Reducing plasma processes

A considerable amount of carbon is formed in the reactor in an arc process, but this can be gready reduced by using an auxiUary gas as a heat carrier. Hydrogen is a most suitable vehicle because of its abiUty to dissociate into very mobile reactive atoms. This type of processing is referred to as a plasma process and it has been developed to industrial scale, eg, the Hoechst WLP process. A very important feature of a plasma process is its abiUty to produce acetylene from heavy feedstocks (even from cmde oil), without the excessive carbon formation of a straight arc process. The speed of mixing plasma and feedstock is critical (6). 

Plasma processes have been successfully demonstrated for production of metals from their oxides and chlorides intermediates. Reducing agents are, of course, to be used. Thus, a plasma-based process involving reduction of tantalum chloride in hydrogenous atmosphere has been claimed to yield highly pure metal powder suitable for making of porous capacitor of high capacitance. 

Before fluorination, the dielectric constant ofpoly(bisbenzocyclobutene) was 2.8, and this value was reduced to 2.1 after plasma treatment. No data were reported in the paper on characterization of structure or properties, except for the dielectric constant of the modified poly(bisbenzocyclobutene). The authors did report that the thermal stability offluorinatedpoly(vinylidenefluoride) was inferior to the original poly(vinylidenefluoride) when treated in a similar way. One of the probable reasons for the low thermal stability is that the NF3 plasma degraded the polymer. According to their results, the thickness of fluorinated poly(bisbenzo-cyclobutene) was reduced by 30%. The same phenomenon was observed for other hydrocarbon polymers subjected to the NF3 plasma process. A remaining question is whether plasma treatment can modify more than a thin surface layer of the cured polymer Additionally, one of the side products generated was hydrogen fluoride, which is a serious drawback to this approach. 

Plasma oxytocin has been shown to be reduced in autistic children and moreover, levels of oxytocin were correlated with social impairment (Modahl et al., 1998). A follow-up study using the same subjects found that the autistic children had higher levels of the precursor of oxytocin when compared with controls, suggesting that reduced plasma oxytocin in autistic children may be related to how oxytocin is processed (Green et al., 2001). Preliminary studies have demonstrated that infusion with oxytocin can reduce repetitive behaviors such as... 

The earliest work reported in this field was by Burguera et al. [103], who applied a flow injection system for on-line decomposition of samples and determined metals (Cu, Fe, Zn) by flame atomic absorption spectroscopy (F-AAS). The methodology involved the synchronous merging of reagent and sample, followed by decomposition of serum, blood, or plasma in a Pyrex coil located inside the microwave oven. This approach permits essentially continuous sample decomposition, drastically reduces sample processing time, and is suitable for those samples that require mild decomposition conditions (especially liquids). 

The deposition temperature for reaction (c) is 700-1150°C, and the chlorosilanes react at 755-850°C . Plasma processing can be used to reduce the deposition temperature to 250-400°C . LCVD has also been used to reduce the deposition temperature to this range . ... 

If nitrogen is used, the ideal deposition temperature is 1000°C. The deposition temperature is lower for the ammonia reaction (575 700°C). Plasma processing can be used to reduce the processing temperature to 500°C . Thermal laser CVD has also been used to deposit TiN at reduced temperature . In an alternate approach, titanium tetraiodide is the precursor (with no plasma) at a deposition temperature under 450°CT... 

Recognition of TiN as a supreb barrier to diffusional and electrical activity has resulted in extensive research on the CVD of TiN for microelectronic layers. Significant advances have been made in the area of plasma-assisted CVD where dc glow , ECR , and helicon plasmas have all been used. Implementation of such plasmas can reduce the processing temperature of reaction (b) to 400°C. For plasma deposition of TiN using titanium isopropoxide, the deposition temperature can be as low as 100°C, where the chemistry is outlined as follows ... 

The advantage of using two precursor gases is a reduced deposition temperature, except in the case of methane. Reactions (d) and (e) yield SiC at 800°C, but plasma processing can lower the temperature to 200°C. If disilane and acetylene are used with excimer LCVD, the deposition temperature for SiC can be reduced to this level . 

Frolova, I.B., Minkin, VM., Frolov, VA. (1976), Treatment of Dispersed Oxides of Iron, Chromium and Nickel by Reducing Gases Heated Up in Electric Arc Discharge, in Plasma Processes in Metallurgy and Technology of Inorganic Materials, A. A. Baikov Institute of Metallurgy of USSR Academy of Sciences, Nauka (Science), Moscow. 

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