Adsorption properties and porous structure of new carbon materials

The adsorption properties of the new carbon materials, sibunites, which are mesoporous samples with a developed surface of pores, were studied. The isotherms of the adsorption of benzene vapor were determined to estimate the porous structure of these materials. The principal methods for calculating the parameters of the porous structure of sibunites were analyzed. The application of the BET equation even in the presence of a small number of micropores can distort the results, therefore the most suitable method for estimating the surface of mesopores is one that is based on the Dubinin—Zaverina equation. The estimation of the surface of sibunites using water vapor adsorption is demonstrated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1377–1380, August, 1993.     

Lifetime predictions for semi-crystalline cable insulation materials: I. Mechanical properties and oxygen consumption measurements on EPR materials

Long-term accelerated aging studies (up to 7 years of aging) were conducted on four typical EPR materials used as cable insulation in nuclear power plant safety applications with the goal of establishing lifetime estimates at typical aging conditions of ∼50 °C. The four materials showed slow to moderate changes in mechanical properties (tensile elongation) until just before failure where abrupt changes occurred (so-called “induction-time” behavior). Time-temperature superposition was applied to derive shift factors and probe for Arrhenius behavior. Three of the materials showed reasonable time-temperature superposition with the empirically derived shift factors yielding an approximate Arrhenius dependence on temperature. Since the elongation results for the fourth material could not be successfully superposed, consistency with Arrhenius assumptions was impossible. For this material the early part of the mechanical degradation appeared to have an Arrhenius activation energy E_a of ∼100 kJ/mol (24 kcal/mol) whereas the post-induction degradation data had an E_a of ∼128 kJ/mol. Oxygen consumption measurements were used to confirm the 100 kJ/mol E_a found from early-time elongation results and to show that the chemistry responsible before the induction time is likely to remain unchanged down to 50 °C. Reasonable extrapolations of the induction-time results indicated 50 °C lifetimes exceeding 300 years for all four materials.     

Polymer analysis: Molecular structure and properties of industrial polymers

Low density polyethylenes made by the known high pressure processes show significantly different molecular structures. The physical and technological properties are closely related to molecular structure and morphology. For example, the adhesive strength of a laminate consisting of an ozone treated low density polyethylene film and an aluminum foil depends strongly on the synthesis conditions. The molecular structures and dilute solution properties of many fully aromatic thermotropic liquid crystalline copolyesters can now be determined using the new solvent 3,5-bis(trifluoromethyl)phenol. A typical random copolyester was fractionated by precipitation from solution, and the fractions were studied in detail by viscometry, integrated and dynamic light scattering, and size exclusion chromatography. From the structure data thus obtained the molecular mass distribution and the persistence length were calculated. Polymer blends, block copolymers, and graft copolymers can be characterized by fractionation procedures using demixing solvents in an ultracentrifuge and subsequent analysis of the fractions.     

Thermal degradation properties of LDPE insulation for new and aged fine wires

Journal of Thermal Analysis and Calorimetry - ZnO–SnO2 nanostructures are of great interest in practical applications such as optoelectronic devices, gas sensors and catalyst supports due to...     

新型电池材料LiNiyCozTi1-x-yO2的结构与性能研究

研究了新型锂离子电池材料LiNiyCozTi1-x-yO2的结构与性能,比较了LiNiyCozTi1-x-yO2与LiNiO2在充放电特性、物性、粒度分布等方面的异同,研究了LiNiyCozTi1-x-yO2的结构和电化学性能.结果表明,部分Ni被Co和Ti取代后,有效地改善了LiNiO2的性能.     

Characterization of ion-exchange membrane materials: properties vs structure

This review focuses on the preparation, structure and applications of ion-exchange membranes formed from various materials and exhibiting various functions (electrodialytic, perfluorinated sulphocation-exchange and novel laboratory-tested membranes). A number of experimental techniques for measuring electrotransport properties as well as the general procedure for membrane testing are also described. The review emphasizes the relationships between membrane structures, physical and chemical properties and mechanisms of electrochemical processes that occur in charged membrane materials. The water content in membranes is considered to be a key factor in the ion and water transfer and in polarization processes in electromembrane systems. We suggest the theoretical approach, which makes it possible to model and characterize the electrochemical properties of heterogeneous membranes using several transport-structural parameters. These parameters are extracted from the experimental dependences of specific electroconductivity and diffusion permeability on concentration. The review covers the most significant experimental and theoretical research on ion-exchange membranes that have been carried out in the Membrane Materials Laboratory of the Kuban State University. These results have been discussed at the conferences "Membrane Electrochemistry", Krasnodar, Russia for many years and were published mainly in Russian scientific sources.     

Synthesis and photophysical properties of dihydroheptacenes: new blue-emitting materials

7,16-Dihydroheptacenes (1-3) substituted at the 6, 8, 15, and 17 positions are synthesized as blue emitters potentially useful in organic light emitting diodes (OLEDs). The photophysical properties of 1-3 (lambda(max) = 424-428 nm, phi(F) = 0.15-0.21, tau(F) = 2.35-2.67 ns in CH2Cl2) are discussed. They are shown to be stable and efficient blue emitters in the solid state (phi(F) = 0.37-0.44). The X-ray crystal structure of 1 is reported.     

Tape polymer materials for anti-corrosion insulation of pipelines

The article discusses peculiar features of polymer tape coatings for protecting pipelines and main methods of applying them in a field environment. It is shown that the design of polymer tape coating depends on operational conditions, the conditions of the coating application, and the method of pipeline construction. The main Russian and Western insulating materials are reviewed and some of the technical characteristics of these materials are presented.     

Utilization of unsymmetrical dimethylhydrazine in the production of polyurethanes: Synthesis, structure, and properties of new products

Unsymmetrical dimethylhydrazine is used to design novel polyurethane-based film materials, film-forming aqueous dispersions, and closed-cell polyurethane foams.     

Prediction of new materials and properties of solids

The total-energy pseudopotential method is described, and some applications are presented with emphasis on the predictive nature of the approach. For several applications, silicon is used as a prototype material, and the successful predictions related to structure and superconductivity at high pressure are discussed.     

Synthesis and properties of new phosphorus-functionalized bithiophene materials

The synthesis and reactivity of the novel dithieno[3,2-b:2′,3′-d]-phosphole system and its potential use in polymeric sensory materials was investigated. Due to the nucleophilic nature of the phosphorus atom, these materials were found to be easily tunable. Classical reactions at the phosphorus center were performed to modify the electronic structure of the system and the corresponding changes were detected by UV/Vis and fluorescence spectroscopy. Depending on the oxidation state of the central phosphorus atom or its substitution pattern, the dithieno[3,2-b:2′,3′-d]-phospholes show varying wavelengths for absorption and emission allowing to distinguish between different compounds by means of optical spectroscopy.     

Using isothermal microcalorimetry for the prediction and testing of long-term properties of materials and products

The use of isothermal microcalorimetry (MC) as a sensitive monitor for slow reactions is demonstrated in a number of examples. In Example 1 the spontaneous decomposition of a nitrate ester propellant is studied and the absolute degradation rate estimated. Example 2 illustrates how MC can be used for comparing the rate of oxidative ageing at different O₂ concentrations. Synergetic effects between oxygen and moisture in accelerated ageing of nitrile rubber are evaluated from a so-called 4-point test in Example 3. The last example shows a simple MC technique for rapid determination of moisture permeability through a polymeric sealant.     

Synthesis and properties of new potentially nonthrombogenic polymeric materials

A new family of block copolymers have been synthesized and characterized. These copolymers have a central block deriving from the polyaddition of N,N′-dimethylethylenediamine to 1,4-bis-acryloylpiperazine, and lateral blocks of polystyrene. Preliminary biocompatibility tests have demonstrated that these new products show promise as long-acting nonthrombogenic materials.     

新型电池材料LiNi_yCo_zTi_(1-y-z)O_2的结构与性能研究

研究了新型锂离子电池材料LiNiyCozTi1 - y-zO2 的结构与性能 ,比较了LiNiyCozTi1 - y-zO2 与LiNiO2 在充放电特性、物性、粒度分布等方面的异同 ,研究了LiNiyCozTi1 -y-zO2 的结构和电化学性能 .结果表明 ,部分Ni被Co和Ti取代后 ,有效地改善了LiNiO2 的性能 .     

Stoichiography for investigation of the functional materials composition,structure, and properties

Principles of the stoichiography and differential dissolution method (DD) providing deep insight into the composition of mixtures containing unknown chemical compounds are considered. Compounds can be identified using their primary feature — the stoichiometry of elemental composition; reference samples of the compounds are not needed. The DD method makes it possible to analyze mixtures of crystalline and/or amorphous phases with constant and/or variable composition in the form of dispersed powders, ceramics, crystals, thin films and nanosize objects. Various aspects of the stoichiography and DD method application to investigation of composition, structure and properties of the functional materials are discussed.     

Optical properties of polymer films for transparent insulation

Commercially available, highly transparent polymer films for transparent insulation applications were investigated systematically as to their relevant optical properties in the solar and infrared wavelength range. The photometric characterisation in the solar range and the calculation of non-spectral, solar optical film properties using models for scattering-absorbing media have shown, that the solar extinction is dominated by scattering occuring mainly at the surface. For various amorphous and semi-crystalline films the root-mean-square surface roughness correlated well with the solar optical thickness. Regarding high infrared absorptance in the wavelength range of about 10 μm the carbon-oxygen single bond is highly effective for commercial materials with maximum service temperatures of about 100°C. For 50 μm thick films of different polymer types with carbon-oxygen single bonds in the molecular structure a good correlation between the concentration of the functional corbon-oxygen group and the nonspectral, infrared optical thickness was found.     

Synthesis and structure of polymerizable titanium complexes: elaboration of new mesoporous organometallic materials

Inertial confinement fusion (ICF) experiments generate a demand of specific organometallic materials, especially titanium-doped porous polymers obtained from specific Ti-containing monomers. Two new polymerizable titanium(IV) complexes were synthesized. Their free radical co-polymerization affords several titanium-containing polymers, which were dried under supercritical conditions to afford organic aerogels. The chemical compositions of these materials were investigated by NMR, IR, and elemental analysis while their structure was characterized by MEB-EDS and by N₂ adsorption/desorption isotherm measurements.     

Comprehensive assessment of physicochemical properties of new energetic materials

The review presents original methodological approaches and summarizes the results of research into the assessment of relationships between the structure of energetic organic compounds and their main physicochemical properties. A large number of experimental values of these parameters were statistically analyzed, and a database of the properties of explosives and rocket propellant ingredients was created. Based on the analysis and integration of these data, approaches were developed to evaluate the fundamental properties of energetic compounds of different chemical classes, such as the enthalpy of formation, the molecular crystal density, and the sensitivity to mechanical impacts. The explosive and ballistic characteristics were calculated. The comprehensive assessment was made of the possible applications of new substances and those poorly characterized by experimental methods.