Electrode surface conditions, particularly on anode surfaces, which influence the vacuum breakdown phenomena, were investigated by using X-ray photoelectron spectroscopy (XPS) under a steady state prebreakdown condition. An experimental apparatus for the prebreakdown currents and the XPS system were built in the same vacuum chamber to enable in-situ measurements. The anode surface conditions were controlled with Ar ion etching and oxidation. Electrode material used was Cu. The anode surface conditions altered the slope of Fowler-Nordheim plots obtained from prebreakdown current-voltage characteristics. The oxidized anode gave a steep slope. Mass analysis of the prebreakdown carrier revealed that dominant ion components were H2O+ for clean anodes and O+ for oxidized anodes. The peak shift of Cu LMM Auger spectra for oxidized anodes was reduced after the prebreakdown current flow. However, O1S, Cu2p1/2 and Cu2p3/2 lines did not show the chemical shift. From these results, it was concluded that desorbed materials from the anode surface deposit on the cathode changed the field electron emission property.
This paper discusses assignments and ionization energy shifts of UPS of xenon atoms adsorbed on metal surfaces. It is suggested that the ordering in split energy levels, which has been controversial in previous publications, may be explained as a function of Xe coverages. It has been shown that the ionization energy shift is due to the final effects. The donimant effect may be a valence force between an adsorbate ion and surrounding Xe atoms.
When I was studying thin Mo films electron beam deposited in high vacuum, I unexpectedly found Mo crystals grown on the surface of a W filament used for an electron gun. SEM observations revealed the simple prismatic shape of the Mo crystals as if they seem to stick in the W surface. Such a crystal growth arouses technological as well as crystallographical interest.
In homogeneous catalysis, bimetallic cluster compounds, possibly as catalytic active species, are expected to provide a synergistic effect for the catalytic activity because of the multi-centered metal atoms simultaneously involved in the catalytic reactions, e.g. CO+H2 into ethylene glycol or olefin hydroformylation. In some cases, metal clusters are easily decomposed into lower-nuclear subclusters as well as mononuclear species under the prevailing reaction conditions. On the other hand, bimetallic carbonyl clusters are used as a precursor to form a surface supported bimetallic ensembles having a high dispersion and well-defind metal compositions. Comparing with the conventionally prepared alloy catalysts, they exhibit a unique catalytic performance in effectively promoting the catalytic activity and in modifying the selectivity in some typical catalytic reactions such as CO+H2 reaction and olefin hydroformylation. The catalysis by supported bimetallic clusters is discussed in terms of their unique structural properties, morphologies, metal compositions and electronic interaction with metal oxides, carbon and polymers, which are studied by the different physical techniques such as EXAFS, Mössbauer, IR, NMR and XPS.
By making the best use of synchrotron radiation with many prominent characteristics in highly polarized intense pulsed white beam from vacuum ultraviolet rays to hard X-rays, there has been a rapid development in dynamic characterization of many kinds of materials from scientific and technological aspects. Studies on structure of surface and/or interface are scientifically and practically important fields in material science. After a description of precursor phenomena in martensitic transfomation in A-15 type superconductors, this brief note is divided into two parts : determination of the surface structure across the surface or interface by specular reflection and within the surface by evanescent wave method. For the former, the measurements of the roughness of the liquid-vapor interface for pure water and the observation of smectic-A layer at the top surface in the bulk nematic as wall as in the isotropic phase are described. For the latter, the method of glacing-incidence X-ray diffraction is given to determine the Au (110) reconstructed surface with a first-layer missing row and a second-layer pairing.
Recent studies on Mössbauer characterization of iron-containing catalysts are presented. Instrumental advances on Mössbauer measurement made possible insitu analysis of the catalysts under reactive atmospheres. With insitu Mössbauer analysis, the surface species produced via reactions with synthetic gas on iron catalysts were identified as various carbides (e.g. χ-Fe5C2). For iron-containing platinum-group-metal catalysts, existence of anchoring iron (III) was estimated and a schematic model for the surface structure was proposed. Good correlations between iron content and chemical states of iron in such bimetallic systems were also observed. Also introduced for their future potentiality are specific applications of Mössbauer effect, source experiment, 99Ru Mössbauer spectroscopy, and depth-selective conversion electron Mössbauer spectroscopy which is a method for surface analysis like electron spectroscopy.
The surface nature and the surface-treatment of silicon-, aluminium-, titanium nitride and zirconium-, titanium boride exposed to an atmosphere were investigated from their X-ray photoelectron spectra and the pyrolyses of nitrides and borides treated with alcohols and organosilylchlorides. It was found that the surface molecules of these nitrides and borides reacted with oxygen and water in an atmosphere and formed the oxide layers. These then reacted further with water in an atmosphere. Thereafter the surface of these nitrides and bromides was composed of these surface hydroxides thus formed. The surface-treatment of these nitrides and borides was found to be applicable to treat similar to that of the corresponding oxide powders.
The outline of the C1 Chemistry project, which is one of the national large scale projects founded by the Agency of Industrial Science and Technology (M.I.T.I.), and the present status of catalyst development in this project are introduced. The establishment of a new manufacturing process for basic chemicals, that is, ethyleneglycol, ethanol, acetic acid, and lower olefins such as ethylene and propylene, from synthesis gas directly or indirectly is the major object of this project. Therefore, development of high performance catalysts is essential to establishing a new process. As a result of a 4-year basic screening test program, several high by active catalyst systems for selective production of these chemicals have been developed. Now, demonstration tests of these systems as bench scale are in progress.