Radiofrequency plasma reactions

In our laboratory, we find that the plasma reaction of trifiuoro-methyl radicals with mercuric iodide is an excellent source of bis(tri-fluoromethyDmercury. For those laboratories that lack access to radiofrequency (rf) equipment (a 100-W, rf source can at present be purchased for less than 1,000), synthesis of bis(trifluoromethyl)mercury by the thermal decarboxylation of (CFgCOjlzHg is also a functional, and quite convenient, source of bis(trifiuoromethyl)mercury (23). 

Other strategies include deposition of a suspension of crosslinked polymer ( ), radiofrequency plasma polymerization ( ), gamma W) or ultra-violet (Funt, L.R. Hoang, P.M., 161 st Electrochemical Society Meeting, Abstract 599, May 9-1, 1982.) irradiation, chemical ( ) or electrochemical reaction or... 

Ullrafine particles (UFPs) of metal and semiconductor nitrides have been synthesized by two major techniques one is the reactive gas condensation method, and the other is the chemical vapor condensation method. The former is modified from the so-called gas condensation method (or gas-evaporation method) (13), and a surrounding gas such as N2 or NII2 is used in the evaporation chamber instead of inert gases. Plasma generation has been widely adopted in order to enhance the nitridation in the particle formation process. The latter is based on the decomposition and the subsequent chemical reaction of metal chloride, carbonate, hydride, and organics used as raw materials in an appropriate reactive gas under an energetic environment formed mainly by thermal healing, radiofrequency (RF) plasma, and laser beam. Synthesis techniques are listed for every heal source for the reactive gas condensation method and for the chemical vapor condensation method in Tables 8.1.1 and 8.1.2, respectively. 

This chapter aims to discuss and summarize theoretical and practical aspects of such plasma interfaces, presenting the existing examples from our own recent work on plasma electrochemical reactions between typical ionic liquids and plasmas. First, we address the plasma state and essential properties with respect to its application in electrochemistry. Today, low temperature plasmas - mostly in the form of radiofrequency or microwave plasmas - play an important role in the treatment or modification of solid surfaces. However, as plasma chemistry is usually not an element of chemistry curricula, we include a very brief introduction but refer the reader to the literature for more detailed information. 

Some routes to (SN), that do not involve (SN)2 as an intermediate are available (see 15.2.12.3). The polymer is obtained in high yield from the reaction of (NSC1)3 with trimethylsilyl azide in acetonitrile - , by the electrochemical reduction of [(SN)5] salts ", and by radiofrequency discharge through (SN)4 vapors in a helium plasma. Other reactions that produce (SN), include the reduction of S2N" with azide ion, the solid state polymerization of impure S4N2 (recrystallized S4N2 does not polymerize) , and the oxidation of (SN)J with certain electrophiles . 

Nanometric boron carbide particles can also be prepared by CVD. The reaction of boron trihalides with carbon or gaseous carbon-containing precursors using radiofrequency (RF) plasma [142, 143] or laser-assisted CVD [144] has been appUed. 

Thermal plasmas have been used for decades as a source of heat for gas-phase reactions. The use of a radiofrequency (RF) plasma has been investigated at a laboratory level for the production of very fine powders of oxides and to a greater extent for nonoxides such as nitrides and carbides (110). The process parameters that control the powder characteristics are the frequency and power level of the plasma source, the temperature of the plasma jet, the flow rate of the gases, and the molar ratio of the reactants. While powders with high purity and very fine particle size (e.g., 10-20 nm) can be produced by this method, a major problem is that the powders are highly agglomerated. 

Among the different types of pretreatment methods proposed, plasma treatment represents probably the most versatile and efficient method for surface modification. The properties of plasma-modified surfaces mainly depend on parameters controlled by the reaction conditions (i.e., type of gas, pressure, radiofrequency, effective power, and time of treatment) and by the physicochemical properties of the polymer used. By using short plasma treatments, the surface modification can be confined to the first atomic layers of the polymer surface. Moreover, plasma treatment offers the ability to choose the nature of the chemical modification as a function of the gas used. As an example, the introduction of amine functionalities on PHB surfaces has been achieved using ammonia plasma [47, 51]. However, the number of functional groups formed at the surface is difficult to control. 

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