Abstract
Conventional sintering is a time- and energy-consuming process used for the densification of consolidated particles facilitated by atomic diffusion at high temperatures. Nanoparticles, with their increased surface free energy, can promote sintering; however, size reduction also promotes agglomeration, so hampering particle packing and complete densification. Here we show how the ordered agglomeration of zirconia primary crystallites into secondary particle assemblies ensures their homogeneous packing, while also preserving the high surface energy to higher temperatures, increasing the sintering activity. When exposed to intense electromagnetic radiation, providing rapid heating, the assembled crystallites are subjected to further agglomeration, coalescence and sliding, leading to rapid densification in the absence of extensive diffusional processes, cancelling out the grain growth during the initial sintering stages and providing a zirconia nanoceramic in only 2 minutes at 1300 °C.
Highlights
Sintering is the oldest method for the effective consolidation of particles into dense monoliths with tailored microstructures and properties
We have previously shown that if the agglomeration of 3 mol.% yttria-stabilized tetragonal zirconia (3YSZ) nanocrystallites is controlled in such a way as to form secondary particle assemblies with a narrow particle size distribution, a highly homogeneous packing of the nanoparticles can be ensured via a colloidal route, producing green bodies with hierarchical heterogeneities in terms of intra- and inter-particle pore packing[11]
Such microstructures (Fig. 1a) have the potential to prevent pore-boundary separation, as well as ensuring that the pores are smaller than the average particle size[6], and simultaneously preserving the high surface free energy of the nanoparticles
Summary
Sintering is the oldest method for the effective consolidation of particles into dense monoliths with tailored microstructures and properties. The orderly agglomeration of 3 mol.% yttria-stabilized tetragonal zirconia (3YSZ) crystallites into secondary particle assemblies was beneficial for the more homogeneous packing of nanoparticles, while preserving their high surface energy to higher temperatures, and as a consequence making it possible to sinter rapidly.
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