OVERVIEW

Regardless of the large variety and development of the methods of production of nanocrystalline materials (this relates in particular to the most likely known methods of gas-phase evaporation and precipitation from colloidal solutions), the investigations of the structure and properties of nanoparticles are very complicated. This is associated with, in particular, the high reactivity of the particles resulting from their highly developed surface. Therefore, bulk nanocrystalline materials are the subject of fundamental and applied science. In many cases, these materials are more suitable for investigation and application. The main methods of production of bulk nanomaterials were described in a review [1]. None of these methods is universal, because each of them is suitable for a limited number of substances.

The conventional methods of powder technology are used most widely, i. e. different types of pressing and sintering (cold pressing and sintering, hot axial and isostatic pressing, magnetic pulsed pressing). Powder technology also includes the method of vacuum compacting of nanoparticles, produced by condensation from the gas phase, proposed by H. Gleiter [2 5]. The main difficulty when using powder technologies for production of pore-free or with least porosity ware from nanopowders is associated with intensive recrystallisation and the residual porosity. By shortening the duration of the high temperature treatment, it is possible to decrease the degree of recrystallisation and grain growth during sintering. The application of high static or dynamic pressure for the pressing of nanopowders at room or high temperatures reduces the residual porosity and increases the relative density...