Catalytic chemical vapor deposition CCVD

CCVD Catalytic chemical vapor deposition. Supported metal catalysts are used 1.5 (1.3-2) Cheapest, commercial, up-scalable. Most feasible from the application point of view... 

Multiwall carbon nanotubes (MWCNTs) have been synthesized by catalytic chemical vapor deposition (CCVD) of ethylene on several mesoporous aluminosilicates impregnated with iron. The aluminosilicates were synthesized by sol-gel method optimizing the Si/Al ratios from 6 to 80. The catalysts are characterized by nitrogen adsorption, X-ray diffraction, 27A1 NMR, thermogravimetric analysis (TGA) and infrared. The MWCNTs are characterized by TGA and transmission and scanning electron microscope. 

The catalytic decomposition of carbon-contaming compounds is an extensively investigated method, also known as catalytic chemical vapor deposition (CCVD). One of the advantages of this method is the potential for large-scale production at a lower energy consumption and overall cost than with other methods. The CCVD method is essentially the same as that used for a long time in the synthesis of other filamentous forms of carbon, such as nanofibers or fibrils. The CCVD method involves the catalytic decomposition of hydrocarbons or carbon monoxide on transition metal particles. The major difference with those processes that produce nanofibers is in the structure of the catalyst. To produce SWNT, the size of the metal cluster needs to be very small. Therefore, the success of a CCVD method lies in the design of the catalyst. 

VAPOR-GROWN CARBON FIBERS (VGCF) AND CATALYTIC CHEMICAL VAPOR-DEPOSITED (CCVD) FILAMENTS... 

The term vapor grown carbon fiber (VGCF) is an International Union of Pure and Applied Chemistry (lUPAC) recommendation and Tibbetts [1] believes that this term has won general acceptance for the class of material where a carbonaceous gas, in the presence of a small metal particle acting as a catalyst, forms a carbon filament. However, Dresselhaus and co-authors [2] use the term CCVD filament in their book, which stands for catalytic chemical vapor deposition and is certainly more descriptive of their mode of preparation, but is, unfortunately, not the generally accepted term. 

Synthesis of CNT over oxides supports by Catalytic Chemical Vapor Deposition (CCVD) is one of the most important techniques for mass production of non-aligned CNT. It could be useful for the production of composite materials, field emission sources, fuel cells, supercapacitors among others technological applications. The CCVD method consists on the decomposition of a gas or a liquid precursor, which supplies carbon to the surface of the catalytic particles (e.g. Fe) in a tube furnace at temperatures around 900 °C. This technique is scalable for mass production at lower temperatures and could be adapted for continuous production. 

The catalytic chemical vapor deposition (CCVD) technique is far more developed and has great potential to be applied industrially. This technique allows for mass production at lower temperatures than the previously described methods and can be adapted for continuous production [69]. This method consists of decomposing a gas or a liquid precursor, which supplies carbon on catalytic particles (Fe, Ni, Co) in a mbe furnace at temperatures between 500 and 1,100 °C (Fig. 5.4). Besides the classic oven, heated by electric heaters, plasma furnaces (PECVD, Plasma-Enhanced Chemical Vapor Deposition) microwaves (nuCTowave, MW-PECVD), or DC (direct current, dc-PECVD) are also used. 

Colomer JF, Stephan C, Lefrant S, Tendeloo GV, Willems 1, Kanya Z, et al. Large-scale synthesis of single-wall carbon nanotubes by catalytic chemical vapor deposition CCVD method. Chem Phys Lett 2000 317 83-9. 

A floating catalyst method, which has been used for the large-scale production of carbon nanotubes, was applied in the synthesis of double-walled BNNTs by Kim et al." Borazine was chosen as the precursor for BN formation because of its chemical composition (1 1 B/N ratio) and high volatility. In this catalytic chemical vapor deposition (CCVD) technique, a mixture of ammonia and nitrogen gas (in a flow ratio of 100 3 sscm), borazine vapor along with a nickelocene catalyst flowed... 

Carbon nanotubes can be synthesized by different techniques including arc-discharge [58,59], laser ablation [60-63] and various catalytic chemical vapor depositions (CCVD) [64-67]. 

Since the reports using the catalytic chemical vapor deposition (CCVD) method for the synthesis of N-CNTs published in 1997 by Yudasaka et al. [32] and Sen et al. [33] and by Terrenes et al. in 1999 [34], CCVD has become the most common and reliable technique to synthesize CNTs and N-CNTs due to its simplicity and scalability. Indeed, the CCVD method requires only a furnace, a tubular reactor, a reactive gas mixture, and an appropriate catalyst. In addition, CCVD can be carried out in a continuous mode and at a relatively low temperature compared with the arc discharge and laser ablation ones. The product is extremely pure and, thus, additional purification is not required, which represents a net gain for the cost-effectiveness of the process. A schematic diagram of the conventional fixed-bed CVD synthesis setup is shown in Figure 9.5. 

Combustion Chemical Vapor Deposition (CCVD) allows deposition of thin films that confer special electronic, catalytic, or optical properties, corrosion and oxidation resistance. The CCVD process is a novel, open-atmosphere process that is environmentally friendly and does not require expensive reaction/vacuum chambers. Often coatings are of equal or better quality than those obtained by vacuum-based methods. Coating costs are significantly lower than for more traditional processes such as Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD). Equally important, this novel technology can be implemented in a production-line environment, thus enabling uninterrupted processing. To date over 70 different inorganic materials have been deposited onto a variety... 

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