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Carbon Deposition (carbon + deposition)
Selected AbstractsCarbon Nanotube Composites: Hierarchical Composites of Single/Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double Hydroxides (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Mater. On page 677, M. Q. Zhao et al. report the fabrication of a hierarchical composite combining one-dimensional single/double walled carbon nanotubes (CNTs) and two-dimensional flakes through direct carbon deposition on layered double hydroxides. The composites can be easily transformed into continuously interlinked CNT layers alternating with calcined lamellar flakes structure. They are found to have the potential for applications in a number or areas, including as an excellent filler for strong polyimide film. [source] Hierarchical Composites of Single/Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double HydroxidesADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Meng-Qiang Zhao Three-dimensional hierarchical nanocomposites consisting of one-dimensional carbon nanotubes (CNTs) and two-dimensional lamellar flakes (such as clay, layered double hydroxides) show unexpected properties for unique applications. To achieve a well-designed structure with a specific function, the uniform distribution of CNTs into the used matrix is a key issue. Here, it is shown that a hierarchical composite of single/double-walled CNTs interlinked with two-dimensional flakes can be constructed via in-situ CNT growth onto layered double hydroxide (LDH) flakes. Both the wall number and diameter of the CNTs and the composition of the flakes can be easily tuned by changing the proportion of the transition metal in the LDH flakes. Furthermore, a structure with continuously interlinked CNT layers alternating with lamellar flakes is obtained after compression. The hierarchical composite is demonstrated to be an excellent filler for strong polyimide films. This study indicates that LDH is an extraordinary catalyst for the fabrication of hierarchical composites with high-quality single/double-walled CNTs. The as-obtained CNTs/calcined LDHs nanocomposite is a novel structural platform for the design of mechanically robust materials, catalysts, ion-transportation, energy-conversion, and other applications. [source] Carbon Nanotube Composites: Hierarchical Composites of Single/Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double Hydroxides (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Mater. On page 677, M. Q. Zhao et al. report the fabrication of a hierarchical composite combining one-dimensional single/double walled carbon nanotubes (CNTs) and two-dimensional flakes through direct carbon deposition on layered double hydroxides. The composites can be easily transformed into continuously interlinked CNT layers alternating with calcined lamellar flakes structure. They are found to have the potential for applications in a number or areas, including as an excellent filler for strong polyimide film. [source] Alternative concept for SOFC with direct internal reforming operation: Benefits from inserting catalyst rodAICHE JOURNAL, Issue 6 2010Pannipha Dokamaingam Abstract Mathematical models of direct internal reforming solid oxide fuel cell (DIR-SOFC) fueled by methane are developed using COMSOL® software. The benefits of inserting Ni-catalyst rod in the middle of tubular-SOFC are simulated and compared to conventional DIR-SOFC. It reveals that DIR-SOFC with inserted catalyst provides smoother temperature gradient along the system and gains higher power density and electrochemical efficiency with less carbon deposition. Sensitivity analyses are performed. By increasing inlet fuel flow rate, the temperature gradient and power density improve, but less electrical efficiency with higher carbon deposition is predicted. The feed with low inlet steam/carbon ratio enhances good system performances but also results in high potential for carbon formation; this gains great benefit of DIR-SOFC with inserted catalyst because the rate of carbon deposition is remarkably low. Compared between counter- and co-flow patterns, the latter provides smoother temperature distribution with higher efficiency; thus, it is the better option for practical applications. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Deposition Mechanism for Chemical Vapor Deposition of Zirconium Carbide CoatingsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2008Yiguang Wang Zirconium carbide (ZrC) coatings were fabricated by chemical vapor deposition (CVD) using ZrCl4, CH4/C3H6, and H2 as precursors. Both thermodynamic calculation results and the film compositions at different temperatures indicated that zirconium and carbon deposited separately during the CVD process. The ZrC deposition rates were measured for CH4 or C3H6 as carbon sources at different temperatures based on coating thickness. The activation energies for ZrC deposition demonstrated that the CVD ZrC process is controlled by the carbon deposition. This is also proven by the morphologies of ZrC coatings. [source] Alloying with copper to reduce metal dusting of nickelMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2005J. Zhang Abstract Copper is thought to be noncatalytic to carbon deposition from gas atmospheres, and owing to its extremely low solubility for carbon, inert to the metal dusting reaction. Thus, the addition of copper to nickel, which forms a near perfect solid solution, may be able to suppress or greatly retard the metal dusting of the alloy, without the need for a protective oxide scale on the surface. The dusting behaviour of Ni-Cu alloys containing up to 50 wt% Cu, along with pure Cu, was investigated in a 68%CO-31%H2 -1%H2O gas mixture (aC: 19) at 680°C for up to 150 h. Surface analysis showed that two types of carbon deposits, graphite particle clusters and filaments, were observed on pure Ni and Ni-Cu alloys with Cu contents of up to 5 wt%. Alloys with more than 10 wt% Cu showed very little coking, forming filaments only. SEM and TEM analyses revealed metal particles encapsulated by graphite shells within the graphite particle clusters, and metal particles at filament tips or embedded along their lengths. A kinetic investigation showed that alloy dusting rates decreased significantly with increasing copper levels up to 10 wt%. At copper concentrations of more than 20 wt%, the rate of metal dusting was negligible. Although pure copper is not catalytic to carbon formation, scattered carbon nanotubes were observed on its surface. The effect of copper on alloy dusting rates is attributed to a dilution effect. [source] A case of nitridation, carburization and oxidation on a stainless steelMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2005H. J. Grabke Abstract A case of corrosion was studied on stainless steel tubes, exposed to a nitriding, carburizing and oxidizing environment (mainly NH3 and CO2) at 390,450°C. Due to the high nitriding potential prior formation of internally nitrided layers occurs, at higher temperatures (> about 425°C) under precipitation of CrN in the layer and at lower temperatures under formation of the ,N -phase, i.e. austenite with high N-content and expanded lattice. The latter process causes more severe corrosion, due to the high expansion, the stresses in the nitrided layers lead to bursting and repeated spalling of the scales. Carburization and oxidation are less important. The carburization is slower than nitridation, Fe3C formation is observed and carbon deposition. Also the oxidation by CO2 is slow and converts the nitrides and carbides formed before, to unprotective oxide flakes. [source] The influence of Metal Dusting on gas reactionsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2004A. T. W. Kempen Abstract Gas composition analysis measurements have been performed in the outlet gas stream of a laboratory metal dusting test furnace in order to study the influence of metal dusting on gas reactions. This analysis has shown that carbon deposition is associated with metal dusting, i.e. the material most severely attacked by metal dusting, catalyses the formation of carbon to the largest extent. Also, metal dusting has not been seen to influence the methanation reactions. A kinetic model has been used to interpret the obtained data with respect to the catalytic activity of several high temperature materials showing that the catalytic activity of the material can vary by orders of magnitude for different reactions. [source] Effect of hydrogen on the synthesis of carbon nanofibers by CO disproportionation on ultrafine Fe3O4ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Wenxin Lu Abstract Carbon nanofibers (CNFs) are grown by catalytic CO disproportionation over ultrafine Fe3O4 catalyst at a hydrogen concentration of 0,29.17%, and the time-depending rates of CNFs growth are continuously monitored and the morphologies of the as-synthesized CNFs are analyzed. Increasing H2 concentration will lower CO dissociation energy and assist catalyst reconstruction so as to shorten the induction period and increase the growth rate of CNFs, but it will also increase the rate of catalyst deactivation because carbon hydrogasification is not possible and carbon diffusion in the catalyst particle is rate limiting. As a result of H2 -induced catalyst reconstruction and carbon deposition, the morphology of the CNFs changes from twisty to helical and to straight and becomes less entangled when the H2 concentration is increased. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Direct utilization of ethanol on ceria-based anodes for solid oxide fuel cellsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009Massimiliano Cimenti Abstract The direct utilization of ethanol was investigated in CuCeO2, CuZr0.35Ce0.65O2 (ZDC) and Cu/RuZr0.35Ce0.65O2 anodes for solid oxide fuel cells (SOFC). The anodes were prepared by impregnation with nitrate precursors on a porous layer of yttria-stabilized zirconia (YSZ) obtained by tape casting, while (La0.8Sr0.2MnO3,,) LSM cathodes were screen-printed. The cells were tested in both hydrogen and ethanol. The outlet gas composition was monitored with a gas chromatograph, which showed that almost all the ethanol was decomposed, mainly to H2, CH4, CO, H2O and C2H4. The maximum power outputs obtained in ethanol were 0.075 and 0.400 W/cm2 on CuCeO2|YSZ|LSM and CuZDC|YSZ|LSM, respectively. All cells were more active in alcohol than in hydrogen with the peak performance occurring after approximately 4 h. That is, the power density initially increased, peaked and then decreased. This behavior was likely a consequence of carbon deposition that initially results in an improvement of the electronic conductivity in the anode but later results in the blocking of the active sites. Zirconia doping (in the ZDC anodes) resulted in better stability and, in addition, the initial activity of the ZDC anodes could be recovered after approximately 1 h of exposure to humidified hydrogen, whereas the initial activity of the ceria anodes could not be recovered. The addition of ruthenium (<0.5 wt%) further improved the stability by delaying the onset of carbon formation. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | |||||||||||||