The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated....The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated. Lamellar structure consisted of Mo_5Si_3 (D8m) phaseand MoSi_2 (C11_b) phase was observed in all the alloys. For Mo_5Si_3-MoSi_2 hypoeutectic alloy, thelamellar structure was found only after annealing and developed well with fine spacing on the orderof hundred nanometers after annealing at 1200℃ for 48 h. But when the annealing time was up to 96h, the well-developed lamellar structure was destroyed. For Mo_5Si_3-MoSi_2 hypereutectic alloy, thelamellar structure was found both before and after annealing. However the volume fraction andspacing of the lamellar structure did not change significantly before and after annealing. Theeffects of the formation, development and destruction of lamellar structure on Vickers hardness ofalloys were also investigated. When Mo_5Si_3-MoSi_2 hypoeutectic alloy annealed at 1200℃ for 48 h,the Vickers hardness was improved about 19% compared with that without annealing and formation oflamellar structure. The highest Vickers hardness of Mo5Si3-MoSi_2 hypereutectic was increasing about18% when annealing at 1200℃ for 48 h.展开更多
Development of new vernacular dwelling of water town in the southern bank of the Yangze River is an important approach to improve rural appearance,infrastructure,quality of life,and to realize new urbanization of this...Development of new vernacular dwelling of water town in the southern bank of the Yangze River is an important approach to improve rural appearance,infrastructure,quality of life,and to realize new urbanization of this area. How would this process to inherit the quintessence of traditional local-style dwelling as well as integrate with low energy consumption technology is also an important problem due to the valuable Chinese traditional architectural culture in this area. Taking SI system as breaking point,this paper analyzes the green ecological characteristics of traditional residence in the south of the lower reaches of the Yangze River,discusses the current residential technology of low energy consumption, and proposes the low energy consumption residential technology integration system in the south of the lower reaches of the Yangze River.Based on this,this paper takes the SDC 2013 entry "solark"as a practical application case study and further expounds the prospects of this technology system.展开更多
The diagram of system Au-Cu-Si was constructed from data of 9 internal sections by DTA in an atmosphere of dry N_2.The composition of ternary eutectic point melting at 337℃ lies in Au(74.7)-Cu(6.1)-Si(19.2) at.-%.The...The diagram of system Au-Cu-Si was constructed from data of 9 internal sections by DTA in an atmosphere of dry N_2.The composition of ternary eutectic point melting at 337℃ lies in Au(74.7)-Cu(6.1)-Si(19.2) at.-%.The liquidus of the 3 side-binary systems have been redetermined.展开更多
The effects of yttrium and cerium on microstructures and properties of Nb-Si system composites were investigated by scanning electron microscopy( SEM), energy dispersive spectrum(EDS), X-ray diffraction(XRD) and high ...The effects of yttrium and cerium on microstructures and properties of Nb-Si system composites were investigated by scanning electron microscopy( SEM), energy dispersive spectrum(EDS), X-ray diffraction(XRD) and high temperature oxidation experiments.It is found that the coarse primary silicide phase became finer and more homogeneous with Y and Ce addition.The results of high temperature oxidation experiments show that the oxidation rates of NbSi system composites with an appropriate amount of Y and Ce decrease compared with those of alloys without Y or Ce addition, and oxidation products mainly distribute along the phase boundaries between the Nb solid solution and silicide.展开更多
Magnesium silicon nitride (MgSiN2) was synthesized without any additives under a nitrogen gas flow (200 mL/min) using a nitriding method. The effects of temperature and holding time on its purity and morphology were i...Magnesium silicon nitride (MgSiN2) was synthesized without any additives under a nitrogen gas flow (200 mL/min) using a nitriding method. The effects of temperature and holding time on its purity and morphology were investigated. A single-phase MgSiN2 powder was obtained at 1350℃ for 1 h and 1250℃ for 11 h. However, the decomposition of MgSiN2 occurred at 1450℃, suggesting that the optimum temperature for the preparation of MgSiN2 from Mg-Si system was 1350℃. The phase purity, morphology, size of the product and elemental composition of the samples were detected by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy spectrometer (EDS), respectively. The evaporation of Mg and Si resulted in the formation of many voids in the blocky product. The temperature gradient promotes the growth of MgSiN2 on the surface of massive products along the tip. The concentration gradient of Mg and Si vapors in the void resulted in the columnar growth of MgSiN2.展开更多
文摘The microstructures and Vickers hardness at room temperature of arc-meltingprocessed intermetallics of Mo_5Si_3-MoSi_2 hypoeutectic alloy and hypereutectic alloy annealed at1200℃ for different time were investigated. Lamellar structure consisted of Mo_5Si_3 (D8m) phaseand MoSi_2 (C11_b) phase was observed in all the alloys. For Mo_5Si_3-MoSi_2 hypoeutectic alloy, thelamellar structure was found only after annealing and developed well with fine spacing on the orderof hundred nanometers after annealing at 1200℃ for 48 h. But when the annealing time was up to 96h, the well-developed lamellar structure was destroyed. For Mo_5Si_3-MoSi_2 hypereutectic alloy, thelamellar structure was found both before and after annealing. However the volume fraction andspacing of the lamellar structure did not change significantly before and after annealing. Theeffects of the formation, development and destruction of lamellar structure on Vickers hardness ofalloys were also investigated. When Mo_5Si_3-MoSi_2 hypoeutectic alloy annealed at 1200℃ for 48 h,the Vickers hardness was improved about 19% compared with that without annealing and formation oflamellar structure. The highest Vickers hardness of Mo5Si3-MoSi_2 hypereutectic was increasing about18% when annealing at 1200℃ for 48 h.
基金Sponsored by the Chinese Nature Science Foundation(Grant No.51278110)the Fundamental Research Funds for the Central Universities+1 种基金the Research Funds of Graduate Student Innovation Planning Program for Jiangsu Province's University(Grant No.KYLX-0143)the Fundamental Research Fundsof Southeast University
文摘Development of new vernacular dwelling of water town in the southern bank of the Yangze River is an important approach to improve rural appearance,infrastructure,quality of life,and to realize new urbanization of this area. How would this process to inherit the quintessence of traditional local-style dwelling as well as integrate with low energy consumption technology is also an important problem due to the valuable Chinese traditional architectural culture in this area. Taking SI system as breaking point,this paper analyzes the green ecological characteristics of traditional residence in the south of the lower reaches of the Yangze River,discusses the current residential technology of low energy consumption, and proposes the low energy consumption residential technology integration system in the south of the lower reaches of the Yangze River.Based on this,this paper takes the SDC 2013 entry "solark"as a practical application case study and further expounds the prospects of this technology system.
文摘The diagram of system Au-Cu-Si was constructed from data of 9 internal sections by DTA in an atmosphere of dry N_2.The composition of ternary eutectic point melting at 337℃ lies in Au(74.7)-Cu(6.1)-Si(19.2) at.-%.The liquidus of the 3 side-binary systems have been redetermined.
基金Project supported by Areonautical Science Foundation of China(03G21003 )
文摘The effects of yttrium and cerium on microstructures and properties of Nb-Si system composites were investigated by scanning electron microscopy( SEM), energy dispersive spectrum(EDS), X-ray diffraction(XRD) and high temperature oxidation experiments.It is found that the coarse primary silicide phase became finer and more homogeneous with Y and Ce addition.The results of high temperature oxidation experiments show that the oxidation rates of NbSi system composites with an appropriate amount of Y and Ce decrease compared with those of alloys without Y or Ce addition, and oxidation products mainly distribute along the phase boundaries between the Nb solid solution and silicide.
文摘Magnesium silicon nitride (MgSiN2) was synthesized without any additives under a nitrogen gas flow (200 mL/min) using a nitriding method. The effects of temperature and holding time on its purity and morphology were investigated. A single-phase MgSiN2 powder was obtained at 1350℃ for 1 h and 1250℃ for 11 h. However, the decomposition of MgSiN2 occurred at 1450℃, suggesting that the optimum temperature for the preparation of MgSiN2 from Mg-Si system was 1350℃. The phase purity, morphology, size of the product and elemental composition of the samples were detected by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy spectrometer (EDS), respectively. The evaporation of Mg and Si resulted in the formation of many voids in the blocky product. The temperature gradient promotes the growth of MgSiN2 on the surface of massive products along the tip. The concentration gradient of Mg and Si vapors in the void resulted in the columnar growth of MgSiN2.
基金the financial support from the Fundamental Research Program of Shanxi Province,China(No.202203021211130)the National Natural Science Foundation of China(Nos.51801132,52075359)。
基金financially supported by the Fundamental Research Funds for the Central Universities,China(No.2020CDJDPT001)the Chongqing Natural Science Foundation,China(No.cstc2021jcyj-msxm X0699)。
