Nanoparticulate materials densification

The successful application of nanomaterials, with their unique mechanical, optical, magnetic and electrical properties, largely depends on the consolidation of powders into engineering components that will preserve an initial metastable microstructure. The key characteristic of the nanopowder consolidation process is to achieve densification without microstructural coarsening. This paper addresses specific densification issues related to the nanocrystalline nature of the consolidating particulates. The theoretical issues that affect the thermodynamics and kinetics of the atomic processes involved in nanopowder densification are related to higher driving force, enhanced interfacial energy and diffusion, and full density values. The experimental aspects cover powder compressibility and differential shrinkage, heating rate and pressure effects, and grain growth. Meaningful results in terms of final density values and grain growth are presented with the emphasis on processes that have demonstrated the capability to form dense specimens with retention of fine grain sizes.