Miniaturizing microscopic metallic objects while enhancing their strength is critical to developing high-performance devices that integrate transistor-like electronics with mechanical components.
When these objects consist of small crystals, or grains, such as polycrystalline nanopillars, their mechanical behavior is difficult to predict because the grains vary in size and orientation. Researchers from the California Institute of Technology, USA, and A*STAR Institute of High Performance Computing (IHPC), Singapore, have now determined how miniaturization and intrinsic granular structure impact the deformation of ultra-small platinum cylinders¹.
The team used a combined experimental and computational approach to overcome the knowledge gap hindering the production of reliable micro- and nano-electromechanical devices. Team member Zhaoxuan Wu from IHPC explains that this approach allowed them to reduce the size of the experimental samples to tens of nanometers. It also allowed them to perform large-scale atomic simulations on comparable nanostructures, which provided a means to directly link structure and mechanical properties. “This is rarely achievable in such studies,” he notes.
The researchers first generated a template by depositing a polymer film on a gold-coated silicon surface and perforating it with nano- to micrometer-sized cylindrical holes. Next, they synthesized the metal nanostructures in these holes from a platinum precursor solution. Dissolving the template then produced nanopillars that displayed well-defined grains of similar sizes and grain boundaries, or interfaces.
Compression experiments on the nanostructures showed that the thinnest nanopillars remained almost cylindrical under low pressure but weakened dramatically, and bent irreversibly, under high pressure. In contrast, wider nanopillars exhibited a smoother deformation and delayed failure. This ‘smaller is weaker’ trend is contrary to the fate observed for metallic single crystals: they become stronger with smaller diameters. Wu and co-workers also found that reducing the number of grains across a nanopillar’s diameter weakened the structure.
In agreement with their experimental results, the researchers’ numerical simulations revealed that the compressed nanopillars gradually underwent reversible and subsequent irreversible deformation (see image). Moreover, the simulations indicated the origin within the nanostructures of the irreversible deformation and dislocation motions. The nanopillars contain a high density of grain boundaries that promote the formation of dislocations. These dislocations, through which a specific type of deformation develops, propagate across an entire grain or from one grain to another inside the cores. Close to the nanopillar surface, the grains easily slide against each other to create atom-sized steps, reducing material strength.
“We are further examining the effects of microstructural flaws and oxidations on the mechanical behavior of nanomaterials,” says Wu.
The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing
Gu, X. W., Loynachan, C. N., Wu, Z., Zhang, Y.-W., Srolovitz, D. J. & Greer, J. R. Size-dependent deformation of nanocrystalline Pt nanopillars. Nano Letters 12, 6385–6392 (2012). | articleAssociated links
New gel-like coating beefs up the performance of lithium-sulfur batteries
22.03.2017 | Yale University
Pulverizing electronic waste is green, clean -- and cold
22.03.2017 | Rice University
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
22.03.2017 | Materials Sciences
22.03.2017 | Physics and Astronomy
22.03.2017 | Materials Sciences