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Sample records for baf2 caf2 laf3

  1. Vacuum ultraviolet thin films. I - Optical constants of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 thin films. II - Vacuum ultraviolet all-dielectric narrowband filters

    NASA Technical Reports Server (NTRS)

    Zukic, Muamer; Torr, Douglas G.; Spann, James F.; Torr, Marsha R.

    1990-01-01

    An iteration process matching calculated and measured reflectance and transmittance values in the 120-230 nm VUV region is presently used to ascertain the optical constants of bulk MgF2, as well as films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on MgF2 substrates. In the second part of this work, a design concept is demonstrated for two filters, employing rapidly changing extinction coefficients, centered at 135 nm for BaF2 and 141 nm for SiO2. These filters are shown to yield excellent narrowband spectral performance in combination with narrowband reflection filters.

  2. Hardness of CaF2 and BaF2 solid lubricants at 25 to 670 deg C

    NASA Technical Reports Server (NTRS)

    Deadmore, Daniel L.; Sliney, Harold E.

    1987-01-01

    Plastic deformation is a prominent factor in determining the lubricating value of solid lubricants. Little information is available and its direct measurement is difficult so hardness, which is an indirect measure of this property was determined for fluoride solid lubricant compositions. The Vickers hardness of BaF2 and CaF2 single crystals was measured up to 670 C in a vacuum. The orientation of the BaF2 was near the (013) plane and the CaF2 was about 16 degrees from the degrees from the (1'11) plane. The BaF2 has a hardness of 83 kg/sq mm at the 25 C and 9 at the 600 C. The CaF2 is 170 at 25 C and 13 at 670 C. The decrease in hardness in the temperature range of 25 to 100 C is very rapid and amounts to 40% for both materials. Melts of BaF2 and CaF2 were made in a platinum crucible in ambient air with compositions of 50 to 100 wt% BaF2. The Vickers hardness of these polycrystalline binary compositions at 25 C increased with increasing CaF2 reaching a maximum of 150 kn/sq mm near the eutectic. The polycrystalline CaF2 was 14% softer than that of the single crystal surface and BsF2 was 30% harder than the single crystal surface. It is estimated that the brittle to ductile transition temperature for CaF2 and BaF2 is less than 100 C for the conditions present in the hardness tester.

  3. Divalent europium doped CaF2 and BaF2 nanocrystals from ionic liquids

    DOE PAGES

    Anghel, Sergiu; Golbert, Sebastian; Meijerink, Andries; ...

    2016-10-11

    A new, facile and quick synthesis method for Eu2+ doped the alkaline earth fluorides was developed using ionic liquids as solvent, precursor and capping agent. Reductive atmosphere and very high temperatures were avoided, while still attaining the desired structure, small particle sizes and divalent oxidation state of the lanthanide. Here, this opens the door for the development of new Ln2+ doped nanomaterials. The successful Eu2+ incorporation was proven by optical spectroscopic measurements which showed the spin and parity allowed f-d transitions of Eu2+ in CaF2:Eu2+/BaF2:Eu2+. 4f7-4f7 transitions could be observed at low temperatures (7 K).

  4. CaF2, BaF2 and SrF2 crystals’ optical anisotropy parameters

    NASA Astrophysics Data System (ADS)

    Snetkov, I. L.; Yakovlev, A. I.; Palashov, O. V.

    2015-09-01

    Using the original method, based on measurements of thermally induced depolarization, the optical anisotropy parameters of CaF2, BaF2 and SrF2 cubic crystals were measured and compared with what is known from the literature. Euler angles of crystallographic axis orientation [C], in which the thermally induced depolarization is minimal, were determined using experimental results for studied fluorides.

  5. Defect-induced wetting on BaF 2(111) and CaF 2(111) at ambient conditions

    NASA Astrophysics Data System (ADS)

    Cardellach, M.; Verdaguer, A.; Fraxedas, J.

    2011-12-01

    The interaction of water with freshly cleaved (111) surfaces of isostructural BaF2 and CaF2 single crystals at ambient conditions (room temperature and under controlled humidity) has been studied using scanning force microscopy in different operation modes and optical microscopy. Such surfaces exhibit contrasting behaviors for both materials: while on BaF2(111) two-dimensional water layers are formed after accumulation at step edges, CaF2(111) does not promote the formation of such layers. We attribute such opposed behavior to lattice match (mismatch) between hexagonal water ice and the hexagonal (111) surfaces of BaF2(CaF2). Optical microscope images reveal that this behavior also determines the way the surfaces become wetted at a macroscopic level.

  6. Absolute refractive indices and thermal coefficients of CaF2, SrF2, BaF2, and LiF near 157 nm.

    PubMed

    Burnett, John H; Gupta, Rajeev; Griesmann, Ulf

    2002-05-01

    We present high-accuracy measurements for wavelengths near 157 nm of the absolute index of refraction, the index dispersion, and the temperature dependence of the index for the ultraviolet optical materials with cubic symmetry: CaF2, SrF2, BaF2, and LiF. Accurate values of these quantities for these materials are needed for designs of the lens systems for F2 excimer-laser-based exposure tools for 157-nm photolithography. These tools are expected to use CaF2 as the primary optical material and possibly one of the others to correct for chromatic aberrations. These optical properties were measured by the minimum deviation method. Absolute refractive indices were obtained with an absolute accuracy of 5 x 10(-6) to 6 x 10(-6).

  7. Enhanced ultraviolet upconversion luminescence of Tm and Yb codoped ZrF4-BaF2-LaF3-AlF3-NaF glass.

    PubMed

    He, Chunfeng; Zhao, Dan; Qin, Guanshi; Zheng, Kezhi; Qin, Weiping

    2011-11-01

    Ultraviolet (UV) upconversion (UC) luminescence properties of Tm3+ ions sensitized by Yb3+ ions in ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) glass were studied in detail. Under the excitation from a 980 nm continuous wave (CW) diode laser, red, blue, and even UV emissions were observed in the fluorozirconate glass. Several fluorescence bands appeared in the UC emission spectrum from 292.8 nm to 805.8 nm. The UC emission peaks at 291 nm, 347 nm, 363 nm, 454 nm, 475 nm, 647 nm, 687 nm, and 804 nm correspond to the transitions of 1I6 --> 3H6, 1I6 --> 3F4, 1D2 --> 3H6, 1D2 --> 3F4, 1G4 --> 3H6, 1G4 --> 3F4, 3F3 --> 3H6, and 3H4 --> 3H6, respectively. Experimental results of intensity dependence of the up-converted fluorescence on the pump power indicate a five-photon excitation scheme of 1I6 energy level.

  8. Temperature Dependence of the Surface Energy of the Low-index Planes of CaF2, BaF2 and SrF2

    NASA Astrophysics Data System (ADS)

    Bebelis, S.; Nikolopoulos, P.

    2017-02-01

    The temperature dependence of the surface energy γ of the low-index (111), (110) and (100) planes of CaF2, BaF2 and SrF2 was evaluated for the first time, using a simple method which is based on physical and thermodynamic quantities and considerations. The extrapolated to 0 K surface energy values agree well with the available theoretical data reported in the literature for the (111) plane and are close to those for the (110) plane, whereas they are significantly lower than those for the (100) plane. The calculated γ111 values for 298 K agree well with the corresponding experimentally determined literature values. The calculated γ100/γ111 ratio revealed formation of crystals with truncated octahedron structure in thermodynamic equilibrium. This structure remains practically constant with temperature. The surface energy values of fluoride melts formed by melting of octahedron structures, calculated via extrapolation of the surface energy of the solids to the melting points, were compared with experimentally determined literature values for melts resulting from single or polycrystalline materials.

  9. Temperature Dependence of the Surface Energy of the Low-index Planes of CaF2, BaF2 and SrF2

    NASA Astrophysics Data System (ADS)

    Bebelis, S.; Nikolopoulos, P.

    2017-03-01

    The temperature dependence of the surface energy γ of the low-index (111), (110) and (100) planes of CaF2, BaF2 and SrF2 was evaluated for the first time, using a simple method which is based on physical and thermodynamic quantities and considerations. The extrapolated to 0 K surface energy values agree well with the available theoretical data reported in the literature for the (111) plane and are close to those for the (110) plane, whereas they are significantly lower than those for the (100) plane. The calculated γ111 values for 298 K agree well with the corresponding experimentally determined literature values. The calculated γ100/γ111 ratio revealed formation of crystals with truncated octahedron structure in thermodynamic equilibrium. This structure remains practically constant with temperature. The surface energy values of fluoride melts formed by melting of octahedron structures, calculated via extrapolation of the surface energy of the solids to the melting points, were compared with experimentally determined literature values for melts resulting from single or polycrystalline materials.

  10. Ionic, electronic and ion-diffusion controlled relaxation processes in CaF2, BaF2 and LiBaF3 crystals

    NASA Astrophysics Data System (ADS)

    Ziraps, V.; Kulis, P.; Tale, I.; Veispals, A.

    The ionic, electronic and anion-diffusion controlled thermally stimulated relaxation (TSR) processes at 80-700 K in CaF2 BaF2 and LiBaF3 crystals (X-ray irradiated or non-irradiated) have been investigated by means of ionic conductivity, ionic thermally stimulated (TS) depolarization current (TSDC); as well as current (TSC), luminescence (TSL) and bleaching (TSB) techniques. Above 250-290 K broad and overlapping anion TSDC peaks and correlated TSB stages are detected. The TSB kinetics is initiated and controlled by anion detrapping and interaction with the localized charges, i.e., the anion-diffusion controlled TSR processes take place in fluorides. The TSL and TSC data for LiBaF3 indicate that the lifetime and drift of electrons at 80-250 K is very small because of deep retrapping. The main TSL peaks at 132K, 170K and 220 K are caused by Vk center detrapping and hole-diffusion controlled tunnel recombination within pairs like .

  11. Novel and easy access to highly luminescent Eu and Tb doped ultra-small CaF2, SrF2 and BaF2 nanoparticles - structure and luminescence.

    PubMed

    Ritter, Benjamin; Haida, Philipp; Fink, Friedrich; Krahl, Thoralf; Gawlitza, Kornelia; Rurack, Knut; Scholz, Gudrun; Kemnitz, Erhard

    2017-02-28

    A universal fast and easy access at room temperature to transparent sols of nanoscopic Eu(3+) and Tb(3+) doped CaF2, SrF2 and BaF2 particles via the fluorolytic sol-gel synthesis route is presented. Monodisperse quasi-spherical nanoparticles with sizes of 3-20 nm are obtained with up to 40% rare earth doping showing red or green luminescence. In the beginning luminescence quenching effects are only observed for the highest content, which demonstrates the unique and outstanding properties of these materials. From CaF2:Eu10 via SrF2:Eu10 to BaF2:Eu10 a steady increase of the luminescence intensity and lifetime occurs by a factor of ≈2; the photoluminescence quantum yield increases by 29 to 35% due to the lower phonon energy of the matrix. The fast formation process of the particles within fractions of seconds is clearly visualized by exploiting appropriate luminescence processes during the synthesis. Multiply doped particles are also available by this method. Fine tuning of the luminescence properties is achieved by variation of the Ca-to-Sr ratio. Co-doping with Ce(3+) and Tb(3+) results in a huge increase (>50 times) of the green luminescence intensity due to energy transfer Ce(3+) → Tb(3+). In this case, the luminescence intensity is higher for CaF2 than for SrF2, due to a lower spatial distance of the rare earth ions.

  12. Effect of high-energy electron irradiation in an electron microscope column on fluorides of alkaline earth elements (CaF2, SrF2, and BaF2)

    NASA Astrophysics Data System (ADS)

    Nikolaichik, V. I.; Sobolev, B. P.; Zaporozhets, M. A.; Avilov, A. S.

    2012-03-01

    The effect of high-energy (150 eV) electron irradiation in an electron microscope column on crystals of fluorides of alkaline earth elements CaF2, SrF2, and BaF2 is studied. During structural investigations by electron diffraction and electron microscopy, the electron irradiation causes chemical changes in MF2 crystals such as the desorption of fluorine and the accumulation of oxygen in the irradiated area with the formation of oxide MO. The fluorine desorption rate increases significantly when the electron-beam density exceeds the threshold value of ˜2 × 103 pA/cm2). In BaF2 samples, the transformation of BaO into Ba(OH)2 was observed when irradiation stopped. The renewal of irradiation is accompanied by the inverse transformation of Ba(OH)2 into BaO. In the initial stage of irradiation of all MF2 compounds, the oxide phase is in the single-crystal state with a lattice highly matched with the MF2 matrix. When the irradiation dose is increased, the oxide phase passes to the polycrystalline phase. Gaseous products of MF2 destruction (in the form of bubbles several nanometers in diameter) form a rectangular array with a period of ˜20 nm in the sample.

  13. Compact watt-level passively Q-switched ZrF4-BaF2-LaF3-AIF3-NaF fiber laser at 2.8 μm using Fe2+:ZnSe saturable absorber mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Feng, Guoying; Zhang, Hong; Ning, Shougui; Lan, Bin; Zhou, Shouhuan

    2016-08-01

    A midinfrared (mid-IR) saturable absorber mirror (SAM) was fabricated by coating aluminum film on Fe2+:ZnSe crystal, based on the vacuum evaporation method. By employing the prepared SAM, we demonstrated a high-power passively Q-switched Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser at 2.8 μm. The highest output power in excess of 1.01 W was obtained with a pulse energy of 11.37 μJ and pulse duration of 0.73 μs, corresponding to a repetition rate of 88.84 kHz. To the best of our knowledge, these values represent the highest output power/pulse energy from a passively Q-switched ZBLAN fiber laser around 2.8 μm. Our results demonstrate that Fe2+:ZnSe SAM is a promising device for high-power/high-energy pulse generation in compact mid-IR fiber lasers.

  14. Reflectors for canning a BaF 2 crystal

    NASA Astrophysics Data System (ADS)

    Sinha, B. K.; Bhattacharya, R.

    1989-03-01

    The performance of BaF 2 crystals with various reflectors like teflon tape, ZrO 2, Al 2O 3 and CaF 2 powders is tested by measuring the energy and time resolution at different energies. It is shown that CaF 2 powder is a somewhat better reflector than the Al 2O 3 powder so far used by different workers. It is also seen that the reflectivity of CaF 2 powder for the BaF 2 emission spectrum is not much inferior to that of teflon tape which is, however, the best reported so far. Based on these observations a method of canning a BaF 2 crystal is proposed.

  15. Light scattering and computer simulation studies of superionic pure and La-doped BaF2

    NASA Astrophysics Data System (ADS)

    Rammutla, K. E.; Comins, J. D.; Erasmus, R. M.; Netshisaulu, T. T.; Ngoepe, P. E.; Chadwick, A. V.

    2016-03-01

    A combination of both Raman and Brillouin scattering experiments as well as Molecular Dynamics (MD) was used to study the superionic behaviour of BaF2 doped with a wide range of LaF3 concentrations (0 ⩽ x ⩽ 50 mol%). Raman spectroscopy reveals that for undoped BaF2 and those doped with 5% and 10% LaF3, the room temperature spectra show the usual T2g symmetry mode at 241 cm-1 whereas for those doped with 20%, 30% and 50% LaF3, the dominant Raman mode is of the Eg symmetry situated at ∼263, 275 and 286 cm-1, respectively. The Raman linewidths show near linear increases with temperature followed by rapid increases above the characteristic transition temperatures (Tc), being at 1200, 850, 800, 975, 950 and 920 K for LaF3 concentrations of 0, 5, 10, 20, 30 and 50; respectively. The temperature dependence of the squares of the Brillouin frequencies (ΔωB)2 of the LA and TA acoustic modes respectively related to elastic constants C11 and C44 showed linear decreases followed by significant deviations around the same temperatures (Tc), at which the Raman linewidths start to show substantial increases. The complementary studies using MD simulations show that the diffusion coefficients increase markedly above the same temperatures observed experimentally. The extrinsic fluorine ion trajectories were also determined from the MD simulations to better understand the mechanisms of diffusion.

  16. A theoretical study on the LaF3 molecule embedded in argon matrix

    NASA Astrophysics Data System (ADS)

    Lanza, Giuseppe

    The LaF3·Arn (n = 1-21) clusters have been proposed as models to account for the matrix effects on the molecular properties of the LaF3 molecule isolated in argon solid matrix at cryogenic temperature. Because of the strong Lewis acid character of the LaF3 molecule, there is a substantial electron-density transfer from the argon atoms to the molecule that induces important geometrical changes in the structure and vibrational frequencies. The present bottom-up approach reveals the formation of two sets of structures close in energy having the D3h-LaF3 and the C3v-LaF3. The D3h-LaF3 structures are more compact with respect to the C3v series. The largest investigated cluster of the D3h series, the LaF3·Ar21 resembles an hcp structure with the LaF3 occupying the central substitutional site that it is expected to be energetically preferred. The C3v-LaF3 structures are more stable for lighter clusters and their high formation rates in the gas-phase, immediately before matrix incorporation, could explain experimental IR/Raman results that point to a pyramidal shape for the molecule in argon matrix.

  17. Neodymium-doped LaF(3) nanoparticles for fluorescence bioimaging in the second biological window.

    PubMed

    Rocha, Ueslen; Kumar, Kagola Upendra; Jacinto, Carlos; Villa, Irene; Sanz-Rodríguez, Francisco; Iglesias de la Cruz, María del Carmen; Juarranz, Angeles; Carrasco, Elisa; van Veggel, Frank C J M; Bovero, Enrico; Solé, José García; Jaque, Daniel

    2014-03-26

    The future perspective of fluorescence imaging for real in vivo application are based on novel efficient nanoparticles which is able to emit in the second biological window (1000-1400 nm). In this work, the potential application of Nd(3+) -doped LaF(3) (Nd(3+) :LaF(3) ) nanoparticles is reported for fluorescence bioimaging in both the first and second biological windows based on their three main emission channels of Nd(3+) ions: (4) F(3/2) →(4) I(9/2) , (4) F(3/2) →(4) I(11/2) and (4) F(3/2) →(4) I(13/2) that lead to emissions at around 910, 1050, and 1330 nm, respectively. By systematically comparing the relative emission intensities, penetration depths and subtissue optical dispersion of each transition we propose that optimum subtissue images based on Nd(3+) :LaF(3) nanoparticles are obtained by using the (4) F3/2 →(4) I11/2 (1050 nm) emission band (lying in the second biological window) instead of the traditionally used (4) F(3/2) →(4) I(9/2) (910 nm, in the first biological window). After determining the optimum emission channel, it is used to obtain both in vitro and in vivo images by the controlled incorporation of Nd(3+) :LaF(3) nanoparticles in cancer cells and mice. Nd(3+) :LaF(3)nanoparticles thus emerge as very promising fluorescent nanoprobes for bioimaging in the second biological window.

  18. X-Ray Luminescence of LaF3:Tb3+ and LaF3:Ce3+, Tb3+ Water Soluble Nanoparticles

    SciTech Connect

    Liu, Y.; Chen, Wei; Wang, Shaopeng; Joly, Alan G.; Westcott, Sarah L.; Woo, Boon K.

    2008-03-15

    Utilizing scintillation nanoparticles as agents for photodynamic therapy for cancer treatment necessitates the use of biocompatible and water soluble nanoparticles. In this article, we report the synthesis and X-ray luminescence of water soluble Ce and Tb doped LaF3 nanoparticles. The nanoparticles are conjugated with folic acid and meso-tetra (o-carboxyphenyl) porphyrin. X-ray luminescence is observed from the nanoparticles in both powder and solution samples. More importantly, singlet oxygen has been detected from the conjugated system following X-ray excitation. These preliminary observations indicate that water-soluble scintillation nanoparticles can be potentially used in photodynamic therapy for deep-tissue cancer treatment.

  19. Effect of local environment on crossluminescence kinetics in SrF2:Ba and CaF2:Ba solid solutions

    NASA Astrophysics Data System (ADS)

    Terekhin, M. A.; Makhov, V. N.; Lebedev, A. I.; Sluchinskaya, I. A.

    2015-10-01

    Spectral and kinetic properties of extrinsic crossluminescence (CL) in SrF2:Ba(1%) and CaF2:Ba(1%) are compared with those of intrinsic CL in BaF2 and are analyzed taking into account EXAFS data obtained at the Ba LIII edge and results of first-principles calculations. The CL decay time was revealed to be longer in SrF2:Ba and CaF2:Ba compared to BaF2. This fact contradicts the expected acceleration of luminescence decay which could result from an increased overlap of wave functions in solid solutions due to shortening of the Ba-F distance obtained in both EXAFS measurements and first-principles calculations. This discrepancy is explained by the effect of migration and subsequent non-radiative decay of the Ba(5p) core holes in BaF2 and by decreasing of the probability of optical transitions between Ba(5p) states and the valence band in SrF2:Ba and CaF2:Ba predicted by first-principles calculations.

  20. CaF2:Yb laser ceramics

    NASA Astrophysics Data System (ADS)

    Akchurin, M. Sh.; Basiev, T. T.; Demidenko, A. A.; Doroshenko, M. E.; Fedorov, P. P.; Garibin, E. A.; Gusev, P. E.; Kuznetsov, S. V.; Krutov, M. A.; Mironov, I. A.; Osiko, V. V.; Popov, P. A.

    2013-01-01

    CaF2:Yb fluoride laser ceramics, prepared by hot-forming, exhibit the same optical properties as starting single crystals. Slope efficiency of the Сa0.95Yb0.05F2.05 is equal to 35% in the pulsed mode of laser operation. Decrease of ytterbium concentration in CaF2:Yb samples down to 3 mol.% resulted in the essential improvement of Сa0.97Yb0.03F2.03 thermal conductivity from 3.5 to 4.5 W/m K, but slightly decreased (down to 30%) slope efficiency of the samples under both pulsed and CW mode of operation. Alternative hot-pressing synthesis of CaF2:Yb fluoride laser ceramics provided materials with superior mechanical properties (microhardness Н = 3.2 GPa and fracture toughness К1С = 0.65 МPа m1/2) in comparison with hot-formed and/or single crystal CaF2:Yb specimens. For the first time, lasing has been observed for the novel aforementioned hot-pressed CaF2:Yb ceramics.

  1. Longitudinal conductivity of LaF3/SrF2 multilayer heterostructures

    PubMed Central

    Vergentev, Tikhon; Banshchikov, Alexander; Filimonov, Alexey; Koroleva, Ekaterina; Sokolov, Nikolay; Wurz, Marc Christopher

    2016-01-01

    Abstract LaF3/SrF2 multilayer heterostructures with thicknesses of individual layers in the range 5–100 nm have been grown on MgO(100) substrates using molecular beam epitaxy. The longitudinal conductivity of the films has been measured using impedance spectroscopy in the frequency range 10−1–106 Hz and a temperature range 300–570 K. The ionic DC conductivities have been determined from Nyquist impedance diagrams and activation energies from the Arrhenius–Frenkel equation. An increase of the DC conductivity has been observed to accompany decreased layer thickness for various thicknesses as small as 25 nm. The greatest conductivity has been shown for a multilayer heterostructure having thicknesses of 25 nm per layer. The structure has a conductivity two orders of magnitude greater than pure LaF3 bulk material. The increasing conductivity can be understood as a redistribution of charge carriers through the interface due to differing chemical potentials of the materials, by strong lattice-constant mismatch, and/or by formation of a solid La1-xSrxF3-x solution at the interface during the growth process. PMID:27933119

  2. Radiolysis of LaF3 crystals with rare-earth impurities

    NASA Astrophysics Data System (ADS)

    Radzhabov, E. A.

    2016-10-01

    The absorption spectra of LaF3 crystals, both pure and doped with rare-earth fluorides (YF3, CeF3, NdF3, PrF3, SmF3, EuF3, GdF3, TbF3, DyF3, HoF3, ErF3, TmF3, YbF3, and LuF3) have been investigated. All these impurities can be separated into two groups with respect to the shape of the absorption spectra of irradiated crystals. The spectra of the crystals doped with Nd, Sm, Tm, and Yb exhibit, along with 200-nm hole band F 3 - , weak bands due to RE2+-anion vacancy centers. The spectra of LaF3 crystals with Y, Ce, Pr, Gd, Tb, Dy, Ho, Er, and Lu impurities exhibit, along with the hole-center bands (F 3 - at 200 nm and VkA at 320 nm), bands of comparable intensity, which can be attributed to RE3+- F centers. This conclusion is confirmed by preliminary quantum-chemical calculations and the estimation of the levels location in the energy-band diagram.

  3. Photoinduced toxicity of PrF3 and LaF3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Pudovkin, M. S.; Zelenikhin, P. V.; Krasheninnikova, A. O.; Korableva, S. L.; Nizamutdinov, A. S.; Alakshin, E. M.; Semashko, V. V.; Safiullin, R. A.; Kadirov, M. K.

    2016-10-01

    PrF3 and LaF3 nanoparticles were synthesized by the hydrothermal method. The size distribution of these nanoparticles in the colloidal solution produced was studied by photon correlation spectroscopy. The mean diameter of the nanoparticles was 42 ± 1 nm. During the study of the toxicity of the nanoparticles, the mixture of a colloidal solution of the nanoparticles with cells to be studied was irradiated by 30-mW continuous lasers at wavelengths of 532 and 473 nm. The concentration of salmonella cells in normal saline was 106 cell/mL, while that of nanoparticles was 0.1 g/L. The cell survival percentage was 39, 34, and 20% for the irradiation times of 5, 10, and 15 min, respectively, at an optimal laser radiation power density of 0.4 W/cm at a wavelength of 532 nm. It was ascertained that LaF3 nanoparticles do not possess the property of photoinduced toxicity and the apoptosing effect. Moreover, the property of photoinduced toxicity is not shared by microparticles, in contrast to nanoparticles.

  4. Longitudinal conductivity of LaF3/SrF2 multilayer heterostructures.

    PubMed

    Vergentev, Tikhon; Banshchikov, Alexander; Filimonov, Alexey; Koroleva, Ekaterina; Sokolov, Nikolay; Wurz, Marc Christopher

    2016-01-01

    LaF3/SrF2 multilayer heterostructures with thicknesses of individual layers in the range 5-100 nm have been grown on MgO(100) substrates using molecular beam epitaxy. The longitudinal conductivity of the films has been measured using impedance spectroscopy in the frequency range 10(-1)-10(6) Hz and a temperature range 300-570 K. The ionic DC conductivities have been determined from Nyquist impedance diagrams and activation energies from the Arrhenius-Frenkel equation. An increase of the DC conductivity has been observed to accompany decreased layer thickness for various thicknesses as small as 25 nm. The greatest conductivity has been shown for a multilayer heterostructure having thicknesses of 25 nm per layer. The structure has a conductivity two orders of magnitude greater than pure LaF3 bulk material. The increasing conductivity can be understood as a redistribution of charge carriers through the interface due to differing chemical potentials of the materials, by strong lattice-constant mismatch, and/or by formation of a solid La1-xSrxF3-x solution at the interface during the growth process.

  5. Ag@SiO2/LaF3:Eu3+ Composite Nanostructure and Its Surface Enhanced Luminescence Effect.

    PubMed

    Han, Qingyan; Zhang, Yaqiong; Ren, Zebin; Wang, Zhaojin; Gao, Wei; He, Enjie; Zheng, Hairong

    2016-04-01

    Ag@SiO2/LaF3:Eu3+ core-shell nanostructure was synthesized with a wet chemical method in which the SiO2 layer functioned as a separation layer between Ag-core and LaF3:Eu3+ luminescence material. With this system, surface enhanced luminescene of LaF3:Eu3+ with Ag substrate was investigated, and an obvious enhancement effect was observed. The dependence of the luminescence enhancement on the distance between the luminescence shell and the metallic core was studied too. It is believed that the enhancement effect presented by the current hybrid nanostructure system has great potential in the development of photovoltaic cells.

  6. Sensitized luminescence of LaF3:Eu3+ nanoparticles through pyromellitic acid.

    PubMed

    Li, S Wen; Ren, H Juan; Ju, S Guang

    2014-05-01

    The LaF3 nanoparticles doped with different concentration Eu3+ ions are prepared by a simple and low temperature synthetic route. The nanoparticles with the size of about 3.5 nm are roughly spherical and monodisperse. The emission of Eu3+ ions is sensitized through pyromellitic acid bonded onto the surface of nanoparticles. The structure, morphology, photoluminescence properties and fluorescence dynamics are studied systemically. The results show that the sensitized nanoparticles have a broad absorption band in the UV domain and high asymmetry radio, and enhanced Eu3+ luminescence by "antenna effect" of ligands. The excited state lifetimes of sensitized nanoparticles are longer than those of un-sensitized nanoparticles and corresponding europium complexes.

  7. Solubility of uranium oxide in molten salt electrolysis bath of LiF-BaF2 with LaF3 additive

    NASA Astrophysics Data System (ADS)

    Alangi, Nagaraj; Mukherjee, Jaya; Gantayet, L. M.

    2016-03-01

    The solubility of UO2 in the molten mixtures of equimolar LiF-BaF2(1:1) with LaF3 as additive was studied in the range of 1423 K-1523 K. The molten fluoride salt mixture LiF-BaF2 LaF3 was equilibrated with a sintered uranium oxide pellet at 1423 K, 1473 K, 1523 K and the salt samples were collected after equilibration. Studies were conducted in the range of 10%-50% by weight additions of LaF3 in the equimolar LiF-BaF2(1:1) base fluoride salt bath. Solubility of UO2 increased with rise in LaF3 concentration in the molten fluoride in the temperature range of 1423 K-1523 K. At a given concentration of LaF3, the UO2 solubility increased monotonously with temperature. With mixed solvent, when UF4 was added as a replacement of part of LaF3 in LiF-BaF2(1:1)-10 wt% LaF3 and LiF-BaF2(1:1)-30 wt% LaF3, there was an enhancement of solubility of UO2.

  8. Ultraviolet optical and microstructural properties of MgF2 and LaF3 coatings deposited by ion-beam sputtering and boat and electron-beam evaporation.

    PubMed

    Ristau, Detlev; Günster, Stefan; Bosch, Salvador; Duparré, Angela; Masetti, Enrico; Ferré-Borrull, Josep; Kiriakidis, George; Peiró, Francesca; Quesnel, Etienne; Tikhonravov, Alexander

    2002-06-01

    Single layers of MgF2 and LaF3 were deposited upon superpolished fused-silica and CaF2 substrates by ion-beam sputtering (IBS) as well as by boat and electron beam (e-beam) evaporation and were characterized by a variety of complementary analytical techniques. Besides undergoing photometric and ellipsometric inspection, the samples were investigated at 193 and 633 nm by an optical scatter measurement facility. The structural properties were assessed with atomic-force microscopy, x-ray diffraction, TEM techniques that involved conventional thinning methods for the layers. For measurement of mechanical stress in the coatings, special silicon substrates were coated and analyzed. The dispersion behavior of both deposition materials, which was determined on the basis of various independent photometric measurements and data reduction techniques, is in good agreement with that published in the literature and with the bulk properties of the materials. The refractive indices of the MgF2 coatings ranged from 1.415 to 1.440 for the wavelength of the ArF excimer laser (193 nm) and from 1.435 to 1.465 for the wavelength of the F2 excimer laser (157 nm). For single layers of LaF3 the refractive indices extended from 1.67 to 1.70 at 193 nm to approximately 1.80 at 157 nm. The IBS process achieves the best homogeneity and the lowest surface roughness values (close to 1 nm(rms)) of the processes compared in the joint experiment. In contrast to MgF2 boat and e-beam evaporated coatings, which exhibit tensile mechanical stress ranging from 300 to 400 MPa, IBS coatings exhibit high compressive stress of as much as 910 MPa. A similar tendency was found for coating stress in LaF3 single layers. Experimental results are discussed with respect to the microstructural and compositional properties as well as to the surface topography of the coatings.

  9. [Study on the Hydrothermal Synthesis and Fluorescence of LaF3 : Tb3+, Ce3+ Nanocrystals].

    PubMed

    Xu, Shi-hua; Huang, Zhong-jing; Liu, Guo-cong; Wei, Qing-min

    2016-03-01

    LaF3 : Tba3+, Ce3+ nanocrystals were prepared with hydrothermal method with the help of cetyltrimethyl ammonium bromide (CTAB). The effects of pH values of the solution, Ce3+/Tb+ ratio value and reaction time on the luminescent properties were investigated. XRD analysis shows that the as-prepared samples possess hexagonal phase and their main diffraction peaks of samples are similar to the standard card (JCPDS 32-0483). Compared with pure LaF3, the main diffraction peaks of the doped samples have a slight shift, showing existing isomorphous substitution between La3+ and the doped rare earth ions in parent lattice of LaF3. It is found from TEM results that the as-prepared samples have good crystallinity and their average grain sizes change in the range of 20-50 nm. The excitation spectra indicate that the stronger excitation spectrum peaks exist at 250 nm, which is assigned to the transition of 4f --> 5d from Ce3+. When activated at 250 nm, all LaF3 : Tb3+, Ce3+ nanocrystals possess weak blue emission at 490 nm (electric dipole transition, 5D4 --> 7F6) and good green emission at 543 nm (magnetic dipole transition, 5D4 -->7F5). As the Ce3+/Tb+ ratio increases, the fluorescence intensities increase at first and then weaken, and reach the strongest green emission at n(Ce)3+ /n(Tb)3+ = 4. The pH values have some influence on the colors and intensities of the LaF3 : Tb3+, Ce3+ nanocrystals. The sample prepared at pH 9 presents the best color, while the one at pH 7 exhibits the strongest green emission. Besides, increasing reaction time is helpful to improve color purity of sample and enhance its green emission.

  10. Vibrational spectra of (BaF2)n (n=1-6) clusters

    NASA Astrophysics Data System (ADS)

    Pandey, Ratnesh K.; Waters, Kevin; Nigam, Sandeep; Pandey, Ravindra; Pandey, Avinash C.

    2016-05-01

    The vibrational properties of alkaline-earth metal fluoride clusters (BaF2)n (n=1-6) are investigated in the framework of density functional theory. The calculated Raman and Infrared (IR) spectra reveals shift in Raman and IR peak position towards lower frequency region with the increase in the cluster size. Further the calculated spectra have been compared with the experimental vibrational spectra of bulk BaF2 crystal. Even though the smaller size cluster lacks translational symmetry, the structural and vibrational characteristic of (BaF2)5-6 are nearer to bulk counterpart.

  11. GEOMETRY AND VIBRATIONAL SPECTRA OF ALKALINE-EARTH DIHALIDES, II. CaF2, SrF2 AND BaF2.

    DTIC Science & Technology

    the shifts of the vibrational modes on isotopic substitution upper and lower limits for the apex angles of these molecules can be established. The...fundamental frequencies, as well as approximate values for the anharmonic corrections to these vibrational modes . The statistical entropies calculated

  12. Trigonal LaF3: a novel SRS-active crystal

    NASA Astrophysics Data System (ADS)

    Kaminskii, A. A.; Lux, O.; Hanuza, J.; Rhee, H.; Eichler, H. J.; Zhang, J.; Tang, D.; Shen, D.; Yoneda, H.; Shirakawa, A.

    2014-12-01

    Trigonal fluoride LaF3, widely known as a host crystal for Ln3+-lasants, was found to be an attractive many-phonon Raman material and a subject for the investigation of different χ(3)-nonlinear optical effects. We present the manifestation of photon-phonon interactions related to stimulated Raman scattering (SRS) and Raman-induced four-wave mixing (RFWM) processes, initiated by picosecond exсitation at room temperature. Sesqui-octave-spanning Stokes and anti-Stokes frequency comb generation as well as many-step cascaded and cross-cascaded up-conversion χ(3)-nonlinear processes have been observed. The recorded spectral lines originated by SRS and RFWM are identified and attributed to the three observed SRS-promoting phonon modes. The lower limit of the steady-state Raman gain coefficient for near-IR first Stokes generation was estimated. Moreover, a brief review of known Ln3+ : LaF3 laser crystals and SRS-active fluorides is given.

  13. Gain characteristics of LaF3:Er, Yb nanoparticle-doped waveguide amplifier.

    PubMed

    Li, Tong; Liu, Tianji; Chen, Cong; Zhang, Dan; Wang, Fei; Zhang, Daming

    2011-11-01

    Fundamental rate equations and power propagation equations were used to simulate the gain factors of LaF3:Er, Yb nanoparticle-doped waveguide amplifiers excited at 980 nm. The gain first increased and then remained nearly constant with pump power increasing. The gain and the threshold pump power increased with increasing concentration of Er3+. The calculated gain of the concentration 0.75 x 10(26) ions/m3 on a 4 cm long waveguide was 3.6 dB. An optimum waveguide length was found for the highest gain and it was getting larger with the increase of the pump power. When the lifetime decreases from the Judd-Ofelt calculated value of 13.34 ms to the measured value of 60 micros, the required pump power of a 0.5 dB gain increased one level. We obtained a longer 4I(13/2) lifetime (100 micros) through decreasing the proportions of Er3+ and Yb3+ in nanoparticles and found that the threshold pump power decreased more at the expenses of saturated gain.

  14. Luminescence and scintillation properties of BaF2sbnd Ce transparent ceramic

    NASA Astrophysics Data System (ADS)

    Luo, Junming; Sahi, Sunil; Groza, Michael; Wang, Zhiqiang; Ma, Lun; Chen, Wei; Burger, Arnold; Kenarangui, Rasool; Sham, Tsun-Kong; Selim, Farida A.

    2016-08-01

    Cerium doped Barium Fluoride (BaF2sbnd Ce) transparent ceramic was fabricated and its luminescence and scintillation properties were studied. The photoluminescence shows the emission peaks at 310 nm and 323 nm and is related to the 5d-4f transitions in Ce3+ ion. Photo peak at 511 keV and 1274 keV were obtained with BaF2sbnd Ce transparent ceramic for Na-22 radioisotopes. Energy resolution of 13.5% at 662 keV is calculated for the BaF2sbnd Ce transparent ceramic. Light yield of 5100 photons/MeV was recorded for BaF2sbnd Ce(0.2%) ceramic and is comparable to its single crystal counterpart. Scintillation decay time measurements shows fast component of 58 ns and a relatively slow component of 434 ns under 662 keV gamma excitation. The slower component in BaF2sbnd Ce(0.2%) ceramic is about 200 ns faster than the STE emission in BaF2 host and is associated with the dipole-dipole energy transfer from the host matrix to Ce3+ luminescence center.

  15. Formation and Luminescence Phenomena of LaF3:Ce3+ Nanoparticles and Lanthanide-Organic Compounds in Dimethyl Sulfoxide

    SciTech Connect

    Yao, Mingzhen; Joly, Alan G.; Chen, Wei

    2010-01-21

    LaF3:Ce3+ doped nanoparticles were synthesized at different temperatures in dimethyl sulfoxide by the chemical reaction of lanthanum nitrate hydrate and cerium nitrate hexahydrate with ammonium fluoride. The formation of Ce3+ doped LaF3 nanoparticles is confirmed by X-ray diffraction and high resolution transmission electron microscopy. An intense emission at around 310 nm from the d - f transition of Ce3+ was observed from the LaF3:Ce3+ powder samples. However, in solution samples, the ultraviolet emission from Ce3+ is mostly absent, but intense luminescence is observed in the visible range from blue to red. The emission wavelength of the solution samples is dependent on the reaction time and temperature. More interestingly, the emission wavelength varies with the excitation wavelength. Most likely, this emission is from the metalorganic compounds of Ce3+ or La3+ and DMSO as similar phenomena are also observed when lanthanum nitrate hydrate or cerium nitrate hexahydrate are heated in DMSO.

  16. Tunable Wavelength Solid-State Lasers and Turbulent Jet Diagnostics by Rayleigh and Fluorescence Scattering.

    DTIC Science & Technology

    1981-09-01

    We did not succeed in achieving laser action from Eu 2+ ions doped in CaF 2, BaF2, SrF2 , CaCl 2, BaC1 2, SrCl2, BaCIF, and SrCIF crystals even...laser action from Ce ions doped in CaF2, BaF2, SrF2 , and LaF3 (see Appendix B). Two other research groups also reported their failures to 3+ achieve laser...sequently, the fact that laser emission for Ce3+ ions is achievable in YLF, and not in YAG, CaF2, BaF2, SrF2 , and LaF3, clearly demonstrates that even a

  17. LaF3:Ln mesoporous spheres: controllable synthesis, tunable luminescence and application for dual-modal chemo-/photo-thermal therapy

    NASA Astrophysics Data System (ADS)

    Lv, Ruichan; Yang, Guixin; He, Fei; Dai, Yunlu; Gai, Shili; Yang, Piaoping

    2014-11-01

    In this report, uniform LaF3:Ln mesoporous spheres have been synthesized by a facile and mild in situ ion-exchange method using yolk-like La(OH)3:Ln mesoporous spheres as templates, which were prepared through a self-produced bubble-template route. It was found that the structures of the final LaF3:Ln can simply be tuned by adding a polyetherimide (PEI) reagent. LaF3:Ln hollow mesoporous spheres (HMSs) and LaF3:Ln flower-like mesoporous spheres (FMSs) were obtained when assisted by PEI and in the absence of PEI. The up-conversion (UC) luminescence results reveal that the doping of Nd3+ ions in LaF3:Ln can markedly influence the UC emissions of the products. It is interesting that an obvious thermal effect is achieved due to the energy back-transfer from Tm3+ to Nd3+ ions under 980 nm near-infrared (NIR) irradiation. The LaF3:Yb/Er/Tm/Nd HMSs show good biocompatibility and sustained doxorubicin (DOX) release properties. In particular, upon 980 nm NIR irradiation, the photothermal effect arising from the Nd3+ doping induces a faster DOX release from the drug release system. Moreover, UC luminescence images of LaF3:Yb/Er/Tm/Nd HMSs uptaken by MCF-7 cells exhibit apparent green emission under 980 nm NIR irradiation. Such a multifunctional carrier combining UC luminescence and hyperthermia with the chemotherapeutic drugs should be of high potential for the simultaneous anti-cancer therapy and cell imaging.In this report, uniform LaF3:Ln mesoporous spheres have been synthesized by a facile and mild in situ ion-exchange method using yolk-like La(OH)3:Ln mesoporous spheres as templates, which were prepared through a self-produced bubble-template route. It was found that the structures of the final LaF3:Ln can simply be tuned by adding a polyetherimide (PEI) reagent. LaF3:Ln hollow mesoporous spheres (HMSs) and LaF3:Ln flower-like mesoporous spheres (FMSs) were obtained when assisted by PEI and in the absence of PEI. The up-conversion (UC) luminescence results reveal that the doping of Nd3+ ions in LaF3:Ln can markedly influence the UC emissions of the products. It is interesting that an obvious thermal effect is achieved due to the energy back-transfer from Tm3+ to Nd3+ ions under 980 nm near-infrared (NIR) irradiation. The LaF3:Yb/Er/Tm/Nd HMSs show good biocompatibility and sustained doxorubicin (DOX) release properties. In particular, upon 980 nm NIR irradiation, the photothermal effect arising from the Nd3+ doping induces a faster DOX release from the drug release system. Moreover, UC luminescence images of LaF3:Yb/Er/Tm/Nd HMSs uptaken by MCF-7 cells exhibit apparent green emission under 980 nm NIR irradiation. Such a multifunctional carrier combining UC luminescence and hyperthermia with the chemotherapeutic drugs should be of high potential for the simultaneous anti-cancer therapy and cell imaging. Electronic supplementary information (ESI) available: The SAED pattern of flower-like LaF3:Yb,Er spheres. FT-IR spectra of the La(OH)3:Ln precursor, LaF3:Ln HMSs and LaF3:Ln FMSs. UC emission spectra of the La(OH)3:Yb/Er(Ho/Tm) precursor, LaF3:Yb/Er(Ho/Tm) HMSs, LaF3:Yb/Er(Ho/Tm) FMSs under 980 nm NIR excitation. CIE chromaticity diagram of LaF3:10% Yb/0.5% Tm/x%Nd (x = 0, 1, 2) under 980 nm NIR excitation. CIE chromaticity diagram of LaF3:Yb/Er/Tm/Nd under 980 nm NIR excitation. Infrared thermal images of LaF3:Yb/Er, LaF3:Yb/Er/Tm, and LaF3:Yb/Er/Tm/Nd samples before and after irradiation for 6-8 min under 980 nm laser irradiation with the pump power of 0.6 W cm-2. See DOI: 10.1039/c4nr04336g

  18. Active Laser and Raman Materials for 1.3-5 Micron Spectral Range

    DTIC Science & Technology

    2006-03-01

    transitions of rare- earth ions in fluorite type crystals”, in the Proceedings volume of the Advanced Solid-State Photonics 2004, author: Gregory Quarles...comparable with those for low phonon fluoride crystals like LaF3 and fluorite - type crystals like SrF2, CdF2, BaF2, and PbF2. Interestingly, the measured...impurities present in the samples. Oxygen - free CaF2: LaF3(0.25%): NdF3(0.25%) and SrF2: LaF3(1%): NdF3(0.2%) crystals with fluorite structure were

  19. LaF3 core/shell nanoparticles for subcutaneous heating and thermal sensing in the second biological-window

    NASA Astrophysics Data System (ADS)

    Ximendes, Erving Clayton; Rocha, Uéslen; Kumar, Kagola Upendra; Jacinto, Carlos; Jaque, Daniel

    2016-06-01

    We report on Ytterbium and Neodymium codoped LaF3 core/shell nanoparticles capable of simultaneous heating and thermal sensing under single beam infrared laser excitation. Efficient light-to-heat conversion is produced at the Neodymium highly doped shell due to non-radiative de-excitations. Thermal sensing is provided by the temperature dependent Nd3+ → Yb3+ energy transfer processes taking place at the core/shell interface. The potential application of these core/shell multifunctional nanoparticles for controlled photothermal subcutaneous treatments is also demonstrated.

  20. Study of structure and antireflective properties of LaF3/HfO2/SiO2 and LaF3/HfO2/MgF2 trilayers for UV applications

    NASA Astrophysics Data System (ADS)

    Marszalek, K.; Jaglarz, J.; Sahraoui, B.; Winkowski, P.; Kanak, J.

    2015-01-01

    The aim of this paper is to study antireflective properties of the tree-layer systems LaF3/HfO2/SiO2 and LaF3/HfO2/MgF2 deposited on heated optical glass substrates. The films were evaporated by the use two deposition techniques. In first method oxide films were prepared by means of e-gun evaporation in vacuum of 5 × 10-5 mbar in the presence of oxygen. The second was used for the deposition of fluoride films. They were obtained by means of thermal source evaporation. Simulation of reflectance was performed for 1M2H1L (Quarter Wavelength Optical Thickness) film stack on an optical quartz glass with the refractive index n = 1.46. The layer thickness was optimized to achieve the lowest light scattering from glass surface covered with dioxide and fluoride films. The values of the interface roughness were determined through atomic force microscopy measurements. The essence of performed calculation was to find minimum reflectance of light in wide ultraviolet region. The spectral dispersion of the refractive index needed for calculations was determined from ellipsometric measurements using the spectroscopic ellipsometer M2000. Additionally, the total reflectance measurements in integrating sphere coupled with Perkin Elmer 900 spectrophotometer were performed. These investigations allowed to determine the influence of such film features like surface and interface roughness on light scattering.

  1. Optical properties of LaF3:Er,Yb nanoparticle-doped organic-inorganic hybrid material.

    PubMed

    Li, Tong; Zhang, Dan; Chen, Cong; Bo, Shuhui; Zhang, Daming

    2010-03-01

    Oleic acid (OA)-modified LaF3:Er,Yb nanoparticle-doped organic-inorganic hybrid material (OIHM) was prepared. The absorption spectrum and photoluminescence spectrum were analyzed. The full width at half maximum (FWHM) of the photoluminescence spectrum was about 83 nm. The Judd-Ofelt theory was used to analyze the absorption spectrum of Er3+ and obtain the intensity parameters: omega2 = 2.11 x 10(-20) cm2, omega4 = 0.78 x 10(-200 cm2, omega6 = 0.56 x 10(-20)cm2. The line strengths predict spontaneous transition probabilities, and the radiative lifetimes are calculated with the Judd-Ofelt intensity parameters. The calculated radiative lifetime of the excited 4I13/2 state of Er3+ is 13.34 ms. Based on the parameters we calculated, OA-modified LaF3:Er,Yb nanoparticle-doped OIHM is a potential material for polymeric optical waveguide amplifiers.

  2. Improved photoluminescence and thermal stabilization of glycine functionalized LaF3: Ce nanoparticles useful in bioimaging and biotagging

    NASA Astrophysics Data System (ADS)

    Singh, Amit T.; Khandpekar, M. M.

    2015-05-01

    LaF3:Ce nanocrystals doped with glycine have been synthesized from water soluble chlorides and subsequent irradiation by microwave. The XRD spectra confirms the hexagonal phase structure with cell parameter a = b = 7.173 Å and c = 7.211 Å with space group P 3 cl and particle size of 15 nm. The value is in confirmation with the density functional calculation of structural properties by LDA and GGA potentials predicting merohedral twinned structure of tysonite like compounds. The SEM and TEM images show narrow distribution of nanoparticles with hexagonal and assorted morphology having particle size of 25 nm. The SAED pattern confirms the formation of crystallinity of nanocrystals and traces of different elements in the nanocrystals have been detected by EDAX pattern. The FTIR spectrum shows peaks due to weak organic attachments indicating the capping on the core LaF3:Ce by the functional groups of the organic ligands. The UV spectrum shows the presence of multiple absorption edges corresponding to band gap energies at 5.17 eV, 4.87 eV,4.28 eV,3.40 eV indicating the quantum dot structure of inorganic nanocrystals. The photoluminescence of the nanocrystals has been observed by excitation and emission spectra. The peak at 616 nm shows emission of red fluorescence, indicating its possible applications in bio imaging and biotagging. The TGA/DTA graph shows the stable phases of the nanocrystals synthesized.

  3. ATOMIC AND MOLECULAR PHYSICS: Infrared-to-visible and infrared-to-violet upconversion fluorescence of rare earth doped LaF3 nanocrystals

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Qin Wei-, Ping; Di, Wei-Hua; Zhang Ji-, Sen; Cao, Chun-Yan

    2008-09-01

    This paper reports that hexagonal-phase LaF3:Yb0.203+, Er0.023+ and LaF3:Yb0.203+, Tm0.023+ nanocrystals (NCs) were synthesized via a hydrothermal method. The transmission electron microscopy, selected area electron diffraction, powder x-ray diffraction, and thermogravimetric analysis are used to characterize the NCs. Under 980 nm excitation, the Yb3+/Er3+ and Yb3+/Tm3+ codoped NCs colloidal solutions present bright green and blue upconversion fluorescence, respectively. These NCs show efficient infrared-to-violet and infrared-to-visible upconversion. The upconversion fluorescence mechanisms of La F3:Yb0.023+ Er0.023+ and LaF3:Yb0.023+, Tm0.023+ NCs are investigated with a 980-nm diode laser as excitation source.

  4. Clock distribution for BaF2 readout electronics at CSNS-WNS

    NASA Astrophysics Data System (ADS)

    He, Bing; Cao, Ping; Zhang, De-Liang; Wang, Qi; Zhang, Ya-Xi; Qi, Xin-Cheng; An, Qi

    2017-01-01

    A BaF2 (Barium Fluoride) detector array is designed to precisely measure the (n, γ) cross section at the CSNS-WNS (white neutron source at China Spallation Neutron Source). It is a 4π solid angle-shaped detector array consisting of 92 BaF2 crystal elements. To discriminate signals from the BaF2 detector, a pulse shape discrimination method is used, supported by a waveform digitization technique. There are 92 channels for digitizing. The precision and synchronization of clock distribution restricts the performance of waveform digitizing. In this paper, a clock prototype for the BaF2 readout electronics at CSNS-WNS is introduced. It is based on the PXIe platform and has a twin-stage tree topology. In the first stage, clock is synchronously distributed from the tree root to each PXIe crate through a coaxial cable over a long distance, while in the second stage, the clock is further distributed to each electronic module through a PXIe dedicated differential star bus. With the help of this topology, each tree node can fan out up to 20 clocks with 3U size. Test results show the clock jitter is less than 20 ps, which meets the requirements of the BaF2 readout electronics. Besides, this clock system has the advantages of high density, simplicity, scalability and cost saving, so it can be useful for other clock distribution applications. Supported by National Research and Development plan (2016 YFA0401602) NSAF (U1530111) and National Natural Science Foundation of China (11005107)

  5. Paclitaxel conjugated Fe3O4@LaF3:Ce3+,Tb3+ nanoparticles as bifunctional targeting carriers for Cancer theranostics application

    NASA Astrophysics Data System (ADS)

    Mangaiyarkarasi, Rajendiran; Chinnathambi, Shanmugavel; Karthikeyan, Subramani; Aruna, Prakasarao; Ganesan, Singaravelu

    2016-02-01

    The bi-functional Chitosan functionalized magnetite doped luminescent rare earth nanoparticles (Fe3O4@LaF3: Ce3+,Tb3+/chi NPs) as a carrier of paclitaxel (PTX) drug was designed using a co-precipitation and facile direct precipitation method. The synthesized nanoparticles are spherical in shape with a typical diameter of 19-37 nm respectively. They are water soluble, super paramagnetic and biocompatible, in which the amino groups on the nanoparticles surface are used for the conjugation with an anticancer drug, paclitaxel. The nature of PTX binding with Fe3O4@LaF3: Ce3+,Tb3+/chi nanoparticles were studied using X-ray diffraction, vibrating sample magnetometer and scanning electron micrograph. The nature of interactions between PTX and Fe3O4@LaF3: Ce3+,Tb3+/chi NPs due to complex formation were conceded out by various spectroscopic methods viz., UV-visible, steady state and excited state fluorescence spectroscopy. The photo-physical characterization reveals that the adsorption and release of PTX from Fe3O4@LaF3:Tb3+/chi nanoparticles is quicker when compared with other nanoparticles and also confirms that this may be due to the hydrogen bond formation between the hydroxyl group of drug and amino group of nanoparticles respectively. The maximum loading capacity and entrapment efficiency of 83.69% and 80.51% were attained at a ratio of 5:8 of PTX and Fe3O4@LaF3: Ce3+,Tb3+/chi NPs respectively. In addition with that, antitumoral activity study of PTX conjugated Fe3O4@LaF3:Tb3+/chi nanoparticles exhibits increased cytotoxic effects on A549 lung cancer cell lines than that of unconjugated PTX.

  6. Scintillation properties of pure CaF 2

    NASA Astrophysics Data System (ADS)

    Mikhailik, V. B.; Kraus, H.; Imber, J.; Wahl, D.

    2006-10-01

    The temperature dependence of the decay time and scintillation light yield of pure CaF 2 crystal was measured over the temperature range 8-305 K using the multiphoton coincidence counting technique. Pure CaF 2 exhibits emission of triplet self-trapped excitons at 280 nm with a slow decay, the time constant of which changes significantly with temperature. The main decay time constant increases by three orders of magnitude when cooled, from 0.96±0.06 μs at 295 K to 930±40 μs at 8 K. The results obtained demonstrate that the scintillation light yield of pure CaF 2 increases with decreasing temperature down to 20 K below which it is roughly constant. At low temperatures the light yield of CaF 2 is estimated to be 60% relative to that of pure CaWO 4. It is concluded that undoped calcium fluoride is a very attractive target material for experimental searches for rare events based on the detection of phonon and scintillation signals.

  7. Ab initio study on pressure induced structural sequence in LaF3 up to 2 Mbar

    NASA Astrophysics Data System (ADS)

    Sahoo, B. D.; Joshi, K. D.; Gupta, Satish C.

    2017-01-01

    Using an evolutionary structure search algorithm lanthanum trifluoride (LaF3) has been examined under hydrostatic compression. The comparison of enthalpies of various candidate structures suggests that at ambient condition the tysonite structure (space group P-3c1) is the lowest enthalpy phase. Further it has been found that this structure transforms to a primitive orthorhombic structure (space group Pmmn) around 19.5 GPa, which is in reasonable agreement with the experimental value of 16 GPa. Upon further compression the orthorhombic structure has been predicted to transform to another orthorhombic phase with space group symmetry Cmcm at 150 GPa. The results of the static lattice calculations have been substantiated by testing the lattice dynamic stability of these phases in the regime of their structural stability. Additionally, various Raman active modes for both the P-3c1 and Pmmn structures have been calculated as a function of pressure. The theoretically derived Raman active modes calculated for both the phases at various pressures display a good agreement with the experimental data.

  8. Spectroscopy of single Pr3+ ion in LaF3 crystal at 1.5 K

    PubMed Central

    Nakamura, Ippei; Yoshihiro, Tatsuya; Inagawa, Hironori; Fujiyoshi, Satoru; Matsushita, Michio

    2014-01-01

    Optical read-out and manipulation of the nuclear spin state of single rare-earth ions doped in a crystal enable the large-scale storage and the transport of quantum information. Here, we report the photo-luminescence excitation spectroscopy results of single Pr3+ ions in a bulk crystal of LaF3 at 1.5 K. In a bulk sample, the signal from a single ion at the focus is often hidden under the background signal originating from numerous out-of-focus ions in the entire sample. To combine with a homemade cryogenic confocal microscope, we developed a reflecting objective that works in superfluid helium with a numerical aperture of 0.99, which increases the signal by increasing the solid angle of collection to 1.16π and reduces the background by decreasing the focal volume. The photo-luminescence excitation spectrum of single Pr3+ was measured at a wing of the spectral line of the 3H4 → 3P0 transition at 627.33 THz (477.89 nm). The spectrum of individual Pr3+ ions appears on top of the background of 60 cps as isolated peaks with intensities of 20–30 cps and full-width at half-maximum widths of approximately 3 MHz at an excitation intensity of 80 W cm−2. PMID:25482137

  9. Monodispersed Silica Nanospheres Encapsulating Fe3O4 and LaF3:Eu3+ Nanoparticles for MRI Contrast Agent and Luminescent Imaging

    NASA Astrophysics Data System (ADS)

    Tian, Yang; Yu, Binbin; Yang, Hong-Yu; Liao, Ji

    2013-03-01

    Bifunctional nanospheres of silica encapsulating Fe3O4 and LaF3:Eu nanoparticles were synthesized in a reverse microemulsion solution. The nanospheres were perfectly monodispersed with a small diameter of 20 nm. The composition of the bifunctional nanospheres was confirmed by powder X-ray diffraction. Their magnetic and luminescent properties were measured at room temperature. The relaxation efficiency and T2-weighted images showed the high-performance for the product as a resonance imaging contrast agent. In addition, a qualitative cell uptake in human cervical cancer HeLa cells demonstrated that the SFLE nanospheres were efficiently up-taken into cytosol. Taken together, these findings suggest that the SiO2/Fe3O4-LaF3:Eu3+ nanospheres are good luminescence probes for bio-imaging.

  10. Sensitized luminescence from water-soluble LaF3:Eu nanocrystals via partially-capped 1,10-phenanthroline: time-gated emission and multiple lifetimes.

    PubMed

    Irfanullah, Mir; Bhardwaj, Navneet; Chowdhury, Arindam

    2016-08-02

    Water dispersible citrate-capped LaF3:Eu(5%) nanocrystals (NCs) have been partially surface-functionalized by 1,10-phenanthroline (phen) via a ligand exchange method to produce novel water dispersed citrate/phen-capped LaF3:Eu(5%) NCs in which citrate ligands preserve the water dispersibility of the NCs and phen ligands act as sensitizers of surface Eu(3+)-dopant sites. The partial ligand exchange and the formation of water dispersed NCs have been monitored by (1)H NMR spectroscopy, as well as luminescence measurements at different time intervals during the reaction. These NCs display a distinct phen-sensitized Eu(3+)-emission profile with enhanced intensity in water as compared to the emission profile and intensity obtained upon direct excitation. Time-resolved (or time-gated) emission spectroscopy (TRES) has been used to probe PL dynamics of Eu(3+)-sites of LaF3:Eu(5%) NCs by taking advantage of selectively sensitizing surface Eu(3+)-dopant sites by phen ligands as well as by exciting all the Eu(3+)-sites in the NCs upon direct excitation. TRES upon direct excitation of the citrate-capped LaF3:Eu(5%) NCs reveals that Eu(3+)-dopants occupy at least three different sites, each with a different emission profile and lifetime, and emission from purely interior Eu(3+)-sites has been resolved due to their long lifetime as compared to the lifetime of purely surface and near surface Eu(3+)-sites. In contrast, the phen-sensitized emission from citrate/phen-capped LaF3:Eu(5%) NCs displays similar emission profiles and lifetimes in TRES measurements, which reveal that phen truly sensitizes purely surface dopant sites of the NCs in water, all of which have nearly the same local environment. The phen-sensitized Eu(3+)-emission of the NCs in water remains stable even upon addition of various buffer solutions at physiological pH, as well as upon addition of water-miscible organic solvents. Furthermore, the two-photon excitation (λex. = 720 nm) of these water-soluble phen-capped NCs produces bright red Eu(3+) emission, which reveals that these NCs are promising for potential applications in biological imaging.

  11. Dependency of built-in potential of LaF3/porous-silicon heterostructure prepared by chemical bath deposition technique on the concentration of LaCl3 and annealing temperature

    NASA Astrophysics Data System (ADS)

    Rahman, Md. Hafijur; Ismail, Abu Bakar Md.

    2015-11-01

    Effect of LaCl3 concentration and annealing temperature on the built-in potential of LaF3/PS heterojunction has been investigated in this report. LaF3 layers have been deposited by a novel chemical bath deposition (CBD) technique. With this simple technique LaF3 produced as LaCl3 are made to react with hydrofluoric acid on the porous silicon (PS) substrate. This enables direct deposition of LaF3 on the pore walls of the PS leading to a successful passivation of PS. The compositions of the deposited LaF3 were confirmed by energy dispersive of X-ray analysis. The built-in potential decreases with LaCl3 concentration and increases with annealing temperature. Therefore, by changing the LaCl3 concentration and annealing temperature quality of the LaF3 layer on PS can be optimized. From the experimental results it can be concluded that lanthanum fluorides can be deposited on the PS surface by the CBD technique, which provides the required passivation for PS. This passivation can enable the PS to be considered as an important material for photonics.

  12. Influence of LaCl3 concentration and annealing temperature on the diode ideality factor of LaF3/porous-silicon structure prepared by chemical bath deposition technique

    NASA Astrophysics Data System (ADS)

    Hafijur Rahman, Md.; Ismail, Abu Bakar Md.

    2015-08-01

    Effect of LaCl3 concentration and annealing temperature on the diode ideality factor of LaF3/PS heterojunction has been investigated in this report. LaF3 layers have been deposited by a novel chemical bath deposition (CBD) technique. With this simple technique LaF3 produced as LaCl3 are made to react with hydrofluoric acid on the porous silicon (PS) substrate. This enables direct deposition of LaF3 on the pore walls of the PS leading to a successful passivation of PS. The compositions of the deposited LaF3 were confirmed by energy dispersive of X-ray analysis. The diode ideality factor increases with LaCl3 concentration and decreases with annealing temperature. Therefore, by changing the LaCl3 concentration and annealing temperature quality of the LaF3 layer on PS can be optimized. It was also seen that the Ag/LaF3/PS/Si/Ag structure showed the formation of Schottky diode with a threshold voltage of about 5.5 V. From the experimental results it can be concluded that lanthanum fluorides can be deposited into the pores as well as on the top of PS by the CBD technique, which provides the required passivation for PS. This passivation can enable the PS to be considered as an important material for photonics.

  13. Dislocations in YbF3 doped BaF2 crystals

    NASA Astrophysics Data System (ADS)

    Cirlan, Florina; Buse, Gabriel; Nicoara, Irina

    2014-11-01

    Three concentrations of YbF3 -doped BaF2 crystals were grown using the conventional Bridgman method. Transparent colorless crystals were obtained in graphite crucible in vacuum (˜10-1 Pa) using a shaped graphite furnace. The crystals have been cooled to room temperature using an established procedure. In order to study the etch pits morphology and the dislocations density the etching method have been used. This method consists in immersing the cleaved sample in 2N HCl at 60°C for 2 minutes. Small etch pits are developed at the emergence points of the dislocations. The etch pits have triangular or hexagonal shapes, depending on the dopant concentration. The dislocations density depends on the dopant concentration.

  14. Additive coloring of CaF2 optical ceramic

    NASA Astrophysics Data System (ADS)

    Shcheulin, A. S.; Ryskin, A. I.; Angervaks, A. E.; Fedorov, P. P.; Osiko, V. V.; Demidenko, A. A.; Garibin, E. A.; Smirnov, A. N.; Dukel'skii, K. V.; Mironov, I. A.

    2011-04-01

    The specificity of additive coloring of CaF2 optical ceramic (formation of color centers in it and photothermochemical transformation of these centers in colored ceramic samples) has been considered. Under the same coloring conditions, this process occurs more slowly in ceramics rather than in crystals; at the same time, the limiting concentration of color centers that can be introduced into ceramics is much higher. The photothermochemical transformations of color centers in crystals and ceramics, which occur under illumination at different wavelengths and upon heating, have been studied. The specific features of introduction of color centers into ceramic and their transformation under illumination and heating are likely to be related to the mass twinning of ceramic grains.

  15. F 3 - molecular ions in fluoride crystals

    NASA Astrophysics Data System (ADS)

    Radzhabov, E. A.

    2016-02-01

    The UV absorption spectra of F 3 - molecular ions in LaF3, SrF2, CaF2, and BaF2 crystals doped with rare-earth elements are studied. Comparison of radiation-colored and additively colored crystals reveals the absorption bands of F 3 - hole centers in the region near 6 eV. Nonempirical calculations of optical transitions agree well with experimental results.

  16. Influence of surface coating on structural, morphological and optical properties of upconversion-luminescent LaF3:Yb/Er nanoparticles

    NASA Astrophysics Data System (ADS)

    Ansari, Anees A.; Yadav, Ranvijay; Rai, S. B.

    2016-07-01

    LaF3:Yb/Er (core), LaF3:Yb/Er@LaF3 (core/shell) and LaF3:Yb/Er@LaF3@SiO2 (core/shell/SiO2) nanoparticles were synthesized using citric-acid-based complexation process. X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, optical absorption, band-gap energy ( E g), Fourier transform infrared and upconversion emission spectroscopy were employed to investigate the structural, morphological and optical properties of the synthesized core and core/shell/SiO2 nanoparticles. These core/shell/SiO2 nanoparticles can be well dispersed in aqueous solvents to form clear colloidal solution. The optical band-gap energy was decreased after shell formation due to increase in the crystalline size. The growth of an inactive and porous silica layers simultaneously on the surface of luminescent core-nanoparticles resulting an increase in average crystalline size of the nanoparticles. As-prepared inert shell-coated core/shell nanoparticles show intensive upconversion-luminescence as compared to the seed-core and silica-surface-modified core/shell/SiO2 nanoparticles because luminescent ions (Yb3+ and Er3+) ions located at the particle surface were protected from the non-radiative decay arising from surface dangling bonds and capping agent. However, our study revealed that there was only a slight reduction in upconversion efficiency for the silica-modified core/shell nanoparticles, indicating that upconversion properties of the upconversion nanoparticles are largely preserved in the core/shell/SiO2 nanoparticles. Absorption and upconversion-luminescence properties were examined for future application in the development of optical devices as well as optical bioprobes.

  17. The upconversion luminescence and magnetism in Yb3+/Ho3+ co-doped LaF3 nanocrystals for potential bimodal imaging

    NASA Astrophysics Data System (ADS)

    Syamchand, Sasidharanpillai S.; George, Sony

    2016-12-01

    Biocompatible upconversion nanoparticles with multifunctional properties can serve as potential nanoprobes for multimodal imaging. Herein, we report an upconversion nanocrystal based on lanthanum fluoride which is developed to address the imaging modalities, upconversion luminescence imaging and magnetic resonance imaging (MRI). Lanthanide ions (Yb3+ and Ho3+) doped LaF3 nanocrystals (LaF3 Yb3+/Ho3+) are fabricated through a rapid microwave-assisted synthesis. The hexagonal phase LaF3 nanocrystals exhibit nearly spherical morphology with average diameter of 9.8 nm. The inductively coupled plasma mass spectrometry (ICP-MS) analysis estimated the doping concentration of Yb3+ and Ho3+ as 3.99 and 0.41%, respectively. The nanocrystals show upconversion luminescence when irradiated with near-infrared (NIR) photons of wavelength 980 nm. The emission spectrum consists of bands centred at 542, 645 and 658 nm. The stronger green emission at 542 nm and the weak red emissions at 645 and 658 nm are assigned to 5S2 → 5I8 and 5F5 → 5I8 transitions of Ho3+, respectively. The pump power dependence of luminescence intensity confirmed the two-photon upconversion process. The nanocrystals exhibit paramagnetism due to the presence of lanthanide ion dopant Ho3+ and the magnetization is 19.81 emu/g at room temperature. The nanocrystals exhibit a longitudinal relaxivity ( r 1) of 0.12 s-1 mM-1 and transverse relaxivity ( r 2) of 28.18 s-1 mM-1, which makes the system suitable for developing T2 MRI contrast agents based on holmium. The LaF3 Yb3+/Ho3+ nanocrystals are surface modified by PEGylation to improve biocompatibility and enhance further functionalisation. The PEGylated nanocrystals are found to be non-toxic up to 50 μg/mL for 48 h of incubation, which is confirmed by the MTT assay as well as morphological studies in HeLa cells. The upconversion luminescence and magnetism together with biocompatibility enables the adaptability of the present system as a nanoprobe for potential bimodal imaging.

  18. Characterization of CaF2 surfaces using Adsorption-Desorption Isotherms and Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Wadleigh, L. R.; Luhman, D. R.; Bumcrot, P. G.

    2012-02-01

    We are interested in using rough CaF2 films to study the superfluid transition in two-dimensional helium systems. These experiments require quantitative information regarding the topography of the CaF2 surfaces. The surface roughness of CaF2 films is known to increase with film thickness as has been shown with previous atomic force microscopy (AFM) measurements [1]. We have fabricated a series of CaF2 samples of different film thicknesses and thus different surface roughnesses. These surfaces were studied using AFM and adsorption-desorption isotherm measurements with liquid nitrogen at T=77 K. The isotherm measurements allow us to determine the pore size distribution of each CaF2 film thickness. We find the emergence of hysteretic capillary condensation due to deep pores in the CaF2 as the film thickness increases. The development of these deep pores is also seen in our AFM measurements. Our combined results provide a detailed description of CaF2 surface roughness which can be utilized in the planned superfluid experiment. [1] D.R. Luhman and R.B. Hallock, Phys Rev. E 70, 051606 (2004).

  19. Photoionization thresholds of rare-earth impurity ions. EuS :CaF2, CeT :YAG, and SmS :CaF2

    SciTech Connect

    Pedrini, C.; Rogemond, F.; McClure, D.S.

    1986-02-15

    The spectral dependence of the photoionization energy of EuS :CaF2, CeT :YAG, and SmS :CaF2 systems have been measured and thresholds experimentally determined and compared with theoretical values calculated from electrostatic models. It is shown that the excited state absorption transitions or the persistent hole burning observed by other authors occur above the threshold energy of photoionization of the impurities and that the states of the crystal which form the bottom of the conduction band may play an important role in the strong probability of these processes. A review of thresholds now known is also given.

  20. CONTROL OF LASER RADIATION PARAMETER: Temporal evolution of a coherent stimulated radiation pulse in the three-level system in a Pr3+ : LaF3 crystal

    NASA Astrophysics Data System (ADS)

    Agafonov, Aleksandr I.; Grigoryan, Grigorii G.; Znamenskiy, Nikolay V.; Manykin, Eduard A.; Orlov, Yurii V.; Petrenko, Evgenii A.; Shashkov, Andrei Yu

    2004-09-01

    The temporal characteristics of coherent stimulated radiation at the 3P0— 3H6 transition in the Pr3+ ion in a LaF3 matrix are studied by tuning the pump frequency in the vicinity of the 3H4— 3P0 transition. It is found that in the case of the exact tuning to the resonance, a laser pulse, consisting of a train of picosecond spikes of total duration about 10 ns, was delayed by 3-4 ns with respect to the pump pulse onset. As the pump pulse detuning was increased, the shape of the coherent laser pulse changes and its delay increased up to 10 ns. The experimental results are interpreted theoretically.

  1. Facile fabrication and upconversion luminescence enhancement of LaF3:Yb3+/Ln3+@SiO2 (Ln = Er, Tm) nanostructures decorated with Ag nanoparticles.

    PubMed

    He, Enjie; Zheng, Hairong; Dong, Jun; Gao, Wei; Han, Qingyan; Li, Junna; Hui, Le; Lu, Ying; Tian, Huani

    2014-01-31

    A novel hybrid nanostructure, that is a Ag nanoparticle decorated LaF(3):Yb(3+)/Ln(3+)@SiO(2) nanosphere (Ln=Er, Tm), was constructed by a facile strategy, and characterized by XRD, TEM, FTIR, XPS and UV-vis-NIR absorption. Obvious spectral broadening and red-shift on the surface plasmon resonance were obtained by adjusting the size and configuration of Ag nanoparticles. Effective upconversion luminescence enhancements for Er(3+) and Tm(3+) containing samples were obtained. It is suggested that the luminescence enhancement results from both the excitation and emission processes, and the configuration of the studied hybrid nanostructure is an efficient system to enhance the luminescence emission of rare earth doped nanomaterials. It is believed that the enhancement from the hybrid nanostructure will find great potential in the development of photovoltaic solar cells.

  2. Non-invasive Photodynamic Therapy in Brain Cancer by Use of Tb3+-Doped LaF3 Nanoparticles in Combination with Photosensitizer Through X-ray Irradiation: A Proof-of-Concept Study

    NASA Astrophysics Data System (ADS)

    Chen, Min-Hua; Jenh, Yi-Jhen; Wu, Sheng-Kai; Chen, Yo-Shen; Hanagata, Nobutaka; Lin, Feng-Huei

    2017-01-01

    The use of photodynamic therapy (PDT) in the treatment of brain cancer has produced exciting results in clinical trials over the past decade. PDT is based on the concept that a photosensitizer exposed to a specific light wavelength produces the predominant cytotoxic agent, to destroy tumor cells. However, delivering an efficient light source to the brain tumor site is still a challenge. The light source should be delivered by placing external optical fibers into the brain at the time of surgical debulking of the tumor. Consequently, there exists the need for a minimally invasive treatment for brain cancer PDT. In this study, we investigated an attractive non-invasive option on glioma cell line by using Tb3+-doped LaF3 scintillating nanoparticles (LaF3:Tb) in combination with photosensitizer, meso-tetra(4-carboxyphenyl)porphyrin (MTCP), followed by activation with soft X-ray (80 kVp). Scintillating LaF3:Tb nanoparticles, with sizes of approximately 25 nm, were fabricated. The particles have a good dispersibility in aqueous solution and possess high biocompatibility. However, significant cytotoxicity was observed in the glioma cells while the LaF3:Tb nanoparticles with MTCP were exposed under X-ray irradiation. The study has demonstrated a proof of concept as a non-invasive way to treat brain cancer in the future.

  3. Formation of nanostructures induced by capillary-discharge soft X-ray laser on BaF2 surfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Yongpeng; Cui, Huaiyu; Zhang, Shuqing; Zhang, Wenhong; Li, Wei

    2017-02-01

    BaF2 was ablated by a capillary-discharge pumped soft X-ray laser at 46.9 nm focused by a toroidal mirror at a grazing incidence of 83°. The damaged area, induced by both single and multiple laser pulses, was determined to be covered with fringe-like nanostructures with spacings of approximately 400 nm and mastoid nanostructures with diameters of approximately 600 nm. In this study, we analyze the morphology of the detected damage patterns and discuss the damage mechanism. Results indicate that the depth of the nanostructures varies with different pulse numbers and laser power densities.

  4. Response of BaF 2 detectors to photons of 3-50 MeV energy

    NASA Astrophysics Data System (ADS)

    Matulewicz, T.; Grosse, E.; Emling, H.; Freifelder, R.; Grein, H.; Henning, W.; Herrmann, N.; Holzmann, R.; Kulessa, R.; Simon, R. S.; Wollersheim, H. J.; Schoch, B.; Vogt, J.; Wilhelm, M.; Kratz, J. V.; Schmidt, R.; Janssens, R. V. F.

    1990-04-01

    BaF 2 detectors of 20 cm length (10 radiation lengths) and hexagonal cross section (diameter 5.2 cm) were tested using monochromatic photons from the tagged-photon facility at the electron accelerator MAMIA at Mainz. The experimental spectra the deposited energy for a single detector and for an array of seven modules compare very well with the predictions of Monte Carlo shower simulations using the code GEANT3. At high photon energies a significant improvement (more than a factor 2) of the energy resolution is observed for the summed energy spectra as compared to the resolution of one single module.

  5. Synergistic effect of microwave irradiation and CaF2 on vanadium leaching

    NASA Astrophysics Data System (ADS)

    Wang, Jing-peng; Zhang, Yi-min; Huang, Jing; Liu, Tao

    2017-02-01

    The effect and mechanism of microwave irradiation on vanadium leaching were studied via a comparison between microwave heating and conventional heating. The results show a synergistic effect of microwave irradiation and calcium fluoride (CaF2) on the vanadium leaching efficiency. It is confirmed that the vanadium leaching process can be improved by microwave irradiation when CaF2 is present. The leaching rate of vanadium under microwave irradiation is increased by 8%-15% when 5wt% CaF2 is added; by contrast, in the absence of CaF2, the leaching rate is almost unaffected compared to that by conventional heating. Morphological analysis reveals that the particles are gradually eroded by acid under microwave irradiation, whereas some of the fine particles in samples subjected to conventional heating are tightly covered by a flocculent silicate product. Moreover, a large amount of Al and V and a small amount of Si are dissolved from samples under microwave heating, as revealed by the elemental analysis of leachates. Fourier transform infrared spectroscopic analysis also indicates a higher mass transfer coefficient in the diffusion layer of the raw material by microwave irradiation. When CaF2 is present, the reaction energy barrier is lowered and the leaching process is controlled by the tightly covered product layer, resulting in a prominent effect of microwave irradiation.

  6. Modification of luminescence spectra of CaF2:Eu2+.

    PubMed

    Singh, Vartika S; Joshi, C P; Moharil, S V; Muthal, P L; Dhopte, S M

    2015-11-01

    CaF2:Eu(2+) is a well known phosphor having efficient excitation in the near ultraviolet (NUV) range. Phosphors with NUV excitation are required in newly emerging applications such as photoluminescence liquid crystal displays (PLLCD), solid-state lighting (SSL), and down-conversion for solar cells. However, emission of CaF2:Eu(2+) is around 424 nm. Eye sensitivity drops considerably at these wavelengths. It is thus not useful for display applications for which emission in one of the primary colours (blue - 450 nm, green - 540 nm or red - 610 nm) is required. Efforts were made to modify the Photoluminescence (PL) spectra of CaF2:Eu(2+) to meet these requirements using co-dopants. A Ca0.49 Sr0.50 Eu0.01 F2 phosphor showing better colour coordinates and having an emission maximum around 440 nm was discovered during these studies.

  7. System design for precise digitization and readout of the CSNS-WNS BaF2 spectrometer

    NASA Astrophysics Data System (ADS)

    Zhang, De-Liang; Cao, Ping; Wang, Qi; He, Bing; Zhang, Ya-Xi; Qi, Xin-Cheng; Yu, Tao; An, Qi

    2017-02-01

    The BaF2 (barium fluoride) spectrometer is one of the experiment facilities at the CSNS-WNS (White Neutron Source at China Spallation Neutron Source), currently under construction. It is designed to precisely measure the (n, γ) cross section, with 92 crystal elements and complete 4π steradian coverage. In order to improve the precision of measurement, in this paper, a new precise digitization and readout method is proposed. Waveform digitizing with 1 GSps sampling rate and 12-bit resolution is used to precisely capture the detector signal. To solve the problem of massive data readout and processing, the readout electronics is designed as a distributed architecture with 4 PXIe crates. The digitized signal is concentrated to the PXIe crate controller through a PCIe bus on the backplane and transmitted to the data acquisition system over gigabit Ethernet in parallel. Besides, the clock and trigger can be fanned out synchronously to every electronic channel over a high-precision distribution network. Test results show that the prototype of the readout electronics can achieve good performance and meet the requirements of the CSNS-WNS BaF2 spectrometer. Supported by National Research and Development plan (2016YFA0401602) and NSAF (U1530111)

  8. Characterization of electron-beam induced damage structures in natural fluorite, CaF2, by analytical electron microscopy

    NASA Technical Reports Server (NTRS)

    Blake, D. F.; Freund, Friedemann; Allard, L. F.; Echer, C. J.

    1988-01-01

    This paper describes the damage structure induced in natural CaF2 by the electron beam when using TEM. The observed 10-20 nm periodic features with coherent fringe patterns and the pronounced loss of fluorine found after the TEM exposure of 100-line-oriented and 111-oriented sections of CaF2 provides support for the mechanism of damage by decomposition of CaF2 into 2F and Ca, with the Ca precipitates maintaining a close topotaxial relationship with the parent CaF2.

  9. Desulfurizing Ability of the CaOsatd.-CaCl2-CaF2 Slags

    NASA Astrophysics Data System (ADS)

    Liu, Jiazhan; Kobayashi, Yoshinao

    2017-04-01

    Desulfurizing ability of the CaO-CaCl2-CaF2 slags saturated with CaO has been investigated from the viewpoint of the sulfide capacity and CaO solubility. The CaO-CaCl2-CaF2 slags containing small amounts of Cu2O and CaS were inserted in a CaO crucible with metallic copper. The CaO crucible was sealed in a nickel holder to prevent the evaporation of CaCl2, then heated up and kept at temperatures from 1573 K (1300 °C) to 1673 K (1400 °C) for 24 hours, which enabled the system inside the CaO crucible to reach the equilibrium. As expected, the sulfide capacity derived from the data obtained as well as CaO solubility of the slag increase with an increase in temperature at a constant ratio of CaCl2/CaF2. The solubility of CaO increases by the replacement of CaF2 with CaCl2, whereas the sulfide capacity slightly decreases and the activity coefficient of CaS ( γ CaS) increases. This suggests that CaF2 has stronger interaction with CaS than CaCl2. The sulfur distribution ratio between carbon-saturated iron melts and the CaO-CaCl2 slag has been calculated to be about 10 000 at 1573 K (1300 °C) using the sulfide capacity obtained, which value is still large enough even with the replacement of CaF2 by CaCl2.

  10. Desulfurizing Ability of the CaOsatd.-CaCl2-CaF2 Slags

    NASA Astrophysics Data System (ADS)

    Liu, Jiazhan; Kobayashi, Yoshinao

    2016-12-01

    Desulfurizing ability of the CaO-CaCl2-CaF2 slags saturated with CaO has been investigated from the viewpoint of the sulfide capacity and CaO solubility. The CaO-CaCl2-CaF2 slags containing small amounts of Cu2O and CaS were inserted in a CaO crucible with metallic copper. The CaO crucible was sealed in a nickel holder to prevent the evaporation of CaCl2, then heated up and kept at temperatures from 1573 K (1300 °C) to 1673 K (1400 °C) for 24 hours, which enabled the system inside the CaO crucible to reach the equilibrium. As expected, the sulfide capacity derived from the data obtained as well as CaO solubility of the slag increase with an increase in temperature at a constant ratio of CaCl2/CaF2. The solubility of CaO increases by the replacement of CaF2 with CaCl2, whereas the sulfide capacity slightly decreases and the activity coefficient of CaS (γ CaS) increases. This suggests that CaF2 has stronger interaction with CaS than CaCl2. The sulfur distribution ratio between carbon-saturated iron melts and the CaO-CaCl2 slag has been calculated to be about 10 000 at 1573 K (1300 °C) using the sulfide capacity obtained, which value is still large enough even with the replacement of CaF2 by CaCl2.

  11. Small angle grain boundary Ge films on biaxial CaF 2/glass substrate

    NASA Astrophysics Data System (ADS)

    Gaire, C.; Clemmer, P. C.; Li, H.-F.; Parker, T. C.; Snow, P.; Bhat, I.; Lee, S.; Wang, G.-C.; Lu, T.-M.

    2010-02-01

    We demonstrated that it is possible to grow single crystal-like Ge films on a glass substrate using a biaxially textured CaF 2 buffer layer at a low temperature of ˜400 °C. The CaF 2 buffer layer with the (1 1 1)<1 2 1> biaxial orientation was grown by the oblique angle deposition technique and characterized by X-ray pole figure analysis. Transmission electron microscopy revealed that the Ge(1 1 1) heteroepitaxial films possess a single crystal-like structure with small angle grain boundaries of ≤2° misorientation.

  12. Synthesis of 5-Fluorouracil conjugated LaF3:Tb3+/PEG-COOH nanoparticles and its studies on the interaction with bovine serum albumin: spectroscopic approach

    NASA Astrophysics Data System (ADS)

    Mangaiyarkarasi, Rajendiran; Chinnathambi, Shanmugavel; Aruna, Prakasarao; Ganesan, Singaravelu

    2015-03-01

    The luminescent lanthanide-doped nanoparticles have gathered considerable attention in many fields especially in biomedicine. In this work, the lanthanum fluoride-doped terbium nanoparticles (LaF3:Tb3+ NPs) via simple chemical precipitation method has been synthesized and functionalized with polyethylene glycol. The size and the shape of the nanoparticles are confirmed using X-ray diffraction and transmission electron microscopy. The conjugation of 5-Fluorouracil (5-FU) and thus synthesized nanoparticles (NPs) were confirmed using various spectroscopic methods such as UV-Visible spectroscopy, fluorescence steady state, and excited state spectroscopy studies. The enhancement in fluorescence emission ( λ = 543 nm) of drug-conjugated nanoparticles confirms the Vander Waals force of attraction due to F-F bonding between the drug and the nanoparticles. Further, the effects of 5FU-NPs in carrier protein were investigated using bovine serum albumin as a protein model. The 5FU-LaF3:Tb3+ nanoparticles binding is illustrated with binding constant and number of binding sites. The structural change of bovine serum albumin has been studied using circular dichroism and Fourier transform infrared spectroscopy analysis.

  13. Ultra-precision process of CaF2 single crystal

    NASA Astrophysics Data System (ADS)

    Yin, Guoju; Li, Shengyi; Xie, Xuhui; Zhou, Lin

    2014-08-01

    This paper proposes a new chemical mechanical polishing (CMP) process method for CaF2 single crystal to get ultraprecision surface. The CMP processes are improving polishing pad and using alkaline SiO2 polishing slurry with PH=8, PH=11 two phases to polish, respectively, and the roughness can be 0.181nm Rq (10μm×10μm). The CMP process can't get high surface figure, so we use ion beam figuring (IBF) technology to obtain high surface figure. However, IBF is difficult to improve the CaF2 surface roughness. We optimize IBF process to improve surface figure and keep good surface roughness too. Different IBF incident ion energy from 400ev to 800ev does not affect on the surface roughness obviously but the depth of material removal is reverse. CaF2 single crystal can get high precision surface figure (RMS=2.251nm) and still keep ultra-smooth surface (Rq=0.207nm) by IBF when removal depth is less than 200nm. The researches above provide important information for CaF2 single crystal to realize ultra-precision manufacture.

  14. Effect of CaF2 on Interfacial Phenomena of High Alumina Refractories with Al Alloy

    NASA Astrophysics Data System (ADS)

    Koshy, Pramod; Gupta, Sushil; Sahajwalla, Veena; Edwards, Phil

    2008-08-01

    An experimental study was conducted to investigate the interfacial phenomena between Al-alloy and industrial grade high alumina refractories containing varying contents of CaF2 at 1250 °C. Interfacial reaction products and phases formed in the heat-treated refractory samples were characterized using electron probe microanalysis (EPMA) and X-ray diffraction (XRD), respectively, while interfacial phenomena including dynamic wetting behavior were analyzed using the sessile drop technique. Refractories containing less than 5 wt pct CaF2 showed good resistance to reactions with the molten alloy, due to the dominance of corundum, and the presence of anorthite at the interface. However, with a further increase in the additive content, a glassy matrix of anorthite with CaF2 was formed. Formation of this phase significantly increased the intensity of reactions resulting in the buildup of an interfacial layer. The study thus revealed the strong catalytic effect of CaF2 on reactions of high alumina refractories with Al-alloy.

  15. A highly sensitive CaF2:Dy nanophosphor as an efficient low energy ion dosimetry

    NASA Astrophysics Data System (ADS)

    Bhadane, Mahesh S.; Hareesh, K.; Dahiwale, S. S.; Sature, K. R.; Patil, B. J.; Asokan, K.; Kanjilal, D.; Bhoraskar, V. N.; Dhole, S. D.

    2016-11-01

    Dysprosium doped calcium fluoride (CaF2:Dy) powers synthesized by co-precipitation method were irradiated with low energy ion beams (LEIB) viz. 100 keV H, 200 keV Ar and 350 keV N beams at different fluences and demonstrated for low energy ion dosimetric application. X-ray Diffraction and Transmission electron microscopy revealed the formation of highly crystalline cubic structured particles with size ∼45-50 nm. FTIR spectra of the CaF2:Dy samples show changes of some bonds such as N-O asymmetric, C-F bonding and C-H aromatic contain stretching mode after LEIB irradiation. The thermoluminescence (TL) glow curve peaks were observed at 207 °C for Ar ion, at 203 °C for H ion and at 216 °C and 270 °C for N ion. It has been found that CaF2:Dy nanophosphor shows a linear response with minimum fading for all the ion species. Computerized Glow Curve Deconvolution was performed for TL curve of high fluence ion irradiated nanophosphor to estimate the trapping parameters and the respective figure of merit (FOM) found to be very appropriate for all the nanophosphor. These results indicated that the CaF2:Dy can be used as a low energy ion detector or dose.

  16. Low temperature epitaxial growth of Ge on CaF2 buffered cube-textured Ni

    NASA Astrophysics Data System (ADS)

    Gaire, C.; Palazzo, J.; Bhat, I.; Goyal, A.; Wang, G.-C.; Lu, T.-M.

    2012-03-01

    Quasi-single crystal Ge films were grown on cube textured Ni substrate at a temperature of 350 °C using an insulating buffer layer of CaF2. A direct deposition of Ge on Ni at 350 °C was shown to alloy with Ni. From x-ray pole figure analysis, it was shown that Ge grew epitaxially with the same orientation as CaF2 and the dispersions in the out-of-plane and in-plane directions were found to be 1.7±0.1° and 6±1°, respectively. In the out-of-plane direction, Ge[111]‖CaF2[111]‖Ni[001]. In addition, the Ge consisted of four equivalent in-plane oriented domains such that two mutually orthogonal directions: Ge<2¯11> and Ge<01¯1> are parallel to mutually orthogonal directions: Ni<1¯10> and Ni<1¯1¯0>, respectively, of the Ni(001) surface. This was shown to originate from the four equivalent in-plane oriented domains of CaF2 created to minimize the mismatch strain between CaF2 and Ni in those directions.

  17. Test of the statistical model in Mo96 with the BaF2γ calorimeter DANCE array

    NASA Astrophysics Data System (ADS)

    Sheets, S. A.; Agvaanluvsan, U.; Becker, J. A.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Parker, W.; Reifarth, R.; Rundberg, R. S.; Sharapov, E. I.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Wu, C. Y.

    2009-02-01

    The γ-ray cascades following the Mo95(n,γ)Mo96 reaction were studied with the γ calorimeter DANCE (Detector for Advanced Neutron Capture Experiments) consisting of 160 BaF2 scintillation detectors at the Los Alamos Neutron Science Center. The γ-ray energy spectra for different multiplicities were measured for s- and p-wave resonances below 2 keV. The shapes of these spectra were found to be in very good agreement with simulations using the DICEBOX statistical model code. The relevant model parameters used for the level density and photon strength functions were identical with those that provided the best fit of the data from a recent measurement of the thermal Mo95(n,γ)Mo96 reaction with the two-step-cascade method. The reported results strongly suggest that the extreme statistical model works very well in the mass region near A=100.

  18. First-principles identification of charge-transition levels of native defects in BaF2

    NASA Astrophysics Data System (ADS)

    Ibraheem, A. M.; Eisa, M. H.; Adlan, W.; Amolo, George O.; Khalafalla, M. A. H.

    2017-03-01

    This paper reports on semilocal and hybrid density functional analysis of charge-transition levels of native defects in BaF2 structure. The transition level is defined as the Fermi level where two defect charge states have the same formation energy. The errors arising from the small supercell size effects have been relieved through extrapolating the formation energies to the limit of infinite supercell size. The level placement in the corrected band gap is achieved using a correction factor obtained from the difference between the valence band maxima in semilocal and hybrid calculations. The band gap size from hybrid calculation is validated using the full-potential, linearized augmented planewave method with the modified Becke-Johnson exchange potential. Our results are sufficiently accurate and, thus, significant for direct comparison with experiments.

  19. One-Pot Solvothermal Synthesis of Highly Emissive, Sodium-Codoped, LaF3 and BaLaF5 Core-Shell Upconverting Nanocrystals

    PubMed Central

    Stecher, Joshua T.; Rohlfing, Anne B.; Therien, Michael J.

    2014-01-01

    We report a one-pot solvothermal synthesis of sub-10 nm, dominant ultraviolet (UV) emissive upconverting nanocrystals (UCNCs), based on sodium-codoped LaF3 and BaLaF5 (0.5%Tm; 20%Yb) and their corresponding core@shell derivatives. Elemental analysis shows a Na-codopant in these crystal systems of ~20% the total cation content; X-ray diffraction (XRD) data indicate a shift in unit cell dimensions consistent with these small codopant ions. Similarly, X-ray photoelectron spectroscopic (XPS) analysis reveals primarily substitution of Na+ for La3+ ions (97% of total Na+ codopant) in the crystal system, and interstitial Na+ (3% of detected Na+) and La3+ (3% of detected La3+) present in (Na)LaF3 and only direct substitution of Na+ for Ba2+ in Ba(Na)LaF5. In each case, XPS analysis of La 3d lines show a decrease in binding energy (0.08–0.25 eV) indicating a reduction in local crystal field symmetry surrounding rare earth (R.E.3+) ions, permitting otherwise disallowed R.E. UC transitions to be enhanced. Studies that examine the impact of laser excitation power upon luminescence intensity were conducted over 2.5–100 W/cm2 range to elucidate UC mechanisms that populate dominant UV emitting states. Low power saturation of Tm3+ 3F3 and 3H4 states was observed and noted as a key initial condition for effective population of the 1D2 and 1I6 UV emitting states, via Tm-Tm cross-relaxation. PMID:28348286

  20. Thermoluminescence in CaF2:Dy and CaF2:Mn induced by monoenergetic, parallel beam, 81-0 meV diffracted neutrons.

    PubMed

    Horowitz, Y S; Shahar, B B; Dubi, A; Pinto, H

    1977-05-01

    The thermal neutron thermoluminescent response of CaF2 : Dy (TLD-200, 0-35% wt Dy) and CaF2 : mn (TLD-400, 2% wt Mn) has been measured by exposure to a monoenergetic, parallel beam of 81-0 meV neutrons from a Kandi-II diffractometer. The TL dosemeters were rectangular and of 0-165 X 0-165 X 0-83 cm dimensions. The measured integral TLD-200 response for a neutron fluence of 10(10) n cm-2 was 0-21 +/- 0-013 R of 60Co which translates to 0-33 +/- 0-021 R 60Co for a Maxwellian neutron energy distribution at T = 293-6 K. The measured integral TLD-400 response for a neutron fluence of 10(10) n cm-2 was 0-09 +/- 0-006 R 60Co which similarly translates to 0-14 +/- 0-010 R 60Co for a Maxwellian neutron energy distribution at T = 293-6 K. The thermoluminescent response of both materials is both theoretically and experimentally shown to be composed of a thermal neutron induced prompt gamma component (approximately 20%) as well as the major component due to the thermal neutron induced beta decay of 165Dy and 56Mn. It is pointed out that the thermal neutron thermoluminescent response of both materials is size and geometry dependent.

  1. On the threshold for ion track formation in CaF2

    NASA Astrophysics Data System (ADS)

    Karlušić, M.; Ghica, C.; Negrea, R. F.; Siketić, Z.; Jakšić, M.; Schleberger, M.; Fazinić, S.

    2017-02-01

    There is an ongoing debate regarding the mechanism of swift heavy ion (SHI) track formation in CaF2. The objective of this study is to shed light on this important topic using a range of complementary experimental techniques. Evidence of the threshold for ion track formation being below 3 keV nm‑1 is provided by both transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy in the channelling mode, which has direct consequences for the validity of models describing the response of CaF2 to SHI irradiation. Furthermore, information about the elemental composition within the ion tracks is obtained using scanning TEM, electron energy loss spectroscopy, and with respect to the stoichiometry of the materials surface by in situ time of flight elastic recoil detection analysis. Advances in the analyses of the experimental data presented here pave the way for a better understanding of the ion track formation.

  2. Statistical characterization of thermally evaporated rough CaF2 films.

    PubMed

    Luhman, D R; Hallock, R B

    2004-11-01

    Thermal deposition of CaF2 onto a glass substrate creates a nanoscale rough surface. A series of samples with differing nominal CaF2 film thicknesses have been fabricated, and the topography has been investigated using atomic force microscopy. Measured values for the statistical characterization of the samples are presented including the exponents describing the scaling behavior of the surfaces. We find that the roughness exponent alpha=0.88+/-0.03 , the growth exponent beta=0.75+/-0.03 , and the dynamical exponent z=alpha/beta=1.17+/-0.06 . We also measure the multifractal spectra and nearest neighbor height difference probability distribution. The results are consistent with noise dominated by a power-law distribution with exponent mu+1 approximately equal to 4.6. Profilometer measurements were used to determine the porosity phi of the deposited films, which we find to be constant for all film thicknesses with phi approximately 0.46 .

  3. Diode-pumped femtosecond mode-locked Nd, Y-codoped CaF2 laser

    NASA Astrophysics Data System (ADS)

    Zhu, Jiangfeng; Zhang, Lijuan; Gao, Ziye; Wang, Junli; Wang, Zhaohua; Su, Liangbi; Zheng, Lihe; Wang, Jingya; Xu, Jun; Wei, Zhiyi

    2015-03-01

    A passively mode-locked femtosecond laser based on an Nd, Y-codoped CaF2 disordered crystal was demonstrated. The Y3+-codoping in Nd : CaF2 markedly suppressed the quenching effect and improved the fluorescence quantum efficiency and emission spectra. With a fiber-coupled laser diode as the pump source, the continuous wave tuning range covering from 1042 to 1076 nm was realized, while the mode-locked operation generated 264 fs pulses with an average output power of 180 mW at a repetition rate of 85 MHz. The experimental results show that the Nd, Y-codoped CaF2 disordered crystal has potential in a new generation diode-pumped high repetition rate chirped pulse amplifier.

  4. Nanostructuring CaF2 surfaces with slow highly charged ions

    NASA Astrophysics Data System (ADS)

    El-Said, A. S.; Wilhelm, R. A.; Heller, R.; Ritter, R.; Wachter, G.; Facsko, S.; Lemell, C.; Burgdörfer, J.; Aumayr, F.

    2014-04-01

    In recent years the potential of slow highly charged ions (HCI) as tools for nanostructuring purposes has received considerable attention and a wide range of material classes, from insulating ionic crystals, polymers and ultrathin films, to semiconducting and conducting substrates have been investigated regarding their response to individual HCI impact. For the majority of investigated materials, however, consistent theoretical modeling to supplement with experimental evidence and to satisfactorily explain the complete physical process from ion approach and impact to the formation of an individual nanostructure is still lacking. CaF2, from both an experimental and theoretical point of view, might be considered the most thoroughly investigated material. Combining results from numerous studies has allowed for the generation of a "phase diagram" for nanostructuring of CaF2 in dependence of ion beam parameters. This paves the way for a first unified picture, as implications from this phase diagram should be applicable to similar materials as well.

  5. Studies of the Facetting of the Polished (100) Face of CaF2

    NASA Astrophysics Data System (ADS)

    Dabringhaus, H.; Schick, M.; Wandelt, K.; Deuster, V.; Kayser, Th.; Klapper, H.

    2003-12-01

    The present paper deals with studies of the facetting of the polished (100) surface of CaF2 during annealing and growth in UHV using low energy electron diffraction (LEED), atomic force microscopy (AFM), and transmission electron microscopy (TEM). First morphological modifications of the polished surfaces become visible at temperatures of T = 874 K. Surfaces annealed at T = 974 K exhibit a micro-roughening with pyramidal protrusions and corresponding depressions. LEED studies indicate the evolution of {111} facets. Reflexes from the (100) surface are not seen. After growth of about 660 monolayers of CaF2 at T = 1093 K and a saturation ratio S = 33 from the vapor phase, larger pyramid-like or hip roof-like crystallites are developed. The results of AFM height profiles as well as of the LEED investigations indicate again the formation of {111} facets as proved by their angles of 54.7° with the base (100) surface. This shows that the crystallites are homoepitaxially grown on the underlying CaF2 substrate.

  6. Studies of the facetting of the polished (100) face of CaF 2

    NASA Astrophysics Data System (ADS)

    Deuster, V.; Schick, M.; Kayser, Th.; Dabringhaus, H.; Klapper, H.; Wandelt, K.

    2003-04-01

    The present paper deals with studies of the facetting of the polished (1 0 0) surface of CaF 2 during annealing and growth in UHV using low energy electron diffraction (LEED), atomic force microscopy (AFM), and transmission electron microscopy (TEM). First morphological modifications of the polished surfaces become visible at temperatures of T=874 K. Surfaces annealed at T=974 K exhibit a micro-roughening with pyramidal protrusions and corresponding depressions. LEED studies indicate the evolution of {1 1 1} facets. Reflexes from the (1 0 0) surface are not seen. After growth of about 660 monolayers of CaF 2 at T=1093 K and a saturation ratio S=33 from the vapor phase, larger pyramid-like or hip roof-like crystallites are developed. The results of AFM height profiles as well as of the LEED investigations indicate again the formation of {1 1 1} facets as proved by their angles of 54.7 o with the base (1 0 0) surface. This shows that the crystallites are homoepitaxially grown on the underlying CaF 2 substrate.

  7. An Evaluation of Former Soviet Union Welding Processes on Commercially Pure Titanium

    DTIC Science & Technology

    2001-12-01

    wire from Reference 8 is given as 40% to 50% CaF2, 18% to 20% LaF3 or CeF3, 5% to 10% BaF 2, and SrF2 (remainder). No information was available about...of under -fill was observed along the fusion line on each side of the weld metal on Plate A; no under -fill was observed on Plates B and C...and Casting Inspection and Repair for Machinery, Piping, and Pressure Vessels," NAVSEA Technical Publication S9074-AR-GIB-010/278, Washington, DC

  8. Studies of EPR spectra and defect structure for Er3+ ions in BaF2 and SrF2 crystals

    NASA Astrophysics Data System (ADS)

    Li, Hui; Kuang, Xiao-Yu; Mao, Ai-Jie; Li, Cheng-Gang

    2013-02-01

    The local lattice structure and electron paramagnetic resonance (EPR) spectra have been studied systematically by diagonalizing 364 × 364 complete energy matrices for a f11 ion in a trigonal ligand-field. By simulating the calculated Stark levels and EPR parameters to the experimental results, the shift parameters are determined for Er3+ ions in BaF2 and SrF2. The results show that the trigonal center is attributed to an interstitial F- ion located at the [1 1 1] axis of the cube, and the nearest ligand close to the charge compensator has a displacement towards central ion by 0.042 Å for L center in BaF2:Er3+ and 0.026 Å for J center in SrF2:Er3+, respectively. Moreover, the relationships between g-factors and shift parameter ΔZ as well as orbit reduction factor k' are discussed.

  9. Test of AN Electromagnetic Calorimeter Using BaF2 Scintillators and Photosensitive Wire Chambers Between 1 and 9 GeV

    NASA Astrophysics Data System (ADS)

    Bouclier, R.; Charpak, G.; Gao, W.; Million, G.; MinÉ, P.; Paul, S.; Santiard, J. C.; Scigocki, D.; Solomey, N.; Suffert, M.

    We describe an electromagnetic calorimeter constructed from layers of BaF2 crystals, coupled to low pressure MWPCs with hot TMAE gas as the photosensitive constituent. By making use of the fast component from the BaF2 scintillation, this detector is well suited for a high rale, intense radiation environment. We present the results of a test performed with our prototype in a 1-9 GeV/c beam, which gives an energy resolution better than 4%/√{E}. a position resolution of 1 mm. and a time resolution better than 1 ns. The detector is highly segmented, with tracking capabilities and good e/π rejection. We discuss the possible application to experiments with intense colliders.

  10. Simultaneous measurement of (n, γ) and (n, fission) cross sections with the DANCE 4π BaF 2 array

    NASA Astrophysics Data System (ADS)

    Bredeweg, T. A.; Fowler, M. M.; Becker, J. A.; Bond, E. M.; Chadwick, M. B.; Clement, R. R. C.; Esch, E.-I.; Ethvignot, T.; Granier, T.; Jandel, M.; Macri, R. A.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Wu, C. Y.

    2007-08-01

    We have recently begun a program of high precision measurements of the key production and destruction reactions of important radiochemical diagnostic isotopes, including several isotopes of uranium, plutonium and americium. The detector for advanced neutron capture experiments (DANCE), a 4π BaF2 array located at the Los Alamos Neutron Science Center, will be used to measure the neutron capture cross sections for most of the isotopes of interest. However, neutron capture measurements on many of the actinides are complicated by the presence of prompt γ-rays arising from low energy neutron-induced fission, which competes with neutron capture to varying degrees. Previous measurements of 235U using the DANCE array have shown that we can partially resolve capture from fission events based on total γ-ray calorimetry (i.e. total γ-ray energy versus γ-ray multiplicity). The addition of a dedicated fission-tagging detector to the DANCE array has greatly improved our ability to separate these two competing processes. In addition to higher quality neutron capture data, the addition of a fission-tagging detector offers a means to determine the capture-to-fission ratio (σγ/σf) in a single measurement, which should reduce the effect of systematic uncertainties. We are currently using a dual parallel-plate avalanche counter (PPAC) with the target material electro-deposited directly on the center cathode foil. This design provides a high efficiency for detecting fission fragments and allows loading of pre-assembled target/detector assemblies into the neutron beam line at DANCE. Results from tests of the fission-tag detector, as well as preliminary results from measurements on 235U and 252Cf that utilized the fission-tag detector will be presented.

  11. Evidence for power-law dominated noise in vacuum deposited CaF2.

    PubMed

    Luhman, D R; Hallock, R B

    2004-06-25

    We have studied the surface roughness of CaF2 vacuum deposited on glass using atomic force microscopy for film coverages spanning an order of magnitude. We find the roughness exponent alpha=0.88+/-0.03, the growth exponent beta=0.75+/-0.03, and the dynamic exponent z=alpha/beta=1.17+/-0.06. Multifractality is also present, along with power-law behavior in the nearest neighbor height difference probability distribution. The results indicate noise dominated by a power-law distribution with exponent micro+1 approximately 4.6.

  12. Creation of nanohillocks on CaF2 surfaces by single slow highly charged ions.

    PubMed

    El-Said, A S; Heller, R; Meissl, W; Ritter, R; Facsko, S; Lemell, C; Solleder, B; Gebeshuber, I C; Betz, G; Toulemonde, M; Möller, W; Burgdörfer, J; Aumayr, F

    2008-06-13

    Upon impact on a solid surface, the potential energy stored in slow highly charged ions is primarily deposited into the electronic system of the target. By decelerating the projectile ions to kinetic energies as low as 150 x q eV, we find first unambiguous experimental evidence that potential energy alone is sufficient to cause permanent nanosized hillocks on the (111) surface of a CaF(2) single crystal. Our investigations reveal a surprisingly sharp and well-defined threshold of potential energy for hillock formation which can be linked to a solid-liquid phase transition.

  13. Optical characterization of Tm3+ doped Bi2O3-GeO2-Ga2O3 glasses in absence and presence of BaF2

    NASA Astrophysics Data System (ADS)

    Han, Kexuan; Zhang, Peng; Wang, Shunbin; Guo, Yanyan; Zhou, Dechun; Yu, Fengxia

    2016-08-01

    In this paper, Two new Bi2O3-GeO2-Ga2O3 glasses (one presence of BaF2) doped with 1mol% Tm2O3 were prepared by melt-quenching technique. Differential thermal analysis (DTA), the absorption, Raman, IR spectra and fluorescence spectra were measured. The Judd–Ofelt intensity parameters, emission cross section, absorption cross section, and gain coefficient of Tm3+ ions were comparatively investigated. After the BaF2 introduced, the glass showed a better thermal stability, lower phonon energy and weaker OH‑ absorption coefficient, meanwhile, a larger ~1.8 μm emission cross section σem (7.56 × 10‑21 cm2) and a longer fluorescence lifetime τmea (2.25 ms) corresponding to the Tm3+: 4F3 → 3H6 transition were obtained, which is due to the addition of fluoride in glass could reduce the quenching rate of hydroxyls and raise the cross-relaxation (3H6 + 3H4 → 3F4 + 3F4) rate. Our results suggest that the Tm3+ doped Bi2O3-GeO2-Ga2O3 glass with BaF2 might be potential to the application in efficient ~1.8 μm lasers system.

  14. Spectroscopic properties and mechanism of Tm3+/Er3+/Yb3+co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Hu, Yue-Bo; Qiu, Jian-Bei; Zhou, Da-Cheng; Song, Zhi-Guo; Yang, Zheng-Wen; Wang, Rong-Fei; Jiao, Qing; Zhou, Da-Li

    2014-02-01

    Transparent Tm3+/Er3+/Yb3+ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals are prepared. Under excitation of a 980-nm laser diode (LD), compared with the glass before heat treatment, the Tm3+/Er3+/Yb3+co-doped oxyfluorogermanate glass ceramics can emit intense blue, green and red up-conversion luminescence and Stark-split peaks; X-ray diffraction (XRD) and transmission electron microscope (TEM) results show that BaF2 nanocrystals with an average diameter of 20 nm are precipitated from the glass matrix. Stark splitting of the up-conversion luminescence peaks in the glass ceramics indicates that Tm3+, Er3+ and (or) Yb3+ ions are incorporated into the BaF2 nanocrystals. The up-conversion luminescence intensities of Tm3+, Er3+ and the splitting degree of luminescence peaks in the glass ceramics increase significantly with the increase of heat treat temperature and heat treat time extension. In addition, the possible energy transfer process between rare earth ions and the up-conversion luminescence mechanism are also proposed.

  15. Optical characterization of Tm(3+) doped Bi2O3-GeO2-Ga2O3 glasses in absence and presence of BaF2.

    PubMed

    Han, Kexuan; Zhang, Peng; Wang, Shunbin; Guo, Yanyan; Zhou, Dechun; Yu, Fengxia

    2016-08-10

    In this paper, Two new Bi2O3-GeO2-Ga2O3 glasses (one presence of BaF2) doped with 1mol% Tm2O3 were prepared by melt-quenching technique. Differential thermal analysis (DTA), the absorption, Raman, IR spectra and fluorescence spectra were measured. The Judd-Ofelt intensity parameters, emission cross section, absorption cross section, and gain coefficient of Tm(3+) ions were comparatively investigated. After the BaF2 introduced, the glass showed a better thermal stability, lower phonon energy and weaker OH(-) absorption coefficient, meanwhile, a larger ~1.8 μm emission cross section σem (7.56 × 10(-21) cm(2)) and a longer fluorescence lifetime τmea (2.25 ms) corresponding to the Tm(3+): (4)F3 → (3)H6 transition were obtained, which is due to the addition of fluoride in glass could reduce the quenching rate of hydroxyls and raise the cross-relaxation ((3)H6 + (3)H4 → (3)F4 + (3)F4) rate. Our results suggest that the Tm(3+) doped Bi2O3-GeO2-Ga2O3 glass with BaF2 might be potential to the application in efficient ~1.8 μm lasers system.

  16. Optical characterization of Tm3+ doped Bi2O3-GeO2-Ga2O3 glasses in absence and presence of BaF2

    PubMed Central

    Han, Kexuan; Zhang, Peng; Wang, Shunbin; Guo, Yanyan; Zhou, Dechun; Yu, Fengxia

    2016-01-01

    In this paper, Two new Bi2O3-GeO2-Ga2O3 glasses (one presence of BaF2) doped with 1mol% Tm2O3 were prepared by melt-quenching technique. Differential thermal analysis (DTA), the absorption, Raman, IR spectra and fluorescence spectra were measured. The Judd–Ofelt intensity parameters, emission cross section, absorption cross section, and gain coefficient of Tm3+ ions were comparatively investigated. After the BaF2 introduced, the glass showed a better thermal stability, lower phonon energy and weaker OH− absorption coefficient, meanwhile, a larger ~1.8 μm emission cross section σem (7.56 × 10−21 cm2) and a longer fluorescence lifetime τmea (2.25 ms) corresponding to the Tm3+: 4F3 → 3H6 transition were obtained, which is due to the addition of fluoride in glass could reduce the quenching rate of hydroxyls and raise the cross-relaxation (3H6 + 3H4 → 3F4 + 3F4) rate. Our results suggest that the Tm3+ doped Bi2O3-GeO2-Ga2O3 glass with BaF2 might be potential to the application in efficient ~1.8 μm lasers system. PMID:27506152

  17. First principle calculation of accurate native defect levels in CaF2

    NASA Astrophysics Data System (ADS)

    Ibraheem, Abdelaziz M.; Khalafalla, Mohammed A. H.; Eisa, Mohamed H.

    2017-03-01

    We report on the first principle density functional calculation of the charge transition levels of native defects (vacancies and interstitials) in CaF2 structure. The transition level was defined as the Fermi level where two charge states of given defect have the same formation energy. The common error in the band gap inherited to semiclocal density functional has been accounted for by incorporating the hybrid density functional method, leading to correct placement of the transition levels within the band gap. The band gap size from hybrid calculation has been validated using the full potential, Linearized Augmented Planewave method with the Modified-Becke-Johnson exchange potential. Prior to level calculations, we ensured that an agreement between the formation energies from small (95-97 atoms) and large (323-325 atoms) supercells was achieved after applying the Makov-Payne correction method. Our calculated transition level for the anion vacancy was 2.97 eV below the conduction band, agreeing with the experimental optical absorption band at 3.3 eV associated with the electron transition from the ground state F-center to the conduction band in CaF2.

  18. Novel CaF2 Nanocomposite with High Strength and Fluoride Ion Release

    PubMed Central

    Xu, H.H.K.; Moreau, J.L.; Sun, L.; Chow, L.C.

    2010-01-01

    Secondary caries and restoration fracture remain common problems in dentistry. This study tested the hypothesis that combining nano-CaF2 and glass fillers would yield nanocomposites with high mechanical properties and F release. Novel CaF2 nanoparticles (56-nm) were synthesized via spray-drying and incorporated into resin. F release increased with increasing the nano-CaF2 content, or with decreasing pH (p < 0.05). F-release rates at 70-84 days were 1.13 µg/(cm2·day) and 0.50 µg/(cm2·day) for nanocomposites containing 30% and 20% nano-CaF2, respectively. They matched the 0.65 µg/(cm2·day) of resin-modified glass ionomer (p > 0.1). The nanocomposites had flexural strengths of 70-120 MPa, after 84-day immersion at pH 4, pH 5.5, and pH 7. These strengths were nearly three-fold that of resin-modified glass ionomer, and matched/exceeded a composite with little F release. In summary, novel CaF2 nanoparticles produced high F release at low filler levels, thereby making room in resin for reinforcement glass. This yielded nanocomposites with high F-release and stress-bearing properties, which may help reduce secondary caries and restoration fracture. PMID:20439933

  19. Study on TL and OSL characteristics of indigenously developed CaF 2:Mn phosphor

    NASA Astrophysics Data System (ADS)

    Bakshi, A. K.; Dhabekar, Bhushan; Rawat, N. S.; Singh, S. G.; Joshi, V. J.; Kumar, Vijay

    2009-02-01

    CaF 2:Mn phosphor is known for its high thermoluminescent sensitivity and dose linearity up to few kGy. In the present study CaF 2 phosphor with different concentration of Mn dopant was prepared and was characterized through different techniques. The phosphor was prepared through chemical root using CaCO 3, HF acid and MnCl 2 as raw materials following co-precipitation method. TL sensitivity of the prepared phosphor was compared with other well established phosphors used for radiation dosimetry. It was found that the TL sensitivity is higher by a factor of 10 with respect to LiF:Mg, Ti, TLD-100 and half to that of CaSO 4:Dy (0.05 mol%) phosphor. X-ray diffraction, TL emission spectrum and ESR spectrum taken of the prepared phosphor confirms the crystal structure, Mn 2+ emission and incorporation Mn in the crystal, respectively. No significant fading of the dosimetric peak was observed of the prepared phosphor for a storage period of 45 days. The dose linearity of the phosphor was found to be in the range of 50 Gy-3 kGy within an uncertainty of about 10%. An attempt was made to determine the kinetic parameters of TL glow curve and the parameters related to optically stimulated luminescence. In view of its long range of dose linearity, it can be used for the dosimetry of commercial irradiator generally used for the irradiation of food and grains in our country.

  20. Ho3+/Yb3+ co-doped TeO2-BaF2-Y2O3 glasses for ∼1.2 μm laser applications

    NASA Astrophysics Data System (ADS)

    Wang, Shunbin; Li, Chengzhi; Yao, Chuanfei; Jia, Shijie; Jia, Zhixu; Qin, Guanshi; Qin, Weiping

    2017-02-01

    Intense ∼1.2 μm fluorescence is observed in Ho3+/Yb3+ co-doped TeO2-BaF2-Y2O3 glasses under 915 nm laser diode excitation. The 1.2 μm emission can be ascribed to the transition 5I6→5I8 of Ho3+. With the introducing of BaF2, the content of OH in the glasses drops markedly, and the 1.2 μm emission intensity increases gradually as increasing the concentration percentage of BaF2. Furthermore, microstructured fibers based on the TeO2-BaF2-Y2O3 glasses are fabricated by using a rod-in-tube method, and a relative positive gain of ∼9.42 dB at 1175.3 nm is obtained in a 5 cm long fiber.

  1. Room temperature fabrication of dielectric Bragg reflectors composed of a CaF2/ZnS multilayered coating.

    PubMed

    Muallem, Merav; Palatnik, Alex; Nessim, Gilbert D; Tischler, Yaakov R

    2015-01-14

    We describe the design, fabrication, and characterization of mechanically stable, reproducible, and highly reflecting distributed Bragg reflectors (DBR) composed of thermally evaporated thin films of calcium fluoride (CaF2) and zinc sulfide (ZnS). CaF2 and ZnS were chosen as the low and high refractive index components of the multilayer DBR structures, with n = 1.43 and n = 2.38 respectively, because neither material requires substrate heating during the deposition process in order to produce optical quality thin films. DBRs consisting of seven pairs of CaF2 and ZnS layers, were fabricated with thicknesses of 96 and 58 nm, respectively, as characterized by high-resolution scanning electron microscopy (HR-SEM), and exhibited a center wavelength of λc = 550 nm and peak reflectance exceeding 99%. The layers showed good adhesion to each other and to the glass substrate, resulting in mechanically stable DBR coatings. Complete optical microcavities consisting of two such DBR coatings and a CaF2 spacer layer between them could be fabricated in a single deposition run. Optically, these structures exhibited a resonator quality factor of Q > 160. When a CaF2/ZnS DBR was grown, without heating the substrate during deposition, on top of a thin film containing the fluorescent dye Rhodamine 6G, the fluorescence intensity showed no degradation compared to an uncoated film, in contrast to a MgF2/ZnS DBR coating grown with substrate heating which showed a 92% reduction in signal. The ability to fabricate optical quality CaF2/ZnS DBRs without substrate heating, as introduced here, can therefore enable formation of low-loss high-reflectivity coatings on top of more delicate heat-sensitive materials such as organics and other nanostructured emitters, and hence facilitate the development of nanoemitter-based microcavity device applications.

  2. Neutron beam tests of CsI(Na) and CaF2(Eu) crystals for dark matter direct search

    NASA Astrophysics Data System (ADS)

    Guo, C.; Ma, X. H.; Wang, Z. M.; Bao, J.; Dai, C. J.; Guan, M. Y.; Liu, J. C.; Li, Z. H.; Ren, J.; Ruan, X. C.; Yang, C. G.; Yu, Z. Y.; Zhong, W. L.; Huerta, C.

    2016-05-01

    In recent decades, inorganic crystals have been widely used in dark matter direct search experiments. To contribute to the understanding of the capabilities of CsI(Na) and CaF2(Eu) crystals, a mono-energetic neutron beam is utilized to study the properties of nuclear recoils, which are expected to be similar to signals of dark matter direct detection. The quenching factor of nuclear recoils in CsI(Na) and CaF2Eu, as well as an improved discrimination factor between nuclear recoils and γ backgrounds in CsI(Na), are reported.

  3. Variable growth modes of CaF2 on Si(111) determined by x-ray photoelectron diffraction

    NASA Astrophysics Data System (ADS)

    Denlinger, J. D.; Rotenberg, Eli; Hessinger, Uwe; Leskovar, M.; Olmstead, Marjorie A.

    1993-04-01

    Chemical discrimination of bulk and interface Ca 2p x-ray photoelectron diffraction modulations is used to identify three growth regimes during the initial stages of CaF2 epitaxy on Si(111). Low flux, high temperature conditions produce island growth atop a nonwetting, chemically reacted Ca-F interface layer. Changing the growth kinetics by increasing the flux produces more laminar growth. Lowering the substrate temperature produces a more stoichiometric CaF2 interface layer that results in immediate wetting and laminar growth.

  4. Self-assembled Fe nanowires using organometallic chemical vapor deposition and CaF2 masks on stepped Si(111)

    NASA Astrophysics Data System (ADS)

    Lin, J.-L.; Petrovykh, D. Y.; Kirakosian, A.; Rauscher, H.; Himpsel, F. J.; Dowben, P. A.

    2001-02-01

    Linear arrays of 3 nm wide Fe stripes with 15 nm spacing are fabricated by self-assembly. They are formed by photolysis of ferrocene that is selectively adsorbed between CaF2 stripes. An ultraviolet nitrogen laser removes the organic ligands from ferrocene. Arrays of CaF2 stripes serve as masks, which are self-assembled on a stepped Si(111) surface. Scanning tunneling microscopy is used to investigate the surface morphology during growth. A generalization of this method to other wire materials is discussed.

  5. Commissioning the DANTE array of BaF2 detectors at TRIUMF-ISAC using a fast-timing lifetime measurement

    NASA Astrophysics Data System (ADS)

    Cross, D. S.; Ball, G. C.; Garrett, P. E.; Triambak, S.; Williams, S. J.; Andreoiu, C.; Churchman, R.; Garnsworthy, A. B.; Hackman, G.; Leslie, J. R.; Orce, J. N.; Sumithrarachchi, C. S.; Svensson, C. E.

    2011-08-01

    The Di-pentagonal Array for Nuclear Timing Experiments (DANTE) is an array of ten BaF2 detectors used in conjunction with the 8π gamma-ray spectrometer at the TRIUMF-ISAC radioactive-ion beam facility. DANTE is used to conduct direct lifetime measurements of nuclear excited states in the picosecond - nanosecond range. This, in turn, will aid in probing the collective structures of deformed nuclei. The capability of DANTE to measure nanosecond-scale lifetimes is demonstrated by using a 152Eu source. The half-life of the Iπ = 21+ state of 152Sm is measured to be 1.426 ± 0.018 ns.

  6. The Detector for Advanced Neutron Capture Experiments: A 4{pi} BaF2 Detector for Neutron Capture Measurements at LANSCE

    SciTech Connect

    Ullmann, J.L.; Esch, E.-I.; Haight, R.C.; Hunt, L.; O'Donnell, J.M.; Reifarth, R.; Agvaanluvsan, U.; Alpizar, A.; Hatarik, R.; Bond, E.M.; Bredeweg, T.A.; Kronenberg, A.; Rundberg, R.S.; Vieira, D.J.; Wilhelmy, J.B.; Folden, C.M.; Hoffman, D.C.; Greife, U.; Schwantes, J.M.; Strottman, D.D.

    2005-05-24

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 162-element 4{pi} BaF2 array designed to make neutron capture cross-section measurements on rare or radioactive targets with masses as little as one milligram. Accurate capture cross sections are needed in many research areas, including stellar nucleosynthesis, advanced nuclear fuel cycles, waste transmutation, and other applied programs. These cross sections are difficult to calculate accurately and must be measured. The design and initial performance results of DANCE is discussed.

  7. Orientation epitaxy of Ge1–xSnx films grown on single crystal CaF2 substrates

    DOE PAGES

    A. J. Littlejohn; Zhang, L. H.; Lu, T. -M.; ...

    2016-03-15

    Ge1–xSnx films were grown via physical vapor deposition below the crystallization temperature of Ge on single crystal (111) and (100) CaF2 substrates to assess the role of Sn alloying in Ge crystallization. By studying samples grown at several growth temperatures ranging from 250 °C to 400 °C we report temperature-dependent trends in several of the films' properties. X-ray diffraction theta vs. two-theta (θ/2θ) scans indicate single orientation Ge1–xSnx(111) films are grown on CaF2(111) substrates at each temperature, while a temperature-dependent superposition of (111) and (100) orientations are exhibited in films grown on CaF2(100) above 250 °C. This is the firstmore » report of (111) oriented Ge1–xSnx grown on a (100) oriented CaF2 substrate, which is successfully predicted by a superlattice area matching model. These results are confirmed by X-ray diffraction pole figure analysis. θ/2θ results indicate substitutional Sn alloying in each film of about 5%, corroborated by energy dispersive spectroscopy. In addition, morphological and electrical properties are measured by scanning electron microscopy, atomic force microscopy and Hall mobility measurements and are also shown to be dependent upon growth temperature.« less

  8. Superconducting tunnel junctions on MgB2 using MgO and CaF2 as a barrier

    NASA Astrophysics Data System (ADS)

    Sakoda, Masahito; Aibara, Masato; Mede, Kazuya; Kikuchi, Motoyuki; Naito, Michio

    2016-11-01

    We report the fabrication of superconducting tunnel junctions, both of superconductor-insulator-normal metal (SIN) and superconductor-insulator-superconductor (SIS), on MgB2 using MgO and CaF2 as a barrier. The SIN junctions fabricated using an MgO barrier showed excellent quasi-particle characteristics, including a large superconducting gap (Δ) of 2.5-3 meV and a low zero-bias conductance. We have also fabricated SIS junctions with an MgO barrier, but the quasi-particle characteristics of the SIS junctions are not as good as those of the SIN junctions, namely a reduced superconducting gap and a high zero-bias conductance. It appears that top MgB2 electrodes do not grow well on an MgO barrier, which is also suggested from in-situ RHEED observation. The SIN junctions fabricated using a CaF2 barrier showed less sharp quasi-particle characteristics than using an MgO barrier. However, the SIS junctions using a CaF2 barrier showed a fairly large IcRN value at 4.2 K over 1 mV and also exhibited finite Josephson current up to almost the film's Tc (∼30 K). The RHEED observation revealed that top MgB2 electrodes grow well on a CaF2 barrier.

  9. Formation of new Tm3+ tetragonal symmetry optical centers in CaF2 hot-formed laser ceramics

    NASA Astrophysics Data System (ADS)

    Doroshenko, M. E.; Alimov, O. K.; Papashvili, A. G.; Martynova, K. A.; Konyushkin, V. A.; Nakladov, A. N.; Osiko, V. V.

    2017-01-01

    By means of time-resolved site-selective spectroscopy the formation of new Tm3+ optical centers with modified local environment and presumably tetragonal local symmetry in CaF2 hot-formed laser quality ceramics is observed. The spectroscopic properties of these new Tm3+ optical centers are investigated and shown to differ strongly from that for regular tetragonal optical centers.

  10. Transmission and reflection studies of thin films in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Peterson, Lennart R.

    1989-01-01

    Both the transmittance and reflectance of 2 mm thick MgF2 substrates and of thin films of BaF2, CaF2, LaF3, MgF2, Al2O3, HfO2, and SiO2 deposited on these substrates were measured for the wavelength range 120 nm to 230 nm. Results for BaF2, LaF2 and MgF2 show promise as being good materials from which interference filters can be made. The software and related hardware needed to take large amounts of data automatically in future measurements of the transmittance and reflectance was developed.

  11. Ab-initio Calculations of Electronic Properties of Calcium Fluoride (CaF2)

    NASA Astrophysics Data System (ADS)

    Bohara, Bir; Franklin, Lashounda; Malozovsky, Yuriy; Bagayoko, Diola

    We have performed first principle, local density approximation (LDA) calculations of electronic and related properties of cubic calcium fluorite (CaF2) . Our non-relativistic computations employed the Ceperley and Alder LDA potential and the linear combination of atomic orbitals (LCAO) formalism. The implementation of the LCAO formalism followed the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). We discuss the electronic energy bands, including the large band gap, total and partial density of states, electron and hole effective masses, and the bulk modulus. Our calculated, indirect (X- Γ) band gap is 12.98 eV; it is 1 eV above an experimental value of 11.8 eV. The calculated bulk modulus (82.89 GPA) is excellent agreement with the experimental result of 82.0 +/-0.7. Our predicted equilibrium lattice constant is 5.42Å. Acknowledgments: This work is funded in part by the National Science Foundation (NSF) and the Louisiana Board of Regents, through LASiGMA [Award Nos. EPS- 1003897, NSF (2010-15)-RII-SUBR], and NSF HRD-1002541, the US Department of Energy, National, Nuclear Security Administration (NNSA) (Award No. DE-NA-0002630), LaSPACE, and LONI-SUBR.

  12. UV-vis spectroscopic studies of CaF2 photo-thermo-refractive glass

    NASA Astrophysics Data System (ADS)

    Stoica, Martina; Herrmann, Andreas; Hein, Joachim; Rüssel, Christian

    2016-12-01

    A photo-thermo-refractive glass based on the system Na2O/K2O/CaO/CaF2/Al2O3/ZnO/SiO2 doped with Ag2O, CeO2, SnO2, Sb2O3 and KBr was investigated. This glass undergoes a permanent refractive index change after UV irradiation and subsequent two step heat treatment at temperatures above Tg. This is due to the formation of Ag metal clusters which act as nucleation centers for CaF2 crystallization. Oxidation of Ce3+ by UV light is the initial reaction and acts as photosensitizer in the glass. The UV-vis absorption spectra during this photo-induced crystallization process were measured. The spectral components that form the absorption spectra of cerium were studied in detail by a band separation with Gaussian functions. Deconvolution of the cerium absorption bands shows an envelope of five spectral components for the trivalent cerium due to the 4f-5d transitions and two spectral components for the tetravalent cerium caused by charge transfer transitions. The effect of different dopants and melting conditions on the photo-thermal process were studied to investigate the influence of glass technology on the photoprocess.

  13. Kinetic parameters of thermally stimulated light emission phenomenon in CaF2 doped with Tm(3+) ions.

    PubMed

    González, P R; Cruz-Zaragoza, E; Furetta, C

    2016-11-01

    The characterization of new materials thermoluminescent used in radiation dosimetry, require the determination of kinetic parameters, which are associated with the number and shape of the peaks which presents its glow curve, among the most important are: the activation energy, E, or depth of the traps, the frequency factor, s, and the kinetics order, b. These parameters are necessary to predict the stability of thermoluminescent information after irradiation of the material. In this work, we present the results obtained for the determination of kinetic parameters of Tm(3+)-doped CaF2, the methods used for the determination of kinetic parameters were; initial growth signal TL, General order Chen method, and Deconvolution of glow curve. The results showed that the glow curve of CaF2 presents three glow peaks, 492K main peak and two smaller peaks, one at 430K and another to 566K. The dosimetric glow peak fits to the general-order kinetics model.

  14. Negative differential resistance of metal (CoSi2)/insulator (CaF2) triple-barrier resonant tunneling diode

    NASA Astrophysics Data System (ADS)

    Watanabe, Masahiro; Suemasu, Takashi; Muratake, Shigeki; Asada, Masahiro

    1993-01-01

    The electron transport and negative differential resistance in metal-insulator nanometer-thick heterostructures are reported for the first time. The structure of the samples is a resonant tunneling diode with three-barriers of 0.9-nm-thick CaF2 layers and two wells of 1.9- and 2.8-nm-thick CoSi2 layers. These layers were grown by means of partially ionized beam epitaxy for CaF2 and a two step growth technique for CoSi2. In the current-voltage characteristics at 77 K, negative differential resistance was observed in the significant number of samples and the typical peak-to-valley ratio was as high as 2. The negative differential resistance observed here can be attributed to the electron transport through the resonant levels in metal/insulator multilayered heterostructures.

  15. Structural plasticity of calmodulin on the surface of CaF2 nanoparticles preserves its biological function

    NASA Astrophysics Data System (ADS)

    Astegno, Alessandra; Maresi, Elena; Marino, Valerio; Dominici, Paola; Pedroni, Marco; Piccinelli, Fabio; Dell'Orco, Daniele

    2014-11-01

    Nanoparticles are increasingly used in biomedical applications and are especially attractive as biocompatible and biodegradable protein delivery systems. Herein, the interaction between biocompatible 25 nm CaF2 nanoparticles and the ubiquitous calcium sensor calmodulin has been investigated in order to assess the potential of these particles to serve as suitable surface protein carriers. Calmodulin is a multifunctional messenger protein that activates a wide variety of signaling pathways in eukaryotic cells by changing its conformation in a calcium-dependent manner. Isothermal titration calorimetry and circular dichroism studies have shown that the interaction between calmodulin and CaF2 nanoparticles occurs with physiologically relevant affinity and that the binding process is fully reversible, occurring without significant alterations in protein secondary and tertiary structures. Experiments performed with a mutant form of calmodulin having an impaired Ca2+-binding ability in the C-terminal lobe suggest that the EF-hand Ca2+-binding motifs are directly involved in the binding of calmodulin to the CaF2 matrix. The residual capability of nanoparticle-bound calmodulin to function as a calcium sensor protein, binding to and altering the activity of a target protein, was successfully probed by biochemical assays. Even if efficiently carried by CaF2 nanoparticles, calmodulin may dissociate, thus retaining the ability to bind the peptide encompassing the putative C-terminal calmodulin-binding domain of glutamate decarboxylase and activate the enzyme. We conclude that the high flexibility and structural plasticity of calmodulin are responsible for the preservation of its function when bound in high amounts to a nanoparticle surface.Nanoparticles are increasingly used in biomedical applications and are especially attractive as biocompatible and biodegradable protein delivery systems. Herein, the interaction between biocompatible 25 nm CaF2 nanoparticles and the ubiquitous calcium sensor calmodulin has been investigated in order to assess the potential of these particles to serve as suitable surface protein carriers. Calmodulin is a multifunctional messenger protein that activates a wide variety of signaling pathways in eukaryotic cells by changing its conformation in a calcium-dependent manner. Isothermal titration calorimetry and circular dichroism studies have shown that the interaction between calmodulin and CaF2 nanoparticles occurs with physiologically relevant affinity and that the binding process is fully reversible, occurring without significant alterations in protein secondary and tertiary structures. Experiments performed with a mutant form of calmodulin having an impaired Ca2+-binding ability in the C-terminal lobe suggest that the EF-hand Ca2+-binding motifs are directly involved in the binding of calmodulin to the CaF2 matrix. The residual capability of nanoparticle-bound calmodulin to function as a calcium sensor protein, binding to and altering the activity of a target protein, was successfully probed by biochemical assays. Even if efficiently carried by CaF2 nanoparticles, calmodulin may dissociate, thus retaining the ability to bind the peptide encompassing the putative C-terminal calmodulin-binding domain of glutamate decarboxylase and activate the enzyme. We conclude that the high flexibility and structural plasticity of calmodulin are responsible for the preservation of its function when bound in high amounts to a nanoparticle surface. Electronic supplementary information (ESI) available: Supplementary methods and figures. See DOI: 10.1039/c4nr04368e

  16. Responsivity enhancement of mid-infrared PbSe detectors using CaF2 nano-structured antireflective coatings

    NASA Astrophysics Data System (ADS)

    Weng, Binbin; Qiu, Jijun; Yuan, Zijian; Larson, Preston R.; Strout, Gregory W.; Shi, Zhisheng

    2014-01-01

    The CaF2 nano-structures grown by thermal vapor deposition are presented. Significant responsivity improvement (>200%) of mid-infrared PbSe detectors incorporating a 200 nm nano-structured CaF2 coating was observed. The detector provides a detectivity of 4.2 × 1010 cm . Hz1/2/W at 3.8 μm, which outperforms all the reported un-cooled PbSe detectors. Structural investigations show that the coating is constructed by tapered-shape nanostructures, which creates a gradient refractive-index profile. Analogy to moth-eye antireflective mechanism, the gradient refractive-index nanostructures play the major roles for this antireflection effect. Some other possible mechanisms that help enhance the device performance are also discussed in the work.

  17. Nano-structuring of CaF2 surfaces by slow highly charged ions: simulation and experiment

    NASA Astrophysics Data System (ADS)

    Wachter, G.; Tökési, K.; Betz, G.; Lemell, C.; Burgdörfer, J.; El-Said, A. S.; Wilhelm, R. A.; Heller, R.; Facsko, S.; Ritter, R.; Aumayr, F.

    2014-04-01

    The impact of individual slow highly charged ions (HCI) on insulators can create nano-scale surface modifications. We present recent experimental results on nano-hillock and etch pit formation on CaF2, where the appearance of surface modifications is observed only above a threshold projectile potential and kinetic energy depending on the type of damage. A proof-of-principle molecular dynamics simulation offers insights into the early stages of damage formation.

  18. Swift heavy ion irradiation of CaF2 - from grooves to hillocks in a single ion track.

    PubMed

    Gruber, Elisabeth; Salou, Pierre; Bergen, Lorenz; El Kharrazi, Mourad; Lattouf, Elie; Grygiel, Clara; Wang, Yuyu; Benyagoub, Abdenacer; Levavasseur, Delphine; Rangama, Jimmy; Lebius, Henning; Ban-d'Etat, Brigitte; Schleberger, Marika; Aumayr, Friedrich

    2016-10-12

    A novel form of ion-tracks, namely nanogrooves and hillocks, are observed on CaF2 after irradiation with xenon and lead ions of about 100 MeV kinetic energy. The irradiation is performed under grazing incidence (0.3°-3°) which forces the track to a region in close vicinity to the surface. Atomic force microscopy imaging of the impact sites with high spatial resolution reveals that the surface track consists in fact of three distinct parts: each swift heavy ion impacting on the CaF2 surface first opens a several 100 nm long groove bordered by a series of nanohillocks on both sides. The end of the groove is marked by a huge single hillock and the further penetration of the swift projectile into deeper layers of the target is accompanied by a single protrusion of several 100 nm in length slowly fading until the track vanishes. By comparing experimental data for various impact angles with results of a simulation, based on a three-dimensional version of the two-temperature-model (TTM), we are able to link the crater and hillock formation to sublimation and melting processes of CaF2 due to the local energy deposition by swift heavy ions.

  19. Structural and optical study of CaF2 nanoparticles produced by a microwave-assisted hydrothermal method

    NASA Astrophysics Data System (ADS)

    Bezerra, Claudiane dos S.; Valerio, Mário E. G.

    2016-11-01

    CaF2 nanoparticles were synthesized by the microwave-assisted hydrothermal method. With the addition of the ethylenediamine (EDA) as chelating agent, the size of the particles was reduced. The CaF2 exhibit single phase identified for X-ray diffraction (XRD) and confirmed by Rietveld refinement. Scanning electron microscopy (SEM) images showed nanoparticles with non-uniform morphology and statistical analysis of collections of particles reviewed that the EDA decreases both the average particle size and average aspect ratio of the particles. The chemical composition of the surface of the particles was investigated by X-ray Photoelectron Spectroscopy (XPS) and the results indicated the presence of reasonable amounts of hydroxyl groups and oxygen ions in the samples produced with EDA. Radioluminescence (RL) measurements showed that both types of nanoparticles presented intrinsic scintillation emission formed by two main bands and that the CaF2 samples produced without EDA presented higher emission intensity. The broad RL band centered at approximately 293 nm is related to self-trapped exciton (STE) emission of calcium fluoride, while the band at 428 nm can be due to the presence of F centers. The STE excitation and optical band gap were measured through photoluminescent excitation spectra in the VUV range.

  20. Swift heavy ion irradiation of CaF2 - from grooves to hillocks in a single ion track

    NASA Astrophysics Data System (ADS)

    Gruber, Elisabeth; Salou, Pierre; Bergen, Lorenz; El Kharrazi, Mourad; Lattouf, Elie; Grygiel, Clara; Wang, Yuyu; Benyagoub, Abdenacer; Levavasseur, Delphine; Rangama, Jimmy; Lebius, Henning; Ban-d'Etat, Brigitte; Schleberger, Marika; Aumayr, Friedrich

    2016-10-01

    A novel form of ion-tracks, namely nanogrooves and hillocks, are observed on CaF2 after irradiation with xenon and lead ions of about 100 MeV kinetic energy. The irradiation is performed under grazing incidence (0.3°-3°) which forces the track to a region in close vicinity to the surface. Atomic force microscopy imaging of the impact sites with high spatial resolution reveals that the surface track consists in fact of three distinct parts: each swift heavy ion impacting on the CaF2 surface first opens a several 100 nm long groove bordered by a series of nanohillocks on both sides. The end of the groove is marked by a huge single hillock and the further penetration of the swift projectile into deeper layers of the target is accompanied by a single protrusion of several 100 nm in length slowly fading until the track vanishes. By comparing experimental data for various impact angles with results of a simulation, based on a three-dimensional version of the two-temperature-model (TTM), we are able to link the crater and hillock formation to sublimation and melting processes of CaF2 due to the local energy deposition by swift heavy ions.

  1. Soft X-ray emission spectroscopy study of CaF 2(film)/Si(111): non-destructive buried interface analysis

    NASA Astrophysics Data System (ADS)

    Iwami, M.; Kusaka, M.; Hirai, M.; Tagami, R.; Nakamura, H.; Watabe, H.

    1997-06-01

    A soft X-ray emission spectroscopy (SXES) study under an energetic electron irradiation is first applied to a non-destructive buried interface analysis of a CaF 2(film ˜ 40 nm)/Si(111) contact system, where the energy of primary electrons, Ep, is ≤ 5 keV. The present work has explored the usefulness of the application of the SXES method to the interface study to give rise to the following findings: the CaF 2/Si(111) interface shows rather sharp transition from the top CaF 2 to the substrate Si, there certainly is a Ca-silicide layer at the CaF 2/Si(111) interface, the thickness of the silicide layer is estimated to be less than several nm, and the e-beam excited SXES non-destructive study is very powerful to analyze a specimen with rather thick top film (> 40 nm) and thin interface layer (< several nm).

  2. 10BaF2:NaF, Na3AlF6/TiO2 composite as a novel visible-light-driven photocatalyst based on upconversion emission

    NASA Astrophysics Data System (ADS)

    Liu, En-Zhou; Fan, Jun; Hu, Xiao-Yun; Hou, Wen-Qian; Dai, Hong-Zhe

    2012-04-01

    A rare-earth free upconversion luminescent material, 10BaF2:NaF, Na3AlF6, is synthesized by a hydrothermal method. The study of fluorescent spectrum indicates that it can convert visible light (550 nm—610 nm) into ultraviolet light (290 nm—350 nm), and two emission peaks at 304 nm and 324 nm are observed under the excitation of 583 nm at room temperature. Subsequently, 10BaF2:NaF, Na3AlF6/TiO2 composite photocatalyst is prepared and its catalytic activity is evaluated by the photocatalytic reduction of CO2 under visible light irradiation (λ > 515 nm). The results show that 10BaF2:NaF, Na3AlF6/TiO2 is a more effective photocatalyst for CO2 reduction than pure TiO2, their corresponding methanol yields are 179 and 0 μmol/g-cat under the same conditions. Additionally, the mechanism of photocatalytic reduction of CO2 on 10BaF2:NaF, Na3AlF6/TiO2 is proposed.

  3. Role of Step and Terrace Nucleation in Heteroepitaxial Growth Morphology: Growth Kinetics of CaF2/Si(111)

    NASA Astrophysics Data System (ADS)

    Hessinger, Uwe; Leskovar, M.; Olmstead, Marjorie A.

    1995-09-01

    The thickness uniformity and the spatial distribution of lattice relaxation in thin ( <8 nm) CaF2/Si(111) films, observed with photoelectron spectroscopy and transmission electron microscopy, are seen to depend strongly on the initial nucleation kinetics. We develop a general model for heteroepitaxial growth that explains both these and literature results. Terrace or step nucleation leads to laminar films, although with different relaxation patterns; combined step and terrace nucleation leads to rough films due to different upper-layer nucleation rates on the differently sized islands.

  4. Structural properties of Bi2Te3 topological insulator thin films grown by molecular beam epitaxy on (111) BaF2 substrates

    NASA Astrophysics Data System (ADS)

    Fornari, Celso I.; Rappl, Paulo H. O.; Morelhão, Sérgio L.; Abramof, Eduardo

    2016-04-01

    Structural properties of topological insulator bismuth telluride films grown epitaxially on (111) BaF2 with a fixed Bi2Te3 beam flux were systematically investigated as a function of substrate temperature and additional Te flux. A layer-by-layer growth mode is observed since the early stages of epitaxy and remains throughout the whole deposition. Composition of the epitaxial films produced here stays between Bi2Te3 and Bi4Te5, as determined from the comparison of the measured x-ray diffraction curves with calculations. The substrate temperature region, where the growth rate remains constant, is found to be the most appropriate to obtain ordered Bi2Te3 films. Line width of the L = 18 Bi2Te3 diffraction peaks as low as 140 arcsec was obtained, indicating high crystalline quality. Twinning domains density rises with increasing growth temperature and reducing Te extra flux. X-ray reflectivity curves of pure Bi2Te3 films with thickness from 165 to 8 nm exhibited well defined interference fringes, evidencing homogeneous layers with smooth surface. Our results demonstrate that Bi2Te3 films with very well controlled structural parameters can be obtained. High structural quality Bi2Te3 films as thin as only eight quintuple layers grown here are promising candidates for intrinsic topological insulator.

  5. Dynamical properties and instability of local fluorite BaF(2) structure around doped Mn(2+) ions-EPR and electron spin echo studies.

    PubMed

    Lijewski, S; Hoffmann, S K; Goslar, J; Wencka, M; Ulanov, V A

    2008-09-24

    The electron paramagnetic resonance (EPR) and electron spin echo (ESE) were measured at the X-band for Mn(2+) in a BaF(2) crystal in the temperature range 4.2-300 K. In addition to the cubic symmetry centre, two other lower concentration tetragonal centres were identified. Temperature variations and computer simulation of the EPR spectrum confirm that the cubic symmetry of the MnF(8) centre is deformed to two T(d) tetrahedra of different dimensions at around 45 K. Electron spin relaxation was measured in the temperature range 4.2-35 K, where the ESE signal was detectable. For higher temperature the Mn(2+) dynamics produces homogeneously broadened EPR lines. At the lowest temperatures the spin-lattice relaxation is governed by ordinary phonon processes with 1/T(1)∼T(5). The efficiency of these processes rapidly decreases and at about 11 K a local mode of energy 17 cm(-1) becomes the relaxation mechanism. Phase relaxation observed as ESE signal dephasing indicates that after the local deformation jumps (tunnelling with frequency 4 × 10(8) s(-1)) between the two tetrahedral configurations appear, with the energy barrier being the local mode energy. This motion is directly visible as a resonance-type enhancement of the ESE dephasing rate 1/T(M) around 11 K. Only the cubic centre displays the above dynamics.

  6. White up-conversion emission in Ho3+/Tm3+/Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Li, Chenxia; Xu, Shiqing; Ye, Rengguang; Deng, Degang; Hua, Youjie; Zhao, Shilong; Zhuang, Songlin

    2011-04-01

    Ho3+/Tm3+/Yb3+ tri-doped glass ceramics with white light emitting have been developed and demonstrated. Pumped by 980 nm laser diode (LD), intensive red, green and blue up-conversions (UC) were obtained. The green emission is assigned to Ho3+ ion and the blue emission is assigned to Tm3+ ion, whereas the red emission is the combination contribution of the Ho3+ and Tm3+ ions. The RGB intensities could be adjusted by tuning the rare-earth ion concentration and pump power intensity. Thus, multicolor of the luminescence, including perfect white light with CIE-X=0.329 and CIE-Y=0.342 in the 1931 CIE chromaticity diagram can be obtained in 0.15 Ho3+/0.2Tm3+/3Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals pumped by a single infrared laser diode source of 980 nm at 500 mW. The up-conversion luminescence mechanism of Yb3+ sensitize Ho3+ and Tm3+ ions and the energy transfer from Ho3+ to Tm3+ in oxy-fluoride silicate glass ceramics were analyzed.

  7. Influence of some impurities on the emission properties of CaF2:YbF3 crystals

    NASA Astrophysics Data System (ADS)

    Stef, Marius; Nicoara, Irina; Cirlan, Florina; Para, Irina; Velazquez, Matias; Buse, Gabriel

    2015-12-01

    Various concentrations of YbF3 -doped and NaF or PbF2 co-doped CaF2 crystals were grown using the conventional Bridgman method. Transparent colorless crystals were obtained in graphite crucible in vacuum using a shaped graphite furnace. The crystals have been cooled to room temperature using an established procedure. Room temperature absorption spectra have been obtained using a Shimadzu 1650PC spectrophotometer. Photoluminescent properties in IR spectral range were analyzed using a spectrofluorimeter Horiba Fluorolog 3. An IR laser diode at 932 nm was also used an directly injected in the equipment. The emission spectra are influenced by the concentration of co-dopant added to the melt, and the excitation wavelength. The high emission peak at 979 nm overlaps with the absorption peak. The highest intensity in the IR emission (around 1029 nm) is obtained for CaF2:0.72 mol% YbF3 crystal by excitation at 932 nm (diode lamp).

  8. Nonlinear luminescence response of CaF2:Eu and YAlO3:Ce to single-ion excitation

    SciTech Connect

    Liu, Peng; Zhang, Yanwen; Xiao, Haiyan; Xiang, Xia; Wang, Xuelin; Weber, William J.

    2014-01-21

    Pulse-height of CaF2:Eu and YAlO3:Ce scintillators to single H+, He+ and O3+ ions are measured over a continuous energy range using a time-of-flight (TOF) - scintillator - photoelectric multiplier tube (PMT) apparatus. A nonlinear response of the scintillators under ionizing ion irradiation is quantitatively evaluated by considering energy partitioning process. The results show that, in a differential energy deposition region with negligible displacement damage, the low, medium and high excitation energy deposition density (Dexci) produced by H+, He+ and O3+ ions irradiation, respectively, have significantly different impacts on the response characteristics of these two benchmark scintillators. For CaF2:Eu, the scintillation efficiency under ion irradiation monotonically decreases with increasing excitation-energy density. In contrast, the response efficiency of YAlO3:Ce scintillation initially increases with excitation-energy density at low excitation-energy densities, goes through a maximum, and then decreases with further increasing excitation-energy density. The fundamental mechanism causing these different response behaviours in the scintillators is based on the competition between the scintillation response and the nonradiative quenching process under different excitation densities, which is also the main origin of the nonlinear response of scintillators to irradiation.

  9. Effects of CaF2 Coating on the Microstructures and Mechanical Properties of Tungsten Inert Gas Welded AZ31 Magnesium Alloy Joints

    NASA Astrophysics Data System (ADS)

    Shen, Jun; Wang, Linzhi; Peng, Dong; Wang, Dan

    2012-11-01

    The effects of CaF2 coating on the macromorphologies of the welded seams were studied by morphological analysis. Microstructures and mechanical properties of butt joints welded with different amounts of CaF2 coatings were investigated using optical microscopy and tensile tests. The welding defects formed in the welded seams and the fracture surfaces were analyzed by scanning electron microscopy. An increase in the amount of CaF2 coating deteriorated the appearances of the welded seams but it improved the weld penetration depth and the depth/width ( D/ W) ratio of the tungsten inert gas (TIG) welded joints. The α-Mg grains and Mg17(Al,Zn)12 intermetallic compound (IMC) were coarser in the case of a higher amount of CaF2 coating. The increase in the amount of CaF2 coating reduced the porosities and total length of solidification cracks in the fusion zone (FZ). The ultimate tensile strength (UTS) value and elongation increased at first and then decreased sharply.

  10. Deformation of as-cast LiF-22 mol pct CaF2 hypereutectic salt between 500 and 1015 K

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Whittenberger, J. D.

    1990-01-01

    Results are presented on compression tests conducted on as-cast LiF-22 mol pct CaF2 hypereutectic specimens at nominal strain rates between 1.8 x 10 to the -6th/sec and 0.25/sec over the temperature range 500-1015 K. In all instances, the stress-strain curves showed broad maxima, with negative strain-hardening rates after the peak stress sigma(max). It was found that, at low temperatures and high stresses, the CaF2 lamellae are rigid while the LiF matrix exhibits extensive transgranular cavitation, while at high temperatures and low stresses the CaF2 lamellae break down and spheroidize while the LiF matrix does not cavitate. It was concluded that the mechanical properties of the as-cast hypereutectic LiF-22 mol pct CaF2 are governed by the rate of deformation of the CaF2 phase. It is suggested that, for thermal energy storage applications, a spheroidal microstructure is more desirable than a lamellar structure.

  11. Ba(OH)2 Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba2YCu3O6.5 + x From BaF2-Precursors

    PubMed Central

    Cook, L. P.; Wong-Ng, W.; Feenstra, R.

    2005-01-01

    The ex situ process for fabricating Ba2YCu3O6.5 + x superconducting tapes from BaF2- based precursors involves a hydration/oxidation reaction at ≈730 °C to 750 °C generally written as: (2BaF2+Y+3Cu)(amorphous)+(2H2O+2.25O2)(g)→Ba2YCu3O6.5+x(s)+4HF(g). However, microscopic observations of partially processed films suggest the presence of a transient liquid phase during conversion. Alternatively, the conversion reaction can be rewritten as the sum of several intermediate steps, including the formation of a barium hydroxide liquid: (BaF2)(amorphous)+2H2O(g)→Ba(OH)2(liq)+2HF(g). To evaluate the possibility of a hydroxide liquid conversion step, thermodynamic calculations on the stability of Ba(OH)2(liq) have been completed from 500 °C to 900 °C at 0.1 MPa ptotal. Based on currently available data, the calculated phase diagrams suggest that a viable hydroxide reaction path exists in the higher part of this temperature range. The calculations indicate that Ba(OH)2(liq) may be stable at log pH2O (Pa) values from ≈4 to 5, provided log pHF (Pa) values can be maintained below 0 to −1. Limited experimental confirmation is provided by results of an experiment on BaF2(s) at 815 °C, 0.1 MPa pH2O, in which essentially all F at the surface was replaced by O. It is therefore possible that processing routes exist for producing Ba2YCu3O6.5 + x based on the presence of a Ba(OH)2 liquid, which might have an effect on conversion rates and texturing in the superconducting film. PMID:27308108

  12. Novel SiO2-deposited CaF2 substrate for vibrational sum-frequency generation (SFG) measurements of chemisorbed monolayers in an aqueous environment.

    PubMed

    Padermshoke, Adchara; Konishi, Shouta; Ara, Masato; Tada, Hirokazu; Ishibashi, Taka-Aki

    2012-06-01

    A novel SiO(2)-deposited CaF(2) (SiO(2)/CaF(2)) substrate for measuring vibrational sum-frequency generation (SFG) spectra of silane-based chemisorbed monolayers in aqueous media has been developed. The substrate is suitable for silanization and transparent over a broad range of the infrared (IR) probe. The present work demonstrates the practical application of the SiO(2)/CaF(2) substrate and, to our knowledge, the first SFG spectrum at the solid/water interface of a silanized monolayer observed over the IR fingerprint region (1780-1400 cm(-1)) using a back-side probing geometry. This new substrate can be very useful for SFG studies of various chemisorbed organic molecules, particularly biological compounds, in aqueous environments.

  13. Negative Differential Resistance of CaF 2/CdF 2 Triple-Barrier Resonant-Tunneling Diode on Si(111) Grown by Partially Ionized Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Watanabe, Masahiro; Aoki, Yuichi; Saito, Wataru; Tsuganezawa, Mika

    1999-02-01

    Room-temperature negative differential resistance (NDR) of triple-barrier cadmium di-fluoride (CdF2)/calcium di-fluoride (CaF2) heterostructure resonant-tunneling diode (RTD) on a Si(111) substrate has been demonstrated. CdF2/CaF2 multilayered heterostructures were grown on a Si(111) substrate using partially ionized beam epitaxy to obtain atomically flat interfaces. The RTD structures, which consist of triple CaF2 energy barriers and double CdF2 quantum wells, were fabricated by electron beam (EB) lithography and dry etching to avoid thermal and chemical damage to the CdF2 layers. In the current-voltage characteristics of the RTD, NDR was clearly observed even at room temperature and the maximum peak-to-valley (P/V) ratio was about 6.

  14. The quasi-binary phase diagram BaF2-BaBr2 and its relation to the x-ray storage phosphor BaFBr : Eu2+

    NASA Astrophysics Data System (ADS)

    Kolb, R.; Schlapp, M.; Hesse, S.; Schmechel, R.; von Seggern, H.; Fasel, C.; Riedel, R.; Ehrenberg, H.; Fuess, H.

    2002-08-01

    In order to understand the formation and stoichiometry of the x-ray storage phosphor BaFBr : Eu2+, the phase diagram of the quasi-binary BaF2-BaBr2 system has been investigated. The phase diagram was obtained by means of differential thermal analysis and temperature controlled x-ray diffraction experiments. The resulting phase diagram indicates that BaFBr forms a compound with no detectable solid solubility for neither BaF2 nor BaBr2. Experiments to obtain non-stoichiometric BaFBr via the synthesis route using BaF2 and NH4Br as proposed in the literature could not be verified. It will be shown that the type of colour centre created during x-ray irradiation is related to the non-stoichiometry of the starting compositions before sintering. A surplus of either barium fluoride or barium bromide during sintering allows the controlled formation of F(Br-)- and F(F-)-centres, respectively.

  15. CO2 laser irradiation enhances CaF2 formation and inhibits lesion progression on demineralized dental enamel-in vitro study.

    PubMed

    Zancopé, Bruna R; Rodrigues, Lívia P; Parisotto, Thais M; Steiner-Oliveira, Carolina; Rodrigues, Lidiany K A; Nobre-dos-Santos, Marinês

    2016-04-01

    This study evaluated if Carbon dioxide (CO2) (λ 10.6 μm) laser irradiation combined with acidulated phosphate fluoride gel application (APF gel) enhances "CaF2" uptake by demineralized enamel specimens (DES) and inhibits enamel lesion progression. Thus, two studies were conducted and DES were subjected to APF gel combined or not with CO2 laser irradiation (11.3 or 20.0 J/cm(2), 0.4 or 0.7 W) performed before, during, or after APF gel application. In study 1, 165 DES were allocated to 11 groups. Fluoride as "CaF2 like material" formed on enamel was determined in 100 DES (n = 10/group), and the surface morphologies of 50 specimens were evaluated by scanning electron microscopy (SEM) before and after "CaF2" extraction. In study 2, 165 DES (11 groups, n = 15), subjected to the same treatments as in study 1, were further subjected to a pH-cycling model to simulate a high cariogenic challenge. The progression of demineralization in DES was evaluated by cross-sectional microhardness and polarized light microscopy analyses. Laser at 11.3 J/cm(2) applied during APF gel application increased "CaF2" uptake on enamel surface. Laser irradiation and APF gel alone arrested the lesion progression compared with the control (p < 0.05). Areas of melting, fusion, and cracks were observed. CO2 laser irradiation, combined with a single APF application enhanced "CaF2" uptake on enamel surface and a synergistic effect was found. However, regarding the inhibition of caries lesion progression, no synergistic effect could be demonstrated. In conclusion, the results have shown that irradiation with specific laser parameters significantly enhanced CaF2 uptake by demineralized enamel and inhibited lesion progression.

  16. The Exicor DUV birefringence measurement system and its application to measuring lithography-grade CaF2 lens blanks

    NASA Astrophysics Data System (ADS)

    Wang, Baoliang; Griffiths, C. O.; Rockwell, Rick R.; List, Jennifer; Mark, Doug

    2003-11-01

    Optical lithography continues its transition to shorter wavelengths to support the semiconductor industry"s production of faster microchips to meet evolving market demands. The next step for optical lithography is likely to use the F2 excimer laser at 157.63 nm (157 nm,according to the industry" s naming convention).At 157 nm, among the limited number of fluoride crystals with acceptable optical properties calcium fluoride is the only practical lens material for step and scan systems due to its readiness for mass production. Since the discovery of intrinsic birefringence in CaF2 at deep ultraviolet (DUV)wavelengths,the optical lithography industry has developed a critical interest in measuring birefringence at 157 nm. In response to this need, we have developed a DUV birefringence measurement system. In this article,we describe the working principle, system construction, technical performance and selected applications for measuring lithography grade calcium fluoride lens blanks at DUV wavelengths.

  17. Mapping of second-nearest-neighbor fluoride ions of orthorhombic Gd 3+-Ag + complexes in CaF 2

    NASA Astrophysics Data System (ADS)

    Nakata, R.; Den Hartog, H. W.

    The ENDOR technique is applied to determine the positions of 24 second-nearest-neighbor F - ions around an orthorhombic Gd 3+-Ag + complex in CaF 2 crystals. Experimental ENDOR data of the second-nearest-neighbor F - ions are analyzed by using the usual spin Hamiltonian and a least-squares fitting method. The best fits of the experimental results give superhyperfine (shf) constants and the F - directions ( K, L, M) with respect to the Gd 3+ ion, from which the distance between the second-nearest-neighbor F - ion and the Gd 3+ ion is determined by assuming that the hyperfine interaction is due to the classical dipole-dipole interaction. The displacements of the F - ions are estimated and compared with the theoretical values calculated by Bijvank and den Hartog on the basis of a polarizable point charge model.

  18. Glass structure and NIR emission of Er3+ at 1.5 μm in oxyfluoride BaF2-Al2O3-B2O3 glasses

    NASA Astrophysics Data System (ADS)

    Shinozaki, Kenji; Pisarski, Wojciech; Affatigato, Mario; Honma, Tsuyoshi; Komatsu, Takayuki

    2015-12-01

    The glass structure, photoluminescence properties of Eu3+, Judd-Ofelt analysis, and near infrared emissions of Er3+ at 1.5 μm in the oxyfluoride glasses and glass-ceramics of 1Eu2O3- or 1Er2O3-doped 50BaF2-xAl2O3-(50 - x)B2O3 (x = 0-25 mol%) were investigated. It was clarified on the ground of Raman scattering spectroscopy and F1s and O1s XPS measurements that the glass with no Al2O3 (1Er2O3-50BaF2-50B2O3) is composed of BO3, BO2F and BO3F units with F-Ba bonds. The glasses with 25Al2O3 (1Er2O3-50BaF2-25Al2O3-25B2O3) is mainly composed of BO3- and Al(O,F)x units. Existence of non-bridging oxygen was not detected by O1s-XPS spectra. It was proposed that these structures are largely affected on crystallization behavior, e.g., the glass with no Al2O3 forms BaF2 and β-BaB2O4 due to Ba-F bonds and the glass with 25Al2O3 forms BaAlBO3F2 because the glass structure composed of BO3 and Al(O,F) units is similar to the BaAlBO3F2 crystal structure. Judd-Ofelt parameters of Er3+ and Eu3+ in the glasses showed almost the same values in Ω4 and Ω6 for each glass, on the other hand Ω2 decreased with addition of Al2O3. The emission spectra of Er3+ at 1.5 μm in the glasses and glass-ceramics with BaAlBO3F2 crystals showed broad peaks. It is proposed that oxyfluoride glasses and glass-ceramics based on the BaF2-Al2O3-B2O3 system have a high potential for optical device applications such as broadband optical amplifiers.

  19. Dynamic change of transmission of CaF2 single crystals by irradiating with ArF excimer laser light

    NASA Astrophysics Data System (ADS)

    Alkemper, Jochen; Kandler, Joerg; Strenge, Lorenz; Moersen, Ewald; Muehlig, Christian; Triebel, Wolfgang

    2000-07-01

    The laser induced absorption of CaF2 caused by ArF excimer laser light has been observed at energy densities of F equals 2-30 mJ/cm2 per pulse and a repetition rate of R equals 50 Hz. The experiments show that the transmission of CaF2 samples depends on the pulse energy density. The change of the absorption coefficient with the time of irradiation can be described by an exponential model. Different experiments were performed where the energy density was increased and decreased stepwise. They prove that color centers not only are formed but also are annihilated by irradiation. Laser induced decrease of absorption was observed in all samples as soon as the energy density was decreased. Coloring and bleaching of the samples are completely reversible processes. The level of transmission depends on the energy density of the laser light and the quality of the material but not on the history of irradiation. The damage resistance of the material can be adjusted by the appropriate choice of the raw material and the process parameters. The reversibility of the laser induced absorption can be explained by a reaction equilibrium. This leads to a model where the concentration of absorbing defects depends on the current irradiation conditions. Using these equations the reversibility and the observed exponential dependence of the change of transmission with time can be explained. Assuming different dependencies of the reaction constants of coloring and bleaching on the energy density, the change of the absorption coefficient with pulse energy density can be calculated.

  20. pH-responsive drug delivery system based on luminescent CaF(2):Ce(3+)/Tb(3+)-poly(acrylic acid) hybrid microspheres.

    PubMed

    Dai, Yunlu; Zhang, Cuimiao; Cheng, Ziyong; Ma, Ping'an; Li, Chunxia; Kang, Xiaojiao; Yang, Dongmei; Lin, Jun

    2012-03-01

    In this study, we design a controlled release system based on CaF(2):Ce(3+)/Tb(3+)-poly(acrylic acid) (PAA) composite microspheres, which were fabricated by filling the pH-responsive PAA inside CaF(2):Ce(3+)/Tb(3+) hollow spheres via photopolymerization route. The CaF(2):Ce(3+)/Tb(3+) hollow spheres prepared by hydrothermal route possess mesoporous structure and show strong green fluorescence from Tb(3+) under UV excitation. Doxorubicin hydrochloride (DOX), a widely used anti-cancer drug, was used as a model drug to evaluate the loading and controlled release behaviors of the composite microspheres due to the good biocompatibility of the samples using MTT assay. The composite carriers provide a strongly pH-dependent drug release behavior owing to the intrinsic property of PAA and its interactions with DOX. The endocytosis process of drug-loaded microspheres was observed using confocal laser scanning microscopy (CLSM) and the in vitro cytotoxic effect against SKOV3 ovarian cancer cells of the DOX-loaded carriers was investigated. In addition, the extent of drug release could be monitored by the altering of photoluminescence (PL) intensity of CaF(2):Ce(3+)/Tb(3+). Considering the good biocompatibility, high drug loading content and pH-dependent drug release of the materials, these hybrid luminescent microspheres have potential applications in drug controlled release and disease therapy.

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

    NASA Technical Reports Server (NTRS)

    Duncan, R. C., Jr.

    1972-01-01

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

  2. Impurity-trapped excitons and electron traps in CaF2:Yb2+ and SrF2:Yb2+ probed by transient photoluminescence enhancement

    NASA Astrophysics Data System (ADS)

    Senanayake, P. S.; Wells, J. P. R.; Reid, M. F.; Berden, G.; Meijerink, A.; Reeves, R. J.

    2013-01-01

    CaF$_2$:Yb$^{2+}$ and SrF$_2$:Yb$^{2+}$ crystals have been investigated by a two-color UV + IR transient photoluminescence enhancement technique. The enhancement gives information about both changes in internal energy levels of the excitons and liberation of electrons from traps in the crystals.

  3. Energy deposition by heavy ions: Additivity of kinetic and potential energy contributions in hillock formation on CaF2

    NASA Astrophysics Data System (ADS)

    Wang, Y. Y.; Grygiel, C.; Dufour, C.; Sun, J. R.; Wang, Z. G.; Zhao, Y. T.; Xiao, G. Q.; Cheng, R.; Zhou, X. M.; Ren, J. R.; Liu, S. D.; Lei, Y.; Sun, Y. B.; Ritter, R.; Gruber, E.; Cassimi, A.; Monnet, I.; Bouffard, S.; Aumayr, F.; Toulemonde, M.

    2014-07-01

    Modification of surface and bulk properties of solids by irradiation with ion beams is a widely used technique with many applications in material science. In this study, we show that nano-hillocks on CaF2 crystal surfaces can be formed by individual impact of medium energy (3 and 5 MeV) highly charged ions (Xe22+ to Xe30+) as well as swift (kinetic energies between 12 and 58 MeV) heavy xenon ions. For very slow highly charged ions the appearance of hillocks is known to be linked to a threshold in potential energy (Ep) while for swift heavy ions a minimum electronic energy loss per unit length (Se) is necessary. With our results we bridge the gap between these two extreme cases and demonstrate, that with increasing energy deposition via Se the Ep-threshold for hillock production can be lowered substantially. Surprisingly, both mechanisms of energy deposition in the target surface seem to contribute in an additive way, which can be visualized in a phase diagram. We show that the inelastic thermal spike model, originally developed to describe such material modifications for swift heavy ions, can be extended to the case where both kinetic and potential energies are deposited into the surface.

  4. The use of the green emission in Er(3+)-doped CaF(2) crystals for thermometry application.

    PubMed

    Chouahda, Z; Jouart, J P; Duvaut, T; Diaf, M

    2009-06-17

    We report here the use of the green upconversion emissions originating from the thermally coupled levels (2)H(11/2) and (4)S(3/2) of the Er(3+) ion in CaF(2):Er (0.01 at.%) for thermometry application in the range 303-423 K. The mechanism responsible for excitation of the green emitting levels is a sequential two-photon absorption process. The fluorescence intensity ratio (FIR) of the green upconversion emissions at wavelengths of about 519 and 551 nm is studied as a function of temperature in the range 303-423 K using a 634 nm tunable dye laser as an excitation source. It is found that the logarithm of the FIR varies linearly with the inverse of temperature. The gap between the two thermally coupled levels (4)S(3/2) and (2)H(11/2) was determined to be about 721 cm(-1). This value is in good agreement with that found by spectroscopic investigations. The calibration curve is established, and the temperature is calculated.

  5. A viscoplastic model with application to LiF-22 percent CaF2 hypereutectic salt

    NASA Technical Reports Server (NTRS)

    Freed, A. D.; Walker, K. P.

    1990-01-01

    A viscoplastic model for class M (metal-like behavior) materials is presented. One novel feature is its use of internal variables to change the stress exponent of creep (where n is approximately = 5) to that of natural creep (where n = 3), in accordance with experimental observations. Another feature is the introduction of a coupling in the evolution equations of the kinematic and isotropic internal variables, making thermal recovery of the kinematic variable implicit. These features enable the viscoplastic model to reduce to that of steady-state creep in closed form. In addition, the hardening parameters associated with the two internal state variables (one scalar-valued, the other tensor-valued) are considered to be functions of state, instead of being taken as constant-valued. This feature enables each internal variable to represent a much wider spectrum of internal states for the material. The model is applied to a LiF-22 percent CaF2 hypereutectic salt, which is being considered as a thermal energy storage material for space-based solar dynamic power systems.

  6. Laser performance of diode-pumped Nd, Y-codoped CaF 2-SrF 2 mixed crystal

    NASA Astrophysics Data System (ADS)

    Liu, J.; Fan, M. W.; Su, L. B.; Jiang, D. P.; Ma, F. K.; Zhang, Q.; Xu, J.

    2014-03-01

    A disordered Nd, Y-codoped CaF2-SrF2 mixed crystal was obtained by the temperature gradient technique (TGT). The absorption and fluorescence spectra of the crystal were measured at room temperature. Diode-pumped continuous-wave (CW) and Q-switched laser operations were demonstrated at 1056 nm with a 0.65 at.% Nd, 10 at.% Y-codoped crystal, for the first time to our knowledge. The CW output power of 724 mW was obtained in a compact linear cavity. Also the Q-switched pulse characteristics of Nd, Y:CaF2-SrF2 laser crystal were reported based on Cr4+:YAG saturable absorbers in a folded cavity. The shortest pulse width of 110 ns and the highest peak power of 383 W were obtained when the initial transmission of the Cr4+:YAG crystals was 90%. The dependence of the operational parameters on the pump power was also investigated experimentally.

  7. Growth kinetics of CaF2/Si(111) heteroepitaxy: An x-ray photoelectron diffraction study

    NASA Astrophysics Data System (ADS)

    Denlinger, J. D.; Rotenberg, Eli; Hessinger, U.; Leskovar, M.; Olmstead, Marjorie A.

    1995-02-01

    Kinetic variations of the initial stages of CaF2 growth on Si(111) by molecular-beam epitaxy are studied with the in situ combination of x-ray photoelectron spectroscopy and diffraction. After the formation of a chemically reacted interface layer, the morphology of the subsequent bulk layers is found to be dependent on the substrate temperature and incident flux rate, as well as the initial interface structure. For substrate temperatures above ~600 °C, subsequent layers do not easily wet the interface layer, and a transition is observed from a three-dimensional island formation at low flux to a laminar growth following the coalescence of bilayer islands at higher flux. At lower substrate temperatures (~450 °C), a different stoichiometry and structure of the interface layer leads to laminar growth at all fluxes, but with a different bulk nucleation behavior. Crystalline heteroepitaxy is not observed when growth initiates at room temperature, but homoepitaxy does proceed at room temperature if the first few layers are deposited at a high temperature. The different growth regimes are discussed in terms of a kinetic model separating step and terrace nucleation where, contrary to homoepitaxy, step nucleation leads to islanded growth.

  8. Energy deposition by heavy ions: additivity of kinetic and potential energy contributions in hillock formation on CaF2.

    PubMed

    Wang, Y Y; Grygiel, C; Dufour, C; Sun, J R; Wang, Z G; Zhao, Y T; Xiao, G Q; Cheng, R; Zhou, X M; Ren, J R; Liu, S D; Lei, Y; Sun, Y B; Ritter, R; Gruber, E; Cassimi, A; Monnet, I; Bouffard, S; Aumayr, F; Toulemonde, M

    2014-07-18

    Modification of surface and bulk properties of solids by irradiation with ion beams is a widely used technique with many applications in material science. In this study, we show that nano-hillocks on CaF2 crystal surfaces can be formed by individual impact of medium energy (3 and 5 MeV) highly charged ions (Xe(22+) to Xe(30+)) as well as swift (kinetic energies between 12 and 58 MeV) heavy xenon ions. For very slow highly charged ions the appearance of hillocks is known to be linked to a threshold in potential energy (Ep) while for swift heavy ions a minimum electronic energy loss per unit length (Se) is necessary. With our results we bridge the gap between these two extreme cases and demonstrate, that with increasing energy deposition via Se the Ep-threshold for hillock production can be lowered substantially. Surprisingly, both mechanisms of energy deposition in the target surface seem to contribute in an additive way, which can be visualized in a phase diagram. We show that the inelastic thermal spike model, originally developed to describe such material modifications for swift heavy ions, can be extended to the case where both kinetic and potential energies are deposited into the surface.

  9. Effect of cryogenic temperature on spectroscopic and laser properties of Er,La:SrF2-CaF2 crystal

    NASA Astrophysics Data System (ADS)

    Švejkar, Richard; Šulc, Jan; Němec, Michal; Jelínková, Helena; Doroshenko, Maxim E.; Nakladov, Andrei N.; Osiko, Vjatcheslav V.

    2016-03-01

    The laser and spectroscopic properties of crystal Er,La:SrF2-CaF2 at temperature range 80 - 300 K, which is appropriate for generation of radiation around 2.7 um is presented. The sample of Er,La:SrF2-CaF2 (concentration Er(0.04), La(0.12):Ca(0.77)Sr(0.07)) had plan-parallel face-polished faces without anti-reflection coatings (thickness 8.2 mm). During spectroscopy and laser experiments the Er,La:SrF2-CaF2 was attached to temperature controlled copper holder and it was placed in vacuum chamber. The transmission and emission spectra of Er,La:SrF2-CaF2 together with the fluorescence decay time were measured in dependence on temperature. The excitation of Er,La:SrF2-CaF2 was carried out by a laser diode radiation (pulse duration 5 ms, repetition rate 20 Hz, pump wavelength 973 nm). Laser resonator was hemispherical, 140 mm in length with at pumping mirror (HR @ 2.7 µm) and spherical output coupler (r = 150 mm, R = 95 % @ 2.5 - 2.8 µm). Tunability of laser at 80 K in range 2690 - 2765 nm was obtained using MgF2 birefringent filter. With decreasing temperature of sample the fluorescence lifetime of manifold 4I11/2 (upper laser level) became shorter and intensity of up-conversion radiation was increasing. The highest slope efficiency with respect to absorbed power was 2.3 % at 80 K. The maximum output of peak amplitude power was 0.3 W at 80 K, i.e. 1.5 times higher than measured this value at 300 K. The wavelength generated by Er,La:SrF2-CaF2 laser (2.7 µm) is relatively close to absorption peak of water (3 µm) and so, one of the possible usage should be in medicine and spectroscopy.

  10. Investigation on the interfacial chemical state and band alignment for the sputtering-deposited CaF2/p-GaN heterojunction by angle-resolved X-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Kexiong; Liao, Meiyong; Sumiya, Masatomo; Koide, Yasuo; Sang, Liwen

    2016-11-01

    The interfacial chemical state and the band alignment of the sputtering-deposited CaF2/p-GaN hetero-structure were investigated by angle-resolved X-ray photoelectron spectroscopy. The dependence of Ga 3p core-level positions on the collection angles proves that the downward band bending of p-GaN is reduced from 1.51 to 0.85 eV after the deposition of CaF2, which may be due to the reduction of Mg-Ga-O-related interface states by the oxygen-free deposition of CaF2. The band gap of sputtering-deposited CaF2 is estimated to be about 7.97 eV with a potential gradient of 0.48 eV obtained by the variation of the Ca 2p3/2 position on different collection angles. By taking into account the p-GaN surface band bending and potential gradient in the CaF2 layer, large valence and conduction band offsets of 2.66 ± 0.20 and 1.92 ± 0.20 eV between CaF2 and p-GaN are obtained. These results indicate that CaF2 is a promising gate dielectric layer on the p-GaN for the application of metal-insulator-semiconductor devices.

  11. Radiation Damage Effects in Far Ultraviolet Filters and Substrates

    NASA Technical Reports Server (NTRS)

    Keffer, Charles E.; Torr, Marsha R.; Zukic, Muamer; Spann, James F.; Torr, Douglas G.; Kim, Jongmin

    1993-01-01

    New advances in VUV thin film filter technology have been made using filter designs with multilayers of materials such as Al2O3, BaF2, CaF2, HfO2, LaF3, MgF2, and SiO2. Our immediate application for these filters will be in an imaging system to be flown on a satellite where a 2 X 9 R(sub E) orbit will expose the instrument to approximately 275 krads of radiation. In view of the fact that no previous studies have been made on potential radiation damage of these materials in the thin film format, we report on such an assessment here. Transmittances and reflectances of BaF2, CaF2, HfO2, LaF3, MgF2, and SiO2 thin films on MgF2 substrates, Al2O3 thin films on fused silica substrates, uncoated fused silica and MgF2, and four multilayer filters made from these materials were measured from 120 nm to 180 nm before and after irradiation by 250 krads from a Co-60 gamma radiation source. No radiation-induced losses in transmittance or reflectance occurred in this wavelength range. Additional postradiation measurements from 160 nm to 300 nm indicated a 3 - 5% radiation-induced absorption near 260 nm in some of the samples with MgF2 substrates. From these measurements it is concluded that far ultraviolet filters made from the materials tested should experience less that 5% change from exposure to up to 250 krads of high energy radiation in space applications.

  12. Characterization of epitaxial EuS(111) thin films on BaF2(111) and SrF2(111) substrates grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Senba, Shinya; Matsumoto, Naoki; Jomura, Mitsuhiro; Asada, Hironori; Koyanagi, Tsuyoshi; Kishimoto, Kengo; Fukuma, Yasuhiro

    2013-06-01

    We have successfully grown EuS (111) epitaxial films on BaF2 (111) and SrF2 (111) substrates by using molecular beam epitaxy at substrate temperatures ( T S 's) between 100 and 500 °C. Pole figures of X-ray diffraction indicate a high degree of in-plane orientation, and all of the samplesshow very high resistivity. The surface roughness for 10-nm-thick EuS films on BaF2 (111) and SrF2 (111) substrates measured by using atomic force microscopy (AFM) are 0.122 and 0.092 nm, respectively. The Curie temperature of the EuS films increases up to ˜16 K with increasing T S . We also try to manipulate the coercive force, which is an important magnetic property, by Te-doping to achieve an anti-parallel magnetization state between two ferromagnetic layers in spin devices. The obtained coercive force for the Te-doped film (110 Oe) is large compared with that for the undoped one (20 Oe).

  13. Enhanced upconversion emission in crystallization-controllable glass-ceramic fiber containing Yb3+-Er3+ codoped CaF2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Peng, Wencai; Fang, Zaijin; Ma, Zhijun; Qiu, Jianrong

    2016-10-01

    Functional nanocrystal-containing materials have been a hot topic in recent years. However, few researches have focused on functional nanocrystals contained in optical glass fibers. In this research, transparent CaF2 glass-ceramic was prepared by a melt-quenching method. Greatly enhanced upconversion luminescence was observed after heat treatment. By applying a novel method called melt-in-tube, precursor fiber free of crystals was fabricated at the drawing temperature where the clad was softened while the core was melted. Glass-ceramic fiber with fiber core containing Yb3+-Er3+ codoped CaF2 nanocrystals was obtained after heat treatment at a relatively low temperature. Electron probe micro-analyzer measurement shows no obvious element diffusion between the core and clad. Greatly enhanced upconversion emission was detected in the glass-ceramic fiber excited by a 980 nm laser, suggesting the developed glass-ceramic fiber is a promising material for upconversion laser.

  14. Enhanced upconversion emission in crystallization-controllable glass-ceramic fiber containing Yb(3+)-Er(3+) codoped CaF2 nanocrystals.

    PubMed

    Peng, Wencai; Fang, Zaijin; Ma, Zhijun; Qiu, Jianrong

    2016-10-07

    Functional nanocrystal-containing materials have been a hot topic in recent years. However, few researches have focused on functional nanocrystals contained in optical glass fibers. In this research, transparent CaF2 glass-ceramic was prepared by a melt-quenching method. Greatly enhanced upconversion luminescence was observed after heat treatment. By applying a novel method called melt-in-tube, precursor fiber free of crystals was fabricated at the drawing temperature where the clad was softened while the core was melted. Glass-ceramic fiber with fiber core containing Yb(3+)-Er(3+) codoped CaF2 nanocrystals was obtained after heat treatment at a relatively low temperature. Electron probe micro-analyzer measurement shows no obvious element diffusion between the core and clad. Greatly enhanced upconversion emission was detected in the glass-ceramic fiber excited by a 980 nm laser, suggesting the developed glass-ceramic fiber is a promising material for upconversion laser.

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

    PubMed

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

    2015-09-16

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

  16. Evaluation of granulated BGO, GSO:Ce, YAG:Ce, CaF 2:Eu and ZnS:Ag for alpha/beta pulse shape discrimination in a flow-cell radiation detector

    NASA Astrophysics Data System (ADS)

    DeVol, T. A.; Chotoo, S. B.; Fjeld, R. A.

    1999-04-01

    Granulated BGO, GSO:Ce, YAG:Ce, and CaF 2:Eu; CaF 2:Eu coated with a fluorescent polymer, and combinations of coated and uncoated CaF 2:Eu with ZnS:Ag were evaluated for their ability to discriminate between alpha and beta particles in a flow-cell radiation detector. The evaluations were based on the analysis of pulse shape spectra. Various granulated scintillators were packed into flow cell detectors that were coils of 3.0 mm OD×1.5 mm ID fluorinated ethylene propylene Teflon ® tubing positioned between dual photomultiplier tubes for analysis. The best pulse shape discrimination was obtained for a combination of equal masses of uncoated CaF 2:Eu (63-90 μm) and ZnS:Ag (10 μm), which had a 9% spillover. Additional research is needed to reduce the spillover.

  17. High-temperature tribological properties of NiCoCrAlY-WSe2-BaF2·CaF2 solid lubricant coatings prepared by plasma spraying

    NASA Astrophysics Data System (ADS)

    Chen, X. H.; Yuan, X. J.; Xia, J.; Yu, Z. H.

    2015-12-01

    In this paper, NiCoCrAlY-WSe2-BaF2·CaF2 solid lubricant coatings were produced on a substrate by plasma spray and investigated at the high temperature, such as 500 °C and 800 °C. The structure of the coatings was characterized using XRD pattern and scanning electron microscopy. The TC1 (83wt% NiCoCrAlY) coating has a low friction coefficient at 500C, where the WSe2 is a good solid lubricant. The TC2 (65wt% NiCoCrAlY) coating has the low friction coefficient (0.279) at 800°C, due to the formation of BaCrO4 on the surfaces. As a result, the TC2 coating has the optimal tribological property in the wide temperature.

  18. Thermoluminescence Response of CaF2:Mn, CaFz:Dy and CaSO4:Tm to Protons and Alpha-Particles,

    DTIC Science & Technology

    1987-06-01

    linear energy tranfer (LET), which is the average stopping power over the ion range, is also shown as it is expected that the response ratio may be LET...were used for the CaSO4 :Tm and CaF 2 :Mn powders, respectively. Small samples of the powders were spread over the heating planchet to avoid self...absorption during reading. A different procedure was required for the alphas. A relatively thick layer of powder was packed onto the heating planchet

  19. Tensile properties of HA 230 and HA 188 after 400 and 2500 hour exposures to LiF-22CaF2 and vacuum at 1093 K

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel

    1990-01-01

    The solid-to-liquid phase transformation of the nominal LiF-20CaF2 eutectic at 1043 K is considered to be an ideal candidate thermal energy storage mechanism for a space based low temperature Brayton cycle solar dynamic system. Although Co, Fe, and Ni superalloys are thought to be suitable containment materials for LiF based salts, long term containment is of concern because molten fluorides are usually corrosive and Cr can be lost into space through evaporation. Two examples of commercially available superalloys in sheet form, the Ni-base material HA 230 and the Co-base material Ha 88, have been exposed to molten LiF-22CaF2, its vapor, and vacuum, at 1093 K, for 400 and 2500 hr. Triplicate tensile testing of specimens subjected to all three environments have been undertaken between 77 to 1200 K. Comparison of the weight gain data, microstructure, and tensile properties indicate that little, if any, difference in behavior can be ascribed to the exposure environment.

  20. Formation and investigation of ultrathin layers of Co2FeSi ferromagnetic alloy synthesized on silicon covered with a CaF2 barrier layer

    NASA Astrophysics Data System (ADS)

    Grebenyuk, G. S.; Gomoyunova, M. V.; Pronin, I. I.; Vyalikh, D. V.; Molodtsov, S. L.

    2016-03-01

    Ultrathin (∼2 nm) films of Co2FeSi ferromagnetic alloy were formed on silicon by solid-phase epitaxy and studied in situ. Experiments were carried out in an ultrahigh vacuum (UHV) using substrates of Si(1 1 1) single crystals covered with a 5 nm thick CaF2 barrier layer. The elemental and phase composition as well as the magnetic properties of the synthesized films were analyzed by photoelectron spectroscopy using synchrotron radiation and by magnetic linear dichroism in photoemission of Fe 3p and Co 3p electrons. The study shows that the synthesis of the Co2FeSi ferromagnetic alloy occurs in the temperature range of 200-400 °C. At higher temperatures, the films become island-like and lose their ferromagnetic properties, as the CaF2 barrier layer is unable to prevent a mass transfer between the film and the Si substrate, which violates the stoichiometry of the alloy.

  1. Optical properties and electronic structure of CaF2 with the screened-exchange (sX)-LDA-FLAPW approach

    NASA Astrophysics Data System (ADS)

    Mannstadt, W.; Zhao, Yu-Jun; Kim, Miyoung; Freeman, A. J.

    2003-03-01

    Optical measurements have provided an extremely difficult challenge to existing electronic band structure calculations. Although CaF_2, an important large gap insulator, has been intensively investigated, no parameter-free first-principles calculations have been done due to the well-known failure of LDA in treating excited states. Here, we present results of fully first-principles calculations of the electronic structure and optical properties of CaF2 with the self-consistent screened-exchange LDA (sX-LDA) method(Asahi, Mannstadt and Freeman, PRB 59), 7486 (1999). implemented in the FLAPW approach.(Wimmer, Krakauer, Weinert, Freeman, PRB 24), 864 (1981). The calculated optical energy gap, 11.3 eV, is in very good agreement with experiment (11.8 eV)(Tsujibayashi, Toyoda, Sakuragi, Kamada, Itoh, APL 80), 2883 (2002) and so greatly improves the LDA result (7.3 eV). The optical properties, including the real and imaginary parts of the dielectric function determined ab initio with full matrix elements and no parameters, are in good agreement with experiment. A comparison with the results from LDA calculations (with and without a scissors operator to correct the band gap) is also presented.

  2. Development of Yb3+-doped oxyfluoride glass-ceramics with low OH- content containing CaF2 nanocrystals for optical refrigeration

    NASA Astrophysics Data System (ADS)

    Krishnaiah, Kummara Venkata; Ledemi, Yannick; de Lima Filho, Elton Soares; Nemova, Galina; Messaddeq, Younes; Kashyap, Raman

    2017-01-01

    Oxyfluoride glasses and glass-ceramics (GCs) have some niche advantages over other oxide and fluoride glasses, as they possess combined properties. This paper reports the structural, thermal, and photoluminescence (PL) properties of Yb3+-doped SiO2-Al2O3-CaO-CaF2 oxyfluoride glasses and transparent GCs containing CaF2 nanocrystals. Special efforts were undertaken to minimize the hydroxyl (OH-) content in the prepared samples to improve their optical features. Differential scanning calorimetry analyses were performed to determine the characteristic temperatures of the base glasses. X-ray diffractometry studies have confirmed the fluorite CaF2 nanocrystals to be 10 nm in size. Reduced transparency in the ultraviolet (UV)-visible to the near-infrared (NIR) regions was observed for the GCs compared to the base glass with increasing thermal treatment temperature. A higher PL intensity upon 920-nm excitation was obtained in the GCs compared to that of the base glass. The absolute photoluminescence quantum yield upon 920-nm laser excitation was evaluated using an integrating sphere and an optical spectrum analyzer. It was observed that the lifetime of the F2 level of the Yb3+ ions decreases with increasing ceramization temperature. The potential advantages of using such oxyfluoride GCs over commonly studied single crystals for laser cooling applications are discussed.

  3. Investigation the role of Fe3O4 in the silica based bioactive polycrystalline modified with ZnO and CaF2

    NASA Astrophysics Data System (ADS)

    Bahrevari, Mohammad Reza; Atefpour, Mina; Beygi Khosrowshahi, Younes; Pourakbari, Ebrahim

    2017-01-01

    The aim of this article was to investigation the function of silica based polycrystalline that modified with ZnO and CaF2 and doped with 6% Fe3O4. The human pulp stem cells cultured in the presence of samples. The effects of heating-induced crystallization on the glass structure were studied by DSC and x-ray diffraction. The particle size of prepared samples was studied by TEM analysis. The bioactivity of samples were analyzed by apatite-formation ability in DMEM solution through SEM-EDX, biocompatibility was evaluated through the SHEDs cells proliferation, adhesion and spreading on surface of samples by MTT assay and ALP activity assay. Optical and SEM images displayed that co-operation of ZnO and CaF2 led to appropriate circumstance for cells proliferation, adhesion and spreading. Proliferation of pulp stem cells after 7 d of incubation in culture media containing ZC8, FC8 and ZFC4 yielded values 0.3, 1.7 and 2.8 in comparison with control, respectively.

  4. Temperature-Dependent Refractive Index Measurements of Caf2, Suprasil 3001, and S-FTM16 for the Euclid Near Infrared Spectrometer and Photometer

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Grupp, Frank D.

    2015-01-01

    Using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center, we measured absolute refractive indices at temperatures from 100 to 310 K at wavelengths from 0.42 to 3.6 microns for CaF2, Suprasil 3001 fused silica, and S-FTM16 glass in support of lens designs for the Near Infrared Spectrometer and Photometer (NISP) for ESA's Euclid dark energy mission. We report absolute refractive index, dispersion (dn/d?), and thermo-optic coefficient (dn/dT) for these materials. In this study, materials from different melts were procured to understand index variability in each material. We provide temperature-dependent Sellmeier coefficients based on our data to allow accurate interpolation of index to other wavelengths and temperatures. For calcium fluoride (CaF2) and S-FTM16, we compare our current measurements with CHARMS measurements of these materials made in the recent past for other programs. We also compare Suprasil 3001's indices to those of other forms of fused silica we have measured in CHARMS.

  5. X-ray Excitation Triggers Ytterbium Anomalous Emission in CaF2:Yb but Not in SrF2:Yb.

    PubMed

    Hughes-Currie, Rosa B; Ivanovskikh, Konstantin V; Wells, Jon-Paul R; Reid, Michael F; Gordon, Robert A; Seijo, Luis; Barandiarán, Zoila

    2017-03-16

    Materials that luminesce after excitation with ionizing radiation are extensively applied in physics, medicine, security, and industry. Lanthanide dopants are known to trigger crystal scintillation through their fast d-f emissions; the same is true for other important applications as lasers or phosphors for lighting. However, this ability can be seriously compromised by unwanted anomalous emissions often found with the most common lanthanide activators. We report high-resolution X-ray-excited optical (IR to UV) luminescence spectra of CaF2:Yb and SrF2:Yb samples excited at 8949 eV and 80 K. Ionizing radiation excites the known anomalous emission of ytterbium in the CaF2 host but not in the SrF2 host. Wave function-based ab initio calculations of host-to-dopant electron transfer and Yb(2+)/Yb(3+) intervalence charge transfer explain the difference. The model also explains the lack of anomalous emission in Yb-doped SrF2 excited by VUV radiation.

  6. Synthesis of Multicolor Core/Shell NaLuF4:Yb3+/Ln3+@CaF2 Upconversion Nanocrystals

    PubMed Central

    Li, Hui; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

    2017-01-01

    The ability to synthesize high-quality hierarchical core/shell nanocrystals from an efficient host lattice is important to realize efficacious photon upconversion for applications ranging from bioimaging to solar cells. Here, we describe a strategy to fabricate multicolor core @ shell α-NaLuF4:Yb3+/Ln3+@CaF2 (Ln = Er, Ho, Tm) upconversion nanocrystals (UCNCs) based on the newly established host lattice of sodium lutetium fluoride (NaLuF4). We exploited the liquid-solid-solution method to synthesize the NaLuF4 core of pure cubic phase and the thermal decomposition approach to expitaxially grow the calcium fluoride (CaF2) shell onto the core UCNCs, yielding cubic core/shell nanocrystals with a size of 15.6 ± 1.2 nm (the core ~9 ± 0.9 nm, the shell ~3.3 ± 0.3 nm). We showed that those core/shell UCNCs could emit activator-defined multicolor emissions up to about 772 times more efficient than the core nanocrystals due to effective suppression of surface-related quenching effects. Our results provide a new paradigm on heterogeneous core/shell structure for enhanced multicolor upconversion photoluminescence from colloidal nanocrystals. PMID:28336867

  7. Influence of substituting B2O3 for CaF2 on the bonding behaviour to bone of glass-ceramics containing apatite and wollastonite.

    PubMed

    Kitsugi, T; Yamamuro, T; Nakamura, T; Yoshii, S; Kokubo, T; Takagi, M; Shibuya, T

    1992-01-01

    Glass-ceramics containing crystalline oxy-fluoroapatite (Ca10(PO4)6(O,F2)) and wollastonite (CaSiO3) (designated AWGC) are reported to have a fairly high mechanical strength as well as the capability of forming a chemical bond with bone tissue. The chemical composition is MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, and CaF2 0.5 in weight ratio. In this study the influence of substituting B2O3 for CaF2 on the bonding behaviour of glass-ceramics containing apatite and wollastonite to bone tissue was investigated. Two kinds of glass-ceramics containing apatite and wollastonite were prepared. CaF2 0.5 was replaced with B2O3 at 0.5 and 2.0 in weight ratio (designated AWGC-0.5B and AWGC-2.0B). Rectangular ceramic plates (15 x 10 x 2 mm, abraded with No. 2000 alumina powder) were implanted into a rabbit tibia. The failure load, when an implant detached from the bone, or the bone itself broke, was measured. The failure load of AWGC-0.5B was 8.00 +/- 1.82 kg at 10 weeks after implantation and 8.16 +/- 1.36 kg at 25 weeks after implantation. The failure load of AWGC-2B was 8.08 +/- 1.70 kg at 10 weeks after implantation and 9.92 +/- 2.46 kg at 25 weeks after implantation. None of the loads for the two kinds of glass-ceramics decreased as time passed. Giemsa surface staining and contact microradiography revealed direct bonding between glass-ceramics and bone. SEM-EPMA showed a calcium-phosphorus rich layer (reaction zone) at the interface of ceramics and bone tissue. The thickness of the reaction zone was 10 to -15 microns and did not increase as time passed.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. DANCE (Detector for Advanced Neutron Capture Experiments) is a 4π array of BaF2 crystals installed at LANSCE, Lujan Center. Neutron capture measurements on ^157Gd and ^89Y nuclei were conducted using this facility.

    NASA Astrophysics Data System (ADS)

    Chyzh, A.; Mitchell, G.; Vieira, D.; Bredeweg, T.; Ullmann, J.; Jandel, M.; Couture, A.; Keksis, A.; Rundberg, R.; Wilhelmy, J.; O'Donnell, J.; Baramsai, B.; Haight, R.; Wouters, J.; Krticka, M.; Parker, W.; Becker, J.; Agvaanlusan, U.

    2009-10-01

    DANCE (Detector for Advanced Neutron Capture Experiments) is a 4π array of BaF2 crystals installed at LANSCE, Lujan Center. Neutron capture measurements on ^157Gd and ^89Y nuclei were conducted using this facility. The absolute cross sections of the ^89Y(n,γ) reaction was measured for the first time ever in the neutron energy range of 10 eV -- 10 keV and improvements were made in the 10 -- 300 keV range. The error bars were significantly reduced and number of cross section points was increased since the past ^89Y(n,γ) experiments. The ^157Gd(n,γ) cross section was determined at En = 20 eV -- 300 keV by normalizing the experimental DANCE data to a well known resonance taken from the ENDF/B-VII library. Computer simulations of the ^157Gd(n,γ) cascades and DANCE pulse height function were made using DICEBOX and GEANT4 codes and simulated Esum and Eγ spectra are compared to the experimental DANCE data. Values of spin and photon strength function (PSF) of the ^157Gd(n,γ) resonances are provided in the range of En = 2 -- 300 eV using spin dependence upon a γ-ray multiplicity.

  9. On the application of CaF2:Eu and SrF2:Eu phosphors in LED based phototherapy lamp

    NASA Astrophysics Data System (ADS)

    Belsare, P. D.; Moharil, S. V.; Joshi, C. P.; Omanwar, S. K.

    2013-06-01

    In the last few years the interest of scientific community has been increased towards solid state lighting based on LEDs because of their superior advantages over the conventional fluorescent lamps. As the GaN based LEDs are easily available efforts of the researchers are now on making the new phosphors which are excitable in the near UV region (360-400nm) for solid state lighting. This paper reports the photoluminescence characteristics of CaF2:Eu and SrF2:Eu phosphor prepared by wet chemical method. The violet emission of these phosphors with near UV excitation can be useful in making a phototherapy lamp based on LEDs for treating various skin diseases like acne vulgaris and hyperbilirubinemia.

  10. Direct comparison of Yb3+:CaF2 and heavily doped Yb3+:YLF as laser media at room temperature.

    PubMed

    Pirri, Angela; Alderighi, Daniele; Toci, Guido; Vannini, Matteo; Nikl, Martin; Sato, Hiroki

    2009-09-28

    We report an extensive comparison of the laser performances of diode-pumped Yb(3+):YLF (30% at.) and Yb(3+):CaF(2) (5% at.) crystals, lasing at room-temperature and operating in two different operation mode, i.e. Continuous Wave (CW) and quasi-CW. An in-depth investigation of the crystals behavior by changing the pump power, clearly shows the crystal absorption depends on the lasing conditions. Therefore, we report an unambiguous definition of the slope efficiency calculated taken into account the real measured crystal absorption under laser action. Finally, we present a study of problems related to thermally induced losses which are expected influencing the laser performance.

  11. Temperature dependence of the elastic moduli and damping for polycrystalline LiF-22 pct CaF2 eutectic salt

    NASA Technical Reports Server (NTRS)

    Wolfenden, A.; Lastrapes, G.; Duggan, M. B.; Raj, S. V.

    1991-01-01

    Young's and shear moduli and damping were measured for as-cast polycrystalline LiF-(22 mol pct)CaF2 eutectic specimens as a function of temperature using the piezoelectric ultrasonic composite oscillator technique. The shear modulus decreased with increasing temperature from about 40 GPa at 295 K to about 30 GPa at 1000 K, while the Young modulus decreased from about 115 GPa at 295 K to about 35 GPa at 900 K. These values are compared with those derived from the rule of mixtures using elastic moduli data for LiF and CaF2 single crystals. It is shown that, while the shear modulus data agree reasonably well with the predicted trend, there is a large discrepancy between the theoretical calculations and the Young modulus values, where this disagreement increases with increasing temperature.

  12. Spin-Hamiltonian parameters for the tetragonal GdM3+-Fi- centers in CaF2 and SrF2 crystals

    NASA Astrophysics Data System (ADS)

    Yang, Wei-Qing; Zhang, Ying; Lin, Yuan; Zheng, Wen-Chen

    2013-02-01

    The spin-Hamiltonian parameters (g factors g//, g⊥ and zero-field splittings b20, b40, b44, b60, b64) of the tetragonal GdM3+-Fi- centers in CaF2 and SrF2 crystals at T ≈ 1.8 K are calculated from the diagonalization (of energy matrix) method based on the one-electron crystal field mechanism. In the calculations, the crystal field parameters used are estimated from the superposition model with the reported defect structural data obtained from the analyses of superhyperfire interaction constants at the same temperature. The calculated results are in reasonable agreement with the experimental values. It appears that the above defect structural data reported in the previous paper are suitable and the diagonalization (of energy matrix) method is effective to the studies of spin-Hamiltonian parameters for 4f7 ions in crystals.

  13. Metal-to-metal charge transfer between dopant and host ions: Photoconductivity of Yb-doped CaF2 and SrF2 crystals

    NASA Astrophysics Data System (ADS)

    Barandiarán, Zoila; Seijo, Luis

    2015-10-01

    Dopant-to-host electron transfer is calculated using ab initio wavefunction-based embedded cluster methods for Yb/Ca pairs in CaF2 and Yb/Sr pairs in SrF2 crystals to investigate the mechanism of photoconductivity. The results show that, in these crystals, dopant-to-host electron transfer is a two-photon process mediated by the 4fN-15d excited states of Y b2+: these are reached by the first photon excitation; then, they absorb the second photon, which provokes the Y b2+ + Ca2+ (Sr2+) → Y b3+ + Ca+ (Sr+) electron phototransfer. This mechanism applies to all the observed Y b2+ 4f-5d absorption bands with the exception of the first one: Electron transfer cannot occur at the first band wavelengths in CaF2:Y b2+ because the Y b3+-Ca+ states are not reached by the two-photon absorption. In contrast, Yb-to-host electron transfer is possible in SrF2:Y b2+ at the wavelengths of the first 4f-5d absorption band, but the mechanism is different from that described above: first, the two-photon excitation process occurs within the Y b2+ active center, then, non-radiative Yb-to-Sr electron transfer can occur. All of these features allow to interpret consistently available photoconductivity experiments in these materials, including the modulation of the photoconductivity by the absorption spectrum, the differences in photoconductivity thresholds observed in both hosts, and the peculiar photosensitivity observed in the SrF2 host, associated with the lowest 4f-5d band.

  14. Metal-to-metal charge transfer between dopant and host ions: Photoconductivity of Yb-doped CaF2 and SrF2 crystals.

    PubMed

    Barandiarán, Zoila; Seijo, Luis

    2015-10-14

    Dopant-to-host electron transfer is calculated using ab initio wavefunction-based embedded cluster methods for Yb/Ca pairs in CaF2 and Yb/Sr pairs in SrF2 crystals to investigate the mechanism of photoconductivity. The results show that, in these crystals, dopant-to-host electron transfer is a two-photon process mediated by the 4f(N-1)5d excited states of Y b(2+): these are reached by the first photon excitation; then, they absorb the second photon, which provokes the Y b(2+) + Ca(2+) (Sr(2+)) → Y b(3+) + Ca(+) (Sr(+)) electron phototransfer. This mechanism applies to all the observed Y b(2+) 4f-5d absorption bands with the exception of the first one: Electron transfer cannot occur at the first band wavelengths in CaF2:Y b(2+) because the Y b(3+)-Ca(+) states are not reached by the two-photon absorption. In contrast, Yb-to-host electron transfer is possible in SrF2:Y b(2+) at the wavelengths of the first 4f-5d absorption band, but the mechanism is different from that described above: first, the two-photon excitation process occurs within the Y b(2+) active center, then, non-radiative Yb-to-Sr electron transfer can occur. All of these features allow to interpret consistently available photoconductivity experiments in these materials, including the modulation of the photoconductivity by the absorption spectrum, the differences in photoconductivity thresholds observed in both hosts, and the peculiar photosensitivity observed in the SrF2 host, associated with the lowest 4f-5d band.

  15. Effect of SiO2 on the Crystallization Behaviors and In-Mold Performance of CaF2-CaO-Al2O3 Slags for Drawing-Ingot-Type Electroslag Remelting

    NASA Astrophysics Data System (ADS)

    Shi, Cheng-Bin; Li, Jing; Cho, Jung-Wook; Jiang, Fang; Jung, In-Ho

    2015-10-01

    The crystallization characteristics of CaF2-CaO-Al2O3 slags with varying amounts of SiO2 were experimentally studied. The effects of slag crystallization behaviors on the horizontal heat transfer and lubrication performance in drawing-ingot-type electroslag remelting (ESR) were also evaluated in terms of as-cast ingots surface quality and drawing-ingot operation. The results show that increasing SiO2 addition from 0 to 6.8 mass pct strongly suppresses the crystallization of ESR type CaF2-CaO-Al2O3 slags. The crystallization temperature of the studied slags decreases with the increase in SiO2 addition. The liquidus temperatures of the slags also show a decreasing trend with increasing SiO2 content. In CaF2-CaO-Al2O3-(SiO2) slags, faceted 11CaO·7Al2O3·CaF2 crystals precipitate first during continuous cooling of the slag melts, followed by the formation of CaF2 at lower temperatures. 11CaO·7Al2O3·CaF2 was confirmed to be the dominant crystalline phase in the studied slags. CaF2-CaO-Al2O3 slags with a small amount of SiO2 addition are favorable for providing sound lubrication and horizontal heat transfer in mold for drawing-ingot-type ESR, which consequently bring the improvement in the surface quality of ESR ingot and drawing-ingot operating practice as demonstrated by plant trials.

  16. Ab initio multiconfiguration self-consistent-field calculations of the excited states of a Mn impurity in CaF2

    NASA Astrophysics Data System (ADS)

    Lewandowski, A. C.; Wilson, T. M.

    1994-08-01

    We analyze Mn absorption in CaF2:Mn by the employment of ab inito quantum-mechanical cluster calculations and ligand-field methods. The [MnF8]6- Oh cluster is chosen to represent the isolated Mn2+ substitutional impurity in an otherwise perfect crystal. The methods of unrestricted open-shell Hartree-Fock self-consistent field (SCF), Mo/ller-Plesset perturbation theory to second- and fourth-order, and singles and doubles configuration interaction are used to calculate the spin sextet and quartet ground states. With the active space consisting of the Mn 3d molecular orbitals, the spin quartet excited states are calculated by the method of multiconfiguration SCF. It was found that the presence of an external field designed to reproduce the Madelung potential difference within the cluster did not significantly affect the Mn d-to-d transitions. The crystal-field term splitting diagrams for the eight-coordinated Mn2+ impurity in Oh symmetry are calculated. The results showed a narrowing of the multiplet terms in energy with respect to the six-coordinated Oh result. This increases the crystal-field parameter Dq from the previously published value of 420-570 cm-1.

  17. Development of very high Jc in Ba(Fe1-xCox)2As2 thin films grown on CaF2

    PubMed Central

    Tarantini, C.; Kametani, F.; Lee, S.; Jiang, J.; Weiss, J. D.; Jaroszynski, J.; Hellstrom, E. E.; Eom, C. B.; Larbalestier, D. C.

    2014-01-01

    Ba(Fe1-xCox)2As2 is the most tunable of the Fe-based superconductors (FBS) in terms of acceptance of high densities of self-assembled and artificially introduced pinning centres which are effective in significantly increasing the critical current density, Jc. Moreover, FBS are very sensitive to strain, which induces an important enhancement in critical temperature, Tc, of the material. In this paper we demonstrate that strain induced by the substrate can further improve Jc of both single and multilayer films by more than that expected simply due to the increase in Tc. The multilayer deposition of Ba(Fe1-xCox)2As2 on CaF2 increases the pinning force density (Fp = Jc × µ0H) by more than 60% compared to a single layer film, reaching a maximum of 84 GN/m3 at 22.5 T and 4.2 K, the highest value ever reported in any 122 phase. PMID:25467177

  18. Storing Hydrogen, by Enhancing Diamond Powder Properties under Hydrogen Plasma with CaF2 and KF for Use in Fuel Cells

    SciTech Connect

    Ochoa, Franklyn E. Colmenares

    2006-12-04

    A fuel cell is like a battery that instead of using electricity to recharge itself, it uses hydrogen. In the fuel cell industry, one of the main problems is storing hydrogen in a safe way and extracting it economically. Gaseous hydrogen requires high pressures which could be very dangerous in case of a collision. The success of hydrogen use depends largely on the development of an efficient storage and release method. In an effort to develop a better hydrogen storage system for fuel cells technology this research investigates the use of 99% pure diamond powder for storing hydrogen. Mixing this powder with a calcium fluoride and potassium fluoride compound in its solid form and treating the surface of the powder with hydrogen plasma, modifies the surface of the diamond. After some filtration through distilled water and drying, the modified diamond is treated with hydrogen. We expect hydrogen to be attracted to the diamond powder surface in higher quantities due to the CaF2 and KF treatment. Due to the large surface area of diamond nanopowder and the electronegative terminal bonds of the fluorine particles on the structure's surface, to the method shows promise in storing high densities of hydrogen.

  19. Abnormal size-dependent upconversion emissions and multi-color tuning in Er3+-doped CaF2-YbF3 disordered solid-solution nanocrystals.

    PubMed

    Chen, Daqin; Lei, Lei; Xu, Ju; Yang, Anping; Wang, Yuansheng

    2013-03-01

    A series of Er(3+)-doped (1 - x)CaF(2)-xYbF(3) (0 ≤ x ≤ 0.6) disordered solid-solution nanocrystals with various mean sizes were successfully prepared by a facile solvothermal route. Interestingly, abnormal size-dependent upconversion emissions were demonstrated in these nanocrystals for the first time. With increasing grain size, an obvious enhancement of red to green emission ratio was observed in the Er(3+) (2 mol%): 0.4CaF(2)-0.6YbF(3) nanocrystals, which is the opposite of the routine size-dependent upconversion emission behavior reported previously. Taking Eu(3+) ions as a structural probe, we investigated the influence of a disordered solid-solution structure on Ln(3+) luminescence, and proposed that Ln(3+) clusters formed in the host should play a key role to induce this unusual size-dependent upconversion emission phenomenon. As a consequence, multi-colors such as green, yellow, and red upconversion emissions can be easily realized by appropriately modifying the Yb(3+) content in the Er(3+)-doped (1 - x)CaF(2)-xYbF(3) nanocrystals. The reported results will deepen the understanding of size effects on the lanthanide upconversion in nanocrystals.

  20. Development of very high Jc in Ba(Fe1-xCox)2As2 thin films grown on CaF2

    DOE PAGES

    Tarantini, C.; Kametani, F.; Lee, S.; ...

    2014-12-03

    Ba(Fe1-xCox)2As2 is the most tunable of the Fe-based superconductors (FBS) in terms of acceptance of high densities of self-assembled and artificially introduced pinning centres which are effective in significantly increasing the critical current density, Jc. Moreover, FBS are very sensitive to strain, which induces an important enhancement in critical temperature,Tc, of the material. In this study we demonstrate that strain induced by the substrate can further improve Jc of both single and multilayer films by more than that expected simply due to the increase in Tc. The multilayer deposition of Ba(Fe1-xCox)2As2 on CaF2 increases the pinning force density (Fp=Jc xmore » μ₀H) by more than 60% compared to a single layer film, reaching a maximum of 84 GN/m3 at 22.5 T and 4.2 K, the highest value ever reported in any 122 phase.« less

  1. Storing Hydrogen, by Enhancing Diamond Powder Properties under Hydrogen Plasma with CaF2 and KF for Use in Fuel Cells

    NASA Astrophysics Data System (ADS)

    Ochoa, Franklyn E. Colmenares

    2006-12-01

    A fuel cell is like a battery that instead of using electricity to recharge itself, it uses hydrogen. In the fuel cell industry, one of the main problems is storing hydrogen in a safe way and extracting it economically. Gaseous hydrogen requires high pressures which could be very dangerous in case of a collision. The success of hydrogen use depends largely on the development of an efficient storage and release method. In an effort to develop a better hydrogen storage system for fuel cells technology this research investigates the use of 99% pure diamond powder for storing hydrogen. Mixing this powder with a calcium fluoride and potassium fluoride compound in its solid form and treating the surface of the powder with hydrogen plasma, modifies the surface of the diamond. After some filtration through distilled water and drying, the modified diamond is treated with hydrogen. We expect hydrogen to be attracted to the diamond powder surface in higher quantities due to the CaF2 and KF treatment. Due to the large surface area of diamond nanopowder and the electronegative terminal bonds of the fluorine particles on the structure's surface, to the method shows promise in storing high densities of hydrogen.

  2. Layer-by-layer resolved core-level shifts in CaF2 and SrF2 on Si(111): Theory and experiment

    NASA Astrophysics Data System (ADS)

    Rotenberg, Eli; Denlinger, J. D.; Leskovar, M.; Hessinger, U.; Olmstead, Marjorie A.

    1994-10-01

    Using x-ray-photoelectron spectroscopy and Auger-electron spectroscopy, we have resolved surface, bulk, and interface Ca and F core-level emission in thin films (3-8 triple layers) of CaF2 and SrF2 on Si(111). We confirmed these assignments using x-ray-photoelectron diffraction (XPD) and surface modification. XPD was also used to identify the growth modes of the films as being either laminar or layer plus islands; in the latter case we have resolved buried and uncovered interface F and Ca/Sr emission. We compare the observed energy differences between surface, bulk, and interface emission to theoretical estimates of the extra-atomic contributions to emission energies. We find excellent agreement considering only the Madelung (electrostatic) potentials for the initial-state contribution and polarization response for the final-state contribution, including the effect of tetragonal strain. Small discrepancies for emission from metal atoms bonded to the Si substrate are interpreted in terms of chemical shifts.

  3. Angular-dependent vortex pinning mechanism and magneto-optical characterizations of FeSe0.5Te0.5 thin films grown on CaF2 substrates

    NASA Astrophysics Data System (ADS)

    Yuan, Pusheng; Xu, Zhongtang; Ma, Yanwei; Sun, Yue; Tamegai, Tsuyoshi

    2016-03-01

    Magneto-optical (MO) characterizations and the angular-dependent critical current density (J c(Θ)) of epitaxial FeSe0.5Te0.5 (FST) thin films grown on CaF2 single-crystalline substrates were performed. The MO images show typical rooftop patterns in the remanent state from which a large, homogeneous, and almost isotropic self-field J c over 2 × 106 A cm-2 at 8 K was obtained. The vortex pinning mechanism is investigated measuring the magnetic field and angular-dependent critical current density J c. The FST films exhibit small anisotropy of J c in the whole applied magnetic field range below 15 K. The Dew-Hughes model and angular scaling analyses prove that pointlike normal cores, which are distributed randomly in the FST film, dominate the pinning in the FST films on CaF2 substrates.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  5. Capillary and van der Waals interactions on CaF2 crystals from amplitude modulation AFM force reconstruction profiles under ambient conditions

    PubMed Central

    Calò, Annalisa; Robles, Oriol Vidal; Santos, Sergio

    2015-01-01

    Summary There has been much interest in the past two decades to produce experimental force profiles characteristic of the interaction between nanoscale objects or a nanoscale object and a plane. Arguably, the advent of the atomic force microscope AFM was instrumental in driving such efforts because, in principle, force profiles could be recovered directly. Nevertheless, it has taken years before techniques have developed enough as to recover the attractive part of the force with relatively low noise and without missing information on critical ranges, particularly under ambient conditions where capillary interactions are believed to dominate. Thus a systematic study of the different profiles that may arise in such situations is still lacking. Here we employ the surfaces of CaF2, on which nanoscale water films form, to report on the range and force profiles that might originate by dynamic capillary interactions occurring between an AFM tip and nanoscale water patches. Three types of force profiles were observed under ambient conditions. One in which the force decay resembles the well-known inverse-square law typical of van der Waals interactions during the first 0.5–1 nm of decay, a second one in which the force decays almost linearly, in relatively good agreement with capillary force predicted by the constant chemical potential approximation, and a third one in which the attractive force is almost constant, i.e., forms a plateau, up to 3–4 nm above the surface when the formation of a capillary neck dominates the tip–sample interaction. PMID:25977852

  6. Structural and thermal characterization of CaO-MgO-SiO2-P2O5-CaF2 glasses

    SciTech Connect

    Kansal, Ishu; Goel, Ashutosh; Tulyaganov, Dilshat U.; Rajagopal, Raghu R.; Ferreira, Jose M.

    2012-08-01

    The paper presents the influence of varying CaO/MgO ratio on the structure and thermal properties of CaO-MgO-SiO2-P2O5-CaF2 glasses. A series of eight glass compositions in the glass forming region of diopside (CaMgSi2O6) - fluorapatite [Ca5(PO4)3F] - wollastonite (CaSiO3) ternary system have been designed and synthesized by varying diopside/wollastonite ratio in glasses. The as prepared melt-quenched glasses have been characterized for their structure by infrared spectroscopy (FTIR) and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy. Silicon is predominantly present as Q2 (Si) species, while phosphorus tends to coordinate in orthophosphate environment in all the investigated glasses. The change in CaO/MgO ratio had an insignificant affect on the structure of glasses. The thermal sintering and crystallization parameters for the studied glasses have been obtained from differential thermal analysis (DTA) while crystalline phase fractions in the sintered glass-ceramics have been analyzed by X-ray diffraction adjoined with Rietveld refinement. Diopside, fluorapatite, wollastonite and pseudowollastonite have crystallized as the main crystalline phases in all the glass-ceramics with their content varying with respect to variation in CaO/MgO ratio in glasses. Scanning electron microscopy (SEM) has been used to shed light on the microstructure of glass-ceramics. The possible implications of structure and sintering behaviour of glasses on their bioactivity have been discussed.

  7. An attempt to apply the inelastic thermal spike model to surface modifications of CaF2 induced by highly charged ions: comparison to swift heavy ions effects and extension to some others material

    NASA Astrophysics Data System (ADS)

    Dufour, C.; Khomrenkov, V.; Wang, Y. Y.; Wang, Z. G.; Aumayr, F.; Toulemonde, M.

    2017-03-01

    Surface damage appears on materials irradiated by highly charged ions (HCI). Since a direct link has been found between surface damage created by HCI with the one created by swift heavy ions (SHI), the inelastic thermal spike model (i-TS model) developed to explain track creation resulting from the electron excitation induced by SHI can also be applied to describe the response of materials under HCI which transfers its potential energy to electrons of the target. An experimental description of the appearance of the hillock-like nanoscale protrusions induced by SHI at the surface of CaF2 is presented in comparison with track formation in bulk which shows that the only parameter on which we can be confident is the electronic energy loss threshold. Track size and electronic energy loss threshold resulting from SHI irradiation of CaF2 is described by the i-TS model in a 2D geometry. Based on this description the i-TS model is extended to three dimensions to describe the potential threshold of appearance of protrusions by HCI in CaF2 and to other crystalline materials (LiF, crystalline SiO2, mica, LiNbO3, SrTiO3, ZnO, TiO2, HOPG). The strength of the electron–phonon coupling and the depth in which the potential energy is deposited near the surface combined with the energy necessary to melt the material defines the classification of the material sensitivity. As done for SHI, the band gap of the material may play an important role in the determination of the depth in which the potential energy is deposited. Moreover larger is the initial potential energy and larger is the depth in which it is deposited.

  8. An attempt to apply the inelastic thermal spike model to surface modifications of CaF2 induced by highly charged ions: comparison to swift heavy ions effects and extension to some others material.

    PubMed

    Dufour, C; Khomrenkov, V; Wang, Y Y; Wang, Z G; Aumayr, F; Toulemonde, M

    2017-03-08

    Surface damage appears on materials irradiated by highly charged ions (HCI). Since a direct link has been found between surface damage created by HCI with the one created by swift heavy ions (SHI), the inelastic thermal spike model (i-TS model) developed to explain track creation resulting from the electron excitation induced by SHI can also be applied to describe the response of materials under HCI which transfers its potential energy to electrons of the target. An experimental description of the appearance of the hillock-like nanoscale protrusions induced by SHI at the surface of CaF2 is presented in comparison with track formation in bulk which shows that the only parameter on which we can be confident is the electronic energy loss threshold. Track size and electronic energy loss threshold resulting from SHI irradiation of CaF2 is described by the i-TS model in a 2D geometry. Based on this description the i-TS model is extended to three dimensions to describe the potential threshold of appearance of protrusions by HCI in CaF2 and to other crystalline materials (LiF, crystalline SiO2, mica, LiNbO3, SrTiO3, ZnO, TiO2, HOPG). The strength of the electron-phonon coupling and the depth in which the potential energy is deposited near the surface combined with the energy necessary to melt the material defines the classification of the material sensitivity. As done for SHI, the band gap of the material may play an important role in the determination of the depth in which the potential energy is deposited. Moreover larger is the initial potential energy and larger is the depth in which it is deposited.

  9. Formation of hydroxyapatite onto glasses of the CaO-MgO-SiO2 system with B2O3, Na2O, CaF2 and P2O5 additives.

    PubMed

    Agathopoulos, S; Tulyaganov, D U; Ventura, J M G; Kannan, S; Karakassides, M A; Ferreira, J M F

    2006-03-01

    New bioactive glasses with compositions based on the CaO-MgO-SiO(2) system and additives of B(2)O(3), P(2)O(5), Na(2)O, and CaF(2) were prepared. The in vitro mineralization behaviour was tested by immersion of powders or bulk glasses in simulated body fluid (SBF). Monitoring of ionic concentrations in SBF and scanning electron microscopy (SEM) observations at the surface of the glasses were conducted over immersion time. Raman and infrared (IR) spectroscopy shed light on the structural evolution occurring at the surface of the glasses that leads to formation of hydroxyapatite.

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  11. Annealing of electron damage in mid-IR transmitting fluoride glass

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Doremus, Robert H.

    1986-01-01

    Damage in ZrF4-BaF2-LaF3 glass induced by high-energy electrons was studied by ESR and optical spectroscopy. An optical absorption band at 314 nm in the irradiated glass annealed rapidly above about 50 C, probably by a second-order reaction at room temperature; the ESR lines annealed very slowly at room temperature.

  12. SiO2 and CaF2 Behavior During Shielded Metal Arc Welding and Their Effect on Slag Detachability of the CaO-CaF2-SiO2 Type ENiCrFe-7-Covered Electrode

    NASA Astrophysics Data System (ADS)

    Wang, Huang; Qin, Renyao; He, Guo

    2016-09-01

    The metallurgical behavior during shielded metal arc welding (SMAW) and the slag detachability of the CaO-CaF2-SiO2 type ENiCrFe-7-covered electrodes was investigated. The results indicated that the slag detachability could be improved as the SiO2 in the flux coatings decreased. When the SiO2 in the flux coating was 10.9 pct, about 28.3 pct CaF2 resulted in the best slag detachability. The CaF2 and SiO2 in the flux coating interacted during SMAW to form gaseous SiF4 to be evacuated. In the reactions, one SiO2 consumed two CaF2, leading to the reduction of the ratio of CaF2/SiO2. After comparing the slag compositions, the best slag detachability was obtained at CaO:CaF2:SiO2 = 1.7:1.8:1, but the worst slag detachability appeared at CaO:CaF2:SiO2 = 1.3:0.9:1. The XRD analysis revealed that the oxides and fluorides in the slags preferred to gather together to form cuspidine and other complex phases. If the CaF2 was dominant in the slags, they intended to form homogenous porous microstructures that were relatively strong and would most likely detach from the weld metal in blocks, exhibiting good slag detachability. If the cuspidine phase was dominant, the slags exhibited a `rock strata'-like microstructure in the intergranular area. Such microstructure was very fragile and could be broken into fine powders that were easily embedded in the weld ripples, leading to slag adhesions. This work provides the researcher with a wealth of information and data, which will also be beneficial to the welding material producers and users.

  13. Influence of heat treatments upon the mechanical properties and in vitro bioactivity of ZrO2-toughened MgO-CaO-SiO2-P2O5-CaF2 glass-ceramics.

    PubMed

    Li, Huan-Cai; Wang, Dian-Gang; Meng, Xiang-Guo; Chen, Chuan-Zhong

    2014-09-01

    Zirconia-toughened MgO-CaO-SiO2-P2O5-CaF2 glass-ceramics are prepared using sintering techniques, and a series of heat treatment procedures are designed to obtain a glass-ceramic with improved properties. The crystallization behavior, phase composition, and morphology of the glass-ceramics are characterized. The bending strength, elastic modulus, fracture toughness, and microhardness of the glass-ceramics are investigated, and the effect mechanism of heat treatments upon the mechanical properties is discussed. The bioactivity of glass-ceramics is then evaluated using the in vitro simulated body fluid (SBF) soaking test, and the mechanism whereby apatite forms on the glass-ceramic surfaces in the SBF solution is discussed. The results indicate that the main crystal phase of the G-24 sample undergoing two heat treatment procedures is Ca5(PO4)3F (fluorapatite), and those of the G-2444 sample undergoing four heat treatment procedures are Ca5(PO4)3F and β-CaSiO3 (β-wollastonite). The heat treatment procedures are found to greatly influence the mechanical properties of the glass-ceramic, and an apatite layer is induced on the glass-ceramic surface after soaking in the SBF solution.

  14. Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

    PubMed

    Li, H C; Wang, D G; Meng, X G; Chen, C Z

    2014-06-01

    A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and β-CaSiO(3). (β-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of β-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell.

  15. Scattering Effect of Iron Metallic Particles on the Extinction Coefficient of CaO-SiO2-B2O3-Na2O-Fe2O3-CaF2 Glasses

    NASA Astrophysics Data System (ADS)

    Yoon, Dae-Woo; Cho, Jung-Wook; Kim, Seon-Hyo

    2016-10-01

    The extinction coefficient of the CaO-SiO2-B2O3-Na2O-Fe2O3-CaF2 glasses has been studied using a FT-IR and a UV-visible spectrometer in the range of 0.5-5 μm to investigate thermal radiation through glassy flux film during continuous casting of steels. In present investigations, iron oxide has been reduced to metallic iron droplets by reaction with graphite crucible during melting, which brings considerable increase of the extinction coefficient due to the scattering. To analyze the scattering effect of these droplets on the extinction coefficient, the number density and size parameter of metallic particles have been measured using an automated scanning electron microscope. The number of metallic particles is intensively proportional to boron contents due to the transition of molar structure, BO4 to BO3, with increasing boron oxide. It is found that calculated scattering coefficients based on Mie scattering theory are in good agreement with measured ones. As the increased scattering coefficient of glassy film would not cause any serious side effects on casting operations, utilization of scattering effects is believed to be significantly essential for the future design of commercial mold fluxes.

  16. Mechanical properties of Haynes Alloy 188 after exposure to LiF-22CaF2, air, and vacuum at 1093 K for periods up to 10,000 hours

    SciTech Connect

    Whittenberger, J.D. )

    1992-08-01

    As part of a program to provide reassurance that the cobalt-base superalloy Haynes Alloy 188 can adequately contain a LiF-CaF2 eutectic thermal energy storage salt, 4900- and 10,000-hr exposures of Haynes Alloy 188 to LiF-22CaF2, its vapor, vacuum, and air at 1093 K have been undertaken. Following such exposures, the microstructure has been characterized and the 77 to 1200 K tensile properties measured. In addition, 1050 K vacuum creep-rupture testing of as-received and molten salt- and vacuum-exposed samples has been undertaken. Although slight degradation of the mechanical properties of Haynes Alloy 188 due to prior exposure was observed, basically none of the losses could be ascribed to a particular environment. Hence, observed decreases in properties are due to thermal aging effects, not corrosive attack. In view of these findings, Haynes Alloy 188 is still deemed to be suitable for containment of the eutectic LiF-CaF2 thermal energy storage media. 8 refs.

  17. Mechanical properties of Haynes Alloy 188 after exposure to LiF-22CaF2, air, and vacuum at 1093 K for periods up to 10,000 hours

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1992-01-01

    As part of a program to provide reassurance that the cobalt-base superalloy Haynes Alloy 188 can adequately contain a LiF-CaF2 eutectic thermal energy storage salt, 4900- and 10,000-hr exposures of Haynes Alloy 188 to LiF-22CaF2, its vapor, vacuum, and air at 1093 K have been undertaken. Following such exposures, the microstructure has been characterized and the 77 to 1200 K tensile properties measured. In addition, 1050 K vacuum creep-rupture testing of as-received and molten salt- and vacuum-exposed samples has been undertaken. Although slight degradation of the mechanical properties of Haynes Alloy 188 due to prior exposure was observed, basically none of the losses could be ascribed to a particular environment. Hence, observed decreases in properties are due to thermal aging effects, not corrosive attack. In view of these findings, Haynes Alloy 188 is still deemed to be suitable for containment of the eutectic LiF-CaF2 thermal energy storage media.

  18. Role of nickel ion coordination on spectroscopic properties of multi-component CaF2-Bi2O3-P2O5-B2O3 glass-ceramics

    NASA Astrophysics Data System (ADS)

    Suresh, S.; Narendrudu, T.; Kumar, A. Suneel; Rao, M. V. Sambasiva; Ram, G. Chinna; Rao, D. Krishna

    2016-10-01

    Multi-component CaF2-Bi2O3-P2O5-B2O3 glasses doped with different concentrations of NiO were crystallized through heat treatment. The prepared glass ceramic samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) as well as conventional spectroscopic studies viz., optical absorption, Fourier transform infrared (FTIR) and Raman. The XRD and SEM studies have indicated that the samples contain well defined and randomly distributed grains of different crystalline phases. The optical absorption studies together with FTIR and Raman measurements indicated the gradual transformation of nickel ions from tetrahedral sites to octahedral sites (lasing sites) as the concentration of NiO is increased beyond 1.5 mol%. All these investigations have indicated that the growing degree of disorder in the glass ceramic network at higher concentrations of NiO. Glass ceramics doped with NiO beyond 1.5 mol% appear to be suitable for getting laser emission due to 3T2(F) → 3A2(F) transition in NIR region. These glass-ceramics can be expected as an amplification medium for tunable lasers and broadband optical amplifiers for wavelength division multiplexing transmission system.

  19. Influence of strontium on structure, sintering and biodegradation behaviour of CaO-MgO-SrO-SiO(2)-P(2)O(5)-CaF(2) glasses.

    PubMed

    Goel, Ashutosh; Rajagopal, Raghu Raman; Ferreira, José M F

    2011-11-01

    The present study investigates the influence of SrO on structure, apatite-forming ability, physico-chemical degradation and sintering behaviour of melt-quenched bioactive glasses with the composition (mol.%): (36.07 - x) CaO-xSrO-19.24MgO-5.61P(2)O(5)-38.49SiO(2)-0.59CaF(2), where x varies between 0 and 10. The detailed structural analysis of the glasses is made by infrared spectroscopy and magic angle spinning-nuclear magnetic resonance spectroscopy. Silicon is predominantly present as Q(2) (Si) species, while phosphorus is found as orthophosphate in all the investigated glasses. The apatite-forming ability of glasses is investigated by immersion of glass powders in simulated body fluid for time durations varying between 1 h and 7 days. While increasing the Sr(2+)/Ca(2+) ratio in the glasses does not affect their structure significantly, their apatite-forming ability is decreased considerably. Further, physico-chemical degradation of glasses is studied in accordance with ISO 10993-14 "Biological evaluation of medical devices - Part 14: Identification and quantification of degradation products from ceramics" in Tris-HCl and citric acid buffer, and the possible implications of the ion release profiles from the glasses in different solutions are discussed. The addition of strontium to the glasses leads to a sevenfold decrease in chemical degradation of glasses in Tris-HCl. The sintering of glass powders renders glass ceramics (GCs) with varying degrees of crystallinity and good flexural strength (98-131 MPa), where the mechanical properties depend on the nature and amount of crystalline phases present in the GCs.

  20. Influence of strontium on structure, sintering and biodegradation behaviour of CaO-MgO-SrO-SiO2-P2O5-CaF2 glasses

    SciTech Connect

    Goel, Ashutosh; Rajagopal, Raghu R.; Ferreira, Jose M.

    2011-11-01

    The present study investigates the influence of SrO on structure, apatite forming ability, physico-chemical degradation and sintering behaviour of melt-quenched bioactive glasses with composition: mol.% (36.07 – x) CaO – x SrO - 19.24 MgO – 5.61 P2O5 – 38.49 SiO2 – 0.59 CaF2, where x varies between 0 – 10. The detailed structural analysis of glasses has been made by infra red spectroscopy (FTIR) and magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR). Silicon was predominantly present as Q2 (Si) species while phosphorus was found in orthophosphate type environment in all the investigated glasses. The apatite forming ability of glasses was investigated by immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1 h – 7 days. While increasing Sr2+/Ca2+ ratio in glasses did not affect the structure of glasses significantly, their apatite forming ability was decreased considerably. Further, physico-chemical degradation of glasses has been studied in accordance with ISO 10993-14 “Biological evaluation of medical devices – Part 14: Identification and quantification of degradation products from ceramics” in Tris HCl and citric acid buffer and the possible implications of ion release profile from glasses in different solutions has been discussed. The addition of strontium in glasses led to a 7-fold decrease in chemical degradation of glasses in Tris-HCl. The sintering of glass powders rendered glass-ceramics (GCs) with varying degree of crystallinity and good flexural strength (98-131 MPa) where the mechanical properties depend on the nature and amount of crystalline phases present in GCs.

  1. Bone bonding behavior of MgO-CaO-SiO2-P2O5-CaF2 glass (mother glass of A.W-glass-ceramics).

    PubMed

    Kitsugi, T; Yamamuro, T; Nakamura, T; Kokubo, T

    1989-06-01

    In this study, it was found that a Ca-P layer and a Si layer were formed on the interface of the mother glass of apatite-wollastonite containing glass-ceramics (designated AW) and bone tissue. The dissolution of Si, Ca, and P from glass (MgO-CaO-SiO2-P2O5-CaF2) is necessary to form a chemical film (a Si layer and a Ca-P layer). The three kinds of glasses used were 1) a mirror surface of the mother glass (MgO 4.6, CaO 44.9, SiO2 34.2, P2O5 16.3, CaF 0.5 weight ratio) of AW (designated G-AW (mirror], 2) an abraded surface of G-AW (designated G-AW (#2000)), 3) a mirror surface SiO2 glass (designated G-Si, 100% SiO2). The glass plates (15 mm x 10 mm x 2 mm) were implanted into the metaphysis of tibia of mature male rabbits for 10 and 25 weeks. The failure load, when an implant detached from the bone or when the bone itself broke, was measured by a detaching test and the interface of glass/bone was observed by SEM-EPMA. Failure loads in G-Si, G-AW (mirror), and G-AW (#2000) 10 weeks after implantation were 0.18 +/- 0.24, 3.06 +/- 1.29, and 2.94 +/- 1.77 kg, respectively. Those in G-Si, G-AW (mirror), and G-AW (#2000) 25 weeks after implantation were 1.30 +/- 1.18, 3.88 +/- 1.06, and 3.55 +/- 1.51, respectively. The failure loads in G-Si vs. G-AW (mirror) and those in G-Si vs. G-AW (#2000) differed significantly (P less than 0.01). There were no significant differences in the failure load according to the surface roughness of G-AW. As shown by SEM-EPMA observation, a Si layer next to G was adjacent to a Ca-P layer next to the bone. The chemical film showed no increase in thickness as time passed. A Ca-P layer did not form on the interface of Si-G and bone.

  2. Materials Data on LaF3 (SG:225) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  3. Materials Data on LaF3 (SG:67) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Particle Morphology Effects on Flow Characteristics of PS304 Plasma Spray Coating Feedstock Powder Blend

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; DellaCorte, Christopher; Eylon, Daniel

    2002-01-01

    The effects of BaF2-CaF 2 particle morphology on PS304 feedstock powder flow ability have been investigated. BaF2-CaF2 eutectic powders were fabricated by comminution (angular) and by gas atomization (spherical). The fluoride powders were added incrementally to the other powder constituents of the PS304 feedstock: nichrome, chromia, and silver powders. A linear relationship between flow time and concentration of BaF2-CaF2 powder was found. Flow of the powder blend with spherical BaF2-CaF2 was better than the angular BaF2-CaF2. Flow ability of the powder blend with angular fluorides decreased linearly with increasing fluoride concentration. Flow of the powder blend with spherical fluorides was independent of fluoride concentration. Results suggest that for this material blend, particle morphology plays a significant role in powder blend flow behavior, offering potential methods to improve powder flow ability and enhance the commercial potential. These findings may have applicability to other difficult-to-flow powders such as cohesive ceramics.

  5. Particle Size Effects on Flow Properties of PS304 Plasma Spray Feedstock Powder Blend

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; DellaCorte, Christopher; Eylon, Daniel

    2002-01-01

    The effects of BaF2-CaF2 particle size and size distribution on PS304 feedstock powder flowability have been investigated. Angular BaF2-CaF2 eutectic powders were produced by comminution and classified by screening to obtain 38 to 45 microns 45 to 106 microns, 63 to 106 microns, 45 to 53 microns, 63 to 75 microns, and 90 to 106 microns particle size distributions. The fluorides were added incrementally from 0 to 10 wt% to the other powder constituents of the PS304 feedstock: nichrome, chromia, and silver powders. The flow rate of the powder blends decreased linearly with increasing concentration of the fluorides. Flow was degraded with decreasing BaF2-CaF2 particle size and with increasing BaF2-CaF2 particle size distribution. A semiempirical relationship is offered to describe the PS304 powder blend flow behavior. The Hausner Ratio confirmed the funnel flow test results, but was slightly less sensitive to differences in BaF2-CaF2 particle size and size distribution. These findings may have applicability to other powders that do not flow easily, such as ceramic powders.

  6. Pulsed periodic laser excitation of upconversion luminescence for deep biotissue visualization

    NASA Astrophysics Data System (ADS)

    Pominova, D. V.; Ryabova, A. V.; Linkov, K. G.; Romanishkin, I. D.; Kuznetsov, S. V.; Rozhnova, J. A.; Konov, V. I.; Loschenov, V. B.

    2016-08-01

    Emission spectral properties and quantum efficiency of upconversion particles NaYF4, SrF2, LaF3, BaF2 i CaF2, doped with rare earth ions pair Yb3+-Er3+ were studied using continuous wave (CW) and pulsed periodic excitation modes in the near infrared (NIR) spectral range. Analysis of the obtained results showed that the intensity ratio of upconversion luminescence in green and red spectral ranges depends on excitation pulse duration. Thus, by changing the pulse duration the spectral properties of upconversion luminescence can be controlled. Crystals with higher phonon energy are more sensitive to the change of pumping mode. Interpretation of results was performed on the rate equation model basis. Using numerical methods for all energy levels involved in the upconversion process the population and depopulation dynamics were obtained with respect to the duration of the excitation pulses. It was shown that about 30 ms was required for the complete population of 4F9/2 state, from which the luminescence in the red spectral range occurs. When the pulse duration was less than 30 ms, the 4F9/2 population did not reach a steady state and the intensity of the luminescence in the red part of the spectrum was reduced. The theoretical dependence of the upconversion luminescence intensity in the green and red ranges of the excitation pulse duration for NaYF4:Yb0.2-Er0.02 composition was obtained and demonstrates good agreement with the experimental results.

  7. Crystallization of heavy metal fluoride glasses

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Bruce, Allan J.; Doremus, R. H.; Moynihan, C. T.

    1984-01-01

    The kinetics of crystallization of a number of fluorozirconate glasses were studied using isothermal and dynamic differential scanning calorimetry and X-ray diffraction. The addition of the fluorides LiF, NaF, AlF3, LaF3 to a base glass composition of ZrF4-BaF2 reduced the tendency to crystallize, probably by modifying the viscosity-temperature relation. ZrF4-BaF2-LaF3-AlF3-NaF glass was the most stable against devitrification and perhaps is the best composition for optical fibers with low scattering loss. Some glasses first crystallize out into metastable beta-BaZr2F10 and beta-BaZrF6 phases, which transform into the most stable alpha-phases when heated to higher temperatures. The size of the crystallites was estimated to be about 600 A from X-ray diffraction.

  8. Formation and Structure of AL(PO3)3 System Glasses,

    DTIC Science & Technology

    1982-08-06

    only the systems con- taining LiF or MgF2 that formed glass. 3) In the four-component systems that only contained NaF, KF, Ca?2 , SrF2 , or BaF2...a joining effect upon networks. Other single valued and dual valued chemicals such as NaF, KF, CaF2, SrF2 9 and BaF2 , belong to the out- er part of

  9. A Study of Mechanochemical Doping of Fluoride Crystals with a Fluorite Structure by Er3+ Ions via Electron Paramagnetic Resonance Spectra

    NASA Astrophysics Data System (ADS)

    Irisova, I. A.; Rodionov, A. A.; Tayurskii, D. A.; Yusupov, R. V.

    2014-05-01

    Using electron paramagnetic resonance (EPR) spectroscopy, we have shown that, upon mecha- noactivated doping of powders of compounds CaF2, SrF2, and BaF2 with Er3+ ions, impurity centers of single erbium ions with cubic symmetry are formed. Investigations of dependences of EPR spectra intensities on the particle size show that the process of mechanochemical doping with Er3+ ions proceeds differently for CaF2, SrF2, and BaF2 host matrices. In the case of CaF2, impurity centers are localized in a very thin near-surface layer of CaF2 particles, in SrF2, the impurity is distributed over the volume of particles, while, in BaF2, there is a layer of a finite thickness for which the probability of doping in the course of mechanosynthesis is very small and the impurity of the rare-earth element is localized in the core of large particles. These data can be explained assuming that the result of mechanosynthesis of particles of fluorides with a fluorite structure doped with Er3+ ions at room temperature is governed by two processes—mechanoactivated diffusion of rare-earth ions into particles and segregation of impurity ions at grain boundaries. In this case, the typical scales for compounds CaF2, SrF2, and BaF2 considerably differ from each other.

  10. Development of infrared sensors using energy transfer/energy upconversion processes: Study of laser excited fluorescence in rare Earth ion doped crystals

    NASA Technical Reports Server (NTRS)

    Nash-Stevenson, S. K.; Reddy, B. R.; Venkateswarlu, P.

    1994-01-01

    A summary is presented of the spectroscopic study of three systems: LaF3:Ho(3+), LaF3:Er(3+) and CaF2:Nd(3+). When the D levels of Ho(3+) in LaF3 were resonantly excited with a laser beam of 640 nm, upconverted emissions were detected from J (416 nm), F (485 nm), and E (546 nm) levels. Energy upconverted emissions were also observed from F and E levels of Ho(3+) when the material was excited with an 800 nm near infrared laser. When the D levels of Er(3+) in LaF3 were resonantly excited with a laser beam of 637 nm, upconverted emissions were detected from the E (540 nm) and P (320, 400, and 468 nm) levels. Energy upconverted emissions were also observed from F, E, and D levels of Er(3+) when the material was resonantly excited with an 804 nm near infrared laser. When the D levels of Nd(3+) in CaF2 were resonantly excited with a laser beam of 577 nm, upconverted emissions were detected from the L (360 and 382 nm), K (418 nm), and I (432 nm) levels. Very weak upconverted emissions were detected when this system was irradiated with a near infrared laser. The numbers in parentheses are the wavelengths of the emissions.

  11. Thermal Effects on a Low Cr Modification of PS304 Solid Lubricant Coating

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; Yanke, Anne M.; DellaCorte, Christopher

    2004-01-01

    PS304 is a high temperature composite solid lubricant coating composed of Ni-Cr, Cr2O3, BaF2-CaF2 and Ag. The effect of reducing chromium content on the formation of voids in the Ni-Cr particles after heat treatment in PS304 coating was investigated. Coatings were prepared with Ni-20Cr or Ni-10Cr powder and in various combinations with the other constituents of PS304 (i.e., chromia, silver and eutectic BaF2-CaF2 powders) and deposited on metal substrates by plasma spray. Specimens were exposed to 650 C for 24 hr or 1090 C for 15 hr and then examined for changes in thickness, coating microstructure and adhesion strength. Specimens with Ni-10Cr generally had less thickness increase than specimens with Ni-20Cr, but there was great variance in the data. Reduction of chromium concentration in Ni-Cr powder tended to reduce the appearance of voids in the Ni-Cr phase after heat exposure. The presence of BaF2-CaF2 resulted in a significant increase in coating adhesion strength after heat treatment, while coatings without BaF2-CaF2 had no significant change. Chemical composition analysis suggested that the void formation was due to oxidation of chromium in the Ni-Cr constituent.

  12. 5 d-4 f luminescence of Nd3+, Gd3+, Er3+, Tm3+, and Ho3+ ions in crystals of alkaline earth fluorides

    NASA Astrophysics Data System (ADS)

    Radzhabov, E. A.; Prosekina, E. A.

    2011-09-01

    The vacuum ultraviolet emission spectra of alkaline-earth fluoride (CaF2, SrF2, BaF2) crystals with rare earth impurity ions (Nd, Gd, Er, Tm, Ho) have been investigated. The main luminescence bands are described well by the transitions from the lowest excited 5 d state to different 4 f levels of rare earth ions.

  13. Versatile fluoride substrates for Fe-based superconducting thin films

    NASA Astrophysics Data System (ADS)

    Kurth, F.; Reich, E.; Hänisch, J.; Ichinose, A.; Tsukada, I.; Hühne, R.; Trommler, S.; Engelmann, J.; Schultz, L.; Holzapfel, B.; Iida, K.

    2013-04-01

    We demonstrate the growth of Co-doped BaFe2As2 (Ba-122) thin films on CaF2 (001), SrF2 (001), and BaF2 (001) single crystal substrates using pulsed laser deposition. All films are grown epitaxially despite of a large misfit of -10.6% for BaF2 substrate. For all films, a reaction layer is formed at the interface confirmed by X-ray diffraction and for the films grown on CaF2 and BaF2 additionally by transmission electron microscopy. The superconducting transition temperature of the film on CaF2 is around 27 K, whereas the corresponding values of the films on SrF2 and BaF2 are around 22 K and 21 K, respectively. The Ba-122 on CaF2 shows almost identical crystalline quality and superconducting properties as films on Fe-buffered MgO.

  14. The Effects of a Magnetic Field on the Crystallization of a Fluorozirconate Glass

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Lapointe, Michael R.; Jia, Zhiyong

    2006-01-01

    An axial magnetic field of 0.1T was applied to ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fibers during heating to the glass crystallization temperature. Scanning electron microscopy and x-ray diffraction were used to identify crystal phases. It was shown that fibers exposed to the magnetic field did not crystallize while fibers not exposed to the field did crystallize. A hypothesis based on magnetic work was proposed to explain the results and tested by measuring the magnetic susceptibilities of the glass and crystal.

  15. Effects of Gravity on ZBLAN Glass Crystallization

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Ethridge, Edwin C.; Smith, G. A.; Workman, G.

    2003-01-01

    The effects of gravity on the crystallization of ZrF4-BaF2-LaF3-AlF3- NaF glasses have been studied utilizing NASA's KC135 and a sounding rocket, Fibers and cylinders of ZBLAN glass were heated to the crystallization temperature in unit and reduced gravity. When processed in unit gravity the glass crystallized, but when processed in reduced gravity, crystallization was suppressed. A possible explanation involving shear thinning is presented to explain these results.

  16. Optical and Mechanical Properties of Infrared Materials.

    DTIC Science & Technology

    1980-07-01

    Eagle- Picher Co. The crystals were grown under an inert gas pressure by using a modified Bridgeman technique. The ingots are polycrystalline with large...ZnSe:Al samples which were annealed under different Se pressures (see part III-A of this report) prior to Li diffusion showed bands after Li diffusion which...grains CaF2 + 0.1% Gd 3+Optovac Crystal CaF2 + 1.0% Gd 3 + ofofo CaF2 + 1.0% Ce3+iiso SrF2 + 1.0% Gd 3 ifofo BaF2 + 1.0% Gd 3+ ’ tII CaF2 + Th 3

  17. Water Atomization of Barium Fluoride: Calcium Fluoride for Enhanced Flow Characteristics of PS304 Feedstock Powder Blend

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; DellaCorte, Christopher

    2003-01-01

    PS304 is a plasma spray deposited solid lubricant coating with feedstock composed of NiCr, Cr2O3, Ag, and BaF2-CaF2 powders. The effects of rounded BaF2-CaF2 particles on the gravity-fed flow characteristics of PS304 feedstock have been investigated. The BaF2-CaF2 powder was fabricated by water atomization using four sets of process parameters. Each of these powders was then characterized by microscopy and classified by screening to obtain 45 to 106 micron particles and added incrementally from 0 to 10 wt% to the other constituents of the PS304 feedstock, namely nichrome, chromia, and silver powders. The relationship between feedstock flow rate, measured with the Hall flowmeter, and concentration of fluorides was found to be linear in each case. The slopes of the lines were between those of the linear relationships previously reported using angular and spherical fluorides and were closer to the relationship predicted using the rule of mixtures. The results offer a fluoride fabrication technique potentially more cost-effective than gas atomization processes or traditional comminution processes.

  18. An overview of DANCE: a 4II BaF[2] detector for neutron capture measurements at LANSCE.

    SciTech Connect

    Ullmann, J. L.

    2004-01-01

    The Detector for Advanced Neutron Capture experiments (DANCE) is a 162-element, 4{pi} BaF{sub 2} array designed to make neutron capture cross-section measurements on rare or radioactive targets with masses as little as 1 mg. Accurate capture cross sections are needed in many research areas, including stellar nucleosynthesis, advanced nuclear fuel cycles, waste transmutation, and other applied programs. These cross sections are difficult to calculate accurately and must be measured. Up to now, except for a few long-lived nuclides there are essentially no differential capture measurements on radioactive nuclei. The DANCE array is located at the Lujan Neutron Scattering Center at LANSCE, which is a continuous-spectrum neutron source with useable energies from below thermal to about 100 keV. Data acquisition is done with 320 fast waveform digitizers. The design and initial performance results, including background minimization, will be discussed.

  19. New observations on the pressure dependence of luminescence from Eu2+-doped MF2 (M = Ca, Sr, Ba) fluorides.

    PubMed

    Su, Fu Hai; Chen, Wei; Ding, Kun; Li, Guo Hua

    2008-05-29

    The luminescence from Eu(2+) ions in MF2 (M = Ca, Sr, Ba) fluorides has been investigated under the pressure range of 0-8 GPa. The emission band originating from the 4f(6)5d(1) --> 4f(7) transition of Eu(2+) ions in CaF2 and SrF2 shows the red-shift as increasing pressure with pressure coefficients of -17 meV/GPa for CaF2 and -18 meV/GPa for SrF2. At atmospheric pressure, the emission spectrum of BaF2:Eu(2+) comprises two peaks at 2.20 and 2.75 eV from the impurity trapped exciton (ITE) and the self-trapped exciton (STE), respectively. As the pressure is increased, both emission peaks shift to higher energies, and the shifting rate is slowed by the phase transition from the cubic to orthorhombic phase at 4 GPa. Due to the phase transition at 4-5 GPa pressure, the ITE emission disappears gradually, and the STE emission is gradually replaced by the 4f(6)5d(1) --> 4f(7) transition of Eu(2+). Above 5 GPa, the pressure behavior of the 4f(6)5d(1) --> 4f(7) transition of Eu(2+) in BaF2:Eu(2+) is the same as the normal emission of Eu(2+) in CaF2 and SrF2 phosphors.

  20. Spectroscopic, luminescent and laser properties of nanostructured CaF2:Tm materials

    NASA Astrophysics Data System (ADS)

    Lyapin, A. A.; Fedorov, P. P.; Garibin, E. A.; Malov, A. V.; Osiko, V. V.; Ryabochkina, P. A.; Ushakov, S. N.

    2013-08-01

    The laser quality transparent СаF2:Tm fluoride ceramics has been prepared by hot forming. Comparative study of absorption and emission spectra of СаF2:Tm (4 mol.% TmF3) ceramic and single crystal samples demonstrated that these materials possess almost identical spectroscopic properties. Laser oscillations of СаF2:Tm ceramics were obtained at 1898 nm under diode pumping, with the slope efficiency of 5.5%. Also, the continuous-wave (CW) laser have been obtained for СаF2:Tm single crystal at 1890 nm pumped by a diode laser was demonstrated.

  1. Biomedical graphite and CaF2 preparation and measurement at PRIME Lab

    NASA Astrophysics Data System (ADS)

    Jackson, George S.; Einstein, Jane A.; Kubley, Tom; Martin, Berdine; Weaver, Connie M.; Caffee, Marc

    2015-10-01

    The biomedical program at PRIME Lab has prepared radiocarbon and 41Ca as tracers for a variety of applications. Over the last decade several hundred 14C samples and several thousand 41Ca samples have been measured per year. Biomedical samples pose challenges that are relatively rare in the AMS community. We will discuss how to prepare and compensate for samples that have isotope ratios above the dynamic range of AMS, high interference rates, and small samples sizes. In the case of 41Ca, the trade off in the chromatography between yield and sample cleanliness will be analyzed. Secondary standards that have isotope ratios commonly encountered in our applications are routinely prepared. We use material from the Joint Research Centre's Institute for Reference Materials and Measurement: IRMM-3701/4, 3701/5, and 3701/6 and a standard produced by PRIME Lab for 41Ca. We use International Atomic Energy Agency's IAEA C-3, IAEA C-7, IAEA C-8, and a ∼12.5× modern oxalic acid secondary standard supplied by Lawrence Livermore National Laboratory for 14C. We will discuss our precision, reproducibility, and the relative agreement between our measured and the reported values for these materials.

  2. Zeeman effect in CaF(2Pi(3/2)).

    PubMed

    Krems, R V; Egorov, D; Helton, J S; Maussang, K; Nguyen, S V; Doyle, J M

    2004-12-15

    The Zeeman effect in the excited A 2Pi(3/2) state of CaF is measured and analyzed over a wide range of magnetic fields. It is found that the splitting of the Zeeman levels is largely determined by the coupling between different rotational states and there are no low-field seeking states in the J=3/2 manifold of Zeeman levels at high magnetic fields. A model of the Zeeman spectrum based on the ligand-field theory of CaF is shown to be accurate in the interval of magnetic fields 0-5 Tesla. This demonstrates that the magnetic moment of the CaF(A 2Pi(3/2)) molecule is effectively determined by the spin angular momentum of a single electron and the orbital motion of the valence electron around the Ca2+ core. An analysis of the Zeeman spectrum as a function of the molecular rotational constant indicates that 2Pi(3/2) molecules should have significant rotational constants (at least as large as twice the rotational constant of CaF) to be amenable to magnetic trapping in high fields.

  3. Phase diagram for nanostructuring CaF(2) surfaces by slow highly charged ions.

    PubMed

    El-Said, A S; Wilhelm, R A; Heller, R; Facsko, S; Lemell, C; Wachter, G; Burgdörfer, J; Ritter, R; Aumayr, F

    2012-09-14

    The impact of individual slow highly charged ions (HCI) on alkaline earth halide and alkali halide surfaces creates nano-scale surface modifications. For different materials and impact energies a wide variety of topographic alterations have been observed, ranging from regularly shaped pits to nanohillocks. We present experimental evidence for the creation of thermodynamically stable defect agglomerations initially hidden after irradiation but becoming visible as pits upon subsequent etching. A well defined threshold separating regions with and without etch-pit formation is found as a function of potential and kinetic energies of the projectile. Combining this novel type of surface defects with the previously identified hillock formation, a phase diagram for HCI induced surface restructuring emerges. The simulation of the energy deposition by the HCI in the crystal provides insight into the early stages of the dynamics of the surface modification and its dependence on the kinetic and potential energies.

  4. Fluoride glass starting materials - Characterization and effects of thermal treatment

    NASA Technical Reports Server (NTRS)

    Chen, William; Dunn, Bruce; Shlichta, Paul; Neilson, George F.; Weinberg, Michael C.

    1987-01-01

    The production of heavy metal fluoride (HMF) glasses, and the effects of thermal treatments on the HMF glasses are investigated. ZrF4, BaF2, AlF3, LaF3, and NaF were utilized in the synthesis of zirconium-barium-lanthanum-aluminum-sodium fluoride glass. The purity of these starting materials, in particular ZrF4, is evaluated using XRD analysis. The data reveal that low temperature heating of ZrF4-H2O is effective in removing the water of hydration, but causes the production of ZrF4 and oxyfluorides; however, dehydration followed by sublimation results in the production of monoclinic ZrFe without water or oxyfluoride contaminants.

  5. Advances in Laser Cooling of Thulium-Doped Glass

    DTIC Science & Technology

    2003-05-01

    Yb31-doped KGd(WO4)2 crystal. 12 Epstein et al. observed bulk cool- ing in Yb31: YAG , recording a net sample temperature change of ;8.9 K below room...energy hn f 2 hn for each absorbed photon. Table 1. Data Analysisa Sample Dimensions (mm) Doping (wt.%) h q̃ ab (cm 21) kfit (cm K/W) kcalc Tm A 4 3...4 3 8 1 0.99 0.0002 591 825 Tm B 3 3 3 3 10 2 0.975 0.0004 1002 1224 a Tm31:ZBLANP (ZrF4-BaF2-LaF3-AlF3-NaF-PbF2) sample parameters for the 3H6 → 3F4

  6. Use of space to commercially produce ZBLAN optical fibers

    NASA Astrophysics Data System (ADS)

    Tucker, Dennis S.; Workman, Gary L.; Smith, Guy A.

    1996-03-01

    Construction of the International Space Station Alpha (ISSA) will provide a platform not only for materials research but also a possible means to produce products in space which cannot be easily produced on the ground. Some products may even be superior to those now produced in 1g due to the lack of gravity induced convection effects. One such product is ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) glass. At the present time this material is being produced on earth in fiber optic form for use in surgical lasers and fiber optic lasers. High attenuation coefficients, however, have kept this material from being used in other applications such as long haul data transmission links. The high attenuation is due to impurities which can be removed through improved processing techniques and crystals which can only be removed or prevented from forming by processing ZBLAN in a microgravity environment.

  7. Blue Up-Conversion Fibre Laser Pumped by a 1120-nm Raman Fibre Laser

    NASA Astrophysics Data System (ADS)

    Qin, Guan-Shi; Huang, Sheng-Hong; Feng, Yan; Shirakawa, A.; Musha, M.; Ueda, Ken-ichi

    2005-05-01

    A Tm3+-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fibre up-conversion laser pumped by a 1120-nm Raman fibre laser is demonstrated with blue output power levels up to 116 mW. For the output mirror with 80% reflectivity, the slope efficiency is about 15%, the optical-to-optical conversion efficiency is 11%, and the maximum un-saturated output power is 116 mW. For 60% reflectivity, the slope efficiency is about 18% and the optical-to-optical conversion efficiency is 12%, whilst the maximum saturated output power is about 80 mW due to the existence of photo-degradation effect in Tm3+ doped ZBLAN glass fibre.

  8. Graphene Q-switched Ho(3+)-doped ZBLAN fiber laser at 1190  nm.

    PubMed

    Liu, Shujing; Zhu, Xiushan; Zhu, Gongwen; Balakrishnan, Kaushik; Zong, Jie; Wiersma, Kort; Chavez-Pirson, Arturo; Norwood, R A; Peyghambarian, N

    2015-01-15

    We report Q-switched pulse operation of holmium (Ho(3+))-doped ZrF(4)-BaF(2)-LaF(3)-AlF(3)-NaF (ZBLAN) at ∼1190  nm in an all-fiber ring laser by using a fiber-optic graphene saturable absorber, which was fabricated by depositing graphene onto the flat surface of a side-polished D-shaped fiber. Stable Q-switched operation was established at a pump power of 180 mW with a repetition rate of 24 kHz and pulse width of 5.7 μs. When the pump power was increased to 1125 mW, 0.44 μJ Q-switched pulses with a repetition rate of 111 kHz and a pulse width of 0.8 μs were generated.

  9. Efficient chirped-pulse amplification based on thulium-doped ZBLAN fibers

    NASA Astrophysics Data System (ADS)

    Nomura, Yutaka; Fuji, Takao

    2017-01-01

    We demonstrate a chirped-pulse amplifier system operating around 1900 nm using thulium-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fibers. The pulses from a thulium-doped ZBLAN fiber laser oscillator are stretched by a passive ZBLAN fiber and subsequently amplified in a double-clad thulium-doped ZBLAN fiber to an average power of 6.9 W at a pump power of 17 W. We found that ZBLAN fibers require a much lower pump and/or seed power than silica fibers for efficient amplification. The amplified pulses are compressed to a duration of 150 fs with an average power of 3.9 W.

  10. Low Gravity Rapid Thermal Analysis of Glass

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Ethridge, Edwin C.; Smith, Guy A.

    2004-01-01

    It has been observed by two research groups that ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) glass crystallization is suppressed in microgravity. The mechanism for this phenomenon is unknown at the present time. In order to better understand the mechanism, an experiment was performed on NASA's KC135 reduced gravity aircraft to obtain quantitative crystallization data. An apparatus was designed and constructed for performing rapid thermal analysis of milligram quantities of ZBLAN glass. The apparatus employs an ellipsoidal furnace allowing for rapid heating and cooling. Using this apparatus nucleation and crystallization kinetic data was obtained leading to the construction of time-temperature-transformation curves for ZBLAN in microgravity and unit gravity.

  11. [Effect of bivalent alkaline earth fluorides introduction on thermal stability and spectroscopic properties of Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses].

    PubMed

    Hu, Yue-bo; Zhang, Xin-na; Zhou, Da-li; Jiao, Qing; Wang, Rong-fei; Huang, Jin-feng; Long, Xiao-bo; Qiu, Jian-bei

    2012-01-01

    Transparent Er3+/Tm3+ /Yb3+ co-doped oxyfluorogermanate glasses alone containing MgF2, CaF2, SrF2 or BaF2 and nano-glass-ceramics only containing BaF2 were prepared. The thermal stabilities and the up-conversion emission properties of the samples were investigated. Analyses of absorbance spectra reveal that the UV cutoff band moves slightly to shortwave band with the doping bivalent cation mass increasing. The results show that the emission color can be adjusted by changing the alkaline earth cation species in the glass matrixes, especially as Mg2+ is concerned, and the emission intensity can increase notably by heating the glass containing alkaline-earth fluoride into glass ceramic containing alkaline-earth fluoride nanocrystals or increasing the content of bivalent alkaline earth fluorides.

  12. Catalog of infrared and cryo-optical properties for selected materials

    NASA Technical Reports Server (NTRS)

    Heaney, James B.; Alley, Phillip W.; Bradley, Scott E.

    1991-01-01

    This report will describe the status of an effort to catalog the refractive index, absorption, reflectance and transmittance of selected IR transmitting materials over the wavelength range from 1 to 1000 microns, and at temperatures from 300 to about 2 K. Data are presented for LiF, CaF2, BaF2, KBr, and TlBr, as well as for KRS-5 (TlBr-I) and KRS-6 (TlBr-Cl). A cryooptical measurements facility at NASA-Goddard, which has been used to generate some of the cataloged data, is also described.

  13. Laser Materials Search and Characterization

    DTIC Science & Technology

    2014-05-30

    digital form using a PC. In addition to unique color-centers tunable lasers, the team used other laser excitation sources: CW and pulsed neodymium lasers...obtained crystals are measured upon excitation by a neodymium YAG laser at a wavelength of 1.319 m. The luminescence kinetics of dysprosium ions in...investigations of the optical properties of bismuth ions Single crystals of CaF2, SrF2, BaF2 and their solid solutions doped with rare-earth neodymium

  14. Optical properties of PbS/CdS superlattices grown by pulsed laser evaporation

    NASA Astrophysics Data System (ADS)

    Musikhin, Sergey F.; Bakueva, Ludmila G.; Il'in, Vladimir I.; Rabizo, Oleg V.; Sharonova, Larissa V.

    1994-06-01

    PbS/CdS superlattices have been grown on BaF 2, CaF 2, Si and glass subtrates. Each specimen contained 10 to 23 pairs of the PbS/CdS layers. Absorption spectra of the structures have shown specific steps. The energy distribution of the steps has been analysed using models of Tipe-I and Tipe-II superlattices. Experimental results have been shown to follow the theoretical values of the steps for Tipe-II superlattices. This gives a foundation for classifying PbS/CdS superlattices as Tipe-II.

  15. Joint NOSC/NRL (Naval Ocean Systems Center/Naval Research Laboratory) InP Microwave/Millimeter Wave Technology Workshop Held in San Diego, California on 25-26 January 1989

    DTIC Science & Technology

    1989-12-01

    California, on 25 and 26 January 1989. Released by Under authority of L. J. Messick H. E. Rast, Head Material and Device Electronic Material Technology...Dielectrics) * II-A FLUORIDES (CaF2, BaF2 , SrF2 and their mixtures) e LATTICE MATCH TO MOST IMPORTANT SEMICON- DUCTORS (Slight mismatch can be used for...AlInAs grown with low Arsenic over- pressure Vd=l.SV, V - -1.2V, Id=265mA/mm 100gm gate width, R5 =0.S5 -mm 6140 .89 L3n4 ’,,]-I:5 ,G-.6 I=20.5 IOL. 32

  16. Theoretical study of Ti0 and Pb+ centers in alkali halide and alkaline earth fluoride type crystals

    NASA Astrophysics Data System (ADS)

    Andriessen, J.; Postma, H.

    1987-04-01

    A theoretical study has been carried out on the hfi of Pb+ defects in KCl, CaF2 and BaF2 using an earlier developed crystal field model. Experimental results can be explained in the same way as was done for Tl0 in KCl. However some parameters seem to have a less physical meaning than in the case of Tl0. A new method is in progress using the ASW band structure procedure in order to estimate genuine solid state effects. Preliminary results are encouraging.

  17. Spatial inhomogeneity in crystalline materials and saddle-type congruent melting points in ternary systems

    NASA Astrophysics Data System (ADS)

    Fedorov, P. P.; Buchinskaya, Irina I.

    2012-01-01

    Solidification of multicomponent melts to solid solutions is considered in terms of thermodynamic topological analysis. The use of phase portraits of systems for finding congruent melting points (invariant points) is discussed. Methods for predicting the existence of invariant points in ternary systems are considered. An example analysis is presented for two series of fluoride systems (CaF2-SrF2-RF3 and SrF2-BaF2-RF3, where R are rare-earth elements). The stability of melt crystallization in the vicinity of congruent melting singular points of solid solutions is discussed. The bibliography includes 104 references.

  18. CdF2:Er(3+)/Si(111) Heterostructure For EL Displays

    DTIC Science & Technology

    1997-01-01

    temperature reduced epitaxy onto pre-made device structures. In principle , II-a and II-b group fluoride film growth on a semiconductor substrate (mainly, on...Review: Main Results on Growth of II-a and IT-b Fluorides on Semiconductor Substrates Recently, group II-a cubic fluorides, CaF2, SrF2 and BaF2, have...If such single-crystalline lattice-matched dielectric films can be grown on a semiconductor substrate, the interface trap densities, in principle

  19. Spectroscopic properties and energy transfer parameters of Er3+- doped fluorozirconate and oxyfluoroaluminate glasses

    PubMed Central

    Huang, Feifei; Liu, Xueqiang; Hu, Lili; Chen, Danping

    2014-01-01

    Er3+- doped fluorozirconate (ZrF4-BaF2-YF3-AlF3) and oxyfluoroaluminate glasses are successfully prepared here. These glasses exhibit significant superiority compared with traditional fluorozirconate glass (ZrF4-BaF2-LaF3-AlF3-NaF) because of their higher temperature of glass transition and better resistance to water corrosion. Judd-Ofelt (J-O) intensity parameters are evaluated and used to compute the radiative properties based on the VIS-NIR absorption spectra. Broad emission bands located at 1535 and 2708 nm are observed, and large calculated emission sections are obtained. The intensity of 2708 nm emission closely relates to the phonon energy of host glass. A lower phonon energy leads to a more intensive 2708 nm emission. The energy transfer processes of Er3+ ions are discussed and lifetime of Er3+: 4I13/2 is measured. It is the first time to observe that a longer lifetime of the 4I13/2 level leads to a less intensive 1535 nm emission, because the lifetime is long enough to generate excited state absorption (ESA) and energy transfer (ET) processes. These results indicate that the novel glasses possess better chemical and thermal properties as well as excellent optical properties compared with ZBLAN glass. These Er3+- doped ZBYA and oxyfluoroaluminate glasses have potential applications as laser materials. PMID:24852112

  20. Spectroscopic properties and energy transfer parameters of Er3+-doped fluorozirconate and oxyfluoroaluminate glasses.

    PubMed

    Huang, Feifei; Liu, Xueqiang; Hu, Lili; Chen, Danping

    2014-05-23

    Er3+-doped fluorozirconate (ZrF4-BaF2-YF3-AlF3) and oxyfluoroaluminate glasses are successfully prepared here. These glasses exhibit significant superiority compared with traditional fluorozirconate glass (ZrF4-BaF2-LaF3-AlF3-NaF) because of their higher temperature of glass transition and better resistance to water corrosion. Judd-Ofelt (J-O) intensity parameters are evaluated and used to compute the radiative properties based on the VIS-NIR absorption spectra. Broad emission bands located at 1535 and 2708 nm are observed, and large calculated emission sections are obtained. The intensity of 2708 nm emission closely relates to the phonon energy of host glass. A lower phonon energy leads to a more intensive 2708 nm emission. The energy transfer processes of Er3+ ions are discussed and lifetime of Er3+:4I13/2 is measured. It is the first time to observe that a longer lifetime of the 4I13/2 level leads to a less intensive 1535 nm emission, because the lifetime is long enough to generate excited state absorption (ESA) and energy transfer (ET) processes. These results indicate that the novel glasses possess better chemical and thermal properties as well as excellent optical properties compared with ZBLAN glass. These Er3+-doped ZBYA and oxyfluoroaluminate glasses have potential applications as laser materials.

  1. Spectroscopic properties and energy transfer parameters of Er3+- doped fluorozirconate and oxyfluoroaluminate glasses

    NASA Astrophysics Data System (ADS)

    Huang, Feifei; Liu, Xueqiang; Hu, Lili; Chen, Danping

    2014-05-01

    Er3+- doped fluorozirconate (ZrF4-BaF2-YF3-AlF3) and oxyfluoroaluminate glasses are successfully prepared here. These glasses exhibit significant superiority compared with traditional fluorozirconate glass (ZrF4-BaF2-LaF3-AlF3-NaF) because of their higher temperature of glass transition and better resistance to water corrosion. Judd-Ofelt (J-O) intensity parameters are evaluated and used to compute the radiative properties based on the VIS-NIR absorption spectra. Broad emission bands located at 1535 and 2708 nm are observed, and large calculated emission sections are obtained. The intensity of 2708 nm emission closely relates to the phonon energy of host glass. A lower phonon energy leads to a more intensive 2708 nm emission. The energy transfer processes of Er3+ ions are discussed and lifetime of Er3+: 4I13/2 is measured. It is the first time to observe that a longer lifetime of the 4I13/2 level leads to a less intensive 1535 nm emission, because the lifetime is long enough to generate excited state absorption (ESA) and energy transfer (ET) processes. These results indicate that the novel glasses possess better chemical and thermal properties as well as excellent optical properties compared with ZBLAN glass. These Er3+- doped ZBYA and oxyfluoroaluminate glasses have potential applications as laser materials.

  2. Pressure induced structural and magnetic phase transition in magnesium nitrides MgNx (x = 1, 2, 3): A first principles study

    NASA Astrophysics Data System (ADS)

    Rajeswarapalanichamy, R.; Sudhapriyanga, G.; Cinthia, A. Jemmy; Santhosh, M.; Murugan, A.

    2014-04-01

    The structural and magnetic properties of magnesium nitrides are investigated by the first principles calculations based on density functional theory using Vienna ab-initio simulation package. The calculated lattice parameters are in good agreement with the available results. A pressure-induced structural phase transition from NaCl to CsCl in MgN, CaF2 to AlB2 in MgN2 and LaF3 to BiF3 phase in MgN3 is observed. At ambient condition MgN and MgN3 are stable in the ferromagnetic state. On further increasing the pressure, a ferromagnetic to non magnetic transition is observed in MgN.

  3. Simultaneous measurement of (n,{gamma}) and (n,fission) cross sections with the DANCE 4{pi} BaF2 array

    SciTech Connect

    Bredeweg, T. A.; Fowler, M. M.; Bond, E. M.; Chadwick, M. B.; Hunt, L. F.; O'Donnell, J. M.; Rundberg, R. S.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Becker, J. A.; Clement, R. R. C.; Esch, E.-I.; Macri, R. A.; Wu, C.-Y.; Ethvignot, T.; Granier, T.; Yurkon, J. E.

    2006-03-13

    Neutron capture cross section measurements on many of the actinides are complicated by low-energy neutron-induced fission, which competes with neutron capture to varying degrees depending on the nuclide of interest. Measurements of neutron capture on 235U using the Detector for Advanced Neutron Capture Experiments (DANCE) have shown that we can partially resolve capture from fission events based on total photon calorimetry (i.e. total {gamma}-ray energy and {gamma}-ray multiplicity per event). The addition of a fission-tagging detector to the DANCE array will greatly improve our ability to separate these two competing processes so that improved neutron capture and (n,{gamma})/(n,fission) cross section ratio measurements can be obtained. The addition of a fission-tagging detector to the DANCE array will also provide a means to study several important issues associated with neutron-induced fission, including (n,fission) cross sections as a function of incident neutron energy, and total energy and multiplicity of prompt fission photons. We have focused on two detector designs with complementary capabilities, a parallel-plate avalanche counter and an array of solar cells.

  4. Evaluation of Advanced Solid Lubricant Coatings for Foil Air Bearings Operating at 25 and 500 C

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher; Fellenstein, James A.; Benoy, Patricia A.

    1998-01-01

    The tribological properties of one chrome oxide and one chrome carbide based solid lubricant coating were evaluated in a partial-arc foil bearing at 25 and 500 C. Start/stop bearing operation up to 20,000 cycles were run under 10 kPa (1.5 psi) static deadweight load. Bearing friction (torque) was measured during the test. Specimen wear and SEM/EDS surface analyses were conducted after testing to understand and elucidate the tribological characteristics observed. The chrome oxide coating which contains both (Ag) and (BaF2/CaF2) for low and high temperature lubrication, exhibited low friction in sliding against Al2O3 coated foils at 25 and 500 C. The chrome carbide coating, which lacked a low temperature lubricant but contained BaF2/CaF2 as a high temperature lubricant, exhibited high friction at 25 C and low friction at 500 C against both bare and Al2O3 coated superalloy foil surfaces. Post test surface analyses suggest that improved tribological performance is exhibited when a lubricant film from the coating transfers to the foil surface.

  5. Tribological and microstructural comparison of HIPped PM212 and PM212/Au self-lubricating composites

    NASA Technical Reports Server (NTRS)

    Bogdanski, Michael S.; Sliney, Harold E.; Dellacorte, Christopher

    1992-01-01

    The feasibility of replacing the silver with the volumetric equivalent of gold in the chromium carbide-based self-lubricating composite PM212 (70 wt. percent NiCo-Cr3C2, 15 percent BaF2/CaF2 eutectic) was studied. The new composite, PM212/Au has the following composition: 62 wt. percent NiCo-Cr3C2, 25 percent Au, 13 percent BaF2/CaF2 eutectic. The silver was replaced with gold to minimize the potential reactivity of the composite with possible environmental contaminants such as sulfur. The composites were fabricated by hot isostatic pressing (HIPping) and machined into pin specimens. The pins were slid against nickel-based superalloy disks. Sliding velocities ranged from 0.27 to 10.0 m/s and temperatures from 25 to 900 C. Friction coefficients ranged from 0.25 to 0.40 and wear factors for the pin and disk were typically low 10(exp -5) cu mm/N-m. HIPped PM212 measured fully dense, whereas PM212/Au had 15 percent residual porosity. Examination of the microstructures with optical and scanning electron microscopy revealed the presence of pores in PM212/Au that were not present in PM212. Though the exact reason for the residual porosity in PM212/Au was not determined, it may be due to particle morphology differences between the gold and silver and their effect on powder metallurgy processing.

  6. Epitaxy versus oriented heterogeneous nucleation of organic crystals on ionic substrates

    NASA Astrophysics Data System (ADS)

    Sarma, K. R.; Shlichta, P. J.; Wilcox, W. R.; Lefever, R. A.

    1997-04-01

    It is plausible to assume that epitaxy is a special case of heterogeneous nucleation in which a restrictive crystallographic relationship exists between substrate and deposit orientations. This would mean that epitaxial substrates should always induce a perceptible reduction in the critical supercooling for nucleation of the deposit. To test this hypothesis, the critical supercoolings of six organic compounds were measured on glass and 11 single-crystal cleaved substrates including (0001) graphite, (001) mica, (111) BaF 2, SrF 2, and CaF 2, and (100) KCl, KBr, KI, NaCl, NaF, and LiF. Reductions in supercooling (with reference to glass substrates) were checked many times for repeatability and reproducibility and shown in almost all cases to have a standard deviation of 1 C or less. Acetanilide, benzoic acid, and p-bromochlorobenzene showed a wide range of supercooling reductions and were oriented on all crystalline substrates. Naphthalene and p-dibromobenzene showed only slight supercooling reductions but were oriented on all substrates, including glass. Benzil showed strong supercooling reductions only for mica and KI but was oriented not only in these cases but also with KI, BaF 2, CaF 2, and graphite. There was little correlation between degree of lattice match and either supercooling reduction or degree of preferred orientation. These results suggest that, for the systems and geometry studied, forces such as molecular dipole binding and growth anisotropy had a stronger effect than lattice match.

  7. A new approach to prepare well-dispersed CaF(2) nanoparticles by spray drying technique.

    PubMed

    Sun, Limin; Chow, Laurence C; Bonevich, John E; Wang, Tongxin; Mitchell, James W

    2011-08-01

    Previously, nano-sized calcium fluoride (CaF₂) particles were prepared using a spray drying method by simultaneously feeding Ca(OH)₂ and NH₄F solutions to a two-liquid nozzle. The aim of the present study was to prepare better-dispersed nano-CaF₂ particles by co-forming a soluble salt, sodium chloride (NaCl). NaCl of various concentrations were added to the NH(4) F solution, leading to formation of (CaF₂ +NaCl) composites with CaF₂ /NaCl molar ratios of 4/1, 4/4, and 4/16. Pure nano-CaF₂ was also prepared as the control. Powder X-ray diffraction analysis showed that the products contained crystalline CaF₂ and NaCl. Scanning electron microscopy examinations showed that both the CaF₂ /NaCl composite and pure CaF₂ particles were about (50-800) nm in size and consisted of primary CaF₂ particles of < 50 nm in size. BET surface area measurements showed similar primary particle sizes for all samples. Dynamic light scattering measurements showed that the washed (CaF₂+NaCl) particles were much smaller than the pure CaF₂ as the dissolution of NaCl "freed" most of the primary CaF₂ particles, leading to a greater degree of particle dispersion. The well-dispersed nano-CaF₂ may be expected to be a more effective anticaries agent than NaF by providing longer lasting elevations of fluoride concentrations in oral fluids.

  8. Investigation of the Environmental Durability of a Powder Metallurgy Material

    NASA Technical Reports Server (NTRS)

    Ward, LaNita D.

    2004-01-01

    PM304 is a NASA-developed composite powder metallurgy material that is being developed for high temperature applications such as bushings in high temperature industrial furnace conveyor systems. My goal this summer was to analyze and evaluate the effects that heat exposure had on the PM304 material at 500 C and 650 C. The material is composed of Ni-Cr, Ag, Cr2O3, and eutectic BaF2-CaF2. PM304 is designed to eliminate the need for oil based lubricants in high temperature applications, while reducing friction and wear. However, further investigation was needed to thoroughly examine the properties of PM304. The effects of heat exposure on PM304 bushings were investigated. This investigation was necessary due to the high temperatures that the material would be exposed to in a typical application. Each bushing was cut into eight sections. The specimens were heated to 500 C or 650 C for time intervals from 1 hr to 5,000 hrs. Control specimens were kept at room temperature. Weight and thickness measurements were taken before and after the bushing sections were exposed to heat. Then the heat treated specimens were mounted and polished side by side with the control specimens. This enabled optical examination of the material's microstructure using a metallograph. The specimens were also examined with a scanning electron microscope (SEM). The microstructures were compared to observe the effects of the heat exposure. Chemical analysis was done to investigate the interactions between Ni-Cr and BaF2-CaF2 and between Cr2O3 and BaF2-CaF2 at high temperature. To observe this, the two compounds that were being analyzed were mixed in a crucible in varied weight percentages and heated to 1100 C in a furnace for approximately two hours. Then the product was allowed to cool and was then analyzed by X-ray diffraction. Interpretation of the results is in progress.

  9. Optical and THz investigations of mid-IR materials exposed to alpha particle irradiation

    NASA Astrophysics Data System (ADS)

    Sporea, Dan; Mihai, Laura; Sporea, Adelina; Vâţã, Ion

    2017-01-01

    The paper is the first comprehensive study on alpha particle irradiation effects on four mid-IR materials: CaF2, BaF2, Al2O3 (sapphire) and ZnSe. The measurements of the optical spectral transmittance, spectral diffuse reflectance, radioluminescent emission, terahertz (THz) spectral response, transmittance, absorbance, refractive index, real and imaginary parts of the dielectric constant and THz imaging are used as complementary investigations to evaluate these effects. The simulations were run to estimate: (i) the penetration depth, (ii) the scattering of alpha particle beam, (iii) the amount of material affected by this interaction, and (iv) the number of vacancies produced by the radiation exposure for each type of material. The simulation results are compared to the off-line measurement outcomes. The delay and spectral composition change of the reflected THz signal highlight the modification induced in the tested materials by the irradiation process.

  10. Generation of high-fidelity few-cycle pulses at 2.1 μm via cross-polarized wave generation.

    PubMed

    Ricci, Aurélien; Silva, Francisco; Jullien, Aurélie; Cousin, Seth L; Austin, Dane R; Biegert, Jens; Lopez-Martens, Rodrigo

    2013-04-22

    We demonstrate the generation of temporally clean few-cycle pulses at 2.1 μm by shortening of 6-optical-cycle pulses via cross-polarized wave (XPW) generation in BaF(2), CaF(2) and CVD-Diamond crystals. By combining spectra and single-shot third-order intensity cross-correlation traces in a novel Bayesian pulse retrieval technique, we measured pulse durations of 20 fs, corresponding to 2.8 optical cycles. Our results show that XPW generation in the infrared could provide a high-fidelity source of few-cycle pulses for strong-field physics applications. It could also serve as an injector for high-peak power ultrafast mid-IR wavelength parametric amplifiers.

  11. Preliminary Evaluation of PS300: A New Self-Lubricating High Temperature Composite Coating for Use to 800 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, C.; Edmonds, B. J.

    1995-01-01

    This paper introduces PS300, a plasma sprayed, self-lubricating composite coating for use in sliding contacts at temperatures to 800 C. PS300 is a metal bonded chrome oxide coating with silver and BaF2/CaF2 eutectic solid lubricant additives. PS300 is similar to PS200, a chromium carbide based coating, which is currently being investigated for a variety of tribological applications. In pin-on-disk testing up to 650 C, PS300 exhibited comparable friction and wear properties to PS200. The PS300 matrix, which is predominantly chromium oxide rather than chromium carbide, does not require diamond grinding and polishes readily with silicon carbide abrasives greatly reducing manufacturing costs compared to PS200. It is anticipated that PS300 has potential for sliding bearing and seal applications in both aerospace and general industry.

  12. The Evaluation of a Modified Chrome Oxide Based High Temperature Solid Lubricant Coating for Foil Gas Bearings

    NASA Technical Reports Server (NTRS)

    DellaCorte, Chris

    1998-01-01

    This paper describes the friction and wear performance of PS304, a modified chrome oxide based coating, for foil gas bearings. PS304 contains 60 wt% NiCr binder, 20 wt% Cr2O3 hardener, and 10 wt% each Ag, and BaF2/CaF2 lubricants. For evaluation, the coating is plasma spray deposited onto test journals which are slid against a superalloy partial arc foil bearing. The test load was 10 KPa (1.5 psi) and the bearings were run under start/stop cyclic conditions. The data show good wear performance of the bearing, especially at temperatures above 25 deg. C. Bearing friction was moderate (micron approx. or equal to 0.4) over the entire temperature range. Based upon the results obtained, the PS304 coating has promise for high temperature, oil-free turbomachinery applications.

  13. Graphitic carbon grown on fluorides by molecular beam epitaxy.

    PubMed

    Jerng, Sahng-Kyoon; Lee, Jae Hong; Kim, Yong Seung; Chun, Seung-Hyun

    2013-01-03

    We study the growth mechanism of carbon molecules supplied by molecular beam epitaxy on fluoride substrates (MgF2, CaF2, and BaF2). All the carbon layers form graphitic carbon with different crystallinities depending on the cation. Especially, the growth on MgF2 results in the formation of nanocrystalline graphite (NCG). Such dependence on the cation is a new observation and calls for further systematic studies with other series of substrates. At the same growth temperature, the NCG on MgF2 has larger clusters than those on oxides. This is contrary to the general expectation because the bond strength of the carbon-fluorine bond is larger than that of the carbon-oxygen bond. Our results show that the growth of graphitic carbon does not simply depend on the chemical bonding between the carbon and the anion in the substrate.

  14. Optical and THz investigations of mid-IR materials exposed to alpha particle irradiation

    PubMed Central

    Sporea, Dan; Mihai, Laura; Sporea, Adelina; Vâţã, Ion

    2017-01-01

    The paper is the first comprehensive study on alpha particle irradiation effects on four mid-IR materials: CaF2, BaF2, Al2O3 (sapphire) and ZnSe. The measurements of the optical spectral transmittance, spectral diffuse reflectance, radioluminescent emission, terahertz (THz) spectral response, transmittance, absorbance, refractive index, real and imaginary parts of the dielectric constant and THz imaging are used as complementary investigations to evaluate these effects. The simulations were run to estimate: (i) the penetration depth, (ii) the scattering of alpha particle beam, (iii) the amount of material affected by this interaction, and (iv) the number of vacancies produced by the radiation exposure for each type of material. The simulation results are compared to the off-line measurement outcomes. The delay and spectral composition change of the reflected THz signal highlight the modification induced in the tested materials by the irradiation process. PMID:28067289

  15. Far Ultraviolet Refractive Index of Optical Materials for Solar Blind Channel (SBC) Filters for HST Advanced Camera for Surveys

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.; Madison, Timothy J.; Petrone, Peter

    1998-01-01

    Refractive index measurements using the minimum deviation method have been carried out for prisms of a variety of far ultraviolet optical materials used in the manufacture of Solar Blind Channel (SBC) filters for the HST Advanced Camera for Surveys (ACS). Some of the materials measured are gaining popularity in a variety of high technology applications including high power excimer lasers and advanced microlithography optics operating in a wavelength region where high quality knowledge of optical material properties is sparse. Our measurements are of unusually high accuracy and precision for this wavelength region owing to advanced instrumentation in the large vacuum chamber of the Diffraction Grating Evaluation Facility (DGEF) at Goddard Space Flight Center (GSFC). Index values for CaF2, BaF2, LiF, and far ultraviolet grades of synthetic sapphire and synthetic fused silica are reported and compared with values from the literature.

  16. Fluorescence and phosphorescence of photomultiplier window materials under electron irradiation

    NASA Technical Reports Server (NTRS)

    Viehmann, W.; Eubanks, A. G.; Bredekamp, J. H.

    1974-01-01

    The fluorescence and phosphorescence of photomultiplier window materials under electron irradiation were investigated using a Sr-90/Y-90 beta emitter as the electron source. Spectral emission curves of UV grade, optical grade, and electron-irradiated samples of MGF2 and LiF, CaF2, BaF2, sapphire, fused silica, and UV transmitting glasses were obtained over the spectral range of 200 nm to 650 nm. Fluorescence yields, expressed as the number of counts in a solid angle of 2 pi steradian per 1MeV of incident electron energy deposited, were determined on these materials utilizing photomultiplier tubes with cesium telluride, bialkali, and trialkali (S-20) photocathodes, respectively.

  17. The Cryogenic, High-Accuracy, Refraction Measuring System (CHARMS): A New Facility for Cryogenic Infrared through Vacuum Far-Ultraviolet Refractive Index Measurements

    NASA Technical Reports Server (NTRS)

    Frey, Bradley J.; Leviton, Douglas B.

    2004-01-01

    The optical designs of future NASA infrared (IR) missions and instruments, such as the James Webb Space Telescope's (JWST) Near-Mixed Camera (NIRCam), will rely on accurate knowledge of the index of refraction of various IR optical materials at cryogenic temperatures. To meet this need, we have developed a Cryogenic, High-Accuracy Refraction Measuring System (CHARMS). In this paper we discuss the completion of the design and construction of CHARMS as well as the engineering details that constrained the final design and hardware implementation. In addition, we will present our first light, cryogenic, IR index of refraction data for LiF, BaF2, and CaF2, and compare our results to previously published data for these materials.

  18. Tribological Performance of PM300 Solid Lubricant Bushings for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Striebing, Donald R.; Stanford, Malcolm K.; DellaCorte, Christopher; Rossi, Anne M.

    2007-01-01

    PM300 is a high temperature solid lubricant material produced through conventional powder metallurgy processing. PM300 is a combination of metal binder (NiCr), hardener (Cr2O3) and lubricant (Ag and BaF2/CaF2) phases and is in commercial use in high temperature furnace conveyors. In this paper, the tribological characteristics of PM300 are evaluated using a newly developed bushing test rig in which PM300 bushings are loaded against rotating steel shafts at temperatures from 25 to 650 C. The data shows that friction and wear are low to moderate and that the lubrication performance (friction) improves with increasing temperature. Several alternative PM300 compositions are evaluated which do not contain silver and are targeted at aircraft gas turbine applications in which environmental compatibility of silver is a concern. It is expected that the data resulting from this research will further the commercialization of this technology.

  19. Effects of Humidity On the Flow Characteristics of PS304 Plasma Spray Feedstock Powder Blend

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; DellaCorte, Christopher

    2002-01-01

    The effects of environmental humidity on the flow characteristics of PS304 feedstock have been investigated. Angular and spherical BaF2-CaF2 powder was fabricated by comminution and by atomization, respectively. The fluorides were added incrementally to the nichrome, chromia, and silver powders to produce PS304 feedstock. The powders were dried in a vacuum oven and cooled to a Tom temperature under dry nitrogen. The flow of the powder was studied from 2 to 100 percent relative humidity (RH) The results suggest that the feedstock flow is slightly degraded with increasing humidity below 66 percent RH and is more affected above 66 percent RH. There was no flow above 88 percent RH. Narrower particle size distributions of the angular fluorides allowed flow up to 95 percent RH. These results offer guidance that enhances the commercial potential for this material system.

  20. Spectroscopic properties of long-lifetime Tm3+ optical centers in Ca-Sr-Ba fluorides in the form of single crystals and ceramics at the 1G4-3H5 magnetic dipole allowed transition

    NASA Astrophysics Data System (ADS)

    Doroshenko, M. E.; Papashvili, A. G.; Martynova, K. A.; Konyushkin, V. A.; Nakladov, A. N.; Osiko, V. V.

    2017-02-01

    The spectroscopic properties of new long-lifetime Tm3+ tetragonal optical centers at low (77 K) temperature were investigated using a site-selective time-resolved technique. The absorption and excitation spectra at the 3H6-1G4 transition and the fluorescence spectra at the 1G4-3H5 transition were measured in CaF2, SrF2, and BaF2 single crystals. The appearance of additional weak lines in the excitation and fluorescence spectra in hot-formed ceramics produced from the same crystals was observed. These lines were attributed to the recently observed long-lifetime tetragonal optical centers with a modified local environment formed in fluoride ceramics.

  1. Ceramic planar waveguide structures for amplifiers and lasers

    NASA Astrophysics Data System (ADS)

    Konyushkin, V. A.; Nakladov, A. N.; Konyushkin, D. V.; Doroshenko, Maxim E.; Osiko, Vyacheslav V.; Karasik, Aleksandr Ya

    2013-01-01

    Ceramic and crystalline weakly guiding optical fibres with the core - cladding refractive index difference of 10-2 - 10-4 are fabricated by a hot pressing method. The waveguides with one or several cores for operation in the spectral range 0.2 - 5 μm are produced. The waveguides are based on CaF2, SrF2, and BaF2 ceramics and crystals and their solid solutions doped with trivalent Pr, Nd, Tb, Dy, Yb, Ho, Er, and Tm ions, as well as on LiF ceramics and crystals with colour centres. The first results of investigation of the lasing properties of ceramic SrF2 : NdF waveguides under diode pumping are presented, and the prospects of further investigation are discussed.

  2. Some electronic and magnetic properties of Fluoride ion in Fluoride structure nanocrystals

    NASA Astrophysics Data System (ADS)

    Imtani, Ali Nasir

    2012-01-01

    We have investigated the effects of the environment potential around Fluoride ion on some important electronic and magnetic properties such as dipole polarisability, moment of oscillator strengths S(k) and magnetic susceptibility. The theoretical procedure is based on the variational-perturbation theory with two parameter trial functions incorporated in an ionic model. We estimate these properties in four cases for Fluoride ion; free ion, ion under different potentials, ion in the crystals and ion in nanocrystal, CdF2, CaF2, PbF2, SrF2 and BaF2. Our results indicate that these properties vary with ion environments and the free state of Fluoride ion has higher values and there is linearity behaviour of these properties with lattice constant. For Fluoride ion in nanocrystal, we have found that there is an extra parameter that can also affect the dipole polarisability, the number of ions in the structure.

  3. Commercial Production of Heavy Metal Fluoride Glass Fiber in Space

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Workman, Gary L.; Smith, Guy A.

    1998-01-01

    International Space Station Alpha (ISSA) will provide a platform not only for materials research but also a possible means to produce products in space which cannot be easily produced on the ground. Some products may even be superior to those now produced in unit gravity due to the lack of gravity induced convection effects. Our research with ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN glass) has shown that gravity does indeed play a major role in the crystallization behavior of this material. At the present time ZBLAN is being produced on earth in fiber optic form for use in surgical lasers and fiber optic lasers among other applications. High attenuation coefficients, however, have kept this material from being used in other applications such as long haul data transmission links. The high attenuation coefficients are due to impurities which can be removed through improved processing techniques and crystals which can only be removed or prevented from forming by processing in a reduced gravity environment.

  4. ZBLAN Microgravity Study

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Smith, Guy A.; OBrien, Sue; Adcock, Leonard

    1995-01-01

    One of the greatest obstacles with the fluorozirconate ZBLAN (ZrF4-BaF2-LaF3-AIF3-NaF) is the problem of devitrification. Fluoride glasses have a narrow working range and the viscosity is a strong function of temperature. Rates of nucleation and growth of crystals in the glass depend on the viscosity, making these glasses unstable and prone to crystallization. The viscosity of ZBLAN at the drawing temperature is low, usually between two to five poise, so it is difficult to obtain fibers from their preform melts without crystallization. The preforms usually contain heterogeneous nuclei which grow into microcrystallites above the glass transition temperature, T(g). Since microcrystallites in an optical fiber cause extrinsic light scattering losses of the optical signal, fiber drawing must be completed in a short time to minimize the generation of light scattering centers. To keep these losses to a minimum and to fabricate low scattering loss fibers and other optical components, this research deals with the possibility of minimizing crystallite formation by removing the gravitational influence of solutal segregation of the ZBLAN elements. This report reviews the early work on the KC-135 aircraft, the development of the ZBLAN Rocket Experiment, preparations at the White Sands Missile Range, analysis of the flight and ground test results, lessons learned and future experimentation.

  5. Commercial production of heavy metal fluoride glass fiber in space

    NASA Astrophysics Data System (ADS)

    Tucker, Dennis S.; Workman, Gary L.; Smith, Guy A.

    1998-01-01

    International Space Station Alpha (ISSA) will provide a platform not only for materials research but also a possible means to produce products in space which cannot be easily produced on the ground. Some products may even be superior to those now produced in unit gravity due to the lack of gravity induced convection effects. Our research with ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN glass) has shown that gravity does indeed play a major role in the crystallization behavior of this material. At the present time ZBLAN is being produced on earth in fiber optic form for use in surgical lasers and fiber optic lasers among other applications. High attenuation coefficients, however, have kept this material from being used in other applications such as long haul data transmission links. The high attenuation coefficients are due to impurities which can be removed through improved processing techniques and crystals which can only be removed or prevented from forming by processing in a reduced gravity environment.

  6. Wavelength-tunable mid-infrared femtosecond Raman soliton generation in birefringent ZBLAN photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Sharma, Sneha; Kumar, Jitendra

    2016-03-01

    A solid core high birefringent ZrF4-BaF2-LaF3-AlF3-NaF photonic crystal fiber (PCF) with low confinement loss is proposed for the generation of Raman soliton source in the mid-infrared region. The birefringence value of the PCF reaches the magnitude of 10- 3 and confinement loss is 0.05 dB/m at 3000 nm wavelength. Numerical simulation of femtosecond Raman soliton generation based on soliton self-frequency shift in the birefringent PCF is analyzed using the coupled nonlinear Schrodinger equation and split-step Fourier method. We investigate the dependence of output pulse width, wavelength shift, and conversion efficiency of Raman soliton formation on several input parameters. A femtosecond Raman soliton source with its wavelength tunable from 1500 to 3600 nm can be obtained. It is found that the maximum conversion efficiency is 93% when the wavelength is tuned by varying the initial input chirp.

  7. Rare-earth doped colour tuneable up-conversion ZBLAN phosphor for enhancing photocatalysis

    NASA Astrophysics Data System (ADS)

    Méndez-Ramos, J.; Acosta-Mora, P.; Ruiz-Morales, J. C.; Sierra, M.; Redondas, A.; Ruggiero, E.; Salassa, L.; Borges, M. E.; Esparza, P.

    2015-03-01

    Rare-earth doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fluoride glasses have been successfully synthesized showing outstanding UV-VIS up-conversion luminescence of Er3+ and Tm3+, sensitized by Yb3+ ions, under near-infrared excitation at 980 nm. The ratio between blue, green and red up-conversion emission bands can be adjusted by varying the pump power density of the incident infrared radiation, resulting in a controlled tuneability of the overall emitting colour from greenish to yellowish. Additionally, the observed high energy UV intense up-conversion emissions are suitable to enhance photocatalytic activity of main water-splitting semiconductor electrodes (such as TiO2) used in sustainable production of hydrogen. Photocatalysis and photolysis degradation of methylene blue in water under sun-like irradiation using benchmark photocatalyst (TiO2 Degussa P25) have been boosted by 20% and by a factor of 2.5 respectively, due to the enhancement of UV radiation that reaches the TiO2 particles by the addition of ZBLAN powder into a slurry-type photo-reactor. Hence, up-conversion ZBLAN phosphors contribute to demonstrate the possibility of transforming the incoming infrared radiation into the UV region needed to bridge the gap of photocatalytic semiconductors.

  8. Intervalence charge transfer luminescence: interplay between anomalous and 5d - 4f emissions in Yb-doped fluorite-type crystals.

    PubMed

    Barandiarán, Zoila; Seijo, Luis

    2014-12-21

    In this paper, we report the existence of intervalence charge transfer (IVCT) luminescence in Yb-doped fluorite-type crystals associated with Yb(2+)-Yb(3+) mixed valence pairs. By means of embedded cluster, wave function theory ab initio calculations, we show that the widely studied, very broad band, anomalous emission of Yb(2+)-doped CaF2 and SrF2, usually associated with impurity-trapped excitons, is, rather, an IVCT luminescence associated with Yb(2+)-Yb(3+) mixed valence pairs. The IVCT luminescence is very efficiently excited by a two-photon upconversion mechanism where each photon provokes the same strong 4f(14)-1A1g→ 4f(13)((2)F7/2)5deg-1T1u absorption in the Yb(2+) part of the pair: the first one, from the pair ground state; the second one, from an excited state of the pair whose Yb(3+) moiety is in the higher 4f(13)((2)F5/2) multiplet. The Yb(2+)-Yb(3+) → Yb(3+)-Yb(2+) IVCT emission consists of an Yb(2+) 5deg → Yb(3+) 4f7/2 charge transfer accompanied by a 4f7/2 → 4f5/2 deexcitation within the Yb(2+) 4f(13) subshell: [(2)F5/25deg,(2)F7/2] → [(2)F7/2,4f(14)]. The IVCT vertical transition leaves the oxidized and reduced moieties of the pair after electron transfer very far from their equilibrium structures; this explains the unexpectedly large band width of the emission band and its low peak energy, because the large reorganization energies are subtracted from the normal emission. The IVCT energy diagrams resulting from the quantum mechanical calculations explain the different luminescent properties of Yb-doped CaF2, SrF2, BaF2, and SrCl2: the presence of IVCT luminescence in Yb-doped CaF2 and SrF2; its coexistence with regular 5d-4f emission in SrF2; its absence in BaF2 and SrCl2; the quenching of all emissions in BaF2; and the presence of additional 5d-4f emissions in SrCl2 which are absent in SrF2. They also allow to interpret and reproduce recent experiments on transient photoluminescence enhancement in Yb(2+)-doped CaF2 and SrF2, the appearance of Yb(2+) 4f-5d absorption bands in the excitation spectra of the IR Yb(3+) emission in partly reduced CaF2:Yb(3+) samples, and to identify the broadband observed in the excitation spectrum of the so far called anomalous emission of SrF2:Yb(2+) as an IVCT absorption, which corresponds to an Yb(2+) 4f5/2 → Yb(3+) 4f7/2 electron transfer.

  9. Intervalence charge transfer luminescence: Interplay between anomalous and 5d - 4f emissions in Yb-doped fluorite-type crystals

    NASA Astrophysics Data System (ADS)

    Barandiarán, Zoila; Seijo, Luis

    2014-12-01

    In this paper, we report the existence of intervalence charge transfer (IVCT) luminescence in Yb-doped fluorite-type crystals associated with Yb2+-Yb3+ mixed valence pairs. By means of embedded cluster, wave function theory ab initio calculations, we show that the widely studied, very broad band, anomalous emission of Yb2+-doped CaF2 and SrF2, usually associated with impurity-trapped excitons, is, rather, an IVCT luminescence associated with Yb2+-Yb3+ mixed valence pairs. The IVCT luminescence is very efficiently excited by a two-photon upconversion mechanism where each photon provokes the same strong 4f14-1A1g→ 4f13(2F7/2)5deg-1T1u absorption in the Yb2+ part of the pair: the first one, from the pair ground state; the second one, from an excited state of the pair whose Yb3+ moiety is in the higher 4f13(2F5/2) multiplet. The Yb2+-Yb3+ → Yb3+-Yb2+ IVCT emission consists of an Yb2+ 5deg → Yb3+ 4f7/2 charge transfer accompanied by a 4f7/2 → 4f5/2 deexcitation within the Yb2+ 4f13 subshell: [2F5/25deg,2F7/2] → [2F7/2,4f14]. The IVCT vertical transition leaves the oxidized and reduced moieties of the pair after electron transfer very far from their equilibrium structures; this explains the unexpectedly large band width of the emission band and its low peak energy, because the large reorganization energies are subtracted from the normal emission. The IVCT energy diagrams resulting from the quantum mechanical calculations explain the different luminescent properties of Yb-doped CaF2, SrF2, BaF2, and SrCl2: the presence of IVCT luminescence in Yb-doped CaF2 and SrF2; its coexistence with regular 5d-4f emission in SrF2; its absence in BaF2 and SrCl2; the quenching of all emissions in BaF2; and the presence of additional 5d-4f emissions in SrCl2 which are absent in SrF2. They also allow to interpret and reproduce recent experiments on transient photoluminescence enhancement in Yb2+-doped CaF2 and SrF2, the appearance of Yb2+ 4f-5d absorption bands in the excitation spectra of the IR Yb3+ emission in partly reduced CaF2:Yb3+ samples, and to identify the broadband observed in the excitation spectrum of the so far called anomalous emission of SrF2:Yb2+ as an IVCT absorption, which corresponds to an Yb2+ 4f5/2 → Yb3+ 4f7/2 electron transfer.

  10. Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials

    PubMed Central

    Lecaplain, C.; Javerzac-Galy, C.; Gorodetsky, M. L.; Kippenberg, T. J.

    2016-01-01

    The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF2, CaF2, MgF2 and SrF2 microresonators. We show that MgF2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF2 and BaF2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date. PMID:27869119

  11. High T(sub c) thin film superconductors: Preparation, patterning and characterization

    NASA Astrophysics Data System (ADS)

    Azoulay, J.

    A conventional oil-pumped vacuum system equipped with resistively heated tungsten boat sources was used for evaporation of bismuth- or yttrium-based cuprates for high T(sub c) thin film superconductors. A well-ground mixture with atomic proportions of bismuth, SrF2, CaF2 and copper for bismuth-based material, and of YF3, BaF2 and copper for yttrium-based material, was inserted into the boat and then resistively evaporated onto different substrates such as MgO, ZrO2 and SrTiO3 kept at room temperature. Yttrium-based thin films were found to have a better quality upon reduction of fluorine in the constituents. Thus, films prepared with an yttrium BaF2 and copper mixture show a metallic-like behavior, sharper transition and higher zero-resistance temperature as compared with that of films obtained by using a YF2 constiuent instead of yttrium. Bismuth-based thin films were found to lose bismuth during heat treatment unless the copper constiuent ended the evaporation process and was subsequently fully oxidized at 400 C. Bismuth-based patterned films were easily obtained by using a lift-off photolithographic method. Typical thickness of the films was measured to be about 0.5 micron after heat treatment.

  12. Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials

    NASA Astrophysics Data System (ADS)

    Lecaplain, C.; Javerzac-Galy, C.; Gorodetsky, M. L.; Kippenberg, T. J.

    2016-11-01

    The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF2, CaF2, MgF2 and SrF2 microresonators. We show that MgF2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF2 and BaF2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date.

  13. Mid-infrared ultra-high-Q resonators based on fluoride crystalline materials.

    PubMed

    Lecaplain, C; Javerzac-Galy, C; Gorodetsky, M L; Kippenberg, T J

    2016-11-21

    The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF2, CaF2, MgF2 and SrF2 microresonators. We show that MgF2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF2 and BaF2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date.

  14. Measurement of the Np237(n,γ) cross section from 20 meV to 500 keV with a high efficiency, highly segmented 4π BaF2 detector

    NASA Astrophysics Data System (ADS)

    Esch, E.-I.; Reifarth, R.; Bond, E. M.; Bredeweg, T. A.; Couture, A.; Glover, S. E.; Greife, U.; Haight, R. C.; Hatarik, A. M.; Hatarik, R.; Jandel, M.; Kawano, T.; Mertz, A.; O'Donnell, J. M.; Rundberg, R. S.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.

    2008-03-01

    The Np237(n,γ)Np238 cross section has been measured in the neutron energy range from 20 meV to 500 keV using the DANCE array at the Los Alamos National Laboratory. This new facility allows experiments with submilligram samples and is therefore well suited to investigate isotopes with half-lives as low as a few hundred days. In this benchmark measurement, only 0.42 mg of Np237 was sufficient to determine differential cross sections relative to the well-known resonance at 0.5 eV. The thermal cross section was measured to σ2200m/s=177±5 barn, σkT=25.3meV=167±4 barn and the resonance integral to RI=693±6 barn.

  15. Static evaluation of surface coatings for compliant gas bearings in an oxidizing atmosphere to 650 C

    NASA Technical Reports Server (NTRS)

    Bhushan, B.; Gray, S.

    1978-01-01

    Hard wear-resistant coatings and soft low shear strength coatings were developed for an air-lubricated compliant journal bearing for a future automotive gas turbine engine. The coatings were expected to function in either 540 or 650 C ambient. Soft lubricant coatings were generally limited in temperature. Therefore emphasis was on the hard wear-resistant coatings. The coating materials covered were TiC, B4C, Cr3C2, WC, SiC, CrB2, TiB2, Cr2O3, Al2O3, Si3N4, Tribaloy 800, CaF2, CaF2-BaF2 eutectic, Ni-Co, silver, CdO-graphite and proprietary compounds. The coatings on test coupons were subjected to static oven screening tests. The test consisted of exposure of material samples in an oven for 300 h at the maximum temperature (540 or 650 C) and ten temperature cycles from room temperature to the maximum service temperature. On the basis of the specimen examinations the following coatings were recommended for future wear tests: TiC (sputtered), Cr2O3 (sputtered), Si3N4 (sputtered), CdO and graphite (fused), Kaman DES (a proprietary coating), CrB2 (plasma sprayed), Cr3C2 (detonation gun) and NASA PS-106 (plasma sprayed).

  16. AC electric properties of nanocomposite (FeCoZr)0.818(CaF2)0.182 annealed in the tubular furnace

    NASA Astrophysics Data System (ADS)

    Bondariev, Vitalii

    2016-12-01

    In this paper the influence of 15-minutes annealing in temperature range 398 K - 723 K with step 25 K on the frequency dependence on conductivity of nanocomposite (FeCoZr)x(CaF2)(100-x) was exanimate. Nanocomposite with metallic phase content x = 81.8 at.% was produced by ion-beam sputtering in mixed argon and oxygen atmosphere. Measurement were made in frequency range 50 Hz - 5 MHz and temperatures from 15 K to 375 K. It was found that to annealing temperature 523 K in measurement temperatures a less than room temperature a weak dependence of dielectric type of conductivity occurs in materials - the conductivity increases with temperature increase. At temperatures above room temperature a phase transition dielectric-metal is observed and a conductivity decreases with temperature increase. Growth stage of conductivity was observed in the frequency range above 105 Hz. The relaxation time for this stage is of the order 10-6 s. Annealing in the temperature above 523 K led to the appearance of additional low temperature stage of conductivity, for which the relaxation time is of the order of 10-4 s. The appearance of the low-frequency stage of conductivity increase is associated with oxidation of surface of nanoparticles of metallic phase during annealing, the growing barrier of potential and relaxation time. Further increase of annealing temperature above 673 K causes a further increase of the width of the barrier, and activation energy becomes so much that relaxation times for low-frequency stage grown above 10-2 s. Therefore, low-frequency stage is moves further into the area of low frequency and it becomes unnoticeable because it go beyond the lower range (50 Hz) of used meter.

  17. Synthesis and down-conversion luminescence properties of Er3+/Yb3+ co-doped AlF3-PbF2-CaF2 powders

    NASA Astrophysics Data System (ADS)

    Liu, Fangchao; Han, Qun; Liu, Tiegen; Chen, Yaofei; Du, Yang; Yao, Yunzhi

    2015-08-01

    Er3+/Yb3+ co-doped oxy-fluoride powders with varying Er/Yb concentration were prepared by a melt quenching method at various sintering temperature. The effect of the Er/Yb doped concentration and sintering temperature were analyzed by using optical absorption and emission techniques. The Judd-Ofelt theory has been used to evaluate the three intensity parameters (Ωλ, where λ = 2, 4 and 6) and calculate the oscillator strengths (fc). Ultraviolet-to-visible emissions were observed under the excitation of a 325 nm CW laser. It was found that the down-conversion fluorescence intensity changes with the sintering temperature and Er/Yb content ratio, the results were explained with the level transitions in Er3+/Yb3+ co-doped systems. The intensity ratios (intensity of 437 nm as reference) of the luminescence spectra that the samples sintered at various temperature are relevant to Ω6 parameter which indicates the vibration amplitude of the Er-O distance. The sintering temperature also has an influence on the intensity ratios via affecting the thermalization of the excited 4I15/2 level.

  18. Near-infrared photocatalysts of BiVO4/CaF2:Er3+, Tm3+, Yb3+ with enhanced upconversion properties

    NASA Astrophysics Data System (ADS)

    Huang, Shouqiang; Zhu, Nanwen; Lou, Ziyang; Gu, Lin; Miao, Chen; Yuan, Haiping; Shan, Aidang

    2014-01-01

    Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO).Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO4 (BVO)/CaF2:Er3+, Tm3+, Yb3+ (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi3+ ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO). Electronic supplementary information (ESI) available: Additional tables and figures. See DOI: 10.1039/c3nr05266d

  19. α-NaYF4:Yb3+-Tm3+@CaF2 nanocrystals for NIR-to-NIR temperature sensing

    NASA Astrophysics Data System (ADS)

    Wu, Ruozhen; Zhou, Jiajia; Lei, Lei; Zhang, Shengjun; Xiao, Zhen; Zhang, Junjie; Xu, Shiqing

    2017-01-01

    The approach of lanthanides doping upconversion temperature sensing exhibits high superiority in bioscience. However, most of the upconversion nanothermometers show their fluorescences temperature sensing beyond biological transparent window (650-950 nm) while suffering from the interference of surrounding environment. Here we report a nanoprobe with ultrasmall size, i.e. α-NaYF4:Yb-Tm@CaF2 nanocrystal, which has a sensitive capability to realize NIR-to-NIR temperature sensing. Temperature sensing sensitivities through 3H4 → 3H6 and 1G4 → 3H6 transitions of Tm3+ ions are evaluated in temperature region of 313-373 K. The results indicate that α-NaYF4:Yb-Tm@CaF2 nanocrystal is a promising candidate for biological temperature sensing.

  20. Controllable assembly of diverse rare-earth nanocrystals via the Langmuir-Blodgett technique and the underlying size- and symmetry-dependent assembly kinetics.

    PubMed

    Zhou, Huan-Ping; Zhang, Chao; Yan, Chun-Hua

    2009-11-17

    The Langmuir-Blodgett (LB) technique provides a facile and robust method for the formation of large-area films of various nanoparticles (NPs), including 24.9 nm NaYF(4):Yb,Er nanospheres, 12.0 nm LiYF(4) nanopolyhedra, 14.1 x 1.8 nm triagonal-shaped LaF(3), 12.6 nm square CaF(2), 9.5 x 2.0 nm hexagonal EuF(3), and so forth. The assembly patterns of the deposited films were studied in accordance with the pi-A isotherms. Combined with the TEM observations, several representative stages of assembly process can be distinguished. The scrutiny of the self-assembly process by means of their pi-A isotherms elucidates that the concentration, size, and symmetry of nanoparticles play crucial roles in this process. The concept of "effective concentration", which is defined as the amount of nanoblocks in the "gas phase" rather than the actual number of nanoparticles at the air-water interface, was first proposed as a control parameter to elucidate the possible assembly kinetics. The similarly shaped 12.0 nm LiYF(4) and the 24.9 nm NaYF(4):Yb,Er were selected as the size-dependent examples. The smaller nanoparticles show a strong tendency of congregation to lower the surface energy. Three representative samples, namely, 24.9 nm NaYF(4):Yb,Er nanospheres (O(h)), 14.1 x 1.8 nm oblate triagonal LaF(3) nanosheets (D(3h)), and 41.3 nm x 24.6 nm NaYF(4) rods (D(6h)), were selected as the shape-dependent samples, which showed that the assembly patterns were contributed by the stability arising from the geometry of the nanoparticles, the tendency of aggregation of nanoparticles, and the probable rotation energy during the compression. More importantly, guided by the above assembly kinetics, for the 9.5 x 2.0 nm hexagonal EuF(3), we can effectively acquire the desirable assembly pattern.

  1. Highly stable, monolithic, single-mode mid-infrared supercontinuum source based on low-loss fusion spliced silica and fluoride fibers.

    PubMed

    Yin, Ke; Zhang, Bin; Yao, Jinmei; Yang, Linyong; Chen, Shengping; Hou, Jing

    2016-03-01

    A 0.8 to 4.5 μm highly stable all-fiber spliced mid-infrared supercontinuum (SC) source was presented. The joint between the single-mode (SM) pump silica fiber and the ZBLAN fiber (ZrF4 - BaF2 - LaF3 - AlF3 - NaF, a type of fluoride fiber) was fusion spliced, which greatly improved the SC's stability. The low-loss splicing was guaranteed by the similar mode field areas of the fundamental mode LP(01) of the silica and ZBLAN fibers. At the splicing joint the ZBLAN fiber enveloped the silica fiber, thus increasing the robustness of the splice. A low splicing loss of less than 0.1 dB was calculated, which ensured that the whole SC source was very reliable. The SC had a maximal average power of 550.8 mW with a 1.5 dB spectral bandwidth ranging from 2642 to 4065 nm. In particular, the SC power for λ>3.8  μm was measured to be 116.1 mW with a power ratio of ∼21.1% of the total SC power. Perfect Gaussian beam profiles of the SC source demonstrated its SM operation. Over 12 h of continuous operation of this SC source showed its outstanding power stability with a root mean square variation of 0.59%, which also demonstrated the high quality of the fusion spliced joint.

  2. High power mid-infrared supercontinuum generation in a single-mode ZBLAN fiber pumped by amplified picosecond pulses at 2 μm

    NASA Astrophysics Data System (ADS)

    Liu, Kun; Liu, Jiang; Shi, Hongxing; Tan, Fangzhou; Jiang, Yijian; Wang, Pu

    2015-03-01

    We report high power all fiber mid-infrared (mid-IR) supercontinuum (SC) generation in a single-mode ZBLAN (ZrF4- BaF2-LaF3-AlF3-NaF) fiber with up to 21.8 W average output power from 1.9 to beyond 3.8 μm pumped by amplified picosecond pulses from a master oscillator power amplifier (MOPA) based on small-core single-mode thulium-doped fiber (TDF) with injected seed pulse width of 24 ps and repetition of 93.6 MHz at 1963 nm. The optical-optical conversion efficiency from the 793 nm pump laser of the last stage thulium-doped fiber amplifier (TDFA) to mid-IR SC output is 17%. It is, to the best of our knowledge, the highest average power mid-IR SC generation in a ZBLAN fiber to date. In addition, a noise-like fiber oscillator based on a nonlinear loop mirror (NOLM) with wavepacket width of ~1.4 ns and repetition rate of 3.36 MHz at 1966 nm is also used as a seed of the MOPA for mid-IR SC generation in the ZBLAN fiber. At last, a mid-IR SC from 1.9 to beyond 3.6 μm with average output power of 14.3W, which is limited by injected noise-like pulses power, is generated. The optical-optical conversion efficiency from the 793 nm pump laser of the last stage TDFA to mid-IR SC output is 14.9%. This proves the amplified noise-like pulses are also appropriate for high power mid-IR SC generation in the ZBLAN fiber.

  3. Monte Carlo simulations of electron thermalization in alkali iodide and alkaline-earth fluoride scintillators

    NASA Astrophysics Data System (ADS)

    Wang, Zhiguo; Xie, YuLong; Campbell, Luke W.; Gao, Fei; Kerisit, Sebastien

    2012-07-01

    A Monte Carlo model of electron thermalization in inorganic scintillators, which was developed and applied to CsI in a previous publication [Wang et al., J. Appl. Phys. 110, 064903 (2011)], is extended to another material of the alkali halide class, NaI, and to two materials from the alkaline-earth halide class, CaF2 and BaF2. This model includes electron scattering with both longitudinal optical (LO) and acoustic phonons as well as the effects of internal electric fields. For the four pure materials, a significant fraction of the electrons recombine with self-trapped holes and the thermalization distance distributions of the electrons that do not recombine peak between approximately 25 and 50 nm and extend up to a few hundreds of nanometers. The thermalization time distributions of CaF2, BaF2, NaI, and CsI extend to approximately 0.5, 1, 2, and 7 ps, respectively. The simulations show that the LO phonon energy is a key factor that affects the electron thermalization process. Indeed, the higher the LO phonon energy is, the shorter the thermalization time and distance are. The thermalization time and distance distributions show no dependence on the incident γ-ray energy. The four materials also show different extents of electron-hole pair recombination due mostly to differences in their electron mean free paths (MFPs), LO phonon energies, initial densities of electron-hole pairs, and static dielectric constants. The effect of thallium doping is also investigated for CsI and NaI as these materials are often doped with activators. Comparison between CsI and NaI shows that both the larger size of Cs+ relative to Na+, i.e., the greater atomic density of NaI, and the longer electron mean free path in NaI compared to CsI contribute to an increased probability for electron trapping at Tl sites in NaI versus CsI.

  4. Up-conversion emission tuning in triply-doped Yb3+/Tm3+/Er3+ novel fluoro-phosphate glass and glass-ceramics

    NASA Astrophysics Data System (ADS)

    Ledemi, Yannick; Trudel, Andrée.-Anne; Rivera, Victor A. G.; Messaddeq, Younes

    2014-03-01

    New Yb3+, Er3+ and Tm3+ triply doped fluoro-phosphate glasses belonging to the system NaPO3-YF3-BaF2-CaF2 have been prepared by the classical melt-casting technique. Glasses containing up to 10 wt.% of rare-earth ions fluorides have been obtained and characterized by using differential scanning calorimetry (DSC), UV-visible-near-infrared spectroscopy and up-conversion emission spectroscopy under excitation with a 975 nm laser diode. Transparent and optically homogeneous glass-ceramics have been reproducibly obtained by appropriate heat treatment in view to manage the red, green and blue emissions upon 975 nm laser excitation. According to the applied thermal heat-treatment, a large enhancement of intensity of the up-conversion emission - from 10 to 160 times higher - has been achieved in the glassceramics compared to that of glasses, suggesting incorporation of the rare-earth ions into the crystalline phase. Furthermore, a large range of color rendering has been observed in these materials by controlling the laser excitation power and material crystallization rate. Time-resolved luminescence experiments as well as X-ray diffractometry and scanning electron microscopy techniques have been employed in order to understand and correlate the multicolor emission changes to the crystallization behavior of this material. A progressive phase transformation of the fluorite-type CaF2-based nanocrystals initially generated was observed along with increasing heat-treatment time, thus modifying the rare earth ions spectroscopic features.

  5. Charge Compensation in RE3+ (RE = Eu, Gd) and M+ (M = Li, Na, K) Co-Doped Alkaline Earth Nanofluorides Obtained by Microwave Reaction with Reactive Ionic Liquids Leading to Improved Optical Properties

    SciTech Connect

    Lorbeer, C; Behrends, F; Cybinska, J; Eckert, H; Mudring, Anja -V

    2014-01-01

    Alkaline earth fluorides are extraordinarily promising host matrices for phosphor materials with regard to rare earth doping. In particular, quantum cutting materials, which might considerably enhance the efficiency of mercury-free fluorescent lamps or SC solar cells, are often based on rare earth containing crystalline fluorides such as NaGdF4, GdF3 or LaF3. Substituting most of the precious rare earth ions and simultaneously retaining the efficiency of the phosphor is a major goal. Alkaline earth fluoride nanoparticles doped with trivalent lanthanide ions (which are required for the quantum cutting phenomenon) were prepared via a microwave assisted method in ionic liquids. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect was thoroughly studied by powder X-ray and electron diffraction, luminescence spectroscopy and 23Na, 139La and 19F solid state NMR spectroscopy. Monovalent alkali ions were codoped with the trivalent lanthanide ions to relieve stress and achieve a better crystallinity and higher quantum cutting abilities of the prepared material. 19F-magic angle spinning (MAS)-NMR-spectra, assisted by 19F{23Na} rotational echo double resonance (REDOR) studies, reveal distinct local fluoride environments, the populations of which are discussed in relation to spatial distribution and clustering models. In the co-doped samples, fluoride species having both Na+ and La3+ ions within their coordination sphere can be identified and quantified. This interplay of mono- and trivalent ions in the CaF2 lattice appears to be an efficient charge compensation mechanism that allows for improved performance characteristics of such co-doped phosphor materials.

  6. High-Performance Method for Determination of Pu Isotopes in Soil and Sediment Samples by Sector Field-Inductively Coupled Plasma Mass Spectrometry.

    PubMed

    Wang, Zhongtang; Zheng, Jian; Ni, Youyi; Men, Wu; Tagami, Keiko; Uchida, Shigeo

    2017-02-21

    Plutonium is extensively studied in radioecology (e.g., soil to plant transfer and radiological assessment) and geochemistry (e.g., sediment dating). Here, we reported a new chemical separation method for rapid determination of Pu in soil and sediment samples, based on the following investigations: extraction behaviors of interfering elements (IEs, for inductively coupled plasma mass spectrometry (ICPMS) measurement) on TEVA resin; decontamination of U using TEVA, UTEVA, and DGA resins; and the impact of coprecipitation on Pu determination. The developed method consists of four steps: HNO3 leaching for Pu release; CaF2/LaF3 coprecipitation for the removal of major metals and U; the proposed TEVA + UTEVA + DGA procedure for the removal of U, Pb, Bi, Tl, Hg, Hf, Pt, and Dy; and ICPMS measurement. The accuracy of this method in determining (239+240)Pu activity and (240)Pu/(239)Pu and (241)Pu/(239)Pu isotopic ratios was validated by analyzing five standard reference materials (soil, fresh water sediment, and ocean sediment). This method is characterized by its stable and high Pu recovery (90-97% for soil; 92-98% for sediment) and high decontamination factor of U (1.6 × 10(7)), which is the highest reported for soil and sediment samples. In addition, the short analytical time of 12 h and the method detection limits, which are the lowest yet reported in literature, of 0.56 μBq g(-1) (0.24 fg g(-1)) for (239)Pu, 1.2 μBq g(-1) (0.14 fg g(-1)) for (240)Pu, and 0.34 mBq g(-1) (0.09 fg g(-1)) for (241)Pu (calculated on the basis of a 1 g soil sample) allow the rapid determination of ultratrace level Pu in soil and sediment samples.

  7. Vacuum tribological behaviour of self lubricant quasicrystalline composite coatings

    NASA Astrophysics Data System (ADS)

    Garcí de Blas, F. J.; Román, A.; de Miguel, C.; Longo, F.; Muelas, R.; Agüero, A.

    2003-09-01

    High temperature resistant self-lubricant coatings are needed in space vehicles for components that operate at high temperatures and/or under vacuum. Thick composite lubricant coatings containing quasicrystalline alloys (QC) as the hard phase for wear resistance, have been deposited by thermal spray. The coatings also comprise lubricating materials (silver and BaF2-CaF2 eutectic) and NiCr as the tough component. This paper describes the vacuum tribological properties of TH103, a coating belonging to this family, with excellent microstructural quality. The coating was deposited by HVOF and tested under vacuum on a pin-on-disc tribometer. Different loads, linear speeds and pin materials were studied. The pin scars and disc wear tracks were characterized by EDS-SEM. A minimum mean steady friction coefficient of 0.32 was obtained employing a X-750 Ni superalloy pin in vacuum conditions under 10 N load and 15 cm/s linear speed, showing moderate wear of the disc and low wear of the pin.

  8. Friction and Wear Characteristics of a Modified Composite Solid Lubricant Plasma Spray Coating

    NASA Technical Reports Server (NTRS)

    Stanford, M. K.; DellaCorte, C.

    2004-01-01

    LCR304 is a solid lubricant coating composed of Ni-10Cr, Cr2O3, BaF2-CaF2 and Ag and developed for dimensional stability in high temperature air. This coating is a modification of PS304, which differs in that the Ni-Cr constituent contains 20wt% Cr. The tribological characteristics of LCR304 were evaluated by pin-on-disk and foil air bearing rig testing from 25 to 650 C and compared to previous test results with PS304. For both tests, the friction coefficient decreased as temperature increased from 25 to 650 C. Wear generally decreased with increasing temperature for all pin-on-disk tests. LCR304 coated components produced the least wear of Inconel X-750 counterface materials at 427 and 650 C. These results indicate that the LCR304 coating has potential as a replacement for PS304 in, for example, low cycle (minimum wear) applications where dimensional stability is imperative.

  9. High-Temperature Solid Lubricants Developed by NASA Lewis Offer Virtually "Unlimited Life" for Oil-Free Turbomachinery

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher; Valco, Mark J.

    1999-01-01

    The NASA Lewis Research Center is capitalizing on breakthroughs in foil air bearing performance, tribological coatings, and computer analyses to formulate the Oil-free Turbomachinery Program. The program s long-term goal is to develop an innovative, yet practical, oil-free aeropropulsion gas turbine engine that floats on advanced air bearings. This type of engine would operate at higher speeds and temperatures with lower weight and friction than conventional oil-lubricated engines. During startup and shutdown, solid lubricant coatings are required to prevent wear in such engines before the self-generating air-lubrication film develops. NASA s Tribology Branch has created PS304, a chrome-oxide-based plasma spray coating specifically tailored for shafts run against foil bearings. PS304 contains silver and barium fluoride/calcium fluoride eutectic (BaF2/CaF2) lubricant additives that, together, provide lubrication from cold start temperatures to over 650 C, the maximum use temperature for foil bearings. Recent lab tests show that bearings lubricated with PS304 survive over 100 000 start-stop cycles without experiencing any degradation in performance due to wear. The accompanying photograph shows a test bearing after it was run at 650 C. The rubbing process created a "polished" surface that enhances bearing load capacity.

  10. Investigation of Thermal Processing on the Properties of PS304: A Solid Lubricant Coating

    NASA Technical Reports Server (NTRS)

    Benoy, Patricia A.; Williams, Syreeta (Technical Monitor)

    2002-01-01

    The effect of thermal processing on PS304, a solid lubricant coating, was investigated. PS304 is a plasma sprayed solid lubricant consisting of 10% Ag and 10% BaF2 and CaF2 in a eutectic mixture for low and high temperature lubricity respectively. In addition, PS304 contains 20% Cr2O3 for increased hardness and 60% NiCr which acts as a binder. All percents are in terms of weight not volume. Previous research on thermal processing (NAG3-2245) of PS304 revealed that substrate affected both the pre- and post-anneal hardness of the plasma spray coating. The objective of this grant was to both quantify this effect and determine whether the root cause was an artifact of the substrate or an actual difference in hardness due to interaction between the substrate and the coating. In addition to clarifying past research developments new data was sought in terms of coating growth due to annealing.

  11. Mesoscopic fast ion conduction in nanometre-scale planar heterostructures

    NASA Astrophysics Data System (ADS)

    Sata, N.; Eberman, K.; Eberl, K.; Maier, J.

    2000-12-01

    Ion conduction is of prime importance for solid-state reactions in ionic systems, and for devices such as high-temperature batteries and fuel cells, chemical filters and sensors. Ionic conductivity in solid electrolytes can be improved by dissolving appropriate impurities into the structure or by introducing interfaces that cause the redistribution of ions in the space-charge regions. Heterojunctions in two-phase systems should be particularly efficient at improving ionic conduction, and a qualitatively different conductivity behaviour is expected when interface spacing is comparable to or smaller than the width of the space-charge regions in comparatively large crystals. Here we report the preparation, by molecular-beam epitaxy, of defined heterolayered films composed of CaF2 and BaF2 that exhibit ionic conductivity (parallel to the interfaces) increasing proportionally with interface density-for interfacial spacing greater than 50 nanometres. The results are in excellent agreement with semi-infinite space-charge calculations, assuming a redistribution of fluoride ions at the interfaces. If the spacing is reduced further, the boundary zones overlap and the predicted mesoscopic size effect is observed. At this point, the single layers lose their individuality and an artificial ionically conducting material with anomalous transport properties is generated. Our results should lead to fundamental insight into ionic contact processes and to tailored ionic conductors of potential relevance for medium-temperature applications.

  12. Tribological and mechanical comparison of sintered and hipped PM212: High temperature self-lubricating composites

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher; Sliney, Harold E.; Bogdanski, Michael S.

    1992-01-01

    Selected tribological, mechanical and thermophysical properties of two versions of PM212 (sintered and hot isostatically pressed, HIPped) are compared. PM212, a high temperature self-lubricating composite, contains 70 wt percent metal bonded chromium carbide, 15 wt percent CaF2/BaF2 eutectic and 15 wt percent silver. PM212 in the sintered form is about 80 percent dense and has previously been shown to have good tribological properties from room temperature to 850 C. Tribological results of a fully densified, HIPped version of PM212 are given. They are compared to sintered PM212. In addition, selected mechanical and thermophysical properties of both types of PM212 are discussed and related to the tribological similarities and differences between the two PM212 composites. In general, both composites display similar friction and wear properties. However, the fully dense PM212 HIPped composite exhibits slight lower friction and wear than sintered PM212. This may be attributed to its generally higher strength properties. The sintered version displays stable wear properties over a wide load range indicating its promise for use in a variety of applications. Based upon their properties, both the sintered and HIPped PM212 have potential as bearing and seal materials for advanced high temperature applications.

  13. Composition optimization of chromium carbide based solid lubricant coatings for foil gas bearings at temperatures to 650 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher

    1987-01-01

    A test program to determine the optimum composition of chromium carbide based solid lubricant coatings for compliant gas bearings is described. The friction and wear properties of the coatings are evaluated using a foil gas bearing test apparatus. The various coatings were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized nickel-chromium alloy foils. The test bearings were subjected to repeated start/stop cycles under a 14 kPa (2 psi) bearing unit load. The bearings were tested for 9000 start/stop cycles or until the specimen wear reached a predetermined failure level. In general, the addition of silver and eutectic to the chromium carbide base stock significantly reduced foil wear and increased journal coating wear. The optimum coating composition, PS212 (70 wt% metal bonded Cr3C2, 15 wt% Ag, 15% BaF2/CaF2 eutectic), reduced foil wear by a factor of two and displayed coating wear well within acceptable limits. The load capacity of the bearing using the plasma-sprayed coating prior to and after a run-in period was ascertained and compared to polished Inconel 718 specimens.

  14. Tribological composition optimization of chromium-carbide-based solid lubricant coatings for foil gas bearings at temperatures to 650 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher

    1988-01-01

    The determination of the tribilogically optimum composition of chromium-carbide-based solid lubricant coatings using a foil gas bearing test apparatus is described. The coatings contain a wear resistant chromium carbide `base stock' with the lubricant additives silver and BaF2-CaF2 eutectic. The coating composition is optimized for air-lubricated foil gas bearings at temperatures ranging from 25 to 650 C. The various compositions were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized Ni-Cr alloy foils, and the test bearings were subjected to repeated start-stop cycles under a bearing unit of 14 kPa. Sliding contact between the coated journal and the smooth foil occurs during bearing start-up before lift-off or hydrodynamic lubrication by the air film and during bearing coast-down. The bearings were tested for 9000 start-stop cycles or until specimen reached a predetermined failure level.

  15. Piezoelectric and electrostrictive materials for transducer applications

    NASA Astrophysics Data System (ADS)

    Cross, L. E.; Newnham, R. E.; Barsch, G. R.; Biggers, J. V.

    1986-07-01

    On the topic of piezoelectric composites, work over the year has focused primarily upon materials with 0:3 phase connectivity. Using chemically co-precipitated powders with high purity and surface perfection, it has been possible to raise the poling field substantially and realize markedly improved properties in lead titanate based materials. X-ray measurements confirm excellent poling and the dhgh figure of merit of 4200x10 to the minus 15th power sq m/N is comparable to the best NGK materials. Work on fired composites which use a low temperature pre-firing yield materials with high d33 and gh values which pole at low fields. New studies of piezoelectrics generated using paint technology permit surprisingly high powder loading and show promising properties for large area receptors. Modelling studies of Safari type 3:1 and 3:2 composites using finite element methods show excellent agreement with measured properties and provide new insights into complex stress distributions in Holey composites. To explore the possibility of patterning ceramics by semiconductor type techniques, etches have been explored for PZT family materials and photo resist defined structures have been produced. In electrostriction, the basic theoretical work has continued upon CaF2, SrF2 and BaF2. Good agreement is found for calculations of third order elastic constants, and for hydrostatic electrostriction, but Q11 and Q12 show large discrepancies with both theoretical models tried.

  16. Photomultiplier window materials under electron irradiation - Fluorescence and phosphorescence

    NASA Technical Reports Server (NTRS)

    Viehmann, W.; Eubanks, A. G.; Pieper, G. F.; Bredekamp, J. H.

    1975-01-01

    The fluorescence and phosphorescence of photomultiplier window materials under electron irradiation have been investigated using a Sr-90/Y-90 beta emitter as the electron source. Spectral emission curves of UV-grade, optical-grade, and electron-irradiated samples of MgF2 and LiF, and of CaF2, BaF2, sapphire, fused silica, and UV-transmitting glasses were obtained over the 200-650-nm spectral range. Fluorescence yields were determined on these materials utilizing photomultiplier tubes with cesium telluride, bialkali, and trialkali (S-20) photocathodes, respectively. Optical-grade MgF2 and LiF, as well as electron-irradiated UV-grade samples of these two materials, show enhanced fluorescence due to color-center formation and associated emission bands in the blue and red wavelength regions. Large variations in fluorescence intensities were found in UV-grade sapphire samples of different origins, particularly in the red end of the spectrum, presumably due to various amounts of chromium-ion content. Phosphorescence decay with time is best described by a sum of exponential terms, with time constants ranging from a few minutes to several days.

  17. X-Ray Absorption Spectroscopy and Computer Modelling Study of Nanocrystalline Binary Alkaline Earth Fluorides

    NASA Astrophysics Data System (ADS)

    Chadwick, A. V.; Düvel, A.; Heitjans, P.; Pickup, D. M.; Ramos, S.; Sayle, D. C.; Sayle, T. X. T.

    2015-04-01

    Nanocrystalline samples of Ba1-xCaxF2 prepared by high-energy milling show an unusually high F- ion conductivity, which exhibit a maximum in the magnitude and a minimum in the activation energy at x = 0.5. Here, we report an X-ray absorption spectroscopy (XAS) at the Ca and Sr K edges and the Ba L3 edge and a molecular dynamics (MD) simulation study of the pure and mixed fluorides. The XAS measurements on the pure binary fluorides, CaF2, SrF2 and BaF2 show that high-energy ball-milling produces very little amorphous material, in contrast to the results for ball milled oxides. XAS measurements of Ba1-xCaxF2 reveal that for 0 < x <1 there is considerable disorder in the local environments of the cations which is highest for x = 0.5. Hence the maximum in the conductivity corresponds to the composition with the maximum level of local disorder. The MD calculations also show a highly disordered structure consistent with the XAS results and similarly showing maximum disorder at x = 0.5.

  18. A New Method for Determining the Optical Constants of Highly Transparent Solids.

    PubMed

    Li, Xingcan; Wang, Chengchao; Zhao, Junming; Liu, Linhua

    2017-01-01

    Highly transparent substrates are of interest for a variety of applications, but it is difficult to measure their optical constants precisely, especially the absorption index in the transparent spectral region. In this paper, a combination technique (DOPTM-EM) using both the double optical pathlength transmission method (DOPTM) and the ellipsometry method (EM) is presented to obtain the optical constants of highly transparent substrates, which overcomes the deficiencies of both the two methods. The EM cannot give accurate result of optical constants when the absorption index is very weak. The DOPTM is suitable to retrieve the weak absorption index; however, two sets of solutions exist for the retrieved refractive index and absorption index, and only one is the true value that needs to be identified. In the DOPTM-EM, the optical constants are measured first by using the EM and set as the initial value in the gradient-based inverse method used in the DOPTM, which ensures only the true optical constants are retrieved. The new method simultaneously obtains the refractive index and the absorption index of highly transparent substrate without relying on the Kramers-Kronig relation. The optical constants of three highly transparent substrates (polycrystalline BaF2, CaF2, and MgF2) were experimentally determined within wavelength range from ultraviolet to infrared regions (0.2-14 µm). The presented method will facilitate the measurement of optical constants for highly transparent materials.

  19. The influence of TeO2 on thermal stability and 1.53 μm spectroscopic properties in Er(3+) doped oxyfluorite glasses.

    PubMed

    Wang, Fengchao; Cai, Muzhi; Chen, Rong; Jing, Xufeng; Li, Bingpeng; Tian, Ying; Zhang, Junjie; Xu, Shiqing

    2015-11-05

    In this work, the thermal and spectroscopic properties of Er(3+)-doped oxyfluorite glass based on AMCSBYT (AlF3-MgF2-CaF2-SrF2-BaF2-YF3-TeO2) system for different TeO2 concentrations from 6 to 21 mol% is reported. After adding a suitable content of TeO2, the thermal ability of glass improves significantly whose ΔT and S can reach to 118 °C and 4.47, respectively. The stimulated emission cross-section reaches to 7.80×10(-21) cm(2) and the fluorescence lifetime is 12.18 ms. At the same time, the bandwidth characteristics reach to 46.41×10(-21) cm(2) nm and the gain performance is 63.73×10(-21) cm(2) ms. These results show that the optical performances of this oxyfluorite glass are very well. Hence, AMCSBYT glass with superior performances might be a useful material for applications in optical amplifier around 1.53 μm.

  20. 2.7 μm emission of high thermally and chemically durable glasses based on AlF3

    NASA Astrophysics Data System (ADS)

    Huang, Feifei; Ma, Yaoyao; Li, Weiwei; Liu, Xueqiang; Hu, Lili; Chen, Danping

    2014-01-01

    AlF3-based glasses (AlF3-YF3-CaF2-BaF2-SrF2-MgF2) with enhanced thermal and chemical stability were synthesized and compared with the well-known fluorozirconate glass (ZBLAN). The 2.7 μm mid-infrared emission in the AlF3-based glasses was also investigated through the absorption and emission spectra. Both the temperature of glass transition and the characteristic temperatures (ΔT, Hr, kgl) of the fluoroaluminate glasses were much larger than those of the ZBLAN glasses. The corrosion phenomenon can be observed by naked-eye, and the transmittance dropped dramatically (0% at 3 μm) when the ZBLAN glass was placed into distilled water. However, the AlF3-based glass was relatively stable. The fluoroaluminate glasses possessed large branching ratio (20%) along with the emission cross section (9.4×10-21 cm-2) of the Er3+:4I11/2-->4I13/2 transition. Meanwhile, the enhanced 2.7 μm emission in highly Er3+-doped AYF glass was obtained. Therefore, these results showed that this kind of fluoride glass has a promising application for solid state lasers at 3 μm.

  1. 2.7 μm emission of high thermally and chemically durable glasses based on AlF3.

    PubMed

    Huang, Feifei; Ma, Yaoyao; Li, Weiwei; Liu, Xueqiang; Hu, Lili; Chen, Danping

    2014-01-09

    AlF3-based glasses (AlF3-YF3-CaF2-BaF2-SrF2-MgF2) with enhanced thermal and chemical stability were synthesized and compared with the well-known fluorozirconate glass (ZBLAN). The 2.7 μm mid-infrared emission in the AlF3-based glasses was also investigated through the absorption and emission spectra. Both the temperature of glass transition and the characteristic temperatures (ΔT, Hr, k(gl)) of the fluoroaluminate glasses were much larger than those of the ZBLAN glasses. The corrosion phenomenon can be observed by naked-eye, and the transmittance dropped dramatically (0% at 3 μm) when the ZBLAN glass was placed into distilled water. However, the AlF3-based glass was relatively stable. The fluoroaluminate glasses possessed large branching ratio (20%) along with the emission cross section (9.4×10(-21) cm(-2)) of the Er(3+):(4)I(11/2)→(4)I(13/2) transition. Meanwhile, the enhanced 2.7 μm emission in highly Er(3+)-doped AYF glass was obtained. Therefore, these results showed that this kind of fluoride glass has a promising application for solid state lasers at 3 μm.

  2. 2.7 μm emission of high thermally and chemically durable glasses based on AlF3

    PubMed Central

    Huang, Feifei; Ma, Yaoyao; Li, Weiwei; Liu, Xueqiang; Hu, Lili; Chen, Danping

    2014-01-01

    AlF3-based glasses (AlF3-YF3-CaF2-BaF2-SrF2-MgF2) with enhanced thermal and chemical stability were synthesized and compared with the well-known fluorozirconate glass (ZBLAN). The 2.7 μm mid-infrared emission in the AlF3-based glasses was also investigated through the absorption and emission spectra. Both the temperature of glass transition and the characteristic temperatures (ΔT, Hr, kgl) of the fluoroaluminate glasses were much larger than those of the ZBLAN glasses. The corrosion phenomenon can be observed by naked-eye, and the transmittance dropped dramatically (0% at 3 μm) when the ZBLAN glass was placed into distilled water. However, the AlF3-based glass was relatively stable. The fluoroaluminate glasses possessed large branching ratio (20%) along with the emission cross section (9.4×10−21 cm−2) of the Er3+:4I11/2→4I13/2 transition. Meanwhile, the enhanced 2.7 μm emission in highly Er3+-doped AYF glass was obtained. Therefore, these results showed that this kind of fluoride glass has a promising application for solid state lasers at 3 μm. PMID:24402172

  3. Preparation and tribological properties of fluorosilane surface-modified lanthanum trifluoride nanoparticles as additive of fluoro silicone oil

    NASA Astrophysics Data System (ADS)

    Hou, Xiao; He, Jie; Yu, Laigui; Li, Zhiwei; Zhang, Zhijun; Zhang, Pingyu

    2014-10-01

    LaF3 nanoparticles surface-modified with fluorosilane were synthesized by surface modification technology. The size, morphology and phase structure of as-prepared surface-modified LaF3 nanoparticles were analyzed by means of X-ray diffraction and transmission electron microscopy. The tribological properties of surface-modified LaF3 nanoparticles as additive of fluoro silicone oil were evaluated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined with a scanning electron microscope and an X-ray photoelectron spectroscope. Results show that 3-(heptafluoroisopropoxy)propyltriethoxysilane as the modifier is able to improve the dispersibility of LaF3 nanoparticles in fluoro silicone oil. Moreover, when the optimum concentration, 0.08 wt.% of fluorosilane surface-modified LaF3 is added into fluoro silicone oil, as-synthesized fluorosilane surface-modified LaF3 nanoparticles exhibit excellent anti-wear as additive in fluoro silicone oil. The wear scar diameter under the optimum concentration is always smaller than that under the lubrication of fluoro silicone oil alone. Especially, when the load is 500 N, 600 N and 700 N, the wear scar diameter is reduced by 17%, 43% and 42%, respectively. In addition, during the friction process, LaF3 nanoparticles are deposited on the rubbed steel surface to form LaF3 deposition layer which functions jointly with the boundary lubricating film thereby resulting in improved tribological properties.

  4. Diopside (CaO-MgO-2SiO2)-fluorapatite (9CaO-3P2O5-CaF2) glass-ceramics: Potential materials for bone tissue engineering

    SciTech Connect

    Kansal, Ishu; Goel, Ashutosh; Tulyaganov, Dilshat U.; Pascual, Maria J.; Lee, Hye-Young; Kim, Hae-Won; Ferreira, Jose M.

    2011-08-18

    Glass-ceramics in the diopside (CaMgSi2O6) - fluorapatite [Ca5(PO4)3F] system are potential candidates for restorative dental and bone implant materials. In the present study, a series of glasses along diopside - fluorapatite binary system have been prepared with varying diopside/fluorapatite ratios for their potential applications in bone tissue engineering. The glasses were obtained from compositions with fluorapatite contents varying between 0-40 wt.%. The sintering ability and crystallization kinetics of as obtained amorphous glasses have been studied through hot-stage microscopy (HSM) and differential thermal analysis (DTA), respectively while crystalline phase evolution in sintered GCs has been followed by X-ray diffraction (XRD) adjoined with Rietveld-R.I.R. technique and scanning electron microscopy (SEM). Further, biodegradation and apatite forming ability of glass-ceramics were investigated by immersion of glass-ceramic discs in simulated body fluid (SBF) solution while chemical degradation and weight loss of glass-ceramics were studied by immersion in Tris-HCl in accordance with standard ISO 10993-14. The addition of fluorapatite (10-25 wt.%) in diopside glass system significantly enhanced the sintering ability of glass-ceramics and improved their apatite forming ability along with their biodegradation behaviour. Moreover, the in vitro cellular responses to glass-ceramics showed good cell viability and significant stimulation of osteoblastic differentiation, suggesting the possible use of the glass-ceramics for bone regeneration.

  5. Picosecond passively mode-locked mid-infrared fiber laser

    NASA Astrophysics Data System (ADS)

    Wei, C.; Zhu, X.; Norwood, R. A.; Kieu, K.; Peyghambarian, N.

    2013-02-01

    Mode-locked mid-infrared (mid-IR) fiber lasers are of increasing interest due to their many potential applications in spectroscopic sensors, infrared countermeasures, laser surgery, and high-efficiency pump sources for nonlinear wavelength convertors. Er3+-doped ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fiber lasers, which can emit mid-IR light at 2.65-2.9 μm through the transition from the upper energy level 4I11/2 to the lower laser level 4I13/2, have attracted much attention because of their broad emission range, high optical efficiency, and the ready availability of diode pump lasers at the two absorption peaks of Er3+ ions (975 nm and 976 nm). In recent years, significant progress on high power Er3+- doped ZBLAN fiber lasers has been achieved and over 20 watt cw output at 2.8 μm has been demonstrated; however, there has been little progress on ultrafast mid-IR ZBLAN fiber lasers to date. We report a passively mode-locked Er3+- doped ZBLAN fiber laser in which a Fe2+:ZnSe crystal was used as the intracavity saturable absorber. Fe2+:ZnSe is an ideal material for mid-IR laser pulse generation because of its large saturable absorption cross-section and small saturation energy along with the excellent opto-mechanical (damage threshold ~2 J/cm2) and physical characteristics of the crystalline ZnSe host. A 1.6 m double-clad 8 mol% Er3+-doped ZBLAN fiber was used in our experiment. The fiber core has a diameter of 15 μm and a numerical aperture (NA) of 0.1. The inner circular cladding has a diameter of 125 μm and an NA of 0.5. Both continuous-wave and Q-switched mode-locking pulses at 2.8 μm were obtained. Continuous-wave mode locking operation with a pulse duration of 19 ps and an average power of 51 mW were achieved when a collimated beam traversed the Fe2+:ZnSe crystal. When the cavity was modified to provide a focused beam at the Fe2+:ZnSe crystal, Q-switched mode-locked operation with a pulse duration of 60 ps and an average power of 4.6 mW was achieved. More powerful and narrower pulses are expected if the dispersion of the cavity can be properly managed.

  6. The Effects of Gravity on the Crystallization Behavior of Heavy Metal Fluoride Glasses

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Smith, Guy A.

    2004-01-01

    Heavy metal fluoride glasses are used in such applications as fiber lasers and laser amplifiers. ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) is one of the more commonly used heavy metal fluoride glasses. ZBLAN is an infrared transmitter and has a theoretical attenuation coefficient of 0.002 db/km. However, due to impurities and small crystallites this attenuation coefficient has not been achieved to date. ZBLAN is a fragile glass which can lead to rapid crystallization, if the glass is not cooled rapidly to below the glass transition temperature or if the glass is reheated near the crystallization temperature for any period of time. Studies carried on at Marshall Space Flight Center and the University of Alabama in Huntsville since 1993 have shown that heating ZBLAN glass at the crystallization temperature in reduced gravity results in a suppression of crystallization when compared to ZBLAN processed in unit gravity. These studies utilized NASA's KC-135 aircraft and the Conquest sounding rocket. In the first series of experiments, short lengths of ZBLAN fiber were heated to the crystallization temperature in reduced gravity on board the KC- 135 and the Conquest sounding rocket and compared with fibers heated in unit gravity. The fibers processed in reduced gravity showed no evidence of crystallization when studied with x-ray diffraction and scanning electron microscopy. However, the fibers processed in unit gravity were completely crystallized. Subsequent experiments included heating small pieces of ZBLAN glass at the crystallization temperature while viewing with a video camera to follow the crystallization phenomenon. In this experiment crystallization was observed in reduced gravity, however, it was suppressed when compared to heating in unit gravity. In the most recent experiment on board the KC-135, rapid thermal analysis of ZBLAN was performed. A mechanism to explain the observations has been proposed. This mechanism is based on shear thinning whereby, the glass undergoes a reduction in viscosity in the 10(exp 5) - 10(exp 7) poise range, allowing more rapid diffusion and thus crystallization. It is proposed that this mechanism is suppressed in reduced gravity. An experiment is presently being conducted to test this theory. With increased knowledge of ZBLAN behavior in reduced gravity, three low earth orbit tiber drawing facilities have been designed. One would be suitable for use on the International Space Station, another while aboard the Space Shuttle and the third system is a fully automated facility which would operate independently of the ISS or Shuttle in a free float mode. The primary benefits of free floating a facility in LEO includes a higher quality of microgravity and reduced safety concerns since it is not in a manned environment.

  7. Effects of Li+ ions on the enhancement of up-conversion emission in Ho3+-Yb3+ co-doped transparent glass-ceramics containing Ba2LaF7 nanocrystals

    NASA Astrophysics Data System (ADS)

    Li, Zhencai; Zhou, Dacheng; Yang, Yong; Gao, Yuan; Ren, Peng; Qiu, Jianbei

    2016-10-01

    The up-conversion (UC) emission of Ho3+-Yb3+ and Li+ co-doped transparent glass ceramics 45SiO2-15Al2O3-12Na2CO3-21BaF2-7LaF3-0.2HoF3-1YbF3-xLi2CO3 (x = 0, 0.5, 1, 2, 4 and 6 mol%) containing Ba2LaF7 nanocrystals were investigated. These glass ceramics samples were prepared using the conventional quenching techniques. The Ba2LaF7 nanocrystals precipitated from the glass matrix was confirmed by X-ray diffraction (XRD). Compared with the glass ceramics sample without Li+, the UC emission intensity of glass ceramics samples with Li+ were enhanced. It can be proved that the Li+ can affect the enhancement up-conversion (UC) emission. Particularly, the green UC emission intensity band centered at 546 nm was strongly increased twice with the concentration of Li+ increasing up to 4 mol%. Through the comparison and analysis of the energy graph, it was shown that the 5F4/5S2→5I8 transition of Ho3+ ion obtained the green (546 nm) light. There are two weak fluorescences in the red (657 nm) region and near infrared (753 nm) region of spectrum, which is the 5F4/5S2→5I7 and 5F5→5I8 transition of Ho3+. Therefore, the emission results showed that the incorporation of Li+ ions into the Ba2LaF7:Eu3+ lattice could induce a remarkable change of the emission intensity in red region (R = IED/IMD) with 393 nm excitation wavelength. It was indicated that the symmetry of the lattice was destroyed by Li+ in glass ceramics. The possible mechanism responsible for the enhancement of UC emission in Ho-Yb co-doped was discussed.

  8. Mechanisms for the Crystallization of ZBLAN

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Tucker, Dennis S.; Kaukler, William; Antar, Basil

    2003-01-01

    The objective of this ground based study is to test the hypothesis that shear thinning (the non-Newtonian response of viscosity to shear rate) is a viable mechanism to explain the observation of enhanced glass formation in numerous low-g experiments. In 1-g, fluid motion results from buoyancy forces and surface tension driven convection. This fluid flow will introduce shear in undercooled liquids in 1-g. In low-g it is known that fluid flows are greatly reduced so that the shear rate in fluids can be extremely low. It is believed that some fluids may have weak structure in the absence of flow. Very small shear rates could cause this structure to collapse in response to shear resulting in a lowering of the viscosity of the fluid. The hypothesis of this research is that: Shear thinning in undercooled liquids decreases the viscosity, increasing the rate of nucleation and crystallization of glass forming melts. Shear in the melt can be reduced in low-g, thus enhancing undercooling and glass formation. The viscosity of a model glass (lithium di-silicate, L2S) often used for crystallization studies has been measured at very low shear rates using a dynamic mechanical thermal analyzer. Our results are consistent with increasing viscosity with a lowering of shear rates. The viscosity of L2S may vary as much as an order of magnitude depending on the shear rate in the temperature region of maximum nucleation and crystal growth. Classical equations for nucleation and crystal growth rates, are inversely related to the viscosity and viscosity to the third power respectively. An order of magnitude variation in viscosity (with shear) at a given temperature would have dramatic effects on glass crystallization Crystallization studies with the heavy metal fluoride glass ZBLAN (ZrF2-BaF2-LaF3-AlF3-NaF) to examine the effect of shear on crystallization are being initiated. Samples are to be melted and quenched under quiescent conditions at different shear rates to determine the effect on crystallization. The results from this study are expected to advance the current scientific understanding of glass formation in low-g and glass crystallization under glass molding conditions and will improve the scientific understanding of technological processes such as fiber pulling, bulk amorphous alloys, and glass fabrication processes.

  9. Generation of broadband mid-infrared supercontinuum radiation in cascaded soft-glass fibers

    NASA Astrophysics Data System (ADS)

    Kneis, C.; Robin, T.; Cadier, B.; Brilland, Laurent; Caillaud, Celine; Troles, Johann; Manek-Hönninger, I.; Eichhorn, M.; Kieleck, C.

    2016-03-01

    The generation of mid-infrared (mid-IR) radiation, ranging from 2 - 5 μm, is getting much attention in recent years thanks to many applications it can be used for, e.g. in free space optical communication, range finding, counter measures and remote chemical sensing systems. It also plays an increasing role in medicine, for instance in optical tissue ablation or optical coherence tomography, owing to the high water absorption in that wavelength range. In this research study, a ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fluoride fiber is pumped by a Q-switched mode-locked (QML) thulium (Tm3+)- doped double-clad silica fiber laser, emitting at around 2 μm, to generate mid-IR supercontinuum (SC). Further spectral broadening of this SC radiation is achieved by coupling it into a chalcogenide arsenide-selenide (AsSe) photonic crystal fiber (PCF). An output power of 24 W at 2 μm has been achieved in QML operation for the Tm3+-doped fiber laser. The SC output power from the ZBLAN fiber has been 7.8 W with a spectrum extending to approximately 4.1 μm. For further wavelength broadening experiments, a long-wave-pass filter with a 3 dB edge around 3.6 μm has been implemented between the ZBLAN and the AsSe fiber to cut out the residual pump light at 2 μm and the radiation between 2 μm and 3.5 μm. The pump power was approximately 120 mW with a spectrum from 3.5 μm to 3.9 μm. First proof of principal experiments has been performed with 20 mW of averaged output power and a spectrum extending to 4.9 μm. The coupling efficiency of the SC radiation from the ZBLAN fiber into the AsSe fiber has been around 30%.

  10. Insulators for Pb(1-x)Sn(x)Te

    NASA Technical Reports Server (NTRS)

    Tsuo, Y. H.; Sher, A.

    1981-01-01

    Thin films of LaF3 were e-gun and thermally deposited on several substrates. The e-gun deposited films are fluorine deficient, have high ionic conductivities that persist to 77 K, and high effective dielectric constants. The thermally deposited material tends to be closer to stoichiometric, and have higher effective breakdown field strengths. Thermally deposited LaF3 films with resistivities in excess of 10 to the 12th power ohms - cm were deposited on metal coated glass substrates. The LaF3 films were shown to adhere well to PbSnTe, surviving repeated cycles between room temperature and 77 K. The LaF3 films on GaAs were also studied.

  11. New infrared detectors and solar cells

    NASA Technical Reports Server (NTRS)

    Sher, A.

    1979-01-01

    The inventions and published papers related to the project are listed. The research with thin films of LaF3 deposited on GaAs substrates is reported along with improvements in photocapacitative MIS infrared detectors.

  12. Chromatic correction for a VIS-SWIR zoom lens using optical glasses

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Williams, Daniel J. L.; McCarthy, Peter; Visconti, Anthony J.; Bentley, Julie L.; Moore, Duncan T.

    2015-09-01

    With the advancement in sensors, hyperspectral imaging in short wave infrared (SWIR 0.9 μm to 1.7 μm) now has wide applications, including night vision, haze-penetrating imaging, etc. Most conventional optical glasses can be material candidates for designing in the SWIR as they transmit up to 2.2 μm. However, since SWIR is in the middle of the glasses' major absorption wavebands in UV and IR, the flint glasses in SWIR are less dispersive than in the visible spectrum. As a result, the glass map in the SWIR is highly compressed, with crowns and flints all clustering together. Thus correcting for chromatic aberration is more challenging in the SWIR, since the Abbé number ratio of the same glass combination is reduced. Conventionally, fluorides, such as CaF2 and BaF2, are widely used in designing SWIR system due to their unique dispersion properties, even though they are notorious for poor manufacturability or even high toxicity. For lens elements in a zoom system, the ray bundle samples different sections of the each lens aperture as the lens zooms. This creates extra uncertainty in correcting chromatic aberrations. This paper focuses on using only commercially available optical glasses to color-correct a 3X dual-band zoom lens system in the VIS-SWIR. The design tools and techniques are detailed in terms of material selections to minimize the chromatic aberrations in such a large spectrum band and all zoom positions. Examples are discussed for designs with different aperture stop locations, which considerably affect the material choices.

  13. Investigations on spectroscopic properties of Dy3+ doped zinc telluro-fluoroborate glasses for laser and white LED applications

    NASA Astrophysics Data System (ADS)

    Suthanthirakumar, P.; Marimuthu, K.

    2016-12-01

    A new series of Zinc telluro-fluoroborate glasses (ZTFB) doped with Dy3+ ions with the chemical composition (30-x) B2O3 + 30TeO2 + 16ZnO + 10ZnF2 + 7CaF2 + 7BaF2 + xDy2O3 (where x = 0.05, 0.1, 0.25, 0.5, 1 and 2 in wt%) have been synthesized by the conventional melt quenching technique and the prepared glass samples were characterized through XRD, FTIR, UV-Vis-NIR optical absorption, photoluminescence and decay spectral measurements. The XRD patterns have been recorded to confirm the amorphous nature. The FTIR spectral measurements were carried out to identify the functional groups present in the title glasses. From the energy band positions of the absorption spectra, bonding parameters (βbar and δ) have been calculated to identify the covalent/ionic nature of the metal-ligand bond present in the prepared glasses. The Judd-Ofelt (JO) intensity parameters Ωλ (λ = 2, 4 and 6) have been calculated from the oscillator strengths of the different absorption bands to understand the nature of the ligand environment around the Dy3+ ions. The radiative parameters such as transition probability (A), stimulated emission cross-section (σPE), radiative lifetime (τR) and branching ratios (βR) corresponding to the 4F9/2 → 6H15/2, 4F9/2 → 6H13/2, and 4F9/2 → 6H11/2 emission transitions have been determined using JO parameters and the refractive index values. The CIE chromaticity coordinates were calculated from the luminescence spectra to explore the dominant emission colour of the title glasses and the obtained results were discussed in detail and reported.

  14. Structural and luminescence behaviour of Er3+ doped telluro-fluoroborate glasses

    NASA Astrophysics Data System (ADS)

    Karthikeyan, P.; Suthanthirakumar, P.; Vijayakumar, R.; Marimuthu, K.

    2015-03-01

    The Er3+ doped telluro-fluoroborate glasses with the chemical composition (30 - x)B2O3 + 30TeO2 + 16ZnO + 10ZnF2 + 7CaF2 + 7BaF2 + xEr2O3 (x = 0.05, 0.1, 0.5, 0.75, 1.0 and 3 in wt%) have been prepared by melt quenching technique and characterized through XRD, SEM, FTIR, Raman, absorption and luminescence spectral analysis. The XRD and SEM measurements were made to examine the amorphous nature. The presence of various stretching and bending vibration modes of functional groups have been investigated through FTIR and Raman spectra. The bonding parameters (β bar and δ) were calculated from the absorption spectra to claim the covalent/ionic nature of the metal-ligand bond in the prepared glasses. From the absorption spectra, optical band gap energies (Eopt) corresponding to the direct and indirect allowed transitions were calculated to analyze the electronic band structure. The Urbach energy values have also been estimated and discussed. The Judd-Ofelt (JO) intensity parameters (Ωλ (λ = 2, 4, 6)) were determined from the absorption spectra in order to study the symmetry around the RE ion site and used to compute the radiative properties such as transition probability (AR), stimulated emission cross-section ( σPE) and branching ratios (βR) for the different emission transitions. The emission intensities of the prepared glasses were characterized through CIE 1931 chromaticity diagram and the results were discussed and compared with the reported literature.

  15. The effect of prolonged exposure to 750 C air on the tribological performance of PM212

    NASA Technical Reports Server (NTRS)

    Bemis, Kirk; Bogdanski, Michael S.; Dellacorte, Christopher; Sliney, Harold E.

    1994-01-01

    The effect of prolonged exposure to 750 C air on the tribological performance and dimensional stability of PM212, a high temperature, self-lubricating composite, is studied. PM212, by weight, contains 70 percent metal-bonded Cr3C2, 15 percent BaF2/CaF2 eutectic, and 15 percent silver. Rub blocks were fabricated from PM212 by cold isostatic pressing followed by sintering. Prior to tribo-testing, the rub blocks were exposed to 750 C air for periods ranging from 100 to 1000 hours. Then, the rub blocks were slid against nickel-based superalloy disks in a double-rub-block tribometer in air under a 66 N load at temperatures from 25 to 750 C with a sliding velocity of 0.36 m/s. Unexposed rub blocks were tested for baseline comparison. Friction coefficients ranged from 0.24 to 0.37 for the unexposed rub blocks and from 0.32 to 0.56 for the exposed ones. Wear for both the composite blocks and superalloy disks was typically in the moderate to low range of 10(exp -5) to 10(exp -6) mm(exp 3)/N-m. Friction and wear data were similar for the rub blocks exposed for 100, 500, and 1000 hours. Prolonged exposure to 750 C air increased friction and wear of the PM212 rub blocks at room temperature, but their triboperformance remained unaffected at higher temperatures, probably due to the formation of lubricious metal oxides. Dimensional stability of the composite was studied by exposing specimens of varying thicknesses for 500 hours in air at 750 C. Block thicknesses were found to increase with increased exposure time until steady state was reached after 100 hours of exposure, probably due to oxidation.

  16. Hydrothermally synthesized barium fluoride nanocubes for thermoluminescence dosimetry

    NASA Astrophysics Data System (ADS)

    Bhadane, Mahesh S.; Dahiwale, S. S.; Bhoraskar, V. N.; Dhole, S. D.

    2016-05-01

    In this work, we report a hydrothermally synthesized Dy doped BaF2 (BaF2:Dy) nanocubes and its Thermoluminescence studies. The synthesized BaF2:Dy samples was found to posses FCC structure and having average size ~ 60-70 nm, as revealed through X-Ray Diffraction. Cubical morphology having size ~90 nm was observed from TEM analysis. The 60Co γ- ray irradiated BaF2:Dy TL dosimetric experiments shows a pre-dominant single glow peak at 153 °C, indicating a single level trap present as a metastable state. Furthermore, BaF2:Dy nanophosphor shows a sharp linear response from 10 Gy to 3 kGy, thus it can be applicable as a gamma dosimeter.

  17. [Study on the vacuum ultraviolet transmittance of barium fluoride crystals at different temperature].

    PubMed

    Peng, Ru-Yi; Fu, Li-Ping; Tao, Ye

    2014-03-01

    Two VUV-grade BaF2 windows with 0.5 mm-thick and 1 mm-thick respectively were selected to study the transmittance variety with the temperature. The results show that the cutoff wavelength of BaF2 crystals will shift towards the long wave with the increase in temperature. In a certain temperature range, BaF2 crystals can depress 130.4 nm radiation well, and also has a high transmittance at 135.6 nm. Compared with the reported method in which SrF2 crystals can be applied to suppress 130.4 nm stray light by heating, BaF2 crystal can inhibit the 130. 4 nm emission line completely, and thus reduce the power consumption of the device at the same time. This indicates that BaF2 crystals can play an important role in the ionosphere optical remote sensing detection.

  18. PS300 Tribomaterials Evaluated at 6500C by Bushing Test Rig

    NASA Technical Reports Server (NTRS)

    Striebing, Donald R.; DellaCorte, Christopher

    2004-01-01

    A new facility has been developed to test the tribological behavior (friction and wear) of PS300 solid lubricant bushings at high temperatures. PS300 is a commercially available solid lubricant invented at the NASA Glenn Research Center. It can be prepared as a plasma spray coating or as a free-standing powder metallurgy component, designated PM300. PS300 and PM300 composites are designed to lubricate sliding components at temperatures above the capability of today's best oils, greases, and solid lubricants. One of the primary applications being pursued for PM300 is the development of bushings for use in high-temperature machinery. Examples include inlet guide vane bushings for gas turbines and conveyors, and bearings for industrial furnaces and ovens. Encouraging preliminary field trials indicate that PS300 and PM300 lubricant materials have been commercialized successfully in several industrial applications. However, the lack of laboratory performance data has hindered further commercialization especially for new applications that differ significantly from the established experience base. The purpose of the newly developed bushing test rig will be to determine the performance characteristics of PM300, and other materials, under conditions closely matching intended applications. The data will be used to determine engineering friction and wear rates and to estimate the life expectancy of bushings for new applications. In the new rig, the bushing is loaded against a rotating shaft inside a furnace enclosure (see the preceding photograph). Loads can vary from 5 to 200 N, speeds from 1 to 400 rpm, and temperatures from 25 to 800 C. Furnace temperature, bushing temperature, shaft speed, and torque are monitored during the test, and wear of both the bushing and the shaft is measured after testing is completed. Initially, PM300 bushings will be evaluated and compared with lower temperature, traditional bushing materials like graphite and porous bronze. The baseline PM304 composition is 60 wt% NiCr (a binder), 20 wt% Cr2O3 (a hardener), 10 wt% BaF2/CaF2 (a high-temperature lubricant), and 10 wt% Ag (a low-temperature lubricant). Future research efforts will include determining the effects of load, sliding speed, and temperature on tribological performance and, possibly, tailoring composition for specific applications. We expect that the availability of measured performance data will enhance the market penetration of PM300 technology.

  19. Microstructures and properties of superconducting Y-ErBaCuO thin films obtained from disordered Y-ErBaF2Cu films

    NASA Technical Reports Server (NTRS)

    Cikmach, P.; Diociaiuti, M.; Fontana, A.; Giovannella, C.; Iannuzzi, M.; Lucchini, C.; Merlo, V.; Messi, R.; Paoluzi, L.; Scopa, L.

    1991-01-01

    The preparation procedure used to obtain superconducting thin films by radio frequency magnetron sputtering of a single mosaic target is described in detail. The single mosaic target is composed of (Y-Er), BaF2, and Cu.

  20. Microstructures and properties of superconducting Y-Er-BaCu-O thin films obtained from disordered Y-Er-BaF2-Cu films

    NASA Technical Reports Server (NTRS)

    Cikmach, P.; Diociaiuti, M.; Fontana, A.; Giovannella, C.; Iannuzzi, M.; Lucchini, C.; Messi, R.; Paoluzi, L.; Scopa, L.; Tripodi, P.

    1990-01-01

    Since the first reports on superconducting thin films obtained by evaporating BaF2, Cu and Y(sup 1), or Yb or Er(sup 2), several others have followed. All these reports describe thin films prepared by means of molecular beam cells or electron guns. Researchers show that films with similar properties can be obtained by radio frequency sputtering of a single mosaic target composed by Y-Er, BaF2 and Cu. Process steps are described.

  1. Neutron beam test of barium fluoride crystal for dark matter direct detection

    NASA Astrophysics Data System (ADS)

    Guo, C.; Ma, X. H.; Wang, Z. M.; Bao, J.; Dai, C. J.; Guan, M. Y.; Liu, J. C.; Li, Z. H.; Ren, J.; Ruan, X. C.; Yang, C. G.; Yu, Z. Y.; Zhong, W. L.

    2016-10-01

    In order to test the capabilities of Barium Fluoride (BaF2) crystal for dark matter direct detection, nuclear recoils are studied with mono-energetic neutron beam. The energy spectra of nuclear recoils, quenching factors for elastic scattering neutrons and discrimination capability between neutron inelastic scattering events and γ events are obtained for various recoil energies of the F content in BaF2.

  2. Raman Scattering from Tin

    DTIC Science & Technology

    2015-09-01

    semiconductor and tin metallic allotropes, and we are developing a fundamental understanding of the spectra. The research has identified that BaF2 is an...semiconductor and tin metallic allotropes, and we are developing a fundamental understanding of the spectra. The research has identified that BaF2 is an...deposited on SiO2 .........................................5 Fig. 6 Raman spectrum from the metallic Sn lump at 300 K ...........................6 Fig

  3. Neutron threshold activation detectors (TAD) for the detection of fissions

    NASA Astrophysics Data System (ADS)

    Gozani, Tsahi; Stevenson, John; King, Michael J.

    2011-10-01

    Prompt fission neutrons are one of the strongest signatures of the fission process. Depending on the fission inducing radiation, their average number ranges from 2.5 to 4 neutrons per fission. They are more energetic and abundant, by about 2 orders of magnitude, than the delayed neutrons (≈3 vs. ≈0.01) that are commonly used as indicators for the presence of fissionable materials. The detection of fission prompt neutrons, however, has to be done in the presence of extremely intense probing radiation that stimulated them. During irradiation, the fission stimulation radiation, X-rays or neutrons, overwhelms the neutron detectors and temporarily incapacitate them. Consequently, by the time the detectors recover from the source radiation, fission prompt neutrons are no longer emitted. In order to measure the prompt fission signatures under these circumstances, special measures are usually taken with the detectors such as heavy shielding with collimation, use of inefficient geometries, high pulse height bias and gamma-neutron separation via pulse-shape discrimination with an appropriate organic scintillator. These attempts to shield the detector from the flash of radiation result in a major loss of sensitivity. It can lead to a complete inability to detect the fission prompt neutrons. In order to overcome the blinding induced background from the source radiation, the detection of prompt fission neutrons needs to occur long after the fission event and after the detector has fully recovered from the source overload. A new approach to achieve this is to detect the delayed activation induced by the fission neutrons. The approach demonstrates a good sensitivity in adverse overload situations (gamma and neutron "flash") where fission prompt neutrons could normally not be detected. The new approach achieves the required temporal separation between the detection of prompt neutrons and the detector overload by the neutron activation of the detector material. The technique, called Threshold Activation Detection (TAD), is to utilize appropriate substances that can be selectively activated by the fission neutrons and not by the source radiation and then measure the radioactively decaying activation products (typically beta and gamma rays) well after the source pulse. The activation material should possess certain properties: a suitable half-life of the order of seconds; an energy threshold below which the numerous source neutrons will not activate it (e.g., 3 MeV); easily detectable activation products (typically >1 MeV beta and gamma rays) and have a usable cross-section for the selected reaction. Ideally the substance would be a part of the scintillator. There are several good material candidates for the TAD, including fluorine, which is a major constituent of available scintillators such as BaF 2, CaF 2 and hydrogen free liquid fluorocarbon. Thus the fluorine activation products, in particular the beta particles, can be measured with a very high efficiency in the detector. The principles, applications and experimental results obtained with the fluorine based TAD are discussed.

  4. Synthesis and characterization of lanthanide based nanomaterials for radiation detection and biomedical applications

    NASA Astrophysics Data System (ADS)

    Yao, Mingzhen

    2011-12-01

    Lanthanide based nanomaterials have shown a great potential in various areas such as luminescence imaging, luminescent labels, and detection of cellular functions. Due to the f-f transitions of the metal ion, luminescence of lanthanide ions is characterized by sharp and narrow emissions. In this dissertation lanthanide based nanoparticles such as Ce3+, Eu3+ and other lanthanide ions doped LaF3 were synthesized, their characterization, encapsulation and embedding into hybrid matrix were investigated and some of their biomedical and radiological applications were studied. DMSO is a common solvent which has been used widely for biological applications. LaF3:Ce nanoparticles were synthesized in DMSO and it was found that their fluorescent emission originates from the metal-to-ligand charge-transfer excited states. After conjugation with PpIX and then encapsulation within PLGA, the particles show efficient uptake by cancer cells and great cytotoxicity, which is promising for applications in cancer treatments. However, the emission of Eu3+ in DMSO is totally different from LaF3:Ce, very strong characteristic luminescence is observed but no emissions from metal-to-ligand charge-transfer excited states as observed in LaF3:Ce in DMSO. Besides, it is very interesting to see that the coupling of Eu 3+ with O-H oscillations after water was introduced has an opposite effect on emission peaks at 617 nm and its shoulder peak at 613 nm. As a result, the intensity ratio of these two emissions has a nearly perfect linear dependence on increasing water concentration in Eu-DMSO, which provides a very convenient and valuable method for water determination in DMSO. Ce3+ has been well known as an emitter for radiation detection due to its very short decay lifetime. However, its emission range limited the environment in which the detection system works. Whereas, Quantum dots have high luminescence quantum efficiency but their low stopping power results in very weak scintillation luminescence. Nanocompounds formed with CdTe quantum dots and LaF3:Ce nanoparticles optimize both stopping power and scintillation efficiency based on energy transfer from LaF3:Ce to CdTe. Hybrid matrix materials such as ORMOSIL have superior mechanical properties and a better processability than pure molecular material which could be used as carrier of radiation material. Moreover, embedding a lanthanide complex in a hybrid matrix enhances its thermal stability and luminescence output. LaF3:Ce doped ORMOSIL was synthesized by using two different LaF3:Ce, the nanoparticle doping concentration can reach up to 15.66% while its transparency and luminescent properties were maintained. These materials are very promising for radiation detection.

  5. Some metal-graphite and metal-ceramic composites for use as high energy brake lining materials

    NASA Technical Reports Server (NTRS)

    Bill, R. C.

    1974-01-01

    Materials were studied as candidates for development as potential new aircraft brake lining materials. These families were (1) copper-graphite composites; (2) nickel-graphite composites; (3) copper - rare-earth-oxide (gadolinium oxide (Gd2O3) or lanthanum oxide (La2O3)) composites and copper - rare-earth-oxide (La2O3) - rare-earth-fluoride (lanthanum fluoride (LaF3)) composites; (4) nickel - rare-earth-oxide composites and nickel - rare-earth-oxide - rare-earth-fluoride composites. For comparison purposes, a currently used metal-ceramic composite was also studied. Results showed that the nickel-Gd2O3 and nickel-La2O3-LaF3 composites were comparable or superior in friction and wear performance to the currently used composite and therefore deserve to be considered for further development.

  6. Infrared-to-Ultraviolet upconversion luminescence of La 0.95Yb 0.49Tm 0.01F 3 nanostructures

    NASA Astrophysics Data System (ADS)

    De, Gejihu; Qin, Weiping; Wang, Weihua; Gui, Bao

    2009-07-01

    In this work, we used the hydrothermal method to synthesize Yb 3+ and Tm 3+ doped LaF 3 nanostructures, which is an ultraviolet upconversion luminescent material. Two distinct shapes such as nanosheets, nanoparticles and bulk samples formed in the products by adjusting the concentrations of the surfactant of the reaction solution. Powder X-ray diffraction analysis showed that the products were pure hexagonal phase, while electron microscopy measurements confirm the formation of different morphologies. These nanostructures exhibit strong ultraviolet upconversion luminescence under the excitation of a 978-nm diode laser. In Yb 3+ and Tm 3+ codoped LaF 3 materials, the relative intensity of ultraviolet and blue upconversion emissions became stronger as the size and morphology of sample changed from bulk to sheets.

  7. Investigation of Water-Soluble X-ray Luminescence Nanoparticles for Photodynamic Activation

    SciTech Connect

    Liu, Yuanfang; Chen, Wei; Wang, Shaopeng; Joly, Alan G.

    2008-01-28

    In this letter, we report the synthesis of LaF3:Tb3+-MTCP (meso-Tetra(4-carboxyphenyl) porphine) nanoparticle conjugates and investigate the energy transfer as well as singlet oxygen generation following X-ray irradiation. Our observations indicate that LaF3:Tb3+-MTCP nanoparticle conjugates are efficient photodynamic agents that can be initiated by X-rays at a reasonably low dose. The addition of folic acid to facilitate targeting to folate receptors on tumor cells has no effect on the quantum yield of singlet oxygen in the nanoparticle-MTCP conjugates. Our pilot studies indicate that water-soluble scintillation nanoparticles can be potentially used to activate photodynamic therapy as a promising deep cancer treatment.

  8. An Investigation of Fast Ion Transport in Solids Using Conductivity and N.M.R. (Fast Ion Transport in Solids).

    DTIC Science & Technology

    1980-10-15

    A crystal grown from one batch of Rare Earth Products material. 3. A crystal grown from the same material as 2 plus 1000 p.p.m. SrF2 (Harshaw crystal...III. 2 C. Sr 2+ doped LaF3 Crystal 3 was doped with 1000 p.p.m. SrF2 and the conductivity plot is shown in Figures 8 and 12. As might have been... SRF2 -S2 - 111.2 D. Th4 doped LaF3 Crystal 4 was doped with 1000 p.p.m. ThF4 and the conductivity plot is shown in Figure 8 and 13. The conductivity

  9. Nanocrystallization in Fluorochlorozirconate Glass-Ceramics.

    PubMed

    Alvarez, Carlos J; Liu, Yuzi; Leonard, Russell L; Johnson, Jacqueline A; Petford-Long, Amanda K

    2013-11-01

    Heat treating fluorochlorozirconate (FCZ) glasses nucleates nanocrystals in the glass matrix, resulting in a nanocomposite glass-ceramic that has optical properties suitable for use as a medical imaging plate. Understanding the way in which the nanocrystal nucleation proceeds is critical to controlling the optical behavior. The nucleation and growth of nanocrystals in FCZ glass-ceramics was investigated with in situ transmission electron microscopy heating experiments. The experiments showed the nucleation and growth of previously unreported BaF2 nanocrystals in addition to the expected BaCl2 nanocrystals. Chemical analysis of the BaF2 nanocrystals shows an association with the optically active dopant previously thought only to interact with BaCl2 nanocrystals. The association of the dopant with BaF2 crystals suggests that it plays a role in the photoluminescent (PL) properties of FCZ glass-ceramics.

  10. Interfacial reactions and microstructure of BaTiO 3 films prepared using fluoride precursor method

    NASA Astrophysics Data System (ADS)

    Fujihara, Shinobu; Schneller, Theodor; Waser, Rainer

    2004-01-01

    Interfacial reactions of BaF 2 and TiO 2 were investigated in preparing BaTiO 3 thin films using a fluoride precursor method. Trifluoroacetate solutions were prepared from barium acetate, titanium tetraisopropoxide (TTIP), and trifluoroacetic acid (TFA, CF 3COOH) with additives such as water and acetylacetone. The solutions were deposited on platinized Si wafers by spin-coating, were pyrolysed at 400 °C in air and were finally heated typically at 700 °C in a water vapor atmosphere. The perovskite BaTiO 3 phase was obtained although a small portion of BaF 2 remained unreacted. Thus, the films were characterized as the mixture of BaTiO 3, BaF 2, and amorphous TiO 2. Influence of the solution chemistry on the phase evolution and microstructure was examined in order to discuss the reaction pathway of the perovskite phase.

  11. Electronic structure evolution during the growth of ultrathin insulator films on semiconductors: From interface formation to bulklike Ca F2 /Si (111) films

    NASA Astrophysics Data System (ADS)

    Klust, Andreas; Ohta, Taisuke; Bostwick, Aaron A.; Rotenberg, Eli; Yu, Qiuming; Ohuchi, Fumio S.; Olmstead, Marjorie A.

    2005-11-01

    The electronic structure of ultrathin (0.3-6nm) epitaxial insulator films grown on semiconductors, represented by the prototypical system CaF2/Si(111) , was studied using scanning tunneling spectroscopy and photoemission spectroscopy. The surface states related to the (7×7) reconstruction of the substrate are completely removed during the formation of the interface and an interface state is established in the CaF2 band gap close to the Fermi level. While the band gap of CaF2 films only 2 molecular layers thick is essentially bulklike, a film thickness of about 3nm is necessary to fully develop the bulk CaF2 valence band structure.

  12. Nanoscale “fluorescent stone”: Luminescent Calcium Fluoride Nanoparticles as Theranostic Platforms

    PubMed Central

    Li, Zhanjun; Zhang, Yuanwei; Huang, Ling; Yang, Yuchen; Zhao, Yang; El-Banna, Ghida; Han, Gang

    2016-01-01

    Calcium Fluoride (CaF2) based luminescent nanoparticles exhibit unique, outstanding luminescent properties, and represent promising candidates as nanoplatforms for theranostic applications. There is an urgent need to facilitate their further development and applications in diagnostics and therapeutics as a novel class of nanotools. Here, in this critical review, we outlined the recent significant progresses made in CaF2-related nanoparticles: Firstly, their physical chemical properties, synthesis chemistry, and nanostructure fabrication are summarized. Secondly, their applications in deep tissue bio-detection, drug delivery, imaging, cell labeling, and therapy are reviewed. The exploration of CaF2-based luminescent nanoparticles as multifunctional nanoscale carriers for imaging-guided therapy is also presented. Finally, we discuss the challenges and opportunities in the development of such CaF2-based platform for future development in regard to its theranostic applications. PMID:27877242

  13. A new gamma camera for positron emission tomography

    NASA Astrophysics Data System (ADS)

    Schotanus, Paul

    1988-06-01

    The detection of annihilation radiation employing radiation absorbed in a barium fluoride (BaF2) crystal is described. The resulting scintillation light is detected in a multiwire proportional chamber filled with a photosensitive vapor. The use of a high density fast scintillator with a low pressure wire chamber offers a good detection efficiency and permits high count rates because of the small dead time. The physical background of the detection mechanism is explored and the performance parameters of a gamma camera using this principle are determined. The scintillation mechanism and physical characteristics of the BaF2 scintillator are examined. Ultraviolet scintillation materials consisting of rare earth doped fluorides are introduced.

  14. Metallic Halide Optical Glasses: Synthesis and Characterization of IR Transmitting Fluoride Glasses.

    DTIC Science & Technology

    1982-10-01

    impurities. For plasses mel ted under react ive atmosphere s and peaks at 2.9 T- were found LO bc due almost rentirely to surface -OH. t was; generally...I at 1400 cm , ln(To/T) at 3400 cm and Appearance of 62ZrF -33BaF 2-5LaF Glasses Prepared Under Various Processing Conditions. 104 -! Table XXI...Values of Thickness, T , a at 1400 cm , In(T^/T) at40-0 3400 cm and Appearance of 62HfF4 -33BaF 2 -5LaF Glasses Prepared Under Various ProcessL-ig

  15. Solid State Research

    DTIC Science & Technology

    1993-02-15

    center formation. 40 4-4 Color centers induced in CaF2 with a 193-nm laser at a fluence of 100 mJ cm_2/pulse. The three grades form color centers...Figure 4-4. Color centers induced in CaF2 witha 193-nm laser at afluence of100 mJ cm𔃼/pulse. The three grades form color centers at rates

  16. Characterization of nanoscopic calcium fluoride films

    NASA Astrophysics Data System (ADS)

    Rehmer, A.; Kemnitz, E.

    2016-09-01

    Nano metal fluorides are appropriate materials for different applications e.g. heterogeneous catalysis, ceramic materials for laser applications and antireflective layers on glass, respectively. An easy way to synthesize such nano metal fluorides is the fluorolytic sol-gel synthesis which was developed some few years ago for HS-AlF3 [1] and MgF2.[2] CaF2 exhibits similar optical properties as MgF2, and thus, is a promising candidate for antireflective (AR) coatings. That means, CaF2 exhibits a lower refractive index (n500 = 1.44) as compared to common soda lime glass (n500 = 1.53). Hence, we present an easy synthesis approach toward nanoscaled CaF2 sols to fabricate finally AR-CaF2 films by dip coating. Irrespective of the choice of the calcium precursor, the CaF2 films are porous in comparison to thin dense CaF2 films which are generated by physical vapor deposition. The characterization of CaF2 films was performed by different analytical methods like HR-SEM, XPS, EDX, EP (ellipsometric porosimetry), DLS (dynamic light scattering) and CA (contact angle measurement). Beside the good optical and mechanical properties, we have investigated the surface properties of CaF2 films on glass and silicon wafer e.g. surface morphology with elemental composition, open porosity, zeta potentials at the surfaces as well as the free energy of interaction between water and the CaF2 film.

  17. Mechanisms for Species-Selective Oriented Crystal Growth at Organic Templates

    SciTech Connect

    Kewalramani,S.; Kim, K.; Evmenenko, G.; Zschack, P.; Karapetrova, E.; Bai, J.; Dutta, P.

    2007-01-01

    Langmuir monolayers floating on supersaturated aqueous subphases can act as templates for the growth of oriented inorganic films--a 'bioinspired' nucleation process. We have performed in situ grazing incidence x-ray diffraction studies of the selective nucleation of BaClF and BaF2 under fatty acid monolayers. The arrangement of the fatty acid headgroups, the monolayer charge, and ion-specific effects all play important roles in selecting the inorganic species. When the monolayer is in a neutral state, both BaClF and BaF2 nucleate at the interface and are well aligned, but when the monolayer headgroup is deprotonated, only oriented BaF2 grows at the interface. We also observe an enhanced alignment of BaF2 crystals during growth from highly supersaturated solutions, presumably due to reorganization of preformed crystals at the organic template. These results show that a delicate interplay between multiple factors governs the oriented growth of inorganic films at organic templates.

  18. Recent Research with the Detector for Advanced Neutron Capture Experiments (dance) at the LOS Alamos Neutron Science Center

    NASA Astrophysics Data System (ADS)

    Ullmann, J. L.

    2014-09-01

    The DANCE detector at Los Alamos is a 160 element, nearly 4π BaF2 detector array designed to make measurements of neutron capture on rare or radioactive nuclides. It has also been used to make measurements of gamma-ray multiplicity following capture and gamma-ray output from fission. Several examples of measurements are briefly discussed.

  19. Exploratory Development on Laser and Optical Materials.

    DTIC Science & Technology

    Judd-Ofelt theory, Quantum efficiencies); Laser materials evaluation; Studies of rare-earth doped CdF2, SrF2 , and BaF2 -- (Electroluminescence of semiconducting CdF2, Analyses of the optical spectra of Gd(3+) and Ce(3+)).

  20. [Using barium fluoride fine particles as stationary phase for TLC/FTIR analysis].

    PubMed

    Liu, Xi; Pan, Qing-hua; Ding, Jie; Zhu, Qing; He, An-qi; Yue, Shi-juan; Li, Xiao-pei; Hu, Li-ping; Xia, Jin-ming; Liu, Cui-ge; Wei, Yong-ju; Yu, Jiang; Yang, Zhan-lan; Zhu, Xi; Xu, Yi-zhuang; Wu, Jin-guang

    2011-07-01

    In situ TLC/FTIR technique has tremendous potential in the analysis of complex mixtures. However, the progress in this technique was quite slow. The reason is that conventional stationary phase such as silica gel etc. has strong absorption in FTIR spectrum and thus brings about severe interference in the detection of samples. To solve the problem, the authors propose to use barium fluoride fine particles as stationary phase of TLC plate. The reasons are as follows: Barium fluoride wafer has been extensively used as infrared window in FTIR experiments and it has no absorbance in an IR region between 4 000 and 800 cm'. As a matter of fact, the atomic mass of barium and fluoride is quite large, thus the normal vibration of BaF2 lattice is limited in far-IR region and low frequency part of mid-IR region. Therefore, the interference caused by IR absorption of stationary phase can be resolved if BaF2 is used as stationary phase of TLC plate. Moreover, BaF2 is quite stable and insolvable in water and most organic solvents and it will not be dissolved by mobile phase or react with samples in TLC separation. Additionally, decreasing the particle size of BaF2 is very important in TLC/FTIR analysis technique. The reason is two-fold: First, decreasing the particle size of stationary phase is helpful to improving the efficiency of separation by TLC plate; second, decreasing the size of BaFz particle can improve the quality of FTIR spectra by alleviating the problem of light scattering. By optimizing the synthetic conditions, fine particles of barium fluoride were obtained. SEM results indicate that the size of the BaF2 particles is around 500 nm. FTIR spectrum of the BaF2 particles shows that no absorption of impurity was observed. Moreover, the elevation of baseline caused by light scattering is insignificant. The authors have developed a new technique named "settlement volatilization method" to prepare TLC plate without polymeric adhesive that may bring about significant interference in FTIR analysis. Preliminary TLC experiments proved that the TLC plate using BaF2 fine particles as stationary phase can separate rhodamine B from methylene blue successfully. Applications of barium fluoride fine particles as stationary phase have bright perspective in the development of new in-situ TLC/FTIR analysis techniques.

  1. Effect of Halide Flux on Physicochemical Properties of MgCl2-Based Molten Salts for Accelerating Zirconium Production: Thermodynamic Assessment

    NASA Astrophysics Data System (ADS)

    Shin, Jae Hong; Park, Joo Hyun

    2016-09-01

    The effective halide flux additive for increasing the density of MgCl2 mixture and for decreasing the activity of MgCl2 was investigated in order to improve the reaction efficiency between gaseous ZrCl4 and fresh Mg melt to produce zirconium sponge. Thermochemical computation using FactSageTM software was primarily carried out, followed by the experimental confirmation. The addition of CaCl2, BaCl2, MgF2, and CaF2 to the molten MgCl2 increases the density of the melts, indicating that these halide additives can be a candidate to increase the density of the MgCl2-based molten salts. Among them, BaCl2, MgF2, and CaF2 are the useful additives. The activity of MgCl2 can be reduced by the addition of BaCl2, KCl, NaCl, MgF2, and CaF2, among which the CaF2 is the most effective additive to reduce the activity of MgCl2 with the strongest negative deviation from an ideality. Thus, the addition of CaF2 to the MgCl2, forming the MgCl2-CaF2 binary melt, is the most effective way not only to increase the density of the melt but also to decrease the activity of MgCl2, which was experimentally confirmed. Consequently, the production rate of zirconium sponge by magnesiothermic reduction process can be accelerated by the addition of CaF2.

  2. Simultaneous determination of tantalum and hafnium in silicates by neutron activation analysis

    USGS Publications Warehouse

    Greenland, L.P.

    1968-01-01

    A neutron activation procedure suitable for the routine determination of tantalum and hafnium in silicates is described. The irradiated sample is fused with sodium peroxide and leached, and the insoluble hydroxides are dissolved in dilute hydrofluoric acid-hydrochloric acid. After LaF3 and AgCl scavenges, tantalum and hafnium are separated by anion exchange. Tantalum is obtained radiochemically pure; 233Pa and 95Zr contaminants in the hafnium fraction are resolved by ??-ray spectrometry. The chemical yield of the procedure is detemined after counting by re-irradiation. Values for the 8 U.S. Geological Survey standard rocks are reported. ?? 1968.

  3. The influence of restricted geometry of diamagnetic nanoporous media on 3He relaxation

    NASA Astrophysics Data System (ADS)

    Alakshin, E. M.; Gazizulin, R. R.; Zakharov, M. Yu.; Klochkov, A. V.; Morozov, E. V.; Salikhov, T. M.; Safin, T. R.; Safiullin, K. R.; Tagirov, M. S.; Shabanova, O. B.

    2015-01-01

    This is an experimental study of the spin kinetics of 3He in contact with diamagnetic samples of inverse opals SiO2, and LaF3 nanopowder. It is demonstrated that the nuclear magnetic relaxation of the absorbed 3He occurs due to the modulation of dipole-dipole interaction by the quantum motion in the two-dimensional film. It is found that the relaxation of liquid 3He occurs through a spin diffusion to the absorption layer, and that the restricted geometry of diamagnetic nanoporous media has an influence on the 3He relaxation.

  4. Optimum conditions for correlation of the temporal shape of an object pulse with a stimulated photon echo response in inhomogeneous external electric fields

    NASA Astrophysics Data System (ADS)

    Nefediev, L. A.; Khakimzyanova, E. I.; Garnaeva, G. I.

    2013-12-01

    We have studied the information locking effect and the effect of correlation of the shape of an object laser pulse with the shape of a stimulated photon echo response in the presence of external spatially inhomogeneous electric fields. We have shown that, for the transition 3H4-3P0 in a LaF3:Pr3+ crystal, one can observe the effect of the correlation of the shape of an object laser pulse with the shape of a stimulated photon echo response and, depending on the scheme of the action of external spatially inhomogeneous electric fields, either the information locking effect or the information destroying effect.

  5. Nanostructured LaF{sub 3}:Ce Quantum Dot Nuclear Radiation Detector

    SciTech Connect

    Guss, P., Guise, R., Reed, M., Mukhopadhyay, S., Yuan, D.

    2010-11-01

    Many radioactive isotopes have low energy X-rays and high energy gamma rays of interest for detection. The goal of the work presented was to demonstrate the possibility of measuring both low-energy X-rays and relatively high-energy gamma rays simultaneously using the nano-structured lanthanum bromide, lanthanum fluoride, or cerium bromide. The key accomplishments of the project was the building and acquisition of the LaF3:Ce nanocomposite detectors. Nanocomposite detectors are sensitive to {gamma}’s as well as n’s and X-rays.

  6. A calcium prerinse required to form calcium fluoride in plaque from a sodium fluoride rinse.

    PubMed

    Vogel, G L; Tenuta, L M A; Schumacher, G E; Chow, L C

    2014-01-01

    The purpose of this study is to determine whether a calcium (Ca) prerinse used before a 228 µg/g (ppm) fluoride (F) rinse would induce the formation of 'calcium fluoride-like' (CaF2-like) deposits in human dental plaque. Sixty minutes after the use of the Ca prerinse/F rinse, plaque samples were collected from 10 volunteers, homogenized, and split into 2 aliquots. The plaque mass from one aliquot was then extracted with a 'plaque-like' solution that extracted all the CaF2-like deposits. The total F in both aliquots was then determined and compared. The results demonstrated that, as in previous studies, the Ca prerinse induced large increases in plaque fluid and total plaque F. However, unlike previous results without the Ca prerinse, 30% of the plaque F deposits were CaF2 or CaF2-like. Given that maintaining an elevated F concentration in the vicinity of a developing lesion may play an important role in the cariostatic effect of this ion, and the potential advantages of CaF2-like deposits as an F source, these results suggest that a Ca prerinse may increase the cariostatic effect of topical agents.

  7. Fluoride coatings on orthodontic wire for controlled release of fluorine ion.

    PubMed

    Lee, Su-Hee; Kim, Hae-Won; Kong, Young-Min; Kim, Hyoun-Ee; Lee, Sung-Ho; Chang, Young-Il

    2005-10-01

    The purpose of this study was to develop a new method of releasing fluorine in a controlled manner for applications in the field of orthodontic Ti-based wire, namely the coating of fluorides on Ti. Thin films of two fluoride compounds, CaF(2) and MgF(2), were coated on Ti via the electron-beam evaporation method. The fluorine was released rapidly from the as-deposited MgF(2) coating within a short period(,) and then the release rate slowed down. When the MgF(2) coating was heat treated, this initial burst effect was decreased, but a significant amount of cracks were generated. On the other hand, in the case of the as-deposited CaF(2) coating, fluorine was released linearly for the entire period, without an initial burst. In the heat-treated CaF(2) coatings the trend was similarly observed. The linear fluorine release from the CaF(2) coatings, even in the as-deposited state, was attributed to the high degree of crystallinity of the coatings. A preliminary cell test showed favorable cell viability on both the fluoride coatings. Given their sustained and controlled fluorine release, these fluoride coatings, particularly CaF(2), are suggested to be potentially useful in the field of orthodontic Ti-based wire.

  8. Mechanical Properties of Calcium Fluoride-Based Composite Materials

    PubMed Central

    Kleczewska, Joanna; Pryliński, Mariusz; Podlewska, Magdalena; Sokołowski, Jerzy; Łapińska, Barbara

    2016-01-01

    Aim of the study was to evaluate mechanical properties of light-curing composite materials modified with the addition of calcium fluoride. The study used one experimental light-curing composite material (ECM) and one commercially available flowable light-curing composite material (FA) that were modified with 0.5–5.0 wt% anhydrous calcium fluoride. Morphology of the samples and uniformity of CaF2 distribution were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Mechanical properties were tested after 24-hour storage of specimens in dry or wet conditions. Stored dry ECM enriched with 0.5–1.0 wt% CaF2 showed higher tensile strength values, while water storage of all modified ECM specimens decreased their tensile strength. The highest Vickers hardness tested after dry storage was observed for 2.5 wt% CaF2 content in ECM. The addition of 2.0–5.0 wt% CaF2 to FA caused significant decrease in tensile strength after dry storage and overall tensile strength decrease of modified FA specimens after water storage. The content of 2.0 wt% CaF2 in FA resulted in the highest Vickers hardness tested after wet storage. Commercially available composite material (FA), unmodified with fluoride addition, demonstrated overall significantly higher mechanical properties. PMID:28004001

  9. First-principles calculations on the structural and electronic properties of cubic KCaF3 and NaCaF3 (001) surfaces

    NASA Astrophysics Data System (ADS)

    Yang, Kun; He, Yanqing; Cheng, Yi; Che, Li; Yao, Li

    2017-03-01

    First-principles density functional theory (DFT) calculations have been used to investigate the structural and electronic properties of the cubic KCaF3 and NaCaF3 (001) surfaces with MF (M = K or Na) and CaF2 terminations. For both KCaF3 and NaCaF3 (001) surfaces, the MF termination has stronger surface rumpling than the CaF2 termination. All the computed band gaps for the KCaF3 and NaCaF3 (001) surfaces are smaller than those of the bulks. Furthermore, separated bands that originate from surface layer F p states are introduced at the top of the valance band of MF-terminated surfaces, indicating the emergence of the surface states. The calculated surface energies show that the MF-terminated surface is energetically more favorable than the CaF2-terminated surface.

  10. Facet-mediated growth of silver nanoparticles on biaxial calcium fluoride nanorod arrays

    NASA Astrophysics Data System (ADS)

    Auer, Mathias; Ye, Dexian

    2017-01-01

    The surface orientation of metal nanoparticles is critical to their physical and chemical properties. This study aims on the understanding of the effect of surface orientation as well as heterogeneous epitaxy of metal nanoparticles at an interface between two materials with a large lattice mismatch. Silver nanoparticles of different diameters were grown on arrays of calcium fluoride (CaF2) nanorods using oblique angle deposition as a model system for this study. Scanning electron microscopy and transmission electron microscopy (TEM) imaging were used to verify that the nanoparticles were selectively grown on the desired {111} facets of the nanorod tips. Using selected area diffraction and dark field imaging in TEM, it was shown that the nanoparticles were grown at a (111) orientation at the CaF2 interface with large lattice strains. Thus biaxially textured CaF2 nanorod arrays can be used as a catalytic support.

  11. Microstructural and ionic transport studies of hydrothermally synthesized lanthanum fluoride nanoparticles

    NASA Astrophysics Data System (ADS)

    Patro, L. N.; Kamala Bharathi, K.; Ravi Chandra Raju, N.

    2014-12-01

    This article presents the structural and transport characteristics of hydrothermally synthesized LaF3 nanoparticles with an average crystallite size of 35nm. The phase formation of the material is confirmed by both X-ray diffraction and transmission electron microscopy techniques. In addition, phase purity of the LaF3 nanoparticles is corroborated by micro-Raman spectroscopy studies. The complex impedance plots at different temperatures reveal that the conductivity is predominantly due to the intrinsic bulk grains and the conductivity relaxation is non-Debye in nature. The frequency variation of conductivity exhibits dispersion at higher frequencies that can be explained with the frame work of Almond-West formalism. The conduction process is controlled by the mobility of the charge carriers and the charge of transport of mobile fluoride ions occur through hopping mechanism. The scaling behavior of both frequency dependence of conductivity and complex impedance plots at different temperatures confirm that the relaxation mechanism of the mobile fluoride ions is independent of temperature.

  12. Up/down conversion switching by adjusting the pulse width of red laser beams in LaF₃:Tm³⁺ nanocrystals.

    PubMed

    Gao, Dangli; Tian, Dongping; Xiao, Guoqing; Chong, Bo; Yu, Genghua; Pang, Qing

    2015-08-01

    We demonstrate a versatile approach to fine-tuning the ratio of blue to near-infrared emission intensity from Tm3+ ions in LaF3 nanocrystals by adjusting the pulse widths and excitation wavelengths of red laser beams. The mechanism of color-tunable Tm3+ emission by pulse widths is explored, and a mechanism based on promoting the population of some luminescence levels and cutting off the population of others by suitably adjusting pulse duration is proposed. The underlying reason of excitation wavelength-modulated emission is ascribed to tuning absorption probability ratio of ground state absorption to excited state absorption by tuning the matching degree between the energies of excitation wavelength and ground (excited) state absorption of Tm3+. The ability of our LaF3:Tm3+ nanocrystals to emit variable emissions on demand in response to pulse width and excitation wavelength provides keen insights into controlling the population processes of luminescent levels and offers a versatile approach for tuning the spectral output.

  13. Growth and characterization of single crystal insulators on silicon

    NASA Technical Reports Server (NTRS)

    Schowalter, Leo J.; Fathauer, Robert W.

    1989-01-01

    An overview of the growth and characterization of epitaxial insulators on semiconductors is presented. The potential applications include semiconductor-on-insulator structures, three-dimensional and/or high-density integrated circuits, optoelectronic applications such as integrated waveguides and improved gate insulators. The growth and physical characterization of epitaxial fluorides on semiconductors are discussed. Consideration is also given to the epitaxial overgrowth of epitaxial metal layers with CaF2 as well as to the formation of a novel superlattice of Ca particles in epitaxial CaF2.

  14. Skylab ultraviolet stellar astronomy experiment S019.

    PubMed

    O'Callaghan, F G; Henize, K G; Wray, J D

    1977-04-01

    An objective-prism stellar spectrograph of 15-cm aperture was flown on all three Skylab missions. The wavelength region from 1300 A to 5000 A was covered by a special optical system containing a combination of reflecting telescope optics, a CaF(2) objective prism, and an achromatized field corrector lens system of CaF(2) and LiF. Observations of 188 star fields, each covering 4.0 degrees 5.0 degrees , were conducted at the Skylab antisolar airlock with the aid of an articulated mirror system (AMS) which allowed acquisition within 30 degrees degrees 360 degrees band of the sky.

  15. Skylab ultraviolet stellar astronomy experiment S019

    NASA Technical Reports Server (NTRS)

    Ocallaghan, F. G.; Henize, K. G.; Wray, J. D.

    1977-01-01

    An objective-prism stellar spectrograph of 15-cm aperture was flown on all three Skylab missions. The wavelength region from 1300 A to 5000 A was covered by a special optical system containing a combination of reflecting telescope optics, a CaF2 objective prism, and an achromatized field-corrector lens system of CaF2 and LiF. Observations of 188 star fields, each covering 4.0 x 5.0 deg of arc, were conducted at the Skylab antisolar airlock with the aid of an articulated mirror system which allowed acquisition within a 30 by 360 deg band of the sky.

  16. Two Photon Detection Techniques for Atomic Fluorine

    DTIC Science & Technology

    1988-06-30

    to the two-photon detection technique. ’.d. %.. %9I Flowing He/F Mixture CaF 2 (20% F) from Pellin- Broca ionization Microwave Discharge Prism 1~~T6th...Stokes (AS) orders are separated using a CaF2 Pellin- Broca prism. The sixth AS at 170 un is propagated through an evacuated beam path (10 .5 torr) and...CaF2 Pellin- Broca prism. The atoms Br (Ref. 5) and Cl (Ref. 6) with limited sensitiv- sixth AS wave at 170 nm is propagated through a series ity6

  17. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Technical Reports Server (NTRS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1990-01-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectric having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writting capability, complex device structures like three-terminal hybrid semiconductors/superconductors transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray defraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  18. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Astrophysics Data System (ADS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1990-04-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectric having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writting capability, complex device structures like three-terminal hybrid semiconductors/superconductors transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray defraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  19. In-situ integrated processing and characterization of thin films of high temperature superconductors, dielectrics and semiconductors by MOCVD

    NASA Technical Reports Server (NTRS)

    Singh, R.; Sinha, S.; Hsu, N. J.; Thakur, R. P. S.; Chou, P.; Kumar, A.; Narayan, J.

    1991-01-01

    In this strategy of depositing the basic building blocks of superconductors, semiconductors, and dielectrics having common elements, researchers deposited superconducting films of Y-Ba-Cu-O, semiconductor films of Cu2O, and dielectric films of BaF2 and Y2O3 by metal oxide chemical vapor deposition (MOCVD). By switching source materials entering the chamber, and by using direct writing capability, complex device structures like three terminal hybrid semiconductor/superconductor transistors can be fabricated. The Y-Ba-Cu-O superconducting thin films on BaF2/YSZ substrates show a T(sub c) of 80 K and are textured with most of the grains having their c-axis or a-axis perpendicular to the substrate. Electrical characteristics as well as structural characteristics of superconductors and related materials obtained by x-ray deffraction, electron microscopy, and energy dispersive x-ray analysis are discussed.

  20. Organometallic Chemical Vapor Deposition of ZrF4-Based Fluoride Glasses

    NASA Astrophysics Data System (ADS)

    Fujiura, Kazuo; Ohishi, Yasutake; Takahashi, Shiro

    1989-01-01

    By organometallic chemical vapor deposition (OMCVD), fluoride glasses in a ZrF4-BaF2 binary system are successfully synthesized. β-Diketone chelates of Zr and Ba as starting materials can be volatilized and completely fluorinated with HF gas into ZrF4-BaF2 compounds. 65 mol%ZrF4-35 mol%BaF2 powder synthesized by OMCVD is identified as homogeneous glass by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). By this method, ZrF4 is also obtained in an amorphous state. The OMCVD is available for preparation of fluoride glass, which is promising for optical fiber.

  1. A simple radionuclide-driven single-ion source.

    PubMed

    Montero Díez, M; Twelker, K; Fairbank, W; Gratta, G; Barbeau, P S; Barry, K; DeVoe, R; Dolinski, M J; Green, M; LePort, F; Müller, A R; Neilson, R; O'Sullivan, K; Ackerman, N; Aharmin, B; Auger, M; Benitez-Medina, C; Breidenbach, M; Burenkov, A; Cook, S; Daniels, T; Donato, K; Farine, J; Giroux, G; Gornea, R; Graham, K; Hagemann, C; Hall, C; Hall, K; Hallman, D; Hargrove, C; Herrin, S; Karelin, A; Kaufman, L J; Kuchenkov, A; Kumar, K; Lacey, J; Leonard, D S; Mackay, D; MacLellan, R; Mong, B; Niner, E; Odian, A; Piepke, A; Pocar, A; Prescott, C Y; Pushkin, K; Rollin, E; Rowson, P C; Sinclair, D; Slutsky, S; Stekhanov, V; Vuilleumier, J-L; Wichoski, U; Wodin, J; Yang, L; Yen, Y-R

    2010-11-01

    We describe a source capable of producing single barium ions through nuclear recoils in radioactive decay. The source is fabricated by electroplating (148)Gd onto a silicon α-particle detector and vapor depositing a layer of BaF(2) over it. (144)Sm recoils from the alpha decay of (148)Gd are used to dislodge Ba(+) ions from the BaF(2) layer and emit them in the surrounding environment. The simultaneous detection of an α particle in the substrate detector allows for tagging of the nuclear decay and of the Ba(+) emission. The source is simple, durable, and can be manipulated and used in different environments. We discuss the fabrication process, which can be easily adapted to emit most other chemical species, and the performance of the source.

  2. Thin-film-formation study of high-Tc superconductors by resistive evaporation

    NASA Astrophysics Data System (ADS)

    Azoulay, Jacob

    1991-10-01

    Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O thin films were prepared with use of a conventional vacuum system for the evaporation of the constituents. This method produces stoichiometric films upon complete evaporation of the constituents. No thickness monitor or any other control system is required. In this study, substrates were kept at room temperature during the evaporation process. The bismuth-based thin films are shown to lose bismuth during heat treatment unless the Cu constituent is evaporated last and fully oxidized at 400 °C subsequently. Y-Ba-Cu-O films prepared by using a pulverized mixture of Y, BaF2, and Cu constituents show an improved quality over films obtained from YF3, BaF2, and Cu starting materials. This improvement is attributed to fluorine reduction in the starting-material mixture.

  3. TMAE vapour of CsI layers as photocathodes in a multiwire proportional counter working at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Guerard, B.; Bruyndonckx, P.; Tavernier, S.; Shuping, Zhang

    1991-12-01

    A multiwire proportional counter (MWPC) coupled to a BaF 2 crystal has been tested at atmospheric pressure for the detection of 511 keV photons. If TMAE is used as a photosensitive agent, we found that addition of H 2O vapour to the chamber gas is very well suited for the detection of single-photoelectrons. Encouraging first results were also obtained with caesium iodide photocathodes.

  4. Development of MBE grown Pb-salt semiconductor lasers for the 8.0 to 15.0 micrometer spectral region

    NASA Technical Reports Server (NTRS)

    Miller, M. D.

    1981-01-01

    Diodes lasers are fabricated using multiple source molecular beam expitaxial growth of (PbSn)Te on BaF2 substrates. Methods for crystal growth, crystal transfer, and device fabrication by photolithographic techniques were developed. The lasers operate in the spectra range from 10 microns to 14 microns and at temperatures from 12K to 60K continuous wave and to 95 K pulsed.

  5. Three Dimensional Positron Annihilation Momentum Measurement Technique Applied to Measure Oxygen-Atom Defects in 6H Silicon Carbide

    DTIC Science & Technology

    2010-03-01

    Start Stop BaF 2 Detectors High Voltage ORTEC 556 High Voltage ORTEC 556 Quad Const Fraction Discriminator ORTEC 935 Quad Logic Module ORTEC...detectors used 30 in 2D ACAR are discrete scintillation detector arrays, multi-wire proportional counters, and Anger cameras . A typical 2D ACAR...semiconductor material, in this experiment, it was planar germanium, by either photoelectric absorption, Compton scattering or pair production based on

  6. Near-IR luminescence from subvalent bismuth species in fluoride glass

    NASA Astrophysics Data System (ADS)

    Romanov, Alexey N.; Haula, Elena V.; Fattakhova, Zukhra T.; Veber, Alexander A.; Tsvetkov, Vladimir B.; Zhigunov, Denis M.; Korchak, Vladimir N.; Sulimov, Vladimir B.

    2011-11-01

    The broadband NIR luminescence of subvalent bismuth species was demonstrated in partially reduced ZrF 4-BiF 3-NaF and ZrF 4-BiF 3-BaF 2 fluoride glasses. The parameters of luminescence were reported and compared with luminescence from other bismuth-doped materials. Since fluoride glass compositions are based on strong Lewis acids (ZrF 4 in present case) they can stabilize NIR photoluminescent subvalent bismuth species.

  7. Ferroelectric Fluoride Memory FET Development

    DTIC Science & Technology

    1993-10-01

    After’ First Metal Definition ..................... 53 Figure 3-30: Initial BMF FEMFETs Demonstrated Ferroelectric Behavior ................ 57 I Figure...as bismuth titanate. 2.0 INTRODUCTION The concept of a thin film ferroelectric memory field-effect transistor (FEMFET) is not new. The first FEMFET...candidate for these studies. BaF2, and MgF 2 have similar melting and evaporation temperatures, and their vapor pressures were also found to be comparable

  8. Hexamer clusters in MeF2:Yb3+ (Me = Ca,Sr,Ba)

    NASA Astrophysics Data System (ADS)

    Chernyshev, V. A.; Nikiforov, A. E.; Nazemnikh, A. D.

    2011-10-01

    The electronic structure and g factors of simple impurity centers and hexamer ytterbium clusters in fluorites have been calculated in terms of the exchange charge model. Preliminarily, their local crystal structures have been calculated in the framework of the shell model with the inclusion of lattice distortions near the impurity. Crystal structure and g factors have been calculated of linear cluster Yb-F-Yb-F oriented along a trigonal axis in BaF2.

  9. Development of low-absorption AR coatings for CO2 laser by ion assisted deposition

    NASA Astrophysics Data System (ADS)

    Iwamoto, Hiromi; Ebata, Keiji; Nanba, Hirokuni

    2003-02-01

    We have developed an anti-reflection (AR) coating technique designed for high power carbon dioxide (CO2) lasers that has low absorption and high resistance to humidity. This was achieved by performing ion-assisted deposition (IAD) using a Xe ion beam to apply BaF2 and ZnSe used as coating materials with extremely low bulk absorption coefficients. It was found that to achieve highly compact BaF2 thin films with low absorption on polycrystalline ZnSe substrates, both a surface flatness treatment using Xe ion bombardment and an optimized IAD condition of relatively low ion energy up to 200 eV are required. The absorption of the new (BaF2/ZnSe) AR coated ZnSe lens is 0.10 to 0.12%, approximately half that of conventional (ThF4/ZnSe) AR coated lenses. The new lens has both excellent anti-aging performance and a high resistance to humidity.

  10. Observation of Charge Inversion of an Ionic Liquid at the Solid Salt-Liquid Interface by Sum Frequency Generation Spectroscopy.

    PubMed

    Peñalber, Chariz Y; Baldelli, Steven

    2012-04-05

    Sum frequency generation (SFG) vibrational spectroscopy of the ionic liquid, 1-butyl-3-methylimidazolium dicyanamide [BMIM][DCA], in contact with two different solid salt surfaces, BaF2(111) single crystal and solid NaCl{100}, are discussed in this Letter. This investigation describes the nature of an ionic liquid-(solid) salt interface using SFG, contributing a new understanding to the molecular-level interactions involved in salts, which are conceptually similar compounds (of purely ionic character) but of different physical properties (liquid versus solid at room temperature). Results show the presence of [BMIM](+) at the NaCl{100} surface and [DCA](-) at the BaF2(111) surface. [BMIM](+) cations adhere closely via Coulombic interactions to the negatively charged NaCl{100} surface, while [DCA](-) anions subsequently have a strong electrostatic affinity to the positively charged BaF2(111) surface. Ions of the ionic liquid adsorb to the solid salt surface to form a Helmholtz-like electric double layer.

  11. Prevention of enamel demineralization with a novel fluoride strip: enamel surface composition and depth profile

    PubMed Central

    Lee, Bor-Shiunn; Chou, Po-Hung; Chen, Shu-Yu; Liao, Hua-Yang; Chang, Che-Chen

    2015-01-01

    There is no topically applicable low concentration fluoride delivery device available for caries prevention. This study was aimed to assess the use of a low concentration (1450 ppm) fluoride strip as an effective fluoride delivery system against enamel demineralization. The enamel surface composition and calcium-deficient hydroxyapatite or toothpaste treatments were investigated using X-ray photoelectron spectroscopy. In vitro enamel demineralization was assayed using a pH cycling model and the dissolution of calcium ions from the treated specimens was quantified using ion chromatography. After 24-hr fluoride-strip treatment, the enamel was covered with a CaF2 layer which showed a granular morphology of 1 μm in size. Below the CaF2 layer was a region of mixed fluorapatite and CaF2. Fluoride infiltrated extensively in enamel to produce highly fluorinated fluorohydroxyapatite. In comparison, low-fluoride-level fluorinated fluorohydroxyapatite was formed on the enamel specimen exposed to toothpaste. The treatments with the fluoride strip as short as 1 hr significantly inhibited enamel demineralization. The fluoride strip was effective for topical fluoride delivery and inhibited in vitro demineralization of enamel by forming CaF2 and fluoride-containing apatites at the enamel surface. It exhibited the potential as an effective fluoride delivery device for general use in prevention of caries. PMID:26293361

  12. The mechanical properties of fluoride salts at elevated temperatures. [candidate thermal energy storage materials for solar dynamic systems

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Whittenberger, J. D.

    1989-01-01

    The deformation behavior of CaF2 and LiF single crystals compressed in the 111 and the 100 line directions, respectively, are compared with the mechanical properties of polycrystalline LiF-22 (mol pct) CaF2 eutectic mixture in the temperature range 300 to 1275 K for strain rates varying between 7 x 10 to the -7th and 0.2/s. The true stress-strain curves for the single crystals were found to exhibit three stages in an intermediate range of temperatures and strain rates, whereas those for the eutectic showed negative work-hardening rates after a maximum stress. The true stress-strain rate data for CaF2 and LiF-22 CaF2 could be represented by a power-law relation with the strain rate sensitivities lying between 0.05 and 0.2 for both materials. A similar relation was found to be unsatisfactory in the case of LiF.

  13. Prevention of enamel demineralization with a novel fluoride strip: enamel surface composition and depth profile.

    PubMed

    Lee, Bor-Shiunn; Chou, Po-Hung; Chen, Shu-Yu; Liao, Hua-Yang; Chang, Che-Chen

    2015-08-21

    There is no topically applicable low concentration fluoride delivery device available for caries prevention. This study was aimed to assess the use of a low concentration (1450 ppm) fluoride strip as an effective fluoride delivery system against enamel demineralization. The enamel surface composition and calcium-deficient hydroxyapatite or toothpaste treatments were investigated using X-ray photoelectron spectroscopy. In vitro enamel demineralization was assayed using a pH cycling model and the dissolution of calcium ions from the treated specimens was quantified using ion chromatography. After 24-hr fluoride-strip treatment, the enamel was covered with a CaF2 layer which showed a granular morphology of 1 μm in size. Below the CaF2 layer was a region of mixed fluorapatite and CaF2. Fluoride infiltrated extensively in enamel to produce highly fluorinated fluorohydroxyapatite. In comparison, low-fluoride-level fluorinated fluorohydroxyapatite was formed on the enamel specimen exposed to toothpaste. The treatments with the fluoride strip as short as 1 hr significantly inhibited enamel demineralization. The fluoride strip was effective for topical fluoride delivery and inhibited in vitro demineralization of enamel by forming CaF2 and fluoride-containing apatites at the enamel surface. It exhibited the potential as an effective fluoride delivery device for general use in prevention of caries.

  14. Lattice dynamics and thermal conductivity of calcium fluoride via first-principles investigation

    NASA Astrophysics Data System (ADS)

    Qi, Yuan-Yuan; Zhang, Tian; Cheng, Yan; Chen, Xiang-Rong; Wei, Dong-Qing; Cai, Ling-Cang

    2016-03-01

    The lattice thermal conductivity of CaF2 is accurately computed from a first-principles theoretical approach based on an iterative solution of the Boltzmann transport equation. The second- and third-order interatomic force constants are generated from a real-space finite-difference supercell approach. Then, the force constants for both the second- and third-order potential interactions are used to calculate the lattice thermal conductivity and related physical quantities of CaF2 at temperatures ranging from 30 K to 1500 K. The obtained lattice thermal conductivity 8.6 W/(m.K) for CaF2 at room temperature agrees better with the experimental value than other theoretical data, demonstrating the promise of this parameter-free approach in providing precise descriptions of the lattice thermal conductivity of materials. The obtained dielectric parameters and phonon spectrum of CaF2 accord well with available data. Meanwhile, the temperature dependence curves of the lattice thermal conductivity, heat capacity, and phonon mean free path are presented.

  15. Calcium fluoride nanoparticles induced suppression of Streptococcus mutans biofilm: an in vitro and in vivo approach.

    PubMed

    Kulshrestha, Shatavari; Khan, Shakir; Hasan, Sadaf; Khan, M Ehtisham; Misba, Lama; Khan, Asad U

    2016-02-01

    Biofilm formation on the tooth surface is the root cause of dental caries and periodontal diseases. Streptococcus mutans is known to produce biofilm which is one of the primary causes of dental caries. Acid production and acid tolerance along with exopolysaccharide (EPS) formation are major virulence factors of S. mutans biofilm. In the current study, calcium fluoride nanoparticles (CaF2-NPs) were evaluated for their effect on the biofilm forming ability of S. mutans in vivo and in vitro. The in vitro studies revealed 89 % and 90 % reduction in biofilm formation and EPS production, respectively. Moreover, acid production and acid tolerance abilities of S. mutans were also reduced considerably in the presence of CaF2-NPs. Confocal laser scanning microscopy and transmission electron microscopy images were in accordance with the other results indicating inhibition of biofilm without affecting bacterial viability. The qRT-PCR gene expression analysis showed significant downregulation of various virulence genes (vicR, gtfC, ftf, spaP, comDE) associated with biofilm formation. Furthermore, CaF2-NPs were found to substantially decrease the caries in treated rat groups as compared to the untreated groups in in vivo studies. Scanning electron micrographs of rat's teeth further validated our results. These findings suggest that the CaF2-NPs may be used as a potential antibiofilm applicant against S. mutans and may be applied as a topical agent to reduce dental caries.

  16. Calcium fluoride formation on sound enamel using fluoride solutions with and without lactate.

    PubMed

    Harding, A M; Zero, D T; Featherstone, J D; McCormack, S M; Shields, C P; Proskin, H M

    1994-01-01

    The formation of calcium (Ca) fluoride (CaF2) on bovine enamel blocks during clinically relevant treatment times using neutral fluoride (F) solutions (0.26 mol/l F) with and without 0.1 mol/l lactate was investigated. Uncoated and pellicle-coated blocks were evaluated for alkali-soluble (1 mol/l KOH, three consecutive 24-hour treatments) Ca, PO4, and F after treatment by the F solutions for 0, 5, 15, 30, and 60 min. There was an overall time-related increase in F recovery, while Ca tended to remain at baseline levels. Less F was recovered from the pellicle-coated blocks. The addition of lactate to the F treatment solution did not result in an overall increase in alkali-soluble F recovery, but did result in the formation of cuboidal shaped crystals which closely approached the morphology of pure CaF2. A 1:2 stoichiometric ratio Ca:2F (mol:mol) was not established based on chemical analyses. The ultrastructural and elemental composition of surface deposits on the samples, as determined using scanning electron microscopy, X-ray diffraction, and energy-dispersive spectroscopy, established the presence of CaF2 after 24-hour F treatments; however, it was not possible to directly demonstrate the formation of CaF2 after clinically relevant treatment times.

  17. Growth and magnetic properties of epitaxial Fe4N films on insulators possessing lattice spacing close to Si(001) plane

    NASA Astrophysics Data System (ADS)

    Ito, Keita; Higashikozono, Soma; Takata, Fumiya; Gushi, Toshiki; Toko, Kaoru; Suemasu, Takashi

    2016-12-01

    We grew ferromagnetic Fe4N films by molecular beam epitaxy on MgO(001), MgAl2O4(MAO)(001), SrTiO3(STO)(001), and CaF2(001) substrates, possessing the lattice spacing close to Si(001) plane. Highly oriented epitaxial growth was confirmed for the Fe4N films on the MgO, MAO, and STO by reflection high-energy electron diffraction and x-ray diffractions. The degree of orientation of the Fe4N film on the STO was the best among these samples. This was attributed to the smallest lattice mismatch of -2.8% between Fe4N(001) and STO(001). On the other hand, crystallinity of the Fe4N film on the CaF2(001) substrate was poor due to a very large lattice mismatch of -30% between Fe4N(001) and CaF2(001) arising from the unexpected epitaxial relationship as Fe4N(001)[100] || CaF2(001)[100]. The saturation magnetization of the Fe4N films was approximately 1200 emu/cm3 at room temperature for all the samples, and the magnetization easy axis was in-plane Fe4N[100]. We consider that STO is the suitable buffer layer for the growth of Fe4N on Si(001), hence to realize the Si-based spintronics devices using highly spin-polarized Fe4N.

  18. Dissociative Binding of Carboxylic Acid Ligand on Nanoceria Surface in Aqueous Solution: A Joint in Situ Spectroscopic Characterization and First-Principles Study

    SciTech Connect

    Lu, Zhou; Karakoti, Ajay S.; Velarde Ruiz Esparza, Luis A.; Wang, Weina; Yang, Ping; Thevuthasan, Suntharampillai; Wang, Hongfei

    2013-11-21

    Carboxylic acid is a common ligand anchoring group to functionalize nanoparticle surfaces. Its binding structures and mechanisms as a function of the oxidation states of metal oxide nanoparticle surfaces are not well characterized experimentally. We present an in situ sum frequency generation vibrational spectroscopy (SFG-VS) study on the binding of deuterated acetic acid on ceria nanoparticles in the aqueous solution. In the SFG experiment, ceria nanoparticles were deposited on the flat surface of a CaF2 hemisphere in contact with acetic acid solutions. While the ceria nanoparticle deprotonated the acetic acid, the CaF2 surface could not. Thus, the binding of the deprotonated acetic acid on ceria can be selectively probed. SFG spectra revealed that the binding modes of the carboxylate group depend on the oxidation states of the ceria surfaces. SFG polarization analysis suggested that the bidentate chelating and bridging binding modes co-exist on the reduced ceria surfaces, while the oxidized ceria surfaces are dominated by the bidentate bridging mode. The direct spectroscopic evidence helps to clarify the binding structures and mechanisms on the ceria nanoparticles. Furthermore, the middle-infrared (IR) transparent CaF2 and its chemical inertness make CaF2 and similar substrate materials good candidates for direct SFG-VS measurement of nanoparticle surface reactions and binding chem-istry.

  19. All-optical Photonic Oscillator with High-Q Whispering Gallery Mode Resonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy A.; Matsko, Andrey B.; Strekalov, Dmitry; Mohageg, Makan; Iltchenko, Vladimir S.; Maleki, Lute

    2004-01-01

    We demonstrated low threshold optical photonic hyper-parametric oscillator in a high-Q 10(exp 10) CaF2 whispering gallery mode resonator which generates stable 8.5 GHz signal. The oscillations result from the resonantly enhanced four wave mixing occurring due to Kerr nonlinearity of the material.

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

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

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

  1. Growth, Structure, and Thermal Conductivity of Yttria-Stabilized Hafnia Thin Films (Postprint)

    DTIC Science & Technology

    2012-01-01

    heated to temperatures higher than 1700 °C.9,10 Further transformation into the cubic polymorphic form having the fluorite structure takes place at 2700...of fluorite -structured (CaF2) oxygen superionic conductors.11 Interest in yttria-stabilized zirconia and hafnia materials is generated because of a

  2. Polishing test of a poly-crystal calcium fluoride lens: toward the development of TMT WFOS

    NASA Astrophysics Data System (ADS)

    Ozaki, Shinobu; Miyazaki, Satoshi; Tsuzuki, Toshihiro; Tanaka, Yoko

    2016-08-01

    Wide-Field Optical Spectrograph (WFOS) is one of the first-light instruments of Thirty Meter Telescope (TMT), and developed in an international collaboration led by University of California Santa Cruz. It covers the wavelength range from 310 nm to 1 μm which is divided at around 550 nm by a dichroic mirror. Calcium Fluoride (CaF2) is very useful to reduce aberration and has good transmittance even at 310 nm. Because a large mono-crystal CaF2 is difficult to be manufactured, we might have to use a poly-crystal CaF2. Comparing a mono-crystal, the poly-crystal is expected to have worse optical index homogeneity and larger surface figure error after polishing. Those effects on an image quality are unclear. To verify those effects, we conducted a polishing test of a small poly-crystal CaF2 lens as a first step. As a result, we found figure error around the boundary. The figure error is 139 nm PV and 26 nm RMS. Comparing a Zemax simulation, it is confirmed that the figure error does not have significant effect on the image quality.

  3. Enhancement of polar crystalline phase formation in transparent PVDF-CaF2 composite films

    NASA Astrophysics Data System (ADS)

    Lee, Sang Goo; Ha, Jong-Wook; Sohn, Eun-Ho; Park, In Jun; Lee, Soo-Bok

    2016-12-01

    We consider the influence of calcium fluoride (CaF2) nanoparticles on the crystalline phase formation of poly(vinylidene fluoride) (PVDF) for the first time. The transparent PVDF-CaF2 composite films were prepared by casting on PET substrates using N,N-dimethylacetamide (DMAc) as a solvent. It was found that CaF2 promoted the formation of polar crystalline phase of PVDF in composites, whereas nonpolar α-phase was dominant in the neat PVDF film prepared at the same condition. The portion of polar crystalline phase increased in proportional to the weight fraction of CaF2 in the composite films up to 10 wt%. Further addition of CaF2 suppressed completely the α-phase formation. Polar crystalline phase observed in as-cast composite films was a mixture of β- and γ-polymorph structures. It was also shown that much ordered γ-phase could be obtained through thermal treatment of as-cast PVDF-CaF2 composite film at the temperatures above the melting temperature of the composite films, but below that of γ-phase.

  4. Fluorspar

    USGS Publications Warehouse

    Miller, M.

    2012-01-01

    World fluorspar demand continued to show signs of recovery from 2008-2009 recession. In 2011, nearly all fluorspar (CaF2) consumed in the United States was imported. Hastie Mining and Trucking Co. produced some fluorspar as a byproduct from its limestone quarry operations in Illinois. In addition, a small amount of usable synthetic fluorspar was produced from industrial waste streams.

  5. Fluorspar

    USGS Publications Warehouse

    Miller, M.

    2002-01-01

    In 2001, one mine in Utah produced a small quantity of fluorspar. The majority of fluorspar consumed in the United States continued to come from imports or material purchased from the US National Defense Stockpile (NDS). In addition, a small amount of synthetic fluorspar (CaF2) was produced from industrial waste streams.

  6. Fluorspar

    USGS Publications Warehouse

    Miller, M.

    2003-01-01

    The United States had a small quantity of fluorspar production from one mine in Utah during 2002. Most of the fluorspar consumed in the United States continued to come from imports or material purchased from the National Defense Stockpile (NDS). In addition, a small amount of synthetic fluorspar (CaF2) was produced from industrial waste streams.

  7. Effect of various additives on microstructure, mechanical properties, and in vitro bioactivity of sodium oxide-calcium oxide-silica-phosphorus pentoxide glass-ceramics.

    PubMed

    Li, H C; Wang, D G; Hu, J H; Chen, C Z

    2013-09-01

    The partial substitution of MgO, TiO2, or CaF2 for CaO in the Na2O-CaO-SiO2-P2O5 (45S5) system was conducted by the sol-gel method and a comparative study on structural, mechanical properties, and bioactivity of the glasses was reported. Based on thermogravimetric and differential thermal analysis, the gels were sintered with a suitable heat treatment procedure. The glass-ceramic properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and so on, and the bioactivity of the glass-ceramic was evaluated by in vitro assays in simulated body fluid (SBF). Results indicate that with the partial substitution of MgO, TiO2, CaF2 for CaO in glass composition, the mechanical properties of the glass-ceramics have been significantly improved. Furthermore, CaF2 promotes glass crystallization and the crystallization does not inhibit the glass-ceramic bioactivity. All samples possess bioactivity; however, the bioactivity of these glass-ceramics is quite different. Compared with 45S5, the introduction of MgO decreases the ability of apatite induction. The addition of TiO2 does not significantly improve the bioactivity, and the replacement of CaO by CaF2 shows a higher bioactivity.

  8. Mirrored stainless steel substrate provides improved signal for Raman spectroscopy of tissue and cells.

    PubMed

    Lewis, Aaran T; Gaifulina, Riana; Isabelle, Martin; Dorney, Jennifer; Woods, Mae L; Lloyd, Gavin R; Lau, Katherine; Rodriguez-Justo, Manuel; Kendall, Catherine; Stone, Nicholas; Thomas, Geraint M

    2017-01-01

    Raman spectroscopy (RS) is a powerful technique that permits the non-destructive chemical analysis of cells and tissues without the need for expensive and complex sample preparation. To date, samples have been routinely mounted onto calcium fluoride (CaF2) as this material possesses the desired mechanical and optical properties for analysis, but CaF2 is both expensive and brittle and this prevents the technique from being routinely adopted. Furthermore, Raman scattering is a weak phenomenon and CaF2 provides no means of increasing signal. For RS to be widely adopted, particularly in the clinical field, it is crucial that spectroscopists identify an alternative, low-cost substrate capable of providing high spectral signal to noise ratios with good spatial resolution. Results show that these desired properties are attainable when using mirrored stainless steel as a Raman substrate. When compared with CaF2, data show that stainless steel has a low background signal and provides an average signal increase of 1.43 times during tissue analysis and 1.64 times when analyzing cells. This result is attributed to a double-pass of the laser beam through the sample where the photons from the source laser and the forward scattered Raman signal are backreflected and retroreflected from the mirrored steel surface and focused towards collection optics. The spatial resolution on stainless steel is at least comparable to that on CaF2 and it is not compromised by the reflection of the laser. Steel is a fraction of the cost of CaF2 and the reflection and focusing of photons improve signal to noise ratios permitting more rapid mapping. The low cost of steel coupled with its Raman signal increasing properties and robust durability indicates that steel is an ideal substrate for biological and clinical RS as it possesses key advantages over routinely used CaF2. © 2016 The Authors. Journal of Raman Spectroscopy Published by John Wiley & Sons Ltd.

  9. Verification of threshold activation detection (TAD) technique in prompt fission neutron detection using scintillators containing 19F

    NASA Astrophysics Data System (ADS)

    Sibczynski, P.; Kownacki, J.; Moszyński, M.; Iwanowska-Hanke, J.; Syntfeld-Każuch, A.; Gójska, A.; Gierlik, M.; Kaźmierczak, Ł.; Jakubowska, E.; Kędzierski, G.; Kujawiński, Ł.; Wojnarowicz, J.; Carrel, F.; Ledieu, M.; Lainé, F.

    2015-09-01

    In the present study ⌀ 5''× 3'' and ⌀ 2''× 2'' EJ-313 liquid fluorocarbon as well as ⌀ 2'' × 3'' BaF2 scintillators were exposed to neutrons from a 252Cf neutron source and a Sodern Genie 16GT deuterium-tritium (D+T) neutron generator. The scintillators responses to β- particles with maximum endpoint energy of 10.4 MeV from the n+19F reactions were studied. Response of a ⌀ 5'' × 3'' BC-408 plastic scintillator was also studied as a reference. The β- particles are the products of interaction of fast neutrons with 19F which is a component of the EJ-313 and BaF2 scintillators. The method of fast neutron detection via fluorine activation is already known as Threshold Activation Detection (TAD) and was proposed for photofission prompt neutron detection from fissionable and Special Nuclear Materials (SNM) in the field of Homeland Security and Border Monitoring. Measurements of the number of counts between 6.0 and 10.5 MeV with a 252Cf source showed that the relative neutron detection efficiency ratio, defined as epsilonBaF2 / epsilonEJ-313-5'', is 32.0% ± 2.3% and 44.6% ± 3.4% for front-on and side-on orientation of the BaF2, respectively. Moreover, the ⌀ 5'' EJ-313 and side-on oriented BaF2 were also exposed to neutrons from the D+T neutron generator, and the relative efficiency epsilonBaF2 / epsilonEJ-313-5'' was estimated to be 39.3%. Measurements of prompt photofission neutrons with the BaF2 detector by means of data acquisition after irradiation (out-of-beam) of nuclear material and between the beam pulses (beam-off) techniques were also conducted on the 9 MeV LINAC of the SAPHIR facility.

  10. Antibacterial and physical properties of calcium-phosphate and calcium-fluoride nanocomposites with chlorhexidine

    PubMed Central

    Cheng, Lei; Weir, Michael D.; Xu, Hockin H. K.; Kraigsley, Alison M.; Lin, Nancy J.; Lin-Gibson, Sheng; Zhou, Xuedong

    2012-01-01

    Objectives Previous studies have developed calcium phosphate and fluoride releasing composites. Other studies have incorporated chlorhexidine (CHX) particles into dental composites. However, CHX has not been incorporated in calcium phosphate and fluoride composites. The objectives of this study were to develop nanocomposites containing amorphous calcium phosphate (ACP) or calcium fluoride (CaF2) nanoparticles and CHX particles, and investigate S. mutans biofilm formation and lactic acid production for the first time. Methods Chlorhexidine was frozen via liquid nitrogen and ground to obtain a particle size of 0.62 µm. Four nanocomposites were fabricated with fillers of: Nano ACP; nano ACP+10% CHX; nano CaF2; nano CaF2+10% CHX. Three commercial materials were tested as controls: A resin-modified glass ionomer, and two composites. S. mutans live/dead assay, colony-forming unit (CFU) counts, biofilm metabolic activity, and lactic acid were measured. Results Adding CHX fillers to ACP and CaF2 nanocomposites greatly increased their antimicrobial capability. ACP and CaF2 nanocomposites with CHX that were inoculated with S. mutans had a growth medium pH > 6.5 after 3 d, while the control commercial composites had a cariogenic pH of 4.2. Nanocomposites with CHX reduced the biofilm metabolic activity by 10–20 folds and reduced the acid production, compared to the controls. CFU on nanocomposites with CHX were three orders of magnitude less than that on commercial composite. Mechanical properties of nanocomposites with CHX matched a commercial composite without fluoride. Significance The novel calcium phosphate and fluoride nanocomposites could be rendered antibacterial with CHX to greatly reduce biofilm formation, acid production, CFU and metabolic activity. The antimicrobial and remineralizing nanocomposites with good mechanical properties may be promising for a wide range of tooth restorations with anti-caries capabilities. PMID:22317794

  11. [Study on the Influence of Mineralizer on the Preparation of Calcium Aluminates Based on Infrared Spectroscopy].

    PubMed

    Fan, Wei; Wang, Liang; Zheng, Huai-li; Chen, Wei; Tang, Xiao-min; Shang, Juan-fang; Qian, Li

    2015-05-01

    In this study, effect of mineralizer on the structure and spectraproperties of calcium aluminates formation was extensively studied. Medium or low-grade bauxite and calcium carbonate were used as raw material and mineralizer CaF2 as additive. Calcium aluminates can be obtained after mixing fully, calcination and grinding. The prepared calcium aluminates can be directly used for the production of polyaluminiumchloride (PAC), polymeric aluminum sulfate, sodium aluminate and some other water treatment agents. The calcium aluminates preparation technology was optimized by investigating the mass ratio of raw materials (bauxiteand calcium carbonate) and mineralizer CaF2 dosage. The structure and spectra properties of bauxite and calcium aluminates were characterized by Fourier transform infrared(FTIR) spectroscopy analysis and the mineralization mechanism of the mineralizer was studied. FTIR spectra indicated that the addition of mineralizer promoted the decomposition and transformation of the diaspore, gibbsite and kaolinite, the decomposition of calcium carbonate, and more adequately reaction between bauxite and calcium carbonate. In addition, not only Ca in calcium carbonate and Si in bauxite were more readily reacted, but also Si-O, Si-O-Al and Al-Si bonds in the bauxite were more fractured which contributed to the release of Al in bauxite, and therefore, the dissolution rate of Al2O3 could be improved. The dissolution rate of Al2O3 can be promoted effectively when the mineralizer CaF2 was added in a mass ratio amount of 3%. And the mineralizer CaF2 cannot be fully functioned, when its dosage was in a mass percent of 1. 5%. Low-grade bauxite was easier to sinter for the preparation of calcium aluminates comparing with the highgrade one. The optimum material ratio for the preparation of calcium aluminates calcium at 1 250 °C was the mass ratio between bauxite and calcium carbonate of 1 : 0. 6 and mineralizer CaF2 mass ratio percent of 3%.

  12. Generation of super-Gaussian modes in Nd:YAG lasers with graded-phase mirrors

    NASA Astrophysics Data System (ADS)

    Gerber, Michael; Graf, Thomas

    2003-11-01

    To change the intensity distribution of the fundamental mode in a Nd:YAG laser resonator to a top-hat profile we developed and used a dielectric graded-phase mirror. A super-Gaussian mode of the sixth order was generated by means of a graded-phase mirror with a simple ring-shaped phase step on a spherical reflector. The depth of the ring was 90 nm. The graded-phase mirror was manufactured with an ordinary vapor deposition technique. An annular mask with a thickness of 10 μm was used to avoid the deposition of the LaF3 vapor at the position of the ring. Laser experiments with continuous-wave and repetitively pulsed dioed-laser pumping were performed and compared. The results are in excellent agreement with the theory.

  13. Upconversion energy transfer in Yb3+/Tm3+ doped tellurite glass

    NASA Astrophysics Data System (ADS)

    Żmojda, J.; Dorosz, D.; Kochanowicz, M.; Dorosz, J.

    2011-06-01

    The paper presents energy transfer in tellurite glass from the system TeO2 - GeO2 - PbO - PbF2- BaO - Nb2O5 - LaF3 doped with Yb3+/Tm3+ ions. Under the excitation of 976 nm laser a strong blue emission (477 nm) corresponding to the transition 1G4 --> 3H6 in thulium ions was observed. Analysing the influence of the content of Tm3+ ions on the level of luminescence obtained by the mechanism of upconversion it was established that the most effective energy transfer between Yb 3+--> Tm3+ ions took place in the matrix doped in the following proportion: 1 Yb3+:0.1 Tm3+ (%mol). Based on the non-resonant process of energy transfer between Yb3+ and Tm3+ ions the mechanism of upconversion was discussed.

  14. Glancing angle deposition for production of optical components in UV region

    NASA Astrophysics Data System (ADS)

    Tolenis, Tomas; GrinevičiÅ«tÄ--, Lina; Buzelis, Rytis; Petronis, Laurynas; Drazdys, Ramutis

    2016-09-01

    Technological developments in laser technology require advancements in optical components. Such demand is particularly important in UV spectral region. Antireflection coatings (AR) and waveplates as a widely used optical elements were produced based on glancing angle deposition (GLAD) method. Superior optical performance was measured for AR thin films. Broadband and broad-angle antireflection coatings were manufactured by using multilayer system when changing the refractive index profile by varying the porosity of material. SiO2, Al2O3 and LaF3 materials were used for formation of waveplates for UV region. An investigation of optical and resistant performance were conducted. All materials showed optical losses at the wavelength of 355 nm. Possible technological solutions are presented and investigated.

  15. Uniformity Masks Design Method Based on the Shadow Matrix for Coating Materials with Different Condensation Characteristics

    PubMed Central

    2013-01-01

    An intuitionistic method is proposed to design shadow masks to achieve thickness profile control for evaporation coating processes. The proposed method is based on the concept of the shadow matrix, which is a matrix that contains coefficients that build quantitive relations between shape parameters of masks and shadow quantities of substrate directly. By using the shadow matrix, shape parameters of shadow masks could be derived simply by solving a matrix equation. Verification experiments were performed on a special case where coating materials have different condensation characteristics. By using the designed mask pair with complementary shapes, thickness uniformities of better than 98% are demonstrated for MgF2 (m = 1) and LaF3 (m = 0.5) simultaneously on a 280 mm diameter spherical substrate with the radius curvature of 200 mm. PMID:24227996

  16. Neodymium-doped nanoparticles for infrared fluorescence bioimaging: The role of the host

    NASA Astrophysics Data System (ADS)

    del Rosal, Blanca; Pérez-Delgado, Alberto; Misiak, Małgorzata; Bednarkiewicz, Artur; Vanetsev, Alexander S.; Orlovskii, Yurii; Jovanović, Dragana J.; Dramićanin, Miroslav D.; Rocha, Ueslen; Upendra Kumar, K.; Jacinto, Carlos; Navarro, Elizabeth; Martín Rodríguez, Emma; Pedroni, Marco; Speghini, Adolfo; Hirata, Gustavo A.; Martín, I. R.; Jaque, Daniel

    2015-10-01

    The spectroscopic properties of different infrared-emitting neodymium-doped nanoparticles (LaF3:Nd3+, SrF2:Nd3+, NaGdF4: Nd3+, NaYF4: Nd3+, KYF4: Nd3+, GdVO4: Nd3+, and Nd:YAG) have been systematically analyzed. A comparison of the spectral shapes of both emission and absorption spectra is presented, from which the relevant role played by the host matrix is evidenced. The lack of a "universal" optimum system for infrared bioimaging is discussed, as the specific bioimaging application and the experimental setup for infrared imaging determine the neodymium-doped nanoparticle to be preferentially used in each case.

  17. Nanoscintillators for radiation detection

    NASA Astrophysics Data System (ADS)

    Hall, Ryan Gregory

    In the search for faster, more effective methods for detection of and protection against radiological weapons, advances in materials for radiation detection are a critical component of any successful strategy. This work focuses on producing inexpensive, but highly sensitive, nanoparticle alternatives to existing single-crystal installations. Attention is given to particular types of promising inorganic scintillators: LaF3, yttrium-aluminum-garnet (YAG), and SrF2, each one an inorganic host doped with additional elements that encourage luminescent decay and increase effective Z-value. I examine the possible routes to synthesize these compounds, and the difficulties and benefits of each method. After synthesizing these materials, testing was performed to determine comparative performance against each other and commercial solutions, identify structural and compositional characteristics, and explore routes for fixing the scintillators into a detector assembly. The unifying goal is to develop a scintillating material suitable for consistent dosimetry and radio-isotope identification applications.

  18. Nano- and micro-sized rare-earth carbonates and their use as precursors and sacrificial templates for the synthesis of new innovative materials.

    PubMed

    Kaczmarek, Anna M; Van Hecke, Kristof; Van Deun, Rik

    2015-04-21

    This review focuses on rare-earth carbonate materials of nano- and micro-size. It discusses in depth the different types of rare-earth carbonate compounds, diverse synthetic approaches and possibilities for chemical tuning of the size, shape and morphology. The interesting luminescence properties of lanthanide doped rare-earth carbonates and their potential applications for example as efficient white light sources and biolabels are reviewed. Additionally the use of these materials as precursors for the synthesis of nano-/micro-sized oxides, and their application as sacrificial templates for morphology-controlled synthesis of other materials such as YVO4, LaF3, NaYF4 and others is overviewed.

  19. Rare earth doped glass-ceramics containing NaLaF4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Elsts, E.; Krieke, G.; Rogulis, U.; Smits, K.; Zolotarjovs, A.; Jansons, J.; Sarakovskis, A.; Kundzins, K.

    2016-09-01

    Oxyfluoride glasses 16Na2O-9NaF-5LaF3-7Al2O3-63SiO2 (mol%) activated with 3% terbium, dysprosium, praseodymium and neodymium fluorides have been prepared and studied by differential thermal analysis, cathodoluminescence, X-ray induced luminescence, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. We found out that the presence of crystalline phase enhances the X-ray induced luminescence intensity. X-ray induced luminescence is the most intense for the sample activated with terbium and treated at 700 °C, whereas the praseodymium and neodymium activated samples have the fastest decay times.

  20. Superionic phase transition of doped fluorites

    NASA Astrophysics Data System (ADS)

    den Hartog, H. W.; van der Veen, J.

    1988-02-01

    In this paper we present new results of specific-heat experiments on superionic mixtures of cubic lead fluoride and some rare-earth fluorides. The results depend very strongly on the rare-earth ion; for samples doped with LaF3 we observe a peak in the specific heat as a function of T, which is located at an approximately fixed position. This peak, which is due to the superionic transition, increases in width with increasing concentrations of LaF3. If we add YbF3, however, the position of the peak varies. It appears that in samples doped with a few mol % YbF3 there are two peaks in the ``specific-heat spectrum'': one very similar to the peak observed in pure PbF2 and a second peak situated at significantly lower temperatures. The results are discussed in view of the experimental data on the clustering properties of the different solid solutions. In addition, we treat some of the specific-heat data with theoretical models, which have been proposed by Vlieg, den Hartog, and Winnink. This analysis suggests that due to the introduction of La impurities the formation of Frenkel pairs is more difficult. The introduction of Yb impurities, however, leads to additional Frenkel-pair formation, because Pb1-xYbxF2+x clusters, consisting of more than one Yb-F interstitial pair, trap extra interstitial F- ions. Because the energy of these extra trapped interstitial F- ions is lower than the energy of free anion interstitials, this leads to an enhancement of the formation of Frenkel pairs.

  1. Luminescence Decay Dynamics and Trace Biomaterials Detection Potential of Surface-Functionalized Nanoparticles

    PubMed Central

    Cheng, Kwan H.; Aijmo, Jacob; Ma, Lun; Yao, Mingzhen; Zhang, Xing; Como, John; Hope-Weeks, Louisa J.; Huang, Juyang; Chen, Wei

    2009-01-01

    We have studied the luminescence decay and trace biomaterials detection potential of two surface-functionalized nanoparticles, poly(ethylene glycol) bis(carboxymethyl) ether-coated LaF3:Ce,Tb (~20 nm) and thioglycolic acid-coated ZnS/Mn (~5 nm). Upon UV excitation, these nanoparticles emitted fluorescence peaking at 540 and 597 nm, respectively, in solution. Fluorescence imaging revealed that these nanoparticles targeted the trace biomaterials from fingerprints that were deposited on various nonporous solid substrates. Highly ordered, microscopic sweat pores within the friction ridges of the fingerprints were labeled with good spatial resolutions by the nanoparticles on aluminum and polymethylpentene substrates, but not on glass or quartz. In solution, these nanoparticles exhibited multicomponent fluorescence decays of resolved lifetimes ranging from nano-to microseconds and of average lifetimes of ~24 and 130 µs for the coated LaF3:Ce,Tb and ZnS:Mn, respectively. The long microsecond-decay components are associated with the emitters at or near the nanocrystal core surface that are sensitive to the size, surface-functionalization, and solvent exposure of the nanoparticles. When the nanoparticles were bound to the surface of a solid substrate and in the dried state, a decrease in the microsecond decay lifetimes was observed, indicative of a change in the coating environment of the nanocrystal surface upon binding and solvent removal. The average decay lifetimes for the surface-bound ZnS:Mn in the dried state were ~60, 30, and 11 µs on quartz, aluminum, and polymethylpentene, respectively. These values were still 2 orders of magnitude longer than the typical fluorescence decay background of most substrates (e.g., ~0.36 µs for polymethylpentene) in trace forensic evidence detections. We conclude that coated ZnS: Mn nanoparticles hold great promise as a nontoxic labeling agent for ultrasensitive, time-gated, trace evidence detections in nanoforensic applications. PMID:20072713

  2. CANDLES project for the study of neutrino-less double beta decay of 48Ca

    NASA Astrophysics Data System (ADS)

    Yoshida, Sei

    2014-09-01

    There is, presently, strong evidence that neutrinos undergo flavor oscillations,and hence must have finite masses. Neutrino-less double beta (0 νββ) decay measurement offers a realistic opportunity to establish the Majorana nature of neutrinos and gives the absolute scale of the effective neutrino mass. CANDLES is the project to search for 0 νββ decay of 48Ca. A distinctive characteristic of 48Ca is the highest Q value (4.3 MeV) among 0 νββ isotopes. Therefore it enables us to measure 0 νββ decay signals in background free contribution. The CANDLES system consists of undoped CaF2 scintillators (CaF2),liquid scintillator (LS), and large photomultiplier tubes (PMTs). A large number of CaF2 crystals in the form of 10 cm cubes are immersed in the LS. Scintillating CaF2 crystals work as an active source detector for 0 νββ decay of 48Ca, together with LS as a multi-purpose detector component to both reject backgrounds and to propagate scintillation photons. PMTs are placed around the LS vessel to detect photons from both scintillators. The simple design concept of CANDLES enables us to increase the 48Ca source amount. 48Ca enrichment is also effective for the high sensitive measurement, because natural abundance of 48Ca is very low (0.19%). We have studied 48Ca enrichment and succeeded in obtaining enriched 48Ca although it is a small amount. Now we have developed the CANDLES III system, which contained with 300kg CaF2 crystals without enrichment, at the Kamioka underground laboratory. New light collection system was installed in 2012, and accordingly photo-coverage has been enlarged by about 80%. Further improvement will be expected in 2014 by installing a detector cooling system in order to increase light emission from CaF2 crystals. The detail of the latest CANDLES III (U.G.) system and its performance will be presented. Recently, we found that gamma rays from neutron captures on materials surrounding detector could be dominant background. These background estimation and prospects of backgrounds shielding will be also discussed.

  3. CANDLES for the study of ^48Ca double beta decay

    NASA Astrophysics Data System (ADS)

    Ogawa, Izumi

    2009-10-01

    CANDLES is the project to search for double beta decay (DBD) of ^48Ca by using CaF2 scintillators. The Q-value of ^48Ca, which is the highest (4.27 MeV) among potential DBD nuclei, is far above energies of γ-rays from natural radioactivities (maximum 2.615 MeV from ^208Tl decay), therefore we can naturally expect small backgrounds in the energy region we are interested in. We gave the best lower limit on the half-life of neutrino-less double beta decay of ^48Ca by using CaF2(Eu) detector system, ELEGANT VI though further development is highly desirable to reach the mass region of current interest. We have constructed the prototype detector, CANDLES III in our laboratory (Osaka U.) at sea level and studied the basic performance of the system, including the light collection, position reconstruction and background rejection. We are now moving the detector system to new experimental room (room D) at Kamioka underground laboratory (2700 m.w.e.) to avoid large background originated from cosmic rays. At the same time, we are increasing the total mass of the ^48Ca compared to the one in the prototype detector. 96 (instead of 60 in prototype) CaF2 modules which contains 350 g of ^48Ca are immersed in a liquid scintillator (LS) which acts as an active veto (veto phase). The conversion phase contains wavelength shifter (Bis-MSB) which converts the emission light of CaF2(pure) which has a peak in the UV region to the visible one where the quantum efficiency of the PMTs is high enough (maximum at ˜400 nm) and materials at the optical path have good transparencies. Scintillation lights from both the CaF2 modules and the liquid scintillator in veto phase are viewed by large PMTs (48 x13'' and 14 x17'' tubes). All the detector system described above are contained in a water tank which is 3 m in diameter and 4 m in height. The water tank and a purification system of the LS together with LS storage tanks were installed at room D. The purification system of the LS removes the radioactive impurities especially U and Th using the techniques of water-extraction and N2 purge. Other components including the CaF2 modules, the PMTs, the liquid scintillator vessel and DAQ system will be installed soon.

  4. Measurement of U-235 Fission Neutron Spectra Using a Multiple Gamma Coincidence Technique

    SciTech Connect

    Ji Chuncheng; Kegel, G.H.R.; Egan, J.J.; DeSimone, D.J.; Alimeti, A.; Roldan, C.F.; McKittrick, T.M.; Kim, D.-S.; Chen, X.; Tremblay, S.E.

    2005-05-24

    The Los Alamos Model of Madland and Nix predicts the shape of the fission neutron energy spectrum for incident primary neutrons of different energies. Verifications of the model normally are limited to measurements of the fission neutron spectra for energies higher than that of the primary neutrons because the low-energy spectrum is distorted by the admixture of elastically and inelastically scattered neutrons. This situation can be remedied by using a measuring technique that separates fission from scattering events. One solution consists of using a fissile sample so thin that fission fragments can be observed indicating the occurrence of a fission event. A different approach is considered in this paper. It has been established that a fission event is accompanied by the emission of between seven and eight gamma rays, while in a scattering interaction, between zero and two gammas are emitted, so that a gamma multiplicity detector should supply a datum to distinguish a fission event from a scattering event. We proceed as follows: A subnanosecond pulsed and bunched proton beam from the UML Van de Graaff generates nearly mono-energetic neutrons by irradiating a thin metallic lithium target. The neutrons irradiate a 235U sample. Emerging neutron energies are measured with a time-of-flight spectrometer. A set of four BaF2 detectors is located close to the 235U sample. These detectors together with their electronic components identify five different events for each neutron detected, i.e., whether four, three, two, one, or none of the BaF2 detectors received one (or more) gamma rays. We present work, preliminary to the final measurements, involving feasibility considerations based on gamma-ray coincidence measurements with four BaF2 detectors, and the design of a Fission-Scattering Discriminator under construction.

  5. Some studies on a solid state sulfur probe for coal gasification systems

    NASA Technical Reports Server (NTRS)

    Jacob, K. T.; Rao, D. B.; Nelson, H. G.

    1977-01-01

    Measurements on the solid electrolyte cell (Ar + H(2) + H(2)S/CaS + CaF(2) + (Pt)//CaF(2)//(Pt) + CaF(2) + CaS/H(2) + H(2)+Ar) show that the emf of the cell is directly related to the difference in sulfur potentials established at the Ar + H(2) + H(2)S/electrode interfaces. The electrodes convert the sulfur potential gradient across the calcium fluoride electrolyte into an equivalent fluorine potential gradient. Response time of the probe varies from approximately 9 hr at 990 K to 2.5 hr at 1225 K. The conversion of calcium sulfide and/or calcium fluoride into calcium oxide is not a problem anticipated in commercial coal gasification systems. Suggestions are presented for improving the cell for such commercial applications.

  6. Microstructure refinement and enhanced critical current density in binary doped SmFeAsO superconductor

    NASA Astrophysics Data System (ADS)

    Anooja, J. B.; Aswathy, P. M.; Varghese, Neson; Aloysius, R. P.; Syamaprasad, U.

    2014-04-01

    The iron-pnictide Sm1-xCaxFeAsO1-2xF2x superconductor was prepared and the combined effect of electron and hole doping was studied in detail. It is observed that the binary doping using CaF2 improves the microstructure tremendously with a preferred orientation of the (00l) planes. Moreover, a maximum TC of 53.8 K and a transport JC of 880 A/cm2 (12 K), which is double to that of the F-doped sample, are achieved. The dopant CaF2 seems to be a potential candidate for solving the grain-connectivity concerns in iron-pnictides paving the way towards conductor development.

  7. High-Tc and high-Jc SmFeAs(O,F) films on fluoride substrates grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ueda, Shinya; Takeda, Soichiro; Takano, Shiro; Yamamoto, Akiyasu; Naito, Michio

    2011-12-01

    Superconducting thin films of SmFeAs(O,F) were prepared by molecular beam epitaxy on fluoride substrates. In our process, F-free SmFeAsO films were grown first, and F was subsequently introduced to the films by diffusion from an overlayer of SmF3. By this simple process, record high Tc, namely, Tcon (Tcend) = 57.8 K (56.4 K) was obtained in a film on CaF2. Furthermore, the films on CaF2 showed high critical current density over 1 MA/cm2 in the self-field at 5 K. The correlation between superconductivity and epitaxial strain in SmFeAs(O,F) films is discussed.

  8. In-situ growth of superconducting SmO1−xFxFeAs thin films by pulsed laser deposition

    PubMed Central

    Haindl, Silvia; Hanzawa, Kota; Sato, Hikaru; Hiramatsu, Hidenori; Hosono, Hideo

    2016-01-01

    Oxypnictide thin film growth by pulsed laser deposition (PLD) is one of many insufficiently resolved issues in the research of iron-based superconductors. Here we report on the successful realization of superconducting SmO1−xFxFeAs oxypnictide thin film growth by in-situ PLD on CaF2 (fluorite) substrates. CaF2 acts as fluorine supplier by diffusion and thus enables superconducting oxypnictide thin film growth by PLD. Films are grown heteroepitaxially and characteristically have a broad resistive normal-to-superconducting transition. Best films have onset transition temperatures around 40 K. The proposed in-situ PLD film growth offers an alternative and cheap route for the fabrication of iron oxypnictides. PLD becomes now an additional option for iron oxypnictide synthesis. PMID:27767066

  9. In-situ growth of superconducting SmO1‑xFxFeAs thin films by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Haindl, Silvia; Hanzawa, Kota; Sato, Hikaru; Hiramatsu, Hidenori; Hosono, Hideo

    2016-10-01

    Oxypnictide thin film growth by pulsed laser deposition (PLD) is one of many insufficiently resolved issues in the research of iron-based superconductors. Here we report on the successful realization of superconducting SmO1‑xFxFeAs oxypnictide thin film growth by in-situ PLD on CaF2 (fluorite) substrates. CaF2 acts as fluorine supplier by diffusion and thus enables superconducting oxypnictide thin film growth by PLD. Films are grown heteroepitaxially and characteristically have a broad resistive normal-to-superconducting transition. Best films have onset transition temperatures around 40 K. The proposed in-situ PLD film growth offers an alternative and cheap route for the fabrication of iron oxypnictides. PLD becomes now an additional option for iron oxypnictide synthesis.

  10. Recovery Behavior of Separating Britholite (Ca3Ce2[(Si,P)O4]3F) Phase from Rare-Earth-rich Slag by Centrifugal Casting

    NASA Astrophysics Data System (ADS)

    Li, Juncheng; Guo, Zhancheng; Yang, Tao; Yue, Zicheng; Ma, Changhao

    2015-05-01

    A new approach to separate britholite phase from the rare-earth-rich slag by super gravity was investigated. With the parameter of G = 500, t = 5 min, T = 1423 K, almost all britholite phase is enriched in the concentrate, while the tailing is made up of CaF2 phase. Under the hypothesis that the RE exists in the slag in terms of RE2O3, with the gravity coefficient G = 500, t = 5 min and T = 1423 K, the mass fraction of RE2O3 in the concentrate is up to 24.67%, while the mass fraction of CaF2 in the tailing is 50.01%. Considering that the mass fraction of RE2O3 is 12.01% in the parallel sample, the recovery ratio of rare earth in the concentrate is up to 76.47% by centrifugal separation.

  11. Low-threshold diode-pumped Yb3+,Na+:CaF2 self-Q-switched laser.

    PubMed

    Su, Liangbi; Xu, Jun; Xue, Yinghong; Wang, Chingyue; Chai, Lu; Xu, Xiaodong; Zhao, Guangjun

    2005-07-25

    For the first time to our knowledge, the laser performance of Yb3+, Na+-codoped CaF2 single crystals was demonstrated. Self-Q-switched laser operation at 1050nm was observed for 976 nm diode pumping at room temperature. On 5 W of incident power, the repetition rate and width of the self-Q-switched pulses reached 28 kHz and 1.5 micros, respectively. A maximal slope efficiency of 20.3% and minimal threshold absorbed pump power of 30 mW were respectively achieved with different output couplers, showing the promising application of Yb3+, Na+-codoped CaF2 crystals as compact and efficient solid-state lasers.

  12. Coupling of phonon-polariton modes at dielectric-dielectric interfaces by the ATR technique

    NASA Astrophysics Data System (ADS)

    Cocoletzi, G. H.; Olvera Hernández, J.; Martínez Montes, G.

    1989-08-01

    We report the calculated ATR dispersion relation of the interface phonon-polariton modes in the prism-dielectric-dielectric configuration. Comparison of electromagnetic dispersion relations (EMDR) with the ATR dispersion relations are presented for three different interfaces: I) GaAs/GaP, II) CdF2/CaF2 and III) CaF2/GaP in two propagation windows, using the Otto and Kretschmann geometries for p-polarized light. We have studied the three cases using angle and frequency scans for each window and geometry. The results indicate that it is possible to excite and detect phonon-polariton modes at the dielectric-dielectric interface.

  13. Canadian Journal of Physics. Volume 69, Number 2 (Revue Canadienne de Physique. Volume 69, Numero 2

    DTIC Science & Technology

    1991-02-01

    both Figs. 4 and 8, are determined by Se, or were impure having been deposited in a high ambient the crystallite nucleation process, which is...patterns indicate that amorphous samples can be small excess of Cd appears to inhibit the growth of larger CdSe fabricated with ambient air pressures near 3...in an oxidizing ambient was investigated as a first step towards the in situ growth of superconducting thin films of YBa2Cu3,O from Y, Cu, and BaF2

  14. Electronic Devices with Barrier Film and Process for Making Same

    DTIC Science & Technology

    1998-08-20

    technique 20 must be developed that will prevent the diffusion of copper into silicon. Among the possible solutions currently under development...processing tool. The pressure within the deposition chamber 30 should be 10Ŝ mbar or less, more -15- preferably 10ŝ mbar or less, and still more...as a precursor in forming the diffusion barrier film, the precursor, e.g., BaF2 or SrF2 , can be deposited for a sufficient duration of time to

  15. Process for Making a Semiconductor Device with Barrier Film Formation Using a Metal Halide and Products Thereof

    DTIC Science & Technology

    1998-08-20

    under development within the semiconductor industry the most prevalent is the use of nitrides of the transition metals titanium and tungsten. The...processing tool. The pressure within the deposition chamber 30 should be 10Ŝ mbar or less, more preferably 10ŝ mbar or less, and still more...precursor in forming the diffusion barrier film, the precursor, e.g., BaF2 or SrF2 , can be deposited for a sufficient duration of time to ensure

  16. Separation of high order harmonics with fluoride windows.

    PubMed

    Allison, T K; van Tilborg, J; Wright, T W; Hertlein, M P; Falcone, R W; Belkacem, A

    2009-05-25

    The ensemble of lower orders produced in high order harmonic generation can be efficiently temporally separated by propagation in a fluoride window while still preserving their femtosecond pulse duration. We present calculations for MgF2, CaF2, and LiF windows for the third, fifth, and seventh harmonics of 800 nm. We use this simple and inexpensive technique in a pump/probe experiment to resolve femtosecond dynamics in the ethylene molecule.

  17. Separation of High Order Harmonics with Fluoride Windows

    SciTech Connect

    Allison, Tom; van Tilborg, Jeroen; Wright, Travis; Hertlein, Marcus; Falcone, Roger; Belkacem, Ali

    2010-08-02

    The lower orders produced in high order harmonic generation can be effciently temporally separated into monochromatic pulses by propagation in a Fluoride window while still preserving their femtosecond pulse duration. We present calculations for MgF2, CaF2, and LiF windows for the third, fifth, and seventh harmonics of 800 nm. We demonstrate the use of this simple and inexpensive technique in a femtosecond pump/probe experiment using the fifth harmonic.

  18. Single Nuclear Spin Magnetic Resonance Force Microscopy

    DTIC Science & Technology

    2010-05-02

    Lab. In work not directly supported by this grant, these projects advanced MRFM detected Ferromagnetic Resonance ( FMR ) to enable studies of...directly supported by this grant, these projects advanced MRFM detected Ferromagnetic Resonance ( FMR ) to enable studies of submicron magnetic structures...our earlier NMR detection of 19F spins in CaF2 we have conducted 65Cu, 63Cu NMR stud- ies for studies of interface phenomena in multilayered magnetic

  19. Effect of Er,Cr:YSGG laser and professional fluoride application on enamel demineralization and on fluoride retention.

    PubMed

    Ana, P A; Tabchoury, C P M; Cury, J A; Zezell, D M

    2012-01-01

    This study evaluated the effect of Er,Cr:YSGG laser irradiation and professional fluoride application on enamel demineralization and on fluoride formation and retention. In a blind in vitro study, 264 human enamel slabs were distributed into 8 groups: G1--untreated; G2--treated with acidulated phosphate fluoride gel (APF gel, 1.23% F) for 4 min; G3, G4 and G5--irradiated with Er,Cr:YSGG at 2.8, 5.6 and 8.5 J/cm2, respectively; G6, G7 and G8--preirradiated with Er,Cr:YSGG at 2.8, 5.6 and 8.5 J/cm2, respectively, and subjected to APF gel application. Twenty slabs of each group were submitted to a pH-cycling regimen, and enamel demineralization was evaluated in 10 slabs of each group. In the other 10 slabs, CaF2-like material was determined. To evaluate F formed, 10 additional slabs of each group, not subjected to the pH cycling, were submitted to analysis of CaF2-like material and fluorapatite, while the other 3 slabs of each group were evaluated by scanning electron microscopy. The F content was also measured in all pH-cycling solutions. Laser at 8.5 J/cm2 and APF treatment reduced enamel demineralization compared to the control (p < 0.05), but the combination of these treatments was not more efficient than their isolated effect. A higher concentration of retained CaF2-like material was found in laser groups followed by APF in comparison with the APF gel treatment group. The findings suggest that laser treatment at 8.5 J/cm2 was able to decrease hardness loss, even though no additive effect with APF was observed. In addition, laser treatment increased the formation and retention of CaF2 on dental enamel.

  20. Search and Characterization of Optical Ceramics and Crystals for Diode-pumped Laser Oscillations

    DTIC Science & Technology

    2013-04-01

    obtained without cooling the ceramic sample. Neodymium doped laser ceramics were obtained and the spectroscopic properties of different optical centers...obtained slope efficiency in this case was not far from the best results obtained from a YAG:Nd 3+ crystal. Unlike neodymium doped SrF2 ceramics...Yb 3+ ions in CaF2:Yb 3+ (30%), efficient CW operation was obtained without cooling the ceramic sample. Neodymium doped laser ceramics were

  1. Mineralization behavior of fluorine in perfluorooctanesulfonate (PFOS) during thermal treatment of lime-conditioned sludge.

    PubMed

    Wang, Fei; Shih, Kaimin; Lu, Xingwen; Liu, Chengshuai

    2013-03-19

    The fate and transport of the fluorine in perfluorooctanesulfonate (PFOS) during the thermal treatment of lime-conditioned sludge were observed using both qualitative and quantitative X-ray diffraction techniques. Two main fluorine mineralization mechanisms leading to the substantial formation of CaF2 and Ca5(PO4)3F phases were observed. They had a close relationship with the thermal treatment condition and the PFOS content of the sludge. At low temperatures (300-600 °C), CaF2 dominated in the product and increases in treatment time and temperature generally enhanced the fluorine transformation. However, at higher temperatures (700-900 °C), increases in treatment time and temperature had a negative effect on the overall efficiency of the fluorine crystallization. The results suggest that in the high temperature environment there were greater losses of gaseous products such as HF and SiF4 in the transformation of CaF2 to Ca5(PO4)3F, the hydrolysis of CaF2, and the reaction with SiO2. The quantitative analysis also showed that when treating sludge with low PFOS content at high temperatures, the formation of Ca5(PO4)3F may be the primary mechanism for the mineralization of the fluorine in PFOS. The overall results clearly indicate the variations in the fate and transport of fluorine in PFOS when the sludge is subject to different PFOS contents and treatment types, such as heat drying or incineration.

  2. Hyper-Parametric Oscillations in a Whispering Gallery Mode Fluorite Resonator

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Strekalov, Dmitry; Mohageg, Makan; Ilchenko, Vladimir; Matsko, Andrey; Maleki, Lute

    2004-01-01

    This viewgraph presentation summarizes the hyper-parametric oscillations observations of the fluorite resonator. The reporters have observed various nonlinear effects in ultra-high Q crystalline whispering gallery mode (WGM) resonators. In particular, it was demonstrated a low threshold optical hyper-parametric oscillations in a high-Q (Q=1010) CaF2 WGM resonator. The oscillations result from the resonantly enhanced four-wave-mixing occurring due to Kerr nonlinearity of the material.

  3. Kosterlitz-Thouless transition for 4He films adsorbed to rough surfaces.

    PubMed

    Luhman, D R; Hallock, R B

    2004-08-20

    We report the study of adsorption isotherms of 4He on several well characterized rough CaF2 surfaces using a quartz crystal microbalance technique at 1.672 K. The signature of decoupled mass observed on crossing the Kosterlitz-Thouless transition as a function of 4He film thickness decreases and becomes increasingly difficult to identify as the surface roughness is increased. A peak in the dissipation, indicative of the onset of superfluidity, changes little with roughness.

  4. Inclusions and Their Influence on Material Behavior: Proceedings of a Symposium Held in Conjunction with the 1988 World Materials Congress, Chicago, Illinois, USA, 24-30 September 1988

    DTIC Science & Technology

    1988-01-01

    a weld. calcium silicide or calcium carbide, or a synthetic slag on the base of CaO-A1203-CaF2 has been widely used for this purpose. Calcium serves...8217 coatings such as titanium carbide or titanium Chips formed during the machining of low and medium carbon nitride. Significant progress has also been made in...ceramic tools, and tools coated by PVD and CVD techniques microstructural parameters. have vastly improved tool life performance. High strain rate Damage

  5. Fluorspar

    USGS Publications Warehouse

    Miller, M.

    2013-01-01

    World fluorspar demand slowed in 2012 and, according to some sources prices decreased, especially in the latter half of the year. In 2012, nearly all fluorspar (CaF2) consumption in the United States was from imports. Hastie Mining and Trucking Co. produced some fluorspar as a byproduct of its limestone quarry operations in Illinois. In addition, a small amount of usable synthetic fluorspar was produced from industrial waste streams.

  6. Lubricating Properties of Some Bonded Fluoride and Oxide Coatings for Temperature to 1500 F

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.

    1960-01-01

    The lubricating properties of some experimental ceramic coatings, diffusion-bonded fluoride coatings, and ceramic-bonded fluoride coatings were determined. The experiments were conducted in an air atmosphere at a sliding velocity of 430 feet per minute and at temperatures from 75 to 1500 F. Several ceramic coatings provided substantial reductions in friction coefficient and rider wear (compared with the unlubricated metals). For example, a cobaltous oxide (CoO) base coating gave friction coefficients of 0.24 to 0.36 within the temperature range of 75 to 1400 F; serious galling and welding of the metal surfaces were prevented. The friction coefficients were higher than the arbitrary maximum (0.2) usually considered for effective boundary lubrication. However, when a moderately high friction coefficient can be tolerated, this type of coating may be a useful antiwear composition. Diffusion-bonded calcium fluoride (CaF2) on Haynes Stellite 21 and on Inconel X gave friction coefficients of 0.1 to 0.2 at 1500 F. Endurance life was dependent on the thermal history of the coating; life improved with increased exposure time at elevated temperatures prior to running. Promising results were obtained with ceramic-bonded CaF2 on Inconel X. Effective lubrication and good adherence were obtained with a 3 to 1 ratio of CaF2 to ceramic. A very thin sintered and burnished film of CaF2 applied to the surface of this coating further improved lubrication, particularly above 1350 F. The friction coefficient was 0.2 at 500 F and decreased with increasing temperature to 0.06-at 1500 F. It was 0.25 at 75 F and 0.22 at 250 F.

  7. Early Risk Reduction Phase 1 FLIR/Laser Designator Window. Revision

    DTIC Science & Technology

    1991-12-31

    Materials," 6 August 1991. 5-5 INTENTIONALLY LEFT BLANK 5-6 Gallium Arsenide Coating Design Report completed under Contract No. E03088, Litton/Itek...flaw.I U An extensive material investigation was also performed on the Alkaline Earth Fluorides (CaF2 and SrF2 ). These materials were found to have...microns to 12.0 microns), survivability/durability under a diversity of stressing environments, RF shielding, and laser compatibility -- all while

  8. The PRIME Lab biomedical program

    NASA Astrophysics Data System (ADS)

    Jackson, George S.; Elmore, David; Rickey, Frank A.; Musameh, Sharif M.; Sharma, Pankaj; Hillegonds, Darren; Coury, Louis; Kissinger, Peter

    2000-10-01

    The biomedical accelerator mass spectrometry (AMS) initiative at PRIME Lab including the status of equipment and sample preparation is described. Several biomedical projects are underway involving one or more of the nuclides: 14C, 26Al and 41Ca. Routine production of CaF 2 and graphite is taking place. Finally, the future direction and plans for improvement of the biomedical program at PRIME Lab are discussed.

  9. Test Operations Procedure (TOP) 1-2-612 Nuclear Environment Survivability

    DTIC Science & Technology

    2008-10-24

    Calcium Fluoride Manganese CaF2 (Mn) Thermoluminescent Dosimeter (TLDs) and Compton diodes, respectively. The measured gamma dose values will be...CaF2(Mn)) Thermoluminescent Dosimeters (TLDs), which provide the GTD received by the monitored location. d. The SUT will be positioned at the...Test and Evaluation Master Plan TIR - Test Incident Report TLD - Thermoluminescent Dosimeter TO - Test Officer TOP - Test Operations

  10. East Europe Report: Political, Sociological and Military Affairs, No. 2229

    DTIC Science & Technology

    2007-11-02

    medical interest in training, research and prac- tice. 1. New Possibilities and Requirements Since the design of the RDC 64 thermoluminescence ...the RDC III. 3. Mode of Operation The RDC III D is a thermoluminescence dosimeter whose persistent phosphorus CaF2:Mn (calcium fluoride activated...Langhans, K., "Military-Medical Aspects of Thermoluminescence Dosimetry," Z. MILITAERMED., Berlin, No 14, 1973, p 2. 5. Langhans, K., "Ueber die

  11. Initial Nuclear Radiation Hardness Validation Test

    DTIC Science & Technology

    2008-11-03

    Measurement Accuracy Photocurrent Photocurrent Probes ±5% Gamma Dose **CaF 2 (Mn) TLD ±10% Gamma Radiation Pulse PIN Diode Compton ...1.02 and cGy(tissue)/cGy(CaF2) = 1.13, respectively. Each radiation pulse will be measured using a PIN or Compton diode and digitized on a transient...photocurrents produce secondary effects that include: a. Error generation in logic and analog circuits. b. Secondary photocurrents. TOP 1-2-618 3

  12. PARAMAGNETIC PROPERTIES OF THE ALKALINE EARTH FLUORIDES.

    DTIC Science & Technology

    constants for Mn(2+) in CaF2 and SrF2 were measured over the temperature range 77 to 850K. In both cases the magnitude of the hyperfine coupling constant...decreases with increasing temperature; and the temperature dependance is stronger for SrF2 . The results have been interpreted using the Simanek-Orbach theory of a phonon-induced hyperfine field. (Author)

  13. Optical Detection System Model.

    DTIC Science & Technology

    1982-04-01

    cases the wavelength 7 II TABLE 2 SAMPLE CONTENTS OF OPTICAL MATERIAL FILE ODSOPT.INP SRF2 3.000 0.120 13.000 9.000 0.120 0.100 0.130 0.600 0.200 0.850...N THESE ARE THE AVAILABLE FILTER TYPES: CORNING VYCOR SILICA MGF2 SRF2 VYC7905 INFRASIL SAPPHIRE MGO 1102 CDISE CBS CDTE SE ZNSE CAF2 DIAMOND

  14. Ultra-high resistive and anisotropic CoPd-CaF2 nanogranular soft magnetic films prepared by tandem-sputtering deposition

    NASA Astrophysics Data System (ADS)

    Naoe, Masayuki; Kobayashi, Nobukiyo; Ohnuma, Shigehiro; Iwasa, Tadayoshi; Arai, Ken-Ichi; Masumoto, Hiroshi

    2015-10-01

    Ultra-high resistive and anisotropic soft magnetic films for gigahertz applications are desirable to demonstrate the really practical films. Here we present a study of novel nanogranular films fabricated by tandem-sputtering deposition. Their electromagnetic properties and nanostructure have also been discussed. These films consisted of nanocrystallized CoPd alloy-granules and CaF2 matrix, and a specimen having a composition of (Co0.69Pd0.31)52-(Ca0.31F0.69)48 exhibited distinct in-plane uniaxial anisotropy after uniaxial field annealing with granule growth. Its complex permeability spectra have a ferromagnetic resonance frequency extending to the Super-High-Frequency band due to its higher anisotropy field, and its frequency response was quite well reproduced by a numerical calculation based on the Landau-Lifshitz-Gilbert equation. Furthermore, it was clarified that the CaF2-based nanogranular film exhibits a hundredfold higher electrical resistivity than conventional oxide or nitride-based films. Higher resistivity enables the film thickness to achieve a margin exceeding threefold against eddy current loss. The greater resistivity of nanogranular films is attributed to the wide energy bandgap and superior crystallinity of CaF2 matrix.

  15. Effects of fluoride on in vitro enamel demineralization analyzed by ¹⁹F MAS-NMR.

    PubMed

    Mohammed, N R; Kent, N W; Lynch, R J M; Karpukhina, N; Hill, R; Anderson, P

    2013-01-01

    The mechanistic action of fluoride on inhibition of enamel demineralization was investigated using (19)F magic angle spinning nuclear magnetic resonance (MAS-NMR). The aim of this study was to monitor the fluoride-mineral phase formed on the enamel as a function of the concentration of fluoride ions [F(-)] in the demineralizing medium. The secondary aim was to investigate fluorapatite formation on enamel in the mechanism of fluoride anti-caries efficacy. Enamel blocks were immersed into demineralization solutions of 0.1 M acetic acid (pH 4) with increasing concentrations of fluoride up to 2,262 ppm. At and below 45 ppm [F(-)] in the solution, (19)F MAS-NMR showed fluoride-substituted apatite formation, and above 45 ppm, calcium fluoride (CaF2) formed in increasing proportions. Further increases in [F(-)] caused no further reduction in demineralization, but increased the proportion of CaF2 formed. Additionally, the combined effect of strontium and fluoride on enamel demineralization was also investigated using (19)F MAS-NMR. The presence of 43 ppm [Sr(2+)] in addition to 45 ppm [F(-)] increases the fraction of fluoride-substituted apatite, but delays formation of CaF2 when compared to the demineralization of enamel in fluoride-only solution.

  16. Effect of aluminum phosphate additions on composition of three-component plasma-sprayed solid lubricant

    NASA Technical Reports Server (NTRS)

    Jacobson, T. P.; Young, S. G.

    1982-01-01

    Image analysis (IA) and electron microprobe X-ray analysis (EMXA) were used to characterize a plasma-sprayed, self-lubricating coating, NASA LUBE PS106, specified by weight percent as 35NiCr-35Ag-30CaF2. To minimize segregation of the powder mixture during the plasma-spraying procedure, monoaluminum phosphate was added to form agglomerate particles. Three concentrations of AlPO4 were added to the mixtures: 1.25, 2.5, and 6.25 percent by weight. Analysis showed that 1.25 wt% AlPO4 yielded a CaF2 deficiency, 2.5 wt% kept the coating closest to specification, and 6.25 wt% yielded excess CaF2 as well as more impurities and voids and a deficiency in silver. Photomicrographs and X-ray maps are presented. The methods of IA and EMXA complement each other, and the reasonable agreement in the results increases the confidence in determining the coating composition.

  17. Impact of mechanical stress on ferroelectricity in (Hf0.5Zr0.5)O2 thin films

    NASA Astrophysics Data System (ADS)

    Shiraishi, Takahisa; Katayama, Kiliha; Yokouchi, Tatsuhiko; Shimizu, Takao; Oikawa, Takahiro; Sakata, Osami; Uchida, Hiroshi; Imai, Yasuhiko; Kiguchi, Takanori; Konno, Toyohiko J.; Funakubo, Hiroshi

    2016-06-01

    To investigate the impact of mechanical stress on their ferroelectric properties, polycrystalline (Hf0.5Zr0.5)O2 thin films were deposited on (111)Pt-coated SiO2, Si, and CaF2 substrates with thermal expansion coefficients of 0.47, 4.5, and 22 × 10-6/ °C, respectively. In-plane X-ray diffraction measurements revealed that the (Hf0.5Zr0.5)O2 thin films deposited on SiO2 and Si substrates were under in-plane tensile strain and that their volume fraction of monoclinic phase decreased as this strain increased. In contrast, films deposited on CaF2 substrates were under in-plane compressive strain, and their volume fraction of monoclinic phase was the largest among the three kinds of substrates. The maximum remanent polarization of 9.3 μC/cm2 was observed for Pt/(Hf0.5Zr0.5)O2/Pt/TiO2/SiO2, while ferroelectricity was barely observable for Pt/(Hf0.5Zr0.5)O2/Pt/TiO2/SiO2/CaF2. This result suggests that the in-plane tensile strain effectively enhanced the ferroelectricity of the (Hf0.5Zr0.5)O2 thin films.

  18. Growth of superconducting SmFeAs(O, F) epitaxial films by F diffusion

    NASA Astrophysics Data System (ADS)

    Takeda, S.; Ueda, S.; Takano, S.; Yamamoto, A.; Naito, M.

    2012-03-01

    We report on our growth of superconducting SmFeAs(O, F) films by F diffusion. In our process, F-free SmFeAsO films were grown by molecular beam epitaxy (MBE) first, and subsequently F was introduced to the films via F diffusion from an overlayer of SmF3. We compared the growth conditions and also the properties of resultant films for CaF2 and LaAlO3 substrates. The best films on CaF2 exhibited a high transition temperature, {T}_{{c}}^{{on}}~({T}_{{c}}^{{end}})=57.8 K (56.4 K) at the highest, which may exceed the highest Tc ever reported for bulk samples. Furthermore, the films on CaF2 also showed high critical current density over 1 MA cm-2 in self-field at 5 K. On the other hand, the {T}_{{c}}^{{on}}~({T}_{{c}}^{{end}}) of the film on LaAlO3 was 50.3 K (49.3 K). The deteriorated superconducting properties on LaAlO3 appear to be due to oxygen diffusion from LaAlO3 to films.

  19. Status and future prospect of 48Ca double beta decay search in CANDLES

    NASA Astrophysics Data System (ADS)

    Iida, T.; Nakajima, K.; Ajimura, S.; Batpurev, T.; Chan, W. M.; Fushimi, K.; Hazama, R.; Kakubata, H.; Khai, B. T.; Kishimoto, T.; Li, X.; Maeda, T.; Masuda, A.; Matsuoka, K.; Morishita, K.; Nakatani, N.; Nomachi, M.; Noshiro, S.; Ogawa, I.; Ohata, T.; Osumi, H.; Suzuki, K.; Tamagawa, Y.; Tesuno, K.; Trang, V. T. T.; Uehara, T.; Umehara, S.; Yoshida, S.

    2016-05-01

    The observation of neutrino-less double beta decay (0vßß) would be the most practical way to prove the Majorana nature of the neutrino and lepton number violation. CANDLES studies 48Ca double beta decay using CaF2 scintillator. The main advantage of 48Ca is that it has the highest Q-value (4.27 MeV) among all the isotope candidates for 0vßß. The CANDLES III detector is currently operating with 300kg CaF2 crystals in the Kamioka underground observatory, Japan. In 2014, a detector cooling system and a magnetic cancellation coil was installed with the aim to increase light emission of CaF2 scintillator and photo-electron collection efficiency of the photo-multipliers. After this upgrade, light yield was increased to 1000 p.e./MeV which is 1.6 times larger than before. According to data analysis and simulation, main background source in CANDLES is turned out to be high energy external gamma-ray originating neutron capture on the surrounding materials, so called (n,γ). Upgrading the detector by installing neutron and gamma-ray shield can reduce the remaining main backgrounds by two order magnitude. In this report, we discuss the detail of (n,γ) and background reduction by additional shielding.

  20. First principles prediction of a new high-pressure phase and transport properties of Mg2Si

    NASA Astrophysics Data System (ADS)

    Kessair, S.; Arbouche, O.; Amara, K.; Benallou, Y.; Azzaz, Y.; Zemouli, M.; Bekki, M.; Ameri, M.; Bouazza, B. S.

    2016-12-01

    We have investigated the structural properties of seven different structure types of Mg2Si which include the cubic CaF2, orthorhombic PbCl2, hexagonal Ni2In, tetragonal Al2Cu, Laves phase (cubic MgCu2), hexagonal MgZn2 and dihexagonal MgNi2 type of structures, using a full potential linearized augmented plane wave method as implemented in WIEN2k within the framework of density functional theory. The exchange-correlation potential is treated by the new form of generalized gradient approximation (GGA-PBEsol). In total energy calculations it is clearly seen that cubic CaF2-type structure is stable at ambient conditions, and it undergoes a first-order phase transition to orthorhombic PbCl2-type, then to the hexagonal Ni2In-type structure and finally to the cubic Laves phase MgCu2-type. A new structure type is predicted to be stable at high pressure. Moreover, we intend to combine the electronic structure calculations performed by mean of generalized gradient approximation and modified Becke-Johnson potential with Boltzmann transport theory as incorporated in BoltzTraP code to interpret and predict the thermoelectric performance of each stable phase as a function of the chemical potential at various temperatures. We find a high thermoelectric thermopower values in cubic CaF2-type structure that could promise an excellent candidate for potential thermoelectric applications.

  1. Patternless light outcoupling enhancement method for top-emission organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kim, Doo-Hoon; Lee, Ho-Nyeon

    2016-11-01

    An increase of 65% in the luminous flux of a top-emission organic light-emitting diode (TE-OLED) was obtained by fabricating a stacked N,N‧-bis(naphthalen-1-yl)-N,N‧-bis(phenyl)benzidine (NPB) (0.2 µm)/CaF2 (2.5 µm) light outcoupling layer on the TE-OLED. The high-refractive-index NPB layer extracted the trapped light energy in the TE-OLED for input into the light outcoupling layer and protected the top cathode of the TE-OLED from damage due to the CaF2 layer. The surface morphology of the CaF2 layer had an irregular shape consisting of randomly dispersed pyramids; the irregular structure scattered the waveguide mode energy into air. By combining the effects of the NPB and CaF2 layers, the external quantum efficiency of the TE-OLED was increased significantly. The light outcoupling layer can be fabricated using a thermal evaporation process without patterning and, hence, provides a practical solution for the enhancement of TE-OLED light outcoupling using a patternless fabrication process.

  2. Two CRM protein subfamilies cooperate in the splicing of group IIB introns in chloroplasts.

    PubMed

    Asakura, Yukari; Bayraktar, Omer Ali; Barkan, Alice

    2008-11-01

    Chloroplast genomes in angiosperms encode approximately 20 group II introns, approximately half of which are classified as subgroup IIB. The splicing of all but one of the subgroup IIB introns requires a heterodimer containing the peptidyl-tRNA hydrolase homolog CRS2 and one of two closely related proteins, CAF1 or CAF2, that harbor a recently recognized RNA binding domain called the CRM domain. Two CRS2/CAF-dependent introns require, in addition, a CRM domain protein called CFM2 that is only distantly related to CAF1 and CAF2. Here, we show that CFM3, a close relative of CFM2, associates in vivo with those CRS2/CAF-dependent introns that are not CFM2 ligands. Mutant phenotypes in rice and Arabidopsis support a role for CFM3 in the splicing of most of the introns with which it associates. These results show that either CAF1 or CAF2 and either CFM2 or CFM3 simultaneously bind most chloroplast subgroup IIB introns in vivo, and that the CAF and CFM subunits play nonredundant roles in splicing. These results suggest that the expansion of the CRM protein family in plants resulted in two subfamilies that play different roles in group II intron splicing, with further diversification within a subfamily to accommodate multiple intron ligands.

  3. Evaluation of outgassing from a fluorinated resist for 157-nm lithography

    NASA Astrophysics Data System (ADS)

    Irie, Shigeo; Fujii, Kiyoshi; Itakura, Yasuo; Kawasa, Youichi; Egawa, Keiji; Uchino, Ikuo; Sumitani, Akira; Itani, Toshiro

    2004-05-01

    We have evaluated the outgassing products and the in-situ transmittance of a contaminated CaF2 substrate for monocyclic fluoropolymers with four protecting groups: methoxymethyl (MOM), tert-butoxycarbonyl (t-BOC), menthoxymethyl (MM), and 2-cyclohexylcyclohexyloxymethyl (CCOM). We have also evaluated the same type of fluoropolymer with seven kinds of photo-acid generators (PAGs) added to a base fluoropolymer solution. We found little correlation between the total amount of outgassing from the polymer and the decreasing rate of the CaF2 substrate transmittance caused by outgassing adhesion. Although the MOM protecting group generated the largest amount of outgassing products, the most substantial decrease in the transmittance was observed for the t-BOC protecting group. Also, the outgassing products due to use of a PAG did not greatly reduce the absorption coefficient of a CaF2 substrate regardless of the kind of PAG. Therefore, the absorption coefficient of the outgassing-contaminated CaF2 substrate appears to be more sensitive to the type of protecting group, especially the t-BOC protecting group including a t-butyl unit, rather than the type of fluoropolymer or PAG. We analyzed the substrate surface contaminant due to the t-butyl unit by x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and time-of-flight secondary ion mass spectrometry (TOF-SIMS), and found that increasing amounts of organic compounds, containing mainly C- and H-atoms, were adhered to and deposited on the substrate surface with an increasing irradiation dose. We speculate that the contaminants on a CaF2 surface with or without an anti-reflective coating were formed not only through mere physical adsorption, but also through certain chemical combinations. We conclude that in terms of material design of the fluoropolymer resist for 157-nm lithography, we need to pay attention to the protecting group of polymers, especially the t-BOC or t-butyl protecting group, which generates isobutene product during 157-nm irradiation.

  4. Growth Kinetics in Epitaxial Growth

    NASA Astrophysics Data System (ADS)

    Hessinger, Uwe

    Growth kinetics in heteroepitaxial growth are related to the nucleation and growth of atomic-height islands during the deposition of a material on a dissimilar substrate. Experimental measurements of the initial morphology of CaF_2 films deposited on Si(111) substrates were performed. These measurements consisted of photoemission spectroscopy and diffraction, which give sub-nanometer scale information averaged over the entire sample, and plan-view transmission electron microscopy, which gives localized information on a scale of several nanometers. These results, combined with others in the literature, revealed four distinct growth morphologies dependent on the deposition rate, substrate temperature and spacing between atomic-height steps on the surface, two of which had not been previously explained. A model based on two extant theories of homoepitaxial growth kinetics was developed to explain the different observed growth morphologies for the heteroepitaxial system CaF_2/Si(111). The first theory deals with whether the initial nucleation will occur at substrate steps or through adatom collisions on flat terraces, while the second deals with the nucleation of subsequent layers as these initial atomic islands increase in size. In extending these theories to heteroepitaxy, very different rates of upper-layer nucleation for the different size islands that nucleated at steps and on terraces are predicted. By applying this theory to CaF_2/Si(111), the diffusion barriers for CaF_2 molecule migration both on the reacted Si-Ca-F interface layer and on subsequent CaF_2 layers was extracted. The four different growth morphologies are explained within a common framework. The theory is quite general, and should apply to most heteroepitaxial systems. These theories were extended to predict a means by which the upper-layer nucleation may be inhibited while the underlying layer is completed. This method involves initiating the growth at conditions favoring many, small islands on atomic terraces, and then completing the growth at conditions inhibiting upper-layer nucleation (lower flux and/or higher temperature). A general formula for either homoepitaxy or heteroepitaxy was developed for the optimal flux and temperature variation during each monolayer to fabricate a flat film in the minimum amount of time.

  5. Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses.

    PubMed

    Taira, Y; Toyokawa, H; Kuroda, R; Yamamoto, N; Adachi, M; Tanaka, S; Katoh, M

    2013-05-01

    High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90° collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF2 scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF2 scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured.

  6. Resonant nature of intrinsic defect energy levels in PbTe revealed by infrared photoreflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Bingpo; Cai, Chunfeng; Jin, Shuqiang; Ye, Zhenyu; Wu, Huizhen; Qi, Zhen

    2014-07-01

    Step-scan Fourier-transform infrared photoreflectance and modulated photoluminescence spectroscopy were used to characterize the optical transitions of the epitaxial PbTe thin film grown by molecular beam epitaxy on BaF2 (111) substrate in the vicinity of energy gap of lead telluride at 77 K. It is found that the intrinsic defect energy levels in the electronic structure are of resonant nature. The Te-vacancy energy level is located above the conduction band minimum by 29.1 meV. Another defect (VX) energy level situated below valance band maximum by 18.1 meV is also revealed. Whether it is associated with the Pb vacancy is still not clear. It might also be related to the misfit dislocations stemming from the lattice mismatch between PbTe and BaF2 substrate. The experimental results support the theory prediction (N. J. Parada and G. W. Pratt, Jr., Phys. Rev. Lett. 22, 180 (1969), N. J. Parada, Phys. Rev. B 3, 2042 (1971)) and are consistent with the reported Hall experimental results (G. Bauer, H. Burkhard, H. Heinrich, and A. Lopez-Otero, J. Appl. Phys. 47, 1721 (1976)).

  7. Thin film growth of a topological crystal insulator SnTe on the CdTe (111) surface by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ishikawa, Ryo; Yamaguchi, Tomonari; Ohtaki, Yusuke; Akiyama, Ryota; Kuroda, Shinji

    2016-11-01

    We report molecular beam epitaxial growth of a SnTe (111) layer on a CdTe template, fabricated by depositing it on a GaAs (111)A substrate, instead of BaF2 which has been conventionally used as a substrate. By optimizing temperatures for the growth of both SnTe and CdTe layers and the SnTe growth rate, we could obtain SnTe layers of the single phase grown only in the (111) orientation and of much improved surface morphology from the viewpoint of the extension and the flatness of flat regions, compared to the layers grown on BaF2. In this optimal growth condition, we have also achieved a low hole density of the order of 1017 cm-3 at 4 K, the lowest value ever reported for SnTe thin films without additional doping. In the magnetoresistance measurement on this optimized SnTe layer, we observe characteristic negative magneto-conductance which is attributed to the weak antilocalization effect of the two-dimensional transport in the topological surface state.

  8. Third-order nonlinear optical response in transparent solids using ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Dota, K.; Dharmadhikari, J. A.; Mathur, D.; Dharmadhikari, A. K.

    2012-06-01

    The third-order optical nonlinearity, χ (3), is measured in transparent glasses (BK7 and fused silica) and crystals (BaF2 and quartz) using 36-fs, 800-nm laser pulses and the optical Kerr gate (OKE) technique; values are found to lie in the range 1.3-1.7×10-14 esu, in accordance with theoretical estimates. We probe the purely electronic response to the incident ultrashort laser pulse in fused silica and BK7 glass. In BaF2 and quartz, apart from the electronic response we also observe contribution from the nuclear response to the incident ultrashort pulses. We observe oscillatory modulations that persist for ˜400 fs. The response of the media (glasses and crystals) to ultrashort pulses is also measured using two-beam self-diffraction; the diffraction efficiency in the first-order grating is measured to be in the range of 0.06-0.13 %. Third harmonic generation due to self-phase matching in the transient grating geometry is measured as a function of temporal delay between the two incident ultrashort pulses, yielding the autocorrelation signal.

  9. Optimal design of TIR prism for the infrared target simulator based on DMD

    NASA Astrophysics Data System (ADS)

    Liu, Fang; Sun, Dan; Gao, Jiaobo; Zheng, Yawei; Hu, Yu; Zhang, Fang; Wang, Xicheng

    2016-10-01

    Overall structure of the infrared target simulator system and the principle of DMD are introduced. When DMD is on "open" state, all of the incidence light can rip into the pupil of the projection system. In addition, when it is on "close" state or "flat" state, all of the incident light can't rip into the pupil of the projection system. Based on this principle, with a specific infrared target simulator, TIR prism with BaF2 as material is designed. And then, this design is improved by ZnSe material instead of BaF2. ZnSe transmission rate is very well in the range of 0.6 microns to 14 microns and the infrared target simulator in this project requires 3 to 5 microns and 8 to 14 microns wavelength. This material is hard and easy to be processed. The design idea and design process are introduced in details in this paper and angle parameters are obtained. To improve light utilization and image quality in infrared target simulator system, two types of thin film on TIR prism different surfaces are designed. One is high transmittance with incidence angle of 0° and 24° - the other is 55°. Finally, this scheme is simulated and optimized by Tracepro software. Approving results were acquired.

  10. Understanding Low Energy Gamma Emission from Fission and Capture with DANCE

    NASA Astrophysics Data System (ADS)

    Wilburn, Grey; Couture, Aaron; Mosby, Shea

    2012-10-01

    Los Alamos National Laboratory's Detector for Advanced Neutron Capture Experiments (DANCE) consists of 160 barium fluoride (BaF2) detectors in a 4π array used to study cross-section measurements from neutron capture reactions. Further, recent studies have taken advantage of DANCE to study the gamma emission from fission, which is not well characterized. Neutron capture is studied because of its relevance to nuclear astrophysics (almost all elements heavier than iron are formed via neutron capture) and nuclear energy, where neutron capture is a poison in the reactor. Gamma ray cascades following neutron capture and fission include photons with energies between 100 keV and 10 MeV. DANCE uses a ^6LiH sphere to attenuate scattered neutrons, the primary background in DANCE. Unfortunately, it also attenuates low energy gamma rays. In order to quantify this effect and validate simulations, direct measurements of low energy gammas were made with a high purity germanium (HPGe) crystal. HPGe's allow for high resolution measurements of low energy gamma rays that are not possible using the BaF2 crystals. The results and their agreement with simulations will be discussed.

  11. Fluoride dielectric films on InP for metal-insulator-semiconductor applications

    NASA Astrophysics Data System (ADS)

    Paul, T. K.; Bose, D. N.

    1990-04-01

    This paper describes the characteristics of thin fluoride films on InP which are used as dielectric for metal-insulator-semiconductor (MIS) devices. Films of Ba1-xSrxF2 (x=0.0, 0.5, 0.83, and 1.0) were deposited by sublimation of mixtures of BaF2 and SrF2 in vacuum under 10-5 Torr pressure. The composition of the films was deduced from x-ray diffraction and energy dispersion analysis by x-ray studies. The electrical activation energies of the films determined between 120 and 300 K were found to be 3.5-22.0×10-3 eV , depending on composition and temperature. The resistivity of the films was in the range of 5.0×1011 to 5.0×1012 Ω cm with the breakdown fields greater than 5.0×105 V cm-1 . The interface state density obtained was as low as 5×1010 cm-2 eV-1 with annealed BaF2 films. Scanning electron microscope studies showed that annealing caused development of cracks resulting in decreased film resistivity. Auger studies gave evidence of broadening of the interface and outdiffusion from the substrate due to annealing.

  12. Monte Carlo simulation studies on scintillation detectors and image reconstruction of brain-phantom tumors in TOFPET

    PubMed Central

    Mondal, Nagendra Nath

    2009-01-01

    This study presents Monte Carlo Simulation (MCS) results of detection efficiencies, spatial resolutions and resolving powers of a time-of-flight (TOF) PET detector systems. Cerium activated Lutetium Oxyorthosilicate (Lu2SiO5: Ce in short LSO), Barium Fluoride (BaF2) and BriLanCe 380 (Cerium doped Lanthanum tri-Bromide, in short LaBr3) scintillation crystals are studied in view of their good time and energy resolutions and shorter decay times. The results of MCS based on GEANT show that spatial resolution, detection efficiency and resolving power of LSO are better than those of BaF2 and LaBr3, although it possesses inferior time and energy resolutions. Instead of the conventional position reconstruction method, newly established image reconstruction (talked about in the previous work) method is applied to produce high-tech images. Validation is a momentous step to ensure that this imaging method fulfills all purposes of motivation discussed by reconstructing images of two tumors in a brain phantom. PMID:20098551

  13. Self-organized homo-epitaxial growth in nonlinear optical BaAlBO3F2 crystal crossing lines patterned by laser in glass

    NASA Astrophysics Data System (ADS)

    Shinozaki, K.; Abe, S.; Honma, T.; Komatsu, T.

    2015-11-01

    Crystallization processing of glasses is important as a novel technique for the development of new optical materials, and laser-induced crystallization provides a new challenge in science and technology of materials. Nonlinear optical BaAlBO3F2 crystal lines with crossing, bending, and spiral shapes were patterned at the surface of 2NiO-49BaF2-24.5Al2O3-24.5B2O3 (mol%) and 2.9NiO-48.5BaF2-24.3Al2O3-24.3B2O3 (mol%) glasses by laser irradiation (Yb:YVO4 laser with a wavelength of 1080 nm) and the orientation state of BaAlBO3F2 crystals was examined from birefringence image observations. The birefringence images indicate that the growth of highly c-axis oriented BaAlBO3F2 crystals follows along the laser scanning direction even if the laser scanning direction changes, and in particular the direction of the c-axis of BaAlBO3F2 crystals changes gradually at the crossing and bending points. The model of "self-organized homo-epitaxial growth" is proposed for the crystal orientation at the crossing and bending points, as a new crystal growth science and engineering beyond the wise providence of nature.

  14. Two-step process of regeneration of acid(s) from ZrF4 containing spent pickle liquor and recovery of zirconium metal

    NASA Astrophysics Data System (ADS)

    Nersisyan, Hayk; Han, Seul Ki; Choi, Jeong Hun; Lee, Young-Jun; Yoo, Bung Uk; Ri, Vladislav E.; Lee, Jong Hyeon

    2017-04-01

    In this paper we describe a progressive two-step process that allows zirconium fluoride (ZrF4) contained in spent baths for etched zirconium alloys to be effectively recycled on a pilot scale and produce a high purity regenerated pickling acid. In the first step, a spent pickling liquor is treated by a BaF2 suspension to produce water insoluble Ba2ZrF8. After filtration of Ba2ZrF8 more than 99.9 wt % purity pickling acid is regenerated. The precipitation mechanism of Ba2ZrF8 is discussed and the role of BaF2 particles size on the precipitation process is demonstrated. In the second step the as-precipitated Ba2ZrF8 is mixed with Mg and Cu metal powders and heat-treated at 1200 °C (or above) to produce CuZr alloy ingot. The characteristics of the ingot are discussed in regard to Cu concentration and the heating temperature.

  15. Experimental study and thermodynamic modelling of the calcium oxide-silicon oxide-aluminum oxide-calcium fluoride system

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Geun

    Mould flux for the continuous casting process is a major concern for the steelmaking industry. Nowadays, more than 90 % of steel is being produced by the continuous casting process, which requires mould flux as an essential additive. The development of mould flux has been achieved by the conventional trial and error approach since it was first introduced in industry in the 1960s. Recently, the interest on the properties of fluorine has increased a lot since it is reported that fluorine has important functions such as playing a critical role on the crystallization behavior, and decreasing the melting point and viscosity of slag. However, the conventional way to find a suitable mould flux is not efficient to face the increasingly stringent requirements of the continuous casting process such as thin slab casting and higher casting speed. Therefore, fundamental phase diagram study on mould flux systems is clearly necessary, and thermodynamic modeling is the most effective way to design new mould flux in terms of time and money saving. The major components of mould flux, the CaO-SiO2-Al2O 3-CaF2 system, are investigated in this study as these four constituents will mostly affect the largest numbers of properties. Unfortunately, fluorine has high volatility at high temperature and high reactivity with other materials. Therefore, the results of previous experiments on F-containing systems are characterized by large discrepancies due to composition alteration and unexpected reactions during the experiment. As literature data show inconsistent results between each other, key phase diagram experiments were performed in this study. The phase diagram experiments were conducted with the quenching method in sealed Pt capsules to prevent fluorine loss during the experiment. The analyses were performed using a FE-SEM equipped with an EDS system, and a newly developed technique which produces more precise quantitative results for the equilibrium phase composition. The CaO liquidus of the CaO-CaF 2 binary system, which the literature data differ from each other by up to 50 mol %, was confirmed. The CaO solubility in solid CaF2 was found for the first time and reaches about 5 mol % at the eutectic temperature. The liquidus of the CaO-Al2O3-CaF2 and CaO-SiO 2-CaF2 systems were carefully studied and the miscibility gap in the CaO-Al2O3-CaF2 system was proved to be much smaller than that reported in literature. Also, thermal analysis was performed using DSC in a Pt crucible. The eutectic temperatures of the CaO-CaF2 and CaAl2O4-CaF2 systems were successfully measured and the alpha to beta-CaF2 polymorphic transition was confirmed. Based on the new experimental data and reliable literature data, thermodynamic modeling of the CaO-SiO2-Al 2O3-CaF2 system was also carried out. The results of thermodynamic calculation can be very beneficial for new mould flux design.

  16. Light-emitting nanocomposites and novel amorphous polymers for optical applications

    NASA Astrophysics Data System (ADS)

    Gipson, Kyle Garrod

    Polymeric optical materials generally are comprised of amorphous polymers that are transparent in at visible wavelengths but exhibit strong absorption bands in the near-infrared making them less useful for many optical applications. Attenuation, which is the absorption per unit length, largely results from the high vibrational energy associated with carbon-hydrogen bonds contained in the polymer backbone. Attenuation can be mitigated by optical amplification utilizing light emitting additives. Investigated in this dissertation are synthesis techniques for the fabrication of light-emitting polymer nanocomposites and their resultant thermal and rheological characteristics for potential use as polymer optical fibers or films. Inorganic nanocrystals doped with optically active rare-earth ions (Tb 3+:LaF3) treated with organic ligands were synthesized in water and methanol in order to produce polymethyl methacrylate (PMMA) light-emitting nanocomposites. Two different aromatic ligands (acetylsalicylic acid, ASA and 2-picolinic acid, PA) were employed to functionalize the surface of Tb 3+:LaF3 nanocrystals. We have used infrared spectroscopy, thermal analysis, elemental analysis, dynamic light scattering, rheological measurements and optical spectroscopy to investigate the nanoparticle structure and composition response of ligand-capped nanocrystals under various synthesis parameters. A theoretical interpretation of particle-to-particle interactions also was conducted which supported our study of the potential of agglomeration within the nanoparticle suspensions. Novel amorphous polymers (e.g. perfluorocyclobutyl aryl ethers, PFCB), which do not exhibit strong C-H vibrations, have been reported to possess excellent optical properties. Little is known of the intrinsic properties of PFCBs (e.g. biphenylvinyl ether, BPVE and hexafluoroisopropylidene vinyl ether, 6F) as well as the behavior of the polymer melt during extrusion. We preformed empirical and experimental thermal and rheological evaluations of BPVE, 6F and polymer nanocomposites of varying loading levels. These studies provide greater understanding of the melt performance of BPVE, 6F and for optically active nanoparticles within PMMA. The data and the use of a fiber melt extrusion modeling package allowed for the construction of viable initial melt fiber extrusion parameters. Many researchers have focused on the development of polymer light-emitting nanocomposites and novel amorphous polymers for optical applications. I, however, have focused particularly on developing a fundamental understanding of the nanoparticle synthesis. My work concentrates on the surface chemistry of the nanoparticle with an emphasis on the interaction between the surface attached ligand and the polymer matrix. This research will aide in the development of a more optimized and compliant polymeric nanocomposites for optical applications.

  17. Decay Processes of Highly Excited Laser Ions in Solids.

    NASA Astrophysics Data System (ADS)

    Collins, John Michael

    Using the techniques of luminescence spectroscopy, we have investigated the luminescent properties of a number of systems following excitation with high-energy UV radiation. After revisiting the two-photon emission from Pr^{3+} in yttrium fluoride, an investigation into the possibility of energy transfer between Pr and other rare-earth ions was carried out in the systems YF_3:Pr,Tb; YF _3:Pr,Eu; LaF_3:Pr,Tb; and LaF_3:Pr,Eu. In all systems, spectroscopic and kinetic data shows no presence of energy transfer among the dopant ions. Investigation of the Pr -Eu doped systems were hindered by the presence of divalent Eu. The cross-relaxation process among Tb ions has been studied in Y_{rm 1-x} F_3:Tb_{ rm x}, with x =.001,.004 and.05, and is shown to increase with both concentration and temperature. Kinetic studies show that at high Tb concentration, the excitation migrates through the Tb sublattice at the ^5 D_3<=vel before the cross -relaxation can occur. The migration is quenched at low temperatures. Al_2O_3 :Ti, when excited with UV radiation shows the existence of as many as three previously unreported emissions. One of these bands, centered at 560 nm and extending throughout the visible region, was studied in more detail. The decay of this emission varies from 30 musec at 300^circK to 710 musec at 20^circK, while intensity actually decreases with temperature. A model is proposed which could explain this behavior. Laser action is also reported from this band and its application as a solid-state tunable laser is discussed. A previously unreported energy transfer from Gd ^{3+} to Er^ {3+} is shown to exist in the system Y _{.34}Gd_ {.65}Er_{.01} F_3. The energy transfer process is of the non-radiative type, and is quite efficient (~80%) in this system. Kinetic studies indicate that the transfer is more efficient at lower temperatures. This behavior is explained by a redistribution with temperature of the population of Gd and Er ions and its affect on the energy mismatch between the levels involved in the transfer.

  18. Novel luminescent nanoparticles for DNA detection

    NASA Astrophysics Data System (ADS)

    Dong, Ling; Yang, Zhihua; Zhang, Yi; Zhu, Yanyu; Wang, Lun; Wang, Leyu

    2010-05-01

    Highly luminescent LaF 3:Ce 3+/Tb 3+ nanocrystals were successfully prepared and surface functionalized via Layer-by-Layer technology. These as-prepared nanocrystals are highly resistant to photobleaching and pretty dispersible in aqueous solution. Due to the efficient luminescence quenching of the nanocrystals by nucleic acids, a facile fluorescence quenching method was developed for the detection of trace amount of nucleic acids. Under optimal conditions, the fluorescence intensity was proportional to the DNA concentration over the range of 0.60-25.0 μg mL -1 for calf thymus DNA (ct-DNA) and 0.60-30.0 μg mL -1 for herring sperm DNA (hs-DNA), respectively. The corresponding detection limit is 0.21 μg mL -1 for ct-DNA and 0.31 μg mL -1 for hs-DNA, respectively. The results indicated that the reported method is simple and rapid with wide linear range. Also, the recovery and relative standard deviation of this method are reasonable and satisfactory.

  19. Gene expression patterns in granulosa cells and oocytes at various stages of follicle development as well as in in vitro grown oocyte-and-granulosa cell complexes.

    PubMed

    Munakata, Yasuhisa; Kawahara-Miki, Ryoka; Shiratsuki, Shogo; Tasaki, Hidetaka; Itami, Nobuhiko; Shirasuna, Koumei; Kuwayama, Takehito; Iwata, Hisataka

    2016-08-25

    Follicle development is accompanied by proliferation of granulosa cells and increasing oocyte size. To obtain high-quality oocytes in vitro, it is important to understand the processes that occur in oocytes and granulosa cells during follicle development and the differences between in vivo and in vitro follicle development. In the present study, oocytes and granulosa cells were collected from early antral follicles (EAFs, 0.5-0.7 mm in diameter), small antral follicles (SAFs, 1-3 mm in diameter), large antral follicles (LAFs, 3-7 mm in diameter), and in vitro grown oocyte-and-granulosa cell complexes (OGCs), which were cultured for 14 days after collection from EAFs. Gene expression was analyzed comprehensively using the next-generation sequencing technology. We found top upstream regulators during the in vivo follicle development and compared them with those in in vitro developed OGCs. The comparison revealed that HIF1 is among the top regulators during both in vivo and in vitro development of OGCs. In addition, we found that HIF1-mediated upregulation of glycolysis in granulosa cells is important for the growth of OGCs, but the cellular metabolism differs between in vitro and in vivo grown OGCs. Furthermore, on the basis of comparison of upstream regulators between in vivo and in vitro development of OGCs, we believe that low expression levels of FLT1 (VEGFA receptor), SPP1, and PCSK6 can be considered causal factors of the suboptimal development under in vitro culture conditions.

  20. Gene expression patterns in granulosa cells and oocytes at various stages of follicle development as well as in in vitro grown oocyte-and-granulosa cell complexes

    PubMed Central

    MUNAKATA, Yasuhisa; KAWAHARA-MIKI, Ryoka; SHIRATSUKI, Shogo; TASAKI, Hidetaka; ITAMI, Nobuhiko; SHIRASUNA, Koumei; KUWAYAMA, Takehito; IWATA, Hisataka

    2016-01-01

    Follicle development is accompanied by proliferation of granulosa cells and increasing oocyte size. To obtain high-quality oocytes in vitro, it is important to understand the processes that occur in oocytes and granulosa cells during follicle development and the differences between in vivo and in vitro follicle development. In the present study, oocytes and granulosa cells were collected from early antral follicles (EAFs, 0.5–0.7 mm in diameter), small antral follicles (SAFs, 1–3 mm in diameter), large antral follicles (LAFs, 3–7 mm in diameter), and in vitro grown oocyte-and-granulosa cell complexes (OGCs), which were cultured for 14 days after collection from EAFs. Gene expression was analyzed comprehensively using the next-generation sequencing technology. We found top upstream regulators during the in vivo follicle development and compared them with those in in vitro developed OGCs. The comparison revealed that HIF1 is among the top regulators during both in vivo and in vitro development of OGCs. In addition, we found that HIF1-mediated upregulation of glycolysis in granulosa cells is important for the growth of OGCs, but the cellular metabolism differs between in vitro and in vivo grown OGCs. Furthermore, on the basis of comparison of upstream regulators between in vivo and in vitro development of OGCs, we believe that low expression levels of FLT1 (VEGFA receptor), SPP1, and PCSK6 can be considered causal factors of the suboptimal development under in vitro culture conditions. PMID:27108636

  1. Evidence of energy transfer in nanoparticle-porphyrins conjugates for radiation therapy enhancement

    NASA Astrophysics Data System (ADS)

    Kudinov, Konstantin; Cooper, Daniel; Tyagi, Pooja; Bekah, Devesh; Bhattacharyya, Dhrittiman; Hill, Colin; Ha, Jonathan Kin; Nadeau, Jay; Bradforth, Stephen

    2015-03-01

    We report progress towards combining radiation therapy (RT) and photodynamic therapy (PDT) using scintillating nanoparticle (NP)-photosensitizer conjugates. In this approach, scintillating NPs are excited by clinically relevant ionizing radiation sources and subsequently transfer energy to conjugated photosensitizers via FRET, acting as an energy mediator between ionizing radiation and photosensitizer molecules. The excited photosensitizers generate reactive oxygen species that can induce local damage and immune response. Advantages of the scheme include: 1) Compared with traditional radiation therapy, a possible decrease of the total radiation dose needed to eliminate the lesion; 2) Compared with traditional PDT, the ability to target deeper and more highly pigmented lesions; 3) The possibility of additional photosensitizing effects due to the scintillation of the nanoparticles. In this work, the photosensitizer molecule chlorin e6 was covalently bound to the surface of LaF3:Ce NPs. After conjugation, the photoluminescence intensity of NPs decreased, and fluorescence lifetime of conjugated chlorin e6 became sensitive to excitation wavelength, suggesting rapid FRET. In addition, scintillation spectra of nanoparticles were measured. Preliminary calculations suggest that the observed scintillation efficiencies are sufficient to enhance RT. In vitro cancer cell studies suggest conjugates are taken up by cells. Survival curves with radiation exposure suggest that the particles alone cause radiosensitization comparable to that seen with gold nanoparticles.

  2. Phase transformation and fluorescent enhancement of ErF3 at high pressure

    NASA Astrophysics Data System (ADS)

    Li, Wentao; Ren, Xiangting; Huang, Yanwei; Yu, Zhenhai; Mi, Zhongying; Tamura, Nobumichi; Li, Xiaodong; Peng, Fang; Wang, Lin

    2016-09-01

    Pressure-induced phase transformation and fluorescent properties of ErF3 were investigated here using in-situ synchrotron X-ray diffraction and photoluminescence up to 32.1 GPa at room temperature. Results showed that ErF3 underwent a reversible pressure-induced phase transition from the β-YF3-type to the fluocerite LaF3-type at 9.8 GPa. The bulk moduli B0 for low- and high-pressure phases were determined to be 130 and 208 GPa, respectively. Photoluminescencent studies showed that new emission lines belonging to the transition of 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 appeared during phase transition, suggesting pressure-induced electronic band splitting. Remarkably, significant pressure-induced enhancement of photoluminescence was observed, which was attributed to lattice distortion of the material under high pressure.

  3. The stable and water-soluble neodymium-doped lanthanide fluoride nanoparticles for near infrared probing of copper ion.

    PubMed

    Xue, Fang-Min; Wang, He-Fang

    2012-09-15

    Neodymium (Nd(3+)) doped nanomaterials exhibited the unique near infrared (NIR) luminescence properties. However, the application of Nd-doped nanomaterials to chemosensors was rarely explored. Herein, the water-soluble 2-aminoethyl dihydrogen phosphate stabilized Nd-doped LaF(3) (ADP-Nd-LaF(3)) nanoparticles were explored as the NIR probe for chemosensors. The NIR emission intensity at 1061 nm of ADP-Nd-LaF(3) nanoparticles kept stable in the aqueous solution of various pH and coexisting of most common metal ions except copper ion, consequently, the ADP-Nd-LaF(3) nanoparticles were developed as a high selective NIR probe for Cu(II). The NIR emission of ADP-Nd-LaF(3) exhibits a linear quenching response to Cu(II) in the range 5-100 μM, with a detection limit of 0.8 μM. The precision of eleven replicate detections of 5 μM Cu(II) was 0.5% (RSD). The recovery of spiked Cu(II) in human urine and waste water samples ranged from 102 to 109%. The possible mechanism of Cu(II)-induced fluorescence quenching of ADP-Nd-LaF(3) nanoparticles was also discussed.

  4. Controllable optical modulation of blue/green up-conversion fluorescence from Tm3+ (Er3+) single-doped glass ceramics upon two-step excitation of two-wavelengths

    PubMed Central

    Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

    2017-01-01

    Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8–1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas. PMID:28368041

  5. On structural and lattice dynamic stability of LaF{sub 3} under high pressure: A first principle study

    SciTech Connect

    Sahoo, B. D. Joshi, K. D.; Gupta, Satish C.

    2015-06-24

    Structural and lattice dynamical stability of the LaF3 has been analyzed as a function of hydrostatic compression through first principle electronic band structure calculations. The comparison of enthalpies of various plausible structures calculated at various pressures suggests a phase transition from ambient condition tysonite structure (space group P-3c1) to a primitive orthorhombic structure (space group Pmmn) at a pressure of ∼19.5 GPa, in line with the experimental value of 16 GPa. Further, it is predicted that this phase will remain stable up to 100 GPa (the maximum pressure up to which calculations have been performed in the present work). The theoretically determined equation of state displays a good agreement with experimental data. Various physical quantities such as zero pressure equilibrium volume, bulk modulus, and pressure derivative of bulk modulus have been derived from the theoretically determined equation of state and compared with the available experimental data. Our lattice dynamic calculations correctly demonstrate that at zero pressure the tysonite structure is lattice dynamically stable whereas the Pmmn structure is unstable lattice dynamically. Further, at transition pressure the theoretically calculated phonon spectra clearly show that the Pmmn phase emerges as lattice dynamically stable phase whereas the tysonite structure becomes unstable dynamically, supporting our static lattice calculations.

  6. Vacuum deposited optical coatings experiment (AO 138-4)

    NASA Technical Reports Server (NTRS)

    Charlier, Jean

    1991-01-01

    The aim of this experiment was to test the optical behavior of 20 components and coatings subjected to space exposure. Most of them are commonly used for their reflective or transmittive properties in spaceborne optics. They consist in several kind of metallic and dielectric mirrors designed for the 0.12 to 10 microns spectrum, UV, and NIR bandpass filters, visible, and IR antireflecting coatings, visible/IR dichroic beam splitters, and visible beam splitter. The coatings were deposited on various substrates such as glasses, germanium, magnesium fluoride, quartz, zinc selenide, and kanigened aluminum. Several coating materials were used such as Al, Ag, Au, MgF2, LaF3, ThF3, ThF4, SiO2, TiO2, ZrO2, Al2O3, MgO, Ge, and ZnSe. Five samples of each component were manufactured. Two flight samples were mounted in such a way that one was directly exposed to space and the other looking backwards. The same arrangement was used for the spare samples stored on ground in a box identical to the flight one and they were kept under vacuum during the LDEF mission. Finally, one set of reference components was stocked in a sealed box under a dry nitrogen atmosphere. By comparing the preflight and postflight optical performances of the five samples of each component, it is possible to detect the degradations due to the space exposure.

  7. Controllable optical modulation of blue/green up-conversion fluorescence from Tm(3+) (Er(3+)) single-doped glass ceramics upon two-step excitation of two-wavelengths.

    PubMed

    Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

    2017-04-03

    Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm(3+) (Er(3+)) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8-1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas.

  8. High performance fluoride optical coatings for DUV optics

    NASA Astrophysics Data System (ADS)

    Zhang, Lichao; Cai, Xikun

    2014-08-01

    In deep ultraviolet region that typical applications are used on the ArF wavelength, coated optics should meet stringent requirements of optical systems. To meet these requirements, systematical researches are carried out on fabrication and characterization methods of fluoride coatings. First, by optimizing of deposition processes, dense coatings with the refractive index of ~1.7 for LaF3 and ~1.4 for MgF2, together with extinction coefficients of ~2×10-4 on 193nm were realized. The transmission of AR coating for 193nm achieved by using optimized deposition techniques is 99.8%. Second, a method of designing shadowing masks was developed to solve the problem of correcting coating thickness distributions for complex DUV systems. By using the method, the thickness distribution error specification of 3% PV has been achieved on substrates with ~300mm diameters and large curvatures. Finally, the laser calorimetry method is used to evaluate the laser radiation stability of fluoride coatings. It is turned out that the damage coefficients of fluoride coatings, which are defined as the values of unrecoverable increase of the absorption during the laser irradiation process, are much lower than that of fused silica substrates. The above progresses could further support the realization of high performance DUV optical systems.

  9. Electrochemical fluorination of La(2)CuO(4): a mild "chimie douce" route to superconducting oxyfluoride materials.

    PubMed

    Delville, M H; Barbut, D; Wattiaux, A; Bassat, J M; Ménétrier, M; Labrugère, C; Grenier, J C; Etourneau, J

    2009-08-17

    The fluorination of La(2)CuO(4) was achieved for the first time under normal conditions of pressure and temperature (1 MPa and 298 K) via electrochemical insertion in organic fluorinated electrolytes and led to lanthanum oxyfluorides of general formula La(2)CuO(4)F(x). Analyses showed that, underneath a very thin layer of LaF(3) (a few atomic layers), fluorine is effectively inserted in the material's structure. The fluorination strongly modifies the lanthanum environment, whereas very little modification is observed on copper, suggesting an insertion in the La(2)O(2) blocks of the structure. In all cases, fluorine insertion breaks the translation symmetry and introduces a long-distance disorder, as shown by electron spin resonance. These results highlight the efficiency of electrochemistry as a new "chimie douce" type fluorination technique for solid-state materials. Performed at room temperature, it additionally does not require any specific experimental care. The choice of the electrolytic medium is crucial with regard to the fluorine insertion rate as well as the material deterioration. Successful application of this technique to the well-known La(2)CuO(4) material provides a basis for further syntheses from other oxides.

  10. Fluoride-based, low temperature solid electrolyte fuel cell

    NASA Astrophysics Data System (ADS)

    Oh, Seajin; Otagawa, T.; Madou, M.

    Lanthanum fluoride electrolytes were tested to determine whether fluoride electrolytes can be used as fuel cell electrolytes at low temperatures. The planar-type fuel cell were operated in oxygen/hydrogen gases with nickel oxide/nickel as the anode and a perovskite structure oxide (La(0.6)Sr(0.4)CoO3) as the cathode. In order to reduce the fuel cell operating temperature while maintaining the highest possible current, various thin and thick film techniques were assessed. They include e-beam evaporation and dc plasma spray methods. Fuel cells incorporating plasma-sprayed LaF3 films yielded a short-circuit current density on the order of 0.4 mA/sq cm at 450 C, and the current density under an overpotential of 0.2V showed no sign of decay over 17 hours. In the co-ionic (fluoride and oxide ion) conduction mode, the lanthanum fluoride electrolyte based fuel cells could sustain current in oxygen/hydrogen gases.

  11. Atomic origin of 3d(9)4 f(1) configuration in La(3+) solids.

    PubMed

    Yu, S-W; Carpenter, M H; Ponce, F; Friedrich, S; Lee, J-S

    2015-10-14

    We have studied the excited electronic structure of LaBr3(Ce) scintillator by soft x-ray spectroscopy such as x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES). The La 3d XAS and XES spectra of LaBr3(Ce) are compared with those of other La(3+) solids (LaF3, La2O3, and La metal). From this comparison, it turns out that the La 3d XAS and XES spectra from all the La(3+) solids considered here appear at almost the same energy, even though the corresponding binding energies of the 3d core holes determined by XPS (x-ray photoelectron spectroscopy) are very different. As a result, we argue that the atomic nature of the 3d⁹4f¹ configuration created by 3d¹⁰4f⁰ → 3d⁹4f¹ x-ray absorption process in La(3+) solids is maintained via the localized 4 f (1) state, which screens the 3d core holes differently from one La(3+) solid to another.

  12. Preparation of surface-modified lanthanum fluoride-graphene oxide nanohybrids and evaluation of their tribological properties as lubricant additive in liquid paraffin

    NASA Astrophysics Data System (ADS)

    Yang, Cuizhen; Hou, Xiao; Li, Zhiwei; Li, Xiaohong; Yu, Laigui; Zhang, Zhijun

    2016-12-01

    Oleic acid surface-modified Lanthanum trifluoride-graphene oxide (OA-LaF3-GO) nanohybrids were successfully prepared by surface modification technology. The morphology and phase structure of as-prepared samples were analyzed by means of X-ray diffraction and transmission electron microscopy, Fourier transform infrared spectrometry, Raman spectrometry and thermogravimetry. The results revealed that OA were bonded onto the surface of LaF3-GO nanohybrids. Subsequently, the tribological properties of OA-LaF3-GO nanohybrids as lubricant additive in liquid paraffin were evaluated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined on a scanning electron microscope with an energy dispersive spectrometer. Tribological results showed that OA-LaF3-GO nanohybrids had excellent friction reduction and antiwear ability at the loading of 0.5 wt.% OA-LaF3-GO nanohybrids, compared to liquid paraffin alone. The results of energy dispersive spectrometer revealed that improved tribological properties resulted from OA-LaF3-GO could transfer to the rubbed steel surface and decompose to form protective layers, which help to improve tribological properties.

  13. Measured 19F(α,n) with VANDLE for Nuclear Safeguards

    NASA Astrophysics Data System (ADS)

    Peters, William; Clement, R. C. C.; Smith, M. S.; Pain, S.; Febbraro, M.; Pittman, S.; Thomspon, S.; Grinder, M.; Cizewski, J. A.; Reingold, C.; Manning, B.; Burcher, S.; Bardayan, D. W.; Tan, W.-P.; Stech, E.; Smith, M. K.; Avetisyan, R.; Gyurjinyan, A.; Lowe, M.; Ilyushkin, S.; Grzywacz, R.; Madurga, M.; Paulauskas, S. V.; Taylor, S. Z.; Smith, K.

    2015-10-01

    One of the most promising non-destructive assay (NDA) methods to monitor UF6 canisters consists of measuring gross neutron rates induced by uranium-decay alpha particles reacting with the fluorine and emitting a neutron. This method currently lacks reliable nuclear data on the 19F(α,n) reaction cross section to determine an accurate neutron yield rate for a given sample of UF6. We have measured the cross section and coincident neutron spectrum for the alpha-decay energy range using the VANDLE system. This experiment had two parts: first at Notre Dame with a LaF3 target and and a pulsed alpha-particle beam, and second at ORNL with a windowless He-gas target and a 19F beam. The motivation for this measurement and cross section results will be presented. This work is funded in part by the DOE Office of Science, the National Nuclear Security Administration SSAA and the Office of Defense Nuclear Nonproliferation R&D, and the NSF.

  14. Optical properties and spectroscopic study of different modifier based Pr3 +:LiFB glasses as optical amplifiers

    NASA Astrophysics Data System (ADS)

    Balakrishna, A.; Babu, S.; Kumar, Vinod; Ntwaeaborwa, O. M.; Ratnakaram, Y. C.

    2017-01-01

    In this paper, we report the preparation and optical characterization of Pr3 + doped lithium fluoro borate (LiFB) glasses for six different chemical compositions of Li2B4O7-BaF2-NaF-MO (where M = Mg, Ca, Cd and Pb), Li2B4O7-BaF2-NaF-MgO-CaO and Li2B4O7-BaF2-NaF-CdO-PbO. The structural and optical properties of these glasses were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), optical absorption and photoluminescence techniques. The optical absorption spectra of Pr3 + ions in LiFB glasses have been recorded in the UV-VIS-NIR region. The optical absorption data are used to calculate various spectroscopic parameters such as Racah (E1, E2, E3) and spin-orbit interaction (ξ4f) parameters. Judd-Ofelt (J-O) (Ωλ where λ = 2, 4 and 6) intensity parameters were determined by applying J-O theory, which in turn used to calculate the radiative properties such as radiative transition probabilities (A), radiative lifetimes (τR), integrated absorption cross-sections (Σ) and branching ratios (βr) for all emission levels of Pr3 + ion in different LiFB glass matrices. By using the J-O theory and luminescence parameters, stimulated emission cross sections (σp) of prominent transitions, 3P0 → 3H4 and 1D2 → 3H4 of Pr3 + ion in all LiFB glasses were calculated. 3P0 → 3H4 possesses higher branching ratios and stimulated emission cross-sections for the Pr3 +:LiFB(Mg-Ca) glass, which can be used as a best laser excitation. The optical gain parameter (σpxτR) was noticed higher in Pr3 +:LiFB(Mg-Ca) and Pr3 +:LiFB(Cd-Pb) glasses for the transition 3P0→ 3H4 transition, and these glasses have potential for optical amplification at 488 nm wavelength.

  15. Arabidopsis orthologs of maize chloroplast splicing factors promote splicing of orthologous and species-specific group II introns.

    PubMed

    Asakura, Yukari; Barkan, Alice

    2006-12-01

    Chloroplast genomes in plants and green algae contain numerous group II introns, large ribozymes that splice via the same chemical steps as spliceosome-mediated splicing in the nucleus. Most chloroplast group II introns are degenerate, requiring interaction with nucleus-encoded proteins to splice in vivo. Genetic approaches in maize (Zea mays) and Chlamydomonas reinhardtii have elucidated distinct sets of proteins that assemble with chloroplast group II introns and facilitate splicing. Little information is available, however, concerning these processes in Arabidopsis (Arabidopsis thaliana). To determine whether the paucity of data concerning chloroplast splicing factors in Arabidopsis reflects a fundamental difference between protein-facilitated group II splicing in monocot and dicot plants, we examined the mutant phenotypes associated with T-DNA insertions in Arabidopsis genes encoding orthologs of the maize chloroplast splicing factors CRS1, CAF1, and CAF2 (AtCRS1, AtCAF1, and AtCAF2). We show that the splicing functions and intron specificities of these proteins are largely conserved between maize and Arabidopsis, indicating that these proteins were recruited to promote the splicing of plastid group II introns prior to the divergence of monocot and dicot plants. We show further that AtCAF1 promotes the splicing of two group II introns, rpoC1 and clpP-intron 1, that are found in Arabidopsis but not in maize; AtCAF1 is the first splicing factor described for these introns. Finally, we show that a strong AtCAF2 allele conditions an embryo-lethal phenotype, adding to the body of data suggesting that cell viability is more sensitive to the loss of plastid translation in Arabidopsis than in maize.

  16. Fluorescence of Er3+:AlN Polycrystalline Ceramic

    DTIC Science & Technology

    2012-01-01

    using heating techniques and sintering aids such as hot pressing with Ca(NO3)2•4H2O [19], spark plasma sintering with CaF2 [20], and pressureless...Cleveland, OH, U.S.A.) to determine the levels of Er before and after sintering . The starting powders (measured using Inductively Coupled Plasma ...optical spectroscopy of Er3+ doped into bulk AlN ceramic. The material was prepared via hot press sintering of AlN with Er2O3 and [NH4][ErF4], which

  17. Preparation and characterization of porous bioceramic layers on pure titanium surfaces obtained by micro-arc oxidation process

    NASA Astrophysics Data System (ADS)

    Chien, Chi-Sheng; Hung, Yu-Chien; Hong, Ting-Fu; Wu, Chung-Chun; Kuo, Tsung-Yuan; Lee, Tzer-Min; Liao, Tze-Yuan; Lin, Huan-Chang; Chuang, Cheng-Hsin

    2017-03-01

    Fluorapatite (FA) has better chemical and thermal stability than hydroxyapatite (HA), and has thus attracted significant interest for biomaterial applications in recent years. In this study, porous bioceramic layers were prepared on pure titanium surfaces using a micro-arc oxidation (MAO) technique with an applied voltage of 450 V and an oxidation time of 5 min. The MAO process was performed using three different electrolyte solutions containing calcium fluoride (CaF2), calcium acetate monohydrate (Ca(CH3COO)2·H2O), and sodium phosphate monobasic dihydrate (NaH2PO4·2H2O) mixed in ratios of 0:2:1, 1:1:1, and 2:0:1, respectively. The surface morphology, composition, micro-hardness, porosity, and biological properties of the various MAO coatings were examined and compared. The results showed that as the CaF2/Ca(CH3COO)2·H2O ratio increased, the elemental composition of the MAO coating transformed from HA, A-TiO2 (Anatase) and R-TiO2 (Rutile); to A-TiO2, R-TiO2, and a small amount of HA; and finally A-TiO2, R-TiO2, CaF2, TiP2O5, and FA. The change in elemental composition was accompanied by a higher micro-hardness and a lower porosity. The coatings exhibited a similar in vitro bioactivity performance during immersion in simulated body fluid for 7-28 days. Furthermore, for in initial in vitro biocompatibility tests performed for 24 h using Dulbecco's Modified Eagle Medium (DMEM) supplement containing 10%Fetal bovine serum, the attachment and spreading of osteoblast-like osteosarcoma MG63 cells were found to increase slightly with an increasing CaF2/Ca(CH3COO)2·H2O ratio. In general, the results presented in this study show that all three MAO coatings possess a certain degree of in vitro bioactivity and biocompatibility.

  18. A microwave-heated infrared reaction cell for the in situ study of heterogeneous catalysts.

    PubMed

    Silverwood, Ian P; McDougall, Gordon S; Gavin Whittaker, A

    2006-12-14

    A transmission infrared microreactor cell which holds a pressed disc in a controlled atmosphere and allows microwave and conventional heating up to 423 K is demonstrated using the oxidation of carbon monoxide over the standard catalyst EUROPT-1. Optical characteristics are determined by the choice of CaF2 as the window material, allowing transmission from 77,000-1000 cm(-1). An oscillating microwave power regime with a peak height of 200 W is used and time-resolved infrared spectra and mass spectrometry show oscillations in the reaction which correspond to the microwave heating.

  19. Thermodynamic studies on SrThO 3(s)

    NASA Astrophysics Data System (ADS)

    Prasad, R.; Dash, Smruti; Parida, S. C.; Singh, Ziley; Venugopal, V.

    2003-01-01

    The Gibbs energy of formation of SrThO 3(s) has been determined using e.m.f. and manometric techniques. In the e.m.f. method, two fluoride cells have been constructed to determine Δ fG0m(SrThO 3,s, T) using CaF 2(s) as a solid electrolyte. The cells used are: (-) O2( g), Pt/ SrO( s)+ SrF2( s)// CaF2//( SrThO3( s)+ ThO2( s)+ SrF2( s)/ Pt, O2( g)(+), ( I) (-) O2( g), Pt/ SrThO3( s)+ SrF2( s)+ ThO2( s)// CaF2( s)// CaO( s)+ CaF2( s)/ Pt, O2( g)(+). ( II) The observed e.m.f. values are represented by following respective expressions: E ( V)±0.0001=0.0998+3.254×10 -5T ( K), ( Cell I) E ( V)±0.0001=0.0285-6.37×10 -5T ( K). ( Cell II) From the measured e.m.f. values of the cells and the Δ fG0m( T) values from the literature, Δ fG0m(SrThO 3,s, T) have been calculated and are respectively given as ΔfG 0m( SrThO3, s,T)±10 kJ mol-1=-1829.2+0.2735T ( K) (978⩽T ( K)⩽1154), ( Cell I) ΔfG 0( SrThO3, s,T)±20 kJ mol-1=-1853.5+0.2867T ( K) (1008⩽T ( K)⩽1168). ( Cell II) In the manometric technique, equilibrium CO 2(g) pressures are measured over the three phase mixture: {SrThO 3(s)+SrCO 3(s)+ThO 2(s)} using a mercury manometer from 1075 to 1197 K. The corresponding Gibbs energy as a function of temperature is given by ΔfG 0m( SrThO3, s,T)( kJ mol-1)±14=-1865.4+0.3086T ( K).

  20. Intergranular fracture of lithium fluoride-22 percent calcium fluoride hypereutectic salt at 800 K

    NASA Technical Reports Server (NTRS)

    Raj, Subramanium V.; Whittenberger, J. Daniel

    1990-01-01

    Substantial strain-hardening was noted during the initial stages of deformation in constant-velocity compression tests conducted on as-cast samples of the LiF-22 mol pct CaF2 hypereutectic salt at 800 K. The deformed specimens exhibited extensive grain-boundary cracking and cavitation, suggesting that such cracking, in conjunction with interfacial sliding, is important for cavity nucleation at grain boundaries and at the LiF-CaF2 interfaces. Cavity growth and interlinkage occur through the preferential failure of the weaker LiF phase.

  1. Background reduction using single-photoelectron counting for WIMP search

    NASA Astrophysics Data System (ADS)

    Ogawa, I.; Hazama, R.; Mukaida, K.; Kishimoto, K.; Kobayashi, T.; Tomii, S.; Sakai, H.; Katsuki, A.; Itamura, T.; Tanaka, Y.; Umehara, S.; Yoshida, S.; Matsuoka, K.; Kishimoto, T.

    2013-03-01

    We have developed a new background reduction method based on single photoelectron counting of scintillators for the WIMP search experiment. We introduced this method to our detector system ELEGANT VI, which has an active shield in all directions (4π) using a pulse height or, equivalently, the difference in the number of photoelectrons between two (left and right) photomultiplier tubes attached to CaF2 scintillators. The number distribution is uniquely described by a binomial function, via which we developed the unambiguous background subtraction method. This method reduces the backgrounds further compared to charge-sensitive ADC and offers improved sensitivity for the search for WIMPs.

  2. A simple F-center laser spectrometer for continuous single frequency scans

    NASA Astrophysics Data System (ADS)

    Nelson, David D., Jr.; Schiffman, Aram; Lykke, Keith R.; Nesbitt, David J.

    1988-12-01

    We report a simple and novel scheme for continuous, single frequency scanning of a commercial F-center laser without any computer interfacing. The scheme utilizes galvo tuning of the cavity length with intracavity CaF 2 Brewster plates with servo loop control of the intracavity etalon. This permits continuous tuning of the F-center frequency over 0.8 cm -1 under complete manual control, as well as arbitrarily long, concatenated scans, and trivial interfacing to a data acquisition system. This scanning spectrometer operation is demonstrated on direct absorption of atomic bromine.

  3. Casting of Halide and Fluoride Alloys for Laser Windows

    DTIC Science & Technology

    1974-07-15

    mechanism leads to an inverse square root dependence of fracture strength on grain size. Since CaF2, SrFp and BaFp all exhibit at least microplastic ...flaws or microplasticity is the strength limiting factor is not known. 4.2.2 Solid-solution strengthening 4.2.2. 1 General If fracture in these...Temperature Microplasticity in SrF2 Single Crystals, " J. Appl. Phys. 41_(4) 1871 (1970). 12. T.S. Liu and C.H. Li, " Plasticity of Barium Fluoride

  4. Coordinated underground measurements of gamma-ray emitting radionuclides for plasma physics research.

    PubMed

    Tzika, Faidra; Hult, Mikael; Fenyvesi, András; Bandac, Iulian; Degering, Detlev; Ianni, Aldo; Laubenstein, Matthias; de Vismes-Ott, Anne; Marissens, Gerd; Stroh, Heiko; Lutter, Guillaume; Son, Soohyun; Hong, Suk-Ho; Kim, Jun Young; Kim, Junghee; Cheon, Mun Seung; Jo, Jungmin; Braun, Mihály; Németh, József; Zoletnik, Sándor; Bonheure, Georges

    2016-12-24

    Forty-eight samples made of CaF2, LiF and YVO4 were placed inside the KSTAR Tokamak and irradiated by neutrons and charged particles from eight plasma pulses. The aim was to provide information for plasma diagnostics. Due to the short pulse durations, the activities induced in the samples were low and therefore measurements were performed in five low-background underground laboratories. Details of the underground measurements, together with data on the quality control amongst the radiometric laboratories, are presented.

  5. Spatially localized measurement of thermal conductivity using a hybrid photothermal technique

    SciTech Connect

    David H Hurley; Marat Khafizov; Zilong Hua; Rory Kennedy; Heng Ban

    2012-05-01

    A photothermal technique capable of measuring thermal conductivity with micrometer lateral resolution is presented. This technique involves measuring separately the thermal diffusivity, D, and thermal effusivity, e, to extract the thermal conductivity, k=(e2/D)1/2. To generalize this approach, sensitivity analysis was conducted for materials having a range of thermal conductivities. Experimental validation was sought using two substrate materials, SiO2 and CaF2, both coated with thin titanium films. The measured conductivities compare favorably with literature values.

  6. Growth and Luminescence Spectroscopy of A CuCl Quantum Well Structure

    DTIC Science & Technology

    1988-07-01

    inti- mate Si-CuCl interface is thermodynamically unstable with respect to the formation of silicon chlorides and Cu metal. Also, CuCl is extremely...hygroscopic. Photoluminesoence analysis of bulk CuCI crystals has shown large numbers of defect states that may be related to 0-- impurities; in any case...powders C, of CuCI and CaF2 heated to 300"C for days by x-ray diffractometry, we conclude that they are thermodynamically stable with respect to each 5 1%V

  7. Dynamics recording of holographic gratings in a photochromic crystal of calcium fluoride

    NASA Astrophysics Data System (ADS)

    Borisov, Vladimir N.; Barausova, Ekaterina V.; Veniaminov, Andrey V.; Andervaks, Alexandr E.; Shcheulin, Alexandr S.; Ryskin, Alexandr I.

    2016-08-01

    Dynamics of diffraction efficiency was monitored during recording a holographic grating in additively coloured CaF2 photochromic crystal at 180-200°C. Reciprocity failure revealed in the study was attributed to diffusion playing the crucial role in grating formation: recording at larger laser power goes faster but requires more energy. The efficiency of a recorded hologram is found to depend on the temperature; maximum diffraction is measured at the temperature far below that of recording, supposedly because of dramatic distortions suffered by the crystal along with exposure.

  8. Ultra-trace analysis of (41)Ca in urine by accelerator mass spectrometry: an inter-laboratory comparison.

    PubMed

    Jackson, George S; Hillegonds, Darren J; Muzikar, Paul; Goehring, Brent

    2013-10-15

    A (41)Ca interlaboratory comparison between Lawrence Livermore National Laboratory (LLNL) and the Purdue Rare Isotope Laboratory (PRIME Lab) has been completed. Analysis of the ratios assayed by accelerator mass spectrometry (AMS) shows that there is no statistically significant difference in the ratios. Further, Bayesian analysis shows that the uncertainties reported by both facilities are correct with the possibility of a slight under-estimation by one laboratory. Finally, the chemistry procedures used by the two facilities to produce CaF2 for the cesium sputter ion source are robust and don't yield any significant differences in the final result.

  9. Low and moderate doses of caffeine late in exercise improve performance in trained cyclists.

    PubMed

    Talanian, Jason L; Spriet, Lawrence L

    2016-08-01

    The aim of the present study was to assess if low and moderate doses of caffeine delivered in a carbohydrate-electrolyte solution (CES) late in exercise improved time-trial (TT) performance. Fifteen (11 male, 4 female) cyclists (age, 22.5 ± 0.9 years; body mass, 69.3 ± 2.6 kg; peak oxygen consumption, 64.6 ± 1.9 mL·min(-1)·kg(-1)) completed 4 double-blinded randomized trials. Subjects completed 120 min of cycling at ∼60% peak oxygen consumption with 5 interspersed 120-s intervals at ∼82% peak oxygen consumption, immediately followed by 40-s intervals at 50 W. Following 80 min of cycling, subjects either ingested a 6% CES (PL), a CES with 100 mg (low dose, 1.5 ± 0.1 mg·kg body mass(-1)) of caffeine (CAF1), or a CES with 200 mg (moderate dose, 2.9 ± 0.1 mg·kg body mass(-1)) of caffeine (CAF2). Following the 120-min cycling challenge, cyclists completed a 6-kJ·kg body mass(-1) TT. There was no difference between respiratory, heart rate, glucose, free fatty acid, body mass, hematocrit, or urine specific gravity measurements between treatments. The CAF2 (26:36 ± 0:22 min:s) TT was completed faster than CAF1 (27:36 ± 0:32 min:s, p < 0.05) and both CAF1 and CAF2 TTs were completed faster than PL (28:41 ± 0:38 min:s, p < 0.05). Blood lactate was similar between trials and rose to a greater extent during the TT (p < 0.05). In summary, both doses of caffeine delivered late in exercise improved TT performance over the PL trial and the moderate dose (CAF2) improved performance to a greater extent than the low dose (CAF1).

  10. Note: Broadband cavity ring-down spectroscopy of an intra-cavity bulk sample.

    PubMed

    Zeuner, T; Paa, W; Mühlig, C; Stafast, H

    2013-03-01

    A cavity ring-down (CRD) setup equipped with a pulsed broadband light source (480 nm ≤ λ ≤ 650 nm) and a multichannel detection system (temporal gate width Δτ = 20 ns) is used to simultaneously record the optical loss spectrum of an intra-cavity CaF2 sample and its changes upon transverse ArF laser irradiation at 193 nm. The CRD setup with mirrors of high reflectivity (R > 99.93%) allows to register loss changes of 5 × 10(-5) with a spectral resolution of 0.3 nm in less than 2 min.

  11. Analysis of the electroluminescence features of silicon metal-insulator-semiconductor structures as a tool for diagnostics of the injection properties of a dielectric layer

    NASA Astrophysics Data System (ADS)

    Illarionov, Yu. Yu.; Vexler, M. I.; Isakov, D.; Fedorov, V. V.; Sing, Yew Kwang

    2013-10-01

    A technique for diagnostics of the injection properties of thin dielectric layers based on analysis of the data on silicon electroluminescence in a metal-insulator-semiconductor structure is proposed. The possibility of applying this technique to control the electron injection energy (in particular, when the barrier parameters are poorly known) is demonstrated by the example of samples with CaF2 and HfO2/SiO2. The results obtained are important for application of the insulators under study in microelectronic devices.

  12. Laser-Induced Damage of Calcium Fluoride

    SciTech Connect

    Espana, A.; Joly, A.G.; Hess, W.P.; Dickinson, J.T.

    2004-01-01

    As advances continue to be made in laser technology there is an increasing demand for materials that have high thresholds for laser-induced damage. Laser damage occurs when light is absorbed, creating defects in the crystal lattice. These defects can lead to the emission of atoms, ions and molecules from the sample. One specific field where laser damage is of serious concern is semiconductor lithography, which is beginning to use light at a wavelength of 157 nm. CaF2 is a candidate material for use in this new generation of lithography. In order to prevent unnecessary damage of optical components, it is necessary to understand the mechanisms for laser damage and the factors that serve to enhance it. In this research, we study various aspects of laser interactions with CaF2, including impurity absorbance and various forms of damage caused by incident laser light. Ultraviolet (UV) laser light at 266 nm with both femtosecond (fs) and nanosecond (ns) pulse widths is used to induce ion and neutral particle emission from cleaved samples of CaF2. The resulting mass spectra show significant differences suggesting that different mechanisms for desorption occur following excitation using the different pulse durations. Following irradiation by ns pulses at 266 nm, multiple single-photon absorption from defect states is likely responsible for ion emission whereas the fs case is driven by a multi-photon absorption process. This idea is further supported by the measurements made of the transmission and reflection of fs laser pulses at 266 nm, the results of which reveal a non-linear absorption process in effect at high incident intensities. In addition, the kinetic energy profiles of desorbed Ca and K contaminant atoms are different indicating that a different mechanism is responsible for their emission as well. Overall, these results show that purity plays a key role in the desorption of atoms from CaF2 when using ns pulses. On the other hand, once the irradiance reaches high levels, like that of the fs case, significant desorption is possible due to multi-photon absorption by the intrinsic material.

  13. Group II Cubic Fluorides as Dielectrics for III-V Compound Semiconductors

    DTIC Science & Technology

    1989-09-01

    bllItY_Code Avail and/or D is t Special * -2- A. Statement of problem investigated Under ARO contract number DAAL03-86-K-0059, we have investigated the...interfaces with a low density of interface states; 3. the vapor pressures of CaF2 or SrF 2 are very low, and their evaporation is compatible with standard...and GaAs makes these systems potential candi- dates for wave guiding and other optoelectronic applications; 6. fluorides decom- pose (loss of F) under

  14. Optical Studies of Glasses Embedded With Inorganic Ions and Organic Dyes

    DTIC Science & Technology

    1993-07-22

    the D or S levels of \\d" were resonantly excited with a 580 nm or 800 nm, ke detected upconvertcd % 1o1ct emission from the L levels in CaF2, SrF2 ...glass thus obtained is strong and then polished on all sides using three different grades of polishing powders as explained under glass polishing...multicomponent oxide glass containing heavier metallic elements as explained under glass preparation (section 5(b)). The resulting glass was found to be

  15. Casting of Halide and Fluoride Alloys for Laser Windows

    DTIC Science & Technology

    1974-10-15

    a lower temperature (900CC) or by annealing at 1000° C under a better vacuum or under a partial pressure of teflon vapor providing a purifying...castings (3 in. diameter) of SrF2 have been produced with low optical absorption coefficients pi, 5.25 jim. High qurlity CaF2 castings have been...Waltham, Massachusetts under Contract No. F19628-74-C-0148 entitled "Casting of Halide and Fluoride Alloys for Laser Windows. " This work is

  16. Laser Induced Desorption Time of Flight Mass Spectrometer Analysis of Adsorbed Contaminants on Vacuum Ultraviolet Lithography Optic Materials

    DTIC Science & Technology

    2004-02-01

    particles or an energy transfer medium absorbed under and around the particles. In the first case, the substrate absorbs the laser energy and causes rapid...when the same areas were reirradiated later. They also observed large site-to-site variation of desorbed fluence from the same sample and under the...efficiency. O. Kreitschitz et al. used TOF-MS to conduct LID of SrF2 , CaF2 and MgO2 to investigate the dependence of yield and kinetic energies of

  17. Technology for Solar Array Production on the Moon

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.

    2002-01-01

    Silicon, aluminum, and glass are the primary raw materials that will be required for production of solar arrays on the moon. A process sequence is proposed for producing these materials from lunar regolith is proposed, consisting of separating the required materials from lunar rock with fluorine. Fluorosilane produced by this process is reduced to silicon; the fluorine salts are reduced to metals by reaction with metallic potassium. Fluorine is recovered from residual MgF and CaF2 by reaction with K2O. Aluminum, calcium oxide, and magnesium oxide are recovered to manufacture structural materials and glass.

  18. Atomic force microscope studies of fullerene films - Highly stable C60 fcc (311) free surfaces

    NASA Technical Reports Server (NTRS)

    Snyder, Eric J.; Tong, William M.; Williams, R. S.; Anz, Samir J.; Anderson, Mark S.

    1991-01-01

    Atomic force microscopy and X-ray diffractometry were used to study 1500 A-thick films of pure C60 grown by sublimation in ultrahigh vacuum onto a CaF2 (111) substrte. Topographs of the films did not reveal the expected close-packed structures, but they showed instead large regions that correspond to a face-centered cubic (311) surface and distortions of this surface. The open (311) structure may have a relatively low free energy because the low packing density contributes to a high entropy of the exposed surface.

  19. Effect of Etching Condition on the Formation of Bioactive Surface of Hydroxyapatite-Glass-Titanium Composite

    NASA Astrophysics Data System (ADS)

    Ban, Seiji; Maruno, Shigeo; Hasegawa, Jiro

    1991-07-01

    X-ray diffraction study shows that an etching solution of 3% HF and 5% HNO3 is the most suitable solution for preparing a bioactive surface layer of HA-glass-titanium composite, since the glass is removed, a great number of HA particles are exposed, and little CaF2 is produced by the etching. Anodic polarization measurement demonstrates that the 3-min etching gives an electrochemically active surface of the composites. These results and SEM observations suggest that this solution provides an adequate surface of the composite for the dental and medical implants.

  20. High Temperature Superconducting Materials: Thin Films, Surfaces, and Interfaces

    DTIC Science & Technology

    1991-06-01

    High T Superconductor Surfaces with CaF2 and Bi, Al, and Si Oxides," Appl. Phys. Lett. 5fc 1657-1659 (1988). 22. T.J. Wagener, Yongjun Hu, Y. Gao, M.B...on YBa 2 Cu 3O 7 _x, Y2 BaCuO5 , and CuO," J. Appl. Phys. 67, 1995-2002 (1990). 30. T.T. Wagener, H.M. Meyer III, Yongjun Hu, M.B. Jost, J.H. Weaver