Viscoelastic wave propagation in the viscoelastic single walled carbon nanotubes based on nonlocal strain gradient theory

In this paper, the viscoelastic wave propagation in an embedded viscoelastic single-walled carbon nanotube (SWCNT) is studied based on the nonlocal strain gradient theory. The characteristic equation for the viscoelastic wave in SWCNTs is derived. The emphasis is placed on the influence of the tube diameter on the viscoelastic wave dispersion. A blocking diameter is observed, above which the wave could not propagate in SWCNTs. The results show that the blocking diameter is greatly dependent on the damping coefficient, the nonlocal and the strain gradient length scale parameters, as well as the Winkler modulus of the surrounding elastic medium. These findings may provide a prospective application of SWCNTs in nanodevices and nanocomposites.     

NH3在硼纳米管表面吸附的密度泛函理论研究

利用密度泛函理论研究了NH₃在完整和含有缺陷的硼纳米管上的吸附行为以及相关电子性质. 计算结果表明, 对于α硼纳米管, 在不同的直径和手性条件下, NH₃均倾向于吸附在配位数为6的顶位上. 电子结构计算结果表明, NH₃能够吸附在纳米管表面主要是由于N和B原子产生了较强的相互作用. 表明硼纳米管是一种潜在的NH₃气气敏材料.     

复合材料柔软性对倒金字塔微结构阵列传感器性能的影响

采用模压成型方法制备了2种柔软性不同的热塑性聚氨酯/短切碳纤维/碳纳米管(TPU/SCF-CNT)复合材料复制物, 其表面上具有倒金字塔微结构阵列, 内部有SCF与CNT共同构成的导电通路. 将复合材料复制物和相应的复合材料平整片封装成柔性传感器. 结果表明, 压力作用下传感器内复制物和平整片之间的接触电阻因倒金字塔底棱的形变而显著降低. 对使用柔软性较高的复合材料封装的传感器, 虽然其相对迟滞稍大, 但压力作用下倒金字塔底棱形变量较大, 且复制物和平整片内导电通路增加量较大, 因此其在0~2.5 kPa的线性区内具有较高的灵敏度(0.32 kPa^?1). 制备的2种传感器均具有快速响应特性, 且能在500 s(约1580次)的循环压缩/释放测试(峰值压力约3 kPa)中保持较稳定的电阻响应. 研究表明, 利用模压成型的表面倒金字塔结构复合材料复制物封装成的柔性压力传感器具有良好的传感性能.     

Barium Titanate-reinforced Acrylonitrile-Butadiene Rubber: Synergy Effect of Carbon-based Secondary Filler

Acrylonitrile rubber(NBR) composites filled with barium titanate(BT) were prepared using an internal mixer and a two-roll mill. Also, a secondary filler, namely carbon nanotubes(CNT), was added in order to find a potential synergistic blend ratio of BT and CNT. The cure characteristics, tensile and dielectric properties(dielectric constant and dielectric loss) of the composites were determined. It was found that NBR/BT composites with CNT secondary filler, at a proper BT:CNT ratio, exhibited shorter scorch time(t_(s1)) and cure time(t_(c90)) together with superior tensile properties and reinforcement efficiency, relative to the one with only the primary filler. In addition, the NBR/BT-CNT composite with 80 phr BT and 1-2 phr CNT had dielectric constant of 100-500, dielectric loss of 12-100 and electrical conductivity below 10~(-4) S/m together with high thermal stability. Thus, with a proper BT:CNT mix and filler loading, we can produce mechanically superior rubber composites that are easy to process and low-cost, for flexible dielectric materials application.     

基于碳纳米管分子封装的一维电子波函数扫描

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．     

Investigating the effect of interphase and surrounding resin on carbon nanotube free vibration behavior

The free vibration analysis of a carbon nanotube (CNT) embedded in a volume element is performed using 3D finite element (FE) and analytical models. Three approaches consist of molecular and continuum mechanics FE methods and continuum analytical method are employed to simulate the CNT, interphase region and surrounding matrix. The bonding between CNT and polymer is treated as non-perfect bonding using van der Waals and triple phase material interaction in first and second approaches. In analytical approach a perfect bonding is assumed between nanotube and matrix. First, natural frequencies of CNT under different boundary conditions and aspect ratios are obtained by three approaches and the results are compared with published data. The results show the frequency response variations of CNT in GHz to THz range. Subsequently, vibration behaviors of CNT/polymer are evaluated and the results revealed the importance of interphase region role in the performance of nanocomposites. The results also showed the convergence of the natural frequencies for 1–2.5% of CNT volume in high aspect ratios using three methods, so that the interphase effects is negligible. In addition, it is observed that the molecular method due to interphase role has proper performance in vibration behavior investigation of volume elements.     

Ferrimagnetic behaviors in a double-wall cubic metal nanotube

A double-wall cubic metal nanotube consists of the ferromagnetic spin-1 inner shell and spin-3/2 surface shell. It is of the ferrimagnetic exchange coupling between two shells. Considering the single-ion anisotropy and transverse field exist together, the magnetization, the initial susceptibility, the internal energy and the specific heat have been investigated by using the effective-field theory with correlations. Some interesting phenomena have been found in the thermal variations of the system. Magnetization appears two or three compensation points in certain parameters. It is an unconventional ferrimagnetic behavior in the nanotube. The shapes of total magnetization and the initial susceptibility are great influenced by the surface exchange coupling, surface single-ion anisotropy and surface transverse field. Some results of nanotube may have potential applications in different research fields, such as electronics, optics, mechanics, and even biomedicine and molecular devices.     

A Non‐Enzymatic Hydrogen Peroxide Sensor Based on Gold Nanoparticles/Carbon Nanotube/Self‐Doped Polyaniline Hollow Spheres

In this study, a novel non‐enzymatic hydrogen peroxide (H₂O₂) sensor was fabricated based on gold nanoparticles/carbon nanotube/self‐doped polyaniline (AuNPs/CNTs/SPAN) hollow spheres modified glassy carbon electrode (GCE). SPAN was in‐site polymerized on the surface of SiO₂ template, then AuNPs and CNTs were decorated by electrostatic absorption via poly(diallyldimethylammonium chloride). After the SiO₂ cores were removed, hollow AuNPs/CNTs/SPAN spheres were obtained and characterized by transmission electron microscopy (TEM), field‐emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The electrochemical catalytic performance of the hollow AuNPs/CNTs/SPAN/GCE for H₂O₂ detection was evaluated by cyclic voltammetry (CV) and chronoamperometry. Using chronoamperometric method at a constant potential of ?0.1 V (vs. SCE), the H₂O₂ sensor displays two linear ranges: one from 5 µM to 0.225 mM with a sensitivity of 499.82 µA mM^?1 cm^?2; another from 0.225 mM to 8.825 mM with a sensitivity of 152.29 µA mM^?1 cm^?2. The detection limit was estimated as 0.4 µM (signal‐to‐noise ratio of 3). The hollow AuNPs/CNTs/SPAN/GCE also demonstrated excellent stability and selectivity against interferences from other electroactive species. The sensor was further applied to determine H₂O₂ in disinfectant real samples.     

Phenylboronate‐diol crosslinked polymer/SWCNT hybrid gels with reversible sol–gel transition

This work demonstrates the successful incorporation of functionalized single‐walled carbon nanotubes (f‐SWCNTs) into the phenylboronate‐diol crosslinked polymer gel to create a hybrid system with reversible sol–gel transition. The phenylboronic acid‐containing and diol‐containing polymers were first separately prepared by the reversible addition–fragmentation chain transfer polymerization. Covalent functionalization of single‐walled carbon nanotubes (SWCNTs) with an azide‐derivatized, diol‐containing polymer was then accomplished by a nitrene addition reaction. Subsequently, the hybrid gels were prepared by crosslinking the mixture of f‐SWCNTs and diol‐containing polymer with the phenylboronic acid‐containing polymer. The hybrid gel has been characterized by scanning electron microscopy (SEM) and rheological analysis. The SEM measurement demonstrated a homogeneous dispersion of f‐SWCNTs within the gel matrices. Rheological experiments also demonstrated that the hybrid gel exhibited storage moduli significantly higher than those of the native gel obtained from the phenylboronic acid‐containing and diol‐containing polymers. The hybrid gel can be switched into their starting polymer (f‐SWCNTs) solutions by adjusting the pH of the system. Moreover, the hybrid gel revealed a self‐healing property that occurred autonomously without any outside intervention. By employing this dynamic character, it is possible to regenerate the used gel, and thus, it has the potential to perform in a range of dynamic or bioresponsive applications Copyright © 2013 John Wiley & Sons, Ltd.     

单壁碳纳米管上毒性苯气体净化的分子模拟(英文)

采用巨正则系综蒙特卡罗(GCMC)方法研究了空气中微量苯组分在单臂碳纳米管(SWNTs)上的吸附净化.模拟表明,具有较大孔径的(20,20)纳米管比较适合吸附纯苯蒸汽,而对于移除空气中的毒性苯物质,苯的吸附选择性分别在(12,12)纳米管及4.0 MPa时和(18,18)纳米管及0.1 MPa时出现最小值和最大值.为了解释这一异常行为,我们进一步分析了N2-O2-C6H6混合物的局部密度分布、吸附分子构型和概率密度分布,发现(18,18)纳米管内外完全被苯分子占据,而对于(12,12)纳米管,由于存在更强的吸附质-吸附剂相互作用,空气分子更倾向于吸附在管与管之间的间隙.此外,吸附分子的空间有序参数表明大多数苯分子采取"平躺"在纳米管表面的定位,而线性的N2和O2分子则多数平行于孔轴方向.最后研究了温度和苯分子主体相浓度对分离效果的影响.我们发现较大孔中的选择性随着温度的增加比小孔下降更加明显.与此对比,主体相苯浓度对小孔中的选择性起到更加重要的作用.