Sintering green density

The particle size distribution affects the shaping processes, green density, the sinterability and the final density. The particles mostly are not single crystallites but contain several crystallites. Therefore, the size measured by XRD is different from that measured by common particle size measurements... 

Stainless steel powder with a mean particle diameter of 50 mm has been compacted to a green density of 58% and sintered in pure H2. The resulting shrinkage measurements are given below. Published diffusion data for this stainless steel show that the activation energies are 225 kJ/mol for surface diffusion, 200 kJ/mol for grain boundary diffusion, and 290 kJ/mol for volume diffusion. Use the data below to determine the mechanism. 

On the other hand, sintering experiments with a similar fine-grained alumina over a wide range of green densities and final porosities carried out by Bruch (1962) could be well described by the exponential equation... 

The apparent density is used (a) in case of deagglomerated powders for a rough and simple grain-size estimation (b) in case of compacts (green density) or sintered specimens to determine the residual porosity. 

Particle size distribution measurements should also be made from lab milled samples only. The particle size distribution influences the compacting behavior and green density as well as the sintering properties. 

Fig. 6.7-12 Vertical and horizontal shrinkage occurring during the firing (sintering) of parts from raw materials with different densities, which were compressed to the same green density and the relation of both [B.21]...

Three kinds of calcite ceramics based on pure CaCOj, containing lwt%, 5wt% and lOwtyo of pure lithium fluoride LiF were evaluated. Testing samples were formed by uniaxial pressing and sintered in temperatures of 450, 470, 490, 510 and 530°C. Green density and apparent density were determined by geometrical method, relative density was calculated on the basis of calcite theoretical density (3,156 g/cm ) and mechanical properties were evaluated on the basis of compression tests. 

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