Modification of the mechanical granule properties via internal structure

Abstract

Disadvantageous mechanical properties of ceramic granules for die pressing applications, such as too high compression strength or too low ductility, may cause imperfections within the resulting component structure. To avoid these inhomogeneities, the granules have to show optimized mechanical properties.The correlation between internal structure parameters and resulting mechanical properties of ceramic granules was investigated systematically by spray-drying of varied α-Al2O3 suspensions. Nine granule samples with different internal structures were produced. The mechanical properties were characterized using a compression test of single granules. Internal granule structures were quantified using image analysis techniques. To detect structure parameters responsible for changed mechanical granule properties, the internal structure parameters were divided in micro- and macrostructure parameters and their influence on resulting mechanical properties was studied individually.The variation of additive type or amount overlaid the effect of changed internal granule structure parameters on the resulting granule compression strength and strain. If the additive type and amount were kept constant and suspension parameters like solid content, primary particle size, particle surface charge or width of the primary particle size distribution were modified, a clear influence of changed internal granule structure parameters on the resulting mechanical granule properties were measured.Increased shell thickness (macrostructure) and reduced microporosity (microstructure) caused a granule strength increase. The effects of micro- and macrostructure parameters on mechanical granule properties can be added up. For the investigated samples a dominant influence of the microstructure on the resulting mechanical properties compared to the macrostructure effect was found.