Layered transition metal solids

Bio-nanohybrids Based on Layered Transition Metal Solids... 

The stmeture of transition metal carbides are closely related to those of the transition metal nitrides. However, transition metal carbides feature generally simpler stmeture elements as compared to the nitrides. In carbides, the metal atoms are arranged in such a way that they form close-packed arrangements of metal layers with a hexagonal (h) or cubic (c) stacking sequence or with a mixtme of these (see Nitrides Transition Metal Solid-state Chemistry). The carbon atoms in these phases occupy the octahedral interstitial sites. A crystallochemical rule claims that the phases of pure h type can have a maximum carbon content of [C]/[T] = 1/2 and the c type phases a maximum carbon content of [C]/[T] = 1 hence in stractures with layer sequences comprising h and c stractme elements the maximum nonmetal content follows suit. 

Interpolation or intercalation (see Intercalation Chemistry) is said to occur when additional species are placed into a host stmcture to change either composition or properties. At one extreme, intercalation can refer to the insertion of gnest molecnles into cage stmctures such as that of the zeolites (see Zeolites), or between the layers of laminated compounds snch as the clays (see Silicon Inorganic Chemistry). At the other extreme, the insertion of small atoms snch as C or N into metal phases to form interstitial alloys (see Alloys Carbides Transition Metal Solid-state Chemistry Nitrides Transition Metal Solid-state Chemistry), is inclnded in the category. A large variety of stmctures can be found in snch materials, and... 

The major classes of conducting host lattices are summarized in Table 2. Of these, graphite and the layered transition metal dichalcogenides see Chalcogenides Solid-state Chemistry) have been investigated in the greatest detail. The conducting host lattices have the feature that... 

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. 

R. A. Huggins, H. Prinz, M. Wohlfahrt-Mehrens, L. Jdrissen, and W. Witschel [1994] Proton Insertion Reactions in Layered Transition Metal Oxides, Solid State Ionics, 70-71, 417-424... 

We have illustrated the room-temperature synthesis of a crystalline structure prepared by the simultaneous modification of both the structure and chemical composition of the host and guest species domains of a layered precursor. This novel room-temperature chimie douce synthesis technique produced a new class of layered transition-metal molybdate (LTM) materials using calcined LDHs as precursors. These materials, being ionic lamellar solids themselves, may be suitable hosts for the synthesis of intercalated derivatives, thereby creating the potential for the preparation of a whole new class of molecularly designed materials. 

Using a series of layered transition metal disulfides, Sutrisno et al. have demonstrated that the wide-line natural abimdance solid-state NMR spectra of in a less symmetric environment can readily be obtained at ultrahigh magnetic field of 21.1 T and that surprisingly these closely related materials display a wide range of quadrupole coupling constant and chemical shift anisotropy values. ... 

Solid-State Metathesis Routes to Layered Transition-Metal Dichalcogenides and Refractory Materials... 

The reactivity of the transition metals towards other elements varies widely. In theory, the tendency to form other compounds both in the solid state (for example reactions to form cations) should diminish along the series in practice, resistance to reaction with oxygen (due to formation of a surface layer of oxide) causes chromium (for example) to behave abnormally hence regularities in reactivity are not easily observed. It is now appropriate to consider the individual transition metals. 

Another application is in tire oxidation of vapour mixtures in a chemical vapour transport reaction, the attempt being to coat materials with a tlrin layer of solid electrolyte. For example, a gas phase mixture consisting of the iodides of zirconium and yttrium is oxidized to form a thin layer of ytnia-stabilized zirconia on the surface of an electrode such as one of the lanthanum-snontium doped transition metal perovskites Lai j.Srj.M03 7, which can transmit oxygen as ions and electrons from an isolated volume of oxygen gas. 

This highhght examines several new hybrid layered structures in the hetero-metallic perrhenate and vanadate families, whereby the late transition-metals are incorporated and their roles probed in the structures of layered solids. From these two families, new structural principles have emerged that not only help us understand key stractural features and correcdy forecast new compositions, but equally, have yielded many surprises (chirality, reduced phases) that show some of the most exciting chemistry is still waiting to be discovered or even imagined ... 

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