Dec 27, 2017 | By Benedict

Researchers at Purdue University have developed a way to 3D print energetic materials using inkjet printing technology. The project allows energetic materials to be deposited with unprecedented precision and safety.

Energetic materials, which include explosives and pyrotechnics, can be something of a handful. But contrary to what you might think, they’re not just used for blowing things up or making firework displays.

Several functional micromechanical systems use energetic materials to carry out their basic task. An airbag system in a car, for example, uses a small amount of solid propellant, a kind of energetic material, to release the airbag at speed. And the smaller the devices, the more critical the need for micro-level energetics.

Researchers at Purdue University have developed a new energetic material system using an inkjet-style 3D printing technique. It’s precise, safe, and combines two areas of research in which the university has great expertise: additive manufacturing and energetic materials.

“Energetic materials is a fairly understood field, and so is additive manufacturing,” said Allison Murray, a Ph.D. candidate in Mechanical Engineering, who built a custom inkjet 3D printer for the project. “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 newly developed 3D printer works by depositing both a fuel and an oxidizer (two largely inert colloidal suspensions of nanoaluminum and nanocopper (II) oxide in dimethylformamide with polyvinylpyrrolidone) in an overlapping pattern, combining them on a substrate to form nanothermite, a metastable intermolecular composite with small particle size.

Murray said it was a “challenge” to configure the droplet volume and pattern, and to actually develop a machine capable of depositing these droplets. The piezoelectric inkjet 3D printer, however, works exactly as it was designed to, being able to hold its nozzle still while moving its print bed or “stage” below to form the desired shape.

“The stage can move with a 0.1 micron precision, which is basically a thousandth the width of a human hair,” Murray said.

The printed nanothermite reacts as quickly and powerfully as thermites applied in traditional ways, burning at 2,500 Kelvin while generating plenty of thrust and heat…and making a loud shockwave.

Using a high-speed camera and scanning transmission electron microscopy apparatus, the researchers were able to observe how the printed nanothermite reacted with differing numbers of layers.

The Purdue scientists say their work proves the feasibility of reactive inkjet printing as a means for depositing energetic materials from two largely inert suspensions. They say 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.”

A research paper documenting the researchers’ findings, “Two-component additive manufacturing of nanothermite structures via reactive inkjet printing,” has been published in the Journal of Applied Physics. Its authors, from from varying disciplines in Mechanical Engineering, were Murray, Tugba Isik, Volkan Ortalan, I. Emre Gunduz, Steven F. Son, George T.-C. Chiu, and Jeffrey F. Rhoads.

“It’s a defining feature of Purdue that professors from such different backgrounds can work  together on a project like this,” said Rhoads. “We can combine all of our experiences to collaborate on technologies that weren’t previously realizable.”

 

 

Posted in 3D Printing Application

 

 

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