Reactive deposition chemical reactions

Plasma Enhanced Chemical Vapour Deposition (PECVD) Chemical vapour deposition (CVD) reactions commonly occur at high temperatures (Table II). The use of a plasma to generate chemically reactive species in conjunction with CVD overcomes one of the most common... 

Chemical vapor deposition (CVD) is a process whereby a thin solid film is synthesized from the gaseous phase by a chemical reaction. It is this reactive process that distinguishes CVD from physical deposition processes, such as evaporation, sputtering, and sublimation.8 This process is well known and is used to generate inorganic thin films of high purity and quality as well as form polyimides by a step-polymerization process.9-11 Vapor deposition polymerization (VDP) is the method in which the chemical reaction in question is the polymerization of a reactive species generated in the gas phase by thermal (or radiative) activation. 

Chemical vapor deposition. Chemical vapor deposition is mainly used to prepare thin films and coatings, and infrequently, supported particles.68,69 The films are formed by the chemical reaction of a gas phase species with the heated surface of a substrate. The process can be assisted by a reactive gas like NH3, a plasma,7a 72 ultraviolet73,74 or laser75 radiation. 

Glow discharges or plasmas have been used extensively to promote chemical reactions for thin-film etching and deposition in a variety of technologically important areas. The reactive chemical atmosphere and complex discharge-surface interactions in these systems permit the attainment of unique etch profiles and film properties. 

Dye Fixation. On the dried fabric, the dye is only deposited on the fiber surface. It must penetrate into the fiber during a fixation step and be incorporated in the fiber by chemical reaction (reactive dyes), aggregation (vat, sulfur dyes), ion-pair formation (acid, cationic dyes), or in the form of a solid solution (disperse dyes). 

In the context of integrated chemical processes however, reactive filtration should be specified as the combination of the solids handling unit operation filtration device and the unit operation chemical reactor . This comprises the separation of solids or aerosols from a fluid stream and the chemical conversion of undesired compounds carried by the stream in one instead of two unit operations. The chemical reaction can proceed either continuously during the separation or stepwise after a certain amount of solids or aerosols has been deposited. Two general cases for the application of a reactive filtration unit may be distinguished ... 

CO oxidation [22, 23]. A similar conclusion was drawn from scanning tunneling microscopy (STM) measurements on the Au/Ti02 system, where again bilayer high deposits turned out to be the most active ones [24, 25]. Naturally, a close structure-reactivity relationship is not restricted to Au particles but can be found for other metal species in a multitude of chemical reactions [26]. 

Reactive Organic Chemical Mass Balance (Friedlander). In the original formulation of the CMB receptor model (1) it was recognized that the fractional amounts of various chemical species emitted by a source are not necessarily conserved during the transport of the species to the receptor site. This could occur through both physical (differential dispersion or deposition) or chemical (removal due to atmospheric reactions) processes. This possibility was acknowledged by writing the CMB equations in the form... 

Chemical reactions occurring in the gas-phase can be more or less important in CVD, depending on the system, and can often be analyzed in detail. Gas-phase reactions are more likely to be important with the use of high temperatures and high total reactor pressures, but less likely to be important at low reactor pressures. Many CVD systems are operated in ways that minimize gas-phase reactions in order to avoid particle formation that could interfere with the desired film deposition. Note that the absence of homogeneous nucleation of particles is not synonymous with the absence of gas-phase chemical reactions. In contrast, other CVD systems utilize gas-phase reactions to convert reactant molecules that are relatively unreactive at the surface into more reactive species. Examples where this strategy is used include the combustion CVD processes discussed in Chapter 4 and plasma-enhanced CVD processes. 

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