## 2 Results and Discussion
### Raman Studies on ZrO\({}_{2}\)@C, ZrC@C and (ZrC,ZrO\({}_{2}\))@C Composites  
Powder XRD analysis is inadequate when exactly determining the ratio of amorphous carbon/graphite components in the nano-(ZrO\({}_{2}\), ZrC)@C composites [40]. However, the Raman spectroscopy is suitable for following the quantitative changes in amorphous carbon, graphite and distorted graphite structures and the graphitization processes [27; 28; 29; 30; 31; 32]. Highly ordered monocrystalline graphite (ideal graphite lattice) has two first-order Raman bands, G (E\({}_{2g}\), degenerated optical mode at the center of the Brillouin zone) and G1 (2D) (harmonic in-plane transverse optical mode close to the zone boundary K point) at around 1580 cm\({}^{-1}\) and 2687 cm\({}^{-1}\), respectively [33; 34]. The disordered graphitic lattice has a band D1 (D) (A\({}_{1g}\), phonon of the in-plane longitudinal optical branch close to the zone center) and D2 (D')  
Figure 11: Images (**a**,**c**), SAED pattern identifying the presence of cubic ZrC (**b**) and HAADF image (**d**) of L-Zr-N-1000-P-H\({}_{2}\) sample, together with the elemental distribution maps for zirconium (red), oxygen (green) and carbon (blue). (E\({}_{2g}\), in-plane acoustic branch close to the K point), or graphene layer edges and surfaces, at around 1350 and 1620 cm\({}^{-1}\), respectively [37; 40; 41; 42]. The amorphous carbon D3 band (D\({}^{\prime\prime}\) or A) is at ca. 1500 cm\({}^{-1}\), whereas the D4 (D\({}^{\prime\prime}\)) band at ca. 1200 cm\({}^{-1}\) contains mixed modes, including a mode of the disordered graphite lattice (A\({}_{1g}\)), and polyenes or ionic impurities induced modes [27; 30; 40; 41]. Moreover, the Raman spectra of carbonaceous materials contain bands belonging to weak combination (D + D\({}^{\prime\prime}\)) and harmonic overtone (2D\({}^{\prime}\)) modes as well [42; 43; 44]. The Raman spectra of composites prepared from L-Zr-X samples between 1000 and 1400 \({}^{\circ}\)C for various times for X=Cl, N and S are given in Supplementary Materials, Table S6 and illustrated in Supplementary Materials, Figures S15-S17. The spectra and peak positions/intensities for plasma-treated samples are given in Figures 12 and 13 and Table 4, respectively. For the L-Zr-Cl-T-t samples, the intensity ratio of the peaks belonging to amorphous/graphitic components (D\({}^{\prime\prime}\)/(D+G)) gradually decreases with an increasing reaction temperature, suggesting an advance in graphitization. The D and G bands become sharper due to the formation of more crystalline phases. The intensities of D\({}^{\star}\) and D\({}^{\prime}\) bands decrease with increasing temperature, showing the partial decomposition of organic polyene structures and surface graphene layers, respectively. Increasing the reaction time does not have a considerable effect. The I\({}_{2D}\)/I\({}_{\rm G}\) ratio, related to the thickness or separation of the monolayer carbon sheets, slightly and irregularly changes with increasing reaction temperature and time, indicating that Zr atoms are not incorporated into the carbon network to a great extent [45]. The formation of graphite may also be attributed to the increased temperature and the catalytic effect of ZrC [46] forming above 1200 \({}^{\circ}\)C. The more ZrC is formed, the more graphite/disordered graphite was detected.