In this paper,ZnO/SnO_(2) core-shell micropyramids were successfully prepared via a chemical vapor deposition process that is based on the epitaxial growth of SnO_(2) on the surface of ZnO hexagonal micropyramids.Upon...In this paper,ZnO/SnO_(2) core-shell micropyramids were successfully prepared via a chemical vapor deposition process that is based on the epitaxial growth of SnO_(2) on the surface of ZnO hexagonal micropyramids.Upon controlling appropriate deposition times and flow rates of the precursor,two epitaxial growth modes of SnO_(2),i.e.a continuous thick film and well-arranged one-dimensional nanostructures were observed in the ZnO/SnO_(2) core-shell micropyramids.Taking advantages of the difference in acid resistance between ZnO and SnO_(2),the as-prepared ZnO/SnO_(2) micropyramids were further converted into SnO_(2) hollow micropyramids with a facile acid-etching treatment.Structural analysis revealed that the lattice mismatch degree between epitaxial planes determines the preferential growth direction of the SnO_(2) epitaxial layer on the ZnO surface.Compared to the pristine ZnO template,interestingly,the ZnO/SnO_(2) core-shell micropyramids exhibited very strong green emission around 504 nm.Such enhanced green emission should be induced by high-density structural defects generated in the interfacial area during the epitaxial growth.展开更多
This study analyzes and predicts the vibration characteristics of fiberreinforced composite sandwich(FRCS)cylindrical-spherical(CS)combined shells with hexagon honeycomb core(HHC)for the first time based on an analyti...This study analyzes and predicts the vibration characteristics of fiberreinforced composite sandwich(FRCS)cylindrical-spherical(CS)combined shells with hexagon honeycomb core(HHC)for the first time based on an analytical model developed,which makes good use of the advantage of the first-order shear deformation theory(FSDT),the multi-segment decomposition technique,the virtual spring technology,the Jacobi-Ritz approach,and the transfer function method.The equivalent material properties of HHC are firstly determined by the modified Gibson’s formula,and the related energy equations are derived for the HHC-FRCS-CS combined shells,from which the fundamental frequencies,the mode shapes,and the forced vibration responses are solved.The current model is verified through the discussion of convergence and comparative analysis with the associated published literature and finite element(FE)results.The effects of geometric parameters of HHC on the dynamic property of the structure are further investigated with the verified model.It reveals that the vibration suppression capability can be greatly enhanced by reducing the ratio of HHC thickness to total thickness and the ratio of wall thickness of honeycomb cell to overall radius,and by increasing the ratio of length of honeycomb cell to overall radius and honeycomb characteristic angle of HHC.展开更多
基金supported by the National Natural Science Foundation of China(21171142)the National Basic Research Program of China(2011CBA00508)+1 种基金the program for New Century Excellent Talents in University(NCET-11-0294)the Fundamental Research Funds for the Central Universities.
文摘In this paper,ZnO/SnO_(2) core-shell micropyramids were successfully prepared via a chemical vapor deposition process that is based on the epitaxial growth of SnO_(2) on the surface of ZnO hexagonal micropyramids.Upon controlling appropriate deposition times and flow rates of the precursor,two epitaxial growth modes of SnO_(2),i.e.a continuous thick film and well-arranged one-dimensional nanostructures were observed in the ZnO/SnO_(2) core-shell micropyramids.Taking advantages of the difference in acid resistance between ZnO and SnO_(2),the as-prepared ZnO/SnO_(2) micropyramids were further converted into SnO_(2) hollow micropyramids with a facile acid-etching treatment.Structural analysis revealed that the lattice mismatch degree between epitaxial planes determines the preferential growth direction of the SnO_(2) epitaxial layer on the ZnO surface.Compared to the pristine ZnO template,interestingly,the ZnO/SnO_(2) core-shell micropyramids exhibited very strong green emission around 504 nm.Such enhanced green emission should be induced by high-density structural defects generated in the interfacial area during the epitaxial growth.
基金supported by the National Natural Science Foundation of China(Nos.52175079 and 12072091)the Science Foundation of the National Key Laboratory of Science and Technology on Advanced Composites in Special Environments of China(No.6142905192512)+2 种基金the Fundamental Research Funds for the Central Universities of China(No.N2103026)the Major Projects of AeroEngines and Gas Turbines of China(No.J2019-I-0008-0008)the China Postdoctoral Science Foundation(No.2020M680990)。
文摘This study analyzes and predicts the vibration characteristics of fiberreinforced composite sandwich(FRCS)cylindrical-spherical(CS)combined shells with hexagon honeycomb core(HHC)for the first time based on an analytical model developed,which makes good use of the advantage of the first-order shear deformation theory(FSDT),the multi-segment decomposition technique,the virtual spring technology,the Jacobi-Ritz approach,and the transfer function method.The equivalent material properties of HHC are firstly determined by the modified Gibson’s formula,and the related energy equations are derived for the HHC-FRCS-CS combined shells,from which the fundamental frequencies,the mode shapes,and the forced vibration responses are solved.The current model is verified through the discussion of convergence and comparative analysis with the associated published literature and finite element(FE)results.The effects of geometric parameters of HHC on the dynamic property of the structure are further investigated with the verified model.It reveals that the vibration suppression capability can be greatly enhanced by reducing the ratio of HHC thickness to total thickness and the ratio of wall thickness of honeycomb cell to overall radius,and by increasing the ratio of length of honeycomb cell to overall radius and honeycomb characteristic angle of HHC.
