Solvothermal synthesis of Fe7C3 and Fe3C nanostructures with phase and morphology control

Abstract

A phase transition, from orthorhombic Fe3C to hexagonal Fe7C3, was observed using a wet synthesis mediated by hexadecyltrimethylammonium chloride (CTAC). In this study, CTAC has been shown to control carbide phase, morphology, and size of the iron carbide nanostructures. Fe7C3 hexagonal prisms were formed with an average diameter of 960 nm, the thickness of 150 nm, and Fe3C nanostructures with an approximate size of 50 nm. Magnetic studies show ferromagnetic behavior with Ms of 126 emu/g, and Hc of 170 Oe with respect to Fe7C3 and 95 emu/g and 590 Oe with respect to Fe3C. The thermal studies using high temperature x-ray diffraction show stability of Fe7C3 up to 500 °C. Upon slow cooling, the Fe7C3 phase is recovered with an intermediate oxide phase occurring around 300 °C. This study has demonstrated a simple route in synthesizing iron carbides for an in depth magnetic study and crystal phase transition study of Fe7C3 at elevated temperatures.

Iron Carbides: Control Synthesis and Catalytic Applications in COx Hydrogenation and Electrochemical HER

“…Once exposed to air, the FeC x surface is easily coated with FeO x shell . FeC x was reported to possess outstanding magnetism and high adsorption of near infrared (NIR) light due to the presence of carbon atoms. As a consequence, electromagnetic or solar energy can be efficiently converted into heat over FeC x .…”

Insight into the Fischer–Tropsch mechanism on hcp-Fe7C3 (211) by density functional theory: the roles of surface carbon and vacancies

“… 26,27 θ-Fe 3 C is always considered as the inactive phase as it mainly appears in deactivated iron-based catalysts. 28,29 Fe 7 C 3 would be present after a long run and high-temperature Fischer–Tropsch synthesis, 30,31 which has been proved to be the active phase by Brent Williams et al and Yongwang Li et al 32,33 …”

“…26,27 q-Fe 3 C is always considered as the inactive phase as it mainly appears in deactivated ironbased catalysts. 28,29 Fe 7 C 3 would be present aer a long run and high-temperature Fischer-Tropsch synthesis, 30,31 which has been proved to be the active phase by Brent Williams et al and Yongwang Li et al 32,33 A comprehensive understanding of the Fischer-Tropsch mechanism on the iron catalysts would assist the researcher to improve the catalysis performance. Since the iron catalysts are composed of different iron carbide phases, the Fischer-Tropsch mechanism on the iron catalysts is also composed of the Fischer-Tropsch mechanism on different iron carbide phases.…”

“…As mentioned before, the hcp-Fe 7 C 3 phase has been proved to be active in Fischer-Tropsch synthesis by experimental research. 32,33 In previous research, DFT calculations were applied to investigate the CO activation pathway on hcp-Fe 7 C 3 (211). 42 The results showed that CO would undergo the Hassisted dissociation pathway on the top site rather than the CO insertion dissociation pathway with the surface carbon.…”

Preparation of Iron Carbides Formed by Iron Oxalate Carburization for Fischer–Tropsch Synthesis

“…Nowadays, the iron carbide phases found associated with FTS are χ-Fe 5 C 2 [11,12], θ-Fe 3 C [13], ε-Fe 2 C [14] and Fe 7 C 3 [15], etc., among which Fe 5 C 2 and Fe 3 C are the most common. After a long period of operation under FTS reaction conditions, the Fe 7 C 3 phase was detected and only existed in the silica-supported iron catalysts [16,17].…”