Alkali Metal Fluorides Research Articles

Theoretical Investigation of 19F NMR Chemical Shielding of Alkaline-Earth-Metal and Alkali-Metal Fluorides

The 19F NMR chemical shieldings of solid-state alkaline-earth-metal fluorides MF2 (M = Be, Mg, Ca, Sr, Ba) and alkali-metal fluorides MF (M = Li, Na, K, Rb, Cs) were systematically studied by the gauge-independent atomic orbital (GIAO) method at the level of density functional theory (DFT). The 6-311+G(d) basis set was used for the inspected fluoride ion. The performance of the effective core potentials (ECP) of LanL2DZ and CRENBL basis sets for metal atoms were compared to 3-21G all-electron basis set. The role of d polarization functions for metal atoms is investigated. The results show that the clusters [FMg3F9]4-, [FM4F6]+ (M = Ca, Sr, Ba), and [FM6]5+ (M = Li, Na, K, Rb, Cs) used to model the bulk solids are reasonable. The electrons in the next outermost shell of metal atoms have significant influence on the 19F NMR calculations and should be treated as valence electrons together with the electrons in the outermost shell, while the remaining electrons can be represented by the ECP of CRENBL basis set. When the CRENBL basis set (with ECP for core electrons) supplemented with two sets of d polarization functions was used for the metal atoms, the approach of locally dense basis sets can be used to successfully reproduce the 19F shielding values. Since only the inspected resonant fluorine atom needs a high-grade all-electron basis set, it is a relatively inexpensive means of obtaining reliable shielding properties for the inspected species. In addition, the different exchange-correlation functional implemented in hybrid DFT method has a minor influence on the calculated shielding. Although all the calculated results are somewhat overestimated, the correlation coefficients and the slopes of the fitting lines between the theoretical predictions and experimental observations are close to unity, indicating the good agreement of the theoretical results to the experimental values.

Development of Methods of Synthesis of Volatile Organogallium and Organoindium Compounds Used to Prepare Semiconductors

Three new methods for large scale synthesis of electronic grade trimethylgallium and trimethylindium are presented. These methods are based on direct synthesis of trialkylgallium compounds from the Ga/Mg alloy or the mixture of this metals and alkyl halides, RX. The first method consists in the cleavage of the stable trimethylgallium-diethyl ether adduct by heating it in the mixture with ether of higher boiling point. The second one is the reaction of the mixture of Ga and Mg with methyl iodide in a high boiling ether solvent such as diisoamyl ether, i-Am2O. The third method consist in preliminary formation of the stable adducts of trimethylgallium or trimethylindium and alkali metal fluorides from their etherates, followed by removing ethers and thermal decomposition of adducts to yield free trimethylgallium or trimethylindium respectively.

Electrolytic Synthesis of Perfluorotrimethylamine with Alkali Metal Fluroide Contained Carbon Anode

The new carbon electrodes containing alkali metal fluorides such as LiF-CaF2 and CaF2 were developed to prevent the occurrence of anode effect in electrochemical fluorination and were used as the anode for electrolytic synthesis of perfluorotrimethylamine, (CF3)3N, from the mixed melt of (CH3)4NF · 5HF and KF · 2HF at 100°C. The ratio of (CF3)3N to the overall anode gas increased with increasing the concentration of (CH3)4NF and decreasing the current density and the best value of 61.7% was obtained in electrolysis of the mixed melt of (CH3)4NF · 5HF (40 mol%) and KF · 2HF (60 mol%) at 20 mA · cm−2 with the 4 wt% CaF2 contained carbon anode. However, the new carbon anode was broken down in the mixed melt of (CH3)4NF · 5HF (50 mol%) and KF · 2HF (50mol%) during electrolysis. From these results, it is concluded that the alkali fluoride contained carbon is available as the anode for electrolytic production of (CF3)3N from the mixed melt having the molar fraction of KF higher than 0.143.

Formation of ZrO2 Nanocrystals in Hydrothermal Media of Various Chemical Compositions

Formation of ZrO2 nanocrystals of various modifications was studied in relation to the chemical composition of the hydrothermal solution and in connection with the kinetic features of the process. The strongest effect on the structure of ZrO2 is exerted by addition to the hydrothermal solution of alkali metal fluorides or potassium iodide, which induce predominant formation of monoclinic ZrO2 nanocrystals. The mechanism by which additions of alkali metal hydroxides and halides affect the phase state of ZrO2 nanocrystals was revealed.

Reactions of oxalyl fluoride with electrophiles

The reactions of oxalyl fluoride with electrophiles in the presence of alkali metal fluoride were carried out. In the reaction with CF 3CH 2OTf (Tf=CF 3SO 2) or CH 3CH 2OTf, the synthesis of di-ether (ROCF 2CF 2OR) and mono-ether (ROCF 2COF) was achieved. The difference of the reactivities between these two compounds was discussed from the result of DFT calculations.

Preparation and Characterization of Porous Carbons By Defluorination of Ptfe with Alkali Metals - Effect of Alkali Metals on the Porous Structure -

Porous carbons were prepared by defluorination of poly-tetrafluoroethylene(PTFE) with various alkali metals and their porous structures were compared. Using sodium for defluorination resulted in a characteristic mesoporous carbon having a large mesopore volume with the narrow pore-size distribution of 2-3 nm diameter, in contrast to using potassium and rubidium which produced also mesoporous carbons but their pore-size distributions were wide spread. This difference seemed to be caused by the dispersion state of the alkali metal fluoride particles formed during defluorination.

Study of the Possibility of Improving the Physico-Chemical and Service Properties of Polycarbonate by Treating it with Alkali Metal Fluorides

Study of the Possibility of Improving the Physico-Chemical and Service Properties of Polycarbonate by Treating it with Alkali Metal Fluorides

Interactions between glass ionomer cement and alkali metal fluoride solutions: the effect of different cations

This study examines the effect of different cations in equimolar alkali metal fluoride solutions on their interactions with glass ionomer cements. Uptake of both fluoride and cation were measured together with change in solution pH and morphological changes in the cement surface. Two cements were used; AH2, a dental restorative cement containing both fluorine and alkali metal (Na) as glass components and LG30, which contained neither. Discs of cement 1×10 mm were set in moulds at 37°C for 1 h then, stored in water for 3 days at 37°C. Discs in each test group ( N=5) were immersed in 10 ml of solutions of either NaF, KF, or RbF, all containing 900 ppm F −, control discs were stored in water, all at 37°C for 24 h. Solutions were analysed for F − by ISE potentiometry, Na + by the same technique and K + and Rb + were analysed by atomic absorption spectrometry. Uptake was obtained by difference between solution used for immersion and the control solution. Solution pH was measured potentiometrically. The surface roughness of the discs was measured by linear stylus profilometry. Fluoride ion uptakes for AH2 were 451 μmol/g NaF, 378 KF, and 318 RbF. The comparable figures for LG30 were 202, 161, and 159. Differences between cements were all statistically significant and also between solutions pairings except for the KF/LG30 vs. RbF/LG30. Uptake of cations was equimolar for AH2/NaF, AH2/RbF and LG30/KF but M + : F − ratios were significantly above unity for AH2/KF and LG30/NaF and significantly below unity for LG30/RbF. The pH changes were all positive and were significantly higher for AH2 than LG30 and for RbF compared to the other fluoride solutions for each cement (probably because of its lower initial pH). The final pH of all solutions were less than 1 pH unit from neutral (pH7). The AH2 cement test discs all showed significant increase in roughness ( R a) compared to control discs stored in water whereas the LG30 discs showed no such difference. Regression analysis showed a significant positive correlation between fluoride uptake and R a. It was concluded that changing the alkali metal cation influenced all four variables examined (F − uptake, M + uptake, pH change and extent of cement surface roughening).

Novel synthetic route to fluorofullerenes: reaction with binary and complex lead fluorides

We have recently developed methods of preparation of fluorofullerenes with specific fluorine content. Our previous successful synthesis of C 60F 36 and C 60F 18 with the use of transition metal fluorides inspired us to probe other high oxidation metal fluorides. In this work we report on the use of the binary lead fluorides (PbF 2, PbF 4, Pb 2F 6) and their complexes with alkali metal and alkaline earth metal fluorides (M 2PbF 6, M 3PbF 7 and M′PbF 6) as fluorinating reagents for fullerenes.

Efficient polymer light emitting diodes with metal fluoride/Al cathodes

We reported efficient polymer light emitting diodes with alkali and alkaline earth metal fluoride Al cathodes. The quantum efficiencies of these devices are more than two orders of magnitude higher than those in devices without fluoride layer, comparable to the best data reported with similar electroluminescent polymers. The mechanism of the metal fluoride/Al bilayer cathodes was also discussed based on photovoltaic, ac impedance, and photoluminescence efficiency measurement.

Alkali metal acetates as effective electron injection layers for organic electroluminescent devices

The effect of alkali metal (Li +, Na +, K +, Rb +, and Cs +) acetates and fluorides at an aluminum/tris(8-hydroxyquinoline) aluminum (Alq 3) interface on performance of organic electroluminescent (EL) devices is described. We also studied the effect of acetates with different metals, such as Mg 2+ and Al 3+, on the performance of the EL devices. EL characteristics of the devices with Al/alkali metal acetates were compared with those of devices with Al/alkali metal fluorides or an Al cathode itself. We found that the bilayer cathodes with alkali metal acetates exhibited better device performance than the bilayer cathodes with alkali metal fluorides. The improvement can be attributed to lowering of the work function of the Al cathode and doping of Alq 3 with alkali metals that were formed by the higher reactivity of alkali metal acetates than alkali metal fluorides with hot Al atoms impinging on these salts during the vapor deposition. The enhanced electron injection resulted in more balanced charge-carrier injection and thus higher EL efficiencies.

Reaction of imines of fluorinated ketones and perfluoronitriles with carbon tetrachloride. A new route to polyfluorinated imines

The reaction of imines of hexafluoroacetone and 1,3-dichlorotetrafluoroacetone with CCl 4 catalyzed by AlCl 3 leads to the formation of (XCF 2) 2CClNCCl 2 in moderate to high yield. The treatment of these imines with alkali metal fluoride in a polar solvent results in high yield formation of (XCF 2) 2CNCF 3 along with isomeric (XCF 2) 2CFNCF 2. A reaction of nitriles of perfluorinated carboxylic acids with CCl 4 proceeds with the formation of a mixture of two products: R fCCl 2NCCl 2 and R fCCl 2NCClR f. Imidoyl chloride C 3F 7CCl 2NCClC 3F 7 isolated in the reaction of C 3F 7CN/CCl 4 is converted into perfluoro-5-azanonene-4 by reaction with HF.

Reactions involving fluoride ion. Part 47. Reactions of perfluorobicycloalkenes

Electron deficient dienes 3 and 4 are obtained by defluorination of perfluorobicyclo-butylidene (1) and -pentylidene (2), using tetrakis(dimethylamino)ethene (TDAE), and these dienes are very reactive. With alkali metal fluorides, 4 gave a stable observable anion while 3 gave oligomers. The corresponding fluorinated allyl anion was however obtained via3 in the presence of TDAE. Further reactions of 3 and 4 are described.

Synthesis of Hexafluoroacetone by Catalytic Oxidation of Hexafluoropropylene

Oxidation of hexafluoropropylene with molecular oxygen in a fixed bed of a catalyst (activated carbon promoted with alkali metal fluorides) was studied.

Anodic dissolution of titanium alloys in hydrofluoric-sulfuric acid electrolytes with additives

Anodic dissolution of VT1-0, VT6, VT16 titanium alloys in hydrofluoric-sulfuric acid solutions with addition of alkali metal fluorides, glycerol, hexamethylenetetramine, and remantadine was studied in a wide range of potentials.

Recent studies on diamond surfaces

The surface properties of diamond have been studied by ultra-violet photoemission spectroscopy (UPS), Kelvin probing and low energy electron diffraction (LEED). The atomic level structure of diamond surfaces was determined by LEED intensity vs. energy [I(E)] measurements in combination with Tensor LEED calculations. The LEED analysis of the C(100)-(2×1)-H surface revealed the formation of symmetrical dimers on the top carbon layer. For the C(100)-(1×1)-O surface, quantitative LEED analysis indicated a structural model where oxygen occupied the bridge site on the surface. Systematic investigations were carried out using UPS and a Kelvin probe measurement to reveal the effect of alkali metal fluoride overlayers on the work function of the diamond surfaces. LiF and RbF have been found to act as effective dipole layers to lower the surface work function and induce a negative electron affinity.

Influence of alkali metals on the diffusive mobility of fluorine ions in GaF3- and InF3-based glasses

The structural inhomogeneity of the glass network due to the sequential replacement of a modifier by alkali metal fluorides in the GaF3- and InF3-based glasses is investigated by the19F NMR spectroscopy. The differences in the topology of the structure-forming networks are revealed from the analysis of the influence of the MeF concentration (10 and 20 mol %) on the dynamic behavior of fluorine ions. The glasses based on indium and gallium trifluorides are characterized by the inhomogeneously and homogeneously connected glass networks, respectively. Comparison of the dynamic behavior of fluorine ions in these glasses suggests that the fluorine subsystem of the InF3-based glasses exhibits a higher mobility.

Isotropic and anisotropic Raman scattering from molten alkali-metal fluorides

Isotropic and anisotropic Raman scattering spectra of molten LiF, KF, and CsF and of molten mixtures KF–LiF and CsF–LiF have been measured at temperatures up to 900°C. For the single component molten salts the reduced representations of the spectra show one anisotropic and two isotropic bands. The data are discussed and interpreted in terms of interaction induced polarisability fluctuations. The dipole–induced-dipole interactions predominate the CsF anisotropic spectra while polarisability fluctuation due to anion–cation overlap interactions give rise to the strong isotropic scattering in LiF. The anisotropic Raman scattering intensity from the binary mixtures appears to be a superposition of the corresponding intensities of the component salts, while the isotropic spectra are characterised by a new band at ∽325 cm−1 which is common for both the KF–LiF and the CsF–LiF binaries. The origin of this band is attributed to the formation of long lived associated configurations of the type (LiFx)A, (A=K, Cs) in the melt mixtures.

Alkali metal coactivators in SrS: Cu,F thin-film electroluminescent devices

A unique approach for obtaining bright and efficient saturated green phosphors for alternating-current thin-film electroluminescent (ACTFEL) device applications is presented. The approach involves color-shifting blue SrS:Cu,F ACTFEL phosphors into the green region of the spectrum via the incorporation of alkali metal ions into the SrS lattice. Alkali metals are incorporated into SrS:Cu,F phosphors by using LiF, NaF, KF, RbF, or CsF coactivators. The best result to date is obtained by using a KF coactivator and results in a saturated green brightness and efficiency of 52.7 cd/m2 and 0.973 lm/W (at a frequency of 60 Hz and an overvoltage of 40 V). In addition to providing a color shift, the alkali-metal fluorides improve the overall performance of the ACTFEL device by increasing the magnitude of the electric field and its uniformity across the phosphor through suppression of positive space charge.

The influence of monovalent cations on the stability of electrochemically formed nickel fluoride films

The stability of electrochemically formed NiF2 film in 1.0 M perchloric acid containing monovalent fluorides namely, NH4F, HF, NaF, KF and LiF, is investigated using cyclic voltammetry, chronoamperometry, atomic absorption spectroscopy and scanning electron microscopy. In addition to direct dissolution of nickel and dissolution through the oxide layer, a new mode of dissolution of NiF2 film as NiF3− and NiF42− through complex formation is proposed. This process is significantly influenced by the alkali metal fluorides. On a comparative basis the stability of NiF2 decreases in the order NH4F > HF > KF > LiF.