T. P. Maslennikova

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.

Effect of heat treatment on structural-chemical transformations in magnesium hydrosilicate [Mg3Si2O5(OH)4] nanotubes

The structural-chemical transformations in nanotubular magnesium hydrosilicate of composition Mg3Si2O5(OH)4 (chrysotile) obtained by hydrothermal synthesis were studied in heating to 1200°C.

Interaction of potassium chloride aqueous solution Mg3Si2O5(OH)4 with the nanotubes based on magnesium hydrosilicate

Interaction of potassium chloride aqueous solution with the hydrosilicate nanotubes at 80°C is studied.

Interaction of Mg3Si2O5(OH)4 nanotubes with potassium hydroxide

Interaction of Mg3Si2O5(OH)4 nanotubes with aqueous solutions of potassium hydroxide in various temperature-time treatment modes was studied.

Synthesis of nanopowders and physicochemical properties of ceramic matrices of the LaPO 4 –YPO 4 –(H 2 O) and LaPO 4 –HoPO 4 –(H 2 O) systems

Sol-gel method was used to synthesize nanosize powders in the LaPO4–YPO4–(H2O) and LaPO4–HoPO4–(H2O) systems. Dense ceramic samples with high microhardness (up to 25 GPa) were formed from these powders by sintering at temperatures of up to 1600°C. The isomorphic capacity of the monoclinic LaPO4 matrix for the second component (yttrium or holmium) simulating radioactive nuclides of the actinide-rare-earth fraction was found to be high. The composites are stable in aqueous solutions, which is indicated by the low concentration of lanthanum and yttrium ions during leaching test (~10–7 g L–1). The results obtained in the study can be used to develop new high-efficiency ceramic matrices for solidification of the actinide-rare-earth fraction of liquid wastes formed in processing of the spent nuclear fuel.

Chemical and thermal stability of phosphate ceramic matrices

Nanosized powders of orthophosphates in the LaPO4–YPO4–H2O system have been synthesized by the sol–gel method using the reverse precipitation. The obtained powders served as a base to produce compact ceramic matrices. The matrices’ microhardness has been determined and the dependence of microhardness on the sintering temperature and duration has been established. The dilatometry method was used to study the thermal behavior of ceramic matrix samples and to estimate their thermal expansion coefficient. The stability of La1–xYxPO4 ceramic matrices to leaching in distilled water at room temperature has been determined.

Materials based on aluminum and iron oxides obtained by the hydrothermal method

The influence of the relation [Al3+] : [Fe3+] on the phase composition and morphology of the products obtained by the hydrothermal method using solutions of salts of metals and combined sols of aluminum and iron (3+) hydroxides has been studied. The hydrothermal treatment of solutions of salts of aluminum and iron (3+) results in the formation of hematite of a cylindrical or capsular shape, while by the treatment of sols, depending on the relation [Al3+] : [Fe3+], it is possible to obtain particles of hematite with an ellipsoidal shape or bundles of amorphous AlOOH.

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.

Temperature factor in interaction of nanotubular magnesium hydrosilicate, Mg3Si2O5(OH)4, with titanium tetrachloride and water vapors

The conditions were found for modification of Mg3Si2O5(OH)4 nanotubes without altering their inherent chrysolite structure by calcination at 400°C, followed by treatment with TiCl4 vapor at 150–400°C and vapor-phase hydrolysis at 400°C. The procedure for modification of Mg3Si2O5(OH)4 nanotubes can be used for the development of high-performance filtration systems, nanocontainers for storage and transportation of substances, supports for heterogeneous catalysts, and modified sorbents.