Showing papers on "Rutile published in 1976"

Semiconductor properties of manganese dioxide

Abstract: Measurements of the d.c. conductivity of different types ofγ-manganese dioxide formed under various conditions and of different thermal history indicate a correlation with the combined water content. The specific conductivity increases exponentially as the water content decreases. The values obtained with anhydrous products which then are transformed to aβ-manganese dioxide are similar to those obtained withβ-manganese dioxide prepared by pyrolysis of manganous nitrate. Any effect which might be attributed to the lattice transformation ofγ- intoβ-manganese dioxide could not be observed. A more detailed examination of two specimens of manganese dioxide shows a semilogarithmic relation between thermoelectric voltage and d.c. conductivity. This relationship allows an estimate to be made of the electron concentration at which the electron gas would begin to degenerate. Hence it follows that both forγ- andβ- manganese dioxide the concentration of the conducting electrons is far below the degeneration limit. This result is in agreement with the measured activation energies of the conductivity. It is suggested that the water content influences the electronic band structure by successively deforming the rutile structure ofβ-manganese dioxide and hence the manganese-manganese distances within the lattice.

Photocatalytic oxidation of propan-2-ol in the liquid phase by rutile

Abstract: The photocatalytic oxidation of liquid propan-2-ol to acetone has been investigated using irradiated suspensions of pure rutile. It is shown that ultraviolet radiation, rutile and a source of oxygen are all necessary for measurable reaction to occur at 310 K. The parameters controlling the photoactivity of pure rutile, together with effects of adding hydrogen peroxide, water or dissolved salts to the reaction mixture, have been investigated. Supporting measurements with doped rutile and less pure anatase have also been made.The experimental results, which include values of the quantum yield, do not support a chain mechanism for acetone formation. Mechanisms are proposed, in which reactive species are formed by the surface trapping of both photoelectrons and photoholes.

Studies of heterogeneous oxidation catalysts. Part 1.—The vanadium(V) oxide + titanium(IV) oxide system

Abstract: The mechanism of promotion of vanadium(V) oxide catalysts by titanium(IV) oxide (anatase, brookite and rutile) has been investigated by a variety of physicochemical techniques with particular reference to the thermal behaviour. With binary mixtures of vanadium(V) oxide and anatase or brookite, oxygen evolution from V2O5 occurs between 873 and 973 K and this is accompanied by a gradual phase-transformation of both modifications of titanium dioxide to rutile. In the case of brookite, an initial phase-change to anatase is followed by a further phase-change to rutile. In all three systems, 10–15 mole % V2O5 represents the optimum concentration for this high temperature solid-state reaction between the components. This composition coincides with the maximum catalytic activity of such mixtures. Studies of other properties of the systems indicate that, during this process, V4+ ions are incorporated into the rutile lattice and are subsequently stabilised. The results obtained, together with other considerations, suggest that at this composition, there is maximum contact between the two types of oxide particle, so that the effective surface area of the V2O5 is increased. Although this appears to be the main role of TiO2, spectroscopic evidence suggests that the presence of titania also weakens the VO bond in vanadia, thus providing an additional promoting action.

A comparative study of the oxidation with water vapor of pure titanium and of Ti-6Al-4V

Abstract: The oxidation kinetics of pure titanium and of Ti-6Al-4 V by water vapor were studied between 650 and 950°C and from 05 to 18 Torr The results showed a marked similarity of the oxidation behavior for both the alloy and pure titanium The rate curves had the same appearance At low temperatures (below 750°C) they exhibited two stages At high temperature the first of these stages was not observed Scanning electron microscopy (SEM) and electron probe analyses of the scale showed that the structure of the scales was also similar over the temperature range 750–900°C: they consisted of two layers of rutile, and, in the case of the alloy, of a thin sublayer of alumina between the other two Furthermore, SEM examination of the surface of oxidized specimens revealed the existence of whiskers

Rutile-containing lustrous pigments

Abstract: OF THE DISCLOSUREMica flake-based lustrous pigments having a plurality of TiO2 and SnO2 layers thereon are provided herein. The pigment has a metal oxide layer comprising the sequence of rutile/SnO2/rutile. The innermost layer is rutile and the thickness thereof is a maximum of 25 nm. Such pigments have im-proved properties, including light and weathering fastness.

A titanium-rich soil clay

Abstract: Summary A peaty podzol developed on glacial drift derived from chlorite-schists near Loch Awe, Argyll, contains up to 25 per cent titanium dioxide in the clay fractions after removal of organic matter and free iron oxides. Electron microscopy reveals that this titanium is almost entirely in the form of cryptocrystalline anatase which is amorphous to X-rays and which is removed by the HF method normally used to concentrate anatase and rutile in soils. The anatase has probably formed as a result of the weathering of sphene.

The dissolution of titanium minerals in hydrochloric and sulfuric acids.

Abstract: Kinetic dissolution experiments of powdered ilmenite and rutile were carried out in sulfuric and hydrochloric acids (0.03–1 M) at temperatures of 40, 65, and 90 °C in order to study the physico-chemical factors and the mechanism for the leaching of titanium and iron from these minerals and rocks under acidic conditions. The dissolution rate of ilmenite was strongly affected by the acidity and temperature of the acid solutions; the rate changes in the H2SO4 solutions were greater than those in the HCl solutions. The dissolution rate of rutile was much slower than that of ilmenite. Ilmenite was decomposed by the dissolution of titanium and iron in a nearly stoichiometric ratio under strongly acidic conditions such as 0.3–1 M. But under milder conditions, such as 0.03–0.1 M at 90 °C, the dissolution rate of titanium dropped rapidly in the initial step and the curved line for iron dissolution was nearly parabolic, suggesting the diffusion of iron through the residual layer of titanium.

Process for producing a synthetic rutile from ilmentite

Abstract: Synthetic rutile is made from ilmenite by pre-oxidizing it, reducing it in a fluid bed, thereafter aeration leaching it, optionally acid leaching, and drying.

Two step oxidation reactions of alcohols on an illuminated rutile electrode

Abstract: Alcohols (methanol, ethanol and iso-propanol) were found to be oxidized by the “current doubling” process on an illuminated rutile electrode The reactivity of alcohols decreased in the order, methanol > ethanol > iso-propanol This tendency seems to correspond to the amount of adsorbed alcohol on rutile

NaCl-induced accelerated oxidation of a titanium alloy

Abstract: The effect of a surface deposit of NaCl on the oxidation characteristics of a high-temperature titanium alloy was studied in the temperature range of 400–600°C. The influence of the water vapor content in the oxidizing environment was examined in the light of an existing electrochemical mechanism proposed for the hot-salt stress-corrosion-cracking phenomenon found in titanium alloys. It was established that the NaCl deposit increased the oxidation rate by a factor of 100 for hygrometry levels of 10 ppm or higher. Further, there exists a hygrometry threshold between 10 and 5×10−3 ppm below which the NaCl-induced accelerated oxidation decreases with decreasing hygrometry level. Electron microprobe analysis suggests that the titanium matrix reacts with chlorine before forming rutile.

Infrared studies of a Ziegler catalyst supported on magnesium oxide and titanium dioxide

Abstract: The interaction of TiCl4 and AlEt3 vapours with partially hydroxylated surfaces of MgO and TiO2(rutile) has been studied by infrared spectroscopy. Microgravimetric measurements are reported for interactions with MgO. Treatment of both MgO and TiO2 with TiCl4 followed by AlEt3 gave catalysts for the polymerization of ethylene and propylene at 293 K.

Titanium dioxide pigment composition and method of manufacturing same

Abstract: PURPOSE: A method of manufacturing the titanium dioxide pigment composition characterized by the improved weather resistance, dispersability and heat resistance resistance comprises coating with aluminum phosphate the rutile titanium dioxide particle covered by the continuous silica coating film. COPYRIGHT: (C)1977,JPO&Japio

Decreasing the photosensitivity of titanium IV dioxide

Abstract: Disclosed are TiO 2 pigments treated to decrease their photosensitizing propensity and their tendency to degrade polymeric materials. Commercial TiO 2 pigments, both anatase and rutile, treated according to the present invention with manganous, cobaltous or cerous salts, particularly acetate, are effectively desensitized.

TiO2 Pigment for industrial paints based on water reducible systems

Abstract: Rutile TiO2 is coated successively with precipitates of titania and alumina, the weight ratio of titania:alumina being about 0.5:1 to 1:1 and the total percentage of titania and alumina being about 7 to 8%, based on the weight of said rutile TiO2. The pigment is especially suited for use in industrial paints, e.g., automotive and appliance coatings, which are based on water reducible systems.

Rutile: Planar Defects and Derived Structures

Abstract: Over the last 25 years there has been a considerable change in the approach to solid-state crystal chemistry, mainly derived from thorough studies of a few transition metal oxide systems among them rutile — reduced and/or admixed with other oxides of lower valent metals, i.e. M2O3 + TiO2, where M = Ti or another trivalent cation. Structural progress was considerably accelerated by the application of the electron microscope and we will summarize some of this work. We demonstrate thereby the inherent weakness of X-ray diffraction and especially of powder techniques to study these systems.

The dissolution of titanium minerals in hydrochloric and sulfuric acids

Abstract: Kinetic dissolution experiments of powdered ilmenite and rutile were carried out in sulfuric and hydrochloric acids (0.03–1 M) at temperatures of 40, 65, and 90 °C in order to study the physico-chemical factors and the mechanism for the leaching of titanium and iron from these minerals and rocks under acidic conditions. The dissolution rate of ilmenite was strongly affected by the acidity and temperature of the acid solutions; the rate changes in the H2SO4 solutions were greater than those in the HCl solutions. The dissolution rate of rutile was much slower than that of ilmenite. Ilmenite was decomposed by the dissolution of titanium and iron in a nearly stoichiometric ratio under strongly acidic conditions such as 0.3–1 M. But under milder conditions, such as 0.03–0.1 M at 90 °C, the dissolution rate of titanium dropped rapidly in the initial step and the curved line for iron dissolution was nearly parabolic, suggesting the diffusion of iron through the residual layer of titanium.

Decomposition of Ilmenite in KOH‐H2O Solutions Under High‐Pressure Conditions

Abstract: Of all the naturally occurring minerals containing T1 as a major constituent only two, i.e. ilmenite and rutile, have been seriously considered as a suitable feedstock for either the metal-producing or pigment industries. Current methods for decomposing ilmenite1 are based mainly on the treatment of ilmenite with sulfuric acid or chlorination at high temperatures. The object of the present work was to study the effects of KOH solution on the decomposition and stability of ilmenite under hydrothermal conditions.