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Electrochemically driven actuation of polypyrrole in aqueous sodium hexafluorophosphate (NaPF6) solution has been shown to produce repeated large strains (>6%) at low voltages and with high conductivity, making it one of the most promising electroactive conducting polymers. Little is known about the voltage dependent stiffness of this version of the polymer. This information is important in determining the strain as a function of load. In this paper the complex Young's modulus (storage and loss components) of a hexafluorophosphate-doped polypyrrole film in aqueous NaPF6 electrolyte at different oxidation states, under various loads and as a function of the frequency of the applied load, is investigated. Uniformity of doping was ensured by allowing enough time to reach steady state charge levels, and the creep during measurements was minimized by using preconditioning cycles. The results of this study show that storage modulus decreases (from 1 GPa to 0.80 GPa) as the polypyrrole oxidation potential increases (from ?0.4 V to +0.4 V versus Ag/AgCl reference electrode). The loss modulus, on the other hand, increases from 55 MPa to 80 MPa. An increasing trend in the Young's modulus is also observed with the applied load. The storage modulus increases from 0.65 GPa to 1 GPa by increasing the applied load from 0.2 MPa to 2.5 MPa. The modulus is found to increase with time through the experiment, which may be due to stretch alignment of the polymer. It is also observed that complex Young's modulus increases in proportion to the logarithm of frequency. 相似文献
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The mechanical actuation of a (5, 5) single-walled carbon nanotube as a result of added charge is simulated using first-principles calculations. It is observed that while both positive and negative charging tend to expand the nanotube in the axial direction for most levels of charge, radial actuation is less even and symmetric with respect to charge. The spin distribution of the additional charges is investigated, and it is predicted that in some cases unpaired spin configurations are energetically favourable, significantly affecting actuation strains. 相似文献
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Hailiang Wang Yongye Liang Tissaphern Mirfakhrai Zhuo Chen Hernan Sanchez Casalongue Hongjie Dai 《Nano Research》2011,4(8):729-736
Supercapacitors operating in aqueous solutions are low cost energy storage devices with high cycling stability and fast charging
and discharging capabilities, but generally suffer from low energy densities. Here, we grow Ni(OH)2 nanoplates and RuO2 nanoparticles on high quality graphene sheets in order to maximize the specific capacitances of these materials. We then
pair up a Ni(OH)2/graphene electrode with a RuO2/graphene electrode to afford a high performance asymmetrical supercapacitor with high energy and power density operating
in aqueous solutions at a voltage of ∼1.5 V. The asymmetrical supercapacitor exhibits significantly higher energy densities
than symmetrical RuO2-RuO2 supercapacitors or asymmetrical supercapacitors based on either RuO2-carbon or Ni(OH)2-carbon electrode pairs. A high energy density of ∼48 W·h/kg at a power density of ∼0.23 kW/kg, and a high power density of
∼21 kW/kg at an energy density of ∼14 W·h/kg have been achieved with our Ni(OH)2/graphene and RuO2/graphene asymmetrical supercapacitor. Thus, pairing up metal-oxide/graphene and metal-hydroxide/graphene hybrid materials
for asymmetrical supercapacitors represents a new approach to high performance energy storage.
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