Image showing the thread-like particles formed by iron and nickel and the more spherical clusters formed by copper. Source: Abbaschian, Zachariah et. al. 2021
In order for metallic nanomaterials to deliver on their energy and electronics promise, they literally have to get in shape.
To deliver reliable mechanical and electrical properties, nanomaterials must have consistent, predictable shapes and surfaces, as well as scalable production techniques. UC Riverside engineers solve this problem by evaporating metals in a magnetic field to direct the rearrangement of metal atoms into predictable shapes. The research was published in the Journal of Physical Chemistry Letters.
Nanomaterials, which consist of particles 1-100 nanometers in size, are typically produced in a liquid matrix, which is expensive for mass production applications and in many cases cannot produce pure metals such as aluminum or magnesium. More economical production techniques typically involve vapor phase approaches to create a cloud of particles that condense from the vapor. These suffer from a lack of control.
Reza Abbaschian, a respected professor of mechanical engineering; and Michael Zachariah, a distinguished professor of chemical and environmental engineering at UC Riverside’s Marlan and Rosemary Bourns College of Engineering; came together to produce nanomaterials from iron, copper and nickel in a gas phase. They placed solid metal in a powerful electromagnetic levitation coil to heat the metal above its melting point and vaporize it. The metal droplets floated in the gas within the coil and moved in directions determined by their inherent responses to magnetic forces. As the droplets combined, they did so in an orderly fashion, so the researchers learned that they could predict based on the type of metal and how and where they applied the magnetic fields.
Iron and nickel nanoparticles formed thread-like aggregates, while copper nanoparticles formed spherical clusters. When deposited on a carbon film, iron and nickel aggregates gave the film a porous surface, while carbon aggregates gave it a more compact, firmer surface. The qualities of the materials on the carbon film reflected, on a larger scale, the properties of each type of nanoparticle.
Since the field can be viewed as an “add-on”, this approach could be applied to any vapor phase nanoparticle generation source where structure is important, such as mechanical properties.
“This ‘field-directed’ approach makes it possible to manipulate the assembly process and change the architecture of the resulting particles from objects with high fractal dimensions to chain-like structures with smaller dimensions. said Zacharias.
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Pankaj Ghildiyal, et al. Magnetic Field Controlled Vapor Phase Arrangement of Metal Nanostructures with Small Fractal Dimensions: Experiment and Theory, The Journal of Physical Chemistry Letters (2021). DOI: 10.1021 / acs.jpclett.0c03463 Provided by University of California – Riverside
citation: Electromagnetic levitation whips nanomaterials into shape (2021, May 11), accessed July 24, 2021 from https://phys.org/news/2021-05-electromagnetic-levitation-nanomaterials.html
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