Vol 43, No 3 (2017)

In our preoccupation with the detailed problems of our daily work of finding out how atoms are arranged in space, we are in danger of losing sight of the whole picture and of not seeing what the picture shows, nor what it means, nor where our part fits in. In the art world there is a place for the critic. A case has been made that there is also scope for the science critic, and yon will indeed see stimulating science criticism, particularly in the pages of Nature, Science and the New Scientist. I think that quite inadequate attention has been paid to the philosophy, ideology and general pattern of our subject, and this is what I want to discuss, bearing in mind that the division of nature and learning into subjects has no natural basis, and is only a concession to human weakness and a convenience for bureaucracy. There is, I believe, a genuine crisis of identity in the field of crystallography, which has followed on the success of the modern techniques of structure determination. Like the art critic, I want to attack the traditional beliefs and to support the view that a science which hesitates to forget its founders is lost. I will therefore not mention von Laue, Bragg or Bernal, but immediately commit the blasphemy of suggesting that crystallography is only incidentally concerned with crystals and that its real objectives today must be different. Our objectives must be to understand regular structures.

Based on the analysis of dissipative processes in solids, the factors which determine the magnitude of internal friction in silica glasses have been highlighted and the main principles of the synthesis of silica glass with low internal friction have been stated. In accordance with the developed principles, the process for the preparation and vacuum melting of the silica raw material has been implemented. The results of the study of the prepared glass specimens, which was performed based on the procedure for the measurement of the oscillation decay time, have shown a sufficiently a low degree of internal friction.

Some photon interaction parameters such as mass attenuation coefficient, effective atomic number, half value layer, mean free path and electron density for 15ZnO–(17.5–x)Al₂O₃–xFe₂O₃–67.5P₂O₅ glass system (x = 0, 7.5, 12.5, 17.5) and 15ZnO–(25–x)Al₂O₃–xFe₂O₃–60P₂O₅ glass system (x = 0, 25) have been investigated in the photon energy range of 1 keV to 100 GeV. It has been observed that all the photon interaction parameters for the selected glass systems vary with the photon energy. Among the selected glass systems, the sample 15ZnO–25Fe₂O₃–60P₂O₅ glass system shows maximum values for mass attenuation coefficients, effective atomic numbers, electron densities and minimum values for mean free path and half value layer in the entire energy grid.

The conditions for the formation of a spinel structure from a NiO–CuO–Fe₂O₃–Cr₂O₃ oxide mixture using several technological approaches have been examined. Addition of KCl is accompanied with the formation of two spinel-like phases, whereas in the absence of KCl just one solid solution of nickel–copper ferrite–chromite with the structure of a cubic spinel is formed. At the temperature of thermal treatment of 900°C, the presence of an admixture phase of the delafossite (CuCrO₂) type was established. The conditions for the fabrication of samples containing two spinel phases (cubic and tetragonal) characterized with the most developed surface and manifesting = increased catalytic activity in the reaction of the decomposition of an organic substance by hydrogen peroxide have been formulated. The studied features of spinel synthesis can be of interest for developing materials with an active surface promising for application as adsorbents of catalysts and sensors.

The magnetite nanoparticles and nanocomposite “Nanotube of hydrosilicate Mg—magnetite nanoparticles—Mg-ChR-NT/Fe₃O₄-NP” were obtained by coprecipitation. The composition of the synthesized samples has been established by X-ray diffraction. Using transmission electron microscopy, the presence of magnetite nanoparticles has been detected both inside the NTs and at the external surface of the NT walls. The specific surface of the NTs, nanoparticles, and composite is determined.

A self-discharge estimation procedure for such an energy storage device as a pseudocapacitor has been developed. The electrode cyclic voltammogram analysis is involved. This procedure is based on the calculation of the energy irreversibly absorbed by an electrode as a result of transformation into heat or chemical energy related to the total energy transferred to the electrode. A single cycle time is considered. A number of model pseudocapacitive electrodes with different electrolytes have been tested according to this computational method. The high correlation coefficient (0.71) between the results obtained by this method and ones by direct potential drop measurement of the electrode in the open circuit is shown.

The possibility of fabricating electroconducting (10¹–10⁴ S cm^–1) ceramics based on In₂O₃, CdO, and LaCrO₃ by liquid-phase synthesis methods has been demonstrated. The results of studies of the effect of temperature, dopants, and partial oxygen pressure on the specific electroconductivity of ceramic composites are presented.