Surface reaction with nitrogen

W., "Interactions of Ion Beams with Surfaces. Reactions of Nitrogen with Silicon and Its Oxides," J. Chem. Phys., Vol. 68, 1978, pp. 1776-1784. 

Polymerisation of HCN species is also possible once the initial monomers have been formed by the reactions with nitrogen HCN polymers have been postulated in many places in the solar system, from the clouds of Jupiter and Saturn to the dark colour of the surface of comet Halley, not to mention its possible role in the formation of the prebiotic molecule adenine. Photolysis of HCN produces CN and then the formation of nitrile polymers ... 

The reverse reaction to ammonia synthesis, the decomposition to nitrogen and hydrogen, is used in the nitriding of iron and carried out industrially at temperatures around 800 K and atmospheric pressure to produce surface-hardening. This dissolution reaction must also play a part in the synthesis of ammonia by the industrial process. The attempt to nitride iron by reaction with nitrogen gas is very slow under atmospheric pressure, presumably due to the stability of the nitrogen molecule. 

To "blanket with nitrogen," the checkers simply prepared the reaction mixture with the flask open, introduced a flow of nitrogen over the surface for a few minutes, and then closed the system with an exit through a mercury bubbler to maintain a positive pressure. 

Carbon dioxide gas diluted with nitrogen is passed continuously across the surface of an agitated aqueous lime solution. Clouds of crystals first appear just beneath the gas-liquid interface, although soon disperse into the bulk liquid phase. This indicates that crystallization occurs predominantly at the gas-liquid interface due to the localized high supersaturation produced by the mass transfer limited chemical reaction. The transient mean size of crystals obtained as a function of agitation rate is shown in Figure 8.16. 

Investigation into the effect has been mainly devoted to reactions with red fuming nitric acid . It seems that in red fuming nitric acid a preliminary reaction results in the formation of a surface deposit of finely divided metallic titanium ignition or pyrophoricity can then be initiated by any slight impact or friction. The tendency to pyrophoricity increases as the nitrogen dioxide content of the nitric acid rises from zero to maximum solubility at about 20%, but decreases as the water content rises, the effect being nearly completely stifled at about 2% water. 

The reaction with small amounts of nitrogen results in an increased hardness, tensile strength and electrical resistivity. Tantalum is embrittled by higher amounts of nitrogen. The reaction takes place at temperature above 400°C. Nitrides among other phases form at the surface, but at higher temperatures these decompose and all the nitrogen is liberated at 2100°C . 

A stainless steel cannula with a 2-mm. inside diameter and both ends sharpened is inserted through the septum into the receiving flask above the surface of the liquid, and a stream of nitrogen is passed briefly through the stopcock and out the cannula to remove air. The other end of the cannula is then inserted through the septum on the reaction vessel, the end of the cannula in the receiver is pushed below the surface of the liquid, and the solvent is forced into the reaction vessel with nitrogen pressure. 

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