Plasma synthesis

The free electrons in the plasma are reactant or catalyst in chemical reactions. Plasmas shift equilibria or they help thermodynamically allowed reactions that have rates that are too low at the low gas temperature (Table 6.3). Table 8.7 lists selected compounds that have been made with PE-CVD at low temperatures with their precursors and the conditions for their synthesis. The amorphous products of PE-CVD are rarely stoichiometric and almost never pure. 

Describe the usual methods for growing single crystals. Choose any solid compound from the text and devise the most suitable method for making a single crystal of it. 

Explain how to shape single crystals during growth. 

Name the three types of epitaxy (growth of solids). Why do they arise, what are their consequences for the product, and how does one control them  

Choose a metal and use the Ellingham diagrams to design a synthesis for a fractal powder of the metal from one of its compounds. 

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Anderson FI, Kodas T T and Smith D M 1989 Vapor phase prooessing of powders plasma synthesis and aerosol deoomposition Am. Ceram. See. Bull. 68 996-1000... 

K. Upadhya, ed.. Plasma Synthesis and Processing of Materials, The Minerals, Metals and Materials Society, Warrendale, Pa., 1993. 

Plasma Synthesis The use of plasma methods has lead to a new range of materials having unique properties. An example is the family of amorphous elemental hydrides (eg cr-C H Of -Si H or-P H) which contain a variable proportion of H from almost zero to 50 atomic %. The carbon films, known variously as "hard carbon", "diamond-like carbon", " a-carbon" etc (9 ) - These layers are of considerable interest because of their optical and abrasion-resistant properties etc (Table I). The properties of these Gr-carbon films, can be tailored by modifying the plasma parameters. 

Merzhanov, A. G., in Combustion and Plasma Synthesis of High-temperature Materials, Munir, Z. A. and Holt, J. B., Eds., VCH Publishers, Weinheim, Germany, 1990, 1. 

Some of the ceramic powders now being researched or made in quantity by plasma synthesis are indicated in Table 3. 

TABLE 3. SOME CERAMIC POWDERS PREPARED BY PLASMA SYNTHESIS... 

Z.A. Munir and J.B. Holt, Eds, Combustion and Plasma Synthesis of High Temperature Materials. (VCH Publishers, New York, 1990). 

I. Mohai, J. Szepvolgyi, I. Bertoti, M. Mohai, J. Gubicza, T. Ungar, Thermal plasma synthesis of zinc ferrite nanopowders, Solid State Ionics 141-142 (2001) 163-168. 

Churilov, G.N. (2000) Plasma synthesis of fullerenes, Instr. Experim. Tech. 1, 1-10. 

Gas-phase nucleation Flame synthesis of particles (e.g., carbon black, silica) cluster formation in chemical vapor deposition manufacture of high-purity silicon cluster structure and energetics plasma synthesis of refractory materials and coatings. 

A seed-assisted chemical reaction at 368 K is found to yield uniform, straight, thin single-crystalline ZnO nanorods on a hectogram scale,181 Zinc oxide nanowires have been synthesized in large quantities using plasma synthesis.1 Variable-aspect-ratio,... 

Table 7.3 lists other possible plasma synthesis reactions. The list includes carbides, nitrides, and oxides. Each of the reactions given is an endothermic reaction requiring heat from the plasma. 

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