Filamentous carbon formation temperature effects

Inhibition of filamentous carbon growth on metal surfaces by addition of titanium oxide has been reported previously (10). In these experiments the titanium oxide was in the fully oxidized state and was an effective physical barrier toward filament formation, provided that the temperature was kept below 920 K. Above this temperature, the oxide tended to spall, and as bare metal was exposed to the gas phase, prolific filament growth occurred. In the present study we have combined electron microscopy studies with... 

Czerwosz et al. s findings might be of particular interest to readers familiar with carbon formation on nickel and nickel-coated catalysts that had been exposed to hydrocarbons or carbon monoxide in hydrocarbon synthesis or in so-called re-forming reactions carried out in petroleum refineries. For example, the formation of filamentous carbon on such solids at temperatures in the same range as that used by Czerwosz et al. was reported by McCarthy in 1982 [115]. However, these authors did not analyze the carbon deposits by Raman spectroscopy, nor were they aware of the existence of fullerenes. Their concern was the removal of these carbons by steam or by combustion, because these carbons inactivated the catalyst. It was also unknown to them that these carbons had the lubricating properties that were demonstrated by Lauer and co-workers [60,62]. By using these catalysts under conditions of continuous wear, they could maintain the catalytic effect of the surface. 

Two forms of flameless atomizer are in use, i.e. the graphite tube or L Vov furnace and the carbon rod or filament. Of these the first has proved to be the most generally effective and popular. It is widely used in a variety of modifications. In both cases, the temperature is raised rapidly to about 2500 K by the passage of a heavy current for a period of 1-2 minutes. Tube furnaces, which are usually 5 or 10 cm x 3 mm, may be flushed through with argon before vaporizing the sample so as to prevent the formation of... 

---