Based on constructal theory,the constructs of three "volume-point" heat conduction models with three-dimensional cylindrical element and rectangular and triangular elements on microscale and nanoscale are op...Based on constructal theory,the constructs of three "volume-point" heat conduction models with three-dimensional cylindrical element and rectangular and triangular elements on microscale and nanoscale are optimized by taking minimum entransy dissipation rate as optimization objective.The optimal constructs of the three "volume-point" heat conduction models with minimum dimensionless equivalent thermal resistance are obtained.The results show that the optimal constructs of the three-dimensional cylindrical assembly based on the minimizations of dimensionless equivalent thermal resistance and dimensionless maximum thermal resistance are different,which is obviously different from the comparison between those of the corresponding two-dimensional rectangular assembly based on the minimizations of these two objectives.The optimal constructs based on rectangular and triangular elements on microscale and nanoscale when the size effect takes effect are obviously different from those when the size effect does not take effect.Because the thermal current density in the high conductivity channel of the rectangular and triangular second order assemblies are not linear with the length,the optimal constructs of these assemblies based on the minimization of entransy dissipation rate are different from those based on the minimization of maximum temperature difference.The dimensionless equivalent thermal resistance defined based on entransy dissipation rate reflects the average heat transfer performance of the construct.The studies on "volume-point" heat conduction constructal problems at three-dimensional conditions and microscale and nanoscale by taking minimum entransy dissipation rate as optimization objective extend the application range of the entransy dissipation extremum principle.展开更多
A facile,precise,and controllable manufacturing technology is desired for hierarchical functional surfaces.In this work,we successfully manufactured porous metallic glass using a water-dissolution material as template...A facile,precise,and controllable manufacturing technology is desired for hierarchical functional surfaces.In this work,we successfully manufactured porous metallic glass using a water-dissolution material as template and the excellent thermoplastic property of metallic glass.The prepared micro/nanostructures have excellent tunability,and the proposed approach can be used to prepare large-area disordered porous structures and ordered regular arrays with nanoscale replication accuracy.In particular,the disordered porous structure prepared by the dissolvable template strategy exhibits a water contact angle of~140°and an oil contact angle of~0°,making it suitable for oil/water separation.It also shows stable wettability after being soaked in strong acid or alkali environments and maintains a~130°water contact angle and a~4°oil contact angle even after severe wear.The proposed strategy also possesses excellent recycling properties.We reconstructed porous structures on the same surface three times and found no significant change in wettability for each reconstructed porous structure.Our research provides a facile and controllable approach for the preparation of hierarchical porous structures and paves the way for the design of other functional surfaces.展开更多
As the first Creative Research Group sponsored by Division of Mechanics of Department of Mathematical and Physical Sciences of NSEC, a project team, including two CAS members （Porf. Kezhi Huang, Prof. Wei Yang） and ...As the first Creative Research Group sponsored by Division of Mechanics of Department of Mathematical and Physical Sciences of NSEC, a project team, including two CAS members （Porf. Kezhi Huang, Prof. Wei Yang） and two Changjiang scholars （Prof. Quanshui Zheng, Prof. Daining Pang） from Tsinghua University, focused their research on ＂Micro/nanoscale mechanics and smart materials＂, and progressed in the following：展开更多
Three-dimensional flowerlike α-Ni（OH）2 nanostructures were successfully synthesized by the microwave-assisted reflux as short as 30 rain. The crystalline structure and morphology of the products were characterized ...Three-dimensional flowerlike α-Ni（OH）2 nanostructures were successfully synthesized by the microwave-assisted reflux as short as 30 rain. The crystalline structure and morphology of the products were characterized by X-ray diffraction, N2 adsorption-desorption isotherms, field emission scanning electron microscopy, and transmission electron microscopy. The α-Ni（OH）2 nanostructure shows a large surface area of 173 m2 g-1 and narrow mesopore distribution. The electrochemical properties of the as-prepared α-Ni（OH）2 as an electrode material for supercapacitor were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements in 6 mol/L KOH electrolyte. The α-Ni（OH）2 nanostructure shows a maximum specific capacitance of 2030 F g-1 at a current density of 1 A g-1 and exhibits excellent rate capability. These results suggest that it is a promising electrode material for supercapacitor application.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 51176203)the Natural Science Foundation of Naval University of Engineering (Grant No. HGDYDJJ10011)the Natural Science Foundation for Youngsters of Naval University of Engineering (Grant No. HGDQNJJ10017)
文摘Based on constructal theory,the constructs of three "volume-point" heat conduction models with three-dimensional cylindrical element and rectangular and triangular elements on microscale and nanoscale are optimized by taking minimum entransy dissipation rate as optimization objective.The optimal constructs of the three "volume-point" heat conduction models with minimum dimensionless equivalent thermal resistance are obtained.The results show that the optimal constructs of the three-dimensional cylindrical assembly based on the minimizations of dimensionless equivalent thermal resistance and dimensionless maximum thermal resistance are different,which is obviously different from the comparison between those of the corresponding two-dimensional rectangular assembly based on the minimizations of these two objectives.The optimal constructs based on rectangular and triangular elements on microscale and nanoscale when the size effect takes effect are obviously different from those when the size effect does not take effect.Because the thermal current density in the high conductivity channel of the rectangular and triangular second order assemblies are not linear with the length,the optimal constructs of these assemblies based on the minimization of entransy dissipation rate are different from those based on the minimization of maximum temperature difference.The dimensionless equivalent thermal resistance defined based on entransy dissipation rate reflects the average heat transfer performance of the construct.The studies on "volume-point" heat conduction constructal problems at three-dimensional conditions and microscale and nanoscale by taking minimum entransy dissipation rate as optimization objective extend the application range of the entransy dissipation extremum principle.
基金supported by the Key Basic and Applied Research Program of Guangdong Province,China(2019B030302010)the National Natural Science Foundation of China(52122105,51871157,and 51971150)the National Key Research and Development Program of China(2018YFA0703604)。
文摘A facile,precise,and controllable manufacturing technology is desired for hierarchical functional surfaces.In this work,we successfully manufactured porous metallic glass using a water-dissolution material as template and the excellent thermoplastic property of metallic glass.The prepared micro/nanostructures have excellent tunability,and the proposed approach can be used to prepare large-area disordered porous structures and ordered regular arrays with nanoscale replication accuracy.In particular,the disordered porous structure prepared by the dissolvable template strategy exhibits a water contact angle of~140°and an oil contact angle of~0°,making it suitable for oil/water separation.It also shows stable wettability after being soaked in strong acid or alkali environments and maintains a~130°water contact angle and a~4°oil contact angle even after severe wear.The proposed strategy also possesses excellent recycling properties.We reconstructed porous structures on the same surface three times and found no significant change in wettability for each reconstructed porous structure.Our research provides a facile and controllable approach for the preparation of hierarchical porous structures and paves the way for the design of other functional surfaces.
文摘As the first Creative Research Group sponsored by Division of Mechanics of Department of Mathematical and Physical Sciences of NSEC, a project team, including two CAS members （Porf. Kezhi Huang, Prof. Wei Yang） and two Changjiang scholars （Prof. Quanshui Zheng, Prof. Daining Pang） from Tsinghua University, focused their research on ＂Micro/nanoscale mechanics and smart materials＂, and progressed in the following：
基金supported by the National Natural Science Foundation of China(Grant No.51472238)the Open Project Program of State Key Laboratory of Chemical Resource Engineering(Grant No.CRE-2014-C-102)
文摘Three-dimensional flowerlike α-Ni（OH）2 nanostructures were successfully synthesized by the microwave-assisted reflux as short as 30 rain. The crystalline structure and morphology of the products were characterized by X-ray diffraction, N2 adsorption-desorption isotherms, field emission scanning electron microscopy, and transmission electron microscopy. The α-Ni（OH）2 nanostructure shows a large surface area of 173 m2 g-1 and narrow mesopore distribution. The electrochemical properties of the as-prepared α-Ni（OH）2 as an electrode material for supercapacitor were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements in 6 mol/L KOH electrolyte. The α-Ni（OH）2 nanostructure shows a maximum specific capacitance of 2030 F g-1 at a current density of 1 A g-1 and exhibits excellent rate capability. These results suggest that it is a promising electrode material for supercapacitor application.
