## 3 Results and Discussion
By contrast, tin-containing composites exhibited a large fraction of the crumble-like particles of a coarse texture with plenty of white precipitiants and numerous cavities and darker regions with sizes of several microns marked by red circles in Figure 3b (more SEM images for deeper insight are presented in Figures S2 and S3 in Supplementary Materials). The EDX elemental maps (Figure 3c-e) show two distinctive regions: the zones composed mainly of carbon, which can be assigned to the graphite flakes, and the remaining part containing silicon, oxygen, carbon, and tin, which corresponds to the ceramic part. One may notice that the tin nanoparticles are accumulated exclusively in the ceramic part, where a low signal coming from carbon is observed. This result suggests that the free carbon phase from the ceramic part is preferably consumed during the carbothermal reduction process, which is also reflected in the Raman spectra analysis. Such behaviour may be explained by a better mixing of the tin source with the preceramic precursor than with graphite (liquid-liquid in contrast to liquid-solid mixing) as well as a very high activation energy for the carbothermal reduction of tin with graphite [45; 46]. This assumption is further supported by the unique morphology of the ceramic region with the cavities and pores coming from the release of CO\({}_{2}\) during the carbothermal reduction. Pure SiOC ceramic is a dense material (specific surface area (SSA) of 3.18 m\({}^{2}\) g\({}^{-1}\)), whereas the SiOC/Sn-40% composite exhibits SSA of 118.1 m\({}^{2}\) g\({}^{-1}\) (results of BET analysis are shown in Table S3 and Figure S4 in Supplementary Materials). In the case of the composite materials, the SSA of ternary composites is smaller than that of the binary composite because of the lower ceramic content, which here is partially replaced by graphite. Moreover, comparing the SSA of the composites with the same amount of ceramic and graphite but different tin contents, one may observe higher SSA for SiOC:C\({}_{0,2}\)/Sn-40% (106.9 m\({}^{2}\) g\({}^{-1}\)) than for SiOC:C\({}_{0,2}\)/Sn-60% (55.1 m\({}^{2}\) g\({}^{-1}\)). This may result from the more intensive carbothermal reduction process in the ceramic phase, in which the release of CO\({}_{2}\) creates and enlarges porosity, and then the enlarged pores may collapse, leading to the decreased SSA. Furthermore, the SiOC:C\({}_{0,1}\)/Sn-60% composite exhibits a higher SSA (94.6 m\({}^{2}\) g\({}^{-1}\)) than SiOC:C\({}_{0,2}\)/Sn-60% because of the higher ceramic content and thus a less intensive CO\({}_{2}\) release during the carbothermal reduction. These results further support the hypothesis that graphite does not take part in the carbothermal reduction process. Figure 2: Diffractograms of SiOC and ternary composite materials. A deeper insight into the microstructure of the ternary composites was provided by transmission electron microscopy. TEM images of the binary SiOC/Sn-40% and the ternary SiOC-C\({}_{0.2}\)/Sn-60% composite are shown in Figure 4a,b, respectively. The microstructure of SiOC/Sn-40% consists of tin nanoparticles, represented by black dots, immersed in a featureless amorphous structure of SiOC [47,48]. In comparison, the SiOC-C\({}_{0.2}\)/Sn-60% composite reveals additional parallel smudges typical for graphite [49], which interpenetrate the ceramic component. In both samples, tin nanoparticles are uniformly distributed within the ceramic part. The average size of tin nanoparticles seems to depend on the amount of the ceramic part in the composite, as presented in Figure S5 in the Supplementary Materials. Figure 5a presents the HAADF image of the ternary SiOC-C\({}_{0.2}\)/Sn-60% composite with clearly separated ceramic and graphitic phases. This image confirms that the tin nanoparticles accumulate mainly in the ceramic part (Figure 5b), while in the graphitic phase, there are only a few randomly distributed tin nanoparticles (Figure 5c).