Direct evidence for continuous linear kinetics in the low-temperature degradation of Y-TZP
Direct evidence for continuous linear kinetics in the low-temperature degradation of Y-TZP
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DOI：
10.1016/j.actbio.2012.08.032
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发表时间：
2013-01-01
影响因子：
9.7
通讯作者：
Nickel, K. G.
中科院分区：
文献类型：
--
作者：
Keuper, M.;Eder, K.;Nickel, K. G.
研究了氧化锆在134 ℃和3巴压力下在含水环境中从四斜晶系向单斜晶系（t-m）转变的动力学。由于通常用于探索进展的表面X射线衍射具有非常有限的信息深度，因此它在层对层的情况下扭曲了定量结果，并且本身不适合这个原因。分析横截面是更合适的，因此，聚焦离子束技术被用来制备无伪影切割。随后通过扫描电子显微镜、电子背散射衍射和拉曼光谱对材料进行了研究。只有将各种方法结合起来，才有可能解决过程中可量化的细节问题。转变开始于近表面区域，形成层，并且该层的生长遵循简单的线性时间定律（对于在所选条件下的材料为0.0624 1 μ m h（-1））进行到体材料中，而没有明显的延迟或限制。该过程产生了具有固定量的残余四氧化锆的无梯度层（在本条件下类似于3 Y-TZP的27%），其通过边界与未受影响的材料分离，该边界仅在晶粒尺寸范围内具有粗糙度。动力学表明反应速率控制，其中水合反应是关键因素，但通过水逐步进入由具有临界水合水平的氧化锆的自催化转化所打开的反应前沿而被修改。(C)2012 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The kinetics of the tetragonal to monoclinic (t-m) transformation of zirconia in a hydrous environment at 134 degrees C and 3 bar pressure was studied. As surface X-ray diffraction, which is conventionally used to explore the progress, has a very limited depth of information, it distorts the quantitative results in a layer-on-layer situation and by itself is ill suited for this reason. Analyzing cross sections is more suitable; therefore, focused ion beam techniques were used to prepare artifact-free cuts. The material was subsequently investigated by scanning electron microscopy, electron backscatter diffraction and Raman spectroscopy. Only the combination of methods makes it possible to resolve the quantifiable details of the process. The transformation starts in the near-surface areas, forms a layer, and the growth of this layer proceeds into the bulk material following a simple linear time law (0.0624 1 mu m h(-1) for material in the chosen condition), without apparent retardation or limit. The progress yields a gradientless layer with a fixed amount of residual tetragonal zirconia (similar to 27% for 3Y-TZP in the present conditions) separated from unaffected material by a boundary, which has a roughness only in the grain size range. The kinetics indicates a reaction rate control, where the hydration reaction is the key factor, but is modified by the stepwise access of water to the reaction front opened by the autocatalytic transformation of zirconia with a critical hydration level. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.