Showing papers on "Iron oxide published in 1981"

Dedolomitization in the Taum Sauk Limestone (Upper Cambrian), Southeast Missouri

Abstract: Coarse dolomite crystals in the Taum Sauk Limestone (Upper Cambrian, southeast Missouri) contain both calcite and iron oxides in rhombohedral zones and along fractures and cleavage traces. The dolomite crystals are demonstrably nonstoichiometric, averaging 57 mole percent CaCO3, and are compositionally zoned, ranging from 1.40 to 4.56 mole percent FeCO3. Cathodoluminescene study and microprobe analyses of the dolomite, coupled with scanning electron microscope (SEM) examination of etched fracture surfaces reveal that: 1) Scattered dolomite within the calcite/iron oxide zones is the most iron-rich. 2) Calcite within dolomite rhombs is brightly luminescent, nonferroan and is intergrown with iron oxides. 3) The iron oxides display two crystal habits--thin, red (hematite?) circular plates, typically 0.7 to 1.0 microns across, grouped in rosettes; and prismatic bundles and prismatic radiating aggregates of brown crystals (goethite?), typically 1 to 3 microns in length. 4) Narrow veinlets of dolomite associated with calcite and iron oxides along cleavage traces form a three-dimensional network. This feature, which aided in interpreting the iagenetic history of the dolomite, was not observed during petrographic examination but was readily observed with the SEM. The occurrence of nonferroan calcite and ferric oxides in rhombohedral zones in Taum Sauk dolomite suggests that dedolomitization occurred by the oxidation and alteration of ferroan dolomite zones and probably reflects alteration related to Recent weathering.

High-pressure polymorphism of the iron oxides

Abstract: Summary. High-pressure shock-wave data for hematite (Fe2O3) and magnetite (Fe3O4) are remarkable for the very large density increases (∼ 10 per cent at 100 GPa) associated with shock-induced transformation from the relatively close-packed corundum and spinel structures. The recently reported data of Jeanloz & Ahrens for wustite (Fe0.94O) also reveal a major shock-induced phase change which they interpret as B1 B2 polymorphism. Reassessment of the wustite data, however, indicates that the zero-pressure density increase, associated with shock-induced polymorphism, is at least 10—16 per cent and very possibly as great as 18–28 per cent. The density increases for all three iron oxides thus appear to be too large to be explained in terms of geometric rearrangement (e.g. B1 B2) of the usual Fe2+, Fe3+ and O2- ions, unless it is assumed that these ions possess substantially smaller effective radii in the high-pressure phases. In this connection, it is proposed that the more covalently bonded nickel arsenide (NiAs) and derivative structures might accommodate very dense iron oxide phases of all stoichiometries at high pressures. Systematics, involving the volume and free energy changes associated with NaCl NiAs polymorphism in various transition metal chalcogenides, suggest a B1 NiAs transformation pressure of ∼ 31 GPa for FeO with an estimated zero-pressure density increase of ∼ 11 per cent. An alternative, or additional, mechanism by which Fe-O bonds might be shortened significantly involves spin-pairing of 3d electrons. Calculations, based on structural data for Co3+ oxides, provide an estimated spin-pairing pressure of ∼ 50 GPa for FeO with a density increase of 9 per cent at the transition. While the occurrence of substantial ‘mixed-phase’ regimes along the Fe2O3 and FeO Hugoniots seems to preclude an exclusively electronic interpretation of the observed phase changes, it is quite possible that spin-pairing augments the density increases due to NaCl NiAs polymorphism. Comparative studies of the high-pressure phase behaviour of MnO, FeO, CoO and NiO should resolve the relative roles of structural and electronic transitions. The high-pressure stability of iron oxides in covalently bonded structures of the NiAs type would enhance their solubility in molten Fe, and thus provide an attractive scenario for the incorporation of oxygen into the Earth's core.

Quantitative analysis of iron oxides using Auger electron spectroscopy combined with ion sputtering

Abstract: Quantitative analysis of α‐Fe2O3, Fe3O4 and FeO films to an accuracy of ±0.3 at.% is achievable using derivative‐mode Auger electron spectroscopy. This requires the use of a sensitivity factor obtained from iron oxide standards. During ion sputtering, the best measure of iron concentration is found to be the magnitude of the negative excursion of the Auger signal rather than the usual peak to peak value. For all the iron oxides sputtered in both argon and xenon (voltage range 1–4 keV) there is a 4.7±0.2 at.% reduction in oxygen content except for 1 keV xenon, where the value is 3.7±0.2 at.%. The rate at which sputter equilibrium is established depends on the ion species, the voltage, and the sample topography. A sputter mixing depth of ∠8 to 60 A is indicated.

Adsorption by zeolitic composition

Abstract: Natural zeolite minerals which have a high silicon-to aluminum atomic ratio (hereinafter referred to as Si/Al ratio)and a fibrous micro-structure in at least some parts are ore-dressed and classified according to the iron impurity content converted in terms of iron oxide Fe2 O3. Zeolite with high Si/Al ratio is excellent in resistance to acid and heat and can be re-activated at high temperatures. The fibrous microstructure is considered to impart a high degree of mechanical strength to the zeolite after pelletization. High-grade natural zeolites with small iron impurity content uniformly exhibit high adsorption performance. In particular, zeolite adsorbents using natural zeolite consisting principally of mordenite are very useful for various purposes. In the case of removing oxygen, the combined use of the zeolite adsorbent and an oxygen removing catalyst provides good results. By cooling the zeolite adsorbent down to low temperatures, its adsorption performance rises sharply. The zeolite adsorbent is of particular utility when employed for purification of gas, removal of water vapor from a vacuum system, removal of undesirable components and so forth.

Manufacture of metallic magnetic powder

Abstract: PURPOSE: To obtain metallic magnetic powder with superior magnetic characteristics by sticking an Al compound to powder of a metallic compound consisting essentially of iron oxyhydroxide or iron oxide, granulating the powder, and carrying out reduction under heating CONSTITUTION: An Al compound is stuck to the particle surfaces of powder of a metallic compound consisting essentially of iron oxyhydroxide or iron oxide The powder is heat treated at 200W600°C, granulated, and optionally heat treated at 200W600°C Reduction under heating is then carried out at about 300W600°C in a reducing atmosphere of gaseous hydrogen or the like By this method the reduction under heating can be carried out sufficiently and uniformly while effectively inhibiting sintering among the granules and the particles of the powder and the deformation of the particles As a result, iron-base metallic magnetic powder with superior magnetic characteristics is obtd COPYRIGHT: (C)1982,JPO&Japio

Development and testing of regenerable hot-coal-gas desulfurization sorbents

Abstract: Investigations over several years at the Morgantown Energy Technology Center have been concerned with the development of a regenerable metal oxide desulfurization sorbent which would function on hot coal-derived fuel gas. In the latest phase of testing, a combination of zinc oxide with iron oxide as zinc ferrite has produced a sorbent which has demonstrated regenerability and capability of removing sulfur from simulated hot coal gas to a level of 1 to 10 ppM by volume. The principal finding at this stage of the project is that the compound zinc ferrite and also iron oxide containing some zinc ferrite have hydrogen sulfide absorption performances very similar to those of zinc oxide. Extruded sorbents made from these compounds have been demonstrated to perform with varying ability in the temperature range 800/sup 0/F (427/sup 0/C) to 1400/sup 0/F (760/sup 0/C) at a space velocity of 2000 hourly and a hydrogen sulfide concentration of 2.7 percent. They have also been shown to be regenerable with a 50/50 percent v/v steam-air mixture at 1000/sup 0/F (538/sup 0/C) and 600 hourly space velocity with no loss of absorptive power. Both zinc ferrite and zinc oxide appear to perform optimally in the middle of the temperaturemore » range, where absorption capacity is greatest. Surprisingly, the experimental results indicate no trend to a lower degree of hydrogen sulfide removal with rise in temperature. Zinc ferrite appears to be superior to zinc oxide in terms of its absorption capacity and resistance to sintering at higher temperatures.« less

Highly reactive iron oxide agents and apparatus for hydrogen sulfide scavenging

Abstract: Substantially dry iron oxide particles having a high surface area, a high kinetic "K" value and composed of a crystalline phase of Fe 3 O 4 together with an amorphous Fe 2 O 3 moiety or portion and having a surface area of at least 4 m 2 / g are useful for scavenging hydrogen sulfide from other gases containing it. A cartridge type device is provided containing such particles intermixed with inert particulate matter, e.g. sand, useful as a means for scavenging hydrogen sulfide from such other gases.

Process for preparing acicular iron oxide particles

Abstract: This disclosure relates to a process for preparing acicular magnetic iron oxide particles by (a) adding an aqueous solution of a ferrous salt to an aqueous solution of a stoichiometric excess of alkaline hydroxide while substantially avoiding local excesses of the ferrous salt, to form an aqueous dispersion of ferrous hydroxide particles, (b) oxidizing these particles to form non-magnetic alpha ferric oxide hydrate particles, and (c) converting the non-magnetic particles to magnetic iron oxide particles by dehydration and reduction or dehydration, reduction and oxidation. The ferrous salt solution is subjected to reducing conditions prior to and/or during the addition to the alkaline hydroxide solution to reduce contaminating ferric ions that are normally present to ferrous ions.

Production of lamellar iron oxide pigments

Abstract: Synthetic, hexagonal, lamellar iron oxide particles, suitable as corrosion-inhibiting or decorative colored pigments, containing about 0.1 to 12% by weight of at least one oxide of an element of the IVth, Vth or VIth Main and Secondary Groups and of the IInd Secondary Group of the Periodic System of Elements.

Process for preparing ferromagnetic particles comprising metallic iron

Abstract: A process for preparing ferromagnetic iron particles comprising metallic iron as the major component by reduction of particles of an iron oxide under heating, characterized in that the iron oxide particles are provided with a first coating layer containing at least one metal compound chosen from compounds of aluminum, zinc and alkaline earth metals at the surfaces and a second coating layer containing at least one silicon compound thereon before the reduction, whereby the coated particles are prevented from sintering and breaking upon reduction so as to give ferromagnetic particles of metallic iron having excellent magnetic characteristics.

Process for producing alkali metal ferrates

Abstract: Alkali metal iron (IV) and iron (VI) ferrates are produced by the reaction at high temperatures of reactant mixtures of either (a) iron oxide and alkali metal oxide or peroxide or (b) elemental iron and alkali metal peroxide, wherein the reactions are conducted at least in their initial stages in the absence of free oxygen, e.g., in a vacuum or in a inert gas atmosphere.

Lustrous pigment and process for producing same

Abstract: Lustrous flaky red iron oxide pigments containing aluminum in solid solution are produced by applying hydrothermal treatment to iron oxyhydroxide or colloidal precipitates of a ferric hydroxide in an aqueous aluminate solution. Lustrous pigments exhibiting various colors different from those of titanium dioxide-coated mica pigments are produced by coating titanium dioxide hydrate or titanium dioxide on the surface of the grains of flaky red iron.

Process for preparing transparent iron oxide pigment dispersions

Abstract: This invention relates to a process for preparing transparent iron oxide pigment dispersions. The dispersions are prepared by milling a mixture of iron oxide pigment and a liquid vehicle in a bead mill containing glass beads as the grinding media. The pigment dispersions can be used in the preparation of paints and coatings which exhibit transparent quality and absorb ultraviolet radiation.

Reduction and dephosphorization of molten iron oxide with hydrogen-argon plasma

Abstract: A laboratory-scale test was made in which iron oxide contained in a water-cooled crucible was melted and reduced by using a 10-50% H/sub 2/-Ar transferred arc plasma. The degree of reduction was found to be proportional to the amount of hydrogen fed. The efficiency of hydrogen utilization for the reduction was 50-70%, which is much higher than equilibrium values below 3000 K. This high efficiency was attributable partially to the reactivity of the hydrogen atom in a plasma and partially to the continuous contact of the hydrogen plasma with the molten iron oxide layer floating over the liquid iron formed. During the plasma reduction, evaporative loss of phosphorus was observed. The degree of phosphorus removal depended on the weight ratio, CaO/(SiO/sub 2/+Al/sub 2/O/sub 3/). H/sub 2/-Ar plasma was shown to be far superior for the phosphorus removal, compared with Ar and Ar-N/sub 2/ plasma.

A method of producing a single crystal of ferrite

Abstract: A single crystal of ferrite is grown toward a polycrystal of ferrite by heating a polycrystal of ferrite and a seed of single crystal of ferrite in contact with each other to effect a solid phase reaction. In this method, as the polycrystal of ferrite use is made of the specific polycrystal of ferrite prepared by using iron oxide containing iron oxide having spinel structure, iron oxide having hysteresis of spinel structure or mixture of these iron oxides in an amount of not less than 60% by weight calculated as Fe 2 O 3 as the starting material of iron oxide of the main component of polycrystal of ferrite and the heating is effected at a temperature lower than the temperature at which the discontinuous grain growth of the polycrystal of ferrite is caused.

Mathematical simulation of direct reduction

Abstract: A finite element analysis is developed for nontopochemical reduction of a porous iron oxide pellet. The reduction kinetics are essentially the same as those used by Trushenski, Li and Philbrook. However, several novel features arise in the present analysis. The computational technique used in this analysis provides an explicit way of calculating gas profiles for each step of the computations. To a limited extent multicomponent gas mixtures (either carbon monoxide, carbon dioxide and inert gases; or hydrogen, steam and inert gases) can be accomodated as the reducing agent. A corresponding analysis for direct reduction of iron oxide in a countercurrent shaft furnace assumes adiabatic conditions to prevail in the furnace as opposed to the usual isothermal assumption. The analysis assumes steady-state operation of the furnace, and plug flow of gas and solid. Profiles of gas and solid temperatures, degree of reduction of iron oxide pellets, bulk gas and solid compositions are calculated.

Effects of Iron on the Corrosion Resistance of Titanium

Abstract: This paper presents the results of extensive laboratory tests and experience in industrial applications to explain the effects of iron on the corrosion resistance of titanium In the great majority of cases where titaniumis being used in corrosive environments, the effect of iron at the levels normally found in unalloyed titanium (≃01 percent) is insignificant and has not led to any problems However, in some cases, high solid-solution iron levels have been blamed for premature failures due to pitting or hydrogen embrittlement Tests conducted at TIMET, Henderson, Nev, suggest that solid-solution iron has little, if any, effect on susceptibility to pitting or hydrogen embrittlement Iron particles embedded in the surface of unalloyed titanium are very deleterious They serve as initiation sites for pitting and also as entry points for hydrogen Ferric ions in the corrosive solution are beneficial and serve as an excellent passivating agent for titanium Iron oxide deposits on the surface of titanium also have a passivating effect Galvanic coupling of titanium and iron can lead to accelerated corrosion of the iron and, in some environments, to hydrogen embrittlement of the titanium The magnitude of the effect is dependent on surface area ratios and the characteristics of the environment Titanium, however, is being widely used successfully in applications where galvanic coupling with iron exists, with comparatively few problems being reported

Self-reducing iron oxide agglomerates

Abstract: Self-reducing agglomerates of an iron oxide-containing material, such as an iron ore concentrate, having a compressive strength of at least about 45 Kg. are produced by preparing a moistened mixture of the ore concentrate, a finely-divided natural pyrolyzed carbonaceous material having a volatile matter (on dry basis) content of about 20% by weight or less in an amount at least sufficient to reduce all the iron oxide to metallic iron, about 1 to about 30% by weight of a bonding agent, such as burned or hydrated lime, and 0 up to about 3% by weight of a siliceous material (as SiO 2 ), such as silica; forming green agglomerates from this mixture; and hydrothermally hardening the green agglomerates by contacting them with steam under pressure.

Compatibility of water-cooled chromia-containing refractories with a high iron oxide acidic coal-ash slag at 1575/sup 0/C

Abstract: Sixteen water-cooled refractories were exposed to a synthetic high iron oxide acidic coal slag at 1575 °C. The importance of high chromia content and density in minimizing corrosive attack was evident. The beneficial effect of water cooling was also clearly demonstrated by the difference in corrosion and penetration between full- and 1/2- length specimens. All of the refractories were found to have reacted with the slag to form complex intermediate spinel layers with the general formula (Fe,Mg)(Cr,Al)2O4. The thickness, coherence, and composition of these layers varied according to the composition and density of the base refractory. Refractories high in chromia were shown to resist fluxing by iron oxide better than refractories high in alumina.

Experimental evaluation of the Rhodes-Hunter model for the particle size effect in X-ray fluorescence analysis of `thin' samples

Abstract: The experimental evaluation of the Rhodes–Hunuer model of the particle size effect in X-ray fluorescence analysis of ‘thin’ and monolayer samples is reported. The calculations and experiments were carried out for samples of iron oxide(Fe3O4) and copper sulphide (Cu2S) having particles of one size and a histog am distribution of particle sizes. For iron oxide particles, it was found that sticking causes a significant systematic discrepancy between the experimental results and the Rhodes–Hunter model prediction. For copper sulphide particles the model was applicable.

Glass-encapsulated magnetic materials and methods for making them

Abstract: Magnetic materials exhibiting ferrimagnetic and/or superparamagnetic behavior, produced by impregnating porous glasses with iron and, optionally, manganese, cobalt and nickel compounds, reacting the compounds with the porous glass to form bound complexes, heating the glass to expel unreacted organometallics, and further heating to convert the bound complexes to ferrimagnetic and/or superparamagnetic oxide crystallites, are described. Ferrimagnetic iron oxide crystallites exhibiting coercivities above 10,000 Oe can be made.