Modelling of compaction and green strength of aggregated ceramic powders

• The behavior of aggregated ceramic powders is investigated using discrete element simulations. Aggregation (particles bonded by fused necks, resulting from calcination) is a common phenomenon observed during ceramic powder processing. In the present study, a small volume element of aggregated powder made of 40 spherical aggregates is modelled. Each aggregate comprises ∼500 spherical crystallites of 100 nm size. Mechanical interactions between crystallites are modelled to take into account strong bonds that form during calcination (with the possibility of breakage to model crushability), and adhesive contacts that form between submicrometer particles due to surface energy effects. The impact of having strongly bonded crystallites (high degree of calcination) or of having strongly adhesive particles (to mimic the use of a binder) is also investigated. Close die compaction and unloading from different compaction densities are carried out. It is observed that the final densification of the powder depends on the selection of process parameters like bond strength and work of adhesion between particles. This study also demonstrates a proportional relationship between the number of broken bonds in the green compacts and its strength. © 2010 The American Ceramic Society.

Nyckelord

Adhesive contact

Adhesive particles

Bond strength

Broken bonds

Ceramic powder

Ceramic powder processing

Compaction densities

Die compaction

Discrete element simulation

Green compacts

Green strength

Mechanical interactions

Process parameters

Spherical aggregates

Spherical crystallites

Submicrometer particle

Surface energies

Volume elements

Work of adhesion

Calcination

Ceramic coatings

Ceramic materials

Compaction

Crystallites

Powders

Surface chemistry

Unloading

Agglomeration

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