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Sample records for al ca cd

  1. White LED based on CaAl2Si2O8:Eu2+ Mn2+ phosphor and CdS/ZnS quantum dots

    NASA Astrophysics Data System (ADS)

    Shen, Changyu; Zhong, Chuan; Hou, Qianglong; Li, Ke

    2011-02-01

    Core/shell CdS/ZnS quantum dots (QDs) with the emission wavelength of 610nm, was synthesized by thermal deposition using cadmium oxide and selenium as precursors in a hot lauric acid and hexadecylamine trioctylphosphine oxide hybrid. CaAl2Si2O8:Eu2+ Mn2+ phosphor was synthesized by high-temperature solid state reaction at 1290 °C for 2 hours under the H2 reducing atmosphere, and X-ray powder diffraction analysis confirmed the formation of it. It has two emission bands peaking at 420 nm and 580nm originated from the transition 5d to 4f of Eu2+ and 4T1-6A1 of Mn2+, respectively. Blends of CaAl2Si2O8:Eu2+,Mn2+ phosphor and CdS/ZnS QDs exhibited the prominent spectral evolution with an increasing content of QDs. A hybrid white LED, which combines a blue LED with the blend of CaAl2Si2O8:Eu2+ Mn2+ phosphor and QDs with a weight ratio of 2:1, with the CIE coordinate of (0.3183, 0.3036) and CRI of 85 was obtained.

  2. New roles for icosahedral clusters in intermetallic phases: micelle-like segregation of Ca-Cd and Cu-Cd interactions in Ca10Cd27Cu2.

    PubMed

    Hadler, Amelia B; Harris, Nicholas A; Fredrickson, Daniel C

    2013-11-20

    Despite significant progress in the structural characterization of the quasicrystalline state, the chemical origins of long- and short-range icosahedral order remain mysterious and a subject of debate. In this Article, we present the crystal structure of a new complex intermetallic phase, Ca10Cd27Cu2 (mC234.24), whose geometrical features offer clues to the driving forces underlying the icosahedral clusters that occur in Bergman-type quasicrystals. Ca10Cd27Cu2 adopts a C-centered monoclinic superstructure of the 1/1 Bergman approximant structure, in which [110] layers of Bergman clusters in the 1/1 structure are separated through the insertion of additional atoms (accompanied by substantial positional disorder). An examination of the coordination environments of Ca and Cu (in the ordered regions) reveals that the structure can be viewed as a combination of coordination polyhedra present in the nearest binary phases in the Ca-Cd-Cu compositional space. A notable feature is the separation of Ca-Cd and Cu-Cd interactions, with Bergman clusters emerging as Ca-Cd Friauf polyhedra (derived from the MgZn2-type CaCd2 phase) encapsulate a Cu-Cd icosahedron similar to those appearing in Cu2Cd5. DFT chemical pressure calculations on nearby binary phases point to the importance of this segregation of Ca-Cd and Cu-Cd interactions. The mismatch in atomic size between Cu and Cd leads to an inability to satisfy Ca-Cu and Ca-Cd interactions simultaneously in the Friauf polyhedra of the nearby Laves phase CaCd2. The relegation of the Cu atoms to icosahedra prevents this frustration while nucleating the formation of Bergman clusters. PMID:24147875

  3. Comparative studies of CdS, CdS:Al, CdS:Na and CdS:(Al-Na) thin films prepared by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Yılmaz, S.; Atasoy, Y.; Tomakin, M.; Bacaksız, E.

    2015-12-01

    In the present study, the spray pyrolysis technique was used to prepare pure CdS, 4 at.% Al-doped CdS, 4 at.% Na-doped CdS and (4 at.% Al, 4 at.% Na)-co-doped CdS thin films. It was found from X-ray diffraction data that all the specimens showed hexagonal wurtzite structure with the preferred orientation of (101). Scanning electron microscopy results indicated that 4 at.% Al-doping caused a grain growth in the morphology of CdS thin films whereas the 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping led to porous structure with small grains. The band gap value of CdS thin films increased to 2.42 eV after 4 at.% Al-doping. However, it reduced to 2.30 eV and 2.08 eV for 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping, respectively. The room temperature photoluminescence measurements illustrated that the peak intensity of CdS thin films enhanced with 4 at.% Al-doping while 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping caused a decline in the intensity. The maximum carrier concentration and minimum resistivity were obtained for 4 at.% Al-doped CdS thin films, which is associated with the grain growth. Furthermore, (4 at.% Al, 4 at.% Na)-co-doping gave rise to a slight reduction in the carrier concentration and a slight increment in the resistivity. As a result, it can be said that 4 at.% Al-doped CdS thin films exhibited the best electrical and optical properties, which is important for the opto-electronic applications.

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

    NASA Technical Reports Server (NTRS)

    Bischoff, A.; Keil, K.

    1983-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

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

  6. Itinerant magnetism in CaMn2Al10

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  7. The role of Ca pathway in Cd uptake and translocation by the hyperaccumulator Sedum alfredii.

    PubMed

    Lu, Lingli; Tian, Shengke; Zhang, Min; Zhang, Jie; Yang, Xiaoe; Jiang, Hong

    2010-11-15

    Effect of Ca on plant growth, Cd uptake and translocation in the hyperaccumulator Sedum alfredii was investigated, as to reveal the possible pathway of Cd entry into the plants system. High Ca increased plant growth under Cd stress after 7 d, and significantly affected the total Cd influx and translocation rate. Short-term kinetics of (109)Cd influx performed using radiotracers confirmed a significant inhibition of (109)Cd influx into the roots induced by high Ca. Under exposure of 5.0 mM Ca, K(m) of (109)Cd influx into roots was 2-fold higher in the hyperaccumulator, although the V(max) value remained at similar level, when compared with the treatments of 0.5 mM Ca. Calcium concentrations in xylem sap of the hyperaccumulator decreased with the increasing Cd levels and significant negative correlationship between the two elements was observed. However, increased xylem loading of Cd was observed in the hyperaccumulator in response to the increasing exogenous Ca level from 0.5 to 4.0 mM, but reverse effect was observed when higher Ca levels (8-32 mM) were presented in the solutions. These results suggest that Cd uptake and translocation in the hyperaccumulator S. alfredii plants is positively associated with Ca pathway. PMID:20674155

  8. Evaluation of liquid metal embrittlement of SS304 by Cd and Cd-Al solutions

    SciTech Connect

    Thomas, J.K.; Iyer, N.C. ); Begley, J.A. )

    1992-01-01

    The susceptibility of stainless steel 304 to liquid metal embrittlement (LME) by cadmium (Cd) and cadmium-aluminum (Cd-Al) solutions was examined as part of a failure evaluation for SS304-clad cadmium reactor safety rods which had been exposed to elevated temperatures. The active, or cadmium (Cd) bearing, portion of the safety rod consists of a 0.756 in. diameter aluminum allow (Al-6061) core, a 0.05 in. thick Cd layer, and a 0.042 in. thick Type 304 stainless steel cladding. The safety rod thermal tests were conducted as part of a program to define the response of reactor core components to a hypothetical LOCA for the Savannah River Site (SRS) production reactor. LME was considered as a potential failure mechanism based on the nature of the failure and susceptibility of austenitic stainless steels to embrittlement by other liquid metals.

  9. Evaluation of liquid metal embrittlement of SS304 by Cd and Cd-Al solutions

    SciTech Connect

    Thomas, J.K.; Iyer, N.C.; Begley, J.A.

    1992-07-01

    The susceptibility of stainless steel 304 to liquid metal embrittlement (LME) by cadmium (Cd) and cadmium-aluminum (Cd-Al) solutions was examined as part of a failure evaluation for SS304-clad cadmium reactor safety rods which had been exposed to elevated temperatures. The active, or cadmium (Cd) bearing, portion of the safety rod consists of a 0.756 in. diameter aluminum allow (Al-6061) core, a 0.05 in. thick Cd layer, and a 0.042 in. thick Type 304 stainless steel cladding. The safety rod thermal tests were conducted as part of a program to define the response of reactor core components to a hypothetical LOCA for the Savannah River Site (SRS) production reactor. LME was considered as a potential failure mechanism based on the nature of the failure and susceptibility of austenitic stainless steels to embrittlement by other liquid metals.

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

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

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

  11. CD19 amplification of B lymphocyte Ca2+ responses: a role for Lyn sequestration in extinguishing negative regulation.

    PubMed

    Fujimoto, M; Poe, J C; Hasegawa, M; Tedder, T F

    2001-11-30

    B lymphocyte antigen receptor (BCR) signals are regulated by CD19, with BCR-induced intracellular calcium ([Ca(2+)](i)) responses enhanced by CD19 co-ligation. In this study, CD19 engagement using a dimeric anti-CD19 antibody induced [Ca(2+)](i) mobilization and significantly enhanced BCR-induced [Ca(2+)](i) responses without a requirement for CD19/BCR co-ligation. Although simultaneous CD19 and BCR engagement significantly enhanced CD19/Lyn complex formation and [Ca(2+)](i) responses, downstream tyrosine phosphorylation of CD22 and multiple other cellular proteins was inhibited, as was SHP1 recruitment to phosphorylated CD22. CD19 overexpression also enhanced BCR-induced [Ca(2+)](i) responses, but down-regulated tyrosine phosphorylation of CD22 and multiple other cellular proteins following BCR ligation. Because CD19 and Lyn expression are genetically titrated in B cells, CD19 engagement may augment BCR-induced [Ca(2+)](i) responses by sequestering the available pool of functional Lyn away from downstream negative regulatory proteins such as CD22. Consistent with this, simultaneous CD19 engagement did not further enhance the BCR-induced [Ca(2+)](i) responses of Lyn- or CD22-deficient B cells. Thus, CD19 recruitment of Lyn may preferentially activate selective signaling pathways downstream of the CD19/Lyn complex to the exclusion of other downstream regulatory and effector pathways. Other receptors may also utilize a similar strategy to regulate kinase availability and downstream intermolecular signaling. PMID:11584010

  12. EFFECTS OF AQUEOUS AL, CD, CU, FE(II), NI, AND ZN ON PB IMMOBILIZATION BY HYDROXYAPATITE

    EPA Science Inventory

    The effects of aqueous Al, Cd, Cu, Fe(II), Ni, or Zn on Pb immobilization by hydroxyapatite (Ca10(PO4),(OH)2) were studied. ead was removed mainly via hydroxyapatite dissolution and hydroxypyromorphite (Pb10(PO4)6(OH)2) precipitation in the presence of these metals with a Pb remo...

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

    NASA Astrophysics Data System (ADS)

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

    1984-02-01

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

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

    SciTech Connect

    Kim, Hyong June

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-03-01

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

  16. Cluster Chemistry in Electron-Poor Ae-Pt-Cd Systems (Ae=Ca, Sr, Ba): (Sr,Ba)Pt2Cd4, Ca6Pt8Cd16, and Its Known Antitype Er6Pd16Sb8

    SciTech Connect

    Samal, Saroj L.; Gulo, Fakhili; Corbett, John D.

    2013-02-18

    Three new ternary polar intermetallic compounds, cubic Ca6Pt8Cd16, and tetragonal (Sr, Ba)Pt2Cd4 have been discovered during explorations of the Ae–Pt–Cd systems. Cubic Ca6Pt8Cd16 (Fm-3m, Z = 4, a = 13.513(1) Å) contains a 3D array of separate Cd8 tetrahedral stars (TS) that are both face capped along the axes and diagonally bridged by Pt atoms to generate the 3D anionic network Cd8[Pt(1)]6/2[Pt(2)]4/8. The complementary cationic surface of the cell consists of a face-centered cube of Pt(3)@Ca6 octahedra. This structure is an ordered ternary variant of Sc11Ir4 (Sc6Ir8Sc16), a stuffed version of the close relative Na6Au7Cd16, and a network inverse of the recent Er6Sb8Pd16 (compare Ca6Pt8Cd16). The three groups of elements each occur in only one structural version. The new AePt2Cd4, Ae = Sr, Ba, are tetragonal (P42/mnm,Z = 2, a ≈ 8.30 Å, c ≈ 4.47 Å) and contain chains of edge-sharing Cd4 tetrahedra along c that are bridged by four-bonded Ba/Sr. LMTO-ASA and ICOHP calculation results and comparisons show that the major bonding (Hamilton) populations in Ca6Pt8Cd16 and Er6Sb8Pd16 come from polar Pt–Cd and Pd–Sb interactions, that Pt exhibits larger relativistic contributions than Pd, that characteristic size and orbital differences are most evident for Sb 5s, Pt8, and Pd16, and that some terms remain incomparable, Ca–Cd versus Er–Pd.

  17. LiCaAl/sub 6/:Cr/sup 3+/

    SciTech Connect

    Payne, S.A.; Chase, L.L.; Newkirk, H.W.; Smith, L.K.; Krupke, W.F. )

    1988-11-01

    The authors report the discovery of a new laser, LiCaAIF/sub 6/:Cr/sup 3/ (Cr/sup 3+/ :LiCAF). The intrinsic (extrapolated maximum) slope efficiency was found to be 67 percent. For comparison, they also measured the intrinsic slope efficiencies of BeAl/sub 2/O/sub 4/:Cr/sup 3+/ (alexandrite), Na/sub 3/Ga/sub 2/Li/sub 3/F/sub 12/:Cr/sup 3+/, and ScBO/sub 3/:Cr/sup 3+/, and obtained values of 65,28, and 26 percent, respectively. The tuning range of LiCaAIF/sub 6/:Cr/sup 3+/ was determined to be at least 720-840 nm. The conventional spectroscopic properties, such as the absorption, emission, and emission lifetimes as a function of temperature, are reported as well.

  18. Synchrotron spectroscopy of confined carriers in CdF2-CaF2 superlattices

    NASA Astrophysics Data System (ADS)

    Ivanovskikh, K. V.; Hughes-Currie, R. B.; Reid, M. F.; Wells, J.-P. R.; Sokolov, N. S.; Reeves, R. J.

    2016-03-01

    Luminescence spectroscopic and temporal dynamic properties of high energy elementary excitations in CdF2-CaF2 superlattices have been studied utilising excitation with vacuum ultraviolet and X-ray synchrotron radiation while comparing the results with those obtained for CdF2 and CaF2 bulk crystals. It is shown that the optical properties of the superlattice structures are determined by exciton emission in the CdF2 monolayers. The experimental manifestations of exciton confinement phenomena are discussed.

  19. Sodium chloride salinity reduces Cd uptake by edible amaranth (Amaranthus mangostanus L.) via competition for Ca channels.

    PubMed

    Mei, XiuQin; Li, SongSong; Li, QuSheng; Yang, YuFeng; Luo, Xuan; He, BaoYan; Li, Hui; Xu, ZhiMin

    2014-07-01

    Soil salinity is known to enhance cadmium (Cd) accumulation in crops. However, the mechanism by which this occurs independent of the surrounding soil remains unclear. In this study, root adsorption and uptake of salt cations and Cd by edible amaranth under NaCl salinity stress were investigated in hydroponic cultures with 0, 40, 80, 120, and 160mM of NaCl and 27nM Cd. The dominant Cd species in the nutrient solution changed from free Cd(2+) to Cd chlorocomplexes as NaCl salinity increased. High salinity significantly reduced K, Ca, and Cd root adsorption and K, Ca, Mg, and Cd uptake. High salinity decreased root adsorption of Cd by 43 and 58 percent and Cd uptake by 32 and 36 percent in salt-tolerant and salt-sensitive cultivars, respectively. Transformation of Cd from free ion to chlorocomplexes is unlikely to have significantly affected Cd uptake by the plant because of the very low Cd concentrations involved. Application of Ca ion channel blocker significantly reduced Na, K, Ca, Mg, and Cd uptake by the roots, while blocking K ion channels significantly reduced Na and K uptake but not Ca, Mg, and Cd uptake. These results suggest that Na was absorbed by the roots through both Ca and K ion channels, while Cd was absorbed by the roots mainly through Ca ion channels and not K ion channels. Salinity caused a greater degree of reduction in Cd adsorption and uptake in the salt-sensitive cultivar than in the salt-tolerant cultivar. Thus, competition between Na and Cd for Ca ion channels can reduce Cd uptake at very low Cd concentrations in the nutrient solution. PMID:24785711

  20. Substantial Cd-Cd Bonding in Ca6PtCd11: A Condensed Intermetallic Phase Built of Pentagonal Cd7 and Rectangular Cd4/2Pt Pyramids

    SciTech Connect

    Gulo, Fakhili; Samal, Saroj L.; Corbett, John D.

    2013-08-19

    The new trail-breaking compound Ca6PtCd11 has been synthesized and its structural and bonding properties investigated. This unusual phase features an unprecedented degree of cadmium aggregation, including linear chains, novel Cd7 PBP aggregates, and edge-shared chains of PtCd4/2 square pyramids. Manifestations of this chemistry elsewhere has evidently been precluded in earlier work by the inclusion of larger amounts of the strong d-metal bonding Au or Pt. Under the right conditions Cd seems quite effective as an open s,p-band metal.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    PubMed

    Marashdeh, Ali; Frankcombe, Terry J

    2008-06-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  5. Tululite, Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36: a new Ca zincate-aluminate from combustion metamorphic marbles, central Jordan

    NASA Astrophysics Data System (ADS)

    Khoury, Hani N.; Sokol, Ella V.; Kokh, Svetlana N.; Seryotkin, Yurii V.; Nigmatulina, Elena N.; Goryainov, Sergei V.; Belogub, Elena V.; Clark, Ian D.

    2016-02-01

    Tululite (Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36 (the hypothetical end-member formula Ca14{Fe3+O6}[SiO4][Zn5Al9]O26) (IMA2014-065) is a new natural Ca zincate-aluminate, identified in medium-temperature (800-850 °C) combustion metamorphic (CM) spurrite-fluorellestadite marbles from central Jordan. The type locality (Tulul Al Hammam area) is situated in the northern part of the Siwaqa complex, the largest area of the "Mottled Zone" Formation in the Dead Sea region. The marbles originated from bitumen-rich chalky marine sediments of the Maastrichtian-Paleogene Muwaqqar Chalk Marl Formation, which have low clay content (and, consequently, low Al) and high Zn, Cd, and U enrichments. The bulk CM rocks derived from the low-Al protolith have unusually high (Zn + Cd)/Al ratios ( 0.2) and, as a result, a mineralogy with negligibly small percentages of Ca aluminates having low Ca:Al molar ratios (minerals of mayenite supergroup, Ca:Al = 6:7) common to most of calcareous CM rocks in the Mottled Zone. Instead, the mineral assemblage of the Zn-rich marbles contains tululite, with high Ca:Al = 2.55 molar ratios and Zn substituting for a large portion of Al (Zn:Al = 1.1). Tululite occurs in thin clusters as irregular grains with indented outlines (20-100 μm in size), having typical open-work textures associated with rock-forming calcite, fluorellestadite, spurrite, and accessory Zn-rich periclase, lime-monteponite solid solutions, calcium uranates, and zincite. Marbles also bear brownmillerite, dorrite, fluormayenite, high-fluorine Ca aluminate, and lakargiite. Secondary phases are brucite, gel-like calcium silicate hydrates and calcium silicate aluminate hydrates, including Zn- and U-bearing and Cd-rich compounds, Si-bearing hydrated compounds after calcium uranates, and basic Cd chlorides. The empirical formula of the holotype tululite (a mean of 32 analyses) is (Ca13.29Cd0.75)Σ14.04(Al5.46Zn5.20Fe3+ 2.23Si0.95Mn3+ 1.01Mg0.78P0.41)Σ16.04O36. Tululite is cubic, space

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

    NASA Astrophysics Data System (ADS)

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

    1987-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  8. Synthesis, Structure and bonding Analysis of the Polar Intermetallic Phase Ca2Pt2Cd

    SciTech Connect

    Samal, Saroj L.; Corbett, John D.

    2012-08-14

    The polar intermetallic phase Ca2Pt2Cd was discovered during explorations of the Ca-Pt-Cd system. The compound was synthesized by high temperature reactions, and its structure refined by single-crystal X-ray diffraction as orthorhombic, Immm, a = 4.4514(5), b = 5.8415(6), c = 8.5976(9) Å, Z = 2. The structure formally contains infinite, planar networks of [Pt2Cd]4– along the ab plane, which can be described as tessellation of six and four-member rings of the anions, with cations stuffed between the anion layers. The infinite condensed platinum chains show a substantial long–short distortion of 0.52 Å, an appreciable difference between Ca2Pt2Cd (26 valence electrons) and the isotypic but regular Ca2Cu2Ga (29 VE). The relatively large cation proportion diminishes the usual dominance of polar (Pt–Cd) and 5d–5d (Pt–Pt) contributions to the total Hamilton populations.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    PubMed

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

    2015-11-01

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

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

    PubMed

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

    2004-04-15

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

  13. Heterogeneous microchemistry between CdSO4 and CaCO3 particles under humidity and liquid water.

    PubMed

    Falgayrac, Guillaume; Sobanska, Sophie; Brémard, Claude

    2013-03-15

    Laboratory experiments using in situ Raman imaging combined with ex situ TOF-S-SIMS demonstrate the behavior of CdSO4·8/3H2O microparticles in contact with 101¯4 CaCO3 (calcite) surface under three different experimental conditions representative of unpolluted atmosphere. The contact of CdSO4·8/3H2O particles with CaCO3 surface in humid air (RH∼40-80%) does not induce any chemical reaction. In contrast, the condensation of a water drop on CdSO4·8/3H2O/CaCO3 interface causes the free dissolution of CdSO4·8/3H2O particle in the drop. A CdSO4·8/3H2O microcrystal is reformed after gentle drying with a CdSO4·H2O coating of the CaCO3 surface. The TOF-S-SIMS image of the CaCO3 surface provides evidence of a thin layer corresponding probably to insoluble coating of CdCO3 (otavite) or CdxCa1-xCO3 solid solution at the liquid-solid interface. This layer armours the CaCO3 from further dissolution and stops the reaction. The deposition of CdSO4·8/3H2O particle in water drop previously in contact with CaCO3 for a long time generates CdCO3 small rhombohedral crystals while gentle drying provokes the crystallization of bar shape crystals of CaSO4·2H2O (gypsum). These laboratory results provide valuable chemical prediction for a possible fate of cadmium rich particles emitted in the atmosphere and thus, can contribute to realistic assessment of human exposure to Cd hazard. PMID:23416486

  14. Porous heterometallic Cd(II)-Ca(II)-terephthalate: Synthesis, structure, luminescent and gas adsorption properties

    NASA Astrophysics Data System (ADS)

    Liu, Haiping; Dong, Yanli; Ren, Hailiang

    2016-03-01

    A new heterometallic poly(dihydrate-one and a half terephthalate-cadmium calcium) coordination polymer, namely [CdCa(pdc)1.5(H2O)2]n (1, H2pdc = terephthalic acid), has been successfully obtained by the solvothermal reactions of H2pdc, Cd(NO3)2·4H2O and Ca(NO3)2·4H2O. Single crystal X-ray diffraction analysis reveals that compound 1 features a 3D porous framework based on 1D chain subunits. Moreover, compound 1 is luminescent and exhibits high adsorption capacities for H2, CH4 and CO2 at room temperature.

  15. Synthesis of Cd/(Al+Fe) layered double hydroxides and characterization of the calcination products

    SciTech Connect

    Perez, M.R.; Barriga, C.; Fernandez, J.M.; Rives, V.; Ulibarri, M.A.

    2007-12-15

    Layered double hydroxides (LDHs) containing Cd(II), Al(III), and Fe(III) in the brucite-like layers with different starting Fe/Al atomic ratios and with nitrate as counteranion have been prepared following the coprecipitation method at a constant pH value of 8. An additional Cd(II),Al(III)-LDH sample interlayered with hexacyanoferrate(III) ions has been prepared by ionic exchange at pH 9. The samples have been characterized by elemental chemical analysis, powder X-ray diffraction (PXRD), and FT-IR spectroscopy. Their thermal stability has been assessed by thermogravimetric and differential thermal analyses (TG-DTA) and mass spectrometric analysis of the evolved gases. The PXRD patterns of the solids calcined at 800 deg. C show diffraction lines corresponding to Cd(Al)O and spinel-type materials, which precise nature (CdAl{sub 2}O{sub 4}, Cd{sub 1-x}Fe{sub 2+x}O{sub 4}, or Cd{sub x}Fe{sub 2.66}O{sub 4}) depends on location and concentration of iron in the parent material or precursor. - Graphical abstract: Layered double hydroxides (LDHs) containing Cd(II), Al(III), and Fe(III) in the brucite-like layers with different starting Fe/Al atomic ratios and with nitrate as counteranion have been prepared following the coprecipitation method. An additional Cd(II),Al(III)-LDH sample interlayered with hexacyanoferrate(III) ions has been prepared by ionic exchange. Calcination at 800 deg. C shows diffraction lines corresponding to CdO and to spinel-type materials. SEM micrograph of sample CdAlFe-N-0.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

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

    2015-08-01

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

  18. Thermoelectric Properties of Mn-Doped Ca5Al2Sb6

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  19. Mechanism of Cd2+ toxicity: Cd2+ inhibits photoactivation of Photosystem II by competitive binding to the essential Ca2+ site.

    PubMed

    Faller, Peter; Kienzler, Katharina; Krieger-Liszkay, Anja

    2005-01-01

    Cadmium (Cd2+) is a well-known highly toxic element. The molecular mechanisms of the Cd2+ toxicity are not well understood. In photosynthetic organisms, toxic Cd2+ concentrations are often in the low-microM range. It has been proposed that low-microM Cd2+ concentrations affect photosynthesis at the level of Photosystem II by inhibiting oxygen evolution. However, in vitro studies on isolated, functional Photosystem II showed that much higher Cd2+ concentrations (mM range) were needed for inhibition. Here we show that Cd2+ in the low-microM range inhibited photoactivation (i.e., assembly of the water splitting complex) in Chlamydomonas reinhardtii and in isolated Photosystem II. Photoactivation is the last step in the assembly of Photosystem II before it becomes functional. The exact Cd2+ concentration necessary for inhibition depended on the concentration of calcium. It is proposed that Cd2+ binds competitively to the essential Ca2+ site in Photosystem II during photoactivation. The low Cd2+ concentration needed to inhibit photoactivation suggests that this event is also involved in the Cd2+-induced inhibition of photosynthesis in vivo. This mechanism is likely to be important for Cd2+ toxicity towards photosynthetic organisms in general, at least in unicellular like C. reinhardtii where Cd2+ has easy access to the photosynthetic apparatus. PMID:15620376

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

    SciTech Connect

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

    2013-02-07

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

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

    PubMed

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

    2011-12-16

    We present the design and synthesis of Ca-rich Ca-Al-O oxides, with Ca(2+)/Al(3+) ratios of 1:1, 3:1, 5:1, and 7:1, which were prepared by hydrothermal decomposition of coprecipitated hydrotalcite-like Ca-Al-CO(3) precursors, for high-temperature CO(2) adsorption at 500-700 °C. In situ X-ray diffraction measurements indicate that the coprecipitated, Ca-rich, hydrotalcite-like powders with Ca(2+)/Al(3+) ratios of 5:1 and 7:1 contained Ca(OH)(2) and layered double hydroxide (LDH) phases. Upon annealing, LDH was first destroyed at approximately 200 °C to form an amorphous matrix, and then at 450-550 °C, the Ca(OH)(2) phase was converted into a CaO matrix with incorporated Al(3+) to form a homogeneous solid solution without a disrupted lattice structure. CaO nanocrystals were grown by thermal treatment of the weakly crystalline Ca-Al-O oxide matrix. Thermogravimetric analysis indicates that a CO(2) adsorption capacity of approximately 51 wt. % can be obtained from Ca-rich Ca-Al-O oxides prepared by calcination of 7:1 Ca-Al-CO(3) LDH phases at 600-700 °C. Furthermore, a relatively high CO(2) capture capability can be achieved, even with gas flows containing very low CO(2) concentrations (CO(2)/N(2) = 10 %). Approximately 95.6 % of the initial CO(2) adsorption capacity of the adsorbent is retained after 30 cycles of carbonation-calcination. TEM analysis indicates that carbonation-promoted CaCO(3) formation in the Ca-Al-O oxide matrix at 600 °C, but a subsequent desorption in N(2) at 700 °C, caused the formation CaO nanocrystals of approximately 10 nm. The CaO nanocrystals are widely distributed in the weakly crystalline Ca-Al-O oxide matrix and are present during the carbonation-calcination cycles. This demonstrates that Ca-Al-O sorbents that developed through the synthesis and calcination of Ca-rich Ca-Al LDH phases are suitable for long-term cyclic operation in severe temperature environments. PMID:22072595

  2. Optically stimulated luminescence in K2SO4:AEu (A=Ca,Na,Al)

    NASA Astrophysics Data System (ADS)

    More, Y. K.; Patil, R. R.; Wankhede, S. P.; Kulkarni, M. S.; Kumar, Munish; Bhatt, B. C.; Moharil, S. V.

    2015-08-01

    Optically stimulated luminescence in doped K2SO4 is reported. K2SO4 was prepared by simple melt quenched process using readymade potassium sulphate. Samples were doped with Eu and AEu (A=Ca, Na and Al). Out of these samples K2SO4:Eu and K2SO4:Ca,Eu shows good OSL response to 470 nm optical stimulation. K2SO4:Eu and K2SO4:Ca,Eu have the sensitivities comparable with that of commercial phosphor Al2O3:C (Landauer).

  3. Cadmium Stabilization Efficiency and Leachability by CdAl4O7 Monoclinic Structure.

    PubMed

    Su, Minhua; Liao, Changzhong; Chuang, Kui-Hao; Wey, Ming-Yen; Shih, Kaimin

    2015-12-15

    This study investigated the stabilization efficiencies of using an aluminum-rich precursor to incorporate simulated cadmium-bearing waste sludge and evaluated the leaching performance of the product phase. Cadmium oxide and γ-alumina mixtures with various Cd/Al molar ratios were fired at 800-1000 °C for 3 h. Cadmium could be crystallochemically incorporated by γ-alumina into CdAl4O7 monoclinic phase and the reaction was strongly controlled by the treatment temperature. The crystal structure details of CdAl4O7 were solved and refined with the Rietveld refinement method. According to the structural refinement results, the stabilization efficiencies were quantified and expressed as a transformation ratio (TR) with optimized processing parameters. The preferred treatment temperature was found to be 950 °C for mixtures with a Cd/Al molar ratio of 1/4, as its TR value indicated the cadmium incorporation was nearly completed after a 3 h treatment scheme. Constant-pH leaching tests (CPLT) were conducted by comparing the leachability of the CdO and CdAl4O7 phases in a pH 4.0 environment. A remarkable reduction in cadmium leachability could be achieved via monoclinic CdAl4O7 structure formation to effectively stabilize hazardous cadmium in the waste stream. The CPLT and X-ray photoelectron spectroscopy (XPS) results suggested incongruent dissolution behavior during the leaching of the CdAl4O7 phase. PMID:26512873

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Xu, Guang; Jiang, Zhouhua; Li, Yang

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Xu, Guang; Jiang, Zhouhua; Li, Yang

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Homes, Christopher

    2002-03-01

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

  8. Ca2+ signaling in taste bud cells and spontaneous preference for fat: unresolved roles of CD36 and GPR120.

    PubMed

    Abdoul-Azize, Souleymane; Selvakumar, Subramaniam; Sadou, Hassimi; Besnard, Philippe; Khan, Naim Akhtar

    2014-01-01

    Recent compelling evidences from rodent and human studies raise the possibility for an additional sixth taste modality devoted to oro-gustatory perception of dietary lipids. Understanding the mechanisms underlying oro-gustatory detection of dietary fat is critical for the prevention and treatment of obesity. A number of studies have suggested that lingual CD36, a glycoprotein, highly expressed by circumvallate papillae of the tongue, is implicated in the perception of dietary fat taste. G protein-coupled receptors (GPCRs) are important signaling molecules for many aspects of cellular functions. It has been shown that these receptors, particularly GPR120, are also involved in lipid taste perception. We have shown that dietary long-chain fatty acids (LCFAs), in CD36-positive taste bud cells (TBC), induce increases in free intracellular Ca(2+) concentrations, [Ca(2+)]i, by recruiting Ca(2+) from endoplasmic reticulum (ER) pool via inositol 1,4,5-triphosphate production, followed by Ca(2+) influx via opening of store-operated Ca(2+) (SOC) channels. GPR120 is also coupled to increases in [Ca(2+)]i by dietary fatty acids. We observed that stromal interaction molecule 1 (STIM1), a sensor of Ca(2+) depletion in the ER, mediated fatty acid-induced Ca(2+) signaling and spontaneous preference for fat in the mouse. In this review article, we discuss the recent advances and unresolved roles of CD36 and GPR120 in lipid taste signaling in taste bud cells. PMID:23774298

  9. Influence of pH and TOC concentration on Cu, Zn, Cd, and Al speciation in rivers.

    PubMed

    Gundersen, Pål; Steinnes, Eiliv

    2003-01-01

    Dissolved ( < approximately 4 nm, dialysis in situ), colloidal ( < 0.45 microm filtered, minus dissolved) and particulate (total, minus < 0.45 microm filtered) concentrations of Cu, Zn, Cd, (Al) in eight (three) mining polluted rivers were determined by atomic absorption spectrometry (flame and graphite furnace). The metal size distribution in the rivers was compared to pH, Ca concentration, alkalinity, conductivity, and total organic carbon (TOC). Data plots based on the present and other studies also yielded information about the interrelations between TOC, pH and metal adsorption in rivers and lakes. Less than 10% of Cu, Zn, and Cd were sorbed on particles or colloids in two rivers with average pH at 3.1 and 5.1, whereas 46%, 21%, and 21% of Cu, Zn, and Cd, respectively, occurred in sorbed form in six pH neutral rivers. In three pH neutral rivers, on average 55% of Al was in colloidal form, whereas the dissolved and particulate fractions were 21% and 23%, respectively. Our data combined with data from similar studies support conclusions from other research suggesting that the percent fraction of metals adsorbed on particles rises steeply from almost zero to nearly 100% within a narrow and element specific pH range. Changes in TOC concentration seem capable of shifting the pH to % metal absorption curves in the order of one pH unit. PMID:12502060

  10. Comparative Studies on Temperature Dependent I-V Characteristics of Al/(p)CdTe and Ni/(n)CdS Schottky Junctions and Their PV Effect

    SciTech Connect

    Wary, G.; Kachari, T.; Rahman, A.

    2010-06-29

    Temperature dependent I-V characteristics of vacuum evaporated Al/(p)CdTe and Ni/(n)CdS Schottky junctions and their photovoltaic effects have been studied and compared. Different junction parameters such as ideality factors, barrier heights, Richardson's constant, short-circuit current density, fill factor, PV efficiency etc. were determined from their I-V characteristics. These parameters were found to change significantly on variation of temperature. The structures showed the change of PV effect. Efficiency found were 2.84% for Al/(p)CdTe and 4.44% for Ni hydro/(n)CdS. Polycrystalline nature, and continuous and ordered structure with bigger grain sizes of the CdS film shows more PV conversion efficiency in making Ni/(n)CdS junction as compare to Al/(p)CdTe junction. However these values were found to vary with doping concentration, and in hydrogen treated samples in both cases.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  12. Temperature dependent performance of Al/ZnCdS Schottky diode and charge transport analysis

    NASA Astrophysics Data System (ADS)

    Das, Mrinmay; Datta, Joydeep; Dey, Arka; Jana, Rajkumar; Ray, Partha Pratim

    2016-05-01

    Here we report the temperature dependent behaviour of Al/ZnCdS interface. In this regard, ZnCdS nanocomposite was synthesized by hydrothermal technique. Detailed study of schottky parameters including rectification ratio, ideality factor, series resistance and barrier height was performed. We explored the underlying charge transport phenomena through the Metal-semiconductor (MS) interface with the help of space charge limited current(SCLC) theory. A compartive analysis of carrier mobility and diffusion length was done.

  13. Human gallbladder carcinoma: Role of neurotrophins, MIB-1, CD34 and CA15-3.

    PubMed

    Artico, M; Bronzetti, E; Alicino, V; Ionta, B; Bosco, S; Grande, C; Bruno, M; Tranquilli Leali, F M; Ionta, G; Fumagalli, L

    2010-01-01

    Gallbladder carcinoma is the most common biliary tract tumor and the fifth most common gastrointestinal tract cancer .The prognosis of gallbladder carcinoma is poor and less than 5% of the patients are still alive five years postoperatively. Gallbladder specimens were obtained during surgical operations performed in eleven patients for resection of a gallbladder carcinoma, and during five autopsies (control cases selected among patients who died from for other causes, excluding those suffering from biliary or hepatic diseases). Immunohistochemical characterization and distribution of neurotrophins, with their respective receptors, were analyzed. The actual role played by these neurotrophic factors in the general regulation, vascular permeability, algic responsiveness, release of locally active substances and potential tumorigenesis in the gallbladder and biliary ducts compartment remains controversial. Our study revealed an increased immunohistochemical expression of NGF and TrKA in the epithelium and in the epithelial glands of the gallbladder carcinoma together with an evident immunoreactivity for BDNF in the same neoplastic areas. An evident immunoreactivity for NGF, TrKA and BDNF was observed in control specimens of gallbladder obtained during autopsies, whereas a weak or quite absent immunoreactivity was observed in the same specimens for NT4, TrKC and p75. On the contrary an appreciable immunoreactivity for p75 was observed in the specimens harvested from patients with gallbladder carcinoma. We also investigated the expression of some known tumor markers such as MIB-1 (anti Ki-67), CD34 and CA15-3, to identify a possible correlation between the expression of these molecular factors and the prognosis of gallbladder carcinoma. They resulted highly expressed in the stroma (CD34 and CA 15-3) and in the epithelium/epithelial glands (MIB-1) of the neoplastic areas and appeared to be almost absent in the control cases, suggesting that these markers, taken together

  14. Human gallbladder carcinoma: Role of neurotrophins, MIB-1, CD34 and CA15-3

    PubMed Central

    Artico, M.; Bronzetti, E.; Alicino, V.; Ionta, B.; Bosco, S.; Grande, C.; Bruno, M.; Tranquilli Leali, F. M.; Ionta, G.; Fumagalli, L.

    2010-01-01

    Gallbladder carcinoma is the most common biliary tract tumor and the fifth most common gastrointestinal tract cancer. The prognosis of gallbladder carcinoma is poor and less than 5% of the patients are still alive five years postoperatively. Gallbladder specimens were obtained during surgical operations performed in eleven patients for resection of a gallbladder carcinoma, and during five autopsies (control cases selected among patients who died from for other causes, excluding those suffering from biliary or hepatic diseases). Immunohistochemical characterization and distribution of neurotrophins, with their respective receptors, were analyzed. The actual role played by these neurotrophic factors in the general regulation, vascular permeability, algic responsiveness, release of locally active substances and potential tumorigenesis in the gallbladder and biliary ducts compartment remains controversial. Our study revealed an increased immunohistochemical expression of NGF and TrKA in the epithelium and in the epithelial glands of the gallbladder carcinoma together with an evident immunoreactivity for BDNF in the same neoplastic areas. An evident immunoreactivity for NGF, TrKA and BDNF was observed in control specimens of gallbladder obtained during autopsies, whereas a weak or quite absent immunoreactivity was observed in the same specimens for NT4, TrKC and p75. On the contrary an appreciable immunoreactivity for p75 was observed in the specimens harvested from patients with gallbladder carcinoma. We also investigated the expression of some known tumor markers such as MIB-1 (anti Ki-67), CD34 and CA15-3, to identify a possible correlation between the expression of these molecular factors and the prognosis of gallbladder carcinoma. They resulted highly expressed in the stroma (CD34 and CA 15-3) and in the epithelium/epithelial glands (MIB-1) of the neoplastic areas and appeared to be almost absent in the control cases, suggesting that these markers, taken together

  15. Influence of Al doping on optical properties of CdS/PVA nanocomposites: Theory and experiment

    SciTech Connect

    Bala, Vaneeta Tripathi, S. K. Kumar, Ranjan

    2014-04-24

    In the present work theoretical and experimental studies of aluminium doped cadmium sulphide polyvinyl alcohol (Al:CdS/PVA) nanocomposites have been carried out. Tetrahedral cluster AlCd{sub 9}S{sub 2}(SH){sub 18}]{sup 1−} has been encapsulated by small segments of polyvinyl alcohol (PVA) chains in order to simulate experimental environment of nanocomposites. Density functional theory (DFT) using local density approximation (LDA) functionals is employed to study the broadening of band gap upon ligation of nanoclusters. We have used in situ chemical route to synthesize nanocomposites. Optical band gap has been calculated from both experimental and theoretical approach.

  16. Photoluminescence Properties of CaAlBO4:M (M: Pb2+, Dy3+, and Sm3+)

    NASA Astrophysics Data System (ADS)

    Erdoğmuş, E.; Pekgözlü, İ.

    2014-07-01

    Pb2+, Dy3+, and Sm3+ doped CaAlBO4 materials were synthesized by the conventional solid state reaction. The synthesized phosphors were characterized by X-Ray powder diffraction. The emission and excitation spectra of these phosphors were measured at room temperature. The emission band of CaAlBO4:Pb2+ appeared as a broad band at 339 nm upon excitation with 272 nm. The second phosphor, CaAlBO4: Dy3+, emits at 477, 570, and 670 nm upon 347 nm excitation. The third phosphor, CaAlBO4:Sm3+, emits at 563, 594, 643, and 705 nm upon 236 nm excitation.

  17. Morphology Control for Al2O3 Inclusion Without Ca Treatment in High-Aluminum Steel

    NASA Astrophysics Data System (ADS)

    He, Shengping; Chen, Gujun; Guo, Yintao; Shen, Boyi; Wang, Qian

    2015-04-01

    Nozzle blockage is a major problem during continuous casting of Al-containing steel. Herein, we analyzed the thermodynamic equilibrium behavior between aluminum and oxygen in steel at 1873 K (1600 °C) and demonstrated that, the dissolved [O] initially decreases with increasing the dissolved [Al] until approximately 0.1 wt pct [Al], and after that, the dissolved [O] increases with dissolved [Al]. Thus, for high-aluminum steel with 1.0 wt pct dissolved [Al], the precipitation of Al2O3 inclusion can be avoided during cooling from deoxidation temperature to the liquidus temperature, if the actual dissolved [O] can be kept from increasing when the dissolved [Al] further increases from 0.1 to 1.0 wt pct. Hence, a method of inclusion control for high-aluminum steel without traditional Ca treatment technology was proposed based on the thermodynamic analysis. Industrial tests confirmed that low-melting point Ca-aluminate inclusions were observed typically through a slag washing with SiO2-minimized high-basicity slag during tapping, accompanied by two-step Al-adding process for production of high-aluminum steel. Moreover, there was no nozzle clogging occurred for five heats of continuous casting.

  18. Study of two tungstates Ca0.5 Cd0.5 WO4 and Ca0.2 Cd0.8 WO4 by transmission electron microscopy.

    PubMed

    Taoufyq, A; Patout, L; Guinneton, F; Benlhachemi, A; Bakiz, B; Villain, S; Lyoussi, A; Nolibe, G; Gavarri, J-R

    2015-01-01

    To better understand the role of crystal structures and local disorder in the photonic properties of the system (1 - x)CaWO4  - xCdWO4 with 0 < x < 1, two specific phases with compositions x = 0.5 (scheelite phase) and 0.8 (wolframite phase) have been studied by scanning and transmission electron microscopies. High-resolution electron microscopy images and image simulations, associated with X-ray diffraction data, allowed confirming the lattices and space groups I41 /a and P2/c of the two scheelite and wolframite phases, at the local scale. The electron microscopy data show the existence of a high degree of crystallization associated with statistical distribution of Ca or Cd atoms on a Ca1- x Cdx site in each lattice. PMID:26372831

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

    PubMed

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

    2015-09-01

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

  20. Pre-Accretionary Distribution of Ca and Al Between Matrix and Chondrules in CV Chondrites

    NASA Astrophysics Data System (ADS)

    Hezel, D. C.; Palme, H.

    2007-03-01

    Ca/Al-ratios in Y-86751 (CV) chondrules are super- and in matrix sub-chondritic. The opposite is true for Allende and Efremovka. Incorporation of spinel in Allende and Efremovka chondrule precursors in a nebular setting can explain this observation.

  1. The first observation of SRS in a trigonal LiCaAlF{sub 6} crystal

    SciTech Connect

    Kaminskii, Alexandr A; Eichler, H J; Gad, G M; Ueda, Ken-ichi; Reiche, P

    2000-12-31

    The Raman parametric generation is excited for the first time in a trigonal LiCaAlF{sub 6} fluoride crystal pumped by picosecond pulses. The energy of the {chi}{sup (3)}-active vibrational mode is determined and all Stokes and anti-Stokes components of SRS are detected for this crystal in the visible region. (letters)

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

    NASA Astrophysics Data System (ADS)

    Xu, Jianfei; Huang, Fuxiang; Wang, Xinhua

    2016-04-01

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

  3. mRNA Electroporation of Dendritic Cells with WT1, Survivin, and TriMix (a Mixture of caTLR4, CD40L, and CD70).

    PubMed

    Coosemans, An; Tuyaerts, Sandra; Morias, Kim; Corthals, Jurgen; Heirman, Carlo; Thielemans, Kris; Van Gool, Stefaan W; Vergote, Ignace; Amant, Frédéric

    2016-01-01

    The immune system is a crucial player in the development of cancer. Once it is in imbalance and immunosuppressive mechanisms supporting tumor growth take over control, dendritic cell immunotherapy might offer a solution to restore the balance. There are several methods to manufacture dendritic cells but none of them has yet proven to be superior to others. In this chapter, we discuss the methodology using electroporation of mRNA encoding Wilms' tumor gene 1, survivin, and TriMix (mixture of caTLR4, CD40L, and CD70) to simultaneously load and mature dendritic cells. PMID:27236806

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1993-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Anawati, Asoh, Hidetaka; Ono, Sachiko

    2016-04-01

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

  7. Directionally solidified Eu doped CaF2/Li3AlF6 eutectic scintillator for neutron detection

    NASA Astrophysics Data System (ADS)

    Kamada, Kei; Hishinuma, Kousuke; Kurosawa, Shunsuke; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

    2015-12-01

    Eu doped CaF2/Li3AlF6 eutectics were grown by μ-PD method. The directionally solidified eutectic with well-aligned 600 nm diameter Eu:CaF2 scintillator fibers surrounded with Li3AlF6 was prepared. The grown eutectics showed an emission peak at 422 nm ascribed to Eu2+ 4f-5d transition from Eu:CaF2 scintillation fiber. Li concentration in the Eu:CaF2-Li3AlF6 eutectic is around 0.038 mol/cm3,which is two times higher than that of LiCaAlF6 single crystal (0.016 mol/cm3). The light yield of Eu:CaF2-Li3AlF6 eutectic was around 7000 ph/neutron. The decay time was about 550 ns (89%) and 1450 ns (11%).

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

    NASA Astrophysics Data System (ADS)

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

    1980-10-01

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

  9. Synthesis and performance of Ca-α/β-SiAlON composites from tailings

    NASA Astrophysics Data System (ADS)

    Hao, Hong-shun; Yang, Yang; Lian, Fang; Gao, Wen-yuan; Liu, Gui-shan; Hu, Zhi-qiang

    2014-05-01

    Ca-α/β-SiAlON composites were prepared using Ca-α/β-SiAlON powder synthesized from gold ore tailings, which contained abundant Si and Al elements as the major raw materials together with minor additives, through a pressure-less sintering method. The influences of sintering temperature on the phase composition and microstructure of the composites were analyzed. The scanning electron microscopy images of the composites show the interlacing of grains with elongated columnar, short columnar and plate-like morphologies. The composites sintered at 1520°C for 6 h have a flexural strength of 352 MPa, Vickers hardness of 11.2 GPa, and fracture toughness of 4.8 MPa·m1/2. The relative content of each phase in the products is I(Ca-α-SiAlON): I(β-SiAlON): I(Fe3Si) = 23:74:3, where I i stands for the diffraction peak intensity of phase i.

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

    NASA Astrophysics Data System (ADS)

    Bereznitsky, Matvey; Mogilyanski, Dmitry; Jacob, Isaac

    2016-04-01

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

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

    DOEpatents

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

    1996-05-14

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

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

    DOEpatents

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

    1996-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

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

  14. The Al-Rich Part of the System CaO-Al 2O 3-MgO . Part I. Phase Relationships

    NASA Astrophysics Data System (ADS)

    Göbbels, M.; Woermann, E.; Jung, J.

    1995-12-01

    In the Al-rich part of the ternary system CaO-Al 2O 3MgO two new ternary phases Ca 2Mg 2Al 28O 46 (CAM-I) and CaMg 2Al 16O 27 (CAM-II) with limited solid solution ranges were found. Due to the fact that the compositions of the Mg-rich end members of these solid solutions lie on the join between hibonite (CaAl 12O 19) and spinel (MgAl 2O 4), the model of the crystal structures of these phases can be constructed by a suitable combination of hibonite and spinel units. Both phases, CAM-I and CAM-II, exhibit solid solution ranges described by a substitution mechanism also found in the binary spinel phase, MgAl 2O 4: 3 Mg 2+ = 2 Al 3+ + □. Thus the ternary phases can be expressed by the chemical formulas. Ca 2Mg 2-3 xAl 28+2 x□ xO 46 for CAM-I with 0 ≤ x ≤ 0.30 and CaMg 2-3 yAl 16+2 y□ yO 27 for CAM-II with 0 ≤ y ≤ 0.2.

  15. Experiments TGV I (double-beta decay of 48Ca) and TGV II (double-beta decay of 106Cd and 48Ca)

    NASA Astrophysics Data System (ADS)

    Štekl, I.; Čermák, P.; Beneš, P.; Brudanin, V. B.; Rukhadze, N. I.; Egorov, V. G.; Kovalenko, V. E.; Kovalík, A.; Salamatin, A. V.; Tsoupko-Sitnikov, V. V.; Vylov, Ts.; Briancon, Ch.; Šimkovic, F.

    2000-04-01

    Present status of experiments TGV I and TGV II is given. The TGV I collaboration has studied the double-beta decay of 48Ca with a low-background and high sensitivity Ge multi-detector spectrometer TGV (Telescope Germanium Vertical). The preliminary results of years and years (90% CL) for double-beta decay of 48 Ca has been found after the processing of experimental data obtained after 8700 hours of measuring time using approximately 1 gramme of 48Ca. The aim of the experiment TGV II is the development of the experimental methods, construction of spectrometers and measurement of the decay (++, β+/EC, EC/EC) of 106Cd particularly the 2νEC/EC mode. The theoretical description and performance of the TGV II spectrometer are also given.

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

    SciTech Connect

    Sawada, Haruo; Marumo, Fumiyuki; Kodama, Nobuhiro

    1998-08-01

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

  17. Development of aluminum (Al5083)-clad ternary Ag In Cd alloy for JSNS decoupled moderator

    NASA Astrophysics Data System (ADS)

    Teshigawara, M.; Harada, M.; Saito, S.; Oikawa, K.; Maekawa, F.; Futakawa, M.; Kikuchi, K.; Kato, T.; Ikeda, Y.; Naoe, T.; Koyama, T.; Ooi, T.; Zherebtsov, S.; Kawai, M.; Kurishita, H.; Konashi, K.

    2006-09-01

    To develop Ag (silver)-In (indium)-Cd (cadmium) alloy decoupler, a method is needed to bond the decoupler between Al alloy (Al5083) and the ternary Ag-In-Cd alloy. We found that a better HIP condition was temperature, pressure and holding time at 803 K, 100 MPa and 10 min. for small test pieces ( ϕ22 mm in dia. × 6 mm in height). Hardened layer due to the formation of AlAg 2 was found in the bonding layer, however, the rupture strength of the bonding layer is more than 30 MPa, the calculated design stress. Bonding tests of a large size piece (200 × 200 × 30 mm 3), which simulated the real scale, were also performed according to the results of small size tests. The result also gave good bonding and enough required-mechanical-strength.

  18. Thermal stability of atomic layer deposition Al2O3 film on HgCdTe

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Sun, C. H.; Zhang, Y.; Chen, X.; He, K.; Chen, Y. Y.; Ye, Z. H.

    2015-06-01

    Thermal stability of Atomic Layer Deposition Al2O3 film on HgCdTe was investigated by Al2O3 film post-deposition annealing treatment and Metal-Insulator-Semiconductor device low-temperature baking treatment. The effectiveness of Al2O3 film was evaluated by measuring the minority carrier lifetime and capacitance versus voltage characteristics. After annealing treatment, the minority carrier lifetime of the HgCdTe sample presented a slight decrease. Furthermore, the fixed charge density and the slow charge density decreased significantly in the annealed MIS device. After baking treatment, the fixed charge density and the slow charge density of the unannealed and annealed MIS devices decreased and increased, respectively.

  19. Evidence from Cd/Ca ratios in foraminifera for greater upwelling off California 4,000 years ago

    USGS Publications Warehouse

    VanGeen, A.; Luoma, N.; Fuller, C.C.; Anima, R.; Clifton, H.E.; Trumbore, S.

    1992-01-01

    UPWELLING of nutrient-rich Pacific deep water along the North American west coast is ultimately driven by the temperature difference between air masses over land and over the ocean. The intensity of upwelling, and biological production in the region, could therefore be affected by anthropogenic climate change. Examination of the geological record is one way to study the link between climate and upwelling. Because Pacific deep water is enriched in cadmium, dissolved cadmium concentrations in coastal water off central California reflect the intensity of upwelling. By demonstrating that the Cd/Ca ratio in the shell of a benthic foraminifer, Elphidiella hannai, is proportional to the Cd concentration in coastal water, we show here that foraminiferal Cd/Ca ratios can be used to detect past changes in mean upwelling intensity. Examination of a sediment core from the mouth of San Francisco Bay reveals that foraminiferal Cd/Ca decreased by about 30% from 4,000 years ago to the present, probably because of a reduction in coastal upwelling. This observation is consistent with predictions of atmospheric general circulation models that northwesterly winds, which drive upwelling, became weaker over this period as summer insolation of the Northern Hemisphere decreased.

  20. Biaxially oriented CdTe films on glass substrate through nanostructured Ge/CaF2 buffer layers

    NASA Astrophysics Data System (ADS)

    Lord, R. J.; Su, P.-Y.; Bhat, I.; Zhang, S. B.; Lu, T.-M.; Wang, G.-C.

    2015-09-01

    Heteroepitaxial CdTe films were grown by metal organic chemical vapor deposition on glass substrates through nanostructured Ge/CaF2 buffer layers which were biaxially oriented. It allows us to explore the structural properties of multilayer biaxial semiconductor films which possess small angle grain boundaries and to test the principle of a solar cell made of such low-cost, low-growth-temperature semiconductor films. Through the x-ray diffraction and x-ray pole figure analysis, the heteroepitaxial relationships of the mutilayered films are determined as [111] in the out-of-plane direction and <1\\bar{1}0>CdTe//<1\\bar{1}0>Ge//{< \\bar{1}10> }{{{CaF}}2} in the in-plane direction. The I-V curves measured from an ITO/CdS/CdTe/Ge/CaF2/glass solar cell test structure shows a power conversion efficiency of ˜η = 1.26%, illustrating the initial success of such an approach. The observed non-ideal efficiency is believed to be due to a low shunt resistance and high series resistance as well as some residual large-angle grain boundary effects, leaving room for significant further improvement.

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

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1981-01-01

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

  2. Advanced treatment of stabilized landfill leachate after biochemical process with hydrocalumite chloride (Ca/Al-Cl LDH).

    PubMed

    Chen, Hua; Sun, Ying; Ruan, Xiuxiu; Yu, Ying; Zhu, Minying; Zhang, Jia; Zhou, Jizhi; Xu, Yunfeng; Liu, Jianyong; Qian, Guangren

    2016-06-01

    This study investigated the effectiveness of Ca/Al-Cl LDH for the treatment of stabilized landfill leachate. Experiments were performed including different dosage of Ca/Al-Cl LDH and comparison with different reagents, such as CaCl2 and AlCl3. As a result, Ca/Al-Cl LDH efficiently removed organic matters in stabilized landfill leachate with the maximum removal (59.41% COD, 62.06% DOC and 70.56% UV254) at the dose of 30g/L. According to UV254 and EEM, it is remarkable that the formation of Ca/Al-LDH has a greater beneficial to organic removal than other reagents, especially for fulvic acid-like and humic acid-like compounds. Moreover, the removal of fulvic acid-like compounds was much better than humic acid-like compounds. The previous compounds had more carboxylic groups, thus had a better removal selectivity. PMID:26920626

  3. Magnetic behaviour of the MTbF6 fluoroterbates (M=Cd, Ca, Sr, (α/β)-Ba)

    NASA Astrophysics Data System (ADS)

    Josse, M.; El-Ghozzi, M.; Avignant, D.; André, G.; Bourée, F.; Isnard, O.

    2012-01-01

    Neutron powder diffraction has been performed on the MTbF6 fluorides (M=Cd, Ca, Sr, (α/β)-Ba). Four of these fluorides (Cd, Ca, Sr, β-Ba) are built of a (pseudo-) tetragonal packing of [TbF6]2- chains and only differs by the chains relative orientations. Thus this series represents a valuable opportunity to evaluate the Tb4+-Tb4+ magnetic interactions. All the compounds displayed antiferromagnetic order (TN=2.70 K (Cd), 2.15 K (Ca), 2.60 K (Sr), 2.10 K (β-Ba)), except for the α form of BaTbF6. The crystal structure of this latter fluoroterbate has also been investigated by means of high-resolution neutron powder diffraction. From Neutron Powder Diffraction data, CdTbF6 and β-BaTbF6 magnetic structures were determined, together with the metamagnetic behaviour of β-BaTbF6 as a function of an external magnetic field. A tentative phase diagram is then given for β-BaTbF6. Advantage was taken of the polymorphism of the BaTbF6 fluoroterbate to analyse, on the basis of topological parameters such as bond distances and angles, the magnetic behaviour of its α and β forms. It was shown that superexchange interactions are present in β-BaTbF6, and that these interactions may also rule the magnetic behaviour of the other MTbF6 (M=Ca, Sr, Cd) tetravalent terbium fluorides.

  4. Observations of the minor species Al, Fe and Ca+ in Mercury's exosphere

    NASA Astrophysics Data System (ADS)

    Killen, R. M.; Bida, T. A.

    2015-12-01

    We report here on the first observational evidence of Al and Fe in the exosphere of Mercury, based on measurements of 4-5-σ resolved emission lines of these metals made with Keck-1/HIRES. AlI emission was observed on two separate runs, in 2008 and 2013, with tangent column densities of 2.4 and 3.0e+07 Al atoms cm-2 at altitudes of 1300 and 1850 km (1.1 and 1.5 RM), respectively. FeI emission has been observed once, yielding a tangent column of 6.2e+08 cm-2 at an altitude of 950 km (1.4 RM) in 2009. We also present observations of 3.5-σ CaII emission features near Mercury's equatorial anti-solar limb in 2011, from which a stringent column abundance upper limit of 4.0e+06 cm-2 is derived for the Ca ion. A simple model for zenith column abundances of the neutral species yields 2.0e+07 Al cm-2, and 8.2e+08 Fe cm-2. The observations appear to be consistent with production of these species by impact vaporization, with a large fraction of the Al ejecta in molecular form, and that for Fe in mixed atomic and molecular forms. The scale height of the Al gas is consistent with a kinetic temperature of 4800-8200 K while that of Fe is 5000-13000 K. The apparent high temperature and low density of the Al gas would suggest that it may be produced by dissociation of molecules. A large fraction of both Al and Fe appear to condense in a vapor cloud at low altitudes.

  5. Observations of the minor species Al, Fe and Ca+ in Mercury’s exosphere

    NASA Astrophysics Data System (ADS)

    Killen, Rosemary M.; Bida, Thomas A.

    2015-11-01

    We report here on the first observational evidence of Al and Fe in the exosphere of Mercury, based on measurements of 4-5-σ resolved emission lines of these metals with Keck-1/HIRES. AlI emission was observed on two separate runs, in 2008 and 2013, with tangent column densities of 2.4 and 3 x 107 Al atoms cm-2 at altitudes of 1300 and 1850 km (1.1 and 1.5 RM), respectively. FeI emission has been observed once, yielding a tangent column of 6.2 x 108 cm-2 at an altitude of 950 km (1.4 RM) in 2009. We also present observations of 3.5-σ Ca+ emission features near Mercury’s equatorial anti-solar limb in 2011, from which a stringent tangent column abundance of 4.0 x 106 cm-2 is derived for the Ca ion.A simple model for zenith column abundances of the neutral species yields 2.0 x 107 Al cm-2, and 8.2 x 108 Fe cm-2. The observations appear to be consistent with production of these species by impact vaporization, with a large fraction of the Al ejecta in molecular form, and that for Fe in mixed atomic and molecular forms. The scale height of the Al gas is consistent with a kinetic temperature of 4800-8200 K while that of Fe is 5000-13000 K. The apparent high temperature and low density of the Al gas would suggest that it may be produced by dissociation of molecules. A large fraction of both Al and Fe appear to condense in a vapor cloud at low altitudes.

  6. Observations of the Minor Species Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report the first detections of Al and Fe, and strict upper limits for Ca(+) in the exosphere of Mercury, using the HIRES spectrometer at the Keck I telescope. We report observed 4-sigma tangent columns of 1.5x10(exp 7) Al atoms per square centimeter at an altitude of 1220 km (1.5 Mercury radii (R(sub M)) from planet center), and that for Fe of 1.6 x 10 per square centimeter at an altitude of 950 km (1.4 R(sub M)). The observed 3-sigma Ca(+) column was 3.9x10(exp 6) ions per square centimeter at an altitude of 1630 km (1.67 R(sub M). A simple model for zenith column abundances of the neutral species were 9.5 x 10(exp 7) Al per square centimeter, and 3.0 x 10(exp 8) Fe per square centimeter. The observations appear to be consistent with production of these species by impact vaporization with a large fraction of the ejecta in molecular form. The scale height of the Al gas is consistent with a kinetic temperature of 3000 - 9000 K while that of Fe is 10500 K. The apparent high temperature of the Fe gas would suggest that it may be produced by dissociation of molecules. A large traction of both Al and Fe appear to condense in a vapor cloud at low altitudes.

  7. Sr isotopic fractionation in Ca-Al inclusions from the Allende meteorite

    USGS Publications Warehouse

    Patchett, P.J.

    1980-01-01

    True relative Sr isotopic compositions, determined by double spiking on Ca-Al inclusions from the Allende meteorite show up to 1.5??? per mass unit mass fractionation relative to the Earth and bulk chondrites. All abnormal inclusions are light-isotope enriched. A lack of isotopically heavy Sr in inclusions would place constraints on the time, place and mechanism of origin of these objects. ?? 1980 Nature Publishing Group.

  8. Crystallization of Ca-Al-Rich Inclusions: Experimental Studies on the Effects of Repeated Heating Events

    NASA Technical Reports Server (NTRS)

    Paque, Julie M.; Lofgren, Gary E.; Le, Loan

    2000-01-01

    The observed textures and chemistry of Ca-Al-rich inclusions (CAIs) are presumed to be the culmination of a series of repeated heating and cooling events in the early history of the solar nebula. We have examined the effects of these heating/cooling cycles experimentally on a bulk composition representing an average Type B Ca-Al-rich inclusion composition. We have tested the effect of the nature of the starting material. Although the most recent and/or highest temperature event prior to incorporation into the parent body dominates the texture and chemistry of the CAI, prior events also affect the phase compositions and textures. We have determined that heating precursor grains to about 1275 C prior to the final melting event increases the likelihood of anorthite crystallization in subsequent higher temperature events and a prior high temperature even that produced dendritic melilite results in melilite that shows evidence of rapid crystallization in subsequent lower temperature events. Prior low temperature pre-crystallization events produce final ran products with pyroxene compositions similar to Type B Ca-Al-rich inclusions, and the glass (residual liquid) composition is more anorthitic than any other experiments to date. The addition of Pt powder to the starting material appears to enhance the ability of anorthite to nucleate from this composition.

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

    NASA Technical Reports Server (NTRS)

    Keil, K.; Fuchs, L. H.

    1971-01-01

    Hibonite was discovered in light-colored, Ca-Al-Ti-rich and Si-Fe-poor, achondritic inclusions of the Leoville and Allende HL-group chondrites. Two varieties of hibonite occur: one emits a bright red-orange luminescence under electron bombardment and has high amounts of Al2O3 (87.7; 87.9) and low amounts of MgO (0.65; 0.8) and TiO2 (0.68; 0.8). The other emits a bright blue luminescence and is low in Al2O3 (78.7; 79.2) and high in MgO (3.3; 3.7) and TiO2 (6.5; 7.9) (in wt. %). The oxide CaO is about the same in both varieties. It is suggested that the change in the color of the visible luminescence results from changes in composition. The origin of hibonite which occurs in complex mineral assemblages together with anorthite, gelhenite, wollastonite, aluminous diopside, andradite, Ca-pyroxene, perovskite, spinel, taenite, chromite, and pentlandite, and in close proximity to nodules containing calcite, whewellite, forsterite and many of the aforementioned phases, is discussed. The proposition that hibonite and associated phases originated by contact metamorphism and metasomatism of calcite-dolomite bearing assemblages cannot, at this time, be completely ruled out.

  10. Crystal growth, polarized spectra, and laser performance of Yb:CaGdAlO4 crystal

    NASA Astrophysics Data System (ADS)

    Di, J. Q.; Xu, X. D.; Xia, C. T.; Zheng, L. H.; Aka, G.; Yu, H. H.; Sai, Q. L.; Guo, X. Y.; Zhu, L.

    2016-04-01

    In this paper, the crystal growth, polarized spectra, and laser performance of Yb:CaGdAlO4 crystal were reported. The segregation coefficient of Yb3+ ions was calculated to be 0.47. The cell parameters were determined to be a  =  b  =  0.3658 nm, c  =  1.1985 nm. The peak absorption cross-section was calculated to be 2.65  ×  10-20 cm2 at 979 nm and the peak stimulated emission cross-section was 2.23  ×  10-20 cm2 at 980 nm for the π polarization. The continuous-wave (CW) laser operations of uncoated Yb:CaGdAlO4 crystals with 5  ×  5  ×  3 mm3 in size were demonstrated. A maximum output power of 1.6 W at 1048 nm was obtained with a slope efficiency of 28%. The results show that Yb:CaGdAlO4 crystal is a promising laser medium.

  11. Polymer Coated CaAl-Layered Double Hydroxide Nanomaterials for Potential Calcium Supplement

    PubMed Central

    Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

    2014-01-01

    We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement. PMID:25490138

  12. Reconstructing the Late Pleistocene Southern Ocean biological pump using the vertical gradient of Cd/Ca in planktic and benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Charidemou, Miros; Hall, Ian; Ziegler, Martin

    2015-04-01

    arise due to δ13C fractionation between the ocean and the atmosphere. Due to the similarity in the distribution of phosphate and cadmium (Cd) in the ocean and the incorporation of this trace metal into the calcite tests of foraminifera, Cd/Ca ratios can provide an additional proxy for reconstructing the vertical nutrient distribution in the ocean in the same way as δ13C. We present downcore records of Cd/Ca in the deep-dwelling planktic species, Globorotalia truncatulinoides (s) and the benthic species, Cibicidoides wuellerstorfi from sediment core MD02-2588. A new core a core-top calibration of Cd/Ca in G. truncatulinoides, combined with the established calibration for benthic species allows us to estimate seawater Cd within intermediate and deep water masses that bath the study site and to reconstruct the vertical seawater Cd gradient (ΔCdsw) over the past 150,000 years. Comparison of ΔCdsw to Δδ13C from the same samples from core MD02-2588 in the Southern Ocean indicate a very similar downcore variability which supports the use of the Δδ13C method to reconstruct the biological pump during the MPT.

  13. Hydrothermal Transformation of the Calcium Aluminum Oxide Hydrates CaAl2O4 . 10H2O and Ca2Al2O. 8H2O to Ca3Al2(OH)12 Investigated by In Situ Synchrotron X-ray Powder Diffraction

    SciTech Connect

    Jensen,T.; Christensen, A.; Hanson, J.

    2005-01-01

    The hydrothermal transformation of calcium aluminate hydrates were investigated by in situ synchrotron X-ray powder diffraction in the temperature range 25 to 170 C. This technique allowed the study of the detailed reaction mechanism and identification of intermediate phases. The material CaAl{sub 2}O{sub 4}{center_dot}10H{sub 2}O converted to Ca{sub 3}Al{sub 2}(OH){sub 12} and amorphous aluminum hydroxide. Ca{sub 2}Al{sub 2}O{sub 5}{center_dot}8H{sub 2}O transformed via the intermediate phase Ca{sub 4}Al{sub 2}O{sub 7}{center_dot}13H{sub 2}O to Ca{sub 3}Al{sub 2}(OH){sub 12} and gibbsite, Al(OH){sub 3}. The phase Ca{sub 4}Al{sub 2}O{sub 7}{center_dot}19H{sub 2}O reacted via the same intermediate phase to Ca{sub 3}Al{sub 2}(OH){sub 12} and mainly amorphous aluminum hydroxide. The powder pattern of the intermediate phase is reported.

  14. Cd(2+) sensitivity and permeability of a low voltage-activated Ca(2+) channel with CatSper-like selectivity filter.

    PubMed

    Garza-López, Edgar; Chávez, Julio César; Santana-Calvo, Carmen; López-González, Ignacio; Nishigaki, Takuya

    2016-07-01

    CatSper is a sperm-specific Ca(2+) channel that plays an essential role in the male fertility. However, its biophysical properties have been poorly characterized mainly due to its deficient heterologous expression. As other voltage-gated Ca(2+) channels (CaVs), CatSper possesses a conserved Ca(2+)-selective filter motif ([T/S]x[D/E]xW) in the pore region. Interestingly, CatSper conserves four aspartic acids (DDDD) as the negatively charged residues in this motif while high voltage-activated CaVs have four glutamic acids (EEEE) and low voltage-activated CaVs possess two glutamic acids and two aspartic acids (EEDD). Previous studies based on site-directed mutagenesis of L- and T-type channels showed that the number of D seems to have a negative correlation with their cadmium (Cd(2+)) sensitivity. These results suggest that CatSper (DDDD) would have low sensitivity to Cd(2+). To explore Cd(2+)-sensitivity and -permeability of CatSper, we performed two types of experiments: 1) Electrophysiological analysis of heterologously expressed human CaV3.1 channel and three pore mutants (DEDD, EDDD and DDDD), 2) Cd(2+) imaging of human spermatozoa with FluoZin-1. Electrophysiological studies showed a significant increase in Cd(2+) and manganese (Mn(2+)) currents through the CaV3.1 mutants as well as a reduction in the inhibitory effect of Cd(2+) on the Ca(2+) current. In fluorescence imaging with human sperm, we observed an increase in Cd(2+) influx potentiated by progesterone, a potent activator of CatSper. These results support our hypothesis, namely that Cd(2+)-sensitivity and -permeability are related to the absolute number of D in the Ca(2+)-selective filter independently to the type of the Cav channels. PMID:27134080

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

    NASA Astrophysics Data System (ADS)

    Lee, Kwang Ro; Suito, Hideaki

    1996-06-01

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

  16. Petrography, mineralogy, and Mg isotope composition of VICTA: A vigarano CaAl4O7-bearing type A inclusion

    NASA Technical Reports Server (NTRS)

    Greenwood, R. C.; Morse, A.; Long, J. V. P.

    1993-01-01

    Thermodynamic calculations predict that Ca-dialuminate (CaAl4O7) condenses from a cooling gas of solar composition after hibonite and before melilite. Although Ca-dialuminate has now been recorded from Ca Al-rich inclusions (CAI's) in at least 9 meteorites, compared to hibonite it is a relatively rare phase. As pointed out by Michel-Levy et al., the absence of Ca-dialuminate from most hibonite-bearing inclusions poses a serious problem for the condensation model of CAI formation. Here we describe an inclusion which contains abundant CA-dialuminate partially altered to a hercynite-rich (FeAl2O4) assemblage. The evidence from VICTA indicates that compared to all other phases in type A inclusions, Ca-dialuminate is the most susceptible to secondary alteration; a feature which may explain its restricted occurrence. Unaltered Ca-dialuminate and melilite in VICTA display excess Mg-26 indicative of in situ decay of Al-26.

  17. Disarrangement of actin filaments and Ca²⁺ gradient by CdCl₂ alters cell wall construction in Arabidopsis thaliana root hairs by inhibiting vesicular trafficking.

    PubMed

    Fan, Jun-Ling; Wei, Xue-Zhi; Wan, Li-Chuan; Zhang, Ling-Yun; Zhao, Xue-Qin; Liu, Wei-Zhong; Hao, Huai-Qin; Zhang, Hai-Yan

    2011-07-15

    Cadmium (Cd), one of the most toxic heavy metals, inhibits many cellular and physiological processes in plants. Here, the involvement of cytoplasmic Ca²⁺ gradient and actin filaments (AFs) in vesicular trafficking, cell wall deposition and tip growth was investigated during root (hair) development of Arabidopsis thaliana in response to CdCl₂ treatment. Seed germination and root elongation were prevented in a dose- and time-dependent manner by CdCl₂ treatment. Fluorescence labelling and non-invasive detection showed that CdCl₂ inhibited extracellular Ca²⁺ influx, promoted intracellular Ca²⁺ efflux, and disturbed the cytoplasmic tip-focused Ca²⁺ gradient. In vivo labelling revealed that CdCl₂ modified actin organization, which subsequently contributed to vesicle trafficking. Transmission electron microscopy revealed that CdCl₂ induced cytoplasmic vacuolization and was detrimental to organelles such as mitochondria and endoplasmic reticulum (ER). Finally, immunofluorescent labelling and Fourier transform infrared (FTIR) analysis indicated that configuration/distribution of cell wall components such as pectins and cellulose was significantly altered in response to CdCl₂. Our results indicate that CdCl₂ induces disruption of Ca²⁺ gradient and AFs affects the distribution of cell wall components in root hairs by disturbing vesicular trafficking in A. thaliana. PMID:21497412

  18. Magnetic behaviour of the MTbF{sub 6} fluoroterbates (M=Cd, Ca, Sr, ({alpha}/{beta})-Ba)

    SciTech Connect

    Josse, M.; El-Ghozzi, M.; Avignant, D.; Andre, G.; Bouree, F.; Isnard, O.

    2012-01-15

    Neutron powder diffraction has been performed on the MTbF{sub 6} fluorides (M=Cd, Ca, Sr, ({alpha}/{beta})-Ba). Four of these fluorides (Cd, Ca, Sr, {beta}-Ba) are built of a (pseudo-) tetragonal packing of [TbF{sub 6}]{sup 2-} chains and only differs by the chains relative orientations. Thus this series represents a valuable opportunity to evaluate the Tb{sup 4+}-Tb{sup 4+} magnetic interactions. All the compounds displayed antiferromagnetic order (T{sub N}=2.70 K (Cd), 2.15 K (Ca), 2.60 K (Sr), 2.10 K ({beta}-Ba)), except for the {alpha} form of BaTbF{sub 6}. The crystal structure of this latter fluoroterbate has also been investigated by means of high-resolution neutron powder diffraction. From Neutron Powder Diffraction data, CdTbF{sub 6} and {beta}-BaTbF{sub 6} magnetic structures were determined, together with the metamagnetic behaviour of {beta}-BaTbF{sub 6} as a function of an external magnetic field. A tentative phase diagram is then given for {beta}-BaTbF{sub 6}. Advantage was taken of the polymorphism of the BaTbF{sub 6} fluoroterbate to analyse, on the basis of topological parameters such as bond distances and angles, the magnetic behaviour of its {alpha} and {beta} forms. It was shown that superexchange interactions are present in {beta}-BaTbF{sub 6}, and that these interactions may also rule the magnetic behaviour of the other MTbF{sub 6} (M=Ca, Sr, Cd) tetravalent terbium fluorides. - Graphical abstract: Powder neutron diffraction revealed magnetic order in four of the five investigated fluoroterbates, while crystal chemical analyses of {alpha} and {beta} forms of BaTbF{sub 6} evidenced the existence of superexchange interactions. Highlights: Black-Right-Pointing-Pointer Five fluoroterbates are investigated by Powder Neutron Diffraction (PND). Black-Right-Pointing-Pointer Four of them are antiferromagnetically ordered at 1.4 K. Black-Right-Pointing-Pointer Magnetic structures of {beta}-BaTbF{sub 6} and CdTbF{sub 6} are determined. Black

  19. Accumulation of Al, Mn, Fe, Cu, Zn, Cd and Pb by the bryophyte Scapania undulata in three upland waters of different pH.

    PubMed

    Vincent, C D; Lawlor, A J; Tipping, E

    2001-01-01

    Measurements were made of the contents of Al, Mn, Fe, Cu, Zn, Cd and Pb in Scapania undulata in three streams (D2, D5, D11) in the English Lake District. The stream waters had average pH values of 5.35 (D2), 5.81 (D5) and 7.26 (D11), the main differences in other major chemical components being in Mg, Al, Ca and alkalinity. There was generally more metal accumulation in the older parts of the plants, but this was not significant in all cases. Extents of accumulation varied with stream pH and dissolved metal concentration. For Al, accumulation was greatest in streams D2 and D5. Mn accumulated most in D5 and Fe was without preference. Cu, Zn and Cd accumulated mostly in the plants in stream D11 and Pb accumulated more in D5 and D11. In terms of enrichment factors (amount of metal in the plants divided by stream water concentration) the sequence was Zn < Cd < Cu < Mn < Pb < Al < Fe. Laboratory experiments supported the findings of the field data, providing evidence that uptake increases with pH at constant total metal concentration. The results are interpreted qualitatively in terms of the chemical speciation of the metals in the stream water and competition between metal ions and protons at the plant-water interface. It is suggested that Al, Cu, Zn, Cd and Pb behave according to chemical complexation, whereas redox processes and/or colloidal interactions may be significant for Mn and Fe. PMID:11444010

  20. Low-temperature heat capacities of CaAl2SiO6 glass and pyroxene and thermal expansion of CaAl2SiO6 pyroxene.

    USGS Publications Warehouse

    Haselton, H.T., Jr.; Hemingway, B.S.; Robie, R.A.

    1984-01-01

    Low-T heat capacities (5-380 K) have been measured by adiabatic calorimetry for synthetic CaAl2SiO6 glass and pyroxene. High-T unit cell parameters were measured for CaAl2SiO6 pyroxene by means of a Nonius Guinier-Lenne powder camera in order to determine the mean coefficient of thermal expansion in the T range 25-1200oC. -J.A.Z.

  1. Nanostructured Al-ZnO/CdSe/Cu2O ETA solar cells on Al-ZnO film/quartz glass templates

    PubMed Central

    2011-01-01

    The quartz/Al-ZnO film/nanostructured Al-ZnO/CdSe/Cu2O extremely thin absorber solar cell has been successfully realized. The Al-doped ZnO one-dimensional nanostructures on quartz templates covered by a sputtering Al-doped ZnO film was used as the n-type electrode. A 19- to 35-nm-thin layer of CdSe absorber was deposited by radio frequency magnetron sputtering, coating the ZnO nanostructures. The voids between the Al-ZnO/CdSe nanostructures were filled with p-type Cu2O, and therefore, the entire assembly formed a p-i-n junction. The cell shows the energy conversion efficiency as high as 3.16%, which is an interesting option for developing new solar cell devices. PACS: 88.40.jp; 73.40.Lq; 73.50.Pz. PMID:22136081

  2. Nanostructured Al-ZnO/CdSe/Cu2O ETA solar cells on Al-ZnO film/quartz glass templates.

    PubMed

    Wang, Xianghu; Li, Rongbin; Fan, Donghua

    2011-01-01

    The quartz/Al-ZnO film/nanostructured Al-ZnO/CdSe/Cu2O extremely thin absorber solar cell has been successfully realized. The Al-doped ZnO one-dimensional nanostructures on quartz templates covered by a sputtering Al-doped ZnO film was used as the n-type electrode. A 19- to 35-nm-thin layer of CdSe absorber was deposited by radio frequency magnetron sputtering, coating the ZnO nanostructures. The voids between the Al-ZnO/CdSe nanostructures were filled with p-type Cu2O, and therefore, the entire assembly formed a p-i-n junction. The cell shows the energy conversion efficiency as high as 3.16%, which is an interesting option for developing new solar cell devices.PACS: 88.40.jp; 73.40.Lq; 73.50.Pz. PMID:22136081

  3. Nanostructured Al-ZnO/CdSe/Cu2O ETA solar cells on Al-ZnO film/quartz glass templates

    NASA Astrophysics Data System (ADS)

    Wang, Xianghu; Li, Rongbin; Fan, Donghua

    2011-12-01

    The quartz/Al-ZnO film/nanostructured Al-ZnO/CdSe/Cu2O extremely thin absorber solar cell has been successfully realized. The Al-doped ZnO one-dimensional nanostructures on quartz templates covered by a sputtering Al-doped ZnO film was used as the n-type electrode. A 19- to 35-nm-thin layer of CdSe absorber was deposited by radio frequency magnetron sputtering, coating the ZnO nanostructures. The voids between the Al-ZnO/CdSe nanostructures were filled with p-type Cu2O, and therefore, the entire assembly formed a p-i-n junction. The cell shows the energy conversion efficiency as high as 3.16%, which is an interesting option for developing new solar cell devices. PACS: 88.40.jp; 73.40.Lq; 73.50.Pz.

  4. Femtosecond laser-induced subwavelength ripples on Al, Si, CaF2 and CR-39

    NASA Astrophysics Data System (ADS)

    Bashir, Shazia; Shahid Rafique, M.; Husinsky, Wolfgang

    2012-03-01

    The formation of self-organized subwavelength ripples on Al, Si, CaF2 and CR-39 induced by 25 fs laser pulses at central wavelength of 800 nm has been observed under certain experimental conditions. In case of Al subwavelength gratings with periodicities ranging from 20 to 220 nm are reported. For CaF2 the periodicity goes up to 625 nm. In case of Si, nano-gratings have the periodicity of 10-100 nm. The interspacing of these gratings is 60 nm in case of CR-39. These features which are significantly shorter than incident laser wavelength are observed at the irradiation fluence slightly higher than the ablation threshold regardless of the target material. In addition to these nanoripples, classical or microripples with an average spacing of 1-2 μm have also been registered on irradiated surfaces of Al and Si. These microripples have appeared at fluence higher than that is required for nanoripple-formation. It has been found that the formation of the laser-induced ripples is strongly dependent and quite sensitive to the incident laser fluence and the selection of material.

  5. Surface micromorphology of dental composites [CE-TZP]-[Al2O3] with Ca(+2) modifier.

    PubMed

    Berezina, Sofia; Il'icheva, Alla Alexandrovna; Podzorova, Lyudmila Ivanovna; Ţălu, Ştefan

    2015-09-01

    The objective of this study was to characterize the three-dimensional (3D) surface micromorphology of the ceramics produced from nanoparticles of alumina and tetragonal zirconia (t-ZrO2) with addition of Ca(+2) for sintering improvement. The 3D surface roughness of samples was studied by atomic force microscopy (AFM), fractal analysis of the 3D AFM-images, and statistical analysis of surface roughness parameters. Cube counting method, based on the linear interpolation type, applied for AFM data was used for fractal analysis. The morphology of non-modified ceramic sample was characterized by the rather big (1-2 μm) grains of α-Al2O3 phase with a habit close to hexagonal drowned in solid solution of t-ZrO2 with smooth surface. The pattern surfaces of modified composite content a little amount of elongated prismatic grains with composition close to the phase of СаСеAl3О7 as well as hexahedral α-Al2O3-grains. Fractal dimension, D, as well as height values distribution have been determined for the surfaces of the samples with and without modifying. It can be concluded that the smoothest surface is of the modified samples with Ca(+2) modifier but the most regular one is of the non-modified samples. A connection was observed between the surface morphology and the physical properties as assessed in previous works. PMID:26190812

  6. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    DOE PAGESBeta

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010]/χ[001] ≈ 3.5. A strong power-lawmore » divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.« less

  7. CaMn2Al10 : Itinerant Mn magnetism on the verge of magnetic order

    NASA Astrophysics Data System (ADS)

    Steinke, L.; Simonson, J. W.; Yin, W.-G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-01

    We report the discovery of CaMn2Al10 , a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83 μB/Mn , significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈9 % of R ln 2 . These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010 ]/χ[001 ]≈3.5 . A strong power-law divergence χ (T ) ˜T-1.2 below 20 K implies incipient ferromagnetic order with a low Curie temperature TC<2 K . Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.

  8. Geochemical modeling of leaching of Ca, Mg, Al, and Pb from cementitious waste forms

    SciTech Connect

    Martens, E.; Jacques, D.; Van Gerven, T.; Wang, L.; Mallants, D.

    2010-08-15

    Results from extraction tests on cement-waste samples were simulated with a thermodynamic equilibrium model using a consistent database, to which lead data were added. Subsequent diffusion tests were modeled by means of a 3D diffusive transport model combined with the geochemical model derived from the extraction tests. Modeling results of the leached major element concentrations for both uncarbonated and (partially) carbonated samples agreed well with the extraction test using the set of pure minerals and solid solutions present in the database. The observed decrease in Ca leaching with increasing carbonation level was qualitatively predicted. Simulations also revealed that Pb leaching is not controlled by dissolution/precipitation only. The addition of the calcite-cerrusite solid solution and adsorption reactions on amorphous Fe- and Al-oxides improved the predictions and are considered to control the Pb leaching during the extractions tests. The dynamic diffusive leaching tests were appropriately modeled for Na, K, Ca and Pb.

  9. (Ca/Sr)Au xCd 1- x: Stacking variants of the CrB-FeB series

    NASA Astrophysics Data System (ADS)

    Harms, Wiebke; Dürr, Ines; Daub, Michael; Röhr, Caroline

    2010-01-01

    The structural chemistry of binary 1:1 alkaline earth metallides AIIM ( M=p-block or late transition element) is dominated by planar M zig-zag chains, which are stacked in different orientations (CrB ( c) to FeB ( h) type) and with variable stacking distances (types I and II). As a case study of the electronic influences, the substitution of Au against Cd in the respective Ca and Sr aurides was examined by means of experimental, crystallographic and computational methods. Starting from CaAu, up to 11% of Au can be substituted by Cd without a change in the CrB structure type (orthorhombic, space group Cmcm, a=398.2(1), b=1122.6(6), c=460.9(2) pm, Z=4, R1=0.0303). Starting from SrAu (stacking sequence (hc)2(h2c)2), depending on the proportion of the Cd substitution a successive change to structures with increased hexagonality is observed: In SrAu0.93Cd0.07 (monoclinic, space group P21/m, a=621.3(4), b=472.4(2), c=1216.1(9) pm, β=96.97(5)∘, Z=6, R1=0.0467) the stacking sequence is h2 c, i.e. the hexagonality is 66.67%. A slightly more increased Cd content in SrAu0.78Cd0.22 (orthorhombic, space group Pnma, a=3243.3(8), b=474.17(8), c=626.20(9) pm, Z=16, R1=0.0682) drives the hexagonality to 75%, with a (h3c)2 stacking sequence known from several rare earth nickel compounds. Further Cd substitution is not possible. However, in the Cd-rich section of the two series, where the CsCl/β-brass structure type occurs for both alkaline earth elements, a small Au substitution, as determined from powder data by Rietveld refinements, is possible. The substitution limit and the stability ranges of the CsCl and the CrB type can be rationalized from the calculated band structures. Geometrical and electronic criteria are used to compare and discuss the stability ranges in a structural map.

  10. Diagnostic performance of CD66c in lung adenocarcinoma-associated malignant pleural effusion: comparison with CEA, CA 19-9, and CYFRA 21-1.

    PubMed

    Son, Seung-Myoung; Han, Hye-Suk; An, Jin Young; Choe, Kang Hyeon; Lee, Ki Man; Lee, Ki Hyeong; Kim, So-Seul; Lee, Yong-Moon; Lee, Ho-Chang; Song, Hyung Geun; Lee, Ok-Jun

    2015-02-01

    Various tumour markers have been evaluated in malignant pleural effusions, but not CD66c. This study evaluated the diagnostic ability of CD66c in lung adenocarcinoma-associated malignant pleural effusions (LA-MPEs) and compared it with other known tumour markers. Forty-seven cases of LA-MPE and 52 cases of benign pleural effusions were collected. The levels of CD66c, CEA, CA 19-9, and CYFRA 21-1 were measured by enzyme immunoassay. The expression of CD66c, CEA, and CA 19-9 in cell blocks was measured by immunocytochemistry. CEA had the best diagnostic values, with a sensitivity of 87.2% and specificity of 92.3%. Both CD66c and CA 19-9 showed the highest specificity of 98.1%, with sensitivities of 63.8% and 55.3%, respectively. CYFRA 21-1 had a sensitivity of 83.0% and specificity of 76.9%. CEA combined with CA 19-9 reached a sensitivity of 91.5% and a specificity of 98.1%. The sensitivities of immunocytochemical staining for CD66c, CEA, and CA 19-9 were 72.5%, 75%, and 40%, respectively. CD66c showed a diagnostic performance comparable to CYFRA 21-1 and CA 19-9 by enzyme immunoassay. Immunocytochemical study showed that CD66c and CEA were more sensitive than CA19-9. Both studies support CD66c as a potential tumour marker to differentiate LA-MPE from benign effusions. PMID:25551300

  11. Large-area CdTe/Al(sub)2O(sub)3 epitaxial films

    NASA Astrophysics Data System (ADS)

    Senokosev, E. A.; Sushkevich, K. D.; Usatyy, A. N.; Federov, V. M.

    1986-08-01

    In the group of A II B IV wide band gap semiconductor compounds, cadmium telluride is one of the most promising materials for converting solar energy into electricity. The wide practical use of CdTe for photoconverters has been restricted primarily by difficulties in growing high quality crystals with a large working surface area. The efficiency factor of polycrystalline film photocells does not exceed 5%. The search for and development of an effective technology for growing monocrystalline layers of CdTe having a large area with specified physical properties is one of the important directions in improving the operational characteristics of photocells. The production, study of the structure and emissive properties of epitaxial n-CdTe/Al2O3 films with an area of approximately equal 20 sq cm is discussed. Films with a thickness of 10 to 50 microns, which were grown in a quasiclosed container under conditions close to thermal equilibrium, were investigated. n-CdTe crystals with a specific resistance of 100,000 to 1,000,000 ohms x cm were used for deposition. A correlation between the type and resistance of the films and the parent material was discovered.

  12. CD36- and GPR120-mediated Ca2+ Signaling in Human Taste Bud Cells Mediates Differential Responses to Fatty Acids and is Altered in Obese Mice

    PubMed Central

    Ozdener, Mehmet Hakan; Subramaniam, Selvakumar; Sundaresan, Sinju; Sery, Omar; Hashimoto, Toshihiro; Asakawa, Yoshinori; Besnard, Philippe; Abumrad, Nada A.; Khan, Naim Akhtar

    2014-01-01

    Background & Aims It is important to increase our understanding of gustatory detection of dietary fat and its contribution to fat preference. We studied the roles of the fat taste receptors CD36 and GPR120 and their interactions via Ca2+ signaling in fungiform taste bud cells (TBC). Methods We measured Ca2+ signaling in human TBC, transfected with small interfering RNAs (siRNAs) against mRNAs encoding CD36 and GPR120 (or control siRNAs). We also studied Ca2+ signaling in TBC from CD36−/− mice and from wild-type lean and obese mice. Additional studies were conducted with mouse enteroendocrine cell line STC-1 that express GPR120 and stably transfected with human CD36. We measured release of serotonin and GLP-1 from human and mice TBC in response to CD36 and GPR120 activation. Results High concentrations of linoleic acid induced Ca2+ signaling via CD36 and GPR120 in human and mice TBC as well as in STC-1 cells, whereas low concentrations induced Ca2+ signaling via only CD36. Incubation of human and mice fungiform TBC with lineoleic acid downregulated CD36 and upregulated GPR120 in membrane lipid rafts. Obese mice had decreased spontaneous preference for fat. Fungiform TBC from obese mice had reduced Ca2+ and serotonin responses but increased release of GLP1, along with reduced levels of CD36 and increased levels of GPR120 in lipid rafts. Conclusions CD36 and GPR120 have non-overlapping roles in TBC signaling during oro-gustatory perception of dietary lipids; these are differentially regulated by obesity. PMID:24412488

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  14. A diode pumped passively mode-locked Nd:CaGdAlO4 laser

    NASA Astrophysics Data System (ADS)

    Rao, H.; Cong, Z. H.; Qin, Z. G.; Feng, C.; Wang, Q. P.; Liu, Z. J.; Zhang, X. Y.; Zhang, S. S.; Liu, Y.; Men, S. J.; Xia, J. B.; Di, J. Q.; Xu, X. D.; Xu, J.

    2016-04-01

    A diode pumped passively mode-locked Nd:CaGdAlO4 (Nd:CGA) laser was demonstrated. By using a semiconductor saturable-absorber mirror (SESAM) as the modulator, stable mode-locked pulses with a duration of 6.0 ps and a repetition rate of 88.3 MHz have been achieved at a central wavelength of 1078.6 nm. The maximum output power of 452 mW was obtained under a pump power of 10 W.

  15. Acid precipitation and food quality: Effects of dietary Al, Ca and P on bone and liver characteristics in American black ducks and mallards

    USGS Publications Warehouse

    Sparling, D.W.

    1991-01-01

    American black ducks (Anas rubripes) and mallards (A. platyrhynchos) were fed diets varying in concentrations of aluminum (Al). calcium (Ca), and phosphorus (P) for 10 weeks to identify toxic effects of Al under conditions representative of areas with acid precipitation. Femur and liver tissues were analyzed for Al. Ca, and P concentrations and structural characteristics. At two weeks of age, both species demonstrated pronounced differences in femur Al and P concentrations and femur mass from dietary Al and interaction between Ca:P regimen and Al:Low Ca:Low P enhanced Al storage and decreased P and mass in femurs. Femur Ca was lowest in the Low Ca:Low P regimen but was not affected by dietary Al. At 10 weeks, femur and liver Al continued to vary with dietary Al. Elevated Al and reduced Ca lowered modulus of elasticity. Femur P increased with elevated dietary P in black ducks. Elevated dietary P negated some of the effects of dietary A! on femur mass in black ducks. Reduced Ca concentrations weakened bones of both species and lowered both Ca and P. An array of clinical signs including lameness, discoloration of the upper mandible, complete and greenstick fractures, and death were responses to elevated Al and Ca:P regimen. Black ducks seemed to display these signs over a wider range of diets than mallards. Diets of 1,000 mg/kg Al had toxic effects on both species, particularly when combined with diets low in Ca and P.

  16. Photoluminescence of Au - formed in 12CaO · 7Al 2O 3 single crystal by Au +-implantation

    NASA Astrophysics Data System (ADS)

    Miyakawa, M.; Kamioka, H.; Hirano, M.; Kamiya, T.; Hosono, H.

    2006-09-01

    Au + ion implantation with fluences from 1 × 10 14 to 3 × 10 16 cm -2 into 12CaO · 7Al 2O 3 (C12A7) single crystals was carried out at a sample temperature of 600 °C. The implanted sample with the fluence of 1 × 10 15 cm -2 exhibited photoluminescence (PL) bands peaking at ˜3.1 and ˜2.3 eV at ⩽150 K when excited by He-Cd laser (325 nm). This was the first observation of PL from C12A7. These two PL bands are possibly due to intra-ionic transitions of an Au - ion having the electronic configuration of 6 s2, judged from their similarities to those reported on Au - ions in alkali halides. However, when the concentration of the implanted Au ions exceeded the theoretical maximum value of anions encaged in C12A7 (˜2.3 × 10 21 cm -3), surface plasmon absorption appeared in the optical absorption spectrum, suggesting Au colloids were formed at such high fluences. These observations indicate that negative gold ions are formed in the cages of C12A7 by the Au + implantation if an appropriate fluence is chosen.

  17. Broadband photoluminescence in the (CaO-Al2O3-SiO2):Eu system

    NASA Astrophysics Data System (ADS)

    Gurin, N. T.; Paksyutov, K. V.; Terent'ev, M. A.; Shirokov, A. V.

    2009-08-01

    Phosphors of the (CaO-Al2O3-SiO2):Eu system obtained by direct solid-state synthesis in air at 1300°C produce broadband photoluminescence (PL) covering the entire visible range under excitation by a nitrogen laser. Upon vacuum annealing, the PL intensity in (CaO-Al2O3-SiO2):Eu and (CaO-Al2O3-2SiO2):Eu samples exhibits a several-fold increase and the latter phosphor yields blue emission according to the CIE color standard. The annealing of a (CaO-Al2O3):Eu composition leads to a change in the emission color from red (close to that according to the EBU scale) to blue (in the same scale). Vacuum-annealed (CaO-2Al2O3):Eu phosphor yields red emission (close to that according to the NTSC scale), while (2CaO-Al2O3):Eu composition exhibits intense purple luminescence.

  18. Network topology for the formation of solvated electrons in binary CaO–Al2O3 composition glasses

    PubMed Central

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J. K. Richard; Benmore, Chris J.

    2013-01-01

    Glass formation in the CaO–Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO–Al2O3 glasses using combined density functional theory–reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O–Ca and O–Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al–O is stronger than that of Ca–O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71–74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass. PMID:23723350

  19. CO₂ sorbents with scaffold-like Ca-Al layered double hydroxides as precursors for CO₂ capture at high temperatures.

    PubMed

    Chang, Po-Hsueh; Lee, Tai-Jung; Chang, Yen-Po; Chen, San-Yuan

    2013-06-01

    A highly stable high-temperature CO₂ sorbent consisting of scaffold-like Ca-rich oxides (Ca-Al-O) with rapid absorption kinetics and a high capacity is described. The Ca-rich oxides were prepared by annealing Ca-Al-NO₃ layered double hydroxide (LDH) precursors through a sol-gel process with Al(O(i)P)₃ and Ca(NO₃)₂ with Ca(2+)/Al(3+) ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca(2+)/Al(3+) ratios of 2:1. However, both LDH and Ca(OH)₂ phases were produced at higher ratios. Both TEM and SEM observations indicated that the Ca-Al-NO₃ LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 °C, a highly stable porous network structure of the CaO-based Ca-Al-O mixed oxide (CAMO), composed of CaO and Ca₁₂Al₁₄O₃₃, was still present. The CAMO exhibited high specific surface areas (up to 191 m(2)g(-1)) and a pore size distribution of 3-6 nm, which allowed rapid diffusion of CO₂ into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO₂ absorption at 700 °C. Thermogravimetric analysis results indicated that a CO₂ capture capacity of approximately 49 wt% could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 °C for 5 min. Also, 94-98% of the initial CO₂ capture capability was retained after 50 cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long-term cyclic operation in high-temperature environments. PMID:23650194

  20. Phase relations for CaAl 2Si 2O 8 (anorthite composition) in the system CaOAl 2O 3SiO 2 at 14 GPa

    NASA Astrophysics Data System (ADS)

    Gautron, L.; Kesson, S. E.; Hibberson, W. O.

    1996-10-01

    Multi-anvil experiments at 14 GPa and 1500°C reveal that CaAl 2Si 2O 8 (anorthite composition) undergoes subsolidus disproportionation into grossular Ca 3Al 2Si 3O 12, stishovite SiO 2 and a calcium aluminosilicate phase of composition CaAl 4Si 2O 11. This last phase (CAS) was first synthesised by Irifune et al. (1994, Earth Planet. Sci. Lett., 126: 351-368) in a continental crust composition, at P, T conditions appropriate for the Transition Zone. In the system CaOAl 2O 3SiO 2, a new three-phase assemblage (grossular + stishovite + CAS) encountered at 14GPa replaces the grossular + stishovite + kyanite assemblage known to be stable at around 10GPa because of an univariant reaction between grossular and kyanite that yields stishovite and CAS. By 1600°C another univariant reaction between grossular and stishovite produces CAS plus liquid. Schreinemakers' analysis suggests that, given Ca,Al-rich lithologies, the CAS phase should be stable at transition-zone pressures.

  1. Temporal variability of bioavailable Cd, Hg, Zn, Mn and Al in an upwelling regime.

    PubMed

    Lares, M Lucila; Flores, Muñoz Gilberto; Lara-Lara, Ruben

    2002-01-01

    Monthly variability of Cd, Hg, Zn, Mn and Al concentrations in mussels (Mytilus californianus) soft tissue and brown seaweed (Macrocystis pyrifera) was studied at a pristine rocky shore off San Quintin Bay, Baja California, México. The results were related to climatic and hydrographic conditions and to the physiological state of the mussels (condition index) by correlation analysis and principal component analysis (PCA). A "normalization" to account for the variability induced by the physiological state of the mussel was performed. The PCA was performed in two ways to relate the environmental variables and the condition index to: (1) the metal concentrations in mussels, and (2) the "normalized" mussel concentrations. The association of the variability of Cd with the upwelling season was revealed in both PCAs. The temporal variability of this metal in mussels was highly correlated to that in seaweed, suggesting that the dissolved phase determined the variability of Cd in mussels. However, for Hg, Zn, Mn and Al the results from both PCAs were different. The first PCA showed the relationship of these metals to pluvial precipitation and to the condition index. The PCA for the normalized mussel concentrations showed that, after eliminating the effect of the condition index, only Al was related to pluvial precipitation. Manganese, and to a less degree Zn, were related to these metals in seaweed. Because zinc is an essential element in mussels, some regulation of their internal concentrations is likely. Mercury was not detected in seaweed, but because of its reactive nature, it is not expected that the dissolved fraction could be a significant pathway; therefore, it can be concluded that its temporal variability was determined by the variability in the condition index only. PMID:12442783

  2. Magnesium doping on brownmillerite Ca{sub 2}FeAlO{sub 5}

    SciTech Connect

    Malveiro, J.; Ramos, T.; Ferreira, L.P.; Waerenborgh, J.C.

    2007-06-15

    Ca{sub 2}FeAl{sub 1-} {sub x} Mg {sub x} O{sub 5} (x=0, 0.05 and 0.1) compounds adopting the brownmillerite-type structure were prepared by a self-combustion route using two different fuels. Characterisation was performed using X-ray powder diffraction, Moessbauer spectroscopy, magnetisation measurements, chemical analysis, scanning electron microscopy and 4-point dc conductivity measurements. Global results indicate that the solubility limit was reached for x=0.1. An antiferromagnetic behaviour was detected for all studied compositions, with magnetic ordering temperatures of 340 and 290 K for x=0 and 0.05, respectively. Mg doping increases the number of iron cations in tetrahedral sites, which induces magnetisation enhancement at low temperatures through the coupling between octahedral iron cations in different octahedral planes. The compounds exhibit semiconductor behaviour and Mg{sup 2+} doping yields a significant enhancement of the total conductivity, which can be essentially attributed to the presence of Fe{sup 4+} ions. - Graphical abstract: Ca{sub 2}FeAl{sub 1-} {sub x} Mg {sub x} O{sub 5} (x=0, 0.05, 0.1) compounds with the brownmillerite structure were prepared and characterised. The paramagnetic Moessbauer spectra presented were obtained at T=363 K (x=0); T=297 K (x=0.05) and T=353 K (x=0.1)

  3. Dynamic behaviour of Cd2+ adsorption in equilibrium batch studies by CaCO3(-)-rich Corbicula fluminea shell.

    PubMed

    Ismail, Farhah Amalya; Aris, Ahmad Zaharin; Latif, Puziah Abdul

    2014-01-01

    This work presents the structural and adsorption properties of the CaCO3(-)-rich Corbicula fluminea shell as a natural and economic adsorbent to remove Cd ions from aqueous solutions under batch studies. Experiments were conducted with different contact times, various initial concentrations, initial solution pH and serial biosorbent dosage to examine the dynamic characterization of the adsorption and its influence on Cd uptake capacity. The characterization of the C. fluminea shell using SEM/EDX revealed that the adsorbent surface is mostly impregnated by small particles of potentially calcium salts. The dominant Cd adsorption mechanism is strongly pH and concentration dependent. A maximum Cd removal efficiency of 96.20% was obtained at pH 7 while the optimum adsorbent dosage was observed as 5 g/L. The Langmuir isotherm was discovered to be more suitable to represent the experimental equilibrium isotherm results with higher correlation coefficients (R(2) > 0.98) than Freundlich (R(2) < 0.97).The correlation coefficient values (p < 0.01) indicated the superiority of the Langmuir isotherm over the Freundlich isotherm. PMID:23771443

  4. Self-reactivated mesostructured Ca-Al-O composite for enhanced high-temperature CO2 capture and carbonation/calcination cycles performance.

    PubMed

    Chang, Po-Hsueh; Huang, Wei-Chen; Lee, Tai-Jung; Chang, Yen-Po; Chen, San-Yuan

    2015-03-25

    In this study, highly efficient high-temperature CO2 sorbents of calcium aluminate (Ca-Al-O) mesostructured composite were synthesized using presynthesized mesoporous alumina (MA) as a porous matrix to react with calcium nitrate through a microwave-assisted process. Upon annealing at 600 °C, a highly stable mesoporous structure composed of poorly crystalline Ca12Al14O33 phase and the CaO matrix was obtained. The Ca-Al-O mesostructured sorbents with a Ca(2+)/Al(3+) ratio of 5:1 exhibit an enhanced increasing CO2 absorption kinetics in the CO2 capture capacity from 37.2 wt % to 48.3 wt % without apparent degradation with increasing carbonation/calcination cycling up to 50 at 700 °C due to the strong self-reactivation effect of the mesoporous Ca-Al-O microstructure. Remarkable improvements in the CaO-CaCO3 conversion attained from the mesostructured Ca-Al-O composite can be explained using the concept combined with available mesoporous structure and Ca12Al14O33 phase content. However, a high Ca(2+)/Al(3+) =8:1 Ca-Al-O composite causes degradation because the pores become blocked and partial sintering induces CaO agglomeration. PMID:25730384

  5. Atomistic and Ab initio modeling of CaAl2O4 high-pressure polymorphs under Earth's mantle conditions

    NASA Astrophysics Data System (ADS)

    Eremin, N. N.; Grechanovsky, A. E.; Marchenko, E. I.

    2016-05-01

    Semi-empirical and ab initio theoretical investigation of crystal structure geometry, interatomic distances, phase densities and elastic properties for some CaAl2O4 phases under pressures up to 200 GPa was performed. Two independent simulation methods predicted the appearance of a still unknown super-dense CaAl2O4 modification. In this structure, the Al coordination polyhedron might be described as distorted one with seven vertices. Ca atoms were situated inside polyhedra with ten vertices and Ca-O distances from 1.96 to 2.49 Å. It became the densest modification under pressures of 170 GPa (density functional theory prediction) or 150 GPa (semi-empirical prediction). Both approaches indicated that this super-dense CaAl2O4 modification with a "stuffed α-PbO2" type structure could be a probable candidate for mutual accumulation of Ca and Al in the lower mantle. The existence of this phase can be verified experimentally using high pressure techniques.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  7. Simultaneous determination of Ca, Cu, Ni, Zn and Cd binding strengths with fulvic acid fractions by Schubert's method

    USGS Publications Warehouse

    Brown, G.K.; MacCarthy, P.; Leenheer, J.A.

    1999-01-01

    The equilibrium binding of Ca2+, Ni2+, Cd2+, Cu2+ and Zn2+ with unfractionated Suwannee river fulvic acid (SRFA) and an enhanced metal binding subfraction of SRFA was measured using Schubert's ion-exchange method at pH 6.0 and at an ionic strength (??) of 0.1 (NaNO3). The fractionation and subfractionation were directed towards obtaining an isolate with an elevated metal binding capacity or binding strength as estimated by Cu2+ potentiometry (ISE). Fractions were obtained by stepwise eluting an XAD-8 column loaded with SRFA with water eluents of pH 1.0 to pH 12.0. Subfractions were obtained by loading the fraction eluted from XAD-8 at pH 5.0 onto a silica gel column and eluting with solvents of increasing polarity. Schuberts ion exchange method was rigorously tested by measuring simultaneously the conditional stability constants (K) of citric acid complexed with the five metals at pH 3.5 and 6.0. The logK of SRFA with Ca2+, Ni2+, Cd2+, Cu2+ and Zn2+ determined simultaneously at pH 6.0 follow the sequence of Cu2+>Cd2+>Ni2+>Zn2+>Ca2+ while all logK values increased for the enhanced metal binding subfraction and followed a different sequence of Cu2+>Cd2+>Ca2+>Ni2+>Zn2+. Both fulvic acid samples and citric acid exhibited a 1:1 metal to ligand stochiometry under the relatively low metal loading conditions used here. Quantitative 13C nuclear magnetic resonance spectroscopy showed increases in aromaticity and ketone content and decreases in aliphatic carbon for the elevated metal binding fraction while the carboxyl carbon, and elemental nitrogen, phosphorus, and sulfur content did not change. The more polar, elevated metal binding fraction did show a significant increase in molecular weight over the unfractionated SRFA. Copyright (C) 1999 Elsevier Science B.V.

  8. Novel humanized anti-CD20 antibody BM-ca binds to a unique epitope and exerts stronger cellular activity than others

    PubMed Central

    Kobayashi, Hideaki; Matsunaga, Yuka; Uchiyama, Yumiko; Nagura, Kenji; Komatsu, Yasuhiko

    2013-01-01

    Cellular activity of BM-ca, a novel humanized anti-CD20 antibody, was quantitatively compared with that of two other anti-CD20 antibodies used for clinical practice, rituximab and ofatumumab. The results of a complement-dependent cytotoxicity (CDC) assay revealed that the strongest antibody was ofatumumab, followed by BM-ca, with rituximab being the weakest. Ofatumumab and BM-ca were effective not only against rituximab-sensitive SU-DHL-4 cells but also against rituximab-resistant RC-K8 cells. In an antibody-dependent cell-mediated cytotoxicity (ADCC) assay, although the effective concentrations against SU-DHL-4 cells were almost the same among these three antibodies, the maximum cytotoxic level was the highest for BM-ca. In an anti-cell proliferation assay using SU-DHL-4 cells, BM-ca was the most effective and ofatumumab, the weakest. Against RC-K8 cells, only BM-ca was effective. When combined with each of four cancer chemotherapeutics (prednisolone, vincristine, hydroxydaunorubicin, and cisplatin), BM-ca exerted the most effective combinatorial anti-cell proliferation activity. To assess the in vivo effect of BM-ca, we intravenously administered BM-ca into cynomolgus monkeys and found that the peripheral B-cell levels did not decrease in half of the animals. Sequencing of cDNA encoding CD20 of cynomolgus monkeys revealed that the responders and nonresponders had Leu/Pro (hetero) and Leu/Leu (homo) at amino acid (a.a.) position 160, respectively, suggesting that the epitope recognized by BM-ca was around this a.a. By analyzing reactivity to synthetic peptides, the epitope recognized by BM-ca was estimated to be a.a.'s 156–166, not shared with rituximab and ofatumumab. These results suggest BM-ca to be a promising anti-CD20 antibody having superior properties and recognizing a unique epitope. PMID:23634281

  9. Evaluating the Utility of Multiple Proxies (Mg/Ca, Li/Ca, Cd/Ca, δ13C and Nd isotopes) in Foraminiferal Shells: New calibrations from the Demerara Rise, western tropical Atlantic

    NASA Astrophysics Data System (ADS)

    Huang, K.; Oppo, D.; Curry, W. B.; Blusztajn, J.

    2011-12-01

    Reconstructions of changes in Antarctic Intermediate Water (AAIW) circulation and its properties across abrupt climate events provides crucial information about the role of AAIW in regulating the climate system and how AAIW responds to changes in North Atlantic overturning. In order to better constrain the ocean conditions in the past, we systematically examine the utility of temperature (Mg/Ca and Mg/Li), carbonate saturation state (B/Ca and Li/Ca), nutrient (Cd/Ca, Zn/Ca and δ13C) and watermass proxies (Nd isotopes) in foraminifera shells using a set of 22 multicore tops (KNR197-3, spanning depths of 380 to 3300 m) and ambient seawaters collected from the Demerara Rise in the tropical northwestern Atlantic. In this study new core-top calibrations will be presented for calcitic foraminifera (i.e., Cibicidoides pachyderma, Cibicidoides wuellerstorfi, Uvigerina peregrina) and aragonitic Hoeglundina elegans through a direct comparison of shell chemistry to physical/chemical properties of ambient seawaters. We will also present new Nd isotope calibrations based on measurements on seawaters, mixed planktonic foraminifera and Fe-Mn oxyhydroxides from the core-top samples, to refine the utility of the Nd isotopes in authigenic marine precipitates as a watermass proxy. These new results enable us to evaluate the impact of environmental parameters (T, S, and Δ[CO32-]) on these paleo-proxies, and to further assess the robustness of down-core reconstructions and interpretations.

  10. Commentary on Myers et al.: Growing role of the innate immunity receptor CD36 in central nervous system diseases

    PubMed Central

    Garcia-Bonilla, Lidia; Park, Laibaik; Iadecola, Costantino

    2016-01-01

    Activation of innate immunity by sterile inflammation has emerged as a key event in selected CNS diseases, with a defining impact on all stages of the pathological process. Due to its multiple functions and assembly with other pattern recognition receptors, the innate immunity receptor CD36 has been implicated in a wide variety of brain pathologies, ranging from acute brain injury to neurodegeneration. However, the role of CD36 is complex involving both tissue destruction, related mainly to oxidative stress and inflammation, and beneficial reparative effects due to the involvement of CD36 in tissue repair and reorganization. A recent paper of Meyer at al. provided novel evidence for a role of CD36 also in spinal cord trauma, a condition in which the effect of CD36 was found to be univocally deleterious. This commentary will provide a brief overview of the pathobiology of CD36 and its expanding role in diseases of the brain and spinal cord. PMID:25157902

  11. Major soil element (Ca, Mg, K, Na, Al, Fe) distribution along the Qinghai-Tibet Railway

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Zhang, Y.; Zhang, H.; Ding, M.; Lin, X.

    2011-12-01

    The Tibetan Plateau (TP), which has been called the third polar region, is the highest plateau in the world. There are a series of special soils present in the TP, which are extremely important in soil sciences for their particularities. Soil chemical composition is one of the necessary indices of soil characteristics. The major element content of the soil, such as Ca, Mg, K, Na, not only can affect the soil pH value and soil fertility but also are the main drivers of soil geochemical processes. It is helpful to understand the TP environmental characteristics, to study the major soil element content.The Qinghai-Tibet Railway (QTR) is the highest-elevation and the longest highland railway on earth. There are nearly all types of TP soil along the QTR. Most of the areas along the QTR are in fairly pristine condition. This offers a good platform to study the natural environmental characteristics of the soil. This study selected 240 soil samples from 28 sample areas along the Qinghai-Tibet Railway, and the aluminum, iron, calcium, sodium, potassium and magnesium content in the soil were measured with ICP-AES. The results indicated: (1) Compared with the national soil background values, the Ca content in soil was higher along the QTR and Al was lower; but the Fe, Mg, K and Na contents were similar. (2) Along the whole QTR, the soil Al, Fe and Mg content showed a decreasing trend from Xining to Lhasa, the changes in K and Na values were relatively complex, and the distribution of Ca could be divided three sections. (3) The soil element contents varied with different soil types and parent materials. Most of the six elements content was minimum in soil, which derived from debris materials for ice and water, and the elements content was maximum in soil, which evolved from debris for flood, and the content of soil Ca developed from debris for lake was maximum. The amount of each element present in the Hapli-Cryic Aridosols and Calci-Cryic Aridosols was relatively higher than

  12. Refinement of Eutectic Si in High Purity Al-5Si Alloys with Combined Ca and P Additions

    NASA Astrophysics Data System (ADS)

    Ludwig, Thomas Hartmut; Li, Jiehua; Schaffer, Paul Louis; Schumacher, Peter; Arnberg, Lars

    2015-01-01

    The effects of combined additions of Ca and P on the eutectic Si in a series of high purity Al-5 wt pct Si alloys have been investigated with the entrained droplet technique and complementary sets of conventional castings. Differential scanning calorimetry (DSC) and thermal analysis were used to investigate the eutectic droplet undercooling and the recalescence undercooling, respectively. Optical microscopy, SEM, EPMA, and TEM were employed to characterize the resultant microstructures. It was found that 250 ppm Ca addition to Al-5Si wt pct alloys with higher P contents leads to a significant increase of the eutectic droplet undercooling. For low or moderate cooling rates, the TEM results underline that Ca additions do not promote Si twinning. Thus, a higher twin density cannot be expected in Ca containing Al-Si alloys after, e.g., sand casting. Consequently, a refinement of the eutectic Si from coarse flake-like to fine plate-like structure, rather than a modification of the eutectic Si to a fibrous morphology, was achieved. This strongly indicates that the main purpose of Ca additions is to counteract the coarsening effect of the eutectic Si imposed by higher P concentrations. Significant multiple Si twinning was observed in melt-spun condition; however, this can be attributed to the higher cooling rate. After DSC heating (slow cooling), most of Si twins disappeared. Thus, the well-accepted impurity-induced twinning mechanism may be not valid in the case of Ca addition. The possible refinement mechanisms were discussed in terms of nucleation and growth of eutectic Si. We propose that the pre-eutectic Al2Si2Ca phase and preferential formation of Ca3P2 deactivate impurity particles, most likely AlP, poisoning the nucleation sites for eutectic Si.

  13. Ca2+ Binding/Permeation via Calcium Channel, CaV1.1, Regulates the Intracellular Distribution of the Fatty Acid Transport Protein, CD36, and Fatty Acid Metabolism.

    PubMed

    Georgiou, Dimitra K; Dagnino-Acosta, Adan; Lee, Chang Seok; Griffin, Deric M; Wang, Hui; Lagor, William R; Pautler, Robia G; Dirksen, Robert T; Hamilton, Susan L

    2015-09-25

    Ca(2+) permeation and/or binding to the skeletal muscle L-type Ca(2+) channel (CaV1.1) facilitates activation of Ca(2+)/calmodulin kinase type II (CaMKII) and Ca(2+) store refilling to reduce muscle fatigue and atrophy (Lee, C. S., Dagnino-Acosta, A., Yarotskyy, V., Hanna, A., Lyfenko, A., Knoblauch, M., Georgiou, D. K., Poché, R. A., Swank, M. W., Long, C., Ismailov, I. I., Lanner, J., Tran, T., Dong, K., Rodney, G. G., Dickinson, M. E., Beeton, C., Zhang, P., Dirksen, R. T., and Hamilton, S. L. (2015) Skelet. Muscle 5, 4). Mice with a mutation (E1014K) in the Cacna1s (α1 subunit of CaV1.1) gene that abolishes Ca(2+) binding within the CaV1.1 pore gain more body weight and fat on a chow diet than control mice, without changes in food intake or activity, suggesting that CaV1.1-mediated CaMKII activation impacts muscle energy expenditure. We delineate a pathway (Cav1.1→ CaMKII→ NOS) in normal skeletal muscle that regulates the intracellular distribution of the fatty acid transport protein, CD36, altering fatty acid metabolism. The consequences of blocking this pathway are decreased mitochondrial β-oxidation and decreased energy expenditure. This study delineates a previously uncharacterized CaV1.1-mediated pathway that regulates energy utilization in skeletal muscle. PMID:26245899

  14. Ethanol Sensor of CdO/Al2O3/CeO2 Obtained from Ce-DOPED Layered Double Hydroxides with High Response and Selectivity

    NASA Astrophysics Data System (ADS)

    Xu, Dongmei; Guan, Meiyu; Xu, Qinghong; Guo, Ying; Wang, Yao

    2013-06-01

    In this paper, Ce-doped CdAl layered double hydroxide (LDH) was first synthesized and the derivative CdO/Al2O3/CeO2 composite oxide was prepared by calcining Ce-doped CdAl LDH. The structure, morphology and chemical state of the Ce doped CdAl LDH and CdO/Al2O3/CeO2 were also investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), solid state nuclear magnetic resonance (SSNMR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing properties of CdO/Al2O3/CeO2 to ethanol were further studied and compared with CdO/Al2O3 prepared from CdAl LDH, CeO2 powder as well as the calcined Ce salt. It turns out that CdO/Al2O3/CeO2 sensor shows best performance in ethanol response. Besides, CdO/Al2O3/CeO2 possesses short response/recovery time (12/72 s) as well as remarkable selectivity in ethanol sensing, which means composite oxides prepared from LDH are very promising in gas sensing application.

  15. Enhanced photoluminescence of Ca2Al2SiO7:Eu3+ by charge compensation method

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Wang, J.; Zhang, M.; Ding, W.; Su, Q.

    2007-09-01

    The effect of compensator on optical properties of Ca2Al2SiO7:Eu3+ is systematically investigated by the X-ray powder diffraction, photo-luminescence (PL) properties and lifetime. It is obviously observed that the PL intensity of Eu3+ under 394 nm excitation increases in the order of Ca1.86Eu0.14Al2SiO7 (CAS), Ca1.72Na0.14Eu0.14Al2SiO7 (CASNa) and Ca1.86Eu0.14Al2.14Si0.86O7 (CASAl), the intensity of Eu3+ are 100%, 134%, 184%, and the lifetime of Eu3+ are 0.75 ms, 1.28 ms and 1.39 ms, respectively. A charge compensation model is proposed to explain the changes in the emission intensity and lifetime of Eu3+ in Ca2Al2SiO7 with different compensation methods.

  16. Photoluminescence and thermoluminescence studies of CaAl2O4:Dy(3+) phosphor.

    PubMed

    Ziyauddin, Mohammad; Tigga, Shalinta; Brahme, Nameeta; Bisen, D P

    2016-02-01

    Calcium aluminate phosphors activated by Dy(3+) have been prepared by a combustion method at a temperature of 600°C. Photoluminescence (PL) and thermoluminescence (TL) properties of gamma-irradiated Dy-doped calcium aluminate were investigated. The PL spectrum shows a broad peak around 488 nm and 573 nm, under 347 nm excitation. Thermoluminescence studies were performed for different concentrations of Dy. Optimum intensity of photoluminescence was found for 0.02 mol% concentration of Dy. It was found that initially the peak TL intensity increases with increasing concentration of Dy in the CaAl2O4 host, attains a maximum value for 0.05 mol% concentration and decreases with further increase in the doping concentration due to concentration quenching. PMID:25920456

  17. Evolution of Ca-Al-rich bodies in the earliest solar system Growth by incorporation

    NASA Technical Reports Server (NTRS)

    Wark, D. A.; Lovering, J. F.

    1982-01-01

    Thirty different Allende Ca-Al-rich inclusions (CAIs), 11 of type A and 19 of type B, were examined for spinel palisades and framboids, and the possible origins of these structures are discussed. Possible mechanisms for in situ formation of palisades are assessed, all of them either being rejected outright or considered highly implausible. The evidence for external formation and incorporation of palisade bodies is then assessed, and possible mechanisms are considered. It is proposed that type B CAIs are residues from the heating and incomplete evaporation of interstellar dust during the accretion of the protosolar nebula, and that type A CAIs are later condensates from completely evaporated dust whose exotic O-16-rich component became more diluted in the gas phase.

  18. Properties and performance of the LiCaAlF6:Cr3+ laser material

    NASA Astrophysics Data System (ADS)

    Payne, Stephen A.; Chase, Lloyd L.; Atherton, L. Jeffrey; Caird, John A.; Kway, Wayne L.; Shinn, Michelle D.; Hughes, Robert S.; Smith, Larry K.

    1990-04-01

    The laser properties of the LiCaAlF6:Cr3+ (Cr:LiCAF) material are reviewed. The impact of the absorption and emission spectra on the laser performance is discussed. Laser-pumping and flashlamp-pumping experiments have shown that Cr:LiCAF has potential for high efficiency, although the presence of scattering losses remains a significant problem. The "gradient freeze" growth technique has been found to generate lower-loss material compared to Czochralski growth. The thermal lensing of Cr:LiCAF has been measured to be small and is in rough agreement with the magnitude expected on the basis of the intrinsic thermo-optical properties.

  19. Growth and spectral characters of Nd:CaGdAlO4 crystal

    NASA Astrophysics Data System (ADS)

    Di, Juqing; Sun, Xiaohui; Xu, Xiaodong; Xia, Changtai; Sai, Qinglin; Yu, Haohai; Wang, Yicheng; Zhu, Liu; Gao, Yuan; Guo, Xueyi

    2016-04-01

    In this paper, crystal growth and polarized spectra of Nd:CaGdAlO4 (Nd:CALGO) crystal were reported. The maximal absorption cross-sections are 6.8 and 7.5 × 10-20 cm2 for π-polarization and σ-polarization, and the emission cross-sections are 12.5 × 10-20 cm2 with full width at half maximum (FWHM) of 18 and 11 nm, respectively. The Judd-Ofelt (JO) theory was used to calculate the spectral parameters and the effective intensity parameters Ω2, Ω4 and Ω6 were 0.8 × 10-20 cm2, 7.5 × 10-20 cm2 and 5.8 × 10-20 cm2, respectively. The lifetime was 123 μs. The results show that Nd:CALGO crystal is a promising medium for laser output.

  20. Hydrogen reduction of wustite single crystals doped with Mg, Mn, Ca, Al, and Si

    NASA Astrophysics Data System (ADS)

    Moukassi, M.; Gougeon, M.; Steinmetz, P.; Dupre, B.; Gleitzer, C.

    1984-06-01

    In order to investigate the reduction mechanism of wustite in the presence of impurities usually met in the ironmaking industry, single crystals have been prepared with Mg, Mn, Ca, Al, and Si as dopants. The amounts of dopant in the lattice is around 4,4,2.5,0.5, and 0.01 mol pct, respectively, at 800 ‡C. For reduction with pure hydrogen, from 600 to 950 ‡C, Ca is the most efficient for accelerating the process at high degrees of reduction (75 pct) Mg and Mn are also active in this respect. Al has only a slowing down effect. Si also slows down the reaction at temperatures between 600 < T < 850 ‡C, but it becomes accelerating at T > 850 ‡C. In the presence of 20 torrs of water vapor in the gas, Mg and Mn are less efficient and unable to prevent the same slowing down of reaction observed with pure wustite at around 850 ‡C and classically called the ‡rate minimum‡. Our interpretation of these results is mainly based upon the observations of microstructures of partly reduced crystals which show a change in the texture of the iron produced which can be correlated with the reduction rate. These observations lead to a possible explanation in terms of the role of inclusions of impurity oxides on the sintering process of the metal, correlated with their ability to dissolve into the wustite lattice. However, this suggestion cannot apply in the case of Si at low temperatures, and this element is therefore supposed to play a role in the stages of reaction associated with the surface of the crystals.

  1. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-09-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage ( C- V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage ( R- V) characteristics of variable-area photodiodes. The minority carrier lifetime, C- V characteristics, and R- V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  2. Passivation Effect of Atomic Layer Deposition of Al2O3 Film on HgCdTe Infrared Detectors

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Ye, Zhen-Hua; Sun, Chang-Hong; Chen, Yi-Yu; Zhang, Tian-Ning; Chen, Xin; Lin, Chun; Ding, Ring-Jun; He, Li

    2016-06-01

    The passivation effect of atomic layer deposition of (ALD) Al2O3 film on a HgCdTe infrared detector was investigated in this work. The passivation effect of Al2O3 film was evaluated by measuring the minority carrier lifetime, capacitance versus voltage (C-V) characteristics of metal-insulator-semiconductor devices, and resistance versus voltage (R-V) characteristics of variable-area photodiodes. The minority carrier lifetime, C-V characteristics, and R-V characteristics of HgCdTe devices passivated by ALD Al2O3 film was comparable to those of HgCdTe devices passivated by e-beam evaporation of ZnS/CdTe film. However, the baking stability of devices passivated by Al2O3 film is inferior to that of devices passivated by ZnS/CdTe film. In future work, by optimizing the ALD Al2O3 film growing process and annealing conditions, it may be feasible to achieve both excellent electrical properties and good baking stability.

  3. Effects of Al2O3 and CaO/SiO2 Ratio on Phase Equilbria in the ZnO-"FeO"-Al2O3-CaO-SiO2 System in Equilibrium with Metallic Iron

    NASA Astrophysics Data System (ADS)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2011-02-01

    The phase equilibria and liquidus temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2 system in equilibrium with metallic iron have been determined experimentally in the temperature range 1383 K to 1573 K (1150 °C to 1300 °C). The experimental conditions were selected to characterize lead blast furnace and imperial smelting furnace slags. The results are presented in a form of pseudoternary sections ZnO-"FeO"-(Al2O3 + CaO + SiO2) with fixed CaO/SiO2 and (CaO + SiO2)/Al2O3 ratios. It was found that wustite and spinel are the major primary phases in the composition range investigated. Effects of Al2O3 concentration as well as the CaO/SiO2 ratio on the primary phase field, the liquidus temperature, and the partitioning of ZnO between liquid and solid phases have been discussed for zinc-containing slags.

  4. Ultrasonically-enhanced mechanochemical synthesis of CaAl-layered double hydroxides intercalated by a variety of inorganic anions.

    PubMed

    Szabados, Márton; Mészáros, Rebeka; Erdei, Szabolcs; Kónya, Zoltán; Kukovecz, Ákos; Sipos, Pál; Pálinkó, István

    2016-07-01

    CaAl-layered double hydroxides (CaAl-LDHs) were synthesised with various interlayer anions (CO3(2-), F(-), Cl(-), Br(-) and I(-)) by mechanochemical pre-treatment followed by ultrasonic irradiation in aqueous media. The parameters of the syntheses (duration of pre-milling and sonication, quality of the aqueous media, temperature) were altered in order to optimise the procedure and to understand the formation of LDH and other secondary products. The products were characterised by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The optimisation resulted in close-to-phase-pure CaAl-LDHs, not only with carbonate and chloride interlayer anions, but the hard-to-intercalate bromide and iodide as well. PMID:26964966

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

    PubMed

    Ling, Chen; Zhang, Ruigang; Jia, Hongfei

    2015-07-01

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

  6. Band bending at Al, In, Ag, and Pt interfaces with CdTe and ZnTe (110)

    NASA Technical Reports Server (NTRS)

    Wahi, A. K.; Miyano, K.; Carey, G. P.; Chiang, T. T.; Lindau, I.

    1990-01-01

    UV and X-ray photoelectron spectroscopic methods are presently used to study the band-bending behavior and interfacial chemistry of Al, In, Ag, and Pt overlayers on vacuum-cleaved p-CdTe and p-ZnTe (110). All four metals are found to yield Schottky barriers on CdTe and ZnTe. The metal-induced gap states model prediction of a difference in barrier heights for two semiconductors which is dependent on their band lineup is borne out by the results for Ag, Pt, and Al, but not for In. Reaction and intermixing for Al, Ag, and Pt overlayers on CdTe and ZnTe indicate that these interfaces are not ideal.

  7. Free-electron-like Hall effect and deviations from free-electron behavior in Ca-Al amorphous alloys

    NASA Astrophysics Data System (ADS)

    Mayeya, F. M.; Hickey, B. J.; Howson, M. A.

    1995-06-01

    The Hall coefficients of Ca-Al amorphous alloys have been measured at 4.2 K over a wide range of compositions. It is shown that the magnitude of the Hall coefficients are close to the nearly-free-electron (NFE) prediction for low Ca concentrations but deviate significantly from the NFE values for Ca concentration greater than 45 at. %. The deviations from the free-electron values have previously been attributed to the effects of s-d hybridization, while a reduction in magnitude by Au doping has been argued to result from the side-jump effect.

  8. Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

    NASA Astrophysics Data System (ADS)

    Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Karim, Saniah Ab; Zaman, Rosyaini Afindi; Ain, Mohd Fadzil; Ahmad, Zainal Arifin; Mohamed, Julie Juliewatty

    2016-07-01

    (1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al2O3 was reduced both dielectric loss and permittivity at least for an order of magnitude.

  9. Thermally and optically stimulated radiative processes in Eu and Y co-doped LiCaAlF6 crystal

    NASA Astrophysics Data System (ADS)

    Fukuda, Kentaro; Yanagida, Takayuki; Fujimoto, Yutaka

    2015-06-01

    Yttrium co-doping was attempted to enhance dosimeter performance of Eu doped LiCaAlF6 crystal. Eu doped and Eu, Y co-doped LiCaAlF6 were prepared by the micro-pulling-down technique, and their dosimeter characteristics such as optically stimulated luminescence (OSL) and thermally stimulated luminescence (TSL) were investigated. By yttrium co-doping, emission intensities of OSL and TSL were enhanced by some orders of magnitude. In contrast, scintillation characteristics of yttrium co-doped crystal such as intensity of prompt luminescence induced by X-ray and light yield under neutron irradiation were degraded.

  10. Effect of salinity on the skeletal chemistry of cultured scleractinian zooxanthellate corals: Cd/Ca ratio as a potential proxy for salinity reconstruction

    NASA Astrophysics Data System (ADS)

    Pretet, Chloé; Reynaud, Stéphanie; Ferrier-Pagès, Christine; Gattuso, Jean-Pierre; Kamber, Balz S.; Samankassou, Elias

    2014-03-01

    The effect of salinity on the elemental and isotopic skeletal composition of modern zooxanthellate scleractinian corals ( Acropora sp., Montipora verrucosa and Stylophora pistillata) was investigated in order to evaluate potential salinity proxies. Corals were cultured in the laboratory at three salinities (36, 38 and 40). The other environmental parameters were kept constant. For all species analyzed, Sr/Ca, Mg/Ca, U/Ca and Li/Ca ratios were not influenced by salinity changes. The Ba/Ca ratio also lacks a systematic relationship with salinity and exhibits high inter-generic variations, up to one order of magnitude. On the contrary, the Cd/Ca ratio decreases as a function of increasing salinity, and δ18O and δ13C also presented a significant response, but with opposite trends to salinity variations. Since Cd/Ca is usually considered as an upwelling proxy, its salinity dependence could compromise the upwelling signal, unless some corrections can be carried out. Regardless, if the dependence found in the present dataset proved to be widespread and systematic, the Cd/Ca ratio could represent a promising salinometer awaiting further investigation. This study also confirmed the reliability of the well-established temperature proxies Sr/Ca, Mg/Ca and U/Ca, as these ratios were insensitive to salinity variations. Moreover, our results showed that δ18O or δ13C can be considered as reliable temperature recorders as far as the salinity effect is removed from the parameter reconstructed (e.g., temperature). Investigating the influence of salinity on the skeletal chemistry of scleractinian corals grown under controlled environmental conditions confirmed previous results, validated isotopic corrections, and identified a promising proxy of salinity.

  11. Evaluating controlling factors to Al(i)/(Ca + Mg) molar ratio in acidic soil water, southern and southwestern China: multivariate approach.

    PubMed

    Guo, Jing-Heng; Zhang, Xiao-Shan; Vogt, Rolf D; Xiao, Jin-Song; Zhao, Da-Wei; Xiang, Ren-Jun; Luo, Jia-Hai

    2007-06-01

    Al(i)/(Ca + Mg) molar ratio in soil water has been used as an indicator to the effects of acid deposition on terrestrial ecosystems. However, the main factors controlling this ratio have not been well documented in southern and southwestern China. In this study, we presented the variation in inorganic aluminum (Al(i)) and Al(i)/(Ca + Mg) molar ratio in different sites and soil horizons based on two to three years monitoring data, and evaluated the main factors controlling Al(i)/(Ca + Mg) molar ratio using principle component analysis (PCA) and partial least square (PLS) regression. Monitoring data showed although Al(i)/(Ca + Mg) molar ratios in most soil water were lower than assumed critical 1.0, higher molar ratios were found in some soil water at TSP and LXH site. Besides acid loading, both soil properties and soil water chemistry affected the value of Al(i)/(Ca + Mg) molar ratio in soil water. Partial least square (PLS) indicated that they had different relative importance in different soil horizons. In A-horizon, soil aluminum saturation (AlS) had higher influence on Al(i)/(Ca + Mg) molar ratio than soil water chemistry did; higher soil aluminum saturation (AlS) led to higher Al(i)/(Ca + Mg) molar ratio in soil water. In the deeper horizons (i.e., B(1)-, B(2)- and BC-horizon), inorganic aluminum (Al(i)) in soil water had more and more important role in regulating Al(i)/(Ca + Mg) molar ratio. On regional scale, soil aluminum saturation (AlS) as well as cation exchange capacity (CEC) was the dominant factor controlling Al(i)/(Ca + Mg) molar ratio. This should be paid enough attention on when making regional acid rain control policy in China. PMID:17057971

  12. Magnetic-field tunable THz detectors based on GaAs/AlGaAs and CdTe/CdMgTe quantum wells

    NASA Astrophysics Data System (ADS)

    Łusakowski, J.; Białek, M.; Grigelionis, I.; Adamus, Z.; Wróbel, J.; Umansky, V.; Karczewski, G.; Wojtowicz, T.; Grynberg, M.

    2014-09-01

    Magnetic-field tunable semiconductor detectors are used in THz spectroscopy due to their sensitivity and possibility to respond to photons in a broad frequency range. We compare THz detectors processed on high electron mobility GaAs/GaAlAs and CdTe/CdMgTe quantum wells. Transmission, photocurrent and photovoltage measurements were carried out as a function of the magnetic field at a constant energy of incident THz photons from a THz laser. The samples investigated were grid-gated and grid-free. The spectra show features resulting from excitation of the cyclotron resonance and magnetoplasmons. Theoretical models allow to analyze quantitatively the frequency of observed excitations and determine plasmon dispersion relations. This study allows to point at advantages and disadvantages of THz cyclotron-resonance and plasmonic detectors fabricated on GaAs- and CdTe-based quantum wells as well as to compare these two types of devices.

  13. Investigation of Al doping concentration effect on the structural and optical properties of the nanostructured CdO thin film

    NASA Astrophysics Data System (ADS)

    Gencer Imer, Arife

    2016-04-01

    Nanostructured aluminium (Al) doped cadmium oxide (CdO) films with highly electrical conductivity and optical transparency have been deposited for the first time on soda-lime glass substrates preheated at 250 °C by ultrasonic spray coating technique. The aluminium dopant content in the CdO film was changed from 0 to 5 at%. The influencing of Al doping on the structural, morphological, electrical and optical properties of the CdO nanostructured films has been investigated. Atomic force microscopy study showed the grain size of the films is an order of nanometers, and it decreases with increase in Al dopant content. All the films having cubic structure with a lattice parameter 4.69 Å were determined via X ray diffraction analysis. The optical band gap value of the films, obtained by optical absorption, was found to increase with Al doping. Electrical studies exhibited mobility, carrier concentration and resistivity of the film strongly dependent on the doping content. It has been evaluated that optical band gap, and grain size of the nanostructured CdO film could be modified by Al doping.

  14. Particulate contacts to Si and CdTe: Al, Ag, Hg-Cu-Te, and Sb-Te

    NASA Astrophysics Data System (ADS)

    Schulz, Douglas L.; Ribelin, Rosine; Curtis, Calvin J.; Ginley, David S.

    1999-03-01

    Our team has been investigating the use of particle-based contacts in both Si and CdTe solar cell technologies. First, in the area of contacts to Si, powders of Al and Ag prepared by an electroexplosion process have been characterized by transmission electron microscopy (TEM), TEM elemental determination X-ray spectroscopy (TEM-EDS), and TEM electron diffraction (TEM-ED). These Al and Ag particles were slurried and tested as contacts to p- and n-type silicon wafers, respectively. Linear current-voltage (I-V) was observed for Ag on n-type Si, indicative of an ohmic contact, whereas the Al on p-type Si sample was non-ideal. A wet-chemical surface treatment was performed on one Al sample and TEM-EDS indicated a substantial decrease in the O contaminant level. The treated Al on p-type Si films exhibited linear I-V after annealing. Second, in the area of contacts to CdTe, particles of Hg-Cu-Te and Sb-Te have been applied as contacts to CdTe/CdS/SnO2 heterostructures prepared by the standard NREL protocol. First, Hg-Cu-Te and Sb-Te were prepared by a metathesis reaction. After CdCl2 treatment and NP etch of the CdTe layer, particle contacts were applied. The Hg-Cu-Te contacted cells exhibited good electrical characteristics, with Voc>810 mV and efficiencies > 11.5% for most cells. Although Voc>800 mV were observed for the Sb-Te contacted cells, efficiencies in these devices were limited to 9.1% presumably by a large series resistance (>20 Ω) observed in all samples.

  15. Microstructural and Mössbauer properties of low temperature synthesized Ni-Cd-Al ferrite nanoparticles

    PubMed Central

    2011-01-01

    We report the influence of Al3+ doping on the microstructural and Mössbauer properties of ferrite nanoparticles of basic composition Ni0.2Cd0.3Fe2.5 - xAlxO4 (0.0 ≤ x ≤ 0.5) prepared through simple sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray, transmission electron microscopy (TEM), Fourier transformation infrared (FTIR), and Mössbauer spectroscopy techniques were used to investigate the structural, chemical, and Mössbauer properties of the grown nanoparticles. XRD results confirm that all the samples are single-phase cubic spinel in structure excluding the presence of any secondary phase corresponding to any structure. SEM micrographs show the synthesized nanoparticles are agglomerated but spherical in shape. The average crystallite size of the grown nanoparticles was calculated through Scherrer formula and confirmed by TEM and was found between 2 and 8 nm (± 1). FTIR results show the presence of two vibrational bands corresponding to tetrahedral and octahedral sites. Mössbauer spectroscopy shows that all the samples exhibit superparamagnetism, and the quadrupole interaction increases with the substitution of Al3+ ions. PMID:21851597

  16. Accelerator mass spectrometry with fully stripped 26Al, 63Cl, 41Ca and (su59)Ni ions

    NASA Astrophysics Data System (ADS)

    Faestermann, H.; Kato, K.; Korschinek, G.; Krauthan, P.; Nolte, E.; Rühm, W.; Zerle, L.

    1990-04-01

    The detection system of accelerator mass spectrometry (AMS) with completely stripped ions of 26Al, 36Cl, 41Ca and 59Ni at the Munich accelerator laboratory and measurements with these ions are presented. Detection limits are given. The presented applications are: dating of groundwater of the Milk River aquifer and deduction of the neutron fluence and spectrum of the Hiroshima A-bomb.

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

    SciTech Connect

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

    1990-03-01

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

  18. Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls MNi(CO)3 (-) (M = Mg, Ca, Al).

    PubMed

    Xie, Hua; Zou, Jinghan; Yuan, Qinqin; Fan, Hongjun; Tang, Zichao; Jiang, Ling

    2016-03-28

    The heteronuclear metal carbonyl anions MNi(CO)3 (-) (M = Mg, Ca, Al) have been investigated using photoelectron velocity-map imaging spectroscopy. Electron affinities of neutral MNi(CO)3 (M = Mg, Ca, Al) are measured from the photoelectron spectra to be 1.064 ± 0.063, 1.050 ± 0.064, and 1.541 ± 0.040 eV, respectively. The C-O stretching mode in these three clusters is observed and the vibrational frequency is determined to be 2049, 2000, and 2041 cm(-1) for MgNi(CO)3, CaNi(CO)3, and AlNi(CO)3, respectively. Density functional theory calculations are carried out to elucidate the geometric and electronic structures and to aid the experimental assignments. It has been found that three terminal carbonyls are preferentially bonded to the nickel atom in these heterobinuclear nickel carbonyls MNi(CO)3 (-1/0), resulting in the formation of the Ni(CO)3 motif. Ni remains the 18-electron configuration for MgNi(CO)3 and CaNi(CO)3 neutrals, but not for AlNi(CO)3. This is different from the homobinuclear nickel carbonyl Ni-Ni(CO)3 with the involvement of three bridging ligands. Present findings would be helpful for understanding CO adsorption on alloy surfaces. PMID:27036444

  19. Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls MNi(CO)3- (M = Mg, Ca, Al)

    NASA Astrophysics Data System (ADS)

    Xie, Hua; Zou, Jinghan; Yuan, Qinqin; Fan, Hongjun; Tang, Zichao; Jiang, Ling

    2016-03-01

    The heteronuclear metal carbonyl anions MNi(CO)3- (M = Mg, Ca, Al) have been investigated using photoelectron velocity-map imaging spectroscopy. Electron affinities of neutral MNi(CO)3 (M = Mg, Ca, Al) are measured from the photoelectron spectra to be 1.064 ± 0.063, 1.050 ± 0.064, and 1.541 ± 0.040 eV, respectively. The C-O stretching mode in these three clusters is observed and the vibrational frequency is determined to be 2049, 2000, and 2041 cm-1 for MgNi(CO)3, CaNi(CO)3, and AlNi(CO)3, respectively. Density functional theory calculations are carried out to elucidate the geometric and electronic structures and to aid the experimental assignments. It has been found that three terminal carbonyls are preferentially bonded to the nickel atom in these heterobinuclear nickel carbonyls MNi(CO)3-1/0, resulting in the formation of the Ni(CO)3 motif. Ni remains the 18-electron configuration for MgNi(CO)3 and CaNi(CO)3 neutrals, but not for AlNi(CO)3. This is different from the homobinuclear nickel carbonyl Ni-Ni(CO)3 with the involvement of three bridging ligands. Present findings would be helpful for understanding CO adsorption on alloy surfaces.

  20. Stabilization of moisture-reactive raw materials for improved synthesis of Ca-α-SiAlON:Eu2+ phosphor

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Myung; Kim, Mi-Ju; Lee, Jae-Wook; Park, Young-Jo

    2014-09-01

    The raw materials needed to make the Ca-α-SiAlON:Eu2+ phosphor contain highly moisture-reactive Ca3N2. Exposing them to a preheating process prior to high-temperature synthesis stabilized the raw materials against oxidation. Preheating above 1200 °C in a tube furnace directly connected to a glove box, resulted in the formation of intermediate phases such as CaAlSiN3, which provided higher moisture resistance to the raw materials. We found that even after exposure to a humid environment, the preheated samples maintained PL characteristics similar to the conventional unexposed samples, while the PL intensity and particle homogeneity of the un-preheated samples were severely deteriorated.

  1. Synthesis and characterization of CdS/CuAl2O4 core-shell: application to photocatalytic eosin degradation

    NASA Astrophysics Data System (ADS)

    Bellal, B.; Trari, M.; Afalfiz, A.

    2015-08-01

    The advantages of the hetero-junction CdS/CuAl2O4 for the photocatalytic eosin degradation are reported. Composite semiconductors are elaborated by co-precipitation of CdS on the spinel CuAl2O4 giving a core-shell structure with a uniform dispersion and intimate contact of the spinel nanoparticles inside the hexagonal CdS. The Mott-Schottky plots ( C -2- V) of both materials show linear behaviors from which flat band potentials are determined. The photoactivity increases with increasing the mass of the sensitizer CdS and the best performance is achieved on CdS/CuAl2O4 (85 %/15 %). The pH has a strong influence on the degradation and the photoactivity peaks at pH 7.78. The dark adsorption eosin is weak (~4 %), hence the change in the eosin concentration is attributed to the photocatalytic process. The degradation follows a zero-order kinetic with a rate constant of 5.2 × 10-8 mol L-1 mn-1 while that of the photolysis is seven times lower (0.75 × 10-8 mol L-1 mn-1).

  2. Czochralski growth of single-crystal gehlenite (Ca 2Al 2SiO 7)

    NASA Astrophysics Data System (ADS)

    Finch, C. B.; Ball, F. L.; Bates, J. B.

    1981-09-01

    Single-crystal boules of gehlenite (Ca 2Al 2SiO 7) were grown from even- and off-stoichiometry melts under differing conditions of oxygen fugacity (ƒ O2). Growth was accomplished by the Czochralski method at 1600°C and 10 5 Pa (1 atm) total pressure, using inductively heated Ir or Pt-20%Rh crucibles. The supra melt gas ambients included air ( ƒ O2 = 0.2 × 10 4Pa), Ar (10 Pa), Ar-50%CO 2-2%H 2 (10 -2 Pa), and Ar-4%H 2-1.5%H 2O (10 -4 Pa). Colorless, transparent material up to 8 mm diam. by 15 mm long was obtained from the evenly stoichiometric melt composition under Ar at growth rates of 1.5 mm/h or less. Growth at rates exceeding 2 mm/h or growth at a high ƒ O2 (e.g., air), led to the formation of bubbles and elongated voids or inclusions, predominantly in the core regions of boules. Optical, X-ray diffraction, and electron-induced X-ray flourescence data are included.

  3. Experimentally Produced Spinel Rims on Ca-Al-Rich Inclusion Bulk Compositions

    NASA Technical Reports Server (NTRS)

    Paque, Julie M.; Le, L.; Lofgren, G. E.

    1998-01-01

    Most Ca-Al-rich inclusions (CAls) from Allende are surrounded by a series of mineralogically distinct rim layers. Proposed modes of formation for these layers include flash heating, evaporation, and condensation. The innermost of these rim layers is generally spinel (SP), in some cases intergrown with perovskite (PV), and commonly containing varying amounts of secondary iron increasing towards the edge of the CAI. The SP or SP+PV rim is not always contiguous with the other rim layers, indicating that it is probably the result of a separate event. We have produced continuous SP rims on synthetic analogs representing Type A/B1, average Type B, and Type B2 bulk compositions by reheating a solid glass experimental charge to subliquidus crystallization temperatures. This experimental result is consistent with the formation of chondrules; and CAIs by more than one sequence of heating and cooling. Previous work indicated that prior crystallization events produced observable effects in the texture and chemistry of the final run product. Information on the nature of the heating/cooling cycles experienced by CAls and chondrules is important in modeling the environment of their formation. Additional information is contained in the original extended abstract.

  4. Discharge properties of Mg-Al-Mn-Ca and Mg-Al-Mn alloys as anode materials for primary magnesium-air batteries

    NASA Astrophysics Data System (ADS)

    Yuasa, Motohiro; Huang, Xinsheng; Suzuki, Kazutaka; Mabuchi, Mamoru; Chino, Yasumasa

    2015-11-01

    The discharge behaviors of rolled Mg-6 mass%Al-0.3 mass%Mn-2 mass%Ca (AMX602) and Mg-6 mass%Al-0.3 mass%Mn (AM60) alloys used as anodes for Magnesium-air batteries were investigated. The AMX602 alloy exhibited superior discharge properties compared to the AM60 alloy, especially at low current density. The discharge products of the AMX602 alloy were dense and thin, and many cracks were observed at all current densities. In addition, the discharge products were detached at some sites. These sites often corresponded to the positions of Al2Ca particles. The comparison of the discharge and corrosion tests indicated that the dense and thin discharge products of AMX602 were easily cracked by dissolution of the Mg matrix around Al2Ca particles, and the cracks promoted the penetration of the electrolyte into the discharge products, retaining the discharge activity. In contrast, concerning the AM60 alloy, thick discharge products were formed on the surface during discharge, and cracking of the discharge products hardly occurred, degrading the discharge properties. Localized and deeply corroded pits that could result from the detachment of metal pieces from the anode during discharge were partly observed in the AM60 alloy. It is suggested that these detached metal pieces are another reason for the low discharge properties of the AM60 alloy.

  5. Nucleosynthetic W isotope anomalies and the Hf-W chronometry of Ca-Al-rich inclusions

    NASA Astrophysics Data System (ADS)

    Kruijer, Thomas S.; Kleine, Thorsten; Fischer-Gödde, Mario; Burkhardt, Christoph; Wieler, Rainer

    2014-10-01

    Ca-Al-rich inclusions (CAI) are the oldest dated objects formed in the solar system and are pivotal reference points in early solar system chronology. Knowledge of their initial 182Hf/180Hf and 182W/184W is essential, not only for obtaining precise Hf-W ages relative to the start of the solar system, but also to assess the distribution of short-lived radionuclides in the early solar nebula. However, the interpretation of Hf-W data for CAI is complicated by nucleosynthetic W isotope variations. To explore their extent and nature, and to better quantify the initial Hf and W isotope compositions of the solar system, we obtained Hf-W data for several fine- and coarse-grained CAI from three CV3 chondrites. The fine-grained CAI exhibit large and variable anomalies in ε183W (εiW equals 0.01% deviation from terrestrial values), extending to much larger anomalies than previously observed in CAI, and reflecting variable abundances of s- and r-process W isotopes. Conversely, the coarse-grained (mostly type B) inclusions show only small (if any) nucleosynthetic W isotope anomalies. The investigated CAI define a precise correlation between initial ε182W and ε183W, providing a direct empirical means to correct the ε182W of any CAI for nucleosynthetic isotope anomalies using their measured ε183W. After correction for nucleosynthetic W isotope variations, the CAI data define an initial 182Hf/180Hf of (1.018±0.043)×10-4 and an initial ε182W of -3.49±0.07. The Hf-W formation intervals of the angrites D'Orbigny and Sahara 99555 relative to this CAI initial is 4.8±0.6 Ma, in good agreement with Al-Mg ages of these two angrites. This renders a grossly heterogeneous distribution of 26Al in the inner solar system unlikely, at least in the region were CAI and angrites formed.

  6. Constraints on Titanite Acitvity in the System CaTiSiO4O-CaAlSiO4F: Implications for Thermobarometry in Metamorphic Rocks

    NASA Astrophysics Data System (ADS)

    Tropper, P.; Manning, C. E.; Essene, E. J.

    2006-12-01

    Titanite is a common accessory mineral that could be used reliably in phase equilibrium calculations, if activity-composition relations in Al-F titanites were known. Troitzsch and Ellis (2001, CMP, 142, 543) and Tropper et al. (2002, JPet., 43, 1787) gave non-ideal mixing models along the join CaTiSiO4O- CaAlSiO4F. Tropper et al. (2002) derived a negative interaction parameter W, whereas Troitzsch and Ellis (2001) derived a regular model with both positive and negative W, but favored positive values. These differences strongly influence calculated CaTiSiO4O activity (attn). Although more experiments are needed, our result that γttn<1 at high T indicates a large degree of non-ideal behavior, even at >900°C, which in turn will affect thermobarometry. Comparing available activity models shows that at these T, attn is substantially underestimated by the fully ionic model used by Manning and Bohlen (1991, CMP, 109, 1), in which attn = XCaXTiXSi(XO)5. This model assumes independent mixing of Al for Ti and random mixing of F and O on all O sites. However, F substitutes only in one O site (O1; Oberti et al., 1991, EJM, 3, 777). A fully ionic model should therefore be recast as attn = XCaXTiXSiXO, where XO indicates the mole fraction of O on the (O1) site. The substitution of F on the O1 site is coupled with Al, so it is called the ideal coupled model. Unlike the regular model, the prefered ionic model departs strongly from ideality at ≤600°C, consistent with independent constraints. However, experimentally determined attn is approximated by an ideal molecular model (XTi) at ≥900°C, so this model is recommended for thermobarometry in high- T metamorphic rocks until more data are available. Recalculation of the P recorded by the three eclogites from Manning and Bohlen (1991) using the different activity models discussed here yields differences that may be as high as 2.0 GPa.

  7. Microstructure and Fatigue Behavior of Friction Stir-welded Noncombustive Mg-9Al-Zn-Ca Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Li, Z. Y.; Nakata, K.; Feng, J. C.; Huang, Y. X.; Liao, J. S.

    2016-06-01

    Microstructure and fatigue behavior of friction stir-welded noncombustive Mg-9Al-Zn-Ca magnesium alloy were investigated. The as-received hot-extruded material consisted of equiaxed α-Mg grains with β-Mg17Al12 and Al2Ca compounds distributed along the grain boundaries. Friction stir welding produced much refined α-Mg grains accompanied by the dissolution of the eutectic β-Mg17Al12 phase, while Al2Ca phase was dispersed homogenously into the Mg matrix. Friction stir welding produced slightly increased hardness and tensile strength in the defect-free welds compared with the base material due to microstructural refinement and uniform distribution of intermetallic compounds. The load-controlled uniaxial tensile high-cycle fatigue tests indicated that fatigue strength of 90 MPa was obtained for the friction stir-welded joint with fatigue crack initiated basically near the specimen's surface and at the retreating side of the joint. Crack propagation was characterized by cleavage and fatigue striations.

  8. Antiferromagnetism in CaAl2Si2-type CaMn2As2 and SrMn2As2 single crystals

    NASA Astrophysics Data System (ADS)

    Sangeetha, N. S.; Pandey, Abhishek; Benson, Zackery A.; Johnston, D. C.

    Magnetic susceptibility versus temperature χ (T) measurements of CaMn2As2 and SrMn2As2 crystals show clear antiferromagnetic (AFM) transitions at TN ~ 65 K and 120 K,1 respectively. The anisotropic behaviors in χ (T <=TN) suggest that both compounds are noncollinear antiferromagnets which may result either from an intrinsic noncollinear structure or from multiple collinear AFM domains that are not aligned collinearly.2 The χ (T) data at T >TN reveal that both compounds exhibit strong short-range AFM ordering, evidently associated with quasi-two-dimensional spin lattices. The electrical resistivities show insulating ground states with activation energies of ~ 63 meV in CaMn2As2 and 44 meV in SrMn2As2 . The experimental results thus reveal that both (Ca , Sr) Mn2As2 materials are AFM insulators at low temperatures and in analogy with the high Tc cuprates, may be potential parent compounds for CaAl2Si2-type superconductors. Work was supported by the USDOE under Contract No. DE-AC02-07CH11358.

  9. Phase equilibrium and structural properties in the Ca-Al-Si-O system up to the P,T conditions of the Earth's lowermost transition zone.

    NASA Astrophysics Data System (ADS)

    Gréaux, S.; Nishiyama, N.; Kono, Y.; Shinmei, T.; Irifune, T.

    2008-12-01

    Ca- and Al-bearing silicates have been extensively investigated for their importance into the mantle processes. In the transition zone, majorite garnet and Ca-perovskite are reported to be the major hosts of Ca as well as deposits of Al [1]. At higher P, Ca gets completely exsolved from the majorite to the Ca-pv. It is observed that Al plays a significant role in the Ca-Si-O system by inducing new phase equilibriums [2,3,4], and influencing the physical properties of the Ca-pv [5]. It is then suggested that phase transitions and chemical reactions involving Ca- and Al-bearing silicates could conciliate mineralogical results and seismological observations in the region of the transition zone [3,6]. We studied the phase equilibrium at HP-HT in the grossular and anorthite systems using a Kawai-type multi- anvil apparatus up to 25 GPa and 2000 K. Grossular garnet is reported to decompose into a mix of corundum and Ca-pv [3] or to transform into a perovskite of grossular composition [7]. Our study shows that grossular mainly decomposes into a mix of Al-Ca-pv and CAS phase in the same P range and higher T. Anorthite is also found to mainly decompose into a mix of Al-Ca-pv and CAS phase. Despite some Al-content in the Ca-pv, the CAS phase is the major host of Al, which suggests according to previous studies [3,5], a lower solubility of Al into the perovskite structure at high T. The Al-content of the Ca-pv as well as the presence of another Al-rich Ca-bearing silicate in zone of variable temperatures and composition as subducting slabs are discussed for their possible implication into the transition zone processes. [1] T. Irifune, 1994. Nature 370, 131-133 [2] L. Gautron et al., 1996. Phys. Earth Planet. Int. 94, 71-81 [3] N. Takafuji et al., 2002. Phys. Chem. Mineral 29, 532-537 [4] S. Zhai and E. Ito, 2008. Phys. Earth Planet. Int. In press [5] T. Kurashina et al., 2004. Phys. Earth Planet. Int. 145, 67-7 [6] L. Stixrude et al., 1996. Am. Mineral. 81, 1293-1296 [7] H

  10. 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.

  11. Phase equilibria and elements partitioning in zirconolite-rich region of Ca-Zr-Ti-Al-Gd-Si-O system

    SciTech Connect

    Knyazev, O.A.; Stefanovsky, S.V.; Ioudintsev, S.V.; Nikonov, B.S.; Omelianenko, B.I.; Mokhov, A.V.; Yakushev, A.I.

    1997-12-31

    Zirconolite-rich ceramics were produced by the cold crucible melting technique in an air atmosphere, at 1550 {+-} 50 C and 1 atm. Four samples with overall composition (in wt.%): 4.9-14.3 CaO; 19.0-41.3 ZrO{sub 2}; 24.1-42.6 TiO{sub 2}; 1.3-11.3 Al{sub 2}O{sub 3}; 6.8-30.0 Gd{sub 2}O{sub 3}; and 1.1-8.5 SiO{sub 2} have been studied. Total phases in the ceramics consist of major zirconolite and minor rutile, perovskite, zirconia, aluminium titanate, and glass. The Gd{sub 2}O{sub 3} content in zirconolite reaches up to 31.4 wt.% corresponding to the formula: (Ca{sub 0.4},Gd{sub 0.7})Zr{sub 1.0}(Ti{sub 1.4},Al{sub 0.5})O{sub 7.0}. The data on the phase composition agree well with coupled Gd incorporation into the mineral structure: Ca(II) + Ti(IV) = Gd(III) + Al(III), and 2Gd(III) = Ca(II) + Zr(IV). The highest Gd contents observed in the other phases are 25.4% for zirconia, 12.6% in glass, 8.8% in perovskite, and 1.4% for rutile. The rest of the elements` distribution in the samples are analyzed.

  12. Teaching the Modes of Ca[superscript 2+] Transport between the Plasma Membrane and Endoplasmic Reticulum Using a Classic Paper by Kwan et al.

    ERIC Educational Resources Information Center

    Liang, Willmann

    2009-01-01

    This teaching article uses the report by Kwan et al., "Effects of methacholine, thapsigargin, and La[superscript 3+] on plasmalemmal and intracellular Ca[superscript 2+] transport in lacrimal acinar cells," where the effects of Ca[superscript 2+]-mobilizing agents in regulating Ca[superscript 2+] fluxes were examined under various conditions.…

  13. Crustal structure of and boundary between the AlCaPa and Tisza terrains in the Pannonian basin

    NASA Astrophysics Data System (ADS)

    Hetényi, György; Ren, Yong; Dando, Ben; Stuart, Graham W.; Houseman, Gregory A.

    2014-05-01

    The evolution of the Pannonian Basin is strongly linked to that of the surrounding Alpine, Carpathian and Dinaric orogens. The eastward extrusion of Alpine-type basement that accompanied lithospheric thinning must have been accompanied by mantle downwelling and/or subduction along the Carpathians but the motive forces for these movements are debated. The internal structure of the crust within the basin is mostly covered by relatively recent sedimentary infill whose variable thickness further complicates seismic imaging. Palaeomagnetic and geological data have, however, shown that two tectonic terrains of distinct origin: AlCaPa and Tisza, occupy the basin's NW and SE part respectively. The two units have undergone different amounts of extension during opposite orientation rotations (counter-clockwise and clockwise, respectively). The boundary between these two units, known as the Mid-Hungarian Zone, is recognized as a major sinistral shear zone, geophysically clearly marked across the basin by a trough in Bouguer gravity. The Carpathian Basins Project deployed 49 broadband seismological stations perpendicular to the boundary between the AlCaPa and Tisza units. A NW-SE oriented swath of three lines covers a 450 km long and 75 km wide area. We use these and 4 permanent stations to image the crustal structure of and the boundary between AlCaPa and Tisza using the receiver function technique. The measured Moho depths show no significant change in crustal thickness between the two terrains, but the Moho is not or very weakly imaged along a ca. 40 km wide strip centred on the MHZ. Our Moho depths elsewhere in the basin agree with earlier controlled-source seismic results and recent shear-wave velocity models deduced from ambient noise analysis. The lack of a sharp Moho image beneath the MHZ implies that the crust-mantle boundary between AlCaPa and Tisza is not a sharp transition but rather a gradual increase in velocity with depth. The distinct low in gravity anomalies

  14. Preparation of Ca-Si Films on (001) Al2O3 Substrates by an RF Magnetron Sputtering Method and Their Electrical Properties

    NASA Astrophysics Data System (ADS)

    Uehara, Mutsuo; Akiyama, Kensuke; Shimizu, Takao; Matsushima, Masaaki; Uchida, Hiroshi; Kimura, Yoshisato; Funakubo, Hiroshi

    2016-06-01

    The constituent phases, electrical conductivity, and Seebeck coefficient of Ca-Si films deposited on (001) Al2O3 substrates by a radio frequency magnetron sputtering method using a Mg disk target with Ca and Si chips are investigated. X-ray diffraction analysis indicates that the films consist of a single phase of CaSi2, CaSi or Ca5Si3 that are deposited together with the films consisting of a mixture of CaSi2 and CaSi. Films with a CaSi2 or CaSi single phase exhibit a metallic behavior. In contrast, films with a Ca5Si3 single phase show p-type conduction and their Seebeck coefficient reaches 90 μV/K at 400°C.

  15. High-pressure synthesis, crystal structure, and electromagnetic properties of CdRh2O4: an analogous oxide of the postspinel mineral MgAl2O4.

    PubMed

    Wang, Xia; Guo, Yanfeng; Shi, Youguo; Belik, Alexei A; Tsujimoto, Yoshihiro; Yi, Wei; Sun, Ying; Shirako, Yuichi; Arai, Masao; Akaogi, Masaki; Matsushita, Yoshitaka; Yamaura, Kazunari

    2012-06-18

    The postspinel mineral MgAl(2)O(4) exists only under the severe pressure conditions in the subducted oceanic lithosphere in the Earth's deep interior. Here we report that its analogous oxide CdRh(2)O(4) exhibits a structural transition to a quenchable postspinel phase under a high pressure of 6 GPa at 1400 °C, which is within the general pressure range of a conventional single-stage multianvil system. In addition, the complex magnetic contributions to the lattice and metal nonstoichiometry that often complicate investigations of other analogues of MgAl(2)O(4) are absent in CdRh(2)O(4). X-ray crystallography revealed that this postspinel phase has an orthorhombic CaFe(2)O(4) structure, thus making it a practical analogue for investigations into the geophysical role of postspinel MgAl(2)O(4). Replacement of Mg(2+) with Cd(2+) appears to be effective in lowering the pressure required for transition, as was suggested for CdGeO(3). In addition, Rh(3+) could also contribute to this reduction, as many analogous Rh oxides of aluminous and silicic minerals have been quenched from lower-pressure conditions. PMID:22663173

  16. Synthesis and hydration behavior of calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cement

    SciTech Connect

    Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye; Choi, Sung-Woo; Hong, Seong-Hyeon

    2014-02-15

    Calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca{sub 7}ZrAl{sub 6}O{sub 18} was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO{sub 3} coexisted with Ca{sub 7}ZrAl{sub 6}O{sub 18} even at higher temperature (1400 °C). Unexpectedly, Ca{sub 7}ZrAl{sub 6}O{sub 18} synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape. The hydration behavior of Ca{sub 7}ZrAl{sub 6}O{sub 18} was similar to that of Ca{sub 3}Al{sub 2}O{sub 6} (C3A), but the hydration products were Ca{sub 3}Al{sub 2}O{sub 6}·6H{sub 2}O (C3AH6) and several intermediate products. Thus, Zr (or ZrO{sub 2}) stabilized the intermediate hydration products of C3A.

  17. A Density Model Based on the Modified Quasichemical Model and Applied to the NaF-AlF3-CaF2-Al2O3 Electrolyte

    NASA Astrophysics Data System (ADS)

    Robelin, Christian; Chartrand, Patrice

    2007-12-01

    A theoretical model for the density of multicomponent inorganic liquids based on the modified quasichemical model has been presented in a previous article. In the present article, this model is applied to the NaF-AlF3-CaF2-Al2O3 electrolyte. By introducing in the Gibbs energy of the liquid phase, temperature-dependent molar volume expressions for the pure fluorides and oxides, and pressure-dependent excess parameters for the binary (and sometimes higher-order) interactions, it is possible to reproduce, and eventually predict, the molar volume and the density of the multicomponent liquid phase using standard interpolation methods. All available density data for the NaF-AlF3-CaF2-Al2O3 liquid were collected and critically evaluated, and optimized pressure-dependent model parameters have been found. This new volumetric model can be used with Gibbs energy minimization software, to calculate the molar volume and the density of cryolite-based melts used for the electroreduction of alumina in Hall-Héroult cells.

  18. In vitro controlled release of vitamin C from Ca/Al layered double hydroxide drug delivery system.

    PubMed

    Gao, Xiaorui; Chen, Le; Xie, Juan; Yin, Yaobing; Chang, Tao; Duan, Yancong; Jiang, Nan

    2014-06-01

    A new drug delivery system for vitamin C (VC), Ca/Al layered double hydroxide (LDH), is demonstrated in this work. VC anions were intercalated successfully in the Ca/Al LDH gallery by a coprecipitation method. The interlayer space of 9.8Å suggests that VC anions are vertical to the LDH layers in the form of interdigitated bilayer. The loading of VC in LDH is 36.4wt.%. The thermal stability of VC is significantly enhanced after intercalation. In vitro VC release results show that the release time of VC in a phosphate buffer at pH7.4 was significantly extended, and the maximal percentage of VC released is 80% of the total. The Avrami-Erofe'ev equation most satisfactorily explains the release kinetics of VC, which is that the release of VC is mainly dominated by the ion-exchange reaction. PMID:24863197

  19. CN-mayenite Ca12Al14O32(CN)2: Replacing mobile oxygen ions by cyanide ions

    NASA Astrophysics Data System (ADS)

    Schmidt, Alexander; Lerch, Martin; Eufinger, Jens-Peter; Janek, Jürgen; Dolle, Raimund; Wiemhöfer, Hans-Dieter; Tranca, Ionut; Islam, Mazharul M.; Bredow, Thomas; Boysen, Hans; Hoelzel, Markus

    2014-12-01

    CN-mayenite (Ca12Al14O32(CN)2) is a promising candidate for high-temperature CN- conductivity in a solid due to its special structural features. It was prepared by a solid-gas reaction. The transport processes were investigated by means of in situ high-temperature neutron diffraction, impedance spectroscopy and additional Hebb-Wagner measurements. Diffusion pathways and activation energies were determined additionally by quantum-chemical calculations. Ca12Al14O32(CN)2 shows a surprisingly high ionic conductivity of σ = 1.4•10-3 S/cm at 1173 K (Ea = 4.3 eV) and can be considered as first example of a new kind of solid anion conductor with a mobile molecular anion.

  20. X-ray crystal structures of Al-doped (Y,Ca)Ba2Cu3O(7-y) whiskers.

    PubMed

    Bertolotti, Federica; Calore, Leandro; Gervasio, Giuliana; Agostino, Angelo; Truccato, Marco; Operti, Lorenza

    2014-04-01

    Al(+3)-doped (Y,Ca)Ba2Cu3O(7-y) (YBCO) whiskers have been synthesized using a solid-state reaction technique. These materials are promising candidates for solid-state THz applications based on sequences of Josephson Junctions (IJJs). Alumina addition was systematically varied and the effect of aluminium incorporation on the structure has been investigated using single-crystal X-ray diffraction. Aluminium only replaces Cu atoms in the O-Cu-O-Cu chains and a gradual transition from orthorhombic to tetragonal space group occurs, thus increasing the Al content. A gradual modification of the coordination sphere of the copper site has also been observed. The Ca(2+) ion substitutes mainly the Y(3+) ion and also, to a small extent, the Ba(2+) ion. PMID:24675593

  1. The Effects of Cd2+ Concentration on the Structure, Optical and Luminescence Properties of MgAl2O4:x% Cd2+ (0 < x ≤ 1.75) Nanophosphor Prepared by Sol-Gel Method

    NASA Astrophysics Data System (ADS)

    Motloung, S. V.; Dejene, F. B.; Sithole, M. E.; Koao, L. F.; Ntwaeaborwa, O. M.; Swart, H. C.; Motaung, T. E.

    2016-06-01

    Cadmium-doped magnesium aluminate (MgAl2O4:x% Cd2+) powders with different cadmium concentrations (0 < x ≤ 1.75) were prepared by the sol-gel method. Energy dispersive x-ray spectroscopy (EDS) analysis confirmed the presence of the expected elements (Mg, Al, O, and Cd). The x-ray diffraction (XRD) analysis revealed that the powders crystallized into the cubic spinel structure. Cd2+ doping influenced crystallinity of the powder samples. The crystallite size and particle morphology were not affected by variation in the Cd2+ concentration. Ultraviolet-visible spectroscopy (UV-vis) measurements revealed that the band gap of the MgAl2O4 was influenced by Cd2+ doping. Un-doped and Cd2+-doped MgAl2O4 nanophosphors exhibited violet emission at 392 nm. There was no evidence of the emission peak shift, which suggested that all emissions originated from the defects within the host material. Increasing the Cd2+ concentration up-to 0.88 mol.% lead to luminescence intensity enhancement, while further increase of Cd2+ concentration lead to concentration quenching. The critical energy transfer distance (R c) between the neighbouring donors and acceptors was found to be 5.21 Å, suggesting that the multipole-multipole interaction (M-MI) is the major cause of concentration quenching. Commission Internationale de l'Elcairage (CIE) colour coordinates confirmed non-tuneable violet emission with intensity dependent on the Cd2+ concentration.

  2. Stable coordination of the inhibitory Ca2+ ion at MIDAS in integrin CD11b/CD18 by an antibody-derived ligand aspartate: Implications for integrin regulation and structure-based drug design

    PubMed Central

    Mahalingam, Bhuvaneshwari; Ajroud, Kaouther; Alonso, Jose Luis; Anand, Saurabh; Adair, Brian; Horenstein, Alberto L; Malavasi, Fabio; Xiong, Jian-Ping; Arnaout, M. Amin

    2011-01-01

    A central feature of integrin interaction with physiologic ligands is the monodentate binding of a ligand carboxylate to a Mg2+ ion hexacoordinated at the metal-ion-dependent-adhesion site (MIDAS) in the integrin A-domain. This interaction stabilizes the A-domain in the high-affinity state, which is distinguished from the default low-affinity state by tertiary changes in the domain that culminate in cell adhesion. Small molecule ligand-mimetic integrin antagonists act as partial agonists, eliciting similar activating conformational changes in the A-domain, which has contributed to paradoxical adhesion and increased patient mortality in large clinical trials. As with other ligand-mimetic integrin antagonists, the function-blocking monoclonal antibody (mAb) 107 binds MIDAS of integrin CD11b/CD18 A-domain (CD11bA), but in contrast, it favors the inhibitory Ca2+ ion over Mg2+ at MIDAS. We determined the crystal structures of the Fab fragment of mAb 107 complexed to the low- and high-affinity states of CD11bA. Favored binding of Ca2+ at MIDAS is caused by the unusual symmetric bidentate ligation of a Fab-derived ligand Asp to a heptacoordinated MIDAS Ca2+. Binding of Fab 107 to CD11bA did not trigger the activating tertiary changes in the domain or in the full-length integrin. These data show that denticity of the ligand Asp/Glu can modify divalent cation selectivity at MIDAS and hence integrin function. Stabilizing the Ca2+ ion at MIDAS by bidentate ligation to a ligand Asp/Glu may provide one approach for designing pure integrin antagonists. PMID:22095715

  3. Charge transport mechanism analysis of Al/CdS:Sr2+/ITO device under dark and light

    NASA Astrophysics Data System (ADS)

    Datta, Joydeep; Das, Mrinmay; Dey, Arka; Jana, Rajkumar; Ray, Partha Pratim

    2016-05-01

    In this study, we have synthesized CdS:Sr2+ by hydrothermal technique. Material property has been studied by X-ray diffraction (XRD), Scanning electron microscope (SEM) and UV-vis absorption spectroscopy. XRD data revealed that there are mixed phases of CdS and SrS in the synthesized sample. The optical band gap of the material was estimated as 3.15 eV from UV-vis data. The synthesized material has been applied in metal-semiconductor device and transport properties have been analyzed by measuring current-voltage characteristics under dark and light conditions at room temperature. Variation in different device parameters like ideality factor, barrier height and series resistance of Al/CdS:Sr2+/ITO device were analyzed by using Cheung's function.

  4. Investigation of the structural, mechanical, dynamical and thermal properties of CsCaF3 and CsCdF3

    NASA Astrophysics Data System (ADS)

    Salmankurt, Bahadır; Duman, Sıtkı

    2016-04-01

    The structural, mechanical, dynamical and thermal properties of CsCaF3 and CsCdF3 are presented by using an ab initio pseudopotential method and a linear response scheme, within the generalized gradient approximation. The obtained structural and mechanical properties are in good agreement with other available theoretical and experimental studies. The calculated elastic constants of these materials obey the cubic stability conditions. It has been found that CsCaF3 is brittle whereas CsCdF3 has ductile manner. The full phonon dispersion curves of these materials are reported for the first time in the literature. We have found that calculated phonon modes are positive along the all symmetry directions, indicating that these materials are dynamically stable at the cubic structure. The obtained zone-center phonon modes for CsCaF3 (IR data) are found to be 83 (98) cm‑1, 104 (115) cm‑1, 120 cm‑1, 180 (192) cm‑1, 231 (250.5) cm‑1, 361 (374) cm‑1, 446 (449) cm‑1. Also, we have calculated internal energy, Helmholtz free energy, constant-volume specific heat, entropy and Debye temperature as function of temperature. At the 300 K, specific heats are calculated to be 113.36 J mol‑1 K‑1 and 115.58 J mol‑1 K‑1 for CsCaF3 and CsCdF3 ,respectively, which are lower than Doulong–Petit limit (12 472 J mol‑1 K‑1).

  5. Ascorbate, added after irradiation, reduces the mutant yield and alters the spectrum of CD59- mutations in A(L) cells irradiated with high LET carbon ions

    NASA Technical Reports Server (NTRS)

    Ueno, Akiko; Vannais, Diane; Lenarczyk, Marek; Waldren, Charles A.; Chatterjee, A. (Principal Investigator)

    2002-01-01

    It has been reported that X-ray induced HPRT- mutation in cultured human cells is prevented by ascorbate added after irradiation. Mutation extinction is attributed to neutralization by ascorbate, of radiation-induced long-lived radicals (LLR) with half-lives of several hours. We here show that post-irradiation treatment with ascorbate (5 mM added 30 min after radiation) reduces, but does not eliminate, the induction of CD59- mutants in human-hamster hybrid A(L) cells exposed to high-LET carbon ions (LET of 100 KeV/microm). RibCys, [2(R,S)-D-ribo-1',2',3',4'-Tetrahydroxybutyl]-thiazolidene-4(R)-ca riboxylic acid] (4 mM) gave a similar but lesser effect. The lethality of the carbon ions was not altered by these chemicals. Preliminary data are presented that ascorbate also alters the spectrum of CD59- mutations induced by the carbon beam, mainly by reducing the incidence of small mutations and mutants displaying transmissible genomic instability (TGI), while large mutations are unaffected. Our results suggest that LLR are important in initiating TGI.

  6. Structure, thermodynamic and transport properties of CaAl 2Si 2O 8 liquid. Part I: Molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Spera, Frank J.; Nevins, Dean; Ghiorso, Mark; Cutler, Ian

    2009-11-01

    Molecular dynamics simulations for liquid CaAl 2Si 2O 8 have been carried out at 72 state points spanning ranges in density ( ρ: 2398-4327 kg/m 3), temperature ( T: 3490-6100 K) and pressure ( P: 0.84-120 GPa) relevant to geosystems. The atomic scale structure of the melt is determined by analysis of nearest neighbor coordination statistics as a function of T and P. Dramatic structural change occurs as pressure increases especially for 0 < P <20 GPa at all temperatures. Changes in structure are encapsulated by examining the coordination of Si, Al, Ca and O around oxygen and vice versa. Si and Al change from predominantly fourfold at low- P to dominantly sixfold for P >˜ 20 GPa. Pentahedrally coordinated Si and Al in distorted trigonal bipyramids attain abundance maxima corresponding to ˜60% of total (Si, Al)O n at 3-5 GPa and weakly depend on T. The coordination of Ca by oxygen increases from 7 to 10 for 0 < P < 20 GPa and changes slowly for P > 20 GPa at 3500 K. Similar behavior is seen at 6000 K except that the interval of rapid changes occurs at higher pressure. Oxygen with only one nearest Si or Al neighbor (i.e., non-bridging oxygen, NBO) decreases whereas oxygen with two or three nearest neighbors of Si, Al or Ca increases as pressure increases. Changes in melt structure are reflected in the variation of thermodynamic and transport properties of the liquid. Values of the self-diffusivities of Ca, Al, Si and O are fit to a modified Arrhenian expression and compare well to limited laboratory data. Self-diffusivities are best fit using 'low P' and 'high- P' expressions, identical in form but with different parameters, with activation energies and activation volumes in the range 150-200 kJ/mol and +5 to -1 cm 3/mol, respectively. Green-Kubo calculations for liquid shear viscosity are presented and compare well with limited laboratory results. Application of the Eyring model to determine the characteristic size and number of atoms in the activated cluster based

  7. High-pressure phase relations and thermodynamic properties of CaAl 4Si 2O 11 CAS phase

    NASA Astrophysics Data System (ADS)

    Akaogi, M.; Haraguchi, M.; Yaguchi, M.; Kojitani, H.

    2009-03-01

    Phase relations in CaAl4Si2O11 were examined at 12-23 GPa and 1000-1800 °C by multianvil experiments. A three-phase mixture of grossular, kyanite and corundum is stable below about 13 GPa at 1000-1800 °C. At higher pressure and at temperature below about 1200 °C, a mixture of grossular, stishovite and corundum is stable, indicating the decomposition of kyanite. Above about 1200 °C, CaAl4Si2O11 CAS phase is stable at pressure higher than about 13 GPa. The triple point is placed at 14.7 GPa and 1280 °C. The equilibrium boundary of formation of CAS phase from the mixture of grossular, kyanite and corundum has a small negative slope, and that from the mixture of grossular, stishovite and corundum has a strongly negative slope, while the decomposition boundary of kyanite has a small positive slope. Enthalpies of the transitions were measured by high-temperature drop-solution calorimetry. The enthalpy of formation of CaAl4Si2O11 CAS phase from the mixture of grossular, kyanite and corundum was 139.5 ± 15.6 kJ/mol, and that from the mixture of grossular, stishovite and corundum was 94.2 ± 15.4 kJ/mol. The transition boundaries calculated using the measured enthalpy data were consistent with those determined by the high-pressure experiments. The boundaries in this study are placed about 3 GPa higher in pressure and about 200 °C lower in temperature than those by Zhai and Ito [Zhai, S., Ito, E., 2008. Phase relations of CaAl4Si2O11 at high-pressure and high-temperature with implications for subducted continental crust into the deep mantle. Phys. Earth Planet. Inter. 167, 161-167]. Combining the thermodynamic data measured in this study with those in the literature, dissociation boundary of CAS phase into a mixture of Ca-perovskite, corundum and stishovite and that of grossular into Ca-perovskite plus corundum were calculated to further constrain the stability field of CAS phase. The result suggests that the stability of CAS phase would be limited at the bottom of

  8. Effect of Al2O3 on the Viscosity and Structure of CaO-SiO2-MgO-Al2O3-FetO Slags

    NASA Astrophysics Data System (ADS)

    Wang, Zhanjun; Sun, Yongqi; Sridhar, Seetharaman; Zhang, Mei; Guo, Min; Zhang, Zuotai

    2015-04-01

    The present paper provided a fundamental investigation on the effect of Al2O3 on the viscosity and structure of CaO-SiO2-MgO-Al2O3-FetO slags for the purpose of efficiently recycling the valuable elements from the steelmaking slags. The results show that the viscosity of CaO-SiO2-Al2O3-MgO-FetO slags slightly increases with increasing Al2O3 content. The degree of the polymerization (DOP) of quenched slags, determined from Raman spectra and magic angle spinning-nuclear magnetic resonance, is also found to increase with increasing Al2O3 content. It can be deduced that the increasing DOP can promote the formation of gehlenite phase (Ca2Al2SiO7), thus facilitating the formation of higher phosphorous (or vanadium) contained solid solution ( n'Ca2SiO4·Ca3((P or V)O4)2). As Al2O3 content increases up to a specific value, the charge compensating ions which present near [AlO4]-tetrahedra and [FeO4]-tetrahedra are not fully supplied due to the scarcity of Ca2+. In this case, the existing Fe3+ in the melt cannot completely form [FeO4]-tetrahedra and part of Fe3+ would form [FeO6]-octahedra to substitute Ca2+ to modify the slags.

  9. Reduced defect density at the CZTSSe/CdS interface by atomic layer deposition of Al2O3

    NASA Astrophysics Data System (ADS)

    Erkan, Mehmet Eray; Chawla, Vardaan; Scarpulla, Michael A.

    2016-05-01

    The greatest challenge for improving the power conversion efficiency of Cu2ZnSn(S,Se)4 (CZTSSe)/CdS/ZnO thin film solar cells is increasing the open circuit voltage (VOC). Probable leading causes of the VOC deficit in state-of-the-art CZTSSe devices have been identified as bulk recombination, band tails, and the intertwined effects of CZTSSe/CdS band offset, interface defects, and interface recombination. In this work, we demonstrate the modification of the CZTSSe absorber/CdS buffer interface following the deposition of 1 nm-thick Al2O3 layers by atomic layer deposition (ALD) near room temperature. Capacitance-voltage profiling and quantum efficiency measurements reveal that ALD-Al2O3 interface modification reduces the density of acceptor-like states at the heterojunction resulting in reduced interface recombination and wider depletion width. Indications of increased VOC resulting from the modification of the heterojunction interface as a result of ALD-Al2O3 treatment are presented. These results, while not conclusive for application to state-of-the-art high efficiency CZTSSe devices, suggest the need for further studies as it is probable that interface recombination contributes to reduced VOC even in such devices.

  10. The influence of Ca-Mg-Al hydrotalcite synthesized from brine water on thermal and mechanical properties of HTlc-EVA composite

    NASA Astrophysics Data System (ADS)

    Karina, Wiwiek; Heraldy, Eddy; Pramono, Edi; Heriyanto, Astuti, Shanti

    2016-02-01

    Ca-Mg-Al hydrotalcite-like compound (Ca-Mg-Al HTlc) was prepared by co-precipitation method using brine water that is well known as the desalination process waste water. The structure of Ca-Mg-Al HTlc was determined by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis. Ca-Mg-Al HTlc was studied as a non-halogenated filler in ethylene vinyl acetate (EVA) matrix. Composites with different filler concentrations were prepared to evaluate the influence of Ca-Mg-Al HTlc on thermal and mechanical properties of EVA.The presence of Ca-Mg-Al HTlc in the composite has been confirmed by FTIR analysis. Thermal properties of composites show significant reduction of degradation temperature as well as the loading of HTlc in EVA. However, the total enthalpies combustion of composites with 1% and 5% HTlc loadings higher compared to neat EVA. Further, mechanical properties were determined by tensile test. The result shows that tensile strength and elongation at break of composites decrease relatively by Ca-Mg-Al HTlc addition.

  11. Study on the Indentation Creep Behavior of Mg-4Al-RE-0.8Ca Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Yaocheng; Yang, Li; Huang, Zedong; Dai, Jun

    2015-11-01

    The indentation creep behavior of Mg-4Al-RE-0.8Ca (AEC4108) alloy was investigated with a homemade apparatus. The microstructure of the AEC4108 alloy and the chemical composition of the precipitation phases in the alloy before and after creep test were investigated by scanning electron microscope and energy-dispersive spectroscopy. The results reveal that the steady-state indentation creep rate of the AEC4108 alloy is increased with increasing temperature and applied stress. The logarithm of the steady-state creep rates is linearly related to the logarithm of the stress and the reciprocal of the absolute temperature. The indentation creep parameters of AEC4108 alloy are correlated using an empirical equation dot{\\varepsilon }_{s} = 1.253 × 10^{ - 8} × \\upsigma^{3.2} { exp }[ { - 33.89/( {RT} )} ]. The thin acicular Al11La3 and the bone-shaped Al2Ca are precipitated along the grain boundaries, and the granular Al2La is formed within the grain. The indentation creep rate of AEC4108 alloy is controlled by the grain boundary slipping led by viscous dislocation movement. The indentation creep resistance of the AEC4108 alloy under temperature 398-448 K and stress 55-95 MPa is guaranteed by the precipitated phases with high thermal stability pinning at the grain boundary and within the grain.

  12. Dependence of acoustic property on Al substitution for Ca3Ta(Ga1‑ x Al x )3Si2O14 single crystals

    NASA Astrophysics Data System (ADS)

    Ohashi, Yuji; Arakawa, Mototaka; Kudo, Tetsuo; Yokota, Yuui; Shoji, Yasuhiro; Kurosawa, Shunsuke; Kamada, Kei; Kushibiki, Jun-ichi; Yoshikawa, Akira

    2016-07-01

    The acoustic properties of Ca3Ta(Ga1‑ x Al x )3Si2O14 (CTGASx) were experimentally studied as a function of the Al substitution content x in the ranges from x = 0 to 0.50. Five specimens, X-, Y-, Z-, 35°Y-, and 140°Y-cut, were prepared from each crystal of CTGASx (x = 0, 0.25, and 0.50) grown by the Czochralski technique. Longitudinal wave and shear wave velocities for CTGASx linearly increase with Al content for all propagation directions. Dielectric constants and density were measured and then elastic and piezoelectric constants were determined from the measured velocities for each crystal. The results revealed that all of the constants change linearly with Al content. From the relationship, the constants for CTAS (x = 1) were estimated. Calculations of the velocities using the determined constants also suggested that the maximum electromechanical coupling factor k 2 for the slow shear wave mode propagating along the rotated Y-axis direction of CTAS was improved to 4.42% compared with 3.83% for CTGS, owing to the Al substitution effect.

  13. The Influence of Na2O on the Solidification and Crystallization Behavior of CaO-SiO2-Al2O3-Based Mold Flux

    NASA Astrophysics Data System (ADS)

    Gao, Jinxing; Wen, Guanghua; Sun, Qihao; Tang, Ping; Liu, Qiang

    2015-08-01

    The reaction between [Al] and SiO2 sharply increased the Al2O3 and decreased SiO2 contents in mold flux during the continuous casting of high-Al steels. These changes converted original CaO-SiO2-based flux into CaO-SiO2-Al2O3-based flux, promoting the crystallization and deteriorating the mold lubrication. Therefore, study on the solidification and crystallization behavior of CaO-SiO2-Al2O3-based mold flux, with the applicable fluidizers, is of importance. The effect of Na2O, predominantly used as the fluidizer in mold flux, on the solidification and crystallization behavior of CaO-SiO2-Al2O3-based mold flux needs to be investigated. In this study, a CaO-SiO2-Al2O3-based mold flux containing 6.5 wt pct Li2O was designed; the effect of Na2O on the solidification and crystallization behavior of these mold fluxes was investigated using the single hot thermocouple technique (SHTT) and the double hot thermocouple technique (DHTT). Moreover, the slag film obtained by a heat flux simulator was analyzed using X-ray diffraction (XRD). The results indicate that the solid fraction of molten slag (Fs) and the crystalline fraction of solid slag (Fc) in the mold slag films decrease with increasing Na2O content from 0 to 2 wt pct. However, Fs and Fc increased when the Na2O content increased from 2 to 6 wt pct. The critical cooling rates initially decreases and then increases with increasing Na2O content. The XRD analysis results show that LiAlO2 and CaF2 were the basic crystals for all the mold fluxes. Increasing the Na2O content both inhibits the Ca2Al2SiO7 formation and promotes the production of Ca12Al14O33, indicating that the mold lubrication deteriorated because of the high melting-point phase formation of Ca2Al2SiO7 in the CaO-SiO2-Al2O3-based mold flux containing 6.5 wt pct Li2O, without Na2O. The strong crystallization tendency also deteriorated the mold lubrication for the mold flux with a higher Na2O content. Therefore, the addition of Na2O was less than 2 wt pct in

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

    SciTech Connect

    Kodama, N.; Yamaga, M.

    1998-01-01

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

  15. Fuel mixture approach for solution combustion synthesis of Ca{sub 3}Al{sub 2}O{sub 6} powders

    SciTech Connect

    Ianos, Robert Lazau, Ioan; Pacurariu, Cornelia; Barvinschi, Paul

    2009-07-15

    Single-phase 3CaO.Al{sub 2}O{sub 3} powders were prepared via solution combustion synthesis using a fuel mixture of urea and {beta}-alanine. The concept of using this fuel mixture comes from the individual reactivity of calcium nitrate and aluminum nitrate with respect to urea and {beta}-alanine. It was proved that urea is the optimum fuel for Al(NO{sub 3}){sub 3} whereas {beta}-alanine is the most suitable fuel for Ca(NO{sub 3}){sub 2}. X-ray diffraction and thermal analysis investigations revealed that heating at 300 deg. C the precursor mixture containing the desired metal nitrates, urea and {beta}-alanine triggers a vigorous combustion reaction, which yields single-phase nanocrystalline 3CaO.Al{sub 2}O{sub 3} powder (33.3 nm). In this case additional annealing was no longer required. The use of a single fuel failed to ensure the formation of 3CaO.Al{sub 2}O{sub 3} directly from the combustion reaction. After annealing at 900 deg. C for 1 h, the powders obtained by using a single fuel (urea or {beta}-alanine) developed a phase composition comprising of 3CaO.Al{sub 2}O{sub 3}, 12CaO.7Al{sub 2}O{sub 3} and CaO.

  16. Experimental study of subsolidus phase relations and mixing properties of pyroxene in the system CaO-Al 2O 3-SiO 2

    NASA Astrophysics Data System (ADS)

    Gasparik, Tibor

    1984-12-01

    Subsolidus phase relations in the system CaO-Al 2O 3-SiO 2 (CAS) were experimentally determined with tight reversals of several univariant curves and with 14 equilibration experiments containing the assemblage pyroxene + anorthite, where pyroxene is a binary solid solution of Ca-Tschermak (CaTs-CaAl 2SiO 6) and Ca-Eskola (CaEs-Ca 0.5AlSi 2O 6) endmembers. Reversals were obtained on the following reactions (bar, °C): 3 An = Gr + 2 Ky + Q ( P = 22 T - 700), 3 An + Cor = Gr + 3 Ky ( P = 21.8 T - 950), 3 CaTs= Gr + 2 Cor( P = 55 T - 53900), and 6 CaTs(1 - x) CaEsx = 2(1 - 2 x) Gr + 4(1 - 2 x) Cor + 9 xAn. Observed slopes indicate 9.8 J/mol · K of Al-Si disorder in Ca-Tschermak pyroxene and 5.3 J/mol·K of Al-Si disorder in anorthite, at 1300°C. It is suggested that Al-Si disorder in anorthite increases by 1.9 J/mol · K from 700°C to 1300°C. Compositions of CaTs-CaEs pyroxene in equilibrium with anorthite and PbO-rich liquid were experimentally determined at 1400-1430°C and 22.7-30.8 kbar. Microprobe measurements gave compositions which are consistent with an ideal pyroxene solution and the following parameters for the reaction 3 An = 2 CaTs + 2 CaEs ( J, bar, K): 2 RTln( XCaTs · XCaEs) + 60200 + 86.4 T - (5.06 + 13 × 10 -7P) P = 0, resulting in ΔH0j = -39.8 kJ/ mol and S0 = 461.8 J/ mol · K for the Ca-Eskola endmember at 1300°C. The obtained properties of the Ca-Eskola component are necessary for thermobarometry based on pyroxene bearing assemblages containing plagioclase, quartz, or kyanite.

  17. Super Smooth Modification of Al2O3 Ceramic Substrate by High Temperature Glaze of CaO-Al2O3-SiO2 System

    NASA Astrophysics Data System (ADS)

    Zhang, Jihua; Zhen, Shanxue; Yang, Lijun; Lou, Feizhi; Chen, Hongwei; Yang, Chuanren

    2011-01-01

    The rough surface of ceramic substrate is an obstacle for the scale down of line-width for thin film passive integrated devices (PID). In this paper, a modification method for Al2O3 ceramic substrate with super smooth in surface was proposed. Coating a layer of CaO-Al2O3-SiO2 (CAS) glass was performed to flat the rough surface of alumina substrate by sol-gel method. It was found that addition of 0.06% V2O5 can inhibit the recrystallization of the glaze. The root-mean-square (RMS) roughness of the glazed substrates reached a surprising flatness as small as 0.5 nm, and its melting temperature is higher than 1300 °C. This substrate with super flatness and high temperature endurance may be promising for high performance thin film devices.

  18. Interaction of overlayers of Al and Rb with single-crystalline surfaces of Bi2Sr2CaCu2O8

    NASA Astrophysics Data System (ADS)

    Lindberg, P. A. P.; Wells, B. O.; Shen, Z.-X.; Dessau, D. S.; Lindau, I.; Spicer, W. E.; Mitzi, D. B.; Kapitulnik, A.

    1990-03-01

    Photoemission results from Al and Rb interfaces with single crystals of Bi2Sr2CaCu2O8 high-temperature superconductors are reported. The Al and Rb adsorbates are found to react quite differently with the Bi2Sr2CaCu2O8 substrate. While adatoms of Rb significantly affect only the Bi and O atoms in the top atomic layer, the Al adsorbate profoundly disrupts the bonding character of the whole Bi2Sr2CaCu2O8 material. For Al, the Bi and Cu states are strongly reduced, and the Sr and O states show evidence of oxidized components. In addition, Al causes a strong out-diffusion of oxygen from the bulk. The differences in the reactivity of Al and Rb are discussed in terms of the different mobility of the two atoms.

  19. Changes of P, Ca, Al and Fe contents in fringe marshes along a pedogenic chronosequence in the Pearl River estuary, South China

    NASA Astrophysics Data System (ADS)

    Xiao, Rong; Bai, Junhong; Zhang, Honggang; Gao, Haifeng; Liu, Xinhui; Wilkes, Andreas

    2011-04-01

    Soil and plant samples were collected in four fringe marsh zones (i.e., A, B, C and D zones) along a pedogenic chronosequence in the Pearl River estuary in the Spring of 2009. Samples were subjected to a total digestion technique and analyzed for P, Ca, Al and Fe in order to study the changes of nutrient contents, storages in soils and their bioavailabilities to wetland plants (e.g. Cyperus malaccensis) in four zones. Results showed that soil Ca increased with depth along soil profiles, while P, Al and Fe generally kept constant in soil profiles in four zones. Al and Fe contents in the top 10 cm soils showed significant decreases from D to A zone, while a significant increase in Ca contents ( P<0.05). Significant increases along pedogenic chronosequence for P, Al and Fe at 30-40 cm soil horizons were also observed. Ca was mainly accumulated in plant aboveground parts; Al and Fe were accumulated in the belowground parts; while P was homogenously distributed among the tissues of C. malaccensis. C. malaccensis in D zone had lower Bio-concentration factors (BCFs) of P in the shoots and Al and Fe in the roots, and higher values of Ca in the shoots than those in older zones ( P<0.05). Compared to Al and Fe, both Ca and P had relatively higher translocation capacities for C. malaccensis, while only lower TFs for P and higher values for Al and Fe in D zone were observed than those in A and B zones ( P<0.05). Except for Al with no significant changes, the total BCFs for P and Fe showed an increasing trend with soil ages, while a decreasing trend for Ca. The total bio-storage factors (TBSFs) of P and Ca declined with the pedogenic time, whereas an increase for Fe. The results of this study can contribute to the wetland conservation and management in the Pearl River estuarine region.

  20. Phase transformations of Ca 3Al 2Si 3O 12 grossular garnet to the depths of the Earth's mantle transition zone

    NASA Astrophysics Data System (ADS)

    Gréaux, Steeve; Nishiyama, Norimasa; Kono, Yoshio; Gautron, Laurent; Ohfuji, Hiroaki; Kunimoto, Takehiro; Menguy, Nicolas; Irifune, Tetsuo

    2011-04-01

    High-pressure and high-temperature phase transformations of Ca 3Al 2Si 3O 12 grossular garnet were examined at 19-26 GPa and 700-2000 K using Kawai-type multi-anvil apparatus coupled with in situ X-ray diffraction (XRD). Recovered samples were analyzed by a combination of micro-focused X-ray diffraction (μ-XRD) and transmission electron microscopy (TEM). The results show that grossular garnet gradually transforms to an Al-rich CaSiO 3 perovskite at 22-26 GPa and 1000-1400 K. The transition boundary can be expressed as P (GPa) = -0.0082 × T (K) + 33.05. When the garnet completely disappears, we observed orthorhombic CaSiO 3 perovskite with a grossular composition. At 20-24 GPa and temperatures above 1500 K the CAS phase with the composition CaAl 4Si 2O 11 appears to accommodate excess Al from the perovskite along with two distinct populations of Al-bearing CaSiO 3 perovskites, with Al content of 3.7 and 10.0 wt% Al 2O 3, respectively. The pressure and temperature of these transitions correspond to the lowermost part of the transition zone and therefore it suggests that Ca-rich aluminosilicates could provide alternative candidates to explain multiple seismic reflections near the 660 km depth discontinuity.

  1. Transesterification of Nannochloropsis oculata microalga's lipid to biodiesel on Al2O3 supported CaO and MgO catalysts.

    PubMed

    Umdu, Emin Selahattin; Tuncer, Mert; Seker, Erol

    2009-06-01

    In this study, we present the activities of Al(2)O(3) supported CaO and MgO catalysts in the transesterification of lipid of yellow green microalgae, Nannochloropsis oculata, as a function of methanol amount and the CaO and MgO loadings at 50 degrees C. We found that pure CaO and MgO were not active and CaO/Al(2)O(3) catalyst among all the mixed oxide catalysts showed the highest activity. Not only the basic site density but also the basic strength is important to achieve the high biodiesel yield. Biodiesel yield over 80 wt.% CaO/Al(2)O(3) catalyst increased to 97.5% from 23% when methanol/lipid molar ratio was 30. PMID:19201601

  2. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    SciTech Connect

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010][001] ≈ 3.5. A strong power-law divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.

  3. Crystallization sequences of Ca-Al-rich inclusions from Allende - The effects of cooling rate and maximum temperature

    NASA Technical Reports Server (NTRS)

    Stolper, E.; Paque, J. M.

    1986-01-01

    The crystallization sequences, mineral chemistries, and textures resulting from the cooling in air from 1275-1580 C to below 100 C at rates between 0.5 and 100 c/hr of an average Type B Ca-Al-rich inclusion composition are investigated. Comparison of experimental results with petrographic observations of Type B CaIs indicates that most inclusions were partially melted and then cooled at rates of the order of a few tenths to tens of degrees per hour, with maximum temperatures of about 1400 C suggested for intermediate Type B Allende inclusions. Data are consistent with the drag heating of particles falling though nebular gas, heating in nebular shock fronts, or other thermal heterogeneities in the early nebula allowing time scales for heating of CAIs much shorter than those for the nebular cloud as a whole.

  4. Cubic structure and canted antiferromagnetism of CaMn7O12 doped with trivalent cations (Fe, Al, Cr)

    NASA Astrophysics Data System (ADS)

    Motin Seikh, Md.; Caignaert, V.; Lebedev, O. I.; Raveau, B.

    2014-02-01

    In this study, we show the dramatic effect of the doping of the octahedral sites with M3+ cations (Fe3+, Al3+ and Cr3+) upon the structure and magnetism of the rhombohedral double perovskite CaMn7O12. In the oxides CaMn7-xMxO12, charge ordering between Mn3+ and Mn4+ octahedral sites is destroyed leading to the cubic structure (Im-3), whereas the initial magnetic properties (TN~90 K) have disappeared leading to canted antiferromagnetism (TN≈50-70 K) for small x values (x ~0.2-1). A spin glass like behaviour is also observed for larger values (x~1) in the case of Fe substitution.

  5. Analysis of single- and double-barrier tunneling diode structures using ultrathin CaF2/CdF2/Si multilayered heterostructures grown on Si

    NASA Astrophysics Data System (ADS)

    Suda, Keita; Kuwata, Yuya; Watanabe, Masahiro

    2015-04-01

    The current-voltage (I-V) characteristics of single-barrier and double-barrier tunneling diode structures using CaF2/CdF2/Si ultrathin multilayered heterostructures grown on Si substrates have been theoretically analyzed and their material parameters, such as the conduction band discontinuity (ΔEC) at the heterointerface and effective mass (m*), have been evaluated by fitting simulation with the measured I-V characteristics. ΔEC between the ultrathin (1-3 nm) CaF2 and Si layers and m* for CaF2 were found to be 1.5-2.3 eV and 0.3-1.0m0, respectively. A clear thickness dependence of these parameters was observed, and the deviations of m* and ΔEC were approximately 30-50%, which probably originated from the thin layer thicknesses in atomic order. Using the estimated values derived from the single-barrier tunneling diodes, m* for CdF2 was also estimated to be 0.36m0 by fitting simulation of double-barrier diodes. These results will contribute to clarifying the design principle of tunneling devices with CaF2 and enhancing quantitative studies on electron transport in atomically thin multilayered heterostructures.

  6. Differentiation between ferroelectricity and thermally stimulated current in pyrocurrent measurements of multiferroic M Mn7O12 (M =Ca , Sr, Cd, Pb)

    NASA Astrophysics Data System (ADS)

    Terada, Noriki; Glazkova, Yana S.; Belik, Alexei A.

    2016-04-01

    This work investigated the electric polarization of M Mn7O12 (M = Ca , Sr, Cd, Pb) by means of both the conventional pyroelectric current (PC) method and the bias electric field (BE) method. All samples generated intense, broad peaks below the highest magnetic ordering temperature (TN 1) during PC measurements. In contrast, these peaks were not observed in the BE data, indicating that they are not intrinsically generated through ferroelectricity but rather are thermally stimulated current (TSC) in origin. In addition to the TSC peaks, we observed anomalous small, sharp peaks in both the PC and BE data at TN 2, leading to a very small relative polarization value of Δ P ˜ 0.2 μ C /m2 at 46 K in the case of CaMn7O12 and values of Δ P ˜0.2 μ C /m2 at 33 K for CdMn7O12 and Δ P ˜4.0 μ C /m2 at 77 K for PbMn7O12 , while SrMn7O12 showed no measurable polarization. In the case of CaMn7O12 , large ferroelectric polarization values below TN 1 have been reported: 440 μ C /m2 for a polycrystalline sample and 2870 μ C /m2 for a single crystal. Nevertheless, we conclude from the present results that these reported large polarization values are not associated with intrinsic ferroelectricity in CaMn7O12 .

  7. Structural, vibrational and luminescence properties of the (1−x)CaWO{sub 4}−xCdWO{sub 4} system

    SciTech Connect

    Taoufyq, A.; Guinneton, F.; Valmalette, J-C.; Arab, M.; Benlhachemi, A.; Bakiz, B.; Villain, S.; and others

    2014-11-15

    In the present work, we investigate the structural, microstructural, vibrational and luminescence properties of the system (1−x)CaWO{sub 4}−xCdWO{sub 4} with x ranging between 0 and 1. Polycrystalline samples were elaborated using a coprecipitation technique followed by thermal treatment at 1000 °C. The samples were then characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and luminescence analyses. X-ray diffraction profile analyses using Rietveld method showed that two kinds of solid solutions Ca{sub 1−x}Cd{sub x}WO{sub 4} having scheelite and wolframite structures, with respectively tetragonal and monoclinic crystal cells, were observed, with a biphasic system for compositions x=0.6 and 0.7. The scanning electron microscopy experiments showed a complex evolution of morphologies and crystallite sizes as x increased. The vibration modes of Raman spectra were characteristic of composition-dependent disordered solid solutions with decreasing wavenumbers as x increased. Luminescence experiments were performed under UV-laser light irradiation. The energies of emission bands increased linearly with cadmium composition x. The integrated intensity of luminescence reached a maximum value for the substituted wolframite phase with composition x=0.8. - Graphical abstract: Luminescence on UV excitation (364.5 nm) of (1−x)CaWO{sub 4−x}CdWO{sub 4} system, elaborated from coprecipitation technique at 1000 °C, with 0Ca{sub 1−x}Cd{sub x}WO{sub 4} polycrystalline phases with 0≤x≤0.5. (b) Maximum of luminescence intensity for the composition x=0.8. - Highlights: • Solid solutions Ca{sub 1−x}Cd{sub x}WO{sub 4} are elaborated from coprecipitation technique. • The structures of two types of solid solutions are refined using Rietveld method. • A maximum of luminescence is obtained for an intermediate composition x=0.8.

  8. Syntheses and luminescent properties of CaAl2Si2O8:Eu2+, Mn2+ phosphors for white LED

    NASA Astrophysics Data System (ADS)

    Kwon, Sook Hyun; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun; Kim, Jung Hwan

    2016-01-01

    Aluminosilicate-based luminescent materials, a series of CaAl2Si2O8:Eu2+ samples were prepared by using a solid-state reaction method. The X-ray diffraction patterns of the samples confirmed their triclinic structure after annealing at 1100 °C. The excitation spectra of CaAl2Si2O8:Eu2+ exhibited a broad band ranging between 220 to 420 nm with a point peak at a longer wavelength. Moreover, a shift in the broad band was also recorded with increasing Eu2+ concentration. The emission spectrum of CaAl2Si2O8:Eu2+ consists of a broad band from 390 to 550 nm with a maximum intensity at about 438 nm, which can be ascribed to the electric-dipole-allowed 4f65d1-8S7/2(4f7) transition of the Eu2+ ions. A series of Eu2+ and Mn2+ co-activated CaAl2Si2O8 samples were synthesized at 1400 °C. The CaAl2Si2O8:Eu2+, Mn2+ samples had a wide emission band ranging from blue to yellow and peaking at 438 and 550 nm under an excitation wavelength of 352 nm. The PL spectrum of the CaAl2Si2O8:Eu2+, Mn2+ samples reveal an effective energy transfer from Eu2+ to Mn2+ in CaAl2Si2O8. By utilizing the principle of energy transfer, we also demonstrated that with appropriate tuning of the activator content, CaAl2Si2O8:Eu2+, Mn2+ phosphors exhibit great potential as a phosphor for white-light-emitting diodes.

  9. Synthesis of a novel green fluorescent material Ca3Al2O6:Tb3+ based on a layered double hydroxide precursor

    NASA Astrophysics Data System (ADS)

    Gao, Xiaorui; Jiang, Kangle; Hao, Yongjing; Chang, Tao; Yin, Yaobing

    2015-08-01

    A novel green light emitting material, Ca3Al2O6:Tb3+ was synthesized by calcination of a terbium doped Ca/Al layered double hydroxide precursor at 1350°C. The precursor was prepared by coprecipitation from metal nitrates with sodium hydroxide. The material shows characteristic green emission at 543 nm when excited with 266 nm UV source. The photoluminescence intensity reaches its maximum at Tb3+ concentration of 0.5 mol %.

  10. Calcium aluminate silicate Ca2Al2SiO7 single crystal applicable to piezoelectric sensors at high temperature

    NASA Astrophysics Data System (ADS)

    Takeda, Hiroaki; Hagiwara, Manabu; Noguchi, Hiroaki; Hoshina, Takuya; Takahashi, Tomoko; Kodama, Nobuhiro; Tsurumi, Takaaki

    2013-06-01

    Ca2Al2SiO7 (CAS) bulk single crystals were grown by the Czochralski method. Material constants of the crystal were determined over the driving temperature range of a typical combustion pressure sensor. The electrical resistivity at 800 °C was found to be of the order of 108 Ωcm. We constructed a measurement system for the direct piezoelectric effect at high temperature, and characterized the crystals in a simulated engine cylinder combustion environment. Output charge signal against applied stress was detected at 700 °C. These observations suggest that CAS crystals are superior candidate materials for high temperature for stress sensing.

  11. Composition and mineralogy of refractory-metal-rich assemblages from a Ca,Al-rich inclusion in the Allende meteorite

    NASA Astrophysics Data System (ADS)

    Bischoff, A.; Palme, H.

    1987-10-01

    Four refractory metal-rich samples (10-190 micrograms) were separated from a single Ca,Al inclusion of the Allende meteorite. Chemical analyses were carried out by INAA; mineral phases from six large fremdlinge and the surrounding inclusion were analyzed by EDS. It is found that three of the four separated samples have variable absolute but similar relative abundances of refractory metals. All six fremdlinge are made up of Ni-rich metal containing 2-9 percent Ir, surrounded by a fine-grained intergrowth of V-magnetite and FeS.

  12. Crystal and local structure refinement in Ca2Al3O6F explored by X-ray diffraction and Raman spectroscopy.

    PubMed

    Xia, Zhiguo; Molokeev, Maxim S; Oreshonkov, Aleksandr S; Atuchin, Victor V; Liu, Ru-Shi; Dong, Cheng

    2014-04-01

    We present a combined structural analysis on the powder of the Ca2Al3O6F phase using X-ray diffraction (XRD) and Raman spectroscopy techniques. The crystal structure of Ca2Al3O6F has been refined in the rhombohedral system, R3[combining macron] space group, a = 17.3237(7) Å, c = 7.00017(4) Å, V = 1819.38(2) Å(3), Z = 6. The Ca2Al3O6F phase consists of almost ideal AlO4 tetrahedrons linked through corners, Ca(2+) ions in voids, and F(-) ions disordered over 6 sites around the Ca2 ion. The two different Ca sites have also been verified by the photoluminescence spectrum and decay curves using Eu(2+) as the probe ion substituted onto the Ca(2+) sites. A lattice dynamics simulation based on the simplified version of the Born-Karman potential model has been produced. Calculated Raman phonon modes agree qualitatively well with the experimental data. The calculations show that the strong line at 538 cm(-1) (Ag) corresponds to the vibrational mode of a six-membered AlO4 tetrahedrons ring, and the line at 572 cm(-1) (Ag) corresponds to the full symmetric vibration of fluorine atoms in the ab crystal plane. PMID:24336518

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1984-04-01

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

  15. Synthesis of Compositionally Defined Single-Crystalline Eu 3+ -Activated Molybdate–Tungstate Solid-Solution Composite Nanowires and Observation of Charge Transfer in a Novel Class of 1D CaMoO 4 –CaWO 4 :Eu 3+ –0D CdS/CdSe QD Nanoscale Heterostructures

    DOE PAGESBeta

    Han, Jinkyu; McBean, Coray; Wang, Lei; Jaye, Cherno; Liu, Haiqing; Fischer, Daniel A.; Wong, Stanislaus S.

    2015-02-10

    As a first step, we have synthesized and optically characterized a systematic series of one-dimensional (1D) single-crystalline Eu³⁺-activated alkaline-earth metal tungstate/molybdate solid solution composite CaW₁₋xMoxO₄ (0 ≤ ‘x’ ≤ 1) nanowires of controllable chemical composition using a modified template-directed methodology under ambient room-temperature conditions. Extensive characterization of the resulting nanowires has been performed using X-ray diffraction, electron microscopy, and optical spectroscopy. The crystallite size and single crystallinity of as-prepared 1D CaW₁₋xMoxO₄: Eu³⁺ (0 ≤ ‘x’ ≤ 1) solid solution composite nanowires increase with increasing Mo component (‘x’). We note a clear dependence of luminescence output upon nanowire chemical composition withmore » our 1D CaW₁₋xMoxO₄: Eu³⁺ (0 ≤ ‘x’ ≤ 1) evincing the highest photoluminescence (PL) output at ‘x’ = 0.8, amongst samples tested. Subsequently, coupled with either zero-dimensional (0D) CdS or CdSe quantum dots (QDs), we successfully synthesized and observed charge transfer processes in 1D CaW1-xMoxO4: Eu3+ (‘x’ = 0.8) – 0D QD composite nanoscale heterostructures. Our results show that CaW₁₋xMoxO₄: Eu³⁺ (‘x’ = 0.8) nanowires give rise to PL quenching when CdSe QDs and CdS QDs are anchored onto the surfaces of 1D CaW₁₋xMoxO₄: Eu³⁺ nanowires. The observed PL quenching is especially pronounced in CaW₁₋xMoxO₄: Eu³⁺ (‘x’ = 0.8) – 0D CdSe QD heterostructures. Conversely, the PL output and lifetimes of CdSe and CdS QDs within these heterostructures are not noticeably altered as compared with unbound CdSe and CdS QDs. The difference in optical behavior between 1D Eu³⁺ activated tungstate and molybdate solid solution nanowires and the semiconducting 0D QDs within our heterostructures can be correlated with the relative positions of their conduction and valence energy band levels. We propose that

  16. Synthesis of Compositionally Defined Single-Crystalline Eu 3+ -Activated Molybdate–Tungstate Solid-Solution Composite Nanowires and Observation of Charge Transfer in a Novel Class of 1D CaMoO 4CaWO 4 :Eu 3+ –0D CdS/CdSe QD Nanoscale Heterostructures

    SciTech Connect

    Han, Jinkyu; McBean, Coray; Wang, Lei; Jaye, Cherno; Liu, Haiqing; Fischer, Daniel A.; Wong, Stanislaus S.

    2015-02-10

    As a first step, we have synthesized and optically characterized a systematic series of one-dimensional (1D) single-crystalline Eu³⁺-activated alkaline-earth metal tungstate/molybdate solid solution composite CaW₁₋xMoxO₄ (0 ≤ ‘x’ ≤ 1) nanowires of controllable chemical composition using a modified template-directed methodology under ambient room-temperature conditions. Extensive characterization of the resulting nanowires has been performed using X-ray diffraction, electron microscopy, and optical spectroscopy. The crystallite size and single crystallinity of as-prepared 1D CaW₁₋xMoxO₄: Eu³⁺ (0 ≤ ‘x’ ≤ 1) solid solution composite nanowires increase with increasing Mo component (‘x’). We note a clear dependence of luminescence output upon nanowire chemical composition with our 1D CaW₁₋xMoxO₄: Eu³⁺ (0 ≤ ‘x’ ≤ 1) evincing the highest photoluminescence (PL) output at ‘x’ = 0.8, amongst samples tested. Subsequently, coupled with either zero-dimensional (0D) CdS or CdSe quantum dots (QDs), we successfully synthesized and observed charge transfer processes in 1D CaW1-xMoxO4: Eu3+ (‘x’ = 0.8) – 0D QD composite nanoscale heterostructures. Our results show that CaW₁₋xMoxO₄: Eu³⁺ (‘x’ = 0.8) nanowires give rise to PL quenching when CdSe QDs and CdS QDs are anchored onto the surfaces of 1D CaW₁₋xMoxO₄: Eu³⁺ nanowires. The observed PL quenching is especially pronounced in CaW₁₋xMoxO₄: Eu³⁺ (‘x’ = 0.8) – 0D CdSe QD heterostructures. Conversely, the PL output and lifetimes of CdSe and CdS QDs within these heterostructures are not noticeably altered as compared with unbound CdSe and CdS QDs. The difference in optical behavior between 1D Eu³⁺ activated tungstate and molybdate solid solution nanowires and the semiconducting 0D QDs within our

  17. Toxic Metals (Pb and Cd) and Their Respective Antagonists (Ca and Zn) in Infant Formulas and Milk Marketed in Brasilia, Brazil

    PubMed Central

    De Castro, Clarissa S. P.; Arruda, Andréa F.; Da Cunha, Leandro R.; SouzaDe, Jurandir R.; Braga, Jez W. B.; Dórea, José G.

    2010-01-01

    In non-ideal scenarios involving partial or non-breastfeeding, cow’s milk-based dairy products are mainstream in infant feeding. Therefore, it is important to study the concentrations of potentially neurotoxic contaminants (Pb and Cd) and their respective counteracting elements (Ca and Zn) in infant dairy products. Fifty-five brands of infant formulas and milk sold in Brasilia, Brazil were analyzed. The dairy products came from areas in the central-west (26%), southeast (29%) and south of Brazil (36%) extending as far as Argentina (7%) and the Netherlands (2%). For toxic Pb and Cd, median concentrations in powdered samples were 0.109 mg/kg and 0.033 mg/kg, respectively; in fluid samples median Pb concentration was 0.084 mg/kg, but median Cd concentration was below the limit of detection and overall values were below reference safety levels. However, 62% of these samples presented higher Pb concentration values than those established by FAO/WHO. Although the inverse correlation between Cd and Zn (Spearman r = −0.116; P = 0.590) was not statistically significant, the positive correlation between Ca and Pb was (Spearman r = 0.619; P < 0.0001). Additionally, there was a significant correlation between Pb and Cd. Furthermore, the study also revealed that provision of the essential trace element Zn in infant formulas can provide adequate amounts of the recommended daily requirements. Infant formulas and milk sold for consumption by infants and children can be an efficient tool to monitor neurotoxic metal risk exposure among young children. PMID:21139877

  18. Role of B2O3 on the Viscosity and Structure in the CaO-Al2O3-Na2O-Based System

    NASA Astrophysics Data System (ADS)

    Kim, Gi Hyun; Sohn, Il

    2013-10-01

    The effect of B2O3 on the viscosity and structure in the calcium-aluminate melt flux system containing Na2O was studied. An increase in the B2O3 content at fixed CaO/Al2O3 ratio lowered the viscosity. Higher CaO/Al2O3 ratio at fixed B2O3 content also decreased the viscosity. The alumino-borate structures were confirmed through Fourier transformed infrared (FTIR) and Raman spectroscopy and consisted of [AlO4]-tetrahedral structural units, [BO3]-triangular structural units, and [BO4]-tetrahedral structural units, which could be correlated to the viscosity. At fixed CaO/Al2O3 ratio, B2O3 additions decreased the [AlO4]-tetrahedral structural units and transformed the 3-D network structures such as pentaborate and tetraborate into 2-D network structures of boroxol and boroxyl rings by breaking the bridged oxygen atoms (O0) to produce non-bridged oxygen atoms (O-) leading to a decrease in the molten flux viscosity. At fixed B2O3 contents and higher CaO/Al2O3 ratio, 3-D complex network structures become 3-D simple and 2-D isolated network structures, resulting in lower viscosities. The apparent activation energy for viscous flow varied from 132 to 249 kJ/mol according to the composition of B2O3 and CaO/Al2O3 ratio.

  19. Probing structure-induced optical behavior in a new class of self-activated luminescent 0D/1D CaWO₄ metal oxide – CdSe nanocrystal composite heterostructures

    SciTech Connect

    Han, Jinkyu; McBean, Coray; Wang, Lei; Hoy, Jessica; Jaye, Cherno; Liu, Haiqing; Li, Zhuo-Qun; Sfeir, Matthew Y.; Fischer, Daniel A.; Taylor, Gordon T.; Misewich, James A.; Wong, Stanislaus S.

    2015-01-30

    In this report, we synthesize and characterize the structural and optical properties of novel heterostructures composed of (i) semiconducting nanocrystalline CdSe quantum dot (QDs) coupled with (ii) both one and zero-dimensional (1D and 0D) motifs of self-activated luminescence CaWO₄ metal oxides. Specifically, ~4 nm CdSe QDs have been anchored onto (i) high-aspect ratio 1D nanowires, measuring ~230 nm in diameter and ~3 μm in length, as well as onto (ii) crystalline 0D nanoparticles (possessing an average diameter of ~ 80 nm) of CaWO₄ through the mediation of 3-mercaptopropionic acid (MPA) as a connecting linker. Composite formation was confirmed by complementary electron microscopy and spectroscopy (i.e. IR and Raman) data. In terms of luminescent properties, our results show that our 1D and 0D heterostructures evince photoluminescence (PL) quenching and shortened PL lifetimes of CaWO₄ as compared with unbound CaWO₄. We propose that a photo-induced electron transfer process occurs from CaWO₄ to CdSe QDs, a scenario which has been confirmed by NEXAFS measurements and which highlights a decrease in the number of unoccupied orbitals in the conduction bands of CdSe QDs. By contrast, the PL signature and lifetimes of MPA-capped CdSe QDs within these heterostructures do not exhibit noticeable changes as compared with unbound MPA-capped CdSe QDs. The striking difference in optical behavior between CaWO₄ nanostructures and CdSe QDs within our heterostructures can be correlated with the relative positions of their conduction and valence energy band levels. In addition, the PL quenching behaviors for CaWO₄ within the heterostructure configuration were examined by systematically varying (i) the quantities and coverage densities of CdSe QDs as well as (ii) the intrinsic morphology (and by extension, the inherent crystallite size) of CaWO₄ itself.

  20. Insulator -- polaron conductor -- metal transitions in a complex oxide 12CaO.7Al2O3.

    NASA Astrophysics Data System (ADS)

    Sushko, P.; Shluger, A.; Stoneham, A.; Hayashi, K.; Matsuishi, S.; Hirano, M.; Hosono, H.

    2006-03-01

    Recent experiments have demonstrated that a complex nano-porous oxide 12CaO.7Al2O3 (C12A7) built of positively charged sub-nanometer cages can be converted from a transparent insulator to a transparent conductor by H2 doping followed by UV-light irradiation with 4--4.5 eV photons [1]. This irradiation induces optical absorption bands with maxima at 0.4 eV and 2.8 eV and high concentrations of unpaired electrons. We use ab initio calculations to reveal the mechanism of photo-induced insulator--conductor transition and the role of H atoms in this process and to elucidate the transport properties of the electrons in this system as a function of electron concentration. Our theoretical modeling suggests that at concentration below 10^20 cm-3 electrons are responsible for the polaron type electrical conductivity with the activation energy close to 0.1 eV as well as for the optical absorption at 0.4 eV and 2.8 eV [2]. We demonstrate that, as the electron concentration exceeds 10^20 cm-3, the character of electronic conductivity changes from polaron type to metallic. [1] K. Hayashi et al., Nature 419, 462 (2002). [2] P.V. Sushko, et al., Phys. Rev. Lett. 91, 126401 (2003); P.V. Sushko et al., Appl. Phys. Lett. 86, 092101 (2005).

  1. Dissolutive Wetting and Spreading Phenomena Between Al2O3 Substrate and CaO-Al2O3 Liquid Slags

    NASA Astrophysics Data System (ADS)

    Kim, Seonjin; Lee, Kyuyong; Chung, Yongsug

    2016-04-01

    The wetting and spreading behavior are influenced by the dissolution reaction. The wetting and spreading behavior between CaO-Al2O3 slag and Al2O3 substrate were investigated using the dispensed drop technique and a high speed camera (1000 frame/s) at 1823 K (1550 °C) using saturated slag and non-saturated slag on Al2O3. The contact angle of the saturated slag and the non-saturated slag was not substantially different. The apparent height of the spreading droplet for the non-saturated slag was lower than that of the saturated slag due to the formation of a crater generated by the dissolution reaction. A spherical cap model is associated with crater formation was suggested by analyzing the spread droplet and a quenched sample. The spreading rate of the non-saturated slag was faster than that of the saturated slag due to convection. For the saturated slag, the experimental values are in good agreement with the De Gennes's theoretical model. (Non-reactive viscous model) In contrast, the non-saturated slag curve shifts the experimental curve to correspond with the saturated slag curve.

  2. Dynamic Wetting of CaO-Al2O3-SiO2-MgO Liquid Oxide on MgAl2O4 Spinel

    NASA Astrophysics Data System (ADS)

    Abdeyazdan, Hamed; Dogan, Neslihan; Rhamdhani, M. Akbar; Chapman, Michael W.; Monaghan, Brian J.

    2015-02-01

    Inclusion type and content in steel is critical in steelmaking, affecting both productivity through clogging, and downstream physical properties of the steel. They are normally removed from steel by reacting with a slag (liquid oxide) phase. For efficient inclusion removal, the inclusions must attach/bond with this liquid phase. The strength of the attachment can be in part characterized by the wettability of the liquid oxide on the inclusions. In this study, the dynamic wetting of liquid oxides of the CaO-Al2O3-SiO2-MgO system on a solid spinel (MgAl2O4) substrate with low porosity of 1.9 pct was measured at 1773 K (1500 °C) using a modified sessile drop technique. The dynamic contact angle between the liquid and solid spinel was determined for different CaO/Al2O3 mass percent ratios ranging from 0.98 to 1.55. Characteristic curves of wettability ( θ) vs time showed a rapid decrease in wetting in the first 10 seconds tending to a plateau value at extended times. A mathematical model for spreading behavior of liquid oxides by Choi and Lee was adopted and shown to provide a reasonable representation of the spreading behavior with time. The chemical interaction at the interface between spinel (MgAl2O4) and slag was analyzed by carrying out detailed thermodynamic evaluation and characterization using scanning electron microscopy/energy dispersive spectroscopy. There is evidence of liquid penetrating the substrate via pores and along grain boundaries, forming a penetration layer in the substrate. The depth of the penetration layer was found to be a function of substrate porosity and sample cooling rate. It decreased from ~350 µm for 6.7 pct-porous substrate to ~190 µm for substrate with porosity of 1.9 pct and from ~190 µm to ~50 µm for a slow-cooled liquid oxide-spinel substrate sample in the furnace to a rapidly cooled liquid cooled-spinel substrate sample, respectively.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  4. Vitality and chemistry of roots of red spruce in forest floors of stands with a gradient of soil Al/Ca ratios in the northeastern United States

    USGS Publications Warehouse

    Wargo, P.M.; Vogt, K.; Vogt, D.; Holifield, Q.; Tilley, J.; Lawrence, G.; David, M.

    2003-01-01

    Number of living root tips per branch, percent dead roots, percent mycorrhizae and mycorrhizal morphotype, response of woody roots to wounding and colonization by fungi, and concentrations of starch, soluble sugars, phenols, percent C and N and C/N ratio, and Al Ca, Fe, K, Mg, Mn, and P were measured for 2 consecutive years in roots of red spruce (Picea rubens Sarg.) in stands in the northeastern United States (nine in 1993 and two additional in 1994) dominated by red spruce and with a gradient of forest floor exchangeable Al/Ca ratios. Root vitality was measured for nonwoody and coarse woody roots; chemical variables were measured for nonwoody (<1 mm), fine woody (1 to <2 mm), and coarse woody (2 to <5 mm) roots. There were significant differences among sites for all variables, particularly in 1993, although few were related to the Al/Ca ratio gradient. Percent mycorrhizae decreased, while some morphotypes increased or decreased as the Al/Ca ratio increased. In nonwoody roots, N increased as the Al/Ca ratio increased. Most sampled trees appeared to be in good or fair health, suggesting that an adverse response of these root variables to high Al concentrations may be apparent only after a significant change in crown health.

  5. Mechanical Properties and Fracture Behaviors of the As-Extruded Mg-5Al-3Ca Alloys Containing Yttrium at Elevated Temperature.

    PubMed

    Son, Hyeon-Taek; Kim, Yong-Ho; Kim, Taek-Soo; Lee, Seong-Hee

    2016-02-01

    Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound. PMID:27433675

  6. Activities of FetO in CaO-Al2O3-SiO2-FetO (<5 pct) slags saturated with liquid iron

    NASA Astrophysics Data System (ADS)

    Lee, Kwang Ro; Suito, Hideaki

    1994-12-01

    The activity coefficients of FetO in CaO-Al2O3 and CaO-Al2O3-SiO2 slags with 0.01 to 5 mass pct FetO were determined at 1873 K from the data obtained in the present and previous slag-metal experiments, using an alumina or lime crucible. It was found that the activity coefficients of FetO obeyed a dilute solution law and increased with increasing the content of SiO2. Based on the findings pertaining to the activity coefficient, the values for the activities of SiO2 and Al2O3 in CaO-Al2O3-SiO2 slags were assessed.

  7. Thermodynamics of Complex Sulfide Inclusion Formation in Ca-Treated Al-Killed Structural Steel

    NASA Astrophysics Data System (ADS)

    Guo, Yin-tao; He, Sheng-ping; Chen, Gu-jun; Wang, Qian

    2016-08-01

    Controlling the morphology of the sulfide inclusion is of vital importance in enhancing the properties of structural steel. Long strip-shaped sulfides in hot-rolled steel can spherize when, instead of the inclusion of pure single-phase MnS, the guest is a complex sulfide, such as an oxide-sulfide duplex and a solid-solution sulfide particle. In this study, the inclusions in a commercial rolled structural steel were investigated. Spherical and elongated oxide-sulfide duplex as well as single-phase (Mn,Ca)S solid solution inclusions were observed in the steel. A thermodynamic equilibrium between the oxide and sulfide inclusions was proposed to understand the oxide-sulfide duplex inclusion formation. Based on the equilibrium solidification principle, thermodynamic discussions on inclusion precipitation during the solidification process were performed for both general and resulfurized structural steel. The predicted results of the present study agreed well with the experimental ones.

  8. Thermodynamics of Complex Sulfide Inclusion Formation in Ca-Treated Al-Killed Structural Steel

    NASA Astrophysics Data System (ADS)

    Guo, Yin-tao; He, Sheng-ping; Chen, Gu-jun; Wang, Qian

    2016-05-01

    Controlling the morphology of the sulfide inclusion is of vital importance in enhancing the properties of structural steel. Long strip-shaped sulfides in hot-rolled steel can spherize when, instead of the inclusion of pure single-phase MnS, the guest is a complex sulfide, such as an oxide-sulfide duplex and a solid-solution sulfide particle. In this study, the inclusions in a commercial rolled structural steel were investigated. Spherical and elongated oxide-sulfide duplex as well as single-phase (Mn,Ca)S solid solution inclusions were observed in the steel. A thermodynamic equilibrium between the oxide and sulfide inclusions was proposed to understand the oxide-sulfide duplex inclusion formation. Based on the equilibrium solidification principle, thermodynamic discussions on inclusion precipitation during the solidification process were performed for both general and resulfurized structural steel. The predicted results of the present study agreed well with the experimental ones.

  9. Molecular dynamics simulation of radiation damage in CaCd{sub 6} quasicrystal cubic approximant up to 10 keV

    SciTech Connect

    Chen, P. H.; Avchachov, K.; Nordlund, K.; Pussi, K.

    2013-06-21

    Due to the peculiar nature of the atomic order in quasicrystals, examining phase transitions in this class of materials is of particular interest. Energetic particle irradiation can provide a way to modify the structure locally in a quasicrystal. To examine irradiation-induced phase transitions in quasicrystals on the atomic scale, we have carried out molecular dynamics simulations of collision cascades in CaCd{sub 6} quasicrystal cubic approximant with energies up to 10 keV at 0 and 300 K. The results show that the threshold energies depend surprisingly strongly on the local coordination environments. The energy dependence of stable defect formation exhibits a power-law dependence on cascade energy, and surviving defects are dominated by Cd interstitials and vacancies. Only a modest effect of temperature is observed on defect survival, while irradiation temperature increases lead to a slight increase in the average size of both vacancy clusters and interstitial clusters.

  10. High temperature carbon dioxide capture on nano-structured MgO-Al2O3 and CaO-Al2O3 adsorbents: an experimental and theoretical study.

    PubMed

    Bang, Yongju; Han, Seung Ju; Kwon, Soonchul; Hiremath, Vishwanath; Song, In Kyu; Seo, Jeong Gil

    2014-11-01

    Nano-structured alkaline-earth metal oxide adsorbents (denoted as MgO-Al2O3 and CaO-Al2O3) were prepared by an epoxide-driven one-pot sol-gel method, and they were applied to the dynamic and static CO2 adsorption. For comparison, a nano-structured aluminum oxide adsorbent (denoted as Al2O3) was also prepared by a similar method. MgO-Al2O3 adsorbent exhibited a well-developed mesopore structure through the formation of MgAl2O4 spinel phase, whereas CaO-Al2O3 adsorbent was composed of nano-sized CaO and CaAl2O4, resulting in a pore plugging. It was revealed that total basicity increased in the order of Al2O3 (0.11 mmol-CO2/g) < MgO-Al2O3 (0.37 mmol-CO2/g) < CaO-Al2O3, (1.21 mmol-CO2/g), which is in concurrent with adsorption energy obtained from DFT calculations. However, it was found that both basicity and base strength of the adsorbents played an important role in determining the CO2 adsorptive performance at different operating temperature. Among the adsorbents tested, MgO-Al2O3, which mostly retained medium basic sites, exhibited a best CO2 adsorptive performance at 200 degrees C. Furthermore, the experimental results are well supported by theoretical estimation, suggesting a useful design method of adsorbents for facile and regenerative adsorption in the applications of CO2 capture. PMID:25958558

  11. Aluminum resistance in wheat involves maintenance of leaf Ca(2+) and Mg(2+) content, decreased lipid peroxidation and Al accumulation, and low photosystem II excitation pressure.

    PubMed

    Moustaka, Julietta; Ouzounidou, Georgia; Bayçu, Gülriz; Moustakas, Michael

    2016-08-01

    The phytotoxic aluminum species (Al(3+)) is considered as the primary factor limiting crop productivity in over 40 % of world's arable land that is acidic. We evaluated the responses of two wheat cultivars (Triticum aestivum L.) with differential Al resistance, cv. Yecora E (Al-resistant) and cv. Dio (Al-sensitive), exposed to 0, 37, 74 and 148 μM Al for 14 days in hydroponic culture at pH 4.5. With increasing Al concentration, leaf Ca(2+) and Mg(2+) content decreased, as well as the effective quantum yield of photosystem II (PSII) photochemistry (Φ PSII ), while a gradual increase in leaf membrane lipid peroxidation, Al accumulation, photoinhibition (estimated as F v /F m ), and PSII excitation pressure (1 - q p ) occurred. However, the Al-resistant cultivar with lower Al accumulation, retained larger concentrations of Ca(2+) and Mg(2+) in the leaves and kept a larger fraction of the PSII reaction centres (RCs) in an open configuration, i.e. a higher ratio of oxidized to reduced quinone A (QA), than plants of the Al-sensitive cultivar. Four times higher Al concentration in the nutrient solution was required for Al-resistant plants (148 μM Al) than for Al-sensitive (37 μM Al), in order to establish the same closed RCs. Yet, the decline in photosynthetic efficiency in the cultivar Dio was not only due to closure of PSII RCs but also to a decrease in the quantum yield of the open RCs. We suggest that Al(3+) toxicity may be mediated by nutrient deficiency and oxidative stress, and that Al-resistance of the wheat cultivar Yecora E, may be due at least partially, from the decreased Al accumulation that resulted to decreased reactive oxygen species (ROS) formation. However, under equal internal Al accumulation (exposure Al concentration: Dio 74 μM, Yecora E 148 μM) that resulted to the same oxidative stress, the reduced PSII excitation pressure and the better PSII functioning of the Al-resistant cultivar was probably due to the larger concentrations of Ca

  12. Phase selection in the containerless solidification of undercooled CaO {center_dot} 6Al{sub 2}O{sub 3} melts

    SciTech Connect

    Li Mingjun; Kuribayashi, Kazuhiko

    2004-07-12

    The CaO {center_dot} 6Al{sub 2}O{sub 3} melts were solidified on an aero-acoustic levitator under a containerless processing condition at various undercoolings. A high-speed video was operated to monitor the recalescence behavior, from which the growth velocity as a function of melt undercooling was determined. The microstructures were observed and the crystalline phases were identified using the X-ray diffraction technique, indicting that the Al{sub 2}O{sub 3} was solidified when the melt temperature was higher than the peritectic temperature, T{sub p}. When the melt was undercooled below T{sub p}, the CaO {center_dot} 6Al{sub 2}O{sub 3} (CA{sub 6}) peritectic phase was crystallized directly from the undercooled melts. With respect to the direct formation of the peritectic phase, further analysis from the viewpoints of competitive nucleation indicated that the minimum free energy principle may be applied to elucidate the nucleation of CA{sub 6} phase. In terms of the competitive growth behavior, the interface attachment kinetics for Al{sub 2}O{sub 3} and CA{sub 6} phases are calculated by using the classical BCT model indicating that although the Al{sub 2}O{sub 3} phase doped by CaO has about four times larger interface kinetic coefficient than that of the CA{sub 6} peritectic phase, the growth kinetics of Al{sub 2}O{sub 3} in the melt with the CaO {center_dot} 6Al{sub 2}O{sub 3} chemical composition is not sufficiently high to replace the CA{sub 6} phase as the primary phase. Therefore, once CA{sub 6} is nucleated, it can develop into a macro crystal as the primary phase. The competitive nucleation and growth behavior in the CA{sub 6} system is different from those in other well-studied peritectic alloys and the present investigation on the phase formation will be an essential supplement to the phase selection theory.

  13. Si-Al-Cl-Mg-Ca Aqueous Fluids in Dora-Maira Pyrope: new Contributions for an old Question

    NASA Astrophysics Data System (ADS)

    Ferrando, S.; Frezzotti, M.; Compagnoni, R.

    2007-12-01

    Recent discovery of multiphase solid inclusions (MSI) in peak minerals from ultra-high pressure (UHP) terranes opened up new prospects for understanding the fluid-rock interaction during deep subduction in both crust and mantle. The first report on MSI in UHP rocks was from Dora-Maira (DM; Case Parigi; western Alps) whiteschists, more than ten years ago (Philippot et al, 1995, CMP, 121, 29-44). Nevertheless, the nature of such a fluid, and its role on the origin of the unusual composition of these rocks is still matter of debate. We report data on inclusions in DM UHP pyropes and HP prograde kyanite, part of them from a new sampling site (SSW Case Parigi). Primary MSI (30 micron) are present only in small UHP pyropes (1 - 6 cm) and often show post-entrapment decrepitation. Each MSI contains Mg-chlorite, Na-phlogopite, minor Cl-rich apatite, talc, pyrite, magnesite, Ca-rich chlorides +/- liquid water. Maps of total water concentrations collected in MSI-rich pyropes by infrared synchrotron radiation show gradients that suggest considerable H diffusion from inclusions into the host garnet (Frezzotti et al, 2007, abstract ECROFI XIX). In prograde kyanite, rare fluid inclusions are high salinity brines, containing different salts. Present data indicate that at HP conditions brines were present in the rocks and that at UHP peak aqueous fluids were enriched in Si, Al, Mg, Na, Ca, but still containing significant amounts of Cl, P, S, C. DM whiteschists are commonly considered metasomatic rocks from a granitic protolith. Our data on MSI in UHP pyrope and on rare brines in prograde HP kyanite strongly support metasomatism by external high-Ca-Mg fluids, probably evolved during serpentinite dehydration as proposed by Sharp and Barnes (2004, EPSL, 226, 243-254). Present data support the model of Compagnoni and Hirajima (2001, Lithos, 57, 219-236), who proposed that metasomatic fluids were introduced into the system during prograde metamorphism, channelled along shear zones

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  15. Isolating /sup 241/Am from waste solutions containing Al, Ca, Fe, and Cr

    SciTech Connect

    Gray, L.W.; Burney, G.A.; King, C.M.

    1982-01-01

    About 2.4 kg of /sup 241/Am contaminated with calcium and aluminum had been recovered from low-activity waste during recycle of 11% /sup 240/Pu. A process was developed and demonstrated to purify the americium before shipment as /sup 241/AmO/sub 2/. The americium and some of the calcium were batch extracted into 50% TBP-n-paraffin from 2.2M Al(NO/sub 3/)/sub 3/ - 0.3M HNO/sub 3/ solution in a canyon tank. Pregnant solvent was scrubbed first with 2.1M Al/sup 3 +/-0.3M Li/sup +/-6.7M NO/sub 3/- and then with 7M LiNO/sub 3/ to reduce the calcium content and to displace the aluminum. Americium was then stripped from the solvent with water and concentrated by evaporation. Before precipitating the americium with oxalic acid, the nitric acid was adjusted with NH/sub 4/OH to yield a 1M NH/sub 4/NO/sub 3/ solution. Recovery across the batch extraction step was 97.8%, while 93% of the calcium and >99% of the aluminum was rejected. Recovery across precipitation averaged >96% while producing a product which was >99.3% pure /sup 241/AmO/sub 2/. The major impurities were water, carbon, calcium, iron, and zinc.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  17. Microstructure and mechanical properties of spray-deposited Mg-12.55Al-3.33Zn-0.58Ca-1Nd alloy

    SciTech Connect

    Bai Pucun; Dong Taishang; Hou Xiaohu; Zhao Chunwang; Xing Yongming

    2010-07-15

    A Mg-Al-Zn-Ca-Nd magnesium alloy was prepared by spray forming technology, and the spray-deposited alloy was subsequently hot-extruded with a reduction rate of 16:1 at 623 K. The mechanical properties of the extruded alloy were investigated, and the result shows that the spray-formed Mg alloy offers superior tensile strength with poor ductility. The morphologies, fracture characteristic and chemical compositions of the extruded alloy were then explored by scanning electron microscopy with energy dispersive spectrometer. Furthermore, microstructure of the extruded alloy was examined by X-ray diffractometry and transmission electron microscopy. The results indicate that the microstructure of the spray-deposited magnesium alloy consists of {alpha}-Mg and Al{sub 2}Ca phases, and the Al{sub 2}Ca compound is distributed along the grain boundaries of the primary {alpha}-Mg. Moreover, twin substructure is found to exist in microstructure of the Al{sub 2}Ca phase, rare earth Nd in the Al{sub 2}Ca phase in the form of solid solution.

  18. Mechanisms of oxygen ion diffusion in a nanoporous complex oxide 12CaO•7 Al2 O3

    NASA Astrophysics Data System (ADS)

    Sushko, Peter V.; Shluger, Alexander L.; Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

    2006-01-01

    We performed a theoretical analysis of O2- diffusion mechanisms in a nanoporous complex oxide 12CaO•7Al2O3 (C12A7). This material can be viewed as a positively charged framework, arranged in subnanometer sized cages, hosting extra-framework O2- ions occupying one in six cages. Using both classical molecular-dynamics simulations and ab initio calculations we demonstrate that the diffusion of O2- species is dominated by the exchange of framework and extra-framework O2- ions rather than by an interstitial diffusion mechanism. The results allow us to rationalize the origins of the experimentally observed high oxide ion conductivity of C12A7 and the stability of its lattice under positive ion-beam irradiation.

  19. Diode-pumped Kerr-lens mode-locked Yb:CaGdAlO4 laser with tunable wavelength

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    We experimentally demonstrated a wavelength tunable Kerr-lens mode-locked femtosecond laser based on an Yb:CaGdAlO4 (Yb:CGA) crystal. The Kerr-lens mode-locked wavelength tuning range was from 1043.5 to 1076 nm, as broad as 32.5 nm, by slightly tilting the end mirror. Pulses as short as 60 fs were generated at the central wavelength of 1043.8 nm with an average output power of 66 mW. By using an output coupler with 1.5% transmittance, the Kerr-lens mode-locked average output power reached 127 mW with a pulse duration of 81 fs at a central wavelength of 1049.5 nm.

  20. Linear energy transfer effects on time profiles of scintillation of Ce-doped LiCaAlF6 crystals

    NASA Astrophysics Data System (ADS)

    Yanagida, Takayuki; Koshimizu, Masanori; Kurashima, Satoshi; Iwamatsu, Kazuhiro; Kimura, Atsushi; Taguchi, Mitsumasa; Fujimoto, Yutaka; Asai, Keisuke

    2015-12-01

    We measured temporal profiles of the scintillation of Ce-doped LiCaAlF6 scintillator crystals at different linear energy transfers (LETs). Based on the comparison of high-LET temporal profiles with those at low LET, a fast component was observed only at low LET. The disappearance of the fast component at high LET is tentatively ascribed to the quenching of excited states at crystal defects owing to the interaction between excited states via the Auger process. In addition, the rise and the initial decay behavior were dependent on the LET. This LET-dependent behavior is explained by an acceleration process and a deceleration process in energy transfer at high LET. The LET-dependent temporal profiles provide the basis for a discrimination technique of gamma-ray and neutron detection events using these scintillators based on the nuclear reaction, 6Li(n,α)t.

  1. Study of photoluminescence properties of CaAl2O4: Eu2+ prepared by combustion synthesis method

    NASA Astrophysics Data System (ADS)

    Hingwe, V. S.; Bajaj, N. S.; Omanwar, S. K.

    2016-05-01

    Eu2+ doped alkaline earth metals such as strontium aluminate, calcium aluminate and barium aluminate prepared by using modified combustion synthesis method at 600°c with Urea as fuel. Crystal structure is determined by using XRD and the sample confirmation by using the FTIR. The effect of the host material on the photoluminescence (PL) and phosphorescence properties were studied by using the Hitachi F-7000 spectrofluorimeter equipped with a 450W Xenon lamp, in the range 200-650 nm. The emission spectra of Eu2+ range from 450 to 500nm in the Blue to aqua region and the transition 4f7-4f6 5d1. The observed emission in CaAl2O4 is 440nm.

  2. Thermal equation of state of CaFe 2O 4-type MgAl 2O 4

    NASA Astrophysics Data System (ADS)

    Sueda, Yuichiro; Irifune, Tetsuo; Sanehira, Takeshi; Yagi, Takehiko; Nishiyama, Norimasa; Kikegawa, Takumi; Funakoshi, Ken-ichi

    2009-05-01

    In situ X-ray diffraction measurements of CaFe 2O 4-type MgAl 2O 4 have been conducted at pressures up to 42 GPa and temperatures to 2400 K using Kawai-type multianvil apparatus with sintered diamond anvils. Additional measurements have also been conducted at pressures to 12 GPa using diamond anvil cell with helium as a pressure medium at room temperature, and at temperatures to 836 K at the ambient pressure using a high-temperature X-ray diffractometer. The analysis of room-temperature data yielded V0 = 240.1(2) Å 3, K0 = 205(6) GPa, and K0=4.1(3). A fit of the present data to high-temperature Birch-Murnaghan equation of state (EOS) yielded (∂ K0/∂ T) P = -0.030(2) GPa/K and α0 = a0 + b0T with values of a0 = 1.96(13) × 10 -5 K -1 and b0 = 1.64(24) × 10 -8 K -2. The present data set was also fitted to Mie-Grüneisen-Debye (MGD) EOS and we obtained γ0 = 1.73(7), q = 2.03(37), and θ0 = 1546(104) K. Density changes of MORB have been estimated using the newly obtained thermoelastic parameters, assuming that the Al-rich phase in this composition possesses the CaFe 2O 4-type structure under the lower mantle P, T conditions. The calculated densities along geotherms for the normal mantle and subducting cold slabs are both significantly higher than those of typical seismological models, confirming the conclusion of some recent results on MORB by laser-heated diamond anvil cell experiments.

  3. Structural features of AgCaCdMg{sub 2}(PO{sub 4}){sub 3} and AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, two new compounds with the alluaudite-type structure, and their catalytic activity in butan-2-ol conversion

    SciTech Connect

    Kacimi, Mohammed; Ziyad, Mahfoud; Hatert, Frederic . E-mail: fhatert@ulg.ac.be

    2005-04-20

    AgCaCdMg{sub 2}(PO{sub 4}){sub 3} and AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, two new compounds with the alluaudite-type structure, were synthesized by a solid state reaction in air at 750 deg. C. The X-ray powder diffraction pattern of AgCaCdMg{sub 2}(PO{sub 4}){sub 3} indicates the presence of small amounts of (Ca, Mg){sub 3}(PO{sub 4}){sub 2} with the whitlockite structure, as impurity, whereas AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3} is constituted by pure alluaudite. The Rietveld refinements of the X-ray powder diffraction patterns indicate an ordered cationic distribution for AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, with Ag on A(2)', Cd on A(1) and M(1), and Mg on M(2), whereas a disordered distribution of Cd and Ca between the A(1) and M(1) sites is observed for AgCaCdMg{sub 2}(PO{sub 4}){sub 3}. The catalytic properties of these compounds has been measured in reaction of butan-2-ol dehydrogenation. In the absence of oxygen, both samples exhibit poor dehydrogenation activity. All samples displayed no dehydration activity. Introduction of oxygen into the feed changed totally the catalytic behavior of the catalysts. The production of methyl ethyl ketone increases with time on stream and the reaction temperature. AgCaCdMg{sub 2}(PO{sub 4}){sub 3} is more efficient than AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}.

  4. Release of metals from a Cd-contaminated streambed in response to experimental acidification and neutralization

    NASA Astrophysics Data System (ADS)

    Curtis, P. Jefferson; Walker, Paddy

    1994-12-01

    Short-term (hours) experimental acidification of a Cd-contaminated Precambrian Shield stream with low buffering capacity caused the release of Ca, Mg, Cd, Mn, Fe, and Al from the streambed. Release of metals was consistent with pH-dependent desorption and dissolution of amorphous hydroxides. Partial neutralization of the stream with MgCO3 inhibited metal release for most metals; however, excess Mg appeared to stimulate Cd release. Thus addition of Mg (and probably Ca) compounds to neutralize acidified water may be ineffective for reducing Cd concentrations in solution because added base cations apparently compete with Cd for adsorption sites.

  5. 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.

  6. Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors

    PubMed Central

    Roy, U. N.; Mundle, R. M.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Pradhan, A. K.; James, R. B.

    2016-01-01

    CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability. PMID:27216387

  7. Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors

    NASA Astrophysics Data System (ADS)

    Roy, U. N.; Mundle, R. M.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Pradhan, A. K.; James, R. B.

    2016-05-01

    CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability.

  8. Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors.

    PubMed

    Roy, U N; Mundle, R M; Camarda, G S; Cui, Y; Gul, R; Hossain, A; Yang, G; Pradhan, A K; James, R B

    2016-01-01

    CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability. PMID:27216387

  9. Spin Hamiltonian parameters and local structures for Co 2+ ions in calcite-type trigonal carbonates MCO 3 (M=Co, Cd and Ca)

    NASA Astrophysics Data System (ADS)

    Wen-Chen, Zheng; Shao-Yi, Wu; Hui-Ning, Dong; Sheng, Tang

    2004-01-01

    From the perturbation formulas based on the cluster approach for 3d 7 ion in trigonal octahedral sites of crystals, the spin Hamiltonian parameters ( g factors g , g⊥ and hyperfine structure constants A , A⊥) for Co 2+ in calcite-type MCO 3 (M=Co, Cd, Ca) crystals are calculated. In the calculations, for CoCO 3 crystal, the structural data of pure crystal are used, whereas for the Co 2+-doped CdCO 3 and CaCO 3 crystals, the local structural data caused by the impurity-induced local lattice relaxation are considered. The calculated results show good agreement with the observed values obtained from electron paramagnetic and antiferromagnetic resonance experiments. The difficulty shown in the previous paper related to the g⊥ value of CoCO 3 obtained from the change of the g factor as a function of the crystallographic data (i.e., the unit cell parameters) a0 and α0 of pure MCO 3 crystals is removed.

  10. Determination of Ca, Mg, Na, Cd, Cu, Fe, K, Li and Zn in acid mine and reference water samples by inductively coupled plasma atomic fluorescence spectrometry

    USGS Publications Warehouse

    Sanzolone, R.F.; Meier, A.L.

    1986-01-01

    An inductively coupled plasma atomic fluorescence spectrometric (ICP-AFS) method was used for the determination of nine elements in natural water. Reference and acid mine water samples were analysed by this method to demonstrate its usefulness for hydrogeochemical exploration. The elements were determined in two groups based on the compatibility of operating conditions and consideration of element abundance levels in natural water. Ca, Mg and Na were determined as a group using one set of instrumental conditions and a 1 + 99 dilution of the sample, and Cd, Cu, Fe, K, Li and Zn were determined using another set of conditions and the undiluted sample. The detection limits for the elements are as follows: Ca, 1.4; Mg, 1.7; Na, 2.0; Cd, 1.8; Cu, 6.2; Fe, 15.8; K, 3.5; Li, 0.3; and Zn, 1.2 ng m1-1. Each element has a linear range spanning about four orders of magnitude. The method has good precision and accuracy, as shown by statistics on replicate analyses and by the agreement between values obtained and those recommended for the reference water samples, and also those obtained by atomic absorption spectrometry for the acid mine water samples.

  11. ABiO2X (A = Cd, Ca, Sr, Ba, Pb; X = halogen) Sillen X1 Series: Polymorphism Versus Optical Properties.

    PubMed

    Olchowka, Jacob; Kabbour, Houria; Colmont, Marie; Adlung, Matthias; Wickleder, Claudia; Mentré, Olivier

    2016-08-01

    The Sillen X1 series of Bi(3+)A(2+)O2X (A = Cd, Ca, Sr, Ba, Pb; X = Cl, Br, I) compounds is composed of three main crystallographic types, namely, the tetragonal form (space group (S.G.) I4/mmm), the orthorhombic form (S.G. Cmcm), and the monoclinic form (S.G. P21/m). Because of Bi(3+)/A(2+) disorder the Bi(3+) based photoluminescence (PL) of the tetragonal polytypes is quenched at room temperature (RT). In the two other ordered forms, the Bi-O-Bi connectivity is different but limited, such that bluish/greenish emission occurs at RT in the monoclinic CdBiO2Cl and CaBiO2Cl and orthorhombic SrBiO2Cl and BaBiO2Cl phases. The crystal structure of BaBiO2Br was refined in the orthorhombic Cmcm space group and also shows RT emission. Focusing on the RT luminescent activity as a key parameter, the PL active compounds were investigated by means of density functional theory calculations and UV-visible reflectance spectroscopy. The influence of A and X ions on the excitation energy is discussed by analyzing the A-O-Bi and Bi-X bonding schemes and gives some insights for rational tuning of both the excitation and emission energies. PMID:27414069

  12. Highly Repeatable and Recoverable Phototransistors Based on Multifunctional Channels of Photoactive CdS, Fast Charge Transporting ZnO, and Chemically Durable Al2O3 Layers.

    PubMed

    Ahn, Cheol Hyoun; Kang, Won Jun; Kim, Ye Kyun; Yun, Myeong Gu; Cho, Hyung Koun

    2016-06-22

    Highly repeatable and recoverable phototransistors were explored using a "multifunctional channels" structure with multistacked chalcogenide and oxide semiconductors. These devices were made of (i) photoactive CdS (with a visible band gap), (ii) fast charge transporting ZnO (with a high field-effect mobility), and (iii) a protection layer of Al2O3 (with high chemical durability). The CdS TFT without the Al2O3 protection layer did not show a transfer curve due to the chemical damage that occurred on the ZnO layer during the chemical bath deposition (CBD) process used for CdS deposition. Alternatively, compared to CdS phototransistors with long recovery time and high hysteresis (ΔVth = 19.5 V), our "multi-functional channels" phototransistors showed an extremely low hysteresis loop (ΔVth = 0.5V) and superior photosensitivity with repeatable high photoresponsivity (52.9 A/W at 400 nm). These improvements are likely caused by the physical isolation of the sensing region and charge transport region by the insertion of the ultrathin Al2O3 layer. This approach successfully addresses some of the existing problems in CdS phototransistors, such as the high gate-interface trap site density and high absorption of molecular oxygen, which originate from the polycrystalline CdS. PMID:27259048

  13. Single-crystal structure and Raman spectroscopy of synthetic titanite analog CaAlSiO4F

    NASA Astrophysics Data System (ADS)

    Krüger, Hannes; Többens, Daniel M.; Tropper, Peter; Haefeker, Udo; Kahlenberg, Volker; Fuchs, Martin R.; Olieric, Vincent; Troitzsch, Ulrike

    2015-10-01

    Synthetic CaAlSiO4F, the Al-F analog of titanite, has been investigated using single-crystal synchrotron diffraction experiments at Beamline X06DA (Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland) and Raman spectroscopy. The presented structural model with 40 parameters was refined against 506 unique reflections to a final R o b s of 0.026 (space group A2/ a, a = 6.9120(11), b = 8.5010(10), c = 6.435(2) Å, β = 114.670(11)°, and Z = 4) and exhibits less distorted coordination polyhedra than earlier models from powder data. Vibrational spectra were calculated in harmonic approximation at the Γ point from fully relaxed energy optimisations of the crystal structure, using 3D-periodic density functional theory with Gaussian basis sets and the software CRYSTAL06. The lattice parameters of the fully relaxed structure were in good agreement with the experimental values, with the calculated values 0.8 ± 0.4 % too large; the monoclinic angle was calculated 0.4° too large. The agreement of the calculated Raman frequencies with the observed ones was very good, with standard deviation ±3 cm-1 and maximum deviations of ±7 cm-1. Furthermore, a detailed discussion of the atomic displacements associated with each Raman mode is given.

  14. How do mineral coatings affect dissolution rates? An experimental study of coupled CaCO 3 dissolution—CdCO 3 precipitation

    NASA Astrophysics Data System (ADS)

    Cubillas, Pablo; Köhler, Stephan; Prieto, Manuel; Causserand, Carole; Oelkers, Eric H.

    2005-12-01

    Coupled CaCO 3 dissolution-otavite (CdCO 3) precipitation experiments have been performed to 1) quantify the effect of mineral coatings on dissolution rates, and 2) to explore the possible application of this coupled process to the remediation of polluted waters. All experiments were performed at 25°C in mixed-flow reactors. Various CaCO 3 solids were used in the experiments including calcite, aragonite, and ground clam, mussel, and cockle shells. Precipitation was induced by the presence of Cd(NO 3) 2 in the inlet solution, which combined with aqueous carbonate liberated by CaCO 3 dissolution to supersaturate otavite. The precipitation of an otavite layer of less than 0.01 μm in thickness on calcite surfaces decreases its dissolution rate by close to two orders of magnitude. This decrease in calcite dissolution rates lowers aqueous carbonate concentrations in the reactor such that the mixed-flow reactor experiments attain a steady-state where the reactive fluid is approximately in equilibrium with otavite, arresting its precipitation. In contrast, otavite coatings are far less efficient in lowering aragonite, and ground clam, mussel, and cockle shell dissolution rates, which are comprised primarily of aragonite. A steady-state is only attained after the precipitation of an otavite layer of 3-10 μm thick; the steady state CaCO 3 dissolution rate is 1-2 orders of magnitude lower than that in the absence of otavite coatings. The difference in behavior is interpreted to stem from the relative crystallographic structures of the dissolving and precipitating minerals. As otavite is isostructural with respect to calcite, it precipitates by epitaxial growth directly on the calcite, efficiently slowing dissolution. In contrast, otavite's structure is appreciably different from that of aragonite. Thus, it will precipitate by random three dimensional heterogeneous nucleation, leaving some pore space at the otavite-aragonite interface. This pore space allows aragonite

  15. Micelle-Assisted Synthesis of Al2O3·CaO Nanocatalyst: Optical Properties and Their Applications in Photodegradation of 2,4,6-Trinitrophenol

    PubMed Central

    Imtiaz, Ayesha; Khaleeq-ur-rahman, Muhammad; Adnan, Rohana

    2013-01-01

    Calcium oxide (CaO) nanoparticles are known to exhibit unique property due to their high adsorption capacity and good catalytic activity. In this work the CaO nanocatalysts were prepared by hydrothermal method using anionic surfactant, sodium dodecyl sulphate (SDS), as a templating agent. The as-synthesized nanocatalysts were further used as substrate for the synthesis of alumina doped calcium oxide (Al2O3·CaO) nanocatalysts via deposition-precipitation method at the isoelectric point of CaO. The Al2O3·CaO nanocatalysts were characterized by FTIR, XRD, TGA, TEM, and FESEM techniques. The catalytic efficiencies of these nanocatalysts were studied for the photodegradation of 2,4,6-trinitrophenol (2,4,6-TNP), which is an industrial pollutant, spectrophotometrically. The effect of surfactant and temperature on size of nanocatalysts was also studied. The smallest particle size and highest percentage of degradation were observed at critical micelle concentration of the surfactant. The direct optical band gap of the Al2O3·CaO nanocatalyst was found as 3.3 eV. PMID:24311980

  16. The pressure-volume equation of state of a synthetic grossular Ca3Al2Si3O12

    NASA Astrophysics Data System (ADS)

    Milani, Sula; Boffa Ballaran, Tiziana; Nestola, Fabrizio

    2014-05-01

    In the framework of a wide research project focused on mineral inclusions in diamonds we have investigated the compressibility of a synthetic grossular garnet (Ca3Al2Si3O12) with the purpose of providing new constraints on the diamond geobarometry. In fact, not only garnets are among the important phases of the Earth upper mantle but at the same time are one of the main phases found as inclusion in diamonds. Garnets are a crucial marker in determining the origin source of diamonds, which can be eclogitic and/or peridotitic. In particular, peridotitic diamonds include garnets characterized by about 90-92% of pyrope-almandine with the grossular component reaching about 6-8%, whereas eclogitic diamonds have garnets with the grossular component increased up to about 20-22%. In order to obtain information about the depth of formation of the diamond-garnet pair, beyond the classical chemical method, we propose the so called "elastic method", which is based on the knowledge of precise and accurate thermoelastic parameters for both diamond and inclusion (e.g. Nestola et al. 2011 and references therein). We have determined the pressure - volume equation of state of a pure synthetic grossular garnet by single-crystal X-ray diffraction up to about 8 GPa. The resulting equation of state coefficients, together with those previously determined for pyrope and almandine end-members and their intermediate compositions (see Milani et al. 2013) will cover the compositional range of garnets found as inclusions in diamonds, allowing to construct a robust model to predict the elastic parameters for any garnet composition typical of eclogitic and/or peridotitic diamond. The research was funded by the ERC Starting Grant to FN (grant agreement n° 307322). References Milani S., Mazzucchelli M., Nestola F., Alvaro M., Angel R.J., Geiger C.A., Domeneghetti M.C. (2013) The P-T conditions of garnet inclusion formation in diamond: thermal expansion of synthetic end-member pyrope. EGU General

  17. Al-doped ZnO contact to CdZnTe for x- and gamma-ray detector applications

    NASA Astrophysics Data System (ADS)

    Roy, U. N.; Camarda, G. S.; Cui, Y.; Gul, R.; Hossain, A.; Yang, G.; Mundle, R. M.; Pradhan, A. K.; James, R. B.

    2016-06-01

    The poor adhesion of common metals to CdZnTe (CZT)/CdTe surfaces has been a long-standing challenge for radiation detector applications. In this present work, we explored the use of an alternative electrode, viz., Al-doped ZnO (AZO) as a replacement to common metallic contacts. ZnO offers several advantages over the latter, such as having a higher hardness, a close match of the coefficients of thermal expansion for CZT and ZnO, and better adhesion to the surface of CZT due to the contact layer being an oxide. The AZO/CZT contact was investigated via high spatial-resolution X-ray response mapping for a planar detector at the micron level. The durability of the device was investigated by acquiring I-V measurements over an 18-month period, and good long-term stability was observed. We have demonstrated that the AZO/CZT/AZO virtual-Frisch-grid device performs fairly well, with comparable or better characteristics than that for the same detector fabricated with gold contacts.

  18. Matrix effects in the energy dispersive X-ray analysis of CaO-Al(2)O(3)-MgO inclusions in steel.

    PubMed

    Pistorius, Petrus Christiaan; Verma, Neerav

    2011-12-01

    Energy dispersive X-ray microanalysis of micron-sized inclusions in steel is of considerable industrial importance. Measured spectra and Monte Carlo simulations show a significant effect of the steel matrix on analysis of CaO-Al(2)O(3)-MgO inclusions: the steel matrix filters the softer (Al and Mg) characteristic X-rays, increasing the relative height of the Ca peak. Bulk matrix correction methods would not result in correct inclusion compositions, but operating at a lower acceleration voltage shifts the effect to smaller inclusion sizes. PMID:22051086

  19. Adsorption of Cd(II) by Mg-Al-CO3- and magnetic Fe3O4/Mg-Al-CO3-layered double hydroxides: Kinetic, isothermal, thermodynamic and mechanistic studies.

    PubMed

    Shan, Ran-ran; Yan, Liang-guo; Yang, Kun; Hao, Yuan-feng; Du, Bin

    2015-12-15

    Understanding the adsorption mechanisms of metal cations on the surfaces of solids is important for determining the fate of these metals in water and wastewater treatment. The adsorption kinetic, isothermal, thermodynamic and mechanistic properties of cadmium (Cd(II)) in an aqueous solution containing Mg-Al-CO3- and magnetic Fe3O4/Mg-Al-CO3-layered double hydroxide (LDH) were studied. The results demonstrated that the adsorption kinetic and isotherm data followed the pseudo-second-order model and the Langmuir equation, respectively. The adsorption process of Cd(II) was feasible, spontaneous and endothermic in nature. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to explain the adsorption mechanisms. The characteristic XRD peaks and FTIR bands of CdCO3 emerged in the LDH spectra after Cd(II) adsorption, which indicated that the adsorption of Cd(II) by LDHs occurred mainly via CdCO3 precipitation, surface adsorption and surface complexation. Furthermore, the magnetic Fe3O4/Mg-Al-CO3-LDH can be quickly and easily separated using a magnet before and after the adsorption process. PMID:26073520

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

    SciTech Connect

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

    2012-10-15

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

  1. Photoluminescence of CaAlSiN3:Eu2+-based fine red-emitting phosphors synthesized by carbothermal reduction and nitridation method

    NASA Astrophysics Data System (ADS)

    Li, Shuxing; Peng, Xia; Liu, Xuejian; Huang, Zhengren

    2014-12-01

    In this research, we have presented the synthesis and characterization of the various Ca1-xEuxAl0.76Si1.18N3 (x = 0.01 ∼ 0.1) red-emitting phosphors, which were successfully prepared by carbothermal reduction and nitridation (CTRN) method without the strict needs of high pressure. Here, raw materials were CaCO3, AlN, Si3N4, Eu2O3, and C. In particular, C was considered as efficient and robust reducing agent. The influences of reaction temperature, holding time, C content, and Eu2+ concentration were investigated in the crystal phase compositions and photoluminescence properties of the as-prepared phosphors. Importantly, CaAlSiN3:Eu2+-based red phosphors with interesting properties were obtained with reaction temperature at 1600 °C for 4 h by atmospheric N2-10%H2 pressure, and the C/O ratio of 1.5:1, respectively. The emission peak positions of as-prepared phosphors were red-shifted from 607 nm to 654 nm with Eu2+ concentration from 1 mol% to 10 mol%. Meanwhile the highest luminescence intensity was achieved with 2 mol% of Eu2+ concentration, which showed high external quantum efficiency up to 71%. Combining the phosphor blend of green-emitting β-sialon:Eu2+, yellow-emitting Ca-α-sialon:Eu2+, and red-emitting Ca0.98Eu0.02Al0.76Si1.18N3 with a blue LED (light emitting diodes), warm white LED can be generated, yielding the color rendering index (Ra) of 93 at correlated color temperature (CCT) of 3295 K. These results indicate that CaAlSiN3:Eu2+-based red-emitting phosphors prepared by facile CTRN are highly promising candidates for warm white LEDs.

  2. Effects of MgO/Al2O3 Ratio and Basicity on the Viscosities of CaO-MgO-SiO2-Al2O3 Slags: Experiments and Modeling

    NASA Astrophysics Data System (ADS)

    Pengcheng, Li; Xiaojun, Ning

    2016-02-01

    The effects of the MgO/Al2O3 ratio and basicity on the viscosities of CaO-MgO-SiO2-Al2O3 slags were investigated at 1733 K, 1773 K, and 1823 K (1460 °C, 1500 °C, and 1550 °C) in this study. At a fixed Al2O3 of 15 and 18 mass pct, increasing the basicity from 1 to 1.2 resulted in lowering the viscosity of slags. At a fixed basicity of 1.0 and 1.2, increasing the MgO from 0 to 15 mass pct decreased the viscosity of slags. The Fourier transform-infrared spectra analysis of the slag structure was made to discuss the depolymerization roles of MgO and basicity. Considering the different depolymerization effects of basic oxides upon the silicate/aluminate network structure as suggested by FT-IT analysis, a fresh model for predicting the viscosity of CaO-MgO-SiO2-Al2O3 slags was constructed. A total of 209 viscosity measurements with large compositional variations showed satisfactory agreement with the results calculated by the present model. With the aid of the current model, the co-effects of the MgO/Al2O3 ratio and basicity on the viscosities of CaO-MgO-SiO2-Al2O3 slags (15 to 20 mass pct Al2O3) were investigated.

  3. Hexagonal Ba-ferrite: a good model for the crystal structure of a new high-pressure phase CaAl 4Si 2O 11?

    NASA Astrophysics Data System (ADS)

    Gautron, Laurent; Gerald, John D. Fitz; Kesson, Sue E.; Eggleton, R. Anthony; Irifune, Tetsuo

    1997-07-01

    A new calcium aluminosilicate phase of composition CaAl 4Si 2O 11 has been encountered amongst the transformation products of CaAl 2Si 2O 8 (anorthite composition) at 14 GPa (Gautron et al., 1996). X-ray diffraction (XRD) confirms that its crystal structure is essentially the same as that of a new complex CaAl-silicate (abbreviated CAS phase) first reported by Irifune et al. (1994). The crystal structure of the CAS phase has been investigated by transmission electron microscopy (TEM). It has a hexagonal unit cell with lattice parameters a = 5.4Å and c = 12.7Å, and its space group is either P6 3mc , P overline62c or P6 3/mmc. It is proposed that this CAS phase has a six-layer, close-packed structure so that Z = 2 and density is 3.94 g cm -3, reasonable for a phase stable at transition-zone pressures. The most plausible model for the structure of this phase arises from published refinements of hexagonal Ba-ferrites. This postulated P6 3/mmc structure consists of octahedral layers, 3/4 occupied, separated by 12-coordinate Ca atoms, and by Al and Si in face-shared octahedra and in complex trigonal bipyramidal polyhedra, i.e. some Si would be five-fold coordinated. Observed TEM and XRD data are compared with calculated reflection intensities for this CAS model.

  4. Preparation of Bi2Sr2CaCu2Oy films on alumina substrates with a CuAl2O4 buffer layer

    NASA Astrophysics Data System (ADS)

    Lee, Kiejin; Song, Insang; Park, Gwangseo

    1993-07-01

    High-Tc Bi2Sr2CaCu2Oy films have been prepared using the surface diffusion process, with the screen printing of Bi2O3, SrCO3, and CaCO3 (Bi:Sr:Ca=2:2:2) mixed powders on Cu-deposited alumina substrates. Through the heating at temperatures above 400 °C, CuAl2O4 buffer layers were formed via an interaction between the Cu layer and alumina. The Bi2Sr2CaCu2Oy films, heat treated at 860 °C for 30 min in air, have a zero resistance at 72 K. The x-ray diffraction, scanning electron microscope, and energy dispersive x-ray analysis studies show that the Bi2Sr2Ca1Cu2Oy films are strongly c-axis oriented along the direction normal to the alumina substrate, and the CuAl2O4 buffer layer acted as a barrier to suppress the interdiffusion of Al ions into the superconducting films.

  5. Effect of calcination temperature on the activity of solid Ca/Al composite oxide-based alkaline catalyst for biodiesel production.

    PubMed

    Meng, Yong-Lu; Wang, Bo-Yang; Li, Shu-Fen; Tian, Song-Jiang; Zhang, Min-Hua

    2013-01-01

    A solid Ca/Al composite oxide-based alkaline catalyst containing Ca(12)Al(14)O(33) and CaO was prepared by chemical synthesis and thermal activation from sodium aluminate solution and calcium hydroxide emulsion. The effect of calcination temperatures ranging from 120 °C to 1000 °C on activity of the catalyst was investigated. The catalyst calcined at 600 °C showed the highest activity with >94% yield of fatty acid methyl esters (i.e. biodiesel) when applied to the transesterification of rapeseed oil at a methanol:oil molar ratio of 15:1 at 65 °C for 3h. Structure and properties of the catalyst were studied and the characterizations with XRD, TGA, FTIR, BET, and SEM demonstrated that the performance of the catalyst was closely related to its specific surface area and crystalline structure. In particular, the generation of crystalline Ca(12)Al(14)O(33) improved the catalytic activity due its synergistic effect with CaO. PMID:23196252

  6. Blue, yellow and orange color emitting rare earth doped BaCa2Al8O15 phosphors prepared by combustion method

    NASA Astrophysics Data System (ADS)

    Yerpude, A. N.; Dhoble, S. J.; Reddy, B. Sudhakar

    2014-12-01

    Eu2+, Dy3+, Sm3+ activated BaCa2Al8O15 phosphors were prepared by the combustion method. The phosphor powders were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and photoluminescence (PL) spectrophotometer. Photoluminescence spectra of BaCa2Al8O15:Eu2+ phosphors show emission wavelength at 435 nm that corresponds to 4f65d1→4f7 transition of Eu2+ ion by keeping excitation wavelength extending broad-band from 270 to 400 nm centered at 334 nm. The Dy3+ doped BaCa2Al8O15 phosphors shows blue emission (485 nm) and yellow emission (566 nm) under the excitation of 347 nm, corresponding to the 4F9/2→6H15/2 transition and 4F9/2→6H13/2 transition of Dy3+ ions, respectively. The Sm3+ doped BaCa2Al8O15 phosphors have shown strong orange emission at 604 nm corresponding to the 4G5/2→6H7/2 transition of Sm3+ with intense excitation wavelength at 406 nm. Scanning electron microscopy has been used for exploring the size and morphological properties of the prepared phosphors. The obtained results show that the phosphors have potential application in the field of solid state lighting.

  7. Optimum Composition of CaO-SiO2-Al2O3-MgO Slag for Spring Steel Deoxidized by Si and Mn in Production

    NASA Astrophysics Data System (ADS)

    Yang, Hulin; Ye, Jiansong; Wu, Xiaoliang; Peng, Yongsheng; Fang, Yi; Zhao, Xinbing

    2016-04-01

    The relations between plasticity of inclusions and contents of oxygen, aluminum, and sulfur in molten steel were overall discussed by thermodynamics and FactSage software. Then, the optimum compositions of slag were obtained and the activities of components of refining slag system were analyzed. Finally, experiments were carried out based on the results of calculation. According to the relations, it could achieve better effect to improve basicity R ( R = CaO/SiO2 by mass pct) and C/ A ( C/ A = CaO/Al2O3 by mass pct) in the low melting temperature [≤1673 K (≤1400 °C)] region of refining slag as far as possible. For the CaO-SiO2-Al2O3-MgO slag, the optimum compositions are MgO: 5-9 pct, CaO: 47.4-50.2 pct, SiO2: 41.9-45.6 pct and Al2O3: ≤2.79 pct, respectively, in which the basicity is at the range of 1.0 to 1.19 and C/ A is above 9.0. It is proved by experiments that the plasticity of inclusions and the contents of [O], [Al], and [S] can be controlled effectively by the optimum composition of refining slag, and the high cleanness is achieved in spring wire rods.

  8. The elastic and thermoelectric properties of the Zintl compound Ca{sub 5}Al{sub 2}Sb{sub 6} under high pressure

    SciTech Connect

    Yang, Gui; Cui, Haitao; Ma, Dongwei; He, Chaozheng

    2014-12-14

    The elastic and thermoelectric properties of Ca{sub 5}Al{sub 2}Sb{sub 6} under pressure are studied using ab initio calculation and semiclassical Boltzmann theory. The calculated elastic constants and minimum thermal conductivity indicate that Ca{sub 5}Al{sub 2}Sb{sub 6} exhibits an anisotropic structure and high thermoelectric performance. The size of the band gap shows a nonlinear change with increasing pressure. Based on the electronic structure, the calculated thermoelectric parameters show that the Seebeck coefficient has no obvious change under pressure, whereas the electrical conductivity improves with increasing pressure. Therefore, the power factor increases at an appropriate pressure of P = 2.6 GPa. P-type doping of Ca{sub 5}Al{sub 2}Sb{sub 6} may achieve better thermoelectric performance than n-type doping, in agreement with experiment. The anisotropic thermoelectric properties of Ca{sub 5}Al{sub 2}Sb{sub 6} indicate that the thermoelectric performance along the z-direction is superior to other directions. This is attributed to the combination of the large dispersion and high band degeneracy along the Γ-Z direction in the band structure.

  9. An ab initio study of the structural, elastic, electronic and optical properties of the newly synthesized nitridoaluminate LiCaAlN2

    NASA Astrophysics Data System (ADS)

    Haddadi, K.; Bouhemadou, A.; Bin-Omran, S.; Maabed, S.; Khenata, R.

    2015-01-01

    The structural parameters, elastic constants, electronic structure and optical properties of the recently reported monoclinic quaternary nitridoaluminate LiCaAlN2 are investigated in detail using the ab initio plane-wave pseudopotential method within the generalized gradient approximation. The calculated equilibrium structural parameters are in excellent agreement with the experimental data, which validate the reliability of the applied theoretical method. The chemical and structural stabilities of LiCaAlN2 are confirmed by calculating the cohesion energy and enthalpy of formation. Chemical band stiffness is calculated to explain the pressure dependence of the lattice parameters. Through the band structure calculation, LiCaAlN2 is predicted to be an indirect band gap of 2.725 eV. The charge-carrier effective masses are estimated from the band structure dispersions. The frequency-dependent dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity coefficient and electron energy loss function spectra are calculated for polarized incident light in a wide energy range. Optical spectra exhibit a noticeable anisotropy. Single-crystal and polycrystalline elastic constants and related properties, including isotropic sound velocities and Debye temperatures, are numerically estimated. The calculated elastic constants and elastic compliances are used to analyse and visualize the elastic anisotropy of LiCaAlN2. The calculated elastic constants demonstrate the mechanical stability and brittle behaviour of the considered material.

  10. Electronic and Optic Properties of Cubic Spinel CdX2O4 (X=In, Ga, Al) through Modified Becke—Johnson Potential

    NASA Astrophysics Data System (ADS)

    Manzar, A.; Murtaza, G.; Khenata, R.; Masood, Yousaf; S., Muhammad; Hayatullah

    2014-06-01

    A new potential approximation known as modified Becke—Johnson based on density functional theory is applied to compute the electronic band profile and optical response of CdIn2O4, CdGa2O4 and CdAl2O4 compounds. The direct band gap with common LDA, GGA and EV-GGA is drastically underestimated compared with modified Becke—Johnson approximation, whose results are significantly closer to the experimental findings. The optical properties like dielectric constant, refractive index, reflectivity, optical conductivity and absorption coefficient are also computed. A unique characteristic associated with cation replacement is studied; the replacement of cation In by Ga and Ga by Al significantly reduces the direct energy band gap in these compounds. This variation is of crucial importance for band gap dependent optical properties of these compounds, which is also proof for applications of these compounds in optoelectronic devices.

  11. Fus1/Tusc2 Is a Novel Regulator of Mitochondrial Calcium Handling, Ca2+-Coupled Mitochondrial Processes, and Ca2+-Dependent NFAT and NF-κB Pathways in CD4+ T Cells

    PubMed Central

    Uzhachenko, Roman; Ivanov, Sergey V.; Yarbrough, Wendell G.; Shanker, Anil; Medzhitov, Ruslan

    2014-01-01

    Abstract Aims: Fus1 has been established as mitochondrial tumor suppressor, immunomodulator, and antioxidant protein, but molecular mechanism of these activities remained to be identified. Based on putative calcium-binding and myristoyl-binding domains that we identified in Fus1, we explored our hypothesis that Fus1 regulates mitochondrial calcium handling and calcium-coupled processes. Results: Fus1 loss resulted in reduced rate of mitochondrial calcium uptake in calcium-loaded epithelial cells, splenocytes, and activated CD4+ T cells. The reduced rate of mitochondrial calcium uptake in Fus1-deficient cells correlated with cytosolic calcium increase and dysregulation of calcium-coupled mitochondrial parameters, such as reactive oxygen species production, ΔμH+, mitochondrial permeability transition pore opening, and GSH content. Inhibition of calcium efflux via mitochondria, Na+/Ca2+ exchanger significantly improved the mitochondrial calcium uptake in Fus1−/− cells. Ex vivo analysis of activated CD4+ T cells showed Fus1-dependent changes in calcium-regulated processes, such as surface expression of CD4 and PD1/PD-L1, proliferation, and Th polarization. Fus1−/− T cells showed increased basal expression of calcium-dependent NF-κB and NFAT targets but were unable to fully activate these pathways after stimulation. Innovation: Our results establish Fus1 as one of the few identified regulators of mitochondrial calcium handling. Our data support the idea that alterations in mitochondrial calcium dynamics could lead to the disruption of metabolic coupling in mitochondria that, in turn, may result in multiple cellular and systemic abnormalities. Conclusion: Our findings suggest that Fus1 achieves its protective role in inflammation, autoimmunity, and cancer via the regulation of mitochondrial calcium and calcium-coupled parameters. Antioxid. Redox Signal. 20, 1533–1547. PMID:24328503

  12. Thermodynamics of Gold Dissolution Behavior in CaO-SiO2-Al2O3-MgOsat Slag System

    NASA Astrophysics Data System (ADS)

    Han, Yun Soon; Swinbourne, Douglas R.; Park, Joo Hyun

    2015-12-01

    Gold solubility in the CaO-SiO2-Al2O3-MgOsat slag system was measured at 1773 K (1500 °C) under a CO2-CO atmosphere over a wide range of compositions, i.e., 8 to 40 mass pct CaO, 26 to 50 mass pct SiO2, and 0 to 36 mass pct Al2O3, to determine the dissolution mechanism of gold in the CaO-based metallurgical slags. Gold solubility in the present slag system increased with increasing oxygen partial pressure and increasing activity of CaO. From the thermodynamic analysis, the dissolution mechanism of gold into the (alumino-)silicate melts is proposed as follows according to the activity of basic oxide, which indicates that the predominant species of gold is dependent on slag basicity. {Au}(s) + 1/4{O}2 (g) + 1/2( {{O}^{2 - } } ) = ( {{AuO}^{ - } } ),quad ( {a_{BO} < 0.1} ) {Au}(s) + 1/4{O}2 (g) + 3/2( {{O}^{2 - } } ) = ( {{AuO}2^{3 - } } ),quad ( {a_{BO} > 0.1} ) The enthalpy change for the dissolution of gold into the CaO-SiO2-Al2O3-MgOsat slag system was measured to be about -80 kJ/mol, indicating that the gold dissolution is exothermic. From the iso-Au solubility contours, the dominant factor affecting the gold dissolution behavior is the (CaO + MgO)/SiO2 ratio, whereas the influence of Al2O3 was negligible. Consequently, less basic slags and higher processing temperatures, in conjunction with a strongly reducing atmosphere, are recommended to increase gold recovery during pyro-processing of Au-containing e-wastes.

  13. Probing structure-induced optical behavior in a new class of self-activated luminescent 0D/1D CaWO₄ metal oxide – CdSe nanocrystal composite heterostructures

    DOE PAGESBeta

    Han, Jinkyu; McBean, Coray; Wang, Lei; Hoy, Jessica; Jaye, Cherno; Liu, Haiqing; Li, Zhuo-Qun; Sfeir, Matthew Y.; Fischer, Daniel A.; Taylor, Gordon T.; et al

    2015-01-30

    In this report, we synthesize and characterize the structural and optical properties of novel heterostructures composed of (i) semiconducting nanocrystalline CdSe quantum dot (QDs) coupled with (ii) both one and zero-dimensional (1D and 0D) motifs of self-activated luminescence CaWO₄ metal oxides. Specifically, ~4 nm CdSe QDs have been anchored onto (i) high-aspect ratio 1D nanowires, measuring ~230 nm in diameter and ~3 μm in length, as well as onto (ii) crystalline 0D nanoparticles (possessing an average diameter of ~ 80 nm) of CaWO₄ through the mediation of 3-mercaptopropionic acid (MPA) as a connecting linker. Composite formation was confirmed by complementarymore » electron microscopy and spectroscopy (i.e. IR and Raman) data. In terms of luminescent properties, our results show that our 1D and 0D heterostructures evince photoluminescence (PL) quenching and shortened PL lifetimes of CaWO₄ as compared with unbound CaWO₄. We propose that a photo-induced electron transfer process occurs from CaWO₄ to CdSe QDs, a scenario which has been confirmed by NEXAFS measurements and which highlights a decrease in the number of unoccupied orbitals in the conduction bands of CdSe QDs. By contrast, the PL signature and lifetimes of MPA-capped CdSe QDs within these heterostructures do not exhibit noticeable changes as compared with unbound MPA-capped CdSe QDs. The striking difference in optical behavior between CaWO₄ nanostructures and CdSe QDs within our heterostructures can be correlated with the relative positions of their conduction and valence energy band levels. In addition, the PL quenching behaviors for CaWO₄ within the heterostructure configuration were examined by systematically varying (i) the quantities and coverage densities of CdSe QDs as well as (ii) the intrinsic morphology (and by extension, the inherent crystallite size) of CaWO₄ itself.« less

  14. The nature and origin of type B1 and B2 Ca-Al-rich inclusions in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Wark, D. A.; Lovering, J. F.

    1982-01-01

    The Type B Ca-Al-rich inclusions in the Allende carbonaceous chondrite form a continuous range from the mineralogically concentrically zoned B1 subtype to the unzoned B2 subtype. These subtypes differ in (1) structure, texture, grain size and shape, (2) mineralogical proportions and compositions, (3) accessory mineralogy, (4) relative abundance of spinel framboids, (5) rim layering, (6) major element chemistry, and (7) degree of secondary alteration. These differences, together with observations on the crystallization of synthetic melts, suggest that the B1 inclusions crystallized relatively rapidly from molten parental material while B2 types crystallized relatively slowly close to the solidus from material that had not been completely melted. The same data are used to construct an evaporative residue model for the origin of the parental Type B materials. In the model, dust in the protosolar nebula was heated with removal of more volatile elements, leaving completely melted (Type B1) residues at the highest temperatures and incompletely melted, less highly evaporated (Type B2) residues at lower temperatures.

  15. Site-sensitive energy transfer modes in Ca3Al2O6: Ce(3+)/Tb(3+)/Mn(2+) phosphors.

    PubMed

    Zhang, Jilin; He, Yani; Qiu, Zhongxian; Zhang, Weilu; Zhou, Wenli; Yu, Liping; Lian, Shixun

    2014-12-28

    Ce(3+)/Eu(2+), Tb(3+) and Mn(2+) co-doping in single-phase hosts is a common strategy to achieve white-light phosphors via energy transfer, which provides a high color rendering index (CRI) value and good color stability. However, not all hosts are suitable for white-light phosphors due to inefficient energy transfer. In this study, the site-sensitive energy transfer from different crystallographic sites of Ce(3+) to Tb(3+)/Mn(2+) in Ca3Al2O6 has been investigated in detail. The energy transfer from purplish-blue Ce(3+) to Tb(3+) is an electric dipole-dipole mode, and the calculated critical distance (Rc) suggests the existence of purplish-blue Ce(3+)-Tb(3+) clusters. No energy transfer is observed from purplish-blue Ce(3+) to Mn(2+). In co-doped phosphors based on greenish-blue Ce(3+), however, the radiative mode dominates the energy transfer from Ce(3+) to Tb(3+), and an electric dipole-quadrupole interaction is responsible for the energy transfer from Ce(3+) to Mn(2+). A detailed discussion on the site-sensitive energy transfer modes might provide a new aspect to discuss and understand the possibilities and mechanisms of energy transfer, according to certain crystallographic sites in a complex host with different cation sites, as well as provide a possible approach in searching for single-phase white-light-emitting phosphors. PMID:25354712

  16. Optimizing the Dopant and Carrier Concentration of Ca5Al2Sb6 for High Thermoelectric Efficiency.

    PubMed

    Yan, Yuli; Zhang, Guangbiao; Wang, Chao; Peng, Chengxiao; Zhang, Peihong; Wang, Yuanxu; Ren, Wei

    2016-01-01

    The effects of doping on the transport properties of Ca5Al2Sb6 are investigated using first-principles electronic structure methods and Boltzmann transport theory. The calculated results show that a maximum ZT value of 1.45 is achieved with an optimum carrier concentration at 1000 K. However, experimental studies have shown that the maximum ZT value is no more than 1 at 1000 K. By comparing the calculated Seebeck coefficient with experimental values, we find that the low dopant solubility in this material is not conductive to achieve the optimum carrier concentration, leading a smaller experimental value of the maximum ZT. Interestingly, the calculated dopant formation energies suggest that optimum carrier concentrations can be achieved when the dopants and Sb atoms have similar electronic configurations. Therefore, it might be possible to achieve a maximum ZT value of 1.45 at 1000 K with suitable dopants. These results provide a valuable theoretical guidance for the synthesis of high-performance bulk thermoelectric materials through dopants optimization. PMID:27406178

  17. Optimizing the Dopant and Carrier Concentration of Ca5Al2Sb6 for High Thermoelectric Efficiency

    PubMed Central

    Yan, Yuli; Zhang, Guangbiao; Wang, Chao; Peng, Chengxiao; Zhang, Peihong; Wang, Yuanxu; Ren, Wei

    2016-01-01

    The effects of doping on the transport properties of Ca5Al2Sb6 are investigated using first-principles electronic structure methods and Boltzmann transport theory. The calculated results show that a maximum ZT value of 1.45 is achieved with an optimum carrier concentration at 1000 K. However, experimental studies have shown that the maximum ZT value is no more than 1 at 1000 K. By comparing the calculated Seebeck coefficient with experimental values, we find that the low dopant solubility in this material is not conductive to achieve the optimum carrier concentration, leading a smaller experimental value of the maximum ZT. Interestingly, the calculated dopant formation energies suggest that optimum carrier concentrations can be achieved when the dopants and Sb atoms have similar electronic configurations. Therefore, it might be possible to achieve a maximum ZT value of 1.45 at 1000 K with suitable dopants. These results provide a valuable theoretical guidance for the synthesis of high-performance bulk thermoelectric materials through dopants optimization. PMID:27406178

  18. Optimizing the Dopant and Carrier Concentration of Ca5Al2Sb6 for High Thermoelectric Efficiency

    NASA Astrophysics Data System (ADS)

    Yan, Yuli; Zhang, Guangbiao; Wang, Chao; Peng, Chengxiao; Zhang, Peihong; Wang, Yuanxu; Ren, Wei

    2016-07-01

    The effects of doping on the transport properties of Ca5Al2Sb6 are investigated using first-principles electronic structure methods and Boltzmann transport theory. The calculated results show that a maximum ZT value of 1.45 is achieved with an optimum carrier concentration at 1000 K. However, experimental studies have shown that the maximum ZT value is no more than 1 at 1000 K. By comparing the calculated Seebeck coefficient with experimental values, we find that the low dopant solubility in this material is not conductive to achieve the optimum carrier concentration, leading a smaller experimental value of the maximum ZT. Interestingly, the calculated dopant formation energies suggest that optimum carrier concentrations can be achieved when the dopants and Sb atoms have similar electronic configurations. Therefore, it might be possible to achieve a maximum ZT value of 1.45 at 1000 K with suitable dopants. These results provide a valuable theoretical guidance for the synthesis of high-performance bulk thermoelectric materials through dopants optimization.

  19. Energetics of multicomponent diffusion in molten CaO-Al 2O 3-SiO 2

    NASA Astrophysics Data System (ADS)

    Liang, Yan; Davis, Andrew M.

    2002-02-01

    The energetics of multicomponent diffusion in molten CaO-Al 2O 3-SiO 2 (CAS) were examined experimentally at 1440 to 1650°C and 0.5 to 2 GPa. Two melt compositions were investigated: a haplodacitic melt (25 wt.% CaO, 15% Al 2O 3, and 60% SiO 2) and a haplobasaltic melt (35% CaO, 20% Al 2O 3, and 45% SiO 2). Diffusion matrices were measured in a mass-fixed frame of reference with simple oxides as end-member components and Al 2O 3 as a dependent variable. Chemical diffusion in molten CAS shows clear evidence of diffusive coupling among the components. The diffusive flux of SiO 2 is significantly enhanced whenever there is a large CaO gradient that is oriented in a direction opposite to the SiO 2 gradient. This coupling effect is more pronounced in the haplodacitic melt and is likely to be significant in natural magmas of rhyolitic to andesitic compositions. The relative magnitude of coupled chemical diffusion is not very sensitive to changes in temperature and pressure. To a good approximation, the measured diffusion matrices follow well-defined Arrhenius relationships with pressure and reciprocal temperature. Typically, a change in temperature of 100°C results in a relative change in the elements of diffusion matrix of 50 to 100%, whereas a change in pressure of 1 GPa introduces a relative change in elements of diffusion matrix of 4 to 6% for the haplobasalt, and less than 5% for the haplodacite. At a pressure of 1 GPa, the ratios between the major and minor eigenvalues of the diffusion matrix λ 1/λ 2 are not very sensitive to temperature variations, with an average of 5.5 ± 0.2 for the haplobasalt and 3.7 ± 0.6 for the haplodacite. The activation energies for the major and minor eigenvalues of the diffusion matrix are 215 ± 12 and 240 ± 21 kJ mol -1, respectively, for the haplodacite and 192 ± 8 and 217 ± 14 kJ mol -1 for the haplobasalt. These values are comparable to the activation energies for self-diffusion of calcium and silicon at the same melt

  20. High-pressure modifications of CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}, and BaAl{sub 2}: Implications for Laves phase structural trends

    SciTech Connect

    Kal, Subhadeep; Stoyanov, Emil; Belieres, Jean-Philippe; Groy, Thomas L.; Norrestam, Rolf; Haeussermann, Ulrich

    2008-11-15

    High-pressure forms of intermetallic compounds with the composition CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}, and BaAl{sub 2} were synthesized from CeCu{sub 2}-type precursors (CaZn{sub 2}, SrZn{sub 2}, SrAl{sub 2}) and Ba{sub 21}Al{sub 40} by multi-anvil techniques and investigated by X-ray powder diffraction (SrAl{sub 2} and BaAl{sub 2}), X-ray single-crystal diffraction (CaZn{sub 2}), and electron microscopy (SrZn{sub 2}). Their structures correspond to that of Laves phases. Whereas the dialuminides crystallize in the cubic MgCu{sub 2} (C15) structure, the dizincides adopt the hexagonal MgZn{sub 2} (C14) structure. This trend is in agreement with the structural relationship displayed by sp bonded Laves phase systems at ambient conditions. - Graphical abstract: CeCu{sub 2}-type polar intermetallics can be transformed to Laves phases upon simultaneous application of pressure and temperature. The observed structures are controlled by the valence electron concentration.

  1. Enhanced Emission from Li2CaSiO4:Dy3+ Phosphors by Doping with Al3+ and B3+

    NASA Astrophysics Data System (ADS)

    Erdoğmuş, E.

    2016-05-01

    Pure Li2CaSiO4, Li2CaSiO4:Dy3+ and Al3+, B3+ co-doped materials were prepared by a solid-state reaction in air at 900°C for 6 h and characterized by using powder XRD. The luminescence properties of the synthesized phosphors were measured at room temperature with a spectrofluorometer. Li2CaSiO4:Dy3+ emits at 484, 575, and 660 nm upon 352 nm excitation. The emission spectrum intensity of Dy3+ increased from 0.01 to 0.06 mol.%, and beyond 0.06 mol.%, concentration quenching was observed. Also, in this study, the effects of boric acid and aluminum oxide concentration on the photoluminescence properties of Dy3+ doped phosphors were investigated. The results showed that boric acid and aluminum oxide were effective in improving the photoluminescence intensity of Li2CaSiO4:Dy3+ compounds.

  2. Ca2+ Influx and Tyrosine Kinases Trigger Bordetella Adenylate Cyclase Toxin (ACT) Endocytosis. Cell Physiology and Expression of the CD11b/CD18 Integrin Major Determinants of the Entry Route

    PubMed Central

    Etxebarria, Aitor; González-Bullón, David; Gómez-Bilbao, Geraxane; Ostolaza, Helena

    2013-01-01

    Humans infected with Bordetella pertussis, the whooping cough bacterium, show evidences of impaired host defenses. This pathogenic bacterium produces a unique adenylate cyclase toxin (ACT) which enters human phagocytes and catalyzes the unregulated formation of cAMP, hampering important bactericidal functions of these immune cells that eventually cause cell death by apoptosis and/or necrosis. Additionally, ACT permeabilizes cells through pore formation in the target cell membrane. Recently, we demonstrated that ACT is internalised into macrophages together with other membrane components, such as the integrin CD11b/CD18 (CR3), its receptor in these immune cells, and GM1. The goal of this study was to determine whether ACT uptake is restricted to receptor-bearing macrophages or on the contrary may also take place into cells devoid of receptor and gain more insights on the signalling involved. Here, we show that ACT is rapidly eliminated from the cell membrane of either CR3-positive as negative cells, though through different entry routes, which depends in part, on the target cell physiology and characteristics. ACT-induced Ca2+ influx and activation of non-receptor Tyr kinases into the target cell appear to be common master denominators in the different endocytic strategies activated by this toxin. Very importantly, we show that, upon incubation with ACT, target cells are capable of repairing the cell membrane, which suggests the mounting of an anti-toxin cell repair-response, very likely involving the toxin elimination from the cell surface. PMID:24058533

  3. An SEM, EDS and vibrational spectroscopic study of the silicate mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Scholz, Ricardo

    2015-02-01

    The mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)] is a crystalline sodium calcium beryllium silicate which has the potential to be used as piezoelectric material and for other ferroelectric applications. The mineral has been characterized by a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and vibrational spectroscopy. EDS analysis shows a material with high concentrations of Si and Ca and low amounts of Na, Al and F. Beryllium was not detected. Raman bands at 1016 and 1050 cm-1 are assigned to the SiO and AlOH stretching vibrations of three dimensional siloxane units. The infrared spectrum of meliphanite is very broad in comparison with the Raman spectrum. Raman bands at 472 and 510 cm-1 are assigned to OSiO bending modes. Raman spectroscopy identifies bands in the OH stretching region. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral meliphanite.

  4. 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.

  5. Optically stimulated luminescence (OSL) response of Al2O3:C, BaFCl:Eu and K2Ca2(SO4)3:Eu phosphors.

    PubMed

    Kumar, Pratik; Bahl, Shaila; Sahare, P D; Kumar, Surender; Singh, Manveer

    2015-12-01

    This paper investigates the optically stimulated luminescence (OSL) response of BaFCl:Eu and K2Ca2(SO4)3:Eu phosphors for different doses and bleaching durations. The results have also been compared with the commercially available Landauer Al2O3:C (Luxel®) dosemeter. Nanocrystalline K2Ca2(SO4)3:Eu is known to be a sensitive thermoluminescent phosphor, but its OSL response is hardly reported. At first, pellets of nanocrystalline K2Ca2(SO4)3:Eu powder were prepared by adding Teflon as a binder. Their OSL signal was compared with that of the material in pure form, i.e. without adding the binder (in 100:1 ratio). It was observed that adding the binder does not appreciably affect the OSL intensity. On comparison with the commercially available Al2O3:C from Landauer, it was found that K2Ca2(SO4)3:Eu is around 15 times less sensitive than Al2O3:C. 'Homemade' BaFCl:Eu phosphor has also been studied. The intensity of BaFCl:Eu was ∼20 times more than the standard Al2O3:C dosemeter and ∼200 times more sensitive than K2Ca2(SO4)3:Eu in the dose range of 13-200 cGy. OSL dosemeters are believed to give luminescence signal even if they are read before, i.e. multiple reading may be possible under suitable conditions after single exposure. This was also checked for all the prepared dosemeters and it was found that Al2O3:C showed the least decrease of <2 %, followed by BaFCl:Eu of 15 % and K2Ca2(SO4)3:Eu with 20 %. Finally, Al2O3:C and BaFCl:Eu phosphors were also studied for their optical bleaching durations to which the respective signals get completely removed so that the phosphor can be re-used. It was observed that BaFCl:Eu is bleached faster and more easily than Al2O3:C. PMID:25646524

  6. Structure-property relationships in an Al matrix Ca nanofilamentary composite conductor with potential application in high-voltage power transmission

    NASA Astrophysics Data System (ADS)

    Tian, Liang

    This study investigated the processing-structure-properties relationships in an Al/Ca composites using both experiments and modeling/simulation. A particular focus of the project was understanding how the strength and electrical conductivity of the composite are related to its microstructure in the hope that a conducting material with light weight, high strength, and high electrical conductivity can be developed to produce overhead high-voltage power transmission cables. The current power transmission cables (e.g., Aluminum Conductor Steel Reinforced (ACSR)) have acceptable performance for high-voltage AC transmission, but are less well suited for high-voltage DC transmission due to the poorly conducting core materials that support the cable weight. This Al/Ca composite was produced by powder metallurgy and severe plastic deformation by extrusion and swaging. The fine Ca metal powders have been produced by centrifugal atomization with rotating liquid oil quench bath, and a detailed study about the atomization process and powder characteristics has been conducted. The microstructure of Al/Ca composite was characterized by electron microscopy. Microstructure changes at elevated temperature were characterized by thermal analysis and indirect resistivity tests. The strength and electrical conductivity were measured by tensile tests and four-point probe resistivity tests. Predicting the strength and electrical conductivity of the composite was done by micro-mechanics-based analytical modeling. Microstructure evolution was studied by mesoscale-thermodynamics-based phase field modeling and a preliminary atomistic molecular dynamics simulation. The application prospects of this composite was studied by an economic analysis. This study suggests that the Al/Ca (20 vol. %) composite shows promise for use as overhead power transmission cables. Further studies are needed to measure the corrosion resistance, fatigue properties and energized field performance of this composite.

  7. Low-noise, low-power HgCdTe/Al2O3 1024 x 1024 FPAs

    NASA Astrophysics Data System (ADS)

    Kozlowski, Lester J.; Vural, Kadri; Cooper, Donald E.; Chen, C. Y.; Stephenson, D. M.; Cabelli, Scott A.

    1996-10-01

    We have developed two high performance 1024 multiplied by 1024 focal plane arrays for astronomy, spectroscopy, surveillance and conventional imaging. Each hybrid consists of a photovoltaic HgCdTe detector array, fabricated on Al2O3 substrate and having photoresponse cutoff wavelength optimized for each specific application, mated to a CMOS silicon readout via indium column interconnects. In addition to updating the performance of our 1024 multiplied by 1024 FPA for astronomy developed in 1994, we introduce a second 1024 multiplied by 1024 having capability for operation at TV-type frame rates. The latter device also has low read noise but at much higher bandwidth by virtue of its capacitive transimpedance amplifier input and pipelined readout architecture. Both devices have been shown capable of consistently achieving background-limited sensitivity at very low infrared backgrounds (less than or equal to 109 photons/cm2-sec) by their low read noise, low dark current including negligible MOSFET self-emission, and high quantum efficiency. FPA pixel operability as high as 99.94% with mean peak D* of 1014 cm-Hz1/2/W has been demonstrated. Proprietary hybridization and mounting techniques are being used to insure hybrid reliability after many thermal cycles. The hybrid methodology has been modeled using finite element modeling to understand the limiting mechanisms; very good agreement has been achieved with the measured reliability.

  8. Low dietary levels of Al, Pb and Cd may affect the non-enzymatic antioxidant capacity in caged honey bees (Apis mellifera).

    PubMed

    Gauthier, Maxime; Aras, Philippe; Jumarie, Catherine; Boily, Monique

    2016-02-01

    Several hypotheses have been proposed to explain the abnormally high mortality rate observed in bee populations in Europe and North America. While studies based on the effects of pesticides are paramount, the metals present in agroecosystems are often overlooked. Sources of metals are linked to the nature of soils and to agricultural practices, namely the use of natural or chemical nutrients as well as residual materials from waste-water treatment sludge. The aim of this study was to investigate the effects of metals on honey bees exposed for 10 days to environmentally realistic concentrations of Al, Pb and Cd (dissolved in syrup). The monitoring of syrup consumption combined with the quantification of metals in bees revealed the following order for metal bioconcentration ratios: Cd > Pb > Al. Alpha-tocopherol, metallothionein-like proteins (MTLPs) and lipid peroxidation were quantified. When bees were exposed to increasing amounts of Cd, a marked augmentation of MTLPs levels was found. Lead (Pb) and Cd caused an increase in α-tocopherol content, while alteration of lipid peroxidation was observed only with Al exposure. These findings raise concerns about the bioavailability and the additional threat posed by metals for pollinators in agricultural areas while providing new insights for potential use of the honey bee as a sentinel species for metal exposure. PMID:26421624

  9. Gas/metal/slag reactions in submerged arc welding using CaO-Al/sub 2/O/sub 3/ based fluxes

    SciTech Connect

    Lau, T.; Weatherly, G.C.; McLean, A.

    1986-02-01

    In this paper, a detailed study is presented of the interactions of Mn, Al and O at the different stages of the welding operation. These interactions have been studied by analyzing the total Mn, Al and O contents, as well as the composition of inclusions formed at the different stages. At the electrode tip and in the arc column, changes in oxygen, aluminum and manganese were dominated by flux decomposition, while at the weld metal stage, slag-metal reactions occurred. These reactions were most extensive in MnO-containing fluxes, and resulted in a significant loss of oxygen, as well as metallic species such as aluminum, by the separation of oxidized products into the slag phase. In the CaF/sub 2/-Al/sub 2/O/sub 3/ containing flux studied, reactions involving CaF/sub 2/, Al/sub 2/O/sub 3/ and dissolved Al and Si led to enhanced Al pickup at the electrode tip. The applicability of equilibrium thermodynamic arguments to welding was assessed by determining the effective temperatures for the pertinent equilibrium reactions. These temperatures were found to be in reasonable agreement with other values in the literature. However, it is the efficiency of inclusion separation to the slag that determines the effective temperature.

  10. SESAM modelocked Yb:CaGdAlO4 laser in the soliton modelocking regime with positive intracavity dispersion.

    PubMed

    Phillips, C R; Mayer, A S; Klenner, A; Keller, U

    2014-03-10

    We demonstrate femtosecond SESAM modelocking in the near-infrared by using cascaded quadratic nonlinearities (phase-mismatched second-harmonic generation, SHG), enabling soliton modelocking in the normal dispersion regime without any dispersion compensating elements. To obtain large and negative self-phase modulation (SPM) we use an intracavity LBO crystal, whose temperature and angles are optimized with respect to SPM, nonlinear losses, and self-starting characteristics. To support femtosecond pulses, we use the very promising Yb:CaGdAlO(4) (CALGO) gain material, operated in a bulk configuration. The LBO crystal provides sufficient negative SPM to compensate for its own GDD as well as the positive GDD and SPM from the gain crystal. The modelocked laser produces pulses of 114 fs at 1050 nm, with a repetition rate of 113 MHz (average output power 1.1 W). We perform a detailed theoretical study of this soliton modelocking regime with positive GDD, which clearly indicates the important design constraints in an intuitive and systematic way. In particular, due to its importance in avoiding multi-pulsed modelocking, we examine the nonlinear loss associated with the cascading process carefully and show how it can be suppressed in practice. With this modelocking regime, it should be possible to overcome the limits faced by current state of the art modelocked lasers in terms of dispersion compensation and nonlinearity management at high powers, suppression of Q-switching in compact GHz lasers, and enabling femtosecond soliton modelocking at very high repetition rates due to the high nonlinearities accessible via cascading combined with eliminating the need for intracavity dispersion compensation. PMID:24663941

  11. [Research on the Relationship between Surface Structure and Fluorescence Intensity of Ca(1-x)Al2Si2O8 : Eu(x)].

    PubMed

    He, Xiao; Zhang, Li-sheng; Zu, En-dong; Yang, Xiao-yun; Dong, Kun

    2016-01-01

    Ca(1-x)Al2Si2O8 : Eu(x)(x = 0, 0.01, 0.05, 0.15) were synthesized by solid-state reaction respectively at 1 150, 1 250 1350 and 1 450 degrees C. With X-ray diffraction(XRD), Raman spectroscopy(Raman), photoluminescence spectroscopy(PL) and X-ray fluorescence spectrometer(XRF), the relationship between surface structure and fluorescence intensity of Ca(1-x) Al2Si2O8: Eu(x) were studied. XRD and Raman results show that, CaAl2Si2O8 anorthite single-phase has formed gradually along with the temperature rising in the process of synthesis. Raman spectroscopy is clear that when the Eu doping amount is the same, Si-O amorphous phase disappear gradually and the CaAl2Si2O8 phase form gradually with the temperature increases. As the temperature increases, vibration peaks position silicon oxygen tetrahedron shift to lower wave number. When 1 450 degrees C, the temperature is too high to destroy the structure of silicon oxygen tetrahedron. At the same time, there is a broadening amorphous peak appears in Raman spectroscopy. The procedure of Al to replace Si is hindered with Eu doped in. It is the result that the peak at 1 620 cm(-1) decreases after the first increases. The change of surface structure associated with the scattering amount of Eu. PL and XRF results show that: as the temperature increases, the amount of Eu atom scattering on the material surface increases gradually, this change lead to the fluorescence intensity raise. Therefore, there is proportional relationship between the fluorescence intensity of the samples and the number of samples per unit surface area of Eu atoms. PMID:27228758

  12. Laboratory Study on Prevention of CaO-Containing ASTM "D-Type" Inclusions in Al-Deoxidized Low-Oxygen Steel Melts During Basic Slag Refining

    NASA Astrophysics Data System (ADS)

    Jiang, Min; Wang, Xin-Hua; Yang, Die; Lei, Shao-Long; Wang, Kun-Peng

    2015-12-01

    Present work was attempted to explore the possibility of preventing CaO-containing inclusions in Al-deoxidized low-oxygen special steel during basic slag refining, which were known as ASTM D-type inclusions. Based on the analysis on formation thermodynamics of CaO-containing inclusions, a series of laboratory experiments were designed and carried out in a vacuum induction furnace. During the experiments, slag/steel reaction equilibrium was intentionally suppressed with the aim to decrease the CaO contents in inclusions, which is different from ordinary concept that slag/steel reaction should be promoted for better control of inclusions. The obtained results showed that high cleanliness of steel was obtained in all the steel melts, with total oxygen contents varied between 0.0003 and 0.0010 pct. Simultaneously, formation of CaO-containing inclusions was successfully prohibited, and all the formed oxide inclusions were MgO-Al2O3 or/and Al2O3 in very small sizes of about 1 to 3 μm. And 90 pct to nearly 98 pct of them were wrapped by relative thicker MnS outer surface layers to produce dual-phased "(MgO-Al2O3) + MnS" or "Al2O3 + MnS" complex inclusions. Because of much better ductility of MnS, certain deformability of these complex inclusions can be expected which is helpful to improve fatigue resistance property of steel. Only very limited number of singular MnS inclusions were with sizes larger than 13 μm, which were formed during solidification because of. In the end, formation of oxide inclusions in steel was qualitatively evaluated and discussed.

  13. Al15Ge4Ni3: A new intergrowth structure with Cu3Au- and CaF2-type building blocks

    NASA Astrophysics Data System (ADS)

    Reichmann, Thomas L.; Jandl, Isabella; Effenberger, Herta S.; Herzig, Peter; Richter, Klaus W.

    2015-05-01

    The new ternary compound Al15Ge4Ni3 (τ2 in the system Al-Ge-Ni) was synthesized in single crystalline form by a special annealing procedure from samples located in the three phase fields [L+Al+τ2] and [L+Ge+τ2]. The crystal structure of Al15Ge4Ni3 was determined by single-crystal X-ray diffraction. The compound crystallizes in a new structure type in space group I4¯3m, Pearson Symbol cI88, cubic lattice parameter a=11.405(1) Å. Phase diagram investigations indicate stoichiometric composition without considerable homogeneity range; τ2 melts peritectically at T=444 °C. The crystal structure of Al15Ge4Ni3 shows a unique combination of simple Cu3Au- and CaF2-type building blocks: a three dimensional network of CaF2-type units, formed by Ni and Al atoms, is interspaced by clusters (Al6Ge8) resembling unit cells of the Cu3Au-type. Both structural motifs are connected by Al-Ge bonds. The ground state energy of the compound was obtained by DFT calculations and the densities of states were analyzed in detail. In addition, electron density maps were calculated in four different sections through the unit cell using the full potential linearized augmented plane-wave (FLAPW) method. The bonding situation in Al15Ge4Ni3 was discussed combining results from electronic calculations with the analysis of the coordination of atoms.

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

    PubMed

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

    2015-07-01

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

  15. Rectification and tunneling effects enabled by Al{sub 2}O{sub 3} atomic layer deposited on back contact of CdTe solar cells

    SciTech Connect

    Liang, Jun; Lin, Qinxian; Li, Hao; Su, Yantao; Yang, Xiaoyang; Wu, Zhongzhen; Zheng, Jiaxin; Wang, Xinwei; Lin, Yuan; Pan, Feng

    2015-07-06

    Atomic layer deposition (ALD) of Aluminum oxide (Al{sub 2}O{sub 3}) is employed to optimize the back contact of thin film CdTe solar cells. Al{sub 2}O{sub 3} layers with a thickness of 0.5 nm to 5 nm are tested, and an improved efficiency, up to 12.1%, is found with the 1 nm Al{sub 2}O{sub 3} deposition, compared with the efficiency of 10.7% without Al{sub 2}O{sub 3} modification. The performance improvement stems from the surface modification that optimizes the rectification and tunneling of back contact. The current-voltage analysis indicates that the back contact with 1 nm Al{sub 2}O{sub 3} maintains large tunneling leakage current and improves the filled factor of CdTe cells through the rectification effect. XPS and capacitance-voltage electrical measurement analysis show that the ALD-Al{sub 2}O{sub 3} modification layer features a desired low-density of interface state of 8 × 10{sup 10 }cm{sup −2} by estimation.

  16. Rectification and tunneling effects enabled by Al2O3 atomic layer deposited on back contact of CdTe solar cells

    NASA Astrophysics Data System (ADS)

    Liang, Jun; Lin, Qinxian; Li, Hao; Su, Yantao; Yang, Xiaoyang; Wu, Zhongzhen; Zheng, Jiaxin; Wang, Xinwei; Lin, Yuan; Pan, Feng

    2015-07-01

    Atomic layer deposition (ALD) of Aluminum oxide (Al2O3) is employed to optimize the back contact of thin film CdTe solar cells. Al2O3 layers with a thickness of 0.5 nm to 5 nm are tested, and an improved efficiency, up to 12.1%, is found with the 1 nm Al2O3 deposition, compared with the efficiency of 10.7% without Al2O3 modification. The performance improvement stems from the surface modification that optimizes the rectification and tunneling of back contact. The current-voltage analysis indicates that the back contact with 1 nm Al2O3 maintains large tunneling leakage current and improves the filled factor of CdTe cells through the rectification effect. XPS and capacitance-voltage electrical measurement analysis show that the ALD-Al2O3 modification layer features a desired low-density of interface state of 8 × 1010 cm-2 by estimation.

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

    PubMed

    Bütev, Ezgi; Esen, Ziya; Bor, Şakir

    2016-07-01

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

  18. New insights into organic-inorganic hybrid perovskite CH3NH3PbI3 nanoparticles. An experimental and theoretical study of doping in Pb2+ sites with Sn2+, Sr2+, Cd2+ and Ca2+

    NASA Astrophysics Data System (ADS)

    Navas, Javier; Sánchez-Coronilla, Antonio; Gallardo, Juan Jesús; Cruz Hernández, Norge; Piñero, Jose Carlos; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; de Los Santos, Desireé M.; Aguilar, Teresa; Martín-Calleja, Joaquín

    2015-03-01

    This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb2+ position with Sn2+, Sr2+, Cd2+ and Ca2+. The incorporation of the dopants into the crystalline structure was analysed, observing how the characteristics of the dopant affected properties such as the crystalline phase, emission and optical properties. XRD showed how doping with Sn2+, Sr2+ and Cd2+ did not modify the normal tetragonal phase. When doping with Ca2+, the cubic phase was obtained. Moreover, DR-UV-Vis spectroscopy showed how the band gap decreased with the dopants, the values following the trend Sr2+ < Cd2+ < Ca2+ < CH3NH3PbI3 ~ Sn2+. The biggest decrease was generated by Sr2+, which reduced the CH3NH3PbI3 value by 4.5%. In turn, cathodoluminescence (CL) measurements confirmed the band gap obtained. Periodic-DFT calculations were performed to understand the experimental structures. The DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy, with the values calculated following the trend Sn2+ ~ Pb2+ > Cd2+ > Sr2+ for the tetragonal structure and Pb2+ > Ca2+ for the cubic phase. The electron localization function (ELF) analysis showed similar electron localizations for undoped and Sn2+-doped tetragonal structures, which were different from those doped with Sr2+ and Cd2+. Furthermore, when Cd2+ was incorporated, the Cd-I interaction was strengthened. For Ca2+ doping, the Ca-I interaction had a greater ionic nature than Cd-I. Finally, an analysis based on the non-covalent interaction (NCI) index is presented to determine the weak-type interactions of the CH3NH3 groups with the dopant and I atoms. To our knowledge, this kind of analysis with these hybrid systems has not been performed previously.This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb2+ position with Sn2+, Sr2+, Cd2+ and Ca2+. The incorporation of the dopants into the crystalline structure was analysed

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Caurant, Daniel; Loiseau, Pascal; Bardez, Isabelle

    2010-12-01

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

  1. Modeling of viscosities of the partly crystallized slags in the Al2O3-CaO-``FeO''-SiO2 system

    NASA Astrophysics Data System (ADS)

    Kondratiev, Alex; Jak, Evgueni

    2001-12-01

    A viscosity model of the partly crystallized slag in the Al2O3-CaO-‘FeO’-SiO2 system has been developed in conjunction with the thermodynamic computer package F*A*C*T. Proportions of solids crystallized out of the liquid phase and compositions of the remaining liquid phase predicted by F*A*C*T are used in the viscosity model. Various heterogeneous viscosity models have been tested using large experimental dataset in the Al2O3-CaO-‘FeO’-SiO2 system in reducing conditions close to the equilibrium with metallic iron. The Roscoe equation with new empirical parameters was found to provide reasonable agreement with experimental data. Examples of model application to industrial nonferrous smelting slag systems are presented. This model can also be applied to coal ash slags.

  2. Low-threshold ultraviolet solid-state laser based on a Ce3+:LiCaAlF6 crystal resonator.

    PubMed

    Le, Thanh; Schowalter, Steven J; Rellergert, Wade; Jeet, Justin; Lin, Guoping; Yu, Nan; Hudson, Eric R

    2012-12-01

    A low-threshold solid-state UV laser using a whispering gallery mode (WGM) resonator constructed from UV transparent crystalline material is demonstrated. Using a Ce3+:LiCaAlF6 resonator, we observe broad bandwidth lasing (280-330 nm) with a low threshold intensity of 7.5×10(9) W/m(2) and an effective slope efficiency of ~25%. The lasing time delay dynamics in the pulsed operation mode are also observed and analyzed. Additionally, a LiCaAlF(6) WGM resonator with Q=2×10(7) at 370 nm is realized. The combination of this high Q and the small WGM mode volume significantly lowers the pump power threshold compared to traditional cavity designs, opening the door for both tunable continuous-wave and mode-locked operation. PMID:23202104

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

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, Isidor

    1988-01-01

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

  4. Crystallization paths in SiO2-Al2O3-CaO system as a genotype of silicate materials

    NASA Astrophysics Data System (ADS)

    Lutsyk, V. I.; Zelenaya, A. E.

    2013-12-01

    The phases trajectories in the fields of primary crystallization of cristobalite (SiO2cr), tridymite (SiO2tr), mullite (3Al2O3-2SiO2) and in a field of liquid immiscibility are analyzed on a basis of computer model for T-x-y diagram of SiO2-Al2O3-CaO system. The concentration fields with unique set of microconstituents and the fields without individual crystallization schemes and microconstituents are revealed.

  5. Mode of formation of hibonite (CaAl12O19) within the U-Th skarns from the granulites of S-E Madagascar

    NASA Astrophysics Data System (ADS)

    Rakotondrazafy, Michel A. F.; Moine, B.; Cuney, M.

    1996-03-01

    In Madagascar, hibonite occurs as a rather frequent mineral within thorianite-bearing skarns which are widespread in the Pan African granulitic formations constituting the S-E part of the Island (Tranomaro area). In these skarns, leucocratic segregations made up of CO3-scapolite to meionite (Anequivalent=89 95% which implies T≥850° C), spinel and corundum were formed at stage 1 of metasomatism in a titanite-bearing matrix consisting of scapolite (Aneq=77 88) and aluminous diopside. During stage 2 of metasomatism, scapolite from the lenses were altered to anorthite+calcite while the less calcic scapolite remained stable which indicates T≈800° C. Hibonite crystallized at the expense of corundum and spinel. Expressed as mol% of the CaAl12O19/Ca(Al10TiR2+)O19/REE(Al11R2+)O19 [+Th (Al10R2+ 2)O19] end-members ( R 2+=Mg, Fe2+, Zn2+; Al=Al, Fe3+; Ti=Ti, Si), its composition varies from 26/72/2 to 50/23/27. The ideal activity of the CaAl12O19 component is about 0.25. Fluid inclusions in corundum, hibonite and anorthite are composed of nearly pure CO2. In corundum, the isochores for primary inclusions are in agreement with the P-T estimates for regional metamorphism and stage 1 metasomatism ( T≈850° C, P≈5 kbar). Inclusions with the highest density in hibonite and anorthite constrain P to about 3 3.5 kbar for T=800° C. Thermodynamic calculations indicate that, in addition to a low activity of CaAl12O19, stability of hibonite in equilibrium with anorthite and calcite implies an extremely low activity of silica (below the zircon-baddeleyite buffer). By contrast the activity of CO2 may be high, in agreement with the observed fluid compositions. These results are corroborated by a short comparison with the other granulite occurrences of hibonite in Tanzania and South India.

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

    PubMed Central

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

    2008-01-01

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

  7. Oxidative stress is involved in the heat stress-induced downregulation of TCR zeta chain expression and TCR/CD3-mediated [Ca(2+)](i) response in human T-lymphocytes.

    PubMed

    Nambiar, Madhusoodana P; Fisher, Carolyn U; Enyedy, Edith J; Warke, Vishal G; Kumar, Anil; Tsokos, George C

    2002-02-01

    Exposure of human T-lymphocytes to heat downregulates TCR zeta chain expression and inhibits (TCR)/CD3-mediated production of inositol triphosphate and [Ca(2+)](i) signaling. Here we investigated whether oxidative stress is involved in the heat-induced downregulation of TCR/CD3-mediated signaling. To this end, we have studied the effect of a thiol antioxidant, N-acetyl-L-cysteine (NAC), and a non-thiol antioxidant, allopurinol, on heat-induced downregulation of TCR/CD3-mediated signaling. We found that preincubation of cells with 10mM NAC significantly reversed the downregulation of TCR/CD3-mediated [Ca(2+)](i) response and restored the suppression of TCR zeta chain protein expression as well as prevented its increased membrane distribution in heat-treated cells. NAC also reversed the downregulation of TCR zeta chain mRNA expression and the active 94kDa TCR zeta chain transcription factor, Elf-1, in heat-treated cells. Consistent with the increase in the TCR zeta chain, preincubation with NAC increased the levels of antigen receptor-induced tyrosine phosphorylation of several cytosolic proteins. Finally, treatment with NAC was able to reverse the suppression of IL-2 production in heat-treated cells. Inactive analog, N-acetylserine, failed to reverse the heat-induced downregulation of TCR/CD3-mediated signaling. Allopurinol, another potent non-thiol antioxidant, also restored the TCR/CD3-mediated [Ca(2+)](i) response in heat-treated cells. These results demonstrate that antioxidants restore the expression of TCR zeta chain and reverse the TCR/CD3-mediated signaling abnormalities associated with heat stress and suggest that heat shock-induced oxidative stress is a mediator of the heat-induced biochemical damage that leads to downregulation of signaling in human T-lymphocytes. PMID:12202152

  8. Superconductivity up to 114 K in the Bi-Al-Ca-Sr-Cu-O compound system without rare-earth elements

    NASA Technical Reports Server (NTRS)

    Chu, C. W.; Bechtold, J.; Gao, L.; Hor, P. H.; Huang, Z. J.

    1988-01-01

    Stable superconductivity up to 114 K has been reproducibly detected in Bi-Al-Ca-Sr-Cu-O multiphase systems without any rare-earth elements. Pressure has only a slight positive effect on T(c). These observations provide an extra material base for the study of the mechanism of high-temperature superconductivity and also the prospect of reduced material cost for future applications of superconductivity.

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

    NASA Astrophysics Data System (ADS)

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

    1994-05-01

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

  10. Upconversion luminescence properties and color tunability of 12CaOṡ7Al2O3:Ho3+/Yb3+ single crystal

    NASA Astrophysics Data System (ADS)

    Qu, Yunfei; Qiu, Zhaozhong; Wang, Rui; Liu, Liang; Tao, Ye; Zhou, Jianjun

    2016-03-01

    Rear earth (RE) ions-doped 12CaOṡ7Al2O3 single crystal has been successfully prepared by Czochralski method. Under 980 nm excitation, a strong green upconversion emission at 548 nm and a weaker red upconversion emission at 662 nm were observed. The green upconversion emission is corresponding to the transition of 5F 4/5S2 →5I8 of Ho3+, and the red one is corresponding to the transition of 5F5 →5I8 of Ho3+. A much weaker NIR band at 762 nm is also observed, which corresponds to the 5F 4/5S2 →5I7 transition of Ho3+. The pump dependence and luminescence decay dynamics spectra show the green and red upconversion are populated by two-photon process, and the upconversion mechanisms are analyzed in detail. The color of the upconversion luminescence can be changed by simply adjusting the excitation power. RE ions-doped 12CaOṡ7Al2O3 single crystal with these properties is expected to have broad application prospects in solid-state multicolor display and instrument integration. RE ions-doped 12CaOṡ7Al2O3 single crystal has the ability to replace some traditional single crystals such as LiNbO3 in many applications.

  11. SiO 2-CaO-B 2O 3-Al 2O 3 ceramic glaze as sealant for planar ITSOFC

    NASA Astrophysics Data System (ADS)

    Zheng, R.; Wang, S. R.; Nie, H. W.; Wen, T.-L.

    A series of ceramic glazes based on the SiO 2-CaO-B 2O 3-Al 2O 3 system as sealant for intermediate temperature solid oxide fuel cell (ITSOFC) were investigated. Different ratios of B 2O 3/SiO 2 and Al 2O 3/CaO were investigated to control softening process, phase separation, and crystallization. When B 2O 3/SiO 2 ratio was in the range of 0.14-0.27, the glazes showed good wetting and bonding behavior with both 8 mol% yttria-stabilized zirconia (8YSZ) electrolyte and stainless steel interconnect which could satisfy the sealing demand at 850 °C. And the dimension stability can be kept for over 100 h by introducing ceramic felt and controlling the glazes viscosity in the range of 10 4 to 10 6 Pa s. By means of controlling Al 2O 3/CaO ratio in the range of 0.4-0.68, phase separation and crystallization were restrained effectively. After holding at 850 °C for 100 h, non-crystalline network in the glazes could be found, and a suitable viscous flow could well relax thermal stress. The sealing was effective even after 10 thermal cycles. Element analysis showed a good chemical stability at the ceramic glazes/stainless steel interconnect and ceramic glazes/8YSZ electrolyte interfaces.

  12. A single-component white-emitting CaSr2Al2O6:Ce3+, Li+, Mn2+ phosphor via energy transfer.

    PubMed

    Li, Yanyan; Shi, Yurong; Zhu, Ge; Wu, Quansheng; Li, Hao; Wang, Xicheng; Wang, Qian; Wang, Yuhua

    2014-07-21

    A series of single-component Ce(3+), Li(+), Mn(2+) ions codoped color-tunable CaSr2Al2O6 phosphors were synthesized by a high-temperature solid-state reaction, and the photoluminescence properties as well as the energy transfer mechanism from Ce(3+) to Mn(2+) ions have been investigated in detail. The Ce(3+) activated phosphors have strong absorption in the range of 250-420 nm and can give a blue emission centered at about 460 nm. When Mn(2+) ions are codoped, the emission of CaSr2Al2O6:Ce(3+), Li(+), Mn(2+) phosphors can be tuned from blue to red through adjusting the doping concentration of the Mn(2+) ions, under the irradiation of 358 nm. When the concentration of Mn(2+) is increased to 0.02, a warm-white light can be obtained with good CIE coordinates of (0.388, 0.323) and a low CCT of 3284 K. The energy transfer mechanism from the Ce(3+) to Mn(2+) ions is demonstrated to be a quadrupole-quadrupole interaction based on the analysis of the decay curves of the phosphors. The thermal quenching stability was also investigated. The results indicate that CaSr2Al2O6:Ce(3+), Li(+), Mn(2+) samples might have potential applications in w-LEDs. PMID:24968122

  13. A Reaction Between High Mn-High Al Steel and CaO-SiO2-Type Molten Mold Flux: Part II. Reaction Mechanism, Interface Morphology, and Al2O3 Accumulation in Molten Mold Flux

    NASA Astrophysics Data System (ADS)

    Kang, Youn-Bae; Kim, Min-Su; Lee, Su-Wan; Cho, Jung-Wook; Park, Min-Seok; Lee, Hae-Geon

    2013-04-01

    Following a series of laboratory-scale experiments, the mechanism of a chemical reaction 4[{Al}] + 3({SiO}_2) = 3[{Si}] + 2({Al}_2{O}_3) between high-alloyed TWIP (TWin-Induced Plasticity) steel containing Mn and Al and molten mold flux composed mainly of CaO-SiO2 during the continuous casting process is discussed in the present article in the context of kinetic analysis, morphological evolution at the reaction interface. By the kinetic analysis using a two-film theory, a rate-controlling step of the chemical reaction at the interface between the molten steel and the molten flux is found to be mass transport of Al in a boundary layer of the molten steel, as long as the molten steel and the molten flux phases are concerned. Mass transfer coefficient of the Al in the boundary layer (k_{{Al}}) is estimated to be 0.9 to 1.2 × 10-4 m/s at 1773 K (1500 ^{circ}C). By utilizing experimental data at various temperatures, the following equation is obtained for the k_{{Al}}; ln k_{{Al}} = -14,290/T - 1.1107. Activation energy for the mass transfer of Al in the boundary layer is 119 kJ/mol, which is close to a value of activation energy for mass transfer in metal phase. The composition evolution of Al in the molten steel was well explained by the mechanism of Al mass transfer. On the other hand, when the concentration of Al in the steel was high, a significant deviation of the composition evolution of Al in the molten steel was observed. By observing reaction interface between the molten steel and the molten flux, it is thought that the chemical reaction controlled by the mass transfer of Al seemed to be disturbed by formation of a solid product layer of MgAl2O4. A model based on a dynamic mass balance and the reaction mechanism of mass transfer of Al in the boundary layer for the low Al steel was developed to predict (pct Al2O3) accumulation rate in the molten mold flux.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  15. Uwachib'alil Qach'ab'al--Asi se Ilustra mi Palabra (Illustrating My Words). [CD-ROM].

    ERIC Educational Resources Information Center

    Academy for Educational Development, Washington, DC.

    This CD-ROM is part of an interactive and dynamic multimedia package of information and games for learning K'iche' and Ixil. This CD-ROM contains a database of 3,000 culturally-relevant vocabulary words in K'iche', Ixil, and Spanish, with appropriate illustrations that describe traditional Mayan rituals, foods, beliefs, clothing, and other topics.…

  16. Synthesis of high-quality, well-characterized CaAlFe-layered triple hydroxide with the combination of dry-milling and ultrasonic irradiation in aqueous solution at elevated temperature.

    PubMed

    Szabados, Márton; Pásztor, Krisztián; Csendes, Zita; Muráth, Szabolcs; Kónya, Zoltán; Kukovecz, Ákos; Carlson, Stefan; Sipos, Pál; Pálinkó, István

    2016-09-01

    The combination of mechanochemical and ultrasonic treatment was applied to synthesize CaAlFe-layered triple hydroxides with carbonate or chloride anions in the interlamellar space. The optimal parameters of the preparation were explored by altering the initial ratio of the metal ions and the temperature of ultrasonic irradiation. The resulting triple hydroxides were characterized by X-ray diffractometry, infrared and X-ray absorption spectroscopies, thermogravimetric analysis and scanning electron microscopy. The products were close-to-phase-pure CaAlFe-layered triple hydroxides. Elevation of the temperature transformed the CaAlFe-Cl(-)-layered triple hydroxide to rare oxyhalides (Ca2FeO3Cl and Ca12Al14O32Cl2). PMID:27150758

  17. High pressure synthesis and crystal structure of a ternary superconductor Ca{sub 2}Al{sub 3}Si{sub 4} containing layer structured calcium sub-network isomorphous with black phosphorus

    SciTech Connect

    Tanaka, Masashi; Zhang, Shuai; Tanaka, Yuki; Inumaru, Kei; Yamanaka, Shoji

    2013-02-15

    The Zintl compound CaAl{sub 2}Si{sub 2} is peritectically decomposed to a mixture of Ca{sub 2}Al{sub 3}Si{sub 4} and aluminum metal at temperatures above 600 Degree-Sign C under a pressure of 5 GPa. The new ternary compound Ca{sub 2}Al{sub 3}Sl{sub 4} crystalizes with the space group Cmc2{sub 1} and the lattice parameters a=5.8846(8), b=14.973(1), and c=7.7966(5) A. The structure is composed of aluminum silicide framework [Al{sub 3}Si{sub 4}] and layer structured [Ca{sub 2}] network interpenetrating with each other. The electron probe microanalysis (EPMA) shows the formation of solid solutions Ca{sub 2}Al{sub 3-x}Si{sub 4+x} (x<0.6). The layer structured [Ca{sub 2}] sub-network is isomorphous with black phosphorus. The new ternary compound shows superconductivity with a transition temperature (T{sub c}) of 6.4 K. The band structure calculation suggests that the superconductivity should occur through the conduction bands mainly composed of 3p orbitals of the aluminum silicide framework. - Graphical abstract: A new ternary superconductor Ca{sub 2}Al{sub 3}Si{sub 4} has been prepared under high pressure and high temperature conditions, which includes layer structured calcium sub-network isomorphous with black phosphorus. Highlights: Black-Right-Pointing-Pointer A typical Zintl compound CaAl{sub 2}Si{sub 2} melts congruently at ambient pressure. Black-Right-Pointing-Pointer Under high pressure CaAl{sub 2}Si{sub 2} decomposes to Ca{sub 2}Al{sub 3}Si{sub 4} and Al at {approx}600 Degree-Sign C. Black-Right-Pointing-Pointer Ca{sub 2}Al{sub 3}Si{sub 4} contains Ca sub-network isomorphous with black phosphorus. Black-Right-Pointing-Pointer Ca{sub 2}Al{sub 3}Si{sub 4} shows superconductivity with a transition temperature of 6.4 K.

  18. Structural and optical characterizations of Ca2Al2SiO7:Ce3+, Mn2+ nanoparticles produced via a hybrid route

    NASA Astrophysics Data System (ADS)

    Teixeira, V. C.; Montes, P. J. R.; Valerio, M. E. G.

    2014-07-01

    Pure, Ce3+ doped and Ce3+ and Mn2+ co-doped Ca2Al2SiO7 ceramic powders were prepared by two different methodologies which are the proteic sol-gel process and a new hybrid route combining the proteic sol-gel with solid state reaction processes. The second one is an eco-friendly method because it uses natural raw materials in replacement of the metal alkoxides used in the traditional sol-gel routes. X-ray diffraction showed that Ca2Al2SiO7 crystalline phase was obtained for both preparations. Differential thermal analysis indicated that the exothermic event around 850 °C, for sample produced by proteic sol-gel method, and around 927 °C, for ceramics prepared by hybrid synthesis, can be associated to crystallization of Ca2Al2SiO7. Transmission electron microscope indicates that regular and spherical nanoparticles were obtained with average sizes of about 12 nm. The Scherrer’s method was used to determine the average crystallite sizes and it was shown that nanometric crystallites were obtained of about 74 nm for samples produced via hybrid route. For all the single phase samples, the crystallite sizes are about the same and that agrees with TEM results. Diffuse optical reflectance measurements were used to estimate the Ca2Al2SiO7 optical band gap and the obtained value is about 6 eV, photoluminescence (PL) spectra presented typical emissions of Ce3+ and Mn2+ ions. Upon excitation at 352 nm the emission spectra showed a broad band centered at 415 nm due to the Ce3+ 4f1 → 5d1 typical transition. This emission is resonant with Mn2+ excitation and it transfers energy to Mn ions generating a second broad emission band centered at 620 nm due to the Mn2+. The PL results were used to obtain, as a fist approach, the Ce3+ energy levels diagram and, using the Tanabe-Sugano diagrams, the transitions due to the Mn2+ were calculated. X-ray excited optical luminescence measurements showed the same emission spectra as the PL emission spectra. Luminescence lifetime decay

  19. Properties of transparent (Gd,Lu)3(Al,Ga)5O12:Ce ceramic with Mg, Ca and Ce co-dopants

    NASA Astrophysics Data System (ADS)

    Wang, Yimin; Baldoni, Gary; Brecher, Charles; Rhodes, William H.; Shirwadkar, Urmila; Glodo, Jarek; Shah, Ishaan; Ji, Chuncheng

    2015-08-01

    Cerium activated mixed lutetium/gadolinium- and aluminum/gallium-based garnets have great potential as host scintillators for medical imaging applications. (Gd,Lu)3(Al,Ga)5O12:Ce and denoted as GLuGAG feature high effective atomic number and good light yield, which make it particularly attractive for Positron Emission Tomography (PET) and other γ-ray detection applications. For PET application, rapid decay and good timing resolution are extremely important. Most Ce-doped mixed garnet materials such as GLuGAG:Ce, have their main decay component at around 80 ns. However, it has been reported that the decays of some single crystal scintillators (e.g., LSO and GGAG) can be effectively accelerated by codoping with selected additives such as Ca, Mg and B. In this study, transparent polycrystalline (Gd,Lu)3(Al,Ga)5O12:Ce ceramics codoped with Ca or Mg or additional Ce, were fabricated by the sinter-HIP approach. It was found the transmission of the ceramics are closely related to the microstructure of the ceramics. As the co-dopant levels increase, 2nd phase occurs in the ceramic and thus transparency of the ceramic decreases. Ca and Mg co-doping in GLuGAG:Ce ceramic effectively accelerate decays of GLuGAG:Ce ceramics at a cost of light output. However, additional Ce doping in the GLuGAG:Ce has no benefit on improving decay time but, on the other hand, reduces transmission, light output. The mechanism under the different scintillation behaviors with Mg, Ca and Ce dopants are discussed. The results suggest that decay time of GLuGAG:Ce ceramics can be effectively tailored by co-doping GLuGAG:Ce ceramic with Mg and Ca for applications with optimal timing resolution.

  20. A CaAl4O7-bearing refractory spherule from Murchison - Evidence for very high-temperature melting in the solar nebula

    NASA Astrophysics Data System (ADS)

    Simon, S. B.; Yoneda, S.; Grossman, L.; Davis, A. M.

    1994-04-01

    Results are presented of analyses (by a SEM equipped with an EDXS system, INAA, and an electron microprobe) of a unique refractory spherule, B6, recovered from the Murchison C2 chondrite. The spinel-, hibonite-, CaAl4O7-, perovskite-bearing spherule appears to have been almost completely molten, requiring exposure to the highest temperature yet inferred for any refractory inclusion. Strong evidence is presented that the spherule crystallized from a liquid. The presence of measurable excess Al2O3 in B6 spinel despite the normal a(Al2O3)/a(MgO) ratio of the inclusion is further evidence of its unusually high temperature history. Despite the high peak temperature, no volatility-derived fractionation of REEs or isotopic fractionation of Mg occurred, probably because cooling was rapid enough for a very rapid formation of a spinel shell which sealed off the molten interior of the inclusion from the nebular gas.

  1. Crystal structure of Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2} and luminescence properties of Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 2+}

    SciTech Connect

    Iwata, Tomoyuki; Haniuda, Masahide; Fukuda, Koichiro

    2008-01-15

    The crystal structure of Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2} was determined from laboratory X-ray powder diffraction data (CuK{alpha}{sub 1}) using the Rietveld method, with the anisotropic displacement parameters being assigned for all atoms. The crystal structure is cubic (space group I4-bar 3d, Z=2) with lattice dimensions a=1.200950(5) nm and V=1.73211(1) nm{sup 3}. The reliability indices calculated from the Rietveld method were R{sub wp}=8.48% (S=1.21), R{sub p}=6.05%, R{sub B}=1.27% and R{sub F}=1.01%. The validity of the structural model was verified by the three-dimensional electron density distribution, the structural bias of which was reduced as much as possible using the maximum-entropy methods-based pattern fitting (MPF). The reliability indices calculated from the MPF were R{sub B}=0.75% and R{sub F}=0.56%. In the structural model there are one Ca site, two Al sites, two O sites and one Cl site. This compound is isomorphous with Ca{sub 12}Al{sub 10.6}Si{sub 3.4}O{sub 32}Cl{sub 5.4}. Europium-doped sample Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 2+} was prepared and the photoluminescence properties were presented. The excitation spectrum consisted of two wide bands, which were located at about 268 and 324 nm. The emission spectrum, when excited at 324 nm, resulted in indigo light with a peak at about 442 nm. - Graphical abstract: A portion of the crystal structure of Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2} showing eight-membered AlO{sub 4} rings and Ca-Cl-Ca unit.

  2. Complete Al-SI Order in Scapolite Me[subscript 37.5], Ideally Ca[subscript 3]Na[subscript 5][Al[subscript 8]Si[subscript 16]O[subscript 48

    SciTech Connect

    Antao, Sytle M.; Hassan, Ishmael

    2011-09-06

    The structure of an intermediate scapolite (Me{sub 36.6}) from Lake Clear, Ontario, was obtained using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinement in space group P4{sub 2}/n. The chemical formula obtained by electron microprobe is Na{sub 2.19}Ca{sub 1.35}K{sub 0.16}[Al{sub 3.95}Si{sub 8.05}O{sub 24}]Cl{sub 0.55}(CO{sub 3}){sub 0.41}(SO{sub 4}){sub 0.04}, equivalent to Me{sub 36.6}. The unit-cell parameters are a 12.07899(1), c 7.583467(9) {angstrom}, and V 1106.443(2) {angstrom}{sup 3}. The average distances are = 1.617(1) {angstrom}, = 1.744(1) {angstrom}, and = 1.601(1) {angstrom}. Therefore, the T1 and T3 sites contain only Si atoms, and the T2 site contains only Al atoms, so the Al and Si atoms are completely ordered. Complete Al-Si order was predicted for Me{sub 37.5}, ideally Ca{sub 3}Na{sub 5}[Al{sub 8}Si{sub 16}O{sub 48}]Cl(CO{sub 3}), and is confirmed in this study. Antiphase domain boundaries (APBs) in scapolite cannot arise from Al-Si order because the average distances indicate complete Al-Si order in Me{sub 36.6}. If APBs were to arise from Al-Si order, switching of the T sites across the APBs will occur, and complete Al-Si order cannot be observed. Therefore, Al-Si order, which is present to various extents across the scapolite series, can be ruled out as the cause for the APBs. Order involving Cl and CO{sub 3} is the cause for the APBs in scapolite.

  3. Estimating Electrical Conductivities of CaO-MgO-Al2O3-SiO2 Using Ion-Oxygen Parameter

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Electrical conductivity of molten slags is one of the most important physicochemical properties and it also has a close relationship to the structure of slag. This article focused on the basic slag system CaO-MgO-Al2O3-SiO2 and made estimations for electrical conductivity. Ion-oxygen parameter was selected to describe the relationship between electrical conductivity with compositions. Moreover, the interaction between composition and temperature was embodied in the final model formula. It was shown that increasing CaO and MgO contents enhanced the ability for electric conduction. Moreover, with a higher temperature, the change of electrical conductivity with ion-oxygen parameter was more remarkable. This model gives reasonable prediction of the electrical conductivity for the slags studied with the mean deviation of 14.3%. Thus, this model would provide a feasible tool for industry to predict and optimize the electrical conductivity of slag system.

  4. Effects of sintering temperature variation on microstructure and magnetic nature of Al diluted La0.7Ca0.3MnO3

    NASA Astrophysics Data System (ADS)

    Kumar, Manish; Choudhary, R. J.; Phase, D. M.

    2013-02-01

    The samples of La0.7Ca0.3Mn1-XAlXO3 (X=0,0.05,0.15) are synthesized at two different sintering temperature 1200°C and 1400°C. The phase purity of the samples is analyzed using x-ray diffraction measurements. The microstructural evolution for different sintering temperatures is carefully tracked using scanning electron microscope (SEM). Increase in grain size with increasing sintering temperature is well identified in SEM images. Variation in the magnetic nature of the samples sintered at different temperature is seen in temperature dependent magnetization M(T) measurements. M(T) results reveal that Al doped samples show strong dependence of their magnetic behavior on sintering temperature as compared to undoped La0.7Ca0.3MnO3.

  5. Constraints on 10Be and 41Ca distribution in the early solar system from 26Al and 10Be studies of Efremovka CAIs

    NASA Astrophysics Data System (ADS)

    Srinivasan, Gopalan; Chaussidon, Marc

    2013-07-01

    Three refractory coarse grained CAIs from the Efremovka CV3 chondrite, one (E65) previously shown to have formed with live 41Ca, were studied by ion microprobe for their 26Al-26Mg and 10Be-10B systematic in order to better understand the origin of 10Be. The high precision Al-Mg data and the inferred 26Al/27Al values attest that the precursors of the three CAIs evolved in the solar nebula over a period of few hundred thousand years before last melting-crystallization events. The initial 10Be/9Be ratios and δ10B values defined by the 10Be isochrons for the three Efremovka CAIs are similar within errors. The CAI 10Be abundance in published data underscores the large range for initial 10Be/9Be ratios. This is contrary to the relatively small range of 26Al/27Al variations in CAIs around the canonical ratio. Two models that could explain the origin of this large 10Be/9Be range are assessed from the collateral variations predicted for the initial δ10B values: (i) closed system decay of 10Be from a "canonical" 10Be/9Be ratio and (ii) formation of CAIs from a mixture of solid precursors and nebula gas irradiated during up to a few hundred thousand years. The second scenario is shown to be the most consistent with the data. This shows that the major fraction of 10Be in CAIs was produced by irradiation of refractory grains, while contributions of galactic cosmic rays trapping and early solar wind irradiation are less dominant. The case for 10Be production by solar cosmic rays irradiation of solid refractory precursors poses a conundrum for 41Ca because the latter is easily produced by irradiation and should be more abundant than what is observed in CAIs. 10Be production by irradiation from solar energetic particles requires high 41Ca abundance in early solar system, however, this is not observed in CAIs.

  6. The effect of H2O gas on volatilities of planet-forming major elements. I - Experimental determination of thermodynamic properties of Ca-, Al-, and Si-hydroxide gas molecules and its application to the solar nebula

    NASA Technical Reports Server (NTRS)

    Hashimoto, Akihiko

    1992-01-01

    The vapor pressures of Ca(OH)2(g), Al(OH)3(g), and Si(OH)4(g) molecules in equilibrium with solid calcium-, aluminum, and silicon-oxides, respectively, were determined, and were used to derive the heats of formation and entropies of these species, which are expected to be abundant under the currently postulated physical conditions in the primordial solar nebula. These data, in conjunction with thermodynamic data from literature, were used to calculate the relative abundances of M, MO(x), and M(OH)n gas species and relative volatilities of Fe, Mg, Si, Ca, and Al for ranges of temperature, total pressure, and H/O abundance ratio corresponding to the plausible ranges of physical conditions in the solar nebula. The results are used to explain how Ca and Al could have evaporated from Ca,Al-rich inclusions in carbonaceous chondrites, while Si, Mg, and Fe condensed onto them during the preaccretion alteration of CAIs.

  7. A clear effect of charge compensation through Na+ co-doping on the luminescence spectra and decay kinetics of Nd3+-doped CaAl4O7

    NASA Astrophysics Data System (ADS)

    Puchalska, M.; Watras, A.

    2016-06-01

    We present a detailed analysis of luminescence behavior of singly Nd3+ doped and Nd3+, Na+ co-doped calcium aluminates powders: Ca1-xNdxAl4O7 and Ca1-2xNdxNaxAl4O7 (x=0.001-0.1). Relatively intense Nd3+ luminescence in IR region corresponding to typical 4F3/2→4IJ (J=9/2-13/2) transitions with maximum located at about 1079 nm was obtained in all samples on direct excitation into f-f levels. The effect of dopant concentration and charge compensation by co-doping with Na+ ions on morphology and optical properties were studied. The results show that both, the Nd3+ concentration and the alkali metal co-doping affected the optical properties but had no influence on the powders morphology. The studies of luminescence spectra (298 and 77 K) in a function of dopant concentration showed an increasing distortion of the local symmetry of Nd3+with raising activator content due to certain defects created in the crystal lattice. On the other hand Na+ addition led to significant narrowing of absorption and luminescence bands and also a reduction of the number of their components, showing smaller disturbance of Nd3+ ions local symmetries. Consequently, charge compensated by Na+ co-doping materials showed significantly enhanced Nd3+ luminescence. The decrease of emission intensity and luminescence lifetimes with increase of activator concentration was attributed mainly to phonon-assisted cross-relaxation processes between Nd3+ ions. Analysis with Inokuti-Hirayama model indicated dipole-dipole mechanism of ion-ion interaction. Na+ addition led to much smaller concentration quenching due to smaller clustering of dopant ions in CaAl4O7 lattice.

  8. Defect chemistry of the cage compound, Ca(12)Al(14)O(33-delta)-understanding the route from a solid electrolyte to a semiconductor and electride.

    PubMed

    Lee, Doh-Kwon; Kogel, Lutz; Ebbinghaus, Stefan G; Valov, Ilia; Wiemhoefer, Hans-Dieter; Lerch, Martin; Janek, Juergen

    2009-05-01

    A crystallographic cage structure endows mayenite (Ca(12)Al(14)O(33) or 12CaO.7Al(2)O(3); C(12)A(7)) with remarkable properties, making it either an oxygen solid electrolyte or an inorganic electride upon reduction. In order to better understand the transport properties of C(12)A(7), we measured the equilibrium total conductivity as well as the electronic partial conductivity of single crystal mayenite as functions of activity of oxygen or water vapor at different temperatures in the range 1073 < or =T/K < or = 1273. A point defect model based on the assumption that the framework [Ca(12)Al(14)O(32)](2+) acts as a pseudo-donor describes well the isothermal conductivity vs. oxygen activity, enabling us to deconvolute the ionic and electronic partial conductivities. The ionic transference number evaluated therefrom clearly demonstrates how C(12)A(7) is converted from a solid electrolyte to an electride depending on the oxygen content. In addition, besides the well known degradation of ionic conductivity by water uptake, a short-term increase of conductivity upon abrupt hydration was recognized and interpreted as due to the transient increase in the concentration of oxygen interstitial along with proton in the initial stage of hydration. For the fully hydrated C(12)A(7), the conductivity relaxation curves upon switching of oxygen activity in a fixed water vapor pressure appear non-monotonic showing the extrema only in the plateau conductivity regime. A defect structure based hypothesis is proposed to explain the 2-fold re-equilibration kinetics. PMID:19370205

  9. [Effect of temperature on the structure of CaO-MgO-Al2O3-SiO2 nanocrystalline glass-ceramics studied by Raman spectroscopy].

    PubMed

    Li, Bao-Wei; Ouyang, Shun-Li; Zhang, Xue-Feng; Jia, Xiao-Lin; Deng, Lei-Bo; Liu, Fang

    2014-07-01

    In the present paper, nanocrystalline glass-ceramic of CaO-MgO-Al2O3-SiO2 system was produced by melting method. The CaO-MgO-Al2O3-SiO2 nanocrystalline glass-ceramic was measured by Raman spectroscopy in the temperature range from -190 to 310 degrees C in order to study the effect of temperature on the structure of this system nanocrystalline glass-ceramics. The results showed that different non-bridge oxygen bond silicon-oxygen tetrahedron structural unit changes are not consistent with rising temperature. Further analyses indicated that: the SiO4 tetrahedron with 2 non-bridged oxygen (Q2), the SiO4 tetrahedron with 3 non-bridged oxygen (Q(1)), which are situated at the edge of the 3-D SiO4 tetrahedrons network, and the SiO4 tetrahedron with 4 non-bridged oxygen (Q(0)), which is situated outside the 3-D network all suffered a significant influence by the temperature change, which has been expressed as: shifts towards the high wave-number, increased bond force constants, and shortened bond lengths. This paper studied the influence of temperature on CMAS system nanocrystalline glass-ceramics using variable temperature Raman technology. It provides experiment basis to the research on external environment influence on CMAS system nanocrystalline glass-ceramics materials in terms of structure and performance. In addition, the research provides experimental basis for controlling the expansion coefficient of nanocrystalline glass-ceramic of CaO-MgO-Al2O3-SiO2 system. PMID:25269298

  10. Facile synthesis of Ca0.68Si9Al3(ON)16:Eu2+ microbelts mat with the enhanced fluorescence and mechanical performance

    NASA Astrophysics Data System (ADS)

    Zhao, Hailei; Cui, Bo; Wang, Hongzhi; Zhang, Qinghong; Li, Yaogang

    2016-01-01

    Yellow-emitting phosphor mat consisting of Ca0.68Si9Al3(ON)16:Eu2+ microbelts was prepared by electrospinning and subsequent nitridation. The as-prepared fiber precursor is smooth and uniform with diameter of 800 to 900 nm. After removing organic templates and nitridation, the morphology of the fiber is well retained and thus a smooth microbelts phosphor mat was obtained. X-ray diffraction and the photoluminescence (PL) spectra reveals that a relatively pure Ca0.68Si9Al3(ON)16 phase and the highest spectral intensity could be obtained at a relatively low temperature of 1500 °C and Eu2+ doping molar concentration of 0.1. The excitation spectra exhibits a broad band, ranging from 300 to 550 nm, which could be excited by blue LED chip at room temperature. The emission spectra of all exhibits a single broad band in the 400 to 700 nm region, with the maximum intensity always being at 580 nm. The Ca0.68Si9Al3(ON)16:Eu2+ microbelts phosphor mat has the bending strength about 4.5 MPa with a photoluminescence quantum yield as high as 65%. By employing it as yellow phosphor, a high-performance warm white LED could be fabricated with low correlated color temperature (2985 K), high-color-rendering index (Ra=86) and luminous efficacy of 129.5 lm W-1. Different color temperatures also could be tuned by employing microbelts phosphor mats with different thicknesses.

  11. The Aqueous Ca2+ System, in Comparison with Zn2+, Fe3+, and Al3+: An Ab Initio Molecular Dynamics Study

    SciTech Connect

    Bogatko, Stuart A.; Cauet, Emilie L.; Bylaska, Eric J.; Schenter, Gregory K.; Fulton, John L.; Weare, John H.

    2013-02-21

    Results of Ab Initio Molecular Dynamics (AIMD) simulations of a Ca2+ ion in an aqueous environment (64 waters, 38ps=5ps equilibration + 33ps data collection, 300K) are reported. The 1st hydration shell contains 6-7 waters with d(OH) = 0.97Å (identical to our bulk water estimate) and average tilt angle, I = 32º. The 1st maximum in the radial distribution function occurs at GCaO(r) = 2.45Å. Our results compare well with published experimental structural data from X-Ray Absorption (XAFS) and Neutron Diffraction. We also generate simulated XAFS spectra using a 1st principles MD-XAFS procedure and show quantitative agreement with experimental XAFS data from a 0.2m Ca(ClO4)2 aqueous solution. The Ca2+ 1st shell water dipole moment of 3.1D is identical to our bulk water estimate (3.1D). The structured 2nd hydration shell, composed of ~16.5 waters, has a maximum at GCaO(r) =4.6Å. The average 2nd shell dipole moment = 2.9D, is suppressed relative to bulk water values. Detailed H-bond analysis demonstrates the waters in this shell predominately coordinate 1st shell waters with a trigonally structured H-bond network. Two exchanges between the 1st hydration shell and the bulk were observed. These were consistent with a dissociative and dissociative interchange Eigen-Wilkins ligand exchange mechanism. Many transfers between the 2nd shell and bulk are detected for Ca2+ allowing an estimation of the 2nd shell mean residence time (MRT) of 4.6ps. Comparison of the Ca2+ hydration shell structure and dynamics with those of the recently reported Zn2+, Fe3+ and Al3+ cation species show that the 1st and 2nd hydration shell parameters, d(M-OI) distance, CNII, H-bond d(OI-OII) distance and %Tetrahedral structure are correlated with cation charge density, the ratio of cation charge (Z) and size (Rion). However, important exceptions are d(M-OII) and the 2nd shell Mean Residence Time (MRT). These differences are explained in terms of the 1st shell structure parameters (d(M-OI) distance

  12. New insights into the application of the valence rules in Zintl phases-Crystal and electronic structures of Ba7Ga4P9, Ba7Ga4As9, Ba7Al4Sb9, Ba6CaAl4Sb9, and Ba6CaGa4Sb9

    NASA Astrophysics Data System (ADS)

    He, Hua; Stoyko, Stanislav; Bobev, Svilen

    2016-04-01

    Crystals of three new ternary pnictides-Ba7Al4Sb9, Ba7Ga4P9, and Ba7Ga4As9 have been prepared by reactions of the respective elements in molten Al or Pb fluxes. Single-crystal X-ray diffraction studies reveal that the three phases are isotypic, crystallizing in the orthorhombic Ba7Ga4Sb9-type structure (space group Pmmn, Pearson symbol oP40, Z=2), for which only the prototype is known. The structure is based on TrPn4 tetrahedra (Tr=Al, Ga; Pn=P, As, Sb), connected in an intricate scheme into 1D-ribbons. Long interchain Pn-Pn bonds (dP-P>3.0 Å; dAs-As>3.1 Å; dSb-Sb>3.3 Å) account for the realization of 2D-layers, separated by Ba2+ cations. Applying the classic valance rules to rationalize the bonding apparently fails, and Ba7Ga4Sb9 has long been known as a metallic Zintl phase. Earlier theoretical calculations, both empirical and ab-initio, suggest that the possible metallic properties originate from filled anti-bonding Pn-Pn states, and the special roles of the "cations" in this crystal structure. To experimentally probe this hypothesis, we sought to synthesize the ordered quaternary phases Ba6CaTr4Sb9 (Tr=Al, Ga). Single-crystal X-ray diffraction work confirms Ba6.145(3)Ca0.855Al4Sb9 and Ba6.235(3)Ca0.765Ga4Sb9, with Ca atoms preferably substituting Ba on one of the three available sites. The nuances of the five crystal structures are discussed, and the chemical bonding in Ba7Ga4As9 is interrogated by tight-binding linear muffin-tin orbital calculations.

  13. Evidence for Extremely-High-Temperature Melting in the Solar Nebula from a CaAl4O7-bearing Spherule from Murchison

    NASA Astrophysics Data System (ADS)

    Simon, S. B.; Grossman, L.; Davis, A. M.; Beckett, J. R.; Chamberlin, L.

    1993-07-01

    We have recovered a unique refractory spherule (B6) from the Murchison C2 chondrite. Approximately 140 micrometers in diameter, it is concentrically zoned, with an outer rim sequence, from outermost to innermost, of aluminous diopside (10 micrometers thick), anorthite (3 micrometers) and melilite (3 micrometers). Inside the melilite layer is a 7-micrometer-thick, nearly pure (except for a single, diverging-inward spray of hibonite crystals) layer of spinel. Inward from this layer is a 22-micrometer-wide zone of hibonite (~5.5 wt% TiO2) + spinel, in which hibonite laths, 1-4 micrometers across and up to 10 micrometers wide, are predominantly radially oriented and enclosed in spinel. Inward from this zone, presumably at the core of the inclusion, are CaAl4O7, occurring as anhedral grains ~10 micrometers across, and minor perovskite. Some of the hibonite laths protrude into the CaAl4O7. The sequence of mineral assemblages from the spinel shell inward parallels that expected for fractional crystallization of a melt of the composition of B6. Based on this, the inclusion's spherical shape, and its texture (radially oriented hibonite laths, including a diverging-inward spray; laths enclosed in spinel and protruding into CaAl4O7), we conclude that the oxide phases in B6 crystallized from a liquid. The spinel layer indicates that at least some of the spinel was molten; from the bulk composition, calculated liquidus phase relations in the system Al2O3-MgO-CaO [1], and the amount of spinel contained in the layer, we infer a melting temperature >2000 degrees C. This is >500 degrees higher than the maximum temperature at which any condensed major phase is stable at 10-3 atm in a gas of solar composition, but we see no evidence of evaporation. First, the inclusion has a Group II REE pattern, rather than a Group III or an ultrarefractory pattern, which could reflect devolatilization. Second, although evaporation of molten (but not solid) Mg2SiO4 leads to Mg isotopic mass

  14. The abundance and relative volatility of refractory trace elements in Allende Ca,Al-rich inclusions - Implications for chemical and physical processes in the solar nebula

    NASA Technical Reports Server (NTRS)

    Kornacki, Alan S.; Fegley, Bruce, Jr.

    1986-01-01

    The relative volatilities of lithophile refractory trace elements (LRTE) were determined using calculated 50-percent condensation temperatures. Then, the refractory trace-element abundances were measured in about 100 Allende inclusions. The abundance patterns found in Allende Ca,Al-rich inclusions (CAIs) and ultrarefractory inclusions were used to empirically modify the calculated LRTE volatility sequence. In addition, the importance of crystal-chemical effects, diffusion constraints, and grain transport for the origin of the trace-element chemistry of Allende CAIs (which have important implications for chemical and physical processes in the solar nebula) is discussed.

  15. Trace element and petrologic clues to the formation of forsterite-bearing Ca-Al-rich inclusions in the Allende meteorite

    NASA Technical Reports Server (NTRS)

    Wark, D. A.; Boynton, W. V.; Keays, R. R.; Palme, H.

    1987-01-01

    New trace element and petrographic data are presented for the TE, 818a, 110-A forsterite-bearing Ca-Al-rich inclusions (CAIs) from the Allende meteorite; these form a continuum with type B1 and B2 CAIs, and are here accordingly designated 'type B3'. Evidence is adduced to the effect that 818a was strongly reheated and modified in the nebula after its initial crystallization. A three-stage formation process is required for 818a, involving crystallization of the primary CAI, reheating and partial volatilization of Mg and Si from the outer portion of the CAI, and a metasomatic alteration of the melilite-rich mantle.

  16. Synthesis, characterization and optical properties of Ce{sup 3+} activated CaMgAl{sub 10}O{sub 17} phosphor

    SciTech Connect

    Selot, Anupam; Aynyas, Mahendra; Tiwari, Manoj; Dev, Kapil

    2014-04-24

    Phosphor material CaMgAl{sub 10}O{sub 17} with varying concentration of rare earth Ce{sub 3+} synthesis by combustion method at 500°C. The synthesized phosphor material characterized for their crystallinity and nature by XRD measurements. The photoluminescence measurements of phosphor exhibit mainly two PL spectra 382nm and 575 nm in blue and red region, respectively, this is due to crystal field and covalence effect. These results show that concentration quenching occur at 5mol° of Ce dopant. The results suggest the possibility of utilizing as a phosphor may be in solid state lighting.

  17. Continuum emission in Nd3+/Yb3+ co-doped Ca12Al14O33 phosphor: Charge transfer state luminescence versus induced optical heating

    NASA Astrophysics Data System (ADS)

    Verma, R. K.; Rai, S. B.

    2013-02-01

    An unusual phenomenon of local heating and associated emission of continuum in lanthanide doped material has attracted much interest currently because of its use in white light generation and in localized heating. In the present work, Nd3+/Yb3+ co-doped Ca12Al14O33 phosphor has been synthesized, which gives broad continuum emission both by downconversion (DC) and upconversion (UC) processes. On 266 nm excitation, broad continuum emission is achieved through charge transfer state (CTS) luminescence of Yb3+ ion. On the other hand on 976 nm excitation, UC emission is observed from Nd3+ ion, which at higher pump power gives continuum emission.

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

    NASA Astrophysics Data System (ADS)

    Lin, Zong-Han; Wang, Yeong-Her

    2016-08-01

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

  19. Conductor-backed coplanar waveguide resonators of Y-Ba-Cu-O and Tl-Ba-Ca-Cu-O on LaAlO3

    NASA Technical Reports Server (NTRS)

    Miranda, F. A.; Bhasin, K. B.; Stan, M. A.; Kong, K. S.; Itoh, T.

    1992-01-01

    Conductor-backed coplanar waveguide (CBCPW) resonators operating at 10.8 GHz have been fabricated from Tl-Ba-Ca-O (TBCCO) and Y-Ba-Cu-O (YBCO) thin films on LaAlO3. The resonators consist of a coplanar waveguide (CPW) patterned on the superconducting film side of the LaAlO3 substrate with a gold ground plane coated on the opposite side. These resonators were tested in the temperature range from 14 to 106 K. At 77 K, the best of our TBCCO and YBCO resonators have an unloaded quality factor (Qo) 7 and 4 times, respectively, larger than that of a similar all-gold resonator. In this study, the Qo's of the TBCCO resonators were larger than those of their YBCO counterparts throughout the aforementioned temperature range.

  20. Studies on charge transport in Al-doped La0.7Ca0.3Mn1-xAlxO3 manganites

    NASA Astrophysics Data System (ADS)

    Rathod, Jalshikhaba S.; Keshvani, M. J.; Solanki, P. S.; Pandya, D. D.; Kataria, Bharat; Shah, N. A.; Kuberkar, D. G.

    2015-12-01

    In this communication, we report the results of the studies on the effect of non-magnetic Al3+-doping on structure and properties of La0.7Ca0.3Mn1-xAlxO3 (LCMAO) manganites synthesized by conventional solid state reaction (SSR) route. The Rietveld refinement of the X-ray diffraction (XRD) data confirms the single phasic nature of the samples without any detectable impurities. All the samples exhibit metal to insulator transition (TP) which decrease with increase in Al3+ doping concentration while it increases with applied magnetic field. To understand the nature of charge transport in metallic and insulating regions of resistivity, various models and mechanisms have been used to fit the observed experimental data.

  1. FP-LAPW study of the fundamental properties of the cubic spinel CdAl{sub 2}O{sub 4}

    SciTech Connect

    Bouhemadou, A.; Zerarga, F.; Almuhayya, A.; Bin-Omran, S.

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Fundamental properties of CdAl{sub 2}O{sub 4} are investigated. Black-Right-Pointing-Pointer Results obtained for energy band gaps using EV-GGA are larger than that within PBE-GGA. Black-Right-Pointing-Pointer The decomposition of the dielectric function into individual band-to-band contributions is calculated. Black-Right-Pointing-Pointer The effective charge-carrier masses are estimated from the band structure. Black-Right-Pointing-Pointer Pressure and temperature dependences of some macroscopic parameters are obtained. -- Abstract: We have investigated the structural, elastic, electronic, optical and thermodynamic properties of the cubic spinel CdAl{sub 2}O{sub 4} using accurate ab initio calculations. Computed equilibrium structural parameters are in good agreement with the available experimental data. Single-crystals elastic parameters are calculated for pressure up to 30 GPa using a conserving-volume total energy-strain method. Isotropic elastic parameters for ideal polycrystalline CdAl{sub 2}O{sub 4} aggregates are computed in the framework of the Voigt-Reuss-Hill approximation. Result for band structure using the Engel-Vosko scheme of the GGA shows a significant improvement over the common GGA functionals. Optical spectra have been calculated for the energy range 0-30 eV. The peaks and structures in the optical spectra are assigned to interband transitions. Pressure dependence of the band gaps, static dielectric constant and static refractive index are also investigated. Pressure and thermal effects on some macroscopic properties are predicted using the quasi-harmonic Debye model.

  2. Exotic fluoride molecules in IRC +10216: Confirmation of AlF and searches for MgF and CaF

    NASA Technical Reports Server (NTRS)

    Ziurys, L. M.; Apponi, A. J.; Phillips, T. G.

    1994-01-01

    Three new rotational transitions of aluminum fluoride (AlF) at 0.8 and 1.2 mm have been observed. The J = 10-9, J = 8-7, and J = 7-6 lines of AlF at 230, 263, and 329 GHz, respectively, were seen toward IRC +10216 using the Caltech Submillimter Observatory (CSO). Combined with the earlier data obtained for this species at IRAM at 2 and 3 mm, these measurements confirm the presence of the metal halide in this carbon-rich circumstellar shell. Analysis of the CSO and IRAM data suggests that AlF arises from a source with a diameter of theta(sub s) approximately = 5-10 sec and hence is present chiefly in the inner envelope of IRC +10216. In this region, the molecule has a column density of (0.3-1.1) x 10(exp 15)/sq cm, which indicates a fractional abundance of at least approximately 10(exp -9), relative to H2. Searches for the metal fluoride species CaF and MgF have also been conducted toward IRC +10216, but with negative results. The column density upper limits for MgF and CaF are N(sub tot) less than (1-4) x 10(exp 14)/sq cm. Relative abundances of these metal fluoride molecules can be understood in terms of chemical thermodynamic equilibrium. The presence of AlF in IRC +10216 also indicates that large quantities of fluorine must be present in the inner stellar envelope, suggesting that this element may be produced not primarily in explosive nucleosynthesis but rather in helium shell flashes, as indicated also by HF spectroscopy of red giant stars.

  3. Assessment of HgCdTe and GaAs/GaAlAs technologies for LWIR infrared imagers

    NASA Astrophysics Data System (ADS)

    Dewames, Roger E.; Arias, Jose M.; Kozlowski, Lester J.; Williams, G. M.

    1992-12-01

    Imagery of long wavelength infrared HgCdTe and GaAs quantum well staring arrays in size 128 X 128 has been demonstrated. In this paper, we compare detector array performance characteristics, discuss the natural and technological limitations of both technologies and identify the improvements likely to be made in the near future. At this stage of feasibility demonstration in the spectral band 8 - 10 micrometers , the effective quantum efficiency in GaAs FPAs is 4% compared to 60% for HgCdTe and the responsivity is 0.08 A/W compared to 4.5 A/W. This value of 0.08 A/W is significantly below the value 2 A/W reported for single quantum well infrared photodetectors (QWIP) detectors. The peak detectivities and NE(Delta) T at 78 K are (5 X 10(superscript 9) cm (root)Hz/W, 0.037 K) and (2 X 10(superscript 11), 0.005 K) for QWIP and HgCdTe, respectively. The residual nonuniformities after two-point correction are < 0.01% for QWIP arrays and 0.012% for HgCdTe. Crosstalk is currently unsatisfactory in QWIP detector arrays, but design concepts can be used to reduce this effect. For terrestrial imaging, GaAs quantum well detector arrays most likely will need to operate at temperatures below 80 K from fundamental considerations; HgCdTe detector arrays are background limited at operating temperatures CdTe detector arrays with good yield, it is unlikely that HgCdTe will be displaced by this technology for terrestrial applications. For low background space applications at (phi) (subscript b)

  4. Analysis of reaction between c+a and -c+a dislocations in GaN layer grown on 4-inch Si(111) substrate with AlGaN/AlN strained layer superlattice by transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Sugawara, Yoshihiro; Ishikawa, Yukari; Watanabe, Arata; Miyoshi, Makoto; Egawa, Takashi

    2016-04-01

    The behavior of dislocations in a GaN layer grown on a 4-inch Si(111) substrate with an AlGaN/AlN strained layer superlattice using horizontal metal-organic chemical vapor deposition was observed by transmission electron microscopy. Cross-sectional observation indicated that a drastic decrease in the dislocation density occurred in the GaN layer. The reaction of a dislocation (b=1/3[-211-3]) and anothor dislocation (b =1/3[-2113]) to form one dislocation (b =2/3[-2110]) in the GaN layer was clarified by plan-view observation using weak-beam dark-field and large-angle convergent-beam diffraction methods.

  5. Role of hydrogen atoms in the photoinduced formation of stable electron centers in H-doped 12CaO•7 Al2 O3

    NASA Astrophysics Data System (ADS)

    Sushko, Peter V.; Shluger, Alexander L.; Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

    2006-01-01

    In this work we investigate a variety of chemical and photoinduced processes in which different hydrogenous species including H2 molecules, H- ions, and H0 atoms interact with the bulk of a complex nanoporous oxide 12CaO•7Al2O3 . Our results provide a detailed and consistent explanation of the recently observed phenomenon of photoinduced conversion of the insulating H-doped 12CaO•7Al2O3 to a conductor [K. Hayashi , Nature (London) 419, 462 (2002)]. The formation of a large and thermally stable concentration of electron centers in this process is facilitated by a large concentration (up to 1020cm-3 ) of extraframework O2- naturally present in this material and homogeneously distributed in its bulk. We show that these species are able to split H2 molecules into pairs of H+ and H- ions and convert H0 atoms into H+ and e- promoting the photoinduced conversion process. The similarity of the mechanisms described in this work to those known for low-coordinated sites at MgO surfaces indicates that the formation of electronic centers in oxides interacting with hydrogenous species could be a generic feature.

  6. Some thermodynamic properties of the Berman and Brown model for CaO-Al2O3-SiO2

    NASA Astrophysics Data System (ADS)

    Barron, Lawrence M.

    1986-12-01

    The BERMAN and BROWN (1984) excess free energy model (B&B) is extremely convenient to use in modelling multicomponent solutions. However, spinodal calculations reveal that their calibration of this model for CaO-Al2O3-SiO2 produces liquation tielines that do not appear to be in agreement with experimental work. In addition, their calibration contains some strongly negative excess entropy parameters and these permit a most unusual inverted liquation field to start at approximately >2115°C, wt% (SiO2, Al2O3, CaO) = (70, 16, 14). This inverted field expands rapidly to cover most of the ternary for T > 2300°C and continues to expand at all higher temperatures. The Berman and Brown calibration for this system carries these negative excess entropies of mixing because the solution model is very strongly asymmetric as a result of the use of normal oxide mole weights in modelling the configurational entropy of mixing. A suggestion is made for a fairly natural restriction on the relative sizes of empirical models for excess versus configurational entropy. Expressions are presented for the general consolute condition (all solution models) and for the second and third partials of the B&B Gx model.

  7. Chemical Unit Cosubstitution and Tuning of Photoluminescence in the Ca2(Al(1-x)Mg(x))(Al(1-x)Si(1+x))O7:Eu(2+) Phosphor.

    PubMed

    Xia, Zhiguo; Ma, Chonggeng; Molokeev, Maxim S; Liu, Quanlin; Rickert, Karl; Poeppelmeier, Kenneth R

    2015-10-01

    The union of structural and spectroscopic modeling can accelerate the discovery and improvement of phosphor materials if guided by an appropriate principle. Herein, we describe the concept of "chemical unit cosubstitution" as one such potential design scheme. We corroborate this strategy experimentally and computationally by applying it to the Ca2(Al(1-x)Mg(x))(Al(1-x)Si(1+x))O7:Eu(2+) solid solution phosphor. The cosubstitution is shown to be restricted to tetrahedral sites, which enables the tuning of luminescent properties. The emission peaks shift from 513 to 538 nm with a decreasing Stokes shift, which has been simulated by a crystal-field model. The correlation between the 5d crystal-field splitting of Eu(2+) ions and the local geometry structure of the substituted sites is also revealed. Moreover, an energy decrease of the electron-phonon coupling effect is explained on the basis of the configurational coordinate model. PMID:26389578

  8. Optoelectronic response of spinels CdX2O4 with X = (Al, Ga, In) through the modified Becke-Johnson functional

    NASA Astrophysics Data System (ADS)

    Boujnah, M.; Dakir, O.; Zaari, H.; Benyoussef, A.; El Kenz, A.

    2014-09-01

    Structural, electronic, and optical properties of CdAl2O4, CdGa2O4, and CdIn2O4 are investigated using the first principles technique based on the new potential approximation known as the Tran-Blaha modified Becke-Johnson exchange potential approximation (TB-mBJ). We discuss the improvements in the band gap determination using TB-mBJ compared to the standard generalized gradient approximation in density functional theory. The calculated equilibrium lattice parameters are in reasonable agreement with the experimental results. Electronic properties have been studied through the calculation of band structure and density of states. Based on our electronic structure obtained using the mBJ method, we have calculated various optical properties, including the complex dielectric function ɛ(ω), complex index of refraction n(ω), reflectivity coefficient R(ω), absorption coefficient α(ω), and the electron energy-loss function L(ω) as functions of the photon energy. We chose these three representative oxides spinel due to their potential applications in optoelectronics and optical fields.

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

    SciTech Connect

    Kim, H.; Lee, Y.D.

    1999-11-01

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

  10. The CNGRC-GG-D(KLAKLAK)2 peptide induces a caspase-independent, Ca2+-dependent death in human leukemic myeloid cells by targeting surface aminopeptidase N/CD13

    PubMed Central

    Bouchet, Sandrine; Tang, Ruoping; Fava, Fanny; Legrand, Ollivier; Bauvois, Brigitte

    2016-01-01

    The CD13 antigen's binding site for the Asn-Gly-Arg (NGR) motif enables NGR-containing chemotherapeutic drugs to be delivered to CD13-positive tumours. Human CD13-positive acute myeloid leukemia (AML) cells proliferate abnormally and escape death. Here, we show that the CNGRC-GG-D(KLAKLAK)2 peptide induces death in AML cell lines (U937, THP-1, NB4, HL-60) and primary blood cells from AML patients. Cell death was characterized as a caspase-independent mechanism, without DNA fragmentation, but phosphatidylserine externalization and membrane disruption. Our results demonstrate in U937 cells that (i) the NGR-peptide triggers the loss of mitochondrial potential(ΔΨm) and generates superoxide anion (O2−), (ii) N-acetyl-L-cysteine (NAC) and extra/intracellular Ca2+ chelators (BAPTA) prevent both O2− production and cell death, (iii) the Ca2+-channel blocker nifedipine prevents cell death (indicating that Ca2+ influx is the initial death trigger), and (iv) BAPTA, but not NAC, prevents ΔΨm loss (suggesting O2− is a mitochondrial downstream effector). AML cell lines and primary blasts responding to the lethal action of NGR-peptide express promatrix metalloproteinase-12 (proMMP-12) and its substrate progranulin (an 88 kDa cell survival factor). A cell-free assay highlighted proMMP-12 activation by O2−. Accordingly, NGR-peptide's downregulation of 88 kDa progranulin protein was prevented by BAPTA and NAC. Conversely, AML blast resistance to NGR-peptide is associated with the expression of a distinct, 105 kDa progranulin isoform. These results indicate that CNGRC-GG-D(KLAKLAK)2 induces death in AML cells through the Ca2+-mitochondria-O2.-pathway, and support the link between proMMP-12 activation and progranulin cleavage during cell death. Our findings may have implications for the understanding of tumour biology and treatment. PMID:26655501

  11. High pressure study of low compressibility tetracalcium aluminum carbonate hydrates 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaCO{sub 3}{center_dot}11H{sub 2}O

    SciTech Connect

    Moon, Juhyuk; Oh, Jae Eun; Balonis, Magdalena; Glasser, Fredrik P.; Clark, Simon M.; Monteiro, Paulo J.M.

    2012-01-15

    Synchrotron X-ray diffraction data was collected from a sample of monocarboaluminate 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}CaCO{sub 3}{center_dot}11H{sub 2}O from ambient pressure to 4.3 GPa. The refined crystal structure at ambient pressure is triclinic with parameters a = 5.77(2) A, b = 8.47(5) A, c = 9.93(4) A, {alpha} = 64.6(2) Degree-Sign , {beta} = 82.8(3) Degree-Sign , {gamma} = 81.4(4) Degree-Sign , and space group of P1 or P1{sup Macron }. It showed some degree of perfectly reversible pressure-induced dehydration with a non-hygroscopic pressure-transmitting medium. However the dehydration effect does not critically affect a bulk modulus due to its strong framework. The isothermal bulk modulus of monocarboaluminate was found to be 53(5) GPa and 54(4) GPa with 3rd order and 2nd order Birch-Murnaghan Equation of state, respectively. That value is higher than for any other reported AFm or AFt phase. The pressure-volume behavior of the monocarboaluminate was compared with that of previous studied hemicarboaluminate.

  12. Formation Mechanism of CaO-SiO2-Al2O3-(MgO) Inclusions in Si-Mn-Killed Steel with Limited Aluminum Content During the Low Basicity Slag Refining

    NASA Astrophysics Data System (ADS)

    Wang, Kunpeng; Jiang, Min; Wang, Xinhua; Wang, Ying; Zhao, Haoqian; Cao, Zhanmin

    2016-02-01

    Pilot trails were carried out to study the formation mechanism of CaO-SiO2-Al2O3-(MgO) inclusions in tire cord steel. 48 samples were taken from 8 heats of liquid steel during secondary refining, which were subsequently examined by an automatic scanning electron microscope with energy dispersive spectrometer (SEM-EDS). Characteristics of thousands of oxide inclusions at different refining stages were obtained, including their compositions, sizes, morphologies, etc. Based on the obtained information of inclusions, details during formation of CaO-SiO2-Al2O3-(MgO) inclusions were revealed and a new mechanism was proposed, including their origin, formation, and evolution during the refining process. It was found that CaO-SiO2-Al2O3-(MgO) inclusions were initially originated from the CaO-SiO2-MnO-(MgO) inclusions, which were formed during BOF tapping by the coalescence between MnO-SiO2 deoxidation products and the emulsified slag particles because of violent flow of steel. This can be well confirmed by the evaluation of the formation thermodynamics of CaO-SiO2-MnO-(MgO) inclusions, which was proved very difficult to be produced by intrinsic reactions inside liquid steel. Because of chemical reactions between CaO-SiO2-MnO-(MgO) inclusions and molten steel, they were mainly changed into CaO-SiO2-MnO-Al2O3-(MgO) and partially into CaO-SiO2-Al2O3-(MgO), which may be detrimental to the cold drawing ability of coils. Based on this finding, improvements were made in industrial production during BOF tapping and secondary refining. The results indicated that such (CaO-SiO2)-based inclusions existed in conventional process were effectively decreased after the improvements.

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

    SciTech Connect

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

    2015-02-16

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

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

    SciTech Connect

    Poellmann, Herbert

    2012-01-15

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

  15. Melts in the Deep Earth: Calculating the Densities of CaO-FeO-MgO-Al2O3-SiO2 Liquids

    NASA Astrophysics Data System (ADS)

    Thomas, C.; Guo, X.; Agee, C. B.; Asimow, P. D.; Lange, R. A.

    2012-12-01

    We present new equation of state (EOS) measurements for hedenbergite (Hd, CaFeSi2O6) and forsterite (Fo, Mg2SiO4) liquids. These liquid EOS add to the basis set in the CaO-FeO-MgO-Al2O3-SiO2 (CMASF) oxide space at elevated temperatures and pressures; other liquids include: enstatite (En, MgSiO3), anorthite (An, CaAl2Si2O8), diopside (Di, CaMgSi2O6), and fayalite (Fa, Fe2SiO4). The Hd EOS measurement was a multi-technique collaboration using 1-atm double-bob Archimedean, ultrasonic, sink/float, and shock wave techniques. Un-weighted linear fitting of the shock data in shock velocity (US)-particle velocity (up) space defines a pre-heated (1400 °C) Hugoniot US = 2.628(0.024) + 1.54(0.01)up km/s. The slope corresponds to a K' of 5.16(0.04), consistent with piston-cylinder and multi-anvil sink/float experiments. The intercept is fixed at the ultrasonic sound speed (Co) since the unconstrained intercept is within the stated error. This behavior demonstrates consistency across methods and that the liquid is relaxed during shock compression. Shock compression of pre-heated (2000°C) single crystal Fo gives an un-weighted linear Hugoniot of US = 2.674(0.188) + 1.64(0.06)up km/s. The unconstrained Co falls below estimates based on extrapolation in both temperature and composition from two published partial molar sound speed models, 3.195m/s [1] and 3.126 m/s [2]. The shock-derived Co indicates that dC/dT is negative for Fo liquid, contrary to the positive [1] and zero [2] temperature dependences derived over relatively narrow temperature intervals. CMASF liquid isentropes were calculated using five end-members (En, Fo, Fa, An, Di). For modeling crystallization of a fictive magma ocean, we examined two liquids: peridotite [3] (P=.33En+.56Fo+.07Fa+.03An+.007Di) and simplified chondrite [4] (Ch=.62En+.24Fo+.08Fa+.04An+.02Di). Each end-member is defined by a 3rd or 4th order Birch-Murnaghan isentrope, Mie-Grüneisen thermal pressure and a constant heat capacity. The volumes are

  16. NOx uptake on alkaline earth oxides (BaO, MgO, CaO and SrO) supported on γ-Al2O3

    SciTech Connect

    Verrier, Christelle LM; Kwak, Ja Hun; Kim, Do Heui; Peden, Charles HF; Szanyi, Janos

    2008-07-15

    NOx uptake experiments were performed on a series of alkaline earth oxide (AEO) (MgO, CaO, SrO, BaO) on γ-alumina materials. Temperature Programmed Desorption (TPD) conducted on He flow revealed the presence of two kinds of nitrate species: i.e. bulk and surface nitrates. The ratio of these two types of nitrate species strongly depends on the nature of the alkaline earth oxide. The amount of bulk nitrate species increases with the basicity of the alkaline earth oxide. This conclusion was supported by the results of infrared and 15N solid state NMR studies of NO2 adsorption. Due to the low melting point of the precursor used for the preparation of MgO/Al2O3 material (Mg(NO3)2), a significant amount of Mg was lost during sample activation (high temperature annealing) resulting in a material with properties were very similar to that of the γ-Al2O3 support. The effect of water on the NOx species formed in the exposure of the AEO-s to NO2 was also investigated. In agreement with our previous findings for the BaO/γ-Al2O3 system, an increase of the bulk nitrate species and the simultaneous decrease of the surface nitrate phase were observed for all of these materials.

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

    PubMed

    Vitale-Brovarone, C; Verné, E

    2005-09-01

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

  18. Synthesis of layered double hydroxides containing Mg2+, Zn2+, Ca2+ and Al3+ layer cations by co-precipitation methods-A review

    NASA Astrophysics Data System (ADS)

    Theiss, Frederick L.; Ayoko, Godwin A.; Frost, Ray L.

    2016-10-01

    Co-precipitation is a common method for the preparation of layered double hydroxides (LDHs) and related materials. This review article is aimed at providing newcomers to the field with some examples of the types of co-precipitation reactions that have been reported previously and to briefly investigate some of the properties of the products of these reactions. Due to the sheer volume of literature on the subject, the authors have had to limit this article to the synthesis of Mg/Al, Zn/Al and Ca/Al LDHs by co-precipitation and directly related methods. LDHs have been synthesised from various reagents including metal salts, oxides and hydroxides. Co-precipitation is also useful for the direct synthesis of LDHs with a wide range of interlayer anions and various bases have been successfully employed to prepare LDHs. Examples of other synthesis techniques including the urea method, hydrothermal synthesis and various mechanochemical methods that are undoubtedly related to co-precipitation have also been included in this review. The effect of post synthesis hydrothermal has also been summarised.

  19. Properties of blue emitting CaAl2O4:Eu2+, Nd3+ phosphor by optimizing the amount of flux and fuel

    NASA Astrophysics Data System (ADS)

    Wako, A. H.; Dejene, B. F.; Swart, H. C.

    2014-04-01

    Long afterglow CaAl2O4:0.03Eu2+, 0.03Nd3+ phosphor was prepared by solution-combustion synthesis. The active role of boric acid (H3BO3) as a flux in enhancing the Eu2+ photoluminescence and the effect of a varied amount of urea (CO (NH2)2) as a fuel on the morphological, structural and photoluminescent (PL) properties of the CaAl2O4:0.03Eu2+, 0.03Nd3+ systems were investigated. The results of X-ray diffraction, scanning electron microscopy, and PL spectra revealed the influence of the dosage of urea and hence the heated process on the crystallinity, morphology, and luminescence of the phosphor. The addition of H3BO3 favoured the formation of a monoclinic CaAl2O4 phase while the variation of the amount of CO (NH2)2 showed mixed phases although still predominantly monoclinic. Both H3BO3 and CO(NH2)2 to some extent influence the luminescence intensity of the obtained phosphor but unlike the case of CO(NH2)2, the presence of H3BO3 did not evidently shift the emission peak due to no obvious change in the energy level difference of the 4f-5d levels. The broad blue emissions consisting mainly of symmetrical bands having maxima between 440 and 445 nm originate from the energy transitions between the ground state (4f7) and the excited state (4f65d1) of the Eu2+ ions while the narrow emissions in the red region (600-630 nm) arise from the 5D0→7F2 transitions of the remnant unreduced Eu3+ions. Higher concentrations of H3BO3 (0.228 mol and 0.285 mol) reduce both intensity and lifetime of the phosphor. The optimized content of H3BO3 was 0.171 mol for the obtained phosphor with the best optical properties.

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

    SciTech Connect

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

    2015-03-07

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

  1. Preparation and photoluminescence property of a loose powder, Ca{sub 3}Al{sub 2}O{sub 6}:Eu{sup 3+} by calcination of a layered double hydroxide precursor

    SciTech Connect

    Gao Xiaorui; Lei Lixu Lv Changgui; Sun Yueming; Zheng Hegen; Cui Yiping

    2008-08-15

    A novel red light-emitting material, Ca{sub 3}Al{sub 2}O{sub 6}:Eu{sup 3+}, which is the first example found in the Ca{sub 3}Al{sub 2}O{sub 6} host, was prepared by calcination of a layered double hydroxide precursor at 1350 deg. C. The precursor, [Ca{sub 2.9-x}Al{sub 2}Eu{sub x}(OH){sub 9.8}](NO{sub 3}){sub 2+x}.2.5H{sub 2}O, was prepared by coprecipitation of metal nitrates with sodium hydroxide. The material is a loose powder composed of irregular particles formed from aggregation of particles of a few nanometers, as shown in scanning electron microscope (SEM) images. It was found that the photoluminescence intensity reached the maximum when the calcination temperature was 1350 deg. C and the concentration of Eu{sup 3+} was 1.0%. The material emits bright red emission at 614 nm under a radiation of {lambda}=250 nm. - Graphical abstract: Calcination of a layered double hydroxide precursor produces Ca{sub 3}Al{sub 2}O{sub 6}:Eu{sup 3+}, which is very easy to be pulverized. It is proposed that Eu{sup 3+} takes the place of one Ca{sup 2+} (green spheres in the picture, pink pyramids are [AlO{sub 4}] tetrahedrons) in the cell of Ca{sub 3}Al{sub 2}O{sub 6}. The Ca{sup 2+} could be any one of the bigger green spheres without inversion symmetry, and emits red light under a UV radiation of {lambda}=250 nm. Display Omitted.

  2. Synthesis and Luminescent Properties of CaSr(1-x)Al2SiO7:xEu3+ Phosphors for White Light-Emitting Diodes Applications.

    PubMed

    Hakeem, D A; Park, K

    2016-02-01

    CaSr(1-x)Al2SiO7:xEu3+ (0.01 < or = x < or = 0.12) red phosphors are prepared by the solid-state reaction method. The photoluminescence properties of the CaSr(1-x)Al2SiO7:xEu+ phosphors are studied as a function of Eu3+ content. The CaSr(1-x)Al2SiO7:xEu3+ phosphors form an orthorhombic structure with a space group of P2(1)2(1)2(1). The phosphors are effectively excited by 393 nm light. The emission spectra consist of several peaks at 575, 585, 616, 654, and 700 nm, which are attributed to the transitions from the excited 5Do to 7Fj (j = 0, 1, 2, 3, and 4) levels of Eu3+, respectively. The phosphors show intense red emission due to the 5Do --> (7)F2 transition of Eu3+. The strongest red emission is observed for the CaSr0.94Al2SiO7:0.06Eu3+ phosphor. This study proposes that the CaSr(1-x)Al2SiO7:xEu3+ red phosphors have a high potential for near ultraviolet-based white light-emitting diodes. PMID:27433657

  3. Influences of CaO on Crystallization, Microstructures, and Properties of BaO-Al2O3-B2O3-SiO2 Glass-Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Bo; Tang, Bo; Xu, Mingjiang

    2015-10-01

    We have developed BaO-CaO-Al2O3-B2O3-SiO2 glass-ceramics with high thermal coefficient of expansion (TCE) to overcome thermal mismatch at board level. The crystalline phases include quartz (major), cristobalite (minor), and bazirite BaZrSi3O9 (minor). Calculations from whole-pattern fitting show that the crystallinity varies slightly within the range of 33.48% to 34.89%, while the mass fraction of the phases changes remarkably with the CaO content. This indicates that CaO cannot promote crystallization of Ba-Al-B-Si glass, but effectively suppresses the phase transformation from quartz to cristobalite, making the thermal expansion curves linear. An empirical equation for the TCE versus the temperature and the amount of CaO is established. Furthermore, the densification mechanism of Ca modifiers is revealed. Due to its higher field strength than Ba, substitution of Ca increases the glass viscosity and inhibits ion diffusion. Excessive CaO is thus harmful to the density, bending strength, and electrical properties. The sample with 10 wt.% CaO sintered at 950°C exhibited high bending strength (154.1 MPa) and high TCE (12.38 ppm/°C) as well as good electrical properties ( ɛ = 6.2, tan δ = 5 × 10-4, ρ = 3.8 × 1012 Ω cm).

  4. First principles study of the structural, elastic, electronic and phonon properties of CdX{sub 2}O{sub 4} (X=Al, Ga, In) spinel-type oxides

    SciTech Connect

    Candan, Abdullah; Uğur, Gökay

    2014-10-06

    We have performed ab-initio calculations of the structural, electronic, elastic and dynamical properties for the spinel compounds CdX{sub 2}O{sub 4} (X=Al, Ga, In) using the plane wave pseudo-potential method within the generalized gradient approximation (GGA). The calculated lattice parameters, elastic constants for these compounds are in good agreement with the previous calculated values. The computed direct band gaps of CdAl{sub 2}O{sub 4}, CdGa{sub 2}O{sub 4} and CdIn{sub 2}O{sub 4} are 2.90 eV, 1.92 eV and 1.16 eV, respectively. The lattice vibrations were calculated by direct method. The calculated phonon dispersion curves show that all compounds are dynamically stable in the spinel structure.

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

    PubMed

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

    2008-05-01

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

  6. Highly improved reliability of amber light emitting diode with Ca -α-SiAlON phosphor in glass formed by gas pressure sintering for automotive applications.

    PubMed

    Yoon, Chang-Bun; Kim, Sanghyun; Choi, Sung-Woo; Yoon, Chulsoo; Ahn, Sang Hyeon; Chung, Woon Jin

    2016-04-01

    Phosphor in glass (PiG) with 40 wt% of Ca-α-SiAlON phosphor and 60 wt% of Pb-free silicate glass was synthesized and mounted on a high-power blue LED to make an amber LED for automotive applications. Gas pressure sintering was applied after the conventional sintering process was used to achieve fully dense PiG plates. Changes in photoluminescence spectra and color coordination were inspected by varying the thickness of the plates that were mounted after optical polishing and machining. A trade-off between luminous flux and color purity was observed. The commercial feasibility of amber PiG packaged LED, which can satisfy international regulations for automotive components, was successfully demonstrated by examining the practical reliability under 85% humidity at an 85°C condition. PMID:27192294

  7. Development of an optical fiber type detector using a Eu:LiCaAlF6 scintillator for neutron monitoring in boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Watanabe, Kenichi; Kawabata, Yuya; Yamazaki, Atsushi; Uritani, Akira; Iguchi, Tetsuo; Fukuda, Kentaro; Yanagida, Takayuki

    2015-12-01

    We have developed a small neutron detector probe as a thermal neutron flux monitor for boron neutron capture therapy. The detector consists of an optical fiber and a small Eu:LiCaAlF6 scintillator. In order to improve neutron-gamma ray discrimination capability, we use the small-size scintillator, whose size is controlled to be smaller than fast electron range produced by gamma-rays and larger than the range of charged particles induced by 6Li(n,t) reactions. We confirmed the improved neutron-gamma ray discrimination capability by comparing the detector responses between a small-size scintillator and a slab one. We also evaluated the neutron sensitivity of the fabricated optical fiber type neutron detector to be 2×10-4 cm2.

  8. Modelling Equilibrium and Fractional Crystallization in the System MgO-FeO-CaO-Al2O3-SiO2

    NASA Technical Reports Server (NTRS)

    Herbert, F.

    1985-01-01

    A mathematical modelling technique for use in petrogenesis calculations in the system MgO-FeO-CaO-Al2O3-SiO2 is reported. Semiempirical phase boundary and elemental distribution information was combined with mass balance to compute approximate equilibrium crystallization paths for arbitrary system compositions. The calculation is applicable to a range of system compositions and fractionation calculations are possible. The goal of the calculation is the computation of the composition and quantity of each phase present as a function of the degree of solidification. The degree of solidification is parameterized by the heat released by the solidifying phases. The mathematical requirement for the solution of this problem is: (1) An equation constraining the composition of the magma for each solid phase in equilibrium with the liquidus phase, and (2) an equation for each solid phase and each component giving the distribution of that element between that phase and the magma.

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

    SciTech Connect

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

    1991-05-01

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

  10. Transesterification of rapeseed oil for biodiesel production in trickle-bed reactors packed with heterogeneous Ca/Al composite oxide-based alkaline catalyst.

    PubMed

    Meng, Yong-Lu; Tian, Song-Jiang; Li, Shu-Fen; Wang, Bo-Yang; Zhang, Min-Hua

    2013-05-01

    A conventional trickle bed reactor and its modified type both packed with Ca/Al composite oxide-based alkaline catalysts were studied for biodiesel production by transesterification of rapeseed oil and methanol. The effects of the methanol usage and oil flow rate on the FAME yield were investigated under the normal pressure and methanol boiling state. The oil flow rate had a significant effect on the FAME yield for the both reactors. The modified trickle bed reactor kept over 94.5% FAME yield under 0.6 mL/min oil flow rate and 91 mL catalyst bed volume, showing a much higher conversion and operational stability than the conventional type. With the modified trickle bed reactor, both transesterification and methanol separation could be performed simultaneously, and glycerin and methyl esters were separated additionally by gravity separation. PMID:23558183

  11. Yb:CaGdAlO4 thin-disk laser with 70% slope efficiency and 90 nm wavelength tuning range.

    PubMed

    Beil, Kolja; Deppe, Bastian; Kränkel, Christian

    2013-06-01

    Thin-disk laser experiments with Yb:CaGdAlO(4) (Yb:CALGO) have been performed. A slope efficiency of 70% and an optical-to-optical efficiency of 57% could be achieved with a maximum output power of 30.7 W. These are so far the highest efficiencies obtained with this material. Furthermore, tuning experiments were carried out leading to a tuning range of 90 nm in total and 50 nm with more than 20 W of output power. This is to the best of our knowledge the widest wavelength tuning range of any material demonstrated at this power level. For all experiments the thermal evolution of the crystal surface temperature during laser operation was investigated. PMID:23722805

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  13. Growth and Characterization of Ca2Al2SiO7 Piezoelectric Single Crystals for High-Temperature Sensor Applications

    NASA Astrophysics Data System (ADS)

    Hagiwara, Manabu; Noguchi, Hiroaki; Hoshina, Takuya; Takeda, Hiroaki; Fujihara, Shinobu; Kodama, Nobuhiro; Tsurumi, Takaaki

    2013-09-01

    The electrical properties of a piezoelectric single crystal of calcium aluminate silicate Ca2Al2SiO7 (CAS) were studied at elevated temperatures and its applicability to high-temperature pressure sensors was investigated. The CAS bulk single crystal was grown by the Czochralski method. The piezoelectric d14 and d36 constants were respectively evaluated as 6.04 and 4.04 pC/N by the resonance and antiresonance method. The temperature dependence of the piezoelectric constant was investigated at temperatures up to 500 °C. The electrical resistivity at 800 °C was on the order of 108 Ω.cm along both the crystallographic a- and c-axes. The measurement of direct piezoelectric response at 700 °C demonstrated that the CAS crystal could detect a pseudo-combustion pressure change of an automobile engine. Our observations suggest that CAS crystals are superior candidates for sensing pressure at high temperatures.

  14. Built-in Quantum Dots in Nano-Porous Crystal 12CaO\\cdot7Al2O3: Simplified Views for Electronic Structure and Carrier Transport

    NASA Astrophysics Data System (ADS)

    Kamiya, Toshio; Hosono, Hideo

    2005-01-01

    12CaO\\cdot7Al2O3 (C12A7) has a unique crystal structure composed of subnanometer-sized cages and free oxygen ions in the cages. C12A7 exhibits a variety of active functions if the free oxygen ions are substituted with other active anions. Electronic conduction was attained by introducing high-density F+-like centers, which was the first demonstration of electronic conduction in oxides composed only of light elements. Chemical active species such as O- and H- are produced in C12A7 at high densities. In this paper, we first review the structure and properties of C12A7-drived materials and related \\textit{ab-initio} works, and then provide simplified views for the stability of the crystal lattice and the clathrated anions, electronic structure, and carrier transport mechanism using simple models based on crystal chemistry, classical molecular dynamics simulation and effective-mass approximation.

  15. Reddish-orange Ca3-xAl2O6:xEu3+ nanophosphors: Fast synthesis and photophysical properties

    NASA Astrophysics Data System (ADS)

    Barros, B. S.; de Oliveira, R. S.; Kulesza, J.; Melo, V. R. M.; Melo, D. M. A.; Alves, S.

    2015-03-01

    This paper focuses on the synthesis and the photoluminescent properties of Ca3-xAl2O6:xEu3+ (0≤x≤0.1) nanophosphors prepared by microwave-assisted combustion method without any further heat treatment. X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy were used to characterize the produced samples. Nanosized particles smaller than 120 nm were obtained as confirmed by SEM. When exposed to UV light radiation at 254 nm, the europium-doped nanoparticles showed strong reddish-orange luminescence due to the characteristic transitions 5D0→7F1 (orange) and 5D0→7F2, (red). The maximum emission intensity of the visible emission was obtained for x=0.05. It was also found that higher doping concentrations led to the luminescence quenching by a cross-relaxation mechanism between Eu3+ ions in the lattice.

  16. From atomic structure to excess entropy: a neutron diffraction and density functional theory study of CaO-Al2O3-SiO2 melts

    NASA Astrophysics Data System (ADS)

    Liu, Maoyuan; Jacob, Aurélie; Schmetterer, Clemens; Masset, Patrick J.; Hennet, Louis; Fischer, Henry E.; Kozaily, Jad; Jahn, Sandro; Gray-Weale, Angus

    2016-04-01

    Calcium aluminosilicate \\text{CaO}-\\text{A}{{\\text{l}}2}{{\\text{O}}3}-\\text{Si}{{\\text{O}}2} (CAS) melts with compositions {{≤ft(\\text{CaO}-\\text{Si}{{\\text{O}}2}\\right)}x}{{≤ft(\\text{A}{{\\text{l}}2}{{\\text{O}}3}\\right)}1-x} for x  <  0.5 and {{≤ft(\\text{A}{{\\text{l}}2}{{\\text{O}}3}\\right)}x}{{≤ft(\\text{Si}{{\\text{O}}2}\\right)}1-x} for x≥slant 0.5 are studied using neutron diffraction with aerodynamic levitation and density functional theory molecular dynamics modelling. Simulated structure factors are found to be in good agreement with experimental structure factors. Local atomic structures from simulations reveal the role of calcium cations as a network modifier, and aluminium cations as a non-tetrahedral network former. Distributions of tetrahedral order show that an increasing concentration of the network former Al increases entropy, while an increasing concentration of the network modifier Ca decreases entropy. This trend is opposite to the conventional understanding that increasing amounts of network former should increase order in the network liquid, and so decrease entropy. The two-body correlation entropy S 2 is found to not correlate with the excess entropy values obtained from thermochemical databases, while entropies including higher-order correlations such as tetrahedral order, O-M-O or M-O-M bond angles and Q N environments show a clear linear correlation between computed entropy and database excess entropy. The possible relationship between atomic structures and excess entropy is discussed.

  17. Biogeochemistry of Mariana Islands coastal sediments: terrestrial influence on /gd13, Ash, CaCO3, Al, Fe, Si and P

    NASA Astrophysics Data System (ADS)

    Matson, Ernest A.

    1989-01-01

    Stable C isotope ratios (δ13C-PDB), percentages of organic matter, and HCl insoluble ash and soluble carbonates, extractable Fe, Al, Si and P were used to determine the distribution and accumulation of terrestrial material in reef-flat moats and lagoons of two high islands (Guam and Saipan) in the western tropical Pacific. Carbonate sediments of a reef-flat moat infiltrated by seepage of aquifer waters (but without surface runoff) were depleted in both P (by 38%) and 13C (by 41%) and enriched in Si (by 100%) relative to offshore lagoon sediments. Iron and ash accumulated in depositional regimes regardless of the occurrence of runoff but was depleted from coarse-grained carbonates in turbulent regimes. Aluminum (>ca. 10 to 20 μmol g-1), Fe (>ca. 1 to 3 μmol g-1) and ash (>0.5%) indicated terrigenous influence which was corroborated by depletions in both 13C and P. Low-salinity geochemical segregation, natural biochemical accumulation, as well as long-shore currents and eddies help sequester these materials nearshore.

  18. Structure and magnetic properties of Ca{sub 2}Fe{sub 1-x}Mn{sub x}AlO{sub 5+{delta}}

    SciTech Connect

    Carvalho, M.D.; Waerenborgh, J.C.; Tsipis, E.; Godinho, M.

    2008-09-15

    Ca{sub 2}Fe{sub 1-x}Mn{sub x}AlO{sub 5} (0{<=}x{<=}1) compounds were prepared by a self-combustion method under air (x=0, 0.1, 0.2 and 0.3) and nitrogen (x=0.5, 0.7 and 1.0). The samples prepared under nitrogen were successfully oxidized after short annealing under air. Both X-ray powder diffraction (XRD) Rietveld analysis and electron diffraction revealed that all compounds adopt the brownmillerite-type structure. All samples present an overall antiferromagnetic behaviour and data from magnetic measurements and Moessbauer spectroscopy allowed to conclude that the transition temperature decreases as Mn content increases for x{<=}0.3 and increases in the case of the x{>=}0.5 compounds. Except for x=1, chemical disorder due to the occupancy of both octahedral and tetrahedral sites by different metals as well as the competition between different moments' orientation induce a complex magnetic behaviour characterized by magnetic frustration and canted antiferromagnetism. Moessbauer spectroscopy and chemical titrations also allowed to conclude about the preferential oxidation of Mn{sup 3+} over Fe{sup 3+}, obtained by thermal treatment under air of the x=0.5 and 0.7 compositions. - Graphical abstract: Structure of the Ca{sub 2}Fe{sub 1-x}Mn{sub x}AlO{sub 5} compound and electron diffraction pattern obtained along the [1-bar 01] zone axis (x=0.2), showing a brownmillerite structure.

  19. Ageing and structural effects on the sorption characteristics of Cd2+ by clinoptilolite and Y-type zeolite studied using isotope exchange technique.

    PubMed

    Ahmed, I A M; Young, S D; Crout, N M J

    2010-12-15

    This research investigates the long-term kinetics of Cd(2+) sorption and desorption by calcium-exchanged clinoptilolite (CaCpt) and Y-type (CaY) zeolite using isotopic exchange with (109)Cd while maintaining pH at circumneutral values. The effects of Si/Al ratio and crystal structure of these zeolitic materials on intracrystalline transport of Cd are discussed. A first-order kinetic model was developed to describe the progressive transfer of Cd(2+) to a less reactive form within the zeolite structure, following initial sorption and subsequent desorption of Cd subject to different initial contact times. The kinetic model differentiates between two forms of sorbed Cd(2+) designated 'labile' and 'non-labile' in which the labile form is in immediate equilibrium with the free Cd(2+) ion activity in solution. A model combining diffusion and first-order kinetics for cation exchange was also employed to determine Cd(2+) diffusivity and intracrystalline exchange rates in CaY and CaCpt. The efficiency of Permeable Reactive Barriers (PRBs) containing zeolitic materials in protecting water systems against lateral flow of metal-contaminated leachate was simulated for three contrasting zeolites. The slow transfer of Cd between labile and non-labile forms was particularly important in moderating high concentration pulses of Cd traversing the PRB. In addition, the reversibility of Cd fixation effectively restored the sorption capability of the zeolite through slow leakage to drainage water. PMID:20843600

  20. Phase Equilibria Studies in the System ZnO-``FeO''-Al2O3-CaO-SiO2 Relevant to Imperial Smelting Furnace Slags: Part II

    NASA Astrophysics Data System (ADS)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2010-04-01

    The phase equilibria and the liquidus temperatures in the system ZnO-“FeO”-Al2O3-CaO-SiO2 have been determined experimentally in equilibrium with metallic iron. Specifically, the effects of Al2O3 concentrations in Imperial Smelting Furnace slags are identified, and the results are presented in the form of pseudo-ternary sections ZnO-“FeO”-(Al2O3 + CaO + SiO2) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 5.0 and 3.5, respectively. It was found that, in the presence of Al2O3, the spinel phase is formed, the spinel primary phase field expands, and the wustite and melilite primary phase fields are reduced in size with an increasing Al2O3 concentration. The implications of the findings to industrial practice are discussed.

  1. Thermodynamic simulation on mineralogical composition of CaO-SiO2-Al2O3-MgO quaternary slag system.

    PubMed

    Liu, Chao; Zhang, Yu-Zhu; Li, Jie; Li, Jun-Guo; Kang, Yue

    2016-01-01

    It is necessary to elucidate the crystallization thermodynamic of mineralogical phases during the cooling process of the molten BFS with different chemical composition, because the high-melting point mineral phase maybe crystallized during the fiber forming and thereafter cooling process. Thermodynamic calculation software FactSage6.4 and the hot remelting experiments were performed to explore the influence of basicity, Al2O3 content and MgO content on the crystallization of mineralogical components and their transformation. The results showed that the main mineralography of the CaO-SiO2-Al2O3-MgO quaternary slag system was melilite, and a certain amount of anorthite and calcium metasilicate. The crystallographic temperature of melilite is increased with the increasing of basicity, MgO and Al2O3 content, which has a significant impact on the utilization performance of the mineral wool prepared with the hot blast furnace slag directly. With the increasing of basicity, there was a tendency that crystallographic amount of melilite increased to the summit and then declined, while the amount of anorthite and calcium metasilicate decreased consistently. Finally, these two mineralogical components could be replaced by magnesium rhodonite and spinel with the increasing of basicity. When the basicity and MgO content were 1.0 and 9 %, the crystallographic mass ratio of melilite and anorthite increased, while that of calcium silicate declined, and replaced by spinel finally with the increasing of Al2O3 content. When the basicity and Al2O3 content were 1.0 and 13 %, the crystallographic mass ratio of melilite increased, while that of anorthite and calcium silicate declined, and replaced by pyroxene and spinel with the increasing of MgO content. To decline fiberization temperature of the melt BFS, the basicity, MgO and Al2O3 content should be decreased during the modification process of chemical composition, because the crystallization temperature of the primary crystalline

  2. Antigen S1, encoded by the MIC1 gene, is characterized as an epitope of human CD59, enabling measurement of mutagen-induced intragenic deletions in the AL cell system

    NASA Technical Reports Server (NTRS)

    Wilson, A. B.; Seilly, D.; Willers, C.; Vannais, D. B.; McGraw, M.; Waldren, C. A.; Hei, T. K.; Davies, A.; Chatterjee, A. (Principal Investigator)

    1999-01-01

    S1 cell membrane antigen is encoded by the MIC1 gene on human chromosome 11. This antigen has been widely used as a marker for studies in gene mapping or in analysis of mutagen-induced gene deletions/mutations, which utilized the human-hamster hybrid cell-line, AL-J1, carrying human chromosome 11. Evidence is presented here which identifies S1 as an epitope of CD59, a cell membrane complement inhibiting protein. E7.1 monoclonal antibody, specific for the S1 determinant, was found to react strongly with membrane CD59 in Western blotting, and to bind to purified, urinary form of CD59 in ELISAs. Cell membrane expression of S1 on various cell lines always correlated with that of CD59 when examined by immunofluorescent staining. In addition, E7.1 antibody inhibited the complement regulatory function of CD59. Identification of S1 protein as CD59 has increased the scope of the AL cell system by enabling analysis of intragenic mutations, and multiplex PCR analysis of mutated cells is described, showing variable loss of CD59 exons.

  3. Activities of MnO in CaO-SiO2-Al2O3-MnO (<10 Pct)-FetO(<3 pct) slags saturated with liquid iron

    NASA Astrophysics Data System (ADS)

    Ohta, Hiroki; Suito, Hideaki

    1995-04-01

    Activity coefficients of MnO and Fe,0 in CaO-SiO2-Al2O3-MnO(<10 mass pct)-Fe,O(<3 mass pct) slags were determined at 1873 K in an Al2O3 or CaO crucible by using the reported values for the activities of Al2O3 and SiO2 or the analyzed contents of oxygen. The activity coefficients of MnO and FetO were found to be constant in the studied concentration range of MnO and FetO. The former increased with an increase in the CaO content, while the latter increased with an increase in the SiO2 content.

  4. Luminescent and aging characteristics of blue emitting (Ca 1- x,Mg x)Al 2Si 2O 8:Eu 2+ phosphor for PDPs application

    NASA Astrophysics Data System (ADS)

    Im, Won Bin; Kim, Yong-Il; Kang, Jong Hyuk; Jeon, Duk Young

    2005-06-01

    We have evaluated thermal stability and aging property of a blue color-emitting phosphor, CaAl 2Si 2O 8:Eu 2+ (CAS:Eu 2+), synthesized by conventional solid-state reaction method. When both CAS:Eu 2+ and BaMgAl 10O 19:Eu 2+ (BAM) were baked in air at 500 °C for 20 min, the decrease of photoluminescence (PL) intensity of CAS:Eu 2+ was lower than that of BAM. The aging property of CAS:Eu 2+ was also better than that of BAM. Due to its rigid structure and unlimited framework of silicon-oxygen and aluminum-oxygen around Eu 2+ ions, Eu 2+ ions were protected from outer oxidizing atmosphere and plasma discharge. After analysis of aging property and thermal stability, the differences of these thermal stability and aging property of CAS:Eu 2+ from those of BAM were ascribed to its crystal structure which plays a role of a shield for Eu 2+ ions against oxidation atmosphere and Xe ion bombardment.

  5. Ab-initio study of the structural, linear and nonlinear optical properties of CdAl{sub 2}Se{sub 4} defect-chalcopyrite

    SciTech Connect

    Ouahrani, T.; Reshak, Ali H.; Khenata, R.; Amrani, B.; Mebrouki, M.; Otero-de-la-Roza, A.; Luana, V.

    2010-01-15

    The complex density functional theory (DFT) calculations of structural, electronic, linear and nonlinear optical properties for the defect chalcopyrite CdAl{sub 2}Se{sub 4} compound have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code. We employed the Wu and Cohen generalized gradient approximation (GGA-WC), which is based on exchange-correlation energy optimization to calculate the total energy. Also we have used the Engel-Vosko GGA formalism, which optimizes the corresponding potential for band structure, density of states and the spectral features of the linear and nonlinear optical properties. This compound has a wide direct energy band gap of about 2.927 eV with both the valence band maximum and conduction band minimum located at the center of the Brillouin zone. The ground state quantities such as lattice parameters (a, c, x, y and z), bulk modulus B and its pressure derivative B' are evaluated. We have calculated the frequency-dependent complex epsilon(omega), its zero-frequency limit epsilon{sub 1}(0), refractive index n(omega), birefringence DELTAn(omega), the reflectivity R(omega) and electron energy loss function L(omega). Calculations are reported for the frequency-dependent complex second-order nonlinear optical susceptibilities. We find opposite signs of the contributions of the 2omega and 1omega inter/intra-band to the imaginary part for the dominant component through the wide optical frequency range. - Graphical abstract: Calculated band structure and total density of CdAl{sub 2}Se{sub 4}.

  6. Evaluation of Existing Viscosity Data and Models and Developments of New Viscosity Model for Fully Liquid Slag in the SiO2-Al2O3-CaO-MgO System

    NASA Astrophysics Data System (ADS)

    Han, Chen; Chen, Mao; Zhang, Weidong; Zhao, Zhixing; Evans, Tim; Zhao, Baojun

    2016-07-01

    Metallurgical properties of slag are determined to a great extent by its viscosity. High-temperature viscosity measurements are time-consuming and expensive. It is necessary to develop an accurate viscosity model for blast furnace slag in the SiO2-Al2O3-CaO-MgO system using reliable viscosity data. This paper describes a systemic evaluation procedure to determine the viscosity data to be used for model development. 1780 viscosity data from 10 to 65 wt pct SiO2, 3.5 to 40 wt pct Al2O3, 2 to 60 wt pct CaO, and 2 to 38 wt pct MgO in the SiO2-Al2O3-CaO-MgO system have been accepted for model evaluation after critical reviews. The existing 14 viscosity models in SiO2-Al2O3-CaO-MgO system is also reviewed and evaluated. Based on the structure of alumina-silicate slag and evaluated viscosity data, a new viscosity model has been proposed for the system SiO2-Al2O3-CaO-MgO. A new term "probability," based on the basic oxide and electronegativity, is introduced to calculate the integral activation energy of slag. The model has been evaluated and compared with existing viscosity models in three different composition ranges in SiO2-Al2O3-CaO-MgO system for different applications. The new model reports an outstanding agreement between predictions and experimental data. The industrial implications of the new model have also been discussed in ironmaking and steelmaking processes.

  7. Effects of MgO and Al2O3 Addition on Redox State of Chromium in CaO-SiO2-CrO x Slag System by XPS Method

    NASA Astrophysics Data System (ADS)

    Wang, Li-jun; Yu, Ji-peng; Chou, Kuo-chih; Seetharaman, Seshadri

    2015-08-01

    The effects of MgO and Al2O3 on the redox state of chromium in CaO-SiO2-CrO x system have been investigated at 1873 K (1600 °C) under Ar-CO-CO2 atmosphere and analyzed by means of X-ray photoelectron spectroscopy. From the analysis of the Cr 2p core level spectra, it was found that both Cr(II) and Cr(III) exist simultaneously in CaO-MgO/Al2O3-SiO2-CrO x , and the quantitative ratio Cr(II)/Cr(III) has been obtained by deducing from the area under the computer-resolved peaks. Substitutions of CaO by MgO, SiO2 by Al2O3 favored the Cr(II) state existing in the system in the composition ranges of 3 to 10 wt pct MgO and 5 to 20 pct Al2O3. Meanwhile, from the analysis of the O1s spectra in CaO-MgO-SiO2-CrO x , it was found that the ratio of the non-bridging oxygen content increased first due to the CrO contribution to the electron distribution uniformly as O- at MgO low content. Afterward, it went to decreasing with continuing addition of MgO because ionic contribution of MgO is less than that of CaO and the influence of the CrO clustering on the non-Bridging oxygen is limited due to only 5 wt pct CrO x . In CaO-Al2O3-SiO2-CrO x system, Cr(II) acts as a network modifier to compensate Al3+ charge balance to make the structure stable, so the non-bridge oxygen in this system continues decreasing.

  8. Diffusion in silicate melts: I. Self diffusion in CaO-Al{sub 2}O{sub 3}-SiO{sub 2} at 1500{degrees}C and 1 GPa

    SciTech Connect

    Liang, Yan |; Richter, F.M.; Davis, A.M.

    1996-11-01

    Self diffusion coefficients of calcium (D{sub Ca}), aluminum (D{sub A1}), silicon (D{sub Si}), and oxygen (D{sub o}) were measured in molten CaO-Al{sub 2}O{sub 3}-SiO{sub 2} at 1500{degrees}C and 1 GPa over a range of melt compositions, using the isotope tracer method. For all but one composition, the measured self diffusion coefficients decrease in the order D{sub Ca} > D{sub Al} > D{sub o} > D{sub Si}, with D{sub Ca} {approximately} 4-19D{sub Si}, D{sub Al}, {approximately} 2D{sub Si}, and D{sub o} {approximately} 1-2D{sub Si}. The relative uncertainties, based on replicated experiments, are 8% for D{sub Ca}, 27% for D{sub Al}, 28% for D{sub Si}, and 18% for D{sub o}. Although the self diffusion coefficients of calcium, aluminum, silicon, and oxygen increase with the decrease of melt viscosity, they do not obey the Stokes-Einstein equation or the Eyring equation. 69 refs., 6 figs., 6 tabs.

  9. Effect of Slag Composition on the Distribution Behavior of Pb between FetO-SiO2 (-CaO, Al2O3) Slag and Molten Copper

    NASA Astrophysics Data System (ADS)

    Heo, Jung Ho; Park, Soo-Sang; Park, Joo Hyun

    2012-10-01

    The distribution behavior of Pb between molten copper and FetO-SiO2 (-CaO, Al2O3) slags was investigated at 1473 K (1200 °C) and p_{{{{O}}2 }} = 10^{ - 10} {{atm}} in view of the reaction mechanism of Pb dissolution into the slag. Furthermore, the lead capacity of the slag was estimated from the experimental results. The distribution ratio of Pb ( L Pb) decreases with increasing CaO content ( 6 mass pct) irrespective of Fe/SiO2 ratio (1.4 to 1.7). However, the addition of alumina into a slag with Fe/SiO2 = 1.5 linearly decreases the L Pb, whereas a minimum value is observed at about 4 mass pct Al2O3 at Fe/SiO2 = 1.3. The log L Pb continuously decreases with increasing Fe/SiO2 ratio, and the addition of Al2O3 (5 to 15 mass pct) into the silica-saturated iron silicate slag (Fe/SiO2 < 1.0) yields the highest Pb distribution ratio. This is mainly due to a decrease in the FeO activity even at silica saturation. The log L Pb linearly decreases by increasing the log (Fe3+/Fe2+) value. The Pb distribution ratio increases and the excess free energy of PbO decreases with increasing Cu2O content in the slag. However, from the viewpoint of copper loss into the slag, the silica-saturated system containing small amounts of alumina is strongly recommended to stabilize PbO in the slag phase at a low Cu2O content. The lead capacity was defined in the current study and shows a linear correlation with the activity of FeO in a logarithmic scale, indicating that the concept of lead capacity is a good measure of absorption ability of Pb in iron silicate slags, and the activity of FeO can be a good basicity index in iron silicate slag.

  10. Short-lived chlorine-36 in a Ca- and Al-rich inclusion from the Ningqiang carbonaceous chondrite.

    PubMed

    Lin, Yangting; Guan, Yunbin; Leshin, Laurie A; Ouyang, Ziyuan; Wang, Daode

    2005-02-01

    Excesses of sulfur-36 in sodalite, a chlorine-rich mineral, in a calcium- and aluminum-rich inclusion from the Ningqiang carbonaceous chondrite linearly correlate with chorine/sulfur ratios, providing direct evidence for the presence of short-lived chlorine-36 (with a half-life of 0.3 million years) in the early solar system. The best inferred (36Cl/35Cl)o ratios of the sodalite are approximately 5 x 10(-6). Different from other short-lived radionuclides, chlorine-36 was introduced into the inclusion by solid-gas reaction during secondary alteration. The alteration reaction probably took place at least 1.5 million years after the first formation of the inclusion, based on the correlated study of the 26Al-26Mg systems of the relict primary minerals and the alteration assemblages, from which we inferred an initial ratio of (36Cl/35Cl)o > or = 1.6 x 10(-4) at the time when calcium- and aluminum-rich inclusions formed. This discovery supports a supernova origin of short-lived nuclides [Cameron, A. G. W., Hoeflich, P., Myers, P. C. & Clayton, D. D. (1995) Astrophys. J. 447, L53; Wasserburg, G. J., Gallino, R. & Busso, M. (1998) Astrophys. J. 500, L189-L193], but presents a serious challenge for local irradiation models [Shu, F. H., Shang, H., Glassgold, A. E. & Lee, T. (1997) Science 277, 1475-1479; Gounelle, M., Shu, F. H., Shang, H., Glassgold, A. E., Rehm, K. E. & Lee, T. (2001) Astrophys. J. 548, 1051-1070]. Furthermore, the short-lived 36Cl may serve as a unique fine-scale chronometer for volatile-rock interaction in the early solar system because of its close association with aqueous and/or anhydrous alteration processes. PMID:15671168

  11. Role of the chemical substitution on the luminescence properties of solid solutions Ca{sub (1−x)}Cd{sub (x)}WO{sub 4} (0 ≤ x ≤1)

    SciTech Connect

    Taoufyq, A.; Mauroy, V.; Guinneton, F.; Bakiz, B.; Villain, S.; and others

    2015-10-15

    Highlights: • Luminescence can be modified by chemical substitution in solid solutions Ca{sub 1−x}Cd{sub x}WO{sub 4}. • The various emission spectra (charge transfer) were obtained under X-ray excitation. • Scheelite or wolframite solid solutions presented two types of emission spectra. • A luminescence component depended on cadmium substitution in each solid solution. • A component was only characteristic of oxyanion symmetry in each solid solution. - Abstract: We have investigated the chemical substitution effects on the luminescence properties under X-ray excitation of the solid solutions Ca{sub (1−x)}Cd{sub (x)}WO{sub 4} with 0 ≤ x ≤ 1. Two types of wide spectral bands, associated with scheelite-type or wolframite-type solid solutions, have been observed at room temperature. We decomposed each spectral band into several spectral components characterized by energies and intensities varying with composition x. One Gaussian component was characterized by an energy decreasing regularly with the composition x, while the other Gaussian component was only related to the tetrahedral or octahedral configurations of tungstate groups WO{sub 4}{sup 2−} or WO{sub 6}{sup 6−}. The luminescence intensities exhibited minimum values in the composition range x < 0.5 corresponding to scheelite-type structures, then, they regularly increased for cadmium compositions x > 0.5 corresponding to wolframite-type structures.

  12. Lattice vibration spectra. Part LXXXII. Brucite-type hydroxides M(OH)2 (M = Ca, Mn, Co, Fe, Cd) — IR and Raman spectra, neutron diffraction of Fe(OH)2

    NASA Astrophysics Data System (ADS)

    Lutz, H. D.; Möller, H.; Schmidt, M.

    1994-12-01

    Fe3+-free white rust Fe(O(H,D))2 has been prepared and characterized by X-ray, neutron diffraction, and IR and Raman spectroscopic methods. The crystal structure of Fe(OH)2 (space group Poverline3ml, Z = 1, a = 326.289(1) pm and c = 460.4(1)pm; V = 42.45(1) × 106 pm3) was refined to a final RI = 5.6%. The results of IR and Raman spectra of the brucite-type M(O(H,D))2 (M = Ca, Mn, Fe, Co, Cd) are presented and discussed in terms of (i) assignment of the librational and translational modes, (ii) frequency shifts with respect to MO bond lengths, unit-cell volumes and masses of the atoms involved, and (iii) the nature of the large unit-cell group splittings of the OH stretching modes. Due to different bonding, i.e. more or less covalent, the brucite-type hydroxides can be divided into two groups of M = Ca, Mg, and M = Fe, Co, Ni, and Cd, respectively.

  13. Hf W mineral isochron for Ca,Al-rich inclusions: Age of the solar system and the timing of core formation in planetesimals

    NASA Astrophysics Data System (ADS)

    Burkhardt, Christoph; Kleine, Thorsten; Bourdon, Bernard; Palme, Herbert; Zipfel, Jutta; Friedrich, Jon M.; Ebel, Denton S.

    2008-12-01

    Application of 182Hf- 182W chronometry to constrain the duration of early solar system processes requires the precise knowledge of the initial Hf and W isotope compositions of the solar system. To determine these values, we investigated the Hf-W isotopic systematics of bulk samples and mineral separates from several Ca,Al-rich inclusions (CAIs) from the CV3 chondrites Allende and NWA 2364. Most of the investigated CAIs have relative proportions of 183W, 184W, and 186W that are indistinguishable from those of bulk chondrites and the terrestrial standard. In contrast, one of the investigated Allende CAIs has a lower 184W/ 183W ratio, most likely reflecting an overabundance of r-process relative to s-process isotopes of W. All other bulk CAIs have similar 180Hf/ 184W and 182W/ 184W ratios that are elevated relative to average carbonaceous chondrites, probably reflecting Hf-W fractionation in the solar nebula within the first ˜3 Myr. The limited spread in 180Hf/ 184W ratios among the bulk CAIs precludes determination of a CAI whole-rock isochron but the fassaites have high 180Hf/ 184W and radiogenic 182W/ 184W ratios up to ˜14 ɛ units higher than the bulk rock. This makes it possible to obtain precise internal Hf-W isochrons for CAIs. There is evidence of disturbed Hf-W systematics in one of the CAIs but all other investigated CAIs show no detectable effects of parent body processes such as alteration and thermal metamorphism. Except for two fractions from one Allende CAI, all fractions from the investigated CAIs plot on a single well-defined isochron, which defines the initial ɛ 182W = -3.28 ± 0.12 and 182Hf/ 180Hf = (9.72 ± 0.44) × 10 -5 at the time of CAI formation. The initial 182Hf/ 180Hf and 26Al/ 27Al ratios of the angrites D'Orbigny and Sahara 99555 are consistent with the decay from initial abundances of 182Hf and 26Al as measured in CAIs, suggesting that these two nuclides were homogeneously distributed throughout the solar system. However, the

  14. Immunohistochemical distinction of renal cell carcinoma from other carcinomas with clear-cell histomorphology: utility of CD10 and CA-125 in addition to PAX-2, PAX-8, RCCma, and adipophilin.

    PubMed

    Mentrikoski, Mark J; Wendroth, Scott M; Wick, Mark R

    2014-10-01

    Clear-cell renal cell carcinoma (CC-RCC) is the most common primary kidney malignancy, yet this morphology is not unique to renal primary tumors, as clear-cell variants of numerous nonrenal carcinomas of varying lineages exist. Therefore, because of CC-RCC's ability to metastasize to nearly any anatomic location, ancillary studies such as immunohistochemistry are often needed to establish the diagnosis. Despite CD10 and renal cell carcinoma monoclonal antibody (RCCma) being touted as sensitive and specific markers, some have suggested that more recent stains including PAX-2, PAX-8, or adipophilin (ADP) are more robust markers of CC-RCC. In this study, 26 cases of CC-RCC, and 51 nonrenal carcinomas with clear-cell histomorphology (CCM) were stained with CD10, RCCma, PAX-2, PAX-8, and ADP. CA-125 was also included to help distinguish CC-RCC from Müllerian clear-cell carcinomas, due the known expression of PAX-2 and PAX-8 in both these entities. RCCma highlighted 77% of CC-RCC and 27% of the CCM group, whereas CD10 was positive in 85% and 25%, respectively. ADP highlighted all CC-RCC and 45% of CCMs. PAX-2 was positive in 81% of CC-RCC and 24% of CCM, whereas PAX-8 stained 100% of CC-RCC and 39% of CCM. Müllerian-derived tumors (clear-cell carcinomas of the ovary, vagina, and cervix) were positive with PAX-2 and PAX-8 in 69% and 100% of cases, respectively. No cases of CC-RCC stained with CA-125, whereas 88% of the Müllerian-derived tumors were positive. In summary, although new markers such as PAX-2 and PAX-8 tend to be more sensitive markers of CC-RCC, they lose specificity when Müllerian tumors are included. Inclusion of a classic renal marker such as CD10 or RCCma in the immunohistochemical panel, as well as CA-125 obviates this difficulty. PMID:25279712

  15. Direct determination of the NaF/AlF3 molar ratio by Raman spectroscopy in NaF-AlF3-CaF2 melts at 1000 °C.

    PubMed

    Malherbe, Cedric; Gilbert, Bernard

    2013-09-17

    For the last 40 years, Raman spectroscopy has been very useful in investigating the structure of corrosive molten salts, such as the cryolite-based melts widely used as electrolyte in the Hall-Heroult process. Even if this process remains the most economically efficient for metallic aluminum electro-production, it suffers from a high energy loss, which is dependent on the melt composition. Therefore, controlling the chemical composition of the electrolyte is essential. The present paper proposes to apply Raman spectroscopy for the direct determination of the NaF-AlF3 molar ratio in NaF-AlF3-CaF2-based melts. Despite the experimental difficulties, a calibration curve based on equilibria taking place in the melt has been developed and the procedure has been successfully compared to industrial samples of known compositions. The possible exportation of the laboratory scale procedure to an industrial environment application for the control of the Hall-Heroult process is finally discussed. PMID:23988269

  16. Hillesheimite, (K,Ca,□)2(Mg,Fe,Ca,□)2[(Si,Al)13O23(OH)6](OH) · 8H2O, a new phyllosilicate mineral of the Günterblassite group

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Zubkova, N. V.; Pekov, I. V.; Belakovskiy, D. I.; Schüller, W.; Ternes, B.; Blass, G.; Pushcharovsky, D. Yu.

    2013-12-01

    A new mineral, hillesheimite, has been found in the Graulai basaltic quarry, near the town of Hillesheim, the Eifel Mountains, Rhineland-Palatinate (Rheinland-Pfalz), Germany. It occurs in the late assemblage comprising nepheline, augite, fluorapatite, magnetite, perovskite, priderite, götzenite, lamprophyllite-group minerals, and åkermanite. Colorless flattened crystals of hillesheimite reaching 0.2 × 1 × 1.5 mm in size and aggregates of the crystals occur in miarolitic cavities in alkali basalt. The mineral is brittle, with Mohs' hard-ness 4. Cleavage is perfect parallel to (010) and distinct on (100) and (001). D calc = 2.174 g/cm3, D meas = 2.16(1) g/cm3. IR spectrum is given. Hillesheimite is biaxial (-), α = 1.496(2), β = 1.498(2), γ = 1.499(2), 2 V meas = 80°. The chemical composition (electron microprobe, mean of 4 point analyses, H2O determined from structural data, wt %) is as follows: 0.24 Na2O, 4.15 K2O, 2.14 MgO, 2.90 CaO, 2.20 BaO, 2.41 FeO, 15.54 Al2O3, 52.94 SiO2, 19.14 H2O, total is 101.65. The empirical formula is: K0.96Na0.08Ba0.16Ca0.56Mg0.58Fe{0.37/2+}[Si9.62Al3.32O23(OH)6][(OH)0.82(H2O)0.18] · 8H2O. The crystal structure has been determined from X-ray single-crystal diffraction data, R = 0.1735. Hillesheimite is orthorhombic, space group Pmmn, the unit-cell dimensions are: a = 6.979(11), b = 37.1815(18), c = 6.5296(15) Å; V=1694(3) Å3, Z = 2. The crystal structure is based on the block [(Si,Al)13O25(OH)4] consisting of three single tetrahedral layers linked via common vertices and is topologically identical to the triple layers in günterblassite and umbrianite. The strong reflections [ d Å ( I %)] in the X-ray powder diffraction pattern are: 6.857(58), 6.545(100), 6.284(53), 4.787(96), 4.499(59), 3.065(86), 2.958(62), 2.767(62). The mineral was named after its type locality. Type specimens are deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4174/1.

  17. Tissintite, (Ca, Na, □)AlSi2O6, a highly-defective, shock-induced, high-pressure clinopyroxene in the Tissint martian meteorite

    NASA Astrophysics Data System (ADS)

    Ma, Chi; Tschauner, Oliver; Beckett, John R.; Liu, Yang; Rossman, George R.; Zhuravlev, Kirill; Prakapenka, Vitali; Dera, Przemyslaw; Taylor, Lawrence A.

    2015-07-01

    Tissintite is a new vacancy-rich, high-pressure clinopyroxene, with a composition essentially equivalent to plagioclase. It was discovered in maskelynite (shocked plagioclase) and is commonly observed included within, or in contact with, shock-melt pockets in the Tissint meteorite, a depleted olivine-phyric shergottite fall from Mars. The simple composition of tissintite (An58-69) and its precursor plagioclase (An59-69) together with the limited occurrence, both spatially (only in maskelynite less than ˜25 μm of a shock melt pocket) and in terms of bulk composition, make tissintite a "goldilocks" phase. It formed during a shock event severe enough to allow nucleation and growth of vacancy-rich clinopyroxene from a melt of not too calcic and not too sodic plagioclase composition that was neither too hot nor too cold. With experimental calibration, these limitations on occurrence can be used to place strong constraints on the thermal history of a shock event. The kinetics for nucleation and growth of tissintite are probably slower for more-sodic plagioclase precursors, so tissintite is most likely to occur in depleted olivine-phyric shergottites like Tissint and other highly shocked meteorites and lunar and terrestrial rocks that consistently contained calcic plagioclase precursors in the appropriate compositional range for a shock of given intensity. Tissintite, (Ca0.45Na0.31□0.24) (Al0.97Fe0.03Mg0.01) (Si1.80Al0.20)O6, is a C 2 / c clinopyroxene, containing 42-60 mol% of the Ca-Eskola component, by far the highest known. The cell parameters are a = 9.21 (17) Å, b = 9.09 (4) Å, c = 5.20 (2) Å, β = 109.6 (9)°, V = 410 (8) Å3, Z = 4. The density is 3.32 g/cm3 and we estimate a cell volume for the Ca-Eskola end-member pyroxene of 411 ± 13 Å3, which is consistent with a previous estimate and, therefore, supports the importance of this component in clinopyroxenes from ultra-high pressure metamorphic rocks from the Earth's upper mantle. At least in C 2 / c

  18. Distribution of P, K, Ca, Mg, Cd, Cu, Fe, Mn, Pb and Zn in wood and bark age classes of willows and poplars used for phytoextraction on soils contaminated by risk elements.

    PubMed

    Zárubová, Pavla; Hejcman, Michal; Vondráčková, Stanislava; Mrnka, Libor; Száková, Jiřina; Tlustoš, Pavel

    2015-12-01

    Fast-growing clones of Salix and Populus have been studied for remediation of soils contaminated by risk elements (RE) using short-rotation coppice plantations. Our aim was to assess biomass yield and distributions of elements in wood and bark of highly productive willow (S1--[Salix schwerinii × Salix viminalis] × S. viminalis, S2--Salix × smithiana clone S-218) and poplar (P1--Populus maximowiczii × Populus nigra, P2--P. nigra) clones with respect to aging. The field experiment was established in April 2008 on moderately Cd-, Pb- and Zn- contaminated soil. Shoots were harvested after four seasons (February 2012) and separated into annual classes of wood and bark. All tested clones grew on contaminated soils, with highest biomass production and lowest mortality exhibited by P1 and S2. Concentrations of elements, with exception of Ca and Pb, decreased with age and were higher in bark than in wood. The Salix clones were characterised by higher removal of Cd, Mn and Zn compared to the Populus clones. Despite generally higher RE content in young shoots, partly due to lower wood/bark ratios and higher RE concentrations in bark, the overall removal of RE was higher in older wood classes due to higher biomass yield. Thus, longer rotations seem to be more effective when phytoextraction strategy is considered. Of the four selected clones, S1 exhibited the best removal of Cd and Zn and is a good candidate for phytoextraction. PMID:26201656

  19. Attikaite, Ca3Cu2Al2(AsO4)4(OH)4 · 2H2O, a new mineral species

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Pekov, I. V.; Zadov, A. E.

    2007-12-01

    Attikaite, a new mineral species, has been found together with arsenocrandalite, arsenogoyazite, conichalcite, olivenite, philipsbornite, azurite, malachite, carminite, beudantite, goethite, quartz, and allophane at the Christina Mine No. 132, Kamareza, Lavrion District, Attiki Prefecture (Attika), Greece. The mineral is named after the type locality. It forms spheroidal segregations (up to 0.3 mm in diameter) consisting of thin flexible crystals up to 3 × 20 × 80 μm in size. Its color is light blue to greenish blue, with a pale blue streak. The Mohs’ hardness is 2 to 2.5. The cleavage is eminent mica-like parallel to {001}. The density is 3.2(2) g/cm3 (measured in heavy liquids) and 3.356 g/cm3 (calculated). The wave numbers of the absorption bands in the infrared spectrum of attikaite are (cm-1; sh is shoulder; w is a weak band): 3525 sh, 3425, 3180, 1642, 1120 w, 1070 w, 1035 w, 900 sh, 874, 833, 820, 690 w, 645 w, 600 sh, 555, 486, 458, and 397. Attikaite is optically biaxial, negative, α = 1.642(2), β = γ = 1.644(2) ( X = c) 2 V means = 10(8)°, and 2 V calc = 0°. The new mineral is microscopically colorless and nonpleochroic. The chemical composition (electron microprobe, average over 4 point analyses, wt %) is: 0.17 MgO, 17.48 CaO, 0.12 FeO, 16.28 CuO, 10.61 Al2O3, 0.89 P2O5, 45.45 As2O5, 1.39 SO3, and H2O (by difference) 7.61, where the total is 100.00. The empirical formula calculated on the basis of (O,OH,H2O)22 is: Ca2.94Cu{1.93/2+} Al1.97Mg0.04Fe{0.02/2+} [(As3.74S0.16P0.12)Σ4.02O16.08](OH)3.87 · 2.05H2 O. The simplified formula is Ca3Cu2Al2(AsO4)4(OH)4 · 2H2O. Attikaite is orthorhombic, space group Pban, Pbam or Pba2; the unit-cell dimensions are a = 10.01(1), b = 8.199(5), c = 22.78(1) Å, V = 1870(3) Å3, and Z = 4. In the result of the ignition of attikaite for 30 to 35 min at 128 140°, the H2O bands in the IR spectrum disappear, while the OH-group band is not modified; the weight loss is 4.3%, which approximately corresponds to two H2O

  20. Variation of photoluminescence features in Pr{sup 3+} doped lithium-fluoro-borate glass by changing different modifier oxides (MgO, CaO, CdO and PbO)-Judd-Ofelt theory application

    SciTech Connect

    Balakrishna, A.; Rajesh, D.; Babu, S.; Ratnakaram, Y. C.

    2015-06-24

    Pr{sup 3+} (1.0 mol%) doped different modifier oxide based six lithium-fluoro-borate glasses with chemical composition of 49Li{sub 2}B{sub 4}O{sub 7}-20BaF{sub 2}-10NaF-20MO (where M= Mg, Ca, Cd and Pb), 49Li{sub 2}B{sub 4}O{sub 7}-20BaF{sub 2}-10NaF-10MgO-10CaO and 49Li{sub 2}B{sub 4}O{sub 7}-20BaF{sub 2}-10NaF-10CdO-10PbO were prepared by conventional melt quenching technique. Judd-Ofelt theory has been applied for evaluating the Judd-Ofelt intensity parameters for Pr{sup 3+} ion in these glass compositions and are in turn to used to predict radiative properties such as radiative transition probabilities (A{sub T}), branching ratios (β) and stimulated emission cross-section (σ{sub P}). Stimulated emission cross-section (σ{sub p}) of prominent emission transitions, {sup 3}P{sub 0}→{sup 3}H{sub 4} and {sup 1}D{sub 2}→{sup 3}H{sub 4} of Pr{sup 3+} ion in all lithium-fluoro-borate glasses were calculated. Among all the emission transitions, {sup 3}P{sub 0}→{sup 3}H{sub 4} posseses higher branching ratio and stimulated emission cross-section in Mg-Ca glass, which leads to the best laser excitation at 487 nm wavelength.

  1. Formation and decay analysis of Cd *48 98 ,104 isotopes in 40Ca20-induced reactions

    NASA Astrophysics Data System (ADS)

    Gautam, Manjeet Singh; Kaur, Amandeep; Sharma, Manoj K.

    2015-11-01

    We have analyzed the fusion dynamics of Ca4020+Ni 28 58 ,64 reactions by using the energy dependent Woods-Saxon potential (EDWSP) model and coupled channel model and subsequently the decay patterns of Cd *48 98 ,104 nuclei are governed via the dynamical cluster-decay model (DCM). The influence of intrinsic degrees of freedom of colliding pairs, such as low lying surface vibrations and neutron transfer channels, are entertained within the context of coupled channel calculations. Interestingly, the energy dependence in the Woods-Saxon potential induces barrier modification effects (barrier height, barrier position, barrier curvature) in a somewhat similar way as that for coupled channel approach, hence adequately explains the observed fusion dynamics of Ca4020+Ni 28 58 ,64 reactions. In addition, the decay analysis of compound nuclei formed in the fusion of Ca4020+Ni 28 58 ,64 reactions is investigated by using DCM. The calculations are done for quadrupole (β2) deformed fragments having optimum orientations for hot configurations. The experimental data for evaporation residues lying within the wide range of center of mass energy (Ec .m .) of 64 -88 MeV is nicely addressed using the collective clusterization approach of the DCM. The comparative analysis of decay profiles of Cd *48 98 ,104 is worked out by introducing angular momentum and temperature effects in the fragmentation potential and preformation factor.

  2. Thermoelectric properties of metallic antiperovskites AXD3 (A=Ge, Sn, Pb, Al, Zn, Ga; X=N, C; D=Ca, Fe, Co)

    NASA Astrophysics Data System (ADS)

    Bilal, Muhammad; Ahmad, Iftikhar; Asadabadi, Saeid Jalali; Ahmad, Rashid; Maqbool, Muhammad

    2015-05-01

    In this paper we communicate the thermoelectric properties of carbon and nitrogen based metallic antiperovskites ANCa3 (A=Ge, Sn, Pb), BCFe3 (B=Al, Zn, Ga) and SnCD3 (D=Co and Fe) using the ab-initio calculations to explore efficient metallic thermoelectric materials. The consistency of the calculated results of SnCCo3 and SnCFe3 with the experimental results confirms the reliability of our theoretical calculations for the other investigated metallic antiperovskites. The results indicate that the thermopower of these materials can be enhanced by changing the chemical potential. The dimensionless figure of merit for the three nitrides approaches 0.96 at room temperature, which proves the usefulness of these materials in thermoelectric generators. Furthermore, the thermal conductivity is minimum at room temperature for chemical potential values between -0.25 μ(eV) and 0.25 μ(eV), and provides the maximum values of dimensionless figure of merit in this range. The striking feature of these studies is identifying a metallic compound, SnNCa3, with the highest value of Seebeck coefficient at room temperature out of all metals. The results anticipate that these materials could be efficient in thermoelectric generators; however, this needs experimental verification.[Figure not available: see fulltext.

  3. Understanding the reentrant superconducting phase diagram of the iron pnictide Ca4Al2O6Fe2(As1-xPx)2: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Usui, Hidetomo; Suzuki, Katsuhiro; Kuroki, Kazuhiko; Takeshita, Nao; Shirage, Parasharam Maruti; Eisaki, Hiroshi; Iyo, Akira

    2013-05-01

    Recently, a very rich phase diagram has been obtained for an iron-based superconductor Ca4Al2O6Fe2(As1-xPx)2. It has been revealed that nodeless (x˜0) and nodal (x=1) superconductivity are separated by an antiferromagnetic phase. Here we study the origin of this peculiar phase diagram using a five orbital model constructed from first-principles band calculation, and applying the fluctuation exchange approximation assuming spin-fluctuation-mediated pairing. At x=1, there are three hole Fermi surfaces, but the most inner one around the wave vector (0,0) has strong dX2-Y2 orbital character, unlike in LaFeAsO, where the most inner Fermi surface has dXZ/YZ character. Since the Fermi surfaces around (0,0), (π,0), and (π,π) all have dX2-Y2 orbital character, the repulsive pairing interaction mediated by the spin fluctuations gives rise to a frustration in momentum space, thereby degrading superconductivity despite the bond angle being close to the regular tetrahedron angle. As x decreases and the bond angle is reduced, the inner hole Fermi surface disappears, but the frustration effect still remains because the top of the band with dX2-Y2 character lies close to the Fermi level. On the other hand, the loss of the Fermi surface itself gives rise to a very good nesting of the Fermi surface because the number of electron and hole Fermi surfaces are now the same. The pairing interaction frustration and the good nesting combined favors antiferromagnetism over superconductivity. Finally for x close to 0, the band sinks far below the Fermi level, reducing the frustration effect, so that superconductivity is enhanced. There, the Fermi surface nesting is also lost to some extent, once again favoring superconductivity over antiferromagnetism. To see whether the present theoretical scenario is consistent with the actual nature of the competition between superconductivity and antiferromagnetism, we also perform hydrostatic pressure experiment for Ca4Al2O6Fe2(As1-xPx)2. In the

  4. Phase transformation of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} and its disordered crystal structure at 1073 K

    SciTech Connect

    Kurokawa, Daisuke; Takeda, Seiya; Colas, Maggy; Asaka, Toru; Thomas, Philippe; Fukuda, Koichiro

    2014-07-01

    The phase transformation of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} and the crystal structure of its high-temperature phase were investigated by differential thermal analysis, temperature-dependent Raman spectroscopy and high-temperature X-ray powder diffraction (CuKα{sub 1}). We determined the starting temperature of the orthorhombic-to-cubic transformation during heating (=711 K) and that of the reverse transformation during cooling (=742 K). The thermal hysteresis was negative (=−31 K), suggesting the thermoelasticity of the transformation. The space group of the high temperature phase is I4{sup ¯}3m with the unit-cell dimensions of a=0.92426(2) nm and V=0.78955(2) nm{sup 3} (Z=2) at 1073 K. The initial structural model was derived by the direct methods and further refined by the Rietveld method. The final structural model showed the orientational disordering of SO{sub 4} tetrahedra. The maximum-entropy method-based pattern fitting method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. At around the transformation temperature during heating, the vibrational spectra, corresponding to the Raman-active SO{sub 4} internal stretching mode, showed the continuous and gradual change in the slope of full width at half maximum versus temperature curve. This strongly suggests that the orthorhombic-to-cubic phase transformation would be principally accompanied by the statistical disordering in orientation of the SO{sub 4} tetrahedra, without distinct dynamical reorientation. - Graphical abstract: (Left) Three-dimensional electron-density distributions of the SO{sub 4} tetrahedron with the split-atom model, and (right) a bird's eye view of electron densities on the plane parallel to (111). - Highlights: • Crystal structure of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} at 1073 K is determined by powder XRD. • The atom arrangements are represented by the split-atom model

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  6. K -shell ionization cross sections of Al, Si, S, Ca, and Zn for oxygen ions in the energy range 1. 1--8 MeV

    SciTech Connect

    Geretschlaeger, M. ); Smit, Z. ); Steinbauer, E. )

    1992-03-01

    {ital K}-shell ionization cross sections induced by 1.1--8-MeV oxygen ions in Al, Si, S, Ca, and Zn were measured using different target thicknesses. The cross sections for vanishingly thin and for charge-equilibrium targets were obtained by extrapolation. The experimental results are compared to the perturbed stationary-state approximation with energy-loss, Coulomb, and relativistic corrections (ECPSSR) cross sections (Brandt and Lapicki, Phys. Rev. A 23, 1717 (1981)), to the modification of the ECPSSR theory (MECPSSR) (Benka, Geretschlaeger, and Paul, J. Phys. (Paris) Colloq. Suppl. 12, C9-251 (1987)), to the theory for direct Coulomb ionization of the 1{ital s}{sigma} molecular orbital (Montenegro and Sigaud, J. Phys. B 18, 299 (1985)), and to several semiclassical approximation codes using either the united atom binding procedure or the variational approach of Andersen {ital et} {ital al}. (Nucl. Instrum. Methods 192, 79 (1982)). The cross sections were also compared to the statistical molecular-orbital theory of inner-shell ionization for (nearly) symmetric atomic collisions (Mittelman and Wilets, Phys. Rev. 154, 12 (1967)). For fast collisions ({xi}{similar to}1), the ionization cross sections are well reproduced by theories for direct Coulomb ionization. For slower collisions ({xi}{lt}1), the experimental cross sections are systematically higher than the direct-ionization values, but they agree satisfactorily with the summed cross sections for direct Coulomb ionization and for molecular-orbital ionization. Best agreement (within a factor of 2) was found for the sums of MECPSSR and statistical cross sections.

  7. Determination of oxygen self-diffusion in akermanite, anorthite, diopside, and spinel: Implications for oxygen isotopic anomalies and the thermal histories of Ca-Al-rich inclusions

    SciTech Connect

    Ryerson, F.J. ); McKeegan, K.D. )

    1994-09-01

    Oxygen self-diffusion coefficients have been measured for three natural diopsidic clinopyroxenes, a natural anorthite, a synthetic magnesium aluminate spinel, and a synthetic akermanite for oxygen fugacities ranging from the NNO to IW buffers. The oxygen diffusion data are used to evaluate the effects of three different types of thermal histories upon the oxygen isotopic compositions of minerals found in Type B Ca-Al-rich inclusions (CAIBs) in carbonaceous chondrites: (1) gas-solid exchange during isothermal heating, (2) gas-solid exchange as a function of cooling rate subsequent to instantaneous heating, and (3) isotopic exchange with a gaseous reservoir during partial melting and recrystallization. With the assumptions that the mineral compositions within a CAIB were uniformly enriched in [sup 16]O prior to any thermal processing, that effective diffusion dimensions may be estimated from observed grain sizes, and that diffusion in diopside is similar to that in fassaitic clinopyroxene, none of the above scenarios can reproduce the relative oxygen isotopic anomalies observed in CAIBs without improbably long or unrealistically intense thermal histories relative to current theoretical models of nebular evolution. The failure of these simple models, coupled with recent observations of disturbed magnesium isotopic abundances and correlated petrographic features in anorthite and melilite indicative of alteration and recrystallization, suggests that the oxygen isotopic compositions of these phases may have also been modified by alteration and recrystallization possibly interspersed with multiple melting events. Because the modal abundance of spinel remains relatively constant for plausible melting scenarios, and its relatively sluggish diffusion kinetics prevent substantial equilibration, Mg-Al spinel is the most reliable indicator of the oxygen isotopic composition of precursor material which formed Type B CAIs.

  8. A novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} for near UV white light-emitting diodes

    SciTech Connect

    Yang, Zhigang; Zhao, Zhengyan; Shi, Yurong; Wang, Yuhua

    2013-10-15

    Graphical abstract: - Highlights: • Novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} was prepared by solid-state reaction. • Excitation spectra suggested an obvious absorption in near-ultraviolet region. • Under 392 nm excitation, the phosphors exhibited a red emission at 614 nm. • Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} could be potentially applied in near UV white LEDs. - Abstract: A novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} was synthesized using a solid-state reaction method, and its luminescence characteristics and charge compensators effect (Li{sup +}, Na{sup +}, K{sup +}) were investigated. The excitation spectra showed a obvious absorption in near-ultraviolet region. Under 392 nm excitation, the phosphors exhibited an intense red emission at 614 nm. The Commission Internationale de l’Eclairage (CIE) chromaticity coordinates and quantum efficiency (QE) were (0.65, 0.35) and 62.3%, respectively. The good color saturation, high quantum efficiency and small thermal-quenching properties indicate that Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} could be potentially applied in near UV white light-emitting diodes.

  9. Multifunctional effect of Al2O3, SiO2 and CaO on the volatilization of PbO and PbCl2 during waste thermal treatment.

    PubMed

    Wang, Si-Jia; He, Pin-Jing; Shao, Li-Ming; Zhang, Hua

    2016-10-01

    Minerals including Al2O3, SiO2 and CaO are predominant matrixes in waste, and are thought to facilitate lead (Pb) emission control. This study distinguished the inhibition of each mineral on common stable Pb-containing compounds, including highly volatile PbCl2 and less volatile PbO. Al2O3 can lower the volatilization temperature of Pb by 29 °C due to the generation of a eutectic compound and play a minor but non-negligible role in reducing Pb volatilization. The most conspicuous inhibition effect was exerted by SiO2 and a mixture of Al2O3 and SiO2, which completely integrated PbO into the glass phase at 690 °C and prohibited its migration. In contrast, SiO2 had no significant inhibition on volatile PbCl2. CaO inhibited PbO volatilization in the absence of oxygen by controlling its diffusion, while it converted PbO to Ca2PbO4 in the presence of oxygen, thus controlling Pb diffusion and decreasing the Pb volatilization ratio and rate. The influence of CaO on PbCl2 was complex because CaO can convert PbCl2 to PbO with formation of CaCl2, and CaCl2 can also be a Cl-donor for PbO. The roles of mineral matrixes in Pb conversion were shown to be important for Pb emission control. PMID:27434254

  10. Wavelength-shifting fiber signal readout from Transparent RUbber SheeT (TRUST) type LiCaAlF6 neutron scintillator

    NASA Astrophysics Data System (ADS)

    Watanabe, Kenichi; Yamazaki, Takuya; Sugimoto, Dai; Yamazaki, Atsushi; Uritani, Akira; Iguchi, Tetsuo; Fukuda, Kentaro; Ishidu, Sumito; Yanagida, Takayuki; Fujimoto, Yutaka

    2015-06-01

    As an alternative to the standard 3He neutron detector, we are developing the Transparent RUbber SheeT type (TRUST) Eu doped LiCaAlF6 (Eu:LiCAF) scintillator. This type of neutron scintillator can easily be fabricated as a large area sheet. In order to take advantage of a large area detector, we try to readout scintillation photons using a wavelength-shifting fiber (WLSF) from a TRUST Eu:LiCAF scintillator. The TRUST Eu:LiCAF scintillator with the size of 50×50×5 mm3 was mounted on the WLSF plate and the end of the WLSFs was connected with a PMT. In order to reject high pulse height events induced in the WLSFs, we applied the pulse shape discrimination technique. The gamma-ray intrinsic and neutron absolute detection efficiency is evaluated to be 8.8×10-7 and 9×10-3 cps/ng Cf (2 m) for the TRUST Eu:LiCAF scintillator with the size of 50×50×5 mm3.

  11. Dual mode green fluorescence from Tb{sup 3+}:Ca{sub 12}Al{sub 14}O{sub 33} and its applicability as delayed fluorescence

    SciTech Connect

    Verma, R.K.; Kaur, G.; Rai, A.; Rai, S.B.

    2012-11-15

    Highlights: ► Synthesis of Yb{sup 3+}/Tb{sup 3+} co-doped Ca{sub 12}Al{sub 14}O{sub 33} phosphor. ► Dual mode emission in green area on excitation with 976 nm and 266 nm. ► Delayed fluorescence on excitation of 266 nm. ► Effect of time on delayed fluorescence. -- Abstract: A Tb{sup 3+}/Yb{sup 3+} doped calcium aluminate phosphor has been synthesized using well known combustion synthesis. The structural characterization and morphology has been studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The characteristic luminescence of Tb{sup 3+} in both upconversion and down-conversion modes, i.e. dual mode luminescence has been recorded on excitation with 976 nm and 266 nm radiation. The Stokes emission observed on 266 nm excitation also shows a characteristic of delayed fluorescence. The delayed fluorescence has been measured as a function of time and pump power. It has been correlated to the white light emission (broad continuum emission) from the host. The possible reason of association of electron hole trapping to the defect level as well as in crystal potential is suggested.

  12. Effect of hydration temperature on the solubility behavior of Ca-, S-, Al-, and Si-bearing solid phases in Portland cement pastes

    SciTech Connect

    Thomas, Jeffrey J.; Rothstein, David; Jennings, Hamlin M.; Christensen, Bruce J

    2003-12-01

    The concentrations of Ca, S, Al, Si, Na, and K in the pore solutions of ordinary Portland cement and white Portland cement pastes were measured during the first 28 d of curing at temperatures ranging from 5-50 deg. C. Saturation indices with respect to solid phases known to form in cement paste were calculated from a thermodynamic analysis of the elemental concentrations. Calculated saturation levels in the two types of paste were similar. The solubility behavior of Portlandite and gypsum at all curing temperatures was in agreement with previously reported behavior near room temperature. Saturation levels of both ettringite and monosulfate decreased with increasing curing temperature. The saturation level of ettringite was greater than that of monosulfate at lower curing temperatures, but at higher temperatures there was effectively no difference. The solubility behavior of C-S-H gel was investigated by applying an appropriate ion activity product (IAP) to the data. The IAP{sub CSH} decreased gradually with hydration time, and at a given hydration time the IAP{sub CSH} was lower at higher curing temperatures.

  13. The layered antimonides RELi3Sb2 (RE=Ce-Nd, Sm, Gd-Ho). Filled derivatives of the CaAl2Si2 structure type

    NASA Astrophysics Data System (ADS)

    Schäfer, Marion C.; Suen, Nian-Tzu; Raglione, Michaella; Bobev, Svilen

    2014-02-01

    Reported are the synthesis and the structural characterization of an extended family of rare-earth metal-lithium-antimonides with the formula RELi3Sb2 (RE=Ce-Nd, Sm, Gd-Ho). They crystallize in the trigonal space group P3barm1 (No. 164, Pearson symbol hP6) with a structure, best viewed as a filled derivative of the common CaAl2Si2 structure type (ternary variant of α-La2O3). Across the series, the lattice parameters monotonically decrease, following the lanthanide contraction. Temperature-dependent magnetic susceptibility measurements for CeLi3Sb2, PrLi3Sb2 and TbLi3Sb2 reveal paramagnetic behavior in the high temperature range, and the obtained effective moments are consistent with the expected ones for the free-ion RE3+ ground state. Possible ferromagnetic ordering for PrLi3Sb2 and antiferromagnetic ordering for TbLi3Sb2 are observed in the low temperature range (below 20 K). Tight-binding muffin-tin orbital electronic band structure calculations for LaLi3Sb2 are presented and discussed as well.

  14. Raman spectroscopy of the multi-anion mineral schlossmacherite (H 3O,Ca)Al 3(AsO 4,PO 4,SO 4) 2(OH) 6

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; Palmer, Sara J.; Xi, Yunfei

    2012-02-01

    The mineral schlossmacherite (H 3O,Ca)Al 3(AsO 4,PO 4,SO 4) 2(OH) 6, a multi-cation-multi-anion mineral of the beudantite mineral subgroup has been characterised by Raman spectroscopy. The mineral and related minerals functions as a heavy metal collector and is often amorphous or poorly crystalline, such that XRD identification is difficult. The Raman spectra are dominated by an intense band at 864 cm -1, assigned to the symmetric stretching mode of the AsO 43- anion. Raman bands at 809 and 819 cm -1 are assigned to the antisymmetric stretching mode of AsO 43-. The sulphate anion is characterised by bands at 1000 cm -1 ( ν1), and at 1031, 1082 and 1139 cm -1 ( ν3). Two sets of bands in the OH stretching region are observed: firstly between 2800 and 3000 cm -1 with bands observed at 2850, 2868, 2918 cm -1 and secondly between 3300 and 3600 with bands observed at 3363, 3382, 3410, 3449 and 3537 cm -1. These bands enabled the calculation of hydrogen bond distances and show a wide range of H-bond distances.

  15. Comparison of thermoluminescence characteristics in γ-ray and C(5+) ion beam-irradiated LiCaAlF6 :Ce phosphor.

    PubMed

    Yerpude, M M; Dhoble, N S; Lochab, S P; Dhoble, S J

    2016-08-01

    We compare the thermoluminescence (TL) behavior of Ce(3+) ion-activated LiCaAlF6 exposed to γ-rays and a carbon ion beam. The reported phosphor is synthesized using an in-house precipitation method with varying concentrations of activator ion and is characterized by X-ray diffraction (XRD) and TL. Rietveld refinement is performed to study the structural statistics. The TL glow curve consists of a prominent glow peak at 232°C with three shoulders at 115, 159 and 333°C when exposed to γ-rays from a (60) Co source. When exposed to a C(5+) ion beam, the TL glow curve consists of five peaks with peak temperatures near 156, 221, 250, 287 and 330°C, and is found to vary slightly with changing fluence. Glow curve convolution deconvolution (GCCD) functions are applied to the TL curves for complete analysis of the glow curve structure and TL traps. The order of kinetics (b), activation energy (E) and frequency factor are determined using Chen's peak shape method and theoretical curves are drawn using GCCD functions. A track interaction model (TIM) is used to explain the sublinearity/saturation at higher fluences. Ion beam parameters are analyzed using Monte-Carlo simulation-based SRIM-2013 code. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26768666

  16. Elasticity and sound velocities of polycrystalline grossular garnet (Ca3Al2Si3O12) at simultaneous high pressures and high temperatures

    NASA Astrophysics Data System (ADS)

    Gwanmesia, Gabriel D.; Wang, Liping; Heady, Adaire; Liebermann, Robert C.

    2014-03-01

    The elastic wave velocities of a dense polycrystalline specimen (99.7% of theoretical density) of synthetic grossular garnet (Ca3Al2Si3O12) were measured to pressures of ∼10 GPa and temperatures of 1000 K by transfer-function ultrasonic interferometry in conjunction with energy-dispersive synchrotron X-radiation in a deformation DIA-type cubic-anvil apparatus. The calculated elastic bulk (Ks) and shear (G) moduli data were fitted to functions of Eulerian strain to 3rd order, yielding the zero-pressure values [Ks = 171.2 (8) GPa; G = 107.4 (2) GPa] and their pressure derivatives [(∂Ks/∂P)T = 4.47 (2); (∂G/∂P)T = 1.29 (5)]. The temperature dependences of the elastic moduli obtained from linear regression of entire P-T-Ks and P-T-G data are: (∂Ks/∂T)P = -1.38 (3) × 10-2 GPa/K and (∂G/∂T)P = -1.28 (2) × 10-2 GPa/K. These results together with those from previous studies for garnets with varying compositions suggest that most of the thermo-elastic properties of garnet are insensitive to grossular content, with the exception of the shear modulus, which significantly depends on the calcium content.

  17. Structural and electronic properties of AB- and AA-stacking bilayer-graphene intercalated by Li, Na, Ca, B, Al, Si, Ge, Ag, and Au atoms

    NASA Astrophysics Data System (ADS)

    Tayran, Ceren; Aydin, Sezgin; Çakmak, Mehmet; Ellialtıoğlu, Şinasi

    2016-04-01

    The structural and electronic properties of X (=Li, Na, Ca, B, Al, Si, Ge, Ag, and Au)-intercalated AB- and AA-stacking bilayer-graphene have been investigated by using ab initio density functional theory. It is shown that Boron (Lithium)-intercalated system is energetically more stable than the others for the AB (AA) stacking bilayer-graphene systems. The structural parameters, electronic band structures, and orbital nature of actual interactions are studied for the relaxed stable geometries. It is seen that the higher the binding energy, the smaller is the distance between the layers, in these systems. The electronic band structures for these systems show that different intercalated atoms can change the properties of bilayer-graphene differently. For qualitative description of the electronic properties, the metallicities of the systems are also calculated and compared with each other. The Mulliken analysis and electron density maps clearly indicate that the interactions inside a single layer (intralayer interactions) are strong and highly covalent, while the interactions between the two layers (interlayer interactions) are much weaker.

  18. Cr6+-containing phases in the system CaO-Al2O3-CrO42--H2O at 23 °C

    NASA Astrophysics Data System (ADS)

    Pöllmann, Herbert; Auer, Stephan

    2012-01-01

    Synthesis and investigation of lamellar calcium aluminium hydroxy salts was performed to study the incorporation of chromate ions in the interlayer of lamellar calcium aluminium hydroxy salts. Different AFm-phases (calcium aluminate hydrate with alumina, ferric oxide, mono-anion phase) containing chromate were synthesized. These AFm-phases belong to the group of layered double hydroxides (LDHs). 3CaO·Al2O3·CaCrO4·nH2O and C3A·1/2Ca(OH)2·1/2CaCrO4·12H2O were obtained as pure phases and their different distinct interlayer water contents and properties determined. Solid solution of chromate-containing phases and tetracalcium-aluminate-hydrate (TCAH) were studied. The uptake of chromate into TCAH from solutions was proven. Chromate contents in solution decrease to <0.2 mg/l.

  19. Thermodynamic Equilibrium Calculations on Cd Transformation during Sewage Sludge Incineration.

    PubMed

    Liu, Jing-yong; Huang, Limao; Sun, Shuiyu; Ning, Xun'an; Kuo, Jiahong; Sun, Jian; Wang, Yujie; Xie, Wuming

    2016-06-01

    Thermodynamic equilibrium calculations were performed to reveal the distribution of cadmium during the sewage sludge incineration process. During sludge incineration in the presence of major minerals, such as SiO2, Al2O3 and CaO, the strongest effect was exerted by SiO2 on the Cd transformation compared with the effect of others. The stable solid product of CdSiO3 was formed easily with the reaction between Cd and SiO2, which can restrain the emissions of gaseous Cd pollutants. CdCl2 was formed more easily in the presence of chloride during incineration, thus, the volatilization of Cd was advanced by increasing chlorine content. At low temperatures, the volatilization of Cd was restrained due to the formation of the refractory solid metal sulfate. At high temperatures, the speciation of Cd was not affected by the presence of sulfur, but sulfur could affect the formation temperature of gaseous metals. PMID:27225784

  20. Spectroscopic (FT-IR, FT-Raman, 1H, 13C NMR, UV/VIS), thermogravimetric and antimicrobial studies of Ca(II), Mn(II), Cu(II), Zn(II) and Cd(II) complexes of ferulic acid

    NASA Astrophysics Data System (ADS)

    Kalinowska, M.; Piekut, J.; Bruss, A.; Follet, C.; Sienkiewicz-Gromiuk, J.; Świsłocka, R.; Rzączyńska, Z.; Lewandowski, W.

    2014-03-01

    The molecular structure of Mn(II), Cu(II), Zn(II), Cd(II) and Ca(II) ferulates (4-hydroxy-3-methoxycinnamates) was studied. The selected metal ferulates were synthesized. Their composition was established by means of elementary and thermogravimetric analysis. The following spectroscopic methods were used: infrared (FT-IR), Raman (FT-Raman), nuclear magnetic resonance (13C, 1H NMR) and ultraviolet-visible (UV/VIS). On the basis of obtained results the electronic charge distribution in studied metal complexes in comparison with ferulic acid molecule was discussed. The microbiological study of ferulic acid and ferulates toward Escherichia coli, Bacillus subtilis, Candida albicans, Pseudomonas aeruginosa, Staphylococcus aureus and Proteus vulgaris was done.

  1. Preparation and structure of NaSr{sub 0.5}Al{sub 2}B{sub 2}O{sub 7} and NaCa{sub 0.5}Al{sub 2}B{sub 2}O{sub 7}

    SciTech Connect

    Gao Jianhua; Li, R.K. . E-mail: rkli@cl.cryo.ac.cn

    2005-05-15

    Two compounds NaSr{sub 0.5}Al{sub 2}B{sub 2}O{sub 7} and NaCa{sub 0.5}Al{sub 2}B{sub 2}O{sub 7}, have been found to crystallize into a new structure type by Rietveld refinement from X-ray powder diffraction data. Their structure belongs to hexagonal space group P6{sub 3}/m, with lattice parameters of a=4.85640(8)A, c=15.6635(4)A for NaSr{sub 0.5}Al{sub 2}B{sub 2}O{sub 7} and a=4.81292(10)A, c=15.4056(4)A for NaCa{sub 0.5}Al{sub 2}B{sub 2}O{sub 7}, respectively. The structure is built up by [Al{sub 2}B{sub 2}O{sub 7}]{sup 2-} double layer and Na{sup +}/Ca{sup 2+} or Na{sup +}/Sr{sup 2+} ions alternatively stacking along the c-axis. The sites in the inter-double layer are fully occupied jointly by Na and Ca or Sr, but the intra-double layer sites are only half occupied solely by Na. A mechanism of the transition of the structure from CaAl{sub 2}B{sub 2}O{sub 7} to present structure type by replacing only 1% Ca by Na (2%) as observed by Chang and Keszler (Mater. Res. Bull. 33 (1998) 299) is also proposed.

  2. Evaluation of diffusive gradients in thin films technique (DGT) for measuring Al, Cd, Co, Cu, Mn, Ni, and Zn in Amazonian rivers.

    PubMed

    Yabuki, Lauren Nozomi Marques; Colaço, Camila Destro; Menegário, Amauri Antonio; Domingos, Roberto Naves; Kiang, Chang Hung; Pascoaloto, Domitila

    2014-02-01

    Studies concerning the lability and bioavailability of trace metals have played a prominent role in the search for contamination of water resources. This work describes the first application yet of the diffusive gradients in thin films technique (DGT) to the determination of the fraction of free plus labile metals in waters from the Amazon Basin. Due to the complexity of the use of DGT for samples with low ionic strength and high organic matter content (characteristic of Amazonian rivers), a new analytical procedure was developed. The method is based on the determinations of apparent diffusion coefficients (Dap) in the laboratory, by performing deployments in samples collected in the corresponding sites of study. The Dap thereby determined is then used for in situ measurements. The suitability of the proposed approach for determination of labile Al, Cd, Co, Cu, Mn, Ni, and Zn in the Amazon River and Rio Negro (English: Black River) was evaluated. Except for Co, Mn (in a deployment at Rio Negro), Ni and Zn (in a deployment at Amazon River), labile in situ measurements were lower or similar to dissolved concentrations, indicating suitability of the proposed approach. PMID:24052239

  3. Phase Equilibria Studies in the System ZnO-``FeO''-Al2O3-CaO-SiO2 Relevant to Imperial Smelting Furnace Slags: Part I

    NASA Astrophysics Data System (ADS)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2010-04-01

    The phase equilibria and liquidus temperatures in the system ZnO-“FeO”-Al2O3-CaO-SiO2 in equilibrium with metallic iron have been determined experimentally in the temperature range of 1423 K to 1553 K. The experimental conditions were focused on the composition range relevant to Imperial Smelting Furnace slags. The results are presented in the form of a pseudo-ternary section ZnO-“FeO”-(CaO + SiO2 + Al2O3) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 7.0. It was found that wustite and spinel are the major primary phases and that zincite and melilite are also present in the composition range investigated. Wustite (Fe2+,Zn)O and spinel (Fe2+,Zn)O (A1,Fe3+)2O3 solid solutions are formed in this system, and the ZnO concentration in the spinel phase is found to be much greater than in the liquid phase.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  5. Phase Equilibrium Studies of CaO-SiO2-MgO-Al2O3 System with Binary Basicity of 1.5 Related to Blast Furnace Slag

    NASA Astrophysics Data System (ADS)

    Kou, Mingyin; Wu, Shengli; Ma, Xiaodong; Wang, Laixin; Chen, Mao; Cai, Qingwu; Zhao, Baojun

    2016-04-01

    Slags play an important role in blast furnace operation, and their compositions are based on the CaO-SiO2-MgO-Al2O3 quaternary system in many steel companies. The binary basicity (CaO/SiO2 weight ratio) of blast furnace slags, especially primary slag and bosh slag, can be as high as 1.5 or higher. Phase equilibria and liquidus temperatures in the CaO-SiO2-MgO-Al2O3 system with binary basicity of 1.50 are experimentally determined for temperatures in the range 1723 K to 1823 K (1450 °C to 1550 °C). High temperature equilibration, quenching, and electron probe X-ray microanalysis techniques have been used in the present study. The isotherms are obtained in the primary phase fields of Ca2SiO4, melilite, spinel, periclase, and merwinite related to blast furnace slags. Effects of Al2O3, MgO, and binary basicity on liquidus temperatures have been discussed. In addition, extensive solid solutions have been measured for different primary phases and will be used for development and optimization of the thermodynamic database.

  6. Ladle and Continuous Casting Process Models for Reduction of SiO2 in SiO2-Al2O3-CaO Slags by Al in Fe-Al(-Si) Melts

    NASA Astrophysics Data System (ADS)

    Park, Jiwon; Sridhar, S.; Fruehan, Richard J.

    2015-02-01

    Based on a mixed control or two-phase mass transfer model considering mass transport in the metal and the slag phases, process models for ladle and continuous castor mold were developed to predict the changes in the metal and the slag chemistry and viscosity. In the ladle process model, the rate of reaction is primarily determined by stirring gas flow rate, which greatly alters the mass transports of the metal and the slag phases. In the continuous casting process model, the effects of the Al, Si, and SiO2 contents in the incoming flow of the fluid phases, casting speed, mold flux consumption rate, and depth of the liquid mold flux pool on the steady-state compositions of the metal and the mold flux were assessed.

  7. Melting enthalpies of mantle peridotite: calorimetric determinations in the system CaO-MgO-Al 2O 3-SiO 2 and application to magma generation

    NASA Astrophysics Data System (ADS)

    Kojitani, Hiroshi; Akaogi, Masaki

    1997-12-01

    High-temperature drop calorimetry in the temperature range of 1398-1785 K was performed for the samples of mixtures of synthetic anorthite (An), diopside (Di), enstatite (En) and forsterite (Fo) with the same compositions as those of primary melts generated at 1.1, 3 and 4 GPa at most 10° above the solidus of anhydrous mantle peridotite in the CaO-MgO-Al 2O 3-SiO 2 system. From the differences between the heat contents ( H T-H 298) of liquid and that of crystal mixture at the liquidus temperature, melting enthalpies of the samples of 1.1, 3 and 4 GPa-primary melt compositions were determined at 1 atm to be 531 ± 39 J · g -1 at 1583 K, 604 ± 21 J · g -1 at 1703 K, 646 ± 21 J · g -1 at 1753 K, respectively. These heat of fusion values suggest that mixing enthalpy of the melt in the An-Di-En-Fo system is approximately zero within the experimental errors when we use the heat of fusion of Fo by Richet et al. (P. Richet, F. Leclerc, L. Benoist, Melting of forsterite and spinel, with implications for the glass transition of Mg 2SiO 4 liquid, Geophys. Res. Lett. 20 (1993) 1675-1678). The measured enthalpies of melting at 1 atm were converted into those for melting reactions which occur under high pressures by correcting enthalpy changes associated with solid-state mineral reactions. Correcting the effects of pressure, temperature and FeO and Na 2O components on the melting enthalpies at 1 atm, heat of fusion values of a representative mantle peridotite just above the solidus under high pressure were estimated to be 590 J at 1.1 GPa and 1523 K, 692 J at 3 GPa and 1773 K, and 807 J at 4 GPa and 1923 K for melting reactions producing liquid of 1 g, with uncertainties of 50 J. By applying these melting enthalpies to a mantle diapir model which generates present MORBs, a potential mantle temperature of 1533 K has been estimated, assuming an eruption temperature of magma of 1473 K.

  8. Structure and physical properties of RT{sub 2}Cd{sub 20} (R=rare earth, T=Ni, Pd) compounds with the CeCr{sub 2}Al{sub 20}-type structure

    SciTech Connect

    Burnett, V.W.; Yazici, D.; White, B.D.; Dilley, N.R.; Friedman, A.J.; Brandom, B.; Maple, M.B.

    2014-07-01

    Eleven new compounds, R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) and R Pd{sub 2}Cd{sub 20} (R=Ce, Pr, Sm), were grown as single crystals in high temperature cadmium-rich solutions. They crystallize in the cubic CeCr{sub 2}Al{sub 20}-type structure (Fd3{sup ¯}m, Z=8) as characterized by measurements of powder X-ray diffraction. Electrical resistivity, magnetization, and specific heat measurements were performed on R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) single crystals. Whereas YNi{sub 2}Cd{sub 20} and LaNi{sub 2}Cd{sub 20} exhibit unremarkable metallic behavior, when magnetic moments from localized 4f electron states (Gd{sup 3+}–Tb{sup 3+}) are embedded into this host, they exhibit ferromagnetic order with values of the Curie temperature T{sub C} for R Ni{sub 2}Cd{sub 20} (R=Gd, and Tb) which scale with the de Gennes factor. - Graphical abstract: Specific heat divided by temperature C/T vs. T for single crystals of R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Gd, and Tb). Left inset: Low temperature C/T vs. T{sup 2} for LaNi{sub 2}Cd{sub 20}. The solid line represents a linear fit of the data. Right inset: Low-temperature C/T data vs. T for R=Ce–Nd, Gd, and Tb; magnetic ordering temperatures are indicated by arrows. - Highlights: • R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) single crystals synthesized for the first time. • R Pd{sub 2}Cd{sub 20} (R=Ce, Pr, Sm) single crystals synthesized for the first time. • Single crystals are of good metallurgical quality (large RRR values). • NdNi{sub 2}Cd{sub 20} orders antiferromagnetically at T{sub N}=1.5 K. • R Ni{sub 2}Cd{sub 20} (R=Sm, Gd, Tb) order ferromagnetically.

  9. Oxygen isotopic and chemical zoning of melilite crystals in a type A Ca-Al-rich inclusion of Efremovka CV3 chondrite

    NASA Astrophysics Data System (ADS)

    Kawasaki, Noriyuki; Sakamoto, Naoya; Yurimoto, Hisayoshi

    2012-12-01

    Different oxygen isotopic reservoirs have been recognized in the early solar system. Fluffy type A Ca-Al-rich inclusions (CAIs) are believed to be direct condensates from a solar nebular gas, and therefore, have acquired oxygen from the solar nebula. Oxygen isotopic and chemical compositions of melilite crystals in a type A CAI from Efremovka CV3 chondrite were measured to reveal the temporal variation in oxygen isotopic composition of surrounding nebular gas during CAI formation. The CAI is constructed of two domains, each of which has a core-mantle structure. Reversely zoned melilite crystals were observed in both domains. Melilite crystals in one domain have a homogeneous 16O-poor composition on the carbonaceous chondrite anhydrous mineral (CCAM) line of δ18O = 5-10‰, which suggests that the domain was formed in a 16O-poor oxygen isotope reservoir of the solar nebula. In contrast, melilite crystals in the other domain have continuous variations in oxygen isotopic composition from 16O-rich (δ18O = -40‰) to 16O-poor (δ18O = 0‰) along the CCAM line. The oxygen isotopic composition tends to be more 16O-rich toward the domain rim, which suggests that the domain was formed in a variable oxygen isotope reservoir of the solar nebula. Each domain of the type A CAI has grown in distinct oxygen isotope reservoir of the solar nebula. After the domain formation, domains were accumulated together in the solar nebula to form a type A CAI.

  10. Isotopic Measurements in CAIs with the Nanosims: Implications to the understanding of the Formation process of Ca, Al-Rich Inclusions

    NASA Technical Reports Server (NTRS)

    Ito, M.; Messenger, S.; Walker, Robert M.

    2007-01-01

    Ca, Al-rich Inclusions (CAIs) preserve evidence of thermal events that they experienced during their formation in the early solar system. Most CAIs from CV and CO chondrites are characterized by large variations in O-isotopic compositions of primary minerals, with spinel, hibonite, and pyroxene being more O-16-rich than melilite and anorthite, with delta 17, O-18 = approx. -40%o (DELTA O-17 = delta O-17 - 0.52 x delta O-18 = approx. - 20%o ). These anomalous compositions cannot be accounted for by standard mass dependent fractionation and diffusive process of those minerals. It requires the presence of an anomalous oxygen reservoir of nucleosynthetic origin or mass independent fractionations before the formation of CAIs in the early solar system. The CAMECA NanoSIMS is a new generation ion microprobe that offers high sensitivity isotopic measurements with sub 100 nm spatial resolution. The NanoSIMS has significantly improved abilities in the study of presolar grains in various kind of meteorites and the decay products of extinct nuclides in ancient solar system matter. This instrument promises significant improvements over other conventional ion probes in the precision isotopic characterization of sub-micron scales. We report the results of our first O isotopic measurements of various CAI minerals from EK1-6-3 and 7R19-1(a) utilizing the JSC NanoSIMS 50L ion microprobe. We evaluate the measurement conditions, the instrumental mass fractionation factor (IMF) for O isotopic measurement and the accuracy of the isotopic ratio through the analysis of a San Carlos olivine standard and CAI sample of 7R19-1(a).

  11. Al{sub 15}Ge{sub 4}Ni{sub 3}: A new intergrowth structure with Cu{sub 3}Au- and CaF{sub 2}-type building blocks

    SciTech Connect

    Reichmann, Thomas L.; Jandl, Isabella; Effenberger, Herta S.; Herzig, Peter; Richter, Klaus W.

    2015-05-15

    The new ternary compound Al{sub 15}Ge{sub 4}Ni{sub 3} (τ{sub 2} in the system Al–Ge–Ni) was synthesized in single crystalline form by a special annealing procedure from samples located in the three phase fields [L+Al+τ{sub 2}] and [L+Ge+τ{sub 2}]. The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} was determined by single-crystal X-ray diffraction. The compound crystallizes in a new structure type in space group I4-bar3m, Pearson Symbol cI88, cubic lattice parameter a=11.405(1) Å. Phase diagram investigations indicate stoichiometric composition without considerable homogeneity range; τ{sub 2} melts peritectically at T=444 °C. The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} shows a unique combination of simple Cu{sub 3}Au- and CaF{sub 2}-type building blocks: a three dimensional network of CaF{sub 2}-type units, formed by Ni and Al atoms, is interspaced by clusters (Al{sub 6}Ge{sub 8}) resembling unit cells of the Cu{sub 3}Au-type. Both structural motifs are connected by Al–Ge bonds. The ground state energy of the compound was obtained by DFT calculations and the densities of states were analyzed in detail. In addition, electron density maps were calculated in four different sections through the unit cell using the full potential linearized augmented plane-wave (FLAPW) method. The bonding situation in Al{sub 15}Ge{sub 4}Ni{sub 3} was discussed combining results from electronic calculations with the analysis of the coordination of atoms. - Graphical abstract: The new compound Al{sub 15}Ge{sub 4}Ni{sub 3} shows a unique combination of simple Cu{sub 3}Au- and CaF{sub 2}-type building blocks. - Highlights: • The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} (space group I4-bar3m) was determined. • It shows a unique combination of CaF{sub 2}- and Cu{sub 3}Au-type building blocks. • Electronic (DFT) calculations were performed to gain insight to chemical bonding.

  12. Enhanced interleukin-4 production in CD4+ T cells and elevated immunoglobulin E levels in antigen-primed mice by bisphenol A and nonylphenol, endocrine disruptors: involvement of nuclear factor-AT and Ca2+

    PubMed Central

    Lee, Mee H; Chung, Su W; Kang, Bok Y; Park, Jin; Lee, Choon H; Hwang, Seung Y; Kim, Tae S

    2003-01-01

    Bisphenol A (BPA) and p-nonylphenol (NP) are representative endocrine disruptors (EDs) that may have adverse effects on human health. The influence of these compounds on allergic immune responses remains unclear. In this study, we have examined the effects of BPA and NP on production of interleukin-4 (IL-4), a pro-inflammatory cytokine closely associated with allergic immune responses. Both BPA and NP significantly enhanced IL-4 production in keyhole limpet haemocyanin (KLH)-primed CD4+ T cells in a concentration-dependent manner. Treatment with BPA or NP in vivo resulted in significant increase of IL-4 production in CD4+ T cells and of antigen-specific immunoglobulin E (IgE) levels in the sera of KLH-primed mice. Furthermore, BPA and NP enhanced the activation of IL-4 gene promoter in EL4 T cells transiently transfected with IL-4 promoter/reporter constructs, and the enhancing effect mapped to a region in the IL-4 promoter containing binding sites for nuclear factor (NF)-AT. Activation of T lymphocytes by phorbol 12-myristate 13-acetate/ionomycin resulted in markedly enhanced binding activities to the NF-AT site, which significantly increased upon addition of BPA or NP, as demonstrated by the electrophoretic mobility shift assay, indicating that the transcription factor NF-AT was involved in the enhancing effect of BPA and NP on IL-4 production. The enhancement of IL-4 production by BPA or NP was significantly reduced by nitrendipine, a blocker of Ca2+ influx, and by FK506, a calcineurin inhibitor. FK506 inhibited the NF-AT–DNA binding activity and IL-4 gene promoter activity enhanced by BPA or NP. These results represent the first report describing possible enhancement of allergic response by EDs through increasing IL-4 production in CD4+ T cells and antigen-specific IgE levels in the sera via the stimulation of Ca2+/calcineurin-dependent NF-AT activation. PMID:12709020

  13. Role of basicity and tetrahedral speciation in controlling the thermodynamic properties of silicate liquids, part 1: the system CaO-MgO-Al 2O 3-SiO 2

    NASA Astrophysics Data System (ADS)

    Beckett, John R.

    2002-01-01

    Activity coefficients of oxide components in the system CaO-MgO-Al 2O 3-SiO 2 (CMAS) were calculated with the model of Berman (Berman R. G., "A thermodynamic model for multicomponent melts with application to the system CaO-MgO-Al 2O 3-SiO 2," Ph.D. dissertation, University of British Columbia, 1983) and used to explore large-scale relationships among these variables and between them and the liquid composition. On the basis of Berman's model, the natural logarithm of the activity coefficient of MgO, ln(γ MgOLiq), and ln(γ MgOLiq/γ SiO 2Liq) are nearly linear functions of ln(γ CaOLiq). All three of these variables are simple functions of the optical basicity Λ with which they display minima near Λ ˜ 0.54 that are generated by liquids with low ratios of nonbridging to tetrahedral oxygens (NBO/T) (<0.3) and a mole fraction ratio, X SiO 2Liq/X Al 2O 3Liq, in the range 4 to 20. Variations in ln(γ CaOLiq) at constant Λ near the minimum are due mostly to liquids with (X CaOLiq + X MgOLiq)/X Al 2O 3Liq < 1. The correlations with optical basicity imply that the electron donor power is an important factor in determining the thermodynamic properties of aluminosilicate liquids. For a constant NBO/T, ln(γ CaOLiq/γ Al 2O 3Liq) and ln(γ MgOLiqγ Al 2O 3Liq) form curves in terms of X SiO 2Liq/X Al 2O 3Liq. The same liquids that generate minima in the Λ plots are also associated with minima in ln(γ CaOLiqγ Al 2O 3Liq) and ln(γ MgOLiqγ Al 2O 3Liq) as a function of X SiO 2Liq/X Al 2O 3Liq. In addition, there are maxima or sharp changes in slope for NBO/T > 0.3, which occur for X SiO 2Liq/X Al 2O 3Liq ranging from ˜0 to ˜6 and increase with increasing NBO/T. The systematic variations in activity coefficients as a function of composition and optical basicity reflect underlying shifts in speciation as the composition of the liquid is changed. On the basis of correlations among the activity coefficients, it is likely that the use of CaO, an exchange component such as

  14. e/a determination for 4d- and 5d-transition metal elements and their intermetallic compounds with Mg, Al, Zn, Cd and In

    NASA Astrophysics Data System (ADS)

    Mizutani, U.; Sato, H.; Inukai, M.; Zijlstra, E. S.

    2013-08-01

    The present work is devoted to the determination of the effective electrons per atom ratio e/a by means of first-principles full-potential linearized augmented plane wave-Fourier method for elements from Rb to Ag in Period 5 and from Cs to Au in Period 6 of the periodic table and is regarded as a continuation of the preceding work done for elements from K to Cu in Period 4. The value of e/a was determined by reading off the square of the Fermi diameter, ? from the dispersion relation for electrons outside the Muffin-Tin spheres. A straightforward reading of the ordinate at the Fermi level, i.e. local reading method was validated for Rb and Cs in Group 1, Sr in Group 2, Y in Group 3, Pd and Pt in Group 10 and Ag and Au in Group 11. Instead, the nearly free electron (NFE) method was found to be indispensable for TM elements from Zr to Rh in Period 5 and those from Ba to Ir in Period 6. The composition dependence of e/a values for intermetallic compounds in X-TM (X = Mg, Al, Zn, Cd and In) alloy systems was also studied. The new Hume-Rothery electron concentration rule was established by constructing e/uc, the number of electrons per unit cell, vs. square of critical reciprocal lattice vector, ? , diagram for structurally complex metallic alloys having a pseudogap at the Fermi level. A proper use of either the local reading- or the NFE-e/a for the elements as indicated above is found to be essential.

  15. Structure of the quantum spin Hall states in HgTe/CdTe and InAs/GaSb/AlSb quantum wells

    NASA Astrophysics Data System (ADS)

    Klipstein, P. C.

    2015-01-01

    A solution of the k . p model is presented for bulk and quantum spin hall (QSH) edge states in semiconductor topological insulator (TI) quantum wells (QWs), bounded at the edge by an infinite wall potential. The edge states are exponentially localized, with a nonzero amplitude at the QW edge, and obey standard boundary conditions for the wave function and its derivative. Single helical edge states with spin locked to the direction of motion are found in the TI band gap (ETI) of QWs with both strong (HgTe/CdTe) and weak (InAs/GaSb/AlSb) s -p hybridization, but in the second case only below a small critical band gap, Ecrit˜1.6 meV . For ETI>Ecrit , there appear to be two degenerate states for each spin direction. It is suggested that Z2-like topological properties can still be maintained if one of these states is spurious or suppressed by disorder. The effect of interface band mixing, and band mixing due to structural inversion asymmetry and bulk inversion asymmetry is also considered. Simple model Hamiltonians are developed for the bulk and edge states which are calibrated against a bulk eight-band k . p calculation close to the TI transition. At the transition, the zero gap bulk states exhibit a spin splitting, essentially changing the Dirac point to a circle. In the TI phase, there is a small change in the dispersion of the QSH edge states. These results confirm the robustness of the QSH edge states to spatial symmetry breaking interactions.

  16. High-P behavior of anorthite composition and some phase relations of the CaO-Al2O3-SiO2 system to the lower mantle of the Earth, and their geophysical implications

    NASA Astrophysics Data System (ADS)

    Liu, Xi; Ohfuji, Hiroaki; Nishiyama, Norimasa; He, Qiang; Sanehira, Takeshi; Irifune, Tetsuo

    2012-09-01

    Multianvil experiments with long experimental durations have been made with the anorthite composition CaAl2Si2O8at pressure-temperature (P-T) conditions of 14-25 GPa and 1400-2400°C. At subsolidus conditions, these experiments demonstrated three phase assemblages, grossular (Gr) + kyanite (Ky) + stishovite (St) at ˜14 GPa, Gr + calcium-alumino-silicate phase (CAS) + St at ˜18 GPa, and CAS + CaSiO3-perovskite (CaPv) + St at above ˜20 GPa, which are related by the reactions Gr + Ky = CAS + St and Gr + St = CAS + CaPv. Following the method of Schreinemakers, we combined our data with the literature data to deduce aP-Tphase diagram for a portion of the CaO-Al2O3-SiO2system at subsolidus conditions, which subsequently helped to solve some long-lasting discrepancies in the high-Pbehavior of the compositions of anorthite and grossular. The crystal chemistry of the CAS and CaPv solid solutions was examined, and new substitution mechanisms were firmly established. Along the solidus, the melting reaction at ˜14 GPa is peritectic while that at ˜22 GPa is eutectic. For both pressures, St is the first phase to melt out and the melt is generally andesitic. For the An composition, its density starts to be significantly higher than the density of pyrolite at ˜2.5 GPa, a much lower pressure than that for the Or, Ab or Qtz composition (˜7.5-10 GPa), so that the An-enriched continental crust material should readily plunge into the upper mantle.

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

    SciTech Connect

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

    2013-10-15

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

  18. Luminescence and energy-transfer properties of color-tunable Ca2 Mg0.25 Al1.5 Si1.25 O7 :Ce(3+) /Eu(2+) /Tb(3+) phosphors for ultraviolet light-emitting diodes.

    PubMed

    Yuan, Bo; Song, Yanhua; Sheng, Ye; Zheng, Keyan; Huo, Qisheng; Xu, Xuechun; Zou, Haifeng

    2016-03-01

    A series of Ca2 Mg0.25 Al1.5 Si1.25 O7 :Ce(3+) /Eu(2+) /Tb(3+) phosphors was been prepared via a conventional high temperature solid-state reaction and their luminescence properties were studied. The emission spectra of Ca2 Mg0.25 Al1.5 Si1.25 O7 :Ce(3+) ,Eu(2+) and Ca2 Mg0.25 Al1.5 Si1.25 O7 :Ce(3+) ,Tb(3+) phosphors show not only a band due to Ce(3+) ions (409 nm) but also as a band due to Eu(2+) (520 nm) and Tb(3+) (542 nm) ions. More importantly, the effective energy transfer from Ce(3+) to Eu(2+) and Tb(3+) ions was confirmed and investigated by emission/excitation spectra and luminescent decay behaviors. Furthermore, the energy level scheme and energy transfer mechanism were investigated and were demonstrated to be of resonant type via dipole-dipole (Ce(3+) to Eu(2+) ) and dipole-quadrupole (Ce(3+) to Tb(3+) ) reactions, respectively. Under excitation at 350 nm, the emitting color could be changed from blue to green by adjusting the relative doping concentration of Ce(3+) and Eu(2+) ions as well as Ce(3+) and Tb(3+) ions. The above results indicate that Ca2 Mg0.25 Al1.5 Si1.25 O7 :Ce(3+) ,Eu(2+) /Tb(3+) are promising single-phase blue-to-green phosphors for application in phosphor conversion white-light-emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26249728

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

    NASA Astrophysics Data System (ADS)

    Höhn, Sarah; Virtanen, Sannakaisa

    2015-12-01

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

  20. The crystal and magnetic structures of LaCa{sub 2}Fe{sub 3-x}M{sub x}O{sub 8} (M=Al, Ga, In)

    SciTech Connect

    Goossens, D.J.; Henderson, L.S.F.; Trevena, S.; Hudspeth, J.M.; Avdeev, M.; Hester, J.R.

    2012-12-15

    LaCa{sub 2}Fe{sub 3}O{sub 8} (A{sub 3}B{sub 3}O{sub 8}) is an example of a layered structure in that it consists of pairs of octahedral, perovskite-like layers alternating with a single tetrahedral layer. This work explores the doping of non-magnetic group 13 elements, M=Al, Ga and In, onto the B-site of LaCa{sub 2}Fe{sub 3-x}M{sub x}O{sub 8} as a function of x. The structural and magnetic effects are examined using a combination of neutron and X-ray diffraction. Solubility limits are established. It is found that for M=Ga the solubility limit occurs between x=1.0 and x=1.25, for the synthesis conditions used, while there is evidence for low (x<0.25) but non-zero substitution of Al. Structural refinements at x=1 suggest that Ga prefers neither the tetrahedral nor octahedral sites. The magnetic structure of LaCa{sub 2}Fe{sub 2}GaO{sub 8} has been examined using neutron diffraction at 3.2 K and room temperature. At low temperature the staggered moment per Fe{sup 3+} is 3.8(1){mu}{sub B} in LaCa{sub 2}Fe{sub 3}O{sub 8} and 4.8(1){mu}{sub B} in LaCa{sub 2}Fe{sub 2}GaO{sub 8}. The magnetic space group (P{sub 2b}2{sub 1} Prime ma Prime ) and moment direction (along c) does not appear to change with Ga substitution. - Graphical abstract: Solubility limits for group 13 elements in LaCa{sub 2}Fe{sub 3}O{sub 8}. Highlights: Black-Right-Pointing-Pointer Solubility limits for group 13 elements in LaCa{sub 2}Fe{sub 3}O{sub 8} are determined. Black-Right-Pointing-Pointer Evolution of the magnetic structure with temperature and doping is explored using neutron scattering. Black-Right-Pointing-Pointer The magnetic space group is quoted as P{sub 2b}2{sub 1}'ma' and the staggered moments are obtained for LaCa{sub 2}Fe{sub 3}O{sub 8} and LaCa{sub 2}Fe{sub 2}GaO{sub 8}.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  2. White long-lasting phosphorescence generation in a CaAl2Si2O8 : Eu2+, Mn2+, Dy3+ system through persistent energy transfer

    NASA Astrophysics Data System (ADS)

    Zhang, Jinsu; Chen, Baojiu; Sun, Jiashi; Li, Xiangping; Cheng, Lihong; Zhong, Haiyang

    2012-08-01

    Based on the persistent energy transfer principle, Mn2+ was introduced into a CaAl2Si2O8 : Eu2+/Dy3+ phosphor to achieve white long-lasting emissions. Eu2+, Mn2+ and Dy3+ tri-doped CaAl2Si2O8 phosphors with various Mn2+ concentrations were prepared via a solid-state reaction, and the crystal structure of the phosphors was identified by the x-ray diffraction technique. The luminescent properties of the Eu2+, Mn2+ and Dy3+ tri-doped CaAl2Si2O8 phosphors were studied. The energy transfer behaviour from Eu2+ to Mn2+ was analysed within the framework of Dexter theory. The physical mechanism of energy transfer was assigned to the electric dipole-quadrupole interaction. It was also demonstrated that the colour coordinates of the phosphors can be tuned from the blue region to the white region in the colour space. Furthermore, the afterglow decay and thermoluminescence curves were measured, indicating excellent phosphorescence properties of the current phosphors.

  3. Adsorption studies of Cd(II) onto Al 2O 3/Nb 2O 5 mixed oxide dispersed on silica matrix and its on-line preconcentration and determination by flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Mendonça Costa, Lucimara; Ribeiro, Emerson Schwingel; Segatelli, Mariana Gava; do Nascimento, Danielle Raphael; de Oliveira, Fernanda Midori; Tarley, César Ricardo Teixeira

    2011-05-01

    The present study describes the adsorption characteristic of Cd(II) onto Nb 2O 5/Al 2O 3 mixed oxide dispersed on silica matrix. The characterization of the adsorbent has been carried out by infrared spectroscopy (IR), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), energy dispersive X-ray fluorescence analysis (EDXRF) and specific surface area ( SBET). From batch experiments, adsorption kinetic of Cd(II) was described by a pseudo-second-order kinetic model. The Langmuir linear isotherm fitted to the experimental adsorption isotherm very well, and the maximum adsorption capacity was found to be 17.88 mg g -1. Using the effective material, a method for Cd(II) preconcentration at trace level was developed. The method was based on on-line adsorption of Cd(II) onto SiO 2/Al 2O 3/Nb 2O 5 at pH 8.64, in which the quantitative desorption occurs with 1.0 mol L -1 hydrochloric acid towards FAAS detector. The experimental parameters related to the system were studied by means of multivariate analysis, using 2 4 full factorial design and Doehlert matrix. The effect of SO 42-, Cu 2+, Zn 2+ and Ni 2+ foreign ions showed no interference at 1:100 analyte:interferent proportion. Under the most favorable experimental conditions, the preconcentration system provided a preconcentration factor of 18.4 times, consumption index of 1.08 mL, sample throughput of 14 h -1, concentration efficiency of 4.35 min -1, linear range from 5.0 up to 35.0 μg L -1 and limits of detection and quantification of 0.19 and 0.65 μg L -1 respectively. The feasibility of the proposed method for Cd(II) determination was assessed by analysis of water samples, cigarette sample and certified reference materials TORT-2 (Lobster hepatopancreas) and DOLT-4 (Dogfish liver).

  4. Calcioferrite with composition (Ca3.94Sr0.06)Mg1.01(Fe2.93Al1.07)(PO4)6(OH)4·12H2O

    PubMed Central

    Lafuente, Barbara; Downs, Robert T.; Yang, Hexiong; Jenkins, Robert A.

    2014-01-01

    Calcioferrite, ideally Ca4MgFe3+ 4(PO4)6(OH)4·12H2O (tetra­calcium magnesium tetrairon(III) hexakis-phosphate tetra­hydroxide dodeca­hydrate), is a member of the calcioferrite group of hydrated calcium phosphate minerals with the general formula Ca4 AB 4(PO4)6(OH)4·12H2O, where A = Mg, Fe2+, Mn2+ and B = Al, Fe3+. Calcioferrite and the other three known members of the group, montgomeryite (A = Mg, B = Al), kingsmountite (A = Fe2+, B = Al), and zodacite (A = Mn2+, B = Fe3+), usually occur as very small crystals, making their structure refinements by conventional single-crystal X-ray diffraction challenging. This study presents the first structure determination of calcioferrite with composition (Ca3.94Sr0.06)Mg1.01(Fe2.93Al1.07)(PO4)6(OH)4·12H2O based on single-crystal X-ray diffraction data collected from a natural sample from the Moculta quarry in Angaston, Australia. Calcioferrite is isostructural with montgomeryite, the only member of the group with a reported structure. The calcioferrite structure is characterized by (Fe/Al)O6 octa­hedra (site symmetries 2 and -1) sharing corners (OH) to form chains running parallel to [101]. These chains are linked together by PO4 tetra­hedra (site symmetries 2 and 1), forming [(Fe/Al)3(PO4)3(OH)2] layers stacking along [010], which are connected by (Ca/Sr)2+ cations (site symmetry 2) and Mg2+ cations (site symmetry 2; half-occupation). Hydrogen-bonding inter­actions involving the water mol­ecules (one of which is equally disordered over two positions) and OH function are also present between these layers. The relatively weaker bonds between the layers account for the cleavage of the mineral parallel to (010). PMID:24764934

  5. Enhanced stability of CaO and/or La2O3 promoted Pd/Al2O3 egg-shell catalysts in partial oxidation of methane to syngas.

    PubMed

    Wang, Jinlong; Yu, Hongbo; Ma, Zhen; Zhou, Shenghu

    2013-01-01

    An egg-shell Pd/Al2O3 catalyst showed higher activity than a regular Pd/Al2O3 catalyst in the partial oxidation of methane to syngas, but a common problem of this reaction is the catalyst deactivation on stream. We attempted to modify the egg-shell catalyst via impregnation with some metal oxide additives. Although the addition of MgO did not show any beneficial effect, the addition of CaO and/or La2O3 significantly improved the stability due to the suppression of carbon deposition and phase transformation of the Al2O3 support. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, and thermogravimetric analysis (TGA). PMID:23860276

  6. 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.

  7. Bi2Sr2CaCu2O8 + x round wires with Ag/Al oxide dispersion strengthened sheaths: microstructure-properties relationships, enhanced mechanical behavior and reduced Cu depletion

    NASA Astrophysics Data System (ADS)

    Kajbafvala, Amir; Nachtrab, William; Wong, Terence; Schwartz, Justin

    2014-09-01

    Ag/Al alloys with various Al content (0.50 wt%, 0.75 wt%, 1.00 wt%, and 1.25 wt%) are made by powder metallurgy and used as the outer sheath material for Bi2Sr2CaCu2O8 + x (Bi2212)/Ag/AgAl multifilamentary round wires (RW). Bi2212/Ag/AgAl RW microstructural, mechanical and electrical properties are studied in various conditions, including as-drawn, after internal oxidation, and after partial melt processing (PMP). The results are compared with the behavior of a Bi2212/Ag/Ag0.20Mg wire of the same geometry. The grains in as-drawn Ag/Al alloys are found to be ˜25% smaller than those in the corresponding Ag/0.20 wt%Mg, but after PMP, the Ag/Al and Ag/0.20 wt%Mg grain sizes are comparable. Tensile tests show that Bi2212/Ag/AgAl green wires have yield strength (YS) of ˜115 MPa, nearly 65% higher than that of Bi2212/Ag/Ag0.20Mg. After PMP, the Bi2212/Ag/AgAl YS is about 35% greater than that of Bi2212/Ag/Ag0.20Mg. Furthermore, Bi2212/Ag/AgAl wires exhibit higher ultimate tensile strength and modulus and twice the elongation-to-failure. Atomic resolution high-angle annular dark-field scanning transmission electron microscopy, high resolution transmission electron microscopy and energy dispersive spectroscopy demonstrate the formation of nanosize MgO and Al2O3 precipitates via internal oxidation. Large spherical MgO precipitates are observed on the Ag grain boundaries of Ag/0.20 wt%Mg alloy, whereas the Al2O3 precipitates are distributed homogenously in the dispersion-strengthened (DS) Ag/Al alloy. Furthermore, it is found that less Cu diffused from the Bi2212 filaments in the Bi2212/Ag/Ag0.75Al wire during PMP than from the filaments in the Bi2212/Ag/Ag0.20Mg wire. These results show that DS Ag/Al alloy is a strong candidate for improved Bi2212 wire.

  8. Photoluminescence Properties of Efficient Blue-Emitting Phosphor α-Ca1.65Sr0.35SiO4:Ce(3+): Color Tuning via the Substitutions of Si by Al/Ga/B.

    PubMed

    Li, Kai; Shang, Mengmeng; Lian, Hongzhou; Lin, Jun

    2015-08-17

    A series of Ce(3+)-doped α-Ca1.65Sr0.35SiO4 (CSSO) phosphors without and with the substitutions of Si by Al/Ga/B were synthesized via the high-temperature solid-state reaction process. X-ray diffraction patterns and Rietveld refinements were used to demonstrate the successful incorporations of Al/Ga/B into CSSO:Ce(3+). Without Al/Ga/B, the Ce(3+) singly doped CSSO phosphors present intense blue emission, which correspond to the broad emission bands in visible region with the wavelength range from 360 to 580 nm upon 350 nm excitation. The optimal emission intensity occurs in CSSO:0.05Ce(3+) sample with the emission peak wavelength at 436 nm. With the introduction of Al/Ga/B into the CSSO:0.05Ce(3+), the emission peak shifts from 436 to 457/465/446 nm under 365 nm excitation, respectively. The red shift of Ce(3+) emission is attributed to the polyhedral distortion of the cations, resulting in the enhancement of crystal field spitting due to the variations of the adjacent (Al/Ga/B,Si)O4 polyhedron. Moreover, the temperature-dependent photoluminescence was determined to be of light impact to CSSO:Ce(3+) with the introduction of Al/Ga/B. This research is useful for enriching the emission colors of Ce(3+)-activated phosphors. PMID:26247562

  9. Crystal structure of Kuzel's salt 3CaO.Al{sub 2}O{sub 3}.1/2CaSO{sub 4}.1/2CaCl{sub 2}.11H{sub 2}O determined by synchrotron powder diffraction

    SciTech Connect

    Mesbah, Adel; Francois, Michel; Cau-dit-Coumes, Celine; Frizon, Fabien; Leroux, Fabrice; Ravaux, Johann

    2011-05-15

    The crystal structure of Kuzel's salt has been successfully determined by synchrotron powder diffraction. It crystallizes in the rhombohedral R3-bar symmetry with a = 5.7508 (2) A, c = 50.418 (3) A, V = 1444.04 (11) A{sup 3}. Joint Rietveld refinement was realized using three X-ray powder patterns recorded with a unique wavelength and three different sample-to-detector distances. Kuzel's salt is the chloro-sulfoaluminate AFm phase and belongs to the layered double hydroxide (LDH) large family. Its structure is composed of positively charged main layer [Ca{sub 2}Al(OH){sub 6}]{sup +} and negatively charged interlayer [Cl{sub 0.50}.(SO{sub 4}){sub 0.25}.2.5H{sub 2}O]{sup -}. Chloride and sulfate anions are ordered into two independent crystallographic sites and fill successive interlayer leading to the formation of a second-stage compound. The two kinds of interlayer have the compositions [Cl.2H{sub 2}O]{sup -} and [(SO{sub 4}){sub 0.5}.3H{sub 2}O]{sup -}. The crystal structure explains why chloride and sulfate anions are not substituted and why the formation of extended solid solution in the chloro-sulfate AFm system does not occur.

  10. CdS nanoparticles sensitization of Al-doped ZnO nanorod array thin film with hydrogen treatment as an ITO/FTO-free photoanode for solar water splitting

    PubMed Central

    2012-01-01

    Aluminum-doped zinc oxide (AZO) nanorod array thin film with hydrogen treatment possesses the functions of transparent conducting oxide thin film and 1-D nanostructured semiconductor simultaneously. To enhance the absorption in the visible light region, it is sensitized by cadmium sulfide (CdS) nanoparticles which efficiently increase the absorption around 460 nm. The CdS nanoparticles-sensitized AZO nanorod array thin film with hydrogen treatment exhibits significantly improved photoelectrochemical property. After further heat treatment, a maximum short current density of 5.03 mA cm−2 is obtained under illumination. They not only are much higher than those without CdS nanoparticles sensitization and those without Al-doping and/or hydrogen treatment, but also comparable and even slightly superior to some earlier works for the CdS-sensitized zinc oxide nanorod array thin films with indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) as substrates. This demonstrated successfully that the AZO nanorod array thin film with hydrogen treatment is quite suitable as an ITO/FTO-free photoanode and has great potentials in solar water splitting after sensitization by quantum dots capable of visible light absorption. PMID:23098050

  11. EFFECT OF MgO ON STRUCTURE AND DIELECTRIC PROPERTIES OF CaO-Al2O3-B2O3-SiO2 GLASSES

    NASA Astrophysics Data System (ADS)

    Du, Zhao; Zhang, Xuehong; Yue, Yunlong; Wu, Haitao

    2012-12-01

    The effect of MgO on structure and dielectric properties of aluminoborosilicate glasses was investigated. FTIR data indicated that glass network was mainly built by tetrahedral [SiO4], [BO4], [AlO4] and trigonal [BO3]. A small amount of AlO5 or AlO6 units also existed. The glass system was characterized with lower dielectric constant (4.17 4.6) and dielectric loss (12.3 × 10-4 14.77 × 10-4) at 1 MHz. With the increase of MgO content, the quantity of AlO5 or AlO6 units decreased. The variation of density showed a decreasing tendency. The dielectric constant and loss were all found to decrease.

  12. Effects of Al2O3 and MgO on Softening, Melting, and Permeation Properties of CaO-FeO-SiO2 on a Coke Bed

    NASA Astrophysics Data System (ADS)

    Ueda, Shigeru; Kon, Tatsuya; Miki, Takahiro; Kim, Sun-Joong; Nogami, Hiroshi

    2016-04-01

    In ironmaking, maintaining gas permeability in blast furnace with low coke rate operation is essential to reduce carbon emissions. The high pressure loss in the cohesive zone decreases the gas permeability and affects the productivity of blast furnace. In order to increase the gas permeability in the cohesive zone, the thickness of the cohesive layer should be decreased. For this purpose, increasing softening temperature and decreasing dripping temperature of the iron ore are desired. In this study, softening, melting, and permeation of SiO2-FeO-CaO-Al2O3-MgO on a coke bed were investigated. The oxide sample in a tablet form was heated under CO/CO2 atmosphere, and the shape of the tablet was observed. The softening and melting temperatures of the SiO2-FeO-CaO system changed with the addition of Al2O3 and MgO. Oxide tablets with and without Al2O3 softened below and above the solidus temperature, respectively. The melting temperatures varied with the ratio of CO/CO2 in the gas. The permeation temperature was independent of the melting temperature, but dependent on the wettability.

  13. Effects of Al2O3 and MgO on Softening, Melting, and Permeation Properties of CaO-FeO-SiO2 on a Coke Bed

    NASA Astrophysics Data System (ADS)

    Ueda, Shigeru; Kon, Tatsuya; Miki, Takahiro; Kim, Sun-Joong; Nogami, Hiroshi

    2016-08-01

    In ironmaking, maintaining gas permeability in blast furnace with low coke rate operation is essential to reduce carbon emissions. The high pressure loss in the cohesive zone decreases the gas permeability and affects the productivity of blast furnace. In order to increase the gas permeability in the cohesive zone, the thickness of the cohesive layer should be decreased. For this purpose, increasing softening temperature and decreasing dripping temperature of the iron ore are desired. In this study, softening, melting, and permeation of SiO2-FeO-CaO-Al2O3-MgO on a coke bed were investigated. The oxide sample in a tablet form was heated under CO/CO2 atmosphere, and the shape of the tablet was observed. The softening and melting temperatures of the SiO2-FeO-CaO system changed with the addition of Al2O3 and MgO. Oxide tablets with and without Al2O3 softened below and above the solidus temperature, respectively. The melting temperatures varied with the ratio of CO/CO2 in the gas. The permeation temperature was independent of the melting temperature, but dependent on the wettability.

  14. Ferromagnetism and magneto-transport properties of Mn{sub 0.92}Ca{sub 0.08}As thin film grown on Al{sub 2}O{sub 3}(0001) substrate

    SciTech Connect

    Dung, Dang Duc; Van Thiet, Duong; Anh Tuan, Duong; Cho, Sunglae; Feng, Wuwei

    2014-05-07

    The epitaxial Mn{sub 0.92}Ca{sub 0.08}As thin film was grown on Al{sub 2}O{sub 3}(0001) substrate by molecular beam epitaxy. The Curie temperature (T{sub C}) around 340 K was enhanced with the addition of Ca, compared to that of bulk MnAs (T{sub C} ∼ 318 K). The maxima magnetoresistance, ∼2.08% at 0.7 T, was observed near the critical magnetic transition temperature. Moreover, the giant magnetocaloric effect was found with the maximum magnetic entropy change, ∼200 J/kgK, around 330 K at 5 T.

  15. Genetic relationship between Na-rich chondrules and Ca,Al-rich inclusions? - Formation of Na-rich chondrules by melting of refractory and volatile precursors in the solar nebula

    NASA Astrophysics Data System (ADS)

    Ebert, Samuel; Bischoff, Addi

    2016-03-01

    Al-rich objects (Ca,Al-rich inclusions (CAIs), Al-rich chondrules, Al-rich fragments) occur in all chondrite classes. These objects can be centimeter-sized in CV3 carbonaceous chondrites, but they are generally much smaller in other chondrite groups and classes. Within the ordinary chondrites, most Al-rich objects are chondrules that vary from Ca- to Na-rich. Here, we have investigated the mineralogy and major element chemistry of 32 Na-rich chondrules and 3 Na-rich fragments from 15 different chondrites. Most objects (chondrules and chondrule fragments) are from ordinary chondrites (petrologic types 3.2-3.8), but two of the chondrules are from two CO3 chondrites, and three of the chondrules are from one Rumuruti (R)-chondrite. We found that these Na-rich objects have bulk Na2O-concentrations between 4.3 and 15.2 wt%. Texturally, they typically consist of euhedral to subhedral (often skeletal) mafic minerals (olivine and pyroxenes) embedded within a nepheline-normative, glassy mesostasis, which is brownish in transmitted light. In addition, some chondrules contain euhedral to subhedral spinel. Bulk chondrule compositions show group II, group III, and ultrarefractory rare earth element (REE) patterns similar to those found in CAIs. These results clearly demonstrate that the Na-rich chondrules must have been formed by melting of precursors containing an (ultra-)refractory element-rich component and Na-rich constituents. The Na-rich chondrules showed Sm and Eu anomalies, indicating that they must have formed at low oxygen fugacities. Based on the chemical composition of the Na-rich objects, we can rule out that they were formed as a result of planetary formation due to metasomatic processes or processes related to collisions between molten planetesimals.

  16. A comparison of benthic foraminiferal Mn / Ca and sedimentary Mn / Al as proxies of relative bottom-water oxygenation in the low-latitude NE Atlantic upwelling system

    NASA Astrophysics Data System (ADS)

    McKay, C. L.; Groeneveld, J.; Filipsson, H. L.; Gallego-Torres, D.; Whitehouse, M. J.; Toyofuku, T.; Romero, O. E.

    2015-09-01

    Trace element incorporation into foraminiferal shells (tests) is governed by physical and chemical conditions of the surrounding marine environment, and therefore foraminiferal geochemistry provides a means of palaeo-oceanographic reconstructions. With the availability of high-spatial-resolution instrumentation with high precision, foraminiferal geochemistry has become a major research topic over recent years. However, reconstructions of past bottom-water oxygenation using foraminiferal tests remain in their infancy. In this study we explore the potential of using Mn / Ca determined by secondary ion mass spectrometry (SIMS) as well as by flow-through inductively coupled plasma optical emission spectroscopy (FT-ICP-OES) in the benthic foraminiferal species Eubuliminella exilis as a proxy for recording changes in bottom-water oxygen conditions in the low-latitude NE Atlantic upwelling system. Furthermore, we compare the SIMS and FT-ICP-OES results with published Mn sediment bulk measurements from the same sediment core. This is the first time that benthic foraminiferal Mn / Ca is directly compared with Mn bulk measurements, which largely agree on the former oxygen conditions. Samples were selected to include different productivity regimes related to Marine Isotope Stage 3 (35-28 ka), the Last Glacial Maximum (28-19 ka), Heinrich Event 1 (18-15.5 ka), Bølling Allerød (15.5-13.5 ka) and the Younger Dryas (13.5-11.5 ka). Foraminiferal Mn / Ca determined by SIMS and FT-ICP-OES is comparable. Mn / Ca was higher during periods with high primary productivity, such as during the Younger Dryas, which indicates low-oxygen conditions. This is further supported by the benthic foraminiferal faunal composition. Our results highlight the proxy potential of Mn / Ca in benthic foraminifera from upwelling systems for reconstructing past variations in oxygen conditions of the sea floor environment as well as the need to use it in combination with other proxy records such as faunal

  17. Solid solution between Al-ettringite and Fe-ettringite (Ca{sub 6}[Al{sub 1-x}Fe{sub x}(OH){sub 6}]{sub 2}(SO{sub 4}){sub 3}.26H{sub 2}O)

    SciTech Connect

    Moeschner, Goeril Lothenbach, Barbara; Winnefeld, Frank; Ulrich, Andrea; Figi, Renato; Kretzschmar, Ruben

    2009-06-15

    The solid solution between Al- and Fe-ettringite Ca{sub 6}[Al{sub 1-x}Fe{sub x}(OH){sub 6}]{sub 2}(SO{sub 4}){sub 3}.26H{sub 2}O was investigated. Ettringite phases were synthesized at different Al/(Al + Fe)-ratios (= X{sub Al,total}), so that X{sub Al} increased from 0.0 to 1.0 in 0.1 unit steps. After 8 months of equilibration, the solid phases were analyzed by X-ray diffraction (XRD) and thermogravimetric analysis (TGA), while the aqueous solutions were analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). XRD analyses of the solid phases indicated the existence of a miscibility gap between X{sub Al,total} = 0.3-0.6. Some of the XRD reflections showed two overlapping peaks at these molar ratios. The composition of the aqueous solutions, however, would have been in agreement with both, the existence of a miscibility gap or a continuous solid solution between Al- and Fe-ettringite, based on thermodynamic modeling, simulating the experimental conditions.

  18. Soft X-ray absorption spectroscopy of La{sub 0.7}Ca{sub 0.3}Mn{sub 1−X}Al{sub X}O{sub 3} thin films

    SciTech Connect

    Kumar, Manish Choudhary, R. J. Phase, D. M.

    2014-04-24

    Epitaxial thin films of rare earth manganites have generated much attention recently due to their rich phase diagram. The electronic structure of these films is playing a very crucial role and demands a fundamental understanding prior to device fabrication. We have investigated the electronic structure of La{sub 0.7}Ca{sub 0.3}Mn{sub 1−X}Al{sub X}O{sub 3} (X=0, 0.15) epitaxial thin films by soft X-ray absorption spectroscopy technique using the surface sensitive total electron yield (TEY) mode.

  19. Computer simulation of the self-assembly of crystal structures of zeolites Ca64(Sr,K,Ba)48(Cu12(O,Cl))4[Si192Al192O786](H2O) n (tschoertnerite, TSC, V = 31 614 Å3) and Ca2K2[Al6Si6O24](H2O)10 (willhendersonite, cha, V = 804 Å3) from template nanocluster precursors K48 and K12

    NASA Astrophysics Data System (ADS)

    Ilyushin, G. D.; Blatov, V. A.

    2013-07-01

    The self-assembly of zeolites Ca64(Sr,K,Ba)48(Cu12(O,Cl))4[Si192Al192 O786](H2O) n (tschoertnerite, TSC-type framework, V = 31614 Å3) and Ca2K2[Al6Si6O24] (H2O)10 (willhendersonite, CHA-type framework, V = 804 Å3), which form paragenetic associations, has been simulated using computational methods (TOPOS program package). A new method for analyzing zeolites of any complexity has been used, which is based on the complete expansion of the three-dimensional structural graph (3 D factor graph) in tiles and the selection of nonintersecting tiles forming a packing. The code of self-assembly of 3 D structures from complementary linked nanocluster precursors is reconstructed: primary chain → microlayer → microframework. A supracluster precursor K48 with the symmetry bar 43 m, formed of four K12 clusters corresponding to the t-hpr tile, is established for TSC. The K48 cluster contains Ca template cations, which stabilize its local region in the stages of K12 → K24 → K48 self-assembly. Bifurcations of evolution paths (structural branching points) during the self-assembly of TSC and CHA microframeworks are established in the stage of formation of the K24 supracluster from invariant templated K12 clusters. The models under consideration explain the 100% localization of B = Ca cations, which play the role of templates, and the 50% occupation of the positions of K, Sr, and Ba spacer cations (in TSC) and K spacer cations (in CHA).

  20. Chitosan oligosaccharide-Ca complex accelerates the depuration of cadmium from Chlamys ferrari

    NASA Astrophysics Data System (ADS)

    Huang, Guoqing; Sun, Jipeng; Wang, Dongfeng; Xu, Ying; Xu, Wei

    2012-06-01

    This study investigated the effect of a chitosan oligosaccharide-Ca complex (COS-Ca) on the depuration of cadmium (Cd) from Chlamys ferrari. After exposure to 0.5 mg L-1 CdCl2 for 3 or 7 d, the scallops were treated by COS-Ca prior to determination of Cd, calcium (Ca) and zinc (Zn) contents, Cd distribution in organs, malondialdehyde (MDA) content and antioxidant variables. Results showed that COS-Ca reduced Cd content in the viscera of the scallops, with highest Cd depuration rate (47%) observed on day 3. The COS-Ca concentration substantially affected Cd depuration, and the exposure to 8.75 mg L-1 COS-Ca led to significantly higher Cd depuration rate compared with those of lower COS-Ca concentrations (1.75, 3.5, 5.25, and 7.00 mg L-1). Distribution analysis of Cd in scallop organs indicated that COS-Ca significantly reduced Cd content in the kidney throughout the 5-d experiment, as well as in the gill during the early stage of Cd depuration. In addition, COS-Ca treatment decreased glutathione peroxidase (GSH-Px) activity and MDA content while increasing superoxide dismutase (SOD) and catalase (CAT) activities on different days. Our work suggested COS-Ca complex treatment as an effective method for acceleration of Cd depuration from Cd-contaminated bivalves.

  1. Superspin glassy behaviour of La{sub 0.7}Ca{sub 0.3}Mn{sub 0.85}Al{sub 0.15}O{sub 3} thin film

    SciTech Connect

    Kumar, Manish; Choudhary, R. J. Shukla, D. K.; Phase, D. M.

    2014-07-21

    Here, we present the low temperature magnetic behaviour of epitaxial La{sub 0.7}Ca{sub 0.3}Mn{sub 0.85}Al{sub 0.15}O{sub 3} (LCMAO) thin film through a series of DC magnetic measurements. Overall behaviour inferred from the magnetization measurements indicate that the magnetic phases created due to Al doping induced inhomogeneous distribution of Mn{sup 3+} and Mn{sup 4+} ions and oxygen vacancies present in the system act like superspins, and the strong interaction among themselves results in the superspin glassy behaviour. Interactions among the superspins are marked by the aging and zero filed memory effects. The glassy magnetic phase in LCMAO is found to follow the hierarchical model of spin glasses.

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

    NASA Astrophysics Data System (ADS)

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

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

  3. Hydrothermal synthesis and the crystal structure of borate cancrinite (Na,Ca){sub 2}[Na{sub 6}(AlSiO{sub 4}){sub 6}](BO{sub 3}) . 2H{sub 2}O

    SciTech Connect

    Shirinova, A. F. Khrustalev, V. N.; Samedov, H. R.; Chiragov, M. I.

    2006-01-15

    Transparent prismatic single crystals of borate cancrinite (Na,Ca){sub 2}[Na{sub 6}(AlSiO{sub 4}){sub 6}](BO{sub 3}) . 2H{sub 2}O are prepared through hydrothermal crystallization. The parameters of the hexagonal unit cell and intensities of 10806 reflections are measured on an Enraf-Nonius CAD4 automated diffractometer. The compound crystallizes in the hexagonal crystal system with the unit cell parameters a = 12.745(4) A, c = 5.180(2) A, V = 728.6(4) A{sup 3}, and space group P6{sub 3}. The structure is determined by direct methods and refined using the full-matrix least-squares procedure in the anisotropic approximation for the non-hydrogen atoms. The refinement of the structure is performed to the final discrepancy factor R{sub 1} = 0.027 for 2889 unique reflections with I > 2 {sigma} (I). In the structure of the borate cancrinite, the AlO{sub 4} and SiO{sub 4} tetrahedra form a zeolite-like framework in which twelve-membered hexagonal channels are occupied by sodium atoms and BO{sub 3} groups, whereas six-membered channels are filled with sodium and calcium atoms and water molecules. The mean interatomic distances are found to be as follows: (Si-O){sub mean} = 1.614 A and (Al-O){sub mean} = 1.741 A in the AlO{sub 4} and SiO{sub 4} tetrahedra, (Na-O){sub mean} = 2.542 A in the seven-vertex sodium polyhedra, and [(Na,Ca)-O]{sub mean} = 2.589 A in the ditrigonal bipyramids.

  4. Raman spectroscopy of DNA-metal complexes. II. The thermal denaturation of DNA in the presence of Sr2+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, and Cd2+.

    PubMed Central

    Duguid, J G; Bloomfield, V A; Benevides, J M; Thomas, G J

    1995-01-01

    Differential scanning calorimetry, laser Raman spectroscopy, optical densitometry, and pH potentiometry have been used to investigate DNA melting profiles in the presence of the chloride salts of Ba2+, Sr2+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, and Cd2+. Metal-DNA interactions have been observed for the molar ratio [M2+]/[PO2-] = 0.6 in aqueous solutions containing 5% by weight of 160 bp mononucleosomal calf thymus DNA. All of the alkaline earth metals, plus Mn2+, elevate the melting temperature of DNA (Tm > 75.5 degrees C), whereas the transition metals Co2+, Ni2+, and Cd2+ lower Tm. Calorimetric (delta Hcal) and van't Hoff (delta HVH) enthalpies of melting range from 6.2-8.7 kcal/mol bp and 75.6-188.6 kcal/mol cooperative unit, respectively, and entropies from 17.5 to 24.7 cal/K mol bp. The average number of base pairs in a cooperative melting unit () varied from 11.3 to 28.1. No dichotomy was observed between alkaline earth and transition DNA-metal complexes for any of the thermodynamic parameters other than their effects on Tm. These results complement Raman difference spectra, which reveal decreases in backbone order, base unstacking, distortion of glycosyl torsion angles, and rupture of hydrogen bonds, which occur after thermal denaturation. Raman difference spectroscopy shows that transition metals interact with the N7 atom of guanine in duplex DNA. A broader range of interaction sites with single-stranded DNA includes ionic phosphates, the N1 and N7 atoms of purines, and the N3 atom of pyrimidines. For alkaline earth metals, very little interaction was observed with duplex DNA, whereas spectra of single-stranded complexes are very similar to those of melted DNA without metal. However, difference spectra reveal some metal-specific perturbations at 1092 cm-1 (nPO2-), 1258 cm-1 (dC, dA), and 1668 cm-1 (nC==O, dNH2 dT, dG, dC). Increased spectral intensity could also be observed near 1335 cm-1 (dA, dG) for CaDNA. Optical densitometry, employed to detect DNA

  5. Different responses of low grain-Cd-accumulating and high grain-Cd-accumulating rice cultivars to Cd stress.

    PubMed

    Wang, Feijuan; Wang, Min; Liu, Zhouping; Shi, Yan; Han, Tiqian; Ye, Yaoyao; Gong, Ning; Sun, Junwei; Zhu, Cheng

    2015-11-01

    Cadmium (Cd) is a major heavy metal pollutant which is highly toxic to plants and animals. The accumulation of Cd in rice grains is a major agricultural problem in regions with Cd pollution. A hydroponics experiment using low grain-Cd-accumulating rice (xiushui 11) and high grain-Cd-accumulating rice (xiushui 110) was carried out to characterize the different responses of rice cultivars to Cd stress. We found that xiushui 11 was more tolerant to Cd than xiushui 110, and xiushui 11 suffered less oxidative damage. Cell walls played an important role in limiting the amount of Cd that entered the protoplast, especially in xiushui 11. Cd stored in organelles as soluble fractions, leading to greater physiological stress of Cd detoxification. We found that Cd can disturb the ion homeostasis in rice roots because Cd(2+) and Ca(2+) may have a similar uptake route. Xiushui 11 had a faster root-to-shoot transport of Cd, and the expression level of OsPCR1 gene which was predicted related with Cd accumulation in rice was consist with the Cd transport of root-to-shoot in rice and maintain the greater Cd tolerance of xiushui 11. These results suggest there are different Cd detoxification and accumulation mechanisms in rice cultivars. PMID:26318143

  6. Multinuclear high-resolution NMR study of compounds from the ternary system NaF-CaF2-AlF3: from determination to modeling of NMR parameters.

    PubMed

    Martineau, C; Body, M; Legein, C; Silly, G; Buzaré, J-Y; Fayon, F

    2006-12-11

    27Al and 23Na NMR satellite transition spectroscopy and 3Q magic-angle-spinning spectra are recorded for three compounds from the ternary NaF-CaF2-AlF3 system. The quadrupolar frequency nuQ, asymmetry parameter etaQ, and isotropic chemical shift deltaiso are extracted from the spectrum reconstructions for five aluminum and four sodium sites. The quadrupolar parameters are calculated using the LAPW-based ab initio code WIEN2k. It is necessary to perform a structure optimization of all compounds to ensure a fine agreement between experimental and calculated parameters. By a comparison of experimental and calculated values, an attribution of all of the 27Al and 23Na NMR lines to the crystallographic sites is achieved. High-speed 19F NMR MAS spectra are recorded and reconstructed for the same compounds, leading to the determination of 18 isotropic chemical shifts. The superposition model developed by Bureau et al. is used, allowing a bijective assignment of the 19F NMR lines to the crystallographic sites. PMID:17140229

  7. Structural distortions in Sr{sub 3-x}A{sub x}MO{sub 4}F (A=Ca, Ba; M=Al, Ga, In) anti-Perovskites and corresponding changes in photoluminescence

    SciTech Connect

    Sullivan, Eirin; Avdeev, Maxim; Vogt, Thomas

    2012-10-15

    The ordered oxyfluoride family Sr{sub 3}-{sub x}A{sub x}MO{sub 4}F (A=Ca, Ba and M=Al, Ga) has formed the basis of several new inorganic phosphors, and shows great potential for use in phosphor-conversion LED lamp devices. This study examines the correlation between subtle structural changes and photoluminescent behaviour in some of these materials. In order to ascertain whether cation charge compensation has any influence on structure and subsequent photoluminescent behaviour, a comparison was carried out between phases with the nominal compositions Sr{sub 2.975}Ce{sub 0.025}AlO{sub 4}F and Sr{sub 2.95}Ce{sub 0.025}Na{sub 0.025}AlO{sub 4}F using structural characterisation based upon high-resolution neutron powder diffraction (NPD) data. Additionally, NPD data has been used to elucidate the role of different M cations in these materials, using Sr{sub 2.25}Ba{sub 0.6}Eu{sub 0.1}M{sub 0.95}In{sub 0.05}O{sub 4-{alpha}}F{sub 1-{delta}} (M=Al, Ga) to determine the effect M cation size has on structure and photoluminescent properties. - Graphical abstract: The structure of Sr3-xAxMO4F (A=Ca, Ba and M=Al, Ga) and excitation and emission spectra for Sr{sub 2.25}Ba{sub 0.6}Eu{sub 0.1}Ga{sub 0.95}In{sub 0.05}O{sub 4-{alpha}}F{sub 1-{delta}}. Highlights: Black-Right-Pointing-Pointer Correlation between structural changes and photoluminescence in Sr{sub 3-x}A{sub x}MO{sub 4}F (A=Ca, Ba, M=Al, Ga). Black-Right-Pointing-Pointer Comparison of Sr{sub 2.975}Ce{sub 0.025}AlO{sub 4}F and Sr{sub 2.95}Ce{sub 0.025}Na{sub 0.025}AlO{sub 4}F using high-resolution NPD. Black-Right-Pointing-Pointer Study of the effect of cation charge-compensation on structure and photoluminescent behaviour. Black-Right-Pointing-Pointer Examination of high-resolution NPD data for Sr{sub 2.25}Ba{sub 0.6}Eu{sub 0.1}M{sub 0.95}In{sub 0.05}O{sub 4-{alpha}}F{sub 1-{delta}} (M=Al, Ga). Black-Right-Pointing-Pointer Determination of the effect M cation size has on structure and photoluminescent properties.

  8. Preparation of Tl sub 2 Ba sub 2 CaCu sub 2 O sub 8 superconducting thin films on LaAlO sub 3 substrates from metalorganic-chemical-vapor-deposition-prepared precursor films

    SciTech Connect

    Ladd, J.A.; Collins, B.T.; Matey, J.R. ); Zhao, J.; Norris, P. )

    1991-09-09

    Single phase Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8} thin films have been deposited on single-crystal LaAlO{sub 3} substrates, (100) orientation, via a two-step deposition process. First, Ba-Ca-Cu-O precursor films were deposited by metalorganic chemical vapor deposition (MOCVD) using barium, calcium, and copper-tetramethyl-heptanedionate, (tmhd){sub 2}, source materials under reduced pressure in an oxygen/argon atmosphere. Substrate temperatures were between 500 and 600 {degree}C. Thallium was then incorporated by heating the films in a confined surface configuration with an unfired pellet of Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub {ital x}} composition at 870 {degree}C for 0.1 h. The resultant films (0.5--1 {mu}m thick) showed a preferred orientation with the {ital c} axis normal to the substrate. The superconducting properties were characterized by resistance and mutual inductance versus temperature and by critical current measurements. Zero resistance temperatures as high as 98 K and {ital J}{sub {ital c}} values close to 1{times}10{sup 4} A/cm{sup 2} at 77 K were observed.

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

    SciTech Connect

    Mikhailenko, Natalia; Stefanovsky, Sergey

    2007-07-01

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

  10. Crystallization control for remediation of an FetO-rich CaO-SiO2-Al2O3-MgO EAF waste slag.

    PubMed

    Jung, Sung Suk; Sohn, Il

    2014-01-01

    In this work, the crystallization behavior of synthesized FetO-rich electric arc furnace (EAF) waste slags with a basicity range of 0.7 to 1.08 was investigated. Crystal growth in the melts was observed in situ using a confocal laser scanning microscope, and a delayed crystallization for higher-basicity samples was observed in the continuous cooling transformation and time temperature transformation diagrams. This result is likely due to the polymerization of the melt structure as a result of the increased number of network-forming FeO4 and AlO4 units, as suggested by Raman analysis. The complex incorporation of Al and Fe ions in the form of AlO4 and FeO4 tetrahedral units dominant in the melt structure at a higher basicity constrained the precipitation of a magnetic, nonstoichiometric, and Fe-rich MgAlFeO4 primary phase. The growth of this spinel phase caused a clear compositional separation from amorphous phase during isothermal cooling at 1473 K leading to a clear separation between the primary and amorphous phases, allowing an efficient magnetic separation of Fe compounds from the slag for effective remediation and recycling of synthesized EAF waste slags for use in higher value-added ordinary Portland cement. PMID:24410350

  11. Selective Crystallization Behavior of CaO-SiO2-Al2O3-MgO-FetO-P2O5 Steelmaking Slags Modified through P2O5 and Al2O3

    NASA Astrophysics Data System (ADS)

    Wang, Zhanjun; Sun, Yongqi; Sridhar, Seetharaman; Zhang, Mei; Guo, Min; Zhang, Zuotai

    2015-10-01

    In this study, the selective crystallization behavior of synthetic FetO-rich steelmaking slags modified by P2O5 and Al2O3 additions was explored using non-isothermal differential scanning calorimetry, X-ray diffraction, and field emission scanning electron microscopy techniques. Continuous cooling transformation diagrams of Fe-enriched and P-enriched phases were constructed. It was found that P2O5 addition can suppress the crystallization due to the increasing viscosity caused by increasing degree of polymerization; however, an increase of Al2O3 content accelerated the precipitation of dystectic MgFeAlO4, copolymerized by [AlO4]-tetrahedra and [FeO4]-tetrahedra units. It was also noted that the content of phosphorus in P-enriched phase can reach a high value as 28.71 wt pct for the slags modified by 15.17 wt pct Al2O3. The non-isothermal crystallization kinetics derived from activation energy and the structure of the slags explained by Raman spectra were further analyzed, which was well in accordance with the above analysis.

  12. Effect of Ground Rubber vs. ZnSO4 on Spinach Accumulation of Cd from Cd-Mineralized California Soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Certain soils derived from marine shale in Salinas Valley, CA, USA, contain significant levels of natural Cd but normal levels of Zn, all derived from the soil parent materials. Crops grown on these soils contain high levels of Cd, and because of the high Cd:Zn, this Cd is highly bioavailable and a...

  13. SUMMAR OF DISCUSSIONS OF USES OF THE ADVANCED LIGHT SOURCE (ALS)FOR EARTH SCIENCES RESEARCH: WORKSHOP REPORT OF THE ALS USERS'ASSOCIATION ANNUAL MEETING, LAWRENCE BERKELEY LABORATORY, BERKELEY,CA,JUNE 2-3, 1988

    SciTech Connect

    Dillard, J.; Wallenberg, H.; Perry, D.

    1988-09-01

    A workshop to discuss opportunities for research using the Advanced Light Source (ALS) was held as a part of the first annual ALS users meeting at the Berkeley Convention Center, Berkeley, California, June 2--3, 1988. The participants were from university and governmental laboratories, and some of those attending had had experience using synchrotron light sources. Because the Earth Science interests had not been voiced or considered in previous workshops or meetings of the ALS groups, it was the principal task of the group to explore the capabilities of the ALS appropriate to the Earth Sciences, to identify areas of research where the ALS would be of significant benefit, and to provide input regarding desired insertion devices. Discussions of synchrotron radiation phenomena and applications of synchrotron radiation in earth sciences have been highlighted in the literature and in a recent report of a workshop held at Argonne National Laboratory. A summary outline of some typical potential uses and the information to be gained from the use of synchrotron radiation is given. This is not an exhaustive list of earth sciences applications, but indicates the breadth of applications that can be addressed: (A) X-Ray Absorption Near Edge Structure (XANES) Spectroscopy (Oxidation state of elements; Coordination number of metal ions); (B) Extended X-Ray Absorption Fine Structure (EXAFS) Spectroscopy (Glasses and other disordered structures; Solutions; Gels -- silicates, aluminates; Clays -- swelling phenomena, intercation chemistry; Adsorption -- speciation, chemical reactions, kinetics; Polyhedral linkages -- Fe, Mn oxides); (C) Energy Dispersive X-Ray Diffraction (Mineral transformations vs temperature and pressure); (D) Small Angle Scattering (Precipitation phenomena); (E) X-Ray Microprobe (Element mapping). Comments and discussion at the ALS meeting identified the principal areas of interest for earth scientists as: adsorption phenomena; nucleation processes; gel structure

  14. On the Production of He, Ne, and AR Isotopes from Mg, Al, Si, Ca, Fe, and NI in an Artificially Irradiated Meteoroid

    NASA Astrophysics Data System (ADS)

    Wieler, R.; Signet, P.; Rosel, R.; Herpers, U.; Lupke, M.; Lange, H.-J.; Michel, R.

    1992-07-01

    The production of He, Ne, and Ar isotopes from their main target elements was investigated in an experiment (1) by irradiating a 50-cm-diameter gabbro sphere isotropically with 1.6 GeV protons. The model meteoroid contained, among a large number of other targets, pure element foils of Mg, Al, Si, Fe, and Ni at 10 different depths and wollastonite targets at 3 different depths in central bores. After the irradiation, radionuclide production in these targets was measured by gamma spectrometry. Stable He, Ne, and Ar isotopes were measured in statically operated mass spectrometers. Here, we report the results for stable He, Ne, and Ar isotopes and for ^22Na. The production depth profiles vary widely, ranging from profiles with near-surface production 15% higher than in the center (^22Na from Fe) to such profiles with production in the center 45% higher than near the surface (^20Ne from Mg). The isotope ratios ^3He/^4He and ^3He/^21Ne in Mg, Al, Si and ^22Ne/^21Ne in Mg all decrease significantly with increasing shielding. The production rates of He, Ne, and ^22Na from Mg, Al, and Si in the 1600-MeV simulation experiment are 1.5 to 3 times higher than in the model meteoroid of similar size but irradiated earlier with 600 MeV protons (2). This increase is attributed to the increase of the production of secondary neutrons with primary energies rising from 600 to 1600 MeV. This effect also causes the depth dependences of isotope ratios observed in the 1600-MeV simulation that was not seen in the 600-MeV experiment. Model calculations of the production of He, Ne, and Ar isotopes and of ^22Na were performed for the artificial meteorites of the 600- and 1600 MeV-exposures as well as for real meteoroids. Production rates were calculated from depth-dependent p- and n- spectra, which were derived by Monte Carlo techniques using the HERMES code system (3), and from cross sections for the relevant nuclear reactions as described earlier (4). The cross section database for p

  15. Lattice constant grading in the Al.sub.y Ca.sub.1-y As.sub.1-x Sb.sub.x alloy system

    DOEpatents

    Moon, Ronald L.

    1981-01-01

    Liquid phase epitaxy is employed to grow a lattice matched layer of GaAsSb on GaAs substrates through the compositional intermediary of the III-V alloy system AlGaAsSb which acts as a grading layer. The Al constituent reaches a peak atomic concentration of about 6% within the first 2.5.mu.m of the transition layer, then decreases smoothly to about 1% to obtain a lattice constant of 5.74 A. In the same interval the equilibrium concentration of Sb smoothly increases from 0 to about 9 atomic percent to form a surface on which a GaAsSb layer having the desired energy bandgap of 1.1 ev for one junction of an optimized dual junction photovoltaic device. The liquid phase epitaxy is accomplished with a step cooling procedure whereby dislocation defects are more uniformly distributed over the surface of the growing layer.

  16. Reactions of low work function metals Na, Al, and Ca on α,ω-diphenyltetradecaheptaene. Implications for metal/polymer interfaces

    NASA Astrophysics Data System (ADS)

    Dannetun, P.; Lögdlund, M.; Fredriksson, C.; Lazzaroni, R.; Fauquet, C.; Stafström, S.; Spangler, C. W.; Bredás, J. L.; Salaneck, W. R.

    1994-05-01

    The interactions between different low work function metals aluminium, calcium and sodium, and α,ω-diphenyltetradecaheptaene, a model molecule for certain conjugated polymers, have been investigated using both x-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. The spectra are interpreted with the help of the results of quantum chemical calculations performed within the local spin density (LSD) approximation methodology. The metals are found to interact with the conjugated system in very different ways. Aluminium forms a covalent bond, which strongly modifies the π-electronic structure of the conjugated molecule, while both the sodium and the calcium atoms act as doping agents, inducing new states in the otherwise forbidden bandgap. These new gap states can be viewed as a soliton-antisoliton pair for the Na/DP7 and a bipolaronic-like defect for Ca/DP7.

  17. Pronounced matrix effect in YbMo{sub 2}Al{sub 4}-type Ca(Au{sub x}Zn{sub 2−x})Au{sub 4} (x=0.09–0.89)

    SciTech Connect

    Mishra, Trinath; Lin, Qisheng; Corbett, John D.

    2014-10-15

    Electron-poor polar intermetallics Ca(Au{sub x}Zn{sub 2−x})Au{sub 4} have been synthesized through fusion of stoichiometric metals in sealed tantalum tubes at 800 °C and annealing at 400 °C for one week. Single crystal X-ray diffraction analyses reveal that this phase belongs to the YbMo{sub 2}Al{sub 4}-type structure (I4/mmm, Pearson symbol tI14), a≈6.943–7.017 Å, c≈5.278–5.286 Å, Z=2, with homogeneous composition range of x=0.09(1)–0.89(1). The structure exhibits a three-dimensional framework of (Au{sub 8}){sub 1/2} featuring square and octagonal channels extending in c, in which Ca and the infinite linear chains of [(Au,Zn){sub 2}]{sub 1/2} are located, respectively. Mulliken population analyses demonstrate that Zn prefers to form the linear chains in the whole homogeneous composition range, consistent with experimental observations. Crystal orbital Hamilton population (COHP) analyses reveal that the channel-to-chain Au–Zn contact has strong bonding interactions regardless of its large interatomic distance (∼2.85 Å), a signature of pronounced matrix effect. The last mentioned effect in YbMo{sub 2}Al{sub 4}-type structures is expected in case the linear chains are defined by small size atoms. - Graphical abstract: Pronounced matrix effect incurred by Au–Au bonding within the gold substructure in Ca(Au{sub x}Zn{sub 2−x})Au{sub 4} results in an elongation of the channel-to-chain Au–Zn interatomic distance without weakening bonding interactions. - Highlights: • The complete solid solution of Ca(Au{sub x}Zn{sub 2−x})Au{sub 4} was accomplished. • Site preference was explained by “coloring” analyses. • Abnormally large Au–Zn distance but with strong bonding was observed. • Pronounced matrix effect incurred by Au–Au bonding in gold substructure was found.

  18. The effect of SiO2/Al2O3 ratio on the structure and microstructure of the glazes from SiO2-Al2O3-CaO-MgO-Na2O-K2O system

    NASA Astrophysics Data System (ADS)

    Partyka, Janusz; Sitarz, Maciej; Leśniak, Magdalena; Gasek, Katarzyna; Jeleń, Piotr

    2015-01-01

    Ceramic glazes are commonly used to covering of the facing surface of ceramics ware. A well-chosen oxide composition and firing conditions of glazes causes significant improvement of technical parameters of ceramic products. Modern glazes are classified as glass-ceramic composites with different crystalline phases arising during firing. The presence of crystals in the glass matrix is influenced by many factors, especially by oxides molar composition. A crucial role is played by the molar ratio of SiO2/Al2O3. In this work the six composition of glazes from SiO2-Al2O3-CaO-MgO-Na2O-K2O system were examined. The only variable is the ratio of the silicon oxideto alumina at a constant content of other components: MgO, CaO, K2O, Na2O, ZnO. In order to determine the real phase composition of the obtained glazes research on fluorescence spectrometer (XRF) were done. For structural studies X-ray diffraction (XRD) and spectroscopic in the middle infrared (MIR) were performed. In order to determine the state of the surface (microstructure) research on the scanning electron microscope (SEM) with EDX. The research allowed to determine the influence of SiO2/Al2O3 ratio on the structure and phase composition of glazes and the nature, and type of formed crystalline phases.

  19. The layered antimonides RELi{sub 3}Sb{sub 2} (RE=Ce–Nd, Sm, Gd–Ho). Filled derivatives of the CaAl{sub 2}Si{sub 2} structure type

    SciTech Connect

    Schäfer, Marion C.; Suen, Nian-Tzu; Raglione, Michaella; Bobev, Svilen

    2014-02-15

    Reported are the synthesis and the structural characterization of an extended family of rare-earth metal–lithium–antimonides with the formula RELi{sub 3}Sb{sub 2} (RE=Ce–Nd, Sm, Gd–Ho). They crystallize in the trigonal space group P3{sup ¯}m1 (No. 164, Pearson symbol hP6) with a structure, best viewed as a filled derivative of the common CaAl{sub 2}Si{sub 2} structure type (ternary variant of α-La{sub 2}O{sub 3}). Across the series, the lattice parameters monotonically decrease, following the lanthanide contraction. Temperature-dependent magnetic susceptibility measurements for CeLi{sub 3}Sb{sub 2}, PrLi{sub 3}Sb{sub 2} and TbLi{sub 3}Sb{sub 2} reveal paramagnetic behavior in the high temperature range, and the obtained effective moments are consistent with the expected ones for the free-ion RE{sup 3+} ground state. Possible ferromagnetic ordering for PrLi{sub 3}Sb{sub 2} and antiferromagnetic ordering for TbLi{sub 3}Sb{sub 2} are observed in the low temperature range (below 20 K). Tight-binding muffin-tin orbital electronic band structure calculations for LaLi{sub 3}Sb{sub 2} are presented and discussed as well. - Graphical abstract: The large family of rare-earth metal–lithium–antimonides with the formula RELi{sub 3}Sb{sub 2} (RE=Ce–Nd, Sm, Gd–Ho) crystallize in the trigonal space group P3{sup ¯}m1 (No. 164, Pearson symbol hP6) with a structure that is a filled derivative of the CaAl{sub 2}Si{sub 2} structure type (ternary variant of α-La{sub 2}O{sub 3}). Display Omitted - Highlights: • RELi{sub 3}Sb{sub 2} (RE=Ce–Nd, Sm, Gd–Ho) constitute an extended family of rare-earth metal–lithium–antimonides. • The layered structure is a filled derivative of the common CaAl{sub 2}Si{sub 2} structure type. • The valence electron count follows the Zintl–Klemm rules. • Electronic band structure calculations for LaLi{sub 3}Sb{sub 2} indicate small band-gap semiconducting behavior.

  20. A thermodynamic model for subsolidus equilibria in the system CaO-MgO-Al2O3-SiO2

    NASA Astrophysics Data System (ADS)

    Wood, B. J.; Holloway, J. R.

    1984-01-01

    It is shown that the high temperature enthalpy of solution data for pure phases and solid solutions in the CMAS system are, for 'gabbroic' and 'peridotitic' compositions, consistent with available phase equilibrium data for the MAS, CAS and CMAS systems. A refined set of values of thermodynamic properties for these phases and solid solutions is tabulated. The small differences between the new data set and that of Helgeson et al. (1978) arise from new data on heat capacity and enthalpy being incorporated. The important constraints applied and the major difficulties in fitting which arose are summarized.

  1. Uptake of Al, As, Cr, Cd, Cu, Fe, Mn, Ni, Pb, Sr, and Zn in native wheatgrasses, wildryes, and bluegrass on three metal-contaminated soils from Montana

    Technology Transfer Automated Retrieval System (TEKTRAN)

    One of the biggest challenges to successfully phytoremediate contaminated mineland soils is the identification of native plants that possess a broad adaptation to ecological sites and either exclude or uptake heavy metals of interest. This study evaluated forage concentrations of aluminum (Al), ars...

  2. Pressure effects on resistive transition in (Cu,M)Ba{sub 2}Ca{sub 3}Cu{sub 4}O{sub y} (M = C,Al,Tl,Mg,Zn) superconductors

    SciTech Connect

    Tokiwa, K.; Kunugi, C.; Kashiwagi, H.

    1999-11-01

    Single phase samples with the composition of (Cu,M)Ba{sub 2}Ca{sub 3}Cu{sub 4}O{sub y}(CuM-1234; M = C,Al,Tl,Mg,Zn) have been synthesized using high pressure technique. The authors have measured the pressure dependence of superconducting transition temperature ({Tc}) through in situ resistivity measurements up to 8 GPa for these samples, reproducibly. These samples indicated almost the same {Tc}-enhancement by applied pressure, in spite of their different ambient {Tc} values. The enhancement values of 8--10 K at 8 GPa pressure for these samples are found to be comparable to those of Hg-system and (B,C)-system.

  3. Elucidating the mechanism behind the stabilization of multi-charged metal cations in water: A case study of the electronic states of microhydrated Mg2+, Ca2+ and Al3+”

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2014-04-21

    Metal atoms typically have second and higher ionization potentials (IPs) that are larger than the IP of water, resulting in the Coulombic explosion of the first few [M(H2O)n]+q (q ≥ 2) clusters as the M+ + (H2O)n + or MOH+ + H3O+(H2O)n energy levels are energetically more stable than the M2+ + (H2O)n ones for small n. We present a theoretical analysis of the various electronic states correlating with the above channels that are involved in the sequential hydration of the Ca2+, Mg2+ and Al3+ cations with up to six water molecules that, for the first time, quantifies their relative shift with the degree of solvation accounting for the observed stabilization of those multi-charged metal cations in an aqueous solution. *

  4. Thermodynamic tabulations for selected phases in the system CaO-Al2O3-SiO2-H2 at 101.325 kPa (1 atm) between 273.15 and 1800 K

    USGS Publications Warehouse

    Haas, John L., Jr.; Robinson, Glipin R., Jr.; Hemingway, Bruch S.

    1981-01-01

    The standard thermodynamic properties of phases in the lime‐alumina‐silica‐ water system between 273.15 and 1800 K at 101.325 kPa (1 atm) were evalated from published experimental data. Phases included in the compilation are boehmite, diaspore, gibbsite, kaolinite, dickite, halloysite, andalusite, kyanite, sillimanite, Ca‐Al cliniopyroxene, anorthite, gehlenite, grossular, prehnite, zoisite, margarite, wollastonite, cyclowollastonite ( = pseudowollastonite), larnite, Ca olivine, hatrurite, and rankinite. The properties include heat capacity, entropy, relative enthalpy, and the Gibbs energy function of the phases and the enthalpies, Gibbs energies, and equilibrium constants for formation both from the elements and the oxides. Tabulated values are given at 50 K intervals with the 2‐sigma confidence limit at 250 K intervals. Summaries for each phase give the temperature‐ dependent functions for heat capacity, entropy, and relative enthalpy and the experimental data used in the final evaluation.

  5. CaO-MgO-Al2O3-SiO2 (CMAS) corrosion of Gd2Zr2O7 and Sm2Zr2O7

    DOE PAGESBeta

    Wang, Honglong; Bakal, Ahmet; Zhang, Xingxing; Tarwater, Emily; Sheng, Zhizhi; Fergus, Jeffrey W.

    2016-08-08

    Ceramic thermal barrier coatings are applied to superalloys used in gas turbine engineering to increase the operating temperature and the energy conversion efficiency. However, dust consisting of CaO-MgO-Al2O3-SiO2 (CMAS) from the air can be injected into the engines and corrode the thermal barrier coatings. Lanthanide zirconates are promising materials in thermal barrier coatings due to their low thermal conductivities, good phase stability and good corrosion resistance. However, the corrosion resistance mechanism of CMAS on lanthanide zirconates is still not clearly understood. In this work, the corrosion mechanism of Gd2Zr2O7 and Sm2Zr2O7 in CMAS is studied. Here, the results show thatmore » the CMAS can easily react with lanthanide zirconate thermal barrier coatings to form a dense layer, which can resist further corrosion« less

  6. Determination of Oxygen Self-Diffusion in Akermanite, Anorthite, Diopside, and Spinel: Implications for Oxygen Isotopic Anomalies and the Thermal Histories of Ca-Al-rich Inclusions

    NASA Astrophysics Data System (ADS)

    Ryerson, F. J.; McKeegan, K. D.

    1993-07-01

    anomalies observed in CAIBs and/or yield improbably long or unrealistically intense thermal histories relative to both current theoretical models of nebular evolution and inferences from other isotopic systems. The failure of these simple models, coupled with recent observations of "disturbed" Mg isotopic abundances and petrographic features in anorthite and melilite indicative of alteration and recrystallization [5,6], suggests that the oxygen isotopic compositions of these phases may have also been modified by alteration and recrystallization during multiple melting events. Because the modal abundance of spinel remains relatively constant for plausible melting scenarios and its relatively sluggish diffusion kinetics prevent substantial equilibration, Mg-Al spinel is a reliable indicator of the oxygen isotopic composition of precursor material that formed CAIBs. References: [1] Connolly C. and Muehlenbachs K. (1988) GCA, 52, 1585-1592. [2] Elphick S. C. et al. (1988) Contrib. Mineral. Petrol., 100, 490-495. [3] Reddy K. P. and Cooper A. R. (1981) J. Am. Ceram. Soc., 64, 368-371. [4] Yunmoto H. et al. (1989) GCA, 53, 2387-2394. [5] Podosek F. A. et al. (1991) GCA, 55, 1083-1110. [6] MacPherson G. J. and Davis A. M. (1993) GCA, 57, 231-243.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

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

    PubMed

    Chang, E; Lee, T M

    2002-07-01

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

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

    PubMed

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

    2011-10-01

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

  10. Crystallization, densification and dielectric properties of CaO–MgO–Al{sub 2}O{sub 3}–SiO{sub 2} glass with ZrO{sub 2} as nucleating agent

    SciTech Connect

    Hsiang, Hsing-I; Yung, Shi-Wen; Wang, Chung-Ching

    2014-12-15

    SEM micrographs for the pure CaO–MgO–Al{sub 2}O{sub 3}–SiO{sub 2} glass sintered at 850–1000 °C (a) 850 °C, (b) 900 °C, (c) 950 °C, (d) 1000 °C. - Highlights: • ZrO{sub 2} effects on the crystallization of LTCC glass system were investigated. • ZrO{sub 2} effects on the dielectric properties of LTCC glass system were investigated. • LTCC with a dielectric constant of 6.65 and a low dielectric loss can be obtained. - Abstract: The zirconium oxide effects on the crystallization and dielectric properties of CaO–MgO–Al{sub 2}O{sub 3}–SiO{sub 2} (CMAS) glass were investigated. The results showed that phyllosiloxide and anorthite crystallites were observed in sequence during sintering. For glass added with 8 wt% ZrO{sub 2}, homogeneously dispersed tetragonal ZrO{sub 2} crystallites were observed at 850 °C. The as-prepared CMAS glass–ceramics exhibited a dielectric constant of about 6–7 and a dielectric loss below 0.005 at 100 MHz. The dielectric properties of CMAS glass with 8 wt% ZrO{sub 2} sintered at 850 °C show a low dielectric constant of 6.65 and a dielectric loss tangent of about 2.5 × 10{sup −3}, which provides a promising candidate for LTCC applications.

  11. Crystal and electronic structures of CaAl 2Si 2-type rare-earth copper zinc phosphides RECuZnP 2 ( RE=Pr, Nd, Gd-Tm, Lu)

    NASA Astrophysics Data System (ADS)

    Blanchard, Peter E. R.; Stoyko, Stanislav S.; Cavell, Ronald G.; Mar, Arthur

    2011-01-01

    The quaternary rare-earth phosphides RECuZnP 2 ( RE=Pr, Nd, Gd-Tm, Lu) have been prepared by reaction of the elements at 900 °C, completing this versatile series which forms for nearly all RE metals. They adopt the trigonal CaAl 2Si 2-type structure (Pearson symbol hP5, space group P3¯ m1, Z=1), as confirmed by single-crystal X-ray diffraction analysis on ErCuZnP 2 and powder X-ray diffraction analysis on the remaining members. The Cu and Zn atoms are assumed to be disordered over the single transition-metal site. Band structure calculations on a hypothetically ordered YCuZnP 2 model suggest a semimetal, with a zero band gap between the valence and conduction bands. This electronic structure is supported by XPS valence band spectra for RECuZnP 2 ( RE=Gd-Er), in which the intensity drops off smoothly at the Fermi edge. The absence of a band gap permits the electron count to deviate from the precise value of 16 e - per formula unit, as demonstrated by the formation of a solid solution in GdCu xZn 2- xP 2 (1.0≤ x≤1.3), while still retaining the CaAl 2Si 2-type structure. Because the Cu 2 p XPS spectra indicate that the Cu atoms are always monovalent, the substitution of Cu for Zn leads to a decrease in electron count and a lowering of the Fermi level in the valence band. The magnetic susceptibility of RECuZnP 2 ( RE=Gd-Er), which obeys the Curie-Weiss law, confirms the presence of trivalent RE atoms.

  12. Esperanzaite, NaCa2Al2(As5+O4)2F4(OH)*2H2O, a new mineral species from the La Esperanza mine, Mexico: descriptive mineralogy and atomic arrangement

    USGS Publications Warehouse

    Foord, E.E.; Hughes, J.M.; Cureton, F.; Maxwell, C.H.; Falster, A.U.; Sommer, A.J.; Hlava, P.F.

    1999-01-01

    Esperanzaite, ideally NaCa2Al2(As5+O4)2F4(OH)??2H2O, Z = 2, is a new mineral species from the La Esperanza mine, Durango State, Mexico. The mineral occurs as blue-green botryoidal crystalline masses on rhyolite, with separate spheres up to 1.5 mm in diameter. The Mohs hardness is 4 1/2 , and the specific gravity, 3.24 (obs.) and 3.36(3) (calc.). Optical properties were measured in 589 nm light. Esperanzaite is biaxial (-), X = Y = Z = colorless, ?? 1.580(1), ?? 1.588(1), and ?? 1.593(1); 2V(obs) is 74(1)??and 2V(calc) is 76.3??. The dispersion is medium, r < v, and the optic axes are oriented according to a ?? Z = +50.5??, b = Y, c ?? X = +35??. The strongest five X-ray-diffraction maxima in the powder pattern [d in A??(I)(hkl)] are: 2.966(100)(131, 311, 031), 3.527(90)(220), 2.700(90)(221,002,040), 5.364(80)(001,020) and 4.796(80)(011). Esperanzaite is monoclinic, a 9.687(5), b 10.7379(6), c 5.5523(7) A??, ?? 105.32(1)??, space group P21/m. The atomic arrangement of esperanzaite was solved by direct methods and Fourier analysis (R = 0.032). The Fundamental Building Block (FBB) is formed of [001] stacks of heteropolyhedral tetramers; the tetramers are formed of two arsenate tetrahedra and two Al octahedra, corner-linked in four-member rings. The FBBs are linked by irregular Na??5 and Ca??8 polyhedra.

  13. Phase relations of CaAl 4Si 2O 11 at high-pressure and high-temperature with implications for subducted continental crust into the deep mantle

    NASA Astrophysics Data System (ADS)

    Zhai, Shuangmeng; Ito, Eiji

    2008-04-01

    Phase relations of the CAS phase, CaAl 4Si 2O 11, have been investigated at pressures of 10-23 GPa and at temperatures of 1000-1600 °C by means of the quench method using the Kawai-type high-pressure apparatus. An assemblage of grossular (Gr) + corundum (Cor) + kyanite (Ky) is stable up to about 10 GPa and at the temperatures examined. The assemblage converts into the CAS phase at 1600 °C and higher pressures. Below 1450 °C, however, the assemblage first changes to that of Gr + Cor + stishovite (St), corresponding to the dissociation of Ky into Cor + St, and then converts to the CAS phase with increasing pressure. The Gr + Cor + St-CAS boundary has a negative d P/d T slope, and the Gr + Ky + Cor-CAS boundary has a near horizontal slope. The triple point at which Gr, Cor, Ky, St and the CAS phase coexist is located at around 11.5 GPa and 1450 °C. Stability of the CAS phase up to 23 GPa and 1600 °C indicates that the CAS phase is an important host of Al and Ca in the continental crust subducted into deep mantle. Comparison of the densities between the pyrolitic mantle and the subducted continental crust indicates that the continental crust provides a plunging force to the slab subducted into the upper mantle and transition zone, whereas the continental crust in turn gives a buoyancy in the lower mantle as the consequence of the substantial changes in mineral assemblage in both the continental crust and pyrolitic mantle through the 660 km discontinuity. The formation of the CAS phase plays an important role in changing the density of the subducting continental crust.

  14. A vibrational spectroscopic study of the phosphate mineral whiteite CaMn(++)Mg2Al2(PO4)4(OH)2·8(H2O).

    PubMed

    Frost, Ray L; Scholz, Ricardo; López, Andrés; Xi, Yunfei

    2014-04-24

    Vibrational spectroscopy enables subtle details of the molecular structure of whiteite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. The infrared and Raman spectroscopy were applied to compare the molecular structure of whiteite with that of other phosphate minerals. The Raman spectrum of whiteite shows an intense band at 972 cm(-1) assigned to the ν1PO4(3-) symmetric stretching vibrations. The low intensity Raman bands at 1076 and 1173 cm(-1) are assigned to the ν3PO4(3-) antisymmetric stretching modes. The Raman bands at 1266, 1334 and 1368 cm(-1) are assigned to AlOH deformation modes. The infrared band at 967 cm(-1) is ascribed to the PO4(3-)ν1 symmetric stretching vibrational mode. The infrared bands at 1024, 1072, 1089 and 1126 cm(-1) are attributed to the PO4(3-)ν3 antisymmetric stretching vibrations. Raman bands at 553, 571 and 586 cm(-1) are assigned to the ν4 out of plane bending modes of the PO4(3-) unit. Raman bands at 432, 457, 479 and 500 cm(-1) are attributed to the ν2 PO4 and H2PO4 bending modes. In the 2600 to 3800 cm(-1) spectral range, Raman bands for whiteite are found 3426, 3496 and 3552 cm(-1) are assigned to AlOH stretching vibrations. Broad infrared bands are also found at 3186 cm(-1). Raman bands at 2939 and 3220 cm(-1) are assigned to water stretching vibrations. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of whiteite to be ascertained and compared with that of other phosphate minerals. PMID:24491665

  15. How is Cd Incorporated in Biominerals Eliminated by Tobacco Trichomes?

    NASA Astrophysics Data System (ADS)

    Hokura, Akiko

    In tobacco plants, elimination of Zn and Cd via the production of Ca-containing grains at the top of leaf hair