Results of investigations on the adsorption of CO andO₂ on transition metal surfaces by employinguv and x-ray photoelectron spectroscopy and electron energy loss spectroscopy (eels) are presented. Results of molecular orbital calculations on adsorbed CO and O₂ are also discussed. Some of the interesting aspects discussed are, satellites in the O(ls) region due to adsorbed CO, vibrationaleels of adsorbed O₂ and dissociation energy profiles of adsorbed O₂ on clean surfaces as well as surfaces covered with potassium or presorbed atomic oxygen.

Together with hydrotalcite-like layered double hydroxides, bivalent and trivalent metal hydroxides and their hydroxy salts are actually anionic clays consisting of positively charged hydroxide layers with anions intercalated in the interlayer region. The anionic clays exhibit anion sorption, anion diffusion and exchange properties together with surface basicity making them materials of importance for many modern applications. In this article, we discuss many different ways of making anionic clays and compare and contrast the rich diversity of this class of materials with the better-known cationic clays.

Layered hydroxides crystallize in a hexagonal structure and incorporate a number of different types of structural disorders as an exigency of anisotropic bonding. Structural disorder contributes to the non-uniform broadening of lines in the powder X-ray diffraction pattern. Common among the disorders are stacking faults, which broaden theh0ℓ/0kℓ reflections. Interstratification selectively broadens the 00l reflections and turbostratic disorder broadens the 0kℓ reflections. The line broadening caused by structural disorder has to be discounted before estimates of particle size are made by applying the Scherrer formula.

Electrodeposition of BaCO₃ from aminecarboxylate stabilized-Ba(HCO₃)₂ baths, results in oriented crystallization when the bath conditions promote the decomposition of the Ba complex. Crystal growth is predominant along the 𝑐-crystallographic axis. The crystallites orient themselves with their 𝑐-axis normal to the substrate. The crystallites exhibit three-fold twinning (trilling) consequent to the evolution of the {110} planes as planes of reflection. Pairs of trillings are seen to grow about a four-sided polygon formed by the {010} crystal faces whose centre is a point of inversion.

Both crystallite size effects and structural disorder contribute to the broadening of lines in the powder X-ray diffraction (PXRD) patterns of layered materials. Stacking faults, in particular, are ubiquitous in layered materials and aside from broadening also induce peaks due to select reflections to shift away from the Bragg positions. The effect of structural disorder has to be suitably discounted before the application of the Scherrer formula for the estimation of crystallite size.