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Nanoscience and Technology: An International Journal
ESCI SJR: 0.219 SNIP: 0.484 CiteScore™: 0.37

ISSN Druckformat: 2572-4258
ISSN Online: 2572-4266

Nanoscience and Technology: An International Journal

Formerly Known as Nanomechanics Science and Technology: An International Journal

DOI: 10.1615/NanomechanicsSciTechnolIntJ.v5.i3.50
pages 213-221

STRUCTURE FORMATION AND CHANGES IN THE REACTIVITY OF COMPOSITE GRANULES OF THE Nb−Si SYSTEM IN MECHANICAL ACTIVATION

Yu. A. Abuzin
National University of Science and Technology (MISIS), 4 Leninsky Ave., Moscow 119049, Russia
M. N. Kulikova
National University of Science and Technology "MISiS", Moscow, Russia
V. S. Levchenko
National University of Science and Technology "MISiS", Moscow, Russia
T. B. Sagalova
National University of Science and Technology "MISiS", Moscow, Russia
A. G. Gavrilova
National University of Science and Technology "MISiS", Moscow, Russia
N. B. Smirnov
National University of Science and Technology "MISiS", Moscow, Russia

ABSTRAKT

The basic laws governing the structure formation and changes in the activity of composite granules of the Nb-Si system in mechanical activation in order to reach maximum efficiency of the subsequent synthesis of niobium silicides have been considered. The mechanical activation of composite granules was performed using a Retsch PM 400 planetary mill. The activity, characterizing integrally the energy intensity and the reactivity of composite granules, was evaluated by the velocity of propagation of the front of the linearly organized reaction of niobium silicides synthesis. The structure was investigated with the aid of a light and an electronic microscope, as well as an X-ray diffractometer. Typical structures of composite granules and the charts of changes in their activity as a function of processing time are presented. The initial growth of activity is conditioned by the increasing uniformity of distribution and enlargement of the contact area of niobium and silicon, decrease in the share of niobium defect regions, not containing silicon, and accumulation of internal energy related to the increasing imperfection of the crystalline structure of the components. A decrease in the activity after reaching the maximum is related to chemical interaction of the components in microvolumes of composite granules and relaxation of the accumulated energy. We identified the structuring role of silicon: its nanosized particles, having superhigh conglomeration capacity, capture and bond the niobium particles, thus ensuring the formation of structures of composite granules. The regions of niobium that are free from silicon represent the basic structural defect of granules. An increase in the mechanical activation time results in thinning of the niobium particles and silicon layers, thus generating a more homogeneous structure and reducing the relative volume of defect regions. The optimal time of silicon preprocessing was found to be 60 min. The Nb5Si3 composite granules have the maximum activity after 180 min of mechanical activation, while Nb3Si granules after 260 min.


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