Porosity in Spinel Compacts Using Small-Angle Neutron Scattering

Unfired spinel (MgAl₂O₄) compacts and sintered materials with small hard agglomerates (<5 μm) were studied using small-angle neutron scattering (SANS) techniques. The SANS results were compared with those from mercury porosimetry and gas adsorption. The results from green-state samples are consistent with interconnected "ink-bottle"-type porosity. In the latter stages of densification the average void size is significantly larger than that found in the unfired compact. The presence of the hard agglomerates affects the observed SANS scattering much more in the partially densified samples than in the unfired compacts. It was demonstrated that the use of multiple SANS techniques to study large voids (<0.1 μm) and large pore fractions (45%) is a useful, sensitive, nondestructive diagnostic probe for the evaluation of porosity during sintering.