## 3 Results and Discussion
### Combustion Performances
#### 3.4.2 Combustion Performance and Velocity Test  
The combustion performance of Al/MoO\({}_{3}\)-E particles was characterized under confined and unconfined conditions, respectively. For comparison, the combustion performance of Al/MoO\({}_{3}\)-M particles were also conducted under the same conditions. The combustion results under confined and unconfined conditions are displayed in Figures 8 and 9, respectively. For all tests, the combustion sequences were relative to the ignition time; therefore, the moment of ignition was set to 0 ms. In the case of combustion under confined conditions (samples \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Weight/g** & \(P_{\text{max}}\)/MPa & \(\overline{P}_{\text{max}}\)/MPa & \(\sigma\)/MPa \\ \hline \multirow{3}{*}{Al/MoO\({}_{3}\)-M} & 0.096 & 1.23 & & \\  & 0.102 & 1.16 & 1.27 & 0.18 \\  & 0.099 & 1.41 & & \\  & 0.101 & 2.02 & & \\ Al/MoO\({}_{3}\)-E & 0.095 & 1.83 & 1.96 & 0.16 \\  & 0.097 & 2.04 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The maximum pressure for each sample. Figure 7: Typical _P_–_t_ curves of Al/MoO\({}_{3}\)-E and Al/MoO\({}_{3}\)-M (insert: comparison of the mean maximum pressure for each sample). inside the PMMA tube), the situations of the two samples were completely different from each other. For Al/MoO\({}_{3}\)-M particles, it took 12.0 ms to finish the combustion throughout the tube (Figure 8a). And compared with the original PMMA tube, the tube that went through combustion remained intact but was burned to black. On the contrary, in the case of Al/MoO\({}_{3}\)-E, the fierce combustion immediately started after ignition. It took merely 0.7 ms for the combustion of Al/MoO\({}_{3}\)-E particles to be completed throughout the tube (Figure 8b). At that time, the shooting area was suddenly filled with bright light. After the fade of the combustion light, it could be identified that the tube burst into pieces and the ruler next to the tube also fell down. Moreover, there were sparks in the surrounding area from 10.6 ms to 12.0 ms, which indicated the burst reaction of Al/MoO\({}_{3}\)-E. The inserted photo in Figure 8b displays the tube pieces shattered by the fierce combustion. It could be concluded from the combustion phenomena that the combustion rate of electrospray Al/MoO\({}_{3}\)-E was much higher than that of the mechanically mixed counterpart. With such a high combustion rate, a large amount of released heat accumulated in a very short time, which led to the burst of the PMMA tube. In comparison, the combustion of Al/MoO\({}_{3}\)-M was much gentler, indicating a slower reaction rate. The addition of NC not only bonded Al and MoO\({}_{3}\) particles together, but also provided a heat and mass transfer path for the system. Figure 8: Combustion performance of **(a)** Al/MoO\({}_{3}\)-M and **(b)** Al/MoO\({}_{3}\)-E under confined conditions (**(a,b)**) are the comparison of the tube conditions before and after the combustion of Al/MoO\({}_{3}\)-M and Al/MoO\({}_{3}\)-E, respectively). To avoid the fierce burst phenomenon, the combustion velocities of the samples were measured in open air. For each test, 0.2 g of the sample was loosely placed on the surface of the sample. The results of the experiments were obtained using the same method as in the previous section. Figure 9: Combustion history of (**a**) Al/MoO\({}_{3}\)-M and (**c**) Al/MoO\({}_{3}\)-E in an open environment, and their corresponding travel distance vs. time relations: (**b**) Al/MoO\({}_{3}\)-M; (**d**) Al/MoO\({}_{3}\)-E. (The green dot lines in (**a,c**) indicate the ends of the samples. a flat slab in the shape of 20 cm \(\times\) 5 cm \(\times\) 0.5 cm. The sample was ignited by an electric igniter. The corresponding combustion results are shown in Figure 9. Figure 9a,c are the combustion photos of the samples, and their corresponding travel history curves are shown in Figure 9b,d, respectively.