Effect of Green Density on Densification and Creep During Sintering

Abstract

The effect of green density on both the densification rate and the creep rate was measured simultaneously during sintering by loading dilatometry. The experiments were performed on zinc oxide powder compacts with five different green densities covering a range of 0.39 to 0.73 of theoretical. The samples were heated at a constant rate of 4°C/min up to 1100°C in air. The densification rate at any temperature increases significantly with decreasing green density. The data for the densification rate and creep rate as a function of density show two quite distinct regimes of behavior; the rates were strongly dependent on density below 0.80, while above this value they were weakly dependent on density. The ratio of the densification rate to the creep rate was almost independent of temperature but increased almost linearly with increasing green density. The representation of the data in terms of models for sintering and creep is discussed.

Correlation between densification rate and microstructural evolution for pure alpha alumina

“…There is a distinction between the present work and the study of Rahaman et al 17 where they showed that green density has a significant effect on the densification rate for values below 80%. However, they studied powder compacts with different green densities, but with the same grain size.…”

“…For example, in very agglomerated powders, agglomerates themselves can be very densely packed, leading to high green densities, while still leaving behind large inter-agglomerates pores. Thus, the pore size/particle size ratio is not constant in the study of Rahaman et al 17 Nevertheless, this ratio is almost constant in the present work, while green densities are different (see Table 2). At the very beginning of sintering, densification behavior is the same, whatever the kind of alumina powders, their agglomeration and their packing state.…”

Novel method for the identification of the maximum solid loading suitable for optimal extrusion of ceramic pastes

“…7. The final density reached after the heating cycle depends primarily on the bulk density of the dried green body, as already observed in literature for samples obtained by other production techniques [23][24][25]. The densification kinetic is also a function of the green density: the maximum densification rate is slightly faster for higher solid loadings although the overall difference is negligible considering the values ranged between 0.82%/min and 0.87%/min (Fig.…”

Development of Powder Processing Models and Techniques for Meso-scale Devices: Perspirable Skin

“…Lance et al [28] has observed the similar results. However, Rahaman et al [33] did not observe this phenomenon because he changed the load to achieve different initial relative densities.…”