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In order to improve the thermal stability of 2,6-diamino-3,5-dinitropyridine-1-oxide (ANPyO), polydopamine was coated on the surface of ANPyO crystal by in situ polymerization, based on the principle of dopamine oxidation self-polymerization. ANPyO@PDA core-shell composite materials with different coating rates were prepared by adjusting the reaction time. The morphology, crystal structure, molecular structure, and element content of ANPyO@PDA composites were characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). The thermal decomposition performance of the ANPyO@PDA composites was also tested by thermogravimetry-differential scanning calorimetry (TG-DSC). The results show that PDA formed uniform and compact coating on the surface of the ANPyO, and the crystal and molecular structures of the ANPyO remained unchanged after the PDA coating. Additionally, the coating rate gradually increased with the growth of coating time. The thermal decomposition peak temperatures of the ANPyO were increased by 1.97 and 1.95 °C, respectively, as well as the apparent activation energy increased by 25.04 and 139.33 kJ/mol, and the critical temperatures of the thermal explosion were increased by 23.12 and 20.04 t after PDA coating for 3 and 9 h, respectively. The thermal stability and thermal safety of the ANPyO@PDA composites are higher than that of the ANPyO. [ABSTRACT FROM AUTHOR]

The variation of aluminum shear modulus with the melting-mass fraction in the solid-liquid mixed phase has been estimated by the percolation theory. With the total number of calculated sites from 0.125×106 to 8.0×106, it is shown that there are two critical points corresponding to the melting-mass fraction 0.313 and 0.687, respectively. At the critical point 0.313, the longitudinal sound velocity begins to attenuate to bulk sound velocity and completely attenuates to bulk sound velocity at the critical point 0.687. This is in accord with previous independent and our sound velocity data of aluminum in the solid-liquid phase, and suggests a different interpretation of shock sound speed data for melt mass fraction. [ABSTRACT FROM AUTHOR]

The X-ray pulse originating from high altitude nuclear detonation (HAND) is mainly soft X-ray and its intensity is high enough to gasify the penetrated material and then lead to the severe thermo-mechanical deformation of unpenetrated material from the gasified blow-off effect. This effect cannot be directly reproduced in a lab for the lack of the X-ray source like HAND. At present, the low-energy relativistic electron beams resulting from an electron accelerator are usually used to approximately reproduce this effect, but the difference in the energy-deposited profile in materials between the electron and X-ray cannot be eliminated. In this paper, the symmetric linear least squares method was used to optimize the electron spectrum, and the general Monte Carlo N-Particle Transport Code calculations showed the optimized spectrum can produce the same energy-deposited profile in aluminum, copper, and tantalum with the soft X-rays like 1 keV or 3 keV spectrums. This indicates that it is possible to simulate the severe thermo-mechanical deformation resulting from HAND using the optimized electron spectrums. [ABSTRACT FROM AUTHOR]

Metal/fluoropolymer materials are typical reactive materials. Polytetrafluoroethylene (PTFE)/Al/CuO reactive materials were studied in this research. Scanning electron microscopy (SEM), quasi-static compression, the Split Hopkinson pressure bar test, and the drop hammer test were used to study the mechanical properties and induced reaction characteristics of the reactive materials with different Al/CuO thermite contents and different particle sizes. SEM images of the samples demonstrate that the reactive materials were mixed evenly. The compression test results show that, if the particle size of PTFE was too small, the strength of reactive materials after sintering was reduced. After sintering, with the increase in the content of Al/CuO thermite, the strength of the micro-sized PTFE/Al/CuO firstly increased and then decreased. The Johnson–Cook constitutive model can be used to characterize the reactive materials, and the parameters of the Johnson–Cook constitutive model of No. 3 reactive materials (PTFE/Al:Al/CuO = 3:1) were obtained. The reliability of the parameters was verified by numerical simulation. Drop hammer tests show that the addition of Al/CuO aluminothermic materials or the use of nano-sized PTFE/Al reactive materials can significantly improve the sensitivity of the material. The research in this paper can provide a reference for the preparation, transportation, storage, and application of reactive materials. [ABSTRACT FROM AUTHOR]