| 초록 |
In this study, the combination of steric stabilization and depletion stabilization was used to improve the suspension stability of 3Y-TZP. Herein, the concept of colloidal processing by manipulating the interparticle-forces between the 3Y-TZP particles as a combination of steric and depletion stabilization was done by utilization Di-Ammonium Citrate (DAC) and Polyvinylpyrrolidone (PVP). DAC is used to induced steric stabilization due to the strongly bonded between DACs carboxyl group and OH group which is often present on the 3Y-TZP surfaces. While, PVP which could bond neither with 3Y-TZP surface nor DACs as the effects of pH conditions, leaves it free in the suspension as unattached polymer, and further, induced depletion stabilization mechanism. The steric and depletion stabilization mechanism was confirmed by FTIR. In this study, due to the complex stabilization as the combination of steric and depletion stabilization, the stability of 3Y-TZP is highly improved and the uniform and smaller particles size were obtained as confirmed particle size analyzers. Further, the suspension stability was also confirmed by the rheological and sedimentation tests. The rheological properties were confirmed by investigating the relationship between shear rates -vs-viscosity of 3Y-TZP suspensions and a sedimentation test was done for 30 days testing. It was shown by the sedimentation test, that the addition of PVP reduced the sedimentation rate even in re-dispersion cases. Through this study, it shows that the combination of steric and depletion stabilization is highly improving the 3Y-TZP slurries stability, and a uniform and smaller particle size can be obtained. As the result, fine grain and high mechanical properties of the sintered body can be achieved. Compared to the sintered body properties of 3Y-TZP which stabilized with DAC only, better-sintered body properties for 3Y-TZP stabilized with a combination of DAC and PVP can be listed as follow: grain size reduced from 0.313um to 0.281um, theoretical density increases from 98.6% to 99.3%, and Vickers hardness increases from 1269 HV to 1305HV. |
