Metal oxide synthesis pyrolysis

Fig. 20.18 Grain size for different concentration of precursors in solution for metal oxide synthesis vs. growth and calcinations temperature, (a) Sn02 was synthesized using a method based on the pyrolytic reaction of SnCl -SH O dissolved in methanol. In contrast to the conventional spray pyrolysis technique, pyrolytic reaction does not take place during deposition on the surface of nanocrystals. The treatment in the range of 400-900 °C was carried out after drop deposition on the substrate (Adapted with permission from Cirera et al. 1999, Copyright 1999 Elsevier), (b) Sn02 powders were synthesized by hydrothermal method (Adapted with permission from Baik et al. 2000a, b, c. Copyright 2000 John Wiley Sons)...

One of the potential strategies for the synthesis of compound semiconductors is the pyrolysis of a single-molecule precursor that incorporates the elements of a compound into a single molecule. For a number of binary materials, predominantly metal oxides but also compound semiconductors, such as GaAs [101] or metal alloys [102-104], it has been demonstrated that the use of single-molecule precursors (SMPs), which contain both components for the respective material in one molecule rather than applying two independent... 

There are numerous approaches to the synthesis of highly dispersed metal oxides in addition to those discussed. These include some methods that have been less commonly used to prepare metal oxides, such as vapor condensation methods, spray pyrolysis and templated techniques. 

It has been shown that flame spray pyrolysis can be used to produce metal-oxide catalysts with large surface areas. The surface area is strongly influenced by the flame conditions and the burner design. The properties of the final particles can be designed by changing the conditions during the synthesis. 

Several other synthesis methods such as hydrolysis [20], pyrolysis [21,22], hydrothermal [10,23], and free-drying [24] methods are often used to fabricate ceramic nanoparticles, including calcium phosphates and carbonates, metal oxides, as well as nonoxides such as metal sulfates. Due to space limitations, these methods are not expanded here but it is important to note that the versatility of these methods provides rich opportunities to manufacture, modify, and functionalize complex nanoparticles or other nanoarchitectures. 

Azurdia JA, Marchal J, Laine RM. Synthesis and characterization of mixed-metal oxide nanopowder along the CoO t-Al203 tie line using liquid feed flame spray pyrolysis. J Am Ceram Soc 2006 89(9) 2749-56. 

The synthesis of multicomponent oxide materials via polymerizable complex method suffers from the drawbacks common for all techniques that utilize large amount of organic compounds. The pyrolysis ofthe polymer gel yields metal oxides and carbonates. As we have already discussed, the decomposition of an alkaline-earth carbonate slows down the sohd state reaction and requires high temperatures for synthesis despite the good homogeneity and the small size ofthe particles. 

Many different methods have been reported for the production of metal oxide nanoparticles. The most common processes have been developed to synthesize oxide are chemical solution decomposition (CSD) [97], spray pyrolysis [98], CVD [99-101], two-step wet chemical method [102], sol-gel [103], ultrasonic irradiation [104,105], and ethanol thermal and hydrothermal method [106], Literature revealed that sol-gel is the most commonly used method for the preparation of metal oxide nanoparticles. It facilitates the synthesis of nanometer-sized crystallized metal oxide powder of high purity at a relatively low temperature [103]. 

Moreover, a general strategy for the synthesis of carbon-supported metal or metal oxide nanoparticles starting from MOFs was reported by Poddar s group. The authors found a correlation between the redox potential of the metal" /metal redox couple and the ability of a metal" -based MOF to form metal nanoparticles on pyrolysis. Cu and Co have redox potentials of -1-0.34 and -0.28 V versus SHE, whereas Zn , Mn , and Mg have much lower potentials of -0.76, -1.18, and -2.37 V versus SHE, respectively It was concluded from experimental results that metal cations with a potential above ca. -0.27 V SHE could react with the organic ligands of the MOFs to be reduced to zero oxidation state during pyrolysis in inert atmosphere, whereas others resulted in metal oxide nanoparticles after pyrolysis. 

The application oiflame spray pyrolysis to NP synthesis generally resulted in the production of metal oxides and salts [54—57]. Recently, Athanassiou et al. proposed the use of a flame-SP apparatus which operated in continuous fashion in a nitrogen-filled glovebox to produce carbon-coated Cu NPs with a good size uniformity [58]. 

There have been several developments in this area since this manuscript was prepared. The heat of combustion of corannulene was determined by microbomb combustion calorimetry and its gas-phase enthalpy of formation was estimated at 110.8 kcal/mol. All anionic oxidation states of corannulene were observed by optical absorption, EPR, and NMR spectroscopies. More support for the an-nulene-within-annulene model of the corannulene tetraanion was presented. An alternative pyrolysis route to corannulene was reported, as well as some attempts toward the synthesis of bowl-shaped subunits of fullerenes. And in contrast with previous semiempirical studies," ab initio calculations predicted a general concave preference for the metal cation binding to semibuckminsterfullerene 2%. ... 

Laser pyrolysis has been shown to produce a wide variety of crystalline transition metal nitride and carbide nanoparticles with diameters as small as 2 nm. The nanopowders are in many cases monophasic and single crystalline. By varying the reaction conditions it is possible to control the particle diameter, and in some cases, the crystalline phase produced. Improvements in the synthesis are needed to control surface oxidation. 

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