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Thin Coating Technologies and Applications in High-Temperature Solid Oxide Fuel Cells
Published in Sam Zhang, Jyh-Ming Ting, Wan-Yu Wu, Functional Thin Films Technology, 2021
Similar to FAVD, combustion CVD (CCVD) is an open-air, flame-assisted chemical deposition process, capable of producing a wide range of coating morphologies from very dense to highly porous structures. Liu et al. (Liu et al. 2004) successfully employed CCVD to fabricate functionally graded LSM/LSC/GDC cathodes on YSZ electrolyte using nitrate solution precursors. In this method, methane is used as the fuel gas and oxygen as the oxidant for the combustion flame. Grain size as small as ~50 nm can be obtained. By using CCVD method, Dhonge et al. managed to prepare thin zirconia films with monoclinic, tetragonal, and cubic structures depending on the concentration of yttrium-doped (Dhonge et al. 2011). With increased deposition temperature, coagulation of clusters of nanocrystallites (~100 nm) to large grains led to the formation of relatively dense YSZ film.
Nanocatalysts: A New “Dimension” for Nanoparticles?
Published in Claudia Altavilla, Enrico Ciliberto, Inorganic Nanoparticles: Synthesis, Applications, and Perspectives, 2017
Ciambelli Paolo, Sannino Diana, Sarno Maria
Carbon nanotubes are concentric graphitic cylinders, they can be multiwalled (MWNT) with a central tube of nanometric diameter surrounded by graphitic layers separated by about 0.34 nm, while single-walled nanotubes (SWNT) are constituted of only one graphitic layer. The first observed MWNTs were grown in an arc-discharge process, and two years later SWNTs were produced by the laser-ablation technique. During that time, the catalytic chemical vapor deposition (CCVD) method was first used to grow CNTs. CCVD immediately appeared as an effective way to the large-scale production of carbon nano-tubes, at lower cost, for some specific applications. As an example, the capability to grow CNTs directly on a substrate at a desired position (a great challenge from the technological point of view) and at lower temperatures than arc discharge or laser ablation allowed the CNT growth by CCVD to be integrated in the fabrication processes of microelectronic circuits (Cheng et al. 1998).
Carbon Nanotube-Metal Oxide Hybrid Nanocomposites Synthesis and Applications
Published in Zainovia Lockman, 1-Dimensional Metal Oxide Nanostructures, 2018
Zaid Aws Ali Ghaleb, Mariatti Jaafar
Both arc discharge and laser vaporization methods were first used to synthesize CNTs but due to high temperature preparation techniques, these methods have been substituted by low temperature chemical vapor deposition methods (<800°C), since the nanotube length, diameter, alignment, purity, density, and orientation of CNTs can be accurately controlled in the low temperature chemical vapor deposition methods. Chemical vapor deposition is a common method for the commercial production of CNTs. This method is a two-step process, consisting of catalyst preparation step and nanotubes synthesis step. The catalyst is prepared by sputtering transition metal such as Ni, Fe, Co, or a combination which is sputtered onto a substrate. The substrate is thermally annealed to induce the nucleation of catalyst particles. Thermal annealing results in metal cluster formation on the substrate, from which the nanotubes grow (Govindaraj and Rao, 2006). The nanotubes synthesis step entails the use of a carbon source in the gas phase (such as methane, ethylene, ethanol, carbon monoxide, and acetylene) and a plasma or a resistively heated coil, to transfer the energy to the gaseous carbon molecule. The energy source cracks the molecule into atomic carbon and the carbon then diffuses toward the catalyst coated substrate. The carbon is transported to the edges of catalyst particles where nanotubes can be produced. Studies have shown the conventionally accepted models are base growth and tip growth (Tempel et al., 2010). The synthesis or CNTs via CVD (chemical vapor deposition) is generally carried out in the temperature range of 650°C–900°C. A variety of CVD processes have been developed to synthesize CNTs, which include catalytic CVD (CCVD) either thermal, plasma enhanced CVD (PECVD) oxygen-assisted, water-assisted CVD, microwave plasma (MPECVD), thermal chemical CVD, aerogel-supported CVD, radio frequency CVD (RF-CVD), hot filament (HFCVD) and laser-assisted CVD (Govindaraj and Rao, 2006, Caglar, 2010). But catalytic chemical vapor deposition (CCVD) is currently the standard technique for the synthesis of carbon nanotubes. The advantage and disadvantage of three common CNTs synthesis methods (arc-discharge, laser vaporization, and the chemical vapor deposition) are summarized in Table 10.2. Compaing CVD with arc-discharge and laser vaporization, CVD is an economically practical method for large-scale and quite pure CNTs production and so the important advantage of CVDs are high purity obtained material and easy control of the reaction course.
Modulation of silica layer properties by varying the granulometric state of tetraethyl orthosilicate precursor aerosols during combustion chemical vapor deposition (CCVD)
Published in Aerosol Science and Technology, 2020
Björn Sten Mark Kretzschmar, Paul Bergelt, Daniel Göhler, Fabian Firmbach, Ronny Köcher, Andreas Heft, Michael Stintz, Bernd Grünler
Combustion chemical vapor deposition (CCVD) is a cost-effective, large-scale coating method for a defined application of functional thin (nanoscaled) solid layers on substrates under atmospheric pressure. During CCVD, solid particles (i) are synthesized by flame pyrolysis of a precursor substance (gas, liquid) within an ignited combustion gas (e.g., butane-air or propane-air mixtures), (ii) are deposited on the substrate and (iii) form a disperse thin solid film. CCVD (Hunt, Carter, and Cochran 1993), which was developed primary for the purpose of adhesion promotion, is nowadays employed for applying anti-corrosion coatings, layers with increased transmission (for SiOx) (Zunke et al. 2014), semiconducting transparent layers (based on ZnO) (Zunke et al. 2013) or for reflecting noble metal layers (Struppert et al. 2010).