Two projects funded by NASA shed light on the use of a material that is not always used in metal AM: nitinol.
This metal alloy composed of nickel (Ni) and titanium (Ti) (typically about 55% nickel and 45% titanium) is known for shape memory and superelasticity. This means it can be deformed at a certain temperature and then return to its original shape when heated – and it can undergo large amounts of strain and return to its original shape without permanent deformation—unlike most metals.
These properties make nitinol highly useful in applications where flexibility, resilience, and responsiveness to temperature are important.
In the projects led by Penn State University and Arizona State University and supported by 3D Systems’ Application Innovation Group, this material is explored along with titanium, and 3D Systems’ technology portfolio to enable alternatives to current thermal management solutions. 3D Systems’ solutions that are currently used include Direct Metal Printing (DMP) technology and Oqton’s 3DXpert® software.
Focus on one application: heat pipes
For one of the projects, the teams have been able to establish processes to build embedded high-temperature passive heat pipes in heat rejection radiators that are additively manufactured in titanium.
These heat pipe radiators are 50% lighter per area with increased operating temperatures compared with current radiators, allowing them to radiate heat more efficiently for high-power systems.
For the other project, the teams yielded a process to additively manufacture one of the first functional parts using nickel titanium (nitinol) shape memory alloys that can be passively actuated and deployed when heated. This passive shape memory alloy (SMA) radiator is projected to yield a deployed-to-stowed area ratio that is 6× larger than currently available solutions, enabling future high-power communications and science missions in restricted CubeSat volume. When deployed on spacecraft, such as satellites, these radiators can raise operating power levels and reduce thermal stress on sensitive components, preventing failures and prolonging satellite lifespan.
Traditionally, heat pipes have been manufactured with complex processes to form porous internal wick structures that passively circulate fluid for efficient heat transfer. Using Oqton’s 3DXpert® software, the Penn State/Arizona State/NASA Glenn/3D Systems project team embedded an integral porous network within the walls of the heat pipes, avoiding subsequent manufacturing steps and resulting variability. Monolithic heat pipe radiators were manufactured in titanium and nitinol on 3D Systems’ DMP technology. The titanium-water heat pipe radiator prototypes were successfully operated at temperatures of 230°C and weigh 50% less (3 kg/m2 versus over 6 kg/m2), meeting NASA goals for heat transfer efficiency and reduced cost to launch for space-based applications, a press communication explains.
The next step for the research team is to develop a process to 3D print passively deployed radiators with shape memory alloys.
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