共查询到19条相似文献,搜索用时 140 毫秒
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提出了透射电子显微镜(TEM)纳米云纹法的新技术,首次将该方法用于单根单壁碳纳米管的残余变形测量。纳米云纹由计算机显示器扫描线与碳纳米管束TEM图像干涉而成。该方法具有纳米级空间分辨率,可直接测量碳纳米管的力学性能。对TEM纳米云纹法的原理进行了详细的阐述,并利用不同管径的单壁碳管束产生了云纹。对直径为7.5nm的弯曲碳管束的残余变形进行测量,直接得到了其中一根直径为1.0nm的单壁碳管的残余变形场。实验结果证明了该方法的可行性。该方法为纳米尺度的碳管力学性能测量提供了新途径。 相似文献
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本文采用分子动力学模拟方法研究了Si表面间单壁水平碳纳米管束SWCNT (10,10)的变形和摩擦特性.系统在弛豫平衡后,首先对碳纳米管束施加压力至碳纳米管或Si表面结构破坏.之后在无压力和高压力两种情况下使上表面沿水平方向做剪切运动以研究碳纳米管束的摩擦特性.结果表明,由于碳纳米管的柔韧性,碳纳米管束在加载过程中出现明显变形,但直至3.8 GPa高压下并无结构破坏.系统无压力时SWCNT (10,10)在原地轻微随机滚动,压力为3.8 GPa时,碳纳米管束出现了整体的轻微滑动,同时伴随无规律的轻微滚动,
关键词:
碳纳米管束
摩擦
分子动力学模拟 相似文献
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对于颗粒物质,在锥形通道的窄口处容易发生堵塞现象,实验中通常利用机械振动进行疏通.而对于无孔不入的水却不同,即使在纳米尺度的碳纳米管中仍然可以快速通透.本文利用分子动力学模拟研究了由锥形碳纳米管与石墨烯平面构成的无阀纳米泵,发现水输运在一定条件下也会出现反常堵塞.与颗粒物质截然不同的是振动方法无法恢复水流,相反,它促使水在纳米水泵的通道窄口处发生堵塞.通过分析堵塞区水的密度分布、氢键寿命、水分子的结构特征,揭示了反常堵塞是由腔体中振动膜的高频振动引发水的结构相变造成的. 相似文献
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碳纳米管管腔作为分子物质的纳米通道,其储存或输送水的能力具有重要研究价值.为了研究碳纳米管管腔受限空间对水分子团簇结构和分布的影响,本文采用分子动力学方法探究了管径、手性和温度对单壁碳纳米管管腔内水的结构和分布的影响.结果表明:在常温下,管径尺寸范围为1.018—1.253 nm的单壁碳纳米管管内易形成有序的多元环水结构,此范围以外碳纳米管管内难以形成水的有序结构;且随着管径尺寸增大,多元环水呈现由三元环至六元环的结构变化;范德瓦耳斯势分布分析表明,在上述管径范围内,水分子趋向于贴近碳纳米管管壁分布而形成水的有序结构.对比管径尺寸差别较小的碳纳米管,其手性对多元环水结构影响不大.多元环水结构的稳定性表现出温度依赖性,管径较大的碳纳米管内的多元环水的有序结构更易随温度升高而消失. 相似文献
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In this paper we present some simulation results about the behaviour
of water molecules inside a single wall carbon nanotube (SWNT). We
find that the confinement of water in an SWNT can induce a wave-like
pattern distribution along the channel axis, similar phenomena are
also observed in biological water channels. Carbon nanotubes(CNTs)
can serve as simple nonpolar water channels. Molecular transport
through narrow CNTs is highly collective because of tight hydrogen
bonds in the protective environment of the pore. The hydrogen bond
net is important for proton and other signal transports. The average
dipoles of water molecules inside CNTs (7,7), (8,8) and (9,9) are
discussed in detail. Simulation results indicate that the states of
dipole are affected by the diameter of SWNT. The number of hydrogen
bonds, the water--water interaction and water--CNT interaction are
also studied in this paper. 相似文献
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In this work, the electronic properties of the system composed by the CO molecules adsorbed on Ti-coated single-wall carbon nanotubes (SWNTs) are studied through first principles calculations. The changes in the electronic properties of the interaction of the CO molecules with a linear Ti wire covering an (8, 0) semiconductor SWNT are analyzed for different CO concentrations. A strong interaction between CO molecules and the SWCT/Ti system is observed, which decreases when the concentration of CO molecules increases. The resulting system are shown to be very sensitive to the CO concentration adsorbed on the tube/Ti system, making that the SWNT, which is originally semiconductor and becomes metallic after Ti covering, to recover the semiconductor behavior again when enough high concentrations of CO molecules is adsorbed on the SWNT/Ti system. These three distinct steps (semiconductor/metallic/semiconductor) constitute the basis for a feasible, flexible and efficient sensor device for CO molecule recognition. 相似文献
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The motion and equilibrium distribution of water molecules adsorbed inside neutral and negatively charged singlewalled carbon nanotubes (SWNTs) have been studied using molecular dynamics simulations (MDSs) at room temperature based on CHARMM (Chemistry at HARvard Molecular Mechanics) potential parameters. We find that water molecules have a conspicuous electropism phenomenon and regular tubule patterns inside and outside the charged tube wall. The analyses of the motion behaviour of water molecules in the radial and axial directions show that by charging the SWNT, the adsorption efficiency is greatly enhanced, and the electric field produced by the charged SWNTs prevents water molecules from flowing out of the nanotube. However, water molecules can travel through the neutral SWNT in a fluctuating manner. This indicates that by electrically charging and uncharging the SWNTs, one can control the adsorption and transport behaviour of polar molecules in SWNTs for using as a stable storage medium or long transport channels. The transport velocity can be tailored by changing the charge on the SWNTs, which may have a further application as modulatable transport channels. 相似文献
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《中国物理 B》2015,(7)
A novel nanoscale watermill for the unidirectional transport of water molecules through a curved single-walled carbon nanotube(SWNT) is proposed and explored by molecular dynamics simulations. In this nanoscale system, a revolving charge is introduced to drive a water chain confined inside the SWNT, the charge and the tube together serving as a nano waterwheel and nano engine. A resonance-like phenomenon is found, and the revolving frequency of the charge plays a key role in pumping the water chain. The water flux across the SWNT increases with respect to the revolving frequency of the external charge and it reaches its maximum when the frequency is 4 THz. Correspondingly, the number of hydrogen bonds in the water chain inside the SWNT decreases dramatically as the frequency increases from 4 THz to 25 THz. The mechanism behind the resonance phenomenon has been investigated systematically. Our findings are helpful for the design of nanoscale fluidic devices and energy converters. 相似文献
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The chemical reactivity of carbon nanotubes in H2SO4 is investigated using individual, single-walled carbon nanotubes (SWNTs) incorporated into electronic devices. Exploiting the device conductance as a sensitive indicator of chemical reactions, discrete oxidation and reduction events can be clearly observed. During oxidation, a SWNT opens circuits to a nanometer-scale tunnel junction with residual conduction similar to Frenkel-Poole charge emission. When electrochemically reduced, a SWNT returns to its original conductance. This redox cycle can be repeated many times, suggesting a novel chemical method of reversibly switching SWNT conductivity. 相似文献
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Distinctive optical properties of single-wall carbon nanotubes (SWNT) are highly sensitive to variations in the environment.
Here, we have studied SWNT in aqueous suspensions at a low (less than 0.1 μg ml−1) concentration by four-wave mixing (FWM) spectroscopy in the spectral bands of 0.1 to 10 cm−1 (≈300 GHz) and 100 to 250 cm−1 (3 to 7.5 THz). We directly investigated the hydration layers around SWNT. A comparison of the FWM spectra of an SWNT aqueous
suspension and Milli-Q water shows a considerable increase in the intensity of low-frequency Raman modes, which are attributed
to the rotational transitions of H2O2 and H2O molecules. We explain the observed phenomenon by the hydrogen peroxide production and formation of a low-density depletion
layer at the water-nanotube interface. We have observed several SWNT radial breathing modes ω
RBM =118.5, 164.7, and 233.5 cm−1 in an SWNT aqueous suspension and estimated the corresponding SWNT diameters as ≈2.0, 1.5, and 1 nm. 相似文献
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K. Bladh L.K.L. Falk F. Rohmund 《Applied Physics A: Materials Science & Processing》2000,70(3):317-322
The production of single-walled carbon nanotubes (SWNT) by catalytic disproportionation of carbon monoxide on iron particles in the gas phase was studied. The addition of hydrogen to the reactants was found to increase the SWNT yield relative to the competing formation of encapsulated iron particles. Adding acetylene, however, did not result in a significant change of the SWNT growth but gave rise to the formation of unwanted self-pyrolysis products. Iron particles are seen to decorate the SWNT and are shown to be single crystalline with several layers of encapsulation by graphitic carbon. All these observations are discussed with respect to the catalytic growth mechanism of SWNT and encapsulated metal particles from CO and hydrocarbon molecules. 相似文献
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利用第一性原理,设计并研究了一类基于单臂碳纳米管的分子封装的分子体系.计算表明,半环葫芦脲类化合物可有效封装碳纳米管,引入微弱的分子间相互作用,对碳纳米管的电子态能级结构分布
仅带来微弱影响.半环葫芦脲分子与碳纳米管在管径方向的一维电子态波函数充分耦合,进而有效改变了一些前沿分子轨道的波函数在管径两头的分布以及相应的电子布居浓度.基于电子输运的模拟,发现半环葫芦脲分子在碳纳米管一维方向滑动时的某个电压下的电导变化可准确反映电子态波函数在相应分子导电通道上的一维分布信息. 相似文献
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Titanium-decorated carbon nanotubes as a potential high-capacity hydrogen storage medium 总被引:1,自引:0,他引:1
We report a first-principles study, which demonstrates that a single Ti atom coated on a single-walled nanotube (SWNT) binds up to four hydrogen molecules. The first H2 adsorption is dissociative with no energy barrier while the other three adsorptions are molecular with significantly elongated H-H bonds. At high Ti coverage we show that a SWNT can strongly adsorb up to 8 wt % hydrogen. These results advance our fundamental understanding of dissociative adsorption of hydrogen in nanostructures and suggest new routes to better storage and catalyst materials. 相似文献