摘要
Microstructure control is a great challenge in the high-temperature gradient directional solidification of eutectic composite ceramics due to the complex solidification behavior.Herein,the microstructure trans-formation of faceted Al_(2)O_(3)/Er_(3)Al_(5)O_(12) thermal emission eutectic composite ceramics is explored over wide ranges of compositions(13.5 mol%-22.5 mol%Er_(2)O_(3))and solidification rates(2-200μm/s).Entirely cou-pled eutectics with primary phases suppressed are fabricated and the coupled zone is broadened in a wide range of 15.5 mol%-22.5 mol%Er_(2)O_(3) at low solidification rates.The competitive growth between eutectic and dendrite is evaluated on the basis of the maximum interface temperature criterion.In ad-dition,the mechanisms of irregular eutectic spacing selection and adjustment under different solidifi-cation rates are revealed based on Magnin-Kurz model.A successful prediction of lamellar to rod-like eutectics is achieved associated with the dynamic instability of lamellar eutectic and the corresponding enlarged coexistence region is mapped based on the interface undercooling.According to the well mi-crostructure tailoring,the flexural strength of Al_(2)O_(3)/Er_(3)Al_(5)O_(12) eutectic composite ceramics has improved from 508 MPa up to 1800 MPa due to the refined eutectic spacing with low fluctuation.The eutectic composite ceramics show strong selective optical absorption and the intensity increases with the refin-ing microstructure.The as-designed Al_(2)O_(3)/Er_(3)Al_(5)O_(12) composites with microstructural tailoring have great potential as integrations of structural and functional materials.
基金
supported by the National Natural Science Foundation of China (Nos.52130204,52174376,and 51822405)
the Guangdong Basic and Applied Basic Research Foundation (No.2021B1515120028)
the Science and Technology Innovation Team Plan of Shaan Xi Province (No.2021TD-17)
the Youth Innovation Team of Shaanxi Universities,Fundamental Research Funds for the Central Universities (No.D5000210902)
the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University (Nos.CX2021056,CX2021066,and CX2022033),China.
