Materials carbon nanofibers

Electronic Components Basic Specialty Chemicals Ceramic Materials Carbon Nanofiber Graphite... 

A wide variety of carbon materials has been used in this study, including multi-wall carbon nanotubes (sample MWNT) chemically activated multi-wall carbon nanotubes (sample A-MWNT)16, commercially available vapor grown carbon nanofibers (sample NF) sample NF after chemical activation with K.OH (sample A-NF) commercially pitch-based carbon fiber from Kureha Company (sample CF) commercially available activated carbons AX-21 from Anderson Carbon Co., Maxsorb from Kansai Coke and Chemicals and commercial activated carbon fibers from Osaka Gas Co. (A20) a series of activated carbons prepared from a Spanish anthracite (samples named K.UA) and Subituminous coal (Samples H) by chemical activation with KOH as described by D. Lozano-Castello et al.17 18 activated carbon monoliths (ACM) prepared from different starting powder activated carbons by using a proprietry polymeric binder from Waterlink Sutcliffe Carbons, following the experimental process described in the previous paper13. 

The experimental results obtained with carbon nanofibers and nanotubes fit into the tendencies obtained with the other type of carbon materials, indicating that hydrogen adsorption on these materials is also taking place by a physisorption process. 

The aim of this review paper is to give an extensive overview of the different promoters used to develop new or improved Co-based F-T catalysts. Special attention is directed towards a more fundamental understanding of the effect of the different promoter elements on the catalytically active Co particles. Due to the extensive open and patent literature, we have mainly included research publications of the last two decades in our review paper.In addition, we will limit ourselves to catalyst formulations composed of oxide supports, excluding the use of other interesting and promising support materials, such as, e.g., carbon nanofibers studied by the group of de Jong. ... 

Carbon nanofibers consist of near-submicroscopic tubes of carbon atoms. They outclass almost all other known materials in their ability to absorb hydrogen molecules. With carbon nanofibers, for example, a volume of 36,000 liters of hydrogen can be reduced to a mere 35 liters. Carbon nanofibers are a recent discovery, however, and much research is still required to confirm their applicability to hydrogen storage and to develop the technology. 

As reported elsewhere [22], similar to those found on other catalysts, the forms of carbon materials deposited on Fe-loading zeolite molecular sieves are carbon nanotube, carbon nanofiber and amorphous carbon. One obvious phenomenon of the carbon nanotubes formed on Fe/NaY or Fe/SiHMS catalysts is that almost all tips of these tubes are open, indicating the interaction between catalyst particles and supports is strong [23]. On the other hand, the optimal formation time of carbon nanotubes on Fe/SiHMS is longer than that on Fe/NaY. However, the size of carbon nanotubes is easily adjusted and the growth direction of carbon nanotubes on the former is more oriented than on the latter. 

Hydrogen interaction with the carbon nanostructural materials (nanotubes, nanofibers, fullerenes C60 and C70 has been intensively studied over the last years. A developed surface of nanotubes and nanofibers induced a considerable applied interest aimed at hydrogen storage and reduced consumption of organic fuel in modem industry. For the academic studies, of interest is the nature of the hydrogen interaction with the carbon nanomaterials. 

Yoon SH, Park CW, Yang HJ, Korai Y, Mochida I, Baker RTK, Rodriguez NM. Novel carbon nanofibers of high graphitization as anodic materials for lithium ion secondary batteries. Carbon 2004 42 21-32. 

The obtained carbon nanofibers were used for the synthesis of composite materials MgH2-CNF, whose hydrogen storage characteristics were thoroughly studied. 

The investigation of hydrogen sorption properties of the MgH2-CNF composites, obtained by mechanochemical treatment of mixtures of the components, testifies about availability of use of carbon nanofibers for creation of hydrogen storage composite materials. 

Abstract. Nanocarbon materials and method of their production, developed by TMSpetsmash Ltd. (Kyiv, Ukraine), are reviewed. Multiwall carbon nanotubes with surface area 200-500 m2/g are produced in industrial scale with use of CVD method. Ethylene is used as a source of carbon and Fe-Mo-Al- mixed oxides as catalysts. Fumed silica is used as a pseudo-liquid diluent in order to decrease aggregation of nanotubes and bulk density of the products. Porous carbon nanofibers with surface area near 300-500 m2/g are produced from acetylene with use of (Fe, Co, Sn)/C/Al203-Si02 catalysts prepared mechanochemically. High surface area microporous nanocarbon materials were prepared by activation of carbon nanofibers. Effective surface area of these nanomaterials reaches 4000-6000 m2/g (by argon desorption method). Such materials are prospective for electrochemical applications. Methods of catalysts synthesis for CVD of nanocarbon materials and mechanisms of catalytic CVD are discussed. 

Nanocarbons are among the most promising materials developed last years. Nanocarbon materials include fullerenes, carbon nanotubes (CNT), carbon nanofibers (CNF), nanodiamond, onions, and various hybrid forms and 3-dimensional structures based on these. Several years ago these materials were available in milligram-scale quantities. Now many of them are produced by tones per year. TMSpetsmash Ltd. research team has developed some new kinds of nanocarbon materials and processes for their production. 

Surface area of as-obtained CNF is nearly 300-500 m2/g. One of the effective methods of activation of different carbon materials is treatment with melted KOH at 400-900°C. High surface area (up to nearly 3000 m2/g) carbon materials were obtained [16, 17]. This method was also applied to carbon nanotubes. Significant development of surface was observed, from 465 m2/g for starting MWNT to 1184 m2/g after activation [18], Also, KOH activation of carbon nanofibers resulted in increase of surface area from initial 174 m2/g up to 1212 m2/g [19]. When activated our nanofibers, we obtained for some samples very high effective surface area, nearly 2000-4000 m2/g and in some experiments even 6000 m2/g (measured by argon desorption method). In electron image of activated material (Fig. 7) fiber-like structure is observed. 

A test matrix of about 20 different carbon samples, including commercial carbon fibers and fiber composites, graphite nanofibers, carbon nanowebs and single walled carbon nanotubes was assembled. The sorbents were chosen to represent a large variation in surface areas and micropore volumes. Both non-porous materials, such as graphites, and microporous sorbents, such as activated carbons, were selected. Characterization via N2 adsorption at 77 K was conducted on the majority of the samples for this a Quantachrome Autosorb-1 system was used. The results of the N2 and H2 physisorption measurements are shown in Table 2. In the table CNF is used to designate carbon nanofibers, ACF is used for activated carbon fibers and AC for activated carbon. 

Yu Y, Gu L, Wang C, Dhanabalan A, Van Aken PA, Maier J. Encapsulation of Sn carbon nanoparticles in bamboo-like hollow carbon nanofibers as an anode material in lithium-based batteries. Angew Chem Int Ed. 2009 48 6485-9. 

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