## 3 Results and Discussion  
The diffraction pattern of the original sample is presented in Figure 2. The analysis of phase composition revealed that the dominant phase in the original sample is cellulose i.e., a linear polysaccharide whose molecular composition is (C\({}_{6}\)H\({}_{10}\)O\({}_{5}\))\({}_{n}\)[24]. The diffraction pattern of the sample shows a number of diffraction maxima characteristic of this phase, in particular maxima with angular position \(2\theta\approx 16.1^{\circ}\) (\(d\approx 5.5\) A), \(2\theta\approx 22.3^{\circ}\) (\(d\approx 4.0\) A), \(2\theta\approx 28.9^{\circ}\) (\(d\approx 3.1\) A), \(2\theta\approx 34.7^{\circ}\) (\(d\approx 2.6\) A). Apart from maxima related to the crystalline phase, the diffraction pattern reveals broad diffuse maxima corresponding to scattering by the regions exhibiting amorphous structure. They are located close to the scattering angles \(2\theta\approx 19.1^{\circ}\) and \(2\theta\approx 43.6^{\circ}\). Therefore, the structure of the original sample has both amorphous and crystalline features. In order to determine the crystallinity level of the cellulose, the Ruland-Wonka method was used [25]. This approach relies on a comparison of the total integral scattering intensity (with background contribution removed) to the full integral scattering intensity of the amorphous phase. A measure for comparison is the ratio \(=/\,I_{o}\), where \(I_{o}\) stands for the total integral scattering intensity with removed background contribution and \(I_{a}\) is the total integral scattering intensity for the amorphousphase. In order to remove the background scattering contribution, the DHN_ADS software was used. Figure 3 depicts the diffraction pattern of the input raw material in the form of a superposition of diffraction maxima from the crystalline and the amorphous phases. For the analytical description of the profiles, the Lorenz function was used. The presented approach allows one to determine the angular positions, half-widths and integral intensities of the maxima. From the computations, the values of the crystallinity degree were determined as =37.2%. Moreover, the size of the coherent scattering region for the crystalline component of the sample was estimated from the half-width of the most distinctive maximum of the crystalline phase (\(2\theta\approx 22.3^{\circ}\)) from the Debye-Scherer formula \(L=\lambda/(\beta\cos\Theta)\), where \(\lambda=1.5418\) A and \(\beta\) is the half-width of the maximum. From the computations, it follows that \(L\approx 4.2\ \pm\ 0.4\) nm, which indicates that the nanocrystalline structure is being developed. Figure 3: Profile analysis of the diffraction pattern of the raw material. Figure 2: X-ray diffraction pattern of the raw material. The obtained SEM images are shown in Figure 4. As it can be seen from this figure, the synthesized nanocomposites mimic the shape of particles of the initial raw material, regardless of the synthesis method. In addition, the synthesis methods used preserve the developed macro-porous structure of wheat straw. The macropores certainly have a small area (up to 2 m\({}^{2}\)/g), yet they are good transport pores for ions and small molecules, for example, in the case of using synthesized composites as adsorbents or catalysts. Figure 4: SEM images of synthesized NC together with data of EDS analysis of the basic substance: (**a**) NC1_10; (**b**) NC1_5; (**c**) NC2. In addition, the EDS analysis data presented in Figure 4 show the presence of Ni ions in the basic substance. This confirms the fact that nickel entered the structure of the synthesized nanocomposite and was not washed out upon washing of the samples before the test. In addition, in NC1_10 and NC1_5 nanocomposites, nickel content is more concentrated than in NC2. This may indicate a better insertion of nickel into the initial natural raw material compared with a pre-carbonized material.