Combustion CVD

Combustion CVD (CCVD) has also been developed and employed in the deposition of functionally and porosity graded LSM-GDC/LSM-LSC-GDC/LSC-GDC cathodes on a YSZ electrolyte with a NiO-GDC anode also deposited by CCVD. Reasonable performances of 0.48 W/cm2 peak power density and 0.11 Qcm2 electrode RP at 800°C were recorded for the cell [101]. CCVD has also been utilized to deposit anode layers with Sn02 as a sacrificial pore former layer [25] and to deposit an SSC-SDC cathode layer, resulting in a low RP of 0.195 Qcm2 at 600°C at OCV [102],... 

Chemical reactions occurring in the gas-phase can be more or less important in CVD, depending on the system, and can often be analyzed in detail. Gas-phase reactions are more likely to be important with the use of high temperatures and high total reactor pressures, but less likely to be important at low reactor pressures. Many CVD systems are operated in ways that minimize gas-phase reactions in order to avoid particle formation that could interfere with the desired film deposition. Note that the absence of homogeneous nucleation of particles is not synonymous with the absence of gas-phase chemical reactions. In contrast, other CVD systems utilize gas-phase reactions to convert reactant molecules that are relatively unreactive at the surface into more reactive species. Examples where this strategy is used include the combustion CVD processes discussed in Chapter 4 and plasma-enhanced CVD processes. 

Chemical Vapor Deposition (CVD) has been defined as a materials synthesis process whereby constituents of the vapor phase react chemically near or on a substrate surface to form a solid product. With these traditional processes a reaction chamber and secondary energy (heat) source are mandatory making them different from the Combustion CVD process. Numerous flame-based variations of CVD have been used to generate powders, perform spray pyrolysis, create glass forms, and form carbon films including diamond films. 

M.R. Hendrick, The Effects of Combustion CVD-Applied Alumina Coatings on the High Temperature Oxidation of a Ni-Cr Alloy, Thesis, Georgia Institute of Technology, Atlanta, 1996. 

M.R. Hendrick, J.M. Hampikian, and W.B. Carter, Combustion CVD-Applied Alumina Coatings and Their Effects on the Oxidation of a Ni-Based Chromia Former, Journal of Electrochemical Society, Vol.145, No.ll, 1998, pp.3986-3994. 

Besides the MPCVD reactors, other CVD reactors are also used for diamond deposition. They are hot filament, DC plasma, radio-frequency (rf) plasma, thermal rf plasma, plasma jet, and combustion CVD reactors. In the following, hot filament and DC plasma CVD reactors will be described, because they have been used for oriented growth of diamond. 

Figure 2. Schematic diagram of various CVD techniques for diamond synthesis, (a) HFCVD (b) MW PACVD (c) ECR MW PACVD (d) DC PACVD (e) RF PACVD (0 DC thermal plasma CVD (g) RF thermal plasma CVD (h) flame (combustion) CVD.l (Reproduced with permission.)...

Substrates are usually immersed in the plasmas in MW, DC and RF PACVD processes or separated from the plasmas in DC and RF thermal plasma CVD processes. A. substrate is generally placed 0.5-2 cm. fi-om the hot filament in the HFCVD, or fi om the flame burner nozzle in the combustion CVD, and up to 5 cm from the thermal plasma nozzle in the DC thermal plasma CVD.f " Report on distances greater than several centimeters has not been found in published literature, which may be attributable to... 

In addition to the statistical nature of the interface instabilities active in diamond CVD, the orientation effect and anisotropic growth of crystals (i.e., evolutionary selection) play an important role in the observed instability phenomenon. Surface chemical reactions that occur preferentially between the growing diamond surface and oxidizing species in the combustion synthesis ambient also influence the development of the microstructure and morphology of crystals in diamond films. For example, in combustion CVD,... 

EXPLORATION OF COMBUSTION CVD METHOD FOR YSZ THIN FILM ELECTROLYTE OF SOLID OXIDE FUEL CELLS... 

Fig. 20.27 (a) Top view and (b) cross view SEM images of nanostructured SnO films deposited at 850 °C by a combustion CVD process (Adapted with permission from Liu et al. 2005b, Copyright 2005 American Chemical Society)... 

In the 1950s to 1980s, two main techniques were developed for the synthesis of artificial diamond (a) high-pressure/high-temperature synthesis that yielded artificial diamond gems [18], and (b) chemical vapor deposition (CVD) [19] that made possible the synthesis of diamond in thin-film form on various substrates. Different CVD techniques have been adopted in the synthesis of diamond thin films. Three main CVD techniques include hot-filament CVD [20], plasma-assisted CVD [21], and combustion CVD [22]. There are many types of plasma-assisted CVD techniques according to the energy sources, such as the microwave plasma-assisted CVD (also... 

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