Nanotube synthesis methods

Owing to the many possible configurations applicable and several modifiable parameters, the arc method, which can be considered the traditional carbon nanotube synthesis method, has a greater possibility of being improved. 

The direct linking of carbon nanotubes to graphite and the continuity in synthesis, structure and properties between carbon nanotubes and vapor grown carbon fibers is reviewed by the present leaders of this area, Professor M. Endo, H. Kroto, and co-workers. Further insight into the growth mechanism is presented in the article by Colbert and Smalley. New synthesis methods leading to enhanced production... 

Xin and co-workers modified the alkaline EG synthesis method by heating the metal hydroxides or oxides colloidal particles in EG or EG/water mixture in the presence of carbon supports, for preparing various metal and alloy nanoclusters supported on carbon [20-24]. It was found that the ratio of water to EG in the reaction media was a key factor influencing the average size and size distribution of metal nanoparticles supported on the carbon supports. As shown in Table 2, in the preparation of multiwalled carbon nanotube-supported Pt catalysts... 

J.P. Harmon and L.M. Clayton, Polymer/carbon nanotube composites, methods of use and methods of synthesis thereof, US Patent 7 399 794, assigned to University of South Florida (Tampa, FL), July 15, 2008. 

Since the synthesis of carbon nanotubes by Iijima [1, 2], a lot of investigations have been made on this kind of novel material [3-16]. Carbon nanotubes can be conventionally synthesized with several methods [17, 18], Recently, catalytic synthesis method has been developed to prepare carbon nanotubes on Co/Si02 [19, 20]. Hemadi et al. first extended the catalytic synthesis to the use of zeolites (NaY, HY and ZSM-5) as catalyst supports to synthesize carbon nanotubes [21]. 

The advances in nanotechnology and synthesis methods have enabled nanomaterials to be produced in various shapes and structures. Coating of a luminescent layer activated by lanthanide ions on nanoparticles such as SiC>2 or AI2O3 is one of such approaches to develop new nanophosphors. In section 6, we review recent work on interesting spectroscopic features and luminescence dynamics of lanthanide ions in other novel low-dimensional nanostructures including core-shell, one-dimensional (ID) nanowires and nanotubes, two-dimensional (2D) nanofilms, hollow nanospheres, 2D nanosheet and nanodisk which have also attracted extensive attention. 

Our experiment has demonstrated the possibility of the carbon nanotubes synthesis by low temperature (substrate temperature was 500°C) vapor deposition method from the ethanol vapor. Field emission samples were produced with different catalyst distribution on the substrate surface. 

One of the features of the catalysts for production of carbon nanofibers and especially nanotubes consists in a big role of catalyst particle size besides the catalyst chemical composition. The size can not be assigned in advance, and only the change of synthesis method or synthesis condition allows to produce the most active particles. Chemical composition of the catalyst can be changed during pyrolysis. 

Carbon nanotubes represent high potential fillers owing to their remarkably attractive mechanical, thermal and electrical properties. The incorporation of nanotubes in the polymer matrices can thus lead to synergistic enhancements in the composite properties even at very low volume fractions. This chapter provides a brief overview of the properties and synthesis methods of nanotubes for the generation of polymer nanocomposites. 

The synthesis processes for the nanotubes have been continuously refined in the recent years and today, a number of methods are available to synthesize both single and multiwalled carbon nanotubes. These methods include high temperature evaporation using arc-discharge (28-30), laser ablation (31), chemical vapor deposition etc. (32-34). 

A. Loiseau, X. Blase, J.C. Charlier, P. Gadelle, C. Journet, C. Laurent and A. Peigney, Synthesis methods and growth mechanisms, in Understanding Carbon Nanotubes. From Basics to Application, Lecture Notes in Physics 677, Springer, 2006. 

Several main synthesis methods widely applied to produce carbon nanotube-polyurethane nanocomposites were summarized above. In addition, latex technology (27), thermally induced phase separation (28), electrospinning (29,30) and many other methods also show their own advantages and promises, however, these methods will not be discussed here. 

The above analysis takes the synthesis methods, the performance affected by the dispersion of CNTs, enhanced physical properties and the latest applications of carbon nanotube/polyurethane composites described in literature reports as the reference point. In the interest of brevity, this is not a comprehensive review, however, it goes through numerous research reports and applications which have been learned and described in the recent years. Despite that, there are still many opportunities to synthesize new carbon nano-tube/polyurethane systems and to modify carbon nanotubes with new functional groups. The possibility of producing modern biomedical and shape memory materials in that way makes the challenge of the near future. 

In addition, Song et al. (76) used a one-step condensation synthesis method to prepare the PLA-MWCNTnanocomposites. For detailed experimental conditions, refer to Song et al. (76). The nanocomposites were prepared using pure and carboxylic-acid-functionalized MWCNTs. As with the other studies, the carboxylic-acid-functionalized MWCNTs dispersed better in PLA compared with non-functionalized MWCNTs. Overall, it can be inferred from the studies described in this section that the functionalization of MWCNTs is a very important step in the process of making a nanocomposite, as it will help to disperse the nanotubes uniformly, which will eventually create the superior properties of the resulting nanocomposite. In addition, among the currently available methods for functionalization, carboxylic-functionalization is the best for uniform dispersion. 

Synthesis Methods and Structural Properties of Nanotubes/PVA Composites... 

Ortiz et al. have developed and studied a nanocomposite of SnO in a Ti02 nanotube network using a two-step electrochemical synthesis method 230 The Ti02 matrix was fabricated via electrochemical oxidation of a Ti substrate. The Ti02 matrix provides a reasonably conductive substrate for the subsequent electrodeposition of Sn. The conductivity of Ti02 can be further improved... 

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