RHEOLOGICAL INVESTIGATION OF COLLOIDAL SYSTEMS
Omid Akhlaghi Baghoojari
Materials Science and Engineering, PhD Dissertation, 2017
Assist Prof. Dr Ozge Akbulut (Thesis Advisor), Assoc. Prof. Dr. Fevzi Çakmak Cebeci, Assist Prof. Dr. Meltem Elitas, Prof Dr. Nergis Arsu, Prof. Dr. Metin Acar
Date &Time: 12th, July, 2017 – 11:00 AM
Keywords : Suspension, Organic additives, Stability, Shear and Extensional Rheology
Ceramic processing such as cementation and casting are among the most widely used methods for production of commercial products with different size and properties to date. Highly loaded and stable aqueous suspensions whose rheological behavior can be controlled by low content of organic additives are highly desired. To have control over the viscosity and improve fluidity/solid loading of ceramic suspensions, different series of polycarboxylate ether-based copolymers (PCEs) that include acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinylphosphonic acid, and polyethylene glycol-1000 were synthesized. The effect of monomer feed ratio and molecular weight of copolymer on dispersing ability of the copolymers, fluidity of the pastes, and shear and extensional rheological behavior of suspensions were characterized and performance of these copolymers as rheology modifiers was reported.
For the first time in literature, dedicated superplasticizers for i) calcium aluminate cement (CAC) and ii) ordinary portland cement-calcined clay-calcium carbonate ternary blends were synthesized such that they caters to the characteristic properties of these systems; i) high rate of surface development and surface charge in CAC and ii) layered structure of calcined clay and high concentration of sulfate ions in ternary blended cement.
The effect of PCEs on i) shear and extensional rheological behavior of alumina suspensions and ii) fabrication of highly loaded alumina suspensions and machining of solid cast green bodies were also investigated. While 20 vol. % pure alumina suspensions showed severe particle jamming, 35 vol. % alumina suspensions with more than 1 wt. % copolymers displayed Newtonian behavior. These suspensions found to be suitable for fabrication of solid cast green bodies and provided ability of significant removal of material in machining process.