Titanium-nitrogen system

The titanium-nitrogen system was chosen as a case study for systems that exhibit melting, and for further clarification, experiments in the zirconium-nitrogen system were also conducted. Similarly, the tantalum-nitrogen system was extensively studied as an example of a non-melting metal, and further evidence was collected from experiments on the niobium-nitrogen system. 

Figure 12.5 Titanium-nitrogen system Effect of nitrogen pressure and solid phase dilution on combustion temperature. Particle size 29 (rm.

Figure 12.13 Titanium-nitrogen system Effect of particle size and nitrogen pressure on propagation velocity. Solid phase dilution = 50%.

The molybdenum-silicon and titanium-nitrogen systems also belong to this group. For both, it was shown that U decreases when metal (Mo, Ti) particle size increases (curves 6 and 7, Fig. 48). 

It is evident from the earlier discussion of the titanium-nitrogen system that the final volatilization temperature (3540 K) was controlled by the complete vaporization of the titanium formed due to the dissociation of the product titanium nitride. The partial pressure of titanium vapor was equal to 0.666 atm at the final volatilization temperature of 3540 K (see Fig. 8). Indeed, the vaporization temperature of titanium at 0.666 atm is 3530 K. Consequently, to analyze the results... 

A. S. Mukasyan, S. C. Vadchenko, L. O. Khomenko, Combustion Modes in the Titanium-Nitrogen System at Low Nitrogen Pressures, Combustion and Flame 111 (1997), 65. 

It is quite remarkable that with all the effort on dinitrogen fixation with the titanium metallocene systems very little is known about the reactions of these complexes with the oxides of nitrogen. Salzmann (119) reported the formation of a polymeric complex [(tj-CsHs TiNO] from the reaction of 3 and NO in toluene solutions. Later, Bottomley and Brintzinger reported that (T7-C5H )2Ti(CO)2 (39) reacts with NO to yield [( -CsHs TiO] as well as an apparent isocyanate complex (112). With an excess of (tj-C5H5)2Ti(CO)2 to nitric oxide, CO, C02, N2, and a Ti-isocyanate species were observed. With N20, (T -C5H5)2Ti(CO)2 yields N2, CO, and various Ti-oxo species. In contrast to our studies with 37 and CO, (tj-C5H5)2Ti(CO)2 and NH3 did not generate an isocyanate species. 

Ternary phases with structures different from those of the phases of the binary boundary systems are more the exception than the rule. Such phases have been reported in the systems Nb-Mo-N, Ta-Mo-N, Nb-Ta-N, Zr-V-N, Nb-Cr-N, and Ta-Cr-N. Information about ternary transition metal-nitrogen systems is often available for specific temperatmes only. This is even more the case for quaternary nitride systems, which play a role in the production of carbonitride cermets where quaternary compounds of the types (Ti,Mo)(C,N) and (Ti,W)(C,N) are of interest (see Carbides Transition Metal Solid-state Chemistry), as well as in layer technology where titanium nitride-based coatings of the type Ti(C,B,N) are prepared by magnetron sputtering. Layers consisting of ternary compounds of the type (Ti,Al)N and (Ti,V)N also have favorable properties with respect to abrasion resistance. 

The magnets do require expensive helium refrigeration systems to cool the niobium-titanium coils to superconducting temperatures. Thus, a liquid nitrogen system should be less expensive, simpler to operate, and more reliable. But some scientists are dubious. Said John Hulm ... 

One can extend this cycle chemistry by putting electricity to use. In short, it is possible to accomplish electrolytic reduction of nitrogen and to develop the phenomenon into a cycle (Figure 3). Thus, we have achieved true catalytic electrolytic conversion of nitrogen to ammonia, by means of a process based on the behavior of titanium. This system was initiated at Stanford by Akermark (14) and developed by Seeley (J5). 

Addition compounds form with those organics that contain a donor atom, eg, ketonic oxygen, nitrogen, and sulfur. Thus, adducts form with amides, amines, and A/-heterocycles, as well as acid chlorides and ethers. Addition compounds also form with a number of inorganic compounds, eg, POCl (6,120). In many cases, the addition compounds are dimeric, eg, with ethyl acetate, in titanium tetrachloride-rich systems. By using ammonia, a series of amidodichlorides, Ti(NH2) Cl4, is formed (133). 

Metals which are subject to oxidation or attack by nitrogen can be sprayed in a closed system so that air is exluded. The heat necessary to melt the wire is produced by current generated in the wire itself by high-frequency currents flowing in small water-cooled coils. By this means, titanium, niobium and even uranium, can be sprayed without gaseous contamination. 

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