Characterization framework to develop ball-milled thermites as additives to polymer-bound explosives

Bansal, Lakshay Priya

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https://hdl.handle.net/2142/132590 Copy

Description

Title

Characterization framework to develop ball-milled thermites as additives to polymer-bound explosives

Author(s)

Bansal, Lakshay Priya

Issue Date

2025-12-08

Director of Research (if dissertation) or Advisor (if thesis)

Dlott, Dana

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Polymer-bound explosive
• Shock compression
• Ball-milled Composites
• Thermites
• Detonation

Abstract

Increasing the energy density of plastic-bonded explosives (PBXs) by incorporating aluminum (Al) powders has long been of interest. However, Al combustion is kinetically slow, occurring on microsecond to millisecond timescales due to its dependence on external oxidizers. As a result, it contributes little to the early nanosecond-microsecond scale energy release that governs fast phenomena such as detonation and deflagration. In many formulations, the sluggish oxidation of Al can even interfere with the primary decomposition chemistry of explosives, leading to reduced detonation velocity and peak pressure. To address these limitations, arrested reactive milling (ARM) is of interest as a customizable synthesis method for producing composite microparticles with tailored microstructures that contain aluminum along with a dedicated condensed-phase oxidizer capable of rapid, shock-driven reactions. This work presents an experimental framework to streamline the characterization of intrinsic ARM composite batch reactive behavior unaided by packing microstructure, as well as its reactive interplay with surrounding reacting CHNO molecular explosives. The approach is presented by testing six different Al-CuO ARM composite batches. To rapidly assess how distinct microstructural features across different ARM powder batches translate into shock-induced reactivity, a high-throughput, particle-scale characterization test was developed. The tabletop setup uses laser-launched hypervelocity flyer plates to shock-compress isolated particles suspended in transparent polymer wells. The fast, nanosecond-timescale onset of shear-driven reactions, observable as hot spots forming within the first ~50 ns after impact, was tracked optically using a high-speed camera. By shocking and observing hundreds of particles within a single powder batch, the intra-batch variance was quantified as the probability of hot spot formation as a function of particle size. Additionally, an overall hot spot-formation probability metric was constructed for each batch, enabling direct comparison across different ARM-produced powders. To test if ARM batch differences translate to PBX formulations, 28 wt.% ARM composites were added as additives to HMX-based PBX and compared against aluminized PBX. Micron-sized (7.07 × 10-11 m3) cylindrical sample wells were shocked by flyers at 4 km/s, and their reaction behavior was characterized by a 32-channel nanosecond pyrometer. These diagnostics captured hot spot initiation, radiance growth, and temperature evolution from the moment of impact through the transition to full deflagration. All formulations containing Al-CuO additives produced hot spots faster, exhibited stronger emissions, and sustained temperatures exceeding those of aluminized formulations. The Al-CuO-containing formulations exhibited batch-dependent variance in behavior strongly suggestive of the additive’s internal microstructure-driven reactive behavior. To evaluate the effectiveness of such microstructural optimization, the best Al-CuO composite was included in an HMX-based PBX formulation and compared to a formulation containing an unoptimized, but thermodynamically superior Al-MoO3-KNO3 composite. It was found that despite a higher theoretical energy release of the MoO3-based composite, the optimized Al-CuO formulation delivered greater radiance and higher post-shock deflagration temperatures within the PBX. This suggests that nanoscale mixing, interfacial engineering, and optimized composite architecture play a dominant role in governing shock-driven reactions. Thus, the escalation of experimental complexity in this work, together with the detailed methodology at each stage, provides a clear framework for exploring different powder batches of fixed composition as well as other compositions, refining the parametric space of ARM composites, and ultimately developing fast-reacting additives.

Graduation Semester

2025-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/132590

Copyright and License Information

Copyright 2025 Lakshay Bansal

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