- Synthesis of hexagonal NaY(Gd)F4 ultrafine nanocrystals using sodium acetate as ionic mediator
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Hexagonal phase ultrafine nanoparticles of NaY(Gd)F4 were synthesized using chloride precursors and sodium acetate to provide liquid environment for ionic transportand as a source of sodium ions. Prepared ultrafine nanocrystals were analysed by XRD, laser Doppler electrophoresis and TEM measurements. Absence of fluoroacetic acid was confirmed by NMR of wash water obtained by dispersion centrifugation. Synthesized nanocrystals were 8.9?nm in diameter and had a hexagonal crystal structure. The method is appropriate for further experimental development, e.g. the synthesis of luminescent fluorides based on NaY(RE)F4 system, and for possible industrial application because of its ability to prepare large amounts of nanocrystals and due to the fact that the process is affordable and environmental friendly.
- Bart?něk, Vilém,Poryvai, Anna,Ulbrich, Pavel
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- Sorption and desorption of BrF3 on NaF: Studies on thermodynamics and kinetics
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Temperature dependence of bromine trifluoride vapor pressure over its adduct with sodium fluoride has been determined; the adduct normal dissociation temperature has been determined. Kinetics of sorption and desorption processes in BrF3(gas)–NaF(solid) system have been studied. The equation was proposed to illustrate the link between forward reaction rate (Ка) described by Arrhenius equation and experimental value (Ki): Ki= Kа? (Pa/Peq)m, where Ki – observed reaction rate constant, Ka – forward reaction rate constant described by Arrhenius equation; Pa – partial pressure of BrF3; Peq – equilibrium pressure of BrF3 above BrF3?3NaF; m – factor characterizing the interaction area of BrF3 with NaF. The application of this equation makes possible to determine the true reaction rate values and reaction activation energy in chemisorption terms; it also helps to calculate the degree BrF3 sorption on NaF reaction at different temperatures and adsorbate pressures. The possibility of sorption-desorption separation of bromine trifluoride – uranium hexafluoride – iodine pentafluoride system with use of sodium fluoride was shown.
- Zherin,Rudnikov,Ostvald,Sobolev,Amelina
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- New method of beta-NaYF4: Yb3+, Er3+ synthesis by using beta-cyclodextrin
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Abstract The novel method of synthesis of the hexagonal modification beta-NaYF4 doped with Yb3+ (17 at.%) and Er3+ (3 at.%) using beta-cyclodextrin is proposed. Complex fluorides were prepared by decomposition of the mixture of metal fluoroacetates hydrates with and without addition of beta-cyclodextrin and were investigated by X-ray diffraction, energy dispersive X-ray analysis, scanning and transmission electron microscopy. The samples prepared by adding beta-cyclodextrin in the reaction mixture are single phase and have a hexagonal structure. At the same time, decomposition of the mixture of metal trifluoroacetates hydrates without beta-cyclodextrin is accompanied by pyrohydrolysis, leading to a contamination of the products by impurities of yttrium oxyfluorides and sodium fluoride. So a new synthetic approach proposed in this work allows to obtain pure complex fluorides with homogeneous distribution of elements and with homogeneous pore distribution.
- Fedorova, Anna A.,Fedulin, Andrey I.,Morozov, Igor V.
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p. 173 - 177
(2015/08/06)
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- Study of the reaction between boron trifluoride methanol complex and sodium methoxide
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The reaction between boron trifluoride methanol complex and sodium methoxide in methanol solution was investigated using conductivity as the reaction indicator. The reaction conditions were examined and a mechanism of this reaction was proposed. Moreover, proper reaction conditions were proposed for boric acid preparation using this reaction. 2014
- Wuke, Lang,Weijiang, Zhang,Jiao, Xu,Lei, Zhang
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p. 1530 - 1540
(2014/07/08)
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- Preparation and examination of the properties of complex scandium fluorides
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Precipitation of scandium with sodium fluoride from an ammonium hydrogen difluoride solution was examined at the molar ratios of Na to Sc within 1-14 and different initial concentrations of scandium in solution. The composition of the resulting precipitate was determined by X-ray phase analysis method. The solubility of the scandium compounds synthesized was examined. Pleiades Publishing, Ltd., 2011.
- Sokolova, Yu. V.,Cherepanin
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p. 1319 - 1323
(2012/02/03)
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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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- A process for preparing acylfluorides
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A process for preparing acylfluorides by reaction of carbonyl fluoride COF2 with compounds having general formula:T = CR1R2 wherein:T is O or CF2R1 and R2, equal or different, are F or a R(O)t radical, wherein R = linear or branched C1-C7 (per)fluoroalkyl, optionally containing one or more oxygen atoms, t is an integer equal to zero or 1; wherein a catalyst supported on porous compound is used, the catalyst being selected from: CsF, RbF, KF, AgF, each optionally in admixture with one or more of the others.
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Page column 5
(2008/06/13)
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- Process for preparing acylfluorides
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A process for preparing acylfluorides by reaction of carbonyl fluoride COF2 with compounds having general formula: T=CR1R2 ??(I) wherein: T is O or CF2 R1 and R2, equal or different, are F or a R(O)t radical, wherein R=linear or branched C1-C7 (per)fluoroalkyl, optionally containing one or more oxygen atoms, t is an integer equal to zero or 1; wherein a catalyst supported on porous compound is used, the catalyst being selected from: CsF, RbF, KF, AgF, each optionally in admixture with one or more of the others.
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- X-ray and Raman investigations on cyanides of mono- and divalent metals and synthesis, crystal structure and Raman spectrum of Tl5(CO3)2(CN)
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Pseudobinary cyanides of monovalent and divalent metals were synthesized, and X-ray and Raman data of the cyanides were measured. Single crystal X-ray structure analyses were performed on Zn(CN)2 (Pn3m (No. 224), a = 591.32(7) pm), Hg(CN)2 (I42d (No. 122), a = 969.22(14) and c = 890, 15(18) pm) and for the first time on AgCN (I42d (No. 166), a = 600.58(8) and c = 526.28(11) pm). The data are compared with literature data. The reaction of TlF and NaCN in 25% aqueous ammonia solution in air led to Tl5(CO3)2(CN) which was characterized by X-ray (Cmca (No. 64), 1468.1(3), 1171.6(2) and 1266.0(3) pm) and Raman spectroscopy.
- Reckeweg, Olaf,Simon, Arndt
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p. 895 - 900
(2007/10/03)
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- Low-temperature precursor synthesis of crystalline nickel disulfide
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Pure, crystalline nickel disulfide is synthesized within seconds from the solid-state reaction between potassium hexafluoronickelate(IV) and sodium pentasulflde hydrate at ~65°C. The nickel disulfide product is isolated by simply washing away the byproduct salts. The reaction is influenced by the hydration and the sulfur content of the sulfiding agent and by the transition-metal precursor. Increasing the hydration of the sodium pentasulfide or lowering the oxidation state of the nickel in potassium hexafluoronickelate from Ni(IV) to Ni(III) favors a less crystalline product. Reactions containing sulfiding agents with lower sulfur content, such as sodium monosulfide or sodium disulfide, produce mixtures of nickel monosulfide and nickel disulfide. X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry results are presented.
- Bonneau, Philippe R.,Shibao, Robert K.,Kaner, Richard B.
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p. 2511 - 2514
(2008/10/08)
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- PREPARATION OF Rb2NaYF6:Ce3 + AND Cs2NaYF6:Ce3 + - A PROSPECT FOR TUNABLE LASERS IN THE BLUE-GREEN WAVELENGTH.
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A systematic study of the systems RbF-NaF-YF//3 and NaF-CsF-YF//3 has been made in order to synthesize Ce**3** plus -doped Rb//2NaYF//6 and Cs//2NaYF//6. Based on preliminary results of the absorption fluorescence efficiency, lifetime, and excited-state absorption, we conclude that a series of compounds (in the form of single crystals) of the general form A//2BYF//6:Ce**3** plus is a worthy prospect for a broad-band, wavelength tunable laser from 400 to 480 mu m which makes it attractive for optical communication.
- Mroczkowski,Dorain
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p. 259 - 265
(2008/10/08)
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