Carbon nanostructures based on IR-pyrolyzed polyacrylonitrile

For the first time, it is shown that IR pyrolysis of a composite based on polyacrylonitrile and gadolinium chloride produces a metal-carbon nanocomposite where metal particles with a size of 4–11 nm form a fine dispersion in the structure of the carbon matrix. The carbon phase of the composite is a carbon-carbon nanocomposite with a structure in which carbon nanoparticles (bamboolike carbon nanotubes, carbon nanospheres, or octahedral carbon nanoparticles) are incorporated into the matrix graphite-like material.     

Study of Geodesic Acoustic and Alfvén Modes in Toroidal Fusion Devices (Brief Review)

JETP Letters - Geodesic acoustic modes, Alfvén eigenmodes, stationary and oscillating components of the electric field, and their relations to plasma confinement have been studied. Theoretical...     

Determination of Spatial Distributions of Plasma Parameters of a Compact Magnetron Discharge

Physics of Atomic Nuclei - In this paper, the hardware-software high resolution measuring system for studying the spatial and spectral distributions of the radiation intensity of a magnetron...     

Equal-permittivity states induced in a ferroelectric

Conditions under which a ferroelectric subjected to an electric field acquires equal-permittivity paraelectric states at different temperatures are studied. The temperature dependences of the control (inducing) field intensity and feasible permittivity interval (ɛ_min-ɛ_max) are obtained. The effect of intersection of the ɛ(E, T _i ) characteristics of the ferroelectric in the paraelectric state is analyzed. With the control field and temperature varying consistently, the permittivity ɛ_i of strontium titanate films and films of the barium titanate-strontium titanate solid solution may be kept constant in a wide (200–320 K) temperature range and, at the same time, changed by more than twofold by varying the electric field.     

Effect of annealing on the dielectric permittivity of strontium titanate films in the SrTiO3/Al2O3 structure

The paper reports an experimental study of the structure of a strontium titanate film on a sapphire substrate and of the dielectric properties of capacitors based on a SrTiO₃/Pt/Al₂O₃ multilayer system before and after a high-temperature anneal. The macro-and microstructure of SrTiO₃ films and its variation induced by the annealing have been investigated. The temperature and field dependences of the dielectric permittivity of strontium titanate films have been determined, and their comparison with similar data for single crystals carried out. The mechanisms by which annealing can affect the capacitor capacitance and the properties of SrTiO₃ films are discussed. Fiz. Tverd. Tela (St. Petersburg) 40, 1473–1478 (August 1998)     

Nucleophilic trifluoromethylation of arylidene Meldrum’s acids

A method for the trifluoromethylation of arylidene Meldrum’s acids using Me₃SiCF₃ followed by transformation of the initial products to CF₃-substituted esters and alcohols is described. The sequence of reactions is performed without isolation of intermediate compounds furnishing the final products in good overall yields.     

Structure and magnetic properties of metal-carbon nanocomposites based on IR-pyrolized poly(acrylonitrile) and iron

Metal-carbon nanocomposites, namely, IR-pyrolized poly(acrylonitrile)/Fe (IR-PAN/Fe) were produced and studied. The structure and magnetic properties of the composites were studied for various synthesis conditions. Nanosized carbon objects (nanospheres) and iron carbide nanoparticles were revealed in the composite structure. The magnetic properties of the nanocomposites prepared at various IR-annealing temperatures were studied.     

Complexation in the polyacrylonitrile-amide solvent-PtCl4 system

Complexation in the polyacrylontrile-amide solvent-PtCl₄ solvent system has been studied by IR and electronic absorption spectroscopy. It has been shown that Pt is involved in complexation between the amide group of the solvent and the nitrile group of the polymer, thereby promoting retention of the residual solvent in it. Upon full removal of the solvent, Pt forms complexes with the conjugated system of C=N bonds being formed.     

The effect of IR radiation on structurization of butadiene-nitrile rubber

The accelerated aging of butadiene-nitrile rubber (NBR) induced by IR radiation is studied. At 100°C, intensive aging (the formation of imide and anhydride crosslinks) of NBR is observed in air and argon. The activity of aging under IR radiation is significantly higher than the heat aging. The IR radiation selectively activates nitrile groups without any chemical transformation in butadiene units of the rubber. On the basis of the data obtained, it is suggested that the use of IR radiation makes it possible to model processes occurring as a result of local temperature fluctuations during prolonged natural aging of NBR. Thus, the accelerated aging induced by IR irradiation at 100°C can be recommended as an effective method for estimating structural instability of NBR during storage.