## 3 Results and Discussion
Figure 4 shows the thermogravimetry results of primary and post-plasma-chemical treatment materials and obtained fiber using reactive air gas environment. In this case, sample 1 corresponds to wood ash before plasma-chemical treatment, sample 2--wood ash after plasma-chemical treatment, sample 3--fly ash obtained during the processing of household waste via incineration (primary raw material), sample 4--fly ash after plasma-chemical treatment, sample 5--slag obtained from household waste incineration (primary raw material), sample 6--slag after plasma-chemical treatment, sample 7--fiber obtained from slag during the plasma-chemical process when the power was 55.5 kW, sample 8--fiber when the power was 55.6 kW and 9-74 kW. These tests were carried out at temperatures ranging from 0 to 900 \({}^{\circ}\)C. As can be seen from the measurement results, the main weight loss process of the material took place in a temperature range of about 100-900 \({}^{\circ}\)C.  
Figure 4: TG research results of primary and post-plasma–chemical treatment materials and obtained fiber. Figure 3: Temperature distribution in the plasma–chemical channel: 1—during wood ash processing; 2—during slag processing; 3—during the processing of fly ash. In this temperature range, the total mass of wood ash (sample 1) decreased the most. As we can see, in this case, the total mass has decreased from 100 to 70%. Such a mass decrease may be due to the fact that this primary material contains a high relative amount of carbon (this was also confirmed by EDS studies), which was removed in the form of volatile substances as the temperature increased. Meanwhile, the slowest material mass loss process occurred in the case of the fiber (samples 7-9). As can be seen from the TG curves, in this case, the material loss is only from 100 to 98%. This can be explained by the fact that although the fiber contains a lot of carbon, the structure of the fiber material which is formed during the plasma-chemical process is non-reactive. It is believed that a glass-like structure is formed (derived from the vitrification process), so the chemical reactions with the gas used during the TG tests almost do not occur, even when the temperature is increased. A general tendency can be observed (by analyzing the results of the TG tests), suggesting that the original material (untreated in the plasma-chemical channel) loses mass faster than the material after plasma-chemical treatment. In order to identify the predominant compounds, both the raw material and the treated material were subjected to XRD studies. The results of these studies are presented in Figure 5. In this case, sample 1 corresponds to wood ash before plasma-chemical treatment, sample 2--wood ash after plasma-chemical treatment, sample 3--fly ash obtained during the processing of household waste via incineration (primary raw material), sample 4--fly ash after plasma-chemical treatment, sample 5--slag obtained by burning household waste (primary material), sample 6--slag after plasma-chemical treatment, sample 7--fiber obtained from slag during the plasma-chemical process when the power was 55.5 kW. In this case, the analysis of XRD spectra becomes very complicated and difficult because, although only present in vanishingly small amounts, there are many very different compounds which cannot be precisely identified because the radiographs and characteristic peaks of each element overlap with each other. Therefore, it is difficult to name the exact values of the peaks in degrees and the crystallographic orientations. It can be noticed that in the case of wood ash (both when we have the base material and after plasma treatment), the predominant compounds (i.e., those with the most intense peaks) are SiO\({}_{2}\), Ca(OH)\({}_{2}\), CaSO\({}_{4}\), CaSiO\({}_{2}\), and CaO. These compounds are likely to be formed during combustion and also during plasma processing. In both of these cases, oxidation processes occur when combinations of various oxides are formed.