Nano

The interface behavior may significantly influence the mechanical properties of carbon nanotube (CNT)-reinforced composites due to the large interface area per unit volume at the composite. The modeling of CNT/polymer interfaces has been a challenge in the continuum modeling of CNT-reinforced composites. This paper presents a review of recent progress to model the CNT/matrix interfaces via a cohesive law established from the van der Waals force. A simple, analytical cohesive law is obtained from the inter-atomic potential, and is used to study the effect of CNT/matrix interfaces on the macroscopic properties of CNT-reinforced composites.

An electrostatic-force-directed-assembly technique was used to coat multiwalled carbon nano-tubes (MWCNTs) with aerosol Ag nanoparticles produced from a mini-arc plasma source. The deposition of Ag nanoparticles onto CNTs was confirmed by transmission electron microscopy (TEM), high-resolution TEM, scanning electron microscopy, and X-ray photoelectron spectroscopy. Ripening of Ag nanoparticles on CNTs was observed via successive TEM imaging after heating the nanoparticle–nanotube hybrid structures in air to three different temperatures ranging from 100°C to 300°C. With temperatures at and above 200°C, the areal density of Ag nanoparticles decreased and the average particle size increased. In particular, migration and coalescence of Ag nanoparticles have been observed at this relatively low temperature, which suggests a van der Waals nanoparticle–nanotube interaction.

Several single-walled carbon nanotubes (SWCNTs) prepared by different methods have been used to investigate the material dependence on the optimal film performance of flexible transparent conducting films. The nanotubes were dispersed in water with sodium dodecyl sulfate by sonication. These SWCNT solutions were then sprayed onto the Poly(ethylene terephthalate) substrate by a spray coater to form the film. Several factors such as purity, diameter, defects, metallicity, and degree of dispersion were evaluated individually to examine how they affect the film performance. We found that the metallicity of SWCNTs and the degree of dispersion are the most crucial factors in determining the film performance. We also proposed a material quality factor to estimate the material quality of SWCNTs as a figure of merit for the film performance.

In this communication, we report the synthesis of an amino-functionalized ionic liquid (AFIL) and its application as building block in the construction of new functional nanomaterials. This AFIL has been used as surfactant in the synthesis of gold nanoparticles (Au NPs) and in the development of functional CNTs/IL hybrid nanomaterials by mixing the AFIL with multi-walled carbon nanotubes (MWCNTs). The presence of an amine group in the ionic liquid provides to the resultant nanomaterial with new opportunities in several applications in the nanobio field.

A continuum model is developed based on the van der Waals interactions to study the adhesion between multi-wall carbon nanotubes (MWCNT) and substrates. Simple, analytical expressions for the binding energy and pulling force are obtained in terms of the MWCNT radius, number of walls, and parameters in the van der Waals potential. For a 1 cm by 1 cm template with densely packed MWCNTs (50 nm in spacing), the total pulling force can reach 26.6 N and 21.9 N for the graphite and polyethylene substrates, respectively.

Calculations have been made for carbon nanotubes containing substitutional nitrogen impurity atoms using ab initio density functional theory. It is found that the distribution of N atoms depends upon the chirality and diameter of the tube. When two nitrogen atoms are introduced into the (5, 5), (6, 6) and (7, 4) tubes, nitrogen atoms prefer to be adjacent to each other along the circumference, while they tend to be far from each other in other carbon nanotubes. As more nitrogen atoms are incorporated, they prefer to be localized, leading to the broken N–N bond and the interstice is formed in the thin tubes. However, for thick tubes, nitrogen atoms tend to distribute uniformly. It is the finding in this work that the high radial stress plays an important role in nitrogen atom distribution for the thin tubes. For thin N-doped tubes, the major contribution to the structural stabilization comes from the radial stress release after the N–N bond is broken.

Self-organized extremely small Ti nanodots have been formed in the subsurface of SiO₂ by implantation of isotopic ⁴⁸Ti⁺ at a kinetic energy of 9 keV into (0001) Z-cut quartz, followed by a vacuum annealing process. Transmission electron microscopy (TEM) images show that the Ti nanodots have a two-dimensional distribution, i.e., a uniform size as small as 3.8 nm and relatively uniform positions with nearly constant inter-particle spacing of ~ 1.5 nm. A mechanism for the two-dimensional spatial distribution and the inhibition of chemical reactions between Ti and SiO₂ is discussed.

Strontium tungstate nanorods with uniform morphology were controllably synthesized for the first time via a facile liquid–solid–solution (LSS) process through oil/water interface. These nanorods have diameters of about 50 nm and length of about 500 nm. XRD curves indicated that as-obtained nanorods were body-centered tetragonal phases with lattice parameters of a = 5.416 Å and c = 11.95 Å, which is consistent with the values reported in JCPDS card No. 08-0490. Study on the optical properties of as-obtained nanorods showed that SrWO₄ nanorods possess different optical properties from bulk counterpart. A mechanism of the formation process was also discussed.