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Information × Registration Number 0200U004138, 0197U018496 , R & D reports Title Investigation of elementary and collective procosses in solidstatice B4C-TiO2 and B4C-ZrO2 reactions popup.stage_title Head Kakazej Mykola Gavrylovych, Registration Date 15-05-2000 Organization Frantzevich Insitute for Materials Science Problems of the Ukranian National Academy of Sciences popup.description2 Spatial, phase and structure reconctruction in (1-x)B4C+xTiO2 and (1-х)В4С+хZrO2 mixtures during heat treatmentare investigated by means of a complex of physical metods. Interaction in the system occurs in two stages: A - 600-1600 С and В - 1600-2200 С, respectively. On the A stage B4C reacts both with residual oxygen present in the reaction chamber atmosphere, and with oxygen forming as a product of TiO2 dissociation. The data obtained indicate that, in the stage A the specific spatial defective structure of both boron carbide and titanium oxide particles form. Thermal treatment on stage B causes renewed intensive gas evolution, removal of the oxide layer from B4C particles, complete reduction of titanium oxides, formation of surface TiB2 layers, and beginning of sintering. Low-temperature gas-transport reactions in the (1-x)B4C+xZrO2 are rather similar to reactions in the (1-x)B4C+xTiO2, but their intensification occurs at significantly higher temperatures (about 1000C). Formation of defective s tructure of boron particles is set to a great extent by the interactioin with surrounding gas atmosphere. As the treatment temperature increases, a more slow transformation (shifted to the region of high temperatures by 150C) to solid-state interaction, accompanied by the reduction from the oxide to the metal, by the formation of surface zirconium boride layers, and by the formation of solid zirconium solution in the boron carbide. A detailed investigation of the dependence of the nature of EPR signals in boron carbide both on the conditions of their preparation and on the temperature of measurements was carried out. It was shown that inner defects in the boron carbide lattice, interacting in a interchange manner with charge carriers in the samples, are responsible for paramagnetic absorption. The center model which constitutes the radical forms of B3C type with the local concentration 10(19) - 2 10(20)см(-3) is proposed. Product Description popup.authors popup.nrat_date 2020-04-03 Close