Fluorine Release Research Articles

Influence of thermal annealing on bonding structure and dielectric properties of fluorinated amorphous carbon film

The bond structure and dielectric properties of fluorinated carbon films after thermal annealing in N 2 ambience were studied. The results show that dielectric constant and dielectric loss increased, and optical gap decreased with increasing annealing temperature. The composition and bonding structure of the films were obtained by FTIR and XPS analysis. The data indicate that fluorine-to carbon ratio decreased and CC group increased in the films after the films were annealed. It suggests that the structural and dielectric property changes correlate with the release of fluorine and increase of cross-linking during the annealing.

Transition and rare earth metal fluorides as thermal sources of atomic and molecular fluorine

Transition and rare earth metal fluorides (CoF 3 , K 2 NiF 6 , TbF 4 and CeF 4 ) are widely used as solid fluorinating agents. Their thermal decomposition leads to the release of gaseous fluorine. Knudsen cell mass spectrometry has been applied to investigate thermal decomposition of aforementioned fluorinating agents. The characteristic working interval of temperatures and composition of the gas phase for each compound have been determined. According to our findings, fluorine is released both in atomic and molecular forms. F is the main component of the gas phase during TbF 4 and K 2 NiF 6 decomposition, which can be used as thermal generators of atomic fluorine.

Photodegradation Products of a New Antibacterial Fluoroquinolone Derivative, Orbifloxacin, in Aqueous Solution.

A new antibacterial fluoroquinolone derivative, orbifloxacin (ORFX), is decomposed photochemically in aqueous solution. When ORFX solution was irradiated with a chemical lamp or sunlight, three major photodegradation products were isolated by preparative HPLC. These degradation products were identified by electron-impact mass spectrometry, liquid-secondary-ion mass spectrometry and 1-H-NMR spectroscopy. Moreover, the photodegradation pathway was investigated by a similar study using several fluoroquinolone derivatives which were presumed to be the intermediates of the photoreaction of the ORFX. Consequently, it was found that two main photochemical reactions, the decomposition of the dimethylpiperazinyl moiety and the elimination of the cyclopropyl group, take place in ORFX. The detected structures of photodegradation products and the photodegradation studies of the postulated intermediates suggested that the photodecomposition of the dimethylpiperazinyl ring at the 7-position and the elimination of the cyclopropyl group at the 1-position occurred concurrently with the release of fluorine at the 8-position.

Redistribution of rare earth elements, thorium, and uranium over accessory minerals in the course of amphibolite to granulite facies metamorphism: The role of apatite and monazite in orthogneisses from southwestern Norway

The amphibolite to granulite facies transition has been studied in a high-K calc-alkaline, hornblende-biotite, K-feldspar megacrystic augen gneiss series from the Rogaland-Vest-Agder (Rog-VA) sector of the Sveconorwegian province (southwest Norway). Hornblende begins to break down mainly to clinopyroxene at the Cpx-in isograd and biotite mainly to orthopyroxene at the Opx-in isograd (abbreviations for minerals following Kretz, 1983). The magmatic accessory mineral association comprises titanite and allanite, which begin to break down before the Cpx-in isograd. Titanite is preserved as relict inclusions in other minerals at higher grade. Monazite and thorite formed in the breakdown of allanite. Monazite abundance reaches a maximum between the Cpx-in and Opx-in isograds. The middle and heavy rare earth element (M-HREEs, except Eu) content of apatite steeply increases with increasing metamorphic grade and is directly correlated to the decrease of the modal abundances of titanite, hornblende, and biotite. The U contents of apatite are low and do not increase with metamorphic grade. The light rare earth elements (LREEs) and Th content of apatite are not correlated to the breakdown of allanite around the Cpx-in isograd but increase around the Opx-in isograd. A simplified equation is proposed for monazite crystallisation in the vicinity of the Cpx-in isograd that accounts for the allanite, titanite, and hornblende breakdowns and the M-HREE substitution in apatite: 3 (M-HREE) 2 O 3 in hornblende and litanite + 3 ( LREE) 2 in allanite O 3 + 2 Ca 5 (PO 4 ) 3 apatite ( F,OH ) + 6 SiO 2 quartz ⇔ 6 ( LREE)P monazite O 4 + 2 Ca 2 (M-HREE) 3 (SiO 4 ) 3 ( F,OH) lessingite in apatite + 6 CaO in plagioclase . At the Opx-in isograd, the increase of LREEs and Th content of apatite results either from the breakdown of some monazite: 3 ( LREE)PO 4 monazite + 3 SiO 2 quartz + 4 CaO in plagioclase + (F 2 ,H 2 O) fluid ⇔ Ca 5 (PO 4 ) 3 (F,OH) + apatite Ca 2 (LREE) 3 (SiO 4 ) 3 (F,OH) less ingite in apatite . or the breakdown of the remaining allanite: 3 ( LREE) 2 O 3 in allanite + 6 SiO 2 quartz + 4 CaO in plagioclase + (F 2 ,H 2 O) fluid ⇔ 2 Ca 2 (LREE) 3 (SiO 4 ) 3 (F,OH) lessingite in apatite . The release of fluorine from the breakdown of biotite at the Opx-in isograd may increase apatite stability relatively to monazite in the granulite facies. when compared to amphibolite facies, the granulite facies augen gneisses do not show any U or Th depletion. This means that changes in the accessory mineral associations and the simultaneous breakdown of hydrous minerals at the amphibolite-granulite facies transition do not inevitably result in depleted granulite facies rocks but rather to an isochemical element redistribution. The coexistence of small amounts of metamorphic monazite and of relict inclusions of titanite in upper amphibolite facies augen gneisses suggests that (high-K) calc-alkaline orthogneisses are a suitable material to date (with the U-Pb method) prograde path of amphibolite facies regional metamorphism on monazite and the cooling path on titanite.

The Effect of Toothbrush Abrasion on Fluorine Release from Glass-ionomer Cement

The Effect of Toothbrush Abrasion on Fluorine Release from Glass-ionomer Cement

Fluorine Release from Glass-ionomer Cement and its Disintegration

Fluorine Release from Glass-ionomer Cement and its Disintegration

Rapid, Stepwise Substitution of Fluorines In 5-Trifluoromethyl-2′-Deoxyuridine by Bisulfite

Abstract On treatment with bisulfite at neutral pH, 5-trifluoromethyl-2′-deoxyuridine (CF3dUR) underwent rapid substitution of the fluorine atoms by bisulfite to give first the monosulfonate and then the disulfonate derivatives. It was shown that the monosulfonate product has reactivity to bisulfite with a potency half that of CF3dUR. These findings demonstrate the stepwise nature of the fluorine release from CF3dUR and constitute evidence that 5-exo-methylene type intermediates are involved in the nucleophile-mediated release of the fluorine from CF3dUR.

Electrochemical evolution of elemental fluorine under decomposition of solid electrolytes

At present, several methods for obtaining elemental fluorine are known: electrolyses of anhydrous HF/alkali fluoride solutions, thermal decomposition of complex fluorides, photoelectrochemical conversion of HF/NaF solutions on electrodes, etc. Another process which yields elemental fluorine is the electrochemical decomposition of solid ionic conductors (SIC) having F −-ionic conductivity. The characteristic features of the release of elemental fluorine during decomposition of SICs based on PbSnF 4, PbF 2, BiF 3, CeF 3 and LaF 3 were examined. LaF 3 solid electrolyte was found to be the most suitable compound for this purpose. The characteristics of solid state electrochemical cells as a source of elemental fluorine were determined.

Properties and Fluorine Release of Glass Ionomer Cement Containing Tannin Fluoride Preparation(HY-Agent)

Properties and Fluorine Release of Glass Ionomer Cement Containing Tannin Fluoride Preparation(HY-Agent)

Photoelectron spectroscopy studies of chemical vapor deposition of Ta from a TaF5 precursor on Si and SiO2 substrates

The increasing need for metallization of microelectronic structures involving deep trenches and high aspect ratio features has sparked considerable interest in chemical vapor deposition metallization schemes. In this work the results of photoemission investigations of the substrate-driven reduction of TaF5 to Ta metal on Si(111) and SiO2 substrates are reported. At moderate temperatures the reaction showed no selectivity between these two substrates, in contrast to the process with the similar molecule WF6. At 400 °C metallic Ta films could be grown on both Si and SiO2; however, x-ray photoelectron spectroscopy measurements show that the bonding of the film to Si(111) is dominated by fluorine atoms at the interface, whereas film growth on SiO2 tends to form an oxide interface with TaOF3 stoichiometry. Annealing of the deposited film to about 700 °C leads to Si diffusion to the surface which is accompanied by the release of fluorine from the film. The deposition of TaF5 on Si(111) at 250 °C results initially in a partly dissociative metallic deposition followed by a non-dissociative molecular chemisorption. Our experiments suggest the Si substrate to be reactive enough at the initial state of the deposition to break up theTaF5 molecule but that the process is quickly self-passivating.

Comments on the hydrochemical regulation of the halogen elements in rainfall, stemflow, throughfall and stream waters at an acidic forested area in mid-wales

Total fluorine, chloride, bromide and total iodine concentration data from a 5 year study of rainfall, throughfall, stemflow and streamwater at the Hafren conifer plantation are presented. Results show four main features. First, in rainfall a strong maritime influence is observed for chloride and bromide, while enrichment occurs for total fluorine and total iodine relative to chloride, reflecting seawater/atmosphere fractionation processes. Second, variation of chloride, bromide and total iodine is much lower in the streamwaters compared with the rainfall input, showing the ability of the catchment to damp rainfall chemistry even though “flashy” hydrograph response is observed. Total fluorine does not exhibit this damping and the reason for this difference remains unclear. Third, there is a net release of total fluorine from the catchment above that supplied from the rainfall, while net losses for bromide and total iodine occur as water passes from rainfall to the stream. Fourth, marked seasonal oscillations occur for streamwater bromide and total iodine concentrations; it is hypothesised that this relates to organic matter breakdown within the catchment during the summer period when biological activity is at its highest.

Solubility and release of fluorine and molybdenum from oil shale solid wastes

Surface disposal of oil shale solid wastes may contaminate surface water and ground-water resources with toxic levels of fluorine (F) and molybdenum (Mo). Three different oil shale solid wastes produced from processing raw oil shale, at different temperatures, were subjected to equilibrium solubility studies to examine the solid phases responsible for the release of F and Mo from oil shale solid wastes into the infiltrating water. The results suggested that increased retorting temperatures increased pH from 10.75 to 12.35, decreased dissolved F concentrations from 48.8 to 3.5 mg I −1, and increased dissolved Mo concentrations from 1.9 to 3.9 mg I −1 in oil shale solid waste equilibrium waters. Chemical speciation of total soluble F and Mo concentrations in oil shale solid waste equilibrium waters indicated that F was present mainly as F −, NaF°, and CaF +. Molybdenum was present as MoO 4 2− and HMoO 4 −. Further results of this study suggested that dissolved F and Mo concentrations in oil shale solid waste equilibrium waters appear to be controlled by CaF 2 (fluorite) and CaMoO 4 (powellite), respectively.

Thermally stimulated relaxation in NaF X-irradiated at room temperature

The thermally stimulated processes in NaF X-irradiated at room temperature are studied. Three processes are observed whose relative weight depends on the F-coloring stage: (1) electron release; this causes glow peaks to appear at 75 and 115°C, as a result, M+ centers are annealed out; (2) interstitial fluorine release from different traps and subsequent recombination with F-centers and F-aggregate centers, it causes glow peaks at 70, 130, 200, 240, and 280°C; (3) F-center migration causing their annealing by recombination with interstitials or the formation of F-aggregate centers. Nous avons étudié les processus stimulés thermiquement dans le NaF irradié aux rayons X à température ambiante. Trois processus ont été observés dependant de l'étape de coloration: (1) Libération d'électrons qui correspond aux pics luminescents observés à 75 et 115°C. Le résultat principal est la disparition des centres M+. (2) Libération des atomes interstitiels de fluorine provenant de pièges différents avec la postérieure recombinaison des centres F et de ses agrégats. Il correspond aux pics luminescents à 70, 130, 200, 240 et 280°C. (3) Migration des centres F pour se recombiner avec des atomes interstitiels ou pour former des centres agrégats.

Thermal decomposition of lanthanide and actinide tetrafluorides

The thermal stabilities of several lanthanide/actinide tetrafluorides have been studied using mass spectrometry to monitor the gaseous decomposition products, and powder X-ray diffraction (XRD) to identify solid products. The tetrafluorides, TbF 4, CmF 4, and AmF 4, have been found to thermally decompose to their respective solid trifluorides with accompanying release of fluorine, while cerium tetrafluoride has been found to be significantly more thermally stable and to congruently sublime as CeF 4 prior to appreciable decomposition. The results of these studies are discussed in relation to other relevant experimental studies and the thermodynamics of the decomposition processes.

Direct observation of the formation of double-shear structures from Nb 3O 7F

It is shown that slight decomposition of Nb 3O 7F occurs readily in the beam of an electron microscope. Planar faults are produced on at least five different ( hkl) planes. These grow into the crystal from the surface by expansion of partial dislocations. Further decomposition requires much higher beam heating and results in complete recrystallization and void formation giving a poorly ordered double-shear structure based on Nb 3O 7F. It is suggested that the first stage involves some reduction of Nb 5+ with release of oxygen and/or fluorine whereas the different mechanism of the second stage follows from the evolution of NbOF 3, a reaction which does not occur by a simple solid state mechanism.

Pregnancy and fluorine in hard tissues: A preliminary report

The mean fluorine content of the bones and teeth of pregnant rats was in most cases lower than that of non-pregnant animals. This result was obtained when using distilled water and tap water (the latter containing approximately 0.3 ppm fluorine) as a constituent of the diet. It is suggested that the need of fluorine of the growing foetus is related to the lowered values and that a release of fluorine would occur to some extent from the maternal hard tissues.