Papers by Author: Marta Tańcula

Abstract: The high-energy milling uses the mechanical energy to activate chemical reactions by developing structural changes in the powder particles. High-energy milling with an acceleration of 28g was applied for the mechanical activation of the aluminium and silicon nitrides mixture with yttria additive. The activated powders showed the significant damage of the crystal structure and limited formation of a solid solution. Sintering of the activated precursor demonstrated higher ability for densification and started at 300 °C lower temperature in comparison to the standard mixture. The phase evolution during sintering was dependent on the starting composition and degree of powder activation.

Abstract: Nano-structured β-sialon precursor powders were obtained as a result of milling in a planetary mill with a high acceleration. Various mixtures of initial nitrides/oxides have been prepared as β-sialon precursor with low (0.4-1.0z) substitution and were milled in a planetary mill of acceleration 28g (TTD, Russia) with zirconia or silicon nitride balls for a various times (30-45 min). The resultant powder showed various extents of crystalline lattice deformation: smaller crystallites, dislocations, bumpy surface. The degree of lattice destruction was influenced by the milling time and grinding media, however various mixture components showed diverse susceptibility to deformation.

Abstract: The results on the effect of nanostructured β-sialon precursor on the sintering and properties of the resultant ceramics are presented. The standard mixture of β-sialon precursor with 0.4z substitution degree was activated for 30 min in a planetary mill with an acceleration of 28g. Activation in the planetary mill resulted in diminution of the crystallite size and significant imperfection of the crystal lattice of the powder particles. The sintering experiments were performed at 1450-1600 °C in a powder bed. The relative density of the sintered bodies achieved the value of 97 %. The nanostructured material was produced after pressureless sintering at 1500 °C. It is concluded that high activation degree of the powders is necessary to obtain fully dense ceramics.