Combustion Performance of Nanoboron-Based Monodisperse Microfluidic Polymer Spheres Plasticized by Erythritol Tetranitrate

By using microfluidic technology and controlling the difference in flow rate between the oil and water phases, highly spherical nB/nitrocellulose (NC)/1,2,3,4-butanetetraol tetranitrate (ETN) microspheres with a size of approximately 60 µm were prepared, and their structures and elements were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), x-ray diffraction (XRD), infrared (IR), x-ray photoelectron spectroscopy (XPS), and laser microscopy. The catalytic effect of the microspheres on the thermal decomposition of ammonium perchlorate (AP)/DAP-4 was studied in detail using thermogravimetry and differential scanning calorimetry (TG–DSC) testing and burst point testing. The combustion performance of AP/perchloric acid-triethylenediamine ammonium (DAP-4) before and after the addition of nB/NC/ETN microspheres was studied using a high-speed camera, a high-sensitivity IR camera, and a combustion heat measurement instrument. In addition, this study investigated the combustion mechanism of nB/NC/ETN microspheres. After the introduction of nB/NC/ETN microspheres, the thermal decomposition peak temperature of AP/DAP-4 decreased by approximately 30°C, the thermal decomposition activation energy decreased by nearly 150 kJ/mol, and the reaction rate constant increased from 0.37 to 0.77. The results of the combustion experiments revealed that after the addition of nB/NC/ETN microspheres, the combustion of AP/DAP-4 became more intense, and the pressurization rate increased sharply from 1.11 to 6.65 MPa/s. As the burning rate increased, the maximum combustion temperature increased from 1728°C to 1902°C, and the combustion heat increased from −6989 to −13 551 kJ/kg. Moreover, the experimental results indicated that compared with microboron (μB)-based sample, the nanoboron (nB) sample has higher burning rate and combustion efficiency. Therefore, all the experiments simultaneously demonstrated that nB/NC/ETN significantly promoted the thermolysis and combustion of AP/DAP-4. Therefore, the results of this work indicated that nB/NC/ETN microspheres may have potential applications in hypersonic ramjet engines.