Vaneica Y. Young

Low-temperature deep oxidation of hydrocarbons by metal oxides supported on carbonaceous materials

Abstract First row transition metal oxides supported on carbonaceous materials are shown to be effective in the low temperature deep oxidation of hexane, butane and toluene to carbon dioxide and water. The oxides of manganese, cobalt, copper and zinc were supported on several different types of carbon, out of which it was found that manganese and cobalt oxide supported on Ambersorb® 572 were most durable. In addition, Ambersorb® 563 and Ambersorb® 572 were thermally stable under the reaction conditions. Mechanistic studies in cobalt oxide/Ambersorb® 572 indicate a synergism between the metal oxide and carbonaceous material. A catalytic cycle has been described, involving a CoII/CoIII couple, and the stabilizing effect of the support on the reduced form of the metal oxide.

The X-ray photoemission spectra of Nd(OH)3, Sm(OH)3, Eu(OH)3 and Gd(OH)3

Abstract Experimental XPS spectra of lanthanide trihydroxides (Ln(OH)3, where Ln is Nd, Sm, Eu or Gd) at Ln3+5p, 5s, 4d, 4p, 4s, and 3d and OH− 2σ, 3σ and 1π levels are reported. A process of computation obtained by combining Wendins quasi-particle method and the Johansson-Martenssen method with first-order correction is employed in this work to explain the observed physical phenomena. The derived model implies that the spectral function of a long lifetime quasi-particle is a Gaussian function, locates the atomic orbital energy, corrects the variation in binding energy due to the correlation energy, calculates semi-empirically the dipole relaxation energy shift, and accounts for the atom-to-solid core level shift. Valence band XPS spectra, Ln3+ 4d, 4p, 4s, 3d and experimental and theoretical binding energies of Nd3+, Sm3+, Eu3+ and Gd3+ in Ln(OH)3 are tabulated. It is conspicuous that the 4f and 5d orbital collapses are responsible for the interesting features of three giant Coster-Kronig fluctuations, 5 s 1 ⇌ 5 p 2md1 (m = 5, 6, 7, …), 4 p 1 ⇌ 4 d 2mf1 (m = 4, 5, 6, …) and 4 s 1 ⇌ 4 p 14 d 1mf1 (m = 4, 5, 6, …), and the “satellite complex” in the 3d core hole spectra.

A model for analysis and quantification of ion scattering spectroscopy data

Abstract An improved model has been developed for numerically fitting experimental ion scattering spectroscopy data. This model is a combination of the models described previously by Nelson [J. Vac. Sci. Technol. A 4 (1986) 1567] and Young and Hoflund [Anal. Chem. 60 (1988) 269]. It allows for quantification of the neutralization decay rate, accurate fitting of the different elemental peak shapes, extracting information which is usually difficult to obtain due to poor mass resolution, subtraction of the inelastic background and providing a measure of the composition of the outermost atomic layer. The model has been used to analyze ISS spectra obtained from isotopically pure 24 Mg and Mg of natural abundance (79% 24 Mg, 10% 25 Mg and 11% 26 Mg). The factors which influence spectral (mass) resolution have been examined using the model, and calculated results show that both the width of the scattering angle and the energy spread of the primary ion beam significantly affect resolution.

The X-ray photoemission spectra of La(OH)3

Abstract Experimental X-ray photoelectron spectra of lanthanum at La3+ 5p, 5s, 4d, 4p, 4s, and 3d and OH− 1σ, 2σ, 3σ, and 1π levels are reported. An arithmetic method derived from a combination of Wendins quasi-particle model and the Johansson-Martensson model with first-order correction, is developed to explain the physical phenomena observed in this work. The developed working model suggests that the spectral function of a long lifetime quasi-particle coupled with non-lifetime broadening is a Gaussian function, locates the atomic orbital energy, accounts for the atom-to-solid core level shift and corrects the small variation in binding energy caused by the correlation energy. The spectral function also determines the pure solid state energy shift when the correlation energy of the studied atom or ion is known and calculates semi-empirically the dipole relaxation energy shift. Based on this arithmetic method, La3+, 4d1, and 3d1 and OH− 1σ1, 2σ1, 3σ1, and 1π1 holes are normal quasi-particles having a minimal amount of the dipole relaxation energy shift. However, La3+ 5s1, 4p1 and 4s1 holes are quasi-particles that are severely distorted by the dipole relaxation energy shift, ΣCD (eCA). The ΣCD (eCA) values of La3+ 5s1, 4p1, and 4s1 holes are 3.59(28), 11.58(28), and 11.24(28) eV, respectively.

Chemical alteration of thin alumina films on aluminum during hydrogen-atom exposures

Abstract Hot-rolled and partially oxidized Al foil surfaces were examined before and after H-atom exposures using X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) to monitor the changes which occur at the sample surfaces. The near-surface region of the native oxide of the hot-rolled Al foil contains primarily C and O. Cl and Ca contamination also are present at the outermost atomic layer according to ISS. H-atom exposures reduce the amount of carbonates and hydrocarbons but causes an enrichment of sulfur in the outermost layer of the foil. The O-to-Al ratio is reduced, and the AlOx species initially present is converted to Al2O3. After sputtering the Al foil to remove the Cl, C, and Ca contaminants, the Al was exposed to oxygen at 10−7 Torr for 10 min. The near-surface region of this re-oxidized surface contains both Al metal and Al2O3. Exposing this partially oxidized surface to H-atoms produces a chemically-induced driving force which causes subsurface O to migrate toward the surface of the foil. This results in an increase of the Al2O3 concentration at the sample surface. These results suggest that the thickness of Al oxide layers may be controlled using H-atom exposures. Furthermore, the amounts of carbon contamination can be decreased and possibly eliminated without reducing the alumina.

X-RAY PHOTOELECTRON SPECTROSCOPY OF ALUMINUM OXALATE TETRAHYDRATE

Abstract The X-ray photoelectron spectra of aluminum oxalate tetrahydrate have been determined starting at a temperature of −25°C and as a function of elapsed time as the sample warms from −25 to 37°C. At −25°C, two of the oxalate groups are rapidly decomposed by the X-rays. As the sample warms, the third oxalate group decomposes and aluminum oxide is produced. In contrast, aluminum oxalate tetrahydrate is thermally stable to 60°C, where it begins to lose water. Oxalate does not thermally decompose until a temperature of 150°C is reached.

Theoretical and experimental conductivities of silver halide-silver sulfide ISE membranes

Abstract In a previous paper, the Smith-Anderson particulate conductivity model has been extended to particulate ISE membranes. In this paper, theoretically calculated results are compared with experimentally measured results for silver halide-silver sulfide ISE membranes. Calculated and experimental ionic conductivities are in very good agreement. Calculated and experimental electronic conductivities are in poor agreement. The possible reasons for the latter are discussed.

Theory of electronic and ionic conductivity in particulate membrane ion selective electrode systems: All solid state silver sulfide electrode

Abstract In this paper, we have theoretically investigated the behavior of three figures of merit which might be used to characterize ion selective electrode membranes. This has been accomplished by extending the Smith-Anderson model for calculating the electronic conductivity of particulate membranes to the case of the all solid state silver sulfide electrode, one of the simplest such systems which can be treated. The transport number of Ag + is found to be extremely sensitive to membrane composition. This result points to transport number as potentially the most useful figure of merit for ion selective membrane electrodes of this type.

Surface characterization of lead ion selective electrodes: Life after adsorption☆

Abstract The interaction of interfering ions with the lead ion selective electrode membrane is much more complex than comparable interactions on other solid state ion selective electrode membranes. The possible mechanisms of interaction are identified, and a theoretical model, supported by experimental results and developed with the goal of predicting them, is described.

Physical studies of MoO3 catalysts on silica and carbon supports

The nature and characteristics of the catalytic surface of supported MoO3 catalysts were studied. Changes that occurred on oxidizing alcohols in air over carbon and silica supported MoO3 were examined. Structural data were combined with electron microscopy and photoelectron spectroscopy to demonstrate that the carbon support promotes segregation and fragmentation of MoO3, whereas sintering occurs on silica. Results indicated that this may be correlated with a synergism between the carbonaceous material and metal oxide which provides a reoxidation pathway for reduced Mo, thus preventing formation of extended zones of MoO2, which is inactive for the oxidation of alcohols.