Marat I. Lerner

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.

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.

Acid-base and adsorption properties of the AlOOH 2D nanostructures as factors for regulating parameters of model biological solutions

We have studied the acid-base, adsorption, and electrokinetic properties of 2D nanostructures—agglomerates of pseudoboehmite (AlOOH) nanosheets 2–5 nm in thickness—that were synthesized from electro-explosive Al/AlN nanopowder. By the example of adsorption of anionic dye eosin and cationic dye methylene blue, it is found that the synthesized nanostructures have pronounced anion-exchange properties. It is shown that agglomerates of AlOOH nanosheets exhibit properties of a weak base when they are added to the biological model solutions (cell-culture medium and sodium phosphate buffer) and deionized water; in this case, an increase in pH in the media takes place both due to the release of the OH groups and the ionexchange adsorption. The possible impact of the synthesized AlOOH 2D nanostructures on the suppression of tumor-cell proliferation is considered via changes in the parameters (acidity and ionic composition) of their microenvironment.

On the possibility of soft matter nanostructure formation based on mesoporous aluminum hydroxide. Prospects for biomedical applications

The effect of the nonequilibrium structure of 2D aluminum hydroxide-based objects on the macroscopic response (adsorption properties) is studied in the physical mesomechanics framework. Molecular dynamics simulation is performed to examine the nature of selective adsorption of the considered low-dimensional structures. The role of defects and structural elements, such as polar functional groups, is analyzed. Model ions and endotoxin are used to illustrate the selective character of adsorption. Prospects for biomedical applications of the obtained results are discussed.

Novel Micro- and Nanofuels: Production, Characterization, and Applications for High-Energy Materials

In this paper, the problems of production and characterization of nanosized metals (nanosized aluminum) and microsized metal borides (including aluminum, titanium, magnesium) are discussed. The preferences of application for high-energy materials are presented. Also, the technique for production of nanometals is described which is the electric explosion wire method. The results of characterization of nanometals produced by that method are shown and discussed. To protect an active surface of nanoparticles, the different ways for passivation are suggested. Different polymers including Viton and Fluorel are suggested as passivated agents. The problems of chemical stability and chemical compatibility are discussed. A technique for production of metal borides is also described which is known as self-propagating high-temperature synthesis (SHS) and the subsequent mechanical treatment. The result is microsized borides which have an average size of around 5 μm with a sharp curve for distribution sizes. The purity is enough for use as fuel of high-energy materials. The results of TEM, SEM, X-ray, DSC, and TG analyses are also presented and discussed.

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...

Investigation of the hemostatic action of low-dimensional electropositive structures

The paper studies the hemostatic action of the fibrous material containing agglomerates of low-dimensional electropositive structures of aluminum oxyhydroxide. The time of parenchymatous bleeding is found to decrease from 292.5 s at spontaneous hemostasis to 177.8 s with the attached fibrous material and to 215.7 s with gauze. The mixed mechanism of the hemostatic action is possible, i.e. along with the hygroscopic mechanism, plateletes aggregate due to destruction of a diffuse part of the double electrical layer in contact with low-dimensional electropositive structures of aluminum oxyhydroxide.