Nanocomposites and nanomaterials

Model of nanostructural metal forms formation on the surface
of the thermoexfoliated and disperse graphite

T.L. Tsaregradskaya1, L.Yu. Matsui1, I.V. Ovsienko1,  G.V. Saenko1 

1 Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska Street, 
City of Kyiv, 01601 Ukraine

Nanomaterials with developed interfacial surfaces are the subject of research of the newest branches of science, the successes of which is connected with the improvement of synthesis methods.. The set of methods being used for producing of nanocomposite materials is quite wide. There are two principal approaches for solving the problem of nanocomposite materials producing, namely, physical and chemical approaches. The deposition methods are the most spread ones among the physical technologies. The method of metal reduction from the salt solution is commonly used in chemical methods. The using of chemical modifying of the developed surface of graphite supporter in order to deposit the metals or their compound in nanocrystalline state seems to be highly prospective. The graphite supporter of different structure types differ by the characteristics of the surface state. The most developed, porous and imperfect surface is inherent to thermoexfoliated graphite. The disperse graphite is characterized by a chemically activated surface. Taking into account the characteristics of the graphite carrier, the application of methods of chemical modification of its surface for the purpose of depositing metals or their compounds in the nanodispersed state is quite promising. 
The physicochemical model of the formation process of nanostructural forms of metal on the surface of thermally expanded and dispersed graphite carriers was developed. For each stage of the process, a function was introduced that determines the dependence of the appearance of a certain mass of the new phase on the unit surface of the substrate; the dependence of this function on time is described by a system of differential equations. The generalized model of the processes occurring when nanostructural metal forms on the surface of a graphite supporter allows one to describe each stage of this process using different types of graphite materials, different salts, and the conditions for conducting the stages. 
It was experimentally confirmed that the proposed model allows theoretically predicting the characteristics of the final product, that is, the size and nature of the particle size distribution of the metal oxide particles formed on the surface of the graphite supporter, depending on the conditions for carrying out the thermolysis reaction, the characteristics of the surface state of the graphite supporter and the type of salt used.