Phase stability and tensorial thermal expansion properties of single to high‐entropy rare‐earth disilicates
Phase stability and tensorial thermal expansion properties of single to high‐entropy rare‐earth disilicates
复制标题
单相至高熵稀土二硅酸盐的相稳定性和张量热膨胀特性
DOI：
10.1111/jace.18986
复制
发表时间：
2023
影响因子：
3.9
通讯作者：
Ihlefeld, Jon F.
中科院分区：
文献类型：
--
作者：
Salanova, Alejandro;Brummel, Ian A.;Yakovenko, Andrey A.;Opila, Elizabeth J.;Ihlefeld, Jon F.
镍基高温合金的温度限制导致SiC基陶瓷基复合材料的出现，作为航空应用中燃气涡轮机组件的可行替代品。更高的工作温度允许降低燃料消耗，但存在与环境退化相关的材料设计挑战。稀土二硅酸盐（RE 2Si 2 O 7）已被确定为可用作环境屏障并最大限度地减少热部件降解的涂层。在这项工作中，通过溶胶-凝胶法合成了单组分和多组分的稀土二硅酸盐粉末，其组成选择为存在于单斜C2/m相（β相）中。多阳离子组合物的相稳定性遵循混合物的规则，C2/m相可以在含有高达25%镝的组合物中实现，镝通常仅存在于三斜晶系P1 <$${\rm{1}$中。如通过X射线衍射评估的，所有组合物从室温至1200°C表现出相稳定性。每种组合物的热膨胀张量由高温同步加速器X射线衍射和伴随的Rietveld细化确定。观察到含镱组合物随着温度的升高在α 31剪切分量中具有较大的变化，这导致主轴的旋转。观察到二硅酸镱的主轴旋转高达47°。结果表明，微观结构设计和晶体学纹理可能是未来研究的重要途径，以确保稀土二硅酸盐环境屏障涂层的热机械鲁棒性。
Temperature limitations in nickel‐base superalloys have resulted in the emergence of SiC‐based ceramic matrix composites as a viable replacement for gas turbine components in aviation applications. Higher operating temperatures allow for reduced fuel consumption but present a materials design challenge related to environmental degradation. Rare‐earth disilicates (RE2Si2O7) have been identified as coatings that can function as environmental barriers and minimize hot component degradation. In this work, single‐ and multiple‐component rare‐earth disilicate powders were synthesized via a sol‐gel method with compositions selected to exist in the monoclinicC2/mphase (βphase). Phase stability in multiple cation compositions was shown to follow a rule of mixtures and theC2/mphase could be realized for compositions that contained up to 25% dysprosium, which typically only exists in a triclinic,P1¯${\rm{\bar{1}}}$, phase. All compositions exhibited phase stability from room temperature to 1200°C as assessed by X‐ray diffraction. The thermal expansion tensors for each composition were determined from high‐temperature synchrotron X‐ray diffraction and accompanying Rietveld refinements. It was observed that ytterbium‐containing compositions had larger changes in theα31shear component with increasing temperature that led to a rotation of the principal axes. Principal axes rotation of up to 47° were observed for ytterbium disilicate. The results suggest that microstructure design and crystallographic texture may be essential future avenues of investigation to ensure thermo‐mechanical robustness of rare‐earth disilicate environmental barrier coatings.