## 3 Results
### CMC Microstructure  
Figure 2 shows the basic structure of the carboxymethyl used for the experiment, easily observing the characteristics of plant fibers because the substance was collected as waste from a paper factory that used cane as the raw material.  
The preliminary results on the CMC microstructure and on the cooling environments based on water combined with CMC are presented in Figures 3 and 4, respectively. The experiments were performed under a vacuum and the film that remained after evaporation was analyzed. The aspect of the medium before cooling was homogeneous (Figure 3), presenting particles with the same size. The structure had a compact appearance with well-defined bonds, particles and even bubbles forming continuous and coherent film-like films. After 50 cycles, the material presented the effects of the thermal influence (Figure 4) such as cracks or fissures and the modification of particular elements of the material. Discontinuities, a lack of coherence in the structure and foreign particles, such as metal oxides, were easily observed.  
Figure 2: Carboxymethylcellulose with diverse fibrous structure not dissolved in water: **(a)** 2000\(\times\); **(b)** 6000\(\times\).  
In similar experimental conditions, energy-dispersive X-ray (EDX) experiments were performed on the cooling dry medium before and after 50 cooling cycles. Table 2 presents the results of the energy-dispersive X-ray analysis for the environment with 2.5% CMC.  
The difference between the used and unused media from a chemical point of view was firstly given by the loss of water from the medium through vaporization, which decreased the oxygen content and increased the content of Na and Cl (probably through the formation of a NaCl compound). A decrease to half of the nitrogen element was also observed after 50 cycles and was ascribed to the partial degradation of the Na-carboxymethyl cellulose.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Chemical Elements** & \multicolumn{2}{c}{**Cooling Medium (CMC)**} & \multicolumn{2}{c}{**Used Cooling Medium (CMC 50)**} \\ \hline Oxygen & 80.40 & 89.54 & 49.32 & 55.14 \\ \hline Sodium & 15.53 & 11.63 & 35.39 & 27.54 \\ \hline Chlorine & 3.45 & 1.67 & 5.17 & 2.61 \\ \hline Nitrogen & 0.85 & 0.24 & 0.41 & 0.16 \\ \hline Carbon & 1.23 & 1.84 & 9.82 & 14.62 \\ \hline Iron & 0.62 & 0.19 & 0.31 & 0.1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Chemical composition of the carboxymethyl cellulose solution in water after CMC drying and CMC 50 medium.  
Figure 4: Carboxymethyl cellulose 2.5% dissolved in water and cyclically heated 50 times from 800 \({}^{\circ}\)C after drying at various scales of magnification: (**a**) area with obvious discontinuity, 1000\(\times\); (**b**) uneven film structure, 65\(\times\); (**c**) inconsistent structure, 400\(\times\).  
Figure 3: Carboxymethylcellulose 2.5% dissolved in water after drying at various size scales: (**a**) compact zone, 1000\(\times\); (**b**) uniform film structure, 50\(\times\); (**c**) coherent structure, 650\(\times\).  
In the used environment, we observed the appearance of the carbon chemical element in a bigger proportion, with 9.817 wt% comparative to the initial liquid that appeared from the carbonization of the polymer under the thermal effect.