One-dimensional layered α-МоО3 structures have been synthesized via hydrothermal treatment of peroxo molybdenum complexes. Treatment of the structures in aqueous sucrose solutions under hydrothermal conditions after drying at 80°C has been shown to cause partial reduction of their surface. The reduction process is accompanied by a change in Mo–O bond length as a consequence of distortion of the MoO6 octahedra. Local supersaturation with reduction products in aqueous solution under hydrothermal conditions leads to the formation of new crystallization centers and growth of dumbbell-shaped particles. The forming nanostructured α-МоО3/MoO2 two-phase material, with two morphological species of particles, contains no carbon. Such a strategy for designing one-dimensional α-МоО3 structures can be aimed at monitoring electrochemical degradation of high-capacity electrodes and controlling the associated deformation dynamics.

— Nanostructured Li 4 Ti 5 O 12 -based composites in the form of microspheres consisting of randomly packed prism-like particles have been prepared via hydrothermal treatment of TiO 2 xerogel in aqueous LiOH solutions, followed by calcination of the reaction products at t ≥ 550°C. The phase composition of the hydrothermally prepared spherical particles has been shown to correspond to α-Li 2 TiO 3 . According to elemental analysis data, the titanium and oxygen were nonuniformly distributed over the microspheres. Sequential calcination of the microspheres at t ≤ 750°C led first to the α-Li 2 TiO 3 → β-Li 2 TiO 3 phase transformation and then to the formation of nanostructured Li 4 Ti 5 O 12 spinel or spinel-based composites (Li 4 Ti 5 O 12 /TiO 2 and Li 4 Ti 5 O 12 /β-Li 2 TiO 3 ). The Li 4 Ti 5 O 12 microspheres calcined at 750°C consisted of not only the major crystalline phase but also X-ray amorphous TiO 2 (anatase) and β-Li 2 TiO 3 as impurity phases, which could not be detected by X-ray diffraction.

A nanostructured Li4Ti5O12/β-Li2TiO3 composite material has been prepared by hydrothermal treatment of one-dimensional layered Na2Ti3O7 structures in an aqueous LiOH solution, followed by calcination of the reaction products at t ≥ 550°С. It has been shown that, under hydrothermal conditions, Na+ → Li+ ion exchange processes and chemical interaction of components lead to the formation of the metastable cubic phase α-Li2TiO3. Calcination of the hydrothermal synthesis products leads to the α-Li2TiO3 → β-Li2TiO3 phase transformation and Li4Ti5O12 formation. Primary β-Li2TiO3 and Li4Ti5O12 nanocrystals in the powder calcined at 750°C are orientation-disordered and differ in predominant growth direction. The synergistic effect of the nanocrystals joined in the form of fragments of one-dimensional structures and forming chaotic, loosely packed aggregates leads to the formation of a nanostructured Li4Ti5O12/β-Li2TiO3 composite with enhanced grain-boundary conductivity compared to pure Li4Ti5O12 spinel.

The cobalt content of nanostructured powders obtained by means of the hydrothermal treatment of the aqueous solutions of Sn (II) and Co (II) chlorides is studied using two spectral methods - energy-dispersive (EDS) and atomic absorption (AAS). Liquid samples for atomic absorption analysis were prepared along two routes: by boiling the products of hydrothermal synthesis in concentrated acids and by fusing the products of hydrothermal synthesis with a mixture of sodium peroxide and borax, followed by diluting the liquid alloy. It is shown that low-temperature alloying of samples is most preferable to determine cobalt concentration in ferromagnetic Sn1-xCoxO2-delta nanostructures. Results obtained in the present work allow us to better understand the process of the formation of Co-doped SnO2 nanostructures and use these structures to develop new functional materials.

— Nanostructured materials based on cobalt-doped SnO 2 have been prepared through alkaline hydrothermal treatment of aqueous solutions of inorganic Sn(II) and Co(II) salts. It has been shown that raising the cobalt concentration to 10 wt % leads to significant changes in the morphology and ferromagnetic properties of the synthesis products. The phase composition of the materials corresponds to tetragonal SnO 2 with the rutile structure. Calcination above 450°C leads to Co 2 SnO 4 formation. The saturation magnetization and magnetic susceptibility of the materials vary nonlinearly with the amount of cobalt added to the reaction mixture. The nanostructured material obtained in the presence of ~6 wt % Co has an anomalously high room-temperature saturation magnetization, ~3.5 emu/g, which is almost two orders of magnitude higher than that of highly dispersed powders with a similar composition prepared via chemical precipitation.

Three-dimensional flower-like SnO2-based structures have been produced by the alkaline hydrothermal treatment of t-SnO2 powder with no additive and in the presence of aminoterephthalic acid (ATPA). The synthesis products have been characterized by a variety of physicochemical techniques (scanning electron microscopy, transmission electron microscopy, Raman and IR spectroscopies, X-ray diffraction, and others). The results demonstrate that raising the ATPA concentration in the reaction mixture changes the morphology of the materials and leads to the SnO2 → SnO2/Sn3O4 → Sn3O4 phase transformation in the structures through the formation of SnO x nonstoichiometric tin oxide phases with 1 < x < 2. Hydrothermal treatment of the starting reagents in the presence of ≤75 wt % ATPA leads to the formation of hierarchical structures dominated by a nonstoichiometric tin oxide, which is thermally unstable at t ≥ 500°C. The morphology and phase composition of the synthesized structures have been shown to have a significant effect on the electronic conductivity of the material.

Nanostructured TiO2 in the form of elongated one-dimensional structures having a highly ordered layered morphology, with cobalt-containing agglomerates on their surface, has been prepared by hydrothermal treatment of CoTiO3 powder in the presence of chitosan, a bioactive natural polymer. The synthesis products have been characterized by scanning electron microscopy, transmission electron microscopy, IR spectroscopy, X-ray diffraction, elemental analysis, and magnetic measurements. The structures have been shown to be up to several microns in length, and their typical width ranges from 100 to 400 nm. The one-dimensional structures retain high thermal stability at calcination temperatures of up to 800°C. After vacuum heat treatment at 600°C and above, the nanostructured material possesses anomalously high ferromagnetic characteristics.

Quasi-one-dimensional TiO2-based nanostructures have been produced through hydrothermal treatment-without additives and in the presence of chitosan—of anatase nanopowder synthesized by an electrochemical sol-gel process. The morphology, phase composition, and structure of the hydrothermal synthesis products were studied by various physicochemical characterization techniques, including high-resolution electron microscopy, X-ray diffraction, and IR spectroscopy. The results demonstrate that the forming one-dimensional structures are isostructural with β-titanic acid, H2Ti3O7. Heat treatment at t ≥ 500°C yields a mixture of sodium polytitanates, Na y Ti x O2x + 1, with y = 0.5–2 and x = 2–5. The surface morphology and shape of the nanostructures persist up to 700°C. The key features of the formation of quasi-one-dimensional TiO2-based structures in the presence of chitosan have been identified.

Alumina- and titania-based composite coatings containing ferromagnetic nanoparticles have been produced on UKN-5000P carbon fibers by an in situ organo-inorganic hybrid sol-gel process using appropriate aqueous metal chloride solutions containing Fe(III) and Co(II). The morphology, phase composition, and elemental composition of the coatings have been studied by high-resolution electron microscopy, X-ray diffraction, and energy-dispersive X-ray microanalysis. The results demonstrate that the oxide coatings containing ferromagnetic nanoparticles are uniform in thickness along and across the fibers and adhere well to the fiber surface. The coatings range in thickness from 100 to 500 nm. In all of the systems studied, the coatings produced on carbon fibers differ in phase composition from powders prepared from identical hydrosols.

This paper examines the possibility of modifying the surface of carbon fibers with tantalum carbide via reactive chemical vapor deposition at temperatures from 800 to 1000°C. We have studied the surface morphology and topography of the coatings on carbon fibers and determined their phase composition by a variety of physicochemical characterization techniques, including X-ray diffraction, high-resolution scanning electron microscopy, and atomic force microscopy. The strength of the modified fibers has been measured at room temperature. The results demonstrate that the coatings are continuous and uniform in thick-ness along and across the monofilaments, with good surface adhesion. The microstructure and surface topography of the coatings depend on the deposition time and temperature.

Composites of mesoporous alumina and Fe- or Co-containing ferromagnetic nanoparticles have been prepared from appropriate aqueous metal chloride solutions by a sol-gel process. The synthesis products were heat-treated at different temperatures in air or vacuum and then characterized by a variety of techniques. The results indicate that the mesoporous structure of the nanostructured composites has a large specific surface area, a narrow, unior bimodal pore size distribution, and high thermal stability. The phase composition of the magnetic particles in the X-ray amorphous oxide matrix strongly depends on the heat-treatment conditions.

On the basis of data of IR spectroscopy and powder diffraction analysis, an aqueous solution of poly-N-vinylpyrrolidone was shown to interact with hydrated alumina and zirconia synthesized from corresponding metal chlorides by means of sol-gel technology. A change was shown in the nature of polymer interaction with individual components and their binary mixture at different annealing temperatures. Different mechanisms of formation of intermediate substances in the synthesis of alumina and zirconia from hydrosols in the presence of a water-soluble polymer were assumed with respect to the nature of synthesized sols. The phase composition of oxides in the course of crystallization is affected by poly-N-vinylpyrrolidone and its hydrolysis products formed by electrochemical synthesis of metal oxide hydrosols.

Continuous titanium carbide barrier coatings have been grown on UKN-5000 and VMN-4 carbon fibers using chemical vapor transport. The surface morphology and microstructure of as-received and TiC-coated fibers have been studied by scanning electron microscopy. The coating process is shown to raise the tensile strength and Weibull modulus of the fibers.

Mesoporous alumina with a narrow effective pore diameter distribution has been prepared using poly( N -vinylpyrrolidone)-modified sols of hydrous Al 2 O 3 and Al 2 O 3 -ZrO 2 . We compare the microstructures of nanoporous aluminas prepared from electrochemically produced unmodified and modified sols of hydrous oxides and describe the formation of highly ordered mesoporous structures from a mixture of modified sols of hydrous metal oxides differing in chemical nature. Microstructural studies of uni-and biporous permeable nanosystems during heat treatment demonstrate that the pore diameter distribution in the mesoporous oxides prepared from the modified sols remains unchanged at calcination temperatures of 700°C and lower. The microstructure and phase composition of the oxides depend on the initial properties of the sols.

Sols of rare earth stabilized zirconia were used as simple, readily processable and accurate controllable precursors for the tetragonal zirconia interfacial coatings on commercially available SiC-based fibers. The tetragonal zirconia interfacial coatings can be applied to different types of SiC fibers without degrading fiber strength. The morphology, composition, structure, nanorelief and oxidation resistance of coated SiC fibers were evaluated by various analytical techniques, including scanning electron microscopy/energy dispersive analysis, transmission electron microscopy, atomic force microscopy in various modes, and micro-Raman spectroscopy. It was shown that the microstructural peculiarities of the ReZrO2 interfacial coatings on SiC-based fibers may explain some of the differences in the behavior of different types of fibers.

Structural carbon fibers surface-modified with titanium carbide have been studied by atomic force microscopy (AFM). Using statistical analysis of AFM images, quantitative characteristics of fiber surfaces have been determined. The results demonstrate that surface modification has a significant effect on the surface topography of the fibers: their surface becomes smoother and more uniform, as evidenced by the decrease in roughness value and average height and the narrower height distribution.