Processing methods spray pyrolysis

Various methods are applied to the synthesis of titania particles including sol-gel method, hydrothermal method [2], citrate gel method, flame processing and spray pyrolysis [1]. To utilize titania as a photocatalyst, the formation of ultrafme anatase titania particles with large crystallite size and large surface area by various ways has been studied [4]. 

The methods employed in the deposition of thin films of oxides can be divided into two major groups based on the nature of the deposition processes. Physical methods of deposition physical vapor deposition (PVD) (Kueir-Weei et al., 1997), ion beam (Xiaodong et al., 2008) and sputtering (Haiqian et al., 2010). The chemical methods of deposition, which can be subdivided as to the nature of the precursor gas phase and solution. The gas phase methods chemical vapor deposition (CVD) (Bryant, 1977) and atomic layer epitaxy (ALE) (Suntola, 1992). The solution methods spray pyrolysis (Chamberlin Skarman, 1%6), sol-gel (Brinker et al., 1990) and electrodeposition. 

Li2Mn03-LiM02 can be prepared by various methods, as mentioned in Chapters 2 through 5, such as solid-state reaction, ball-milling (BM) method, coprecipitation method, sol-gel process [4], spray pyrolysis, hydrothermal method, and template method [5]. 

Another distinguishing feature of titania prepared by flame spray pyrolysis is the draar e of anatase crystallite size with the increase of flame temperature. Generally, the increase of preparation temperature increases the crystallite size in other processes such as sol-gel method, hydrothermal method [2, 3], flame processing and conventional spray pyrolysis. The decrease of crystallite size was directly related to the decrease of particle size. Fig. 5 shows SEM and TEM images of titania particles prepared by flame spray pyrolysis. 

Films at NASA GRC were deposited using homemade spray or aerosol-assisted chemical vapor deposition (AACVD) reactors to exploit the lower deposition temperature enabled by the simpler decomposition chemistry for the SSPs.6 9 AACVD is a simple and inexpensive process that offers the advantage of a uniform, large-area deposition, just like metal organic CVD (MOCVD), while also offering the low-temperature solution reservoir typical of spray pyrolysis methods. 

The slurry process has been enhanced with vacuum to fabricate planar SOFCs [78], This method is of low cost and thus has been widely used to develop low-cost SOFCs. However, together with other liquid precursor methods such as sol-gel and spray pyrolysis, it is time, labor, and energy intensive because the coating-drying-sintering has to be repeated in order to avoid cracking formation. 

Dry methods and postcalcination methods The industrial micron sized R2O3 powder is commonly made by thermal pyrolysis of rare earth carbonates or oxalates at a temperature of 600-1000 °C. The dry methods usually result in fine powders with a relatively wide size distribution. After the sintering, the surface OH and other solvent related species are generally removed, therefore, the powder may exhibit better luminescence efficiency and longer decay time. Nano-sized rare earth oxide products could be obtained from finely selected precursors like hydroxides gels, premade nanostructures, through heat treatment, spray pyrolysis, combustion, and sol-gel processes. 

Metal acetoacetonates have often been used in spray pyrolysis, as explained in 17.3.8.5.3, but advances in sol-gel processing have tended to reduce the importance of this method. 

Decreasing operation temperature of solid oxide fuel cells (SOFCs) and electrocatalytic reactors down to 800-1100 K requires developments of novel materials for electrodes and catalytic layers, applied onto the surface of solid electrolyte or mixed conducting membranes, with a high performance at reduced temperatures. Highly-dispersed active oxide powders can be prepared and deposited using various techniques, such as spray pyrolysis, sol-gel method, co-precipitation, electron beam deposition etc. However, most of these methods are relatively expensive or based on the use of complex equipment. This makes it necessary to search for alternative synthesis and porous-layer processing routes, enabling to decrease the costs of electrochemical cells. Recently, one synthesis technique based on the use... 

A variant of the spray pyrolysis method based on electrostatic spray-assisted vapor deposition (ESAVD) can also be used [110] in which the mixed co-solvent and precursor electrolyte is atomized by an electric field. The morphology of the thin films obtained from this method is very dependent on the process temperature (Figure 5.14) [110]. For example, in the case of CdS deposition [110] amorphous films are obtained below 300°C (process I in Figure 5.14). Cadmium... 

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