E. N. Korytkova

Formation of ZrO2 Nanocrystals in Hydrothermal Media of Various Chemical Compositions

Formation of ZrO2 nanocrystals of various modifications was studied in relation to the chemical composition of the hydrothermal solution and in connection with the kinetic features of the process. The strongest effect on the structure of ZrO2 is exerted by addition to the hydrothermal solution of alkali metal fluorides or potassium iodide, which induce predominant formation of monoclinic ZrO2 nanocrystals. The mechanism by which additions of alkali metal hydroxides and halides affect the phase state of ZrO2 nanocrystals was revealed.

Modification of films of heat-resistant polyimides by adding hydrosilicate and carbon nanoparticles of various geometries

The possibility of modifying the properties of poly(4,4′-oxydiphenylene)pyromellitimide films by introducing into prepolymer solutions nanoparticles of various compositions and structures [hydrosilicate nanoparticles in the form of layered structures (montmorillonite) and nanotubes; carbon nanofibers] was examined. New intercalating agents, tetranuclear aromatic diamines, were suggested for pretreatment of montmorillonite prior to introduction into heat-resistant polymers. The mechanical characteristics of the nanocomposites with hydrosilicate nanotubes can be optimized by chemical pretreatment of the nanotubes prior to introduction into the polymer matrix. Introduction of the above-named nanoparticles into the polymer matrix appreciably increases the elastic modulus of the material. The largest increase in the elastic modulus is observed with hydrosilicate nanotubes of the chrysotile structure, coated with an aromatic modifier.

Polymer-inorganic nanocomposites based on aromatic polyamidoimides effective in the processes of liquids separation

The polymer-inorganic nanocomposites based on the aromatic polyamidoimides and the silicate nanotubes of chrysotile structure were developed. The polyamidoimides were synthesized from dicarboxyphenylphthalimide dichloride by the polycondensation with either 4,4′-diaminodiphenyl ether or 3,5-diaminobenzoic acid. The morphology, mechanical and transport properties of the nanocomposite films were studied. Distribution of nanotubes in the composites is shown to be defined by the chemical structure of the polyamidoimide. The conditions for the formation of the composites were optimized to provide a significant increase in selective permeability toward alcohol and water in the process of pervaporation at the introduction of the nanotubes in the polymer.

Influence of the physicochemical parameters of synthesis on the growth of nanotubes of the Mg3Si2O5(OH)4 composition under hydrothermal conditions

The growth of nanotubes of the Mg3Si2O5(OH)4 composition with a chrysotile structure has been investigated under hydrothermal conditions. It has been established that the nanotubes in the axial and radial directions grow through the step mechanism due to the recrystallization and mass transfer of the components. The introduction of seeds considerably promotes the growth process, especially at the nanotube ends. The evolution of chrysotile nanotubes with a variation in different physicochemical parameters of synthesis, such as the temperature, time, NaOH concentration in the reaction medium, and introduction of seeds, has been traced. It has been demonstrated that the controllable variation in these parameters makes it possible to perform a controlled hydrothermal synthesis of chrysotile nanotubes with specified lengths and aspect ratios.

Hydrothermal synthesis of nanotubular Co-Mg hydrosilicates with the chrysotile structure

Nanotubes of the chrysotile structure were obtained under hydrothermal conditions in the series of hydrosilicates of the Mg3Si2O5(OH)4-Co3Si2O5(OH)4 system. Substitution of cobalt ions for magnesium ions affects the conditions of formation, morphology, and size of the nanotubes. The formation of nanotubes on hydrothermal treatment of the starting mixtures of cobalt metasilicate and magnesium, cobalt, and, silicon oxides and hydroxides occurs in stages, and the stage of nanotube formation is always preceded by the formation of a lammellar structure.

Interacton of chrisotyl nanotubes with water-alcohol solutons at different temperature-time parameters

The process of filling hydrosilicate nanotubes of composition Mg3Si2O5(OH)4 with water-alcohol solutions at different temperature-time parameters has been investigated. The effect of the nanotubes’ interaction with water-alcohol solutions on the solutions state and of their properties as well as on the nanotube structure, morphology, and size has been established.

The synthesis and thermochemical study of (Mg,Fe)3Si2O5(OH)4 nanotubes

Nanotubular (Mg,Fe2+,Fe3+)3Si2O5(OH)4 hydrosilicates with a chrysotile structure were synthesized under hydrothermal conditions. The phases prepared were studied thermochemically on a high-temperature Tian-Calvet microcalorimeter by solution calorimetry. The standard enthalpies of formation of magnesium-iron nanotubular hydrosilicates were determined. The formation of iron-containing nanotubes was shown to be lass favorable energetically than the formation of magnesium nanotubes.

Synthesis and growth of nanotubes Mg3Si2O5(OH,F)4 composition under hydrothermal conditions

Nanotubes of magnesium hydrosilicate Mg3Si2O5 (OH, F)4 having the structure of chrysotile and increased thermostability in comparison with hydroxyl-chrysotile were synthesized under hydrothermal conditions at temperatures of 300–450°C and pressure of 30–100 MPa from mixtures of oxides of magnesium and silicon with the use NaF and NaOH as mineralizers. The conditions of the synthesis of the chrysotile nanotubes with varying content of fluorine (0.4–4.0 wt %) in the composition of chrysotile were determinated. The effect of the physical-chemical parameters of the synthesis on the growth of the OH-F-chrysotile tubes was tracked. The core role of concentration of F-containing mineralizer was shown.

Effect of temperature on the synthesis of nanoparticles with different morphology in the system MgO–SiO2–TiO2–H2O under hydrothermal conditions

Nanoparticles with different morphology have been obtained by hydrothermal method in the system MgO–SiO2–TiO2–H2O. It has been found that in the investigated temperature–time interval the formation of nanotubes of hydrosilicate with the structure of chrysotile with a small amount of impurity phases predominantly takes place.

Influence of synthesis of physicochemical parameters on growth of Ni3Si2O5(OH)4 nanotubes and their filling with solutions of hydroxides and chlorides of alkaline metals

The growth processes of nanotubes of the Ni3Si2O5(OH)4 composition with a chrysotile structure have been studied under hydrothermal conditions for both axial and radial directions. The tubes of optimal sizes needed to fill them with liquid substances were obtained by the well-directed control of the synthesis physicochemical parameters. The processes responsible for the filling of nanotubes with solutions of hydroxides and chlorides of alkaline metals (Na, K, and Cs) and for their interactions with the tubes have been investigated.