- Electron microscopy and krypton adsorption characterization of high purity LiF powders
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In the present work, a comparative study of LiF powders has been undertaken. Methods for the preparation of well-defined, high-purity LiF powders are reported. Sample characterization is carried out by combining transmission electron microscopy (TEM) with krypton gas adsorption isotherms. LiF crystallites obtained via precipitation in aqueous solutions are perfect regular cubes surrounded by {100} faces. However, fine particles produced by evaporation of LiF powders in an inert gas grow to more complicated polyhedra, surrounded by a predominant plane, which has been identified as a {111} plane.
- Dericbourg J.
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- Stability of Li2CO3 in cathode of lithium ion battery and its influence on electrochemical performance
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Lithium carbonate is an unavoidable impurity at the cathode side. It can react with LiPF6-based electrolyte and LiPF6 powder to produce LiF and CO2, although it presents excellent electrochemical inertness. Samples of Li2CO3-coated and LiF-coated LiNi0.8Co0.1Mn0.1O2 were prepared to compare their influence on a cathode's behavior. After 200 cycles at 1C, in contrast to 37.1% of capacity retention for the Li2CO3-coated material, the LiF-coated LiNi0.8Co0.1Mn0.1O2 retained 91.9% of its initial capacity, which is similar to the fresh sample. This demonstrates that decomposition of Li2CO3 can seriously deteriorate cyclic stability if this occurs during working.
- Bi, Yujing,Wang, Tao,Liu, Meng,Du, Rui,Yang, Wenchao,Liu, Zixuan,Peng, Zhe,Liu, Yang,Wang, Deyu,Sun, Xueliang
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- Orange-Emitting Li4Sr4[Si4O4N6]O:Eu2+ - A Layered Lithium Oxonitridosilicate Oxide
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We report on the structure and properties of the lithium oxonitridosilicate oxide Li4Sr4[Si4O4N6]O:Eu2+ obtained from solid-state metathesis. The crystal structure was solved and refined from single-crystal X-ray data in the space group P42/nmc (No. 137) [Z = 2, a = 7.4833(6), c = 9.8365(9) ?, and R1(obs) = 0.0477]. The structure of Li4Sr4[Si4O4N6]O:Eu2+ is built up from a layered 2D network of SiN3O tetrahedra and exhibits stacking disorder. The results are supported by transmission electron microscopy and energy-dispersive X-ray spectroscopy as well as lattice energy, charge distribution, and density functional theory (DFT) calculations. Optical measurements suggest an indirect band gap of about 3.6 eV, while DFT calculations on a model free of stacking faults yield a theoretical electronic band gap of 4.4 eV. Samples doped with Eu2+ exhibit luminescence in the orange spectral range (λem 625 nm; full width at half-maximum 4164 cm-1 internal quantum efficiency at room temperature = 24%), extending the broad field of phosphor materials research toward the sparsely investigated materials class of lithium oxonitridosilicate oxides.
- Niklaus, Robin,Neudert, Lukas,Stahl, Juliane,Schmidt, Peter J.,Schnick, Wolfgang
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- Crystal Structure and Nontypical Deep-Red Luminescence of Ca3Mg[Li2Si2N6]:Eu2+
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Rare-earth-doped nitridosilicates exhibit outstanding luminescence properties and have been intensively studied for solid-state lighting. Here, we describe the new nitridolithosilicate Ca3Mg[Li2Si2N6]:Eu2+ with extraordinary luminescence characteristics. The compound was synthesized by the solid-state metathesis reaction in sealed Ta ampules. The crystal structure was solved and refined on the basis of single-crystal X-ray diffraction data. Ca3Mg[Li2Si2N6]:Eu2+ crystallizes in the monoclinic space group C2/m (no. 12) [Z = 4, a = 5.966(1), b = 9.806(2), c = 11.721(2) ?, β = 99.67(3)°, V = 675.9(2) ?3] and exhibits a layered anionic network made up of edge- and corner-sharing LiN4 tetrahedra and [Si2N6]10- bow-tie units. The network charge is compensated by Ca2+ and Mg2+ ions. Upon irradiation with UV to blue light, red emission at exceptionally long wavelengths (λem = 734 nm, fwhm ≈2293 cm-1) is observed. According to emission in the near-infrared, application in LEDs for horticultural lighting appears promising.
- Poesl, Christine,Schnick, Wolfgang
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- YHO, an Air-Stable Ionic Hydride
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Metal hydride oxides are an emerging field in solid-state research. While some lanthanide hydride oxides (LnHO) were known, YHO has only been found in thin films so far. Yttrium hydride oxide, YHO, can be synthesized as bulk samples by a reaction of Y2O3 with hydrides (YH3, CaH2), by a reaction of YH3 with CaO, or by a metathesis of YOF with LiH or NaH. X-ray and neutron powder diffraction reveal an anti-LiMgN type structure for YHO (Pnma, a = 7.5367(3) ?, b = 3.7578(2) ?, and c = 5.3249(3) ?) and YDO (Pnma, a = 7.5309(3) ?, b = 3.75349(13) ?, and c = 5.3192(2) ?); in other words, a distorted fluorite type with ordered hydride and oxide anions was observed. Bond lengths (average 2.267 ? (Y-O), 2.352 ? (Y-H), 2.363 ? (Y-D), >2.4 ? (H-H and D-D), >2.6 ? (H-O and D-O), and >2.8 ? (O-O)) and quantum-mechanical calculations on density functional theory level (band gap 2.8 eV) suggest yttrium hydride oxide to be a semiconductor and to have considerable ionic bonding character. Nonetheless, YHO exhibits a surprising stability in air. An in situ X-ray diffraction experiment shows that decomposition of YHO to Y2O3 starts at only above 500 K and is still not complete after 14 h of heating to a final temperature of 1000 K. YHO hydrolyzes in water very slowly. The inertness of YHO in air is very beneficial for its potential use as a functional material.
- Zapp, Nicolas,Auer, Henry,Kohlmann, Holger
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- Study of the reaction dynamics of Li + HF, HCl by the crossed molecular beams method
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The reactions of (I) Li + HF --> LiF + H and (II) Li + HCl --> LiCl + H have been studied by the crossed molecular beams method.Anguylar distributions of product molecules have been measured at 4 collision energies (Ec) ranging from about 2 to 9 kcal/mole and time-of-flight (TOF) measurements of product velocity distributions were made at approximately Ec = 3 and 9 kcal/mole for both reactions (I) and (II).The combined N(Θ) and TOF results were used to generate contour maps of lithium-halide product flux in angle and recoil velocity in the center-of-mass (c.m.) frame.For reaction (I) at Ec = 3 kcal/mole the c.m. angular distribution shows evidence of complex formation with near forward-backward symmetry; slightly favored backward peaking is observed.The shape of this T(θ) indicates there is significant parallel or antiparallel spatial orientation of initial and final orbital angular momentum L and L', even though with H departing L' must be rather small and L ca.J', where J' is the final rotational angular momentum vector.It is deduced that coplanar reaction geometries are strongly favored.At Ec = 8.7 kcal/mole the T(θ) of reaction (I) becomes strongly forward peaked.The product translational energy distributions P(ET') at both these collision energies give an average ET' of ca. 55percent of the total available energy; this appears consistent with a theoretically calculated late exit barrier to reaction.The T(θ) at Ec = 2.9 and 9.2 kcal/mole for reaction (II) are forward-sideways peaked.Most of the available energy (ca. 70percent) goes into recoil velocity at both Ec for LiCl formation.This suggests a late energy release for this 11 kcal/mole exoergic reaction.Both reactions (I) and (II) show evidence of on more than a minor partitioning of energy into product vibrational excitation.Integral reactive cross sections (?R) are evaluated by integrating the product distributions in the c.m. frame and using small angle nonreactive scattering of Li as an absolute calibrant.Values of ?R are: for LiF formation ?R ca. 0.8 Angstroem2 and 0.94 Angstroem2 at Ec = 3 and 8.7 kcal/mole, while for LiCl formation ?R = 27 Angstroem2 and 42 Angstroem2 at Ec = 2.8 and 9.2 kcal/mole, with estimated absolute and relative uncertainties of a factor of 2, and 30percent, respectively.Average opacities for reaction have been estimated from the reaction cross sections and the extent of rotational excitation of products to be about 0.1 for reaction (I) and 1 for reaction (II), for L values allowed to react.These results are discussed in some detail with regard to the kinematic constraints, reaction dynamics, and potential energy surfaces for these two reactions, and related experimental and theoretical works are noted.In addition, angular distributions of nonreactive scattering of Li off HF and HCl are measured at 4 different Ec each. ...
- Becker, Christopher H.,Casavecchia, Piergiorgio,Tiedemann, Peter W.,Valentini, James J.,Lee, Yuan T.
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- Li2B3O4F3, a new lithium-rich fluorooxoborate
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The new lithium fluorooxoborate, Li2B3O 4F3, is obtained by a solid state reaction from LiBO 2 and LiBF4 at 553 K and crystallizes in the acentric orthorhombic space group P212121 (no. 19) with the cell parameters a=4.8915(9), b=8.734(2), and c=12.301(2) A. Chains of fluorinated boroxine rings along the b axis consists of BO3 triangles and BO2F2 as well as BO3F tetrahedra. Mobile lithium ions are compensating the negative charge of the anionic chain, in which the fourfold coordinated boron atoms bear a negative formal charge. Annealing Li2B3O4F3 at temperatures above 573 K leads to conversion into Li2B6O9F 2. The title compound is an ionic conductor with the highest ion conductivity among the hitherto know lithium fluorooxoborates, with conductivities of 1.6×10-9 and 1.8×10-8 S cm-1 at 473 and 523 K, respectively.
- Pilz, Thomas,Nuss, Hanne,Jansen, Martin
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- PREPARATION OF HIGHLY PURE LITHIUM AND SODIUM FLUORIDES USING SOLVENT EXTRACTION.
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LiF and NaF can be purified by solvent extraction. The impurity concentrations in the purified NaF are 2. 5 ng g** minus **1 for chromium, 60 ng g** minus **1 for iron, 0. 03 ng g** minus **1 for cobalt, and 1. 5 ng g** minus **1 for copper. The concentra
- Kobayashi
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- Pyrolytic synthesis and Eu3+→Eu2+ reduction process of blue-emitting perovskite-type BaLiF3:Eu thin films
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Perovskite-type barium lithium fluoride (BaLiF3) was synthesized by pyrolysis of metal trifluoroacetates. The reaction temperature necessary for producing a single-phase material was found to be 600°C, which was lower than that for a conventional solid-state reaction or a melting method. Eu-doped BaLiF3 was also prepared and characterized to examine the suitability of trifluoroacetates for precursors in synthesizing homogeneous complex metal fluoride materials. It was demonstrated that trivalent Eu3+, which was used as acetate for a starting material, was reduced to divalent Eu2+ in the pyrolysis process of BaLiF 3, as indicated by a broad blue emission due to an allowed 4f 65d→4f7 transition at 408nm with a ultraviolet excitation at 254nm. The concentration quenching of the blue emission occurred at 5at% of Eu in BaLiF3, indicating that Eu was homogeneously dispersed in the BaLiF3 host lattice. Mechanisms of the formation and reduction process of BaLiF3 were discussed based on pertinent chemical reactions.
- Fujihara, Shinobu,Kishiki, Yoko,Kimura, Toshio
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- Flux crystal growth, structure, magnetic and optical properties of a family of alkali uranium(IV) phosphates
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A family of alkali uranium(IV) phosphates, AU2(PO4)3 (A = Li – Cs), was synthesized as single crystals by the reaction of US2 and (NH4)2HPO4 in the respective ACl (A = Li – Cs) flux contained in a sealed fused-silica tube at 850 °C, and as phase pure powders from a similar reaction using UF4 as the uranium source. AU2(PO4)3 (A = Li – Rb) crystallize in the NaTh2(PO4)3 (NTP) structure type with monoclinic space group C2/c and consist of a 3D structure that features a framework composed of edge- and corner-sharing polyhedra. The cesium analogue, CsU2(PO4)3, crystallizes in a different structure with space group P21/n that is related to the NaZr2(PO4)3 (NZP) structure type and consists of a framework composed of corner-sharing polyhedra. Two new alkali uranium phosphates, Li2U(PO4)2 and Cs4U4(P2O7)5, were also grown as single crystals at 700 °C. Li2U(PO4)2 was isolated in approximately 30% yield based on uranium. Li2U(PO4)2 crystallizes in space group P21/c exhibiting a layered structure while Cs4U4(P2O7)5, crystallizes in space group P21/n in a new structure type featuring a 3D framework. The magnetic susceptibilities and the field dependent magnetizations were measured for AU2(PO4)3 (A = Li, Na, K and Cs); all compounds exhibited negative Weiss temperatures with no obvious antiferromagnetic transition. Optical properties were measured by UV–vis and IR spectroscopy.
- Usman, Mohammad,Morrison, Gregory,Klepov, Vladislav V.,Smith, Mark D.,zur Loye, Hans-Conrad
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- Effect of synthesis temperature on morphological and luminescent properties of lithium fluoride crystals
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The precipitation method was used to synthesize pure lithium fluoride crystals using water as solvent at different synthesis temperature, from 10 to 90 °C. The effect of temperature on crystalline structure, sizes of cube like particles, and the luminescent response is reported. The synthesized materials were characterized by scanning electron m icro scopy and their morphology and size distributions were determined. Particle sizes were found to be de pendent on the synthesis temperature, varying from 1.38 to 9.01 μm. A single cubic cr ystalline phase was determined by X-ray diffraction (XRD) for all synthesized samples. The photoluminescence (PL) spectra as well as UV-Vis absorbance were also analyzed and showed a clear dependence with the particle size. The thermoluminescent (TL) response to X-ray irradiation was studied for an exposition of 43 R. A TL intensity dependence of lithium fluoride crystals with the synthesis temperature is observed. The micro crystalline cube size can be controlled by varying the synthesis temperature.
- Vallejo, Miguel A.,Rivera, Esteban,Azorín, Juan C.,Bernal, Jesús,Camacho, Cristhoper,Navarro, Ricardo,Encarnación, Emma K.,Díaz-Torres, Luis A.,Sosa, Modesto A.
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- A new alkali metal salt of tetrafluoroterephthalic acid (H 2tF-BDC)
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The DMF solvate of lithium tetrafluoroterephthalate [Li2(tF-BDC) (DMF)2] (H2tF-BDC = tetrafluoroterephthalic acid) was synthesized and structurally characterized from X-ray single crystal data (Pbcn, Z = 8). Li+ (CN = 4) is coordinated tetrahedrally by four oxygen atoms of three different tF-BDC2- linkers and one DMF molecule. The LiO4 tetrahedra are connected by common vertices to chains, which are bridged by tF-BDC2- linkers to form a 2D polymeric unit. The DMF molecules are oriented perpendicular to these polymeric sheets, which are stacked along [100] in an AB fashion and held together by weak van der Waals interactions. Single crystals of [Li2(tF-BDC)(DMF)2] were synthesized by precipitation from an ethanol/DMF solvent mixture, but single-phase samples were only obtained by a mechanochemical approach starting from lithium acetate and H2tF-BDC by adding DMF. The thermal stability of [Li2(tF-BDC)(DMF)2] was investigated by DTA/TG measurements. The (endothermic) decomposition starts at 170 °C and is followed by a second exothermic decomposition at approx. 300 °C. The weight losses are in good agreement with a release of DMF and CO2. LiF is identified in the residue after heating at 500 °C. Copyright
- Dolfus, Benedikt,Ruschewitz, Uwe
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- Thermal decomposition of lithium-inserted NbO2F
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The thermal decomposition of lithium-inserted NbO2F was studied by differential scanning calorimetry. Samples of LixNbO2F (O ≤ x ≤ 1.8) were heated to 800 and 950 K. The thermograms revealed that decomposition started within the temperature range 640 - 780 K, followed by a second step at approximately 900 K. The products were characterized by X-ray powder diffraction and electron diffraction patterns and by high-resolution electron microscopy. The following phases were obtained at 800 K: LiF, NbO2F, the low pressure form of Nb3O7F, and lithium-enriched forms of P-Nb2O5, NbO2 and LiNbO3. At 950 K, NbO2F disappeared, and LiNb3O8 and the high pressure form of Nb3O7F coexisted with the other phases obtained at 800 K. The formation of structures built up of approximately hexagonally close-packed anion arrangements is discussed.
- Permer,Lundberg
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- STRUCTURAL AND THERMODYNAMIC ASPECTS OF ELECTRON DIFFRACTION BY LITHIUM FLUORIDE DIMERS
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Electron-diffraction and spectral data for Li2F2 have been combined to derive the equilibrium parameters, force field in the harmonic approximation, and vibrational frequencies inactive in the IR spectrum.The proportions of the molecular forms in the satu
- Lapshina, S. B.,Girichev, G. V.
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- Synthesis, Luminescence and Nonlinear Optical Properties of Homoleptic Tetracyanamidogermanates ARE[Ge(CN2)4] (A = K, Cs, and RE = La, Ce, Pr, Nd, Sm, Eu, Gd)
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Two new series of tetracyanamidogermanates were prepared by solid-state reaction of appropriate amounts of REF3 (RE = rare earth), A2[GeF6] (A = alkaline), and Li2(CN2) in evacuated silica tubes. Powder X-ray diffraction patterns of crystalline samples of KRE[Ge(CN2)4] and CsRE[Ge(CN2)4] were indexed isotypically to KRE[Si(CN2)4] and RbRE[Ge(CN2)4], respectively. Luminescence properties of Ce3+, Eu3+, and Tb3+ doped compounds and non-linear optical properties (NLO) of KRE[Ge(CN2)4] are reported.
- Dolabdjian, Konstantin,Schedel, Christine,Enseling, David,Jüstel, Thomas,Meyer, Hans-Jürgen
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- HF-Free Synthesis of Li2SiF6:Mn4+: A Red-Emitting Phosphor
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Li2SiF6:Mn4+ was synthesized via a new HF-free synthesis route by a high-pressure/higherature doping experiment at 5.5 GPa and 750 °C. It is proven that the phosphor cannot be synthesized by the common wet-chemical precipitation route in aqueous HF. The sample was characterized by powder X-ray diffraction, EDX, and luminescence spectroscopy. At room temperature, Li2SiF6:Mn4+ exhibits seven emission lines with the strongest line at max 630 nm and a dominant wavelength of dom 618 nm. The CIE coordinates are 0.688 and 0.312 for x and y, respectively. The compound shows a luminous efficacy of radiation (LER) of 218 lm Wopt-1, which exceeds the LER of current state-of-the-art red LED phosphor K2SiF6:Mn4+ by 7% due to a blue-shift of the emission. It reveals excellent thermal quenching behavior up to 125 °C.
- Stoll, Christiane,Bandemehr, Jascha,Kraus, Florian,Seibald, Markus,Baumann, Dominik,Schmidberger, Michael J.,Huppertz, Hubert
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p. 5518 - 5523
(2019/03/29)
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- The role of “ZrF4-modification” on the structure and electrochemical performance of Li4Ti5O12 anode material
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In order to determine the reaction mechanism of the fluoride modification process and its influence on the electrochemical properties of Li4Ti5O12 anode material, the “ZrF4-modified” Li4Ti5O12 was prepared via a co-precipitation method. Structural characterization results shows that both Zr4+ and F? ions were not incorporated into the lattice structure of Li4Ti5O12 after the modification process. Instead, F? reacts with Li4Ti5O12 chemically to generate new impurity phase such as anatase TiO2 and LiF, while Zr4+ forms amorphous ZrO2 nano-particles over the Li4Ti5O12 particles. There was no dense coating layer formed on the surface of the Li4Ti5O12 particles. These results indicate the reaction mechanism of the ZrF4-modification process was different from that previously reported (such as “AlF3, MgF2, ZnF2, SrF2 and CaF2-modification”). The rate capability and cycling stability of Li4Ti5O12 can be enhanced due to the “ZrF4-modification” process. Specifically, the 2 wt% “ZrF4-modified” Li4Ti5O12 shows the best electrochemical performance.
- Li, Wen,Bai, Xue,Zhang, Lihui,Wei, Aijia,Li, Xiaohui,Liu, Zhenfa
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p. 659 - 668
(2018/03/01)
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- Sonochemical synthesis of lithium fluoride nano cubic as an active and simple catalyst for thia-Michael addition process: Synthesis and structural characterization of β-aryl-β-mercapto ketones
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LiF nano cubic, with an average particle size of 21.6 nm, was synthesized sonochemically, using tetrabutylammonium fluoride as the fluoride source and characterized by SEM-EDX and XRD. This was applied, as a heterogeneous nano-catalyst, to synthesize some
- Shobeiri, Zohreh,Pourayoubi, Mehrdad,Neas, Marek,Divjakovic, Vladimir,Babiak, Michal
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p. 245 - 255
(2015/02/19)
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- Optically active uniform potassium and lithium rare earth fluoride nanocrystals derived from metal trifluroacetate precursors
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This paper reports the first systematical synthesis of near-monodisperse potassium and lithium rare earth (RE) fluoride (K(Li)REF4) nanocrystals with diverse shapes (cubic KLaF4 and KCeF4 wormlike nanowires, nanocubes and
- Du, Ya-Ping,Zhang, Ya-Wen,Sun, Ling-Dong,Yan, Chun-Hua
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p. 8574 - 8581
(2011/01/06)
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- In situ formation and rapid decomposition of Ti (BH4) 3 by mechanical milling LiBH4 with TiF3
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Mechanically milled 3 LiBH4 / TiF3 mixture can rapidly release over 5 wt % hydrogen at moderate temperatures (70-90 °C) without undesired gas impurity. Structure analyses results show that the favorable dehydrogenation performance of the material should b
- Fang,Ma,Kang,Wang,Wang,Cheng
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- Thermal reactions of lithiated graphite anode in LiPF6-based electrolyte
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The thermal reactions of a lithiated graphite anode with and without 1.3 M lithium hexafluorophosphate (LiPF6) in a solvent mixture of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were investigated by means of differential scanning calorimetry (DSC). The products of the thermal decomposition occurring on the lithiated graphite anode were characterized by Fourier transform infrared (FT-IR) analysis. The lithiated graphite anode showed two broad exothermic peaks at 270 and 325 °C, respectively, in the absence of electrolyte. It was demonstrated that the first peak could be assigned to the thermal reactions of PF5 with various linear alkyl carbonates in the solid electrolyte interphase (SEI) and that the second peak was closely related to the thermal decomposition of the polyvinylidene fluoride (PVdF) binder. In the presence of electrolyte, the lithiated graphite anode showed the onset of an additional exothermic peak at 90 °C associated with the thermal decomposition reactions of the SEI layer with the organic solvents.
- Choi, Nam-Soon,Profatilova, Irina A.,Kim, Sung-Soo,Song, Eui-Hwan
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- Thermal behavior of ammonium-containing titanium and germanium fluoride complexes (NH4)4Li2(AF6)3 and NH4NaAF6 (A = Ge or Ti)
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The compounds (NH4)4Li2A3F 18 and NH4NaAF6 (A = Ge or Ti) were studied thermogravimetrically. These fluoro complexes are thermolyzed in the range 230-450°C. Measurements on a differential scanning microcalorimeter revealed reversible phase transitions in NH4NaAF6 at T 1 = 126°C and T 2 = 111°C.
- Antokhina,Flerov,Savchenko,Kaidalova,Merkulov,Ignat'eva,Fokina
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p. 583 - 587
(2009/01/21)
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- Luminescence characteristics of LiCaAlF6: Eu phosphor
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A simple method for preparing LiCaAlF6:Eu2+ phosphor is reported. Photoluminescence (PL) and thermoluminescence (TL) studies were carried out. The TL sensitivity of the phosphor is nearly twice that of CaSO4: Dy TLD phosphor. Several other properties required for TL dosimetry are superior as well. It is suggested that the phosphor can be a suitable replacement for CaSO4:Dy.
- Aghalte,Omanwar,Moharil
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p. 1561 - 1566
(2008/10/09)
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- Solubilities of lanthanum oxide in fluoride melts: Part I. Solubility in M3AlF6 (M = Li, Na, K)
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Solubility of lanthanum oxide was measured by thermal analysis. The solubility in alkali cryolites is rather high, because of chemical reactions between lanthanum oxide and cryolites. In Li3AlF6-La 2O3, alumina
- Ambrová,Jurisová
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p. 105 - 108
(2008/10/09)
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- Syntheses and structures of Li3ScF6 and high pressure LiScF4-, luminescence properties of LiScF4, a new phase in the system LiF-ScF3
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Colorless single crystals of Li3ScF6 have been prepared by reacting the binary components LiF and ScF3 at 820°C for 16 h in argon atmosphere. This complex fluoride is the only stable phase in the system LiF-ScF3 under ambient pressure. According to a structure refinement based on single crystal X-ray diffraction data it crystallizes in the centrosymmetric space group P3c1 with a=8.78.3(1)A and c=9.518(1)A. The new structure of Li3ScF6 is a filled variant of the Na2GeF6 type structure and can be described in terms of a hexagonal close packing of fluorine in which 2/3 of the octahedral holes are occupied by Sc and Li. High pressure/high temperature studies of the system LiF-ScF3 show that the new phase LiScF 4 is formed at around 5.5 GPa and 575°C. According to Rietveld refinements of powder X-ray diffraction data LiScF4 adopts the Scheelite type structure (space group I41/a) with a=4.980(1)A and c=10.074(1)A. A sample of LiScF4 doped with 1% Er exhibits an intense luminescence in the far IR region.
- Tyagi,Koehler,Balog,Weber
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p. 2620 - 2625
(2008/10/09)
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- On the thermal stability of LiPF6
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The results of a comprehensive study of the thermal stability of the salt LiPF6, using both accelerating rate (ARC) and differential scanning (DSC) calorimetry, are presented. Pressure monitoring during ARC experiments permits also the study of endothermic processes. The origins of apparently inconsistent results and conflicting interpretations in previous reports in the literature are explicated. In a confined volume, LiPF6(s) melts reversibly at 467 K with a heat of melting of 2.0 ± 0.2 kJ mol -1. Reversible decomposition to PF5(g) and LiF(s) commences with melting, but the autogenic development of PF5(g) pressure makes the temperature profile of decomposition a function of volume and sample size. The heat of this reaction at constant volume, ΔU r, as determined by a variety of methods is in the range 60 ± 5 kJ mol-1, and is approximately temperature independent in range 490-580 K.
- Zinigrad, Ella,Larush-Asraf, Liraz,Gnanaraj, Josef S.,Sprecher, Milon,Aurbach, Doron
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p. 184 - 191
(2008/10/09)
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- The phase diagram of the system LiF-GdF3
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The phase diagram of the system LiF-GdF3 has been revised, using differential thermal analysis (DTA). We observed a eutectic reaction at 25mol% of GdF3 and 698°C and a peritectic reaction at 34mol% of GdF 3 and 755°C. We found indications for a GdF3 phase transformation from hexagonal to orthorhombic at 900°C. An identification of the formed phases was made by X-ray diffraction and SEM.
- Ranieri,Bressiani,Morato,Baldochi
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- Thermodynamic properties and decomposition of lithium hexafluoroarsenate, LiAsF6
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The heat capacity of lithium hexafluoroarsenate is determined in the temperature range 50-750 K by adiabatic and differential scanning calorimetry techniques. The thermodynamic properties of LiAsF6 under standard conditions are evaluated: Cp0 (298.15 K)= 162.5 ± 0.3 J/(K mol), S0(298.15 K) = 173.4 ± 0.4 J/(K mol), Φ0(298.15 K) = 81.69 ± 0.20 J/(K mol), and H 0(298.15 K) - H0(0) = 27 340 ± 60 J/mol. The C p(T) curve is found to contain a lambda-type anomaly with a peak at 535.0 ± 0.5 K, which is due to the structural transformation from the low-temperature, rhombohedral phase to the high-temperature, cubic phase. The enthalpy and entropy of this transformation are 5.29 ± 0.27 kJ/mol and 10.30 ± 0.53 J/(K mol), respectively. The thermal decomposition of LiAsF6 is studied. It is found that LiAsF6 decomposes in the range 715-820 K. The heat of decomposition, determined in the range 765-820 K using a sealed crucible and equal to the internal energy change ΔU r(T), is 31.64 ± 0.08 kJ/mol.
- Gavrichev,Sharpataya,Gorbunov,Golushina,Plakhotnik,Goncharova,Gurevich
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p. 175 - 182
(2008/10/08)
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- Calorimetric study of thermal decomposition of lithium hexafluorophosphate
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Enthalpy of formation of lithium hexafluorophosphate was calculated based on the differential scanning calorimetry study of heat capacity and thermal decomposition. It was found that thermal decomposition of LiPF6 proceeds at normal pressure in
- Gavritchev,Sharpataya,Smagin,Malyi,Matyukha
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- From a Transient 3-Germa-1-phosphabutadiene to a 1,2-Bis(phosphaalkenyl)-1,2-digermacyclobutane
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Dehydrofluorination of the fluoro(fluorenyl)(phosphaalkenyl)germane 7 by tert-butyllithium in the presence of chlorotrimethylsilane affords the 1,2-bis(phosphaalkenyl)-1,2-digermacyclobutane 2. This reaction probably involves the prior formation of the transient 3-germa-1-phosphabutadiene 1, followed by its head-to-head dimerization. 2 contains a distorted four-membered ring with long intracyclic Ge-Ge (2.5567(8) ?), Ge-C(R2) (2.058(4) ?), and (R2)C-C(R2) (1.592(6) ?) bonds; mesityl groups are trans in relation to this heterocycle.
- Pailhous, Isabelle,Ranaivonjatovo, Henri,Escudié, Jean,Declercq, Jean-Paul,Dubourg, Antoine
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p. 1622 - 1628
(2008/10/08)
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- Gas-phase characterization by photoelectron spectroscopy of unhindered, low-coordinate germanium compounds: Germaimines, germylenes, and germaisonitriles
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Low-coordinate, unhindered germanium compounds, germaimines, germylenes, and germaisonitriles, have been generated and characterized by the combination of flash vacuum thermolysis (FVT) of appropriately substituted germacyclopentenes and ultraviolet photo
- Foucat, Séverine,Pigot, Thierry,Pfister-Guillouzo, Geneviève,Lavayssière, Hélène,Mazières, Stéphane
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p. 5322 - 5329
(2008/10/08)
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- Studies on the reaction of ammonium fluoride with lithium carbonate and yttrium oxide
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The reaction of Y2O3 and Li2CO3 with NH4F to produce LiYF4 was studied by thermogravimetric and X-ray diffraction methods. NH4F reacts easily with Li2CO3 in a one-step exothermic process. Fluorination of yttrium oxide gives first YF3 . 1.5NH3 which decomposes at 300-380°C to YF3 +NH3. This process is exothermic. In the absence of excess NH4F, an amou nt of YOF is produced, in addition to YF3, as a product of the reaction of YF3 and unreacted Y2O3. This reaction is endothermic. In the ternary system NH4F-Li2CO3-Y2O3, the first reacts separately with each of the other two and the resulting mixture of simple yttrium and lithium fluorides is converted into LiYF4 at high temperatures.
- Kowalczyk, Ewa,Diduszko, Ryszard,Kowalczyk, Zbigniew,Leszczynski, Tomasz
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p. 189 - 196
(2008/10/09)
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- Thermodynamically unstable fluorides of nickel: NiF4 and NiF3 syntheses and some properties
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F- acceptors (BF3, AsF5, SbF5, or BiF5) added to solutions of NiF62- salts in anhydrous hydrogen fluoride (aHF) below -65 °C precipitate the tan solid NiF4. This solid, preserved at ≤-65 °C, is quantitatively converted, by 2 equiv of F- donor (XeF6 or KF) in aHF, to dissolved NiF62-. Dry NiF4 loses F2 above -60 °C, the decomposition to nearly black NiF3 becoming rapid at ~0 °C. When the dry NiF4 is prepared from K2NiF6, inclusion of some K+ leads, on thermolysis at 0 °C, to a pyrochlore form of NiF3 (P-NiF3). P-NiF3 contains K+ in the open channels, with KxMiF3, x ≈ 0.1. The nearly cubic P-NiF3 unit cell is rhombohedral: a0 = 9.933(3) A?, α = 91.01(3)°, V = 980 A?3, z = 16, with absent reflections coincident with those of the cubic space group Oh7-Fd3m, appropriate for pyrochlore. Decomposition of NiF4 in aHF begins at -65 °C and is rapid at 0 °C, giving black rhombohedral NiF3 (A-NiF3) with a0 = 5.168(2) A?, α = 55.46(3) A°, V = 87.3 A?3, z = 2. When the NiF4 is made and decomposed at ~20 °C, with K+ present, a hexagonal tungsten bronze form of NiF3 is precipated (H-NiF3), with a0 = 7.074(6) A?, c0 = 7.193(6) A?, V = 312A?3, z = 6. R- and H-NiF3 can also be made by mixing solutions of Ni2+ salts [e.g., Ni(AsF6)2] with NiF62- salts (e.g. K2NiF6) in aHF. All forms of the trifluoride (R, H, and P) lose F2 on warming (R > 39°, H > 72° and P > 138 °C) to yield NiF2, but an intermediate red-brown phase is observed for R-NiF3. R-NiF3 at ~20 °C, oxidizes Xe to Xe(VI), perfluoropropene, C3F6, to perfluoropropane, C3F8, and solid LiCl with incandescence. H-NiF3 and P-NiF3 interact similarly but less energetically.
- ?emva,Lutar,Chacón,Fele-Beuermann,Allman,Shen,Bartlett
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p. 10025 - 10034
(2007/10/03)
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- Dibisyl(fluorenylidene)stannene: evidence of its formation
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The dibisyl(fluorenylidene)stannene 4, obtained by dehydro-chlorination or -fluorination of the corresponding chloro- or fluoro-stannanes 5 and 6 by tert-butyllithium is an extremely air-sensitive compound.It has not been isolated, but identified by trapp
- Anselme, G.,Couret, C.,Escudie, J.,Richelme, S.,Satge, J.
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p. 321 - 328
(2007/10/02)
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- Fluorine-oxygen exchange reactions in IF5, IF7, and IF5O
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When reacted with alkali-metal nitrates, IF5 readily exchanges two fluorine ligands for a doubly bonded oxygen atom. In all cases MIF4O salts (M = Li, K, Cs) and FNO2 are formed as the primary products. The FNO2 byproduct undergoes a fast secondary reaction with MNO3 to yield equimolar amounts of N2O5 and MF. The N2O5 decomposes to N2O4 and 0.5 mol of O2, while the MF, depending on the nature of M, does or does not undergo complexation with the excess of IF5. Pure MIF4O salts, free of MF or MF·nIF5 byproducts, were prepared from MF, I2O5, and IF5 in either CH3CN or IF5 as a solvent. The new compounds LiIF4O, NaIF4O, RbIF4O, and NOIF4O were characterized by vibrational spectroscopy. It was also shown that, contrary to a previous report, FNO2 does not form a stable adduct with IF5 at temperatures as low as -78°C. An excess of IF7 reacts with MNO3 (M = Li, Na) to give MF, FNO2, IF5, and 0.5 mol of O2, but surprisingly no IF5O. With CsNO3, the reaction products are analogous, except for the CsF reacting with both the IF5 product and the excess of IF7 to give CsIF6·2IF5 and CsIF8, respectively. When in the IF7 reaction an excess of LiNO3, is used, the IF5 product undergoes further reaction with LiNO3, as described above. The IF5O molecule was found to be rather unreactive. It does not react with either LiF or CsF at 25 or 60°C or with LiNO3 or CsNO3 at 25°C. At 60°C with LiNO3, it slowly loses oxygen, with the IF5 product reacting to yield LiIF4O, as described above.
- Christe, Karl O.,Wilson, William W.,Wilson, Richard D.
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p. 904 - 908
(2008/10/08)
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- The standard molar enthalpies of formation of the lithium zirconates
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The enthalpies of solution of Li2ZrO3, Li6Zr2O7, and Li8ZrO6 in HF*100H2O have been measured.The results have been used to derive the standard molar enthalpies of formation at 298.15 K: ΔfH0m(Li2ZrO3) = -(1742.8 +/- 1.2) k
- Wyers, G. P.,Cordfunke, E. H. P.,Ouweltjes, W.
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p. 1095 - 1100
(2007/10/02)
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- Synthesis and Structures of New 1,3,2,4-Diphosphadiboretanes
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Three methods have been devised to prepare new diphosphadiboretanes: a) Base-induced hydrogen halide elimination from (amino)phosphinoboron halides precursors, b) tris(trimethylsilyl)phosphane elimination from R2N-B2 intermediates prepared in situ from combination of R2N-B(Cl)-P(SiMe3)2 and LiP(SiMe3)2, and organylphosphane elimination from aminobis(organylphosphino)boranes R2N-B(PHR')2.The molecular structures of three new 1,3,2,4-diphosphadiboretanes (3, 4a, 4c) were determined by X-ray diffractometry.These are characterized by a planar four-membered B2P2 ring with the phosphorus substituents in trans positions.Their BP bomnds represent single bond distances.Experimental results are compared with MNDO III calculations which reveal a low barrier (ΔE = 5 kcal/mol) for the dimerization of the boraphosphane H2N-B=PMe to the diphospadiboretane (H2N-BPMe)2.
- Koelle, Peter,Linti, Gerald,Noeth, Heinrich,Wood, Gary L.,Narula, Chaitanya K.,Paine, Robert T.
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p. 871 - 880
(2007/10/02)
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- Novel Iminoboranes and their Reactions
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The iminoboranes RBNR', 2a-f, are formed by the elimination of Me3SiHal from the corresponding aminoboranes 1a-f.Stabilization occurs either through cyclodimerisation (-->3b-d,f), cyclotrimerisation (-->4e), bicyclotrimerisation (-->5b) or cyclotetramerisation (-->6a).Trialkylboranes BX3 are added to give the diboryl amines RXBN(R')BX2, 7a-f.The Δ2-tetraazaborolines (R)B(R')N-N=N-N(X')>, 8a-f, are the (3-2)-cycloaddition products from 2a-f and azides X'N3.A CH-bond of cyclopentadiene adds to one BN bonds of 2f, giving a mixture of the corresponding 1,3- and 1,4-cyclopentadienyl boranes, 9f, 9'f. - Keywords: Iminoboranes, Cyclodimers, Cyclotrimers, Cyclotetramers
- Bonn, Karl-Heinz van,Bennigsen-Mackiewicz, Theo von,Kiesgen, Jutta,Plotho, Christoph von,Paetzold, Peter
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- Structure of the stable germaphosphene Mes2Ge=PAr: A Ge=P connection with the geometry of a true double bond
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The structure of the stable germaphosphene Mes2Ge=PAr has been determined by X-ray crystallography (orthorhombic, Pna 21; a = 1931.7 (4), b = 997.5 (2), c = 1794.6 (2) pm; V = 3458.106 pm3; Z = 4; R = 0.0540). The germanium-phosphorus double bond length (213.8 (3) pm) is substantially shorter than the standard germanium-phosphorus single bond (~233-235 pm); this rather important shortening (about 8.5%) and the essentially planar double-bond geometry support the existence of a true germanium-phosphorus double bond. Raman emission of Ge=P bond is 503 cm-1.
- Dr?ger, Martin,Escudie, Jean,Couret, Claude,Ranaivonjatovo, Henri,Satge, Jacques
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p. 1010 - 1013
(2008/10/08)
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