V. A. Bogolepov

Carbon Nano/Microstructures for Hybrid Hydrogen Storage Based on Specially Treated Carbon Fibers

The fabrication of carbon 3D-nano/microstructures based on the nanostructure deposition from gas phase on the surface of specially treated carbon fibres is proposed as an initial preparative stage to produce a carbonaceous scaffold for hybrid (adsorption-absorption) hydrogen storage materials. This materials design approach is focused toward the hybrids/composites, which could combine the capacity of compounds consuming hydrogen chemically with high specific surface area of systems adsorbing hydrogen intensively by physisorption. The fullerene molecules in the reaction zone can serve not only as a source of carbon pair (arc discharge) but as the catalyst of synthesis of carbon nanostructures (pyrolysis of hydrocarbons). In the present work the carbon fibres were impregnated by fullerene solution in toluene that catalyzed the process of carbon nanotubes growth at the fibres surface.

Hydrogen Accumulators for Various Purposes

The hydrogen storage in metal hydrides is the urgent problem of hydrogen power engineering and the demand for metal hydrides as capacitive, safe and convenient in service sources of hydrogen has stimulated the study of hydrogen capacity of multicomponent alloys. In recent years, much attention has been given by scientists to the investigation of hydrogen-sorption and desorption properties of different materials, including nanocarbon structures and composites on their base, the study of peculiarities of the reversible hydrogen interaction with hydride forming metals and alloys, the development of high-pure hydrogen storage and transportation in solids. This chapter deals with the designed hydrogen metal-hydride torches with piezoelectric firing of flame, two models of accumulators/compressors of great capacity on hydrogen, and three modifications of laboratory hydrogen accumulators used in operation of fuel cells. We show the construction of all torches and accumulators, their technical operating characteristics, the special features and advantages of devices developed and produced in our department and their extremely effective applications in conditions of high ecological requirements.

The Prospects for Use of Hydrogen Accumulators on the Basis of Lanthan-Magnesium-Nickel Store Alloys

A theoretical study of hydrogen solubility in alloys with structures of the L22, D2d, L60 types and in phase mixtures of these alloys has been developed on the basis of the molecular-kinetic concept. The absorption and desorption isotherms have been investigated, their dependence on the hydrogen activity and the magnesium concentration has been found. It is presented that horizontal plateau appears and is lengthened in the isotherms with increasing concentration of magnesium and with decreasing activity of hydrogen atoms. Considering volume effects, the hysteresis phenomena have been studied and hysteresis constants have been evaluated. A fall in hysteresis constant with reduced activity of hydrogen atoms has been shown. Our calculation results are in agreement with experimental data.

Synthesis of Carbon Nanotubes on Zirconium Alloys Surface

The radiation-stimulated structural phase transformations can significantly affect the processes influencing on the structural materials operation under radiation and high temperatures conditions. These processes lower reliability and service life of shells and covers thus reducing the times of safe operation of nuclear reactors. Therefore the search for the way and technologies directed to the increase in reliability and durability of fuel element (tvels) shells and thermal converter covers is a special issue of the present day. The purpose of the present paper is to give the description of the performed series of experiments on carbidization of the zirconium substrate surface. Such carbidization has been conducted through the carbon nanostructures dissolution in the matrix volume under various conditions of heat treatment. Metallic and nonmetallic catalysts have been used to synthesize carbon nanostructures on the zirconium alloys surfaces. The surface of test specimens of thermal fuel elements (tvels) has been subjected to grinding and also to the electrolytic polishing in acid-water solution for taking the strain hardening. Carbon nanostructures have been synthesized on the substrate surfaces by the method of acetylene pyrolysis. Nickel nanoparticles deposited on the substrate by cladding have been used as a metallic catalyst. Synthesis of carbon nanostructures on such catalysts allows the formation of uniform layer of carbon nanotubes on the sample surface. The microhardness has been measured for the synthesized specimens with nanotubes on the zirconium substrate cladded with nickel and compared with initial samples. The study has revealed that the microhardness of treated specimens increases, resulting in the hardening of tvel covers by carbidization and in doing so authors have found a way to the rise of reliability and durability of tvel shells and thermal converter covers hardenable by heat-treatment.

The Designed Metal-Hydride Torches and Hydrogen Accumulators for Various Purposes

The hydrogen storage in metal hydrides is the urgent problem of hydrogen power engineering and the demand for metal hydrides as capacitive, safe and convenient in service sources of hydrogen has stimulated the study of hydrogen capacity of multicomponent alloys. In recent years much attention has been given by scientists to the investigation of hydrogen-sorption and desorption properties of different materials including nanocarbon structures and composites on their base, the study of peculiarities of the reversible hydrogen interaction with hydride forming metals and alloys, the development of high-pure hydrogen storage and transportation in solids. This paper deals with the designed hydrogen metal-hydride torches with piezoelectric firing of flame, two models of accumulators/compressors of great capacity on hydrogen, and three modifications of laboratory hydrogen accumulators used in operation of fuel cells. We show the construction of all torches and accumulators, their technical operating characteristics, the special features and advantages of devices developed and produced in our department and their extremely effective applications in conditions of high ecological requirements.

Hydrogenation of Fullerite C60 in Gaseous Phase

The fullerene is the fourth allotropic modification of carbon and its properties, as volume, gravimetric and electrochemical capacities, are in excess of many similar properties of metal hydrides and hydrocarbons. The solution of the problem of the reversible hydrogenation of each carbon atom in the frame of fullerene molecule will allow to create the hydrogen storage with the capacity up to 7.7 wt.% H. A series of experiments have been conducted to evaluate the full hydrogenation of fullerite C60; hydrofullerenes have been produced experimentally with the variable content of hydrogen. The optimum regime of C60 hydrogenation has been determined resulting in the full hydrogenation of fullerene molecule C60. As was apparent after the tests, the sequence of formation of hydrogenated fullerene molecule C60H60 in fullerite has been going in the following order: the molecular hydrogen dissolution in octahedral interstices of fcc lattice of fullerite, the dissociation of hydrogen molecules in going from octa- to tetrahedral interstices, the interaction of hydrogen atoms with fullerene molecule. It has been demonstrated that chemisorption process of hydrogen by molecule C60 is limited by diffusive processes in fullerite after hydrogen concentration conformed to C60H36. The spectral analysis have shown that the second stage process of chemisorption follows the compressive shell model. The suggestion of the model of processes going on at the interaction between H2 and fullerite C60 has been made. The mechanism for the definition of hydrogenation degree of molecule C60 has been proposed in the present paper.

Fullerene Molecule as Catalyst of Synthesis of Carbon Nanotubes

Advantage was taken of new materials produced by original (developed by authors) technology with the use of non-metallic catalysts. It is common knowledge that metals of iron group (Fe, Ni, Co and their mixtures) are most often used as an catalysts for synthesis of carbon nanostructures. After synthesis the catalyst which content amounts to as much as 30 wt.% is dissolved in mineral acids by boiling. The carbon nanostructures prepared by pyrolysis of hydrocarbons on the non-metal catalysts don’t require the harmful and power-intensive stage of chemical treatment and they contain on their surface the molecules of inorganic acids in adsorbed form and another associated impurities. In the present work the carbon fibres were impregnated by fullerene solution in toluene that catalyzed the process of carbon nanotubes growth at the fibres surface.