## 2 Results and Discussion
This mass loss indicated the quantity of free carbon within the CF ceramics, with values of 23.52%, 35.24%, 38.93%, and 44.25%, and can be attributed to the torsion of the segments between FeAC and PMHS, which disrupted the regular crosslinking structure that PMHS and DVB should have had, thereby causing branching of the cross-linked polymer. This resulted in a reduction in the precursor's crosslinking density and the consequent reduction in the yield of the ceramic [36]. Specifically, for CF-25, due to the lower DVB content, there was minimal steric hindrance, and considering the flexibility of the PMHS molecular chains,  
Figure 2: Structural characterization of the CF series samples: (**a**) FT-IR spectra, (**b**) TG spectra, (**c**) XRD spectra, (**d**) Raman spectra, (**e**) N\({}_{2}\) adsorption–desorption isotherm curves, (**f**) BJH pore size distribution curves. DVB in this sample was more likely to fully participate in crosslinking. However, as the DVB content increased, structural changes in the precursor affected the reaction. After some vinyl groups reacted with one Si-H bond, the remaining reaction sites were unable to connect with other Si-H bonds, thus not contributing to a tight crosslinking. To further verify the changes in carbon content in the pyrolysis products, the mass percentage of carbon in the CF series samples was measured using a carbon-sulfur analyzer. The carbon contents of CF-25, CF-50, CF-75, and CF-100 were 24.24%, 26.53%, 30.87%, and 34.60%, respectively. This result indicated that the free carbon content in CF ceramics could be controlled by introducing different amounts of vinyl and phenyl groups into PMHS. To analyze the crystallization characteristics of the ceramics obtained from the precursors, XRD tests were conducted on different CF series samples following their pyrolysis at a temperature of 1000 \({}^{\circ}\)C. As illustrated in Figure 2c, the CF series samples primarily exhibited an amorphous structure, with a wide peak at approximately 22\({}^{\circ}\), which was indicative of the SiOC glass phase. Additionally, diffraction peaks of graphite carbon were observed at 26.4\({}^{\circ}\) and 43.3\({}^{\circ}\), corresponding to the (002) and (100) planes of graphite carbon, respectively. Notably, a diffraction peak characteristic of the (110) plane of \(\alpha\)-Fe appeared at 44.6\({}^{\circ}\), and with increasing free carbon content in the CF ceramics, the peaks of graphite carbon and \(\alpha\)-Fe became more pronounced. This indicated that FeAC in the precursor was reduced to metallic Fe during pyrolysis, with the transition metal iron catalyzing the conversion of amorphous carbon into a structured carbon, thereby promoting the formation of graphite carbon [37]. To further compare and confirm whether it was Fe that promoted the graphitization of free carbon, we also prepared pure SiOC materials without adding FeAC and conducted XRD testing, the results of which are shown in Figure S1. As expected, the material exhibited only a broad peak, attributed to amorphous SiOC, and no other crystalline peaks. It is well known that the extent of graphitization of carbon affects the conductivity properties of electrode materials. Therefore, the carbon structure in the CF ceramics was characterized using Raman spectroscopy, as depicted in Figure 2d. In the case of carbon-containing materials, the characteristic Raman spectrum is typically marked by two significant bands: the D band at approximately 1335 cm\({}^{-1}\) and the G band at approximately 580 cm\({}^{-1}\). The D band is indicative of the vibrational mode associated with disordered carbon structures, whereas the G band signifies the in-plane stretching vibration of SP\({}^{2}\) hybridized carbon atoms in a more ordered arrangement [38]. Typically, the extent of carbon orderliness within a material is evaluated by examining the intensity ratio of the D peak to the G peak, represented as \(\rm I_{D}/I_{G}\).