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Now showing items 65 - 80 of 6688

  • Site-related near-infrared luminescence in MAl12O19 (M=Ca, Sr, Ba):Fe3+ phosphors

    Li, Y.J.   Ma, Y.Y.   Ye, S.   Hu, G.P.   Zhang, Q.Y.  

    Intense and broad near-infrared (NIR) photoluminescence (PL) peaks locating at 777, 808 and 810 nm is observed for BaAl 12O 19 (BA 6):1%Fe 3+, CaAl 12O 19 (CA 6):1%Fe 3+ and SrAl 12O 19 (SA 6):1%Fe 3+, respectively. Electron paramagnetic resonance (EPR) spectra show that Fe 3+ ions substitute for the different types of Al 3+ sites simultaneously. Meanwhile, the luminescence of Fe 3+ in MAl 12O 19 (M = Ca, Sr and Ba) are ascribed to octahedral Fe 3+. In addition, the site symmetry of Fe 3+ in CA 6/SA 6 is lower compared with BA 6, deduced from the photoluminescence excitation (PLE), EPR and Fourier-transform infrared (FT-IR) spectra. These phosphors can be considered as good candidates for the applications in the field of high-resolution bioimaging. [All rights reserved Elsevier].
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  • Luminescence of Pb2+in MAl2B2O7(M = Ca, Sr)

    ?lhan Pekg?zlü   Sülin Ta?c??lu   Ayhan Menger  

    Pb 2+ doped SrAl 2B 2O 7 was prepared by solution combustion synthesis. The synthesized material was determined by powder XRD. The photoluminescence properties of the synthesized phosphor were investigated at room temperature using a spectrofluorometer. The emission peak of Pb 2+ doped SrAl 2B 2O 7 was observed at 420 nm upon excitation at 277 nm. The Stokes shift of SrAl 2B 2O 7:Pb 2+ was calculated to be 12292 cm -1. The luminescence behavior of Pb 2+ in both SrAl 2B 2O 7 and CaAl 2B 2O 7 was discussed.
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  • Luminescence studies of MBrCl: Eu(2+) (M=Ca, Sr, Ba)

    Meng Xianguo   Wang Yongsheng   He Dawei  

    Europium doped MBrCl (M=Ca, Sr, and Ba) phosphors were prepared by solid state reaction in reductive atmosphere. Photoluminescence (PL), photostimulated luminescence (PSL) after X-ray irradiation and optical absorption studies of MBrCl:Eu(2+) (M=Ca, Sr, and Ba) revealed that: (1) blue light emission, under the excitation of 300 nm, was observed in all these phosphors; (2) the shape of the emission spectra in CaBrCl:Eu(2+) could be changed by varying the bromine/chlorine ratio during synthesis, while that in SrBrCl:Eu(2+) and BaBrCl:Eu(2+) showed no change; and (3) PSL was observed in SrBrCl:Eu(2+) and BaBrCl:Eu(2+) after X-ray irradiation. Difference absorption spectrum (DAS) in SrBrCl:Eu(2+) showed two broad bands centered at about 470 and 570 nm, and DAS in BaBrCl:Eu(2+) showed two bands at about 550 and 675 nm, respectively. This enabled the use of He-Ne laser (633 nm) or even semiconductor light-emitting diodes (LED) instead of gas lasers for photostimulation.
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  • Photoluminescence property of vanadates M2V2O7 (M: Ba, Sr and Ca)

    T. Nakajima   M. Isobe   T. Tsuchiya   Y. Ueda   T. Manabe  

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  • Structure-dependent photocatalytic activities of MWO(4) (M = Ca, Sr, Ba)

    Shan, Zhichao   Wang, Yaoming   Ding, Hanming   Huang, Fuqiang  

    The photocatalytic activities of the isostructural photocatalysts MWO(4) (M = Ca, Sr, Ba) for decomposing methyl orange, which were synthesized by a solid state reaction, were investigated. In the experiments, the photocatalytic activity is in the increasing order of CaWO(4) < SrWO(4) < BaWO(4) under both neutral and acidic conditions. The factors, which influence the photocatalytic processes and the final activity, were analyzed the difference of their photocatalytic behaviors. The further investigation indicates that the higher structural openness degree, corresponding to a lower packing factor, leads to the better photocatalytic activity. (C) 2008 Elsevier B.V. All rights reserved.
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  • Chemistry of the M (M=Fe, Ca, Ba)-Se-H(2)O Systems at 25 degrees C

    Nishimura, Tadahisa   Hata, Ryosuke   Hasegawa, Fumihiko  

    The chemistry of the M (M=Fe, Ca, Ba)-Se-H(2)O systems at 25 degrees C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III)-Se(IV)-H(2)O, Ca-Se(IV,VI)-H(2)O and Ba-Se(IV,VI)-H(2)O systems at 25 degrees C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI) < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high concentration levels of selenium to below 0.1 mg/L.
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  • Endohedral metalloborofullerenes M@B-44 (M =3D Ca,Sr,Ba):a computational investigation

    Yang, Le   Jin, Peng   Hou, Qinghua   Li, Lanlan  

    For the first time, the structures, stabilities and electronic properties of alkaline-earth metal doped B-44 fullerenes were investigated by means of density functional theory calculations. Our results reveal that M@B-44 (M =3D Ca, Sr, Ba) possess endohedral configurations as their lowest energy structures, whereas the exohedral form is favored when metal is Be or Mg. The large binding energies and sizable HOMO-LUMO gap energies of Ca@B-44, Sr@B-44 and Ba@B-44 suggest the considerable possibility to achieve these novel endohedral borofullerenes experimentally. Born-Oppenheimer molecular dynamics (BO-MD) simulations at various temperatures further confirmed the extreme dynamic stabilities of these endohedral complexes. Their bonding patterns were also analyzed in detail. Finally, we simulated their infrared absorption spectra and B-11 nuclear magnetic resonance spectra to help future structural characterization.
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  • Luminescent properties of MMgP(2)O(7):Eu(3+) (M=Ca, Sr, Ba) phosphor

    Wang Rongfang   Zhou Liya   Wang Yilin  

    A series of red phosphors Eu(3+)-doped MMgP(2)O(7) (M=Ca, Sr, Ba) were synthesized by solid-state reaction method. X-ray powder diffraction (XRD) analysis confirmed the formation of pure CaMgP(2)O(7), SrMgP(2)O(7) and BaMgP(2)O(7) phase. Photoluminescence spectra of MMgP(2)O(7) (M=Ca, Sr, Ba):Eu(3+) phosphors showed a strong excitation peak at around 400 nm, which was coupled with the characteristic emission (350-400 nm) from UV light-emitting diode. The CaMgP(2)O(7):Eu(3+), SrMgP(2)O(7):Eu(3+) and BaMgP(2)O(7):Eu(3+) phosphors showed strong emission bands peaking at 612, 593 and 587 nm, respectively. Due to the difference of the ion sizes between Ba(2+) (0.142 nm), Sr(2+) (0.126 nm), Ca(2+) (0.112 nm), Mg(2+) (0.072 nm) and Eu(3+) (0.107 nm), Eu(3+) ions were expected to substitute for different sites in CaMgP(2)O(7), SrMgP(2)O(7) and BaMgP(2)O(7) lattice.
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  • Luminescence studies of MBrCl: Eu2+ (M=Ca, Sr, Ba)

    Xianguo MENG   Yongsheng WANG   Dawei HE  

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  • Electrical conductivity and thermal expansion behavior of MMoO4 (M=Ca, Sr and Ba)

    Maji, Binoy Kumar   Jena, Hrudananda   Asuvathraman, R.   Kutty, K.V. Govindan  

    Highlights • CaMoO4, SrMoO4 and BaMoO4 are scheelite type oxides exhibit electrical conduction. • These are the interaction products of radio-nuclides in the nuclear fuel cycle. • Decrease in thermal expansion shows decrease in bond strength from CaMoO4 to BaMoO4. • Decrease in σ from CaMoO4 to BaMoO4 is due to decrease in electropositive character. • Diffusion coefficient (D) of oxide ion conduction decreases from CaMoO4 to BaMoO4. Abstract Alkaline earth (Ca, Sr, Ba) molybdates were synthesized by solid state reaction route. The compounds were characterized by powder-XRD, TG–DTA techniques. The electrical conductivities of these compounds were measured by AC-impedance technique at 673–1073 K. The activation energies of electrical conduction of CaMoO4, SrMoO4 and BaMoO4 were found to be 1.29 ± 0.01 eV, 1.33 ± 0.01 eV and 1.31 ± 0.01 eV respectively. The linear thermal expansion of these molybdates was measured by dilatometry. The mean coefficients (αm) of thermal expansion for these compounds were found to be in the range of 9.38 ± 0.18 × 10−6–12.96 ± 0.25 × 10−6 K−1 at 305–1005 K temperature range. The diffusion coefficient (D) values of oxide ion conduction for these molybdates were determined and found to be in the range of 9.48 ± 0.02 × 10−14–3.32 ± 0.01 × 10−10 for CaMoO4, 5.86 ± 0.02 × 10−14–2.50 ± 0.01 × 10−10 for SrMoO4 and 3.46 ± 0.02 × 10−14–1.22 ± 0.01 × 10−10 cm2 s−1 for BaMoO4 at 673–1073 K range of temperature. Graphical abstract
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  • X-ray diffraction study of ErMFe2O5.5(M = Ca, Sr, Ba) double ferrites

    B. K. Kasenov   E. S. Mustafin   M. A. Akubaeva   S. T. Edil’baeva   S. M. Sergazina   R. Sh. Erkasov   E. K. Zhumadilov  

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

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

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  • Synthesis and dehydrogenation of M(AlH4)(2) (M = Mg, Ca) RID A-4971-2011

    Komiya, K.   Morisaku, N.   Shinzato, Y.   Ikeda, K.   Orimo, S.   Ohki, Y.   Tatsumi, K.   Yukawa, H.   Morinaga, M.  

    Mg(AlH4)(2) was synthesized by a metathesis reaction Of MgCl2 and NaAlH4. It was decomposed in the two-step reactions, in agreement with the previous report [1]. The first reaction is characteristic of the decomposition to form MgH2, and the second reaction is the further decomposition of this MgH2 into some aluminum alloy phases. The decomposition temperature of the first reaction could be reduced remarkably when it was mixed with 1-5 mol% TiCl3. For example, in the case of Mg(AlH4)(2) mixed with 5 mol% TiCl3 by ball-milling for 10.8 ks, a large portion of hydrogen was released during the milling at ambient temperature. The decomposition temperature of the first reaction decreased with increasing content of TiCl3 in the specimen. However, the re-hydrogenation reaction scarcely occurred even in the pre-decomposed TiCl3 containing specimen. For example, only 0.3 mass% of hydrogen was absorbed in the 1 mol% TiCl3-doped specimen by exposing it for a long period to the hydrogen atmosphere of 30MPa at 353 K. This result indicates that Mg(AlH4)2 is too unstable to progress the re-hydrogenation reaction smoothly. Therefore, Ca(AlH4)(2) was chosen next, because this seems more stable than Mg(AlH4)(2), judging from the phase stability diagram of complex hydrides proposed by us [2]. Ca(AlH4)(2) was synthesized and its decomposition reactions were investigated in a fundamental manner. (C) 2007 Elsevier B.V. All rights reserved.
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  • Radiation stability of M(1) (-) (x)Pr(x)F(2) (+) (x) (M = Ca, Sr, Ba) crystals

    Boyarintseva, Y.   Shiran, N.   Gektin, A.   Nesterkina, V.   Shimamura, K.   Villora, E.  

    The radiation stability of the mixed crystals M(1) (-) (x)B(x)F(2) (+) (x) (M = Ca, Sr, Ba) depends on types of the alkaline-earth and rare-earth ions. Different to Eu- and Ce-containing systems, M(1) (-) (x)Pr(x)F(2) (+) (x) solid solutions have a low radiation resistance, which may be associated with hole trapping on praseodymium ion according to the reaction Pr(3+) -> Pr(4+) which is typical for praseodymium. The coloration efficiency of M(1) (-) (x)Fr(x)F(2) (+) (x) crystals grows in the row Ca -> Sr -> Ba, which is explained satisfactorily within the model of rare-earth clusters, the structure of which is determined by the ratio of the base alkaline-earth cation to the praseodymium ion radii. (C) 2009 Elsevier Ltd. All rights reserved.
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  • M3V2B10O23 (M = Ca, Sr): Two new vanadoborates with new [V2B10O23]∞ double layers

    Chen, Zhaohui   Liu, Yaqin   Shi, Yunjing   Zhang, Wenyao   Jing, Qun   Fang, Yuan   Dong, Xiaoyu  

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  • Synthesis of nanocomposites based on MO-Bi2O3-B2O3(M = Ca, Sr, Ba) glasses

    A. V. Egorysheva   V. D. Volodin   V. M. Skorikov   G. Yu. Yurkov   N. I. Sorokin  

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