An USAXS-SAXS study of nano-TATB under uniaxial die pressures

The microstructure of a compressed explosive solid is closely related to its shock sensitivity and mechanical properties. In this study, ultra-small-angle and small-angle X-ray scattering (USAXS and SAXS) techniques were combined to explore the hierarchical microstructure of die-pressed 2,4,6-trinitro-1,3,5-benzenetriamine (TATB) discs obtained from nanostructured TATB (nano-TATB) powder as the precursor. Using the Guinier-Porod model, the pseudo-invariants, and Porod's law, this study analyzed the microstructures of the materials on a nanometer scale to track the changes in void size, porosity, and interfacial area, which reflected the response of TATB under applied pressures of 1, 2, 5, 10, 15 ​kN and 30 ​kN. Results show that there existed three populations of voids in the measured q range. The intergranular voids with sizes of tens of nanometers were sensitive to low pressures (<15 ​kN) and presented a smooth interface with the TATB matrix. The intragranular voids with sizes of 7–8 ​nm exhibited a fairly small volume-filling ratio under high pressures (>15 ​kN), as indicated by the decrease in the volume fractal dimension. Porosities of the voids with sizes of 1–900 ​nm, which were determined by the pseudo-invariants obtained from the scattering data, decreased from 6% to 1% as the pressures increased from 1 ​kN to 30 ​kN. The response of these structural parameters to external pressures implies that the main densification mechanisms under die compression include the flow, fracturing, and plastic deformation of the TATB granules. This study provides a direct insight into the structural evolution of TATB during compression.