This article describes the efforts that led to the development of surface-loaded preforms that may be used to significantly improve the compression-after-impact strength of high-temperature composites and correspondin...This article describes the efforts that led to the development of surface-loaded preforms that may be used to significantly improve the compression-after-impact strength of high-temperature composites and correspondingly to dramatically reduce the area of damage because of impact.Moreover,by matching the toughening polymer surface-loaded and design of the surface pattern,in-plane mechanical properties are unaffected or even improved over laminates made from the identical materials.The proprietary preforms,so-called ESTM-Fabrics,may be handled and infused with the high-temperature RTMable resins such as bismaleimide and polyimide in exactly the same manner as traditional fabrics without surface modification.The RTM conditions for the preform-based toughening is fully compatible with the traditional process procedure,making the technology cost-effective in production.This technology represents a key enabler for the use of low-cost RTM processes for high-temperature resins to supplant prepreg as the building-block material of choice for aeronautical composite structures.展开更多
Ordered epitaxial ZrO2 films were grown on Pt(111) and characterized by low energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The ...Ordered epitaxial ZrO2 films were grown on Pt(111) and characterized by low energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The films were prepared by vapor deposition of zirconium in an O2 atmosphere followed by annealing under ultra high vacuum. At low coverages, the films grew as discontinuous two-dimentional islands with ordered structures. The size and structure of these islands were dependent on the coverage of ZrO2 films. At coverage <0.5 monolayer (ML), ( 19^(1/2) × 19^(1/2)) R23.4° and (5×5) structures coexisted on the surface. As the coverage increased, the (19^(1/2) × 19^(1/2) ) R23.4° structure developed with increasing degree of long-range order, while the (5×5) structure gradually faded. When the coverage reached >6 ML, a continuous ZrO2(111) film was formed with a (1×1) surface LEED pattern coexisting with a (2×2) pattern. These ordered thin ZrO2 films provide good model surfaces of bulk ZrO2 and can be used for further fundamental studies of the surface chemistry of ZrO2 using modern surface science techniques.展开更多
哥特复兴风格19世纪40年代,对哥特艺术极为狂热的英国建筑师普金接受了什鲁斯伯里伯爵(the Earl of Shrewsbury)的委托,为之设计著名的奥尔顿塔(Alton Towers),这是一座哥特式大厦,普金为该建筑设计制作了这块极富装饰性的瓷砖艺术品。...哥特复兴风格19世纪40年代,对哥特艺术极为狂热的英国建筑师普金接受了什鲁斯伯里伯爵(the Earl of Shrewsbury)的委托,为之设计著名的奥尔顿塔(Alton Towers),这是一座哥特式大厦,普金为该建筑设计制作了这块极富装饰性的瓷砖艺术品。作品表面的图案以中心的三捆小麦与周围的两重边框为设计主题。展开更多
Wrinkling and buckling of nano-films on the compliant substrate are always induced due to thermal deformation mismatch.This paper proposes effective means to control the surface wrinkling of thin film on the compliant...Wrinkling and buckling of nano-films on the compliant substrate are always induced due to thermal deformation mismatch.This paper proposes effective means to control the surface wrinkling of thin film on the compliant substrate,which exploits the curvatures of the curve cracks designed on the stiff film.The procedures of the method are summarized as:1)curve patterns are fabricated on the surface of PDMS(Polydimethylsiloxane)substrate and then the aluminum film with the thickness of several hundred nano-meters is deposited on the substrate;2)the curve patterns are transferred onto the aluminum film and lead to cracking of the film along the curves.The cracking redistributes the stress in the compressed film on the substrate;3)on the concave side of the curve,the wrinkling of the film surface is suppressed to be identified as shielding effect and on the convex side the wrinkling of the film surface is induced to be identified as inductive effect.The shielding and inductive effects make the dis-ordered wrinkling and buckling controllable.This phenomenon provides a potential application in the fabrication of flexible electronic devices.展开更多
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2010CB631100)
文摘This article describes the efforts that led to the development of surface-loaded preforms that may be used to significantly improve the compression-after-impact strength of high-temperature composites and correspondingly to dramatically reduce the area of damage because of impact.Moreover,by matching the toughening polymer surface-loaded and design of the surface pattern,in-plane mechanical properties are unaffected or even improved over laminates made from the identical materials.The proprietary preforms,so-called ESTM-Fabrics,may be handled and infused with the high-temperature RTMable resins such as bismaleimide and polyimide in exactly the same manner as traditional fabrics without surface modification.The RTM conditions for the preform-based toughening is fully compatible with the traditional process procedure,making the technology cost-effective in production.This technology represents a key enabler for the use of low-cost RTM processes for high-temperature resins to supplant prepreg as the building-block material of choice for aeronautical composite structures.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP, 200803580012)the National Natural Science Foundation of China (20873128)+2 种基金the Program for New Century Excellent Talents in University (NCET)the National Basic Research Program of China (2010CB923302)the Hundred Talents Program of the Chinese Academy of Sciences
文摘Ordered epitaxial ZrO2 films were grown on Pt(111) and characterized by low energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS). The films were prepared by vapor deposition of zirconium in an O2 atmosphere followed by annealing under ultra high vacuum. At low coverages, the films grew as discontinuous two-dimentional islands with ordered structures. The size and structure of these islands were dependent on the coverage of ZrO2 films. At coverage <0.5 monolayer (ML), ( 19^(1/2) × 19^(1/2)) R23.4° and (5×5) structures coexisted on the surface. As the coverage increased, the (19^(1/2) × 19^(1/2) ) R23.4° structure developed with increasing degree of long-range order, while the (5×5) structure gradually faded. When the coverage reached >6 ML, a continuous ZrO2(111) film was formed with a (1×1) surface LEED pattern coexisting with a (2×2) pattern. These ordered thin ZrO2 films provide good model surfaces of bulk ZrO2 and can be used for further fundamental studies of the surface chemistry of ZrO2 using modern surface science techniques.
文摘哥特复兴风格19世纪40年代,对哥特艺术极为狂热的英国建筑师普金接受了什鲁斯伯里伯爵(the Earl of Shrewsbury)的委托,为之设计著名的奥尔顿塔(Alton Towers),这是一座哥特式大厦,普金为该建筑设计制作了这块极富装饰性的瓷砖艺术品。作品表面的图案以中心的三捆小麦与周围的两重边框为设计主题。
基金supported by the National Basic Research Program of China(Grant Nos.2010CB631005 and 2011CB606105)the National Natural Science Foundation of China(Grant Nos.11232008,91216301,11072125 and 11272175)Tsinghua University Initiative Scientific Research Program
文摘Wrinkling and buckling of nano-films on the compliant substrate are always induced due to thermal deformation mismatch.This paper proposes effective means to control the surface wrinkling of thin film on the compliant substrate,which exploits the curvatures of the curve cracks designed on the stiff film.The procedures of the method are summarized as:1)curve patterns are fabricated on the surface of PDMS(Polydimethylsiloxane)substrate and then the aluminum film with the thickness of several hundred nano-meters is deposited on the substrate;2)the curve patterns are transferred onto the aluminum film and lead to cracking of the film along the curves.The cracking redistributes the stress in the compressed film on the substrate;3)on the concave side of the curve,the wrinkling of the film surface is suppressed to be identified as shielding effect and on the convex side the wrinkling of the film surface is induced to be identified as inductive effect.The shielding and inductive effects make the dis-ordered wrinkling and buckling controllable.This phenomenon provides a potential application in the fabrication of flexible electronic devices.
