Nanotubes and Nanowires

Chen and co-workers [14] have produced carbon nanotubes using HEBM. They used graphite as precursor and milled it for about 150 h at ambient temperature, followed by a heat treatment at 1,400 °C for 6 h in a nitrogen atmosphere. The outer diameter of the resulting material was 20 nm. The main contaminants found in these carbon nanotubes were iron and chromium originated from the balls and the inner wall of the steel container. 

These authors also produced SiC nanowires using HEBM. A mixture of silicon monoxide (SiO) and iron (II) phthalocyanine was milled for 100 h. The milling was conducted in a nitrogen atmosphere at 300 kPa at room temperature. After milling, the powder was first heated at 1,000 °C for 30 min, and then the temperature was raised to 1,200 °C for 1 h. During the first annealing, cylindrical, multiwalled CNTs with a diameter of about 15 mn were produced. When the temperature was increased to 1,200 °C, SiC nanowires with a diameter of 40 mn were obtained. 

The role of HEBM on nanotube and nanowire formation could be divided into three effects  

For example, HEBM of graphite powder produces a disordered and nano-porous structure through agglomeration of nanosized particles under ball impacts nucleation. The contaminations from milling act as catalysts to promote nanotube formation during the subsequent annealing. 

HEBM produces smaller grain sizes and higher surface areas. Both contribute to reduce the reaction temperature and to promote higher chemical reactivity in comparison with samples without the milling treatment. 

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For either conventional polycrystalline semiconductors or nanotubes and nanowires to be successful, the development of model and simulation tools that can be used for device and circuit design as well as for predictive engineering must be available. Since these devices are not necessarily based on single wires or single crystals, but rather on an ensemble of particles, the aggregate behavior must be considered. Initial efforts to provide the necessary physical understanding and device models using percolation theory have been reported.64,65... 

Y. Li, Y. Bando, and D. Golberg, Quasi-ahgned single-crystalline W18O49 nanotubes and nanowires, Adv. Mater. 15(15), 1294-1296 (2003). 

Nanowires increase efficiency because they directly deliver the electrons from the interface of the nanowire with the polymer to their electrode, while the electrode holes travel in the opposite direction to the tip of the wire and pass through the very thin polymer layer before reaching their electrode. Earlier carbon nanotube and nanowire designs were not directly connected to their electrodes and therefore did not provide the electrons with a direct path. 

Polyferrocenylsilane Block Copolymers Nanotubes and Nanowires through Self-Assembly... 

C.N.R. Rao and A. Govindaraj, Nanotubes and Nanowires, Royal Society of Chemistry, London, 2005. 

Nanotubes and nanowires of II—VI semiconductor compounds such as CdS and CdSe have been obtained by a soft chemical route involving surfactant-assisted synthesis.28,75 For CdSe nanotubes, the metal oxide was reacted with the selenidizing reagent in the presence of a surfactant such as Triton 1G0X. Substantial amounts of nanotubes were obtained by this method (Fig. 25a and b). Annealing of the as-prepared nano-... 

An exhaustive study has been carried out recently on the synthesis of BN nanotubes and nanowires by various CVD techniques.17 The methods examined include heating boric acid with activated carbon, multi-walled carbon nanotubes, catalytic iron particles or a mixture of activated carbon and iron particles, in the presence of ammonia. With activated carbon, BN nanowires are obtained as the primary product. However, with multi-walled carbon tubes, high yields of pure BN nanotubes are obtained as the major product. BN nanotubes with different structures were obtained on heating boric acid and iron particles in the presence of NH3. Aligned BN nanotubes are obtained when aligned multi-walled nanotubes are used as the templates (Fig. 40). Prior to this report, alignment of BN nanotubes was achieved by the synthesis of the BN nanotubule composites in the pores of the anodic alumina oxide, by the decomposition of 2,4,6-trichloroborazine at 750 °C.116 Attempts had been made earlier to align BN nanotubes by... 

A. Govindaraj obtained his PhD degree from University of Mysore and is a Senior Scientific Officer at the Indian Institute of Science, and Honorary Faculty Fellow at the Jawaharlal Nehru Centre for Advanced Scientific Research. He works on different types of nanomaterials. He has authored more than 100 research papers and co-authored a book on nanotubes and nanowires. 

Rao CNR and Govindaraj A 2005 Nanotubes and Nanowires (London Nanotechnolgy Royal Society of Chemistry)... 

The use of nanoparticles has extended throughout the field of biosensors in the electrochemical detection of DNA and immunoreactions (Murphy 2006). A wide range of nanoparticles including nanotubes and nanowires, prepared from metals, semiconductor, carbon or polymeric species, have been investigated. The enhanced electrochemistry is due to the ability of the small nanoparticles to reduce the distance between the redox site of a protein and the electrode, since the rate of electron transfer is inversely dependent on the exponential distance between them (Balasubramanian and Burghard 2006). CNT-modified electrodes have been most frequently used for the development of biosensors (Gooding 2005). 

Carbon nanotubes (CNTs) were discovered as an electron microscopic marvel in 1991. Since then, there has been intense activity related to the synthesis, structure, properties and applications of CNTs. The discovery of CNTs has triggered much research on other one-dimensional nano-objects such as inorganic nanotubes and nanowires. This chapter covers the highlights of the entire variety of nanotubes and nanowires. 

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