Showing papers on "Oxide published in 1975"
TL;DR: In this article, the temperature dependence of poly(ethylene oxide) complexes with sodium iodide and the thiocyanates of sodium, potassium and ammonium has been investigated.
Abstract: The temperature dependence of d.c. conductivity of poly(ethylene oxide) complexes with sodium iodide and the thiocyanates of sodium, potassium and ammonium has been investigated. In each case a transition to a lower activation energy at higher temperatures was observed. For the sodium complexes this transition occurs at ca 55°C which is well below the crystalline melting points at 200°C. For the potassium and ammonium complexes however, the transitions coincide with the melting points at ca 100 and 70°C respectively. It is proposed that at the transitions, thermal disintegration of complexes in the amorphous regions occurs. The complexes involve coordination of the cations to the ether oxygen atoms in the polymer backbone.
1,025 citations
655 citations
TL;DR: In this paper, the authors discuss the requirements for a porous transparent Al2O3 from aluminium alkoxides to retain its integrity during drying and pyrolysis, and show that there is a critical electrolyte concentration at which the gelling volume goes through a pronounced minimum.
Abstract: Formation of a porous transparent Al2O3 from aluminium alkoxides has been previously reported. During the process, alkoxides are hydrolyzed and the resultant hydroxide is peptized to a clear sol. The sol then must be gelled and pyrolyzed to 500° C to obtain the aluminium oxide. This paper discusses the gel state and the requirements for the system to retain its integrity during the drying and pyrolysis. Influence of electrolytes on the sol-gel transformation shows that there is a critical electrolyte concentration at which the gelling volume goes through a pronounced minimum. Deviation in either direction of this electrolyte concentration causes a sharp increase in the relative gelling volume and detrimentally effects the capability of the gel to retain its integrity. The sols that gel at concentrations less than ∼4 g equivalent oxide per 100 ml do not retain their integrity during pyrolysis.
534 citations
TL;DR: In this paper, the conductivity of doped ceria with divalent or trivalent cations is investigated and compared to calcia-stabilized zirconia (CSZ), showing a higher conductivity, lower activation energy (0.76 eV), and absence of polarization effects to lower temperatures.
Abstract: Ceria doped with divalent or trivalent cations is a mixed conductor; conduction occurs predominantly by the motion of oxygen vacancies or by electrons, depending on the departure from stoichiometry. In order to establish the electrolytic domain at which behaves primarily as an ionic conductor with transference number , a careful study was made of the conductivity, σ, as a function of temperature and oxygen partial pressure, covering the range of 100;–10−22 atm in small steps. From these data the electrolytic domain was determined; it extends to about 10−13 atm at 600°C. When compared to calcia‐stabilized zirconia (CSZ), doped ceria shows a higher conductivity, lower activation energy (0.76 eV) for anion vacancy migration, and absence of polarization effects to lower temperatures. These results indicate that doped ceria may be an attractive candidate for fuel cells and other applications at temperatures below those at which CSZ is useful.
438 citations
TL;DR: The mean escape depths of Si 1s, Si 2p, and O 1s photoelectrons from silicon−silicon dioxide structures were determined over a wide kinetic energy range with magnesium, aluminum, and chromium x−ray sources as discussed by the authors.
Abstract: The mean escape depths of Si 1s, Si 2p, and O 1s photoelectrons from silicon−silicon dioxide structures were determined over a wide kinetic−energy range with magnesium, aluminum, and chromium x−ray sources. Variations in photoelectron line intensity were measured as a function of oxide film thickness. Film thicknesses were determined from ellipsometric data assuming an index of refraction of 1.47 for the oxide. Discrepancies in fitting intensity data to an escape−depth curve for films <20−A thick are associated with nonstoichiometry of the oxide film near the interface. The incompletely oxidized interfacial region is identified by variations in linewidth and in binding energies of the spectral lines as well as by the deviations from predicted intensity data.
237 citations
TL;DR: In this article, the infrared spectra of ammonia adsorbed on CoO, NiO, SiO 2, CaO, MgO, ZrO2, ZnO, TiO 2, BeO and Al 2 O 3, have been studied in the NH stretching and bending vibration regions at various stages of sample dehydroxylation.
229 citations
TL;DR: In this paper, the authors measured the Raman spectrum of poly(ethylene oxide) (PEO) M w = 3 × 10 6 and 6 × 103 in bulk and in aqueous and chloroform solution as a function of solvent concentration.
224 citations
205 citations
TL;DR: In this article, the authors applied X-Ray photoelectron spectroscopy (XPS) to the study of molybdenum oxides and supported oxide catalysts and showed that the reduction behavior of supported oxide is substantially different from that of unsupported MoO3.
195 citations
TL;DR: In this article, the X-ray excited photoelectron spectrum during exposure of clean magnesium, aluminium, chromium and manganese to oxygen and water vapour, provide data on the kinetics of reaction with these gases.
195 citations
Patent•
27 Mar 1975TL;DR: In this article, a novel fluoropolymer can be made by copolymerizing a small amount (e.g., about 0.5-3 mole %) of bromotrifluoroethylene (Bromotetrafluorobutene) with certain combinations of monomers comprising selected fluorine-containing compounds.
Abstract: A novel fluoropolymer can be made by copolymerizing a small amount (e.g. about 0.5-3 mole %) of bromotrifluoroethylene or bromotetrafluorobutene with certain combinations of monomers comprising selected fluorine-containing compounds. A fluoropolymer composition useful in the manufacture of cured fluoropolymer articles can be made by mixing the resulting fluoropolymer or a closely related fluoropolymer with an organic peroxide such as a dialkyl peroxide, and preferably also adding a divalent metal oxide and/or hydroxide and a suitable coagent such as triallyl isocyanurate.
TL;DR: In this paper, it was deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries.
Abstract: Cr was oxidized in 1 aim O2 at 980, 1090, and 1200°C. ElectropolishedCr and some orientations of etched Cr oxidize rapidly and develop compressive stress in the growing Cr2O3; other orientations oxidize slowly, apparently free of stress. SEM examination of fracture sections shows that the thick oxide is polycrystalline whereas the thin oxide on etched Cr is monocrystalline. It is deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries. The consequent formation of oxide within the body of the polycrystalline layer generates compressive stress and leads to wrinkling by plastic deformation. The activation energy for oxidation of Cr by cation lattice transport is 58 kcal/mole. Polycrystalline Cr2O3 forms on Fe-26Cr alloy, whether electropolished or etched; oxidation is accordingly rapid and accompanied by compressive stress.
TL;DR: In this article, the authors showed that the fraction of the added Ca (Sr) adsorbed depended principally on the suspension pH, the amount of solid present, and to a lesser extent on the NaNO3 concentration.
Abstract: Freshly prepared Fe and Al hydrous oxide gels and the amorphous product of heating gibbsite selectively adsorbed traces of Ca and Sr from solutions containing a large excess (∼1M) of NaNO3. The fraction of the added Ca (Sr) adsorbed depended principally on the suspension pH, the amount of solid present, and to a lesser extent on the NaNO3 concentration. Significant Ca and Sr adsorption occurred on the Fe and Al gels, and heated gibbsite, at pH values below the points of zero charge (8.1, 9.4, and 8.3±0.1, respectively), indicating specific adsorption. The pH (± 0.10) at which 50% of the Ca was adsorbed (pH50) occurred at pH 7.15 for the Fe gel (0.093M Fe), 8.35 for the Al gel (0.093M Al), and 6.70 for the heated gibbsite (0.181M Al); for Sr, the pH50 values were 7.10, 9.00, and 6.45, respectively. For the Fe gel and heated gibbsite, an empirical model based on the law of mass action described the pH dependence of adsorption reasonably well and suggested that for each Ca or Sr fraction adsorbed, approximately one proton was released. Failure of the Al gel to fit this model may have resulted from its rapid aging.
TL;DR: In this article, the positive ion composition was measured in the D- and E-regions above Sardinia during the maximum of the Geminid meteor Shower, during which a magnetic sector type mass spectrometer with dual collector and a liquid helium cryopump was used.
TL;DR: The dissociative chemisorption of oxygen and water was reported on both (111) and [6(111) × (100) crystal faces of gold.
TL;DR: In this paper, the ultraviolet and visible reflectance spectra of high surface area MgO and CaO were studied in vacuo and in the presence of O2, N2O, CO2 and H2O.
Abstract: The ultraviolet and visible reflectance spectra (52 000–15 000 cm–1) of high surface area MgO (250–300 m2 g–1) and CaO (100–200 m2 g–1) have been studied in vacuo and in the presence of O2, N2O, CO2 and H2O. The effect of outgassing MgO and CaO at increasing temperatures (773–1073 K) is to develop u.v. absorption bands in the range 30 000–50 000 cm–1. The absorption can be progressively destroyed by chemisorption, and also by sintering. The bands are attributed to excitons bound in surface states.
In vacuo the outgassed oxides exhibit a fluorescence which is readily quenched by exposure to a low pressure of oxygen. Absorption bands occur at 37 000 and 46 000 cm–1 for MgO and at 35 500 and 44 500 cm–1 for CaO. With each oxide the chemisorption of gases erodes the lower energy band preferentially, and a similar effect occurs on sintering. The two bands are ascribed to exciton absorption at surface oxide ions in different states of coordinative unsaturation, the lower energy exciton band corresponding to the lower coordination.The influence of gases on the exciton spectra of outgassed MgO and CaO is shown to depend on their chemical reactivity, increasing in the sequence O2, N2O, CO2 and H2O. The effects with each gas are reversible on outgassing. Exposure of CaO to O2 gives rise to an absorption band at 23 500 cm–1, tentatively attributed to an O–3 adsorbed species.The surface states observed on CaO can be produced on MgO by adsorbing Ca ions from solution and heating to 1073 K.
TL;DR: In this article, a reproducible oxide layer was prepared by the high temperature reaction of H2O at 10−6 torr with Fe(001), and the initial oxygen sticking coefficient was observed to be close to unity, which suggests that the chemisorption is nonactivated and involves a mobile adsorption step.
TL;DR: In this article, the transmission infra-red technique has been used to investigate the surface of tin(IV) oxide as a function of evacuation temperature in the range 293-773 K.
Abstract: The transmission infra-red technique has been used to investigate the surface of tin(IV) oxide as a function of evacuation temperature in the range 293–773 K. Molecular water is largely removed by evacuation at 320 K and is fully removed at 473 K. Hydrogen-bonded hydroxyl groups are present after evacuation at 773 K, and isolated hydroxyl groups exhibit a stretching frequency at 3640 cm–1. Room temperature carbon dioxide adsorption has been studied as a function of thermal pretreatment in the range 320–618 K and the spectra obtained indicate a surface carbonate and a surface bicarbonate. The adsorption of carbon monoxide has been investigated in a similar manner. A carbonate species is proposed from the infra-red data, and the partial reduction of the tin(IV) oxide to a tin(II) species has been confirmed by tin-119 m Mossbauer spectroscopy. No evidence was obtained for the physical adsorption of either carbon dioxide or carbon monoxide.
TL;DR: In this paper, the use of the indium chelate derived from dipivaloyl methane, in combination with dibutyl tin diacetate, has been investigated as a CVD technique for the preparation of transparent highly conducting layers of tin-doped indium oxide.
TL;DR: In this paper, the oxide films produced by anodic oxidation of gold and platinum have been studied by X-ray photoelectron spectroscopy and the change in the amount of each species present, with electrode potential, has been investigated.
Abstract: The oxide films produced by anodic oxidation of gold and platinum have been studied by X-ray photoelectron spectroscopy. The change in the amount of each species present, with electrode potential, has been investigated. It is demonstrated that X-ray reduction occurs for these systems but that it can be minimised by a suitable choice of experimental conditions.A study of the intensities of the photoelectron peaks demonstrates how the thickness of an oxide layer and the true surface area of the electrode may be determined.
TL;DR: In this paper, the formation of oxide films on resistively heated silicon in dry oxygen was followed in situ using a computer controlled ellipsometer, and two distinct growth regions were observed.
Abstract: The formation of oxide films on resistively heated silicon in dry oxygen was followed in situ using a computer controlled ellipsometer. For (111) silicon surfaces two distinct growth regions were observed. Our results on the growth above 300A were found to agree with previous investigations. For films 200A or less (for which little previous data exist) the kinetics did not obey any existing model of the growth process. The rate of growth of the oxide on (111) surfaces in the 20–200A region was investigated from 700° to 950°C and at oxygen pressures between 50 and 1200 Torr. A possible explanation of the thin film kinetics is given and its relation to the thick film data is discussed.
TL;DR: In this article, the lattice parameters for the perovskite phase of MgSiO3 are ao = 4.790 ± 0.002, bo = 4,943 ± 0.,002, and co = 6.897 ± 0,003 A with Z= 4.083 g/cm³, or 2.8% denser than its isochemical mixed oxides with rocksalt and rutile structures.
Abstract: Both forsterite (Mg2SiO4) and enstatite (MgSiO3) enter a post-oxide phase characterized by the orthorhombic perovskite structure when subjected to high pressure and temperature in the diamond-anvil press coupled with laser heating. The lattice parameters for the perovskite phase of MgSiO3 are ao = 4.790 ± 0.002, bo = 4.943 ± 0.002, and co = 6.897 ± 0.003 A with Z = 4. The calculated density of MgSiO3 (perovskite) is thus 4.083 g/cm³, or 2.8% denser than its isochemical mixed oxides with rocksalt and rutile structures. The density of a mixture of MgSiO3 (perovskite) plus MgO (periclase) is 1.9% greater than that of the mixed oxides with the forsterite stoichiometry.
TL;DR: The distribution of ammonium citrate-leachable lead, zinc and cadmium among size fractions in stream sediments is strongly influenced by the presence of hydrous Mn-Fe oxides in the form of coatings on sediment grains.
TL;DR: In this article, it was concluded from these experiments that the high dark conductivity observed is an interface phenomenon that is due to localized field enhancement near the injecting contact, not being due to positive oxide charge.
Abstract: Several dark‐current and photocurrent techniques have been used to determine the nature of high dark conductivity observed in oxides grown from polycrystalline silicon. Photocurrent measurements on polycrystalline Si‐SiO2‐Al MOS structures give idential interface energy barrier heights to those on single‐crystal Si‐SiO2‐Al MOS structures, and do not show the presence of any measurable oxide charge. Dark‐current measurements on polycrystalline Si MOS structures oxidized to varying degrees show an abrupt conductivity decrease when the polycrystalline Si is completely oxidized to the underlying single‐crystal Si substrate. It is concluded from these experiments that the high dark conductivity observed is an interface phenomenon that is due to localized field enhancement near the injecting contact. This field enhancement, not being due to positive oxide charge, is speculated to be caused by surface asperities.
TL;DR: In this article, the amplitude ratio s of the O (510 eV)/Fe (703 eV) lines was, to a first approximation, directly proportional to the ratio of oxygen and iron in the chemical formula.
TL;DR: In this paper, a review of the relevant structural, thermodynamic and transport properties of transition metal oxides is presented, and a confrontation of theory and experiment for both the low and hightemperature r6gimes is presented.
TL;DR: In this paper, a new method of forming an anodic native oxide of GaAs with excellent dielectric and interface properties is described, and the oxide is grown in a stable and reproducible manner in an electrolyte which is a suitable mixture of water, weak carboxylic acid (tartaric or citric acid), and polyhydric alcohol.
Abstract: A new method of forming an anodic native oxide of GaAs with excellent dielectric and interface properties is described. The oxide is grown in a very stable and reproducible manner in an electrolyte which is a suitable mixture of (i) water, (ii) weak carboxylic acid (tartaric or citric acid), and (iii) polyhydric alcohol. The breakdown field strength of the as‐grown oxide is 5×106 V/cm and the specific resistivity is 1014–1016 Ω cm. Relatively low temperature annealing in hydrogen results in greatly improved interface properties with a density of fast interface states near midgap of 1–2×1011 cm−2 eV−1, with only a small capacitance/voltage hysteresis, and only small frequency dispersion of capacitance in the accumulation region.
TL;DR: In this paper, the coverage of the clean polar (111) faces of GaAs, prepared by Ar+ bombardment and proper annealing, was quantitatively determined using empirical values for the escape depth of the Auger electrons from literature.
TL;DR: The anodic behavior of iridium in the oxide layer region has been investigated using conventional electrochemical techniques such as cyclic voltammetry as discussed by the authors, and the mechanism of charge storage is discussed in terms of both an expanded lattice theory for oxide growth on noble metals and a more recent theory of irreversible oxide formation with subsequent stoichiometry changes.
Abstract: The anodic behaviour of iridium in the oxide layer region has been investigated using conventional electrochemical techniques such as cyclic voltammetry. Applying a triangular voltage sweep at 10 Hz, 0.01 to 1.50 V increases the amount of electric charge which the surface can store in the oxide region. This activation effect and the mechanism of charge storage is discussed in terms of both an expanded lattice theory for oxide growth on noble metals and a more recent theory of irreversible oxide formation with subsequent stoichiometry changes. The lack of hysteresis between the anodic and cathodic peaks at ca. 0.9 V suggests that the process involved here is proton migration in a relatively thick surface layer, i.e. that the reaction involved is some type of oxide-hydroxide transition. Lack of chloride ion inhibition in the anodic region also supports the irreversible oxide formation theory; however, to account for the hydrogen region of the potential sweep a compromise theory involving partial reduction of the outer regions of iridium oxide film is proposed. The loss of charge storage capacity when the activated iridium surface is anodized for a short time above ca. 1.60 V is attributed to loss by corrosion of the outer active layer from the metal surface.
01 Jan 1975
TL;DR: Correlation and coupling effects in Diffusion in Ionic Materials are discussed in this paper, where a model of Ionic and Electronic Relaxation in glass is presented, as well as the effect of diffusion and shear on concentration correlation in binary systems.
Abstract: Correlation and Coupling Effects in Diffusion in Ionic Materials.- Non-Random Diffusion in Ionic Crystals.- Correlation Effects in Ionic Transport Processes.- Correlation and Isotope Effects for Cation Diffusion in Simple Oxides.- Coupling, Cross Terms, Correlation and Conduction.- Irreversible Thermodynamics in Materials Problems.- Oxygen Redistribution in UO2 Due to a Temperature Gradient.- The Thermodynamics of Diffusion Controlled Metamorphic Processes.- Multi-Component Spinodal Decomposition.- Fast Ion Transport.- Microstructural Aspects of Optimized Ion-Conduction in Solids.- Correlation Factor and Nernst-Einstein Relation in Solid Electrolytes.- Alkali Ion Transport in Materials of the Beta Alumina Family.- Ionic Conductivity of Doped Cerium Dioxide.- Low Temperature Oxygen Transport in Nonstoichiometric CeO2.- Self Diffusion Constant Measurement by Continuous-Wave Nuclear Magnetic Resonance.- Diffusion and Electrical Conductivity in Crystalline and Giassy Oxides.- On the Interpretation of Lattice Diffusion in Magnesium Oxide.- High Temperature Electrical Conductivity of Aluminum Oxide.- Concentration Dependent Diffusion of H+ in TiO2: Analysis of Electronic Effects in Ion Diffusion.- Measurement of Chemical Diffusion Coefficients in Non-Stoichiometric Oxides Using Solid State Electrochemical Techniques.- Comparison of Atom Mobility in Crystalline and Glassy Oxides.- Oxygen Diffusion in Liquid Silicates and Relation to Their Viscosity.- Silicon and Oxygen Diffusion in Oxide Glasses.- Alkali Ion Conductivity in Fused Silica.- Cation Migration in Electrode Glasses.- A Structural Model of Ionic and Electronic Relaxation in Glass.- Molecular Diffusion in Glasses and Oxides.- Applications of Diffusion to Oxidation and Other Processes of Current Interest.- Mass Transport Phenomena in Oxidation of Metals.- The High-Temperature Oxidation of Hot-Pressed Silicon Carbide.- Sintering of Silicon Carbide.- Determination of Phase Diagrams Using Diffusion Techniques.- Ambipolar Diffusion and Its Application to Diffusion Creep.- Crystal Growth and Glass Formation.- The Effect of Diffusion and Shear on Concentration Correlations in Binary Systems.- The Dissolution Kinetics of Lithiated NiO in Aqueous Acid Solutions.