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Feasibility of in situ de‐agglomeration during powder consolidation
Author(s) -
Giuntini Diletta,
Bordia Rajendra K.,
Olevsky Eugene A.
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15899
Subject(s) - materials science , economies of agglomeration , agglomerate , consolidation (business) , creep , porosity , shrinkage , sintering , composite material , grain size , rheology , grain growth , chemical engineering , accounting , engineering , business
Consolidation of nano‐sized powders is a growing area in manufacturing of advanced materials, thanks to the reduced processing times, enhanced mechanical properties and high potential for the introduction of multi‐functionality enabled by such reduced particle sizes. Nanopowders, however, are particularly prone to the agglomeration phenomena, and thus to the formation of hierarchical porous structures. The presence of pores differing up to several orders of magnitude in size leads to undesired differential shrinkage and localized grain growth. In order to avoid such issues, strategies for in situ de‐agglomeration are proposed here. These optimization strategies are based on the development of an analytical model for shrinkage kinetics and mechanical properties of a hierarchical porous structure, containing both small‐size intra‐agglomerate pores and large‐size inter‐agglomerate ones. The modeling approach is an expansion of the continuum theory of sintering to the case of biporous materials presenting nonlinear viscous rheology, as expected for nano‐sized crystalline powders. Considering the nonlinear viscous constitutive behavior of the solid phase also allows assessing the influence of the temperature on the microstructural evolution during processing, due to the dependence of the creep characteristic parameter, strain‐rate sensitivity, on the thermal history. Material structure optimization strategies, aimed at de‐agglomeration or at the design of tailored porous structures, become then possible and are here explored.

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