Characterization of Ceramic Powders through Powder Rheology

Frequently in the literature, it has been shown that any single characterization technique is incapable of sufficiently describing the overall rheology properties of a powder. Consequently, much work has gone into exploring multivariate relationships between common rheological tests. However, such efforts have been primarily focused on powders used in pharmaceutical and food industries. Much less rheology work has been conducted for powders of other industries, such as ceramic powders used in making grinding media and crucibles. Yet, it has been shown that supplementing particle size distribution and chemical composition measurements of ceramic powders with powder rheology techniques can greatly increase characterization capability. This work aims to advance said knowledge by investigating relationships among rheological parameters and the general importance of each parameter towards powder characterization for multiple ceramic powders.

Rheological characterization methods used were the Freeman Technology FT4 Powder Rheometer Stability and Variable Flow Rate, Compressibility, Shear Cell, and Direct Pressure Consolidation tests. As the last test has not been used in other works, a novel methodology and data fitting method were developed herein. Additional tests were conducted using the GranuTools' GranuPack, GranuHeap, and GranuFlow equipment. All tests were conducted on grades of varying size of the materials of aluminum oxide, boron carbide, silicon carbide, silicon nitride, and tungsten carbide.

Correlative and principal component analyses were used to ascertain how rheological parameters related with one another, and the relative importance of each based on information captured. Additional rheological parameters to analyze were created from novel calculations and fits to data. It was found that tested powders could be sufficiently characterized using just two tests, the Direct Pressure Consolidation test and Stability and Variable Flow Rate test. One calculated parameter, and a novel parameter from fitting data, from the Stability and Variable Flow Rate test were found to be key contributors to captured information. Most notably, all Direct Pressure Consolidation measurement points and fit parameters were found to capture the majority of information. This novel test was observed to be the strongest characterization method out of all applied tests.