Scientists at Lawrence Livermore National Laboratory Control Reactive Materials through 3D Printing

December 17, 2015 by Bridget O'Neal 3D Printing 3D Printing Materials

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Optimization of materials. It’s may sound like a simple enough goal, but it is an ongoing and progressive challenge in many 3D printing research and development projects, with a wide range of different enhancements being possible today–especially with conductivity. Scientists at Lawrence Livermore National Laboratory are now also looking at using 3D printing to control materials that historically have presented difficulty in doing so.

In their paper, Controlling Material Reactivity Using Architecture-–by Kyle T. Sullivan, Cheng Zhu, Eric B. Duoss, Alexander E. Gash, David B. Kolesky, Joshua D. Kuntz, Jennifer A. Lewis, and Christopher M. Spadaccini–the researchers examine how material architecture can be used to control dynamic materials and especially those that are more unpredictable–namely, reactive (energetic) materials.

Through the creation of 3D reactive material architectures (RMAs), the idea is that they can ‘modulate reactivity’ through overseeing the way the particular energy is transported.

“Energy transport in RM involves convection of gases as well as advection of particles as gases and temperature rapidly evolve after ignition. To clarify, in this work when we use the term convection, we are referring to gas transport (convection includes both advection and diffusion by definition), and the term advection applies specifically to the transport of molten or solid particles,” state the researchers in their paper.
“Using RMAs, we hypothesize that both the convective and advective components of energy transport can be controlled by the architecture, so long as the architectural length scales are commensurate with the length scale over which these transport phenomena occur.”

3D printing comes into play as they use the technology to actually make the architectures and then apply it to a surface with sufficient depth. With the hope being to rein in some of the unpredictability while also harnessing the benefits of reactive materials, the RMAs were created through making 3D conductive electrodes. Then, with electrophoretic deposition (EPD), they were able to use thermite nanoparticles to coat the reactive micro-architectures.

Lawrence Livermore Laboratory scientists Cheng Zhu (left) and Kyle Sullivan are 3D printing new architectures. [Credit: Julie Russell/Eric Duoss LLNL]

Through a 3D printing process called direct ink writing, researchers first constructed 3D conductive electrodes. Then, through another printing process called electrophoretic deposition (EPD), the team coated the surface of the conductive micro-architectures with a composite film of thermite nanoparticles. With 3D printing, again, control was key, as they were able to control the thermite particles, which are actually a very random mixture.

“3D printing has allowed us to make high-quality parts with the feature sizes commensurate with the length scales of dynamic phenomena,” said Kyle Sullivan, a staff scientist and the paper’s lead author. “It’s allowed us to make precision geometries, with careful control over several length scales. With this spatial control, we wanted to examine how, and to what extent, this translates into controlling dynamic behavior.”
“The big message here is we’re showing 3D printing can be used to change the dynamic behavior of materials,” Sullivan said. “It’s very promising moving forward.”

The team was able to work with a range of materials and platforms which allowed for the best release rates of energy from the thermite particles. They plan to continue their study with even more advanced and complex architectures like lattices–often created through 3D printing in the medical industry.

“If you look at the history of energetic materials, the scary part is that the performance is slowly plateauing,” Sullivan said. “While it’s only a matter of time for new formulations to be developed, this technique gives us an additional knob of using material architecture to tailor, and improve, the energetic materials we already have.”
The ultimate hope is that in perfecting this process in manipulating reactive materials, components of superior strength and durability can eventually be produced in industries that make items such as airbags, ejector seats, and other items that require quick-release materials and mechanisms. Discuss this story in the 3D Printing to Control Reactive Matter forum on 3DPB.com.

[Source: Phys Org]

From the research paper, as follows: “Combustion studies of RMAs. For schematics, particles are represented by black dots and the orange region represents the gas. a) Optical image of a channel structure with d = 4.8 mm, < 2Lf . b) Still image from high-speed videography of the combustion process for this channel structure. c) Schematic illustration of the resultant pressurization region (red, indicated by arrow) which promotes forward convective transport. d) Optical image of a channel structure with d = 8 mm, > 2Lf . e) Still image from high-speed videography of the combustion process for this channel structure. f) Schematic illustration of the uncoupled reaction. g) Optical image of a hurdle structure with d = 2.4 mm, < Lf . h) Still image from high-speed videography of the combustion process for this hurdle structure. i) Schematic illustration of the interrupted expansion. j) Optical image of a hurdle structure with d = 9.6 mm, > Lf . k) Still image from high speed videography of the combustion process for this hurdle structure. l) Schematic illustration of the uninterrupted expansion, and the resultant advective transport and interception of particles (arrow), as facilitated by the architecture.”