## 3 Results and Discussion
### MicroCT of Nanocomosities  
To study the microstructure of nanocomposites using X-ray tomography, the samples were fixed on object tables made of a polymer transparent for X-ray radiation. The scanning parameters were selected in accordance with the density and geometric dimensions of the nanocomposites. The rotation step was 0.1\({}^{\circ}\) when the sample was rotated 360\({}^{\circ}\) around its axis. This corresponded to \(\sim\)4000 shadow projections and a spatial resolution of up to 10 \(\upmu\)m. Figure 4 shows shadow projections and 3D views of nanocomposites from different types of nanotubes and with different concentrations. The analysis of projections and 3D views shows that nanocomposites take an even shape in the process of layer-by-layer formation. The middle part of all samples is lower in level than the peripheral region of the nanocomposites. This is due to the Gaussian shape of the laser beam with a maximum radiation intensity in the central region. To visualize the internal structure of the nanocomposites, visual sections were made with a step of 100 \(\upmu\)m along the vertical axis of the sample. The main sections of the nanocomposite at distances of 0.5, 1.3 and 1.7 mm from the bottom point of the sample are shown in Figure 4. Each section is accompanied by three views--front view, top view and side view. When analyzing the images of sections of the SWCNT1-based nanocomposite with a concentration of 0.001 wt.%, it was determined that the average pore size was \(\sim\)48 \(\upmu\)m (Figure 4a). Almost the entire sample volume was homogeneous with a uniform pore distribution. Several single pores were observed with size of \(\sim\)80 \(\upmu\)m. With an increase in the concentration of SWCNT1 to 0.01 wt.% in dispersion to obtain a nanocomposite, a significant increase in pores with a size of 100-200 \(\upmu\)m was obtained. In this case, the average pore size was \(\sim\)86 \(\upmu\)m (Figure 4b). In the case of using carbon nanotubes with a large diameter and length (SWCNT2) with a concentration of 0.001 wt.% as a filler of the nanocomposite, a significant porosity with a large pore size--200-280 \(\upmu\)m was obtained (Figure 4c). In this case, the average pore size was \(\sim\) 101 \(\upmu\)m. An increase in the concentration of SWCNT2 to 0.01 wt.% in nanocomposite contributed to an increase in the number of pores; however, their diameter decreased to 150-200 \(\upmu\)m (Figure 4d). At the same time, the number of large pores increased and the average pore size increased to \(\sim\)73 \(\upmu\)m. A decrease in the structure density and an increase in the number of pores were observed at the edges of all samples of nanocomposites. Most likely, a more uniform central part with fine pores was obtained due to the nonuniform front of the distribution of thermal heating by the Gaussian profile of laser radiation. The quantitative parameters of the internal nanocomposites microstructure are shown in Table 1. The table shows the results of the quantitative analysis for nanocomposites, which was performed for three-dimensional models of each of the samples. Samples's preparation using SWCNT2 with concentrations of 0.001 and 0.01 wt.% was accompanied by a large number of pores and their sizes. Most likely, this depended on the large size of SWCNT2, as well as their bundles, into which nanotubes in a protein dispersion were stuck together due to van der Waals forces. The SWCNT2 consisted mostly of bundles versus SWCNT1. For composites based on both types of SWCNT, it was found that an increase in the concentration of nanotubes entails an increase in the total pore volume by 17 and 9%, respectively for SWCNT1 and SWCNT2. In this case, the fraction of open pores from the entire sample volume for nanocomposites with two concentrations of SWCNT1 exceeded this value for samples with SWCNT2. This is probably due to the orientation of SWCNT1, which protruded beyond the boundaries of the nanocomposite. Since nanotubes of the first type were in an isolated form, it is easier to control them by laser radiation.