## 4 Discussion  
The method of coating ammonium nitrate with various types of nitrocellulose, presented in the literature and investigated in this work, raises questions in terms of efficacy and the final product. Issues with the complete dissolution of nitrocellulose in acetone were already observed at the solution preparation stage. These issues were particularly pronounced in the case of materials obtained by in situ synthesis of nitric acid (potassium nitrate/sulphuric acid route). This may be caused by the presence of residual cellulose sulphate, as SEM-EDS analyses revealed that in all cases of the samples prepared using KNO\({}_{3}\), sulphur appeared as small precipitates on the sample surface, indicating the co-precipitation of cellulose sulphate. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **Impact [J]** & **Friction [N]** \\ \hline NC & 15 & 252 \\ NC-KNO\({}_{3}\) & 30 & 288 \\ MNC & 20 & 120 \\ MNC-KNO\({}_{3}\) & 25 & 252 \\ ANNC & 25 & 252 \\ ANNC-KNO\({}_{3}\) & 30 & 252 \\ ANMNNC & 30 & 216 \\ ANMNCE-KNO\({}_{3}\) & 35 & 288 \\ ANNC-D & 35 & 288 \\ ANNC-KNO\({}_{3}\)-D & 40 & 324 \\ ANMNC-D & 30 & 252 \\ ANMNCE-KNO\({}_{3}\)-D & 40 & 288 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Impact and sensitivity parameters of the tested samples. [PERSON] and blue row colours respectively denote the use of NC and MNC; lighter colours are used for cellulose nitrates produced using the HNO\({}_{3}\)-based esterifying mixture, darker ones are for the KNO\({}_{3}\)-based mixture. Another issue of the proposed coating process is tied to its resource consumption, i.e., the need to use high volumes of solvents (on average, 150 to 200 mL of acetone and 200 to 300 mL of hexane were used for 0.5 g of nitrocellulose). While not critical, reducing the use of solvents or using them in a closed loop needs to be considered before any industrial scale implementations could be feasible. The final product of the process, which should be NC-coated AN, is not reliably obtained. In turn, our investigations (SEM, Raman spectroscopy) have shown that the degree of coating is limited: no core-shell structure is produced and, in some cases, AN appears to be deposited onto NC rather than the opposite. Raman spectroscopy confirmed the presence of NC on the surface of AN in all samples (characteristic NC band at 1128 cm\({}^{-1}\)). Samples with microcrystalline nitrocellulose (MNC) showed narrower bands, suggesting a higher degree of structural order. SEM images demonstrated the absence of the expected core-shell structure, which was the intended goal of the process. Furthermore, the observations reveal a reverse effect: instead of uniform encapsulation of ammonium nitrate particles, uncontrolled deposition of the ammonium salt occurs on the nitrocellulose surface. This layer inversion suggests improper coating kinetics or unsuitable physicochemical conditions, leading to system destabilization. In terms of pseudo-activation energy, it is worth noting that the use of the KNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) mixture results in higher E\({}_{\text{A}}\) values than in the case of HNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\), regardless of the type of cellulose used and of the follow-up processing of the cellulose nitrate sample (e.g., addition of AN and fuel oil). In conjunction with other analyses, this indicates the presence of residual cellulose sulphate in the samples produced via the KNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) route rather than significant deviations in nitrogen content of the samples. The addition of AN resulted in a decrease in pseudo-activation energy, largely due to the shift of the oxygen balance of the system towards more positive values (NC exhibits a negative oxygen balance value, dependent on its nitrogen content) and the relatively facile decomposition of AN. Conversely, the addition of the auxiliary fuel (diesel oil) yielded an increase in pseudo-activation energy values, due to both its strongly negative oxygen balance and limited reactivity.