L. N. Ignatieva

Spectroscopic Study of Modified Polytetrafluoroethylene

The effect of thermal gas dynamic destruction of polytetrafluoroethylene on its microscopic and supramolecular structure and dynamic properties is investigated by IR and 19F NMR spectroscopy. It is demonstrated that thermal gas dynamic dispersing changes the structure of polytetrafluoroethylene molecules. One of the possible mechanisms of PTFE depolymerization is the formation of oligomers with terminal –CF3 and –C=CF2 groups. This forms macromolecular packing with higher ordering and with dynamic characteristics other than those inherent in standard PTFE.

IR Spectroscopic Study of Glasses Based on InF3 and AlF3

New compositions of fluoride glasses in the PbF2–AlF3–InF3–BaF2–LiF system were investigated by IR spectroscopy. It is shown that the glass nets are built from octahedral polyhedra. Isomorphous substitution takes place when aluminum trifluoride is added to the fluoroindate glass. At high contents (∼15 mol. %) of aluminum trifluoride, the latter forms its own net, which is close to the structural motif in crystalline Pb3Al2F12.

Vibrational Spectroscopy Study of Fluorozirconate Glasses Containing Tin Difluoride and Gallium Trifluoride

A series of fluorozirconate glasses in ZrF4-SnF2-GaF3 and ZrF4-SnF2-BaF2 systems have been studied by vibrational spectroscopy. The glass net contains not only fluorozirconate polyhedra, but also fluorostannate and fluorogallate groups. When contained in amounts of more than 10 mol.% in a glass, tin difluoride is a glass-forming agent. Gallium trifluoride in the same amount or higher forms GaF6 polyhedra.

Role of Tin Difluoride and Gallium Trifluoride in Glass Formation in SnF2–GaF3–BaF2

The structure of glasses in SnF2–GaF3 and SnF2–GaF3–BaF2 systems was investigated by IR spectroscopy. It is shown that the glass structure in systems of this type is formed by two glass-forming agents: gallium trifluoride and tin difluoride. The introduction of 5 mole % barium difluoride shifts the edge of the absorption band to the low-frequency region.

Quantum chemical study of the structure of glasses based on niobium oxytrifluoride

DV-Xα electronic structure calculations are repotted for NbF5, NbF5−, NbOF5−, NbOF52− and for the clusters Nb2O2F93−, NbAl2OF156−, and AlNb2O2F145−. The charges, bond orders, and system stability are analyzed. The results of calculations are used to discuss the structural peculiarities of glasses based on niobium oxytrifluoiide and aluminum tnfluoride.

Thermal studies of sodium tetrahydroborate–potassium tetrafluoroborate mixtures

The results of DSC studies of NaBH4–KBF4 mixtures are presented. It is shown by chemical analysis, XRD analysis, IR spectroscopy, and 11B and 9F MAS NMR that the decomposition of the mixtures starts at ~563 K to yield polyhedral borohydride compounds (predominantly B12H122-) in the solid residue. This temperature is much lower than the decomposition temperature of pure NaBH4 (749 K). The mechanism of formation of the B12H122- anion has been proposed and confirmed. According to this mechanism, boron atoms from KBF4 are involved in the formation of this anion.

Glass transition and composite formation in InF3-containing oxyfluoroniobate system

The glasses in the system MnNbOF5-BaF2-InF3 have been firstly synthesized and studied. The thermal parameters of these glasses are analyzed. It was stated that glass of the composition 40MnNbOF5-40BaF2-20InF3 is the most thermal stable in the system under study. By X-ray analysis the compositions of the crystalline phases obtained at the glass thermal treatment were determined: the main phases are Ba3In2F12 and BaNbOF5. By Raman and IR spectra analysis it was stated that the networks of glasses in the system are built by the structural type of the glasses in NbO2F-BaF2 system: (NbOnFm) polyhedra joined oxygen bridges. Indium trifluoride forms InF6 polyhedra, which are embeded between oxyfluoroniobate ions, forming a common networks or forms its own layers from InF6 polyhedra. IR-spectroscopy method showed that at devitrification of the sample 30MnNbOF5-50BaF2-20InF3 the band position and shape change in going from glass state to crystalline. The bands in the range 900–700 cm−1 shift into the low-frequency...

A quantum chemical NMR study of branched and unbranched fluoropolymers

The work demonstrates the results of quantum chemical calculations of 19F and 13C NMR spectra of model fluorocarbon CnF2n+2 molecules with various configurations and hydrocarbon chain molecules. The possibilities to determine the chain length, formation of branches, identification of fluorine substitution for hydrogen during the fluorination of hydrocarbon paraffins and polymers are discussed.

Bismuth-containing fluoride glasses

The example of bismuth-containing glasses based on InF3 and ZrF4 is used to consider the effect of bismuth on glass formation, properties, and structure and the appearance of broadband luminescence at low wavelengths in the IR spectra of fluorozirconate glasses.