Oxidising gases

Finely divided barium is susceptible to rapid, violent combination with atmospheric oxygen. Therefore, in powdered form it must be considered pyrophoric and very dangerous to handle in the presence of air or other oxidising gases. Barium powder must be stored under dry argon or helium to avoid the possibihty of violent explosions. Massive pieces of barium, however, oxidize relatively slowly and present no explosion hazard if kept dry. 

Oxidizing gases Tantalum reacts with oxidising gases at elevated temperatures. 

Another cause of growth which is of equal importance with graphitisation is the penetration of oxides into the metal along the graphite flakes. This presumably takes place because oxidising gases can be adsorbed on to the... 

When an iron is exposed to an oxidising atmosphere, it develops a scale which consists of a series of layers of oxides of varying composition. The thickness of the scale naturally depends on the temperature and the duration of oxidation (/). The scale does not, however, thicken at a uniform rate with time since its very presence reduces the accessibility of the metal surface to the oxidising gases. Ideally, the thickness of the scale should increase as /t, but in practice cracks develop in the scale, and these allow the gases to reach the metal surface somewhat more readily than is postulated by this relationship. Cracking will always tend to occur as the film... 

The oxidation reactions in different carbons are thus very different at low temperatures, but this is less true as the oxidation temperature increases. In porous samples the rapid reaction essentially suppresses the diffusion of gas within the pores and oxidation takes place only on the surface. The Oxidation rate then becomes independent of the type of carbon and is determined by the flow of oxidising gases. This condition is reached at about SOO C in pure materials. 

Environment (gaseous) Remove O2 or other oxidising gases in which the metal is unstable Use of inert atmospheres (H2, N2, A) or of vacuo... 

Powdered barium combusts spontaneously in air and oxidising gases. 

The finely divided metal may ignite or explode in air or other oxidising gases. 

Polarons are epr-active by virtue of their unpaired spin. Consequently, another technique to be applied relatively soon after the discovery of conducting polymers was epr. Again the early studies were carried out ex situ on free-standing films, usually by monitoring the epr response (and the conductivity) of the completely reduced film on various exposures to oxidising gases such as I2 or 02 (cf. the UV-visible experiments discussed above). 

This influences the structural features of the mesophase which remains more disordered, a point made by Cranmer et al. (43). Stadelhofer (107) found that the presence of QI did not change rates of formation of mesophase. Romovacek et al. (108) consider that pyrolytic particles in pitch (primary QI) retard the development of mesophase and suppress coalescence. Decrease in size of optical texture, as brought about by mechanical modification as distinct from chemical modification of pitch properties can increase both the strength and reactivity to oxidising gases of the resultant coke, as recently put forward by Markovic et al. (109). ... 

Copper, chromium, iron, most metals or their salts, any flammable liquid, combustible materials, aniline, nitromethane Fuming nitric acid, oxidising gases Acetylene, ammonia (anhydrous or aqueous)... 

Compressor lubricants Lubrication in the pressurised area of a compressor presents many problems. Lubricants must not only seal, cool and reduce friction and wear but also cope with the presence of compressed aggressive or oxidising gases. 

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