Intercalation of ammonia

Involvement of higher stages at the early stages of intercalation has been shown in several experiments. For example, intercalation of ammonia in TaS2 was shown by in... 

Another reagent, hexamethylenetetramine (HMT) has also been used in place of urea for the homogeneous preparation of LDHs. HMT hydrolyzes at high temperature in aqueous solution with the release of ammonia, which makes the solution alkahne, and formaldehyde, which would not be expected to be incorporated into the LDH. Using HMT, well-crystalhzed 1-5 p.m -sized particles of chloride-intercalated LDHs were prepared in a pressure... 

Intercalation of alkali-metal atoms into zirconium disulphide has been reviewed.254 Only alternate layers of vacant sites are occupied by alkali-metal atoms when ZrS2 is treated with a dilute solution of alkali metal in liquid ammonia.255 At higher con-... 

Figure 3.10 Three steps in preparing an ammonia intercalation reaction cell (a) introduction of ammonia (b) condensation into sidearm (c) sealing of sample cell and vaporization of ammonia.

This rapid intercalation-deintercalation of ammonia can form the basis for a chemical sensing device. Thomas and Cleary (1996) used Mn2 2S6, a layered material similar to PM2, as the host material for ammonia intercalation and showed a rapid change in the dielectric properties of the host upon exposure to ppm concentrations of ammonia. 

A natural clay has been pillared with mixed solutions containing both A1 and Fe, Ti or Cr. The intercalation-generated solids distribution of acid strengths measured by calorimetric adsorption of ammonia is comparable to that of zeoUtes. The surfaces appear as heterogeneous and show initial adsorption heats close to 150-160 kJ moT if one excludes the first point of the differential heat versus coverage curves, which is much higher (=190kJ mol" ) [109]. 

By the simultaneous intercalation of the metal and ammonia the graphite lattice is expanded more than for pure alkali metal-graphite compounds. The distance between the carbon planes is 6.6 A for the ammonia derivatives of all the alkali metals and of calcium for those of strontium and barium a value of 6.4 A has been found. 

The approximately constant expansion of the graphite lattice, which is practically independent of the size of the intercalated metal atom, appears at first sight unusual for, in the ammonia-free compounds, the distance between the layer planes increases, as expected, with increasing size of the alkali metal atom from potassium to cesium. The constancy of the expansion for the ammoniates is perhaps attributable to the effect of the positions of the ammonia molecules in the lattice in determining the increase in the interplanar distance. If this were so, metal atoms or ions could perhaps find sufficient room in holes in the ammonia lattice. In support of this view it may be added that the expansion becomes greater if, in place of ammonia, a layer of amine such as methylamine or ethylamine is intercalated. 

E.W. Ong, J. Eckert, L.A. Dotson Sc W.S. Glaunsinger (1994). Chemistry of Materials, 6, 1946-1954. Nature of guest species within alkaline-earth ammonia intercalates of titanium disulfide. 

Studies have continued on the intercalation of the alkaline-earth metals into lattices of the transition-metal sulphides. Calcium and strontium are intercalated into M0S2 from liquid ammonia solution. X-Ray data reveal a lowering of the crystal symmetry of the sulphide and an increase in the complexity of the structure on intercalation. The intercalation compounds begin to superconduct at ca 4 K (for Ca) and 5.6 K (for Sr), and they show considerable anisotropy with respect to the critical magnetic field. Calcium in liquid ammonia also intercalates with TiS2- Two Ca,TiS2 phases have been identified. The limits of the first are 0.03 0.50, for which a relationship between x and cell parameters a and c... 

Zr, Nb, Ta, Mo and W are assuming interest as possible ionic cathodes. The structures.of these and other chalcogenides have been reviewed by Flahaut. Certain of these compounds can be intercalated readily by electron donor molecules such as ammonia, pyridine etc. Thus TiS and TaS, which are layer compounds with the Cd(0H)p structure, can absorb substantial amounts of ammonia by intercalation between the layers resulting in expansion of the Unit cell. ... 

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