## 3 Results and Discussion
In the X-ray diffraction patterns of synthesized NC samples (Figure 5), apart from diffuse peaks of the disordered carbon phase, there are a number of distinct peaks (111), (200), (220), (311), and (222) of polycrystalline nickel, the presence of which causes ferromagnetic properties of the samples. For a more detailed analysis of the disordered structure of carbon phase, Figure 6 shows the diffuse peaks of synthesized NC in the form of a superposition of two Gaussian peaks. A characteristic feature of patterns is the presence at small scattering angles (\(2\theta\approx 11^{\circ}\)) of the so-called pre-peak in the main peak, the position of which corresponds to the diffraction angles \(2\theta\approx 22.0\)-\(22.5^{\circ}\). The parameters of peaks (angular positions 20, interplanar distances \(d\), half width at half maximum FWHM, relative integrated intensity \(I/I_{\rm o}\)) are presented in Table 1.  
The occurrence of an additional peak (pre-peak) on the left side of the main peak may indicate the formation of a cluster structure of the carbon phase. The effects of this type are often observed in the diffraction patterns of amorphous metal alloys of the Al-TM-RZM system (TM--a transition element, RZM--a rare-earth element) [26; 27]. The chemically ordered clusters with a predominant interaction of Al-RZM atoms are formed in these alloys. It is possible that, in the studied materials, along with the short-range atomic order, the so-called intermediate order is observed, caused by the correlation in the arrangement of carbon atoms at distances significantly exceeding the typical interatomic distances. As seen in Table 1, the angular position of the pre-peak corresponds to the interplanar distance approximately twice as great as the corresponding value for the main peak \(d_{\rm prep. }\approx 2d_{\rm o}\). The \(d_{\rm prep}\) value can be considered as a characteristic spatial scale of the intermediate order. Thus, if the main peak occurs due  
(d\({}_{(002)}\approx 0.335\) nm), which is the evidence of a disordered structure of the samples. The correlation distance, which corresponds to the characteristic size of carbon clusters (\(L_{c}\)), can be estimated by the half-width of the additional maximum. As seen in Table 1, in a number of samples NC1\({}_{10}\)\(\rightarrow\)NC1\({}_{5}\)\(\rightarrow\)NC2, an increase in the size of clusters from 1.3 to 2.2 nm is observed, which can be explained as an increase in the degree of their atomic ordering. On the other hand, there is a decrease in the pre-peak contribution to the integrated intensity of the diffuse peak, which may be associated with a decrease in the volume fraction of cluster structural units. Figure 6: _Cont._  
The analysis of X-ray diffraction patterns indicated the presence of metallic nickel in the structure of all samples. The mechanism of metallic Ni formation is most likely the same as that of metallic Fe [28]: at high temperatures, nickel is reduced to zero valence by carbon. The parameters of the unit cells of Ni phase in different samples were calculated by the angular positions of Ni lines (Table 2). A clear tendency to an increase in the Ni cell parameter in a number of samples NC1_10\(\rightarrow\)NC1_5\(\rightarrow\) NC2 (Table 3) was observed. The calculation of average grain sizes and relative micro-deformation of Ni crystal lattice by half-widths of (111) and (222) Ni lines was performed using the Laue method. The obtained results revealed an increase in the grain size and a decrease in the relative deformation of the lattice during the transition from the sample NC1_10 to NC2. Figure 7 shows the dependence of the intensity of scattering by the samples on the wave vector modulus after the collimation correction for the height of the detector receiving slit, made on the basis of the SAXS patterns. All scattering intensity curves \(l(s)\) are presented in double logarithmic scales.