Nanocomposites and nanomaterials.

Investigation of the mechanical activation effect on diffusion processes in zirconia during the initial sintering stage.

M. V. Lakusta, G.K. Volkova, L.V. Loladze, I.K. Nosolev,  I.I. Bruchanova, G.N. Golovan, V. V. Burkhovetsky, I.A. Danilenko, T.E. Konstantinova

Donetsk Institute for Physics and Engineering named after O.O. Galkin of NAS of Ukraine, Nauky av., 46, Kiev, 03680, Ukraine.
E-mail: Marharyta.lakusta@outlook.com

 	Yttria-stabilized zirconia (3Y-TZP) has excellent mechanical properties, such as high fracture toughness, strength, and hardness and widely used in medicine and in manufacture of refractory and structural products [1]. Nevertheless the problem of improving the quality of zirconia based ceramic materials remains relevant today. It is known that properties of ceramics strongly depend on the microstructure of powders which can be controlled by applying different modifications. To achieve perfect properties of zirconia materials usually use different types of treatments, such as chemical, mechanical in order to prepare it to the main and the most important technological stage - sintering. For the producing the ceramic products with excellent properties the several steps should be realized: i) reduction of the grain size of the material; ii) developing methods of nanopowders synthesis; iii) activation of sintering by dopants addition [1].
Mechanical milling is the most optimal and cheap way to improve the nanopowders structure. Thus, in the present study the mechanical modification effect on the zirconia nanopowders has been investigated. It was found significant influence of the mechanical treatment on the densification kinetics and mass transfer mechanisms at the initial sintering stage in the tetragonal zirconia nanopowders. 
According to the dilatometry analyses results the densification rate during the sintering of 3Y-TZP was changed due to the different duration of mechanical activation (1-16 hours). It has determined that the dominant mass transfer mechanism in 3Y-TZP specimens was changed from volume diffusion mechanism to the grain boundary diffusion mechanism and this accompanied by activation energy increasing. 

1.	Matsui K., Sintering Kinetics at Constant Rates of Heating: Mechanism of Silica-Enhanced Sintering of Fine Zirconia Powder // J. Am. Ceram. Soc. - 91 [8]. - 2534–2539. - 2008.