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Sopicka-Lizer, Malgorzata,Pawlik, Tomasz The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.4
Mechanochemical processing (MCP) involves several high-energy collisions of powder particles with the milling media and results in the increased reactivity/sinterability of powder. The present paper shows results of mechanochemical processing (MCP) of silicon nitride powder mixture with the relevant sintering additives. The effects of MCP were studied by structural changes of powder particles themselves as well as by the resulting sintering/densification ability. It has been found that MCP significantly enhances reactivity and sinterability of the resultant material: silicon nitride ceramics could be pressureless sintered at $1500^{\circ}C$. Nevertheless, a degree of a silicon nitride crystal lattice and powder particle destruction (amorphization) as detected by XRD studies, is limited by the specific threshold. If that value is crossed then particle's surface damage effects are prevailing thus severe evaporation overdominates mass transport at elevated temperature. It is discussed that the cross-solid interaction between particles of various chemical composition, triggered by many different factors during mechanochemical processing, including a short-range diffusion in silicon nitride particles after collisions with other types of particles plays more important role in enhanced reactivity of tested compositions than amorphization of the crystal lattice itself. Controlled deagglomeration of $Si_3N_4$ particles during the course of high-energy milling was also considered.
Application of Mechanochemical Processing for Preparation of Si3N4-based Powder Mixtures
Malgorzata Sopicka-Lizer,Tomasz Pawlik 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.4
Mechanochemical processing (MCP) involves several high-energy collisons of powder particles with the milling media and results in the increased reactivity/sinterability of powder. The present paper shows results of mechanochemical processing (MCP) of silicon nitride powder mixture with the relevant sintering additives. The effects of MCP were studied by structural changes of powder particles themselves as well as by the resulting sintering/densification ability. It has been found that MCP significantly enhances reactivity and sinterability of the resultant material: silicon nitride ceramics could be pressureless sintered at 1500oC. Nevertheless, a degree of a silicon nitride crystal lattice and powder particle destruction (amorphization) as detected by XRD studies, is limited by the specific threshold. If that value is crossed then particle’s surface damage effects are prevailing thus severe evaporation overdominates mass transport at elevated temperature. It is discussed that the cross-solid interaction between particles of various chemical composition, triggered by many different factors during mechanochemical processing, including a short-range diffusion in silicon nitride particles after collisions with other types of particles plays more important role in enhanced reactivity of tested compositions than amorphization of the crystal lattice itself. Controlled deagglomeration of Si3N4 particles during the course of high-energy milling was also considered.
OWNERSHIP, INTRA-INDUSTRY TRADE AND FACTOR INTENSITIES: THE CASE OF POLAND 1993-2002
Jørgen Ulff Møller Nielsen,Konrad Pawlik 사람과세계경영학회 2004 Global Business and Finance Review Vol.9 No.2
This paper investigates the association between intra-industry trade (IIT) for foreign, private domestic and public domestic companies in Poland and the size of multinational activity measured by the stock of FDI. Using a unique database on imports and exports from companies in Poland 1993-2002 divided along three ownership types, the paper finds in a pooled regression model a positive association between the size of foreign presence and the level of IIT for foreign-owned companies, but no significant spill-over effects from foreign presence to the level and development of IIT for private and public domestic companies. A negative IIT growth for private and public companies and a small positive growth for foreign-owned companies in science-based industries indicate that advanced technological spill-over effects to the Polish economy are still in their infancy.