.2}Sr{sub 0.8}TiO{sub 3} ceramics prepared by the conventional solid state ceramic route have been investigated. The formation of solid solutions (1−x) LaAlO{sub 3}-xCa{sub 0.2}Sr{sub 0.8}TiO{sub 3} was confirmed by the X-ray diffraction patterns and the EDS analysis. The lattice parameter, average grain size and dielectric constant (ε{sub r}) increase with increasing amount of Ca{sub 0.2}Sr{sub 0.8}TiO{sub 3} whereas the quality factor (Q × f) decreases. The increasing temperature coefficient of resonant frequency (τ{sub f}) caused by the decreasing tolerance factor with x ranging from 0.3 to 0.7. The τ{sub f} can be tuned near zero at x = 0.5. Specimen with the composition of 0.5LaAlO{sub 3}–0.5Ca{sub 0.2}Sr{sub 0.8}TiO{sub 3} possesses an excellent combination of microwave dielectric properties: ε{sub r} ∼ 32.7, Q × f ∼ 33400 GHz, τ{sub f} ∼ −2.5 ppm/°C. - Highlights: • A novel (1−x) LaAlO{sub 3}-xCa{sub 0.2}Sr{sub 0.8}TiO{sub 3} microwave ceramics were investigated. • The ceramics formed a solid solution confirmed by XRD and EDS. • When x increases, the ceramics Q × f·τ{sub f} decrease, while ε{sub r} increased nonlinearly. • 0.5LaAlO{sub 3}–0.5Ca{sub 0.2}Sr{sub 0.8}TiO{sub 3}ε{sub r} ∼ 32.7, Q × f ∼ 33400 GHz, τ{sub f} ∼ −2.5 ppm/°C.

  6. Tailoring the sealing properties of TiO2-CaO-SrO-B2O3-SiO2 glass-ceramic seals: Thermal properties, chemical compatibility and electrical property

    Science.gov (United States)

    Chen, Jialin; Zou, Qi; Zeng, Fanrong; Wang, Shaorong; Tang, Dian; Yang, Hsiwen; Zhang, Teng

    2013-11-01

    In this paper, TiO2 is added to CaO-SrO-B2O3-SiO2 sealing system to tailor the sealing properties of glass-ceramic seals. The coefficient of thermal expansion (CTE) of quenched glasses and glass-ceramics (held at 750 °C for 100 h) does not change significantly with the addition of TiO2; whereas, the glass stability (ΔTxg = Tx - Tg) decreases systematically with increasing TiO2. The addition of TiO2 accelerates the crystallization of sealing glasses. The formation of Sr-containing phase, e.g., Sr(TiO3), contributes to the improved chemical compatibility as well as the increase in conductivity of sealing glasses (e.g., from 7.9 × 10-8 S cm-1 to 6.9 × 10-5 S cm-1 at 800 °C). In addition, the good bonding is observed at the interface between Cr-containing interconnect (430SS) and glasses containing 4-8 mole % TiO2, held at 750 °C for 100 h.

  7. Effects of Cr2O3 doping on the microstructure and electrical properties of (Ba,Ca)(Zr,Ti)O3 lead-free ceramics

    Science.gov (United States)

    Xia, Xiang; Jiang, Xiangping; Chen, Chao; Jiang, Xingan; Tu, Na; Chen, Yunjing

    2016-06-01

    Lead-free ceramics (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3- x wt.%Cr2O3 (BCZT- xCr) were prepared via the conventional solid-state reaction method. The microstructure and electrical properties of BCZT- xCr samples were systematically studied. XRD and Raman results showed that all samples possessed a single phased perovskite structure and were close to the morphotropic phase boundary (MPB). With the increase of the Cr content, the rhombohedral-tetragonal phase transition temperature ( T R-T) increases slightly, and the Curie temperature ( T C) shifts towards the low temperature side. XPS analysis reveals that Cr3+ and Cr5 + ions co-existed in Cr-doped BCZT ceramics, indicating the different impact on the electrical properties from Cr ions as "acceptor" or "donor". For the x = 0.1 sample, relative high piezoelectric constants d 33 (˜316 pC/N) as well as high Q m (˜554) and low tanδ (˜0.8%) were obtained. In addition, the AC conductivity was also investigated. Hopping charge was considered as the main conduction mechanism at low temperature. As the temperature increases, small polarons and oxygen vacancies conduction played important roles.

  8. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

    Directory of Open Access Journals (Sweden)

    Ashis Tripathy

    2016-07-01

    Full Text Available Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s and recovery (34.27 s, and very low hysteresis (3.2% in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors.

  9. Structural, dielectric and electrocaloric properties in lead-free Zr-doped Ba0.8Ca0.2TiO3 solid solution

    Science.gov (United States)

    Asbani, B.; Gagou, Y.; Dellis, J.-L.; Lahmar, A.; Amjoud, M.; Mezzane, D.; Kutnjak, Z.; El Marssi, M.

    2016-07-01

    We investigate in the present work the additional data points (x=0.02, 0.06 and 0.08) to the previous reported paper (Asbani et al., 2015) [21] that sufficiently enrich to understand the EC properties and underlying phase diagram of the lead-free Ba0.8Ca0.2Ti(1-x)ZrxO3 (xBCTZ) system. X-ray diffraction analysis performed at room temperature, confirms a continuous tetragonal solid solution with P4mm (No. 99) space group that evolved to pseudo-cubic symmetry for the high Zr-content compounds. Ferroelectric and paraelectric behaviors were highlighted using P-E hysteresis data versus temperature. Phase transition was confirmed by dielectric permittivity measurements versus temperature showing a decrease of the Curie temperature when Zr-content increases. From P-E hysteresis recording the electrocaloric temperature change (ΔT) was calculated that ranged in between 0.12 and 0.27 K and the electrocaloric responsivity (ξ) in 0.15 to 0.34×10-6 K·m/V under 7.95 kV/cm applied electric field. The zero-field entropy is compared to electrocaloric isothermal entropy to estimate the extent the EC is being under-driven.

  10. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

  11. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Azrin Shah, Nabila Farhana; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E″/E′: 0.225) and glass transition temperature (Tg: −58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials. PMID:26927116

  12. Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption.

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Bhuyan, Satyanarayan; Azrin Shah, Nabila Farhana; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%-95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors. PMID:27455263

  13. Magnetic properties of SrTiO{sub 3}/Pr{sub 2/3}Ca{sub 1/3}MnO{sub 3} multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Niebieskikwiat, D; Guitarra, S R [Colegio de Ciencias e Ingenieria, Universidad San Francisco de Quito, Quito (Ecuador); Haberkorn, N F; Guimpel, J, E-mail: niebied@usfq.edu.e [Instituto Balseiro - Centro Atomico Bariloche, 8400 Bariloche (Argentina)

    2010-01-01

    Nanoscale ferromagnetic (FM) clusters embedded within insulating (I) layers of the antiferromagnetic Pr{sub 2/3}Ca{sub 1/3}MnO{sub 3} (PCMO) are known to improve the magnetoresistance ratio of FM-I magnetoresistive multilayers. Here, we study the magnetic properties of perovskite superlattices comprised of five PCMO layers of variable thickness t separated by 5nm-thick spacers of SrTiO{sub 3} (STO). Several multilayers (1.5 nm {<=} t {<=} 8 nm) were grown on (001) STO substrates by magnetron sputtering. We show that the magnetic moment of PCMO due to the FM inclusions presents a maximum for t {approx} 3 nm, accompanied by an abrupt increase of coercivity and exchange bias field. The nonmagnetic nature of the neighboring STO layers demonstrates that the observed behavior is not related to any interlayer exchange coupling, but the geometrical matching between layer thickness and FM domain size is the key driver for the enhancement of the FM moment and anisotropy energy. These results open a new door for the optimization of perovskite based spintronic devices.

  14. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors.

    Science.gov (United States)

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Shah, Nabila Farhana Azrin; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx), their chemical reactions and bonding with polydimethylsiloxane (PDMS) were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz) was obtained for the ceramic sintered at 1050 °C (S1050) and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz) film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%), viscoelastic property (tanδ = E″/E': 0.225) and glass transition temperature (Tg: -58.5 °C) were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000%) and its flexible S1050/PDMS composite film (306%) based humidity sensors was found to be at 100 Hz, better than conventional materials. PMID:26927116

  15. Novel magnetic–dielectric composite ceramic obtained from Y{sub 3}Fe{sub 5}O{sub 12} and CaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Paiva, D.V.M. [Grupo de Química de Materiais Avançados (GQMAT), Departamento de Química Analítica e Físico-Química, Universidade Federal do Ceará – UFC, Campus do Pici, CP 12100, CEP 60451-970 Fortaleza, CE (Brazil); Silva, M.A.S. [Laboratório de Telecomunicações e Ciência e Engenharia de Materiais (LOCEM), Departamento de Física, Universidade Federal do Ceará (Brazil); Ribeiro, T.S.; Vasconcelos, I.F. [Laboratório de Magnetismo e Materiais Magnéticos, Departamento de Engenharia Metalúrgica e de Materiais, UFC (Brazil); Sombra, A.S.B.; Góes, J.C. [Laboratório de Telecomunicações e Ciência e Engenharia de Materiais (LOCEM), Departamento de Física, Universidade Federal do Ceará (Brazil); Fechine, P.B.A., E-mail: fechine@ufc.br [Grupo de Química de Materiais Avançados (GQMAT), Departamento de Química Analítica e Físico-Química, Universidade Federal do Ceará – UFC, Campus do Pici, CP 12100, CEP 60451-970 Fortaleza, CE (Brazil)

    2015-09-25

    Highlights: • The density of composites was improved with addition of CTO. • Dielectric permittivity of the composites presented values above the expected. • The composites presented magnetic permeability higher than YIG after 500 MHz. - Abstract: This work investigates the microstructure and magnetic–dielectric properties of the CaTiO{sub 3} (CTO) and Y{sub 3}Fe{sub 5}O{sub 12} (YIG) composite ceramic. CTO is a paramagnetic ceramic, presents a positive value of Resonant Frequency Temperature Coefficients (τ{sub f}) and has high dielectric permittivity (ε{sub r}) while YIG is ferromagnetic, has low ε{sub r} and negative τ{sub f} values. Therefore, it is expected that the composite from these individual phase shows new properties, or a mix of them derived from each component. X-ray powder diffraction (XRPD), Scanning Electron Microscope (SEM), Raman and {sup 57}Fe Mössbauer spectroscopy were performed to confirm the phases of the composites. The dielectric and magnetic properties in Radio-Microwave frequencies were studied by impedance spectroscopy using different geometries. It was observed a densification improvement resulting from the insertion of the CTO in composites and a chemical reaction between YIG and CTO phases. This new composite has potential applications in bulk and thick/thin films devices.

  16. Relativistic fine structure oscillator strengths for Li-like ions C IV - Si XII, S XIV, Ar XVI, Ca XVIII, Ti XX, Cr XXII, and Ni XXVI

    CERN Document Server

    Nahar, S N

    2002-01-01

    Ab initio calculations including relativistic effects employing the Breit-Pauli R-matrix (BPRM) method are reported for fine structure energy levels and oscillator strengths upto n = 10 and 0.leq. l .leq.9 for 15 Li-like ions: C IV, N V, O VI, F VII, Ne VIII, Na IX, Mg X, Al XI, Si XII, S XIV, Ar XVI, Ca XIII, Ti XX, Cr XXII, and Ni XXVI. About one hundred bound fine structure energy levels of total angular momenta, 1/2 .leq. J .leq. 17/2 of even and odd parities, total orbital angular momentum, 0 .leq L .leq. 9 and spin multiplicity (2S+1) = 2, 4 are considered for each ion. The levels provide almost 900 dipole allowed and intercombination bound-bound transitions. The BPRM method enables consideration of large set of transitions with uniform accuracy compared to the best available theoretical methods. The CC eigenfunction expansion for each ion includes the lowest 17 fine structure energy levels of the core configurations 1s^2, 1s2s, 1s2p, 1s3s, 1s3p, and 1s3d. The calculated energies of the ions agree with ...

  17. Effects of adding HfO2 on the microstructure and dielectric properties of giant dielectric constant ceramic CaCu3Ti4O12

    Science.gov (United States)

    Yuan, W. X.; Hark, S. K.

    2010-03-01

    CaCu3Ti4O12 (CCTO), an unusual perovskite-like ceramic, is known for its extraordinarily high (˜10^4) and relatively frequency independent dielectric constant. It has drawn a lot of attention recently because of its potential applications in microelectronics and microwave devices. In this investigation, HfO2 powder was added to a pre-reacted CCTO powder, which was synthesized by a conventional solid-state reaction, at different concentrations from 1 to 70 wt% and the mixture was sintered into disc-shaped ceramic samples. The effects of adding HfO2 on the microstructure and dielectric properties of CCTO ceramics were investigated. In general, we found that the dielectric constant tends to increase with HfO2 addition up to 8 wt% and then decrease with further addition. Moreover, the dielectric loss was also influenced by the addition of HfO2, and a low loss tangent of ˜0.035 was obtained. The ac conductivity, impedance, complex dielectric permittivity and electric modulus graphs were used to analyze the data. These observations were explained on the basis of the internal-barrier-layer capacitor model with Maxwell-Wagner relaxations.

  18. Structural analysis, optical and dielectric function of [Ba0.9Ca0.1](Ti0.9Zr0.1)O3 nanocrystals

    Science.gov (United States)

    Herrera-Pérez, G.; Morales, D.; Paraguay-Delgado, F.; Borja-Urby, R.; Reyes-Rojas, A.; Fuentes-Cobas, L. E.

    2016-09-01

    This work presents the identification of inter-band transitions in the imaginary part of the dielectric function (ɛ2) derived from the Kramers-Kronig analysis for [Ba0.9Ca0.1](Ti0.9Zr0.1)O3 (BCZT) nanocrystals synthesized by the modified Pechini method. The analysis started with the chemical identification of the atoms that conform BCZT in the valence loss energy region of a high energy-resolution of electron energy loss spectroscopy. The indirect band energy (Eg) was determined in the dielectric response function. This result is in agreement with the UV-Vis technique, and it obtained an optical band gap of 3.16 eV. The surface and volume plasmon peaks were observed at 13.1 eV and 26.2 eV, respectively. The X-ray diffraction pattern and the Rietveld refinement data of powders heat treated at 700 °C for 1 h suggest a tetragonal structure with a space group (P4 mm) with the average crystal size of 35 nm. The average particle size was determined by transmission electron microscopy.

  19. Increased fluorescence intensity in CaTiO3:Pr3+ phosphor due to NH3 treatment and Nb Co-doping

    Science.gov (United States)

    Holliday, K. S.; Kohlgruber, T. A.; Tran, I. C.; Åberg, D.; Seeley, Z. M.; Bagge-Hansen, M.; Srivastava, A. M.; Cherepy, N. J.; Payne, S. A.

    2016-10-01

    Development of next generation red phosphors for commercial lighting requires understanding of how increased luminescence is achieved by various treatment strategies. In this work, we compare co-doping with Nb to NH3 treatment of CaTiO3:Pr phosphors to reveal a general mechanism responsible for the increased luminescence. The phosphors were synthesized using standard solid-state synthesis techniques and the fluorescence was characterized for potential use in fluorescent lighting, with 254 nm excitation. The lifetime of the fluorescence was determined and used to identify a change in a trap state by the co-doping of Nb5+ in the phosphor. The oxidation state of the Pr was probed by NEXAFS and revealed that both Nb5+ co-doping and NH3 treatment reduced the number of non-fluorescing Pr4+ centers. Calculations were performed to determine the energetically favorable defects. Vacuum annealing was also used to further probe the nature of the trap state. It was determined that NH3 treatments reduce the number of Pr4+ non-fluorescing centers, while Nb5+ co-doping additionally reduces the number of excess oxygen trap states that quench the fluorescence.

  20. Structure, tribocorrosion and biocide characterization of Ca, P and I containing TiO2 coatings developed by plasma electrolytic oxidation

    Science.gov (United States)

    de Viteri, V. Sáenz; Bayón, R.; Igartua, A.; Barandika, G.; Moreno, J. Esteban; Peremarch, C. Pérez-Jorge; Pérez, M. Martínez

    2016-03-01

    In hip joint implants, in particular in the stems, wear-corrosion effects can accelerate the degradation of the biomaterial. The lack of osseointegration and the risk of contracting implant-associated infections may be other reasons for a premature failure of the implant. In this work, TiO2 coatings have been developed by means of plasma electrolytic oxidation (PEO) technique in order to achieve wear-resistant hard coatings with osseointegration ability and biocide characteristics. During the PEO process, elements that favor cell growth, like Ca and P, were introduced into the coating. With the purpose of providing the coating with antibacterial properties iodine was added like biocide agent. The microstructure and chemical composition of the developed coatings were analyzed in order to see if the surface of the films was suitable for the cell attachment. The effect of wear-corrosion synergy was studied by means of tribocorrosion tests. Finally, the biocide capacity of iodine against Staphylococcus aureus and Staphylococcus epidermidis was analyzed through bacterial adhesion tests. High wear and corrosion resistance was shown in one of the developed coatings. The achieved surface microstructures seem to be appropriate to improve the osseointegration with proper pore size and porosity index. The antibacterial capacity of iodine was confirmed for S. epidermidis.

  1. Multiferroic behavior on nanometric La2/3Ca1/3MnO3 / BaTiO3 bilayers

    Science.gov (United States)

    Prieto, Pedro; Ordoñez, John Edward; Gomez, Maria Elena; Lopera, Wilson

    2014-03-01

    We have deposited bilayers of the FM La2/3Ca1/3MnO3 and FE BaTiO3 as a route to design systems with artificial magnetoelectric coupling on LCMO/BTO/Nb:STO system. We maintain a fixed magnetic layer thickness (tLCMO = 48 nm) and varying the thickness of the ferroelectric layer (tBTO = 20, 50, 100 nm). We analyze the influence of the thickness ratio (tBTO/ tLCMO) in electrical and magnetic properties of manganite. From X-ray diffraction analysis we observed that the samples grew textured. Magnetization and transport measurements indicate a possible multiferroic behavior in the bilayer. We found an increase in the Curie and metal-insulator transition temperature in the bilayer in comparison with those for LCMO (48nm)/STO. Hysteresis loops on bilayers show ferromagnetic behavior. This work has been supported by the ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC'' Colciencias-CENM Research Projects: No. 1106-48-925531 and CI7917-CC 10510 contract 0002-2013 COLCIENCIAS-UNIVALLE.

  2. Synthesis and Characterizations of Novel Ca-Mg-Ti-Fe-Oxides Based Ceramic Nanocrystals and Flexible Film of Polydimethylsiloxane Composite with Improved Mechanical and Dielectric Properties for Sensors

    Directory of Open Access Journals (Sweden)

    Ashis Tripathy

    2016-02-01

    Full Text Available Armalcolite, a rare ceramic mineral and normally found in the lunar earth, was synthesized by solid-state step-sintering. The in situ phase-changed novel ceramic nanocrystals of Ca-Mg-Ti-Fe based oxide (CMTFOx, their chemical reactions and bonding with polydimethylsiloxane (PDMS were determined by X-ray diffraction, infrared spectroscopy, and microscopy. Water absorption of all the CMTFOx was high. The lower dielectric loss tangent value (0.155 at 1 MHz was obtained for the ceramic sintered at 1050 °C (S1050 and it became lowest for the S1050/PDMS nanocomposite (0.002 at 1 MHz film, which was made by spin coating at 3000 rpm. The excellent flexibility (static modulus ≈ 0.27 MPa and elongation > 90%, viscoelastic property (tanδ = E″/E′: 0.225 and glass transition temperature (Tg: −58.5 °C were obtained for S1050/PDMS film. Parallel-plate capacitive and flexible resistive humidity sensors have been developed successfully. The best sensing performance of the present S1050 (3000% and its flexible S1050/PDMS composite film (306% based humidity sensors was found to be at 100 Hz, better than conventional materials.

  3. Microwave-Assisted Synthesis of High Dielectric Constant CaCu3Ti4O12 from Sol-Gel Precursor

    Science.gov (United States)

    Ouyang, Xin; Cao, Peng; Huang, Saifang; Zhang, Weijun; Huang, Zhaohui; Gao, Wei

    2015-07-01

    CaCu3Ti4O12 (CCTO) powders derived from sol-gel precursors were calcined and sintered via microwave radiation. The obtained CCTO powders were compared with that obtained via a conventional heating method. For microwave heating, 89.1 wt.% CCTO was achieved from the sol-gel precursor, after only 17 min at 950°C. In contrast, the conventional calcination method required 3 h to generate 87.6 wt.% CCTO content at 1100°C. In addition, the CCTO powders prepared through 17 min of microwave calcination exhibited a small particle size distribution of D50 = 3.826 μm. It was found that a lengthy hold time of 1 h by microwave sintering is required to obtain a high dielectric constant (3.14 × 103 at 102 Hz) and a reasonably low dielectric loss (0.161) in the sintered CCTO ceramic. Based upon the distinct microstructures, the dielectric responses of the CCTO samples sintered by different methods are attributed to space charge polarization and internal barrier layer capacitor mechanism.

  4. Pulsed SC Proton Linac

    OpenAIRE

    Ouchi, N.; Chishiro, E.; Tsukishima, C.; Mukugi, K.

    2000-01-01

    The superconducting (SC) proton linac is proposed in the JAERI/KEK Joint Project for a high-intensity proton accelerator in the energy region from 400 to 600 MeV. Highly stable fields in the SC cavities are required under the dynamic Lorentz force detuning. A new model describing the dynamic Lorentz detuning has been developed and the validity has been confirmed experimentally. The model has been applied successfully to the rf control simulation of the SC proton linac.

  5. Fabrication of TiO2-strontium loaded CaSiO3/biopolymer coatings with enhanced biocompatibility and corrosion resistance by controlled release of minerals for improved orthopedic applications.

    Science.gov (United States)

    Raj, V; Raj, R Mohan; Sasireka, A; Priya, P

    2016-07-01

    Titanium dioxide (TiO2) arrays were fabricated on Ti alloy by anodization method. Synthesis of CaSiO3 (CS) and various concentrations (1X-5X) of Sr(2+) substitutions in CS coatings on TiO2 substrate was achieved through an electrophoretic deposition technique. Fast release of mineral ions from implant surface produce over dosage effect and it is a potential hazardous factor for osteoblasts. So, in order to prevent the fast release of minerals, biopolymer coating was applied above the composite coatings. The coatings were characterized by FTIR, XRD, FE-SEM and EDX techniques. The mechanical, anticorrosion, antimicrobial properties and biocompatibility of the coatings were evaluated. Studies on the mechanical properties indicate that the addition of Sr(2+) and biopolymer increase the hardness strength of the coatings. The metal ion release from the coatings was studied by ICP-AES. The electrochemical properties of the coatings were studied in Ringer's solution, in which CS-3X/Chi-PVP coating on TiO2 exhibits good anticorrosion property and high resistivity against Escherichia coli and Staphylococcus aureus compared to CS-3X coating on TiO2. In vitro cell experiments indicate that osteoblasts show good adhesion and high growth rates for CS-3X/Chi-PVP coated TiO2 substrate, indicating that the surface cytocompatibility of CS-3X/Chi-PVP coated TiO2 substrate is significantly improved by the controlled release of mineral ions. In conclusion, the surface modification of TiO2/CS-3X/Chi-PVP coated titanium is a potential candidate for implant coating.

  6. Dielectric and Electrical Transport Properties of the Fe~(3+)-doped CaCu_3Ti_4O_(12)%Dielectric and Electrical Transport Properties of the Fe~(3+)-doped CaCu_3Ti_4O_(12)

    Institute of Scientific and Technical Information of China (English)

    Zhi Yang; Yue Zhang; Guang You; Kun Zhang; Rui Xiong; Jing Shi

    2012-01-01

    CaCu(3-x)FexTi4O(12)(x=0, 0.015, 0.03, 0.045, 0.06) ceramics were synthesized by sol-gel method. The electrical conduction and dielectric measurements show that the doping of a very small amount of Fe(3+) ions greatly reduces the low-frequency dielectric constants and leakage, and enhances grain resistivity. For the doped samples, the appearance of the strong low-frequency peaks in the spectra of dielectric loss confirms that the doping of Fe(3+) ions induces the contact-electrode effect on ceramic surface. These great changes of electrical properties may originate from the reduced amount of oxygen vacancies by doping Fe(3+)

  7. Ferroelectric domain structures of epitaxial CaBi2Nb2O9 thin films on single crystalline Nb doped (1 0 0) SrTiO3 substrates

    Science.gov (United States)

    Ahn, Yoonho; Seo, Jeong Dae; Son, Jong Yeog

    2015-07-01

    Epitaxial CaBi2Nb2O9 (CBNO) thin films were deposited on Nb-doped SrTiO3 substrates. The CBNO thin films as a lead-free ferroelectric material exhibit a good ferroelectric property with the remanent polarization of 10.6 μC/cm2. In the fatigue resistance test, the CBNO thin films have no degradation in polarization up to 1×1012 switching cycles, which is applicable for non-volatile ferroelectric random access memories (FeRAMs). Furthermore, piezoresponse force microscopy study (PFM) reveals that the CBNO thin films have larger ferroelectric domain structures than those of PbTiO3 thin films. From the Landau, Lifshiftz, and Kittel's scaling law, it is inferred that the domain wall energy of CBNO thin films is probably very similar to that of the PbTiO3 thin films.

  8. Study of LiF:Mg,Ti and CaSO4:Dy dosimeters TL response to electron beams of 6 MeV applied to radiotherapy using PMMA and solid water phantoms

    International Nuclear Information System (INIS)

    The performance of CaSO4:Dy and LiF:Mg,Ti dosimeters to electron beams applied to radiotherapy was investigated. The TL response of these dosimeters was studied for 6 MeV electron beams using PMMA and Solid Water (SW) phantoms. The dosimeters were previously separated in groups according to their TL individual sensitivities to 60Co gamma-radiation in air under electronic equilibrium conditions. After that, they were irradiated with 6 MeV electron doses of 0.1, 0.5, 1, 5 and 10 Gy using a linear accelerator Clinac 2100C Varian of Hospital Israelita Albert Einstein – HIAE. The electron beam irradiations were performed using a 10 × 10 cm2 field size, 100 cm source-phantom surface distance and the dosimeters were positioned at the depth of maximum dose (1.2 cm). The TL readings were carried out between 24 and 32 h after irradiation using a Harshaw 3500 TL reader. The TL dose–response of both type of dosimeters and phantoms presented linear behavior on the electron dose range from 0.1 to 5 Gy CaSO4:Dy dosimeter is 21 times more sensitive than LiF:Mg,Ti, dosimeter commonly used in clinical dosimetry. The obtained results indicate that the performance of CaSO4:Dy dosimeters is similar to LiF:Mg,Ti dosimeters and this material can be an alternative dosimetric material to be used to clinical electron beams dosimetry.

  9. (La2/5Ba2/5Ca1/5)(Mn(2/5)–NiTi3/5)O3: Rietveld studies, dielectric and magnetic properties of new perovskite-related oxides

    Indian Academy of Sciences (India)

    Pika Jha; Saroj L Samal; Kandalam V Ramanujachary; Samuel E Lofland; Ashok K Ganguli

    2005-10-01

    Oxides of the type (La2/5Ba2/5Ca1/5)(Mn(2/5)–NiTi3/5)O3 (0 ≤ ≤ 0.4) have been synthesized by the ceramic route. All the above oxides have been found to crystallize in the cubic perovskite structure. Rietveld refinement of the Ni-based oxide, (La2/5Ba2/5Ca1/5)(Ni2/5Ti3/5)O3 gave rise to a composition (La0.44Ba0.38Ca0.18) (Ni0.42Ti0.58)O2.85(6) and the refined lattice parameter obtained was 3.9411(2) Å (space group $\\bar{3}$; (2) = 0.026, p = 0.074, p = 0.087). A shift from antiferromagnetic to paramagnetic behaviour is observed with increase in nickel concentration, the Mn-rich phases showing antiferromagnetism around 5 K. There is a systematic decrease in the dielectric constant, and loss tangent with increase in Ni concentration (from = 592 for = 0 to = 78 for = 0.4).

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

    Science.gov (United States)

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

    2016-10-01

    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.

  11. 45Ti extraction using hydroxamate resin

    DEFF Research Database (Denmark)

    Gagnon, K.; Severin, Gregory; Barnhart, T. E.;

    2012-01-01

    As an attractive radionuclide for positron emission tomography, this study explores the extraction and reactivity of 45Ti produced via the 45Sc(p,n)45Ti reaction on a GE PETtrace. Using a small hydroxamate column, we have demonstrated an overall recovery of >50% of 45Ti in ~1 mL of 1M oxalic acid...

  12. A percepção dos gestores operacionais sobre os impactos gerados nos processos de trabalho após a implementação das melhores práticas de governança de TI no TRE/SC

    Directory of Open Access Journals (Sweden)

    Rosangela Klumb

    2014-08-01

    Full Text Available Este estudo objetivou compreender a percepção dos gestores operacionais da Secretaria de Tecnologia da Informação (STI do TRE/SC acerca dos impactos gerados nos processos de trabalho internos do órgão após a implementação das melhores práticas de governança de TI. Em termos metodológicos, trata-se de um estudo de caso descritivo-avaliativo, de abordagem qualitativa no que concerne às características e ao modo de investigação. Como resultados, verificou-se que até março de 2013 foram implementados oito dos 24 processos de governança de TI baseados no modelo Cobit, versão 4.1, definidos como meta do Planejamento Estratégico de TI para 2013. Concluiu-se que a percepção dos gestores é positiva em relação à governança de TI, embora existam algumas falhas, como na comunicação intra e interáreas e na centralização de informações por alguns setores.

  13. Crystal-field study for the orthorhombic Yb{sup 3+} centers in Ca{sub 3}Sc{sub 2}Ge{sub 3}O{sub 12} and Lu{sub 3}Ga{sub 5}O{sub 12} garnets

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hong-Gang, E-mail: kezhouliu@163.com; Zheng, Wen-Chen

    2015-03-25

    Highlights: • Optical and EPR spectra for CaSGG:Yb{sup 3+} and LuGG:Yb{sup 3+} garnets were explained. • The reliability and standardization of fitted CFPs were performed and discussed. • The unavailability of SPM for LuGG:Yb{sup 3+} garnet was found and analyzed briefly. - Abstract: The crystal-field modeling based on superposition model (SPM) for the orthorhombic Yb{sup 3+} centers in Ca{sub 3}Sc{sub 2}Ge{sub 3}O{sub 12} (CaSGG) and Lu{sub 3}Ga{sub 5}O{sub 12} (LuGG) garnets has been employed to explain their recent experimental optical spectroscopy. Furthermore, the electron paramagnetic resonance (EPR) principal g values for orthorhombic Yb{sup 3+} centers in LuGG garnet have been interpreted and the predicted g factors for CaSGG:Yb{sup 3+} garnet are also given. Both calculated optical spectra and EPR g factors for the two Yb{sup 3+}-doped garnets could be regarded as in reasonable agreement with the experimental ones. Two important facts about reliability and standardization of the fitted phenomenological crystal-field parameters (CFPs) have been discussed and the unexpected unavailability of direct parametric modeling by SPM for LuGG:Yb{sup 3+} garnet is also found and analyzed briefly.

  14. Optimization of reaction conditions for the radiolabeling of DOTA and DOTA-peptide with 44m/44Sc and experimental evidence of the feasibility of an in vivo PET generator

    International Nuclear Information System (INIS)

    Introduction: Among the number of generator systems providing radionuclides with decay parameters promising for imaging and treatment applications, there is the 44Ti (T1/2 = 60 years)/44Sc (T1/2 = 3.97 h) generator. This generator provides a longer-lived daughter for extended PET/CT measurements compared to the chemically similar system 68Ge/68Ga. Scandium also exists as 47Sc, a potential therapeutic radionuclide. It is possible to produce 44Sc in a cyclotron using, for example, the 44Ca (d, n) 44Sc nuclear reaction. In that case, the isomeric state 44mSc (T1/2 = 58.6 h) is co-produced and may be used as an in vivo44mSc/44Sc generator. The aim of this study is to evaluate the feasibility of this in vivo44mSc/44Sc generator and to demonstrate that the daughter radionuclide stays inside the chelator after decay of the parent radionuclide. Indeed, the physico-chemical process occurring after the primary radioactive decay (EC, IT, Auger electron …) has prevented in many cases the use of in-vivo generator, because of the post-effect as described in the literature. Methods: The DOTA macrocyclic ligand forms stable complexes with many cations and has been shown to be the most suitable chelating moiety for scandium. Initially, the radiolabeling of DOTA and a DOTA-peptide (DOTATATE) with Sc was performed and optimized as a function of time, pH, metal-to-ligand ratio and temperature. Next, the physico-chemical processes that could occur after the decay (post-effect) were studied. 44mSc(III)-labeled DOTA-peptide was quantitatively adsorbed on a solid phase matrix through a hydrophobic interaction. Elutions were then performed at regular time intervals using a DTPA solution at various concentrations. Finally, the radiolabelled complex stability was studied in serum. Results: Radiolabeling yields ranged from 90% to 99% for metal-to-ligand ratio ranging from 1:10 to 1:500 for DOTA or DOTATATE respectively. The optimum physico-chemical parameters were pH = 4–6, t = 20 min, T

  15. Influence of the sintering temperature on the Sr content in a Ca(1-x-y)CexSryAlzTi(1-z)O3 perovskite (x = 0.04-0.16) co-doped with Ce

    Science.gov (United States)

    Kamel, Nour-el-hayet; Mouheb, Yasmina; Kamel, Ziane; Moudir, Dalila; Aouchiche, Fairouz; Arabi, Azeddine

    2016-08-01

    A Sr-Ce co-doped perovskite, with the chemical formula: Ca(1-x-y)CexSryAlzTi(1-z)O3 (y = 0.04, 0.08, 0.12 and 0.16, x = 0.05) is synthesized by sol-gel process. The influence of the sintering temperature, Ts, on the rate of inserted Sr was investigated at 1223, 1373 and 1473 K. The Sr amount sequestered in the perovskite reaches 85% (y = 0.16, 9.50 wt%) for Ts = 1373 K, giving sintering densities between 3.520 and 4.400. XRD analysis reveals an orthorhombic CaTiO3 structure. The lattice parameters obey to Vegard's law for Ts = 1373 and 1473 K. SEM analysis shows orthorhombic grains of 0.514 μm × 1 μm mean dimensions. MCC1 and MCC2 tests, performed on minerals sintered at 1373 K, indicate that the most durable one is that containing 9.50 wt% Sr. MCC1 test gave 6.998·10-6 g/cm2 d of Sr, and MCC2 2.143·10-4 g/cm2 d of Ce. The temperature favors the Sr dissolution to the detriment of Ce. The Ca dissolution rate reaches 1.002·10-6 to 2.005·10-6 g/cm2 d.

  16. Effect of La2O3-Dopant on Microstructure and Microwave Dielectric Properties of CaO-MgO-Nb2O5-TiO2 System Ceramics

    Institute of Scientific and Technical Information of China (English)

    Wang Hao; Chen Wen; Liu Tao

    2005-01-01

    La2O3-doped CaO-MgO-Nb2O5-TiO2 system ceramics were prepared by solid-state ceramic technique. The microstructure and microwave dielectric properties of CaO-MgO-Nb2O5-TiO2-La2O3 ceramics can be adjusted by varying the amount of La3+ ions. The results show that the replacement of Ca2+ by La3+ at A-site of the ceramics can increase the quality factor Q*f value as well as the temperature coefficient of resonant frequency τf and decrease the dielectric constant εr. With increase of La3+ contents, the dielectric constant decreases from 57 to 35 and Q*f value increases from 33400 GHz to 35000 GHz (at 7.6 GHz). Meanwhile, the temperature coefficient of resonant frequency is improved towards near zero. The dielectric properties of these compounds are related to octahedra tilting due to deficient vacancies at A-site.

  17. Effects of CaBi4Ti4O15 and Rare-earth Oxide Doping on Microstructure and Dielectric Properties of BaTiO3 Ceramics%钛酸铋钙和稀土复合掺杂对BaTiO3陶瓷微结构和介电性能的影响

    Institute of Scientific and Technical Information of China (English)

    王丽娜; 陈国华

    2011-01-01

    研究了稀土及CaBi4Ti4O15(CBT)的复合掺杂对BaTiO3(BT)陶瓷微结构及介电性能的影响.结果表明:单独添加CBT使晶粒细化,促进了陶瓷的烧结致密化,居里温度随着CBT含量的增加(≤0.5mol%)而逐渐移向高温端;当CBT含量由0.3 mol%增加到0.5 mol%时,BT陶瓷的电容量变化率逐渐减小;当CBT含量超过0.5mol%时,电容量变化率又增大.在BaTiO3-CBT(BT-CBT)基础上单独添加1.0mol% LaO3,四方率减小,居里点移向低温端;保持La2O3掺杂量不变,随着CeO2含量的增加,BT-CBT陶瓷的晶胞体积呈现先减小后增大的变化趋势,四方率保持不变;1.0mol% La2O3和0.01mol% CeO2掺杂BT-CBT(0.5 mol%)陶瓷在- 55℃和125℃的电容变化率分别为- 14.78%和- 11.44%,完全符合EIA X7R标准,有望用于X7R型多层陶瓷电容器的制备.

  18. Application of the Functional Theory in studying the adsorption of carbon monoxide on the TiO2 rutile surface of 110, defected surface and the surface modified by some metallic ions

    International Nuclear Information System (INIS)

    Density functional theory (DFT) is used to investigate properties of TiO2 (110) surface with defects and metal-doped TiO2. The results of our calculations of structure of TiO2 surface have been shown in good agreement with those of experiments and other ab-initio calculations. The differences of band structure between TiO2 (110) and TiO2 surface defected show that visible light can excite surface with defects easily. We also investigate density of states (DOS) of metal-doped surface (Li, Ca, Sc, V, Mo, Mn, Fe, Co, Ni) and find that the Mo-doped surface has very small band gap (∼ 0 eV). This surface may have higher photo-chemical activity in visible light. (author)

  19. Low-temperature sintered ZnNb{sub 2}O{sub 6}–CaTiO{sub 3} ceramics with near-zero τ{sub f}

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Mei; Li, Yuxia [Key Laboratory for Robot and Intelligent Technology of Shandong Province, College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590 (China); Dou, Gang, E-mail: dougang521@163.com [Key Laboratory for Robot and Intelligent Technology of Shandong Province, College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590 (China); Gong, Shuping [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-10-15

    The phases, microstructure and microwave dielectric properties of ZnNb{sub 2}O{sub 6}–xCaTiO{sub 3} ceramics with BaCu(B{sub 2}O{sub 5}) glass additions prepared by solid state reaction method were charactered by using X-ray diffraction, Scanning electron microscopy and Advantest network analyzer. The τ{sub f} of ZnNb{sub 2}O{sub 6} was modified to near 0 ppm °C{sup −1} by incorporating CaTiO{sub 3} with opposite τ{sub f} values on the basis of Lichtenecker empirical rule. The microwave dielectric properties of ZnNb{sub 2}O{sub 6}–xCaTiO{sub 3} (x = 8.0 wt.%) samples with BaCu(B{sub 2}O{sub 5}) glass additives sintered in 900–1000 °C were investigated, and the results indicated that the behaviors of the ε{sub r} and Q × f were associated with the sintering temperature and the amount of BaCu(B{sub 2}O{sub 5}) glass. The sintering temperature of the ceramics was reduced to 950 °C from 1175 °C. Addition of 5.0 wt.% BaCu(B{sub 2}O{sub 5}) glass in ZnNb{sub 2}O{sub 6}–xCaTiO{sub 3} (x = 8.0 wt.%) ceramics sintered at 950 °C showed excellent dielectric properties of ε{sub r} = 20.2, Q × f = 14,100 GHz (f = 7.3 GHz) and τ{sub f} = 0 ppm °C{sup −1}. Moreover, the material had a chemical compatibility with silver, which represented a promising candidate materials for low-temperature-co-fired ceramics applications. - Highlights: • The τ{sub f} of ZnNb{sub 2}O{sub 6} was modified to near 0 ppm °C{sup −1} by incorporating CaTiO{sub 3}. • The sintering temperature of ZnNb{sub 2}O{sub 6}–xCaTiO{sub 3} ceramics with BCB was reduced to 950 °C. • The good dielectric properties of ε{sub r} = 20.2, Q × f = 14,100 GHz, τ{sub f} = 0 ppm °C{sup −1} were achieved. • It represented a promising candidate materials for LTCC applications.

  20. Structural properties of CaTi 1-x(Nb 2/3Li 2/3) xO 3-δ (CNLTO) and CaTi 1-x(Nb 1/2Ln 1/2) xO 3 (Ln=Fe (CNFTO), Bi (CNBTO)), modified dielectric ceramics for microwave applications

    Science.gov (United States)

    Costa, R. C. S.; Bruno Costa, A. D. S.; Freire, F. N. A.; Santos, M. R. P.; Almeida, J. S.; Sohn, R. S. T. M.; Sasaki, J. M.; Sombra, A. S. B.

    2009-05-01

    This paper presents an investigation of the structural characteristics of Nb 1/2Bi 1/2 (CNBTO), Nb 1/2Fe 1/2 (CNFTO) and Nb 2/3Li 1/3 (CNLTO) substitution into the B-site of calcium titanate ceramics. The modified CaTiO 3 (CTO) ceramics were prepared by the conventional solid-state method. The compounds were investigated, by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDXS). The X-ray analysis shows that all samples have an orthorhombic structure. The refinement analysis of all samples were also performed and discussed in this paper. For all studied samples, a Raman mode at 805 cm -1 was detected and its intensity increases as the substitution increases. The dielectric permittivity and loss at microwave frequencies (MW) were investigated. The CNLTO phase, present the highest dielectric constant ( k=35.8) at 3.9 GHz with loss (tg α=7×10 -3). The lowest value of k=25.7 ( f=4.8 GHz) and tg α=3×10 -3, was obtained for the CNFTO phase. These measurements confirm the possible use of such material for microwave devices like dielectric resonator antennas.

  1. CaCu{sub 3}Ti{sub 4}O{sub 12} thin films on conductive oxide electrode: A comparative study between chemical and physical vapor deposition routes

    Energy Technology Data Exchange (ETDEWEB)

    Catalano, Maria R.; Malandrino, Graziella [Dipartimento di Scienze Chimiche, Universita di Catania, and INSTM, UdR Catania, Viale A. Doria 6, 95125 Catania (Italy); Bongiorno, Corrado [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy); Toro, Roberta G. [Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Via dei Taurini, 19, 00185 Roma (Italy); Fiorenza, Patrick [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy); Bodeux, Romain [Laboratoire LEMA, UMR 6157 CNRS/CEA, Universite F. Rabelais, Parc de Grandmont, 37200 Tours (France); STMicroelectronics, R and D, Rue Pierre et Marie Curie, 37000 Tours (France); Wolfman, Jerome; Gervais, Monique; Lambert, Cecile Autret; Gervais, Francois [Laboratoire LEMA, UMR 6157 CNRS/CEA, Universite F. Rabelais, Parc de Grandmont, 37200 Tours (France); Lo Nigro, Raffaella, E-mail: raffaella.lonigro@imm.cnr.it [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Dielectrics growth and characterization is one of the most hot topics of materials science and microelectronics. Black-Right-Pointing-Pointer CaCu{sub 3}Ti{sub 4}O{sub 12} perovskite, recently, demonstrated to possess peculiar dielectric properties (Science, 2001, 293, 673-676). Black-Right-Pointing-Pointer To date no deep discussion on the growth processes, properties and perspective of CCTO thin films has been proposed. Black-Right-Pointing-Pointer Our paper is an effective example of interdisciplinarity, since the comparison between PLD and MOCVD has been addressed. Black-Right-Pointing-Pointer Great attention has been paid to CaCu{sub 3}Ti{sub 4}O{sub 12} film/substrate interfaces since dielectric properties are strongly affected. - Abstract: Metal Organic Chemical Vapor Deposition (MOCVD) and Pulsed Laser Deposition (PLD) techniques have been used for the growth of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) thin films on La{sub 0.9}Sr{sub 1.1}NiO{sub 4}/LaAlO{sub 3} (LSNO/LAO) stack. (1 0 0) oriented CCTO films have been formed through both deposition routes and film complete structural and morphological characterizations have been carried out using several techniques (X-ray diffraction, scanning electron microscopy, energy-filtered transmission electron microscopy). The comparative study demonstrated some differences at the CCTO/LSNO interfaces depending on the adopted deposition technique. Chemical/structural modification of the LSNO electrode probably occurred as a function of the different oxygen partial pressure used in the PLD and MOCVD processes.

  2. Transport and transient photovoltaic properties of La{sub 0.4}Ca{sub 0.6}MnO{sub 3}/Nb:SrTiO{sub 3} heterojunction at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ni, Hao [China University of Petroleum, State Key Laboratory of Heavy Oil Processing, Beijing (China); China University of Petroleum, Laboratory of Optical Sensing and Detecting Technology, Beijing (China); Da, Shilian; Zhao, Songqing [China University of Petroleum, Laboratory of Optical Sensing and Detecting Technology, Beijing (China); Zhao, Kun [China University of Petroleum, Laboratory of Optical Sensing and Detecting Technology, Beijing (China); Chinese Academy of Sciences, International Center for Materials Physics, Shenyang (China); Kong, Yu Chau; Wong, Hong Kuen [The Chinese University of Hong Kong, Department of Physics, Hong Kong (China)

    2012-09-15

    We have investigated the electronic transport and transient photovoltaic properties on the La{sub 0.4}Ca{sub 0.6}MnO{sub 3}/Nb(0.05 wt%):SrTiO{sub 3} heterojunction at high temperatures up to 723 K. The temperature-dependent reversal of the rectifying polarity and the decrease of the photosensitivity and response time were observed in the junction with increasing temperature from 293 to 723 K. The mechanism of the energy-band structure evolvement with increasing temperature is presented to understand the experimental results. (orig.)

  3. Structural studies of CaAl{sub 12}O{sub 19}, SrAl{sub 12}O{sub 19}, La{sub 2/3+δ}Al{sub 12-δ}O{sub 19}, and CaAl{sub 10}NiTiO{sub 19} with the hibonite structure; indications of an unusual type of ferroelectricity

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jun; Medina, Elena A.; Sleight, Arthur W.; Subramanian, M.A. [Oregon State University, Corvallis, OR (United States). Dept. of Chemistry; Stalick, Judith K. [National Institute of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research

    2016-08-01

    Various oxides with the hibonite structure were synthesized and structurally analyzed using powder neutron diffraction. The structure of CaAl{sub 12}O{sub 19} at 298 and 11 K shows dipoles that are apparently too dilute to order unless subjected to a suitable electric field. Magnetoplumbites, such as BaFe{sub 12}O{sub 19}, are isostructural with hibonite. These compounds possess ferromagnetic properties, which combined with the electric dipoles may influence multiferroic behavior. Our SrAl{sub 12}O{sub 19} sample showed two distinct hexagonal phases, a major phase with the normal hibonite structure and a minor phase having a closely related structure. Our sample of the defect hibonite phase La{sub 2/3+δ}Al{sub 12-δ}O{sub 19} shows a distinctly higher δ value (0.25) vs. that reported (∝ 0.15) for samples made from the melt. Finally, we used to advantage the negative scattering length of Ti to determine the site occupancies of Ni and Ti in CaAl{sub 10}NiTiO{sub 19}.

  4. Electrical and piezoelectric properties of BiFeO3 thin films grown on SrxCa1−xRuO3-buffered SrTiO3 substrates

    KAUST Repository

    Yao, Yingbang

    2012-06-01

    (001)-oriented BiFeO 3 (BFO) thin films were grown on Sr xCa 1-xRuO 3- (SCRO; x = 1, 0.67, 0.33, 0) buffered SrTiO 3 (001) substrates using pulsed laser deposition. The microstructural, electrical, ferroelectric, and piezoelectric properties of the thin films were considerably affected by the buffer layers. The interface between the BFO films and the SCRO-buffer layer was found to play a dominant role in determining the electrical and piezoelectric behaviors of the films. We found that films grown on SrRuO 3-buffer layers exhibited minimal electrical leakage while films grown on Sr 0.33Ca 0.67RuO 3-buffer layers had the largest piezoelectric response. The origin of this difference is discussed. © 2012 American Institute of Physics.

  5. Homogeneous interface-type resistance switching in Au/La0.67Ca0.33MnO3/SrTiO3/F(:)SnO2heterojunction memories

    Institute of Scientific and Technical Information of China (English)

    Zhang Ting; Ding Ling-Hong; Zhang Wei-Feng

    2012-01-01

    La0.67Ca0.33MnO3 thin films are fabricated on fluorine-doped tin oxide conducting glass substrates by a pulsed laser deposition technique with SrTiO3 used as a buffer layer.The current-voltage characteristics of the heterojunctions exhibit an asymmetric and resistance switching behaviour.A homogeneous interface-type conduction mechanism is also reported using impedance spectroscopy.The spatial homogeneity of the charge carrier distribution leads to fieldinduced potential-barrier change at the Au-La0.67Ca0.33MnO3 interface and a concomitant resistance switching effect.The ratio of the high resistance state to the low resistance state is found to be as high as 1.3 × 104% by simulating the AC electric field.This colossal resistance switching effect will greatly improve the signal-to-noise ratio in nonvolatile memory applications.

  6. Structural, Dielectric and Complex Impedance Spectroscopy Studies of Lead Free Ca0.5 +xNd0.5-x(Ti0.5Fe0.5)O3

    Institute of Scientific and Technical Information of China (English)

    M.R.Shah; A.K.M.Akther Hossain

    2013-01-01

    Structural and various electrical properties of polycrystalline Ca0.5+xNd0.5-x(Ti0.5Fe0.5)O3,prepared by standard solid state reaction technique,were studied.Formation of single phase orthorhombic structure of the compositions was confirmed by X-ray diffraction study.The composition dependence of lattice parameters,density and microstructural study show that they vary significantly with Ca content.The dielectric measurements were carried out at room temperature as function of frequency and composition.The experimental results reveal that the dielectric constant (ε') increases with increasing Ca content.Similar behavior is observed for the dielectric loss (tanδ) and ac conductivity (σac).In complex impedance analysis it is observed that the real part (Z') vs imaginary part (Z") graph exhibits a tendency of formation of a single semicircular arc for each composition of samples.Different parameters were determined by fitting the experimental data in Cole-Cole empirical formula.A dominance of grain boundary resistance (Rgb) is observed.The Rgb decreases with increasing Ca content.The high ε' observed in present samples are suitablefor fabrication of devices.

  7. New tumor-associated antigen SC6 in pancreatic cancer

    Institute of Scientific and Technical Information of China (English)

    Min-Pei Liu; Xiao-Zhong Guo; Jian-Hua Xu; Di Wang; Hong-Yu Li; Zhong-Min Cui; Jia-Jun Zhao; Li-Nan Ren

    2005-01-01

    AIM: To examine the concentration of a new antigen SC6 (SC6-Ag) recognized by monoclonal antibody (MAb)in patients with pancreatic cancer and other malignant or benign diseases and to understand whether SC6-Ag has any clinical significance in distinguishing pancreatic cancer from other gastrointestinal diseases.METHODS: Six hundred and ninety-five serum specimens obtained from 115 patients with pancreatic cancer, 154 patients with digestive cancer and 95patients with non-digestive cancer were used and classified in this study. Serum specimens obtained from 140 patients with benign digestive disease and 89 patients with non-benign digestive disease served as controls. Ascites was tapped from 16 pancreatic cancer patients, 19 hepatic cancer patients, 16 colonic cancer patients, 10 gastric cancer and 6 severe necrotic pancreatitis patients. The samples were quantitated by solid-phase radioimmunoassay. The cut-off values (CV)of 41, 80, and 118 U/mL were used.RESULTS: The average intra- and interassay CV detected by immunoradiometric assay of SC6-Ag was 5.4% and 8.7%, respectively. The sensitivity and specificity were 73.0% and 90.9% respectively. The levels in most malignant and benign cases were within the normal upper limit. Among the 16 pancreatic cancer cases, the concentration of SC6-Ag in ascites was over the normal range in 93.8% patients. There was no significant difference in the concentration of SC6-Ag.Decreased expression of SC6-Ag in sera was significantly related to tumor differentiation. The concentration of SC6-Ag was higher in patients before surgery than after surgery. The specificity of SC6-Ag and CA19-9 was significantly higher than that of ultrasound and computer tomography (CT) in pancreatic cancer patients. Higher positive predictive values were indicated in 92.3% SC6-Ag and 88.5% CA19-9, but lower in 73.8% ultrasound and 76.2% CT.CONCLUSION: The combined test of SC6-Ag and CA19-9 may improve the diagnostic rate of primary cancer. The detection of

  8. Effect of Sb2O3 on the electrical properties of Ba0.9Ca0.1Zr0.1Ti0.9O3 ceramics fabricated using nanocrystals seed

    Science.gov (United States)

    Parjansri, P.; Intatha, U.; Guo, R.; Bhalla, A. S.; Eitssayeam, S.

    2016-09-01

    This work was to investigate the effects of antimony oxide (Sb2O3) on the electrical properties of Ba0.9Ca0.1Zr0.1Ti0.9O3 (BCZT) ceramics and was prepared by adding 1 mol% of BCZT nanocrystals. The seed is nanocrystals of BCZT which was synthesized by the molten salt method. The ceramics powders were prepared by the mixed oxide method using BaCO3, CaCO3, ZrO2, TiO2 as starting materials, and the BCZT seed was added as nanocrystal for induce phase transition. They were doped with x mol% Sb2O3 ( x = 0.0-0.5). Results indicated that all samples show pure perovskite phase. The Sb2O3 enhanced the electrical properties of the ceramic systems. Excellent values of a dielectric constant ( ɛ r) at room temperature ( T r) were 4086 with sample of x = 0.5, and at Curie temperature ( T c) was 15,485 for samples with x = 0.1. The highest remnant polarization ( P r), piezoelectric charge coefficient ( d 33), piezoelectric voltage coefficient ( g 33), electromechanical coefficient for planar mode ( k p) and thickness mode ( k t) values were 6.3 μC/cm2, 346 pC/N, 15.6 × 10-3 Vm/N, 42 and 41 %, respectively, which were obtained for the sample of x = 0.2 mol% Sb.

  9. Ti substituted La{sub 0.67}Ca{sub 0.33}MnO{sub 3} ortho-perovskites: Dominant role of local structure on the electrical transport and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Seetha Lakshmi, L. [XS and CGS, Materials Science Division, Indira Gandhi Centre For Atomic Research, Kalpakkam, 603102 Tamil Nadu (India)], E-mail: slaxmi73@gmail.com; Rawat, R. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452 017, Madhya Pradesh (India); Sridharan, V.; Sastry, V.S. [XS and CGS, Materials Science Division, Indira Gandhi Centre For Atomic Research, Kalpakkam, 603102 Tamil Nadu (India)

    2008-02-15

    We report the effects of local structure on the electrical transport and magnetic properties of La{sub 0.67}Ca{sub 0.33}Mn{sub 1-x}Ti{sub x}O{sub 3} (0{<=}x{<=}0.10) system. Linear increase in the lattice parameters, consequent expansion of unit cell and a monotonic decrease in the relative Mn{sup 4+} concentration with x suggest that Ti{sup 4+} predominantly replaces Mn{sup 4+} in La{sub 0.67}Ca{sub 0.33}Mn{sub 1-x}Ti{sub x}O{sub 3} (x{<=}0.10). The ferromagnetic-metallic ground state modifies to a glassy insulator for x{>=}0.05. No field induced metallic state could be discerned for x=0.10 even at a field of 8 T and at as low a temperature as 4.2 K. Ti substitution significantly enhances the colossal magnetoresistance (CMR) effect. Both the metal to insulator transition temperature and Curie temperature (T{sub c}) decrease at a rate of {approx}26 K/at% up to x=0.05. T{sub c} levels off for higher compositions. Modification of the major carrier concentration (decreased Mn{sup 4+} concentration) seems to be insufficient to account for the observed reduction in the transition temperatures. This in turn emphasizes the significance of local structural effects: systematic elongation of the Mn-O bond lengths and decrease of Mn-O-Mn angles leading to strong suppression of itinerant ferromagnetism and metallicity of the compounds. The additional features in the ac susceptibility, viz., a broad shoulder just below T{sub c} followed by a sharp decrease in the susceptibility signal at low temperatures and a non-closure of MR at zero field as high as {approx}75% at 5 K indicate a frustrated magnetic ground state for x=0.07. Based on the inter-comparison of the structural, electrical transport and magnetic properties of the Mn site substituted La{sub 0.67}Ca{sub 0.33}MnO{sub 3} with iso-valent diamagnetic and paramagnetic ions, we argue that local structural effects have a decisive role to play, compared to the local spin coupling effects, in the ferromagnetic-metallic ground

  10. Structure and ferroelectric studies of (Ba{sub 0.85}Ca{sub 0.15})(Ti{sub 0.9}Zr{sub 0.1})O{sub 3} piezoelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Venkata Ramana, E., E-mail: venkataramanaesk@rediffmail.com [I3N-Aveiro, Department of Physics, University of Aveiro, Aveiro 3810 193 (Portugal); Mahajan, A. [Department of Materials and Ceramics Engineering, University of Aveiro, Aveiro 3810 193 (Portugal); Graça, M.P.F.; Mendiratta, S.K.; Monteiro, J.M.; Valente, M.A. [I3N-Aveiro, Department of Physics, University of Aveiro, Aveiro 3810 193 (Portugal)

    2013-10-15

    Graphical abstract: - Highlights: • (Ba{sub 0.85}Ca{sub 0.15})(Ti{sub 0.9}Zr{sub 0.1})O{sub 3} (BCTZO) ceramic was synthesized by the ceramic method. • In situ XRD and Raman spectra showed the phase transition of BCTZO around 360 K. • The ceramics showed a tunability of 82% at 40 kV cm{sup −1} electric field. • BCTZO exhibited good quality factor of 111 at microwave frequencies. • Piezoforce microscopy studies indicated the switchability of ferroelectric domains. - Abstract: We have synthesized and studied the structural and ferroelectric properties of lead-free 0.5(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3}–0.5Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3} ceramics in the temperature region of its ferroelectric transition. The synthesized material showed high dielectric constant, low loss and good pyroelectric figure of merit. From the temperature dependent X-ray diffraction measurements, we determined the tricritical point to be in the temperature range of 303–400 K. The dielectric measurements indicate a diffuse ferroelectric phase transition (DPT) around 360 K in agreement with the X-ray measurements. We studied the evolution of Raman spectra with temperature to understand the nature of phase transition in BaTiO{sub 3} (BTO) and the BCTZO. The results indicates that the transition of ferroelectric–paraelectric state is not sharp as in the case of BTO and the polar state persists through the paraelectric state. In general, our study indicates that there are ferroelectric domains of nanometer size beyond the commonly defined transition temperature. The observation of local piezoelectric hysteresis loop indicated the existence of intrinsic ferroelectric property of the ceramic at the nanoscale. The ceramics exhibited electric field tunable dielectric properties with a tunability of 82% at an applied DC field of 40 kV cm{sup −1}, low dielectric loss of 0.001 and room temperature pyroelectric coefficient of 6 × 10{sup −8} C cm{sup −2} K{sup −1} and the

  11. SC tuning fork

    CERN Multimedia

    The tuning fork used to modulate the radiofrequency system of the synchro cyclotron (SC) from 1957 to 1973. This piece is an unused spare part. The SC was the 1st accelerator built at CERN. It operated from August 1957 until it was closed down at the end of 1990. In the SC the magnetic field did not change with time, and the particles were accelerated in successive pulses by a radiofrequency voltage of some 20kV which varied in frequency as they spiraled outwards towards the extraction radius. The frequency varied from 30MHz to about 17Mz in each pulse. The tuning fork vibrated at 55MHz in vacuum in an enclosure which formed a variable capacitor in the tuning circuit of the RF system, allowing the RF to vary over the appropriate range to accelerate protons from the centre of the macine up to 600Mev at extraction radius. In operation the tips of the tuning fork blade had an amplitude of movement of over 1 cm. The SC accelerator underwent extensive improvements from 1973 to 1975, including the installation of a...

  12. Biomimetic Multispiked Connecting Ti-Alloy Scaffold Prototype for Entirely-Cementless Resurfacing Arthroplasty Endoprostheses—Exemplary Results of Implantation of the Ca-P Surface-Modified Scaffold Prototypes in Animal Model and Osteoblast Culture Evaluation

    Directory of Open Access Journals (Sweden)

    Ryszard Uklejewski

    2016-06-01

    Full Text Available We present here—designed, manufactured, and tested by our research team—the Ti-alloy prototype of the multispiked connecting scaffold (MSC-Scaffold interfacing the components of resurfacing arthroplasty (RA endoprostheses with bone. The spikes of the MSC-Scaffold prototype mimic the interdigitations of the articular subchondral bone, which is the natural biostructure interfacing the articular cartilage with the periarticular trabecular bone. To enhance the osteoinduction/osteointegration potential of the MSC-Scaffold, the attempts to modify its bone contacting surfaces by the process of electrochemical cathodic deposition of Ca-P was performed with further immersion of the MSC-Scaffold prototypes in SBF in order to transform the amorphous calcium-phosphate coating in hydroxyapatite-like (HA-like coating. The pilot experimental study of biointegration of unmodified and Ca-P surface-modified MSC-Scaffold prototypes was conducted in an animal model (swine and in osteoblast cell culture. On the basis of a microscope-histological method the biointegration was proven by the presence of trabeculae in the interspike spaces of the MSC-Scaffold prototype on longitudinal and cross-sections of bone-implant specimens. The percentage of trabeculae in the area between the spikes of specimen containing Ca-P surface modified scaffold prototype observed in microCT reconstructions of the explanted joints was visibly higher than in the case of unmodified MSC-Scaffold prototypes. Significantly higher Alkaline Phosphatase (ALP activity and the cellular proliferation in the case of Ca-P-modified MSC-Scaffold pre-prototypes, in comparison with unmodified pre-prototypes, was found in osteoblast cell cultures. The obtained results of experimental implantation in an animal model and osteoblast cell culture evaluations of Ca-P surface-modified and non-modified biomimetic MSC-Scaffold prototypes for biomimetic entirely-cementless RA endoprostheses indicate the

  13. High Permittivity (1 - x)Ba(Zr(0.2)Ti(0.8))O3 - x(Ba(0.7)Ca(0.3))TiO3 (x = 0.45) Epitaxial Thin Films with Nanoscale Phase Fluctuations.

    Science.gov (United States)

    Scarisoreanu, Nicu D; Craciun, Floriana; Moldovan, Antoniu; Ion, Valentin; Birjega, Ruxandra; Ghica, Corneliu; Negrea, Raluca F; Dinescu, Maria

    2015-11-01

    Epitaxial (1 - x)Ba(Ti0.8Zr0.2)TiO3 - x(Ba0.7Ca0.3)TiO3, x = 0.45 (BCZT 45), thin films have been deposited on (001) SrTiO3 (STO) and (001/100) SrLaAlO4 (SLAO) substrates by pulsed laser deposition. X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) confirmed the epitaxial growth of the films. A high structural quality has been evidenced for the BCZT/STO films. Geometric phase analysis (GPA) associated with the HRTEM enabled us to obtain microstrain analysis and the in-plane and out-of-plane lattice parameter variation on different areas. Tetragonality ratio fluctuations at nanoscale level which are relevant for the existence of nanodomains have been evidenced on the BCZT/STO films. The in-plane dielectric constant has been measured on interdigital electrodes deposited by lift-off technique on the top of the films. High values of dielectric permittivity (>3000) combined with low dielectric loss (reading domains during topography scanning. PMID:26488203

  14. RECTIFYING AND MAGNETORESISTANCE PROPERTIES OF THE HETEROJUNCTION COMPOSED OF La1/8 Ca7/8 MnO3 AND NB-DOPED SrTiO3%La1/8Ca7/8MnO3/Sr0.95Nb0.05TiO3异质结的整流特性和磁输运性质

    Institute of Scientific and Technical Information of China (English)

    王能语; 周桃飞; 李广

    2007-01-01

    在5%Nb掺杂的SrTiO3衬底上用磁控溅射法外延生长了La1/aCa7/aMnO3薄膜形成异质结,该异质结有类似于传统P-n结的整流特性.磁场下扩散电压减小,当温度低于130 K以下,扩散电压的减小非常明显.这和在此温度以下,La1/8Ca7/aMnO3出现自旋倾斜态密切相关.我们计算出异质结的结电阻和磁致电阻(MR),在不同大小的正负偏压,不同磁场下,都得到负的MR值.我们给出界面附近的La1/8Ca7/8MnO3的能带结构并分析了外加磁场对洪德耦合,Jahn-Teller畸变等机制的作用,来解释该异质结的磁输运行为.结果有助于了解高Ca掺杂锰氧化物异质结的性质.%A heterojunction composed of La1/8 Ca7/8 MnO3 and Nb-doped SrTiO3 was fabricated, which shows rectifying characteristic like conventional p-n junctions. The diffusion voltage is slightly decreased under magnetic fields at high temperature and the effect of magnetic fields is more obvious at temperatures below 130 K, at which spin canting state appears in La1/8Ca7/8MnO3. A negative magnetoresistance was found in this heavily Ca-doped manganite heterojunction due to the majority spin carriers (MASCs) transport at the manganite-titanate interface. An energy band structure employing both Jahn-Teller distortion and Hund's coupling of electrons at the interface is used to explain the MASCs' magneto-transport behaviors.

  15. Cyclotron production of 44Sc: From bench to bedside

    International Nuclear Information System (INIS)

    Introduction: 44Sc, a PET radionuclide, has promising decay characteristics (T1/2 = 3.97 h, Eβ+av = 632 keV) for nuclear imaging and is an attractive alternative to the short-lived 68Ga (T1/2 = 68 min, Eβ+av = 830 keV). The aim of this study was the optimization of the 44Sc production process at an accelerator, allowing its use for preclinical and clinical PET imaging. Methods: 44CaCO3 targets were prepared and irradiated with protons (~ 11 MeV) at a beam current of 50 μA for 90 min. 44Sc was separated from its target material using DGA extraction resin and concentrated using SCX cation exchange resin. Radiolabeling experiments at activities up to 500 MBq and stability tests were performed with DOTANOC by investigating different scavengers, including gentisic acid. Dynamic PET of an AR42J tumor-bearing mouse was performed after injection of 44Sc-DOTANOC. Results: The optimized chemical separation method yielded up to 2 GBq 44Sc of high radionuclidic purity. In the presence of gentisic acid, radiolabeling of 44Sc with DOTANOC was achieved with a radiochemical yield of ~ 99% at high specific activity (10 MBq/nmol) and quantities which would allow clinical application. The dynamic PET images visualized increasing uptake of 44Sc-DOTANOC into AR42J tumors and excretion of radioactivity through the kidneys of the investigated mouse. Conclusions: The concept “from-bench-to-bedside” was clearly demonstrated in this extended study using cyclotron-produced 44Sc. Sufficiently high activities of 44Sc of excellent radionuclidic purity are obtainable for clinical application, by irradiation of enriched calcium at a cyclotron. This work demonstrates a promising basis for introducing 44Sc to clinical routine of nuclear imaging using PET

  16. Structural phase transition in early growth of Bi2Sr2CaCu2O8+x films on SrTiO3 substrates

    Science.gov (United States)

    Abrecht, M.; Ariosa, D.; Onellion, M.; Margaritondo, G.; Pavuna, D.

    2002-02-01

    We used pulsed laser deposition, with a Bi2Sr2CaCu2O8+x target, to grow films ranging from (1/4) to 10 unit cells thick. We studied these films, and reference Bi2Sr2CaCu2O8+x single crystal samples, using angle-integrated photoemission, core level photoemission, and x-ray diffraction. The data indicate that all films exhibit a metallic-like Fermi edge in the photoemission data. More strikingly, a structural phase transition occurs at a nominal Bi2Sr2CaCu2O8+x thickness of approximately one unit cell, converting the precursor Bi2O2.33 highly coherent thin film into a Bi2Sr2CaCu2O8+x structure.

  17. Composition dependence of ferroelectric and piezoelectric properties of epitaxial (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} thin films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Q.R.; Wang, D.Y., E-mail: dy.wang@unsw.edu.au; Luo, B.C.; Ding, R.; Lorenzen, D.L.; Li, S.

    2015-03-15

    Highlights: • Epitaxial (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT–xBCT) thin films were successfully grown on (0 0 1)-oriented SrTiO{sub 3} (STO) substrates by pulsed laser deposition (PLD). • Both structural and physical properties of BZT–xBCT thin films exhibited strong composition dependence. • An MPB-like behaviour was found at around x = 0.5 with highest dielectric, ferroelectric and piezoelectric properties. • The piezoelectric coefficients of our BZT–0.5BCT thin films were in upper range of the existing piezoelectric thin film materials. - Abstract: Lead-free (1 − x)Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}–x(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT–xBCT) (x = 0.3, 0.4, 0.5, 0.6, 0.7) thin films were deposited on SrRuO{sub 3} (SRO)-electroded (0 0 1)-oriented SrTiO{sub 3} (STO) single crystal substrates by pulsed laser deposition (PLD). X-ray diffraction and selected area electron diffraction (SAED) patterns verified epitaxial growth for all the thin films. High ferroelectric activities were evidenced by the well-defined polarization-electric field hysteresis loops. Both structural and physical properties of the thin films demonstrated a strong composition dependence and an MPB-like behaviour was found at around x = 0.5, which is in agreement with that of its bulk counterparts. The superior ferroelectric and piezoelectric responses were attained at x = 0.5 with remanent polarization P{sub r} of 17.8 μC/cm{sup 2} and piezoelectric coefficient d{sub 33} of 100 ± 5 pm/V.

  18. The Influence of Biomimetic Deposition Ca-P Coatings on the Release of Simvastatin from TiO2 Nanotube Array

    Directory of Open Access Journals (Sweden)

    Xie Chunlin

    2016-01-01

    Full Text Available In order to improve the capacity of simvastatin and extend the time of the release of the drug, this experiment adopts bionic-deposition to decorate a layer of octacalcium phosphate (OCP on the face of TiO2 nanotube array,and respectively discusses what are the appropriate parameters of octacalcium phosphate (OCP can be generated. Experiments show that loading a layer of octacalcium phosphate can extend the time of the release of the drug. In addition, the presence of simvastatin on the TiO2 nanotube array will be a certain influence on the morphology of octacalcium phosphate. However, simvastatin can be dissolved into the bionic fluid by using bionic deposition. Therefore, by step concentration soaking and then using this method to load OCP with simvastatin can effectively improve the amount of simvastatin loaded and extend drug release

  19. Magnetic dipole moment of the doubly closed-shell plus one proton nucleus $^{49}$Sc

    CERN Multimedia

    Gaulard, C V; Walters, W; Nishimura, K; Muto, S; Bingham, C R

    It is proposed to measure the magnetic moment of $^{49}$Sc by the Nuclear Magnetic Resonance on Oriented Nuclei (NMR-ON) method using the NICOLE on-line nuclear orientation facility. $^{49}$Sc is the neutron rich, doubly closed-shell, nucleus $^{48}$Ca plus one proton. Results will be used to deduce the effective g-factors in the $^{48}$Ca region with reference to nuclear structure and meson exchange current effects.

  20. Rotation of ferromagnetic clusters induced magnetoresistance in the junction composed of La0.9Ca0.1MnO3+δ and 1 wt.% Nb-doped SrTiO3

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A junction composed of ultrathin La0.gCa0.1MnO3+δ (LCMO) film and 1 wt.% Nb-doped SrTiO3 was fabricated and its magnetoresistance (MR) was studied and compared with LCMO film. It was found that the resistance of the junction has a similar dependence on magnetic field as that of the LCMO film: the curvature of R-H curves is upward above Curie temperature (To) and downward below TC. These behaviours strongly suggest that the rotation of ferromagnetic clusters in manganite also causes MR in the corresponding junction. This MR can be qualitatively understood by the change of the width of the barrier induced by the rotation of ferromagnetic clusters. These results suggest a possibility to obtain junctions with large low-field MR.

  1. Structural and electronic properties of epitaxial YBa2Cu3O7-δ-La0.67Ca0.33MnO3 bilayers grown on SrTiO3 (1 1 0) substrates

    Science.gov (United States)

    Mustafa, L.; Driza, N.; Soltan, S.; Le Tacon, M.; Habermeier, H.-U.; Keimer, B.

    2014-10-01

    Epitaxial bilayers of the high-temperature-superconductor YBa2Cu3O7-δ (YBCO) and the ferromagnetic metal La0.67Ca0.33MnO3 (LCMO) were prepared by pulsed laser deposition on (1 1 0)-oriented SrTiO3 substrates, such that the CuO2 planes of YBCO are perpendicular to the YBCO-LCMO interface. X-ray diffraction and Raman scattering demonstrate complete (1 1 0) orientation of both YBCO and LCMO overlayers. The resistivity and magnetization of the bilayer films are highly anisotropic. The critical temperatures for superconductivity and ferromagnetism as well as the saturation magnetization exhibit modest reductions compared to corresponding bulk values.

  2. Multiferroic and magnetoelectric properties of Ba0.85Ca0.15Zr0.1Ti0.9O3-CoFe2O4 core-shell nanocomposite

    Science.gov (United States)

    Kumar, Ajith S.; Lekha, C. S. Chitra; Vivek, S.; Saravanan, Venkata; Nandakumar, K.; Nair, Swapna S.

    2016-11-01

    Lead-free magnetoelectric (ME) composites with remarkable ME coupling are required for the realization of eco-friendly multifunctional devices. This work demonstrates the ME properties of Ba0.85Ca0.15Zr0.1Ti0.9O3-CoFe2O4 (BCZT-CFO) core-shell composites synthesized via co-sol-gel technique. Room temperature ferroelectric and ferromagnetic characterization have shown that the samples are magnetic and ferroelectric along with an adequate magnetoelectric coupling of 12.15 mV/(cm Oe). The strong dependence of electric parameters on applied magnetic DC bias fields demonstrated in ferroelectric and magnetoelectric measurements provide a framework for the development of potential magnetoelectric devices. Also, the high sensitivity of magnetoelectric coupling towards the applied AC magnetic field can be used for its application in magnetoelectric sensors.

  3. Dynamical plasma study during CaCu{sub 3}Ti{sub 4}O{sub 12} and Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} pulsed laser deposition by local thermodynamic equilibrium modelling

    Energy Technology Data Exchange (ETDEWEB)

    Lagrange, J F; Wolfman, J; Motret, O [Laboratoire d' Electrodynamique des Materiaux Avances (LEMA), UMR 6157 CNRS-CEA, Universite Francois Rabelais de Tours, Faculte des Sciences and Techniques, Parc Grandmont - bat. E-37200 Tours (France); Hermann, J [Laboratoire Lasers, Plasmas et Procedes Photoniques (LP3), UMR 6182 CNRS, Universite Aix-Marseille II, 163 Avenue de luminy, C. 917-13288 Marseille (France)

    2010-07-21

    We performed space- and time-resolved plasma diagnostics during pulsed laser deposition of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) and Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} (BSTO) thin films. A KrF excimer laser irradiation at 248 nm with 25 ns pulse duration irradiates targets with a fluence varying from 1 to 2 J cm{sup -2} under an oxygen pressure varying from 5 to 30 Pa. The plasma is shown to be optically thick and strongly non-uniform during the early expansion stage and the resonance lines Ca II 393 and 396 nm are strongly self-reversed during this time. Plasma temperature, electron density and relative elemental concentrations were obtained by comparing the experimental emission spectra with the spectral radiance computed for a non-uniform plasma in local thermal equilibrium. In this way, it was possible to evaluate very low concentrations of pollutants present in irradiated samples.

  4. Magneto-transport properties of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction

    Indian Academy of Sciences (India)

    P Raychaudhuri; C Mitra; K Dorr; K H Muller; G Kobernik; R Pinto

    2002-05-01

    Hole-doped rare-earth manganite La0.7Ca0.3MnO3 and the electron-doped manganite La0.7Ce0.3MnO3 both show a metal–insulator transition around 250 K associated with a ferromagnetic transition and colossal magnetoresistance. In an earlier publication we have reported the rectifying characteristic of La0.7Ca0.3MnO3/SrTiO3/La0.7Ce0.3MnO3 tunnel junction at room temperature, showing that it is possible to fabricate a diode out of the polaronic insulator regime of doped manganites. Here we report the magneto-transport properties of such a tunnel junction above and below the metal–insulator transition. We show, from the large positive magnetoresistance of the tunnel junction at low temperature, that La0.7Ce0.3MnO3 could be a minority spin carrier ferromagnet. The implication of this observation is discussed.

  5. Microstructure of epitaxial La0.7Ca0.3MnO3 thin films grown on LaAlO3 and SrTiO3

    International Nuclear Information System (INIS)

    Epitaxial La0.7Ca0.3MnO3 (LCMO) thin films of a thickness ∼170 nm were grown on (001) LaAlO3 (LAO) and (001) SrTiO3 (STO) substrates by pulsed laser deposition. Transmission electron microscopy and associated techniques have been applied to investigate the microstructures introduced by lattice mismatch that are responsible for the observed differences in properties between these two films. Numerous secondary phase rods were observed in both films. For the LCMO/LAO film, Ca-deficient secondary-phase rods originated in the film after a thickness of about 25 nm and were found to be responsible for relieving in-plane compressive stress during the island growth. In the case of STO substrate, however, almost all of secondary-phase rods initiated at the film-substrate interface. The lattice mismatch between LCMO and STO is relaxed into regions of good coherent fit separated by such secondary phases, possibly resulting from interfacial reaction. The two types of substrates lead to the formation of two different crystallographic domain structures in the LCMO films. The film on LAO exhibits an almost pure [110] out-of-plane texture with 90 degree sign domains in plane. In contrast, the film grown on STO consists of mixed domains of [001] and [110] orientations and is dominated by [001] texture. (c) 2000 American Institute of Physics

  6. Correlative characterization of primary Al{sub 3}(Sc,Zr) phase in an Al–Zn–Mg based alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, J.H., E-mail: jie-hua.li@hotmail.com [Institute of Casting Research, Montanuniversität Leoben, A-8700 Leoben (Austria); Wiessner, M. [Materials Center Leoben Forschung GmbH, A-8700 Leoben (Austria); Albu, M. [Institute for Electron Microscopy and Nanoanalysis, Graz University of Technology, Center for Electron Microscopy (Austria); Wurster, S. [Department of Materials Physics, Montanuniversität Leoben, Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences, A-8700 Leoben (Austria); Sartory, B. [Materials Center Leoben Forschung GmbH, A-8700 Leoben (Austria); Hofer, F. [Institute for Electron Microscopy and Nanoanalysis, Graz University of Technology, Center for Electron Microscopy (Austria); Schumacher, P. [Institute of Casting Research, Montanuniversität Leoben, A-8700 Leoben (Austria); Austrian Foundry Research Institute, A-8700 Leoben (Austria)

    2015-04-15

    Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al{sub 3}(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al{sub 3}(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al{sub 3}(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al{sub 3}(Sc,Zr) phases. Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al{sub 3}(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al{sub 3}(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al{sub 3}(Sc,Zr) particle enhances the heterogeneous nucleation of Al{sub 3}(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al{sub 3}(Sc,Zr) phases were observed within the α-Al matrix. • A layer by layer growth within primary Al{sub 3}(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al{sub 3}(Sc,Zr)

  7. Correlative characterization of primary Al3(Sc,Zr) phase in an Al–Zn–Mg based alloy

    International Nuclear Information System (INIS)

    Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al3(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al3(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al3(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al3(Sc,Zr) phases. Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al3(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al3(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al3Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al3(Sc,Zr) particle enhances the heterogeneous nucleation of Al3(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al3(Sc,Zr) phases were observed within the α-Al matrix. • A layer by layer growth within primary Al3(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al3Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al3(Sc,Zr)

  8. Evaluation of the thermoluminescent detector answers of CaSO{sub 4}:Dy, LiF:Mg,Ti and micro LiF:Mg,Ti in photon clinical beams dosimetry using water simulator; Avaliacao da resposta de detectores termoluminescentes de CaSO4:Dy, LiF:Mg,Ti e microLiF:Mg,Ti na dosimetria de feixes clinicos de fotons utilizando simulador de agua

    Energy Technology Data Exchange (ETDEWEB)

    Matsushima, Luciana C.; Veneziani, Glauco R.; Campos, Leticia L., E-mail: lmatsushima@usp.b, E-mail: veneziani@ipen.b, E-mail: lcrodri@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (GMR/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Gerencia de Metrologia das Radiacoes; Sakuraba, Roberto K.; Cruz, Jose C. da, E-mail: rsakuraba@einstein.b, E-mail: jccruz@einstein.b [Sociedade Beneficente Israelita Brasileira, Sao Paulo, SP (Brazil). Hospital Albert Einstein (HAE)

    2011-10-26

    This paper perform the comparative study of thermoluminescent answer of calcium sulfate dosemeter doped with dysprosium (DaSO{sub 4}:Dy) produced by the IPEN, Sao Paulo, with answer of lithium fluoride dosemeters doped with magnesium and titanium (LiF:Mg, Ti) in the dosimetry of clinical beams of photons (6 and 15 MV) by using water simulator object. Dose-answer curves were obtained for gamma radiation of cobalt-60 in the air and in conditions of electronic equilibrium (plate of PMMA), and clinical photons of CLINAC model 2100C accelerators of the two evaluated hospitals: Hospital das Clinicas of the Faculty of Medicine of Sao Paulo university and Hospital Albert Einstein. It was also evaluated the sensitivity and reproduction of the three dosemeters

  9. Mechanisms Responsible for the Large Piezoelectricity at the Tetragonal-Orthorhombic Phase Boundary of (1-x)BaZr0.2Ti0.8O3-xBa0.7Ca0.3TiO3 System.

    Science.gov (United States)

    Yang, Tao; Ke, Xiaoqin; Wang, Yunzhi

    2016-01-01

    Recently it was found that in the lead-free (1-x)BaZr0.2Ti0.8O3-xBa0.7Ca0.3TiO3 (BZT-xBCT) system, the highest piezoelectric d33 coefficient appears at the tetragonal (T) - orthorhombic (O) phase boundary rather than the O - rhombohedral (R) phase boundary, but the physical origin of it is still unclear. In this work we construct the phase diagram of the BZT-xBCT system using a generic sixth-order Landau free energy polynomial and calculate the energy barrier (EB) for direct domain switching between two variants of the stable low-symmetry ferroelectric phase. We find that the EB at the T-O phase boundary is lower than that at the O-R phase boundary and EB may serve as a rigorous quantitative measure of the degree of polarization anisotropy through Landau potential. The calculations may shed some light on the physical origin of the highest piezoelectric coefficients as well as the softest elastic compliance at the T-O phase boundary observed in experiments. PMID:27633664

  10. Mechanisms Responsible for the Large Piezoelectricity at the Tetragonal-Orthorhombic Phase Boundary of (1-x)BaZr0.2Ti0.8O3-xBa0.7Ca0.3TiO3 System

    Science.gov (United States)

    Yang, Tao; Ke, Xiaoqin; Wang, Yunzhi

    2016-09-01

    Recently it was found that in the lead-free (1-x)BaZr0.2Ti0.8O3-xBa0.7Ca0.3TiO3 (BZT-xBCT) system, the highest piezoelectric d33 coefficient appears at the tetragonal (T) – orthorhombic (O) phase boundary rather than the O – rhombohedral (R) phase boundary, but the physical origin of it is still unclear. In this work we construct the phase diagram of the BZT-xBCT system using a generic sixth-order Landau free energy polynomial and calculate the energy barrier (EB) for direct domain switching between two variants of the stable low-symmetry ferroelectric phase. We find that the EB at the T-O phase boundary is lower than that at the O-R phase boundary and EB may serve as a rigorous quantitative measure of the degree of polarization anisotropy through Landau potential. The calculations may shed some light on the physical origin of the highest piezoelectric coefficients as well as the softest elastic compliance at the T-O phase boundary observed in experiments.

  11. Mechanisms Responsible for the Large Piezoelectricity at the Tetragonal-Orthorhombic Phase Boundary of (1-x)BaZr0.2Ti0.8O3-xBa0.7Ca0.3TiO3 System.

    Science.gov (United States)

    Yang, Tao; Ke, Xiaoqin; Wang, Yunzhi

    2016-09-16

    Recently it was found that in the lead-free (1-x)BaZr0.2Ti0.8O3-xBa0.7Ca0.3TiO3 (BZT-xBCT) system, the highest piezoelectric d33 coefficient appears at the tetragonal (T) - orthorhombic (O) phase boundary rather than the O - rhombohedral (R) phase boundary, but the physical origin of it is still unclear. In this work we construct the phase diagram of the BZT-xBCT system using a generic sixth-order Landau free energy polynomial and calculate the energy barrier (EB) for direct domain switching between two variants of the stable low-symmetry ferroelectric phase. We find that the EB at the T-O phase boundary is lower than that at the O-R phase boundary and EB may serve as a rigorous quantitative measure of the degree of polarization anisotropy through Landau potential. The calculations may shed some light on the physical origin of the highest piezoelectric coefficients as well as the softest elastic compliance at the T-O phase boundary observed in experiments.

  12. 溶胶-凝胶法制备Ca10(PO4)6(OH)2/TiO2复合涂层及其在模拟生理体液中的行为%HAP/TiO2 Composite Films: Preparation, Characterisation and Their Behaviors in Simulated Body Fluid

    Institute of Scientific and Technical Information of China (English)

    苏冰; 于旭东; 郭连峰; 王成焘

    2005-01-01

    The composite films consisting of hydroxyapatite (HAP) submicron particles embedded in the gel composed of the titania nanoparticles were prepared on commercial Ti6A14V plates with titania buffer layer obtained by a spin-coating technique. The films were calcined in air at various temperatures, and the bioactivities of the films were investigated by immersing them in acellular simulated body fliud (SBF). X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), Field emission-scanning electron microscopy(FESEM) and Energy dispersive X-ray (EDS) analysis were employed to investigate the phase formation and structure of the films before and after immersion, and the variations of Ca and P contents in SBF were measured by Inductively Coupled Plasma Spectroscopy(ICP). The results show that the as-prepared films were dense, homogeneous, all well-crystallized, and there was a close interracial bond between the film and the substrate. The characterisatics of the grown layer on the surfaces of the HAP/TiO2 films after immersion in SBF for different periods of time are specially discussed.

  13. Local distortions in La0.7Ca0.3Mn1-bAbO3 (A=Ti and Ga) colossal magnetoresistance samples: Correlations with magnetization and evidence for cluster formation

    International Nuclear Information System (INIS)

    X-ray absorption fine structure (XAFS) measurements as a function of temperature have been carried out at the Mn K edge for La0.7Ca0.3Mn1-xTixO3 and La0.7Ca0.3Mn1-yGayO3 (x and y=0.01 to 0.10) and correlated with transport and magnetization measurements. Most samples exhibit colossal magnetoresistance (CMR) at low temperature. The magnetization data show a concentration dependence: the ferromagnetic phase transition broadens as x or y increases, and both the transition temperature Tc and the saturated magnetization decrease with increasing dopant concentration. The transport measurements show that the resistivity increases as x or y increases, and that the resistivity peak, which we associated with the metal-to-insulator (MI) transition temperature TMI, moves rapidly to lower temperatures with x or y. In contrast to the La1-aCaaMnO3 materials, for which the resistivity peak normally occurs very close to Tc, TMI is usually far below Tc for these cosubstituted materials. The increase in resistivity well below Tc strongly suggests the formation of clusters. We also find that TMI has a much smaller magnetic field dependence than that for La1-aCaaMnO3 CMR materials. The XAFS data show that a non-Debye broadening, associated with polaron formation, also develops as T approaches Tc, as observed for other CMR samples, but the magnitude of this extra broadening, Δσ2, decreases with x or y, with a larger effect for Ti than for Ga. We find that for a given type of dopant, the resistivity peak occurs when σ2 is decreased to a specific value that is essentially independent of concentration and that this corresponds to nearly the same value of the sample magnetization. These results indicate that the addition of either Ga or Ti distorts the local Mn-O environment which likely promotes cluster formation. Measurements of the absorption edge shift as a function of x for these materials do not quite follow the calculated edge positions based on concentrations, possibly suggesting

  14. 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

    Science.gov (United States)

    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.

  15. Investigation of the structural, optical and dielectric properties of highly (1 0 0)-oriented (Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20})TiO{sub 3} thin films on LaNiO{sub 3} bottom electrode

    Energy Technology Data Exchange (ETDEWEB)

    Pontes, D.S.L. [Laboratorio Interdisciplinar de Eletroquimica e Cerâmica, Department of Chemistry, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil); Pontes, F.M., E-mail: fenelon@fc.unesp.br [Department of Chemistry, Universidade Estadual Paulista, P.O. Box 473, 17033-360 Bauru, São Paulo (Brazil); Chiquito, A.J. [NanO LaB, Transporte Eletrônico em Nanoestruturas, Department of Physics, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil); Longo, E. [Laboratorio Interdisciplinar de Eletroquimica e Cerâmica, Department of Chemistry, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905 São Carlos, São Paulo (Brazil); Institute of Chemistry, Universidade Estadual Paulista, Araraquara, São Paulo (Brazil)

    2014-07-01

    Highlights: • Highly (h 0 0) oriented LNO and PCST thin films were grown on LAO(1 0 0) substrate. • PCST/LNO/LAO structure shown classic ferroelectric–paraelectric phase transition. • PCST/LNO/LAO structure shows superior dielectric properties. • PCST/LAO films showed a direct allowed optical transition. - Abstract: Highly (1 0 0)-oriented Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3}/LNO/LAO structure was fabricated using a chemical deposition process via spin-coating technique. XRD revealed that both LNO and Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3} films grown on LAO(1 0 0) substrate and LNO/LAO(1 0 0) structure were crystallized to be highly (h 0 0)-oriented, respectively. AFM images revealed smooth surfaces, spherical-shaped grains and a crack-free surface with a roughness of about 3–7 nm. The tetragonal perovskite phase was confirmed by Raman spectroscopy for Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3}/LNO/LAO and Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3}/LAO structures. The optical transmittance of 340 nm thick Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3} films on a LAO(1 0 0) substrate exhibited an average transmittance above 80% in the wavelength range of 500–1000 nm and an optical band gap E{sub g} of 3.56 and 2.87 eV for the direct and indirect transition processes, respectively. The Au/Pb{sub 0.60}Ca{sub 0.20}Sr{sub 0.20}TiO{sub 3}/LNO/LAO structure has a hysteresis loop with remnant polarization, P{sub r}, of 12 μC/cm{sup 2}, and a coercive field, E{sub c}, of 46 kV/cm for an electric field at 370 kV/cm along with a dielectric constant over 1200.

  16. Monitor of SC beam profiles

    CERN Multimedia

    1977-01-01

    A high-resolution secondary emission grid for the measurement of SC beam profiles. Modern techniques of metal-ceramic bonding, developed for micro-electronics, have been used in its construction. (See Annual Report 1977 p. 105 Fig. 12.)

  17. First coil for the SC

    CERN Multimedia

    CERN PhotoLab

    1955-01-01

    The coils for the SC magnet were stored in the large hangar of the Cointrin Airport (to make sure that they would be available before snow and ice would block the roads and canals from Belgium, where they were built).

  18. Atomic site preferences and its effect on magnetic structure in the intermetallic borides M{sub 2}Fe(Ru{sub 0.8}T{sub 0.2}){sub 5}B{sub 2} (M=Sc, Ti, Zr; T=Ru, Rh, Ir)

    Energy Technology Data Exchange (ETDEWEB)

    Brgoch, Jakoah, E-mail: jrbrgoc@gmail.com [Department of Chemistry, Iowa State University, Ames, IA 50011 (United States); Mahmoud, Yassir A. [Department of Chemistry, Iowa State University, Ames, IA 50011 (United States); Miller, Gordon J., E-mail: gmiller@iastate.edu [Department of Chemistry, Iowa State University, Ames, IA 50011 (United States)

    2012-12-15

    The site preference for a class of intermetallic borides following the general formula M{sub 2}Fe(Ru{sub 0.8}T{sub 0.2}){sub 5}B{sub 2} (M=Sc, Ti, Zr; T=Ru, Rh, Ir), has been explored using ab initio and semi-empirical electronic structure calculations. This intermetallic boride series contains two potential sites, the Wyckoff 2c and 8j sites, for Rh or Ir to replace Ru atoms. Since the 8j site is a nearest neighbor to the magnetically active Fe atom, whereas the 2c site is a next nearest neighbor, the substitution pattern should play an important role in the magnetic structure of these compounds. The substitution preference is analyzed based on the site energy and bond energy terms, both of which arise from a tight-binding evaluation of the electronic band energy, and are known to influence the locations of atoms in extended solids. According to these calculations, the valence electron-rich Rh and Ir atoms prefer to occupy the 8j site, a result also corroborated by experimental evidence. Additionally, substitution of Rh or Ir at the 8j site results in a modification of the magnetic structure that ultimately results in larger local magnetic moment on the Fe atoms. - Graphical abstract: The site preference for electron rich atoms to occupy the 8j (gray) site is identified in these intermetallic borides, while the magnetic structure is modified as a function of the substituted atoms band center. Highlights: Black-Right-Pointing-Pointer We identify the energetics dictating the site preference in a series of intermetallic borides. Black-Right-Pointing-Pointer Establish substitution rules for use in future directed synthetic preparations. Black-Right-Pointing-Pointer Identified changes in magnetic structure that accompany the site preference.

  19. Elastic properties of perovskite ATiO{sub 3} (A = Be, Mg, Ca, Sr, and Ba) and PbBO{sub 3} (B = Ti, Zr, and Hf): First principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Pandech, Narasak; Limpijumnong, Sukit, E-mail: sukit@sut.ac.th [School of Physics and NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); Thailand Center of Excellence in Physics (ThEP Center), Commission on Higher Education, Bangkok 10400 (Thailand); Sarasamak, Kanoknan [College of Nanotechnology, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand)

    2015-05-07

    The mechanical properties of perovskite oxides depend on two metal oxide lattices that are intercalated. This provides an opportunity for separate tuning of hardness, Poisson's ratio (transverse expansion in response to the compression), and shear strength. The elastic constants of series of perovskite oxides were studied by first principles approach. Both A-site and B-site cations were systematically varied in order to see their effects on the elastic parameters. To study the effects of A-site cations, we studied the elastic properties of perovskite ATiO{sub 3} for A being Be, Mg, Ca, Sr, or Ba, one at a time. Similarly, for B-site cations, we studied the elastic properties of PbBO{sub 3} for B being Ti, Zr, or Hf, one at a time. The density functional first principles calculations with local density approximation (LDA) and generalized gradient approximation (GGA) were employed. It is found that the maximum C{sub 11} elastic constant is achieved when the atomic size of the cations at A-site and B-site are comparable. We also found that C{sub 12} elastic constant is sensitive to B-site cations while C{sub 44} elastic constant is more sensitive to A-site cations. Details and explanations for such dependencies are discussed.

  20. Coupling of electric charge and magnetic field via electronic phase separation in (La,Pr,Ca)MnO3/Pb(Mg1/3Nb2/3)O3-PbTiO3 multiferroic heterostructures

    Science.gov (United States)

    Zheng, Ming; Wang, Wei

    2016-04-01

    The electric-field-tunable non-volatile resistivity and ferromagnetism switching in the (La0.5Pr0.5)0.67Ca0.33MnO3 films grown on (111)-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ferroelectric single-crystal substrates have been investigated. By combining the 180° ferroelectric domain switching and in situ X-ray diffraction and resistivity measurements, we identify that this voltage control of order parameters stems from the domain switching-induced accumulation/depletion of charge carriers at the interface rather than induced lattice strain effect. In particular, the polarization-induced charge effect (i.e., ferroelectric field effect) is strongly dependent on the magnetic field. This, together with the charge-modulated magnetoresistance and magnetization, reveals the strong correlation between the electric charge and the magnetic field. Further, we found that this coupling is essentially driven by the electronic phase separation, the relative strength of which could be determined by recording charge-tunability of resistivity [ (Δρ/ρ)c h arg e ] under various magnetic fields. These findings present a potential strategy for elucidating essential physics of perovskite manganites and delivering prototype electronic devices for non-volatile information storage.

  1. Pressure-induced electrical and structural anomalies in Pb{sub 1-x}Ca{sub x}TiO{sub 3} thin films grown at various oxygen pressures by chemical solution route

    Energy Technology Data Exchange (ETDEWEB)

    Pontes, F M; Galhiane, M S; Santos, L S; Rissato, S R [Department of Chemistry, Universidade Estadual Paulista (UNESP), PO Box 473, 17033-360, Bauru, SP (Brazil); Pontes, D S L; Longo, E [Chemistry Institute, Universidade Estadual Paulista (UNESP), PO Box 355, 14801-970 Araraquara, SP (Brazil); Leite, E R [LIEC-CMDMC, Department of Chemistry, UFSCar, Via Washington Luiz, km 235, CP-676, CEP-13565-905, Sao Carlos, SP (Brazil); Chiquito, A J; Pizani, P S [Department of Physics, UFSCar-Via Washington Luiz, km 235, CEP-13565-905, Sao Carlos, SP (Brazil); Jardim, R F [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05315-970 Sao Paulo, SP (Brazil); Escote, M T [Centro de Engenharia, Modelagem e Ciencias Sociais Aplicadas, Universidade Federal do ABC, Rua Catequese, 242, CEP 09090-400, Santo Andre, SP (Brazil)], E-mail: fenelon@fc.unesp.br

    2008-06-07

    Lead calcium titanate (Pb{sub 1-x}Ca{sub x}TiO{sub 3} or PCT) thin films have been thermally treated under different oxygen pressures, 10, 40 and 80 bar, by using the so-called chemical solution deposition method. The structural, morphological, dielectric and ferroelectric properties were characterized by x-ray diffraction, FT-infrared and Raman spectroscopy, atomic force microscopy and polarization-electric-field hysteresis loop measurements. By annealing at a controlled pressure of around 10 and 40 bar, well-crystallized PCT thin films were successfully prepared. For the sample submitted to 80 bar, the x-ray diffraction, Fourier transformed-infrared and Raman data indicated deviation from the tetragonal symmetry. The most interesting feature in the Raman spectra is the occurrence of intense vibrational modes at frequencies of around 747 and 820 cm{sup -1}, whose presence depends strongly on the amount of the pyrochlore phase. In addition, the Raman spectrum indicates the presence of symmetry-breaking disorder, which would be expected for an amorphous (disorder) and mixed pyrochlore-perovskite phase. During the high-pressure annealing process, the crystallinity and the grain size of the annealed film decreased. This process effectively suppressed both the dielectric and ferroelectric behaviour. Ferroelectric hysteresis loop measurements performed on these PCT films exhibited a clear decrease in the remanent polarization with increasing oxygen pressure.

  2. Improved Electrical Properties of Low-Temperature Sintered Cu Doped Ba0.99Ca0.01Zr0.02Ti0.98O3 Ceramics

    Science.gov (United States)

    Zhang, Yong; Sun, Huajun; Chen, Wen

    2016-10-01

    In this study, a series of Ba0.99Ca0.01Zr0.02Ti0.98O3- x mol.% Cu (BCZT- xCu) ceramics were fabricated with a conventional solid state reaction method. The effects of sintering temperature and doping level of Cu ions on the microstructure development and electrical properties were studied systematically. The optimal sintering temperature could be lowered by 200°C compared to pure BCZT ceramics, due to the addition of Cu. Optimized properties were obtained for BCZT-2.0 mol.% Cu ceramics sintered at 1250°C, showing improved ferroelectric properties with a high remnant polarization ( P r = 8.25 μC/cm2) and a low coercive field ( E c = 0.395 kV/mm). Of particular significance is that the dielectric properties were found to show high thermal stability. The dielectric constant ( {ɛr } ) is within the scope of 1900-2350, while the dielectric loss (tan δ) is in the range of 1.15-2.2% within a temperature range of 30-105°C. In general, the BCZT-2.0Cu ceramics mainly display the characteristic of normal ferroelectrics.

  3. In-situ Electric Field-Induced Modulation of Photoluminescence in Pr-doped Ba0.85Ca0.15Ti0.90Zr0.10O3 Lead-Free Ceramics

    Science.gov (United States)

    Sun, Hai Ling; Wu, Xiao; Chung, Tat Hang; Kwok, K. W.

    2016-06-01

    Luminescent materials with dynamic photoluminescence activity have aroused special interest because of their potential widespread applications. One proposed approach of directly and reversibly modulating the photoluminescence emissions is by means of introducing an external electric field in an in-situ and real-time way, which has only been focused on thin films. In this work, we demonstrate that real-time electric field-induced photoluminescence modulation can be realized in a bulk Ba0.85Ca0.15Ti0.90Zr0.10O3 ferroelectric ceramic doped with 0.2 mol% Pr3+, owing to its remarkable polarization reversal and phase evolution near the morphotropic phase boundary. Along with in-situ X-ray diffraction analysis, our results reveal that an applied electric field induces not only typical polarization switching and minor crystal deformation, but also tetragonal-to-rhombohedral phase transformation of the ceramic. The electric field-induced phase transformation is irreversible and engenders dominant effect on photoluminescence emissions as a result of an increase in structural symmetry. After it is completed in a few cycles of electric field, the photoluminescence emissions become governed mainly by the polarization switching, and thus vary reversibly with the modulating electric field. Our results open a promising avenue towards the realization of bulk ceramic-based tunable photoluminescence activity with high repeatability, flexible controllability, and environmental-friendly chemical process.

  4. Investigating the effect of SiO2-TiO 2-CaO-Na 2O-ZnO bioactive glass doped hydroxyapatite: characterisation and structural evaluation.

    Science.gov (United States)

    Yatongchai, Chokchai; Wren, Anthony W; Curran, Declan J; Hampshire, Stuart; Towler, Mark R

    2014-07-01

    The effects of increasing bioactive glass additions, SiO2-TiO2-CaO-Na2O-ZnO up to 25 wt% in increments of 5 wt%, on the physical and mechanical properties of hydroxyapatite (HA) sintered at 900, 1000, 1100 and 1200 °C for 2 h was investigated. Increasing both the glass content and the temperature resulted in increased HA decomposition. This resulted in the formation of a number of bioactive phases. However the presence of the liquidus glass phase did not result in increased densification levels. At 1000 and 1100 °C the additions of 5 wt% glass resulted in a decrease in density which never recovered with increasing glass content. At 1200 °C a cyclic pattern resulted from increasing glass content. There was no direct relationship between strength and density with all samples experiencing no change or a decrease in strength with increasing glass content. Weibull statistics displayed no pattern with increasing glass content. PMID:24748516

  5. Dual-band LTCC antenna based on 0.95Zn2SiO4-0.05CaTiO3 ceramics for GPS/UMTS applications

    Institute of Scientific and Technical Information of China (English)

    窦刚; 李玉霞; 郭梅

    2015-01-01

    In this paper, we present a compact low-temperature co-fired ceramic (LTCC) dual-band antenna by using the elec-tromagnetic coupling effect concept for global positioning system (GPS) and universal mobile telecommunication system (UMTS) applications. The overall dimension of the antenna is 8.6 mm × 13.0 mm × 1.1 mm. It consists of double meander lines and a via hole line. The top meander line operates at the upper band, and the bottom radiating patch is designed for the lower band. The via-hole line is employed to connect the double meander lines. Because of the effect of the coupled line, total dimension of the proposed antenna is greatly reduced. With the 2.5:voltage standing wave ratio (VSWR) impedance bandwidth definition, the lower and upper bands have the bandwidths of 110 MHz and 150 MHz, respectively. The pro-posed antenna is successfully designed, simulated, and analyzed by a high frequency structure simulator (HFSS). And the antenna is manufactured by using the 0.95Zn2SiO4-0.05CaTiO3 ceramics (εr=7.1, tanδ =0.00038) that is prepared by ourselves. The results show that the antenna is compact, efficient, and of near omnidirectional radiation pattern.

  6. In-situ Electric Field-Induced Modulation of Photoluminescence in Pr-doped Ba0.85Ca0.15Ti0.90Zr0.10O3 Lead-Free Ceramics

    Science.gov (United States)

    Sun, Hai Ling; Wu, Xiao; Chung, Tat Hang; Kwok, K. W.

    2016-01-01

    Luminescent materials with dynamic photoluminescence activity have aroused special interest because of their potential widespread applications. One proposed approach of directly and reversibly modulating the photoluminescence emissions is by means of introducing an external electric field in an in-situ and real-time way, which has only been focused on thin films. In this work, we demonstrate that real-time electric field-induced photoluminescence modulation can be realized in a bulk Ba0.85Ca0.15Ti0.90Zr0.10O3 ferroelectric ceramic doped with 0.2 mol% Pr3+, owing to its remarkable polarization reversal and phase evolution near the morphotropic phase boundary. Along with in-situ X-ray diffraction analysis, our results reveal that an applied electric field induces not only typical polarization switching and minor crystal deformation, but also tetragonal-to-rhombohedral phase transformation of the ceramic. The electric field-induced phase transformation is irreversible and engenders dominant effect on photoluminescence emissions as a result of an increase in structural symmetry. After it is completed in a few cycles of electric field, the photoluminescence emissions become governed mainly by the polarization switching, and thus vary reversibly with the modulating electric field. Our results open a promising avenue towards the realization of bulk ceramic-based tunable photoluminescence activity with high repeatability, flexible controllability, and environmental-friendly chemical process. PMID:27339815

  7. Batievaite-(Y), Y2Ca2Ti[Si2O7]2(OH)2(H2O)4, a new mineral from nepheline syenite pegmatite in the Sakharjok massif, Kola Peninsula, Russia

    Science.gov (United States)

    Lyalina, L. M.; Zolotarev, A. A.; Selivanova, E. A.; Savchenko, Ye. E.; Krivovichev, S. V.; Mikhailova, Yu. A.; Kadyrova, G. I.; Zozulya, D. R.

    2016-05-01

    Batievaite-(Y), Y2Ca2Ti[Si2O7]2(OH)2(H2O)4, is a new mineral found in nepheline syenite pegmatite in the Sakharjok alkaline massif, Western Keivy, Kola Peninsula, Russia. The pegmatite mainly consists of nepheline, albite, alkali pyroxenes, amphiboles, biotite and zeolites. Batievaite-(Y) is a late-pegmatitic or hydrothermal mineral associated with meliphanite, fluorite, calcite, zircon, britholite-group minerals, leucophanite, gadolinite-subgroup minerals, titanite, smectites, pyrochlore-group minerals, zirkelite, cerianite-(Ce), rutile, behoite, ilmenite, apatite-group minerals, mimetite, molybdenite, and nickeline. Batievaite-(Y) is pale-cream coloured with white streak and dull, greasy or pearly luster. Its Mohs hardness is 5-5.5. No cleavage or parting was observed. The measured density is 3.45(5) g/cm3. Batievaite-(Y) is optically biaxial positive, α 1.745(5), β 1.747(5), γ 1.752(5) (λ 589 nm), 2V meas. = 60(5)°, 2V calc. = 65°. Batievaite-(Y) is triclinic, space group P-1, a 9.4024(8), b 5.5623(5), c 7.3784(6) Å, α 89.919(2), β 101.408(2), γ 96.621(2)°, V 375.65(6) Å3 and Z = 1. The eight strongest lines of the X-ray powder diffraction pattern [d(Å)(I)(hkl)] are: 2.991(100)(11-2), 7.238(36)(00-1), 3.061(30)(300), 4.350(23)(0-1-1), 9.145(17)(100), 4.042(16)(11-1), 2.819(16)(3-10), 3.745(13)(2-10). The chemical composition determined by electron probe microanalysis (EPMA) is (wt.%): Nb2O5 2.25, TiO2 8.01, ZrO2 2.72, SiO2 29.96, Al2O3 0.56, Fe2O3 0.43, Y2O3 11.45, La2O3 0.22, Ce2O3 0.33, Nd2O3 0.02, Gd2O3 0.07, Dy2O3 0.47, Er2O3 1.07, Tm2O3 0.25, Yb2O3 2.81, Lu2O3 0.45, CaO 24.98, MnO 1.31, MgO 0.01, Na2O 1.13, K2O 0.02, F 2.88, Cl 0.19, H2O 6.75 (determined on the basis of crystal structure data), O = (F,Cl) -1.25, total 97.09 wt.%. The empirical formula based on the EPMA and single-crystal structure analyses is (Y0.81Ca0.65Mn0.15Zr0.12Yb0.11Er0.04Fe3+ 0.04Ce0.02Dy0.02Lu0.02La0.01Tm0.01)Σ2.00((H2O)0.75Ca0.70□0.55)Σ2.00Ca2.00(□0.61Na0.25( H2O

  8. Structural properties of CaTi{sub 1-x}(Nb{sub 2/3}Li{sub 2/3}){sub x}O{sub 3-d}elta (CNLTO) and CaTi{sub 1-x}(Nb{sub 1/2}Ln{sub 1/2}){sub x}O{sub 3} (Ln=Fe (CNFTO), Bi (CNBTO)), modified dielectric ceramics for microwave applications

    Energy Technology Data Exchange (ETDEWEB)

    Costa, R.C.S. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Departamento de Engenharia de Teleinformatica, CP 6007, Universidade Federal do Ceara, CEP 60455-760, Fortaleza, Ceara (Brazil); Bruno Costa, A.D.S. [Departamento de Engenharia de Teleinformatica, CP 6007, Universidade Federal do Ceara, CEP 60455-760, Fortaleza, Ceara (Brazil); Freire, F.N.A.; Santos, M.R.P.; Almeida, J.S.; Sohn, R.S.T.M. [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Sasaki, J.M. [Laboratorio de Raios-X, Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil); Sombra, A.S.B., E-mail: sombra@fisica.ufc.b [Laboratorio de Telecomunicacoes e Ciencia e Engenharia dos Materiais (LOCEM), Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60455-760, Fortaleza, Ceara (Brazil)

    2009-05-01

    This paper presents an investigation of the structural characteristics of Nb{sub 1/2}Bi{sub 1/2} (CNBTO), Nb{sub 1/2}Fe{sub 1/2} (CNFTO) and Nb{sub 2/3}Li{sub 1/3} (CNLTO) substitution into the B-site of calcium titanate ceramics. The modified CaTiO{sub 3} (CTO) ceramics were prepared by the conventional solid-state method. The compounds were investigated, by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDXS). The X-ray analysis shows that all samples have an orthorhombic structure. The refinement analysis of all samples were also performed and discussed in this paper. For all studied samples, a Raman mode at 805 cm{sup -1} was detected and its intensity increases as the substitution increases. The dielectric permittivity and loss at microwave frequencies (MW) were investigated. The CNLTO phase, present the highest dielectric constant (k=35.8) at 3.9 GHz with loss (tg alpha=7x10{sup -3}). The lowest value of k=25.7 (f=4.8 GHz) and tg alpha=3x10{sup -3}, was obtained for the CNFTO phase. These measurements confirm the possible use of such material for microwave devices like dielectric resonator antennas.

  9. Atomistic modeling of ternary additions to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt and Ni-Ti-Hf shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mosca, H.O., E-mail: hmosca@cnea.gov.ar [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, B1650KNA San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Bozzolo, G. [Loyola University Maryland, 4501 N. Charles St., Baltimore, MD 21210 (United States); Grosso, M.F. del [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, B1650KNA San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, CONICET (Argentina)

    2012-08-15

    The behavior of ternary and quaternary additions to NiTi shape memory alloys is investigated using a quantum approximate method for the energetics. Ternary additions X to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt, and Ni-Ti-Hf alloys, for X=Au, Pt, Ir, Os, Re, W, Ta,Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Zn, Cu, Co, Fe, Mn, V, Sc, Si, Al and Mg are considered. Bulk properties such as lattice parameter, energy of formation, and bulk modulus of the B2 alloys are studied for variations due to the presence of one or two simultaneous additives.

  10. Microwave dielectric properties of (1 − x)Mg{sub 0.95}Zn{sub 0.05}TiO{sub 3}–(x)Ca{sub 0.6}La{sub 0.8/3}TiO{sub 3} ceramic composites

    Energy Technology Data Exchange (ETDEWEB)

    Rajput, Shailendra Singh [Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India); Keshri, Sunita, E-mail: s_keshri@bitmesra.ac.in [Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India); Gupta, Vibha Rani [Department of Electronics and Communication Engineering, Birla Institute of Technology, Mesra, Ranchi 835215 (India)

    2013-03-05

    Highlights: ► This report presents the microwave dielectric properties of (1 − x)MZT–(x)CLT samples. ► The 0.79MZT-0.21CLT composite sample shows a nearly zero τ{sub f} ∼ −0.8 ppm/°C. ► A dielectric resonator antenna has been fabricated using 0.79MZT-0.21CLT sample. ► The probe fed DRA provides higher gain as compared to the microstrip line fed DRA. -- Abstract: In this paper the structural and microwave dielectric properties of the (1 − x)(Mg{sub 0.95}Zn{sub 0.05})TiO{sub 3}–(x)(Ca{sub 0.6}La{sub 0.8/3})TiO{sub 3} ceramic composites have been investigated with the variation of x as well as sintering temperature. The grown samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX) spectroscopy analysis. The Rietveld analysis of the XRD data has been carried out for structure refinement of the phases. The relative permittivity (∊{sub r}), quality factor (Q) and temperature coefficient of resonant frequency τ{sub f} of the grown samples have been thoroughly studied. Out of all samples of this series, the sample with x = 0.21 shows excellent dielectric properties with ∊{sub r}∼26.26, Q × f ∼ 60,738 GHz (at 6.44 GHz) and a nearly zero τ{sub f} ∼ −0.8 ppm/°C. Two types of dielectric resonator antennas with different feeding mechanisms have been fabricated using this sample to study their performance. The experimental results have been compared with the simulated results obtained using Ansoft High Frequency Structure Simulator software.

  11. Al-Cu based welding wire with minor Sc-Zr alloying and its application

    Institute of Scientific and Technical Information of China (English)

    尹志民; 郭飞跃; 潘青林; 宋练鹏

    2003-01-01

    A kind of Al-Cu-(Sc, Zr, Mn, Ti, V, B) welding wire was developed by adding minor Sc, Zr, Mn, V, B, and was used for welding 2195 aluminum alloy plate with a thickness of 2 mm. Mechanical properties and microstructure of welding wire and welding joint were studied. The results show that strength coefficient of the welding joint is 0.70 and the weakest area lies in the softened zone of HAZ. It is indicated that this welding wire adding minor Sc, Zr, Mn, V, B is an ideal welding wire for 2195 Al-Li alloy plate. The high strength of the weld comes from grain-refining strengthening and precipitation strengthening of Al2Cu, Al3Sc and Al3Zr.

  12. Quaternary equilibrium diagrams ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}-(CaO, MgO, TiO{sub 2}). A powerful tool for the development of new materials by reaction sintering; Diagramas de equilibrio cuaternarios ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}- (CaO, MgO, TiO{sub 2}). Una poderosa herramienta para el desarrollo de nuevos materiales por sinterizacion reactiva

    Energy Technology Data Exchange (ETDEWEB)

    Moya, J. S.; Bartolome, J. F.; Pena, P.

    2011-07-01

    In this paper we set out, discuss and evaluate the work on Mullite-zirconia composites obtained by reaction sintering led and inspired by Salvador de Aza on the basis of ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}-(CaO, MgO, TiO{sub 2}) multicomponent phase equilibrium diagrams. We analyze their impact on different areas of ceramic science and technology such as refractory grogs, aluminum industry, etc. The possible fields of future applications such as dental prosthesis replacing partially stabilized zirconia materials with rare earths are also reported. (Author) 42 refs.

  13. Instrumental neutron-activation analysis applications in the assessment of Al, Ca, Dy, K, Mg, Na, Ti, and V contents in soils of the adjacent Khamar-Daban mountain range

    International Nuclear Information System (INIS)

    Full text: With consideration of predominating winds in the region, the Baikal Pulp and Paper Complex (BPPC) is likely to be a key source of industrial air emissions on the southern shore of the Baikal Lake to the North-East of the Baikalsk city. About thirty years ago on-going drying of dark coniferous forests growing on the North- Western slopes of the Khamar-Daban Range to the North-East of the Complex was revealed. Numerous biogeocenoses surveys of impaired and drying forests allowed to concluding on the primary impact of BPPC air emissions. The presence of toxic chemicals is reasoned by solid fuel combustion at the BPPC heat and power plant (HPP). Solid fuel burning is known to release a wide range of chemicals, including heavy metals, into the atmospheric air. Their excessive concentrations are also likely to produce negative impact on various ecosystems, including land-based. Indirect retrospective assessment of the regional pollution level is achievable through a survey focused on environment objects that accumulate both major, minor, and trace elements present in industrial air emissions. Topsoil is a more appropriate subject for such surveys. Contaminants are retained in soil for significantly longer time than in other biosphere components - most likely eternally. Soil serves as a mighty absorber of many chemical elements. It retains them in topsoil, which is the most fertile soil layer. As research subjects were used topsoil samples taken on the Khamar-Daban mounts to the North-East of BPPC at a height of about 1200 - 1500 m above sea level in two areas located 11 and 84 km away, respectively. For chemical element content analysis soil samples were taken from topsoil 4 cm thick as an average mixed sample. Mass fractions of 9 chemical elements (Al, Ca, Dy, K, Mg, Mn, Na, Ti and V) were measured by the instrumental neutron activation analysis using short-lived radionuclides. Ampoules with soil samples were irradiated in the thermal column of the IRT

  14. Low-temperature sintering and microwave dielectric properties of Ca[(Li1/3Nb2/3)0.8Ti0.2]3- δ with glass frit added

    Science.gov (United States)

    In, Chi-Seung; Yeo, Dong-Hun; Shin, Hyo-Soon; Nahm, Sahn; Choi, Won-Youl

    2015-04-01

    In accordance with the trend for mobile terminals to be high intensity and to have thinner layers, low temperature co-fired ceramics (LTCC) materials with outstanding dielectric loss characteristics and diverse dielectric constants have been in demand, and the need for high-strength materials that can withstand external shocks has increased. Ca[(Li1/3Nb2/3)1- x Ti x ]O3- δ (CLNT) has a quality factor over 14,000 and τ f ≤ 10 when the dielectric constant is 41 ˜ 46, but its sintering temperature is high at 1150 °C. Therefore, it cannot be used as a LTCC component. This study aimed to lower the sintering temperature to 900 °C by adding a low-melting-point glass such as B2O3·SiO2·BaO and B2O3·SiO2·Al2O3. As the glass content in CLNT was increased from 10 wt% to 20 wt%, the density and the Q·f0 property decreased, and the dielectric constant rose. When B2O3·SiO2·BaO was added to CLNT at 15 wt%, the dielectric constant was found to be 27, the Q·f0 property to be 3470, and the τ f to be -18 ppm/°C. When B2O3·SiO2·Al2O3 was added to CLNT at 10 wt%, the dielectric constant was 20, the Q·f0 property was 3990, and the τ f was -15 ppm/°C. As such, in both cases, excellent dielectric properties were observed.

  15. Dual-band LTCC antenna based on 0.95Zn2SiO4-0.05CaTiO3 ceramics for GPS/UMTS applications

    Science.gov (United States)

    Dou, Gang; Li, Yu-Xia; Guo, Mei

    2015-10-01

    In this paper, we present a compact low-temperature co-fired ceramic (LTCC) dual-band antenna by using the electromagnetic coupling effect concept for global positioning system (GPS) and universal mobile telecommunication system (UMTS) applications. The overall dimension of the antenna is 8.6 mm × 13.0 mm × 1.1 mm. It consists of double meander lines and a via hole line. The top meander line operates at the upper band, and the bottom radiating patch is designed for the lower band. The via-hole line is employed to connect the double meander lines. Because of the effect of the coupled line, total dimension of the proposed antenna is greatly reduced. With the 2.5: voltage standing wave ratio (VSWR) impedance bandwidth definition, the lower and upper bands have the bandwidths of 110 MHz and 150 MHz, respectively. The proposed antenna is successfully designed, simulated, and analyzed by a high frequency structure simulator (HFSS). And the antenna is manufactured by using the 0.95Zn2SiO4-0.05CaTiO3 ceramics (εr = 7.1, tanδ = 0.00038) that is prepared by ourselves. The results show that the antenna is compact, efficient, and of near omnidirectional radiation pattern. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20133718120009), the Natural Science Foundation of Shandong Provence, China (Grant Nos. ZR2013FQ002 and ZR2014FQ006), the China Postdoctoral Science Foundation (Grant No. 2014M551935), the Qingdao Municipality Postdoctoral Science Foundation, China, and the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents, China (Grant Nos. 2013RCJJ042 and 2014RCJJ052).

  16. CaMn0.875Ti0.125O3 as oxygen carrier for chemical-looping combustion with oxygen uncoupling (CLOU)—Experiments in a continuously operating fluidized-bed reactor system

    KAUST Repository

    Rydén, Magnus

    2011-03-01

    Particles of the perovskite material CaMn0.875Ti0.125O3 has been examined as oxygen carrier for chemical-looping with oxygen uncoupling, and for chemical-looping combustion of natural gas, by 70h of experiments in a circulating fluidized-bed reactor system. For the oxygen uncoupling experiments, it was found that the particles released O2 in gas phase at temperatures above 720°C when the fuel reactor was fluidized with CO2. The effect increased with increased temperature, and with the O2 partial pressure in the air reactor. At 950°C, the O2 concentration in the outlet from the fuel reactor was in the order of 4.0vol%, if the particles were oxidized in air. For the chemical-looping combustion experiments the combustion efficiency with standard process parameters was in the order of 95% at 950°C, using 1000kg oxygen carrier per MW natural gas, of which about 30% was located in the fuel reactor. Reducing the fuel flow so that 1900kg oxygen carrier per MW natural gas was used improved the combustion efficiency to roughly 99.8%. The particles retained their physical properties, reactivity with CH4 and ability to release gas-phase O2 reasonably well throughout the testing period and there were no problems with the fluidization or formation of solid carbon in the reactor. X-ray diffraction showed that the particles underwent changes in their phase composition though. © 2010 Elsevier Ltd.

  17. The non-ohmic and dielectric behavior evolution of CaCu{sub 3}Ti{sub 4}O{sub 12} after heat treatments in oxygen-rich atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Qiaoli [College of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou 450011 (China); Li Tao, E-mail: hnlt529@163.com [Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Chen Zhenping; Xue Renzhong; Wang Yongqiang [Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the percent of oxygen at grain boundaries of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the dielectric properties of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can improve the non-ohmic behaviors of CCTO ceramics. Black-Right-Pointing-Pointer Heat-treating in oxygen-rich atmosphere can enhance the potential barrier of CCTO ceramics. Black-Right-Pointing-Pointer We have explained behavior between the permittivity and the non-ohmic characteristics of CCTO ceramics by the Schottky potential barrier theory. - Abstract: CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics pellets were prepared using the solid-state reaction method, and then they were heat-treated at different temperatures in oxygen-rich atmosphere. The effect of heat treatments on the non-ohmic behaviors and dielectric properties were investigated. EDS analysis results indicate that the percent of oxygen at grain boundaries of CCTO ceramics heat-treated in oxygen-rich atmosphere increases markedly with the rise of temperature and approaches saturation state at about 850 Degree-Sign C. The breakdown voltage and nonlinear coefficient also exhibit an increase trend with the rise of temperature. In addition, the calculated results manifest that the height of Schottky potential barrier is closely related to the oxygen content at the grain boundaries. The permittivity and dielectric loss of samples heat-treated present a relatively intense decrease with the rise of temperature. But the permittivity has a behavior just reverse to the non-ohmic characteristics, which can be explained by the Schottky potential barrier theory.

  18. Structure property relationships in the ATi2O4 (A=Na, Ca) family of reduced titanates

    International Nuclear Information System (INIS)

    Reduced titanates in the ATi2O4 (A=Li, Mg) spinel family exhibit a variety of interesting electronic and magnetic properties, most notably superconductivity in the mixed-valence spinel, Li1+x Ti2-x O4. The sodium and calcium analogs, NaTi2O4 and CaTi2O4, each differ in structure, the main features of which are double rutile-type chains composed of edge-sharing TiO6 octahedra. We report for the first time, the properties and band structures of these two materials. XANES spectroscopy at the Ti K-edge was used to probe the titanium valence. The absorption edge position and the pre-edge spectral features observed in the XANES data confirm the assignment of Ti3+ in CaTi2O4 and mixed-valence Ti3+/Ti4+ in NaTi2O4. Temperature-dependent resistivity and magnetic susceptibility studies are consistent with the classification of both NaTi2O4 and CaTi2O4 as small band-gap semiconductors, although changes in the high-temperature magnetic susceptibility of CaTi2O4 suggest a possible insulator-metal transition near 700 K. Band structure calculations agree with the observed electronic properties of these materials and indicate that while Ti-Ti bonding is of minimal importance in NaTi2O4, the titanium atoms in CaTi2O4 are weakly dimerized at room temperature. -- Graphical abstract: Normalized titanium K-edge XANES spectra confirm mixed-valence for NaTi2O4 with an edge energy intermediate between Ti3+ oxides such as CaTi2O4, MgTi2O4 and Ti2O3, and Ti4+ containing oxides such as TiO2

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

    Energy Technology Data Exchange (ETDEWEB)

    Loiseau, P. [Laboratoire de Chimie de la Matiere Condensee de Paris (UMR CNRS 7574), Ecole Nationale Superieure de Chimie de Paris (ENSCP, Chimie-ParisTech), 11 rue Pierre et Marie Curie, 75231 Paris (France); Caurant, D., E-mail: daniel-caurant@chimie-paristech.f [Laboratoire de Chimie de la Matiere Condensee de Paris (UMR CNRS 7574), Ecole Nationale Superieure de Chimie de Paris (ENSCP, Chimie-ParisTech), 11 rue Pierre et Marie Curie, 75231 Paris (France)

    2010-07-01

    Glass-ceramic materials containing zirconolite (nominally CaZrTi{sub 2}O{sub 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{sub 2}-Al{sub 2}O{sub 3}-CaO-ZrO{sub 2}-TiO{sub 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{sub 5} and CaAl{sub 2}Si{sub 2}O{sub 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{sub 2} precipitates in the layer. The crystal growth thermal treatment duration (2-300 h) at high temperature (1050-1200 {sup o}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.

  20. Physical conditions in CaFe interstellar clouds

    OpenAIRE

    Gnacinski, P.; Krogulec, M.

    2007-01-01

    Interstellar clouds that exhibit strong Ca I and Fe I lines were called CaFe clouds. The ionisation equilibrium equations were used to model the column densities of Ca II, Ca I, K I, Na I, Fe I and Ti II in CaFe clouds. The chemical composition of CaFe clouds is that of the Solar System and no depletion of elements onto dust grains is seen. The CaFe clouds have high electron densities n=1 cm^-3 that leads to high column densities of neutral Ca and Fe.

  1. An orange emitting phosphor Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe with pure garnet phase for warm white LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Yaoqing [Engineering Research Center of Advanced Glasses Manufacturing Technology, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China); School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Zhang, Qinghong [Engineering Research Center of Advanced Glasses Manufacturing Technology, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China); Xu, Jiayue [School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418 (China); Li, Yaogang, E-mail: yaogang_li@dhu.edu.cn [Engineering Research Center of Advanced Glasses Manufacturing Technology, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China); Wang, Hongzhi, E-mail: wanghz@dhu.edu.cn [Engineering Research Center of Advanced Glasses Manufacturing Technology, College of Materials Science and Engineering, Donghua University, Shanghai 201620 (China)

    2015-09-15

    A new silicate garnet phosphor, Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe was synthesized by a high temperature solid-state reaction under reductive atmosphere. X-ray diffraction (XRD) showed that the powder was pure garnet phase. The emission and excitation spectrum indicated that the Lu{sub 2−x}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:xCe phosphors could absorb blue light in the spectral range of 400–550 nm efficiently and exhibit bright yellow–orange emission in the range of 520–750 nm. With the increase of Ce{sup 3+} concentration, the emission band of Ce{sup 3+} showed a red shift. Interestingly, the concentration quenching occurred when the Ce{sup 3+} concentration exceeded 4 mol%. The temperature-dependent luminescent properties of the phosphors were discussed and the Lu{sub 1.96}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:0.04Ce phosphors showed good performances in color temperature (2430 K) and potential applications for warm white LEDs. - Graphical Abstract: This image shows that the phosphor of Lu{sub 1.96}CaMg{sub 2}Si{sub 2.9}Ti{sub 0.1}O{sub 12}:0.04Ce can generate a uniform yellow tint under natural light illumination and emit orange–red light when excited by blue light. With a fixed 467 nm emission light, warm white light can be produced by this phosphor, which indicates that the phosphor is potentially applicable in warm white light emitting diodes based on GaN chips. - Highlights: • A new silicate garnet phosphor was synthesized by solid-state method. • Secondary phases can be avoided when a small amount of Si{sup 4+} were replaced by Ti{sup 4+}. • A broad emission band of Ce{sup 3+} in the phosphors was described. • The phosphors are potentially applicable in warm white light emitting diodes.

  2. Search for beta sup - and beta sup -beta sup - decays of sup 4 sup 8 Ca

    CERN Document Server

    Bakalyarov, A; Barabash, A; Briançon, C; Brudanin, V; Egorov, V; Hubert, F; Hubert, P; Kovalik, A; Lebedev, V I; Rukhadze, N I; Stekl, I; Umatov, V; Vylov, T D

    2002-01-01

    A sup 4 sup 8 CaCO sub 3 powder sample containing 20.18 g of sup 4 sup 8 Ca was measured for 797 h with a 400 cm sup 3 low-background HPGe detector. New limits on decays of sup 4 sup 8 Ca were obtained. For single beta transitions to sup 4 sup 8 Sc the limits are equal to 0.71x10 sup 2 sup 0 y, 1.1x10 sup 2 sup 0 y, and 0.82x10 sup 2 sup 0 y for transitions to the ground state, excited 5 sup + and 4 sup + states, respectively. The new limits on double beta decay to excited states of sup 4 sup 8 Ti are equal to 0.47x10 sup 2 sup 0 y, 1.1x10 sup 2 sup 0 y, and 0.90x10 sup 2 sup 0 y for transitions to the first 2 sup + , second 2 sup + and first 0 sup + excited states, respectively. All limits are given at the 90% CL.

  3. Synthesis and properties of Yb:Sc2O3 transparent ceramics

    Institute of Scientific and Technical Information of China (English)

    JIANG Benxue; HU Chen; LI Jiang; KOU Huamin; SHI Yun; LIU Wenbin; PAN Yubai

    2011-01-01

    Yb:Sc2O3 transparent ceramics were fabricated by solid-state reaction and vacuum sintering method.CaO was added as sintering aids by a high energy ball milling.Transparent nearly-fully dense samples were obtained after 1840 ℃ sintering.Using transmitted-light microscope we get the grain sizes are more than 1 00 μm.Using spectrophotometer we get the absorption coefficient centered at 975 nm was 2.65 cm-1.The phosphorescence spectra showed that the line-widths (FWHM) at 975 and 1041 nm were about 4 and 10 nm and the lifetime of Yb ions in Sc2O3 transparent ceramics was about 883 μs.According to the absorption and fluorescence band centers of Yb:Sc2O3 transparent ceramics,the level scheme of Yb3+ ions in Sc2O3 ceramics could be gotten.

  4. Strain dependence of the electronic properties of LaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Moon, S. J. [Hanyang University, Seoul (Korea, Republic of); Kim, Y. S. [Seoul National University, Seoul (Korea, Republic of)

    2014-11-15

    We report on the transport and the core-level X-ray photoemission spectroscopy data of fully strained LaTiO{sub 3} thin films grown on GdScO{sub 3} and SrTiO{sub 3} substrates. We observed that LaTiO{sub 3} thin film grown on GdScO{sub 3} showed insulating behavior but that grown on SrTiO{sub 3} exhibited a metallic character. We found that while the La 4d photoemission spectra of the two films were nearly the same, their Ti 2p and O 1s data revealed a difference. Our results suggest that strain induced changes in the Ti-O bonding play an important role in the electronic properties of LaTiO{sub 3} thin films.

  5. Effect of minor Sc and Zr addition on grain refinement of as-cast AI-Zn-Mg-Cu alloys

    Institute of Scientific and Technical Information of China (English)

    He Yongdong; Zhang Xinming; Cao Zhiqiang

    2009-01-01

    The optical microscopy and scanning electron microscopy as well as energy dispersive spectroscopy were employed to investigate the influence of joint addition of Sc and Zr on grain refinement of AI-Zn-Mg-Cu alloys.Results show that the addition of 0.20% Sc has a little effect on grain refinement because Sc is mainly dissolved into the matrix and hardly any primary Al3Sc particles are precipitated. The alloy with addition of 0.30% Sc and 0.16%Zr has more equiaxed grains than that of others,giving cast grain sizes as fine as 13μm. This is because the Sc substitutes for AI atom in the AI-Zr crystal cell and forms AI-Sc-Zr unit cell,which grows and becomes AI3(Scx,Zr1.x)particle,acting as a nucleus for the formation of a-AI. The addition of 0.04% Ti and 0.008% B makes the grain size drop from 250 μm to 50 μm. Its refinement effect is less than the 13 μm achieved by the alloy including 0.30% Sc and 0.16% Zr.

  6. Midbrain dopamine neurons bidirectionally regulate CA3-CA1 synaptic drive.

    Science.gov (United States)

    Rosen, Zev B; Cheung, Stephanie; Siegelbaum, Steven A

    2015-12-01

    Dopamine (DA) is required for hippocampal-dependent memory and long-term potentiation (LTP) at CA1 Schaffer collateral (SC) synapses. It is therefore surprising that exogenously applied DA has little effect on SC synapses, but suppresses CA1 perforant path (PP) inputs. To examine DA actions under more physiological conditions, we used optogenetics to release DA from ventral tegmental area inputs to hippocampus. Unlike exogenous DA application, optogenetic release of DA caused a bidirectional, activity-dependent modulation of SC synapses, with no effect on PP inputs. Low levels of DA release, simulating tonic DA neuron firing, depressed the SC response through a D4 receptor-dependent enhancement of feedforward inhibition mediated by parvalbumin-expressing interneurons. Higher levels of DA release, simulating phasic firing, increased SC responses through a D1 receptor-dependent enhancement of excitatory transmission. Thus, tonic-phasic transitions in DA neuron firing in response to motivational demands may cause a modulatory switch from inhibition to enhancement of hippocampal information flow.

  7. The temporoammonic input to the hippocampal CA1 region displays distinctly different synaptic plasticity compared to the Schaffer collateral input in vivo: significance for synaptic information processing

    Directory of Open Access Journals (Sweden)

    Ayla eAksoy Aksel

    2013-08-01

    Full Text Available In terms of its sub-regional differentiation, the hippocampal CA1 region receives cortical information directly via the perforant (temporoammonic path (pp-CA1 synapse and indirectly via the tri-synaptic pathway where the last relay station is the Schaffer collateral-CA1 synapse (Sc-CA1 synapse. Research to date on pp-CA1 synapses has been conducted predominantly in vitro and never in awake animals, but these studies hint that information processing at this synapse might be distinct to processing at the Sc-CA1 synapse. Here, we characterized synaptic properties and synaptic plasticity at the pp-CA1 synapse of freely behaving adult rats. We established that field excitatory postsynaptic potentials at the pp-CA1 have longer onset latencies and a shorter time-to-peak compared to the Sc-CA1 synapse. LTP (> 24h was successfully evoked by tetanic afferent stimulation of pp-CA1 synapses. Low frequency stimulation evoked synaptic depression at Sc-CA1 synapses, but did not elicit LTD at pp-CA1 synapses unless the Schaffer collateral afferents to the CA1 region had been severed. Paired-pulse responses also showed significant differences. Our data suggest that synaptic plasticity at the pp-CA1 synapse is distinct from the Sc-CA1 synapse and that this may reflect its specific role in hippocampal information processing.

  8. 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

    Science.gov (United States)

    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.

  9. Influence of Li2CO3 and V2O5 combined additions on the sintering and dielectric properties of Ca0.5Sr0.5TiO3 ceramics prepared from powders synthesized by sol-gel method

    Directory of Open Access Journals (Sweden)

    Nouara Lamrani

    2014-06-01

    Full Text Available In this work, we have studied the influence of lithium carbonate (Li2CO3 associated with the vanadium oxide (V2O5 on sintering and dielectrics properties of Ca0.5Sr0.5TiO3 ceramic materials obtained from nanopowder synthesized by sol-gel method. The nanopowder was obtained by controlled mixing of titanium butoxide dissolved in butanol-2 and acetic acid with a saturated aqueous solution of calcium acetate and strontium carbonate and subsequent drying of the formed gel at 80 °C and calcination at 1100 °C. The synthesized nanopowder was mixed with different amount of additives, and then uniaxally pressed and sintered in air atmosphere at temperature determined by dilatomertic measurements. The pure Ca0.5Sr0.5TiO3 sample obtained by this process required a sintering temperature around 1500 °C. The addition of Li2CO3 combined with V2O5 improved sinterability and caused a shift of dilatimeric shrinkage curve to much lower temperatures. Thus, dense ceramics (98% of theoretical density were obtained at sintering temperature ≤ 1300 °C. The effect of adding Li2CO3-V2O5 on the structure of ceramics and the dielectric properties is discussed and show that type I dielectric properties (linear variation of the permittivity are conserved, but with an increase of dielectric loss.

  10. Electrical and magnetic properties of YBa_2Cu_3O_7-δ / La_2/3Ca_1/3MnO3 bilayers

    Science.gov (United States)

    Pérez, Felio; Saldarriaga, Wilmer; Gross, Katherine; Castro, Luis; Baca, Eval; Gómez, Maria Elena; Prieto, Pedro; Moran, Oswaldo; Hott, Roland

    2004-03-01

    Ferromagnetic /superconducting proximity effect has been a subject of intense research due to the rich variety of effects resulting from the competition between both long-range order phenomena. In this work, we analyze the proximity effect on perosvkite oxide materials. La_2/3Ca_1/3MnO3 (FM)/ YBa_2Cu_3O_7-δ (SC) and YBa_2Cu_3O_7-δ (SC)/ La_2/3Ca_1/3MnO_3(FM) bilayers have been prepared by a DC sputtering technique at high oxygen pressures, on (001) SrTiO3 single-crystal substrates. The crystalline quality and surface morphology of the bilayers were analyzed by x-ray diffraction (XRD) and atomic force microscopy (AFM). Electrical resistance measurements, R(T), were performed from 300 K to 20 K. demonstrating the coexistence of ferromagnetism and superconducting in this system. Transport and magnetic measurements revealed a strong dependence of the superconducting T_C, as well as Curie temperature and magnetization with the thickness of the ferromagnetic layers. Work supported by COLCIENCIAS project No 1106 -05-11458

  11. Soft spin dipole giant resonances in 40Ca

    CERN Document Server

    Stuhl, L; Csatlos, M; Marketin, T; Litvinova, E; Adachi, T; Algora, A; Daeven, J; Estevez, E; Fujita, H; Fujita, Y; Guess, C; Gulyas, J; Hatanaka, K; Hirota, K; Ong, H J; Ishikawa, D; Matsubara, H; Meharchand, R; Molina, F; Okamura, H; Perdikakis, G; Rubio, B; Scholl, C; Suzuki, T; Susoy, G; Tamii, A; Thies, J; Zegers, R; Zenihiro, J

    2013-01-01

    High resolution experimental data has been obtained for the 40,42,44,48Ca(3He,t)Sc charge exchange reaction at 420 MeV beam energy, which favors the spin-isospin excitations. The measured angular distributions were analyzed for each state separately, and the relative spin dipole strength has been extracted for the first time. The low-lying spin-dipole strength distribution in 40Sc shows some interesting periodic gross feature. It resembles to a soft, dumped multi-phonon vibrational band with $\\hbar\\omega$= 1.8 MeV, which might be associated to pairing vibrations around $^{40}$Ca.

  12. 46 CFR 7.70 - Folly Island, SC to Hilton Head Island, SC.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Folly Island, SC to Hilton Head Island, SC. 7.70 Section... BOUNDARY LINES Atlantic Coast § 7.70 Folly Island, SC to Hilton Head Island, SC. (a) A line drawn from the southernmost extremity of Folly Island to latitude 32°35′ N. longitude 79°58.2′ W. (Stono Inlet Lighted...

  13. Bioactivity studies on TiO{sub 2}-bearing Na{sub 2}O–CaO–SiO{sub 2}–B{sub 2}O{sub 3} glasses

    Energy Technology Data Exchange (ETDEWEB)

    Jagan Mohini, G. [Department of Physics, Andhra Loyola College, Vijayawada 520 008, Andhra Pradesh (India); Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522 510, A.P. (India); Sahaya Baskaran, G. [Department of Physics, Andhra Loyola College, Vijayawada 520 008, Andhra Pradesh (India); Ravi Kumar, V. [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522 510, A.P. (India); Piasecki, M. [Institute of Physics, J. Dlugosz University, Al. Armii Krajowej 13/15, Czestochowa (Poland); Veeraiah, N., E-mail: nvr8@rediffmail.com [Department of Physics, Acharya Nagarjuna University, Nagarjuna Nagar 522 510, A.P. (India)

    2015-12-01

    Soda lime silica borate glasses mixed with different concentrations of TiO{sub 2} are synthesized by the melt-quenching technique. As a part of study on bioactivity of these glasses, the samples were immersed in simulated body fluid (SBF) solution for prolonged times (~ 21 days) during which weight loss along with pH measurements is carried out at specific intervals of time. The XRD and SEM analyses of post-immersed samples confirm the formation of crystalline hydroxyapatite layer (HA) on the surface of the samples. To assess the role of TiO{sub 2} on the formation of HA layer and degradability of the samples the spectroscopic studies viz. optical absorption and IR spectral studies on post- and pre-immersed samples have been carried out. The analysis of the results of degradability together with spectroscopic studies as a function of TiO{sub 2} concentration indicated that about 6.0 mol% of TiO{sub 2} is the optimal concentration for achieving better bioactivity of these glasses. The presence of the maximal concentration octahedral titanium ions in this glass that facilitates the formation of HA layer is found to be the reason for such a higher bioactivity. - Highlights: • Soda lime silica borate glasses mixed with TiO{sub 2} are synthesized. • Bioactivity of the glasses is studied by immersing them in SBF solution. • XRD and SEM studies indicated the formation of hydroxyapatite layer on the surface. • Quantum of degradability is the highest in the glasses mixed with 6.0 mol% of TiO{sub 2.} • The results are analyzed using IR and optical absorption studies.

  14. Large electrostrictive effect and bright upconversion luminescence in Er-modified 0.92(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}–0.08(Ba{sub 0.90}Ca{sub 0.10})(Ti{sub 0.92}Sn{sub 0.08})O{sub 3} lead-free ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoli; Wu, Meihua; Diao, Wenxin; Zhang, Bing; Hao, Jigong, E-mail: haojigong@lcu.edu.cn; Xu, Zhijun; Chu, Ruiqing

    2015-10-01

    In this study, a new lead-free luminescent electrostrictive material has been obtained by introducing trivalent Er{sup 3+} as the activator into 0.92(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}–0.08(Ba{sub 0.90}Ca{sub 0.10})(Ti{sub 0.92}Sn{sub 0.08})O{sub 3} (BNT–0.08BCST). A high, purely electrostrictive effect (the electrostrictive coefficient Q{sub 33} reaches up to 0.028 m{sup 4}/C{sup 2}) with exceptionally good fatigue resistance (up to 10{sup 6} cycles) and thermostability (25–140 °C) is obtained in 0.2 mol%Er-modified BNT–0.08BCST ceramics. Besides the excellent electrostrictive properties, Er{sup 3+}-modified BNT–0.08BCST samples exhibit a strong green-red upconversion emission, and the emission intensities are strongly dependent on the doping concentration, which reaches the optimal value as the doping concentration is 0.4 mol%. These results suggest that this kind of material may have potential application as a multifunctional device by integrating its excellent upconversion luminescence and electrostrictive properties.

  15. rotor of the SC rotating condenser

    CERN Multimedia

    1974-01-01

    The rotor of the rotating condenser was installed instead of the tuning fork as the modulating element of the radiofrequency system, when the SC accelerator underwent extensive improvements between 1973 to 1975 (see object AC-025). The SC was the first accelerator built at CERN. It operated from August 1957 until it was closed down at the end of 1990.

  16. Academic Training - Pulsed SC Magnets

    CERN Multimedia

    Françoise Benz

    2006-01-01

    2005-2006 ACADEMIC TRAINING PROGRAMME LECTURE SERIES 2, 3, June 29, 30, 31 May, 1, 2 June 11:00-12:00 - Auditorium, bldg 500 Pulsed SC Magnets by M. Wilson Lecture 1. Introduction to Superconducting Materials Type 1,2 and high temperature superconductors; their critical temperature, field & current density. Persistent screening currents and the critical state model. Lecture 2. Magnetization and AC Loss How screening currents cause irreversible magnetization and hysteresis loops. Field errors caused by screening currents. Flux jumping. The general formulation of ac loss in terms of magnetization. AC losses caused by screening currents. Lecture 3. Twisted Wires and Cables Filamentary composite wires and the losses caused by coupling currents between filaments, the need for twisting. Why we need cables and how the coupling currents in cables contribute more ac loss. Field errors caused by coupling currents. Lecture 4. AC Losses in Magnets, Cooling and Measurement Summary of all loss mech...

  17. Cs3ScCl6

    Directory of Open Access Journals (Sweden)

    Matthew D. Ward

    2014-06-01

    Full Text Available Crystals of tricaesium scandium(III hexachloride were obtained as a side product from the reaction of U, SnCl2, Sc, and S in a CsCl flux at 1073 K. Cs3ScCl6 crystallizes in the Rb3YCl6 structure type. The asymmetric unit comprises three Cs sites, two Sc sites, and six Cl sites, all of which have site symmetry 1, except for the two Sc sites that have site symmetries of 2 and -1, respectively. The structure is composed of isolated [ScCl6]3− octahedra that are surrounded by Cs+ cations. Two Cs+ cations have interactions with eight Cl− anions, while the third has interactions with ten Cl− anions.

  18. Influences of Sr-Incorporated TiO2 Layer on the Photovoltaic Properties of Dye-Sensitized Solar Cells.

    Science.gov (United States)

    Kim, Eun Seong; Kim, Dae-Hwan; Lee, Sang-Ju; Han, Yoon Soo

    2016-03-01

    Effects of a mixed overlayer composed of TiO2 and TiSrO3 on the performance of dye-sensitized solar cells (DSSCs) were investigated. The surface of TiO2 photoelectrode formed on F-doped SnO2 (FTO) was modified by soaking it in a TiCl4:SrCl2 mixed aqueous solution with various molar ratios and then calcining to produce the TiCl4:SrCl2-treated TiO2 photoelectrode (Ti:Sr-TiO2/FTO). The highest power conversion efficiency (PCE) was obtained from DSSC with Ti:Sr(7:3)-TiO2/FTO, which was prepared from the mixed solution with the molar ratio of 7:3 (TiOl4:SrCl2). An enhancement in short-circuit photocurrent (J(sc)) and open-circuit voltage (V(oc)) of DSSC with Ti:Sr(7:3)-TiO2/FTO was achieved, compared to those of the reference device with Ti:Sr(10:0)-TiC2/FTO (i.e., TiO2-coated TiO2/FTO). The incorporation of the mixed overlayer on the nanoporous TiO2 photoelectorde led to an improvement in the electron collection efficiency by a prolonged electron lifetime, thereby increasing the J(sc) value. The increase in V(oc) value of the device with Ti:Sr(7:3)-TiO2/FTO was due to the suppression of the charge recombination between injected electrons and I3(-) ions.

  19. Calciothermic reduction of titanium oxide in molten CaCl2

    Science.gov (United States)

    Suzuki, Ryosuke O.; Inoue, Shuichi

    2003-06-01

    Titanium oxides were reduced to metallic titanium using the liquid calcium floating on the molten CaCl2. A part of Ca dissolved into CaCl2 and reacted with TiO2 settled below CaCl2. The by-product CaO also dissolved by about 20 mol pct into CaCl2, which was effective in reducing the oxygen concentration in the obtained Ti particles. The compositional region in the Ca-CaCl2-CaO system was examined for the less oxygen contamination in Ti and the better handling in leaching. A large amount of the residual calcium oxidized the titanium powder in leaching. The metallic Ti powder less than 1000 mass ppm oxygen could be obtained only for 3.6 ks using 5 to 7 mol pct Ca-CaCl2 at 1173 K. The powder was slightly sintered like sponge, and contained approximately 1500 ppm Ca. The anatase phae, the intermediate product in the refining process of TiO2, could be also supplied as raw material as well as rutile.

  20. SC-FDMA for mobile communications

    CERN Document Server

    Abd El-Samie, Fathi E

    2013-01-01

    SC-FDMA for Mobile Communications examines Single-Carrier Frequency Division Multiple Access (SC-FDMA). Explaining this rapidly evolving system for mobile communications, it describes its advantages and limitations and outlines possible solutions for addressing its current limitations. The book explores the emerging trend of cooperative communication with SC-FDMA and how it can improve the physical layer security. It considers the design of distributed coding schemes and protocols for wireless relay networks where users cooperate to send their data to the destination. Supplying you with the re

  1. Effect of scandium on structure and hardening of Al–Ca eutectic alloys

    International Nuclear Information System (INIS)

    The phase composition, structure and hardening of alloys in the aluminium corner of the Al–Ca–Sc system were studied in the range up to 10% Ca and up to 1% S≿. The experimental study (optical, scanning and transmission electron microscopy with electron-microprobe analysis, differential thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was shown that only phases of the binary systems (Al4Ca and Al3Sc) might be in equilibrium with the aluminium solid solution. It was shown that the (Al) + Al4Ca eutectic had a much finer structure as compared with the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. The influence of the annealing temperature within the range up to 600 °C on the structure and hardness of the Al–Ca–Sc experimental alloys was studied. It was determined that the maximum hardening corresponded to the annealing at 300 °C, which was due to the precipitation of Al3Sc nanoparticles with their further coarsening. With an example of an Al-7.6% Ca-0.3% Sc model experimental alloy, a principal possibility of manufacturing aluminium casting alloys based on the (Al) + Al4Ca eutectic was demonstrated. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of casting. - Highlights: • Al–Ca–Sc phase diagram in aluminum corner. • Formation of Al3Sc nanoparticles in eutectic (Al) + Al4Ca during heating at 300–450 °C. • Hardening and thermal stability of proposed (Al–Ca–Sc) and commercial (Al–Si–Mg, 356 type) eutectic alloys

  2. Production of a 44 Ti target and its cross section of thermal neutron capture

    International Nuclear Information System (INIS)

    A study of the production of a 44 Ti target was carried out aiming the determination of its thermal neutron capture cross-section. With this purpose, the cross-section of the reaction 45 Sc(p,2 n) 44 Ti was determined in the energies 16-, 18-, 20-22- and 45 MeV. The cross-section of the reactions (p,n) 45 Ti, (p,pn) 44m Sc, (p,pn) 44g Sc and (p,p2n)43 Sc were also measured. The results in the low energy region are in good agreement with a previous work by McGee et al. On the other hand, the cross-section at 45 MeV is different from McGee's result and indicates the existence of an abnormal behavior of the excitation function at higher energies. Furthermore, a radiochemical separation method was developed in order to eliminate Sc from the 44 Ti target which was irradiated with neutrons. It was possible to determine an upper limit for the cross-section of the reaction 44 Ti (n, γ) of 4 x 103 b. At last, it is presented a discussion of the results obtained and their possible astrophysical implications. (author)

  3. A Global Record of Surface Earth Oxygenation from Sedimentary V/Sc

    Science.gov (United States)

    Keller, C. B.; Schoene, B.; Johnston, D. T.

    2015-12-01

    One of the simplest methods to investigate changes in oxidation potential in geologic environments is to examine a pair of otherwise similar elements with dramatically different redox chemistry. The first-row transition metals Sc and V represent one such pair, with generally similar mass, radius, and ionization energies up to the trivalent redox state. However, as a d3 transition metal, Sc is limited to a maximum oxidation state of 3+, while d5 vanadium may be further oxidized to form tetravalent and pentavalent ions. Due to the greater incompatibility of pentavalent (relative to trivalent) metal cations in silicate melts, V/Sc ratio has been applied to the silicate rock record as a tracer of magma redox - indicating roughly constant mantle oxygen fugacity over Earth history1,2. As a result, the solid earth represents a boundary condition with constant V/Sc observed over geologic time1. However, oxidation state also affects the weathering, solubility, and coordination behaviour of V and Sc, resulting in a potential redox signal in the sedimentary V/Sc record. We apply the weighted bootstrap resampling approach of [2] to a geochemical dataset of ~87,000 sedimentary whole-rock analyses from the EarthChem portal3. The resulting trends reveal a 4 Gyr record of V/Sc redox chemistry, with the great oxidation event represented as an upward step ca. 2.5 Ga, and Phanerozoic variation suggestive of low oxygen in the early Paleozoic, increasing to twin maxima circa 270 Ma and 130 Ma, remarkably similar to that predicted by the COPSE model4, and broadly congruent with the Phanerozoic biochar record5. Li, Z.-X. A. & Lee, C.-T. A. EPSL 228, 483-493 (2004). Keller, C. B. & Schoene, B. Nature 485, 490-493 (2012). EarthChem Bergman, N. M. Am. J. Science 304, 397-437 (2004). Glasspool, I. J. & Scott, A. C. Nat. Geosci. 3, 627-630 (2010).

  4. The effect of site geometry, Ti content and Ti oxidation state on the Ti K-edge XANES spectrum of synthetic hibonite

    Science.gov (United States)

    Doyle, P. M.; Berry, A. J.; Schofield, P. F.; Mosselmans, J. F. W.

    2016-08-01

    The Al-rich oxide hibonite (CaAl12O19) is modeled to be the second mineral to condense from a gas of solar composition and is found within calcium-aluminum-rich inclusions and the matrix of chondritic meteorites. Both Ti3+ and Ti4+ are reported in meteoritic hibonite, so hibonite has been proposed as a single mineral oxybarometer that could be used to elucidate conditions within the first 0.2 Myrs of the Solar System. Synthetic hibonites with Ti3+/(Ti3+ + Ti4+) (hereafter Ti3+/ΣTi) ranging between 0 and 1 were prepared as matrix-matched standards for meteoritic hibonite. The largest yield of both Ti-free and Ti-bearing hibonite at ∼1300 and ∼1400 °C was obtained by a single sinter under reducing conditions. In situ micro-beam Ti K-edge X-ray absorption near edge structure (XANES) spectra were recorded from the synthetic hibonites, as well as from terrestrial hibonite. Spectral features in the post-crest region were shown to correlate with the Ti4+ content. Furthermore, Ti4+ on the M2 trigonal bipyramidal and the adjoining M4 octahedral sites appears to cause variability in the post-crest region as a function of orientation. For this suite of synthetic hibonites it was observed that the pre-edge peak region is not influenced by orientation, but is controlled by Ti3+/ΣTi, site geometry and/or Ti concentration. In particular, the pre-edge peak intensities reflect Ti coordination environment and distortion of the M4 octahedral site. Therefore, although pre-edge peak intensities have previously been used to determine Ti3+/ΣTi in meteoritic minerals, we excluded use of the pre-edge peak intensities for quantifying Ti valence states in hibonite. The energy of the absorption edge at a normalized intensity of 0.8 (E0.8) and the energy of the minimum between the pre-edge region and the absorption edge (Em1) were found to vary systematically with Ti3+/ΣTi. Ti3+/ΣTi in hibonite as a function of Em1 was modeled by a quadratic function that may be used to quantify Ti3

  5. Ca. 2.7 Ga ferropicritic magmatism: A record of Fe-rich heterogeneities during Neoarchean global mantle melting

    Science.gov (United States)

    Milidragovic, Dejan; Francis, Don

    2016-07-01

    Although terrestrial picritic magmas with FeOTOT ⩾13 wt.% are rare in the geological record, they were relatively common ca. 2.7 Ga during the Neoarchean episode of enhanced global growth of continental crust. Recent evidence that ferropicritic underplating played an important role in the ca. 2.74-2.70 Ga reworking of the Ungava craton provides the impetus for a comparison of ca. 2.7 Ga ferropicrite occurrences in the global Neoarchean magmatic record. In addition to the Fe-rich plutons of the Ungava craton, volumetrically minor ferropicritic flows, pyroclastic deposits, and intrusive rocks form parts of the Neoarchean greenstone belt stratigraphy of the Abitibi, Wawa, Wabigoon and Vermillion domains of the southern and western Superior Province. Neoarchean ferropicritic rocks also occur on five other Archean cratons: West Churchill, Slave, Yilgarn, Kaapvaal, and Karelia; suggesting that ca. 2.7 Ga Fe-rich magmatism was globally widespread. Neoarchean ferropicrites form two distinct groups in terms of their trace element geochemistry. Alkaline ferropicrites have fractionated REE profiles and show no systematic HFSE anomalies, broadly resembling the trace element character of modern-day ocean island basalt (OIB) magmas. Magmas parental to ca. 2.7 Ga alkaline ferropicrites also had high Nb/YPM (>2), low Al2O3/TiO2 (<8) and Sc/Fe (⩽3 × 10-4) ratios, and were enriched in Ni relative to primary pyrolite mantle-derived melts. The high Ni contents of the alkaline ferropicrites coupled with the low Sc/Fe ratios are consistent with derivation from olivine-free garnet-pyroxenite sources. The second ferropicrite group is characterized by decisively non-alkaline primary trace element profiles that range from flat to LREE-depleted, resembling Archean tholeiitic basalts and komatiites. In contrast to the alkaline ferropicrites, the magmas parental to the subalkaline ferropicrites had flat HREE, lower Nb/YPM (<2), higher Al2O3/TiO2 (8-25) and Sc/Fe (⩾4 × 10-4) ratios, and

  6. z206sc_video_observations

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents video observations from cruise Z206SC for the Santa Barbara Channel region and beyond in southern California. The vector data file is...

  7. z107sc_video_observations

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of DS 781 presents video observations from cruise Z107SC for the Santa Barbara Channel region and beyond in southern California. The vector data file is...

  8. Bandwidth challenge teams at SC2003 conference

    CERN Multimedia

    2003-01-01

    Results from the fourth annual High-Performance Bandwidth Challenge, held in conjunction with SC2003, the international conference on high-performance computing and networking which occurred last week in Phoenix, AZ (1 page).

  9. Low energy 40Ca + 40Ca collisions

    International Nuclear Information System (INIS)

    This paper deals with the classical microscopic study of 40Ca + 40Ca collisions. Fusion cross-sections (σsub(CF)) for various incident energies, energy variations with time, shape deformation and the life time of resonance scattering (T) have been studied. Comparison of 40Ca + 40Ca results with those of 16O + 16O have also been made. (author)

  10. Density function study on La, Ca modified and vacancy defect lead titate nanocrystals%La,Ca改性及缺陷PbTiO3纳米晶的DFT-DVM计算研究

    Institute of Scientific and Technical Information of China (English)

    于海涛; 傅宏刚; 闵新民; 池玉娟; 陈旭

    2000-01-01

    采用DFT-DVM计算程序中的原子簇模型对La,Ca改性及含有缺陷的La,Ca改性PbTiO3纳米晶进行了量子化学计算,得到了晶体中的电荷分布规律、总能、总态密度及轨道能级,并对晶体的成键情况进行了分析.

  11. Sc3N and Sc2C2 encapsulated B40: Smarter than its carbon analogue

    Science.gov (United States)

    Shah, Esha V.; Roy, Debesh R.

    2016-10-01

    A detailed comparative investigation on the recently synthesised B40 and C40 along with their metal nitride (Sc3N)and carbide (Sc2C2) encapsulated endohedral fullerenes, is performed under density functional theory for the first time. The structures, electronic, thermodynamic and magnetic properties of all the considered compounds are explored in detail. The present study identifies borospherene (B40) and its encapsulated nitride (Sc3N@B40) and carbide (Sc2C2@B40) endohedral borofullerenes as the better candidates for future novel nano-applications compared to their carbon bucky ball analogues.

  12. 41Ca in Circumstellar Graphite from Supernovae

    Science.gov (United States)

    Amari, S.; Zinner, E.; Lewis, R. S.

    1995-09-01

    We have measured isotopic ratios of C, N, O, Si, K, Ca, and Ti in 13 carbon grains from the low density graphite fraction KE3 (1.65-1.72g/cm3). These grains show the same isotopic signatures as KE3 grains previously measured [1]. Many of them have isotopically heavy C (up to x13 solar) and heavy N (up to x9.7 solar); nine have ^18O excesses (up to x183 solar); 26Al/27Al ratios range up to 0.07. Type II supernovae have previously been proposed as stellar sources of low density graphite grains [1,2,3]. Grain KE3c-551 (14 micrometers in size) has the most extreme C-, N-, and O-isotopic ratios ever measured in a graphite grain (^12C/^13C=7223+/-111, 14N/15N=28+/-2, 16O/18O=2.72+/-0.08). Interestingly, the isotopic ratios of these elements changed during analysis, becoming more anomalous with time. This suggests that isotopically "normal" components had been absorbed onto the grain surface or that partial exchange of the indigenous component had occurred. The above ratios are therefore lower (for C) and upper (for N and O) limits. High ^12C/^13C and ^16O/^17O (4595+/-858) and low ^16O/^18O ratios as well as the Ti isotopic ratios of the grain (delta 46Ti/48Ti=12+/-10 permil, delta ^47Ti/^48Ti=-62+/-9 permil, delta ^49Ti/^48Ti=901+/-16 permil, delta ^50Ti/^48Ti=200+/-12 permil) show the signature of the He/C zone in presupernova stars [4]. Eleven grains were measured for their K, Ca, and Ti isotopic ratios. Four of them, including KE3c-551, have ^41K excesses (218+/-50 permil to 10610+/-326 permil), apparently due to the decay of ^41Ca (T(sub)1/2=1.03 x 10^5a). Inferred ^41Ca/^40Ca ratios range from (1.94+/-0.43) x 10^-3 to (1.65+/-0.38) x 10^-2. In supernovae, ^41Ca is produced by neutron capture in the He/C, the O/C, and the O/Ne zones, as well as by explosive nucleosynthesis in the Si/S zone [4,5]. The expected ^41Ca/^40Ca ratios in the neutron capture zones are 1.6-1.8 x 10^-2 and in the Si/S zone 8 x 10^-4. Two of the 4 grains with ^41K excesses have Ca isotopic

  13. sup 4 sup 4 Ti atom counting for nuclear astrophysics

    CERN Document Server

    Hui, S K; Berkovits, D; Boaretto, E; Ghelberg, S; Hass, M; Hershkowitz, A; Navon, E

    2000-01-01

    The nuclide sup 4 sup 4 Ti (T sub 1 sub / sub 2 =59.2 yr) has recently become an important asset to nuclear astrophysics through the measurement of its cosmic radioactivity, yielding significant information on fresh sup 4 sup 4 Ti nucleosynthesis in supernovae. We propose to use AMS to determine the production rate of sup 4 sup 4 Ti by the main channel believed to be responsible for sup 4 sup 4 Ti astrophysical production, namely sup 4 sup 0 Ca(alpha,gamma). A preliminary experiment conducted at the Koffler 14UD Pelletron accelerator demonstrates a sensitivity of 1x10 sup - sup 1 sup 4 for the sup 4 sup 4 Ti/Ti ratio. The AMS detection was performed using sup 4 sup 4 Ti sup - ions sputtered from a TiO sub 2 sample, reducing considerably the sup 4 sup 4 Ca isobaric interference. The present limit corresponds effectively to sup 4 sup 4 Ti production with resonance strength in the range 10-100 meV for a one-day sup 4 sup 0 Ca(alpha,gamma) activation. Several such resonances are known to be responsible for sup 4 ...

  14. Recrystallization and Morphology of Microstructure in Al-Sc Alloys

    Institute of Scientific and Technical Information of China (English)

    Zhang Jun; Zhang Zonghua

    2007-01-01

    Minor addition of Sc to aluminum results in the rapid precipitation of homogeneously distributed Al3Sc dispersoids. The presence of Al3Sc dispersoids is more effective recrystallization inhibitors. Our work established the precipitation of homogeneously distributed Al3Sc dispersoids, which are coherent with the matrix, have the L12 structure. It was also established that the addition of Sc was effective in improving the recrystallization resistance.

  15. Improve photovoltaic performance of titanium dioxide nanorods based dye-sensitized solar cells by Ca-doping

    Energy Technology Data Exchange (ETDEWEB)

    Li, Weixin; Yang, Junyou, E-mail: jyyang@mail.hust.edu.cn; Zhang, Jiaqi; Gao, Sheng; Luo, Yubo; Liu, Ming

    2014-09-15

    Highlights: • TiO{sub 2} nanorods doped with Ca ions were synthesized by one-step hydrothermal method. • The flat band edge of rutile TiO{sub 2} shifted positively via Ca-doping. • The photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs) based on TiO{sub 2} electrode was much enhanced by Ca-doping. • A relatively high open circuit voltage was obtained by adopting Ca-doped TiO{sub 2} nanorods electrode. - Abstract: Ca-doped TiO{sub 2} nanorod arrays were prepared via the one-step hydrothermal method successfully, and the effect of Ca ions content on the photovoltaic conversion efficiency of dye-sensitized solar cells has been fully discussed in the paper. Although no obvious change on the microstructure and morphology was observed by field emission scanning electron microscope and transmission electron microscope for the Ca-doped samples, the results of X-ray diffraction and X-ray photoelectron spectroscopy confirmed that Ti{sup 4+} was substituted with Ca{sup 2+} successfully. UV–vis spectroscopy results revealed that the flat band edge shifted positively by Ca ions doping. The photovoltaic conversion efficiency of the dye-sensitized solar cells based on the 2 mol% Ca-doped TiO{sub 2} electrode was 43% higher than that of the undoped one due to the less recombination possibility.

  16. Effect of TiO2 Content on the Crystallization Behavior of Titanium-Bearing Blast Furnace Slag

    Science.gov (United States)

    Hu, Meilong; Wei, Ruirui; Yin, Fangqing; Liu, Lu; Deng, Qingyu

    2016-09-01

    The content of TiO2 has an important influence on both the basic structure and the crystallization behavior of titanium-bearing blast furnace (BF) slag. The results of thermodynamic calculations show that, when the mass content of TiO2 is smaller than 25%, CaTiO3 increases as the content of TiO2 increases. However, when the TiO2 content is more than 25%, the CaTiO3 content decreases and TiO2 gradually increases. The results of a confocal laser scanning microscopy (CLSM) experiment show that, when the TiO2 mass content is 10%, Ca2MgSi2O7 and Ca2Al2SiO7 are the main crystallized phases resulting from the molten slag. Furthermore, when the TiO2 mass content is 20%, CaMgSi2O6, Ca(Ti,Mg,Al)(Si,Al)2O7 and dendrite CaTiO3 are the crystallized phases, while when the TiO2 mass content increases to 30%, CaTiO3 is the sole phase. The discrepancy between the CLSM results and the thermodynamic calculations occurs mainly due to the high melting point of the titanium-bearing BF slag. During the cooling process for the molten slag, CaTiO3 is crystallized first, due to its high crystallization temperature. Furthermore, the molten slag is solidified in its entirety before the other phases crystallize.

  17. A New Process for Titanium Aluminides Production from TiO2

    Institute of Scientific and Technical Information of China (English)

    A.R.Kamali; H. Razavizadeh; S.M.M. Hadavi

    2007-01-01

    This paper describes a new process for producing titanium aluminides, in particular TiAl, from TiO2 raw material. On the basis of obtained results, the non-completed reaction of TiO2 with Al and Ca in a special reaction vessel results in the production of granulates of titanium aluminides especially Ti3Al and other TiAl phases as the metallic product and Ca12Al14O33 as the non-metallic product. By adding KClO4 in the mixture, a nearly completed reaction can be carried out. The products of this reaction are titanium aluminide particularly TiAl as the metallic part and CaAl4O7 (grossite) as the non-metallic slag part. Both product and slag are produced in a separated form. This process, called KRH-method is described in this article.The scanning electron microscopic microstructure of metallic part of the product shows different phases: the matrix phase is TiAl, where the needle form precipitation is TiAl2 and the plate form precipitation includes TiAl and Ti3Al phases. The microstructure of the remelted metallic part indicates dendritic phase with a lamellar structure comprising of TiAl and Ti3Al phases. The interdendritic phase of TiAl is also seen.

  18. Sc20C60: a volleyballene

    Science.gov (United States)

    Wang, Jing; Ma, Hong-Man; Liu, Ying

    2016-06-01

    An exceptionally stable hollow cage containing 20 scandium atoms and 60 carbon atoms has been identified. This Sc20C60 molecular cluster has a Th point group symmetry and a volleyball-like shape that we refer to below as ``Volleyballene''. Electronic structure analysis shows that the formation of delocalized π bonds between Sc atoms and the neighboring pentagonal rings made of carbon atoms is crucial for stabilizing the cage structure. A relatively large HOMO-LUMO gap (~1.4 eV) was found. The results of vibrational frequency analysis and molecular dynamics simulations both demonstrate that this Volleyballene molecule is exceptionally stable.An exceptionally stable hollow cage containing 20 scandium atoms and 60 carbon atoms has been identified. This Sc20C60 molecular cluster has a Th point group symmetry and a volleyball-like shape that we refer to below as ``Volleyballene''. Electronic structure analysis shows that the formation of delocalized π bonds between Sc atoms and the neighboring pentagonal rings made of carbon atoms is crucial for stabilizing the cage structure. A relatively large HOMO-LUMO gap (~1.4 eV) was found. The results of vibrational frequency analysis and molecular dynamics simulations both demonstrate that this Volleyballene molecule is exceptionally stable. Electronic supplementary information (ESI) available: Sc20C60: a Volleyballene_SI. See DOI: 10.1039/c5nr07784b

  19. Investigations of the effect of nonmagnetic Ca substitution for magnetic Dy on spin-freezing in Dy₂Ti₂O₇.

    Science.gov (United States)

    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(ac)(T), dc magnetic susceptibility χ(T), isothermal magnetization M(H) and heat capacity C(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(ac)(T) data of Dy1.8Ca0.2Ti2O7 show that the spin-freezing behavior is significantly influenced by Ca substitution. The effect of partial nonmagnetic Ca(2+) substitution for magnetic Dy(3+) is similar to the previous study on nonmagnetic isovalent Y(3+) substituted Dy(2-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% Ca(2+) substitution for Dy(3+) ions.

  20. Separation of cyclotron-produced 44Sc from a natural calcium target using a dipentyl pentylphosphonate functionalized extraction resin

    Science.gov (United States)

    Valdovinos, H.F.; Hernandez, R.; Barnhart, T.E.; Graves, S.; Cai, W.; Nickles, R.J.

    2014-01-01

    Significant interest in 44Sc as a radioactive synthon to label small molecules for positron emission tomography (PET) imaging has been recently observed. Despite the efforts of several research groups, the ideal 44Sc production and separation method remains elusive. Herein, we propose a novel separation method to obtain 44Sc from the proton irradiation of calcium targets based on extraction chromatography, which promises to greatly simplify current production methodologies. Using the commercially available Uranium and Tetravalent Actinides (UTEVA) extraction resin we were able to rapidly ( 80% of the activity generated at end of bombardment (EoB) in small ~1 M HCl fractions (400 μL). The chemical purity of the 44Sc eluates was evaluated through chelation with DOTA and DTPA, and by trace metal analysis using microwave induced plasma atomic emission spectrometry. The distribution coefficients (Kd) of Sc(III) and Ca(II) in UTEVA were determined in HCl medium in a range of concentrations from zero to 12.1 M The 44Sc obtained with our method proved to be suitable for the direct labeling of small biomolecules for PET imaging, with excellent specific activities and radiochemical purity. PMID:25464172

  1. Adsorption property of citrate dispersant on BaTiO3 particles in aqueous solution

    Institute of Scientific and Technical Information of China (English)

    SU Tao-long; ZHUANG Zhi-qiang

    2007-01-01

    Dispersion behavior of ultra fine BaTiO3 particles in the aqueous solution of ammonium citrate (NH4-CA) or citric acid lanthanum chelate (NH4-La-CA) was investigated. The dispersion property was characterized with sedimentation value. It is easier to obtain well dispersed slurry with NH4La-CA than NH4-CA. In an attempt to better understand the role of citric acid radical,simulation of the dispersant adsorption on BaTiO3 particle was performed with universal force field (UFF). It is demonstrated that the interaction between citric acid radical and BaTiO3 particle surface is a weak chemical adsorption. Trivalent citric acid radical is adsorbed on BaTiO3 particle surface with maximal adsorption energy. And, larger molecules of NH4-La-CA formed by adding La3+ lead to better dispersion property than NH4-CA.

  2. Norma Audio Revo SC-/PA-150

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Norma audio是意大利一间顶级HI-Fi音响器材生产商。这款IRevo SC-2/PA-150为正是公司旗下的一款高端型号产品。其中,Revo SC-2前置放大器的放大电路以低噪音、高速和宽频作为设计重点,能反映出音频信号中的每一个细节。

  3. Sc20C60: a volleyballene.

    Science.gov (United States)

    Wang, Jing; Ma, Hong-Man; Liu, Ying

    2016-06-01

    An exceptionally stable hollow cage containing 20 scandium atoms and 60 carbon atoms has been identified. This Sc20C60 molecular cluster has a Th point group symmetry and a volleyball-like shape that we refer to below as "Volleyballene". Electronic structure analysis shows that the formation of delocalized π bonds between Sc atoms and the neighboring pentagonal rings made of carbon atoms is crucial for stabilizing the cage structure. A relatively large HOMO-LUMO gap (∼1.4 eV) was found. The results of vibrational frequency analysis and molecular dynamics simulations both demonstrate that this Volleyballene molecule is exceptionally stable. PMID:26878201

  4. K2SC: K2 Systematics Correction

    Science.gov (United States)

    Aigrain, Suzanne; Parviainen, Hannu; Pope, Benjamin

    2016-05-01

    K2SC (K2 Systematics Correction) models instrumental systematics and astrophysical variability in light curves from the K2 mission. It enables the user to remove both position-dependent systematics and time-dependent variability (e.g., for transit searches) or to remove systematics while preserving variability (for variability studies). K2SC automatically computes estimates of the period, amplitude and evolution timescale of the variability for periodic variables and can be run on ASCII and FITS light curve files. Written in Python, this pipeline requires NumPy, SciPy, MPI4Py, Astropy (ascl:1304.002), and George (ascl:1511.015).

  5. Production of scandium-43 and -47 from a powdery calcium oxide target via the (nat/44)Ca(α,x)-channel.

    Science.gov (United States)

    Minegishi, Katsuyuki; Nagatsu, Kotaro; Fukada, Masami; Suzuki, Hisashi; Ohya, Tomoyuki; Zhang, Ming-Rong

    2016-10-01

    We produced (43)Sc and (47)Sc via the (nat/44)Ca(α,x)-channel using a vertical beam coupled with a ceramic target box. After activation, the powdery CaO target material was dissolved in HCl in the target box in situ and remotely recovered as a radio-Sc solution. The respective yields of (43)Sc and (47)Sc following isolation via a precipitation method with a typical 0.22µm sterile filter were 54.8MBq/µAh (1.48mCi/µAh) and 780kBq/µAh (21.1µCi/µAh) at the end of separation (approximately 1.5h from the EOB). In addition, we discuss the recycling of target Ca.

  6. Production of scandium-43 and -47 from a powdery calcium oxide target via the (nat/44)Ca(α,x)-channel.

    Science.gov (United States)

    Minegishi, Katsuyuki; Nagatsu, Kotaro; Fukada, Masami; Suzuki, Hisashi; Ohya, Tomoyuki; Zhang, Ming-Rong

    2016-10-01

    We produced (43)Sc and (47)Sc via the (nat/44)Ca(α,x)-channel using a vertical beam coupled with a ceramic target box. After activation, the powdery CaO target material was dissolved in HCl in the target box in situ and remotely recovered as a radio-Sc solution. The respective yields of (43)Sc and (47)Sc following isolation via a precipitation method with a typical 0.22µm sterile filter were 54.8MBq/µAh (1.48mCi/µAh) and 780kBq/µAh (21.1µCi/µAh) at the end of separation (approximately 1.5h from the EOB). In addition, we discuss the recycling of target Ca. PMID:27472825

  7. Surface Characterization of Laser Surface Melted NiTi Shape Memory Alloy in Hanks' Solution

    Institute of Scientific and Technical Information of China (English)

    CUI Zhen-duo; ZHU Sheng-li; MAN Hauchung; YANG Xian-jin

    2004-01-01

    The surface of Ti-50.8Ni at% shape memory alloy was melted by an Nd-YAG laser. The Ti/Ni and Ti4+/Ti atomic concentration ratios at the surface were changed significantly. The Ni ion release rate of the laser melted surface was much lower than that of the mechanical polished samples. A calcium-phosphorous layer with high Ca/P ratio was detected after immersion in Hanks' solution.

  8. CORRELATION BETWEEN SEED TESTS AND FIELD EMERGENCE OF TWO MAIZE HYBRIDS (SC704 AND SC500

    Directory of Open Access Journals (Sweden)

    A.A. ALILOO

    2011-11-01

    Full Text Available Early emergence and stand establishment of maize (Zea mays L. are considered to be the most important yield-contributing factors. The influence of seed vigor on these factors is vital. Therefore, five laboratory tests and field experiment were conducted on basis of a randomized complete block design (RCBD with five replications in 2011, to evaluate the correlation among the seed vigor tests and field emergence of two maize hybrids (SC704 and SC500. In laboratory tests, differences between two hybrids for cold test and electrical conductivity test were significant (P≤0.01. The leachates of hybrid SC500 was 35% higher than the leachates of hybrid SC704. However, high germination percentage was obtained by hybrid SC740 in cold test. A Statistically significant difference was found between hybrids in field emergence percentage (P≤0.05. The field emergence of hybrid SC704 and hybrid SC500 was 71% and 37%, respectively. The farm emergence percentage had the significant negative correlation (-0.71 with conductivity test, but positive correlation (0.79 with cold test. No significant correlation between the standard seed germination and the field emergence was detected. Therefore, the standard germination test was not a good indicator for field emergence percentage. However, cold and conductivity tests were the best predictor of field emergence than all the other laboratory tests.

  9. Production of a {sup 44} Ti target and its cross section of thermal neutron capture; Producao de um alvo de {sup 44} Ti e sua secao de choque para captura de neutrons termicos

    Energy Technology Data Exchange (ETDEWEB)

    Ejnisman, R

    1993-12-31

    A study of the production of a {sup 44} Ti target was carried out aiming the determination of its thermal neutron capture cross-section. With this purpose, the cross-section of the reaction {sup 45} Sc(p,2 n) {sup 44} Ti was determined in the energies 16-, 18-, 20-22- and 45 MeV. The cross-section of the reactions (p,n) {sup 45} Ti, (p,pn) {sup 44m} Sc, (p,pn) {sup 44g} Sc and (p,p2n){sup 43} Sc were also measured. The results in the low energy region are in good agreement with a previous work by McGee et al. On the other hand, the cross-section at 45 MeV is different from McGee`s result and indicates the existence of an abnormal behavior of the excitation function at higher energies. Furthermore, a radiochemical separation method was developed in order to eliminate Sc from the {sup 44} Ti target which was irradiated with neutrons. It was possible to determine an upper limit for the cross-section of the reaction {sup 44} Ti (n, {gamma}) of 4 x 10{sup 3} b. At last, it is presented a discussion of the results obtained and their possible astrophysical implications. (author) 94 refs.

  10. The Synchrocyclotron (SC) in building 300

    CERN Multimedia

    Maximilien Brice

    2012-01-01

    The red magnet of CERN's first accelerator, the Synchrocyclotron (SC), has occupied a large part of Hall 300 since it was installed in the late 1950s. The remaining part of the 300-square-metre building has been used as a storage room since the accelerator was shut down in 1990. Now a public exhibition will breathe new life into the hall.

  11. Electrolytic reduction of mixed solid oxides in molten salts for energy efficient production of the TiNi alloy

    Institute of Scientific and Technical Information of China (English)

    ZHU Yong; MA Meng; WANG Dihua; JIANG Kai; HU Xiaohong; JIN Xianbo; George Z. CHEN

    2006-01-01

    Direct electrochemical reduction of mixed TiO2 and NiO powders to TiNi alloy has been successfully demonstrated in molten CaCl2 at 900℃ by constant voltage electrolysis. The electrolysis energy consumption was as low as 23.4 kWh/kg-TiNi,although the current efficiency was 20.5% in the preliminary experiments. During the process, NiO was first reduced to Ni at high speed, accompanied by TiO2 being perovskitized to CaTiO3-x which was gradually reduced to Ni3Ti and TiNi, assisted by the depolarization of the preformed Ni. The cell voltage for preparation of the TiNi alloy was lower than that for Ti. Adjusting the cell voltage not only affected the reduction speed, but also offered a convenient access to the preparation of the nickel/perovskite composite.

  12. INTERVIU CU DOAMNA SIMONA CAROBENE, ADMINISTRATORUL SC PROIECT MOZAIC SRL

    Directory of Open Access Journals (Sweden)

    Gheorghe Pascaru

    2013-12-01

    Full Text Available Fabrica de mozaic, înregistrată la Oficiul Registrului Comerţului în aprilie 2012 a luat fiinţă în cadrul unui proiect cu finanţare europeană nerambursabilă și are în prezent statutul de unitate protejată autorizată. În cadrul acesteia sunt angajați 10 tineri post instituţionalizați, pentru care integrarea în viaţa socială şi profesională este dificilă. Întreprinderea socială SC Proiect Mozaic SRL este rezultatul întâlnirii dintre sectorul social, non-profit şi sectorul business, deoarece are la bază un parteneriat cu un important grup de firme din domeniul construcţiilor şi amenajărilor interioare din București. În paralel cu activitatea de producţie a mozaicului, ocazional, Proiect Mozaic oferă către clienți și servicii de ambalare și asamblare produse.

  13. Band structure engineering of anatase TiO{sub 2} by metal-assisted P-O coupling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jiajun; Meng, Qiangqiang [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Huang, Jing [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); School of Materials and Chemical Engineering, Anhui Jianzhu University, Hefei, Anhui 230601 (China); Li, Qunxiang, E-mail: liqun@ustc.edu.cn; Yang, Jinlong [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2014-05-07

    In this work, we demonstrate that the metal-assisted P-O coupling is an effective approach to improve the photoelectrochemical properties of TiO{sub 2}. The (Sc + P) and (In + P) codoping effects on electronic structures and photocatalytic activities of anatase TiO{sub 2} are examined by performing hybrid density functional theory calculations. It is found that the coupling of P dopant with the second-nearest neighboring O atom assisted by acceptor metals (Sc/In) leads to the fully occupied and delocalized intermediate bands within the band gap of anatase TiO{sub 2}, which is driven by the P-O antibonding states (π*). This metal-assisted P-O coupling can prevent the recombination of photogenerated electron-hole pairs and effectively reduce the band gap of TiO{sub 2}. Moreover, the band edge alignments in (Sc + P) and (In + P) codoped anatase TiO{sub 2} are desirable for water-splitting. The calculated optical absorption curves indicate that (Sc + P) and (In + P) codoping in anatase TiO{sub 2} can also effectively enhance the visible light absorption.

  14. New tumor-associated antigen SC6 in pancreatic cancer

    OpenAIRE

    Liu, Min-Pei; Guo, Xiao-Zhong; Xu, Jian-Hua; Wang, Di; Li, Hong-Yu; Cui, Zhong-Min; Zhao, Jia-Jun; Ren, Li-Nan

    2005-01-01

    AIM: To examine the concentration of a new antigen SC6 (SC6-Ag) recognized by monoclonal antibody (MAb) in patients with pancreatic cancer and other malignant or benign diseases and to understand whether SC6-Ag has any clinical significance in distinguishing pancreatic cancer from other gastrointestinal diseases.

  15. Electric-Field-Tunable Ferroelastic Control of Nonvolatile Resistivity and Ferromagnetic Switching in Multiferroic La0.67Ca0.33MnO3/[PbMg1/3Nb2/3O3] 0.7[PbTiO3]0.3 Heterostructures

    Science.gov (United States)

    Zheng, Ming; Zheng, Ren-Kui

    2016-04-01

    The electric-field-modulated nonvolatile resistivity and magnetization switching in elastically coupled La0.67Ca0.33MnO3 films grown on (111)-oriented 0.7 Pb (Mg1 /3Nb2 /3)O3-0.3 PbTiO3 substrates is achieved through the ferroelastic effect. By taking advantage of the 180° ferroelectric and non-180° ferroelastic domain switching, we identify that such changes in order parameters stem from domain-switching-induced strain rather than accumulation or depletion of charge carriers at the interface. Specifically, the strong correlation between the ferroelastic strain and the magnetic field is manifested not only by the strain-tunable magnetoresistance effect but also by the magnetically manipulated strain effect, which is essentially driven by the electronic phase separation. These findings present a potential strategy for elucidating the essential physics of the ferroelastic-strain effect and delivering prototype devices for energy-efficient and nonvolatile information storage.

  16. Localized Ca2+ uncaging induces Ca2+ release through IP3R in smooth muscle

    Institute of Scientific and Technical Information of China (English)

    Min WANG; Zheng CHEN; Yan XING; Xu ZHANG; Xian-zhi DONG; Guang-ju JI

    2006-01-01

    Aim: Our previous study indicated that there are two types of Ca2+ release events seen in intact mouse bladder tissue. In this study our aim is to investigate the mechanism that underlies the phenomena of Ca2+ release in smooth muscle. Methods: Single cells were isolated and tissue segments were prepared by cutting the detrusor into 0.1 cm × O.5 cm strips running along the axis from the neck to the fundus. Single cells and intact tissue strips were co-loaded with the Ca2+ indicator and caged Ca2+ by incubation with 10 μmol/L Fluo-4 AM and DMNP-EDTA-AM. Fluo-4 AM fluorescence was detected by laser scanning confocal microscopy, and local uncaging of DMNP-EGTA was achieved by brief exposure to the output of a diode-pumped, Ti:sapphire laser tuned to 730 nm. Results: Local uncaging of caged Ca2+ was able to trigger Ca2+ release events in both single cells and tissue strips from mouse bladder. The Ca2+ release events could not be blocked by ryanodine alone, but the property of the Ca2+ release was markedly altered. Surprisingly, in the presence of ryanodine, Xestospongin C completely inhibited the Ca2+ release events both in single cell and tissue experiments. Conclusion: (1) Two photon flash photolysis (TPFP) triggers Ca2+ induced Ca2+ release. This process involves release through type 2 ryanodine receptor channels; (2) TPFP results in the release of Ca2+ through inositol 1,4,5-trisphosphate receptors in the absence of phospholipase C activation.

  17. Energy-dispersion XRFS Determination of SiO2,CaO and Total Iron in Sintered V-Ti Ore%能量色散X荧光分析仪分析钒钛烧结矿中SiO2、CaO和TFe

    Institute of Scientific and Technical Information of China (English)

    王颖

    2004-01-01

    在烧结矿生产中,SiO2、CaO、TFe的准确含量是烧结成球造粒的最为重要指标,其分析准确与否直接关系到烧结矿的物化性能以及高炉产量。目前,国内外分析行业主要采用波长色散X荧光分析仪,很少使用能量色散X荧光分析仪。本法使用CIT-3000SJ钙硅铁能量色散X荧光分析仪,该仪器分析速度快、准确度高、操作简单、使用方便,能同时分析钒钛烧结矿中的SiQ、CaO、TFe等含量,分析结果完全达到了炼铁厂生产对分析的要求。

  18. Dielectric relaxation of Ba1-xCaxTiO3 (x = 0.0-0.3)

    International Nuclear Information System (INIS)

    Ba1-xCaxTiO3 samples (x = 0.0-0.30) were prepared by a solid state reaction method. X-ray diffraction patterns of the prepared samples show that the samples containing Ca2+ concentration lower than 14 at% were identified to tetragonal phase of BaTiO3. In the samples with Ca2+ concentration higher than 14 at% CaTiO3 appears and coexists with BaTiO3. The dielectric constant at room temperature of all the samples was measured in a frequency range from zero to 2.5 MHz. A modified Cole-Cole formula was used to fit the experimental data. The fitting results show that the samples exhibit a single relaxation process that suggests BaTiO3 and CaTiO3 coexist in a nested hybrid form in the samples with Ca concentration in a range of (0.14-0.30). An abnormal dependence on the Ca2+ concentration of the dielectric relaxation time was observed and supposed to be related with a pinning effect due to the local point-deformation caused by Ca2+ substitution and/or with a nesting of BaTiO3 and CaTiO3 in a hybrid form. (author)

  19. The elemental composition of the Sun II. The iron group elements Sc to Ni

    CERN Document Server

    Scott, Pat; Grevesse, Nicolas; Bergemann, Maria; Sauval, A Jacques

    2014-01-01

    We redetermine the abundances of all iron group nuclei in the Sun, based on neutral and singly-ionised lines of Sc, Ti, V, Mn, Fe, Co and Ni in the solar spectrum. We employ a realistic 3D hydrodynamic model solar atmosphere, corrections for departures from local thermodynamic equilibrium (NLTE), stringent line selection procedures and high quality observational data. We have scoured the literature for the best quality oscillator strengths, hyperfine constants and isotopic separations available for our chosen lines. We find $\\log \\epsilon_\\mathrm{Sc}=3.16\\pm0.04$, $\\log \\epsilon_\\mathrm{Ti}=4.90\\pm0.04$, $\\log \\epsilon_\\mathrm{V}=3.89\\pm0.08$, $\\log \\epsilon_\\mathrm{Cr}=5.62\\pm0.04$, $\\log \\epsilon_\\mathrm{Mn}=5.42\\pm0.04$, $\\log \\epsilon_\\mathrm{Fe}=7.47\\pm0.04$, $\\log \\epsilon_\\mathrm{Co}=4.93\\pm0.05$ and $\\log \\epsilon_\\mathrm{Ni}=6.20\\pm0.04$. Our uncertainties factor in both statistical and systematic errors (the latter estimated for possible errors in the model atmospheres and NLTE line formation). The ...

  20. Are Ti44-Producing Supernovae Exceptional?

    CERN Document Server

    The, L S; Diehl, R; Hartmann, D H; Iyudin, A F; Leising, M D; Meyer, B S; Motizuki, Y; Schönfelder, V

    2006-01-01

    According to standard models supernovae produce radioactive $^{44}$Ti, which should be visible in gamma-rays following decay to $^{44}$Ca for a few centuries. $^{44}Ti production is believed to be the source of cosmic $^{44}$Ca, whose abundance is well established. Yet, gamma-ray telescopes have not seen the expected young remnants of core collapse events. The $^{44}$Ti mean life of $\\tau \\simeq$ 89 y and the Galactic supernova rate of $\\simeq$ 3/100 y imply $\\simeq$ several detectable $^{44}Ti gamma-ray sources, but only one is clearly seen, the 340-year-old Cas A SNR. Furthermore, supernovae which produce much $^{44}Ti are expected to occur primarily in the inner part of the Galaxy, where young massive stars are most abundant. Because the Galaxy is transparent to gamma-rays, this should be the dominant location of expected gamma-ray sources. Yet the Cas A SNR as the only one source is located far from the inner Galaxy (at longitude 112 degree). We evaluate the surprising absence of detectable supernovae fro...

  1. Electronic structures and properties of Ti, Zr and Hf metals

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The electronic structures of pure Ti, Zr and Hf metals with hcp structure were determined by one-atom (OA) theory. According to the electronic structures of these metals,their potential curves, cohesive energies, lattice constants, elasticities and the temperature dependence of linear thermal expansion coefficients were calculated. The electronic structures and characteristic properties of these metals with bcc and fcc structures and liquids were also studied. The results show that the electronic structures of Ti, Zr and Hf metals are respectively [Ar](3dn)0.481 0(3dc)2.085 7(4sc)1.000 0(4sf)0.433 3, [Kr](4dn)0.396 8(4dc)2.142 8(5sc)1.262 0(5sf)0.198 4, [Xe](5dn)0.368 0(5dc)2.041 4(6sc)1.406 6(6sf)0.184 0. It is explained why the pure Ti, Zr and Hf metals with hcp and bcc structures can exist naturally, while those with fcc structure can not.

  2. Calcium platinum aluminium, CaPtAl

    Directory of Open Access Journals (Sweden)

    Charles Fon Abi

    2011-10-01

    Full Text Available A preliminary X-ray study of CaPtAl has been reported previously by Hulliger [J. Alloys Compd (1993, 196, 225–228] based on X-ray powder diffraction data without structure refinement. With the present single-crystal X-ray study, we confirm the assignment of the TiNiSi type for CaPtAl, in a fully ordered inverse structure. All three atoms of the asymmetric unit have .m. site symmetry. The structure features a ∞3[AlPt] open framework with a fourfold coordination of Pt by Al atoms and vice versa. The Ca atoms are located in the large channels of the structure.

  3. Genetic and physical fine-mapping of the Sc locus conferring indica-japonica hybrid sterility in rice (Oryza sativa L.)

    Institute of Scientific and Technical Information of China (English)

    YANG Cunyi; CHEN Zhongzheng; ZHUANG Chuxiong; MEI Mantong; LIU Yaoguang

    2004-01-01

    Hybrid sterility is a major hindrance to utilizing the heterosis in indica-japonica hybrids. To isolate a gene Sc conferring the hybrid sterility, the locus was mapped using molecular markers and an F2 population derived from a cross between near isogenic lines. A primary linkage analysis showed that Sc was linked closely with 4 markers on chromosome 3, on which the genetic distance between a marker RG227 and Sc was 0.07 cM. Chromosome walking with a rice TAC genomic library was carried out using RG227 as a starting probe, and a contig of ca. 320 kb covering the Sc locus was constructed. Two TAC clones, M45E14 and M90J01 that might cover the Sc locus, were partially sequenced. By searching the rice sequence databases with sequences of the TACs and RG227 a japonica rice BAC sequence, OSJNBb0078P24 was identified. By comparing the TAC and BAC sequences, six new PCR-based markers were developed. With these markers the Sc locus was further mapped to a region of 46 kb. The results suggest that the BAC OSJNBb0078P24 and TAC M45E14 contain the Sc gene. Six ORFs were predicted in the focused 46-kb region.

  4. LHCb Data Replication During SC3

    CERN Multimedia

    Smith, A

    2006-01-01

    LHCb's participation in LCG's Service Challenge 3 involves testing the bulk data transfer infrastructure developed to allow high bandwidth distribution of data across the grid in accordance with the computing model. To enable reliable bulk replication of data, LHCb's DIRAC system has been integrated with gLite's File Transfer Service middleware component to make use of dedicated network links between LHCb computing centres. DIRAC's Data Management tools previously allowed the replication, registration and deletion of files on the grid. For SC3 supplementary functionality has been added to allow bulk replication of data (using FTS) and efficient mass registration to the LFC replica catalog.Provisional performance results have shown that the system developed can meet the expected data replication rate required by the computing model in 2007. This paper details the experience and results of integration and utilisation of DIRAC with the SC3 transfer machinery.

  5. Crystal structure of the Sc{sub 2}PbX{sub 4} (X = S and Se) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Shemet, V.Ya. [Department of General and Inorganic Chemistry, Volyn State University, Voli Ave. 13, 43009 Lutsk (Ukraine); Gulay, L.D. [Department of General and Inorganic Chemistry, Volyn State University, Voli Ave. 13, 43009 Lutsk (Ukraine)]. E-mail: gulay@lab.univ.lutsk.ua; Stepien-Damm, J. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland); Pietraszko, A. [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw (Poland); Olekseyuk, I.D. [Department of General and Inorganic Chemistry, Volyn State University, Voli Ave. 13, 43009 Lutsk (Ukraine)

    2006-01-05

    The crystal structure of the Sc{sub 2}PbX{sub 4} (X = S and Se) compounds (space group Pnma, Pearson symbol oP28) were determined by means of X-ray single crystal diffraction (a = 1.1642(4) nm, b = 0.3757(1) nm, c = 1.3711(4) nm, R {sub 1} = 0.0420 (Sc{sub 2}PbS{sub 4})) and X-ray powder diffraction (a = 1.22029(5) nm, b 0.39061(2) nm, c = 1.42801(6) nm, R {sub Bragg} = 0.0954 (Sc{sub 2}PbSe{sub 4})). Both compounds crystallize in the CaFe{sub 2}O{sub 4} structure type. The Sc-centered octahedra and Pb-centered trigonal prisms with two additional atoms form columns along the Y-axis in the structure of the Sc{sub 2}PbX{sub 4} (X = S and Se) compounds.

  6. The SC gets ready for visitors

    CERN Multimedia

    Antonella Del Rosso

    2012-01-01

    Hall 300, which houses the Synchrocyclotron (SC), CERN’s first accelerator, is getting ready to host a brand-new exhibition. The site will be one of the stops on the new visit itineraries that will be inaugurated for the 2013 CERN Open Day.   The Synchrocyclotron through the years. Just as it did in the late 1950s, when the accelerator was first installed, the gigantic red structure of the Synchrocyclotron's magnet occupies a large part of the 300-square-metre hall. “We have completed the first phase of the project that will give the SC a new lease of life,” says Marco Silari, the project leader and a member of CERN’s Radiation Protection Group. “We have removed all the equipment that was not an integral part of the accelerator. The hall is now ready for the civil-engineering work that will precede the installation of the exhibition.” The SC was witness to a big part of the history of CERN. The accelerator produced ...

  7. Spin distribution in preequilibrium reactions for 48Ti + n.

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D

    2005-04-06

    Cross section measurements were made of prompt {gamma}-ray production as a function of incident neutron energy on a {sup 48}Ti sample. Partial {gamma}-ray cross sections for transitions in {sup 45-48}Ti, {sup 44-48}Sc, and {sup 42-45}Ca have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction {gamma} rays were detected with the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The {gamma}-ray excitation functions were converted to partial {gamma}-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). The data are presented for neutron energies E{sub n} between 1 to 200 MeV. These results are compared with model calculations which include compound nuclear and pre-equilibrium emission. The model calculations are performed using the STAPRE reaction code for E{sub n} up to 20 MeV and the GNASH reaction code for E{sub n} up to 120 MeV. Using the GNASH reaction code the effect of the spin distribution in preequilibrium reactions has been investigated. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshbach, Kerman, and Koonin (FKK). The multistep direct (MSD) part of the FKK theory was calculated for a one-step process. The contribution from higher steps is estimated to be small. The spin distribution of the multistep compound (MSC) part of FKK theory is assumed to be the same as in the compound nucleus. The FKK preequilibrium spin distribution was incorporated into the GNASH calculations and the {gamma}-ray production cross sections were calculated and compared with experimental data. The difference in the partial {gamma}-ray cross sections using spin distributions with and without

  8. Mass measurement of 56Sc reveals a small A=56 odd-even mass staggering, implying a cooler accreted neutron star crust

    CERN Document Server

    Meisel, Z; Ahn, S; Bazin, D; Brown, B A; Browne, J; Carpino, J F; Chung, H; Cole, A L; Cyburt, R H; Estradé, A; Famiano, M; Gade, A; Langer, C; Matoš, M; Mittig, W; Montes, F; Morrissey, D J; Pereira, J; Schatz, H; Schatz, J; Scott, M; Shapira, D; Smith, K; Stevens, J; Tan, W; Tarasov, O; Towers, S; Wimmer, K; Winkelbauer, J R; Yurkon, J; Zegers, R G T

    2015-01-01

    We present the mass excesses of 52-57Sc, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The masses of 56Sc and 57Sc were determined for the first time with atomic mass excesses of -24.85(59)(+0 -54) MeV and -21.0(1.3) MeV, respectively, where the asymmetric uncertainty for 56Sc was included due to possible contamination from a long-lived isomer. The 56Sc mass indicates a small odd-even mass staggering in the A = 56 mass-chain towards the neutron drip line, significantly deviating from trends predicted by the global FRDM mass model and favoring trends predicted by the UNEDF0 and UNEDF1 density functional calculations. Together with new shell-model calculations of the electron-capture strength function of 56Sc, our results strongly reduce uncertainties in model calculations of the heating and cooling at the 56Ti electron-capture layer in the outer crust of accreting neutron stars. We found that, in contrast to prev...

  9. The thermal release of scandium from titanium metal. A simple way to produce pure {sup 44}Sc for PET application

    Energy Technology Data Exchange (ETDEWEB)

    Wittwer, D.; Eichler, R.; Gaeggeler, H.W.; Serov, A.; Tuerler, A. [Bern Univ. (Switzerland). Dept. of Chemistry and Biochemistry; Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab. fuer Radiochemie und Umweltchemie; Dressler, R.; Piguet, D.; Voegele, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab. fuer Radiochemie und Umweltchemie

    2011-07-01

    The radionuclide-generator based access to radiopharmaceutical isotopes represents a valuable alternative to directly produced isotopes at particle accelerators or nuclear reactors. The {sup 44}Ti based generator is of increasing interest for the delivery of PET-radiopharmaceutical isotopes used for imaging. The product of this generator {sup 44}Sc represents with its 3.97 h half-life and 94.3% positron branching [1] a very promising candidate for labeling PET radiopharmaceuticals. The long half-life of 58.9 {+-} 0.3 y [2] of the {sup 44}Ti assures a constant and long lasting production of the daughter nuclide. Here we present a gas phase separation method of scandium from titanium via thermal release in vacuum. Titanium foils were irradiated with {sup 40}Ar to produce scandium in multi-nucleon transfer reactions. Another production reaction used was the irradiation of titanium by neutrons from the SINQ neutron source at the Paul Scherrer Institute (PSI). The titanium metal foils containing {sup 44m}Sc and {sup 46}Sc were heated up for time periods of 15 and 60 min to temperatures between 900 C and 1500 C in vacuum. Thus, release properties of scandium from titanium under these conditions were studied. The released scandium was collected on tantalum foils and could be rinsed of with concentrated nitric acid resulting in carrier free scandium nitrate solutions. From the experimental results optimum release conditions are suggested. (orig.)

  10. Gamma-ray production cross sections in multiple channels for neutron induced reaction on 48Ti for En=1 to 200 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D; Mitchell, G E; Garrett, P E; Agvaanluvsan, U; Becker, J A; Bernstein, L A; Chadwick, M B; Devlin, M; Fotiades, N; Kawano, T; Nelson, R O; Younes, W

    2006-07-06

    Prompt {gamma}-ray production cross sections were measured on a {sup 48}Ti sample for incident neutron energies from 1 MeV to 200 MeV. Partial {gamma}-ray cross sections for transitions in {sup 45-48}Ti, {sup 45-48}Sc, and {sup 43-45}Ca were determined. The observation of about 130 transitions from 11 different isotopes in the present work provides a demanding test of reaction model calculations, and is the first study in this mass region to extract partial {gamma}-ray cross sections for many different reaction channels over a wide range of incident neutron energies. The neutrons were produced by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction {gamma} rays were detected with the large-scale Compton-suppressed GErmanium Array for Neutron Induced Excitations (GEANIE). Event neutron energies were determined by the time-of-flight technique. The {gamma}-ray excitation functions were converted to partial {gamma}-ray cross sections and then compared with model calculations using the enhanced GNASH reaction code. Compound nuclear, pre-equilibrium emission and direct reaction mechanisms are included. Overall the model calculations of the partial {gamma}-ray cross sections are in good agreement with measured values.

  11. Electrochemical behavior of hydroxyapatite/TiN multi-layer coatings on Ti alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun-Ju [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University (Korea, Republic of); Jeong, Yong-Hoon [Biomechanics and Tissue Engineering Laboratory, Division of Orthodontics, College of Dentistry, The Ohio State University, Columbus, OH (United States); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials, Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University (Korea, Republic of); Brantley, William A. [Division of Restorative Science and Prosthodontics, College of Dentistry, The Ohio State University, Columbus, OH (United States)

    2014-12-01

    The electrochemical behavior of hydroxyapatite (HA) and titanium nitride (TiN) multi-layer coatings on Ti–Nb–Zr alloys was investigated by a variety of surface analytical methods. The HA/TiN layers were deposited using a magnetron sputtering system. The HA target was made of human tooth-ash sintered at 1300 °C for 1 h and had an average Ca/P ratio of 1.9. From X-ray diffraction patterns, the Ti–29Nb–5Zr alloy was composed entirely of equiaxed β-phase exhibiting the principal (110) reflection, and the coating exhibited the (111) and (200) reflections for TiN and the (112) and (202) reflections for HA. At the coating surface the HA films consisted of granular particles, and the surface roughness was 4.22 nm. The thickness of the coating layers increased in the order of HA/TiN (lowest), TiN, and HA (highest). Potentiodynamic polarization measurements revealed that the corrosion current density was the lowest, and the corrosion potential and polarization resistance the highest, when the Ti–29Nb–5Zr surface was covered by the HA/TiN film, compared to solely HA or TiN films. - Highlights: • HA/TiN films were deposited by magnetron sputtering on a Ti–29Nb–5Zr biomedical alloy. • The corrosion current density for the HA/TiN films was lower than that of the non-coated alloy. • The polarization resistance of the HA/TiN films was higher than that of the non-coated alloy.

  12. Effects of additives on the phase transformation, occurrence state, and the interface of the Ti component in Ti-bearing blast furnace slag

    Science.gov (United States)

    Zhang, Li; Zhang, Wu; Zhang, Ju-hua; Li, Guang-qiang

    2016-09-01

    The influences of additives on the phase transformation, occurrence state, and the interface of the Ti component in Ti-bearing blast furnace slag were investigated. After oxidation, most of the Ti component in the slag was enriched into the perovskite phase, which served as the Ti-rich phase during the crystallization process. The phase transformation, occurrence state, and the interface of the Ti component were observed to be affected by the addition of different types of agents. During the oxidation process, titanaugite and Ti-rich diopside phases gradually transformed into non-Ti phases (anorthite: CaMgSi2O6 and CaAl2Si2O8) in the form of dendrites or columns, which were observed to be distributed at the surface of the perovskite phase. Several more cracks appeared along the grain boundaries of the perovskite phase after the addition of P2O5, facilitating the liberation of the perovskite phase. Composite additives combining both an acid and a base, such as CaO + CaF2 or P2O5 + CaF2, were used. We observed that the disadvantages of using single additives were successfully overcome.

  13. Catalytic effect of nano-sized ScH{sub 2} on the hydrogen storage of mechanically milled MgH{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Xuanli, E-mail: Xuanli.Luo@nottingham.ac.uk; Grant, David M., E-mail: David.Grant@nottingham.ac.uk; Walker, Gavin S., E-mail: Gavin.Walker@nottingham.ac.uk

    2015-02-15

    Highlights: • The ScH{sub 2} nanoparticles improved the MgH{sub 2} dehydrogenation kinetics. • Low activation energy of the dehydrogenation reaction (62 ± 5 kJ mol{sup −1}). • Optimal ScH{sub 2} catalyst content was ca. 12 mol.% to achieve lowest activation energy. • High cycling stability at relatively high temperature up to 450 °C. • The ScH{sub 2} nano-structure remained throughout cycling. - Abstract: The hydrogen storage properties of ball milled xMgH{sub 2}/(1 − x)ScH{sub 2} (x = 0.65-1) samples including capacity, kinetics, thermodynamics and cycling stability, were investigated. The effect of ScH{sub 2} catalyst content and ball milling duration on the kinetics of MgH{sub 2} dehydrogenation were studied. It was found that the optimal content of the catalyst ScH{sub 2} was ca. 12 mol.%, which gave an activation energy (E{sub a}) value of 62 ± 5 kJ mol{sup −1} and a hydrogen storage capacity of 5.8 ± 0.1 wt.% for the sample. There was no loss in kinetics in the ScH{sub 2} catalysed MgH{sub 2} system even after cycling at relatively high temperatures up to 450 °C, and the nano-sized ScH{sub 2} (ca. 70 nm) formed during ball milling remained after (de)hydrogenation cycling. Typical MgH{sub 2} dehydrogenation enthalpy (76 ± 1 kJ mol{sup −1} (H{sub 2})) and entropy (138 ± 2 J mol{sup −1} K{sup −1} (H{sub 2})) values observed by the 0.65MgH{sub 2}/0.35ScH{sub 2} sample demonstrated the effect of ScH{sub 2} was purely a catalytic improvement of the kinetics.

  14. Genetic interactions between the Golgi Ca2+/H+ exchanger Gdt1 and the plasma membrane calcium channel Cch1/Mid1 in the regulation of calcium homeostasis, stress response and virulence in Candida albicans.

    Science.gov (United States)

    Wang, Yanan; Wang, Junjun; Cheng, Jianqing; Xu, Dayong; Jiang, Linghuo

    2015-11-01

    The Golgi-localized Saccharomyces cerevisiae ScGdt1 is a member of the cation/Ca(2+) exchanger superfamily. We show here that Candida albicans CaGdt1 is the functional homolog of ScGdt1 in calcium sensitivity, and shows genetic interactions with CaCch1 or CaMid1 in response to ER stresses. In addition, similar to ScCCH1 and ScMID1, deletion of either CaCCH1 or CaMID1 leads to a growth sensitivity of cells to cold stress, which can be suppressed by deletion of CaGDT1. Furthermore, deletion of CaCCH1 leads to a severe delay in filamentation of C. albicans cells, and this defect is abolished by deletion of CaGDT1. In contrast, CaGDT1 does not show genetic interaction with CaMID1 in filamentation. Interestingly, C. albicans cells lacking both CaMID1 and CaGDT1 exhibit an intermediate virulence between C. albicans cells lacking CaCCH1 (non-virulent) and C. albicans cells lacking CaGDT1 (partially virulent), while C. albicans cells lacking both CaCCH1 and CaGDT1 are not virulent in a mouse model of systemic candidiasis. Therefore, CaGdt1 genetically interacts with the plasma membrane calcium channel, CaCch1/CaMid1, in the response of C. albicans cells to cold and ER stresses and antifungal drug challenge as well as in filamentation and virulence.

  15. Electrodeposited Ultrathin TiO2 Blocking Layers for Efficient Perovskite Solar Cells

    Science.gov (United States)

    Su, Tzu-Sen; Hsieh, Tsung-Yu; Hong, Cheng-You; Wei, Tzu-Chien

    2015-11-01

    In this study, the electrodeposition (ED) of ultrathin, compact TiO2 blocking layers (BLs) on fluorine-doped tin oxide (FTO) glass for perovskite solar cells (PSCs) is evaluated. This bottom-up method allows for controlling the morphology and thickness of TiO2 films by simply manipulating deposition conditions. Compared with BLs produced using the spin-coating (SC) method, BLs produced using ED exhibit satisfactory surface coverage, even with a film thickness of 29 nm. Evidence from cyclic voltammetry shows that an ED BL suppresses interfacial recombination more profoundly than an SC BL does, consequently improving the photovoltaic properties of the PSC significantly. A PSC equipped with an ED TiO2 BL having a 13.6% power conversion efficiency is demonstrated.

  16. Strain effects on Coherent Epitaxial Ferroelectric Pb(Zr0.2Ti0.8)O3

    Science.gov (United States)

    Khan, Asif; Salahuddin, Sayeef

    2012-02-01

    A comprehensive study of strain coupling to ferroelectricity in coherent epitaxial Pb(Zr0.2Ti0.8)TiO3 thin films is presented. The epitaxial strain variants are obtained by growing coherent PZT thin films on three different substrates, SrTiO3, DyScO3 and GdScO3 by pulsed laser deposition technique. The strain sensitivity of remnant polarization is found to be less in the epitaxial strain variants with larger tetragonality. Despite the fact that the tetragonality of PZT is more sensitive to the epitaxial strain than that of BaTiO3, the polarization-strain coupling is weaker in PZT than in BTO. These results underpins that the strong sensitivity of ferroelectricity to epitaxial strain is not a universal characteristic of complex oxide ferroelectrics and may depend on the intricate details of individual material systems.

  17. Effect of scandium on structure and hardening of Al–Ca eutectic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Belov, N.A., E-mail: nikolay-belov@yandex.ru [National Research and Technological University “MISIS”, 4, Leninsky pr., Moscow 119049 (Russian Federation); Naumova, E.A. [Bauman Moscow State Technical University, 5, 2 ul. Baumanskaya, Moscow, 105005 (Russian Federation); Alabin, A.N. [National Research and Technological University “MISIS”, 4, Leninsky pr., Moscow 119049 (Russian Federation); UC RUSAL, 13/1, Nikoloyamskaya st., Moscow, 109240 (Russian Federation); Matveeva, I.A. [UC RUSAL, 13/1, Nikoloyamskaya st., Moscow, 109240 (Russian Federation)

    2015-10-15

    The phase composition, structure and hardening of alloys in the aluminium corner of the Al–Ca–Sc system were studied in the range up to 10% Ca and up to 1% S≿. The experimental study (optical, scanning and transmission electron microscopy with electron-microprobe analysis, differential thermal analysis and hardness measurements) was combined with Thermo-Calc software simulation for the optimization of the alloy composition. It was shown that only phases of the binary systems (Al{sub 4}Ca and Al{sub 3}Sc) might be in equilibrium with the aluminium solid solution. It was shown that the (Al) + Al{sub 4}Ca eutectic had a much finer structure as compared with the Al–Si eutectic, which suggests a possibility of reaching higher mechanical properties as compared to commercial alloys of the A356 type. The influence of the annealing temperature within the range up to 600 °C on the structure and hardness of the Al–Ca–Sc experimental alloys was studied. It was determined that the maximum hardening corresponded to the annealing at 300 °C, which was due to the precipitation of Al{sub 3}Sc nanoparticles with their further coarsening. With an example of an Al-7.6% Ca-0.3% Sc model experimental alloy, a principal possibility of manufacturing aluminium casting alloys based on the (Al) + Al{sub 4}Ca eutectic was demonstrated. Unlike commercial alloys of the A356 type, the model alloy does not require quenching, as hardening particles are formed in the course of annealing of casting. - Highlights: • Al–Ca–Sc phase diagram in aluminum corner. • Formation of Al{sub 3}Sc nanoparticles in eutectic (Al) + Al{sub 4}Ca during heating at 300–450 °C. • Hardening and thermal stability of proposed (Al–Ca–Sc) and commercial (Al–Si–Mg, 356 type) eutectic alloys.

  18. STS study of TiO2 film and Pt-deposited TiO2 film in air

    Institute of Scientific and Technical Information of China (English)

    Zhang Min; Jin Zhensheng

    2004-01-01

    Direct investigation of the electronic structure of catalyst surfaces on the near-atomic scale in general has not been impossible in the past. However, with the advent of the scanning tunneling microscope (STM), the opportunity arises for incorporating the scanning tunneling spectroscopy (STS) for correlation in-situ surface electronic structure with topography on a sub-nanometer scale. In this paper, we report the STS results of thin film TiO2 and Pt-deposited TiO2 annealed at 450℃. It was found that the TiO2 semiconductor changes from n-type to p-type after Pt deposition.Fig. 1 shows the surface electronic property (Ⅰ-Ⅴ curve) of thin TiO2 film measured in air by STS. A steep descent of the anodic tunneling current at ca.- 1.0 Ⅴ and a rapid ascent of cathodic tunneling current at ca. +2.0V. The zero bias represents the Fermi level (Ef). Ef is situated at the Ecb side indicating that the thin TiO2 film possesses the same band gap as that of bulk TiO2 phase ( Egs =3.0 to 3.2 eV). For the sample of Pt-deposited TiO2 film, Pt/(Pt+Ti+O) atomic ratio≈0.2, which indicates that the surface of TiO2 film is partly covered by Pt particles, and there are two types of Ⅰ-Ⅴ curves to be detected. One of them (Fig.2a)is attributed to the electronic property of TiO2, which has same Egs as that shown in Fig. 1. However, the Ef is transferred to valence side (△≈1eV). This phenomenon hints that TiO2 is doped by an impurity which can introduce h+ into TiO2 lattice.Such a type of defects may be described by Ti1-xPtxO2(h )2x, here Pt+2 as a substitutional site of Ti+4. Fig.2b is the Ⅰ-Ⅴ curve of a Pt particle situated on a TiO2 particle contained Ti1-xPtxO2(h )2x.

  19. Contraceptive efficacy and safety of DMPA-SC.

    Science.gov (United States)

    Jain, J; Jakimiuk, A J; Bode, F R; Ross, D; Kaunitz, A M

    2004-10-01

    DMPA-SC 104 mg/0.65 mL is a new, low-dose subcutaneous (SC) formulation of Depo-Provera contraceptive injection (150 mg/mL medroxyprogesterone acetate injectable suspension) that provides efficacy, safety and immediacy of onset equivalent to Depo-Provera intramuscular (IM) injection. Two large, open-label, Phase 3 studies assessed the 1-year contraceptive efficacy, safety and patient satisfaction with DMPA-SC administered every 3 months (12-13 weeks). Zero pregnancies were reported in both studies, which included a total of 16,023 woman-cycles of exposure to DMPA-SC and substantial numbers of overweight or obese women. DMPA-SC was well-tolerated and adverse events were similar to those reported previously with Depo-Provera IM. Thus, DMPA-SC offers women a new, highly effective and convenient long-acting contraceptive option. PMID:15451329

  20. SC response characteristics of two kinds of coagulant

    Institute of Scientific and Technical Information of China (English)

    杨万东; 宋爽; 史惠祥

    2002-01-01

    Automatic coagulant dosage control with streaming current (SC) technique is in troduced inthis paper. Aluminum and ferric coagulants are widely used in surface water treatment. The SC response characteristics of P-AiCI3 aluminum coagulant and P-FeCI3 ferric coagulant were investigated in this work. Bench-scale water treatment results were obtained from jar tests including rapid mixing,flocculation and undisturbed sedimentation. Results showed that aluminum coagulant is more sensitive than ferric coagulant to SC response.

  1. SC response characteristics of two kinds of coagulant

    Institute of Scientific and Technical Information of China (English)

    杨万东; 宋爽; 史惠祥

    2002-01-01

    Automatic coagulant dosage control with streaming current (SC) technique is introduced in this paper. Aluminum and ferric coagulants are widely used in surface water treatment. The SC response characteristics of P-AlCl3 aluminum coagulant and P-FeCl3 ferric coagulant were investigated in this work. Bench-scale water treatment results were obtained from jar tests including rapid mixing, flocculation and undisturbed sedimentation. Results showed that aluminum coagulant is more sensitive than ferric coagulant to SC response.

  2. Treatment of TiO2 with COOH-functionalized germanium nanoparticles to enhance the photocurrent of dye-sensitized solar cells.

    Science.gov (United States)

    Kim, Chang-Ho; Ha, Eun-Sung; Baik, Hionsuck; Kim, Kang-Jin

    2011-03-01

    A dye-sensitized solar cell (DSSC) containing a TiO(2) film treated with COOH-functionalized germanium nanoparticles (Ge-COOH Nps) exhibited a higher short-circuit photocurrent density (J(sc); 15.4 mA cm(-2)) compared to the corresponding untreated DSSC (13.4 mA cm(-2)) using N719 and a 12 μm thick TiO(2) film at 100 mW cm(-2). The amount of N719 attached to the treated TiO(2) film was 21% greater than that attached to the untreated TiO(2) film. Enhancement of the J(sc) value by 15% was attributed mostly to an intramolecular charge transfer from N719 attached to the Ge-COOH Nps to the TiO(2) conduction band through the Ge-COOH Nps.

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

    Science.gov (United States)

    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.

  4. Relationship Between Net Photosynthetic Rate of Cassava SC205 and Its Physio-ecological Factors

    Institute of Scientific and Technical Information of China (English)

    Yong SONG; Xuan LIN; Jinhui YANG; Yuping DENG; Xingyao XIONG

    2014-01-01

    [Objective]The aim was to measure photosynthetic characters of SC 205, a cassava cultivar, and explore the relationships of the net photosynthetic rate (Pn) with physiological and ecological factors. [Method] The diurnal variations of photosyn-thesis in leaves of SC205 were studied by LICOR-6400 portable photosynthesis system, and the relationships of the net photosynthetic rate (Pn) with physiological and ecological factors were studied by simple correlation analysis and path analysis. [Result] The curve of diurnal variation of Pn showed single peak at 10:00 am at 24.07 μ mol CO2 m2/s, without showing midday depression; the diurnal changes of stomatal conductance (Gs), transpiration rate (Tr), leaf temperature (Tl), air tempera-ture (Ta) and photosynthetic active radiation (PAR) al showed single peak curves, and there were positive relationships of Pn with Gs, Tr, Tl, Ta and PAR. The diur-nal variations of intercellular CO2 concentration (Ci), atmospheric CO2 concentration (Ca), relative humidity (RH) showed in a U-shape curve. There were highly signifi-cant positive correlation of Pn with Gs and PAR; the diurnal variation of Pn had highly significant negative correlations with Ci and Ca. The direct impact of physio-logical factors on Pn was as fol ows: Ci>Gs>Tl>Tr, and the direct impact of ecologi-cal factors was RH>PAR>Ca>Ta. [Conclusion] The research showed that Ci, Gs and Tr play very important roles in the changes of Pn among the physiological fac-tors, and PAR and Ca affect the changes of Pn among the ecological factors.

  5. Surface Characterization of Laser Surface Melted NiTi Shape Memory Alloy in Hanks' Solution

    Institute of Scientific and Technical Information of China (English)

    CUIZhen-duo; ZHUSheng-li; MANHauchung; YANGXian-jin

    2004-01-01

    The surface of Ti-50.8Ni at% shape memory alloy was melted by an Nd-YAG laser. The Ti/Ni and Ti4+/ Tiatomic concentration ratios at the surface were changed significantly. The Ni ion release rate of the laser melted surface was much lower than that of the mechanical polished samples. A calcium-phosphorous layer with high Ca/P ratio was detected after immersion in Hanks' solution.

  6. CaFeAs2: A staggered intercalation of quantum spin Hall and high-temperature superconductivity

    Science.gov (United States)

    Wu, Xianxin; Qin, Shengshan; Liang, Yi; Le, Congcong; Fan, Heng; Hu, Jiangping

    2015-02-01

    We predict that CaFeAs2, a newly discovered iron-based high-temperature (Tc) superconductor, is a staggered intercalation compound that integrates topological quantum spin Hall (QSH) and superconductivity (SC). CaFeAs2 has a structure with staggered CaAs and FeAs layers. While the FeAs layers are known to be responsible for high Tc superconductivity, we show that with spin orbital coupling each CaAs layer is a Z2 topologically nontrivial two-dimensional QSH insulator and the bulk is a three-dimensional weak topological insulator. In the superconducting state, the edge states in the CaAs layer are natural one-dimensional topological superconductors. The staggered intercalation of QSH and SC provides us a unique opportunity to realize and explore physics, such as Majorana modes and Majorana fermion chains.

  7. Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

    Science.gov (United States)

    Atli, K. C.; Karaman, I; Noebe, R. D.; Garg, A.; Chumlyakov, Y. I.; Kireeva, I. V.

    2010-01-01

    A Ti(50.5)Ni(24.5)Pd25 high-temperature shape memory alloy (HTSMA) is microalloyed with 0.5 at. pct scandium (Sc) to enhance its shape-memory characteristics, in particular, dimensional stability under repeated thermomechanical cycles. For both Ti(50.5)Ni(24.5)Pd25 and the Sc-alloyed material, differential scanning calorimetry is conducted for multiple cycles to characterize cyclic stability of the transformation temperatures. The microstructure is evaluated using electron microscopy, X-ray diffractometry, and wavelength dispersive spectroscopy. Isobaric thermal cycling experiments are used to determine transformation temperatures, dimensional stability, and work output as a function of stress. The Sc-doped alloy displays more stable shape memory response with smaller irrecoverable strain and narrower thermal hysteresis than the baseline ternary alloy. This improvement in performance is attributed to the solid solution hardening effect of Sc.

  8. Final Report: DOE Award Number: DE-SC0006398, University of CA, San Diego

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Jennifer [Univ. of California, San Diego, CA (United States)

    2015-05-27

    The focus of the proposed research is to direct the assembly of single or binary nanoparticles into meso- or macroscale three-dimensional crystals of any desired configuration and crystallographic orientation without using prohibitively expensive lithographic processes. The epitaxial nucleation of defect-free, surface-bound bulk single crystals will revolutionize technologies for energy to generate new types of solar cells that yield maximum conversion efficiencies. It has been proposed that having a nanostructured bulk hetero-interface will enable efficient charge-carrier separations, similar to organic based heterojunction cells but with potential improvements, including thermal and long-term stability, tunability of energy levels, large adsorption coefficients and carrier multiplication. However, engineering such devices requires nanoscale control and ordering in both 2- and 3-dimensions over macroscopic areas and this has yet to be achieved. In Nature, bulk organic and inorganic materials are arranged into precise and ordered programmed assemblies through the sequestration of raw materials into confined spaces and association through highly specific non-covalent interactions between biomolecules. Using similar strategies, the proposed research will focus on confining metal and semiconductor nanocrystals to pre-determined surface patterns and controlling their arrangement through tunable, orthogonal biomolecular binding. Once a perfect two-dimensional seed layer has been constructed, successive layers of single nanocrystals will be nucleated epitaxially with long-range order and tunable crystallographic orientations. The proposed research exploits the ability of biomolecules to bind specific targets in a tunable, orthogonal, multivalent, and reversible manner to the arrangements of DNA-nanoparticle conjugates on chemically defined surfaces. Through careful balance of the attractive and repulsive forces between the particles, the array, and the outside surface, it is envisioned that single or mixed nanoparticles can be packed to adopt uniform crystal orientation in two and three dimensions from simple mixing and annealing of biomolecule-nanoparticle conjugates with biomolecule-stamped surfaces. To control the crystallographic alignment of each particle with its neighbors, the nanoparticles will be assembled using a mixture of non-covalent biomolecular interactions. To create solar cells in which layers of donor and acceptor nanocrystals that are not only oriented normal to the top and bottom electrodes but are also arranged in a checkerboard pattern, multicomponent nanocrystals (e.g. CdSe, CdTe) will be conjugated with biochemical linkers such that only interactions between the CdTe and CdSe promote particle packing within the array. The proposed research will: (1) elucidate the role of single and binary cooperative particle-DNA interactions in influencing nanoparticle crystallographic orientation in two and three dimensions; (2) understand how confinement of nanoparticles on patterned arrays of biomolecules and modification of the surrounding substrate can nucleate long-range order over macroscopic areas via predefined grain boundaries; and (3) synthesize and characterize DNA conjugated semiconductor nanocrystals and assemble them into 2- and 3-D binary superlattice arrays for photovoltaics.

  9. Dispersing and Doping of BaTiO3 Powder by Adsorption

    Institute of Scientific and Technical Information of China (English)

    SU Taolong

    2008-01-01

    Dispersing and doping of BaTiO3 powder by adsorption method were investigated.Ultrafine BaTiO3 powders were dispersed in the aqueous with ammoniumized citrate (NH4-CA) or ammoniumized citric Ianthanum chelate (NH4-La-CA) as dispersant by ultrasonic bath. Better dispersion of BaTiO3 slurry was obtained in the aqueous with NH4-La-CA than that of NH4-CA when the mass ratio of citric acid (CA) to BaTiO3.Was less than 0.007. The pH value hardly affects the dispersion property of BaTiO3 suspension dispersed by NH4-La-CA. BaTiO3 powder could be well dispersed (median size D50=0.45 μm) and also doped with high uniformity of added components by adsorbing citric acid chelate on surface. Compared with solid mixing, better microstructure and properties of La/Mn codoped ceramics were obtained by adsorption method.

  10. New ternary CeScSi-type RTi0.85Mo0.15Ge compounds (R=Gd-Tm,Lu)

    International Nuclear Information System (INIS)

    Investigations made by powder X-ray diffraction on new ternary RTi0.85Mo0.15Ge compounds (R=Gd-Tm,Lu) are reported. The compounds GdTi0.85Mo0.15Ge (a=0.4032(1) nm,c=1.5467(1) nm),TbTi0.85Mo0.15Ge(a=0.4014(1) nm,c=1.5315(1) nm),DyTi0.85Mo0.15Ge(a=0.4010(1) nm,c=1.5264(1) nm),HoTi0.85Mo0.15Ge(a=0.3990(1) nm,c=1.5144(1) nm),ErTi0.85Mo0.15Ge(a=0.3993(1) nm,c=1.5107(2) nm),TmTi0.85Mo0.15Ge(a=0.3970(1) nm, c=1.5004(2) nm) and LuTi0.85Mo0.15(a=0.3955(1) nm,c=1.4875(3) nm) crystallize in the tetragonal CeScSi-type structure (space group I4/mmm). (orig.)

  11. Synthesis of square-like anatase TiO2 nanocrystals based on TiOF2 quantum dots

    International Nuclear Information System (INIS)

    Graphical abstract: The square-like anatase TiO2 nanocrystals were successfully synthesized and found that the intermediate TiOF2 quantum dots formed before the hydrothermal reaction played a key role for the formation of TiO2 with a high percentage of exposed {0 0 1} facets. Highlights: ► A simple hydrothermal route was developed for the synthesis of the square-like anatase TiO2 nanocrystals without HF. ► The anatase TiO2 nanocrystals exhibited a high percentage 64% of exposed {0 0 1} facets and highly crystalline. ► The intermediate TiOF2 QDs played a key role for the formation of square-like anatase TiO2 nanocrystals. - Abstract: In this study, a simple hydrothermal route was developed for the synthesis of the square-like anatase TiO2 nanocrystals starting from TiOA and NH4F raw materials. The synthesized nanocrystals exhibited a high percentage 64% of exposed {0 0 1} facets and highly crystalline. The size of square-like nanocrystals was found to be ca. 50–80 nm and their thickness was 10–20 nm. It was found that the intermediate TiOF2 QDs formed before the hydrothermal reaction played a key role for the formation of square-like anatase TiO2 nanocrystals. Based on a series of experimental results, a possible mechanism for the formation of square-like anatase TiO2 nanocrystals with a highly exposed {0 0 1} facet was proposed.

  12. Effect of Ti-OH groups on microstructure and bioactivity of TiO2 coating prepared by micro-arc oxidation

    Science.gov (United States)

    Zhang, Peng; Zhang, Zhiguo; Li, Wei; Zhu, Min

    2013-03-01

    Titanium and its alloys are promising biomedical metal materials. In order to improve the bioactivity of TiO2 coatings, three processes including micro-arc oxidation (MAO) in a Ca and P ion electrolyte (Ti-MAO), MAO in a 1 M NaOH electrolyte (Ti-NaOH) which was heated to 60 °C and a two-step MAO process in which specimens were first treated by MAO in Ca and P ion solution and then further in a 1 M heated NaOH electrolyte in succession (Ti-MAO-NaOH) were carried out. Round pores were found to form on the surface of the Ti-MAO sample while homogeneously distributed hollow spherical particles were found on both the Ti-NaOH and Ti-MAO-NaOH sample surfaces. The bioactivity evaluation showed that the combination of MAO processes in different electrolytes induced more rapid formation of apatite in contrast to the simple MAO treatment in heated alkaline electrolyte. The Ti-OH groups formed in alkaline electrolyte are found to be response for the rapid formation of hydroxyapatite during a SBF soaking. The previous introduction of Ca and P can increase the opportunity to form hydroxyapatite.

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

    Science.gov (United States)

    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.

  14. Human bulbar conjunctival hemodynamics in hemoglobin SS and SC disease.

    Science.gov (United States)

    Wanek, Justin; Gaynes, Bruce; Lim, Jennifer I; Molokie, Robert; Shahidi, Mahnaz

    2013-08-01

    The known biophysical variations of hemoglobin (Hb) S and Hb C may result in hemodynamic differences between subjects with SS and SC disease. The purpose of this study was to measure and compare conjunctival hemodynamics between subjects with Hb SS and SC hemoglobinopathies. Image sequences of the conjunctival microcirculation were acquired in 9 healthy control subjects (Hb AA), 24 subjects with SC disease, and 18 subjects with SS disease, using a prototype imaging system. Diameter (D) and blood velocity (V) measurements were obtained in multiple venules of each subject. Data were categorized according to venule caliber by averaging V and D for venules with diameters less than (vessel size 1) or greater than (vessel size 2) 15 µm. V in vessel size 2 was significantly greater than V in vessel size 1 in the AA and SS groups (P ≥ 0.009), but not in the SC group (P = 0.1). V was significantly lower in the SC group as compared to the SS group (P = 0.03). In AA and SS groups, V correlated with D (P ≤ 0.005), but the correlation was not statistically significant in the SC group (P = 0.08). V was inversely correlated with hematocrit in the SS group for large vessels (P = 0.03); however, no significant correlation was found in the SC group (P ≥ 0.2). Quantitative assessment of conjunctival microvascular hemodynamics in SS and SC disease may advance understanding of sickle cell disease pathophysiology and thereby improve therapeutic interventions.

  15. 76 FR 58401 - Safety Zone; Swim Around Charleston, Charleston, SC

    Science.gov (United States)

    2011-09-21

    ... Zone; Swim Around Charleston, Charleston, SC in the Federal Register (76 FR 38586). We received no... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Swim Around Charleston, Charleston, SC... temporary moving safety zone during the Swim Around Charleston, a swimming race occurring on waters of...

  16. Sc III Spectral Properties of Astrophysical Interest

    CERN Document Server

    Nandy, D K; Sahoo, B K; Li, Chengbin

    2011-01-01

    Transition properties such as oscillator strengths, transition rates, branching ratios and lifetimes of many low-lying states in the doubly ionized scandium (Sc III) are reported. A relativistic method in the coupled-cluster framework has been employed to incorporate the electron correlations due to the Coulomb interaction to all orders by considering all possible singly and doubly excited electronic configurations conjointly with the contributions from the leading order triple excitations in a perturbative approach. Present results are compared with the previously available results for the transition lines of astrophysical interest and the role of the correlation effects are also discussed concisely. Some of the transition rates, oscillator strengths and lifetimes are acquainted.

  17. SC2: Secure Communication over Smart Cards

    DEFF Research Database (Denmark)

    Dragoni, Nicola; Lostal, Eduardo; Papini, Davide;

    2012-01-01

    The Security-by-Contract (S×C) framework has recently been proposed to support software evolution in open multi-application smart cards. The key idea lies in the notion of contract, a specification of the security behavior of an application that must be compliant with the security policy...... of the card hosting the application. In this paper we address a key issue to realize the S×C idea, namely the outsourcing of the contractpolicy matching service to a Trusted Third Party (TTP). In particular, we present the design and implementation of (SC)2 (Secure Communication over Smart Cards), a system...... securing the communication between a smart card and the TTP which provides the S×C matching service....

  18. Hydrothermal treatment for TiN as abrasion resistant dental implant coating and its fibroblast response

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Xingling, E-mail: shixingling1985@hotmail.com [School of Material Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Department of Biomaterials, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582 (Japan); Jiangsu Provincial Key Laboratory for Interventional Medical Devices, Huaiyin Institute of Technology, Huaian 223003 (China); Xu, Lingli [School of Material Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Munar, Melvin L.; Ishikawa, Kunio [Department of Biomaterials, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582 (Japan)

    2015-04-01

    Dental implant made of pure titanium (Ti) is prone to scratch and abrasion during routine oral hygiene procedures. This results an increase in surface roughness and therefore, facilitates the adhesion of bacteria. In severe cases, this could lead to peri-implantitis. To overcome this problem, surface modification of Ti is necessary to improve its abrasion resistance. Besides, a strong implant–gingiva interface should also be guaranteed to prevent the adhesion of bacteria. In this study, titanium nitride (TiN) coating was first prepared with gas nitriding to increase surface hardness of pure the substrate. Then, the TiN was hydrothermally treated in CaCl{sub 2} solution in order to improve its soft tissue biocompatibility. The effect of hydrothermal treatment temperature on surface properties of TiN was investigated and its biocompatibility was assessed in vitro using NIH3T3 fibroblast cell. It was determined that 120 °C was the critical temperature for the hydrothermal treatment condition. Treatment below 120 °C could incorporate Ca into TiN surface, oxidize TiN surface partially and then improve the wettability while preserving its morphology and hardness. Fibroblast cell attachment and proliferation were improved and cell spreading was enhanced on hydrothermally treated specimens compared with untreated ones. Improved wettability, Ca incorporation and negative surface due to interstitial N were believed to be the main reasons. Hydrothermal treatment is expected to make TiN a promising dental implant coating with excellent abrasion resistance and good soft tissue affinity. - Highlights: • Ca was incorporated into TiN surface while not sacrificing its hardness. • Interstitial N due to oxidation promoted Ca adsorption and cell adhesion. • Hydrothermal treatment makes TiN a promising coating for dental implant.

  19. Hydrothermal treatment for TiN as abrasion resistant dental implant coating and its fibroblast response

    International Nuclear Information System (INIS)

    Dental implant made of pure titanium (Ti) is prone to scratch and abrasion during routine oral hygiene procedures. This results an increase in surface roughness and therefore, facilitates the adhesion of bacteria. In severe cases, this could lead to peri-implantitis. To overcome this problem, surface modification of Ti is necessary to improve its abrasion resistance. Besides, a strong implant–gingiva interface should also be guaranteed to prevent the adhesion of bacteria. In this study, titanium nitride (TiN) coating was first prepared with gas nitriding to increase surface hardness of pure the substrate. Then, the TiN was hydrothermally treated in CaCl2 solution in order to improve its soft tissue biocompatibility. The effect of hydrothermal treatment temperature on surface properties of TiN was investigated and its biocompatibility was assessed in vitro using NIH3T3 fibroblast cell. It was determined that 120 °C was the critical temperature for the hydrothermal treatment condition. Treatment below 120 °C could incorporate Ca into TiN surface, oxidize TiN surface partially and then improve the wettability while preserving its morphology and hardness. Fibroblast cell attachment and proliferation were improved and cell spreading was enhanced on hydrothermally treated specimens compared with untreated ones. Improved wettability, Ca incorporation and negative surface due to interstitial N were believed to be the main reasons. Hydrothermal treatment is expected to make TiN a promising dental implant coating with excellent abrasion resistance and good soft tissue affinity. - Highlights: • Ca was incorporated into TiN surface while not sacrificing its hardness. • Interstitial N due to oxidation promoted Ca adsorption and cell adhesion. • Hydrothermal treatment makes TiN a promising coating for dental implant

  20. Nuclear spectroscopy of 24Na and 46Sc by thermal neutron capture

    International Nuclear Information System (INIS)

    The measurement of the intensity and the energy of γ-rays produced by capture of thermal neutrons in 45Sc is reported. Of the total primary transition strength 99% could be accounted for and 426 lines could be placed in a 46Sc level scheme containing 27 previously unobserved levels. The reaction Q-value was determined as 8760.77. Of the 158 γ-rays ascribed to the 23Na(n,γ)24Na reaction, 143 have been placed in a 24Na decay scheme accounting for 100% of the total primary strength. The reaction Q-value amounts to 6959.42. The data resulted in spin assignments for four and spin restrictions for six levels. The circular polarization of 14 γ-rays from the capture of polarized neutrons has been measured. The Jsup(π) = 2+ channel spin contribution has been determined model-independently and unambiguously for 22 primary transitions. The average Jsup(π) = 2+ channel contribution is 5.8%. Spins of final levels are in agreement with previous assignments. For three levels spin restrictions have been made. The energies of positive parity levels are in agreement with a shell model calculation in the complete sd shell. Finally, the nuclear level densities of the 24Na, 46Sc, 484950Ti, 60Co, 6465Cu and 239U nuclei recently investigated by means of thermal neutron capture are described with the Fermi gas theory. Experimentally observed pairing effects in the level density parameter for nuclei in the mass region A = 40-81 are explained theoretically. (Auth.)