Effect Of Oxygen Potential Research Articles

Effect of oxygen potential on mineral formation in lime-fluxed iron ore sinter.

In industrial iron ore sintering, the raw material is heated in a reducing atmosphere and cooled in an oxidizing atmosphere. In order to study the characteristics of mineral formation under different regimes of heating and cooling in industrial sintering, small tablet specimens made from powdered materials were sintered in a tube furnace under controlled gas atmospheres. The results obtained are summarized as follows.In the heating stage acicular calcium ferrite can be produced from the reaction of hematite and the flux below 1 180°C. With an increase of temperature, the calcium ferrite crystal size increases and at higher temperature the calcium ferrite transforms to magnetite and silicate melt. During the cooling stage, the magnetite tends to react with the silicate melt and oxygen to generate calcium ferrite at a medium oxygen partial pressure (around 1×10-2 atm). Reoxidized hematite is formed from magnetite at a higher oxygen potential (e.g., 5×10-2 atm). The magnetite (produced in the heating stage) is preserved at a low oxygen potential. Acicular calcium ferrite may also be generated from magnetite ore at high oxygen potential (e.g., PO2>5×10-3 atom) during the heating stage of sintering.Calcium ferrite produced from the reaction of hematite and the flux in heating stage is a form of calcium diferrite (CaO·2Fe2O3) with some substitution of Si and Al. The composition of calcium ferrite generated from magnetite depends on the amounts of SiO2 and CaO from silicate melt reacting with magnetite. The basicity (mole ratio of CaO/SiO2) of silicate melt consumed in the reaction is around 2.

Effect of oxygen potential on the initial sintering of UO 2 and UO 2-Gd 2O 3 compacts

The initial sintering kinetics of UO 2 and UO 2-Gd 2O 3 (5 and 10 wt%) compacts have been studied at controlled oxygen potentials in the temperature range of 925–1100 ° C, by using a dilatometer. Most of the initial shrinkage of both the compacts appeared to be caused by neck growth between two adjacent UO 2 particles, and could be interpreted as controlled by the grain boundary diffusion of cations. The diffusion coefficients calculated from the isothermal sintering rates were significantly decreased with decreasing oxygen potential and with increasing Gd 2O 3 concentration. The activation energy for the diffusion obtained in a reducing atmosphere of P H 2 O / P H 2 = 10 −3 was 377 kJ/mol for UO 2 and 418 kJ/mol for the UO 2-10 wt% Gd 2O 3 compact. The dependence of the grain boundary diffusion coefficient, D B , on x in UO 2+x at 1000°C could be described by log D B ( cm 2/ s) = − 8.57 + 1.67 log x, from the known relation between x and the oxygen potential of UO 2+x. These phenomena were attributed to nonstoichiometric effects on the diffusions for UO 2 and (U, Gd)O 2 solid solutions.

石灰系フラックス吹き込みによる溶銑の同時脱りん脱硫処理に及ぼす酸素ポテンシャルの影響

石灰系フラックス吹き込みによる溶銑の同時脱りん脱硫処理に及ぼす酸素ポテンシャルの影響

The effect of oxygen potential on phosphorus in the CaO−Al2O3 system

The effect of oxygen potential on phosphorus in the CaO−Al2O3 system

Production of Matte, White Metal, and Blister Copper by Flash Furnace

Outokumpu Oy has intensively studied the production of high-grade copper matte in a flash smelting furnace since the 1950s. Blister copper was first produced in the pilot furnace of the Metallurgical Research Centre at Pori in 1969 and the first commercial plant for direct blister production was commenced in 1978 in Poland. This paper is a survey on the effect of oxygen potential or matte grade on the metallurgy of smelting copper concentrates in a flash smelting furnace. Increasing the matte grade in the smelting step improves the smelter operation in many ways. For instance, it increases the use of the combustion energy of concentrates, converts a higher portion of sulfur to a continuous and concentrated gas stream, decreases matte handling, and gives less fugitive gas. However, copper recirculation via slag cleaning increases. In general, the volatilization of harmful impurities slightly decreases when increasing the matte grade in flash smelting. Simultaneously, the partition coefficients of minor elements between matte and slag normally decline, so that higher portions of impurities are slagged when there are higher oxygen potentials. Only the responses of arsenic, antimony, and bismuth are somewhat different at higher matte grade.

Effect of Oxygen Potential on the Thermal Creep of Niobia Doped UO2

Compressive and tensile creep were measured on UO2 doped with 0.4 wt % niobia at controlled oxygen potentials. Kinetic results were almost identical, irrespective of the nature of the applied stress, but differences in after‐test microstructures were observed. Formation of “plastic” UO2 with increases in strain rate of more than two orders of magnitude were recorded when oxygen potential changed from −560 to −410 kJ/mol; this was associated, primarily, with the formation of the Nb4+ ion. Over the same range of oxygen potential, creep activation energy decreased linearly from −425 to −225 kJ/ mol. In contrast, strain rate and activation energy for undoped UO2 remain almost constant under these conditions.

The Effect of Oxygen Potential on the Surface Self-Diffusion Coefficient of Silver

The Effect of Oxygen Potential on the Surface Self-Diffusion Coefficient of Silver

銀の表面自己拡散係数におよぼす酸素ポテンシャルの影響

銀の表面自己拡散係数におよぼす酸素ポテンシャルの影響

ChemInform Abstract: EFFECT OF OXYGEN ON THE REACTION BETWEEN COPPER AND SAPPHIRE

AbstractDer Einfluß des Sauerstoffpotentials auf die Benetzung und die Grenzflächenspannung zwischen geschmolzenem Cu und Sapphir wird in einer CO‐CO2‐Atmosphäre untersucht.

Effect of Oxygen on the Reaction Between Copper and Sapphire

The effect of oxygen potential on the wetting behavior and interfacial energy between Cu and sapphire was studied using the sessile drop technique in a CO‐CO2 atmosphere. A linear relation was found between γSL and logpO2 (atm) from 10−16 to 10−5. Beyond 10−5 atm γSL approached a constant value asymptotically. A barrier surface layer was proposed to explain this change. The Gibbs adsorption equation was used to evaluate the characteristics of the interfaces. Formation of a Cu2O film at the liquid‐vapor interface and a CuAlO2 film at the solid‐liquid interface is suggested. The work of adhesion reached a maximum at ∼ 0.01 at.% oxygen, corresponding to pO2∼ 10−9atm. Measurements of the basal radius as a function of oxygen content were used to evaluate the role of oxygen in promoting spreading. Spreading on sapphire is directly proportional to the logarithm of oxygen present in the molten Cu drops.