High strength and high porosity YB₂C₂ ceramics prepared by a new high temperature reaction/partial sintering process

Heng Chen^1,2，Huimin Xiang²，Fuzhi Dai²，Jiachen Liu¹，Yanchun Zhou²

1. Key Laboratory of Advanced Ceramics and Machining Technology of Ministry of Education, School of Materials Science and Engineering, Tianjin University2. Science and Technology on Advanced Functional Composite Laboratory, Aerospace Research Institute of Materials & Processing Technology

摘 要：Porous ultrahigh temperature ceramics（UHTCs） are potential candidates as reusable thermal protection materials of transpiration cooling system in scramjet engine. However, low strength and low porosity are the main limitations of porous UHTCs. To overcome these problems, herein, a new and simple in-situ reaction/partial sintering process has been developed for preparing high strength and high porosity porous YB₂C₂. In this process, a simple gas-releasing in-situ reaction has been designed, and the formation and escape of gases can block the shrinkage during sintering process, which is favorable to increase the porosity of porous YB₂C₂. In order to demonstrate the advantages of the new method, porous YB₂C₂ ceramics have been fabricated from Y₂O₃, BN and graphite powders for the first time. The as-prepared porous YB₂C₂ ceramics possess high porosity of 57.17%–75.26% and high compressive strength of 9.32–34.78 MPa.The porosity, sintered density, radical shrinkage and compressive strength of porous YB₂C₂ ceramics can be controlled simply by changing the green density. Due to utilization of graphite as the carbon source, the porous YB₂C₂ ceramics show anisotropy in microstructure and mechanical behavior. These features render the porous YB₂C₂ ceramics promising as a thermal-insulating light-weight component for transpiration cooling system.

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