  Transparent Al2O3 ceramics have attracted considerable interest for use in a
wide range of optical, electronic and structural applications. The fabrication
of these ceramics using powder metallurgy processes requires the development of
theoretical approaches to the compaction of nanopowders. In this work, we
investigate the compaction processes of two model granular systems imitating
Al2O3 nanosized powders. System I is a loosely aggregated powder, and system II
is a powder strongly inclined to agglomeration (for instance, calcined powder).
The processes of isostatical (uniform), biaxial, and uniaxial compaction as
well as uniaxial compaction with simultaneous shear deformation are studied.
The energy parameters of compaction such as the energy change of elastic
interparticle interactions and dispersion interactions, dissipative energy
losses related to the processes of interparticle friction, and the total work
of compaction are calculated for all the processes. The nonapplicability of the
associated flow rule to the description of deformation processes of oxide
nanopowders is shown and an alternative plastic flow rule is suggested. A
complete system of determining the relationship of the flow including
analytical approximations of yield surfaces is obtained.
