Showing papers on "Oxide published in 1969"

Identification of rapid changes at plasma–solid interfaces

Abstract: Recording ellipsometers and surface film balance, breath patterns, and ferric oxide powder “staining” were used to observe adsorption of normal plasma constituents onto metal oxide, silicon oxide, and polymer surfaces. Adsorbed proteins could be identified by their ability to adsorb matter from corresponding antihuman sera. Data indicate that oxidized silicon crystal surfaces adsorbed fibrinogen out of plasmas within 2 sec; within 20 sec, these films lost their ability to attract antifibrinogen and were later partially removed if intact factor XII was present in the solution. One aminated nonheparinized polymer formed films that adsorbed large amounts of fibrinogen and some gamma globulins out of plasma in the ellipsometer, and platelets out of platelet-rich plasma, as well as ferric oxide out of aqueous suspension. After taking up heparin, these polymer films appeared able to adsorb only small amounts of protein or oxide, and no detectable amounts of fibrinogen or platelets. On another aminated polymer, heparin seemed without effect. Interaction of metal surfaces with plasma may be complicated by oxidation.

Aluminum + water reaction

Abstract: During the aluminum + water reaction, aluminum ions and electrons are removed in separate steps at different sites on the surface. Ions are removed nearly uniform over the entire surface, which is covered at all times with a thin amorphous oxide film. The outer surface of this oxide is first hydrolyzed and then dissolves to yield soluble species which either remain in solution or, at intermediate values of pH, precipitate as a porous hydroxide of extremely small particle size. The hydroxide appears to be identical to pseudoboehmite. The overall rate of the corrosion reaction is controlled by this dissolution of the film and by the disposition of the soluble products. The corrosion rate is nearly independent of specimen potential, solution pH below 10, and of the presence in solution of many salts at concentrations as high as 1 mole/1. The rate is strongly dependent on temperature, on the presence of specific inhibitive salts, and increases rapidly at high pH. In environments which preclude oxide dissolution, e.g., water + dioxane mixtures or water vapour, the corrosion rate is drastically reduced. The corrosion rate is constant when no solid hydroxide is formed, and is otherwise a strong function of the amount of reaction. At high temperatures the rate decreases with time as the precipitated hydroxide hinders transport. At lower temperatures the rate may first increase with time as nucleation of hydroxide provides sinks for soluble species close to the interface, and then at long times the rate decreases as the hydroxide layer thickens. Electrons are removed more readily at special sites, and in our specimens these sites were primarily at the grain boundaries. Electron removal results in increased hydroxyl ion concentration, and this in turn results in more rapid attack on the protective oxide. At such cathodes the oxide film is maintained at a small constant thickness at which there is a balance between the rates of its dissolution by the basic solution and growth because of the great affinity of aluminum for oxygen. At cathodic sites there is thus anodic activity as well, but electron removal predominates. The metal is corroded more rapidly at cathodes, producing pronounced grain boundary attack in our specimens. Application of anodic potentials eliminates grain boundary attack.

Oxide phonon spectra

Abstract: An attempt is made to apply ‘group frequency’ assignments to the vibrational spectra of oxides. The following oxides are considered: TiO2(both anatase and rutile), SnO2(cassiterite), ZnO, WO3, CeO2, ThO2, B-Nb2O5,V2O5, MoO3, and MoO3′. The experimental data on V2O5(single-crystal Raman study), B-Nb2O5(single-crystal Raman study), WO3, CeO2, ThO2, and MoO3′ are new. There are also additional results for SnO2 and new i.r. data (including single-crystal studies) on MoO3.

AVALANCHE INJECTION CURRENTS AND CHARGING PHENOMENA IN THERMAL SiO2

Abstract: Injection of carriers into thermally grown SiO2 from an avalanche plasma in silicon is a new way of achieving high current densities in SiO2. Electron injection from p‐type silicon and hole injection from n‐type silicon by hot carrier emission have been observed. Average electron current densities as high as 10−2 A/cm2 have been observed to flow through 1000 A of SiO2. The oxide becomes negatively charged as a result of electron injection and positively charged as a result of hole injection. These charging effects appear to be related to the presence of water in the oxide.

Infrared Reflection Studies of the Oxidation of Copper and Iron

Abstract: Infrared multiple reflectance spectra were used to record the growth of oxide films on copper and iron mirrors. Cuprous oxide and cupric oxide films were readily distinguished since they exhibit intense single bands at 640 cm−1 and ~560 cm−1, respectively. Iron oxide films of a single composition also exhibit highly characteristic bands in the 230 to 1100 cm−1 region of the reflectance spectra. Spectra of mixed iron oxide films were composed of many highly overlapping bands making quantitative interpretations difficult. The intensities of the infrared bands from the copper oxide and iron oxide films were directly proportional to the oxide film thicknesses. Using a seven reflection −73° incidence optical accessory, sensitivity to detect oxide films as thin as about 5Aa was achieved.

Model for Radiation‐Induced Charge Trapping and Annealing in the Oxide Layer of MOS Devices

Abstract: A model is proposed to explain radiation damage and charge trapping in the oxide layer of MOS devices after exposure to ionizing radiation. This model is based upon the close similarity between radiation effects in the silicon dioxide layer and in fused silica. In addition to explaining the production of damage by ionization, the model has an advantage over other models inasmuch as the charge trapping in a relatively impurity‐free silicon dioxide layer can be explained. The model explains radiation‐induced charge trapping in the oxide and subsequent annealing of the charge as a function of temperature and exposure to ultraviolet radiation. In addition, the model suggests that the sensitivity of MOS devices to ionizing radiation can be reduced by decreasing the amorphous structure of the oxide.

Oxidation, defects and vacancy diffusion in silicon

Abstract: The mechanism causing extrinsic faults to grow into a silicon wafer during thermal oxidation has been investigated by annealing experiments on thin electron microscope foils. The defects grow on annealing in air at 1100°C and shrink on annealing in vacuo at the same temperature; this behaviour is explained in terms of the diffusion of vacancies between defect and surface. The sense of this flow is dependent on the vacancy concentration in equilibrium with the surface which is reduced to approximately 0·8 of the bulk equilibrium value because the vacancies are annihilated by the inward-growing oxide. During oxidation the faults emit vacancies to the surface, causing fault growth, whereas the vacancy flow is reversed on annealing in vacuo. The activation energy for fault shrinkage has been determined to be 2·1 ev, which is consistent with pipe diffusion along the core of the bonding Frank dislocation. The shrinkage rate of these faults at constant temperature is proportional to the equilibrium vaca...

High Performance, Platinum Activated Tungsten Oxide Fuel Cell Electrodes

Abstract: HYDROCARBON fuels (methane, propane and so on) are relatively inert and can only be electrochemically oxidized using either high loading noble metal-black electrodes in phosphoric acid at 150° C or high temperature molten carbonate (or solid oxide) electrolyte cells at 600–1,000° C (ref. 1). Alternatively the fuel may be “reformed”, producing impure hydrogen (containing carbon dioxide and some carbon monoxide) which may be fed into a low temperature (> 100° C) acid fuel cell. Carbon monoxide, however, poisons platinum black by strongly adsorbing on its surface (with high coverage) at normal fuel cell anode potentials. Little opportunity exists for water molecules to adsorb on sites adjacent to surface CO molecules—a necessary condition for the removal of the latter by anodic oxidation2

Structural studies of crystalline poly(p‐phenylene oxides) I. Poly(p‐phenylene oxide)

Abstract: Using X-ray diffraction the structure of crystalline poly(p-phenylene oxide), has been determined. The unit cell is orthorhombic, with the dimensions: a = 8.07 A, b = 5.54 A, and c (fiber axis) = 9.72 A. The unit cell contains four monomeric units. Two molecular chains pass through a unit cell, one through the center, the other through a corner. Two monomeric units are contained in the fiber identity period. The space group is Pbcn – D. The oxygen atoms and the centers of gravity of the phenylene groups are at special positions. The oxygen atoms of one molecular chain are arranged in a zig-zag manner in the (100) plane. The oxygen bond angle is about 124°. The rotation angle of the phenylene groups round the O–O axis has been determined by comparing calculated and observed intensities. Die Struktur von kristallinem Poly(p-phenylenoxid), wurde mit Hilfe von Rontgenstrahlbeugungsmethoden ermittelt. Die Einheitszelle ist orthorhombisch; die Dimensionen sind folgende: a = 8,07 A, b = 5,54 A und c (Faserachse) = 9,72 A. Die Einheitszelle enthalt vier monomere Einheiten. Zwei Molekulketten laufen durch eine Elementarzelle, eine durch das Zentrum und eine durch eine Ecke. Die Periode in der Richtung der Faserachse enthalt zwei monomere Einheiten. Die Raumgruppe ist Pbcn – D. Die Sauerstoffatome und die Zentren der Phenylengruppen befinden sich an speziellen Stellen. Die Sauerstoffatome einer Molekulkette sind in der (100)-Ebene im Zickzack angeordnet. Der Sauerstoffvalenzwinkel betragt etwa 124°. Der Rotationswinkel der Phenylengruppen um die OO-Achse herum wurde durch Vergleichen von berechneten und beobachteten Intensitaten ermittelt.

Electrochemical Dissociation of Water Vapor in Solid Oxide Electrolyte Cells: I . Thermodynamics and Cell Characteristics

Abstract: This paper describes the dissociation of water vapor in high‐temperature, solid oxide electrolyte cells. The characteristics of these cells are related to a composition‐dependent open‐circuit voltage, which can be obtained from thermodynamic considerations, to ohmic resistance, and to mass transport overvoltages. The problem of maintaining a heat balance in a system consisting of such cells is considered in terms of the heat loss through the leads connecting the cells with the surroundings. A conclusion is that the electrical energy requirement for dissociation can be reduced substantially by series connection of individual cells within the high‐temperature region of the system, but that ohmic resistance limits the optimized current density through the electrolyte to values well below the maximum values that are feasible.

Mechanical Properties of Metal Oxide Films

Abstract: A brief review is given of mechanical property measurements on oxide films. This review is followed by a detailed discussion of the mechanical and fracture properties of anodic aluminum oxide films as observed in the author's laboratory. Extensive measurement of Young's modulus, ,and fracture strain, , for separated films 3000Aa thick is reported as a function of environmental water vapor pressure. The fracture of these unsupported films is shown to occur by a brittle mechanism. Mechanical properties of adhering aluminum oxide films are given as a function of their thickness. These oxides were observed to fracture either at slip steps, or at right angles to the tensile axis in a regularly spaced fashion. A theory of adhering oxide fracture is discussed which accounts well for the observations. An equation which describes the spacing of regular oxide fracture cracks as a function of substrate strain e is given in the form , where () are the initial conditions for regular fracture, is the oxide thickness, and is a constant.

Elastic Properties of Polycrystalline Yttrium Oxide, Dysprosium Oxide, Holmium Oxide, and Erbium Oxide: Room Temperature Measurements

Abstract: The Young's and shear moduli of polycrystalline yttrium oxide, dysprosium oxide, holmium oxide, and erbium oxide were determined at room temperature as a function of volume fraction porosity using the sonic resonance technique. Linear relations empirically described the data for Y2O3, Hr2O3, and Er2O3. The Young's and shear moduli data for Dy2O3 were empirically described by Hasselman's and Spriggs’equations, respectively. The empirical curves which best fit the data were compared to theoretical expressions and agreed closely with a modified form of Mackenzie's equation. Values for bulk modulus, Poisson's ratio, and the Debye temperature were computed for each oxide, and the bulk modulus-volume relation was determined and compared to that of other oxides.

The theory of recoil implantation

Abstract: The basic physical principles underlying the technique of recoil implantation are discussed in some detail. The number of recoils as a function of recoil energy passing from an evaporated layer into the substrate is calculated for a particular case; and the final penetration distribution within the substrate is compared with that expected for a direct implantation. The number and distribution of unwanted contaminant impurities which inevitably recoil into the substrate during direct implantation through an oxide layer, is also discussed.

Formation and decomposition of surface oxide in carbon combustion

Abstract: The formation of surface oxide on graphitized carbon black by reaction with oxygen at 500°C and the subsequent desorption of the oxide as CO at 600–750°C have been studied gravimetrically. The surface oxide is formed exclusively during the initial transient period of fast combustion observed by previous workers, and for each O atom chemisorbed one labile C atom is removed from the surface. The kinetics of desorption follow the relation: –dθ/dt=Dθ exp {–[E1+β(1 –θ)]/RT}, where log10Dθ= log10D1+α(1 –θ), and θ is the fraction of O on the surface at time t related to that present during steady combustion. D1, E1, α and β are constants. Values of 70 and 57 kcal mole–1 were found for E1 with two specimens at lower and higher burn-off respectively; the corresponding values of β were 43 and 47 kcal mole–1. Apart from the effect of catalytic impurities, two distinct processes are required to account for the kinetics of combustion. Only one of these produces stable oxide. A hypothesis is proposed which identifies this with reaction at “arm-chair”{112l} edges of the carbon lattice.