Characterization of HIGH PURITY Alumina SLURRIES by analytical centrifugation

L. Marra1, S. Gressier2
1Baikowski SAS, 1046 Rte de Chaumontet, 74330 Poisy, France
2LUM GmbH, Justus-von-Liebig-Str.3 12489 Berlin
 
Keywords: sedimentation, flocculation, alumina dispersions, slurries, particle sizing
 
 
 
Slurries based on High Purity Alumina particles are promising candidates for broad range of applications such as polishing, CMC, coating, technical ceramics... This requires methods for in-depth characterization and fast screening of particles interactions, (re-)dispersibility of the agglomerated particles, primary and hydrodynamic size, the composition of the carrier fluid and the absence of oversized particles.
 
During its formulation Baikowski® has in-house analysis capabilities and state-of-the-art measurement and characterization methods. Thanks to our reliable methods and equipment, we run daily analysis to monitor our processes and to provide accurate characterization of our products. Sedimentation analysis and particle sizing by CLS using a multi-sample analytical centrifugation with photometric detection is a rather simple but powerful method to characterize dispersed state and particle size distribution of such submicronic dispersions.
 
Sedimentation analysis using a multi-sample analytical centrifugation with photometric detection of spatially resolved concentration changes (LUMiSizer®) is powerful to characterize the dispersed state/degree of particle interaction. In situ visualization of separation behavior ranks, records, and quantifies very clearly from the fingerprints, a swarm sedimentation (stable dispersion) and zone sedimentation (flocculation, agglomeration). Complex systems with subfractions of particles exhibiting different separation behavior can be identified.
 
Dispersion of fine particles in a solvent plays a key role in most processes of particle technology. Complete dispersion of fine particles in a suspension is a prerequisite to its success. Separation behavior of solid particles of High purity Alumina in water were investigated in dependance of dispersion methods and solvent properties.
 
The distributions of separation velocities determined by multisampling analytical centrifugation can be used for this purpose, even in case of very complex composition. The separation velocity of particles is influenced by the properties of the dispersed phase (density, size) and its material composition as well as by the properties of the continuous phase (density, viscosity).
 
Quality control is the essential part for producing satisfying products. This relates to the control of the raw materials, intermediate and final products. For dispersion related products there may be changes in particle size of a single component, of the whole system or in material composition, which would affect the quality / stability of the final product. Therefore, an integral method measuring changes in size and density or rather their distribution has advantages over determining particle size distribution only.