The effect of low temperature aging on the mechanical property & phase stability of Y-TZP ceramics.
The effect of low temperature aging on the mechanical property & phase stability of Y-TZP ceramics.
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DOI：
10.4047/jap.2009.1.3.113
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发表时间：
2009-11
期刊：
影响因子：
--
通讯作者：
Kim SH
中科院分区：
文献类型：
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作者：
Kim HT;Han JS;Yang JH;Lee JB;Kim SH
最近，钇稳定的四方氧化锆多晶 (Y-TZP) 被推出，因为与其他牙科陶瓷系统相比，它具有优异的弯曲强度和断裂韧性。尽管氧化锆具有优异的机械性能，但已有报道称，低温老化后弯曲强度下降导致氧化锆寿命下降的现象。本研究的目的是研究 Y-TZP 陶瓷在各种低温时效处理后弯曲强度的退化情况，并通过使用 X 射线衍射分析和扫描电子显微镜 (SEM) 评估时效后的相稳定性和微观结构变化。 Vita In-Ceram YZ（Vita Zahnfabrik，Bad Säckingen，德国）的 Y-TZP 块制备成 40 mm（长）× 4 mm（宽）× 3 mm（高）的样品。将试样在蒸馏水中进行人工时效，在75、100、125、150、175、200和225℃的温度下热处理10小时，以诱导表面相变。为了测量机械性能，使用万能试验机（Instron 型号 3365；Instron，Canton，Mass，USA）对样品进行四点弯曲试验。此外，还进行了 X 射线衍射分析（DMAX 2500；Rigaku，东京，日本）和 SEM（Hitachi s4700；Jeol Ltd，东京，日本）来估计相变。使用SAS 9.1.3（SAS研究所，美国）进行统计分析。通过单向方差分析对实验组的弯曲强度数据进行分析，并检测统计显着性差异 (α= .05)。未经高压灭菌的烧结 Vita In-Ceram YZ 的平均弯曲强度为 798 MPa。当在低于125℃的温度下老化10小时时，Vita In-Ceram YZ的弯曲强度增加至1,161 MPa。但在150℃以上，弯曲强度开始下降。尽管低温时效引起了与温度相关的四方相到单斜相的转变，但最小弯曲强度仍高于700 MPa。 100℃以上时效处理后开始出现单斜相。随着时效温度的升高，单斜晶相的比例增加。在175℃以上，单斜/四方+单斜相的比例达到稳定值，约75%。弯曲强度开始下降的单斜晶浓度点在12%至54%之间。
Recently Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) has been introduced due to superior flexural strength and fracture toughness compared to other dental ceramic systems. Although zirconia has outstanding mechanical properties, the phenomenon of decrease in the life-time of zirconia resulted from degradation in flexural strength after low temperature aging has been reported. The objective of this study was to investigate degradation of flexural strength of Y-TZP ceramics after various low temperature aging treatments and to evaluate the phase stability and micro-structural change after aging by using X-ray diffraction analysis and a scanning electron microscope (SEM). Y-TZP blocks of Vita In-Ceram YZ (Vita Zahnfabrik, Bad Säckingen, Germany) were prepared in 40 mm (length) × 4 mm (width) × 3 mm (height) samples. Specimens were artificially aged in distilled water by heat-treatment at a temperature of 75, 100, 125, 150, 175, 200, and 225℃ for 10 hours, in order to induce the phase transformation at the surface. To measure the mechanical property, the specimens were subjected to a four-point bending test using a universal testing machine (Instron model 3365; Instron, Canton, Mass, USA). In addition, X-ray diffraction analysis (DMAX 2500; Rigaku, Tokyo, Japan) and SEM (Hitachi s4700; Jeol Ltd, Tokyo, Japan) were performed to estimate the phase transformation. The statistical analysis was done using SAS 9.1.3 (SAS institute, USA). The flexural strength data of the experimental groups were analyzed by one-way analysis of variance and to detect statistically significant differences (α= .05). The mean flexural strength of sintered Vita In-Ceram YZ without autoclaving was 798 MPa. When applied aging temperature at below 125℃ for 10 hours, the flexural strength of Vita In-Ceram YZ increased up to 1,161 MPa. However, at above 150℃, the flexural strength started to decrease. Although low temperature aging caused the tetragonal-to-monoclinic phase transformation related to temperature, the minimum flexural strength was above 700 MPa. The monoclinic phase started to appear after aging treatment above 100℃. With the higher aging temperature, the fraction of monoclinic phase increased. The ratio of monoclinic/tetragonal + monoclinic phase reached a plateau value, circa 75% above 175℃. The point of monoclinic concentration at which the flexural strength begins to decrease was between 12% and 54%.