Chemists develop 'fresh, new' approach to making alloy nanomaterials

Aug 09, 2013
Associate professor Mathew M. Maye, right, supervises research assistant Wenjie Wu G'11, G'13. The two led a team that has figured out how to synthesize nanomaterials with stainless steel-like interfaces. Credit: Stephen Sartori

Chemists in The College of Arts and Sciences have figured out how to synthesize nanomaterials with stainless steel-like interfaces. Their discovery may change how the form and structure of nanomaterials are manipulated, particularly those used for gas storage, heterogeneous catalysis and lithium-ion batteries.

The findings are the subject of a July 24 article in the journal Small, co-authored by associate professor Mathew M. Maye and research assistant Wenjie Wu G'11, G'13.

Until now, scientists have used many wet-chemical approaches—collectively known as colloidal synthesis—to manipulate reactions in which metallic ions form alloys at the nanoscale. Here, are typically 2 to 50 in size and have highly unique properties, including various colors, high reactivity and novel chemistry.

Maye and Wu are part of a growing team of international chemists and devising new ways to alter the size, shape and composition of nanoparticles.

"At SU, we have developed a new synthetic pathway to tailor the internal microstructure of nanomaterials," says Maye, whose research spans inorganic chemistry, catalysis, materials science, self-assembly and biotechnology.

Maye's approach begins with a pre-synthesized iron nanoparticle core. After synthesizing the core in its crystalline metallic form, he and Wu chemically deposit thin shells of chromium onto the iron. When the "core/shell" nanoparticles are exposed to , they anneal. Moreover, the iron and chromium diffuse into one another, forming an iron-chromium alloy shell. Thus, the "core/alloy" product has an interface similar to some forms of stainless steel.

Since stainless steel is known for its resistance to oxidation, the big challenge for Maye and Wu has been finding out how nanoparticles cope during this process.

"We've discovered that nanoparticles exhibit a unique behavior when oxidized," he says. "A thin, iron-chromium oxide shell forms, leaving behind an unoxidized iron core. Even more interesting is the fact that a void forms, separating the core from the shell. This phenomenon is known in materials science as Kirkendall Diffusion, or Vacancy Coalescence."

This kind of work, he adds, wouldn't be possible without high-resolution electron microscopy, X-ray diffraction and magnetic measurements.

Although "core/alloy" fabrication is a new approach, it may allow for more diverse forms of alloy nanomaterials.

"Most alloys we take for granted at the macroscale, such as steel, are hard to fabricate at the nanoscale, because of ease of oxidation and other specific conditions that are required," says Maye. "Our approach may open new doors."

A recipient of many honors and awards, including the Presidential Early Career Award for Scientists and Engineers, Maye joined SU's faculty in 2008.

Wu, whose expertise encompasses synthesis, was the lead graduate student on the project. In August, she earns a Ph.D. in from SU.

Explore further: Demystifying nanocrystal solar cells

More information: onlinelibrary.wiley.com/doi/10… l.201301420/abstract

Related Stories

Complexity in core-shell nanomagnets

Feb 15, 2011

The magnetic exchange bias coupling between core and shell depends critically on the "frozen spins" that reside at the interface between the two different magnetic nanomaterials, according to users from Purdue ...

Disorder creates rust protection

Aug 09, 2013

Corrosion eats away 75 billion euros of economic output annually in Germany alone. But it may soon be possible to better assess which steels and other alloys will be affected, and how to limit the damage: ...

Researchers use nanotechnology to harness power of fireflies

Jun 15, 2012

What do fireflies, nanorods and Christmas lights have in common? Someday, consumers may be able to purchase multicolor strings of light that don't need electricity or batteries to glow. Scientists in Syracuse University's ...

A novel nanobio catalyst for biofuels

Aug 31, 2012

(Phys.org)—Nanoparticles synthesized from noble metals such as ruthenium, rhodium, palladium, silver (Ag), osmium, iridium, platinum, and gold (Au) are attracting increased attention by researchers around ...

Recommended for you

Demystifying nanocrystal solar cells

Jan 28, 2015

ETH researchers have developed a comprehensive model to explain how electrons flow inside new types of solar cells made of tiny crystals. The model allows for a better understanding of such cells and may ...

Researchers use oxides to flip graphene conductivity

Jan 26, 2015

Graphene, a one-atom thick lattice of carbon atoms, is often touted as a revolutionary material that will take the place of silicon at the heart of electronics. The unmatched speed at which it can move electrons, ...

Researchers make magnetic graphene

Jan 26, 2015

Graphene, a one-atom thick sheet of carbon atoms arranged in a hexagonal lattice, has many desirable properties. Magnetism alas is not one of them. Magnetism can be induced in graphene by doping it with magnetic ...

The latest fashion: Graphene edges can be tailor-made

Jan 23, 2015

Theoretical physicists at Rice University are living on the edge as they study the astounding properties of graphene. In a new study, they figure out how researchers can fracture graphene nanoribbons to get ...

Nanotechnology changes behavior of materials

Jan 23, 2015

One of the reasons solar cells are not used more widely is cost—the materials used to make them most efficient are expensive. Engineers are exploring ways to print solar cells from inks, but the devices ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.