טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKadosh Tamar
SubjectIn-Situ Characterization of Spinel Nanoceramic Suspensions
DepartmentDepartment of Materials Science and Engineering
Supervisors Professor Wayne D. Kaplan
Professor Emeritus Yeshayahu Talmon
Professor Yachin Cohen
Full Thesis textFull thesis text - English Version


Abstract

In this study an approach to characterize ceramic colloidal suspensions has been developed, based on vitrification of aqueous ceramic suspensions and microstructural characterization by cryogenic-temperature scanning electron microscopy (cryo-SEM), augmented by conventional rheological measurements. The flocculation phenomenon in as-milled and aged Mg-spinel (MgAl2O4) aqueous suspensions was characterized. A microstructure based on hard particle agglomerates separated by long-chain deflocculant molecules was directly observed, and correlated to the rheological properties of the suspension. Several levels of flocculation were detected as function of suspension preparation conditions. While suspensions at solid-loading levels appropriate for ceramic processing cannot be characterized by conventional particle size measurement techniques, cryo-SEM can be used to measure characteristic sizes, and distinguish between agglomerated and flocculated particles, opening a new approach for optimizing solid-loading conditions for slip-casting, in terms of viscosity and green density. “Green compacts” were cast from the investigated suspensions, and their density and pore size-distribution were characterized using Archimedes' principle and mercury porosimetry, respectively. Comparing green compacts cast from fresh and aged suspension, similar densities and pore size distributions were found. Hence, it was concluded that the duration of the drying process (and the fixation of the suspended particles in the cast), is longer than the aging time of the cast suspension.