Contribution of K. A. Andrianov to the development of heat-resistant adhesives

Listed are the grades of heat-resistant adhesives developed under the Andrianov’s scientific guidance at the All-Russia Institute of Aviation Materials on the basis of organosilicon polymers.     

Polyaniline–water interactions: A theoretical investigation with the polarisable continuum model

The simulations of emeraldine hydrochloride tetramers were performed for the first time in implicit water solvent using the polarisable continuum model (PCM) with the density functional theory (DFT) method. This approach should be more appropriate for the study of the conducting form of polyaniline as all known processes of synthesis and further transformations take place in polar medium. Our results confirm this hypothesis and clearly indicate that the geometry and electronic structure of the emeraldine salt depend on the dielectric properties of the medium. In polar environment the protons are bound tighter to the chains compared to vacuum and this leads to stronger impact of the dopant on the structural parameters of PANI. As a consequence, the density distribution in the emeraldine hydrochloride obtained by PCM is more realistic compared to vacuum estimates. The stability in polar medium of two possible salt configurations with respect to counterions position is assessed. Each configuration is simulated in singlet and triplet state (bipolaron and polaron). The results show that at the tetramer level the bipolaron form is always preferred in accordance to available experimental results.     

Determination of the composition of copolyester based on glycolide and dℓ-lactide by chromatography

Conclusions A procedure has been developed for determining the composition of copolyesters based of glycolide and dl-lactide.The procedure has reasonable analytical accuracy and can be used for operative analytical control in copolymer synthesis.Translated from Khimicheskie Volokhna, No. 4, pp. 59–61, July–August, 1989.     

Effect of saccharose and sorbit on indices of carbohydrate metabolism in mixed saliva of patients with diabetes mellitus and dental caries

The content of lactate in mixed saliva in severe diabetes mellitus associated with multiple caries was 5 times and in diabetes of medium severity 3.5 times greater than in caries-resistant subjects. This increase was largely caused by diabetes proper, since in multiple caries without diabetes, the lactate content was increased only 2-fold. The amount of pyruvate in saliva in multiple caries without diabetes was approximately the same as that in diabetes mellitus coupled with multiple caries. Preliminary administration to the oral cavity of 100 ml of 50% saccharose for 10 minutes (without swallowing) raised the saliva lactate content several times as compared to that in the same subjects before saccharose administration. The lactate content in saliva was particularly high in severe diabetes mellitus. Administration of 50% sorbitol of the oral cavity for 10 minutes did not increase the lactate content in saliva. Upon administration of saccharose lactate dehydrogenase activity in saliva significantly descended while sorbitol dehydrogenase activity significantly increased. Administration of sorbitol solution to the oral cavity did not produce any essential effect on sorbitol dehydrogenase activity in saliva.     

Total external x-ray reflection and infrared spectroscopy study of porous silicon and its aging

Study of p-type porous silicon has been carried out by x-ray reflectometry for the first time. Its critical total-external-reflection angle and its reflection coefficient in the subcritical angle range are much smaller than for c-Si, which was grown by the Czochralski method. The critical angle decreases with increase of the porosity. The critical angle and the reflection coefficient increase with aging. These results are attributable to the much smaller electron density of porous silicon in comparison with c-Si, to the microgeometry of its surface, and to changes in both of these factors attendant to aging due to an increase in the concentration of atmospheric constituents observed in the infrared absorption spectra. As the porosity increases, the concentration of atmosmopheric impurities also increases, and in high-porosity material in addition to chemically adsorbed oxygen, carbon and water seem to contribute appreciably. Fiz. Tekh. Poluprovodn. 31, 957–960 (August 1997)     

X-ray and synchrotron studies of porous silicon

The results of comprehensive studies of layers of porous silicon of different conductivity types, grown by anodizing standard Si(111) substrates in an electrolyte based on fluoric acid and ethanol with the addition of 5% of iodine and kept in air for a long time, are discussed. Measurements are performed by scanning electron microscopy, high-resolution X-ray diffraction, and ultrasoft X-ray spectroscopy using synchrotron radiation. The structural parameters of the layers (thickness, strain, and porosity) and atomic and chemical composition of the porous-silicon surface are determined. It is found that an oxide layer 1.5–2.3-nm thick is formed on the surface of the silicon skeleton. The near-edge fine structure of the Si 2p absorption spectrum of this layer corresponds to the fine structure of the 2p spectrum of well coordinated SiO₂. In this case, the fine structure in the Si 2p-edge absorption region of the silicon skeleton is identical to that of the 2p absorption spectrum of crystalline silicon.     

Effect of Ultraviolet Radiation and Electric Field on the Conductivity of Structures Based on α- and ε-Ga2O3

Semiconductors - The effect of ultraviolet radiation and a strong electric field on the conductivity of structures based on two types of polymorphic gallium-oxide films is studied. Both types of...     

Properties of TiO2 films on silicon substrate

Influence of the substrate material and the effect of oxygen plasma on the microprofile and electrical properties of TiO₂ films deposited by radio-frequency magnetron sputtering are studied. It is shown that the most continuous films with the smallest roughness are obtained when deposited onto silicon substrates. The change in the capacitance-voltage and conductance-voltage characteristics of the structures upon their exposure to oxygen plasma is accounted for by the diffusion of oxygen atoms across the titanium-dioxide film and by the appearance of a SiO₂ layer at the Si-TiO₂ interface.