Nanoporous ‘Black Gold’ Is 30% Lighter But Twice As Solid

Researchers have developed an ultralight nanoporous gold which has increased strength and durability, while still maintaining the quality of standard gold.

AsianScientist (Apr. 11, 2016) – Researchers in South Korea have recently announced that they have successfully developed a way to fabricate an ultralight, high-density nanoporous gold (np-Au).

Published in Nano Letters, the Ulsan National Institute of Science and Technology study reported that this newly developed material, which has been dubbed “black gold” is 30 percent lighter and twice as solid than standard gold.

According to team leader, Professor Kim Ju-Young from the School of Materials Science and Engineering, “This particular nanoporous gold has a 100,000 times wider surface when compared to standard gold. Moreover, due to its chemical stablity, it is also harmless to humans.”

The surfaces of np-Au are rough, and the metal loses its shine and eventually turns black when at sizes less than 100 nanometers, hence the name.

In their study, the team investigated grain boundaries in nanocrystalline np-Au and found a way to improve the mechanical strength of this material. They used a ball milling technique to increase the ability of the three gold-silver precursor alloys to resist structural deformation. Then, using free corrosion dealloying of silver from gold-silver alloys, they were able to achieve the nanoporous surface.

According to the team, “The size of the pores can be controlled by the temperature and concentration of nitrate.”

Moreover, they also note that this crack-free nanoporous gold samples exhibit excellent durability in three-point bending tests. The researchers suggest that this newly developed technique can be also applied to many other metals, as the np-Au produced by this technique have shown increased strength and durability while still maintaining the quality of standard gold.

This means that this technique can be also used in other technologies, like catalytic-converting as observed by platinum, the automobile catalyst, and palladium, the hydrogen sensor catalyst.

The article can be found at: Gwak and Kim (2016) Weakened Flexural Strength of Nanocrystalline Nanoporous Gold by Grain Refinement.


Source: Ulsan National Institute of Science and Technology.
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