Characterization of phases formed in the iron carbide process by X-ray diffraction, mossbauer, X-ray photoelectron spectroscopy, and raman spectroscopy analyses

Soot aerosol, which is a major pollutant in the atmosphere of urban areas, often contains not only carbonaceous matter but also inorganic material. These species, for example, iron compounds, originated from impurities in fuel or lubricating oil, additives or engine wear may change the physico-chemical characteristics of soot and hence its environmental impact. We studied the change of composition, structure, and oxidation reactivity of laboratory-produced soot aerosol with varying iron content. Soot types of various iron contents were generated in a propane/air diffusion flame by adjusting the doping amount of iron pentacarbonyl Fe(CO) 5 to the flame. Scanning electron microscopy (SEM)/energy-dispersive Xray spectroscopy (EDX) was combined with cluster analysis (CA) to separate individual particles into definable groups of similar chemical composition representing the particle types in dependence of the iron content in soot. Raman microspectroscopy (RM) and infrared spectroscopy were applied for the characterization of the graphitic soot structure, hydrocarbons, and iron species. For the analysis of soot reactivity, temperature-programmed oxidation

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“…Unfortunately, Fe 3 C, which is the carbide we most probably expect, is Raman inactive (Park et al 2001). …”

Section: Composition and Structure Analysismentioning

confidence: 99%

Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition, Structure, and Thermo-Chemical Properties

Bladt

Schmid

Kireeva

et al. 2012

Aerosol Science and Technology

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“…The mass fraction of the iron-containing phases was determined by quantitative XRD. A number of samples were also analysed using Mössbauer spectroscopy to validate XRD data as described in work 19) . Results of XRD and Mössbauer analyses were in a good agreement.…”

Section: Cementite Formation In Reduction Of Titanomag-mentioning

confidence: 99%

Formation of Cementite from Titanomagnetite Ore

2006

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This paper examines the formation of cementite in reduction of titanomagnetite ore by methane-containing gas. The reduction of titanomagnetite ore (New Zealand ironsand) by hydrogen-methane-argon gas mixtures was investigated from 600 to 1 100°C. Iron oxides were reduced by hydrogen to metallic iron, which was carburised by methane to form cementite. The reduction rate increased with increasing hydrogen content in the reducing gas, while the methane content had no effect on the reduction process. Preoxidation of the titanomagnetite accelerated its reduction. Reduced iron in titanomagnetite was converted to cementite more slowly than in hematite.KEY WORDS: titanomagnetite; cementite; direct reduced iron; reduction; carburisation. ExperimentalThe composition of the titanomagnetite ore (New Zealand ironsand) studied in this paper is given in Table 1. The reduction behaviour of the Mt Whaleback hematite ore was examined for a comparison. Its composition is also given in Table 1. The ore was sized, with only the 150 to 255 mm fraction being used in this study. The titanomagnetite ore was pre-oxidised in a muffle furnace at 1 000°C under air for 4 d.Reduction and cementation of iron ores by CH 4 -H 2 -Ar gas mixtures was studied using a lab-scale fixed bed reactor in a vertical tube electric furnace. The experimental set-up has been described elsewhere.18) The gas flow rate was maintained at 1 L · min Ϫ1, which was sufficient to neglect the external mass transfer resistance in the gas phase.A nominally 1 g sample of iron ore was lowered into the hot zone of the furnace under argon. When the sample reached the experimental temperature a reducing/carburising gas of varying composition was passed through the reactor. A summary of the experimental conditions is presented in Table 2.The sample was quenched after the experiment under argon.The specific surface area of samples was measured by a single-point BET method.The degree of reduction was defined as a fraction of oxygen removed in the reduction of iron oxides on the basis of the on-line mass-spectrometric analysis of off-gas composition.Cementite formation was analysed using quantitative XRD analysis, which was conducted using a copper Ka source. The scans were done at a rate of 1°/min with a step size of 0.2°2q. The morphology of samples was examined by both optical microscopy and SEM. Etching of the optical microscopy samples in a basic sodium picrate solution allowed differentiation between cementite and metallic iron. Results Reduction of Titanomagnetite Ore at DifferentTemperatures and Gas Compositions The effect of temperature on titanomagnetite reduction was studied in the temperature range 600 to 1 100°C using gas containing 25 vol% H 2 , 5 vol% CH 4 and 70 vol% Ar. The change in the degree of reduction with time at different temperatures is shown in Fig. 1.Increasing the temperature from 600 to 1 000°C increased the rate of reduction, which is expected as the reduction rate constant increases with temperature. Further increasing the temperature from 1 000 to ...

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“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Despite of these many studies, the details of the reaction mechanism of Fe3C formation and its physical properties have not yet been established well. The reason for the lack in knowledge mainly comes from the metastability of the carbide causing experimental difficulties.…”

Section: Introductionmentioning

confidence: 99%

Cementite Formation from Magnetite under High Pressure Conditions

2013

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Measurements have been made of the rate of Fe3C formation from Fe3O4 powder and Fe3O4 single crystals at 773 K and 1 023 K under the high pressure of 0.5 and 1.0 MPa by using thermo-gravimetric method. Along with the kinetic study of Fe3C formation, high resolution TEM observation around the interface between Fe3O4 matrix and the formed Fe3C have been carried out to confirm the thermodynamically possible direct Fe3C formation from Fe3O4 without the formation of intermediate metallic Fe. Analysis of the rate results suggests that the reaction mechanism of Fe3C formation was possibly described by the sequential reactions of the conversion of Fe3O4 to Fe3C via intermediate metallic Fe although the metallic Fe existence was not confirmed by TEM observation. This inconsistency was explained by considering the relative reaction rates of Fe3C formation from Fe and Fe formation from Fe3O4. It was also found that not only the carbon activity of more than unity but also the low oxygen potential enough for metallic Fe existence might be required for the Fe3C formation.

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Characterization of phases formed in the iron carbide process by X-ray diffraction, mossbauer, X-ray photoelectron spectroscopy, and raman spectroscopy analyses

Cited by 105 publications

References 17 publications

Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition, Structure, and Thermo-Chemical Properties

Impact of Fe Content in Laboratory-Produced Soot Aerosol on its Composition, Structure, and Thermo-Chemical Properties

Formation of Cementite from Titanomagnetite Ore

Cementite Formation from Magnetite under High Pressure Conditions

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