- Electron-beam induced crystallization transition in self-developing amorphous AIF3 resists
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Transmission electron microscopy is used to investigate electron-induced crystallization of thermally evaporated amorphous AlF3(α-AlF3). It is shown that this material undergoes a very complicated crystallization process with three crystalline substances (Al, AlF3, and Al2O3) formed as the dose increases. The sequence of the crystallization is highly sensitive to the presence of water, which inhibits radiolytic dissociation of α-AlF3 into Al and fluorine, reduces the dose required for the crystallization of α-AlF3, and causes the transformation of AlF3 into Al2O3.
- Chen,Boothroyd,Humphreys
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- Improvement of the electrochemical properties of Li [Ni0.5 Mn0.5] O2 by AlF3 coating
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An ~10 nm AlF3 layer was coated on the surface of a Li [Ni 0.5Mn0.5]O2 positive electrode material for lithium-ion batteries, and the effects of this coating on battery performances and thermal stability of the cathode materials were studied. Although no significant bulk structural differences were observed between the coated and pristine material, a slightly higher capacity was seen for the AlF3 -coated Li [Ni0.5Mn0.5]O2 electrode, and the rate capability was also greatly enhanced by the AlF3 coating. These improvements are mainly attributed to the suppression of the transition metal dissolution benefited from the AlF3 coating. This suppression contributed to the reduction in the charge-transfer resistance. Time-of-flight secondary ion mass spectroscopic analysis showed that insulating LiF, as a product of decomposed LiPF6, was deposited on the surface of pristine and AlF3 -coated Li [Ni0.5Mn0.5]O2. The deposition of LiF was greatly suppressed by AlF3 coating on the outer surface of Li [Ni0.5Mn0.5]O2. The protection of the active material by the AlF3 coating substantially improved the capacity, capacity retention, and rate capability of the batteries. It also enhanced the thermal stabilities of the positive electrode material.
- Sun, Yang-Kook,Myung, Seung-Taek,Park, Byung-Chon,Yashiro, Hitoshi
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- Characterization of four phase transitions in Pb5Al3F19, including a new transition at 670 K, by impedance and NMR spectroscopy
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X-ray diffraction, thermal, optical, and dielectric studies of Pb5Al3F19 undertaken previously between 100 and 400 K showed this material undergoes three phase transitions. The four known phases are ferroelectric phase V, with a transition to antiferroelectric phase IV at 270 K on heating, 140 K on cooling. The transition from phase IV to ferroelastic phase III is at 320 K on heating, 305 K on cooling; that from phase III to paraelastic phase II is at 360 K without thermal hysteresis. Impedance and NMR spectroscopy in the complementary temperature ranges 279-743 and 125-430 K characterized the influence of these phases on the ionic conductivity and F- ion diffusion properties in this material.
- El Omari,Reau,Senegas,Ravez,Abrahams,Nadiri,Yacoubi
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- Reactivity of fluorinated γ-alumina and β-aluminium(III) fluoride surfaces towards hydrogen halides and tert-butyl chloride
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The Lewis acids β-aluminium(III) fluoride and γ-alumina, fluorinated at room temperature with sulfur, tetrafluoride, both interact with hydrogen fluoride and chloride, as demonstrated by radiotracer measurements using [18F] and [36Cl
- Barclay, Christopher H.,Bozorgzadeh, Hamid,Kemnitz, Erhard,Nickkho-Amiry, Mahmood,Ross, Debbie E.M.,Skapin, Tomaz,Thomson, James,Webb, Geoffrey,Winfield, John M.
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- Thermal and XRD analysis of synthesis of fluoro-topaz
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The present work deals with thermal and XRD analysis of fluoro-topaz synthesis by sintering of aluminium and silicon oxides (in the form of corundum and quartz) with ammonium fluoride and carried out in open Pt crucibles (for XRD studies) and a closed furnace of simultaneous DTA/TG thermoanalytical apparatus called MOM Derivatograph. The furnaces are connected to a gas suction device to remove gas decomposition products. The study shows the endothermic peak at 125-155°C, representing the formation of ammonium aluminium hexafluoride and cryptohalite. The endothermic peak at 220-240°C represents the beginning of dissociation of ammonium aluminium hexafluoride to the more stable ammonium aluminium tetrafluoride. The endothermic peak at 340-350°C represents the dissociation of cryptohalite and ammonium aluminium tetrafluoride with the formation of aluminium fluoride. The formation of fluoro-topaz is represented by the wide endothermic peak at 770-800°C. The medium wide or sharp endothermic peaks at 950°C and 1000°C represent the subsequent dissociation of fluoro-topaz to corundum or mullite, respectively.
- Abdel-Rehim
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- Zeolite catalysts for Halon conversion
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The chemical states of Al and Ni in NiZSM-5 catalyst used for the pyrolysis and hydrodehalogenation with methane of Halon 1301 (CF3Br) were characterized using Al and Ni K-edge XANES and EXAFS experiments. Reaction products were CF4
- Howe,Lee,Thomson,Kennedy,Yang,Dlugogorski
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- Vibrational analysis study of aluminum trifluoride phases
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The vibrational modes of three solid AlF3 phases (α, β, and amorphous high surface area AlF3) are investigated. Calculations have been performed using hybrid exchange correlation functionals to determine the equilibrium geometries an
- Gross, Udo,Ruediger, Stephan,Kemnitz, Erhard,Brzezinka, Klaus-Werner,Mukhopadhyay, Sanghamitra,Bailey, Christine,Wander, Adrian,Harrison, Nicholas
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- The effects of AlF3 coating on the performance of Li[Li 0.2 Mn0.54 Ni0.13 Co0.13]O 2 positive electrode material for lithium-ion battery
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Al F3 -coated Li [Li0.2 Mn0.54 Ni0.13 Co0.13] O2 materials have been synthesized as positive electrode materials for lithium-ion batteries. The pristine and Al F3 -coated Li [Li0.2 Mn0.54 Ni0.13 Co0.13] O2 materials were characterized by X-ray diffraction
- Zheng,Zhang,Wu,Dong,Zhu,Yang
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- AlF3-coating to improve high voltage cycling performance of Li[Ni1/3Co1/3Mn1/3]O2 cathode materials for lithium secondary batteries
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Li [Ni13 Co13 Mn13] O2 powders were modified by coating their surface with amorphous AlF3 as a new coating material. The AlF3 -coated Li [Ni13 Co13 Mn13] O2 electrode showed improved cycle performance and rate capability under a high cutoff voltage range of 4.5 and 4.6 V. AC impedance results showed that the AlF3 -coated Li [Ni13 Co13 Mn13] O2 has stable charge transfer resistance (Rct) regardless of the cycle number. Electron diffraction analysis also showed that no structural transition of the primary particles was observed for the AlF3 -coated electrode. Electrochemical impedance spectroscopy and electron microscopy indicate that AlF3 coating plays an important role of stabilizing the interface between cathode and electrolyte.
- Sun,Cho,Lee,Yoon,Amine
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- CaF2-AlF3-SiO2 glass-ceramic with low dielectric constant for LTCC application
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Low temperature co-fired ceramic (LTCC) materials based on CaF2-AlF3-SiO2 oxyfluoride glass-ceramics were prepared. The sintering behaviors, phase transition, microstructures, and the dielectric properties of the glass-cer
- Wang, Rui,Zhou, Ji,Li, Bo,Li, Longtu
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- Investigation of the systems KAlF4-M3AlF6 (M=Rb, Cs)
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Phase relations in the systems KAlF4-Rb3AlF6 and KAlF4-Cs3AlF6 were investigated by DTA and XRD methods for the purpose of finding a low melting, non-corrosive aluminum flux. In each system, congruent compounds Rb3AlF6·2KAlF4 and 2Cs3AlF6·3KAlF4 were observed, respectively. Eutectics located at 46 mol% Rb3AlF6 and 511°C, 25 mol% Rb3AlF6 and 512°C for the former system, and 48 mol% Cs3AlF6 and 550°C, 25 mol% Cs3AlF6 and 480°C in the latter were confirmed. The phase α-2Cs3AlF6·3KAlF4 was XRD indexed as having an orthorhombic cell a=10.401±0.003, b=10.078±0.006, c=8.792±0.006 A?. (C) 2000 Elsevier Science B.V.
- Chen,Zhang
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- Adsorption properties of various forms of aluminium trifluoride investigated by PulseTA
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The current study employs the Pulse Thermal Analysis (PTA) method to investigate the adsorption of gaseous methanol onto various forms of aluminium trifluoride drawing special attention to the strongly adsorbing β-AlF3 and the recently describe
- Feist,K?nig,B??ler,Kemnitz
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- Tossing and turning: Guests in the flexible frameworks of metal(III) dicarboxylates
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Single crystals of Ga(OH)(C8H4O4) ·0.74C8H6O4 (2) and Ga(OH,F)(C 8H4O4)·0.74C8H 6O4 (3) were obtained under hydrothermal conditions. The structures of 2 and 3 have the same topological framework as the previously reported aluminum 1,4-benzenedicarboxylate (BDC), Al(OH)(C8H 4O4)·0.7C8H6O4 (1). The frameworks are built by interconnecting M-OH-M chains (M = Al, Ga) with BDC anions to form large diamond-shaped one-dimensional channels filled with additional H2BDC guest molecules occupying disordered positions in the channels. Upon removal of H2BDC, other guest molecules such as H2O and pyridine can be inserted. In this work, we present a study of the intercalation of aromatic guests (BDC and pyridine) into frameworks of 1-3 by liquid and vapor diffusion into the empty channels of 1 and by single-crystal-to-single-crystal solvothermal guest exchange for 2 and 3. In the case of Al(OH)BDC and Ga(OH,F)BDC, two interconvertible, guest-concentration- dependent phases with different orientations of the pyridine guests have been observed, while only one pyridine orientation is found in Ga(OH)BDC.
- Vougo-Zanda, Marie,Huang, Jin,Anokhina, Ekaterina,Wang, Xiqu,Jacobson, Allan J.
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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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- Structural insights into aluminum chlorofluoride (ACF)
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The structure of the very strong solid Lewis acid aluminum chlorofluoride (ACF, AlClxF3-x = 0.05-0.3) was studied by IR, ESR, Cl K XANES, 19F MAS NMR, and 27Al SATRAS NMR spectroscopic methods and compared with amorphous aluminum fluoride conventionally prepared by dehydration of α-AlF3·3H2O. The thermal behavior of both compounds was investigated by DTA and XRD. In comparison to ACF, amorphous AlF3 prepared in a conventional way is not catalytically active for the isomerization reaction of 1,2-dibromohexafluoropropane, which requires a very strong Lewis acid. Both compounds are mainly built up of corner-sharing AlF6 octahedra forming a random network. The degree of disorder in ACF is higher than in amorphous AlF3. Terminal fluorine atoms were detected in ACF by 19F NMR. The chlorine in ACF does not exist as a separate, crystalline AlCl3 phase. Additionally, chlorine-containing radicals, remaining from the synthesis, are trapped in cavities of ACF. These radicals are stable at room temperature but do not take part in the catalytic reaction.
- Krahl, Thoralf,Stoesser, Reinhard,Kemnitz, Erhard,Scholz, Gudrun,Feist, Michael,Silly, Gilles,Buzare, Jean-Yves
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- Desorption behaviour of HF,HCFC-133a and HFC-134a on a catalyst supported on γ-AlF3
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The desorption behaviour (desorption temperature and extent of desorption) of HF,HCFC-133a (CF3CH2Cl) and HFC-134a (CF3CH2F) on γ-AlF3 or catalyst supported on γ-AlF3 was studied using an adsorption apparatus and TG, DTA and DSC methods. On the basis of the results a reaction mechanism was proposed for the preparation of HFC-134a. The γ-AlF3 employed for preparing the catalyst was expected to be stable below 550°C based on the crystalline phase transition temperature of γ-AlF3.
- Quan,Ge,Li,Yin,Zhong,Hao,Li,Ji
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- Hypothetical AlF3 crystal structures
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Applying a structure prediction computer programme (GRINSP=Geometrically Restrained INorganic Structure Prediction), the occurrence of 6-connected 3D networks was investigated, through AlF6 octahedra exclusive corner sharing. The five known AlF3 varieties were reproduced (α-, β-, η-, κ- and τ-AlF3) and seven hypothetical models were predicted. Among these still to be synthesized AlF3 phases, one can recognize two known structure types (TlCa2Ta5O15, Ba4CoTa10O30) and some easy to imagine intergrowths; however, a few others are completely unexpected, though simple. A comparison of the ab initio total energies of all the structures is provided, leading to the conclusion that the virtual models could well be viable.
- Le Bail, Armel,Calvayrac, Florent
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- Infrared Surface Characterization of AlF3
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Three specimens of crystalline AlF3, coming from different preparation routes, have been examined: no major differences were found in the spectral region of the (ν3) fundamental mode, whereas the preparation process was observed to introduce appreciable differences in the background spectra that were ascribed to different bulk and surface impurities.Oxidic islands exist both in the bulk and at the surface of all preparations and when AlF3 is derived from non-oxygen-containing precursors.In the latter case, species containing NHx moieties exist, both in the bulk and at the surface.The surface hydrated layer of AlF3 is made up of an extensive 'regular' component (i.e. a large amount of undissociated water molecules, coordinated to unsaturated surface AlVI cations), and not an 'anomalous' component (i.e. some OH groups that are eliminated upon vacuum activation at relatively low temperatures).The adsorption of pyridine on samples activated by vacuum treatment at temperatures in the range 300-673 K indicates that on all specimens there are variable amounts of 'irregular' surface cations , some of which are strong enough as Lewis-acidic centres to adsorb CO at ambient temperature.Coordinatively unsaturated surface Al ions with the 'regular' octahedral coordination are very weakly acidic, as revealed by the end-on adsorption of CO2 at 300 K and by CO uptake at ca. 78 K.
- Morterra, C.,Cerrato, G.,Cuzzato, P.,Masiero, A.,Padovan, M.
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- Preparation and characterization of high surface area α-AlF 3
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High surface area α-AlF3 has been prepared by a carbon hard template method, Wherein γ-Al2O3 is immersed with sucrose aqueous solution and the dried mixture thermally treated under N2 flow at 450°C to obtain the C γ-Al2O 3. C γ-Al2O3 can be completely transformed to C α-AlF3 with hydrogen fluoride at 400°C. After the carbon template in C α-AlF3 is removed by high temperature combustion, a high surface area α-AlF3 (66 m 2 g-1) is obtained. It is found that the fluorination process is crucial for the resulting α-AlF3. Although high fluorination temperature is favorable to the formation of α-AlF 3, it also results in the decline of surface area.
- Yu, Hongbo,Jia, Wenzhi,Wang, Yuejuan,Lu, Jiqing,Luo, Mengfei
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p. 927 - 930
(2012/11/06)
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- SMARTER crystallography of the fluorinated inorganic-organic compound Zn3Al2F12·[HAmTAZ]6
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We present in this paper the structure resolution of a fluorinated inorganic-organic compound - Zn3Al2F12· [HAmTAZ]6 - by SMARTER crystallography, i.e. by combining powder X-ray diffraction crystallography, NMR crystallography and chemical modelling of crystal (structure optimization and NMR parameter calculations). Such an approach is of particular interest for this class of fluorinated inorganic-organic compound materials since all the atoms have NMR accessible isotopes (1H, 13C, 15N, 19F, 27Al, 67Zn). In Zn3Al2F 12·[HAmTAZ]6, 27Al and high-field 19F and 67Zn NMR give access to the inorganic framework while 1H, 13C and 15N NMR yield insights into the organic linkers. From these NMR experiments, parts of the integrant unit are determined and used as input data for the search of a structural model from the powder diffraction data. The optimization of the atomic positions and the calculations of NMR parameters (27Al and 67Zn quadrupolar parameters and 19F, 1H, 13C and 15N isotropic chemical shifts) are then performed using a density functional theory (DFT) based code. The good agreement between experimental and DFT-calculated NMR parameters validates the proposed optimized structure. The example of Zn 3Al2F12·[HAmTAZ]6 shows that structural models can be obtained in fluorinated hybrids by SMARTER crystallography on a polycrystalline powder with an accuracy similar to those obtained from single-crystal X-ray diffraction data.
- Martineau, Charlotte,Cadiau, Amandine,Bouchevreau, Boris,Senker, Juergen,Taulelle, Francis,Adil, Karim
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p. 6232 - 6241
(2012/06/15)
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- Preparation and characterization of high-purity metal fluorides for photonic applications
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We combine chelate-assisted solvent extraction (CASE) and hot hydrogen fluoride gas treatment to enable a general method for the preparation of high-purity binary metal fluorides. The fluorozirconate glass ZBLANI:Yb 3+ (ZrF4-BaF2-LaF3-AlF 3-NaF-InF3-YbF3), a solid-state laser-cooling material, is used as a test case to quantitatively assess the effectiveness of the purification method. The reduction of transition-metal and oxygen-based impurities is quantified directly by inductively coupled plasma mass spectrometry (ICP-MS) and indirectly by laser-induced cooling, respectively. The concentrations of Cu, Fe, Co, Ni, V, Cr, Mn, and Zn impurities in the ZrCl 2O precursor solution were measured individually by ICP-MS at various stages of the purification process. CASE was found to reduce the total transition-metal concentration from 72500 to ~100 ppb. Laser cooling was most efficient in ZBLANI:Yb3+ glass fabricated from CASE-purified metal fluoride precursors, confirming the results of the ICP-MS analysis and demonstrating the effectiveness of the purification methods in a finished optical material. High-purity metal fluorides prepared by the methods presented herein will enable new high-performance optical materials for solid-state optical refrigerators, crystals for vacuum ultraviolet (VUV) spectroscopy of the Thorium-229 nucleus, VUV optics, fibers, and thin-film coatings.
- Patterson, Wendy M.,Stark, Peter C.,Yoshida, Thomas M.,Sheik-Bahae, Mansoor,Hehlen, Markus P.
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p. 2896 - 2901
(2011/12/22)
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- Highly selective metal fluoride catalysts for the dehydrohalogenation of 3-chloro-1,1,1,3-tetrafluorobutane
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For the first time, dehydrochlorination and dehydrofluorination reactions are studied on the same substrate, 3-chloro-1,1,1,3-tetrafluorobutane, employing nanoscopic metal fluorides AlF3, MgF2, CaF2, SrF2, and BaF2 as catalysts that are prepared according the fluorolytic sol-gel synthesis. AlF3 is exclusively selective toward dehydrofluorination, whereas BaF2 is 100% selective toward dehydrochlorination. The acid-base character of the catalysts is investigated and, as a result, mechanistic proposals for the dehydrofluorination and the dehydrochlorination are given. Thus, at high conversion level, selective catalysts for both dehydrofluorination and dehydrochlorination on the same substrate have been developed.
- Teinz, Katharina,Wuttke, Stefan,Boerno, Fabian,Eicher, Johannes,Kemnitz, Erhard
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p. 175 - 182
(2011/10/18)
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- Quantum-chemical calculations and IR spectra of the (F2)MF 2 molecules (M = B, Al, Ga, In, Tl) in solid matrices: A new class of very high electron affinity neutral molecules
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Electron-deficient group 13 metals react with F2 to give the compounds MF2 (M = B, Al, Ga, In, Tl), which combine with F 2 to form a new class of very high electron affinity neutral molecules, (F2)MF2, in solid argon and neon. These (F 2)MF2 fluorine metal difluoride molecules were identified through matrix IR spectra containing new antisymmetric and symmetric M-F stretching modes. The assignments were confirmed through close comparisons with frequency calculations using DFT methods, which were calibrated against the MF3 molecules observed in all of the spectra. Electron affinities calculated at the CCSD(T) level fall between 7.0 and 7.8 eV, which are in the range of the highest known electron affinities.
- Wang, Xuefeng,Andrews, Lester
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p. 3768 - 3771
(2011/04/26)
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- Fluoride ion donor properties of group 13 trifluorides (MF3, M = Al, Ga, In, Tl) and crystal structures of InF3·3SbF 5, TlF3·3SbF5 and TlF 3·AsF5·2HF
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Reactions between strong Lewis acids (i.e. AsF5, SbF 5) and MF3 (M = Al, Ga, In, Tl) in anhydrous hydrogen fluoride at ambient temperature proceeded only in three cases, yielding InF 3·3SbF5, TlF3·3SbF5, TlF3·AsF5·2HF and TlF3· AsF5. Crystal structure of InF3·3SbF5 consists from infinite chains of In atoms connected by three SbF6 units, with two bridging fluorine atoms (Fb) in cis-position. Due to the strong interaction of SbF6 units with In3+, the Sb-Fb bonds are significantly elongated (200.7(4) pm). Such long Sb-Fb bonds have been observed in the crystal structure of SbF 5. The crystal structure of TlF3·3SbF5 is built from slabs where thallium atoms are connected by SbF6 units. The thallium is nine-fold coordinated by fluorine atoms in the shape of a tricapped trigonal prism. In the crystal structure of TlF3· AsF5·2HF there are puckered layers, composed of rectangular rings made of Tl and F atoms. The seven-fold coordination around each Tl is completed by three axial fluorine atoms, provided by one HF molecule and two AsF6 units arranged below and above the puckered layers forming infinite slabs on that way. The second molecule of HF is placed between the slabs. Vibrational spectra of isolated InF3·3SbF5, TlF3·3SbF5, and TlF3·AsF 5 are consistent with the presence of highly deformed SbF 6/AsF6 octahedra. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Mazej, Zoran,Goreshnik, Evgeny
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p. 2806 - 2812
(2011/02/18)
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- The influence of HS-AlF3 on the decomposition reaction of MgH2
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The influence of nanoscopic aluminium fluoride prepared via a sol-gel-synthesis route developed by our group on the thermal decomposition of MgH2 used as hydrogen storage material has been comprehensively investigated. Combined XRD and MAS NMR experiments have been performed to follow structural changes in ball milled MgH2/HS-AlF3 mixtures at thermal decomposition. Although the behaviour of Lewis acidic metal fluorides is discussed being catalytic, our results with HS-AlF3 clearly give a different picture. We found strong evidence for a decrease of the decomposition temperature in combination with a significant acceleration of the decomposition rate; however, the action of at least AlF3 is not catalytic in nature. As shown, a fluoride against hydride exchange is taking place, thus transforming AlF3 irreversibly into AlH3, which is followed by decomposition into metallic Al (MgAl alloy).
- Noack, Johannes,Scholz, Gudrun,Rüdiger, Stephan,Feist, Michael,Kemnitz, Erhard
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- A simple aqueous phase synthesis of high surface area aluminum fluoride and its bulk and surface structure
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A simple novel synthesis route to aluminum fluoride, AlF3, from aqueous phase is reported. Al2O3 is dissolved in aqueous hydrofluoric acid, HF, and re-precipitated as AlF3 · 3H2O. Thermal decomposition results in thermally stable AlF3 with high specific surface areas between 120 and 60 m2/g depending on treatment temperatures (up to 450 °C). Bulk and surface structures of the resulting amorphous and crystalline materials were characterized by X-ray powder diffraction, infrared and solid state NMR spectroscopy (27Al, MAS), nitrogen physisorption and adsorption of paramagnetic probe molecules (vanadium complexes).
- Kleist, Wolfgang,Hae?ner, Carmen,Storcheva, Oksana,K?hler, Klaus
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p. 4851 - 4854
(2008/10/09)
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- Synthesis and crystal structures of new mixed-valence terbium (III/IV) fluorides with a random distribution between Tb3+ and Tb4+
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The thermal decomposition of terbium tetrafluoride was already used for the synthesis of mixed-valence terbium fluorides such as KTb3F 12 or K2Tb4F17. In this paper, new mixed-valence terbium (III/IV) fluorides with formula Rb2AlTb 3F16 and RbAl2Tb4F22 with a statistical distribution between Tb(III) and Tb(IV) are presented. The Rb2AlTb3F16 compound which crystallizes in the hexagonal system, space group P63/mmc (n° 194) with unit cell parameters a=7.556(6)A? and c=12.397(3)A? exhibits an uncommon structural unit [Tb3F22]11- resulting from the association of three monocapped square antiprisms TbF9 by sharing edges about a common corner. The RbAl2Tb4F22 compound crystallizes in the tetragonal system, space group I4/mmm (n° 139) with unit cell parameters a=10.662(2)A? and c=6.911(3)A?. The structure is built of chains of edge-sharing TbF8 dodecahedra. These chains arranged in a tetragonal packing are further held together by sharing vertices to form the three-dimensional framework. This polyhedral linking delimits two kinds of channels parallel to the tetragonal c-axis. The first ones, star shaped, are occupied by isolated zigzag chains of trans corner-sharing [AlF6]3- octahedra whereas the second ones accommodate the Rb+ ions in 8-coordination.
- Josse,Dubois,El-Ghozzi,Avignant
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p. 213 - 218
(2008/10/09)
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- Amorphous aluminum bromide fluoride (ABF)
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Different octahedral units form the basis of the structures of the very strong Lewis acids aluminum bromide fluoride (ABF) and aluminum chloride fluoride (ACF) (see picture). A structure model for these phases is established in which the octahedra are linked through μ-bridging fluorine atoms and μ3-bridging X atoms (X = Cl, Br). The bridging of three octahedra by a heavy halogen atom explains the results of NMR and EXAFS analysis.
- Krahl, Thoralf,Kemnitz, Erhard
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p. 6653 - 6656
(2007/10/03)
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- Reactivity of Tin Difluoride
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A new value of the enthalpy of formation of tin difluoride was used to calculate the thermodynamic parameters of reactions of SnF2 with elemental substances and several metal oxides. SnF2 can act as an oxidizer and is useful for the synthesis of higher fluorides of group III-V transition metals, including those that have previously been prepared only by reactions with elemental fluorine (TiF4, NbF5, TaF5). The fact that such reactions occur was verified experimentally.
- Goryacheva,Rakov,Solov'ev
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p. 949 - 952
(2008/10/08)
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- Improved procedures for the generation of diborane from sodium borohydride and boron trifluoride
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Improved procedures for the generation of diborane by the reaction of NaBH4 in triglyme or tetraglyme with the BF3 adducts of di-n-butyl ether, tert-butyl methyl ether, monoglyme, dioxane, and tetrahydropyran were developed. In these
- Kanth, Josyula V. B.,Brown, Herbert C.
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p. 1795 - 1802
(2008/10/08)
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- The courses of the ammonolyses of the ammonium hexafluorometalates of aluminum, gallium, and indium, (NH4)3MF6 (M = Al, Ga, In)
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The courses of the ammonolysis reactions of the ammonium hexafluorometalates (NH4)3MF6 (M = Al, Ga, In) were investigated with the aid of in-situ powder diffractometry and differential thermal analysis. Under these conditions, the reaction of (NH4)3AlF6 with gaseous ammonia yields at about 360 °C AlF3 via the intermediates NH4AlF4, Al(NH3)2F3 and Al(NH3)F3. The ammonolysis of (NH4)3GaF6 produces GaN at about 400 °C. Depending upon the actual reaction conditions, the intermediates NH4GaF4 and Ga(NH3)3 as well as their ammonia adducts NH4GaF4 · NH3 and Ga(NH3)2F3 and the amide-ammoniate Ga(NH3)(NH2)F2 are observed. In the case of (NH4)3InF6 the intermediates (NH4)3InF6 · NH3 and In(NH3)F3 may exist; there are also indications for the reduction of In(III) to In(I) and for the existence of In(NH3)2F and InF as products of the ammonolysis of (NH4)3InF6.
- Roos, Meike,Wittrock, Joerg,Meyer, Gerd,Fritz, Silvia,Straehle, Joachim
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p. 1179 - 1185
(2008/10/08)
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- Thermal behavior of aluminum fluoride trihydrate
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The thermal decomposition of aluminum fluoride trihydrate was investigated by TG-DTG. The process was recognized to involve three stages. It was found that the apparent activation energy, E, and the preexponential factor, A, for stage I reaction were 41.9 kJ mol-1 and 102.49 S-1, respectively. For stage II reaction, the value of E was 47.5 kJ mol-1 and the most probable differential mechanism function was in the form of (1-α), and magnitude of 80.4 kJ mol-1 of E and a function in the form of 3/2(1-α)[-1n(1-α)(1/3)] were derived for stage III reaction. From the measurements conducted under increasing temperature conditions, contents of fluorine, C(F)(%), on moisture-free basis and water, CW(%), on current mass basis contained in the AlF3·3H2O sample were determined and correlation between the temperature range dictated by the quality specification of AlF3, C(F)≥61.0%, CW0.5%, and the heating rate were presented. The content of fluorine and water were also determined under isothermal conditions and correlation between the time duration of the treating temperature necessary for the quality specification to be met, and the magnitude of temperature were presented. (C) 2000 Elsevier Science B.V.
- Delong,Yongqin,Ying,Longbao,Wenkui
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- Synthesis, crystal structure and thermal behaviour of fluoroaluminates of the composition (NH4)[M(H2O)6](AlF6) (M = Zn, Ni), [Zn(H2O)6][AlF5(H2O)], and (PyH)4[Al2F10] ? 4 H2O
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Four new fluoroaluminates were obtained from fluoroacidic solutions of respective metal salts. The compounds of zinc (Ia: P21/c, a = 12.688(3), b = 6.554(1), c = 12.697(3) ?, β = 95.21(3)°, V = 1051.5(4) ?3, Z = 4) and nickel (Ib: P21/c, a = 12.685(3), b = 6.517(1), c = 12.664(2)?, β = 94.55(2)°, V = 1043.6(4) ?3, Z = 4) are isotypic and represent a new structure type consisting of two different cations, NH4+ and [M(H2O)6]2+ and [AlF6]3--anions. [Zn(H2O)6][AlF5(H2O)] (II: C2/m, a = 10.769(2), b = 13.747(3), c = 6.487(1)?, β= 100.02(3)°, V = 945.7(3) ?3, Z = 4) is characterized by a H2O/F-disorder in the [AlF5(H2O)]-octahedra in two trans positions. In (PyH)4[Al2F10] ? 4 H2O (III: Cmc21, a = 15.035(3), b = 20.098(4), c = 12.750(4) ?, V = 5364(2) ?3, Z = 8), bioctahedral [Al2F10]4- anions have been found for the first time. The structures are described and discussed in comparison. The new compounds were used as precursors in order to obtain new AlF3-phases. However, the thermal decomposition did not result in the formation of any new metastable AlF3-phase. Instead, phase mixtures of either α-AlF3 and β-AlF3 or AlF3 and MF2 were obtained.
- Adamczyk,Troyanov,Schneider,Kemnitz
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p. 2543 - 2548
(2008/10/08)
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- Pseudo-binary systems CsAlF4-KAlF4 and Cs3AlF6-K3AlF6
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Phase relations in the system CsAlF4-KAlF4 and Cs3AlF6-K3AlF6 were investigated by DTA and XRD methods. In the system CsAlF4-KAlF4, two intermediate compounds 3CsAlF4·KAlF4 and CsAlF4·KAlF4 were confirmed. The first one was indexed as orthorhombic with a=9.079±0.003, b=7.958±0.002, c=7.648±0.004A?. The second one α-CsAlF4·KAlF4 is also orthorhombic, a=10.982±0.005, b=10.093±0.006, c=6.160±0.002A?. Among the two compounds and KAlF4, two eutectic temperatures e1 and e2 are formed. The first eutectic temperature e1 is located in 42mol % KAlF4 at 525°C, and e2 in 70mol % KAlF4 at 510°C. The system Cs3AlF6-K3AlF6 is a successive solid solution system with the lowest melting point, the composition of which is 75mol % Cs3AlF6 at 775°C. In the solid solution, compound 2Cs3AlF4·K3AlF6 was formed at 656°C, and was indexed as a cubic cell with a=8.891A?.
- Chen, Rong,Zhang, Qiyun
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p. 135 - 139
(2008/10/09)
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- Thermische untersuchungen der kristallisation von korund
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With thermal analysis (DTA/TG) the crystallization behaviour of corundum with influence of the fluor compounds were investigated. The formation of aluminum fluoridhydroxide in the temperature range 400-600 °C are observed. Through the influence of AlF3 or HF the strong exothermic effect increased and a rapid loss of mass were noticed. The particle of corundum grow more, when the exothermic effects are large. We supposed, that also these exothermic effect will be due to the decomposition of may be adsorbed AlOF gas molecules.
- Plewa,Wojcik,Uphoff,Munser,Altenburg
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- Calorimetric investigations of some phases in the system sodium fluoride-aluminum fluoride
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Beside the two well-known minerals cryolite, Na3AlF6, and chiolite, Na5Al3F14, the binary system NaF-AlF3 also contains a third compound, NaAlF4, sodium tetrafluoroaluminate. Solid NaAlF4 has been prepared from its vapour under controlled conditions. The stability of NaAlF4 has been investigated by differential scanning calorimetry. It is shown that the disproportionation of the compound: 5NaAlF4(s) = Na5Al3F14(s)+2AlF3(s) takes place at considerable rate between 700 and 900 K. The enthalpy of this reaction is calculated and found to be -66.9 kJ. Enthalpies of the two solid state transitions α-Na3AlF6→β-Na3AlF6 and α-AlF3→β-AlF3 have also been measured and new values are reported. The enthalpy of formation of chiolite, Na5Al3F14, at 900 K has been recalculated from enthalpy increment data obtained by drop calorimetry. A value of ΔH°900 = -7513.6±12.0 kJ mol-1 has been obtained. This value is in disagreement with the recommended value given in JANAF Thermochemical Tables given at 900 K ΔH°f = -7559.2 kJ mol-1.
- Bruno,Herstad,Holm
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- Structures and thermal decomposition of enH2(H3O)[AlF6] and enH2[AlF5(H2O)]
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By precipitation with ethylene diamine (en) from a hydrofluoric acid solution of aluminium enH2(H3O)[AlF6] is formed. It crystallizes in the orthorhombic space group Pnma, a = 1084.9(1), b = 1079.4(1), c = 682.0(1) pm, R = 0.032. H3O+ cations and [AlF6]3- anions are connected via strong H bonds to layers which are further linked to a 3 D network by H bonds from the enH22+ cations. By recrystallization from water or precipitation from a less acid solution enH2[AlF5(H2O)] is formed, which crystallizes monoclinic in the space group P21 (a = 660.0(1), b = 563.5(1), c = 994.4(2) pm, β = 98.44(3)°, R = 0.029). The [AlF5(H2O)]2- anions are linked by strong O-H...F bonding to form 'einer-double chairs' interconnected again via the enH22+ cations to a 3 D framework. Thermoanalytical investigations show that enH2[AlF5(H2O)], by loss of water above 150°C, as well as enH2(H3O)[AlF6], by loss of water and HF above 120°C, transform to enH2AlF5. The subsequent decomposition goes over NH4+ containing intermediates towards β-AlF3. Before decomposition the oxonium fluoroaluminate reveals a reversible phase transition at 99°C.
- Bentrup,Ahmadi,Kang,Massa
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p. 1465 - 1470
(2008/10/09)
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- The crystal structure of Ba2Cu2AlF11: A new structure type in copper fluoride crystal chemistry
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Ba2Cu2AlF11 is trigonal: a = 7.301(1) A, c = 14.145(2) A. γ = 120°, Z = 3. The crystal structure was solved in the space group P32 (no 145), from X-ray single crystal data using 2675 unique reflections (2476 with F/σ(F) > 4). It consists in a complex tridimensional arrangement of copper-fluorine and aluminium-fluorine octahedra, with an original kind of linkage which involves simultaneously edges and vertices.
- Dupont, Nathalie,De Kozak, Ariel,Gredin, Patrick,Samoue, Maurice
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p. 331 - 334
(2008/10/09)
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- Energy release in the reaction of metal powders with fluorine containing polymers
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Fluorine and its derivatives have been used as a substitute to oxygen-containing oxidizers in higher performing propellants and other energetic materials. They typically react rapidly with metals or thin oxide layers of the metals to produce metal fluorides, generally in the gaseous state. Thermal reactions of stoichiometric mixtures of metal (M=Al, Ti)-F containing polymers have been studied using thermal analyzers and their energetics are compared with the metals in other halogen element containing oxidizers. The experimental results indicated that thermal reaction becomes more exothermic as the bond strength between Al-X (X=F, Br, I) becomes stronger. It was also found that oxidation of metal powders is largely affected by the size of metal powders as well as the nature of existing oxide layer.
- Lee,Reed,Brady,Finnegan
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p. 1699 - 1705
(2008/10/08)
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- A study on the phase diagram of A1F3-CsF system
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Phase relations of the AlF3-CsF system have been investigated by the methods of DTA and XRD with quenching technique. Four compounds were identified: Cs3AlF6, CsAlF4, CsF·2AlF3 and CsF·3AlF3. Cs3AlF6 melts congruently at 790°C. The first eutectic, E1, between Cs3AlF6 and CsF is located in 10.0 mol% AlF3 at 654°C. CsF-2AlF3 and CsF-3AlF3 melt incongruently at 508° and 653°C, respectively. The second eutectic, E2, was observed in 42.0 mol% AlF3 at 471°C. The compound CsAlF4 formed in the solid eutectic when cooled below 443°C. CsAlF4 has α and β forms, transformation of which takes place reversibly at 422°C. All phase structures in the system were confirmed by X-ray powder diffraction analysis.
- Chen, Rong,Cao, Jie,Zhang, Qiyun
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p. 145 - 150
(2008/10/09)
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- The Crystal Structure of LiPdGaF6, RbPdAlF6 and K1.06Pd0.95Fe1.05F6
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Single crystals of LiPdGaF6 (blue; trigonal, P3-1C-D(2)3d (No. 163), a=505.72(2), c=923.7(2) pm; LiCaAlF6-Type [1]), RbPdAlF6 (violet; orthorhombic, PNMA-D(16)2h (No. 62), a=729.0(1), b=711.1(1), c=1006.5(2) pm; CsAgFeF6-Type [2]) and K1.06Pd0.95Fe1.05F6 (greenish-blue; tetragonal, P42/MBC-D(13)4h (No.135), a=1279.07(7), c-800.2(1) pm; K1.08MnFeF6-Type [3]; four cycle diffractometer data, Siemens AED2) are obtained by heating the binary fluorides in sealed Pd-tubes under dry argon [solid state reaction, T~650, t~ 19 d) (39 d, 24 d)].
- Mueller, Markus,Mueller, Bernd G.
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- New fluorination reactions of ammonium bifluoride
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This paper describes a novel route for the production of low-oxygen-containing fluorozirconate glasses. The process involves the use of a hitherto unknown solid-state chemical reaction between ammonium bifluoride and specific anhydrous and hydrated metal fluoride salts. The products are defined as ammonium fluoride-metal fluoride complexes. The kinetics of their formation and subsequent dissociation were followed by thermogravimetric analysis. It was observed that these complexes decompose with the evolution of HF above temperatures at which ammonium bifluoride decomposes and where its supply may be exhausted. These materials have been used to melt fluorozirconate glasses. The oxygen contents of these glasses have been dramatically reduced to approximately 10 ppm. The glass stability, as defined by the lack of devitrification on reheating, also appears to increase with a lowering of the oxygen content. This implies that the mechanism of nucleation and growth is predominantly heterogeneous and not homogeneous nucleation. Furthermore, the production of long lengths of crystal-free fluoride fibers for transcontinental optical communication systems appears to be a realistic goal, especially if the heterogeneities can be eliminated.
- Sanghera,Hart,Sachon,Ewing,Aggarwal
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p. 1339 - 1346
(2008/10/08)
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- Activation of the BCO unit in the ketenylidene analogue (μ-H)3Os3(CO)9(μ3-BCO) by electrophiles: Syntheses of vinylidene and alkyne analogues
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The Lewis acids BX3 (X = Cl, Br), BH3, B-Cl-9-BBN, and PhBCl2 react with (μ-H)3Os3(CO)9(μ3-BCO) (I), a ketenylidene analogue, apparently through electrophilic attack at the oxygen of the unique carbonyl. Reactions of I with BX3 (X = Cl, Br) result in an exchange of B and C atom positions in the BCO unit to form a vinylidene analogue, (μ-H)3Os3(CO)9(μ3-CBX 2). Boron-10-labeling experiments indicate that this transformation occurs through an intramolecular interchange of the boron and carbon atom positions. The ketenylidene analogue (μ-H)3Os3(CO)8(PPh3)(μ 3-BCO) reacts similarly with BCl3 to produce (μ-H)3Os3(CO)8(PPh3)(μ 3-CBCl2). The nucleophiles PMe3, PPh3, and NMe3 add to the tricoordinate boron of (μ-H)3Os3-(CO)9(μ3-CBCl 2). Above -10°C the NMe3 adduct is converted to the salt [NMe3H][(μ-H)2Os3(CO)9(μ 3-CBCl2)] and the PMe3 adduct dissociates. The PPh3 adduct decomposes above 30°C. The reaction of (μ-H)3Os3(CO)9(μ3-BCO) with THF·BH3 produces (μ-H)3Os3(CO)9(μ3-BCH 2), a second type of vinylidene analogue. In this case the boron and carbon atoms do not change positions. Alkyne analogues, (μ-H)3Os3(CO)9[μ3-η 2-C(OBC8H14)B(Cl)] and (μ-H)3Os3(CO)9[μ3-η 2-C{OB(Ph)Cl}B(Cl)] are obtained from reactions of (μ-H)3Os3(CO)9(μ3-BCO) with B-Cl-9-BBN and PhBCl2. These compounds react with BCl3 to produce (μ-H)3Os3(CO)9(μ3-CBCl 2). They also react with HCl to produce (μ-H)3Os3(CO)9(μ3-CH).
- Workman, David P.,Jan, Deng-Yang,Shore, Sheldon G.
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p. 3518 - 3525
(2008/10/08)
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- Aluminium-27 N.M.R. Studies of Aluminium Fluoro Complexes in Dichloromethane Solution: Evidence for the Tetrafluoroaluminate Anion
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Mixed aluminium chloro/fluoro anions are formed in dichloromethane solution by the interaction of AlCl3 and .Aluminium-27 n.m.r. studies are restricted to the stoichiometric ranges F/Al from 1:1 to 3:1 and F/Al>8:1.Between these limits rapid precipitation reactions occur.In the Fluoride-rich stoichiometric range there is rapid exchange on the n.m.r. time scale between the aluminium fluoro anion and free fluoride, so that a direct identification of the species by the multiplicity of the resonance is not possible.Indirect evidence strongly suggests that the aluminium species is -.In the F/Al stoichiometry range from 1:1 to 3:1 aluminium-27 resonances were observed for all the other possible - species.Studies on the aluminium iodo/fluoro system support the identification of -, but the system is labile and the mixed iodo/fluoro species undergo rapid disproportionation.
- Colton, Ray,Eller, Gary P.
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p. 1605 - 1610
(2007/10/02)
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- Crystal structure of the metastable form of aluminum trifluoride β-AlF3 and the gallium and indium homologs
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The crystal structure of the metastable phase β-AlF3, which is related to the hexagonal tungsten bronze structure, has been solved by X-ray powder and single-crystal diffraction methods. The crystal habit is pseudo-hexagonal with systematic twinning (rotation of 120° around the c axis), but the true symmetry is orthorhombic. The network is built from very regular AlF6 octahedra rotated by approximately 7.2° from the positions of the ideal HTB structure. A similar network, with the same propagation of the tilting, was observed in the compound (H2O)0.33FeF3 and in the metastable polymorphs of CrF3 and of VF3.
- Bail, A. le,Jacoboni, C.,Leblanc, M.,Pape, R. de,Duroy, H.,Fourquet, J. L.
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- Synthesis and thermal decomposition of (NH4)2[MIIIF5(H2O)] (M = Al, Fe and Cr)
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Ammonium pentafluorometallate monohydrates were prepared by different methods and characterized by chemical analysis, IR spectrometry and X-ray diffraction. Unit cell parameters were determined for the Fe and Cr compounds, which were found to be isostruct
- Bentrup. U.,Kolditz, L.
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p. 827 - 832
(2008/10/08)
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- Comparison of the thermal behaviour of α-AlF3 and aluminium fluoride hydrates
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The thermal decompositions of β-AlF3·3H2O, AlF3·3.5H2O, AlF3·1.5H2O, β-AlF3 and hydroxyfluorides of aluminium were investigated. The literature data were complemented with X-ray
- Menz,Zacharias,Kolditz
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p. 811 - 815
(2008/10/08)
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- Reaction of liquid aluminum with gaseous ClO3F
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The reaction of liquid Al with gaseous perchloryl fluoride, ClO3F, is highly exothermic and has potential for stored chemical energy applications. We have established the mode of thermal decomposition of ClO3F mass spectrometrically using the low pressure Knudsen effusion method and, also, using a transpiration method in which a high pressure cell is directly sampled through a differentially pumped vacuum system. The results show that ClO3F begins decomposition at approximately 500°C and that by 700°C, decomposition to Cl2, F2, and O2 is nearly complete. We have also studied the reaction of dissociated ClO3F with liquid Al by Knudsen and transpiration mass spectrometry and by direct thermogravimetric analysis at 700-800°C. The experimental data indicate that reaction occurs primarily with the F2 component of the gas, resulting in formation of a passivating film of AlF3. Analysis of the kinetic data suggests that film growth progresses as follows: (1) nucleation and growth of AlF3 precipitation sites; (2) edge growth of AlF3 islands on the metal surface; (3) island coalescence; and (4) complete film coverage with diffusion-controlled thickening, according to a parabolic rate law. The reactant gas flow geometry is important since there is evidence for kinetically-favored gas phase reactions that can, under certain circumstances, interfere with formation of the AlF3 product layer. We conclude that under the experimental conditions studied, equilibrium is achieved only in an interfacial sense. In order to completely react the ClO3F and form chloride and oxide products, it may be necessary to first deplete the fluorine component of the gas, followed by disruption of any passivationg film to expose fresh aluminum.
- Cook,Plante,Bonnell,Hastie
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p. 293 - 312
(2008/10/08)
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- Reactions of aluminum with uranium fluorides and oxyfluorides
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Every 30 to 40 million, or so, operating hours a destructive reaction is observed in one of the approximately 4000 large compressors that move UF6 through the gaseous diffusion plants. Despite its infrequency, the reaction can be costly in terms of equipment and time. Laboratory experiments reveal that the presence of moderate pressures of UF6 actually cools heated aluminum, although thermodynamic calculations indicate the potential for a 3000-4000°C temperature rise. Within a narrow and rather low (6 or UO2F2. 1. An initiating source of heat must be provided. 2. The film protecting the aluminum must be breached. 3. Reaction products must not be allowed to build up and smother the reaction.
- Leitnaker,Nichols,Lankford
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p. 271 - 291
(2008/10/08)
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