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Preparation and Performances of Aluminum Oxide Coated Zirconia Composite Powders

Author: TianRanRan
Tutor: ZhouZhuFa
School: Suzhou University
Course: Materials Science
Keywords: Zirconia-alumina ceramic Dispersant Surface modification Sintering performance
CLC: TB383.3
Type: Master's thesis
Year: 2011
Downloads: 154
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Abstract

Zirconia ceramics have been paid great attention in the field of the functional and structural materials for their excellent properties, such as high melting point, corrosion-resistant, wear-resisting dereasing, low heat conduction, and so on. But the development of ceramics was limited by the phase transformation of zirconia. To develop the temperature performance of the zirconia ceramics, forming zirconia matrix ceramic composites with high strength and toughness,some compounds with high elastic modulus, such as Al2O3, SiC, mullite, etc, were mixed in zirconia ceramics. In previous studies, ceramic composites were prepared by mixing Al2O3 and ZrO2 nanoparticles. But the problem of grain growth in sintering process has not improved yet by the traditional method. In this study, nano-Al2O3-coated ZrO2 composites were prepared by a liquid co-deposition method to restrain the grain growth. The innovation was the use of silane coupling agent to improve the coating effect on the ZrO2 surface.Firstly, PAM was added as the dispersant to change the ZrO2 surface activity in different pH value, and the coating effect was studied by varing the aluminium concentration. The results showed that zeta potential of coated particles reached the highest value in pH=5 with PAM as a dispersant, and the coated dispersion effect also was best. As the pH value was equal to 5 and the AlCl3 molarity was 0.3 mol/L, solution dispersity was better than others. And a layer of the amorphous Al2O3 with the thickness from 5 to 10 nm was deposited on ZrO2 surfaces. Surface element analysis showed that the content of Al element was higher than Zr element, which indicated that Al2O3 was successfully coated on zirconia powder surface.Secondly, after the surface modified by adding silane coupling agent, the influence of the amount of A-151 and SCA-603 and the aluminium concentration on the coating effects were discussed. The powders were characterized by FT-IR, TEM and EDS. Bands of Si-O-Zr and Si-O-Al were displayed on FT-IR spectra when A-151 was surface modifier. The two bands was highest when the amount of A-151 was 1.0 % and aluminium concentration was 0.1mol/L. Using SCA-603 as surface modifier, the two bands were also exhibited on FT-IR spectra, but weaker than those of modified by A-151.Properties of the ZrO2 composite ceramics synthesized by different methods were compared after pressing the powders. The results showed that, grain growth was serious in sintering process of Al2O3 doped in ZrO2 phases sintered bodies directly, and particle size distribution was wide. The grain growth was controlled a little by adding dispersant, but size distribution was also wide. After adding coupling agent, the grain growth of the sintered bodies was controlled more, and size distribution was narrowest. Sintering test results showed that the temperature of 1550℃was advisable in sintering, and the properties of composite ceramics prepared in this study were better than that of prepared by traditional method.

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