Kinetics of sintering for powder systems with bimodal pore-size distribution

Feasibility of in situ de‐agglomeration during powder consolidation

“…It is also interesting to compare our results with the work of Olevsky and Rein for an analogous spherical biporous domain with linear viscous constitutive properties of the skeleton. They reported the following kinetics equations…”

“…As a rule of thumb to roughly estimate what scales we are considering in the two cases, one needs to think that agglomerates reach a size of ~10 μm, while nanopowder particles sizes range in the 10‐100 nm order of magnitude. It is reasonable, also based on experimental data, to evaluate the large inter‐agglomerates pores average size as slightly lower with respect to the agglomerate size itself. This implies that with this shift in domain from biporous to monoporous we are moving to a scale about one or two orders of magnitude lower.…”

“…This work will adopt an analytical approach and will mainly refer to the work started by Olevsky and Rein and later expanded by Kuz'mov et al on hierarchical porous structures of powder materials with linear viscous rheology . A nonlinear rheology is however required when it comes to the densification of nanosized powders, since the large local curvature at the pores’ free surfaces, to which the sintering stress is proportional, leads to internal stresses such that the powder compact's material deforms via creep instead of linear viscous flow, even when external stresses are not applied .…”

Stress‐induced anisotropy during sintering of hierarchical porosity ceramics

“…In these microstructures, based on pore origin and size, the pores have been classified as extrinsic (e.g., from the burn out of the pore former—typical significantly larger size than particle or grain size) and intrinsic (interparticle residual pores due to incomplete densification—typically of the order of particle size) . The sintering behavior of hierarchical porous ceramics, with a focus on evolution of pores of different size, has been investigated experimentally, and using theory and simulations . These studies have shown that the ceramic with the intrinsic pores can be treated as the matrix whose densification is not affected by the presence of the extrinsic pores and the shrinkage strain of the extrinsic pores is the same as the overall shrinkage strain of the ceramic with intrinsic pores.…”

Sintering stability of biporous materials under kinematic constraints

“…Nevertheless, this paper differs from the cited publications, which were restricted to homogeneous pore distribution, by focusing on the volume distribution of each type of pores. The inhomogeneity results from kinematic constraints on the displacement of some surface regions of the body sintered and from the contact friction between the body and the tool [10][11][12][13].…”