I. A. Drozdova

Formation of Mg3Si2O5(OH)4 Nanotubes under Hydrothermal Conditions

The formation of nanotubes of magnesium hydrosilicate Mg3Si2O5(OH)4 with a chrysotile structure is investigated. It is found that the nanotubes of magnesium hydrosilicate Mg3Si2O5(OH)4 are formed through different mechanisms depending on the initial state of reactants, the composition of the hydrothermal solution, and temperature. It is shown that the rate of formation of nanotubes is determined by the stability of intermediate compounds, the chemical composition of the reaction mixture, and the synthesis temperature.

Synthesis and investigation of the structure of ceramic nanopowders in the ZrO2-CeO2-Al2O3 system

A new technological scheme has been developed for synthesizing nanocrystalline powders in the ZrO2-CeO2-Al2O3 system. The powders have been used for preparing nanoceramic materials with an open porosity of ∼1%. The physicochemical properties of these ceramic materials have been investigated.

Structural transformations in thermally modified porous glasses

The changes in the structural parameters of porous glasses (pore radius, pore volume, specific surface of pores, structural resistance coefficients) upon heating are investigated as a function of the composition of initial two-phase alkali borosilicate glasses with the use of a number of independent methods, such as the adsorption techniques (water vapor adsorption, mercury porosimetry, thermal desorption of nitrogen), transmission electron microscopy, small-angle X-ray scattering, and membrane conductivity measurements. It is demonstrated that the structural transformations in thermally modified porous glasses are associated with the processes of overcondensation of pores and viscous flow in the silica network.

Synthesis and study of antimicrobial activity of bioconjugates of silver nanoparticles and endogenous antibiotics

Bioconjugates of silver nanoparticles and antimicrobial peptides of the bactenecin family, which are endogenous antibiotics, have been synthesized. The biological activity of the prepared bioconjugates has been evaluated. It has been established that the conjugates of silver nanoparticles with the peptide G-Bac3.4 exhibit an antimicrobial activity, including the activity with respect to the strain Pseudomonas aeruginosa resistant to traditional antibiotics and the strain Staphylococcus aureus (MRSA ATCC 33591) resistant to methicillin. It has been demonstrated that the complexes of silver nanoparticles with antimicrobial peptides do not possess a pronounced membranolytic effect inherent in peptides. The results obtained have made it possible to draw the conclusion that the properties of the synthesized conjugates differ from those characteristic of constituting peptides and silver nanoparticles.

Electron Microscopic Investigation of the Structure of Gas-Sensitive Nanocomposites Prepared by the Hydropyrolytic Method

Polycrystalline films in the SnO2–In2O3 and SnO2–ZnO systems, which are of interest for use in gas-sensitive sensors, are grown from metal chlorides on a 22-XC ceramic substrate by the hydropyrolytic method. The nanocomposites based on tin dioxide are studied. The structure of polycrystalline grains is investigated by electron spectroscopy and X-ray diffractometry. The distribution of components in the samples prepared is examined using electron probe X-ray microanalysis. It is established that homogeneous films in the SnO2–In2O3 system up to 10 mol % In2O3 in the initial solution can be grown by the hydropyrolytic method.

Hydrothermal synthesis of nanotubular Mg-Fe hydrosilicate

Magnesium iron hydrosilicate nanotubes with a chrysotile ((Mg,Fe)3Si2O5(OH)4) structure have been synthesized hydrothermally at t = 250–450°C and p = 30–100 MPa. In the hydrothermal synthesis of (Mg,Fe)3Si2O5(OH)4 chrysotile, part of the Fe2+ ions oxidize to Fe3+ and are incorporated into the octahedron and tetrahedron layers of the chrysotile structure. The limiting iron content of chrysotile has been determined up to which cylindrically rolled layers can form to yield nanotubes. The hydrothermal treatment of precursors richer in FeO yields platelike hydrosilicates. The iron ions present in the starting components affect the synthesis parameters, morphology, size, optical properties, and thermal stability of the nanotubes.

Preparation and thermal transformations of nanocrystals in the LaPO4-LuPO4-H2O system

Powders of nanosized particles of individual and mixed lanthanum and lutetium orthophosphates are synthesized. The grain growth process is studied in the temperature range of 200–1100°C. Temperature and concentration regions of existence of the solid solutions based on hexagonal and monoclinic forms of LaPO4 as well as on tetragonal LuPO4 are determined.

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.

Synthetic nanoclays with the structure of montmorillonite: Preparation, structure, and physico-chemical properties

Nanosized layered silicates with a montmorillonite structure of varying composition were synthesized under hydrothermal conditions (350°C, 700 atm). The hydrothermal treatment was applied to gels with the compositions calculated with the use of an ideal formula of the final product Na2x(Al2(1 − x), Mg2x) Si4O10(OH)2 · nH2O (0 ≤ x ≤ 1). The obtained samples were investigated by X-ray diffraction, IR and NMR spectroscopy, electron microscopy, and mercury porosimetry. The values of the cation-exchange capacity and specific surface are determined. The mean size of the particles of the synthesized samples is 40 ± 7 nm. A gradual substitution of aluminum for part of the magnesium in the initial gel made it possible to obtain samples with well-defined composition-dependent characteristics.

Synthesis, mutual solubility, and thermal behavior of nanocrystals in the LaPO4-YPO4-H2O system

Nanopowders of lanthanum and yttrium orthophosphates have been synthesized. The growth of nanocrystals has been investigated in the temperature range 200–1100°C. The temperature-concentration limits of the existence of the solid solutions have been determined. The thermal behavior of the orthophosphates has been studied over the entire range of lanthanum and yttrium concentrations.