Vol 7, No 1 (2016)

The investigation is devoted to phase transitions initiated by pulsed laser radiation in Cd_xHg_1–xTe solid solutions. Direct measurements show the formation of new phases and determine their composition.

Rheological properties of low-concentrated carbon-fiber suspensions of binder on the basis of poly(methylphenylsiloxane) were investigated and it was shown that those liquid systems may display dilatant, Newtonian, or pseudoplastic properties. Experiments proved that dynamic flow field is separated by the critical shear stress into two regions: a system displays dilatant properties at low stresses and pseudoplastic properties at high stresses. It was shown that transition from one state to another is due to the fact that, in the shear stress field, the colloid-dispersed particles of the binder reversibly change spherical form to asymmetrical form, resulting in thixotropic properties of the system, which are strongly pronounced at 1–3 wt % of the fiber content.

On the basis of the macromolecular concept of the structure of solids and quantitative assessment of the reactivity of the surface of solids using the values of inductive constants, the possibility of the predicted synthesis of nanostructures on the surface of pre-ceramic oxide matrices is shown. The substantiation of the selected approach and the experimental results for the reaction succession of several solid oxides are presented.

A database (DB) on the bandgap of inorganic substances available via the Internet (http://bg.imet-db.ru) was developed for the information service of specialists in the sphere of inorganic chemistry and materials science. The DB is integrated with other information systems on the properties of inorganic substances and materials, which provides the search of a wide range of parameters of a specific substance. The possibility of the use of the information from the developed DB for the search of relations between the bandgap width and other parameters of thermoelectric materials and for predicting the bandgap of chalcopyrites is considered.

The evolution of the morphology of pores in single crystals of nickel superalloys at high-temperature annealing, creep, and hot isostatic pressing is studied. It is found that, depending on the conditions of growth and annihilation, the surface of pores can take many forms: spherical, polyhedral, dendritic, faceted, and irregular.

The effect of addition of low-density polyethylene and/or cellulose powder on the structure of isotactic polypropylene was investigated using methods of wide-angle X-ray scattering and differential scanning calorimetry. The effect of polyethylene and cellulose on the structure and properties of the crystalline phase of isotactic polypropylene was demonstrated.

It is found that a ceramic based on zirconia modified with oxides of yttrium and ytterbium (Yb–TZP) maintains high mechanical properties after hydrothermal treatment, equivalent to 20 years of residence of an implant in vivo. The study of the surface of ceramic samples before and after hydrothermal treatment by atomic force microscopy is carried out. The change in the grain composition of the microstructure of this ceramic is shown, defined by subsurface change in the phase composition caused by martensitic transformation of zirconia.

Significant changes in infrared absorption spectra of polystyrene upon the addition of cesium sulfate nanoparticles to it are observed, which is due to two variants of attachment of organic molecules to nanoparticles (through hydrogen and pi bonds). The relation between the bonds changes significantly during deformation of polystyrene/cesium sulfate composite owing to differences in the mechanical strength thereof. In its turn, the differences in atomic and electronic bond structures result in a significant differentiation of their influence on light emission processes, making it possible to control the scintillation characteristics of polystyrene/nanoparticle composites via regulating their composition and morphology.

An explosive-welded copper–aluminum composite was heat-treated at 570°C. The microhardness, chemical composition, and electrical conductance of the composite were investigated before and after thermal treatment.

The effect of high humidity and temperature on a hardened phthalonitrile matrix is studied in this work. The kinetic dependences of a weight change in the samples during their exposure in a climatic chamber in a stationary mode are presented. The structural modifications in the matrix after thermal and humidity impacts are probed via thermal mechanical analysis. Moisture absorption is found to exhibit predominantly a surface behavior. In addition, the thermal treatment of the phthalonitrile matrix samples in an inert environment is substantiated to reduce moisture absorption.

Magnesium alloys are of great interest to the modern aircraft industry owing to rather high specific strength values. However, the problem of corrosion prevention is not still solved. Plasma electrolytic oxidation is the most promising protective technique for magnesium alloys. In this paper, improving the protective properties of plasma-sprayed electrolytic coating on ML5 casting magnesium alloy via optimization of the current regime is considered. The coatings formed at alternating pulses of the polarizing current are investigated by the electrochemical method. Formation of plasma-sprayed electrolytic coating on ML5 magnesium alloy is theoretically described.

The possibility is studied and the features of the use of Rietveld X-ray diffraction method are revealed for the quantitative determination of maghemite and magnetite in their mixtures. Comparison of the data obtained with the data of Mössbauer spectroscopy is performed.

The interaction between the Nb–Si–Ti matrix and single-crystal α-Al₂O₃ fibers with and without the interfacial coating on interphase boundaries is studied: fiber–coating–matrix and fiber–matrix. It is established that at 1300°C the bending strength of the composite material reinforced by fibers without coating is 1.5 times higher than that of the matrix, and the bending strength of the material reinforced by fibers with coating is 2.5 times higher.