Enhancing the Ignition and Combustion Performances of Solid Propellants Incorporating Al Particles Inside Oxidizers

Abstract

The combustion efficiency of Al plays a critical role in the combustion of high-energy aluminum-based solid propellants. For traditional formulations, the Al powders are dispersed in the binder matrix, leading to limited contact with the oxidizers and hence usually insufficient combustion and higher values of the pressure exponent. In this paper, various core–shell structural Al/oxidizer composites such as Al@HMX, Al@AP, and AP@Al have been prepared by a spray-drying technique based on which solid propellants with precise interfacial control between Al particles and oxidizers were realized. Compared to the control sample, the modified propellants have a greater heat of explosion of 5890 J g–1 (15% higher) and a reduced ignition delay time of 58 ms (65% decrease). Without changing the content of components, the burn rates of propellants can be easily modulated by tuning the interfacial contact of Al and oxidizers, where it varies in a wide range of 4.56–5.79 mm s–1 at the same pressure of 1 MPa. After introducing Al/oxidizer composites, the lowest pressure exponent of 0.19 within 1–15 MPa could be achieved by using Al@HMX and AP@Al composites. The agglomeration of Al was also inhibited by using Al/oxidizer composites, and the mechanism can be interpreted by using a classical “pocket” model. Moreover, the improved combustion efficiency of the solid propellants was verified by a noticeable reduction in the unreacted Al content.

Preparation and Decomposition of Spherical CL-20 Composites with Enhanced Laser Absorbance and Decreased Mechanical Sensitivity

“…It can be seen that Al and catalyst are uniformly distributed in composite particles and the Al particles are fully covered with CL-20. This structure, where Al particles are isolated in small cells composed of CL-20, can improve the uniformity of the composites and facilitate more effective reaction between Al particles and the gaseous products of CL-20, thereby greatly inhibiting the accumulation and aggregation of Al particles 22 and improving combustion efficiency of SCCs. For other SCCs, the distribution of each additive is similar (see it in Figure S2) to that of the composites shown in Figure 2, which means the concentration of GO-CHZ-Co has minor impact on the morphology and microstructure of the composites.…”

Preparation and Reactivity of Core–Shell Al@CL-20 Composites Embedded with Graphene-Based Complexes as Catalysts

“…In the meantime, the agglomeration of molten Al particles has been effectively inhibited. Other studies have shown that the catalyzed Al@HMX composite material enhanced the heat of reaction by 9.8% and reduced ignition delay by 55 ms compared to that of the mechanical mixture. , For Al@HMX-containing propellants, the value of n decreased to 0.19 within the pressure range of 1–15 MPa, indicating an improved ignition and combustion performance was achieved. With other oxidizers to be integrated, the Al@AP propellants precisely catalyzed with CuO have been found to greatly suppress n from 0.42 to 0.21 .…”