Vol 42, No 1 (2016)

Thermal transformations of glasses with formulations derived from Bioglass 45S5 with Al₂O₃ (≤2.5 wt %) and K₂O additions through K-feldspar were studied. Crystallization kinetics and transformations were followed-up by X-ray diffraction and differential thermal analysis. The activation energy of crystallization of Na₂CaSi₂O₆ was found to be lower than that of Bioglass 45S5 for the prepared samples. This behavior was attributed to an increase in phase separation in glasses. Nevertheless, transformations shifted towards higher temperatures with addition of feldspar, due to a decrease in pre-exponential factor. Cell parameters evolved progressively with increasing temperature without any abrupt changes. Al₂O₃ and K₂O remained as a part of a residual glassy phase.

The results of studying the iron oxide-containing two-phase sodium borosilicate glass and porous glass based on it using the method of optical spectroscopy in the visible and infrared regions are presented. Decoding the transmittance spectra of this glass in these spectral ranges using the literary data and their comparative analysis with two-phase sodium borosilicate glass that does not contain iron were carried out.

Dopant atoms of platinum do not change the parameters of electric conductivity and optical band gap width of glass-like arsenic selenides, they are stabilized as ions Pt²⁺ and Pt⁴⁺ with different local environment symmetries, and the ratio of their concentration depends on the composition of glass and the speed of melt solidification process during its production. It is assumed that platinum forms amphoteric two-electron centers with negative correlation energy in a glassy network. Dopant atoms of gold decrease the energy of electric conductivity activation and the optical band gap width of glass-like arsenic selenides and form a compound of trivalent gold with arsenic and selenium in the glassy network. The decrease of the band gap width of glass doped with gold is associated with the formation of solid solutions in the glass, which include a narrow-bandgap semiconducting gold compound.

The process of the formation of coatings based on zirconium boride, silicon, and aluminum oxide on graphite by the thermal treatment of the mixtures of the initial components in air has been studied. During the chemical reactions, a vitreous melt encapsulating the particles of zirconium boride and silicon is formed, which provides high heat resistance of the material. The effect of the composition, temperature, and mode of heating on the kinetics of oxidation of graphite samples with the coatings during their thermal treatment at 1400°C has been studied via the methods of thermogravimetric, thermal, and X-ray phase (XPA) analyses. The compositions of the coatings that effectively protect graphite from oxidation in air at temperatures of up to 1400°C have been proposed based on the results of the study.

In this paper, multilayer TiO₂–SiO₂ containing polydimethylsiloxane (PDMS) coatings were produced by using sol-gel method. To further investigate, the effect of triton as a non-ionic surfactant on PDMS modified single and multilayer silica and titania coatings was studied. The results showed stability of optical triton containing coatings disappears with time due to this material improve the wetting properties of PDMS sols and helps to instability by water absorption. But without triton, antireflective multilayer coatings with high transmittance 98% and excellent durability were obtained by using PDMS as additive material. This coating can be used as well as in solar applications.

Bioinorganic complexes based on silver nanoparticles coated with lysozyme shell (bioconjugates) and aluminosilicate matrices have been synthesizeed. Layered aluminosilicates with the structure of montmorillonite of grade K10 were used as matrices. Complexes with the silver mass fraction 0.3% (from the chemical analysis data) were obtained through fivefold treatment of the aluminosilicate matrix by a sol of bioconjugates with an average particle size of 18 nm and a thickness of the biological cell of ∼4 nm. The produced biocomplexes were investigated by the methods of X-ray diffraction, scanning electron microscopy, and UV spectroscopy. The samples’ antibacterial activity against Gram-negative (E. coli ML-35p, P. aeruginosa ATCC 27853) and Gram-positive (MRSA ATCC 33591, L. monocytogenes EGD) bacteria has been studied. The presence of the biocomplex activity toward antibiotic-resistant strains E. coli ML-35p and MRSA has been revealed.

Ceramic samples of Na_0.55Co_0.9M_0.1O₂ (M = Sc, Ti, Cr–Zn, Mo, W, Pb, Bi) solid solutions are synthesized using the solid-phase method; their crystal structure parameters are determined; their microstructure, thermal expansion, thermal and electrical conductivity, and thermal e.m.f. are studied; and the values of their power factor and thermoelectric figure of merit are calculated. It is revealed that Na_0.55Co_0.9M_0.1O₂ cobaltites are p type conductors with the linear thermal expansion coefficient (LTEC) changed within limits of (12.2–16.2) × 10^–6 K^–1. The effect of the substitution of other metal cations for cobalt cations in Na_0.55CoO₂ on the parameters of the crystal structure, as well as the physicochemical and functional properties of Na_0.55Co_0.9M_0.1O₂ solid solutions, which are formed, is analyzed. It is shown that ceramic samples of the Na_0.55Co_0.9Cr_0.1O₂ and Na_0.55Co_0.9Bi_0.1O₂ compositions have the maximal power factor values among those studied at 0.917 and 1.018 mW/(m K²), respectively, at a temperature of 1100 K.

The specific conductivity and tracer of diffusion of sodium and barium ions have been determined and the values of the transport numbers and correlation factor for diffusion have been calculated in two melts of the Na₂O–BaO–Ga₂O₃–SiO₂ system.