## 3 Results  
### Spectroscopic Investigation  
The Raman spectra of the cellulose nitrate samples (Figure 1a) show that the four types of samples have identical chemical structures. However, as expected, the signal widths from MNC are lower, confirming a better degree of ordering in MNC. An intense band characterises the Raman spectrum of cellulose nitrate at 1284 cm\({}^{-1}\), attributed to the stretching vibrations of the nitrate group. Other bands from the nitrate groups are observed at 1656 cm\({}^{-1}\)[19]. The bending vibrations of the CH and CH\({}_{2}\) groups are observed at 1371 and 1456 cm\({}^{-1}\), respectively. Bands observed between 1000 and 1215 cm\({}^{-1}\) are attributed to the structure of the cellulose acetal, i.e., the cyclic ether and glycosidic bond. The Raman spectra of AN (Figure 1b) consist of secondary Raman bands belonging to other vibrational modes, \(\
u\)2, \(\
u\)3 and \(\
u\)4, combinations of fundamental modes and lattice modes. Out-of-plane bending (\(\
u\)2) is usually not active in Raman spectroscopy; asymmetric stretching (\(\
u\)3) is typically observed in the spectral range of 1300 to 1500 cm\({}^{-1}\). The set of combination modes (\(\
u\)1 + \(\
u\)4) observed near 1600 and 1700 cm\({}^{-1}\) of the spectrum is also \begin{table}
\begin{tabular}{|c c c c c|} \hline \hline
**Sample Code** & **Cellulose Used** & **Esterification** & **Coated AN** & **ANFO** \\ \hline NC & Standard & HNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) & No & No \\ \hline NC-KNO\({}_{3}\) & Standard & **KNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\)** & No & No \\ \hline MNC & Microcrystalline & HNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) & No & No \\ \hline MNC-KNO\({}_{3}\) & Microcrystalline & **KNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\)** & No & No \\ \hline ANNC & Standard & HNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) & Yes & No \\ ANNC-KNO\({}_{3}\) & Standard & KNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) & Yes & No \\ \hline ANMNC-KNO\({}_{3}\) & Microcrystalline & **KNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\)** & Yes & No \\ \hline ANNC-D & Standard & HNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) & Yes & Yes \\ \hline ANMNC-KNO\({}_{3}\)-D & Standard & KNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) & Yes & Yes \\ \hline ANMNC-D & Microcrystalline & HNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) & Yes & Yes \\ \hline ANMNC-KNO\({}_{3}\)+D & Microcrystalline & KNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) & Yes & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Scheme for coating cellulose nitrate, coated AN and ANFO samples used in this work. Samples containing NC and MNC are shaded in green and blue, respectively. Lighter colours denote the use of the HNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) esterification mixture and darker colours denote the use of the HNO\({}_{3}\)/H\({}_{2}\)SO\({}_{4}\) esterification mixture. characteristic of AN. In the spectra (Figure 1b), only the signals originating from AN can be seen and since Raman spectroscopy is a surface technique, this confirms that AN covers NC and MNC rather than the opposite, as postulated in the literature. The IR spectra of the produced NC samples (Figure 2a) all contain signals at approx. 3440 cm\({}^{-1}\), corresponding to the stretching of the hydroxyl group (-OH). Additionally, in the 2900-3000 cm\({}^{-1}\) range, carbon-hydrogen (C-H) bond stretching signals, characteristic of tetrahedral carbon atoms, are present. The signal at 1060 cm\({}^{-1}\) originates from C-O-C bond stretching, whereas the signal at 800 cm\({}^{-1}\) arises from the vibrations of C-H bonds in glucose ring repeat units. These signals are well-described in the literature and in line with previous reports [20]. The addition of AN (Figure 2b) results in the signals originating from AN overshadowing other signals.