Tag Archives: catalytic converters

Mimicking the architecture of materials like wood and bone

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Caption: Microstructures like this one developed at Washington State University could be used in batteries, lightweight ultrastrong materials, catalytic converters, supercapacitors and biological scaffolds. Credit: Washington State University

A March 3, 2017 news item on Nanowerk features a new 3D manufacturing technique for creating biolike materials, (Note: A link has been removed)

Washington State University nanotechnology researchers have developed a unique, 3-D manufacturing method that for the first time rapidly creates and precisely controls a material’s architecture from the nanoscale to centimeters. The results closely mimic the intricate architecture of natural materials like wood and bone.

They report on their work in the journal Science Advances (“Three-dimensional microarchitected materials and devices using nanoparticle assembly by pointwise spatial printing”) and have filed for a patent.

A March 3, 2017 Washington State University news release by Tina Hilding (also on EurekAlert), which originated the news item, expands on the theme,

“This is a groundbreaking advance in the 3-D architecturing of materials at nano- to macroscales with applications in batteries, lightweight ultrastrong materials, catalytic converters, supercapacitors and biological scaffolds,” said Rahul Panat, associate professor in the School of Mechanical and Materials Engineering, who led the research. “This technique can fill a lot of critical gaps for the realization of these technologies.”

The WSU research team used a 3-D printing method to create foglike microdroplets that contain nanoparticles of silver and to deposit them at specific locations. As the liquid in the fog evaporated, the nanoparticles remained, creating delicate structures. The tiny structures, which look similar to Tinkertoy constructions, are porous, have an extremely large surface area and are very strong.

Silver was used because it is easy to work with. However, Panat said, the method can be extended to any other material that can be crushed into nanoparticles – and almost all materials can be.

The researchers created several intricate and beautiful structures, including microscaffolds that contain solid truss members like a bridge, spirals, electronic connections that resemble accordion bellows or doughnut-shaped pillars.

The manufacturing method itself is similar to a rare, natural process in which tiny fog droplets that contain sulfur evaporate over the hot western Africa deserts and give rise to crystalline flower-like structures called “desert roses.”

Because it uses 3-D printing technology, the new method is highly efficient, creates minimal waste and allows for fast and large-scale manufacturing.

The researchers would like to use such nanoscale and porous metal structures for a number of industrial applications; for instance, the team is developing finely detailed, porous anodes and cathodes for batteries rather than the solid structures that are now used. This advance could transform the industry by significantly increasing battery speed and capacity and allowing the use of new and higher energy materials.

Here’s a link to and a citation for the paper,

Three-dimensional microarchitected materials and devices using nanoparticle assembly by pointwise spatial printing by Mohammad Sadeq Saleh, Chunshan Hu, and Rahul Panat. Science Advances  03 Mar 2017: Vol. 3, no. 3, e1601986 DOI: 10.1126/sciadv.1601986

This paper appears to be open access.

Finally, there is a video,

Gold nanoparticles and the air that you breathe

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Scientists at the (US Dept. of Energy) Brookhaven National Laboratory can turn gold nanoparticles into catalysts using a room temperature process. From the June 11, 2013 news item on ScienceDaily,

Gold bars may signify great wealth, but the precious metal packs a much more practical punch when shrunk down to just billionths of a meter. Unfortunately, unlocking gold’s potential often requires complex synthesis techniques that produce delicate structures with extreme sensitivity to heat.

Now, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have discovered a process of creating uniquely structured gold-indium nanoparticles that combine high stability, great catalytic potential, and a simple synthesis process. The new nanostructures — detailed online June 10 in the Proceedings of the National Academy of Sciences — might enhance many different commercial and industrial processes, including acting as an efficient material for catalytic converters in cars.

“We discovered a room-temperature process that transforms a simple alloy into a nanostructure with remarkable properties,” said physicist Eli Sutter, lead author on the study. “By exposing the gold-indium alloy nanoparticles to air, ambient oxygen was able to drive an oxidation reaction that converted them into an active core-shell structure.”

The Brookhaven National Laboratory June 11, 2013 news release, which originated the news item, explains the issues with gold nanoparticles and how the ‘room temperature’ discovery was made,

The Brookhaven Lab researchers were studying oxidation processes through which metals and alloys combine with oxygen when they made the discovery. For this study, they examined alloys of a noble metal and a non-noble metal through a remarkably simple reaction technique: giving gold-indium nanoparticles a little room to breathe. Once nanoparticles of the metal alloy were exposed to oxygen, highly reactive shells of gold-indium oxide formed across their surfaces.

“Conventional wisdom would say that oxidation should push the gold atoms into the center while pulling the less noble indium to the surface, creating a noble metal core that is surrounded by a shell of non-reactive indium-oxide,” Peter Sutter said. “Instead, the oxygen actually penetrated the alloy. After oxidation, the alloy core of the nanoparticles was encapsulated by a newly formed thin shell of mixed gold-indium oxide.”

Trapping gold in the amorphous oxide shell retains its catalytic properties and prevents the gold from sintering and becoming inert. The new nanostructures proved capable of converting oxygen and carbon monoxide into carbon dioxide, demonstrating their activity as a catalyst.

“The indium and gold in the shell are not mobile, but are frozen in the amorphous, oxide,” Eli Sutter said. “Importantly, the structural integrity holds without sintering at temperatures of up to 300 degrees Celsius, making these remarkably resilient compared to other gold nanocatalysts.”

The research was conducted at Brookhaven Lab’s Center for Functional Nanomaterials (CFN), whose unique facilities for nanoscale synthesis and characterization proved central to the discovery of this new process.

“The CFN brings a wide range of state-of-the-art instruments and expertise together under one roof, accelerating research and facilitating collaboration,” Eli Sutter said. “We used transmission electron microscopy to characterize the structures and their composition, x-ray photoelectron spectroscopy to determine the chemical bonding at the surface, and ion-scattering spectroscopy to identify the outermost atoms of the nanoparticle shell.”

Further investigations will help determine the properties of the gold-indium oxide particles in different catalytic reactions, and the same oxidation process will be applied to other metal alloys to create an entire family of new functional materials.

You can find a citation and a link to the researchers’ paper if you click on the ScienceDaily news item link earlier in this posting.