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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Fe5C2 by Materials Project

Fe5C2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are ten inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted bent 150 degrees geometry to two C atoms. There is one shorter (1.97 Å) and one longer (2.00 Å) Fe–C bond length. In the second Fe site, Fe is bonded in a distorted bent 150 degrees geometry to two C atoms. There is one shorter (1.96 Å) and one longer (2.00 Å) Fe–C bond length. In the third Fe site, Fe is bonded in a bent 150 degrees geometry to two C atoms. There is one shorter (1.96 Å) and one longer (2.00 Å) Fe–C bond length. In the fourth Fe site, Fe is bonded in a bent 150 degrees geometry to two C atoms. There is one shorter (1.97 Å) and one longer (2.01 Å) Fe–C bond length. In the fifth Fe site, Fe is bonded in a 2-coordinate geometry to three C atoms. There are a spread of Fe–C bond distances ranging from 1.95–2.22 Å. In the sixth Fe site, Fe is bonded in a 2-coordinate geometry to three C atoms. There are a spread of Fe–C bond distances ranging from 1.94–2.23 Å. In the seventh Fe site, Fe is bonded in a 2-coordinate geometry to three C atoms. There are a spread of Fe–C bond distances ranging from 1.94–2.26 Å. In the eighth Fe site, Fe is bonded in a 2-coordinate geometry to three C atoms. There are a spread of Fe–C bond distances ranging from 1.94–2.27 Å. In the ninth Fe site, Fe is bonded to four C atoms to form distorted edge-sharing FeC4 tetrahedra. There are three shorter (2.02 Å) and one longer (2.03 Å) Fe–C bond lengths. In the tenth Fe site, Fe is bonded to four C atoms to form distorted edge-sharing FeC4 tetrahedra. There are three shorter (2.02 Å) and one longer (2.03 Å) Fe–C bond lengths. There are four inequivalent C sites. In the first C site, C is bonded in a 7-coordinate geometry to seven Fe atoms. In the second C site, C is bonded in a 7-coordinate geometry to seven Fe atoms. In the third C site, C is bonded in a 7-coordinate geometry to seven Fe atoms. In the fourth C site, C is bonded in a 7-coordinate geometry to seven Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe5C2 by Materials Project

Fe5C2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are ten inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted bent 150 degrees geometry to two C atoms. There is one shorter (1.97 Å) and one longer (2.01 Å) Fe–C bond length. In the second Fe site, Fe is bonded in a 2-coordinate geometry to three C atoms. There are two shorter (1.96 Å) and one longer (2.25 Å) Fe–C bond lengths. In the third Fe site, Fe is bonded in a 2-coordinate geometry to three C atoms. There are a spread of Fe–C bond distances ranging from 1.95–2.29 Å. In the fourth Fe site, Fe is bonded in a bent 150 degrees geometry to two C atoms. There is one shorter (1.97 Å) and one longer (2.01 Å) Fe–C bond length. In the fifth Fe site, Fe is bonded in a bent 150 degrees geometry to two C atoms. There is one shorter (1.97 Å) and one longer (2.01 Å) Fe–C bond length. In the sixth Fe site, Fe is bonded to four C atoms to form distorted edge-sharing FeC4 tetrahedra. There are a spread of Fe–C bond distances ranging from 2.01–2.03 Å. In the seventh Fe site, Fe is bonded in a bent 150 degrees geometry to two C atoms. There is one shorter (1.97 Å) and one longer (2.01 Å) Fe–C bond length. In the eighth Fe site, Fe is bonded in a 2-coordinate geometry to three C atoms. There are a spread of Fe–C bond distances ranging from 1.95–2.25 Å. In the ninth Fe site, Fe is bonded in a 2-coordinate geometry to three C atoms. There are a spread of Fe–C bond distances ranging from 1.95–2.22 Å. In the tenth Fe site, Fe is bonded to four C atoms to form distorted edge-sharing FeC4 tetrahedra. There are a spread of Fe–C bond distances ranging from 2.01–2.05 Å. There are four inequivalent C sites. In the first C site, C is bonded in a 7-coordinate geometry to seven Fe atoms. In the second C site, C is bonded in a 7-coordinate geometry to seven Fe atoms. In the third C site, C is bonded in a 7-coordinate geometry to seven Fe atoms. In the fourth C site, C is bonded in a 6-coordinate geometry to seven Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Efficient conversion of syngas to linear α-olefins by phase-pure χ-Fe5C2

Abstract Oil has long been the dominant feedstock for producing fuels and chemicals, but coal, natural gas and biomass are increasingly explored alternatives 1–3 . Their conversion first generates syngas, a mixture of CO and H 2 , which is then processed further using Fischer–Tropsch (FT) chemistry. However, although commercial FT technology for fuel production is established, using it to access valuable chemicals remains challenging. A case in point is linear α-olefins (LAOs), which are important chemical intermediates obtained by ethylene oligomerization at present 4–8 . The commercial high-temperature FT process and the FT-to-olefin process under development at present both convert syngas directly to LAOs, but also generate much CO 2 waste that leads to a low carbon utilization efficiency 9–14 . The efficiency is further compromised by substantially fewer of the converted carbon atoms ending up as valuable C 5 –C 10 LAOs than are found in the C 2 –C 4 olefins that dominate the product mixtures 9–14 . Here we show that the use of the original phase-pure χ-iron carbide can minimize these syngas conversion problems: tailored and optimized for the process of FT to LAOs, this catalyst exhibits an activity at 290 °C that is 1–2 orders higher than dedicated FT-to-olefin catalysts can achieve above 320 °C (refs. 12–15 ), is stable for 200 h, and produces desired C 2 –C 10 LAOs and unwanted CO 2 with carbon-based selectivities of 51% and 9% under industrially relevant conditions. This higher catalytic performance, persisting over a wide temperature range (250–320 °C), demonstrates the potential of the system for developing a practically relevant technology.

Science & Technology - Other Topics↗
DOE OSTI2026

Enhanced coercivity in Fe5C2/SiO2 core/shell nanocrystals

Rod-shaped Fe5C2 and core/shell Fe5C2/SiO2 nanocrystals were synthesized via a solution-based chemical method. Structural analysis confirmed the monoclinic phase of Fe5C2 with space group C2/c. Zero-field-cooling (ZFC) and field-cooling (FC) magnetization curves revealed distinct magnetic behaviors: uncoated Fe5C2 exhibited a low-temperature FC plateau indicative of strong dipolar interactions, while Fe5C2/SiO2 showed a monotonic increase in FC magnetization, suggesting reduced dipolar interactions due to SiO2 surface passivation. Isothermal remanent magnetization (IRM) and DC demagnetization (DCD) measurements supported this trend, with δM plots confirming weaker dipolar interactions in the coated sample. Bloch’s law fitting of temperature-dependent saturation magnetization showed a smaller Bloch’s constant for pure Fe5C2 and a larger value for Fe5C2/SiO2, reflecting enhanced surface disorder and reduced exchange coupling in the latter. Notably, Fe5C2/SiO2 demonstrated increased coercivity, attributed to decreased dipolar interaction and elevated surface anisotropy. Kneller’s law fitting yielded higher blocking temperatures for Fe5C2 (476 K) than Fe5C2/SiO2 (456 K), highlighting the impact of dipolar interactions on magnetic relaxation. These findings illustrate how SiO2 coatings effectively modulate dipolar interactions and enhance coercivity in Fe5C2 nanocrystals.

Joshi, Pramanand [Department of Physics, Universit↗