Papers by Author: Victor Ivanov

Abstract: The method of electrochemical extraction of oxygen from air employing a solid oxide electrolyte (SOE) is presented. The prototype of electrochemical oxygen generator (pump) for medical applications has been developed and fabricated. It is based on thin-walled tubular segments of YSZ electrolyte (170 μm) with LSM based electrodes (~20 μm). Different technologies: nanopowder production by laser ablation, casting of polymer-ceramic tapes, formation of electrodes-electrolyte green structures by radial magnetic pulsed compaction followed by cosintering at 1200°C, were used for segments fabrication. The magnetron sputtering method was applied to protect metallic interconnects (Crofer 22 APU) with (Mn-Co)3O4 layer. Presented oxygen generator prototype produced 9 liters of pure oxygen per hour under applied power of 50 W at 800°C. No noble metals were used in construction.

Abstract: By means of magnetic pulsed compaction and sintering of weakly aggregated alumina based nanopowders the jet forming nozzle samples for hydroabrasive cutting were fabricated. The ceramics were obtained from pure alumina, as well as from alumina, doped by TiO2, MgO and AlMg. The ceramic properties of the channel surface and the nozzle volume were investigated. It was shown that the samples sintered from AlMg doped Al2O3 powder had the best desired mechanical properties and structural characteristics: relative density ~0.97, channel microhardness – 18-20 GPa, channel surface roughness ~0.7 /m, average crystallite size ~1 /m.

Abstract: Fabrication of dense YSZ electrolytes and porous LSM cathodes in the shape of tubes using a radial magnetic pulsed compaction of multilayered tubular blanks of powder tapes has been investigated. The tapes were prepared with butyral resin binder. The multilayered blanks were compacted magnetically. Magnetic pressures of 0.2-0.3 GPa in amplitude, sintering temperatures as low as 1100-1300 °C (in air) with holding time of 20-540 min have been used. Cathode tubes of 0.2-1.0 mm thick exhibited the reproducible open porosity up to 45 %. YSZ electrolyte tubes with the wall of 100-450 microns thick had near full relative density, 0.97-0.99, and were characterized with grains of 200-500 nm in size on the average depending on the sintering temperature. The electrochemical cells built up of as-prepared tubular electrolytes and traditional research electrodes were tested under the air-hydrogen fuel cell conditions. The specific output power, 0.6 W cm-2, was realized at temperature of 885 °C.

Abstract: An influence of aggregation degree of alumina nanopowder and of radial magnetic pulsed compaction conditions on the powder densification and on the density distribution inside compacts has been investigated experimentally. The usage of radial magnetic pulsed compaction allows to compact alumina nanopowders up to high densities at low degree of aggregation. The compacts homogeneity is attained by appropriate compaction pulse duration and by the usage of powder packing prior to compaction until the condition with high local sound speed is achieved.

Abstract: Magnetic Pulse Compaction (MPC), as a dynamic compaction, can be possible to reach higher relative density of nano metallic compacts owing to sufficiently high pressure and adiabatic heating in very short duration of an order of µsec. The present work is concerned with the magnetic pulsed compaction of the nano-sized aluminum powders, which particle size was a range of 50 ~ 100 nm passivated in air. The compaction pressure was 1.5 GPa for 300 µsec in the temperature range from 20°C to 500°C. The grain size of compacts was maintained less than 50 nm, which was analyzed by X-ray diffraction (XRD) using Scherrer method. From the calculation of adiabatic heat and of pressure induced by thermal expansion, and the observation by transmission electron microscopy (TEM), it was found that Al₂O₃ could be broken and dispersed with a few nano-meter sizes in the Al matrix and that the ultra fine and uniform bulk structure was maintained up to 400°C of compaction temperature.e