Flash sintering(FS)is a novel technique for rapidly densifying silicon carbide(SiC)ceramics.This work achieved a rapid sintering of SiC ceramics by the utilization of ultra-high temperature flash sintering within 60 s...Flash sintering(FS)is a novel technique for rapidly densifying silicon carbide(SiC)ceramics.This work achieved a rapid sintering of SiC ceramics by the utilization of ultra-high temperature flash sintering within 60 s.Pyrolysis carbon(PyC)“bridges”were constructed between SiC particles through the carbonisation of phenolic resin,providing a large number of current channels.The incubation time of the flash sintering process was significantly reduced,and the sintering difference between the centre and the edge regions of the ceramics was minimized,with an average particle size of the centre region and edge region being 12.31 and 9.02μm,respectively.The results showed that the porosity of the SiC ceramics after the flash sintering was reduced to 14.79% with PyC“bridges”introduced,and the Vickers hardness reached 19.62 GPa.PyC“bridges”gradually evolved from amorphous eddy current carbon to oriented graphite carbon,indicating that the ultra-high temperature environment in which the sample was located during the flash sintering was successfully constructed.Ultra-high temperature flash sintering of SiC is expected to be applied to the local repair of matrix damage in SiC ceramic matrix composites.展开更多
Current-conductive mold was recently developed to extend electroslag remelting(ESR)functions to overcome some solidification defects by changing the current path.The macrostructures,microstructures,macrosegregation,an...Current-conductive mold was recently developed to extend electroslag remelting(ESR)functions to overcome some solidification defects by changing the current path.The macrostructures,microstructures,macrosegregation,and microsegregation of the Inconel 718 ingots produced by the custom laboratory-scale ESR furnace under different current paths(the classical ESR and the single power,and two circuits ESR process with current-conductive mold(ESR-STCCM))with the same power input were compared and investigated.The results indicate that when the ingot was produced during ESR and ESR-STCCM processes,at the same power input,the pool depth was 104 and 90 mm,respectively.A flatter and shallower molten pool was obtained during ESR-STCCM process.Moreover,compared with a classical ESR ingot,the cooling rate of the centerline of ESR-STCCM ingot was increased from 12.7 to 16.7 K min^(−1).The increased cooling rates caused by decreased melting rate and thinner slag skin reduced the growth angle of columnar crystal to the vertical axis and the secondary dendrite arm spacing.Furthermore,the macrosegregation and microsegregation of segregation elements for ESR-STCCM process were dramatically reduced compared with ESR process.The average volume fraction of Laves phase was reduced from 7.39%to 6.14%,and the segregation of Nb in Laves phase was significantly reduced.展开更多
Nantong is a typical region of large population and little land.The conflict between resources and environment is growing.Thus,the improvement of independent innovation ability based on current situations,oriented tow...Nantong is a typical region of large population and little land.The conflict between resources and environment is growing.Thus,the improvement of independent innovation ability based on current situations,oriented towards the future and relying on scientific and technological force directly decides the effect of strong economic city construction.Through analysis on achievements of agricultural sci-tech innovation works,existing problems and demand for developing modern agriculture in Nantong,we present development ideas,target orientation and basic principles of agricultural sci-tech innovation works in Nantong,and put forward eight paths.展开更多
基金supported by the National Natural Science Foundation of China(No.92160202)the National Natural Science Foundation of China(No.52375188)+1 种基金the National Key R&D Program of China(No.2021YFB3703100)the Ningbo Key Technology Research and Development(No.2023T007).
文摘Flash sintering(FS)is a novel technique for rapidly densifying silicon carbide(SiC)ceramics.This work achieved a rapid sintering of SiC ceramics by the utilization of ultra-high temperature flash sintering within 60 s.Pyrolysis carbon(PyC)“bridges”were constructed between SiC particles through the carbonisation of phenolic resin,providing a large number of current channels.The incubation time of the flash sintering process was significantly reduced,and the sintering difference between the centre and the edge regions of the ceramics was minimized,with an average particle size of the centre region and edge region being 12.31 and 9.02μm,respectively.The results showed that the porosity of the SiC ceramics after the flash sintering was reduced to 14.79% with PyC“bridges”introduced,and the Vickers hardness reached 19.62 GPa.PyC“bridges”gradually evolved from amorphous eddy current carbon to oriented graphite carbon,indicating that the ultra-high temperature environment in which the sample was located during the flash sintering was successfully constructed.Ultra-high temperature flash sintering of SiC is expected to be applied to the local repair of matrix damage in SiC ceramic matrix composites.
基金This project was supported by the National Natural Science Foundation of China(Grant Nos.51674070,51874085,and U1435205)Also,this project was supported by the Transformation Project of Major Scientific and Technological Achievements in Shenyang(Grant No.Z17-5-003)and the"Innovation&Entrepreneurship Talents”Introduction Plan of Jiangsu Province in 2018.
文摘Current-conductive mold was recently developed to extend electroslag remelting(ESR)functions to overcome some solidification defects by changing the current path.The macrostructures,microstructures,macrosegregation,and microsegregation of the Inconel 718 ingots produced by the custom laboratory-scale ESR furnace under different current paths(the classical ESR and the single power,and two circuits ESR process with current-conductive mold(ESR-STCCM))with the same power input were compared and investigated.The results indicate that when the ingot was produced during ESR and ESR-STCCM processes,at the same power input,the pool depth was 104 and 90 mm,respectively.A flatter and shallower molten pool was obtained during ESR-STCCM process.Moreover,compared with a classical ESR ingot,the cooling rate of the centerline of ESR-STCCM ingot was increased from 12.7 to 16.7 K min^(−1).The increased cooling rates caused by decreased melting rate and thinner slag skin reduced the growth angle of columnar crystal to the vertical axis and the secondary dendrite arm spacing.Furthermore,the macrosegregation and microsegregation of segregation elements for ESR-STCCM process were dramatically reduced compared with ESR process.The average volume fraction of Laves phase was reduced from 7.39%to 6.14%,and the segregation of Nb in Laves phase was significantly reduced.
基金Supported by Action Plan Project of Scientific and Technical Personnel of Ministry of Science and Technology for Serving Enterprises(2009GJC10025)Agricultural Sci-tech Innovation Project of Nantong City (HL2011010)
文摘Nantong is a typical region of large population and little land.The conflict between resources and environment is growing.Thus,the improvement of independent innovation ability based on current situations,oriented towards the future and relying on scientific and technological force directly decides the effect of strong economic city construction.Through analysis on achievements of agricultural sci-tech innovation works,existing problems and demand for developing modern agriculture in Nantong,we present development ideas,target orientation and basic principles of agricultural sci-tech innovation works in Nantong,and put forward eight paths.
