Researchers Develop a Safe Way to 3D Print Explosives
Additive manufacturing (aka 3D printing) will continue to be one of the biggest ways engineers look to construct increasingly complex designs and materials. But one group of engineers just used the process to craft something truly unique. A team of researchers from Purdue University just created a way to put materials like thermites and nanothermites into an explosive using additive manufacturing.
In short, this means that energetic materials like explosives and pyrotechnics can now potentially be safely 3D printed.
The group of seven researchers used their knowledge of energetics with updated inject deposition systems in order to create a new type of printer -- one that's able to put two substances on a bed of substrate in a particular and highly specific order.
The inert materials combine together to form a nanothermite -- a substance made of nanoparticles that doesn't release its high energy without being ignited or from another stimulus.
Doctoral student Allison Murray was a key part in building the 3D printer capable of carefully printing nanothermite materials. Unlike other styles of 3D printers, Murray's printer opted for a stationary nozzle and a moving platform below rather than a moving nozzle. According to Murray, platform (or the "stage") can move with just a micron of precision.
She also said the project combined two seemingly unrelated fields of interest together to create a surprisingly functional result.
"Energetic materials is a fairly understood field, and so is additive manufacturing," Murray said. "What’s unique about this project is the intersection of those two fields, and being able to safely deposit energetic materials with this level of precision."
The 3D printed samples of nanothermite were ignited and set off as part of the research. The team got to 'blow up' their creations for analysis. Each sample was set off electrically. The researchers used high-speed thermal imaging as well as scanning transmission electron microscopy (STEM) to see just how powerful their printed creations were.
"It burns at 2,500 Kelvin [over 4,000 degrees Fahrenheit]," Murray said. "It generates a lot of thrust, a lot of heat, and makes a nice loud shockwave!"
The team said they hope that the work can prove the usefulness and feasibility of using a reactive inkjet printer as a way to place energetic materials into larger constructs. The Purdue team said this opens the doors for “safer material handling and the development of a wide array of energetic materials that were previously deemed incompatible with inkjet printing.”
"It’s a defining feature of Purdue that professors from such different backgrounds can work together on a project like this," said Murray’s supervisor Prof. Jeffrey Rhoads. "We can combine all of our experiences to collaborate on technologies that weren’t previously realizable."
The results themselves can also show how micro-mechanical engineering can be combined with other seemingly unrelated fields. Further research, according to the team, will look into how much impact the deposition's shape plays into the overall energy output and performance of the material.
The entire paper can be found on the Journal of Applied Physics.