Elena A. Glazkova

Synthesis of core-shell AlOOH hollow nanospheres by reacting Al nanoparticles with water

A novel route for the synthesis of boehmite nanospheres with a hollow core and the shell composed of highly crumpled AlOOH nanosheets by oxidizing Al nanopowder in pure water under mild processing conditions is described. The stepwise events of Al transformation into boehmite are followed by monitoring the pH in the reaction medium. A mechanism of formation of hollow AlOOH nanospheres with a well-defined shape and crystallinity is proposed which includes the hydration of the Al oxide passivation layer, local corrosion of metallic Al accompanied by hydrogen evolution, the rupture of the protective layer, the dissolution of Al from the particle interior and the deposition of AlOOH nanosheets on the outer surface. In contrast to previously reported methods of boehmite nanoparticle synthesis, the proposed method is simple, and environmentally friendly and allows the generation of hydrogen gas as a by-product. Due to their high surface area and high, slit-shaped nanoporosity, the synthesized AlOOH nanostructures hold promise for the development of more effective catalysts, adsorbents, vaccines and drug carriers.

Effect of low-dimensional alumina structures on viability of L 929 cells

In the study, we estimated the cytotoxicity of alumina nanoparticles differing in shape (nanofibers, nanoplates, nanosheets, agglomerates of nanosheets) and close in physicochemical properties (particle size, specific surface area, phase composition, and zeta potential). The alumina structures were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) data, low-temperature nitrogen adsorption, and dynamic light scattering (DLS). The cytotoxicity was estimated on fibroblast cells of the L929 line. It was found that a more adverse effect on the cells was exerted by alumina nanofibers and nanosheets. The action of nanosheets on the cells was inhibitory and was of about the same level, irrespective of the observation period. The effect of alumina nanosheet agglomerates and nanoplates on the cell proliferation was weak even at an exposure time of 72 h.

Synthesis of low-size flower-like AlOOH structures

Al/Cu, Al/Zn, and Al/Fe bimetallic nanoparticles have been obtained using the method of simultaneous electrical explosion of metal pairs in an argon atmosphere. The nanoparticles are chemically active and interact with water at 60°C forming flower-like hierarchical porous structures with a high specific surface area. As the Al/Cu nanopowder is oxidized with water, flower-like pseudoboehmite composite structures are formed with the size of under 1.0 μm; structurally heterogeneous electron-dense spherical inclusions of unreacted metal copper and intermetallides are identified inside them. Al/Fe product transformations are presented by the flower-like pseudoboehmite surrounded by lamellar structures enriched with ferric oxides. Al/Zn nanoparticles react with water, forming the flower-like pseudoboehmite and mainly hexagonal zinc oxide laminae. The composite particles obtained can be used as antibacterial agents in manufacturing medical supplies.

Formation of micro/nanostructured AlOOH hollow spheres from aluminum nanoparticles

Micro/nanostructured AlOOH hollow spheres have been obtained via one-step synthesis. Spherical aluminum nanoparticles coated with amorphous oxide film are used as a precursor. Hollow spheres of AlOOH are formed during the oxidation of aluminum nanoparticles with water. In order to study the evolution of hollow spheres, electron microscopy studies of the reaction intermediates at various stages of the process are carried out. Micro/nanostructured AlOOH hollow spheres have a diameter of 500–800 nm, and their shells consist of boehmite nanosheets with a planar size of 200–300 nm and a thickness of 2–10 nm. It is shown that the formation of AlOOH hollow spheres occurs through dissolution of aluminum core, the diffusion of Al3+ ions through the surface oxide film, and the formation of islands of amorphous Al(OH)3 at the particle–water interface. Further, the formation and growth of AlOOH nanosheets and the formation of a porous shell from nanosheets take place. As a result, the oxide film serves as a substrate for growth of boehmite nanosheets and the formation of micro/nanostructured AlOOH hollow sphere. Morphology and physicochemical properties of the hollow spheres are characterized by transmission and scanning electron microscopy, X-ray diffraction, energy-dispersive analysis, and low-temperature nitrogen adsorption.

Specific features of aluminum nanoparticle water and wet air oxidation

The oxidation processes of the electrically exploded aluminum nanopowders in water and in wet air are examined in the paper. The morphology of the intermediate reaction products of aluminum oxidation has been studied using the transmission electron microscopy. It was shown that the aluminum nanopowder water oxidation causes the formation of the hollow spheres with mesoporous boehmite nanosheets coating. The wedge-like bayerite particles are formed during aluminum nanopowder wet air oxidation.

Formation regularities of AlOOH hollow spheres during aluminum nanopowder water oxidation

There described a novel environmentally friendly synthesis route of micro/nanostructured hollow spheres of AlOOH by oxidation of Al nanopowder in pure water under mild processing conditions. The reaction kinetics of the aluminum nanopowder interaction with water was studied using the method of continuous recording of suspension pH and temperature. There observed the change in Al3+ concentration in the reaction medium and the rate of hydrogen release as well as TEM investigations of the intermediate reaction products at different stages of the process were performed. It is shown that AlOOH hollow spheres are formed through the aluminum core dissolution, Al3+ ion diffusion through the surface oxide film and AlOOH nanosheets formation on the surface of the precursor oxide film.

Low-dimensional pseudoboehmite structures for microorganism adsorption

Low-dimensional structures consisting of pseudoboehmite nanopetals are synthesized by hydrolysis of electroexplosive aluminum nanopowder. The physical and chemical properties of the synthesized nanostructures are studied, such as morphology, particle size, specific surface area, phase composition, and zeta-potential. The production of a hybrid material on the basis of cellulose acetate microfibers and low-dimensional pseudoboehmite structures is described. Using the example of gram-negative and gram-positive bacteria, we show the microorganism adsorption capacity of pseudoboehmite nanopetals and the hybrid material.

Phase state of matter during metal and binary alloy conductor dispersion by a pulse of current

The paper covers the evolution of the liquid phase formed under heating metal conductors by a pulse of current with the density of j ≈ 106÷106 A/cm2. Following the theoretical assessment and experimental data, it was shown that the two-phase state (condensed phase – gas) during the early expansion of products of electric explosion of wires can be caused by the development of density fluctuations in the liquid phase of the metal. The density fluctuation formation is caused by the destruction of liquid phase clusters of short-range order. The study demonstrated the absence of the complete transition of the semiconductor matter into gas after the injection of energy exceeding the energy of sublimation Es.

Bimodal metal micro-nanopowders for powder injection molding

The paper studies a bimodal metal powder composition designed to prepare feedstock for powder injection molding, as well as microstructure and porosity of sintered pats. Two kinds of metal powder compositions are used, in particular, a mixture of micro- and nanopowders and a bimodal powder prepared with dispersion of steel wire. The feedstock is prepared by mixing a bimodal metal powder composition with acetylacetone and paraffin wax. The microstructure of the debound parts is observed by scanning electron microscopy. The sintered parts are characterized by density measurements and metallographic analysis. The technique of the metal powder composition proves to affect the characteristics of sintered parts. Nanoparticles are shown in the interstitial spaces among the microparticles upon mixing micro- and nanopowders, but the regular distribution of nanoparticles on the surface of microparticles is observed in the bimodal powder providing the reduction of the porosity of sintered parts and increasing the de...

Antimicrobial activity of nanostructured composites produced in Al/Zn nanoparticle oxidation in aqueous-alcoholic solutions

The paper studies the morphology, phase and elemental composition of bimetallic Al/Zn nanoparticles. It is found that metallic Al and Zn phases have interfaces within a single particle. The conversion mechanisms of Al/Zn nanoparticles in aqueous-alcoholic solutions with different water concentration are studied. It is shown that at 7 mass% water content aluminum oxidation and pseudoboehmite formation begin. Aluminum conversion increases with water content growth. At 20 mass% water content aluminum is oxidized completely, giving way to zinc oxidation. Microbiological studies show that samples containing AlOOH-Zn-ZnO phases exhibit the highest antimicrobial activity. Two-component metallic Al/Zn nanoparticles and composite particles in which initial components are completely oxidized to AlOOH-ZnO have the smallest inhibition zone.