Oxygen plasma ablation

Ismail also examined the surface of the pitch fibers using SEM. He found that the plasma ablated fibers were smooth while the HTO fibers had pits in the surface whose size correlated with the length of the oxidation. He proposed that ...with plasma, oxygen atoms are simultaneously attacking the edge and basal plane carbon atoms, peeling off one complete outer basal layer after another. On the other hand, the... 

THE STRUCTURE OF ASYMMETRIC HOLLOW FIBER MEMBRANES BY OXYGEN PLASMA ABLATION... 

Oxygen plasma ablation combined with scanning electron microscopy has been used to define the structure of hollow fiber membranes prepared from polysulfone in N-formylpiperidine/formamide solvent/nonsolvent mixtures (23). These asymmetric hollow fiber membranes possess a microscopically observable skin supported by a porous open cellular matrix. The oxygen plasma ablation studies indicated that the effective separating layer of the asymmetric hollow fiber membrane is only a small fraction of the thickness of this microscopically observable skin. Below the effective separating layer, this skin contains pores and channels with dimensions below the limits of resolution of the scanning electron microscope. 

The oxygen plasma ablated samples and the unetched controls were measured for their uncoated helium and nitrogen flux rates at 100 psig at room temperature. The helium and nitrogen permeabilities were calculated by equation 1. 

Fig 5 The Performance of Asymmetric Polysulfone Hollow Fiber Membranes spun from N-methylpyrrolidone/Formamide as Function of Oxygen Plasma Ablation Time... 

Newly developed methods for characterizing membranes include electron spin resonance spectroscopy (ESR), Raman spectroscopy, atomic force microscopy (AFM), X-ray, Infrared, oxygen plasma ablation and nuclear magnetic resonance (NMR) and neutron scattering technique. 

Figure 34. Change in the oxygen/nitrogen selectivity (permeability ratio) as a function of plasma ablation time of PPO membrane. (A) PPO-CS2, (B) PPO-TCE...

Figure 35. Permeability (barrer) of oxygen and nitrogen as a function of oxygen plasma ablation time of PPO-CS2. (A) O2, (B) N2...

Fritzsche AK, Cruse CA, Resting RE, Murphy MK. Hollow fiber membranes spun from Lewis Acid Base complexes. I. Structure determination by oxygen plasma ablation. J. Appl. Polym. Sci. 1990 40 19-40... 

The decrease of Si due to F-containing contaminants and the role of the oxygen plasma treatment can be explained by the principle of CAP. The key factor to explain the change of elementary composition at the interface is the plasma sensitivity of elements involved on the surface and in the plasma phase. The ablation of materials exposed to plasmas appears to follow the plasma sensitivity series of the elements involved, which is in the order of the electronegativity of the elements, i.e., elements with higher electronegativity in the condensed phase are more prone to ablate in plasma that contains elements with lower electronegativity [5]. 

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