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.
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.
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.
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.
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
Characterization of surfacial basic sites of sol gel-prepared alkaline earth fluorides by means of PulseTA
Feist,Teinz,Manuel, S. Robles,Kemnitz
, p. 170 - 178 (2011)
The CO2 adsorption properties of a series of different sol gel-prepared metal fluorides of the alkaline earth row and aluminium, among them two mixed (doped) metal fluorides was investigated by applying Pulse Thermal Analysis. The alkaline earth flurorides, which exhibit nanoscopic properties, have not only acid, but basic sites as well. For the first time, these basic sites have been characterized by the exothermicity of the first CO2 injection pulse. If the basicity is weak or absent, the alternating injection of water can generate OH groups at the surface of the fluorides. They mostly act as basic sites and allow a stronger differentiation of the basic properties, but the formed OH groups can exhibit an acid character as well. The impact of OH groups can affect a different influence on the sorption properties of the solids: the adsorption ability vs. CO2 can be promoted, suppressed or remain unaffected.
EFFECT OF GRAIN GROWTH ON HOT-PRESSED OPTICAL MAGNESIUM FLUORIDE CERAMICS.
Lin,Hon,Yang
, p. c. 136-c. 137 (1988)
An optical MgF//2 ceramic was hot-pressed at 838 to 983 K with 241-MPa pressure. In the early stages of grain growth the mechanical strength was directly proportional to grain size, which appeared to contradict the expectations of the Petch and Knudsen relations. Optical transmission was inversely proportional to grain size, especially in the visible wavelength. This study thus demonstrates a particular case in which increasing grain size promotes higher mechanical strength but lower optical transmission.
Synthesis and studies of magnesium hexafluorozirconates MgZrF6 ? nH2O (n = 5, 2, 0)
Didenko,Gaivoronskaya,Voit,Gerasimenko,Kavun, V. Ya.
, p. 1339 - 1346 (2010)
Crystalline magnesium hexafluorozirconate MgZrF6 ? 5H 2O isostructural to MnZrF6 ? 5H2O, and having a chain-like structure, was synthesized and studied. According to thermogravimetry, the compound undergoes stepwise dehydration in the temperature range of 50-420°C to give the stable phase MgZrF6 ? 2H 2O and the final product MgZrF6 isostructural to the cubic modification of MZrF6 (M = Cu, Fe). The vibrational spectra of the initial compound and the dehydration products are analyzed and the structures of the compounds are considered.
Upgrading of furfural to biofuel precursors: Via aldol condensation with acetone over magnesium hydroxide fluorides MgF2- x(OH)x
Xu, Minrui,Célérier, Stéphane,Comparot, Jean-Dominique,Rousseau, Julie,Corbet, Matthieu,Richard, Frédéric,Clacens, Jean-Marc
, p. 5793 - 5802 (2019/11/05)
Wastes from lignocellulosic materials, especially hemicellulose, are extremely promising resources to produce fuels from renewable raw materials. Furfural, resulting from the depolymerization of hemicellulose, is often considered as an extremely interesting platform molecule. Particularly, new biofuels containing molecules with 8 and 13 carbon atoms can be produced from aldol condensation of furfural and acetone followed by a deoxygenation reaction. In this work, several magnesium hydroxide fluorides MgF2-x(OH)x were prepared by a sol-gel method with various F/Mg ratios (0 to 2) at 100 °C. All solid samples were fully characterized by several techniques (nitrogen adsorption-desorption, TEM, IR, XRD and ICP). MgF2-x(OH)x were mainly composed of an intimate mixture of MgF2 and Mg(OH)2-x(OCH3)x and exhibited both acid-base properties and high surface areas. From CO2 adsorption experiments, a basicity scale corresponding to basic sites with moderate strength was established: MgF1.5(OH)0.5 > MgF(OH) ～ MgF1.75(OH)0.25 > MgF0.5(OH)1.5 > Mg(OH)2 ? MgF2. It was proposed that the presence of fluorine allowed stabilization of the basic sites with moderate strength at ambient atmosphere. The aldol condensation of furfural and acetone was carried out under mild reaction conditions (50 °C, Patm) over MgF2-x(OH)x. These catalysts were involved in this reaction without using a classical activation step for basic solid catalysts, which constitutes a major advantage of energy conservation and thus, economic efficiency. The solid with a F/Mg ratio equal to 1.5 (MgF1.5(OH)0.5) exhibited the highest activity, the furanic dimer (1,5-di(furan-2-yl)penta-1,4-dien-3-one) being the main product. A good correlation between the catalytic activity and the basicity scale was highlighted. Based on these results, the nature of active sites was proposed: a combination of a Lewis acid site (coordinatively unsaturated metal site) in the vicinity of a basic site (hydroxyl groups of Mg(OH)2-x(OCH3)x). The effect of the furfural/acetone ratio on the catalytic properties of MgF1.5(OH)0.5 was also investigated.
How does TiF4 affect the decomposition of MgH2 and its complex variants?-An XPS investigation
Jain, Ankur,Agarwal, Shivani,Kumar, Sanjay,Yamaguchi, Shotaro,Miyaoka, Hiroki,Kojima, Yoshitsugu,Ichikawa, Takayuki
, p. 15543 - 15551 (2017/08/10)
Magnesium hydride and its complex variants, i.e. Mg(AlH4)2 and Mg(BH4)2 are known for their high hydrogen capacity. The theoretical capacities of these three are 7.6 wt%, 9.3 wt% and 14.4 wt%, respectively. In spite of having very attractive H2 capacities, their high operating temperature, i.e. more than 300 °C and sluggish kinetics are big issues to be solved before these can be realized for a practical hydrogen storage system. There are several efforts devoted to reduce the working temperature and enhance the sorption kinetics using various additives. Ti-based additives have always been interesting contenders in enhancing the kinetics as well as altering thermodynamics thus reducing the working temperature for various hydrides. Recently, TiF4 has shown superior catalytic activity on the decomposition of Mg(AlH4)2. This motivates us to study its effect on the decomposition of all the above-mentioned Mg-based hydrides. It is observed that the addition of 10 wt% TiF4 to the above materials greatly influences the decomposition temperature. The decomposition temperature for all three reactions is shifted to the lower temperature side. The oxidation state of the catalyst surface has been investigated using the XPS technique and then the detailed mechanism associated with this improvement is proposed herein.
