Enhanced Decomposition of Ammonium Perchlorate-Ethyl Cellulose-Molybdenum Disulfide Nanocomposites

Ammonium perchlorate (AP) is commonly used in propulsiontechnology.Recent studies have demonstrated that two-dimensional (2D) nanomaterialssuch as graphene (Gr) and hexagonal boron nitride (hBN) dispersedwith nitrocellulose (NC) can conformally coat the surface of AP particlesand enhance the reactivity of AP. In this work, the effectivenessof ethyl cellulose (EC) as an alternative to NC was studied. Usinga similar encapsulation procedure as in recent work, Gr and hBN dispersedwith EC were used to synthesize the composite materials Gr-EC-APand hBN-EC-AP. Additionally, EC was used because thepolymer can be used to disperse other 2D nanomaterials, specificallymolybdenum disulfide (MoS2), which has semiconducting properties.While Gr and hBN dispersed in EC had a minimal effect on the reactivityof AP, MoS2 dispersed in EC significantly enhanced thedecomposition behavior of AP compared to the control and other 2Dnanomaterials, as evidenced by a pronounced low-temperature decompositionevent (LTD) centered at 300 degrees C and then complete high-temperaturedecomposition (HTD) below 400 degrees C. Moreover, thermogravimetricanalysis (TGA) showed a 5% mass loss temperature (T (d5%)) of 291 degrees C for the MoS2-coated AP,which was 17 degrees C lower than the AP control. The kinetic parametersfor the three encapsulated AP samples were calculated using the Kissingerequation and confirmed a lower activation energy pathway for the MoS2 (86 kJ/mol) composite compared to pure AP (137 kJ/mol). Thisunique behavior of MoS2 is likely due to enhanced oxidation-reductionof AP during the initial stages of the reaction via a transition metal-catalyzedpathway. Density functional theory (DFT) calculations showed thatthe interactions between AP and MoS2 were stronger thanAP on the Gr or hBN surfaces. Overall, this study complements previouswork on NC-wrapped AP composites and demonstrates the unique rolesof the disperagent and 2D nanomaterial in tuning the thermal decompositionof AP.