Pyrolysis metal oxide deposition

In this section various existing lanthanide and actinide metal-organic enolate precursors for rare earth metal oxide deposition are discussed and the rationale of their selection is addressed. CVD, ALD and ultrasonic spray pyrolysis (USP) of the lanthanide or actinide enolate starting materials has been carried out under a variety of conditions as can be seen from Table 7. 

Spray pyrolysis An appropriate metal salt is sprayed from an atomizer onto a hot substrate where decomposition occurs yielding the metal oxide. There are advantages to be gained by electrically charging the droplets using an electrostatic atomizer Deposition rates are quite low, typically in the range 1-10 /unh-1. 

Different methods have been used to deposit microporous thin films, including solgel, pyrolysis, and deposition techniques [20], Porous inorganic membranes are made of alumina, silica, carbon, zeolites, and other materials [8], They are generally prepared by the slip coating method, the ceramic technique, or the solgel method (Section 3.7). In addition, dense membranes are prepared with metals, oxides, and other materials (Chapter 2). 

Sn02 has been one of the most attractive metal oxides in the experimental studies during the last decades due to its gas sensor and catalysis application. Various methods were tested for deposition of SnOz films. They were fabricated by sputtering, sol-gel, spray pyrolysis, CVD, ALE, thermal evaporation, etc. However, not all methods are able to produce Sn02 films with high porosity and small size of crystallites (/<10 nm). 

Spray pyrolysis (Fig. 13.3) is a technique similar to AACVD, where the precursors for the metal oxide film are aerosolized and sprayed on to the target substrate. The deposited droplets then react on the surface when the substrate is heated, forming the desired film. 

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)...

Korotcenkov G, Cho BK (2011) Instability of metal oxide-based conductometric gas sensors euid approaches to stability improvement (short survey). Sens Actuators B Chem 156 527-538 Korotcenkov G, Han SD (2009) (Cu, Fe, Co and Ni)-doped SnO films deposited by spray pyrolysis doping influence on thermal stability of SnO film structure. Mater Chem Phys 113 756-763 Korotcenkov G, Boris I, Brinzari V, Luchkovsky Y, Karkotsky G, Golovanov V, Comet A, Rossinyol E, Rodriguez J, Cirera A (2004) Gas sensing characteristics of one-electrode gas sensors on the base of doped In O ceramics. Sens Actuators B Chem 103 13-22... 

ESD or electrostatic spray pyrolysis (ESP) has been applied to fabricate metal oxide thin films [122-124]. This technique holds some advantages, including simple setup and high deposition efficiency [116]. During the ESD process, a precursor... 

Porous aluminum oxide can be used as a template for the production of nanowires and nanotubes. For example, metals can be deposited on the pore walls by the following procedures deposition from the gas phase, precipitation from solution by electrochemical reduction or with chemical reducing agents, or by pyrolysis of substances that have previously been introduced into the pores. Wires are obtained when the pore diameters are 25 nm, and tubes from larger pores the walls of the tubes can be as thin as 3 nm. For example, nanowires and nanotubes of nickel, cobalt, copper or silver can be made by electrochemical deposition. Finally, the aluminum oxide template can be removed by dissolution with a base. 

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