表面改質對氧化鋯強度的影響

Effects of Surface Modification on the Strength of Zirconia

劉軒志(Hsuan-Chih Liu)

指導教授 ： 段維新

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.00475

摘要

正方相氧化鋯(TZ3Y)的相變行為和撓曲強度深受表面處理影響。在本研究中，以不同方式進行表面改質：研磨、拋光、退火和於還原氣氛中燒結改變表面組成，探討表面處理對氧化鋯撓曲強度的影響。為著重於表面處理的探討，避免因導角等因素產生的偏差，本研究以雙軸向(biaxial)四球測試的方式量測撓曲強度，此外採用同步輻射(NSRRC.)繞射光束進行相鑑定、並利用韋伯模數描述其可靠度、及XRD分析高角度繞射峰進行殘留應力的測量。表面經過研磨處理的氧化鋯試樣展現最高的撓曲強度，並且於正方相(111)面繞射峰左側發現不對稱的寬度改變。表面經研磨後再退火的試樣則於退火過程中，有缺陷癒合的現象發生。於不同表面處理下，殘留壓應力和撓曲強度呈現正相關的趨勢。
　　本研究另一部分實驗中嘗試將氧化鋯試樣於氮氫混合氣氛(氮氣=95％、氫氣=5%)、和在石墨坩堝中以炭粉覆蓋使得在燒結中產生一氧化碳還原氣氛，兩種不同還原氣氛下進行燒結，改變表面性質。於氮氫混合氣氛下和於空氣中燒結的試樣在晶粒大小、楊氏模數、緻密度和撓曲強度上皆十分相似；但於石墨坩堝中燒結的試樣卻有異常大的氧化鋯晶粒出現，依據相鑑定推測於石墨坩堝中燒結下處在低氧壓的氣氛中，使得氧化鋯轉變為立方相造成晶粒成長快速而形成異常大晶粒。

關鍵字

氧化鋯 ； 表面處理 ； 相分析 ； 撓曲強度 ； 殘留應力 ； 還原氣氛

並列摘要

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.

並列關鍵字

zirconia ； surface treatment ； phase analysis ； flexural strength ； residual strength ； reducing atmosphere

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