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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1839-1845 
    ISSN: 0887-624X
    Keywords: plasma ; cascade arc ; surface modification ; fluorination ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The depth of surface modification by low-temperature cascade arc torch is investigated. A stack of 10 sheets of nonwoven fabrics of polyester fibers is exposed to a low-temperature cascade arc torch containing CF4 or C2F4, and the fluorination effect is examined by ESCA. It is shown that interaction of chemically reactive species, created in a low-temperature cascade arc torch, with the surface is not limited to the surface contacted by the torch (flame). The results indicate that the fluorination effect is observed on surfaces which are shadowed from the torch by overlying fibers. The highest degree of fluorination is found on the second layer, rather than on the first layer which the torch contacts directly. No significant differences in the trends of penetration of CF4 and C2F4 treatment through porous samples are observed. However, ESCA data show principal differences in chemical structures of the surfaces treated with CF4 (nonpolymer-forming gas) and C2F4 (polymer-forming gas). These results indicate that chemically reactive species induced by the excited species of argon rather than primary species created by the ionization process seem to play predominant roles in the surface treatment as well as the low-temperature cascade arc torch polymerization of perfluorinated compounds. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 2887-2892 
    ISSN: 0887-624X
    Keywords: plasma ; cascade arc ; surface modification ; fluorination ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The depth and possible mechanisms of the penetration of surface modification into porous media by a low temperature cascade are torch are investigated. Two different modes of such penetration (“flow controlled” and “diffusion controlled”) are evaluated. Three porous samples [stacks of 10 sheets of nonwoven fabrics of poly(ethylene terephthalate)each], placed at an axial distance of 24, 28, and 32 cm from the cascade are anode, are exposed to a low temperature cascade arc torch containing argon and CF4 or C2F4, and surface properties of each of the sheets within treated porous samples are examined by ESCA. It is shown that interaction of chemically reactive species, created in the low temperature cascade arc torch, with the surface is not limited to the surface directly contacted by the torch. The flow controlled penetration is more pronounced for the outer layers, while diffusion controlled penetration is within the inner layers of the porous structure. Substantial differences in the fluorination effect of CF4 (nonpolymer forming gas) and C2F4 (polymer forming gas) discharges for the second and third stacks are observed, that can be explained by the fact that the major effect of the CF4 cascade arc torch treatment is based on the reaction of reactive species with the surface polymer molecules. The effect of C2F4 cascade arc torch treatment is based on the reactions of reactive species with polymers as well as reactions of reactive species themselves at the surface (plasma polymerization). Reactivity of the species created in C2F4 discharge is much higher compared to that created in CF4 discharge, which is one of the major factors influencing penetration trends of low temperature cascade arc treatment into porous media. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 14 (1994), S. 251-275 
    ISSN: 1572-8986
    Keywords: Plasma jet ; nonequilibrium plasma ; plasma diagnostics ; excited argon ; cascade arc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Plasma diagnostic techniques have been employed to determine particle densities and temperatures in a low-pressure argon plasma jet generated by a cascade arc. These measurements allow characterization of the extent to which the plasma jet deviates from thermodynamic equilibrium and provide a basis for predicting how reactive gases will interact with the excited and ionized species in the plasma jet. It was found that the distribution of atomic states in the plasma jet is not adequately described by either local thermodynamic equilibrium (LTE) or partial local thermodynamic equilibrium (pLTE), and the jet was optically thick for 3p→4s transitions across the jet radius. Excited argon neutrals outnumber ions by a large ratio, and dominate subsequent dissociation/excitation phenomena. The rate of methane destruction in the plasma jet shows that estimates for particle densities, temperature, and jet velocity are self-consistent.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 14 (1994), S. 277-299 
    ISSN: 1572-8986
    Keywords: Plasma polymer ; plasma jet ; cascade arc ; plasma modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An overall mechanism for plasma polymer deposition from a methane-seeded argon plasma jet was established from experimental measurements and a simplified model of reaction kinetics within the plasma jet. Total mass deposition rates were obtained at various substrate positions and methane flow rates. Methane consumption was estimated from residual gas analysis. The influence of substrate coolant temperature on deposition rate was evaluated. The model was based on particle densities, jet temperature, and jet velocity data published previously, and reaction rate constants from the literature were used. No adjustable parameters were employed in this model. Experimental results for total deposition rate and methane consumption were in good agreement with model predictions. The overall deposition mechanism consists of three steps: Penning ionization of methane by excited argon neutrals, followed by dissociative recombination of CN x + to yield CH, followed by incorporation of CH into the growing film upon impact. Contributions of species other than CH to the total deposition rate are minor, and adsorption is not a prerequisite for incorporation into the growing film.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 18 (1998), S. 461-485 
    ISSN: 1572-8986
    Keywords: Plasma jet ; cascade arc ; optical emission spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The optical emission spectra from expanding low-temperature cascade arc plasmas were studied. The objective of this study was to examine the distinctive features of low-temperature cascade arc plasmas in comparison with a radio frequency (RF) plasma source. The principal results obtained in this study were: (1) in an expanding cascade arc plasma jet, active heavy particles (mainly excited argon or helium neutral species under our operating conditions), rather than electrons, are responsible for the excitation of reactive species when a reactive gas is injected into the plasma jet, (2) the excitation of reactive species was found to be controlled by the electronic energy levels of these excited argon or helium neutrals, (3) changing the operating parameters affected only the emission intensities of excited species, and no effect on the emission nature of plasmas was observed.
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1583-1592 
    ISSN: 0887-624X
    Keywords: optical emission spectroscopy ; cascade arc ; surface modification ; fluorination ; plasma polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical Emission Spectroscopy (OES) was used to identify reactive species and their excitation states in low-temperature cascade arc plasmas of N2, CF4, C2F4, CH4, and CH3OH. In a cascade arc plasma, the plasma gas (argon or helium) was excited in the cascade arc generator and injected into a reactor in vacuum. A reactive gas was injected into the cascade arc torch (CAT) that was expanding in the reactor. What kind of species of a reactive gas, for example, nitrogen, are created in the reactor is dependent on the electronic energy levels of the plasma gas in the cascade arc plasma jet. OES revealed that no ion of nitrogen was found when argon was used as the plasma gas of which metastable species had energy less than the ionization energy of nitrogen. When helium was used, ions of nitrogen were found. While OES is a powerful tool to identify the products of the cascade arc generation (activation process), it is less useful to identify the reactive species that are responsible for surface modification of polymers and also for plasma polymerization. The plasma surface modification and plasma polymerization are deactivation processes that cannot be identified by photoemission, which is also a deactivation process. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1583-1592, 1998
    Additional Material: 12 Ill.
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