Description of mechanical properties of particulate-filled nanostructured polymer composites using fractal analysis

A number of the main mechanical characteristics (yield strength, impact toughness, microhardness) of particulate-filled polymer nanocomposites are quantitatively described using fractal analysis. The approach is used to study the main mechanical behavior features of these materials. The influence of the initial particle size of nanofiller and the degree of particle aggregation on the mechanical properties of nanocomposites is shown.     

Investigation of crystalline polymers and their mixtures in the region of melting and crystallization by the dynamic and tribometric methods

The authors report the experimental results of an investigation of the temperature dependence of the dynamic elastic and loss moduli and the force of friction for linear polyethylene, isotactic polypropylene, and their mixture in proportions of 9 : 1, 5 : 5, and 1 : 9, respectively. The results obtained permit a detailed characterization of the processes of polymer melting and crystallization and determination of the successive regions of melting of the mixture components or formation of a single-phase mixture in the region of concentrations at which the polymers are compatible. It is shown that the higher-melting polymer forms a structural framework that reinforces the melt. The results of dynamic and tribometric experiments confirm the data derived from micrographs of polymer films obtained in polarized light.Mekhanika Polimerov, Vol. 2, No. 6, pp. 895–902, 1966     

Spatial Configuration of Derivatives of 5,5a,6,7-Tetrahydropyrido[1,2-a]benzimidazole and 6,7-Dihydro-5aH-pyrido[1,2-b]benzoxazole

The spatial configurations of 7,9-diphenyl-5a,6-tetramethylene-5,5a,6,7-tetrahydropyrido[1,2-a]benzimidazole and 7,9-diphenyl-5a,6-tetramethylene-2,5a,6,7-tetrahydropyrido[1,2-a]benzimidazol-2-one have been established by X-ray crystallography. Analogous configurations are proposed for a series of other derivatives of 5,5a,6,7-tetrahydropyrido[1,2-a]benzimidazoles and some derivatives of 6,7-dihydro-5aH-pyrido[1,2-b]benzoxazoles on the basis of ¹H NMR spectroscopic data and the results of quantum chemical calculations using the MNDO, AM1, and PM3 methods.     

Synthesis and X-ray diffraction study of K2.92Nb2.58Ti1.42P2.5O17 single crystals

Single crystals of the composition K_2.92Nb_2.58Ti_1.42P_2.5O₁₇ possessing ionic conductivity σ = 10³ Ω cm^?1 at 300°C were grown by the method of spontaneous crystallization from flux in the quaternary K₂O-TiO₂-Nb₂O₅-P₂O₅ system. The X-ray diffraction study of the single crystals grown showed that they are monoclinic with the unit-cell parameters a = 13.800(1), b = 6.412(2), c = 16.893(3) Å, β = 83.33(1)°, Z = 16, sp. gr. P2/n and provided the determination of the structure of this new compound. The Nb and Ti atoms statistically (with different probabilities) occupy four crystallographically independent octahedra. The (Nb,Ti) and P-tetrahedra form the three-dimensional framework with the channels along the diagonal [101] direction occupied by potassium atoms.     

Crystal structure of KTi0.93Sn0.07OPO4

To reveal correlations between the atomic structure and properties of the KTi_1-x SnxOPO₄ solid solutions, single crystals of the KTi_0.93Sn_0.07OPO₄ composition were synthesized and their structure was determined. The crystals belong to the KTiOPO₄ family; orthorhombic, sp. gr. Pna2₁. The unit-cell parameters are a = 12.831, b = 6.410, and c = 10.584 Å. The partial substitution of Sn atoms for Ti atoms results in the formation of more symmetric coordination polyhedra in the structure framework and the change of the physical properties of the crystals.     

Crystal structure of K2.47Nb2.85Ti1.15P2.5O17

The structure of a crystal grown by crystallization from flux in the K₂O-TiO₂-Nb₂O₅-P₂O₅ system was studied by the methods X-ray diffraction analysis at room temperature. The crystals of the composition K_2.47Nb_2.85Ti_1.15P_2.5O₁₇ are monoclinic, a = 13.7864(7) Å, b = 6.4078(3) Å, c = 16.9384(7) Å, β = 83.15(1)°, sp. gr. P2/n. The structure was solved by the direct method using the SHELXS86 program package and refined by the JANA96 program. The crystal structure consists of a three-dimensional framework of sharing-vertices (Nb,Ti)O₆-octahedra and the PO₄-tetrahedra and two types of channels along the diagonal [101] direction, which are statistically occupied by potassium cations providing ionic transport in the compound.     

Study of nanostructures on a solar cell surface exposed on the <Emphasis Type="Italic">Mir</Emphasis> orbital station

It is shown that atomic-force microscopy under normal conditions makes it possible to obtain important information on the topography and features of nanostructures formed on the surface of cover glasses of solar cells exposed on the Mir orbital station for more than ten years. It is found that the nanostructures are multiscale; they are present on all vertical visualization scales from ∼1000 to ∼17 nm and on horizontal scales from ∼1000 to ∼100 nm. The nanoindentation study of mechanical properties of the exposed surface layer shows that the exposed surface at nanodepths is characterized by higher plastic deformation, but lower hardness and effective modulus, in comparison with unexposed surface.     

Polymeric multideck sandwich complex of trimeric perfluoro-o-phenylenemercury with bromide anion

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1466–1467, June, 1991.