Capacity characteristics of carbon anodic materials based on Russian natural graphite for lithium-ion batteries

The effect of structural and surface properties of carbon anodic materials based on natural graphite of the Taiginka Deposit obtained using different technologies on the capacity characteristics of the negative electrode of a lithium-ion battery is studied. It is shown that the key factors determining the value of irreversible capacity of the negative electrode in the first cycle are the value of graphite specific surface area, the state of the surface, in particular, the content of disordered carbon, and functional groups on the surface of graphite particles, and also the composition of the active electrode layer. A change in the specific surface area value and content of functional groups is due to the efficiency of the pyrocarbon coating in the case of samples subjected to milling on vibration and cavitation mills, and also of finely dispersed samples obtained by milling on a jet mill. The observed decrease in the specific surface irreversible capacity at an increase in the specific surface area of carbon is apparently caused by inhomogeneity of the latter and nonparticipation of its microporous part in formation of the solid-phase surface passivating film. The minimum irreversible specific capacity of electrodes of the studied natural graphite for the optimum electrode material composition was about 20 mA h/g or 6%. The specific surface capacity changed as dependent on the value and state of the graphite sample surface more than threefold (from 2.5 to 7.7 mA h/m²) and by an order of magnitude at an additional change in the electrode composition (from 2.5 to 20.3 mA h/m²).     

Magnetic Study of Nanostructural Composite Material Based on Cobalt Compounds and Porous Silicon

In present work, an investigation of a magnetically ordered material, which is a composite structure obtained by embedding of cobalt-containing substance into pores of silicon matrix, was performed. The samples were characterized by steady-state magnetometry and electron microscopy. The methods of longitudinal nonlinear response to a weak ac magnetic field and registration of electron magnetic resonance were used for detail study of their properties. It was established that the material forms a structure of ferromagnetic particles at the inner surface of pores. It was agued that they are mainly nonmetallic magnetic particles like Co₂B and/or Co₃B. The possibility to apply the concept of blocking temperature to specify the magnetic behavior of the compound on temperature confirmed the single-domain state of these particles.     

The statistical distribution of magnetic critical currents determined by HTSC film morphology

An analysis is made of the geometric and morphological properties of YBCO superconducting films and of their effect on the magnetic and transport phenomena. A study is presented of the statistical characteristics of critical currents derived from the variation of trapped magnetic flux induced by passing a pulsed transport current. It is shown that the critical currents in the materials under study have a specific statistical distribution, whose main properties are due to the morphology of their structure and can be determined by geometric-probability analysis. The superconducting film is considered as a percolation system. An empirical normal-phase cluster-area distribution function was used to derive the distribution function of magnetic critical currents, which describes adequately the experimental data on how transport current affects trapped magnetic flux. The critical current for transition of a film to the resistive state has been calculated. Fiz. Tverd. Tela (St. Petersburg) 41, 1739–1742 (October 1999)     

Noncondensed polypiperidine systems

The synthesis of noncondensed dipiperidylbenzene and tripiperidyl systems has been effected. Some derivatives of compounds of this series have been obtained.     

Mass spectrometric study of methyl-substituted 4-azaphenanthrenes and their nitration products

The mass spectral behavior of five derivatives of the 4-azaphenanthrene series — 1,3-dimethyl-(I), 2,3-dimethyl-(II), 1,2,3,-trimethyl-(III), 1,2,3-trimethyl-8-nitro-(IV), and 1,3-dimethyl-6,7-dinitro-4-azaphenanthrene (V) — was studied. The stabilities of the molecular ions with respect to gragmentation (W_M) are higher by a factor of two or more for the methyl-substituted I–III than for nitro derivatives IV and V. The intensity of the [M-H]⁺ ion peak in the mass spectra of I–V does not depend on the number of methyl groups but only on their positions: the presence of a CH₃ group in the 2 position leads to an [M-H]⁺ ion that is 1.5 times more intense than when there is a methyl group in the 1 position. The molecular ions of I–V do not eliminate HCN molecules; this constitutes evidence for the absence of randomization of their methyl groups. The presence of a CH₃ substituent in the 1 or 2 position does not affect the intensity of the [M-CH₃]⁺ ion peaks, while the simultaneous presence of CH₃ groups attached to the C₁ and C₂ atoms increases the intensity of the [M-CH₃]⁺ fragment peak by a factor of two. In the mass spectra of nitro derivatives IV and V, [M-O]⁺, [M-OH]⁺, [M-NO]⁺, and [M-NO₂]⁺ fragments are observed in the first step of the fragmentation of the M⁺ ion, whereas the [M-CO]⁺ ion peak characteristic for the dissociative ionization of 1-nitronaphthalene is also observed for 8-nitro-substituted IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1365–1369, October, 1977.     

Mass spectrometric study of 2-azafluorenes

The fragmentation of 2-azafluorene and its methyl and phenyl-substituted derivatives was studied. It is shown that ejection of an RCN fragment (R=CH₃, C₆H₅) by the molecular ions leads to a more intense peak if R is in the 3 position of the azafluorene ring. It was established that, in contrast to the dissociative ionization of fluorene, all of the ions of which are formed from the (M-H)⁺ fragment, the fragmentation of 2-azafluorene and its derivative also takes place from the molecular ion. Randomization of the deuterium atoms attached to C₉ with the remaining hydrogen atoms was observed.Translated from Khimiya Geterotisiklicheskikh Soedinenii, No. 1, pp. 101–105, January, 1977.     

The influence of an organosilicon modifier on the properties of a compound based on epoxy-urethane oligomer

To improve the performance characteristics of products made of highly-filled polymer compositions, modification of a compound based on epoxy-urethane oligomer was performed. The SH 198 amino functional organosilicon oligomer was used as a modifier. The performed studies established that an organosilicon modifier increases the gel time and the curing time of the composition based on epoxy-urethane oligomer, shows the plasticizing effect on a compound, decreases its glass transition temperature from 16.5 to 9°C, and increases the deformation in the temperature range of from–40 to +50°C.     

A Study of the Properties of Unsaturated Polyketone as a Representative of New-Type Reactive Oligomers for the Development of an Adhesive Composition on Its Basis

The properties of unsaturated polyketone, which is a representative of new-type reactive oligomers, were studied. It was shown that unsaturated polyketone is compatible with a polar plasticizer (dibutyl phthalate), to some extent compatible with a nonpolar plasticizer (transformer oil), and can be cured by dinitrile oxide and EKh-1 quinol ester. An adhesive composition based on unsaturated polyketone cured by quinol ester and epoxy-containing components was developed. It was established that the adhesive composition based on unsaturated polyketone limitedly swells in transformer oil and has two glass-transition temperatures. The adhesive composition based on unsaturated polyketone provides bonding of a high-filled polymer composition with a rigid multilayered substrate.     

Study of the composite based on iron-containing nanoparticles dispersed in the polyethylene matrix

A composite representing a system of iron-based nanoparticles about 5 nm in size embedded in a high-pressure polyethylene matrix has been studied. The technology of preparation of this material has been described. The transmission electron microscopy, X-ray powder diffraction, and nuclear gamma-resonance spectroscopy data presented have been used to establish the volumes of the metal and oxide phases of a nanoparticle and the composition of its oxide shell.