基于La₂O₃ - Y₂O₃ - HfO₂体系的陶瓷的汽化与热力学：高温质谱法研究 - Suppr

Kablov Eugene N, Stolyarova Valentina L, Vorozhtcov Viktor A, Lopatin Sergey I, Fabrichnaya Olga В, Ilatovskaya Mariia O, Karachevtsev Fedor N

All-Russian Research Institute of Aviation Materials, Radio st. 17, 105005, Moscow, Russia.

Saint Petersburg State University, Universitetskaya nab.7/9, 199034, Saint Petersburg, Russia.

Rapid Commun Mass Spectrom. 2018 May 15;32(9):686-694. doi: 10.1002/rcm.8081.

RATIONALE

Materials based on the La O -Y O -HfO system are promising for the production of highly refractory ceramics, e.g., thermal barrier coatings and molds for casting of elements of gas turbine engines. When these ceramics are synthesized or used at high temperatures, selective vaporization of components may take place, resulting in changes in the physicochemical properties of the materials. Consequently, development of materials based on the La O -Y O -HfO system requires information on vaporization in this system as well as on its thermodynamics, without which prediction and modeling of their physicochemical properties are impossible.

METHODS

Vaporization processes and thermodynamic properties in the La O -Y O -HfO system were studied by the high-temperature Knudsen effusion mass spectrometric method using a MS-1301 mass spectrometer. Electron ionization of vapor species was employed at an ionization energy of 25 eV. The samples under study and reference substances were vaporized from a tungsten twin effusion cell.

RESULTS

At 2337 K the main vapor species over samples in the La O -Y O -HfO system were shown to be LaO, YO and O. The partial pressures of the vapor species mentioned and the La O and Y O activities in the samples were obtained at 2337 K. The Gibbs energies of mixing and excess Gibbs energies were found in the solid solution of this system.

CONCLUSIONS

Vaporization of ceramics based on the La O -Y O -HfO system at 2337 K led to selective transition of La O and Y O to the gaseous phase, with the La O vaporization rate being higher than that of Y O . The directions of composition changes of samples due to their vaporization at 2337 K were determined. In the solid solution of this system negative deviations from ideal behavior were found. The ability to estimate the excess Gibbs energies in the solid solution of the La O -Y O -HfO system by the Kohler method was shown.

原理

基于La₂O₃ - Y₂O₃ - HfO₂体系的材料在生产高耐火陶瓷方面具有潜力，例如热障涂层和燃气涡轮发动机部件铸造用模具。当这些陶瓷在高温下合成或使用时，组分可能会发生选择性蒸发，从而导致材料的物理化学性质发生变化。因此，开发基于La₂O₃ - Y₂O₃ - HfO₂体系的材料需要有关该体系蒸发及其热力学的信息，否则无法对其物理化学性质进行预测和建模。

方法

采用MS - 1301质谱仪，通过高温克努森泻流质谱法研究了La₂O₃ - Y₂O₃ - HfO₂体系中的蒸发过程和热力学性质。在25 eV的电离能下对蒸汽物种进行电子电离。研究样品和参比物质从钨双泻流池蒸发。

结果

在2337 K时，La₂O₃ - Y₂O₃ - HfO₂体系样品上方的主要蒸汽物种为LaO、YO和O。获得了上述蒸汽物种的分压以及样品在2337 K时La₂O₃和Y₂O₃的活度。在该体系的固溶体中发现了混合吉布斯自由能和过量吉布斯自由能。

结论

基于La₂O₃ - Y₂O₃ - HfO₂体系的陶瓷在2337 K下蒸发导致La₂O₃和Y₂O₃选择性地转变为气相，La₂O₃的蒸发速率高于Y₂O₃。确定了样品在2337 K下蒸发导致的成分变化方向。在该体系的固溶体中发现了与理想行为的负偏差。展示了用科勒方法估算La₂O₃ - Y₂O₃ - HfO₂体系固溶体中过量吉布斯自由能的能力。