'Metallic Wood' Is Our Next Innovative Material, Better Than Titanium

Titanium is an impressive metal that is equally strong but half as heavy as steel. However, scientists say they can do even better than that.

A research team including scientists from the University of Illinois, University of Pennsylvania, and the University of Cambridge has built a nickel sheet with nanoscale pores which make it equally strong but four or five times as light as titanium. The journal Nature Scientific Reports published their paper.

A sample of the "metallic wood"

Since the pores are made in a self-assembly process and there is empty space, the material looks natural, like wood.

According to the researchers, the empty space of this “metallic wood” allows infusing it with other materials, similar to porous wood grain transporting energy. For instance, the scaffolding can be infused with cathode and anode materials to make a prosthetic leg or plane wing.

Research lead James Pikul from Pennsylvania said that the term “metallic wood” is based on the material’s density which is similar to wood and its cellular nature.

In cellular materials, there are thick and dense parts to hold the structure, along with porous parts that support biological functions such as transporting from and to cells.

Pikul added that “metallic wood” has a similar structure, but they’re working to maximize the strength of struts. Apparently, there are atomic arrangement defects in even the best metals of nature, if we can avoid or fix the defects, we can limit the limits.

The researchers also stated that a titanium block with a perfect arrangement of atoms and their neighbors will be ten times more powerful than normal.

The fabrication process for a unit cell of the material

Exploiting this phenomenon under architecture approach, material scientists have been designing structures in which they control the geometric arrangement to unlock the mechanical characteristics which arise at the nanoscale, reducing defects.

According to Pikul, smaller structures can be stronger, but so far, no one can make something large enough for practical use. Currently, most samples generated from strong materials are as small as a flea, and the team can make something 400 times bigger with metallic wood.

The researchers have this approach from nanometer plastic spheres suspended in water which, after the water evaporates, settle and stack like cannonballs to create an orderly, crystalline framework.

They use electroplating to infiltrate nickel into the plastic spheres. When the nickel is in place, they dissolve the plastic sphere with a solvent, revealing an open network of metallic struts.

Since the resulting material includes 70 percent empty space, its density is dramatically low relative with its strength. With this level of density, the metallic wood brick would float. However, bringing this production process into commercial purposes is challenging due to limited infrastructure.

If the team can make larger samples from metallic wood, they can head to macroscale tests to find out how much larger the material can go, which is critical.

Pikul said they need to understand how metallic wood’s struts defects can influence the material’s overall properties.