Amazing Science

Laser powder bed fusion, a 3D-printing technique, offers potential in the manufacturing industry, particularly when fabricating nickel-titanium shape memory alloys with complex geometries. Although this manufacturing technique is attractive for applications in the biomedical and aerospace fields, it has rarely showcased the superelasticity required for specific applications using nickel-titanium shape memory alloys. Defects generated and changes imposed onto the material during the 3D-printing process prevented the superelasticity from appearing in 3D-printed nickel-titanium.

Researchers from Texas A&M University recently showcased superior tensile superelasticity by fabricating a shape memory alloy through laser powder bed fusion, nearly doubling the maximum superelasticity reported in literature for 3D printing.

This study was recently published in vol. 229 of the Acta Materialia journal.

Nickel-titanium shape memory alloys have various applications due to their ability to return to their original shape upon heating or upon removal of the applied stress. Therefore, they can be used in biomedical and aerospace fields for stents, implants, surgical devices and aircraft wings. However, developing and properly fabricating these materials requires extensive research to characterize functional properties and examine the microstructure.

"Shape memory alloys are smart materials that can remember their high-temperature shapes," said Dr. Lei Xue, a former doctoral student in the Department of Materials Science and Engineering and the first author of the publication. "Although they can be utilized in many ways, fabricating shape memory alloys into complex shapes requires fine-tuning to ensure the material exhibits the desired properties."

Aerogels are among the world’s lightest materials. Graphene aerogel, a record holder in that category, is so light that a large block of it wouldn’t make a dent on a tiny ball of cotton. Water is about one thousand times more dense. The minimal density of aerogels allows for a number of possible applications, researchers have found, ranging from soaking up oil spills to “invisibility” cloaks.

Now, scientists from State University of New York (SUNY) at Buffalo and Kansas State University report in the journal Small that they have found a way to 3D print graphene aerogel, which has only been used in lab prototypes. This technology will make the material much easier to use, and open it, and hopefully other aerogel materials, up to wider applications.

Graphene is just a single layer of carbon atoms. Since it was isolated for the first time in 2004, it has been touted as a wonder material for its strength, pliability and conductivity. Aerogel is essentially a gel where the liquid is replaced by air. Graphene aerogel is known to be highly compressible (so it can bear pressure without breaking apart) and highly conductive (so it can carry electricity efficiently). The very structure of the material that gives it these properties, however, makes it difficult to manufacture using 3D printing technology.

SUNY Buffalo and Kansas State University researchers came up with a solution. They mixed graphene oxide—graphene with extra oxygen atoms—with water and deposited layers on a surface at -25°C. This instantly froze each layer, and allowed the undisrupted construction of the aerogel, with ice as its support.