Plasma processes

In this section, the wide diversity of teclmiques used to explore ion chemistry and ion structure will be outlined and a sampling of the applications of ion chemistry will be given in studies of lamps, lasers, plasma processing, ionospheres and interstellar clouds. 

The deposition of amoriDhous hydrogenated silicon (a-Si H) from a silane plasma doped witli diborane (B2 Hg) or phosphine (PH ) to produce p-type or n-type silicon is important in tlie semiconductor industry. The plasma process produces films witli a much lower defect density in comparison witli deposition by sputtering or evaporation. 

Estimates for a number of economic aspects of plasma fractionation can be made (200—206). The world capacity for plasma fractionation exceeded 20,000 t of plasma in 1990 and has increased by about 75% since 1980, with strong growth in the not-for-profit sector (Fig. 4). The quantity of plasma processed in 1993 was about 17,000 t/yr the commercial sector accounts for about 70% of this, with over 8000 t/yr in the form of source plasma from paid donors (Fig. 5). Plant capacities and throughput are usually quoted in terms of principal products, such as albumin and Factor VIII. These figures may not encompass manufacture of other products. 

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). 

Table 7. Characteristic Data of Electric Plasma Processes ...

Hydrogen plasma process using naphtha. Case A secondary injection of naphtha Case B radial injection of the naphtha feed. Hydrogen plasma process using cmde oil. 

Table 8. Operational Results of the Hbls Plasma Process in the Cracking of Light Hydrocarbons, ...

Fig. 4. Examples of emission spectrometry as a diagnostic monitoring tool for plasma processing, (a) The removal of chlorine contamination from copper diode leads using a hydrogen—nitrogen plasma. Emissions are added together from several wavelengths, (b) The etching and eventual removal of a 50-p.m thick polyimide layer from an aluminum substrate, where (x ) and (° ) correspond to wavelengths (519.82 and 561.02 nm, respectively) for molecular CO2...

Fig. 7. Schematic of a self-contained plasma processing unit designed to continuously plasma-treat and impregnate with resin, reinforcing fibers for enhanced composite strength. The unit can also be used to plasma-treat wires to be coated or treated for improved adhesion. Throughput speeds of over...

J. L. Cecchi, ia S. M. Rossnagel, J. J. Cuomo, and W. D. Westwood, eds.. Handbook of Plasma Processing Technology, Noyes PubHcations, Park Ridge,... 

H. J. Oskam, ed.. Plasma Processing of Materials, Noyes Data Corp., Park Ridge, N.J., 1985. 

J. W. Cobum, R. A. Gottscho, andD. W. Hess, eds.. Plasma Processing, Materials Research Society, Pittsburgh, Pa., 1986. 

Staff of Panel on Plasma Processing of Materials, United States Nation Research Council, Plasma Processing of Materials Scientific Opportunities and Technological Challenges, Books on Demand, Ann Arbor, Mich., 1994. 

G. S. Mathad and D. W. Hess, eds.. Proceedings of the International Symposium of Plasma Processing 10th, Electrochemical Society, Inc., Pennington, N.J.,... 

Plasma processing technologies ate used for surface treatments and coatings for plastics, elastomers, glasses, metals, ceramics, etc. Such treatments provide better wear characteristics, thermal stability, color, controlled electrical properties, lubricity, abrasion resistance, barrier properties, adhesion promotion, wettability, blood compatibility, and controlled light transmissivity. 

Fig. 1. Vacuum deposition system having a plasma processing capabiHty, where the dashed lines represent optional additions to a system.

Ti02/Na2C02/Na2AlF2/NaCl/Na2B40, at 1050°C (20). Very fine titanium diboride may be made by a gas-phase plasma process in which titanium tetrachloride and boron trichloride are reacted in a hydrogen gas heated by a d-c plasma (21). 

Gas plasma treatment operates at low pressure and relatively low temperature. While the corona treatment is applicable to substrates in sheet or film form, the gas plasma process can treat objects of virtually any shape. The gases most widely used to generate plasma by free-radical reactions include air, argon, helium, nitrogen, and oxygen. All these, with the exception of oxygen. 

When the films were treated in either an oxygen plasma environment or under UV/ozone irradiation, the rates of oxidation were faster for the plasma process. Irradiation of chitosan solution showed that UV/ozone induces depolymerization. In both plasma and UV/ozone reactions, the main active component for surface modification was UV irradiation at a wavelength below 360 nm [231]. 

HANDBOOKOF PLASMA PROCESSING TECHNOLOGY edited by Stephen M. Rossnagel, Jerome J. Cuomo, and William D. Westwood... 

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