On the Mössbauer study of cementite

Ron, M.; Shechter, H.; Hirsch, A.A.; Niedzwiedz, S.

doi:10.1016/0031-9163(66)90962-0

Cited by 31 publications

(7 citation statements)

References 3 publications

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“…Other peaks are evident, corresponding to about 15% of the total sample, with an isomer shift 8 = 0.19 mm/s and Hint = 20.8 T, which are characteristic of cementite, Fe3C [17,18].…”

Section: Resultsmentioning

confidence: 99%

The surface chemistry of chloroform as an extreme-pressure lubricant additive at high concentrations

et al. 1995

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Carbon tetrachloride is an extremely good extreme-pressure (EP) lubricant additive at low concentrations (< 3 wt% chlorine) since it can react to form a high-melting-point Fe3C antiseizure layer. In contrast, small hydrogen-containing additive molecules (CH2C12, CHC13) decompose to form FeC12 which melts at ,,~940 K and limits the maximum seizure load to N 3500 N as measured in a pin and v-block apparatus. However, both thermodynamic calculations and results of a Mfssbauer analysis of an iron foil heated in CHCI3 at 830 K indicate that iron carbide can be formed from chloroform. In addition, it is also found in that case that a plot of seizure load versus concentration, after initially forming a plateau, once again increases with higher additive concentrations (> 4 wt% chlorine) in accord with the idea that a higher melting point carbide film can be formed. It has been shown previously that asymptotes in the plot of removal rate versus applied load correspond to melting of the interracial anti-seizure film. When using 9.0 wt% chlorine from chloroform as the additive, a drastic increase in removal rate is found at an interfacial temperature of-~ 940 K corresponding to the melting of FeC12 and an additional asymptote is evident at ,-~ 1500 K due to the melting of Fe3C in accord with the thermodynamic and M6ssbauer results.

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“…Other peaks are evident, corresponding to about 15% of the total sample, with an isomer shift 8 = 0.19 mm/s and Hint = 20.8 T, which are characteristic of cementite, Fe3C [17,18].…”

Section: Resultsmentioning

confidence: 99%

The surface chemistry of chloroform as an extreme-pressure lubricant additive at high concentrations

et al. 1995

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“…The experimentally assigned, averaged hyperfine fields for cementite θ-Fe 3 C can be obtained from studies by Bi et al and Kniep et al and have values of 20.8 � 0.3 T and 20.0 � 0.3 T. [157,158] However, as the values are very close to each other, commonly only one average hyperfine field value of 20.8 � 0.5 T is used for the MAS fitting of θ-Fe 3 C. [59,132,159,160] Neither Bi et al nor Kniep et al report the MAS-based relative spectral contribution areas for the θ-Fe 3 C assigned hyperfine fields. Thus, how the crystallographically expected 2 : 1 non-equivalent Fe site ratio is assigned to the hyperfine fields, is unclear for the time being for the θ-Fe 3 C phase.…”

Section: Fe Carbide Hyperfine Fieldsmentioning

confidence: 99%

Carbon Pathways, Sodium‐Sulphur Promotion and Identification of Iron Carbides in Iron‐based Fischer‐Tropsch Synthesis

Paalanen

Weckhuysen

2020

ChemCatChem

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Fisher‐Tropsch Synthesis (FTS) is industrially used for converting a carbon‐containing feedstock, such as coal, natural gas, biomass, and municipal waste, via the production of synthesis gas (a mixture of CO+H2) into hydrocarbons. This review article focuses on Fe‐based FTS catalysis, thereby focusing on the process conditions available for steering the various carbon pathways from input CO and their associated reactions. We will also discuss the effects of alkali‐sulphur chemical promotion and the identification of the FTS reaction active Fe carbides, which are assigned with precise crystal structures and nomenclature. Each observed Fe carbide crystal structure is further assigned with corresponding Mössbauer Absorption Spectroscopy (MAS) hyperfine fields. The expected formation temperatures and experimental conditions for the identified Fe carbides encountered in FTS research, namely ϵ‐Fe3C, η‐Fe2C, χ‐Fe5C2, θ‐Fe3C and θ‐Fe7C3, are reviewed.

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“…The measured average isomer shift and hyperfine fields (together with those of each component) are very close to each other in both samples and typical of Fe 3+ cations (Table 1), thus confirming previous results obtained at 300 K. These results are very important because they show that Fe-C like links cannot be formed but only oxygen-mediated bonds are produced. Indeed, surface iron Fe atoms involved in carbide like Fe-C bonds should exhibit a closer to zero isomer shift (typically, d = 0.019 mm/s in Fe3C bulk cementite carbide at room temperature (Ron et al 1966) with an iron atom oxidation state close to that of metal (Ron et al 1966 ;Fang, van Huis, et Zandbergen 2009). Besides, surface iron Fe 2+ or Fe 3+ ions involved in Fe-C hydrocarbon bonds like in alkyl, alkynyl, carbine, vinylidene or allenylidene complexes must exhibit an isomer shift significantly smaller than that in Fe-O oxide bonds.…”

Section: )mentioning

confidence: 99%

Grafting of diazonium salts on oxides surface: formation of aryl-O bonds on iron oxide nanoparticles

et al. 2015

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On the Mössbauer study of cementite

Cited by 31 publications

References 3 publications

The surface chemistry of chloroform as an extreme-pressure lubricant additive at high concentrations

The surface chemistry of chloroform as an extreme-pressure lubricant additive at high concentrations

Carbon Pathways, Sodium‐Sulphur Promotion and Identification of Iron Carbides in Iron‐based Fischer‐Tropsch Synthesis

Grafting of diazonium salts on oxides surface: formation of aryl-O bonds on iron oxide nanoparticles

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