Manufacturing Bits: Oct. 9

World’s strongest silver
A group has developed what researchers say is the world’s strongest silver.

The silver demonstrated a hardness of 3.05 GPa, which is 42% stronger than the previous world record. The University of Vermont, Lawrence Livermore National Lab, the Ames Laboratory, Los Alamos National Laboratory and UCLA contributed to the work.

Silver is an element with high electrical and thermal conductivity. Using a new process, researchers not only developed a new and hard form of silver, but the technology could pave the way for a new class of other types of metals. The technology could one day enable better solar cells, lighter airplanes and even safer nuclear power plants.

To make silver hard, meanwhile, the University of Vermont and others mixed a trace amount of copper into the silver. This in turn created two types of defects. But the end result was a silver compound with a strong structure.

Researchers took a different approach to strengthen silver. It manipulated the grain boundaries and coherent twin boundaries in the structure.

In doing so, researchers devised a new class of nanocrystalline and nanotwinned materials. Researchers refer to them as nanocrystalline- nanotwinned materials.

In the lab, they synthesized nanocrystalline-nanotwinned silver with hardness of 3.05 GPa. This was done by segregating trace concentrations of copper impurity into the microalloy.

Electrical conductivity remained stable in the compound. “We’ve discovered a new mechanism at work at the nanoscale that allows us to make metals that are much stronger than anything ever made before—while not losing any electrical conductivity,” said Frederic Sansoz, a materials scientist and mechanical engineering professor at the University of Vermont.

“This is a new class of materials and we’re just beginning to understand how they work,” he said. “When you can make material stronger, you can use less of it, and it lasts longer, and being electrically conductive is crucial to many applications.”

Boron-on-silver devices
A group has developed a borophene on silver process that enables a new class of wearable and transparent electronics.

Rice University, Northwestern, the Nanjing University of Aeronautics and Astronautics and Argonne National Laboratory contributed to the work.

Borophene, a crystalline atomic monolayer of boron, is a two-dimensional material. Also known as a boron sheet, borophene has some intriguing electronic and optical properties.

In the past, various researchers attempted to grow borophene on various materials using molecular-beam epitaxy (MBE) systems. This is a slow and difficult process, however.

Instead, researchers from Rice and others devised a substrate using silver. Then, by controlling the temperature in a deposition process, researchers have grown elongated hexagon-shaped flakes of borophene on silver.

This in turn could one day pave the way for borophene ribbons, which could be used for wearable electronics, plasmonic sensors and energy storage, according to researchers.

“Silver provides a landing for boron atoms, which then diffuse along the surface to find the edges of a growing borophene flake,” said Zhuhua Zhang, a professor at Nanjing. “Upon arrival, the boron atoms are lifted onto the edges by silver, but how difficult such a lift is depends on the edge’s orientation. As a result, a pair of opposite zigzag edges grow very slowly while all other edges grow very fast, manifested as an elongation of the boron flake.”

Rice materials scientist Boris Yakobson added: “Graphene-based electronics that have been conceived so far mostly rely on ribbonlike building blocks. Metallic boron ribbons with high conductivity will be a natural match as interconnects in circuitry.”

Silver rush
In 2018, global silver mine production fell by 2.4% to 920.1Moz, according to a report from GlobalData.

“The largest decline was recorded in the US (12.6%) where labor strikes at the Lucky Friday mine severely impacted the overall output. This was followed by Peru (5.8% decrease) and Mexico (5.6%) where lower ore grades and lower recovery rates were of major concern. However, increases in production in China (2%) and Russia (3.4%) partially offset the 2018 declines,” according to GlobalData.

From 2019 to 2023, though, global silver production is expected to grow at an annual rate of 3% and reach 1,029.3Moz in 2023, according to the firm.

“Major projects that are due to begin operations during the forecast period include the El Cajon in Mexico, the Candelaria 2030 in Chile, Fruta del Norte and Mirador in Ecuador and the Ozernoe and Udokan projects in Russia,” according to the firm.