ZnF2 Research Articles

Calcium fluoride production on marble surfaces

Acid resistance zeta potential and ESCA (electron spectroscopy for chemical analysis) experiments were performed on emperador marble and four calcium carbonate samples (onyx calcite, travertine calcite, Iceland spar calcite and aragonite). Six fluorine-containing reagents were used to treat the surfaces of these materials: magnesium hexafluorosilicate, zinc hexafluorosilicate, sodium fluoride zinc fluoride, strontium fluoride, and stannous fluoride. The acid resistance of treated samples proved to be much higher than that of their untreated equivalents. The isoelectric point of treated samples approaches the isoelectric point of fluorite. Also, the fluorine content as measured by ESCA, of a marble surface treated with magnesium hexafluorosilicate is much higher than that of an untreated sample. The binding energy of fluorine and calcium of the treated marble is consistent with the formation of calcium fluoride.

Ion-Solvent Interactions of Zinc(II) Salts in Water- Pyridine Mixtures

Abstract The ion-solvent interactions involving zinc(II) salts viz. iodate, fluoride and benzoate in waterpyridine mixtures have been investigated by solubility and solvent transport number measurements. The standard Gibbs transfer energies of the salts (Δ Gtº), determined from their saturation solubilities in the solvent mixtures, decrease up to xpy = 0.1 for zinc(II) iodate, but up to Xpy = 0.4 for zinc(II) benzoate, and subsequently increase with the addition of pyridine. For zinc(II) fluoride, however, a continuous increase of ΔGtº with the addition of pyridine is observed. The transfer energy of Zn2 + is negative and that of anions is positive with the former decreasing and the latter increasing continuously with the addition of pyridine. The solvent transport number of pyridine (<Δpy) is positive and passes through a maximum for all the salts in the range xpy = 0.25 to 0.55. These results indicate a heteroselective solvation of the salts with Zn2 + being preferentially solvated by pyridine and the anions by water

Surface analysis of copper, brass, and steel foils exposed to fluorine containing atmospheres

The composition and thickness of fluoride films that form upon exposure of various metals to F2/N2 at room temperature were studied using x-ray photoelectron and Auger electron spectroscopy (AES). Depth profiles were obtained using AES with argon ion sputtering. The metals studied included low carbon steel, 302 stainless steel, copper, and brass (70% Cu/30% Zn). Samples treated in 0.12% F2/N2 display small amounts of surface fluorine, primarily in the form of fluorinated hydrocarbons rather than metal fluorides. In contrast, exposure to 25% F2 produces thicker films, consisting mainly of metal fluorides with some metal oxides. Fluorine does not seem to penetrate beyond the native oxide initially present on the metal foil surface. Iron fluorides form on low carbon steel, and copper fluorides form on copper. Surprisingly, iron fluorides preferentially form on stainless steel, and zinc fluorides preferentially form on brass. These results provide new insight about the passivation of metals by F2 and raise new questions.

Crystal Growth of Transition Metal Fluorides

Abstract Kinetics of crystal growth of transition-metal fluorides, MF2(M=ZnII and PbII) has been studied by the use of both constant composition and conventional methods. The effective orders in an empirical reaction-rate function of supersaturation were 1.71 (2.0) for ZnF2·4H2O and 0.88 (1.2) for PbF2 (The values in the parentheses are from the conventional method). These findings suggest that the crystals of zinc fluoride grow by a spiral growth (surface reaction) mechanism and lead fluoride by a bulk diffusion controlled mechanism.

A medicated polycarboxylate cement to prevent complications in composite resin therapy

Preparative treatment is the preferred method to protect the dentin and pulp from complications in composite resin therapy. This study investigated the in vivo effects of the polycarboxylate cement containing zinc fluoride and tannic acid in composite resin restorations. Scanning electron micrographs established that the composite resin failed to contact the axial wall. The gaps varied from 10 to 60 microns. However, this polycarboxylate cement was shown to provide excellent adaptation to dentin when used as a base and its chemical adhesion allowed it to make close contact with the unetched dentin. The newly developed electron probe x-ray microanalyzer revealed that the in vivo penetration of fluoride and zinc occurred through the dentinal tubules. When this polycarboxylate cement was used, the orifices of dentinal tubules were partially occluded, possibly with the smear layer fixed by tannic acid. In addition, by releasing the components, this polycarboxylate cement adds acid resistance to dentin and increases the resistance of dentin collagen to proteolytic enzymes. As such this polycarboxylate cement offers advantages as a base to composite resin therapy.

Study of formation and properties of the vitreous oxyfluoride system based on GeO 2, PbF 2 and ZnF 2

The vitreous region of the oxyfluoride system based on germanium dioxide, lead fluoride and zinc fluoride is obtained by using platinum crucibles. The physical properties such as the transition temperature, crystallization temperature, refractive index, density, thermal expansion coefficient and elastic modulus are measured. A description to the change rules of the physical properties of this system is given in detail. The glasses have a good transparency in the mid-infrared region. Their chemical durability is much better than that of fluoride glasses.

Electron diffraction investigation of the structure of a molecule of zinc difluoride

The available data in the literature on the molecular constants of ZnF 2 are totally contradictory. The authors of an electron diffraction investigation [4] carried out using the visual method recommend a linear structure for this molecule. The absence of defocusing of the molecular beams in an inhomogeneous electric field led the authors of [5] to an analogous conclusion. At the same time, from an analysis of isotopic shifts of the frequency of the ant• oscillation v3 [6, 7] we have concluded that the ZnF 2 molecule is characterized by an angular equilibrium configuration. However it is essential to note that on the basis of these very same values of the isotope effects the authors of [6-9] give different values for the bond angle F--Zn--F: 157 • 2 ~ [6], 165 • 8 ~ [8], 160-180 ~ [9], 150 ~ [7]. Quantum chemical calculations [I0], which come out in favor of a linear structure for zinc difluoride, lead to numerical values for the internuclear distance r(Zn-F) and the frequency of the totallysymmetric vibration ~I , of 1.74 ~ and 719 cm -I respectively. These values do not agree with experimental data obtained in electron diffraction [4] and spectroscopic [7] investigations.

Dynamical properties of crystals of MgF2, ZnF2and FeF2. II. Lattice dynamics and infrared spectra

For pt.I see ibid., vol.21, p.2749 (1988). Very careful studies of infrared spectra of crystals of magnesium, zinc and iron fluoride are reported. Using several models and methods, the authors discussed the experimental infrared spectra temperatures from 10 to 300 K in a previous paper. Using a full shell model with both ions polarisable, the optical frequencies and elastic constants are calculated and compared with existing data. Dielectric properties such as effective charges, ionic polarisabilities, dielectric constants and infrared mode strengths are determined. These models are applied to the study of the behavior of B1g, A2u and Eu modes, and C44 and Cs elastic constants with temperature in ZnF. They show that, above 100 K, this behaviour can be explained by the change of some short-range force constants, while, below 100 K, it is necessary to take into account the increase of the effective charge ZF. Lastly the authors have calculated the contribution of the second-order processes to the infrared spectra. Comparison with experimental data allows a precise interpretation to be made of supplementary IR bands. These results explain the difficulties encountered in trying to represent the IR data by a classical oscillator model particularly for the Eu spectrum in ZnF2 and FeF2.

Luminescence of copper in barium zinc fluoride (Ba 2ZnF 6-Cu)

Crystals of composition Ba 2ZnF 6-Cu show a strong yellow-green luminescence under ultraviolet excitation. Evidence is presented that this luminescence is due to a copper-oxygen charge-transfer transition.

ChemInform Abstract: N,N‐Diethylamidofluorochlorophosphite.

AbstractThe title compound (II) is prepared from O‐methyl diethylamidochlorophosphite (I) and zinc fluoride.

Infrared spectra of iron, zinc and magnesium fluorides: I. Analysis of results

In this work the authors review the different models and methods used to analyse the IR reflection spectra of iron, zinc and magnesium fluorides, between 4.2 and 300 K. They especially show that the four-parameter oscillator model, presented by Gervais (1974), gives results similar to those obtained by other methods, but also a more accurate determination of the longitudinal-mode frequencies. The authors have shown clearly, for the mode A2u, the occurrence of abnormal behaviour of the longitudinal frequencies with temperature. This result allowed them to consider, for zinc and magnesium fluorides, the presence of an incipient ferroelectric order at low temperature. They show also how they have been forced to consider an additional oscillator in the symmetry spectrum Eu.

Promotion of ZnAl2O4 formation by LiF

Details of the formation of ZnAl2O4 in the presence of AlF3 was studied for the purpose of elucidating the effect of fluoride anion on the reaction. In the ZnO-AlF3 binary system, sublimation of AlF3 and successive reaction of ZnO with AlF3 vapour were the first route of ZnAl2O4 formation. ZnAl2O4 formation with AlF3 was initiated at the ZnO-AlF3 interface as well as that of the ZnO-AlF3 binary system. This reaction was used to predict the formation of unstable zinc fluoride or zinc oxyfluoride. When the fluoride anions bound with zinc cations were transported to the surface of an Al2O3 particle, the intermediate phase was formed at the site. In addition, the vapour transport of AlF3 to the ZnO-Al2O3 interface was expected to form an intermediate phase containing fluoride anions such as Zn a Al b O x F y phase. The ZnAl2O4 formation was promoted by the material transport through the intermediate phase around Al2O3 particles.

The magnetic properties of mixed cobalt and zinc fluorides

An investigation of the magnetic properties of powder samples of Co x Zn 1- x F 2 for a complete range of compositions was undertaken using low field dc magnetic susceptibility and diffuse polarised neutron scattering measurements. The Néel temperature, as determined from the cusp in the powder susceptibility, was found to agree with percolation theory predictions. There was no evidence of spin glass behaviour from any of the measurements above 2.6 K for Co 0.26Zn 0.74F 2, or above 4.2 K for Co 0.2Zn 0.8F 2 and Co 0.1Zn 0.9F 2. All susceptibility data are fitted in the paramagnetic region with a simple molecular field model allowing for crystal field effects and spin-orbit coupling.

Bactericidal properties of urine for Neisseria gonorrhoeae.

Some human urine is bactericidal for the F-62 strain of Neisseria gonorrhoeae. Gonococci of three auxotypes (Pro-; Arg-, Hyx-, Ura-; and Pro-, Arg-. (Orn*), Ura-) were tested by in-vitro exposure to 31 samples of urine from 14 men. Nineteen of the urine specimens were bactericidal, and 12 were not. Except for one sample, all cidal urines came from five men. Cidal activity was associated with acidic, concentrated urines; it was unaffected by exposure to lowered pH, pronase, heat or cold, and was dialyzable with use of a dialysis membrane with a cut-off molecular weight of 1000. Neutralization of the acid urines removed the antigonococcal activity. Noncidal acid urines became cidal urines when concentrated by lyophilization. Zinc, lysozyme, fluoride ions, and fatty acids are substances that have antibacterial activity and are also present in urine. These substances were examined for antigonococcal activity. Neither zinc salts, fluoride ions, lysozyme, nor fatty acids in concentrations exceeding those found in urine were bactericidal for the gonococci. These results show that sufficiently concentrated, acidic urines kill gonococci by an unknown mechanism.

The influence of zinc iontophoresis on in vitro adherence of fibroblasts to periodontally‐diseased cementum

This in vitro study examined whether iontophoresis of zinc ions aided adherence of fibroblasts to the root surfaces of periodontally‐diseased teeth. Iontophoresis of zinc ions into extracted, periodontally‐diseased human teeth was performed. Controls consisted of untreated diseased teeth and healthy unerupted teeth. Comparison was also made with teeth that were rinsed in zinc fluoride solution or in 45% phenol. Fibroblasts (L929) adherence was measured by trypan blue staining or by cell counting. The results demonstrate that fibroblasts adhere equally well to: 1) healthy root surfaces, 2) diseased root surfaces treated with 45% phenol, or 3) diseased root surfaces treated by iontophoresis of zinc ions. Cell adherence in these groups was significantly greater than adherence in groups of periodontally‐diseased teeth which were either untreated or rinsed with ZnCl2. Iontophoresis with zinc ions appears to be an effective method of increasing cellular adherence to periodontally‐diseased roots.

Temperature dependence of IR spectra of zinc and magnesium fluoride

The reflective infrared spectra of zinc and magnesium fluoride are investigated from 40 to 5000 cm-1 between 4.2 and 300 K. These spectra are analysed by two methods: the first is a classical analysis of an oscillator response and the second is a Kramers-Kronig analysis. This second method shows in the MgF2 spectrum the presence of a supplementary band near 350 cm-1 which is not explained by the group theory in this case. For ZnF2, the comparison of the two methods shows a three-oscillators simple model gives an imperfect representation of the spectrum of Eu symmetry. In the case of MgF2, the frequency shifts of the transverse modes with temperature confirm the Raman scattering data. The transversal frequencies of ZnF2 for the A2u and E3u modes present a maximum near 80 K. It could be possible that this result was the consequence of the presence of a para-ferroelectric transition situated at lower temperature.

Surface adhesion and retentive force of cements

Z inc phosphate cement has been used as a standard luting agent for cast restorations for many years. The retentive force of the cement measured 13% surface adhesion and 87% interlocking force when analyzed by Fusayama et al.’ with cylindric inlays. Polycarboxylate cement proved to be superior to zinc phosphate cement in adhesion to tooth substances and in pulpal compatibility.’ The technical and chemical properties of this type of cement were improved by the development of a water-settable cement.3 A new type of polycarboxylate cement (HY Bond Carbocement, Shofu Dental Mfg. Co., Kyoto, Japan) was recently developed by adding HY agent, a cariespreventing agent that contains zinc fluoride, strontium fluoride, tannic acid, and other components prescribed by Yamaga.4 When tested by Yamada et a1.,5 the addition of the HY agent did not significantly alter the compressive strength, diametral tensile strength, or film thickness, but it slightly decreased disintegration in lactic acid. The three above-mentioned types of cements (Table I) were compared for surface adhesion to tooth substances and dental casting alloys, as well as retentive force of cemented restorations.

Polarization dependence in the X-ray absorption spectrum of zinc fluoride

Abstract X-ray absorption spectra of a single crystal of zinc fluoride have been measured at and above the K-edge of zinc using synchrotron radiation. Observations were made for X-ray electric-field-vector polarizations parallel and perpendicular to the crystal c 0 axis. A quantitative analysis of the EXAFS and a qualitative analysis of the ‘white line’ are shown to be in general agreement with the known crystal structure. EXAFS results show that anisotropies in bond lengths of 0·03 Å between the two polarizations may be easily resolved. Atomic EXAFS and white-line anisotropies indicate that the local potential at the zinc absorbing site is not spherically symmetric.

Reactions of copper(II) and zinc(II) fluoride with hydrazine

Reactions of copper(II) and zinc(II) fluoride with hydrazine

Electronic Raman scattering in (Fe,Zn)F2

Electronic Raman scattering is reported for Fe1−xZnxF2 as a function of temperature and dilution. The Raman-shifts indicate a linear change of the magnetic anisotropy with zinc concentration. The low temperature linewidths are interpreted as originating from the random distribution of Fe2+ environments and strains introduced by the Zn-ions.