Sintering behavior of an ultrafine alumina powder shaped by pressure filtration and dry pressing

Master sintering curve (MSC) was used as a practical approach to analyse the sintering behavior of an ultrafine alumina powder. Non-isothermal sintering was carried out at three heating rates. The concept of the MSC has been used to investigate the effect of different shaping methods, i.e. dry pressing (DP) and pressure filtration (PF) on the apparent activation energy for sintering. Although no change in the dominant densification mechanism is expected, the interplay between different diffusion mechanisms taking place during the heating ramp may be affected by the shaping method. Values of 605 ± 15 and 700 ± 20 kJ/mol were determined for PF and DP samples, respectively. The lower activation energy for PF samples may be explained by the higher green density and homogeneity, smaller pore size in comparison with the DP samples. Furthermore, the mechanical properties (hardness and fracture toughness) of the samples are presented.