7783-40-6Relevant articles and documents
Synthesis of bimetallic trifluoroacetates through a crystallochemical investigation of their monometallic counterparts: The case of (A, A′)(CF3COO)2·: N H2O (A, A′ = Mg, Ca, Sr, Ba, Mn)
Dulani Dhanapala,Mannino, Natalie A.,Mendoza, Laura M.,Tauni Dissanayake,Martin, Philip D.,Suescun, Leopoldo,Rabuffetti, Federico A.
, p. 1420 - 1430 (2017)
Owing to their potential as single-source precursors for compositionally complex materials, there is growing interest in the rational design of multimetallic compounds containing fluorinated ligands. In this work, we show that chemical and structural principles for a materials-by-design approach to bimetallic trifluoroacetates can be established through a systematic investigation of the crystal-chemistry of their monometallic counterparts. A(CF3COO)2·nH2O (A = Mg, Ca, Sr, Ba, Mn) monometallic trifluoroacetates were employed to demonstrate the feasibility of this approach. The crystal-chemistry of monometallic trifluoroacetates was mapped using variable-temperature single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analysis. The evolution with temperature of the previously unknown crystal structure of Mg(CF3COO)2·4H2O was found to be identical to that of Mn(CF3COO)2·4H2O. More important, the flexibility of Mnx(CF3COO)2x·4H2O (x = 1, 3) to adopt two structures, one isostructural to Mg(CF3COO)2·4H2O, the other isostructural to Ca3(CF3COO)6·4H2O, enabled the synthesis of Mg-Mn and Ca-Mn bimetallic trifluoroacetates. Mg0.45Mn0.55(CF3COO)2·4H2O was found to be isostructural to Mg(CF3COO)2·4H2O and exhibited isolated metal-oxygen octahedra with Mg2+ and Mn2+ nearly equally distributed over the metal sites (Mg/Mn: 45/55). Ca1.72Mn1.28(CF3COO)6·4H2O was isostructural to Ca3(CF3COO)6·4H2O and displayed trimers of metal-oxygen corner-sharing octahedra; Ca2+ and Mn2+ were unequally distributed over the central (Ca/Mn: 96/4) and terminal (Ca/Mn: 38/62) octahedral sites.
Photoluminescence of nanocrystalline SrMgF4 prepared by a solution chemical route
C.Veitsch,Kubel,Hagemann
, p. 168 - 175 (2008)
SrMgF4 was prepared by precipitation in aqueous solution. Alkaline earth metal acetates and ammonium fluoride were used as precursors. After drying and annealing the samples at different temperatures and times, single phase SrMgF4 was obtained. By varying the annealing conditions, the mean crystallite size could be adjusted. Furthermore, the thermally treated samples displayed UV-excited intensive broad band luminescence in the visible region. The emissions colour and intensity can be adjusted by the tempering conditions. X-Ray diffraction, TEM-microscopy, fluorescence and IR-spectroscopy were used for analysis.
Defluorination of graphite fluoride applying magnesium
Koch, Ernst-Christian
, p. 512 - 516 (2001)
Consolidated stoichiometric mixtures of graphite fluoride (1) and magnesium (2) upon ignition under argon atmosphere (0,1 MPa) yield very high flame temperature of ～ 5600 K as determined by infrared emission spectroscopy. The combustion product was analysed by X-ray powder diffraction and revealed the presence of magnesium fluoride and graphite as well as structurally low ordered carbon. A possible reaction mechanism is discussed.
The influence of HS-AlF3 on the decomposition reaction of MgH2
Noack, Johannes,Scholz, Gudrun,Rüdiger, Stephan,Feist, Michael,Kemnitz, Erhard
, p. 82 - 86 (2009)
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).
Synthesis and characterization of MgF2 and KMgF3 nanorods
Cao, Minhua,Wang, Yonghui,Qi, Yanjuan,Guo, Caixin,Hu, Changwen
, p. 2205 - 2209 (2004)
MgF2 nanorods with diameters of 60-100nm were synthesized by a microemulsion method. Subsequent hydrothermal reaction of as-synthesized MgF2 nanorods and KF at 240°C for 3 days or 140°C for 7 days resulted in KMgF3 nanorods, which retained the rod-like morphology of the source material MgF2 in the reaction process. The morphology of as-synthesized MgF2 strongly depended on the molar ratio between water and the surfactant CTAB and the concentration of CTAB.
Synthesis and characterization of new Mg-O-F system and its application as catalytic support
Zieliński, Micha?,Kiderys, Angelika,Pietrowski, Mariusz,Tomska-Foralewska, Iwona,Wojciechowska, Maria
, p. 54 - 57 (2016)
The Mg-O-F system (MgF2-MgO) with different contents of MgF2 (100-0%) and MgO is tested as support of iridium catalysts in the hydrogenation of toluene as a function of the MgF2/MgO ratio. Mg-O-F samples have been prepared by the reaction of magnesium carbonate with hydrofluoric acid. The MgF2-MgO supports, after calcination at 500 °C, are classified as mesoporous of surface area (34-135 m2·g- 1) depending on the amount of MgO introduced. The Ir/Mg-O-F catalysts have been tested in the hydrogenation of toluene. The highest activity, expressed as TOF, min- 1, was obtained for the catalyst supported on Mg-O-F containing 75 mol%MgF2.
BaSr(NH4)Mg5F15, A tetragonal tungsten bronze structure with ammonium barium disorder and its solid solutions Ba xSr2-x(NH4)Mg5F15 (x = 1.8-0.6)
Kubel,Pantazi
, p. 752 - 756 (2007)
The new fluoride BaSr(NH4)Mg5F15 precipitates as a nanocrystalline powder from aqueous solutions of the alkaline earth ions and ammonium fluoride. The compound crystallizes in the tetragonal tungsten bronze structure type with lattice parameters of a,b = 12.4492(14) A and c = 3.9421(4) A (space group P4/mbm [Nr. 127], structure refinement from powder data, RBragg = 4.0%). Corner-linked magnesium-fluoride octahedra form a channel structure which contains one empty triangular channel, one channel filled with Sr2+ [CN = 8+4] and one channel with disordered Ba2+ and NH4+ (ratio 1:1) with CN = 7+8. Solid solutions between the composition limits Ba(Ba0.8Sr 0.2)(NH4)Mg5F15 and (Ba 0.6Sr0.4)Sr(NH4)Mg5F15 were obtained. The crystallite size increases from 15 to 75 nm with increasing barium concentration. The thermal stability between 350 to 450°C depends on the amount of absorbed (NH4)F. Heated samples show luminescence and phosphorescence.
Improving hydrogen sorption kinetics of MgH2 by mechanical milling with TiF3
Ma, Lai-Peng,Wang, Ping,Cheng, Hui-Ming
, p. L1-L4 (2007)
MgH2 + TiF3 system was mechanically prepared and investigated with regard to hydrogen absorption/desorption performance. It was found that the sorption kinetics of MgH2 can be markedly improved by mechanical milling with 4 mol% TiF3, in particular at reduced operation temperatures. Even at a moderate temperature range (313-373 K), the hydrogen absorption can be largely completed within about 25 s. On the desorption aspect, the catalytic enhancement arising upon adding TiF3 allows the sample to desorb near 5 wt.% hydrogen within 600 s at 573 K. Furthermore, such enhancement in kinetics was observed to persist in the absorption/desorption cycles. Preliminary XRD examination was also performed to understand the observed catalytic effect of TiF3 additive.
Reaction of magnesium oxide and magnesium silicates with ammonium hydrodifluoride
Nesterov,Makarov,Kalinnikov
, p. 712 - 716 (2006)
The reactions of magnesium oxide and magnesium silicates (forsterite and serpentines) with ammonium hydrodifluoride is studied using DTA, X-ray powder diffraction, and IR spectroscopy. The conditions for the formation of intermediate phases are determined
Sol-gel-fluorination synthesis of amorphous magnesium fluoride
Krishna Murthy,Gross, Udo,Ruediger, Stephan,Kemnitz, Erhard,Winfield, John M.
, p. 739 - 746 (2006)
The sol-gel fluorination process is discussed for the reaction of magnesium alkoxides with HF in non-aqueous solvents to give X-ray amorphous nano-sized magnesium fluoride with high surface areas in the range of 150-350 m 2/g (HS-MgF2). The H2 type hysteresis of nitrogen adsorption-desorption BET-isotherms is indicative for mesoporous solids. A highly distorted structure causes quite high Lewis acidity, shown by NH 3 temperature-programmed desorption (NH3-TPD) and catalytic test reactions. XPS data of amorphous and conventionally crystalline MgF2 are compared, both show octahedral coordination at the metal site. Thermal analysis, F-MAS NMR- and IR-spectroscopy give information on composition and structure of the precursor intermediate as well as of the final metal fluoride. The preparation of complex fluorides, M+MgF 3-, by the sol-gel route is reported. From the magnesium fluoride gel of the above process thin films for optical application are obtained by, e.g., spin coating.
