Manufacturing Bits: Nov. 19

World’s lightest foam
Lawrence Livermore National Laboratory (LLNL) has developed what researchers say is the world’s lightest gold foam.

LLNL has devised gold aerogel foam. The foam is light enough where it could be carried on the back of tiny insects. Applications for the technology include electronics, catalysis, sensors and energy conversion and storage.

An aerogel is based on a solid framework of gel. “Aerogels are a diverse class of porous, solid materials that exhibit an uncanny array of extreme materials properties. Most notably aerogels are known for their extreme low densities,” according to Aerogel.org, an open source nanotech initiative.

One type of aerogel–silica aerogel—is only three times heavier than air. It could be made lighter than air by evacuating the air out of its pores, according to Aerogel.org. Aerogels have densities between 1 and 1,000 milligrams per cubic centimeter.

Monolithic foams can be made using metals and alloys. This includes nickel, cobalt, copper and silver, but gold foams have been a challenge to make.

Source: Lawrence Livermore National Lab. Illustration by Amy Henke/LLNL

LLNL has devised ultralight gold foam by starting with tiny gold nanowires. Then, researchers freeze-cast the nanowires. This in turn created aerogels with densities down to 6 milligrams per cubic centimeter. Low-density gold foams can be used as targets for X-ray sources. They could play a vital role in the exploration of high-energy-density physics.

“These gold aerogels were so light that they could be carried on the back of fragile insects, or even blown away by gentle breath, which used to be a big technical challenge in the experiments,” said LLNL material scientist Fang Qian. “We have created new approaches to prepare high-quality gold nanowires in large quantities to ensure sufficient material supply for the foam fabrication, with densities tuned in a predictable manner. Density tunability is important because key physical properties of metal foams — such as stiffness, strength, electrical conductivity, thermal conductivity and X-ray opacity — scale with density.”

Brent Blue, the director of the National Security Program at LLNL, added: “These gold foams are mechanically stable, compared to early samples that were similar in strength to a long cigarette ash. They can be squeezed or dropped, and they bounce back and hold their shape very well, which is a critical quality for use as a bright, X-ray source. This is an amazing feat given that even though they look solid, they are 99.9 percent void, or 0.1 percent solid.”

Strong aluminum
HRL Laboratories has developed the world’s strongest aluminum for use in additive manufacturing applications.

The aluminum, which comes in a powder form, is robust with strengths over 600MPa. An aluminum alloy can be printed from the powder using additive manufacturing equipment such as a 3D printer.

HRL Additive, a new commercial effort launched by HRL Laboratories, has secured the first commercial sale of its aluminum 3D-printing powder to NASA’s Marshall Space Flight Center.

HRL has a production plant, which produces the printable aluminum powder called 7A77. “Our goal is to provide the highest quality powder to HRL’s members in the aerospace and automotive industries, as well as other commercial customers,” said Zak Eckel for HRL Additive.

“Certainly, the 7A77 feedstock powder could unlock the production of large-scale components produced via fusion-based additive manufacturing,” said Omar Rodriguez of NASA’s Marshall Space Flight Center. “Printed test articles will be subjected to a comprehensive characterization regime expanding several length-scales. The end-goal of this research effort is to expand MSFC’s range of fusion-based additive feedstock materials. If successful in our research endeavor, the feedstock powder could be part of the aerospace-related assets produced at the planned large-scale, advanced manufacturing facility.”

Tubulanes
Rice University has developed a new and hard 3D printed polymer structures called tubulanes.

Turbulanes are theoretical structures, which are crosslinked to carbon nanotubes. Turbulanes are lightweight materials full of holes. This in turn makes them nearly as hard as diamonds.

Potential applications include construction and the oil and gas industry. These structures can be used in hydraulic fracturing.

“The unique properties of such structures comes from their complex topology, which is scale-independent,” said Chandra Sekhar Tiwary, co-principal investigator on the project and now an assistant professor at the Indian Institute of Technology. “Topology-controlled strengthening or improving load-bearing capability can be useful for other structural designs as well.”