AGGLOMERATES AND AGGREGATES OF AIN, MORPHOLOGY AND COMPRESSIBILITY

Agglomerates and aggregates of A1N, morphology and compressibility. Agglomerate with different size and strength were prepared either by sieving or heat treating the raw powder. Agglomerate characterization was performed by measuring surface specific areas, grain size distribution and pore diameter within the agglomerates. The surface area evolution is linked with the agglomerate density rather than elementary grain size. Such an analysis leads to classify these agglomerates into three classes: soft agglomerates with low relative density (0.4), hard agglomerates with higher density (0.5) but with the same pore dimension, and dense sintered aggregates with smaller pores. Two kinds of compressibility diagrams for soft agglomerates and aggregates were obtained: the first is composed of three straight lines with decreasing slopes, the second of three straight lines with increasing slopes. Inter and intraagglomerate porosity changes during the compaction process permit us to explain the deformation mechanism operating on each segment. This work allows a classification of the different agglomerates according to their compaction curves.