The mechanism and kinetics of zinc ferrite formation in steelmaking processes—A review

A series of cationic polyurethane-fluorinated acrylic hybrid latex (PUFA) have been synthesized by solvent-free method. In the method, vinyl monomers acted as dilution agent and the polyurethane (PU) having quaternary ammonium groups acted as macromolecular emulsifier without using any other solvent and surfactant. The structure and properties of PUFA were characterized by Fourier transform infrared spectroscopy (FT-IR), F19 nuclear magnetic resonance (F19 NMR), particle size distribution (PSD) analysis, transmission electron microscopy (TEM), contact angle (CA), surface free energy analysis, scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometry (EDS), and thermogravimetric (TG) analysis. The FT-IR, F19 NMR, and EDS confirmed that the FA monomer had been introduced into the chain of the PUFA hybrid polymer. The PSD analysis indicated the particles of PUFA were smaller than corresponding pure PU dispersion and narrower in particle size distribution. The CA and surface free energy analysis proved the PUFA hybrid latex film with fluorine possessed higher contact angle and lower surface free energy in contrast with the film without fluorine. The FPUA films exhibited good surface property which could be enhanced at higher annealing temperature. The EDS of PUFA confirmed the fluorine enrichment on the surface of PUFA. TG analysis suggested the PUFA hybrid latex film had a better thermal stability than pure PU.

The formation of zinc ferrite (ZnFe2O4) during the fluidized-bed roasting of zinc concentrates presents subsequent processing difficulties both for zinc recovery and for iron separation and disposal. A major source of iron in these concentrates is from the iron sulfides — pyrite and pyrrhotite. This study examined the changes undergone by these iron minerals when roasted together with sphalerite at 1223 K in a fluidizing gas mixture of 3 pct oxygen and 97 pct nitrogen. Optical microscopy and electron microprobe analysis were employed to identify the three stages that lead to ferrite formation and to examine the processes that occur within each stage. The first stage is oxidation of the sulfides to highly vesicular, amorphous magnetite particles containing small amounts of zinc. The second stage involves both densification of these particles by sintering and counterdiffusion of iron and zinc cations to form a continuous phase of homogeneous zinc-rich spinel and a precipitate of hematite. In the third stage, continuation of cation diffusion and increasingPo 2 results in the formation of stoichiometric zinc ferrite. These observations have been interpreted by reference to the established phase relationships that occur in the Zn-Fe-O system, and a detailed, solid state reaction mechanism for the formation of zinc ferrite has been proposed.

Gossan ore of sulfide zinc deposit contains abundant zinc, iron, and other metal elements, which is a significant resource with complex components and can be utilized. In this study, a new technology of preparing zinc ferrite from zinc sulfide deposit gossan was proposed. The effects of Al2O3, CaO, and SiO2 in gossan on the formation of zinc ferrite were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and specific surface area and pore size analysis (BET). The results show that the presence of Al2O3 and CaO could hinder the formation of zinc ferrite, while silica had no effect on the formation of zinc ferrite. Under the conditions of the molar ratio of ZnO and Fe2O3 to Al2O3, CaO, and SiO2 of 1:1:1, an activation time of 60 min, and a roasting temperature of 750 °C for 120 min, the products, which had good crystallinity, smooth particle surface, and uniform particle size could be obtained. In addition, compared to the roasted products with Al2O3 and CaO, the specific surface area, pore volume, and pore size of the products with SiO2 were the largest.

Influence of cobalt and manganese content on the dehydrogenation capacity and kinetics of air-exposed LaNi 5+ x-type alloys in solid gas and electrochemical reactions

Co-utilization of electric arc furnace dust and copper slag for preparing zinc ferrite based on microwave roasting

The formation of zinc ferrite from zinc oxide and iron oxide is evaluated with high temperature X-ray diffraction experiments. Despite the problem of accurately determining the temperature of the part of the sample actually investigated, a kinetic analysis of the isothermal formation is shown to be possible. From these data the energy and entropy of activation are derived. It is further shown that neither corrections for grain growth during formation nor the presence of impurities have any influence on these results. On the other hand, the size of the reactant iron oxide particles is found to have a strong influence on both the energy and entropy of activation.

The reaction kinetics, activation energy, and reduction rates of different carbon reductant properties with electric arc furnace (EAF) slag determine the effectiveness of carbon in EAF steelmaking. This article investigates the interaction between slag and carbonaceous materials derived from palm char and coke. Palm shells were converted into palm char using chemical activation method (phosphorus acid, H3PO4) and pyrolyzed at 450 °C for 2 h in a horizontal tube furnace. Then, all the carbonaceous materials were mixed with iron oxide from slag with mass ratio of 1:3.73. The reduction reaction was carried out in a horizontal tube furnace at different temperature ranges of 1250–1550 °C under argon gas to understand the reaction kinetics, activation energies, and reduction rates of iron oxide from EAF slag with palm char and coke. All iron oxides in EAF slag were completely reduced into metallic iron at 1550 °C for both reductants. The phase and quantity of reduced iron were confirmed by Rietveld refinement method using X-ray diffraction (XRD) pattern and energy-dispersive X-ray spectroscopy (EDX). Palm char/slag has lower activation energy value, E (38.52 kJ/mol), than coke/slag (47.75 kJ/mol). The reaction rate of palm char was found faster (4.99 × 10–5 mol/cm2 s) than coke due to larger specific surface area, higher pore volume, amorphous carbon structure, and higher fixed carbon with high volatile content leading to lower activation energy, thus accelerating the iron oxide reduction rates. This finding forms the basic understanding of the reaction between EAF slag and carbonaceous materials for future research on the production of palm char as a feasible carbon reductant in EAF steelmaking.

The problems of the presence and formation of hexavalent chromium during smelting in electric arc furnaces are discussed. The schemes of gas cleaning systems from chromium-containing gases of electric arc furnaces DS-0,5 and DSP-1,5, The gas cleaning system of furnace DS-0,5 includes a cyclone, two Venturi scrubbers and an electrostatic precipitator. The gas cleaning system of DSP-1,5 furnace consists of a cyclone, regulated and diffuzor scrubbers and two electrostatic precipitators BVKO. It is shown that industrial production of fused chrome-containing refractories can be ensured under safe conditions by using the mentioned dust and gas cleaning systems. Ill. 4. Ref. 4. Tab. 1.

The nanocrystalline zinc ferrite (ZnFe2O4) powder was synthesized by high energy reactive ball milling (RM) in a planetary mill. As starting materials a mixture of commercial zinc oxide (ZnO) powder and iron oxide (Fe2O3) powder was used. The starting mixture was milled for different periods of time, up to 30 h. The milled powders were annealed for 4 h at 350 oC in order to eliminate the internal stress and to finish the solid state reaction of ferrite formation. Zinc ferrite formation was investigated by X-ray diffraction. The obtained powder has a mean crystallite size of 12 nm after 20 h of milling. Using scanning electron microscopy (SEM) the particle morphology was studied. Particles size range of the powders was also determined using a laser particle size analyser.

Facile synthesis of zinc ferrite as adsorbent from high‑zinc electric arc furnace dust

Unusual redox activity of the central heteroatom manganese in Anderson anion: Modulating its oxidation state in a gas solid reaction

During sluicing operations of tank 241-C-110, a significant amount of solids were unable to be retrieved. These solids (often referred to as the tank 'heel') were sampled in 2010 and chemically and mineralogically analyzed in the 222-S Laboratory. Additionally, dissolution tests were performed to identify the amount of undissolvable material after using multiple water contacts. This report covers the solid phase characterization of six samples from these tests using scanning electron microscopy, polarized light microscopy, and X-ray diffraction. The chemical analyses, particle size distribution analysis, and dissolution test results are reported separately. Two of the samples were from composites created from as-received material - Composite A and Composite B. The main phase in these samples was sodium-fluoride-phosphate hydrate (natrophosphate) - in the X-ray diffraction spectra, this phase was the only phase identifiable. Polarized light microscopy showed the presence of minor amounts of gibbsite and other phases. These phases were identified by scanning electron microscopy - energy dispersive X-ray spectroscopy as sodium aluminosilicates, sodium diuranate, and sodium strontium phosphate hydrate (nastrophite) crystals. The natrophosphate crystals in the scanning electron microscopy analysis showed a variety of erosive and dissolution features from perfectly shaped octahedral to well-rounded appearance. Two samples were from water-washed Composites A and B, with no change in mineralogy compared to the as-received samples. This is not surprising, since the water wash had only a short period of water contact with the material as opposed to the water dissolution tests. The last two samples were residual solids from the water dissolution tests. These tests included multiple additions of water at 15 C and 45 C. The samples were sieved to separate a coarser fraction of > 710 {mu}m and a finer fraction of < 710 {mu}m. These two fractions were analyzed separately. The coarser fraction contained mostly gibbsite with minor amounts of sodium aluminosilicates (cancrinite) and bismuth aluminum-rich phases. The finer fraction was mostly composed of gibbsite, the sodium alumino silicate phase, cancrinite, and a poorly crystalline to non-crystalline phase containing varying amounts of iron, bismuth, aluminum, and phosphorus.

Processing of biomorphic Si 3N 4 ceramics by CVI-R technique with SiCl 4/H 2/N 2 system

Physical and geotechnical properties of clay phyllites

The reactions of zinc oxide with α-Fe2O3 and with γ-Fe2O3 leading to the formation of zinc ferrite (ZnFe2O4) have been studied at different partial pressures of oxygen in the temperature range 500–800°C. The ferrite spinel is formed more readily when γ-Fe2O3 is used as the reactant. The DTA and X-ray diffraction results indicate that the γ-Fe2O3 phase is stabilized in presence of ZnO. The lowering of partial pressure of oxygen in the ambient atmosphere favours the formation of zinc ferrite, indicating a cyclic redox process featuring Fe3+, Fe2+ and oxygen at the phase boundaries. At very low oxygen pressures, conversion to zinc ferrite is not facilitated, apparently due to the formation of an intermediate species, Fe3−xZnxO4, which, under these conditions, is not easily converted to ZnFe2O4.