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Studies on the recrystalization of nanocrystalline metals

100%
Lendzion-Bieluń Z., Gleń M.
Polish Journal of Chemical Technology
|
2007
|
vol. 9
|
issue 4
5-7
EN
The influence of the promoters such as CaO, Al2O3 and K2O on the specific surface area of the nanocrystalline cobalt was determined. The recrystalization process of the nanocrystalline cobalt was determined and compared with the examinations conducted on the iron catalyst for ammonia synthesis. The triply promoted nanocrystalline obtained cobalt after the annealing process, has got greater specific surface area than the triply promoted iron.
2
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Study of the anatase to rutile transformation kinetics of the modified TiO2

81%
Grzmil B., Gleń M., Kic B., Lubkowski K.
Polish Journal of Chemical Technology
|
2013
|
vol. 15
|
issue 2
73-80
EN
TiO2 attracts much interest because of its many potential applications. The use of titanium dioxide strongly depends on its polymorphic form: brookite, anatase, or rutile. Only rutile and anatase play an important role in industry. Anatase as a metastable form undergoes a non-reversible transformation into rutile. Understanding the kinetics of phase transformation and the processes of crystal growth of a material is essential for controlling its structure and, thus, its specific properties. The main purpose of this paper is to explain the anatase to rutile recrystallization kinetics in the modified TiO2 calcined from industrial hydrated titanium dioxide. The apparent activation energy of anatase to rutile transformation and the average size of titanium dioxide crystallites were determined for the unmodified TiO2 and TiO2 modified with P, K, Al, B, Zn, Zr, Ce, Sn, or Sb introduced in the amount of 0.5 mol% and 1.0 mol% when recalculated for their oxides. The growth of TiO2 crystallites during calcination was strongly inhibited by P, Ce and Zr, and inhibited to a lesser degree by Al, Sn and Sb. B and Zn did not affect the investigated process and K accelerated crystallites growth. The values of apparent activation energy depending on a modifier formed a relationship: Al
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