Showing papers on "Iron oxide published in 1977"

Mechanisms of phosphate sorption by soils and hydrous ferric oxide gel

Abstract: Summary Data for the sorption of added inorganic phosphate (P) by contrasting soils and iron oxide gel were resolved by a method of successive approximation of the Langmuir sorption constants. Three distinct Langmuir equations described the overall isotherm irrespective of the experimental conditions used. Free energies of sorption (ΔG) for a particular region were similar for each soil and for iron oxide gel under all experimental conditions. In contrast, the sorption maximum for each region was influenced by the sorbent and experimental conditions. Because of the pronounced similarities in their P sorption characteristics iron oxide gel was used as a model surface for P sorption by soils. Three mechanisms for P sorption by iron oxide gel and by soils are proposed: (i) chemisorption at protonated surface sites, (ii) chemisorption by replacement of surface hydroxyls, and (iii) a more-physical sorption of P as a potential-determining ion.

The rate of reduction of iron oxides by carbon

Abstract: The rate of reduction of Fe2O3 and FeO by coconut charcoal, coal char and coke, in an inert atmosphere within the temperature range 900 to 1200°C was investigated. The effects of pressure, particle size, and the amount of carbon were determined. The results indicate that the reaction takes place by means of the gaseous intermediates CO and CO2, and that the overall rate is controlled by the oxidation of the carbon by CO2. The rates of reduction of FeO and Fe2O3 by CO are relatively fast, and the CO2/CO ratio for the oxidation of carbon is determined by their equilibria. The reduction of Fe2O3 by carbon is accomplished in two stages, with FeO forming first. The reduction of Fe2O3 to FeO is faster than that of FeO to Fe because its CO2/CO equilibrium ratio is higher and hence the rate of oxidation of carbon is faster. A direct comparison was made between the rate constants for the reduction of FeO by carbon and those for the oxidation of carbon in the appropriate CO2-CO gas mixtures, and they are in good agreement. Apparently the iron formed by the reduction does not significantly catalyze the oxidation of carbon; whereas for the reduction of NiO by carbon, the Ni formed does catalyze the oxidation of carbon.

Iron Oxide Semiconductor Electrodes in Photoassisted Electrolysis of Water

Abstract: The preparation of polycrystalline n-type iron oxide electrodes by heating of iron samples in air is reported. The behavior of these electrodes in aqueous solutions of different pH values in the presence and absence of illumination is shown. The photocurrent response of these electrodes to all wavelengths in the visible region is seen. Photoassisted electrolysis of water occurs at these wavelengths resulting in the evolution of oxygen bubbles at the iron oxide electrodes with no noticeable corrosion problems in pH 40 acetate buffer to 5.5M KOH solutions.

Use of auger and x‐ray photoelectron spectroscopy to study the locus of failure of structural adhesive joints

Abstract: The techniques of Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) have been used to study the locus of failure of epoxy resin joints. The effects of a long water immersion and the application of a silane-based primer have also been studied. Results indicated that for dry joints fracture occurred near an epoxy resin/metal interface while with water-soaked unprimed joints, fracture occurred interfacially between the adhesive and iron oxide. The application of the primer to the metal surface prior to bonding prevented the formation of a water-formed oxide although fracture was then found to occur through the primer.

β Fe2 O 3: Preparation of Thin Films by Chemical Vapor Deposition from Organometallic Chelates and Their Characterization

Abstract: Thin films of a new iron oxide phase, , were prepared by chemical vapor deposition (CVD) from tris(trifluoroacetylacetonato) iron (III) at 300°C in the presence of oxygen onto a variety of substrates. The films were characterized by x‐ray diffraction analysis, scanning electron microscopy, and Mossbauer spectroscopy. For the latter measurements the films were prepared from enriched . The ultraviolet, visible, and infrared spectra of the films were also recorded. The iron (III) oxide phase prepared was bcc having the bixbyite structure, Ia3 space group and the lattice constant . There are 16 formula molecules to the unit cell and the two iron atoms occupy two nonequivalent distorted octahedral lattice sites: (8b); 2(24d).

Tritium exchange studies on metal oxide colloidal dispersions

Abstract: The tritium exchange technique has been used to detemine the maximum number of surface protons at the oxide-water interface for oxide colloids including silicas, TiO2 (rutile) and the iron oxides goethite, hematite and amorphous iron oxide. The effects of heat treatment, crystal structure and exchange conditions are considered and tritium exchange values for the number of surface protons are compared with values calculated from crystal structures.

Process for oxidizing sulfur and sulfur compounds

Abstract: Sulfur and sulfur compounds contained in a gas are oxidized in contact with a catalyst comprising vanadium oxide, iron oxide and alumina, said catalyst having a surface higher than 30 m 2 /g and being obtained by impregnation of aluminum with soluble vanadium and iron compounds.

Production of iron oxide pigments with improved resistance to oxidation

Abstract: An Fe3 O4 iron oxide black pigment having incorporated therein up to about 50 mole percent of γ-Fe2 O3 plus Me Fe2 O4 (wherein Me is at least one of magnesium, manganese, cobalt, nickel, aluminum, chromium, titanium, copper, zinc and cadmium) having a specific surface according to BET of greater than about 12 m2 /g, up to about 10% by weight of a substantially insoluble inorganic compound as coating and a stability to oxidation with air under standardized conditions of greater than about 130° C. Advantageously the coating comprises at least one of zinc hydroxide, zinc phosphate, zinc phosphite, aluminum phosphate and silica, being precipitated onto the suspended pigment from a solution. The resulting pigments are of improved resistance to oxidation, rendering them especially useful for pigmenting inorganic and organic dispersions and for use on magnetogram supports.

Characterization of iron oxide compounds in soils by Mössbauer and other methods

Abstract: Iron oxide compounds in 12 selected Canadian soil samples have been characterized by Mossbauer, X-ray, chemical, infrared absorption, and differential thermal methods. Chemical differentiation prov...

Anomalous increase of coercivity in iron oxide powder coated with sodium polyphosphate

Abstract: An anomalous increase of coercivity in a non-stoichiometric acicular iron oxide powder which was treated with a chain like sodium metaphosphate was investigated. The coercivity increased by a factor of about 2 in the acicular iron oxides and about 3 in the granular one, respectively. The magnetization decreased in inverse proportion to the increased coercivity. The coercivity of the treated iron oxides which was washed with water to remove the sodium metaphosphate returned to the value or to less than the value of the untreated iron oxides. The large magnetic anisotropy was estimated from the magnetic hysteresis loop. A constricted hysteresis loop was observed in treated iron oxides. The experiment suggests that an origin of the increased coercivity is due to the surface magnetic anisotropy which is based on the electrostatic coupling, participating in a absorbed compound.

Iron oxide magnetic pigments for the production of magnetic coatings

Abstract: An iron oxide pigment having a coating of a silane of the formula R.sub.n Si(OR').sub.4-n wherein R is an, in some cases, branched or oxygen-bridge-containing alkyl or alkenyl moiety of 1 to 18 carbon atoms, or an aryl moiety, R' is an, in some cases, branched and, in some cases, oxygen-bridge-containing alkyl moiety of 1 to 8, n=1 to 3, or a hydrolysis product thereof; a magnetic tape containing such coated iron oxide pigment and a process for coating such iron oxide pigment. There is particularly disclosed the treatment of iron oxide magnetic pigments to thereby improve their wear resistance and dispersibility in organic mediums.

Process for treating a waste gas containing sulfur oxides

Abstract: A waste gas containing sulfur oxides is contacted with an adsorbent comprising an intimate mixture of an iron oxide and/or a copper oxide and a titanium oxide at a temperature of 250°-500° C. The sulfur oxides thus adsorbed are desorbed with a reducing gas and recovered as sulfur material. The efficiency of the adsorbent is not reduced even after many repetitions of the adsorption-desorption cycle. Since the adsorbent exhibits a high resistance to sulfuric acid mist (SO3) contained in the waste gas.

Thermal spray powdered composite

Abstract: A composite powder suitable for use in thermal spray applications as a wear and/or corrosion resistant coating comprising chromic oxide, magnesium oxide, iron oxide, titanium oxide, and aluminum oxide.

Reduction mechanism of molten iron oxide by solid carbon

Abstract: The reduction of molten iron oxide by solid carbon takes place in the form of a chain of reactions consisting in reduction by CO gas and the Boudouard reaction and seems to be controlled by the Boudouard reaction.

Disproportionation Equilibrium in Iron-Bearing Systems at Pressures above 100 Kbar with Applications to Chemistry of the Earth’s Mantle

Abstract: Chemical disproportionation of ferrous iron-bearing phases to an equilibrium mixture of ferric iron-bearing phases plus metallic iron is stabilized at high pressures. The effect is observed in olivine, and is the basis of a model of the earth’s mantle and core that is evolved from a primitive earth. The model is consistent with an equilibrium process of formation of the earth, and satisfies known physical properties of materials that are suitable for the mantle.

Production of acicular magnetic iron oxides

Abstract: In the production of acicular ferromagnetic iron oxide of highly uniform particle size by oxidizing an iron (II) hydroxide suspension at a pH of at least 11 with an oxygen-containing gas to form acicular iron (III) oxide hydroxide, reducing and optionally further reoxidizing this into ferromagnetic iron oxide, the improvement which comprises providing the iron (II) hydroxide suspension with a water-soluble silicate in an amount of less than 1.7% by atom based on the amount of the iron (II) hydroxide in the suspension and calculated as the ratio of Si to Fe (II) while prior to the oxidation of the suspension with the oxygen-containing gas.

Process for producing a recording medium of magnetic iron oxide

Abstract: PURPOSE:To eliminate the need of a strong acid solution which has an adverse influence on a magnetic disc substrate such as Al, for instance, which corrodes the surface thereof, by coating onto a substrate a suspension in which crystalline fine particles of (aqueous) iron oxide are uniformly dispersed, and heat-treating the resultant film.

Extractable sesquioxides in six mediterranean soils developed on basalt and scoria

Abstract: Summary Iron, Al, and Mn were extracted by oxalate and dithionite from two Brown Mediterranean Soils, two Red Mediterranean Soils, one Vertisol and one Gley soil, all derived from basalt or scoria in the sub-humid and humid Mediterranean regions of the Golan Heights. Ratios of oxalate: dithionite extracted iron (Feo:Fed) were low in all soils, indicating that the predominant form of free iron is crystalline. Feo accumulates in the argillic B horizons of the Mediterranean soils, while Fed accumulates in the surface horizons. A large part of the free iron oxide in the surface horizons of Mediterranean soils is associated with non-clay fractions. While manganese behaves in a manner somewhat similar to that of iron, no definite trends could be discerned in the vertical distribution of free aluminium. In the Vertisol, Feo and Mno accumulate in the subsoil. Fed and Mnd increase slightly with soil depth. In the Gley soil, amorphous iron accumulates in the surface horizon, total free iron in the bottom horizon. Both amorphous and total free Mn had been depleted from the upper horizons of the Gley soil.

Process for recovery of iron oxide and chlorine from dust produced in chlorination of titaniferous ores

Abstract: The dust produced in the chlorination of titaniferous ores comprises essentially particulate ferrous chloride plus solid contaminants including coke and various metal chlorides and oxides and is oxidized in successive stages at relatively low temperatures to recover particulate iron oxide and gaseous chlorine.

Thermal dehydrochlorination of poly(vinyl chloride). I. Effect of iron oxide on the rate of dehydrochlorination

Abstract: The thermal degradation of poly(vinyl chloride) (PVC) was studied by following the rates of dehydrochlorination at temperatures between 180°C in pure nitrogen and air flow Iron oxide accelerates the elimination of hydrogen chloride from PVC The accelerating effect depends on the concentration of the oxide, and it has a maximum This work tried to explain these behaviors A mechanism of dehydrochlorination is suggested for polymer containing iron oxide

Method for reducing particulate iron oxide to metallic iron with solid reductant

Abstract: A method and apparatus for reducing particulate iron oxide to metallic iron utilizing solid carbonaceous fuel as reductant in a shaft type reducing furnace, in which a furnace burden is formed of a mixtue of iron oxide lumps or pellets and particulate solid fuel. Reacted top gas is upgraded and recirculated through the burden in counter-flow relationship thereby heating and partially reducing the burden. The heat for final reduction is generated by passing electric current through the burden.

Method of reducing finely grained material containing iron oxides in a fluid bed

Abstract: Fine-grained iron oxide reduction in a fluidized bed; a reducing agent in the form of fine-grained solid carbonaceous material containing volatile constituents is introduced into at least one zone of the fluidized bed; in said zone the volatile constituents are driven off, and a tarry material is temporarily formed on the surface of the particles of the carbonaceous material; the fine-grained iron oxide to be reduced is introduced into said zone; iron oxide particles adhere to the tarry carbonaceous particles; in this manner micro-aggregates which are especially desired are formed; but the formation of bigger aggregates is prevented.