Anyuan Cao

Adsorption of fluoride from water by amorphous alumina supported on carbon nanotubes

A new candidate for fluoride adsorption from water, amorphous Al2O3 supported on carbon nanotubes (Al2O3/CNTs), is reported in this Letter. The adsorption isotherms show that the best fluoride adsorption of Al2O3/CNTs occurs at a pH range of 5.0-9.0. The adsorption capacity for Al2O3/CNTs is about 13.5 times higher than that of AC-300 carbon, 4 times higher than that of gamma-Al2O3 at equilibrium fluoride concentration of 12 mg/l. The broad range of the pH values and high adsorption capacity of Al2O3/CNTs make it very suitable for potential applications in fluoride removal from water

Hydrogen storage of dense-aligned carbon nanotubes

Abstract It has been considered so far that the inner cavities of carbon nanotubes are the desired place for the storage of hydrogen molecules. Here we show that the inter-nanotube space between densely aligned carbon nanotubes, produced by catalytic pyrolysis of ferrocene, could also contribute to the effective uptake of molecular hydrogen. This provides a new way to improve the properties of carbon nanotubes in storing hydrogen or other elemental molecules.

Vertical aligned carbon nanotubes grown on Au film and reduction of threshold field in field emission

Vertical aligned carbon nanotubes were synthesized on quartz glass and Au film by catalytic decompositon of ferrocene and xylene. Morphological differences between aligned nanotubes grown on the two substrates are studied and discussed through SEM images. Field emission testing shows that aligned nanotubes grown on Au have a lower threshold field than those grown on quartz glass. This reduction of threshold field indicates a new way to improve field emission properties through the selection of a highly conductive growth substrate for carbon nanotubes.

Grapevine-like growth of single walled carbon nanotubes among vertically aligned multiwalled nanotube arrays

Large arrays of self-oriented, multiwalled carbon nanotubes (MWNTs) have been obtained by chemical vapor deposition. It has so far been impossible to translate this idea for growing single walled nanotubes (SWNTs) but we show here that oriented growth of SWNTs among vertically aligned MWNT arrays can be realized by the catalytic pyrolysis of ferrocene and xylene. The MWNTs act as the support structures for SWNTs, forcing them to grow upward steadily, like grapevines. The growth of vertically aligned SWNT over large areas brings about the possibility of exploring their properties in select configurations.

Tandem structure of aligned carbon nanotubes on Au and its solar thermal absorption

Parallel, close-arranged carbon nanotubes are promising candidates for sunlight trapping. A tandem structure was made by synthesizing aligned carbon nanotube arrays on an Au film. With the nanotube length greater than 10 μm, the tandem structure shows an ultra-high absorption in both the visible and infrared regions. With shorter length (less than 5 μm), infrared reflectance is enhanced due to the presence of the underlying Au film; however, the visible absorptance also decreases at the same time. Carbon nanotubes themselves have no selectivity of solar absorption. They could be used in solar thermal plants where sunlight is collected with high concentration ratios.

Aligned carbon nanotube growth under oxidative ambient

Carbon nanotubes (CNTs) are always produced under a reductive ambient with hydrogen present using the chemical vapor deposition method. Oxidative media, such as carbon dioxide and oxygen, could damage the tubular structures by opening the nanotube ends or etching the tube walls. Here we report the synthesis of aligned defective, but clean, CNTs in the presence of water vapor. The tube walls were found broken as well as the tube ends. CNTs with a large amount of exposed broken sites on their tube walls have potential applications in many areas such as energy storage.

Self-organized arrays of carbon nanotube ropes

Abstract Aligned carbon nanotubes (CNTs) distributed uniformly on various substrates have been synthesized by chemical vapor deposition (CVD) method. Here, we report that by first depositing a film of amorphous carbon and random nanotubes, the aligned CNTs can self-organize into arrays of long macroscopic ropes on this film. The ropes have a uniform diameter (within 5∼30 μm ) and their length can reach 0.7 mm in 30 min. The CNTs in each rope are either parallel to or entangled with each other, implying high mechanical strength of these ropes, which have potential applications as a composite enhancer or a high-strength nanostructure.

Synthesis of well-aligned carbon nanotube network on a gold-patterned quartz substrate

A network of carbon nanotubes with high alignment was synthesized on a gold-patterned quartz substrate due to the different growth rates of nanotubes on Au and quartz. Controlled fabrication of nanotube networks on a large area could be realized simply by treating the Au film into a corresponding pattern. This provides a practical way to obtain aligned nanotube networks on combined substrates for further building large-scale functional devices.

Carbon nanotube dendrites: availability and their growth model

Here we report the observation of the carbon nanotube dendrites, in which a carbon nanotube grows up from the outer wall of another one, in the catalytic pyrolytic product of ferrocene. A simple dendrite consists of two nanotubes directly connected with each other, without any foreign particles between them. The dendritic structure is formed due to the continuous feeding of catalyst particles during the nanotube growth process, and the growth model is proposed. Carbon nanotube dendrites are promising candidates of building blocks in nanoscale electronic devices.

Field emission behavior of aligned carbon nanofiber arrays

Aligned carbon nanofiber arrays are synthesized on plain silicon surface by thermal decomposition of propylene with Ni film as the catalyst at 600°C. These arrays consist of carbon nanofibers with uniform diameters and heights, standing vertically on the substrate. TEM examinations show that carbon nanofibers have unique layer structure. These arrays also show excellent field emission properties comparable to those of carbon nanotubes during subsequent testing.