TiS2 Titanium sulfide

Titanium(II) sulfide, TiS titanium(III) sulfide, Ti2S3 titanium(IV) sulfide, TiS2 zirconium sulfide, ZrS2 hafnium selenide, HfSe2 hafnium sulfide, HfS2. 

Titanium disulfide has been proposed as a soHd lubricant. The coefficient of friction between steel surfaces is 0.3, compared to only 0.2 for molybdenum disulfide. However, because it does not adhere strongly to metal surfaces, TiS2 is generally less effective than molybdenum sulfide. 

The sulfides of titanium are, in this connection, of particular interest. Inasmuch as TiS crystallizes with the NiAs structure and TiS2 with the Cdl2 structure, the existence of an intermediate compound of the sesquisulfide type has long been the object of speculation (I, 3), until the last few years when its existence has been definitely established (4, 5,9). For our part, we have concentrated our attention on titanium disulfide, titanium sesquisulfide, and the manner of transition from one to the other. 

The two sulfur planes adjacent to a plane of titanium draw closer to it, the nearer the sulfide is to the stoichiometric composition. The latter corresponds to a Ti-S distance of 2.32 A. The S-S distance between two (TiS2)n sheets is 3.62 A. This value is in exact agreement with the Van der Waals radius of sulfur. When titanium is inserted between these sulfur atoms, the sulfur planes tend toward positions at a height of 1/4. And, whether the sulfides are prepared at 1000° or 800° C., the phase limit corresponds to z— 1/4. The octahedra formed by sulfur atoms are all identical in this case, whether or not they contain titanium atoms. We consider this criterion as decisive in the transition from the TiS2 structure to another structure characterizing the next phase. 

The mean systematic deviation between the observed and the calculated values of the unit cell s mass—or, what amounts to the same thing, the density-increases as S/Ti decreases. Now, the sulfides belonging to the TiS2 and Ti2S3 phases are always well crystallized, and the errors in measuring lattice parameters and densities are of the same order. It is thus not unreasonable that the increase of this deviation should be due to the creation of sulfur vacancies, which proceeds simultaneously with the insertion of titanium. The observation has been previously made in connection with other analogous systems in which there is a transition from the compound MX2 to MX. 

We have not studied sulfides of higher titanium content than those constituting the Ti2S3 phase. We concentrated on determining the nature of the defects responsible for the deviations from stoichiometry that can occur in titanium disulfide. Next, we inquired into the alteration of the structure of this system as titanium is inserted. This led us to encounter a whole series of complex forms, in the nature of superlattices, which account for the transition between TiS2 and Ti2S3. To make the study complete, it would be necessary also to determine the conditions required for the transition from Ti2S3 to TiS, and to elucidate in particular the structure of the compound which occurs between these two phases. 

With sulfur titanium forms the three sulfides, TiS, Ti2S3, and TiS2, besides corresponding normal, basic, and double sulfates. The ability to form sulfates distinguishes titanium rather sharply from silicon and germanium. 

TITANIUM (IV) SULFIDE TiCl4 + 2H2S -> TiS2 + 4HC1... 

Titanium(IV) sulfide is analyzed for titanium by igniting the sample in air and weighing as the dioxide. The ignition temperature must be held below 800° since titanium tends to form nitrides at higher temperatures. Anal. Calcd. for TiS2 Ti, 42.75. Found Ti, 43.49. The high titanium value is due to the presence of a small quantity of titanium(III) sulfide. 

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