Reactivity and structure of CF3I on Ru(001)
A variety of surface-sensitive techniques are used to elucidate the reaction pathways, as well as adsorbate structures, associated with thermal activation of CF{sub 3}J following adsorption on Ru(001) at 100 K. XPS shows that the C-I bond of CF{sub 3}I dissociates below 200 K to form CF{sub 3}(ad) and I(ad); the subsequent reactions of CF{sub 2} are best viewed as being regulated by the availability of surface sites. CF{sub 3}(ad) dissociates to CF{sub 2}(ad) below 200 K. Further CF{sub 3} dissociation, some of which is activated by H(ad), occurs between 200 and 400 K until all available sites are filled. Desorption of the remaining CF{sub 3}, peaking at 705 K, once again opens surface sites for decomposition. This is followed by recombination of the products to form CF{sub 3}(g). No evidence for CF(ad) is ever observed. Hydrogen coadsorption studies explain interesting features associated with fluorine evolution. HREELS and ESDIAD results indicate that CF{sub 3} adopts a tilted configuration on Ru(001). 53 refs., 11 figs., 3 tabs.
Organic chemistry on solid surfaces
Abstract Chemistry on solid surfaces is central to many areas of practical interest such as heterogeneous catalysis, tribology, electrochemistry, and materials processing. With the development of many surface-sensitive analytical techniques in the past decades, great advances have been possible in our understanding of such surface chemistry at the molecular level. Earlier studies with model systems, single crystals in particular, have provided rich information about the adsorption and reaction kinetics of simple inorganic molecules. More recently, the same approach has been expanded to the study of the surface chemistry of relatively complex organic molecules, in large measure in connection with the selective synthesis of fine chemicals and pharmaceuticals. In this report, the chemical reactions of organic molecules and fragments on solid surfaces, mainly on single crystals of metals but also on crystals of metal oxides, carbides, nitrides, phosphides, sulfides and semiconductors as well as on more complex models such as bimetallics, alloys, and supported particles, are reviewed. A scheme borrowed from the organometallic and organic chemistry literature is followed in which key examples of representative reactions are cited first, and general reactivity trends in terms of both the reactants and the nature of the surface are then identified to highlight important mechanistic details. An attempt has been made to emphasize recent advances, but key earlier examples are cited as needed. Finally, correlations between surface and organometallic and organic chemistry, the relevance of surface reactions to applied catalysis and materials functionalization, and some promising future directions in this area are briefly discussed.
Concentrated solar energy in materials processing
Solar energy, which is available in abundant in nature, is least utilised. As per primary energy product, solar energy conversion can be of three different ways: solar fuels, solar electricity, and solar thermal systems. These three approaches are presently not being fully utilised. Concentrated solar energy (CSE) is an alternative to other types of energy for modifying the surfaces of metallic materials. Attempt has been made to overview the current status of CSE in materials processing technology. In this paper, applications of CSE through solar furnace and Fresnel lens for hardening, coatings, sintering, nitriding, synthesis and welding are discussed.