During sintering of the silica-based ceramic core of turbine blades,a phenomenon called"nonuniform sintering"occurs that negatively affects the thermal and mechanical properties of the core.Standard samples ...During sintering of the silica-based ceramic core of turbine blades,a phenomenon called"nonuniform sintering"occurs that negatively affects the thermal and mechanical properties of the core.Standard samples of silica-based core were prepared by an injection molding method and sintered with alumina backfilling powder with different sodium contents.The effect of sodium content on the nonuniform sintering of silica-based cores and the thermal and mechanical properties was evaluated.Results show that the sintering level and the content ofα-cristobalite in the surface layer are significantly higher than that of the sample interior.A considerable number of microcracks are found in the surface layer due to theβtoα-phase transition of cristobalite.As the sodium content in the alumina powder decreases,the level of the nonuniform sintering and the amount of crystallized cristobalite in the surface layer decrease,which is beneficial to the thermal expansion and flexural strength at ambient temperature.The flexural strength and thermal deformation at high temperature are improved by reducing the surface cracks,but deteriorated with the decrease of the cristobalite crystallization when the surface cracks are macroscopically invisible.展开更多
1.Introduction Sudden cardiac death(SCD)refers to sudden death due to a variety of cardiac causes.It is manifested as a sudden loss of consciousness,cardiac arrest,and respiratory arrest and generally shows early symp...1.Introduction Sudden cardiac death(SCD)refers to sudden death due to a variety of cardiac causes.It is manifested as a sudden loss of consciousness,cardiac arrest,and respiratory arrest and generally shows early symptoms that are atypical and not easily detected[1].According to a recent study,nearly 544000 patients suffer from SCD every year in China[2].展开更多
Three Laves phase-based alloys with nominal compositions of Cr2Nb-xTi （x = 20, 30, 40, in at%） have been prepared through vacuum non-consumable arc melting. The results show that the microstructures of Cr2Nb-（20, 3...Three Laves phase-based alloys with nominal compositions of Cr2Nb-xTi （x = 20, 30, 40, in at%） have been prepared through vacuum non-consumable arc melting. The results show that the microstructures of Cr2Nb-（20, 30） Ti alloys are composed of the primary Laves phase C15-Cr2（Nb,Ti） and bcc solid solution phase, while the microstructure of Cr2Nb-40Ti alloy is developed with the eutectic phases C15-Cr2（Nb,Ti）/bcc solid solution. The measured fracture toughness of ternary Laves phase C15-Cr2（Nb,Ti） is about 3.0 MPa m1/2, much larger than 1.4 MPa m1/2 for binary Laves phase Cr2Nb. Meanwhile, the fracture toughness of Cr2Nb-xTi （x = 20, 30, 40） alloys increases with increasing Ti content and reaches 10.6 MPa m1/2 in Cr2Nb-40Ti alloy. The eutectic microstructure and addition of Ti in Cr2Nb are found to be effective in toughening Laves phase-based alloys.展开更多
基金funded by the Shenzhen Development and Reform Commission Project(SZDRC 20181000)made possible through funding from the Wedge Central South Research Institute,Chinasupported by the State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,China。
文摘During sintering of the silica-based ceramic core of turbine blades,a phenomenon called"nonuniform sintering"occurs that negatively affects the thermal and mechanical properties of the core.Standard samples of silica-based core were prepared by an injection molding method and sintered with alumina backfilling powder with different sodium contents.The effect of sodium content on the nonuniform sintering of silica-based cores and the thermal and mechanical properties was evaluated.Results show that the sintering level and the content ofα-cristobalite in the surface layer are significantly higher than that of the sample interior.A considerable number of microcracks are found in the surface layer due to theβtoα-phase transition of cristobalite.As the sodium content in the alumina powder decreases,the level of the nonuniform sintering and the amount of crystallized cristobalite in the surface layer decrease,which is beneficial to the thermal expansion and flexural strength at ambient temperature.The flexural strength and thermal deformation at high temperature are improved by reducing the surface cracks,but deteriorated with the decrease of the cristobalite crystallization when the surface cracks are macroscopically invisible.
基金Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences(No.2019-I2M-5-023)Hainan Provincial Science and Technology Major Project(No.ZDKJ201804)+2 种基金National Natural Science Foundation of China(No.81871611)National Natural Science Foundation of China(No.81760352)Project of Hainan Provincial Department of Education(No.Hnjg2019ZD-16)
文摘1.Introduction Sudden cardiac death(SCD)refers to sudden death due to a variety of cardiac causes.It is manifested as a sudden loss of consciousness,cardiac arrest,and respiratory arrest and generally shows early symptoms that are atypical and not easily detected[1].According to a recent study,nearly 544000 patients suffer from SCD every year in China[2].
基金financially supported by the National Natural Science Foundation of China (Nos.51074127 and 51104120)the SRF for ROCS,SEM
文摘Three Laves phase-based alloys with nominal compositions of Cr2Nb-xTi （x = 20, 30, 40, in at%） have been prepared through vacuum non-consumable arc melting. The results show that the microstructures of Cr2Nb-（20, 30） Ti alloys are composed of the primary Laves phase C15-Cr2（Nb,Ti） and bcc solid solution phase, while the microstructure of Cr2Nb-40Ti alloy is developed with the eutectic phases C15-Cr2（Nb,Ti）/bcc solid solution. The measured fracture toughness of ternary Laves phase C15-Cr2（Nb,Ti） is about 3.0 MPa m1/2, much larger than 1.4 MPa m1/2 for binary Laves phase Cr2Nb. Meanwhile, the fracture toughness of Cr2Nb-xTi （x = 20, 30, 40） alloys increases with increasing Ti content and reaches 10.6 MPa m1/2 in Cr2Nb-40Ti alloy. The eutectic microstructure and addition of Ti in Cr2Nb are found to be effective in toughening Laves phase-based alloys.
