标题：The fabrication of tungsten reinforced silicon nitride ceramics by altering nitrogen pressure
作者：Wang, Lujie; Qi, Qian; Zhang, Hui; Yang, Xiao; Liu, Zehua; Wu, Haibo; Liu, Xuejian; Huang, Zhengren
作者机构：[Wang, Lujie; Qi, Qian; Zhang, Hui; Yang, Xiao; Liu, Zehua; Wu, Haibo; Liu, Xuejian; Huang, Zhengren] Chinese Acad Sci, Shanghai Inst Ceram, State Key 更多
通讯作者：Wang, LJ;Liu, XJ;Huang, ZR;Wang, Lujie
通讯作者地址：[Wang, LJ; Liu, XJ; Huang, ZR]Chinese Acad Sci, Shanghai Inst Ceram, State Key Lab High Performance Ceram & Superfine, Shanghai 200050, Peoples R Chin 更多
关键词：Silicon nitride; Tungsten; Thermodynamics; Fracture toughness
摘要：Due to high ductility, high-temperature melting, low thermal expansion coefficient, etc., tungsten (W) might be considered to be an ideal reinforcement in toughening or strengthening Si3N4 ceramics. However, it is difficult to fabricate W/Si3N4 composites due to the possible reactions between W and Si3N4 during sintering process at the high temperature. In this work, a novel way to avoid the reactions and fabricate the W/Si3N4 composites was proposed by thermodynamic analysis and verified by experiment. Firstly, the phase equilibrium between W and Si3N4 as a function of temperature and nitrogen pressure was thermodynamically calculated, which indicates that one critical nitrogen pressure exists for reactions between W and Si3N4 at a certain temperature. As the nitrogen pressure is higher than the critical value, the reactions would be inhibited or adversely proceeded. Based on the results, W was innovatively in-situ introduced in the form of WSi2 after sintering at 1750 degrees C under 50 bar nitrogen pressure. Moreover, the fracture toughness of Si3N4 ceramics was enhanced from 7.1 +/- 0.2 to 8.0 +/- 0.4 MPa m(1/2), which proposes a new reinforcement or method in toughening Si3N4 ceramics.