Based on the unbounded matrix, a void growth model is proposed inthis paper. In this mod- el, extending the Griffith criterion ofenergy conservation during the expanding of cracks to the case ofimpact loading, we prop...Based on the unbounded matrix, a void growth model is proposed inthis paper. In this mod- el, extending the Griffith criterion ofenergy conservation during the expanding of cracks to the case ofimpact loading, we propose an assumption that the strain energy inmatrix can transform into its surface energy and kinetic energyduring the micro-void growth. The void growth velocities of the OFHCcopper and LY12 alu- minim are calculated, and the result of whichagrees with that of Seaman展开更多
To date,wet syntheses of single-crystalline ZnO micro-and nanotubes have been carried out using a two-step indirect approach in which a selective dissolution step is required in order to create the vacant space in the...To date,wet syntheses of single-crystalline ZnO micro-and nanotubes have been carried out using a two-step indirect approach in which a selective dissolution step is required in order to create the vacant space in the tubular structures.In this work,we develop a direct growth process for preparation of single-crystal ZnO nanotubes and nanorods.We also report that a concave shaped crystal growth front is generally reactive and offers a large surface area for matter deposition during rapid expansion of unidirectional nanomaterials.Depending on the degree of supersaturation of nutrients in solution,the concave growth front can either remain unaltered or undergo a concave-to-convex transformation,leading to the growth of solid nanorods and/or hollow nanotubes.The observed volume inversion should,in principle,also be applicable to the nanoarchitecture of other one-dimensional wurtzite structured nanomaterials,although individual sets of synthesis parameters need to be developed for each target material.展开更多
文摘Based on the unbounded matrix, a void growth model is proposed inthis paper. In this mod- el, extending the Griffith criterion ofenergy conservation during the expanding of cracks to the case ofimpact loading, we propose an assumption that the strain energy inmatrix can transform into its surface energy and kinetic energyduring the micro-void growth. The void growth velocities of the OFHCcopper and LY12 alu- minim are calculated, and the result of whichagrees with that of Seaman
基金The authors gratefully acknowledge the financial support of the Ministry of Education,Singapore.B.L.would also like to thank the National University of Singapore for providing his postgraduate scholarship.
文摘To date,wet syntheses of single-crystalline ZnO micro-and nanotubes have been carried out using a two-step indirect approach in which a selective dissolution step is required in order to create the vacant space in the tubular structures.In this work,we develop a direct growth process for preparation of single-crystal ZnO nanotubes and nanorods.We also report that a concave shaped crystal growth front is generally reactive and offers a large surface area for matter deposition during rapid expansion of unidirectional nanomaterials.Depending on the degree of supersaturation of nutrients in solution,the concave growth front can either remain unaltered or undergo a concave-to-convex transformation,leading to the growth of solid nanorods and/or hollow nanotubes.The observed volume inversion should,in principle,also be applicable to the nanoarchitecture of other one-dimensional wurtzite structured nanomaterials,although individual sets of synthesis parameters need to be developed for each target material.
