CARBON-ENCAPSULATED Fe3C NANOPARTICLES FORMED DURING CVD ON AISI 1095 HIGH-CARBON STEEL

Fe-based substrates are increasingly recognized as active growth media for carbon nanostructures, but the phase state of Fe during growth is often difficult to establish because Fe-bearing domains may remain embedded within a carbon-rich product. Mössbauer spectroscopy is particularly valuable in such systems because it can resolve Fe-specific local environments even when XRD contrast is weak or surface-sensitive methods detect only carbon [1,2]. In this study, carbon nanostructures were synthesized on AISI 1095 high-carbon steel using a two-zone water-assisted chemical vapor deposition process at 800 C, conceptually following upstream oxygen–hydrogen preheating strategies for in situ water generation [3]. A time-evolution (TEV) series was prepared in the range from 25 s to 120 min. The 90 min growth process was selected for detailed material characterization and examined for substratereusability. The 57Fe transmission Mössbauer spectrum of the TEV-90min sample shows an Fecarbide-type environment. Complementary XRD identified carbon structures as the dominant phase with a minor Fe3C contribution, HR-TEM revealed iron carbide embedded in a carbonaceous matrix, and XPS detected no Fe-related photoelectron signal at the outermost surface. These results support a model in which water-assisted CVD on AISI 1095 produces a graphitic carbon layer containing buried Fe3C-like domains that are encapsulated by carbon.