Nano News: 04/29/15

Physics of heavy ion induced damage in nanotwinned metals revealed

A group of researchers in the Department of Mechanical Engineering and the Department of Materials Science and Engineering at Texas A&M University led by Dr. Xinghang Zhang has investigated defect dynamics in heavy ion (Krypton) irradiated nanotwinned Ag and revealed twin boundary-defect clusters interactions via in situ radiation.

study on twin boundary (TB) affected zone in irradiated nanotwinned Ag

High energy particles introduce severe radiation damage in metallic materials, such as Ag. This paper reports on the study on twin boundary (TB) affected zone in irradiated nanotwinned Ag wherein time accumulative defect density and defect diffusivity are substantially different from those in twin interior. In situ studies also reveal surprising resilience and self-healing of TBs in response to radiation. This study provides further support for the design of radiation-tolerant nanotwinned metallic materials. © ACS) The design of next generation nuclear reactors calls for materials with superior radiation tolerance. Under the extreme radiation conditions, a large number of defects and their clusters are generated and consequently result in mechanical instability of irradiated metallic materials. While studying radiation damage in nanotwinned Ag by in-situ irradiation technique at the IVEM facility at Argonne National Laboratory, Zhang’s students, Jin Li and Kaiyuan Yu discovered two interesting phenomena. First, they identified twin boundary affected zones wherein time accumulative defect density and defect diffusivity are substantially different from those in twin interior. Additionally, in situ studies also revealed excellent resilience of twin boundaries in response to radiation: twin boundaries continue to change their geometry to facilitate the capture, transportation and removal of defect clusters. Furthermore twin boundaries can recover by absorbing opposite type of defects. “Without performing time accumulative studies, we would have missed the existence of twin boundary affected zones”, said Li. “This study provides further support for the implementation of twin boundaries as effective defect sinks for the design of radiation tolerant nanostructured metallic materials”, added Yu, who is now an assistant professor in China. The paper, "In situ Study of Defect Migration Kinetics and Self-Healing of Twin Boundaries in Heavy Ion Irradiated Nanotwinned Metals" was published in the April 2015 issue in .

How to grow nanostructures in a controlled manner on a variety of metals

Materials scientist Irem Tanyeli from energy research institute DIFFER has discovered how you can grow nanostructures in a controlled manner on a variety of metals, by bombarding the metals with helium particles. Such controlled nanostructures provide the possibility of advanced electrodes that produce sustainable fuel using solar energy. Tanyeli and her fellow researchers from DIFFER, ITER and the University of Basel published their results in on 28 April 2015 ("Surface Modifications Induced by High Fluxes of Low Energy Helium Ions").

A nanostructured electrode produced from widely available iron can use sunlight to cheaply produce the energy carrier hydrogen on a large scale. (Image: ICMS / DIFFER) Blowing bubbles in metal In their research Tanyeli and her colleagues exposed different metal surfaces to a hot intense beam of charged helium gas (plasma) in DIFFER's plasma experiment Magnum-PSI. Helium easily penetrates into the metal lattice where it forms bubbles that push the surrounding metal outwards. In this way different structures of tens to hundreds of nanometres in size arise per metal. By describing the differences, Tanyeli could analyse which underlying processes formed the nanostructures such as the temperature and the structure of the metal lattice. That helium plasma can cause a metal to explode in nanostructures had previously been discovered when researchers tested wall materials for fusion energy reactors. They then discovered strange shapes on the metal wall surface. In a fusion reactor these nanostructures are undesirable because they reduce the discharge of heat, but in other applications the nanostructures are very useful, thinks co-researcher and DIFFER director Richard van de Sanden.

Nanostructures on aluminium. Overview (a) and cross-section (b) of nanostructures on an aluminium surface. (©Tanyeli et al. / Nature Scientific Reports) Fundamental insight "Irem Tanyeli's research is important due to the fundamental insight", says Van de Sanden. "How do such nanostructures grow on a surface, which processes play a role in that, what are the bottlenecks, and how can you manage the process? If you understand that then you can produce advanced materials on a large-scale that can be given properties to order." That has a wide range of applications in sustainable energy technologies. Converting sunlight into hydrogen Tanyeli's nanostructures are interesting for catalyst applications such as the use of solar energy to produce hydrogen from water. Widely available and cheap materials can usually not compete against the efficiency of expensive but rare record holders such as platinum. But with the right nanostructures the cheaper materials can still be made competitive. That opens up possibilities for the large-scale storage and conversion of sustainable energy in the form of chemical compounds: solar fuels. Such fuels have no net CO2-emission and therefore offer opportunities for the transport sector. Solar fuels are seen as an important way of storing sustainable energy, for example the solar energy that is generated during the sun-rich summer can be stored for use during the dark winter.

Developing portable, highly sensitive gold detection down to nanoparticles

University of Adelaide researchers are developing a portable, highly sensitive method for gold detection that would allow mineral exploration companies to test for gold on-site at the drilling rig. Using light in two different processes (fluorescence and absorption), the researchers from the University’s Institute for Photonics and Advanced Sensing (IPAS), have been able to detect gold nanoparticles at detection limits 100 times lower than achievable under current methods. Australia is the world’s second largest gold producer, worth $13 billion in export earnings. "Gold is not just used for jewellery, it is in high demand for electronics and medical applications around the world, but exploration for gold is extremely challenging with a desire to detect very low concentrations of gold in host rocks," says postdoctoral researcher Dr Agnieszka Zuber, working on the project with Associate Professor Heike Ebendorff-Heidepriem. "The presence of gold deep underground is estimated by analysis of rock particles coming out of the drilling holes. But current portable methods for detection are not sensitive enough, and the more sensitive methods require some weeks before results are available. "This easy-to-use sensor will allow fast detection right at the drill rig with the amount of gold determined within an hour, at much lower cost." The researchers have been able to detect less than 100 parts per billion of gold in water. They are now testing using samples of real rock with initial promising results. The work is funded by the Deep Exploration Technologies Cooperative Research Centre. The gold detection project is one of a series of projects which will be presented at the IPAS Minerals and Energy Sector Workshop today, aimed at linking resources specific research to local companies. Industry representatives will also hear about the Photonics Catalyst Program, a joint State Government and IPAS initiative which supports connections between advanced photonics technologies and SA industry. Manufacturing and Innovation Minister Kyam Maher says IPAS’s collaboration with partners is stimulating new technologies and contributing to the State’s reputation as a knowledge economy. "The Photonics Catalyst Program helps South Australian businesses, including resources-related companies, identify the emerging laser and sensor technologies that could transform their products or business models," Mr Maher says. "Technology plays a central role in the competitiveness of South Australian manufacturing, supporting innovation, driving product and service development and improving manufacturing performance. It will play a key role in driving change and will underpin the transformation of the South Australian economy."