A shape‐memory, fiber‐shaped supercapacitor is developed by winding aligned carbon nanotube sheets on a shape‐memory polyurethane substrate. Despite its flexibility and stretchability, the deformed shapes under ben...
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A shape‐memory, fiber‐shaped supercapacitor is developed by winding aligned carbon nanotube sheets on a shape‐memory polyurethane substrate. Despite its flexibility and stretchability, the deformed shapes under bending and stretching can be “frozen” as expected and recovered to the original state when required. Its electrochemical performances are well‐maintained during deformation, at the deformed state and after the recovery.
We present data on the optical conductivity of URu2−x(Fe,Os)xSi2. While the parent material URu2Si2 enters the enigmatic hidden order (HO) phase below 17.5 K, an antiferromagnetic (AFM) phase is induced by the substit...
We present data on the optical conductivity of URu2−x(Fe,Os)xSi2. While the parent material URu2Si2 enters the enigmatic hidden order (HO) phase below 17.5 K, an antiferromagnetic (AFM) phase is induced by the substitution of Fe or Os onto the Ru sites. We find that both the HO and the AFM phases exhibit an identical gap structure that is characterized by a loss of conductivity below the gap energy with spectral weight transferred to a narrow frequency region just above the gap, the typical optical signature of a density wave. The AFM phase is marked by strong increases in both transition temperature and the energy of the gap associated with the transition. In the normal phase just above the transition the optical scattering rate varies as ω2. We find that in both the HO and the AFM phases, our data are consistent with elastic resonant scattering of a Fermi liquid. This indicates that the appearance of a coherent state is a necessary condition for either ordered phase to emerge. Our measurements favor models in which the HO and the AFM phases are driven by the common physics of a nesting-induced density wave gap.
Crystallizable polymers often form multiple stacks of uniquely oriented lamellae, which have good registry despite being separated by amorphous fold surfaces. These correlations require multiple synchronized, yet unid...
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Crystallizable polymers often form multiple stacks of uniquely oriented lamellae, which have good registry despite being separated by amorphous fold surfaces. These correlations require multiple synchronized, yet unidentified, nucleation events. Here, we demonstrate that in thin films of isotactic polystyrene, the probability of generating correlated lamellae is controlled by the branched morphology of a single primary lamella. The nucleation density ns of secondary lamellae is found to be dependent on the width w of the branches of the primary lamella such that ns∼w−2. This relation is independent of molecular weight, crystallization temperature, and film thickness. We propose a nucleation mechanism based on the insertion of polymers into a branched primary lamellar crystal.
Photoinduced structural change (PSC) is a fundamental excited‐state dynamic process in chemical and biological systems. However, precise control of PSC processes is very challenging, owing to the lack of guidelines f...
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Photoinduced structural change (PSC) is a fundamental excited‐state dynamic process in chemical and biological systems. However, precise control of PSC processes is very challenging, owing to the lack of guidelines for designing excited‐state potential energy surfaces (PESs). A series of rationally designed butterfly‐like phosphorescent binuclear platinum complexes that undergo controlled PSC by Pt–Pt distance shortening and exhibit tunable dual (greenish‐blue and red) emission are herein reported. Based on the Bell–Evans–Polanyi principle, it is demonstrated how the energy barrier of the PSC, which can be described as a chemical‐reaction‐like process between the two energy minima on the first triplet excited‐state PES, can be controlled by synthetic means. These results reveal a simple method to engineer the dual emission of molecular systems by manipulating PES to control PSC.
Nearly all species of modern birds are capable of flight;therefore mechanical competency of appendages and the rigidity of their skeletal system should be optimized. Birds have developed extremely lightweight skeletal...
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ISBN:
(纸本)9781118771396
Nearly all species of modern birds are capable of flight;therefore mechanical competency of appendages and the rigidity of their skeletal system should be optimized. Birds have developed extremely lightweight skeletal systems that help aid in the generation of lift and thrust forces as well as helping them maintain flight over, in many cases, extended periods of time. The humerus and ulna of different species of birds (flapping, flapping/soaring, flapping/gliding, and non-flying) have been analyzed by optical microscopy and mechanical testing. The reinforcing structures found within bones vary from species to species, depending on how a particular species utilizes its wings. Interestingly, reinforcing ridges and struts have been found within certain sections of the bones of flapping/soaring and flapping/gliding birds (vulture and sea gull), while the bones from the flapping bird (raven) and non-flying bird (domestic duck) did not have supporting structures of any kind. The presence of these reinforcing structures increases the resistance to torsion and flexure with a minimum weight penalty, and is therefore of importance in flapping/gliding birds. Vickers hardness testing was performed on the compact section of the bones of all bird species. The data from the mechanical testing were compared with microstructural observations to determine the relevance behind the reinforcing structures and its mechanical and biological role. Finite element analysis was used to model the mechanical response of vulture ulna in torsion.
The ferrum ammonium phosphate/halloysite (FAP/MWCNT) was synthesized and employed in combination with Exolit® OP 1230 to enhance the flame retardancy and mechanical properties of epoxy by chemical crosslinking an...
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ISBN:
(纸本)9781934551165
The ferrum ammonium phosphate/halloysite (FAP/MWCNT) was synthesized and employed in combination with Exolit® OP 1230 to enhance the flame retardancy and mechanical properties of epoxy by chemical crosslinking and doping methods. Energy Dispersive Spectrometer(EDS), Scanning Electron Microscope (SEM), Thermal Gravity Analysis (TGA), micro-scale combustion calorimetry (MCC) and UL-94 were conducted to determine the components, structure and performance of EP/FAP/MWCNT polymer nanocomposites (PNCs). The effects of Fe2+-to-NH4-to-PO43-mole ratio on the composition and yield of FAP/MWCNT and FAP/MWCNT-to-OP 1230-to-epoxy ratio on the mechanical and flame retardancy properties of of PNCs were discussed and optimum conditions of this process were determined. Results of this work show a potential application in the environmental/materialsengineering cross-disciplinary field: wastewater treatment and recycling. Copyright 2014. Used by the Society of the Advancement of Material and Process engineering with permission.
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