Search

Aluminum particles have the problems of difficult ignition, easy agglomeration, incomplete combustion, etc. Therefore, it is of great scientific significance and engineering value to find ways to improve the ignition and combustion performance of aluminum particles in order to promote the full release of energy of aluminum particles. In this paper, spherical nano-sized ferric oxide (nFe2O3) and ammonium perchlorate (AP), a commonly used oxidizer in propellants, were used to synergistically improve the ignition and combustion performance of aluminum particles. AP modified the aluminum particles by both mixing and coating methods, respectively. On the basis of coating AP, nFe2O3 was added in order to further enhance the ignition and combustion performance of the aluminum particles. Scanning electron microscope, laser particle size analyzer, thermal analysis system and laser ignition experiment system were used to test the physicochemical properties and ignition combustion performance of different samples. The results showed that AP and nFe2O3 could be coated relatively uniformly on the surface of aluminum particles using the recrystallization method. The thermal reaction behavior of the samples showed that coating was beneficial to the decomposition of AP compared with mixing, and the addition of nFe2O3 could further improve the decomposition efficiency of AP. Ignition and combustion experiments showed that coating AP was more conducive to improving the ignition and combustion performance of aluminum particles than mixing AP, and the addition of nFe2O3 could further significantly enhance the combustion intensity and flame propagation speed of the sample. However, the addition of nFe2O3 increased the ignition delay time of the sample, which may be related to the cold agglomeration phenomenon caused by the nanoparticles. The microscopic combustion flame morphology of different samples showed that coating AP and the introduction of nFe2O3 could significantly reduce the agglomeration phenomenon of aluminum particles. Overall, coating AP reduces the distance between the aluminum particles and the oxidizer, thus significantly improving the ignition and combustion performance of the aluminum particles. The addition of nFe2O3 can further improve the combustion performance of aluminum particles, but at the same time, it also increases the ignition delay time. Hence, the cold agglomeration problem caused by nanoparticles should be fully considered when nFe2O3 is used to improve the ignition and combustion performance of aluminum particles. [ABSTRACT FROM AUTHOR]

Incorporating outstanding flame retardancy and electromagnetic interference shielding effectiveness (EMI SE) into polymers is a pressing requirement for practical utilization. In this study, we first employed the principles of microencapsulation and electrostatic interaction-driven self-assembly to encapsulate polyethyleneimine (PEI) molecules and Ti 3 C 2 T x nanosheets on the surface of ammonium polyphosphate (APP), forming a double-layer-encapsulated structure of ammonium polyphosphate (APP@PEI@Ti 3 C 2 T x ). Subsequently, flame-retardant thermoplastic polyurethane (TPU) composites were fabricated by melting the flame-retardant agent with TPU. Afterwards, by using air-assisted thermocompression technology, we combined a reduced graphene oxide (rGO) film with flame-retardant TPU composites to fabricate hierarchical TPU/APP@PEI@Ti 3 C 2 T x /rGO composites. We systematically studied the combustion behavior, flame retardancy, and smoke-suppression performance of these composite materials, as well as the flame-retardant mechanism of the expansion system. The results indicated a significant improvement in the interface interaction between APP@PEI@Ti 3 C 2 T x and the TPU matrix. Compared to pure TPU, the TPU/10APP@PEI@1TC composite exhibited reductions of 84.1%, 43.2%, 62.4%, and 85.2% in peak heat release rate, total heat release, total smoke release, and total carbon dioxide yield, respectively. The averaged EMI SE of hierarchical TPU/5APP@PEI@1TC/rGO also reached 15.53 dB in the X-band.