Flowability of ceramic bulk materials. Pt.1: Methods

Components based on powder technological processing routes are of growing importance in the development of designed processes under high temperatures and pressures, in corrosive and highly abrasive conditions. The disperse raw material has to be conditioned into an agglomerated state and optimized for the uniaxial or isostatic compaction process, which consists of the transport of the bulk solid from the hopper into the punching tool and compaction of the loosely packed granules into a homogeneous prototype. Characterization of the bulk material during processing from the powder mixture into the granulated / agglomerated state is a decisive tool for product design and product processing, i.e. for the producers and processors of ceramic, metal or carbide mixtures or spray powders. Whereas the compaction behaviour describes the transformation of the material structure from bulk density into green density under pressure, the flowability characterizes the behaviour of the bulk solid during discharge, transport storage and metering. The paper describes common and novel granule and bulk solids characterization methods and the related standards. The interaction between single granule properties and the flowability of the complex granule mixture, i.e. the bulk solid, is demonstrated based on an alumina bulk solid. A brief outlook on the simulation of flowability by DEM methods is also provided.