Fast deflagration to detonation transition of energetic material based on a quasi-core/shell structured nanothermite composite

• A quasi-core/shell structured material was designed for fast DDT accelerations.
• A surface modifying – ultrasonic method is proposed to fabricate the composite.
• The DDT of the synthesized materials can be accelerated to primer explosive level.
• The DDT acceleration mechanism of the composite material is demonstrated.
• The synthesized material is safer and greener than traditional primer explosives.

Nanothermites (also called metastable intermolecular composites), composed of nanoscale metals and metal oxides, have drawn increasing interests as energetic materials over the past two decades. Nanothermites have twice the energy density of 2,4,6-trinitroluene, and their nanostructures, functions, energy release, and reaction performance are continuously being improved. However, these materials suffer from low pressure because of low gas expansion from the reaction and incapability of deflagration to detonation transition (DDT). Fast DDT is necessary to substantially improve the reaction velocity and output pressure not only of nanothermites but also of other monomolecular organic energetic materials, such as cyclotrimethylene trinitramine (RDX) and octogen. Accordingly, this study aims to produce energetic composites material that are safe, green, and free from heavy metals. A strategy of rapid DDT acceleration is proposed by fabricating quasi-core/shell structured materials of RDX@Fe2O3–Al based on Fe2O3–Al nanothermites. A surface modifying and ultrasonic synthesis technology is also demonstrated. Scanning electron microscopy and X-ray photoelectron spectroscopy characterizations prove that the material comprises an RDX core and an Fe2O3–Al nanothermite shell. Results of closed vessel combustion tests show that the RDX@Fe2O3–Al combustion velocity accelerates to an average pressurization rate of 2.527 MPa/μs. DDT tube tests further confirm that DDT accelerates to a primer explosive level in which the run-to-detonation distances of DDT is below the test-condition limitation (<15 mm). Sensitivity tests also reveal that the RDX@Fe2O3–Al composite has low sensitivity to impact, friction, and electric spark. Therefore, the RDX@Fe2O3–Al composite with a quasi-core/shell structure is a potential green and safe fast DDT energetic material that is easy to synthesize and applicable to other quasi-core/shell structures.