Authors:V. Turov, P. Gorbik, V. Ogenko, O. Shulga, and A. Chuiko
A study has been made on samples of dispersed vanadium dioxide (VO2) in a matrix of polyethylene glycol (PEG) doped with a quaternary ammonium salt (QAS), namely tetraethylammonium bromide.
It has been established that under the influence of the dopant the heating of a sample up to the temperature of the metal-semiconductor
phase transition (MSPT) results in a phase in homogeneity of the sample. On the basis of the results of this study it is possible
to conclude that small concentrations of QAS in a PEG matrix can exert a strong effect on the electronic structure of dispersed
VO2 particles. This is accompanied by the appearance of phase heterogeneity of VO2 which manifests itself in the fact that - with the onset of MSPT with increasing temperature - one portion of the substance
passes into the metallic state, and the other remains in the semiconductive state.
Authors:L. Semko, L. Dzyubenko, V. Ogenko, and S. Revo
Composite materials (CM) based on poly(ethylene) (PE) and nanocrystalline nickel (Ni) have been produced. The effect of the
content of nanocrystalline Ni and processes of structure formation of its particles on a melting temperature (Tm), interval of melting, true melting heat (ΔHm), degree of crystallinity (χ) as well as characteristics of CM thermodestruction have been determined by DTA and thermogravimetry
techniques. It was found that these characteristics are changed non-linearly when the content of nanocrystalline Ni increases.
The most efficient influence of Ni on the above mentioned characteristics was observed for its low content (0.01 volume part
of Ni). It was shown that a formation of a branched multifractal cluster of nickel above a percolation threshold favored a
decrease in Tm, ΔHm, χ of filled PE and a majority of thermal characteristics of CM thermodestruction as well.
Authors:G. Zagorowsky, G. Prikhod'ko, V. Ogenko, and G. Koval'chuk
The kinetics of the interaction between lithium carbonate and silica with various degrees of dispersion was investigated by
TG and DTA methods. It was found that the utilization of pyrogenic silica with a specific surface area of about 300 m2g-1 instead of aerosil with one of 175 m2g-1 leads to an increase of the reaction rate between lithium carbonate and silica, which depends on the formation and growth
of lithium orthosilicate crystals in the first stage, and is conditioned by the diffusion of lithium and oxygen ions through
the lithium orthosilicate layer formed at temperatures above 800 K. This supposition is supported by the kinetic analysis
results obtained with the use of the different models. The optimal regime of heating is recommended.