Argon, exposure conditions

Plasma surface treatment increases the surface energy of a substrate hy bombarding the substrate surface with ions of a gas such as argon. Plasma treatment can be performed at atmospheric conditions or in a sealed chamber under extremely low pressures. By selecting appropriate gases and exposure conditions, the surface can be cleaned, etched or chemically activated. The results typically show up to a two- or three-fold increase in surface wetting [3]. 

Figure 11.9 Cyclic voltammograms in Me O [0.1 M (Et4N)C104] for (a) Ph-NHNHPh, (b) an equimolar mixture of PhNHNHPh and Oj (electrogenerated) in an argon atmosphere, (c) solution b after exposure to 02 (1 atm) for 3 min followed by a 5-min purge with argon, and (d) 10 mM PhNHNHPh in an 02 (1 atm)-saturated solution after the in situ electrogeneration of 0.05 mM Oj (1 min) followed by a 5-min purge with argon. Conditions a platinum electrode (area 0.23 cm2) at a scan rate of 0.1 V s l.

Despite the remarkable tolerance of the system to many changes in experimental conditions, Schauzer observed no reduction of nitrogen upon irradiation of iron-doped titania in aqueous suspensions [58, 59], Reports by some other investigators (see Section II.B.l) contradict this observation. However, no detailed description of the experiments of Schrauzer and co-workers with aqueous suspensions has been found and so other workers may have used different conditions. The TiOz preirradiated under argon did not reduce N2 upon immediate subsequent exposure in the dark. Schrauzer and Guth reported that the rate of ammonia production increased linearly with increasing nitrogen pressure up to about 0.6 atm, then more slowly to... 

Figure 5. XRD patterns (CuKa) of reduced catalyst PdZr-i before (trace 1) and after (trace 2) exposure to CO disproportionation conditions 1730 ppm CO in argon, 170°C for 18 hrs Pd, + Zr02 monoclinic.

Figure 6. Behaviour of catalyst PdZr-i (A) and reference Pd powder catalyst (B) during alternate cycling between 02/Ar and CO/Ar feed. Conditions 150°C, 9 min exposure to 1730 ppm O2 in argon, then 9 min to 1730 ppm CO in argon flow rate, 178.5 ml min-7.

The tensile strength of Si-C-0 fibers decreases after exposure to elevated temperatures. When Nicalon NL 200 fibers are exposed for 1 hour to 1300 C in argon (P = 100 kPa), their mean tensile strength and scale parameter, Co, decrease by 45% while their Weibull modulus remains unchanged [80-83]. Fibers exposed to more severe conditions (e.g., for 5 hours in a vacuum at 1500°C) are so weak that they cannot be tested. Finally, the fact that oxygen-free fibers maintain their tensile strength under similar conditions relates to the absence of silicon oxycarbide and its decomposition process. 

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