Stability, Magnetism and Hardness of Iron Carbides from First-Principles Calculations

Electrodeposition of Iron with Co-deposition of Carbon: On the Nature of Nanocrystalline Fe-C Coatings

“…Both ε-Fe2C and η-Fe2C carbides are associated with excellent mechanical properties [31][32][33][34], but also the nanocrystallinity of ferrite grains and the detected additional elements of H and O, comprising the peculiar nature of electrodeposited coatings, contribute to the high hardness.…”

First-principles calculations of elastic constants for epsilon-carbide and the consequences

“…First-principles calculations within the framework of density functional theory were conducted using the [13] Note: The two rows represent different calculation parameters [13]. Vienna ab-initio simulation package [16,17].…”

“…The structure assumed in [12] incorrectly has carbon and iron atoms in the same plane. The hexagonal Fe 2 C structure of [13] has a lattice parameter a = 0.3636 nm, which does not match with the known parameters of ε-carbide. The calculations 1 2 , those Fe atoms coloured white are at heights 0 and 1; the smaller carbon atoms that are hatched and cross-hatched are at heights 3 4 and 1 4 , respectively.…”

“…(a) Space group P6 3 22 with one set of octahedral interstices (2d) occupied by carbon and some further carbon (not illustrated) in the 2b sites which would be 25% occupied to make the overall structure consistent with the formula F 2.4 C. (b) The carbon atoms (not illustrated) are now randomly distributed in any of the three kinds of octahedral interstices, so that the overall symmetry becomes P6 3 /mmc. relating to the hexagonal Fe 3 C structure [13], with lattice parameters a = 0.463 nm and c = 0.430 nm may be representative of the elastic properties of ε-carbide (Table 1), but further work is needed to express these as a function of the iron to carbon ratio.…”

Fabrication of iron carbide by plasma-enhanced atomic layer deposition

“…On the other hand, the later transition metals such as Fe, Co, and Ni form weak metal-carbon bonds, demonstrating more complex structures. In the Fe-C system, the carbon can be found in and form various iron carbide phases, including Fe 5 C 2 , Fe 2 C, Fe 7 C 3 , Fe 3 C, and Fe 23 C 6 [11]. For these weak carbide formers, the formation enthalpy is less negative or even positive, so these compounds are thermodynamically unstable.…”