Improving ignition and combustion performance of Al@Ni in CMDB Propellants: Effect of nickel coating

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-01, Vol.456, p.141010, Article 141010
• Main Authors: Zhang, Jiankan, Zhao, Fengqi, Li, Hui, Yuan, Zhifeng, Zhang, Ming, Yang, Yanjing, Pei, Qing, Wang, Ying, Chen, Xueli, Qin, Zhao
• Format: Article
• Language: English
• Subjects: Core–shell; Energetic materials; Fuel; Nickel, aluminum; Solid propellant
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.141010

The excellent reduction in mean size of the condensed combustion products validate the potential of Al@Ni as a high efficiency fuel for HMX-CMDB propellants. Association between enhanced combustion mechanism of Al@Ni and improved performance of propellant were established. [Display omitted] •The application of Al@Ni in CMDB propellants was investigated for the first time.•The critical role of Ni in the combustion mechanism of Al@Ni was disclosed.•Ni promotes the oxidation of Al@Ni and drives its ignition on propellant burning surface.•Ni and Al get alloyed to induce vigorous melt dispersion and make the residues size smaller. Micron-sized aluminum particles tend to melt into agglomerates, leading to incomplete combustion, two-phase flow losses, and energy decrease of propellants. The higher ignition performance of core–shell Al@Ni makes it a promising candidate fuel with high combustion efficiency. However, little work has been done to study the combustion of Al@Ni in propellants. Here, we report a first attempt to investigate the combustion mechanism of core–shell Al@Ni in the double-based propellant containing high energy explosive HMX, and evaluate its potential as a fuel. Nickel in Al@Ni is determined to play a critical role during its intrinsic combustion and the combustion in propellants. In the condensed phase, the presence of Ni enhances the oxidation process by forming a porous oxide layer on the aluminum surface that promotes oxygen diffusion. Subsequently the phase transition and expansion of Ni break down this oxide layer, leading to the earlier ignition on the burning surface. Upon Al melting, the alloying of Ni and Al accelerates the volume expansion and surface tension reduction of the fuel, giving rise to vigorous melt-dispersion combustion and enhanced energy release. Enhanced thermal feedback and thermal decomposition exotherm combined to increase the burning rate of propellant. The resulting higher flame temperature allows the evaporation of small aluminum droplets into vapor to form smoke oxide productions, further reducing the size distribution of the condensed combustion products (CCPs). This study demonstrates the potential of Al@Ni as an effective fuel for double-based propellants, and provides the insight into its combustion mechanism in HMX-CMDB propellants, which is believed to be important for the development of novel aluminum-based fuels for solid propellants.