Formation Of Fe3C Research Articles

Microstructure and Mechanical Properties of CK35 Steel by Using Nano Fluid (Water/TiO2) and Oil (SAE 10W40/TiO2) as Quenching Media

Four different quenching media (water, oil(SAE 10W40), Water/TiO2 nanofluid and oil(SAE 10W40/TiO2) nanofluid were used to compare the influence of quenching media on the mechanical properties and microstructure of CK35 steel. The results have proved that the microstructure for nanofluid (water base) quenching and tempering sample is the combination of tempered martensite and retained austenite with best mechanical properties and for water quenching and tempering specimen is mostly tempered martensite. While for Nanofluid (oil base) quenching and tempering specimen the microstructure is the heterogeneous mixture of ferrite and perlite with formation of Fe3C during the quenching, while for oil quenching and tempering specimen is an equi-axed arrangement of ferrite grains with grainy spheroidized spots of cementite at the ferrite grains and along the grain boundaries.

Microstructure and Mechanical Properties of CK35 Steel by Using Nano Fluid (Water/TiO2) and Oil (SAE 10W40/TiO2) as Quenching Media

Four different quenching media (water, oil(SAE 10W40), Water/TiO2 nanofluid and oil(SAE 10W40/TiO2) nanofluid were used to compare the influence of quenching media on the mechanical properties and microstructure of CK35 steel. The results have proved that the microstructure for nanofluid (water base) quenching and tempering sample is the combination of tempered martensite and retained austenite with best mechanical properties and for water quenching and tempering specimen is mostly tempered martensite. While for Nanofluid (oil base) quenching and tempering specimen the microstructure is the heterogeneous mixture of ferrite and perlite with formation of Fe3C during the quenching, while for oil quenching and tempering specimen is an equi-axed arrangement of ferrite grains with grainy spheroidized spots of cementite at the ferrite grains and along the grain boundaries.

The influence of the formation of Fe3C on graphitization in a carbon-rich iron-amorphous carbon mixture processed by Spark Plasma Sintering and annealing

Abstract A promising fabrication method of bulk porous graphitic materials is based on consolidation of metal-amorphous carbon powder mixtures, in which the metal serves as both a graphitization catalyst and a removable space holder. In this work, iron was evaluated for this purpose. The phase formation and evolution in a carbon-rich iron-amorphous carbon mixture during Spark Plasma Sintering (SPS) and subsequent annealing was studied to reveal the peculiarities of the low-temperature catalytic graphitization process determined by the transformations of the iron catalyst. Mixtures of carbon black with iron of the Fe-20 wt%C composition were ball milled, Spark Plasma Sintered at 600–900 °C for 5 min and further annealed at 800 °C for 2 h. During the SPS, iron carbide Fe 3 C formed, while the free carbon remained poorly graphitized. In the compact sintered at 900 °C, Fe 3 C was the only iron-containing phase and metallic iron was not detected. For conducting structural studies of the free carbon by X-ray diffraction and Raman spectroscopy, iron was dissolved from the sintered compacts in HCl solution. It was found that during annealing, the graphitization degree increased only in the compacts that still contained free (metallic) iron. These results suggest that Fe 3 C does not catalyze graphitization in a carbon-rich mixture of iron and carbon black making the presence of residual (metallic) iron crucial for the advancement of catalytic graphitization during annealing.

Effect of the extent of pre-reduction of γ-Fe2O3 by H2 on the synthesis of Fe3C powder from CH4

The present study aims to investigate effect of the extent of pre-reduction of γ-Fe2O3 (maghemite) on the synthesis of Fe3C (cementite). Initially, pre-reduced powders with oxygen contents of 12.36, 3.26 and 0.59wt.% were obtained at 800K in H2 atmosphere for 2.5, 5 and 10min, respectively. Carburization behaviors of these pre-reduced powders were then explored using undiluted CH4 at 800K. Mass change measurements, XRD and SEM analyses were used to characterize the samples. It was found that single Fe3C phase was obtained from the pre-reduced powders containing 3.26 and 0.59wt.% oxygen for carburization periods of 15 and 30min. The kinetic data for the carburization under pure CH4 indicates that there are essentially two successive distinct regimes: reduction of the remaining oxides and Fe3C formation. When the pre-reduced powder with oxygen contents of 3.26 and 0.59wt.% are used, CH4 pyrolysis rate suffices for the reduction of the remaining oxides and carburization. The pre-reduced powder with the highest oxygen (12.36wt.% oxygen) did not yield Fe3C, but iron and iron oxides, because the extent of the reduction by CH4 is found to be too small for such high oxygen content. It was postulated that the reduction product H2O vapor hinders the formation of Fe3C. The carburization process was discussed in terms of reaction pathways using equilibrium thermodynamic analysis and reaction kinetics.

Pomegranate-Structured Conversion-Reaction Cathode with a Built-in Li Source for High-Energy Li-Ion Batteries.

Transition metal fluorides (such as FeF3 or CoF2) promise significantly higher theoretical capacities (>571 mAh g(-1)) than the cathode materials currently used in Li-ion batteries. However, their practical application faces major challenges that include poor electrochemical reversibility induced by the repeated bond-breaking and formation and the accompanied volume changes and the difficulty of building an internal Li source within the material so that a full Li-ion cell could be assembled at a discharged state without inducing further technical risk and cost issues. In this work, we effectively addressed these challenges by designing and synthesizing, via an aerosol-spray pyrolysis technique, a pomegranate-structured nanocomposite FeM/LiF/C (M = Co, Ni), in which 2-3 nm carbon-coated FeM nanoparticles (∼10 nm in diameter) and LiF nanoparticles (∼20 nm) are uniformly embedded in a porous carbon sphere matrix (100-1000 nm). This uniquely architectured nanocomposite was made possible by the extremely short pyrolysis time (∼1 s) and carbon coating in a high-temperature furnace, which prevented the overgrowth of FeM and LiF in the primordial droplet that serves as the carbon source. The presence of Ni or Co in FeM/LiF/C effectively suppresses the formation of Fe3C and further reduces the metallic particle size. The pomegranate architecture ensures the intimate contact among FeM, LiF, and C, thus significantly enhancing the conversion-reaction kinetics, while the nanopores inside the pomegranate-like carbon matrix, left by solvent evaporation during the pyrolysis, effectively accommodate the volume change of FeM/LiF during charge/discharge. Thus, the FeM/LiF/C nanocomposite shows a high specific capacity of >300 mAh g(-1) for more than 100 charge/discharge cycles, which is one of the best performances among all of the prelithiated metal fluoride cathodes ever reported. The pomegranate-structured FeM/LiF/C with its built-in Li source provides an inspiration to the practical application of conversion-reaction-type chemistries as next-generation cathode materials for high-energy density Li-ion batteries.

Performance of CeO2-Modified Iron-Based Oxygen Carrier in the Chemical Looping Hydrogen Generation Process

The iron-based oxygen carrier with high oxygen transfer capacity has always been the key point in the chemical looping hydrogen generation (CLHG) process. In this study, CeO2-modified iron-based oxygen carriers with the porous reticular structure were prepared by the sol–gel method. Samples were tested in a thermogravimetric analyzer (TGA) and lab-scale fixed-bed reactor, respectively, to evaluate their capacities of hydrogen production and the resistance to carbon deposition or Fe3C formation. The effects of preparation conditions (CeO2 loading and [C6H8O7·H2O]/[PEG400] molar ratio) and experimental conditions (reducing atmosphere and temperature) on the physicochemical properties of CeO2-modified iron-based oxygen carriers were investigated. The initial screening test in TGA was done to select the samples with excellent reducibility and strong resistance to carbon deposition or Fe3C formation. Subsequent tests in the fixed-bed reactor were conducted to evaluate the redox characteristics and cyclic perfo...

Carbon deposition on iron surfaces in CO–CO2 atmosphere

Thermodynamic calculations and thermogravimetric (TG) analysis were performed in order to understand the mechanism of carbon deposition on the surfaces of iron particles during the reduction of iron ore in a CO–CO2 atmosphere. The results of the thermodynamic equilibrium phase analysis indicate that the phases of the carbon deposition process can be predicted on the basis of the carbon potential, reaction temperature and gas pressure. The optimal thermodynamic conditions for carburisation are a low temperature (T < Tm) and a high carbon potential (αc>1). TG analysis is performed in a gas mixture of 65 vol.-% CO and 35 vol.-% CO2 at 650, 706 and 750°C. Cementite (Fe3C) is generated as an intermediate product, which acts as a catalyst for carbon deposition. Carbon deposition is inhibited at high temperatures (T>791°C) owing to the high stability of Fe3C. When the reaction temperature is higher than the thermodynamic limit for the formation of Fe3C, carbon deposition cannot occur. A mechanism for carbon deposition is proposed based on the experimental results.

A new magnetic nano zero-valent iron encapsulated in carbon spheres for oxidative degradation of phenol

In this study, magnetic carbon encapsulated nano iron hybrids (nano Fe0/Fe3C@CS) were synthesized via a novel one-pot hydrothermal method followed by self-reduction in N2 atmosphere. The structural, morphological, and physicochemical properties of the samples were thoroughly investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), N2 sorption isotherms and thermogravimetric analysis–differential scanning calorimetry (TGA–DSC). Catalytic performance of the as-synthesized nanoparticles was tested in activation of oxone® for phenol degradation in aqueous solutions. Superior catalytic performance was observed by complete removal of 20ppm phenol within 10min. The formation of Fe3C was found to contribute to a better stability and magnetic separation of Fe0/Fe3C@CS in its repeated uses. Both electron paramagnetic resonance (EPR) and classic quenching tests were carried out to investigate the mechanism of radical generation and evolution in phenol oxidation. Different from Co- and Mn-based catalysts in generation of sulfate radicals, Fe0/Fe3C@CS selectively induced hydroxyl radicals for phenol degradation.

In situ time resolved wide angle X-ray diffraction study of nanotube carpet growth: Nature of catalyst particles and progressive nanotube alignment

Catalytic chemical vapor deposition is the most promising process to obtain vertically aligned carbon nanotube (VACNT) carpets. Live analysis of growing VACNT is crucial to reveal their nucleation and growth mechanisms. We present novel time resolved in situ X-ray diffraction (XRD) analysis on growing macroscopic VACNT carpets enabling us to get statistical information on catalytic phase together with nanotube progressive alignment. A specific synthesis set-up has been developed to perform such in situ synchrotron XRD experiments. Nucleation kinetics of the different phases are evidenced: first, orthorhombic Fe3C crystalline phase is formed, followed by the formation of CNTs and finally of γ-Fe, demonstrating that Fe3C particles are the nucleation seeds for CNT growth. The additional formation of Fe3C or γ-Fe nanowires inside CNTs is associated with capillary forces and mobility of them at 850°C. Experiments also reveal the progressive formation and alignment of VACNT carpets during the continuous precursor injection. Quantification of the alignment degree allows one to get a better understanding of the effect of precursor injection rate and CNT length on VACNT alignment. The overall results are key issues for the scaling-up of VACNT synthesis and their applications towards commercialization.

Use of heavy fraction of bio-oil as fuel for hydrogen production in iron-based chemical looping process

Chemical looping hydrogen (CLH) process with renewable energy sources as fuel shows the potential of producing pure hydrogen with inherent capture of CO2 in a low-cost and sustainable way. The heavy fraction (HF) of bio-oil, derived from the fast pyrolysis of biomass and characterized as an energy carrier with difficulty in upgrading itself to bio-fuel or chemicals, was used in this study to generate H2. Four low-cost iron-based oxygen carriers including an ilmenite and three iron ores were initially evaluated with respect to their reducibility and the ability to minimize carbon or iron carbide (Fe3C) formation in a thermogravimetric analyzer (TGA). The reactivity and cyclic performance of the selected best candidate was then assessed in a laboratory scale fixed-bed reactor with HF bio-oil as fuel. The screening test in TGA showed that ilmenite was superior over the three iron ores in terms of promoting CO conversion and minimizing carbon or Fe3C formation. Ilmenite could maintain its increasing reducibility with the increase of surrounding CO concentration, in contrast with the iron ores that were deactivated seriously by the formed carbon or Fe3C. Subsequent CLH test with ilmenite and HF bio-oil showed that the reducibility and H2 production capacity of ilmenite were strongly dependent on the operating temperature. The steam oxidation step at 950 °C yielded H2 concentration and hydrogen yield exceeding all of those observed at the other investigated temperatures because of the deepest reduction degree of ilmenite at 950 °C. The decrease in the reducibility and H2 production capacity of ilmenite in the cyclic test could be ascribed to the poorer physical structure of ilmenite with cycles.

Synthesis of high-quality double-walled carbon nanotubes using porous MgO nanowire supported iron oxide as catalyst

Fe2O3/MgO catalyst was prepared by a simple conventional impregnation method, porous MgO nanowire as catalyst support. After calcination at 950°C for 3h, MgFe2O4/MgO solid solution was formed, which presents high efficiency for the synthesis of high-quality double-walled carbon nanotubes (DWCNTs) through the thermal chemical vapor deposition (CVD) of methane at 900°C. The obtained DWCNTs were characterized by high-resolution transmission electron microscopy, thermal gravimetric analysis and Raman spectroscopy. The carbon yield was 29.2wt%. The growth of the DWCNTs was attributed to the base-growth model. The formation of Fe3C during the CVD process plays key roles in the DWCNTs growth.

A Carbon/Iron–Cerium/Alumina Catalyst as Potential Substitution for Noble Metal Three-way Catalyst for Auto Emission Control

Abstract Alumina-supported Fe and Ce catalysts with carburization treatment were prepared to investigate their performance for auto emission control. The carburization treatment in flowing CO at 525 °C significantly promoted the catalytic activity of C/Fe–Ce, even comparable to a noble metal catalyst 1.0 wt % Pt/CeO2. The XRD result suggests that the formation of Fe3C is a possible interpretation for the promoted activity by the carburization treatment. The T50 contour lines of NOx and CO were used to quickly optimize catalyst composition, and C/18Fe–18Ce–64Alumina was considered to be the optimization result.

Characterization of Precipitated Carbon by XPS and Its Prevention Mechanism of Sticking during Reduction of Fe2O3 Particles in the Fluidized Bed

The Fe2O3 particles with the diameter between 74 and 150 mu m were pre-reduced with CO at 923 K to precipitate the carbon on the surface. Then the particles were reduced by CO at 1 173 K in the fluidized bed for examining the efficiency of the precipitated carbon for preventing the sticking. The result showed that the sticking of particles with high metallization ratio could be retarded or prevented by the precipitated carbon. For clarifying the prevention mechanism of the sticking, the carbon in different states was characterized by X-ray Photoelectron Spectroscopy (XPS) and its effects on sticking were discussed. The carbon on the surface was divided into two states, the graphitic carbon and the carbon in Fe3C. On account of the sticking of Fe3C at approximately 1 054 K and the sticking of the sponge iron at the micron scale, the structural change of the precipitated iron by the carburization and the formation of Fe3C only retard the sticking. Therefore, the prevention of the sticking at 1 173 K was attributed to the graphitic carbon. Due to the formation of metallic iron layer avoiding the consumption of the carbon and the formation of Fe3C restraining the dissolution of the graphitic carbon, the graphitic carbon accumulated on the surface of the particles, resulted in n(c)/n(Fe) above 1.0, so that Fe3C and the metallic iron was coated by the graphitic carbon to block their contact among the particles.

Thermodynamic Study of Cementite Formation in Fe–C–O–H System

In general, due to the failure in the formation of Wustite (FeO) in reduction process at temperatures less than 617°C, Magnetite (Fe3O4) can be reduced and carburized at one stage and be directly changed into Cementite (Fe3C). In this study, the effect of temperature, pressure, and chemical combination on the formation of Fe3C from iron oxides is investigated thermodynamically by plotting triple-diagrams (C–H–O). In fact, the thermodynamic calculations were performed for the formation of Fe3C from iron oxides under an atmosphere containing CH4, CO2, CO, H2O, and H2; pressures ranging from 0.1 to 10 atm; and especially within a temperature ranging from 300 to 617°C. Finally, the results obtained from the thermodynamic calculations in this area showed that the conditions for the formation of Fe3C from Fe3O4 at one stage were facilitated by enriching the atmosphere with carbon monoxide and conversely were weakened by its enrichment with methane. Also, the most suitable conditions for the formation were determined to be a temperature ranging from 427 to 617°C at pressures ranging from 1 to 3 atm.

The Phase of Iron Catalyst Nanoparticles during Carbon Nanotube Growth

We study the Fe-catalyzed chemical vapor deposition of carbon nanotubes by complementary in situ grazing-incidence X-ray diffraction, in situ X-ray reflectivity, and environmental transmission electron microscopy. We find that typical oxide supported Fe catalyst films form widely varying mixtures of bcc and fcc phased Fe nanoparticles upon reduction, which we ascribe to variations in minor commonly present carbon contamination levels. Depending on the as-formed phase composition, different growth modes occur upon hydrocarbon exposure: For γ-rich Fe nanoparticle distributions, metallic Fe is the active catalyst phase, implying that carbide formation is not a prerequisite for nanotube growth. For α-rich catalyst mixtures, Fe3C formation more readily occurs and constitutes part of the nanotube growth process. We propose that this behavior can be rationalized in terms of kinetically accessible pathways, which we discuss in the context of the bulk iron–carbon phase diagram with the inclusion of phase equilibrium lines for metastable Fe3C. Our results indicate that kinetic effects dominate the complex catalyst phase evolution during realistic CNT growth recipes.

Fe3O4 Anchored onto Helical Carbon Nanofibers as High‐Performance Anode in Lithium‐Ion Batteries

Lithium-ion batteries (LIBs) have been receiving increasing attention as attractive power sources, motivated especially by the rapid development of electric vehicles and portable devices. 2] As anode materials for LIBs, transition metal oxides utilize all of a metal’s redox potentials by the formation of metal through a chemical conversion mechanism, resulting in high theoretical capacities (500–1000 mAhg ) compared to commercially used graphite based on an intercalation mechanism (372 mAhg ). Among the oxides, Fe3O4 has gained considerable attention due to its low cost, abundance in nature, the fact that it is environmentally benign, and its high theoretical capacity of 926 mAhg 1 through the reaction Fe3O4+8Li + + 8e $3Fe+4Li2O. However, the application of Fe3O4 is hampered by a large volume expansion and structural rearrangements upon electrochemical cycling (problems that are common for conversion materials). To circumvent these problems, several hybrid nanostructures have been designed by mixing Fe3O4 with carbon. [4–6] Carbon plays a dual role in the electrodes: it can increase the electronic conductivity ; furthermore, it can work as a structural buffering material to accommodate the strain caused by the large volume change during the charge–discharge process. Various carbon materials, such as carbon nanotubes, carbon fibers, graphene, and others, have been successfully utilized to host Fe3O4 nanoparticles. Several approaches, such as hydrothermal, co-precipitation, as well as template syntheses, have been developed. Most strategies involve time-consuming procedures, usually requiring a separate step to, for example, deposit the carbon onto the surface of the presynthesized iron oxide or to fill or disperse iron oxide nanoparticles into pores or onto the carbon’s surface. Multistep processes or the use of several reagents might be required. It is thus desirable to develop a facile synthetic route to generate such functional composite materials. The present work describes a simple solvent-free process to obtain Fe3O4–C nanocomposites. In these composites Fe3O4 nanoparticles are anchored onto self-developed helical carbon fibers. Ferrocene, as a single precursor, acts as both iron and carbon source. As illustrated in Scheme 1, the synthesis is accomplished by a pyrolysis–oxidation route: pyrolysis of ferrocene in a closed stainless-steel reactor produces a fine black powder, referred to as “Fe–C” composite, consisting of two iron-rich phases: Fe and Fe3C; then, further mild oxidization of Fe–C under CO2, yields the final oxide product, referred to as “Fe3O4–C”. It is known that Fe and Fe3C can catalyze the formation of helical carbon. In the present procedure, Fe and Fe3C formed during pyrolysis of ferrocene and act as catalysts for the growth of helical carbon. Upon oxidation, both Fe and Fe3C are fully converted into Fe3O4, while the carbon morphology remains helical. Fe or Fe3C and later their transformation product (Fe3O4) are firmly embedded in the helical carbon structure. The thus-obtained Fe3O4–C composite shows a high reversible capacity, and good cycling and rate capability. Synergistic effects, through combining the redox reaction of metal oxide and carbon nanofibers, are discussed. X-ray diffraction (XRD) patterns of the material before and after oxidation (Figure 1a) show that upon pyrolysis of ferrocene, two distinct iron-rich phases of Fe3C (Joint Committee on Powder Diffraction Standards (JCPDS) card number 0350772) and a-Fe (JCPDS 006-0696) form in the Fe–C composite. The formation of Fe3C was due to the partial dissolution of carbon atoms into Fe. Upon further oxidation of the Fe–C composite, both Fe and Fe3C were oxidized to Fe3O4 (JCPDS 019-0629). In the Fe3O4–C composite, the narrow and sharp peaks suggest that the obtained Fe3O4 is of a highly crystalline nature. The mean crystallite size of Fe3O4 was calculated as 44 nm, according to the Scherrer equation. A strong peak due to graphitic carbon (2q=26.58) was observed in both Fe–C and Fe3O4–C composites. That the carbon morphology was well-maintained was confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). N2 isotherms of the Fe3O4–C composite showed type IV curves with an H3 hysteresis loop (Figure 1b), indicating a mesoporous structure. The sample had a high Brunauer–Emmett– Teller (BET) surface area of 126 mg . The pore-size distribution (inset of Figure 1b) indicated the coexistence of both micropores (0.026 cmg ) and mesopores (0.08 cmg ). The relatively large specific surface area and high porosity offer a large material/electrolyte contact area and promote the diffusion of Li ions. Scheme 1. Fabrication of Fe–C and Fe3O4–C composites.

EEL-spectroscopy analysis for a metallic film covering on an as-grown diamond single crystal from Fe–Ni–C system

The variation of sp3 fractions from carbon K-edge and the 3d-state occupancy on Fe–L2–3 edges in different layers of Fe-based metallic film covering on an as-grown diamond single crystal in diamond synthesis have been investigated by electron energy loss spectroscopy (EELS). It shows that from the diamond/film interface to the inner, the sp3 fractions decrease from 87.33% to 78.15%, the 3d-state occupancy for Fe increase from 4.54 to 5.64 electrons/atom. Moreover, by X-ray diffraction (XRD), only γ-Fe, Fe3C and (Fe,Ni)23C6 are found on the interface, which suggests that these carbon atoms with changed electronic configuration come from Fe3C. Based on the valence bonding theory, formation of Fe3C should make 3d occupancy increase, inconsistent with experimental observations. It can be concluded that, the 3d unpaired electrons of γ-Fe affect carbon atoms in Fe3C lattice and make them transform into sp3-like state. These sp3-like carbon atoms are separated from Fe3C and stack on the growing diamond crystal, eventually resulting in the reduction of 3d-state occupancy of Fe on the interface.

Carbon-Supported Fe–Nx Catalysts Synthesized by Pyrolysis of the Fe(II)–2,3,5,6-Tetra(2-pyridyl)pyrazine Complex: Structure, Electrochemical Properties, and Oxygen Reduction Reaction Activity

Carbon-supported Fe–Nx/C catalysts were synthesized at several pyrolysis temperatures such as 600, 700, 800, and 900 °C in the effort to investigate the temperature effect on the catalyst structures. The Fe contents in the synthesized catalysts were found to be about 1 wt % more than that in the Fe–TPPZ/C precursor complex (5 wt %), indicating that both the carbon support and complex ligand might be decomposed during the pyrolysis. X-ray diffraction (XRD) analysis revealed that the samples at 600–800 °C had no iron species segregation, while that formed at 900 °C showed the formation of Fe3C and Fe3O4, confirmed by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and energy dispersive X-ray analysis (EDX) measurements. TEM images clearly showed that the large sizes of Fe3C and Fe3O4 species with a diameter of about 500 nm were wrapped up by a thin carbon layer. For Fe states, X-ray photoelectron spectroscopy (XPS) data revealed that Fe3+ was the dominant Fe species in the Fe–Nx/C sample. Several nitrogen-containing species such as pyridinic N, the Fe–N(pyr) bond, quaternary N,N-oxides, as well as graphitic nitrogen were identified by XPS in the catalyst samples. Electrochemical characterization revealed a reversible Fe(III)–Nx/Fe(II)–Nx redox wave at 0.63 V vs RHE, which is believed to be the active sites for the oxygen reduction reaction (ORR). The density of this active site was found to be dependent on the pyrolysis temperature, and high densities were obtained in the temperature range of 700–800 °C. In addition, the morphology of the catalyst samples was also analyzed using the change of double-layer charge with the potential scan rate. Furthermore, the Fe–Nx/C catalysts were found to have strong catalytic activity toward oxygen reduction reaction with an overall electron transfer number of 3.6.

Properties of magnesium based composite materials exhibiting ferromagnetism fabricated by spark plasma sintering

In order to possess magnetic properties in the Mg-based composite materials, pure magnesium and Ni–Cu–Zn ferrite (FR) powders were mechanically alloyed (MAed) using a vibrational ball mill, and the produced composite powders were consolidated into the bulk materials by spark plasma sintering (SPS) . Solid-state reaction, hardness, microstructure and magnetic properties of the bulk materials were characterised by X-ray diffraction, Vickers hardness, optical microscopy and vibrating sample magnetometer, respectively. Solid-state reactions between Mg and FR in the bulk materials occurred to form α-Fe and MgO at a sintering temperature of 673 K. In contrast, the formation of Fe3C occurred at 773 K and 873 K. The Vickers hardness of the bulk materials fabricated from MAed 8 h powder at 773 K showed the highest value of 198 HV. This is due to an increase of composite phases formed the intermetallic compounds, such as MgO, α-Fe and Fe3C as increasing MA time. The magnetic property (magnetization) of the bulk materials fabricated at 673 K exhibited the highest value of 1.0×10−5 Wbm/kg due to the formation of α-Fe. The magnetic property (magnetization) of the bulk materials decreased due to the formation of Fe3C as increasing sintering temperature. Ferromagnetism of the Mg-based composite materials was enhanced by the formation of the α-Fe and Fe3C.

Effect of Fe3C on Carburization and Smelting Behavior of Reduced Iron in Blast Furnace

Suppression of CO2 discharged from iron- and steel- making companies is an example of the biggest issues for the protection of global environment and sustainable growth of steelmaking industry. One of the efforts made to decrease the emission of CO2 in ironmaking process is blowing of hydrogen gas into blast furnace. Hydrogen gas can reduce iron oxide and form harmless H2O. Cementite (Fe3C) may be formed by introduction of hydrogen into blast furnace and play an important role on carburization and smelting behavior of reduced iron. The conditions that Fe3C was formed were experimentally determined by changing CO–CO2–H2 gas composition in the present work. As the result, it was found that there is a possibility of Fe3C formation by hydrogen gas introduction into blast furnace. Therefore, the effect of Fe3C on smelting behavior of reduced iron was also observed, and it was confirmed that the presence of Fe3C will have positive effect on enhancing carburization and smelting of reduced iron.