Creep Behavior of Improved High Temperature Silicon Nitride
Creep Behavior of Improved High Temperature Silicon Nitride
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改进的高温氮化硅的蠕变行为
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
U. Täffner
中科院分区：
文献类型：
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作者：
S. Wiederhorn;R. Krause;F. Lofaj;U. Täffner
给出了用Lu2O_3烧结氮化硅的拉伸蠕变行为的新数据。这些数据与之前在同一材料上收集的两组数据进行了比较。较老的集合给出了难以从理论上解释的结果：应力指数值很高，n=5.33，并且没有空化。这组新的数据也没有给出空化，但给出了一个应力指数n=1.81，该指数可以根据氮化硅颗粒的溶解析出蠕变在理论上得到合理解释。方差分析表明，较早的一组数据与较新的一组数据在统计上是一致的，而另一组数据则不是。将统计上一致的两组数据结合在一起，得到了一致的蠕变图像，应力指数较低，并且没有空化。组合数据的应力指数为n=1.87±0.48(95%置信限)。含Ru_2O_3的氮化硅的拉伸蠕变机制不同于其他氮化硅的拉伸蠕变机制，后者的拉伸蠕变机制被归因于空化。烧结后的氮化硅的蠕变抗力的提高可能是由于在两个晶界处产生了比Y2O_3或Yb_2O_3更抗形变的非晶相。同时，将第二相的数量减少到临界极限以下，或增加两个晶界相对于三个晶界的粘度，都会降低材料在蠕变过程中产生空化的能力，并迫使蠕变机制从空化转变为溶解析出。
New data are presented on the tensile creep behavior of silicon nitride sintered with Lu2O3. The data are compared with two earlier sets of data collected on the same material. The older sets gave results that are difficult to explain theoretically: a high value for the stress exponent, n=5.33, and no cavitation. The new set of data also gave no cavitation, but gave a stress exponent, n=1.81, that can be rationalized theoretically in terms of solution-precipitation creep of the silicon nitride grains. An analysis of variance showed that one of the earlier sets of data was statistically consistent with the newer set, whereas the other set of data was not. Combining the two sets of data that agreed statistically yields a consistent picture of creep with a low value of the stress exponent and no cavitation. The stress exponent for the combined set of data is n=1.87±0.48 (95 % confidence limits). The tensile creep mechanism of the silicon nitride containing Lu2O3, solution-precipitation, differs from those of other silicon nitrides, for which tensile creep has been attributed to cavitation. Enhancement of the creep resistance of the silicon nitride sintered with Lu2O3 may be a consequence of the fact that Lu2O3 produces a more deformation resistant amorphous phase at the two grain junctions, than do Y2O3 or Yb2O3. In parallel, reducing the amount of secondary phase below a critical limit, or increasing the viscosity of the two grain boundaries relative to three-grain junctions reduces the ability of the material to cavitate during creep, and forces the creep mechanism to change from cavitation to solution-precipitation.