| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 94 === Stabilized zirconia is applied to the crucibles, jets, spacers, refractory materials and thermal barrier coatings because the thermal conductivity coefficient of zirconia is quite low, and the thermal expansion coefficient of zirconia is near to that of metals. In order to form thermal barrier coatings, it is necessary to prepare the zirconia suspensions using dispersants. Therefore, understanding the rheological behaviors of suspensions becomes the most important research motive. In this study, effects of different dispersants and pH value on rheological behaviors of zirconia suspensions were investigated.
The particle sizes of zirconia raw materials were reduced by ball milling, and the suspensions were prepared by adjusting pH value or adding various dispersants. The relationships among rheological behaviors, turbidity, and ζ-potential were discussed. The ZrO2-1(monoclinic) suspension showed the better dispersive state in the pH range of 2.5～4.5 after adding HNO3. The ZrO2-2(tetragonal) suspension showed the better dispersive state after adding 0.1wt% poly(ethyleneimine). The addition of 0.1, 0.5, 1.0wt% D305 or Darvan 7 dispersant caused a reduction in the zeta potential of ZrO2-1 and ZrO2-2 because of the worse dispersive state of these suspensions as mentioned.
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