Magnetization Reversal of Ferromagnetic CoFeB Films and CoFeB/Ta/CoFeB Heterostructures in the Stray Field of Fe/Fe3O4 Nanoparticles

Journal of Experimental and Theoretical Physics - The magnetization reversal of the MgO/CoFeB/Ta/CoFeB/MgO/Ta/GaAs heterostructures and the ultrathin MgO/CoFeB/MgO/Ta/GaAs films with a...     

Structure of trisphaeridine

The structure of the alkaloid trisphaeridine has been established with the aid of IR and UV spectroscopy, high-resolution mass spectroscopy, and PMR and¹³C NMR spectroscopy.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 356–358, May–June, 1981.     

Thermo-stimulated luminescence of gamma-irradiated polytetrafluoroethylene

The thermo-stimulated luminescence of γ-irradiated commercial polytetrafluoroethylene (PTFE) was explored. There are up to four intense maxima in the luminescence curves of different formulations of PTFE. The position and number of maxima remain constant at doses up to 30 kGy. The differences of the glow curves in the different copolymers may be the result of impurities capable of reacting with ions or radicals formed under irradiation and by differences in the polymer’s topological structures.     

Thermomechanical properties of polytetrafluoroethylene in different zones of impact of continuous CO2 laser radiation

The pseudo-network structure of the amorphous block of polytetrafluoroethylene is formed by branching points, the crystallites of low- and high-melting crystalline polymorphs and the cluster segments of macromolecules. The polymer treated by laser irradiation is amorphized, with the degree of amorphization and other changes depending on the radiation fluence. A depression of the molecular flow onset and initial melting temperatures of the crystalline polymorphs, a decrease in the molecular mass, and the disappearance of the crystalline branching points characteristic of the original polymer have been observed in the irradiated polymer. Areas with different degrees of modification of the molecular structure appear in the dynamic mode with moving boundaries during continuous CO₂ laser irradiation. The difference in absorbance of the crystalline and amorphous portions of the polymer at the laser emission wavelength and a relatively high transmittance make laser-induced degradation differ from thermolysis in contact with a hot surface.     

Effect of bombardment with helium ions on the molecular-topological structure and elemental composition of the surface of Kynar polyvinylidene fluoride resin

A polyvinylidene fluoride film has been bombarded with accelerated (1–5 MeV) helium ions at a fluence of 10¹⁵ ion/cm². Unlike the completely amorphous structure of the unirradiated polymer, the weight fraction of the crystalline modification in the irradiated polymer is 0.86–0.90, which is indicative of the efficient conversion of the amorphous structures of the polymer pseudo-network into the crystalline ones. Irradiation with 1-MeV ions leads to the greatest changes in the fraction of the crystalline modification and the glass-transition and flow temperatures of the polymer. The detachment of fluorine and the surface carbonization of the irradiated polymer occur under the ion beam.     

The study of polymerization initiated by gamma-irradiated perfluoroacids and their derivatives

Polymerization of tetrafluoroethylene and methyl methacrylate has been initiated by active sites arising upon γ-radiolysis of perfluorinated organic acids and their derivatives. In the low-temperature radiolysis, two types of active sites are formed. The active sites of the first type (supposedly, -ĊF-COO⁻), which provide the most efficient polymerization at low temperatures, are accumulated during radiolysis of NaPFNA both at 77 and 300 K. The active sites of the second type, supposedly, of the radical type, are accumulated during radiolysis at 77 K and annealed during heating the sample to room temperature.     

A new stable perfluoroalkyl radical

Conclusions The radiolysis of perfluoro-4-methyl-2-pentene gives a stable radical whose ESR spectrum corresponds to (CF₃)₂CFFCF(CF₃)₂.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1667–1669, July, 1985.The authors express their gratitude to Yu. L. Bakhmutov for assistance in this work.