Carbon nanotubes template technique

Bando and co-workers271 have prepared BN nanolubes by the reaction of MgO, FeO and B in the presence of NH, at 1400 °C. Reaction of boric acid or B20, with N2 or NH, at high temperatures in the presence of carbon or catalytic metal particles has been employed in the preparation of BN nanotubes.2 2 Boron nitride nanotubes can be grown directly on substrates at 873 K by a plasma-enhanced laser-deposition technique.172 Recently, GaN nanotube brushes have been prepared using amorphous carbon nanotubes templates obtained using AAO membranes.274... 

By applying the template technique, Kyotani et al. and Che et al. succeeded in preparing Pt and Pt/Ru metal-filled uniform carbon nanotubes in which the metal is present as either nanorods or nanoparticles. It should be noted that no metal was observed on the outside wall of the tubes. This is due to the preparation procedure, in which the metal precursor was loaded into the carbon-deposited alumina film before the dissolution of alumina by HF (see Fig. 10.1.9). Thus, there is no other space for metal to be loaded except in the channels. 

Encapsulation of other material into carbon nanotubes would also open up a possibility for the applications to electrodevices. By applying the template method, perfect encapsulation of other material into carbon nanotubes became possible. No foreign material was observed on the outer surface of carbon nanotubes. The metal-filled uniform carbon nanotubes thus prepared can be regarded as a novel onedimensional composite, which could have a variety of potential applications (e.g novel catalyst for Pt metal-filled nanotubes, and magnetic nanodevice for Fe304-filled nanotubes). Furthermore, the template method enables selective chemical modification of the inner surface of carbon nanotubes. With this technique, carbon... 

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... 

Pyramidal pits of 20 mn were formed at the surface of annealed Al. This technique allowed us to form an individual carbon nanotube (CNT) in PAA template. CNT deposition was performed by commonly used PECVD process. Also, we formed the arrays of vertically aligned CNT in PAA with cathodically deposited and evaporated metal catalyst. 

Zhong, D.Y., Liu, S., Wang, E.G., 2003. Patterned growth of coiled carbon nanotubes by a template-assisted technique. Appl. Phys. Lett. 83, 4423—4425. 

Carbon nanotubes can be readily dispersed in a solvent using ultrasound. However, because of a strong van der Waals forces, they can quickly aggregate and precipitate. This problem can be alleviated by various pretreatments. For example, Table 5 shows the effect of HNO3 on properties of nanotubes. An increase in the content of carboxylic, lactone and hydroxyl groups was noted. At the same time, the total amount of base was decreased to zero. However, the CNT prepared by the template technique could be dispersed in water without requiring any pretreatment. °... 

V. Paunov and M in het Panhuis, Fabrication of carbon nanotube-based microcap>sules by a colloid templating technique. Nanotechnology, 16,1522-1525 (2005). 

Very recently, experimentalists have succeeded in developing template-based chemical vapor deposition CVD),[30] and pyrolysis of organometallic precursor with nickelocene and thiophene techniques[31] that allows for the reproducible and high-yield fabrication of carbon nanotube Y-junctions.[30, 31] The conductance measurements on these Y-j unctions have shown intrinsic rectifying I-V behavior at room temperature.[31, 32)... 

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