Preparation Of Submicron Zinc Oxide Water Slurry And Research On Rheologic Behavior

Submicron Zinc Oxide (ZnO) is applied in the coating for foundry extensively because of its many excellent performances. But its outstanding properties can't perform sufficiently because of the large special surface area, the high special surface energy and the trend of easy agglomerating of powders. So the dispersal stability of Zinc Oxide in water and its rheologic behavior which had large effect on its usage were studied in this thesis.This text used polyacry lamide and polyethylene glycol (PEG) 20000 as dispersant agent, used settlement test to judge the stability of slurry, used orthogonal design method to study the effects of the addition of dispersant agent, the value of pH, ball-milling speed and ball-milling time on preparing stable ZnO water slurry, and also analyzed its mechanics. The experimental results pointed out that: the pH value was the most remarkable factor if the polyacry lamide was chosen as the dispersant; and the milling time was the most remarkable factor if the PEG 20,000 was chosen as the dispersant. In the end, the optimum formulation of the addition of dispersant agent, the value of pH, mixing speed and mixing time was obtained to prepare 20wt.% ZnO water slurry with fine stability and dispersibility.The pattern and state of Zinc Oxide in ZnO water slurry were observed by TEM. It was discovered that dispersible effect of ZnO was quite well in ZnO water slurry which was prepared by two kinds of optimum formulation respectively. And the big aggregates were dispersed to the small ones, which had a certain distance to each other, and the ZnO powders being like bead chain shape to compose small aggregation. Moreover ZnO powders boundary became smoother.The rheologic behavior of ZnO water slurry was measured by a suit of experimental device which was designed by ourselves. Through series experiments, the suitable distance between surface of flake and inwall of barrel in the device was fixed as approximately 10mm, when using PEG 20,000 and polyacry lamide as dispersant agent separately. The test result of rheologic behavior of two kinds of suspending liquid indicated: ZnO water slurry with dispersant agent had instantaneous deformation as soon as load-on. But then deformation amount of ZnO water slurry with PEG 20,000 increased gradually by time; deformation amount of ZnO water slurry with polyacry lamide still maintained invariable basically by time.The viscosity of ZnO water slurry was tested to go a step further by viscosimeter. It was found that ZnO water slurry belonged to pseudoplastic fluid with yield value, having the characteristics of complete shearing desaturation and fairly good rheologic performance. And, the viscosity of ZnO water slurry with polyacry lamide as dispersant agent was slightly bigger than that with PEG 20,000.