Effects of Surface Modification on the Strength of Zirconia
Date Issued
2007
Date
2007
Author(s)
Liu, Hsuan-Chih
DOI
zh-TW
Abstract
Transformation behavior and flexural strength of tetragonal zirconia (TZ3Y) are affected significantly by surface modification. In this study, we discussed the relationships between the effects of surface modification such as grinding, polishing, annealing, and sintering in reducing atmosphere on the flexural strength of zirconia. In order to focus on the effects of surface treatment and avoid the influence of sharp edge, the flexural strength was determined by using a biaxial 4-ball test. Besides, the phase identification was performed by using the X-ray scattering facility of NSRRC. The reliability was described by using Weibull modulus. The residual stress was measured by analyzing the high angle peak of XRD. The ground specimens exhibit the highest flexural strength and the asymmetry of t(111) peak was discovered. The defects recovery was found in the annealed specimens after annealing. The residual compressive stress was proportional to the flexural stress under different surface treatment.
In another part of this study, the zirconia compacts were sintered in reducing atmospheres: the mixture atmosphere of hydrogen and nitrogen (H2=5%, N2=95%), and CO produced by sintering within a covered graphite crucible. The samples sintered in air are almost the same as those sintered in the mixture atmosphere of hydrogen and nitrogen in grain size, elastic modulus, relative density, and flexural strength; however, the samples sintered in graphite crucible formed unusually large grain. According to the phase identification, we supposed that the low partial oxygen pressure made tetragonal zirconia transform to cubic zirconia which caused fast grain growth during sintering, and then formed unusually large grain.
Subjects
氧化鋯
表面處理
相分析
撓曲強度
殘留應力
還原氣氛
zirconia
surface treatment
phase analysis
flexural strength
residual strength
reducing atmosphere
Type
thesis
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