Reactive atmosphere processing

In specialized processes associated with the materials science industry, a reactive atmosphere is generated by reactions in which charged species are participants. A gaseous system wherein charged particles (electrons, ions) are important species is called a plasma, and the response of charged particles to an external field is used to increase... 

The past five years have witnessed significant progress in the understanding and control of plasma etch processes. Nevertheless, much of the fundamental chemistry and physics occurring in these reactive atmospheres remains ill-understood, or indeed unknown. The following sections assimilate the information currently available on dry etch processes, and present a framework within which plasma etching can be viewed. 

Often it is essential to characterize the formation of a catalytically active state of a highly dispersed phase by XRD under reactive atmospheres. Investigations of reduction and calcination processes, for example (Thomas and Sankar, 2001 Sankar et al., 1991), guided the determination of recipes for catalyst preparation (Gunter et al., 2001d Kirilenko et al., 2005 Ressler et al., 2001, 2002 Wienold et al., 2003) in a complex parameter space. 

Reference Methods used to complement XRD Sample/process Issues Postmortem tion in reactive atmosphere Catalytic reaction atmosphere Reaction... 

Other Factors. Several other factors influence, at least to some extent, the course of the pyrolysis process. These include particle size, bed configuration, pressure/vacuum during pyrolysis, nature of the coal ash, secondary reactions, etc.37 It is beyond the scope of this chapter to consider these items, but the interested reader can find additional information in the literature, including reports on pressure effects,21,38 effect of vacuum,23 effect of inorganics,26,39 and effect of a reactive atmosphere.23,40... 

Activation always involves some form of chemical attack. However, chemical activation is a term often used to indicate the prior impregnation of the precursor with a chemical agent such as phosphoric acid or zinc chloride before heat treatment. Physical activation, on the other hand, signifies the heat treatment of the char in a mildly reactive atmosphere such as steam or carbon dioxide. This type of process is preferably referred to as thermal activation (Baker, 1992). The apparent distinction between chemical and physical is somewhat unsatisfactory for two reasons first, it implies a fundamental difference in the mechanism of activation and second, it does not allow for the many procedures which involve both types of treatment. 

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