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Thermodynamics of densification of powder compact Yoshihiro Hirata a,*, Akihiro Hara a

Summary: Thermodynamics of densification of powder compact
Yoshihiro Hirata a,*, Akihiro Hara a
, Ilhan A. Aksay b
Department of Advanced Nanostructured Materials Science and Technology, Kagoshima University,
1-21-40 Korimoto, Kagoshima 890-0065, Japan
Department of Chemical Engineering, Princeton University, Engineering Quadrangle,
Room A 311, Olden Street, Princeton, NJ, USA
Received 19 December 2008; received in revised form 21 February 2009; accepted 1 March 2009
Available online 27 March 2009
This paper established a necessary condition for the sintering of powder compacts by examining the total free energy balance in terms of the
particle size, neck size and contact number. The thermodynamic analysis of the proposed model clarifies the relation of shrinkage (q) of powder
compact-contact angle (f)-relative density at a given dihedral angle (fe) of a grain boundary. Faster densification proceeds in the region with a
larger coordination number (n) of particles at a small q value. A large shrinkage is needed to eliminate the large pores formed in the structure of
small n value. Full density can be achieved in the range of 1178 < fe < fc, where fc is the critical dihedral angle allowing the shrinkage required
for full densification. The derived concepts are effective to interpret the densification of hierarchical particle clusters. The relative density of ceria
powder compact approached nonlinearly unity with decreasing ratio of pore size (r(P)) to grain size (r) and this tendency was well expressed by the
present densification model. The influence of grain growth on the densification of powder compact and size of large pore isolated in a dense matrix


Source: Aksay, Ilhan A. - Department of Chemical Engineering, Princeton University


Collections: Materials Science