Study Of Explosives Interfacial Assembly Mechanism And Performance Based On Solvent And Heat Induced Strategy

The morphology and microstructure of explosive crystals have a great influence on their performance.Energetic crystals with different structures and morphologies can cause different macroscopic properties due to their unique physical and chemical properties.Based on the explosive-induced interface self-assembly technology to study the morphological evolution of single-component explosives and the assembly mechanism of multi-component explosives,it is hopeful to understand the crystallographic behavior and mechanism and obtain crystal morphologies which are beneficial to improve the performance of explosives.As a starting point,this thesis selected typical nitramine explosives?CL-20,HMX,RDX?as the research object of the experiment,the concrete research mixed assembly behaviors of nano-CL-20 and HMX,constructing RDX crystal hierarchical structure via dye-assisted solvent and the effect of dyes on the assembly behavior of HMX crystals was further studied at the molecular level,assembled crystals structure and physical and chemical properties were analyzed.The main contents of this paper are as follows:?1?CL-20/HMX co-crystals with a purity of more than 90%were obtained by assembling the nano CL-20 and HMX crystals in a pure water environment.The single crystal X-ray?SCXRD?powder X-ray diffraction?PXRD?and THz spectra indicated that the as-prepared samples were CL-20/HMX co-crystal.The condensed-state strength of the crystal reached223.4 MPa,its specific surface area was 0.94 m²/g.The crystal density of CL-20/HMX was1.9812 g/cm³,which was close to CL-20's 1.9838 g/cm³,and the thermal decomposition temperature of as-prepared samples appeared at 242.5 ^oC which were higher than CL-20?239.8 ^oC?.Combining the above characterization results,the assembled CL-20/HMX co-crystals with good crystal integrity,uniform morphology,uniform particle size,excellent crystal strength,few defects,high density,good thermal stability were obtained.In addition,the whole morphological evolution process and assembly mechanism of CL-20/HMX co-crystals were studied,and an assembly route of nanoparticle induction,directional agglomeration,surface interface integration,and formation of single crystals was proposed.Furthermore,the impact energy of as-prepared CL-20/HMX co-crystal was 4.5J,which was significantly higher than CL-20 crystal?3J?,and its performance was improved by 50%.This simple strategy also enables scale-up preparation of CL-20/HMX co-crystals.?2?The fractal RDX crystals?H-RDX?were obtained based on the NR dye-induced nano-RDX crystal self-assembly strategy.The molecular dynamics simulation method was used to explain theoretically that the H-RDX crystal with this specific structure can be formed under the interaction of van der Waals force?vdW?and electrostatic force?ES?.The hexapod-shaped RDX crystals with uniformly distributed dyes were?-RDX crystal form and exhibit an obvious preferred orientation.Specifically,the strongest crystal plane of H-RDX changes from?0 2 1?crystal plane to?1 0 2?crystal plane.In addition,HPLC analysis results showed that the content of NR dye in the H-RDX crystal reached 0.6 wt%.XPS analysis revealed detailed chemical and electronic relationships between NR and RDX.The formation of this complex result in a significant shift in the C-H bond from the C=N bond on the H-RDX crystal.In addition,H-RDX crystals show thermal decomposition characteristics of part nano-particles.The activation energy of H-RDX crystal was 152.1 kJ·mol^-1,which was lower than that of M-RDX crystal.Based on the decomposition characteristics,a 1-?thermal decomposition mechanism that conforms to H-RDX crystal was proposed.Furthermore,the peak explosion pressure P_max and explosion rate dP/dt of H-RDX crystals were 1.83 MPa and49.86 MPa S^-1,respectively,which were higher than those of recrystallized M-RDX(P_max=1.58 MPa,dP/dt=39.70 MPa S^-1).In addition,the impact energy of H-RDX crystals reached15 J,which was much larger than 7 J of M-RDX crystals.In general,the H-RDX composite crystals obtained by this strategy can significantly reduce the impact sensitivity while improving its energy release efficiency.?3?Based on the preparation of hierarchical RDX using dye as a template,the effect of dyes on the crystal morphology of HMX explosives were studied at the molecular level.Systematic experiments show that dye molecules and HMX explosive crystals can be assembled to form HMX crystals with different morphologies in HMX-DMF/HMX-DMSO solutions such as sheet,polyhedron,short rod,and wire-like HMX crystals.During the study,it was found that the crystal violet dye?CV?had a greater impact on HMX crystals.This section focuses on the study of CV-HMX crystals.The CV-HMX crystals exhibited sheet morphologies,and its surface area reached 21.21 m²/g.The CV-HMX crystal density was1.873 g/cm³.In addition,it was explained from the perspective of neutron diffraction that the existence of CV dyes were more likely to form stable?-HMX crystals.The thermal decomposition temperature of CV-HMX was 268.81 ^oC which was also easier to achieve rapid energy release.The BAM drop weight results show that the impact energy of the CV-HMX crystal was 12.5 J,which was much larger than the 5 J of the PW-HMX crystal.In general,the proposed self-assembly strategy of induced explosives has further enriched the strategy of energetic crystal regulation,which is of great significance for the regulation of crystal morphology.Among them,the research on the hybrid assembly of nanometer energy-containing particles has certain reference value for the evolution law and mechanism of energy-containing crystals in the crystallization process.While the explosive crystals obtained based on the dye as a soft template show interesting thermal decomposition characteristics,excellent safety properties,and high-yielding advantages,etc.,which makes the energetic crystals prepared have good application value in the formulation of high-performance PBX explosives.