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Showing papers on "Oxide published in 1979"


Journal ArticleDOI
TL;DR: In this article, the reaction of catalytic oxidation over oxide catalysts has been extensively studied in recent years following expansion of their applications in petrochemistry as well as their wide theoretical interest.
Abstract: Reactions of catalytic oxidation over oxide catalysts have been extensively studied in recent years following expansion of their applications in petrochemistry as well as their wide theoretical interest. Studies in this field have also contributed greatly to our understanding of the general mechanisms of catalyst action.

397 citations


Journal ArticleDOI
TL;DR: In this paper, the chemical structures of thin SiO2 films, thin native oxides of GaAs (20-30 A), and the respective oxide-semiconductor interfaces, have been investigated using high-resolution X-ray photoelectron spectroscopy.
Abstract: The chemical structures of thin SiO2 films, thin native oxides of GaAs (20-30 A), and the respective oxide-semiconductor interfaces, have been investigated using high-resolution X-ray photoelectron spectroscopy. Depth profiles of these structures have been obtained using argon ion bombardment and wet chemical etching techniques. The chemical destruction induced by the ion profiling method is shown by direct comparison of these methods for identical samples. Fourier transform data-reduction methods based on linear prediction with maximum entropy constraints are used to analyze the discrete structure in oxides and substrates. This discrete structure is interpreted by means of a structure-induced charge-transfer model.

292 citations



Journal ArticleDOI
TL;DR: The structural or intrinsic type of interface state charge related to thermal oxidation and annealing processes has been characterized with respect to silicon thermal oxidation variables using quasistatic C-V techniques.
Abstract: The structural or intrinsic type of interface state charge, related to thermal oxidation and annealing processes, has been characterized with respect to silicon thermal oxidation variables using quasistatic C‐V techniques. Those variables include oxidation ambient (, , ), annealing/cooling ambient (, , Ar), oxidation temperature (800°–1200°C), silicon type (p‐ and n‐type), and orientation [(111) and (100)]. Oxides (1200–2200A thick) annealed and cooled from any oxidation temperature in nitrogen or argon exhibit large interface state densities as oxidized. However after a low temperature hydrogen anneal these densities are lower than those of comparable oxygen‐cooled oxides. Interface state densities of oxides cooled in oxygen vary inversely with oxidation temperature before and after postmetallization anneals. This temperature relationship is very similar to that reported previously for oxide fixed charge and helps to substantiate a model based on a common origin of interface states and oxide fixed charge.

241 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of thermal aging on catalytic activity was studied under oxidizing (air), inert (N2), and reducing (H2) conditions, and the results showed that small amounts of Ce oxide (0.6-1.3 wt% Ce) enhance the oxidation of CO over fresh Pt and Pd catalysts.

226 citations


Journal ArticleDOI
TL;DR: In this article, it has been shown that monolithic oxide glasses can be formed by chemical polymerization at low temperatures and that high-temperature reactions such as crystallization, phase separation, etc., which restrict glass formation in certain systems and regions, can largely avoid.
Abstract: Historically, glasses have been formed by solidification of oxide melts from elevated temperatures. Recently it has been demonstrated that monolithic oxide glasses can be formed by chemical polymerization at low temperatures. By the use of this technique, high-temperature reactions such as crystallization, phase separation, etc., which restrict glass formation in certain systems and regions, can be largely avoided. Thus, the technique not only permits investigation of glass structure from a fundamentally different point of view, but also allows the formation of new glasses which can not be formed by thermal means.

226 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used transmission electron microscopy (TEM) to study the behavior of Pt oxide on γ -Al 2 O 3 during various heat treatments and found that the Pt oxide concentration in the dispersed phase increases proportionally with Pt loading until a saturation concentration of 2.2 μ mol Pt/m 2 (BET) is reached.

194 citations



Journal ArticleDOI
TL;DR: In this paper, the structure of the particles was very disordered at sizes ≲100 A but changed to become single crystal with a disordered core as the size increased to 100-200 A.
Abstract: Colloidal iron dispersions have been prepared by the thermolysis of Fe(CO)5 in solutions of functional polymers. The structure of the particles was very disordered at sizes ≲100 A but changed to become single crystal with a disordered core as the size increased to 100–200 A. Particles ≲100 A were superparamagnetic, and particles in the 100–200‐A range had a time‐dependent hysteresis. On exposure to the atmosphere an ∼30‐A‐thick γ‐Fe2O3 oxide film was produced on the surface of the particles. This is the ’’passive oxide film’’ detected previously by a number of techniques but never before imaged directly in situ. As water was absorbed from the atmosphere the chlorinated solvent‐based dispersions reacted further to give β‐FeOOH. This reaction was promoted by chloride‐ion impurity. The magnetic moment decayed with oxidation roughly in proportion to the quantities of Fe, γ‐Fe2O3, and β‐FeOOH present. Disorder in the structure of ≲100‐A particles formed in nonchlorinated solvent‐based dispersions produced an i...

183 citations


Journal ArticleDOI
TL;DR: Antireflective (AR) coatings, which are produced from organometallic driven solutions containing oxide constituents in a chemically polymerized form, are presented and showed as much as 49% improvement in efficiency over the uncoated state.
Abstract: Antireflective (AR) coatings, which are produced from organometallic driven solutions containing oxide constituents in a chemically polymerized form, are presented. These solutions leave a film on substrates which, upon heat treatment, converts to a glasslike oxide film having the desired optical thickness and index of refraction. The index can be varied continuously from 1.4 to 2.4; thus the AR coatings can be fine-tuned for different substrates and for specific wavelengths of light. Silicon solar cells AR-coated by this technique showed as much as 49% improvement in efficiency over the uncoated state. The real advantage of the process, however, lies in the fact that it is simple, well-suited for automated mass production of photovoltaic cells, and reduces the cost of coating application from an estimated $0.20 per W-package to about $0.01 per W-package.

181 citations


Journal ArticleDOI
TL;DR: In this article, the authors discuss the kinetics and mechanism of the electrochromic reaction in anodic iridium oxide films with particular reference to the requirement for preserving electroneutrality within the bulk oxide.
Abstract: The oxidation state of iridium ions in an oxide film, grown electrochemically on an Ir metal reflector electrode, can be rapidly and reversibly modulated according to the electrochromic redox reactionBy suitable choice of electrolyte composition and potential limits, the coloration and bleaching processes can be effected without causing oxide film growth or dissolution, or electrolyte decomposition. Color‐bleach (c‐b) cycles exhibit reflectance contrast changes, , and charging times, τ, suitable for electrooptic display devices, e.g., for a film 320 nm thick, at and . Long term corrosion stability is obtainable in mildly acidic sulfate electrolytes, e.g., at pH 3.5. Sulfate electrolytes are also apparently unique in preventing degradation of c‐b response times owing to changes in film structure. East write‐erase times are made possible by the highly porous and hydrated nature of the oxide film and the ready availability of the protons required for bleaching from an 'internal' source—free molecules in the electrolyte contained within the film pores and/or bound or OH groups on the oxide surface. The kinetics and mechanism of the electrochromic reaction in anodic iridium oxide films are discussed with particular reference to the requirement for preserving electroneutrality within the bulk oxide. Recent claims that this redox reaction can occur without exchange of protons with the electrolyte are shown not to be substantiated. Attractive features of the electrochromic iridium oxide system for display devices include: (i) broad spectral absorption; (ii) good contrast ratio; (iii) fast response; (iv) good corrosion stability; (v) good open‐circuit memory in the presence of water and dissolved ; (vi) suitable threshold and switching voltage levels; and (vii) the ability to grow and reform the oxide layer in situ in the electrooptic display cell. The charge (~20 mC cm−2) and energy (~30 mJ cm−2) required for coloration and bleaching are similar to those required for other electrochromic oxide systems, e.g., the tungsten bronzes.

Journal ArticleDOI
TL;DR: In this article, the adsorption of hydrogen on Pt(100), (110) and (111) electrodes from 0.5 M H2SO4 has been investigated by measuring potentiodynamic adaption and desorption spectra.

Journal ArticleDOI
TL;DR: In this article, high resolution stereo micrographs obtained in this manner provide striking visual evidence for fine oxide protrusions which apparently interlock with the adhesive to enhance bond strength.

Journal ArticleDOI
TL;DR: In this article, the formation of "bimetallic clusters" supports the Alloy explanation for the improved performance of this type of bimetallic reforming catalyst, and it is shown that in the presence of adsorbed oxygen the Pt-Re clusters are thermodynamically unstable but that under mild conditions the rate of segregation is slow.


Journal ArticleDOI
TL;DR: In this article, a review of hydrogen in thermally grown films on silicon with hydrogen as the most important contaminant or additive is presented, and the possible sources of hydrogen are (i) in the oxidizing ambient, deliberately introduced or resulting from permeation through hot furnace tubes, (ii) hydrogen in room ambient oxide film on silicon, and (iii) deliberate or unintentional or in the ambient of postoxidation heat-treatments.
Abstract: This review discusses within a unified framework various phenomena occurring in thermally grown films on silicon with hydrogen as the most important contaminant or additive. The possible sources of hydrogen are (i) in the oxidizing ambient, deliberately introduced or resulting from permeation through hot furnace tubes, (ii) hydrogen in the room ambient oxide film on silicon, and (iii) deliberate or unintentional or in the ambient of postoxidation heat‐treatments. The "critical oxide thickness," which separates the linear oxidation regime from the parabolic one, is a very sensitive indicator of present in the oxidizing ambient. There is plenty of evidence, both direct and indirect, of hydrogen in films. In particular, infrared spectroscopy shows that OH and groups are present whose concentration and distribution depend strongly on preparation conditions. These groups can be H‐bonded to an oxygen; this feature and the presence of distinguishes films from fused which is another form of non‐crystalline. The H‐bonded OH groups in grown films may be preferentially aligned along structural channels and responsible for various transport processes characterized by ~0.3 eV activation energy. Hydrogen greatly affects the properties of the interface, particularly its behavior under negative bias stress and irradiation. In fact, practically all properties of interface structures depend so strongly on hydrogen that its proper control and the understanding of its complicated role are probably the most important problems associated with these structures. This is particularly true for silicon‐based chemical sensors whose operation is basically determined by hydrogen in the film. Various aspects of the hydrogen in interface structures are similar to the role of hydrogen in and polymer films as well as in passivating films on metals.

Journal ArticleDOI
TL;DR: In this article, the concentration profiles of oxide films on Si have been studied by using ESCA and ellipsometry, and the oxide films were found to be composed mostly of stoichiometric SiO 2 with a very thin (about 0.3 nm) layer of SiO at the SiSiO 2 interface.

Journal ArticleDOI
TL;DR: In this article, the mechanism of thermal oxidation of silicon in dry oxygen was studied using 18O as the tracer, and the results suggest that the oxide grows mainly through long-range migration of oxygen, favoring models based on the transport of molecular oxygen.
Abstract: The mechanism of thermal oxidation of silicon in dry oxygen was studied using 18O as the tracer. SiO2 layers first grown in natural oxygen (1300–3000 A) were further grown in highly 18O‐enriched oxygen for 8.5 h at 930 °C. 18O profiling was carried out using the 629‐keV narrow resonance in the nuclear reaction 18O(p,α) 15N. The resulting SiO2 films consist of two 18O‐rich layers, 7% near the SiO2 surface and 93% near the Si‐SiO2 interface, while the bulk 18O concentration is very low. The results suggest that the oxide grows mainly through long‐range migration of oxygen, favoring models based on the transport of molecular oxygen.

Journal ArticleDOI
TL;DR: In this paper, the variation of voltammetric charge with real surface area was investigated for RuO2-coated titanium foils with a view to establishing an electrochemical technique for the estimation of the latter.

Patent
17 Dec 1979
TL;DR: An electrochemical cell incorporating cathode materials comprising at least one metal oxide or metal element, or mixture of metals or metal oxides incorporated in the matrix of a host metal oxide is defined in this article.
Abstract: An electrochemical cell incorporating cathode materials comprising at least one metal oxide, at least one metal, or mixture of metals or metal oxides incorporated in the matrix of a host metal oxide. The cathode materials of this invention are constructed by the chemical addition, reaction, or otherwise intimate contact of various metal oxides and/or metal elements during thermal treatment in mixed states. The materials thereby produced contain metals and oxides of the groups IB, IIB, IIIB, IVB, VB, VIB, VIIB, and VIII, which includes the noble metals and/or their oxide compounds. The incorporation of the metal oxides, metals or mixtures thereof substantially increases the discharge capacity and the overall performance of the cathode materials.

Journal ArticleDOI
TL;DR: In this article, the adsorption isotherm of benztriazole (BTA) on copper reveals that the inhibitor molecule is weakly held on the oxide covered surface until a critical solution concentration of BTA is reached above which good corrosion inhibition results.

Journal ArticleDOI
TL;DR: The surface of molybdenum metal was examined by XPS after exposure to gaseous and liquid systems and after electrochemical treatment as discussed by the authors, the latter being conducted in a specially designed electrochemical cell situated in a vacuum chamber attached to the main spectrometer chamber.

Journal ArticleDOI
TL;DR: In this article, the structure, sintering rates and chemical composition of 20 to 200-A-diameter Pt-O and Pd-O alloys were examined using scanning transmission electron microscopy and energy dispersive X-ray microanalysis.

Journal ArticleDOI
TL;DR: In this article, the corrosion and polarization characteristics of zinc have been studied in molar, quiescent solutions of NaClO4, NaCl and Na2SO4 in the pH range 3.0-5.8.

Journal ArticleDOI
TL;DR: In this article, a study of the contact between metal specimens in an UHV scanning electron microscope incorporating an Auger facility for characterising the surfaces in situ is described, and the results show that with clean surfaces, the loading-unloading cycle is not reversible.

Journal ArticleDOI
TL;DR: In this article, the densities of 21 silicate liquids have been determined from 1,000 ° to 1,600 ° C. The compositions studied contain from two to eight oxide components and have the following ranges in composition (mole %): SiO2, 35−79%; TiO2 4−36; Al2O3, 5−25%; FeO, 11−41%; MgO, 7−28%; CaO,7−35%; Na2O, 5-50%; and K2O 4−20%.
Abstract: Densities of 21 silicate liquids have been determined from 1,000 ° to 1,600 ° C. The compositions studied contain from two to eight oxide components and have the following ranges in composition (mole %): SiO2, 35–79%; TiO2, 4–36%; Al2O3, 5–25%; FeO, 11–41%; MgO, 7–28%; CaO, 7–35%; Na2O, 5–50%; and K2O, 4–20%. The compositions thus cover the upper range observed in magmas for each oxide. Precision for each determination of liquid density is always better than ±1%.

Journal ArticleDOI
TL;DR: In this paper, the photoluminescent and reflectance spectra of MgO smoke have been compared with the spectra for ex-hydroxide and ex-carbonate, and a strong correlation exists between the optical spectra and the different morphology of the particles obtained by the different routes.
Abstract: The photoluminescent and reflectance spectra of MgO smoke have been compared with the spectra of MgO ex-hydroxide and ex-carbonate. Parallel studies by electron microscopy have shown that a strong correlation exists between the optical spectra and the different morphology of the particles obtained by the different routes. The spectra observed are associated with the surface of the oxide particles and the excitation and absorption bands are associated with oxygen ions in 3- and 4-fold coordination. The same kinds of sites are present on all samples but the ions of lowest coordination are much less abundant on the nearly perfect cubes of MgO smoke. The number of 3-fold coordinated sites on the smoke particles is considerably increased after exposure to water vapour for several h. This picture is consistent with the electron micrographs which show erosion of the edges and corners of the MgO smoke after treatment with water vapour. A model involving the removal of ion pairs from the corners and edges of the cube by water is shown to give the observed increase in the sites of lowest coordination.

Journal ArticleDOI
TL;DR: In this paper, the massive Mn oxides were synthesized and their anodic characteristics were investigated in aqueous solutions, and it was suggested that the oxidation process of the electrode surface is a common rate-determining step in both reactions on massive Mn oxide electrodes.

Journal ArticleDOI
TL;DR: The thermal stability of a monolayer catalyst is related to the parameter z/a, i.e., the ratio of the carrier cation charge to the sum of ionic radii of carrier cations and oxide anion.
Abstract: Vanadium oxide catalysts of the monolayer type have been prepared by means of chemisorption of vanadate(V)-anions from aqueous solutions and by chemisorption of gaseous V2O3(OH)4. Using Al2O3, Cr2O3, TiO2, CeO2 and ZrO2, catalysts with an approximately complete monomolecular layer of vanadium(V) oxide on the carrier oxides can be prepared, if temperature is not too high. Divalent metal oxides like CdO and ZnO may already form threedimensional surface vanadates at moderate temperature. The thermal stability of a monolayer catalyst is related to the parameter z/a, i. e. the ratio of the carrier cation charge to the sum of ionic radii of carrier cation and oxide anion. Thus, monolayer catalysts will be thermally stable only under the condition that z/a is not too high (aggregated catalyst) nor too small (ternary compound formation).