Thermal granulation - an effective means for the production of tailored materials

Thermal granulation is an important technological step especially in the processing of nano- and colloidal disperse ceramic or hardmetal powders. High energy milling and homogenization require a fluid phase (water, organic solvents) - dry pressing or thermal spraying techniques require granule bulks with tailored properties (size distribution, flowability, densification behavior; specific fracture load and surface structure of the granules ). Thus direct granulation methods are necessary for the processing of the suspension to a homogeneous bulk. While the spray drying is introduced as a high productive technique for large quantities, the fluidized bed granulation is used up to now for the processing of smaller batches of different materials. Based on a short illustration of the relevant micro - processes, the development of tailored siliconnitride - bulks for dry pressing by spray drying and fluidized bed granulation in a pilot scale is described. The examples show the significant int eraction between granulation technique - binder system - granules properties. Some conclusions for optimized granule structures are derived.