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In this work, Si@NC/AP and Si@PVDF/CL-20 composites with different Si contents have been fabricated by spray-drying technique. The flame structure, ignition delay time and combustion process have been investigated. It has been shown that the ignition delay of Si-based fuel with 40 wt% of Si is the shortest. This means that oxygen balance and the catalytic effect of Si on the energetic composites are playing a dominant role during the combustion processes of these composites. The solid composite propellants (SCP, named as SCP-1 and SCP-2) contains two typical Si-based composites Si-80@NC/AP and Si-80@PVDF/CL-20 have been prepared for propellant applications. Their propellants containing the corresponding mechanical mixtures (named as SCP-3 and SCP-4) have been fabricated as a comparison. It has been observed that the cross sections of propellants containing Si-based composites are denser than that of the reference propellants. The burn rate of SCP-1 (with Si-80@NC/AP) and SCP-2 (with Si-80@PVDF/CL-20) are 5.74 and 5.10 mm s−1 at 2.0 MPa, respectively, which are lower than those of the reference samples SCP-3 (6.51 mm s−1) and SCP-4 (5.70 mm s−1). However, the pressure exponent of former is slightly lower than that of the latter. Moreover, the combustion products (CCPs) of SCP-1 and SCP-3 are more fluffy and smaller in particles size than those of SCP-2 and SCP-4. This indicates that the core-shell structured composites have much better combustion performances due to better heat and mass transfer between the oxidizers and Si as fuel. [ABSTRACT FROM AUTHOR]

• ECs can enhance the combustion of Si/Ta. • Core-shell structure has some advantages compared with traditional mechanical mixing preparation method. • The reaction mechanism for ECs enhanced Si/Ta combustion was summarized. • Heat release efficiency of the composites could be well tuned by using different content and type of the ECs. This paper reports a group of new energetic materials (EMs) based on Si/Ta coated with recently developed high energetic composites (ECs), such as AP/NC and PVDF/CL-20. These Si/Ta-based nano-energetic composites have been prepared by both mechanical mixing method and an advanced technique of electrostatic self-assembly followed with a spray-drying process. The heat of reaction and combustion behavior of these novel Si/Ta@ECs composites, as well as the morphologies and compositions of their condensed combustion products (CCPs) have been comprehensively studied. It has been shown that the combustion efficiency of Si-Ta could be largely enhanced with the inclusion of two types of ECs. The maximum energy release was 18.39 kJ cm−3 of Si/Ta with the inclusion of ECs prepared by electrostatic self-assembly followed with spray-drying technique, which was 51.6% of the theoretical energy density of the pure Si/Ta and it is about 9.58 kJ cm−3 higher than the mechanically mixed one. It shows that the enhanced flame has improved luminosity and radiation due to increased energy content with higher reaction rate. The maximum flame-front propagation rate and the condensed phase reaction rate of Si/Ta with the addition of 10 wt% of ECs are 30.1 mm s−1 and 120.7 mg s−1, respectively. The maximum combustion wave temperature of Si/Ta-based composite was 2.4 times higher than that of pure Si/Ta without the ECs inclusion. The typical phase composition of the CCPs is composed of TaSi 2 , which is combined with a minor inclusion of Ta 2 O 5 , TaN 0.25 , TaC and Ta 5 Si 3. The two-step reaction mechanism includes the activation and propagation of the fast combustion wave of the ECs and the initiation of the post-burning reaction. [ABSTRACT FROM AUTHOR]

Electrically controlled solid propellant (ECSP) is one promising solution for thrust adjustment and repeated ignition of conventional solid rocket motors (SRM). However, the widely studied ECSP based on hydroxylammonium nitrate (HAN) faces the problems of strong hygroscopicity and low thermal stability, which can lead to failure of ECSP. Inspired by polyethylene oxide-polyacrylonitrile (PEO-PAN) based solid polymer electrolyte, the new PEO-PAN based ion conductive energetic composites (ECs) have been designed and evaluated in this paper. The formulation was theoretically determined based on the energy content, and the samples were prepared by a conventional milling mixing method. The morphology, ionic conductivity, thermal reactivity, decomposition gaseous products and combustion behavior of these new ECs have been comprehensively studied. It has been shown that the initial decomposition temperature of PEO-PAN based ECs is around 243 °C with heat release of 1677.8–1873.9 J·g−1 depending on the oxidizer and polymer content. Meanwhile, the dependences of the ionic conductivity on the burning rate are evaluated. The results showed that the burning rate decreases as ionic conductivity increases. One of these ECs has a high ionic conductivity with a low burning rate under pressure, which is suitable for controllable ECSP. [ABSTRACT FROM AUTHOR]

Owing to the novel insensitive high-energy-density material 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide (ICM-102) has lower sensitivity and higher energy(see in Table S1, Supporting Information), it has great advantages in the application of low-vulnerability propellants. In this paper, the evaluation of ICM-102-containing composite propellants has been carried out, where the decomposition and combustion performances of these propellants have been comprehensively investigated. It has been shown that the main exothermic decomposition peak temperature can be increased from 235 ºC to 350 ºC, when 6 to 10 wt% of ICM-102 was used to replace RDX, but heat release rate was largely increased. Moreover, the burning rate of ICM-102 containing propellants at 3 MPa is in the range of 6.97–7.75 mm• s − 1, depending on its content. The pressure exponent (0.5–3 MPa) is between 0.34–0.44. Compared with the typical propellants with RDX, the burn rate and the flame temperature of ICM-102- containing propellants are higher. In addition, the particle size distributions of condensed combustion products of ICM-102 propellants are narrower and smaller than that of RDX-based one. It also shows that extra products such as aluminum carbide (Al20C) and aluminum oxide nitride (Al5O6N) were produced once ICM-102 was used. [ABSTRACT FROM AUTHOR]