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One of the main reasons for limiting the operating lifetimes of nuclear reactors is that metals exposed to the strong radiation environment near the reactor core become porous and brittle, which can lead to cracking and failure. Now, a team of researchers at MIT and elsewhere has found that, at least in some reactors, adding a tiny quantity of carbon nanotubes to the metal can dramatically slow this breakdown process. For now, the method has only proved effective for aluminum, which limits its applications to the lower-temperature environments found in research reactors. But the team says the method may also be usable in the higher-temperature alloys used in commercial reactors. The findings are described in the journal Nano Energy, in a paper by MIT Professor Ju Li, postdocs Kang Pyo So and Mingda Li, research scientist Akihiro Kushima, and 10 others at MIT, Texas A&M University, and universities in South Korea, Chile, and Argentina. Aluminum is currently used in not only research reactor components but also nuclear batteries and spacecraft, and it has been proposed as material for storage containers for nuclear waste. So, improving its operating lifetime could have significant benefits, says Ju Li, who is the Battelle Energy Alliance Professor of Nuclear Science and Engineering and a professor of materials science and engineering. The metal with carbon nanotubes uniformly dispersed inside “is designed to mitigate radiation damage” for long periods without degrading, says Kang Pyo So. Helium from radiation transmutation takes up residence inside metals and causes the material to become riddled with tiny bubbles along grain boundaries and progressively more brittle, the researchers explain. The nanotubes, despite only making up a small fraction of the volume — less than 2 percent — can form a percolating, one-dimensional transport network, to provide pathways for the helium to leak back out instead of being trapped within the metal, where it could continue to do damage. Testing showed that after exposure to radiation, the carbon nanotubes within the metal can be chemically altered to carbides, but they still retain their slender shape, “almost like insects trapped in amber,” Ju Li says. “It’s quite amazing — you don’t see a blob; they retain their morphology. It’s still one-dimensional.” The huge total interfacial area of these 1-D nanostructures provides a way for radiation-induced point defects to recombine in the metal, alleviating a process that also leads to embrittlement. The researchers showed that the 1-D structure was able to survive up to 70 DPA of radiation damage. (DPA is a unit  that refers to how many times, on average, every atom in the crystal lattice is knocked out of its site by radiation, so 70 DPA means a lot of radiation damage.) After radiation exposure, Ju Li says, “we see pores in the control sample, but no pores” in the new material, “and mechanical data shows it has much less embrittlement.” For a given amount of exposure to radiation, the tests have shown the amount of embrittlement is reduced about five to tenfold. The new material needs only tiny quantities of carbon nanotubes (CNTs) — about 1 percent by weight added to the metal — and these are inexpensive to produce and process, the team says. The composite can be manufactured at low cost by common industrial methods and is already being produced by the ton by manufacturers in Korea, for the automotive industry. Even before exposure to radiation, the addition of this small amount of nanotubes improves the strength of the material by 50 percent and also improves its tensile ductility — its ability to deform without breaking — the team says. “This is a proof of principle,” says Kang Pyo So. While the material used for testing was aluminum, the team plans to run similar tests with zirconium, a metal widely used for high-temperature reactor applications such as the cladding of nuclear fuel pellets. “We think this is a generic property of metal-CNT systems,” he says. “This is a development of considerable significance for nuclear materials science, where composites — particularly oxide dispersion-strengthened steels — have long been considered promising candidate materials for applications involving high temperature and high irradiation dose,” says Sergei Dudarev, a professor of materials science at Oxford University in the U.K., who was not involved in this work. Dudarev adds that this new composite material “proves remarkably stable under prolonged irradiation, indicating that the material is able to self-recover and partially retain its original properties after exposure to high irradiation dose at room temperature. The fact that the new material can be produced at relatively low cost is also an advantage.” Sergei Kucheyev, a physicist at the Lawrence Livermore National Laboratory who also was not involved in this research, says, “These results could have important technological implications. They also point to our still-limited understanding of the physics of radiation defects at interfaces in technologically relevant regimes.” The team also included researchers Sangtae Kim, Yang Yang, and Ziqiang Wang at MIT; Di Chen and Shao Lin at Texas A&M University; Jong Gil Park and Young Hee Lee at the Institute for Basic Science in South Korea; Rafael Gonzalez and Miguel Kiwi at the University of Chile; and Eduardo Bringa at the National University of Cuyo, in Argentina. The work was supported by the U.S. Department of Energy and the National Research Foundation of Korea.


Home > Press > Carbon nanotubes improve metal’s longevity under radiation: Aluminum used in nuclear reactors and other harsh environments may last longer with new treatment Abstract: One of the main reasons for limiting the operating lifetimes of nuclear reactors is that metals exposed to the strong radiation environment near the reactor core become porous and brittle, which can lead to cracking and failure. Now, a team of researchers at MIT and elsewhere has found that, at least in some reactors, adding a tiny quantity of carbon nanotubes to the metal can dramatically slow this breakdown process. For now, the method has only proved effective for aluminum, which limits its applications to the lower-temperature environments found in research reactors. But the team says the method may also be usable in the higher-temperature alloys used in commercial reactors. The findings are described in the journal Nano Energy, in a paper by MIT Professor Ju Li, postdocs Kang Pyo So and Mingda Li, research scientist Akihiro Kushima, and 10 others at MIT, Texas A&M University, and universities in South Korea, Chile, and Argentina. Aluminum is currently used in not only research reactor components but also nuclear batteries and spacecraft, and it has been proposed as material for storage containers for nuclear waste. So, improving its operating lifetime could have significant benefits, says Ju Li, who is the Battelle Energy Alliance Professor of Nuclear Science and Engineering and a professor of materials science and engineering. Long-term stability The metal with carbon nanotubes uniformly dispersed inside “is designed to mitigate radiation damage” for long periods without degrading, says Kang Pyo So. Helium from radiation transmutation takes up residence inside metals and causes the material to become riddled with tiny bubbles along grain boundaries and progressively more brittle, the researchers explain. The nanotubes, despite only making up a small fraction of the volume — less than 2 percent — can form a percolating, one-dimensional transport network, to provide pathways for the helium to leak back out instead of being trapped within the metal, where it could continue to do damage. Testing showed that after exposure to radiation, the carbon nanotubes within the metal can be chemically altered to carbides, but they still retain their slender shape, “almost like insects trapped in amber,” Ju Li says. “It’s quite amazing — you don’t see a blob; they retain their morphology. It’s still one-dimensional.” The huge total interfacial area of these 1-D nanostructures provides a way for radiation-induced point defects to recombine in the metal, alleviating a process that also leads to embrittlement. The researchers showed that the 1-D structure was able to survive up to 70 DPA of radiation damage. (DPA is a unit that refers to how many times, on average, every atom in the crystal lattice is knocked out of its site by radiation, so 70 DPA means a lot of radiation damage.) After radiation exposure, Ju Li says, “we see pores in the control sample, but no pores” in the new material, “and mechanical data shows it has much less embrittlement.” For a given amount of exposure to radiation, the tests have shown the amount of embrittlement is reduced about five to tenfold. The new material needs only tiny quantities of carbon nanotubes (CNTs) — about 1 percent by weight added to the metal — and these are inexpensive to produce and process, the team says. The composite can be manufactured at low cost by common industrial methods and is already being produced by the ton by manufacturers in Korea, for the automotive industry. Strength and resilience Even before exposure to radiation, the addition of this small amount of nanotubes improves the strength of the material by 50 percent and also improves its tensile ductility — its ability to deform without breaking — the team says. “This is a proof of principle,” says Kang Pyo So. While the material used for testing was aluminum, the team plans to run similar tests with zirconium, a metal widely used for high-temperature reactor applications such as the cladding of nuclear fuel pellets. “We think this is a generic property of metal-CNT systems,” he says. “This is a development of considerable significance for nuclear materials science, where composites — particularly oxide dispersion-strengthened steels — have long been considered promising candidate materials for applications involving high temperature and high irradiation dose,” says Sergei Dudarev, a professor of materials science at Oxford University in the U.K., who was not involved in this work. Dudarev adds that this new composite material “proves remarkably stable under prolonged irradiation, indicating that the material is able to self-recover and partially retain its original properties after exposure to high irradiation dose at room temperature. The fact that the new material can be produced at relatively low cost is also an advantage.” The team also included researchers Sangtae Kim, Yang Yang, and Ziqiang Wang at MIT; Di Chen and Shao Lin at Texas A&M University; Jong Gil Park and Young Hee Lee at the Institute for Basic Science in South Korea; Rafael Gonzalez and Miguel Kiwi at the University of Chile; and Eduardo Bringa at the National University of Cuyo, in Argentina. The work was supported by the U.S. Department of Energy and the National Research Foundation of Korea. ### Written by David L. Chandler, MIT News Office For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


Home > Press > New type of nanowires, built with natural gas heating: UNIST research team developed a new simple nanowire manufacturing technique Abstract: A team of Korean researchers, affiliated with UNIST has recently pioneered in developing a new simple nanowire manufacturing technique that uses self-catalytic growth process assisted by thermal decomposition of natural gas. According to the research team, this method is simple, reproducible, size-controllable, and cost-effective in that lithium-ion batteries could also benefit from it. In their approach, they discovered that germanium nanowires are grown by the reduction of germanium oxide particles and subsequent self-catalytic growth during the thermal decomposition of natural gas, and simultaneously, carbon sheath layers are uniformly coated on the nanowire surface. This study is a collaboration among scientists, including Prof. SooJin Park (School of Energy and Chemical Engineering) and Prof. Sang Kyu Kwak (School of Energy and Chemical Engineering), Dr. Sinho Choi (UNIST), Combined M.S./Ph.D. Student Dae Yeon Hwang (UNIST), and Researcher Jieun Kim (Korea Research Institute of Chemical Technology). In a study, reported in the January 21, 2016 issue of Nano Letters, the team demonstrated a new redox-responsive assembly method to synthesize hierarchically structured carbon-sheathed germanium nanowires (c-GeNWs) on a large scale by the use of self-catalytic growth process assisted by thermally decomposed natural gas. According to the team, this simple synthetic process not only enables them to synthesize hierachially assembled materials from inexpensive metal oxides at a larger scale, but also can likely be extended to other metal oxides as well. Moreover, the resulting hierarchically assembled nanowires (C-GeNWs) show enhanced chemical and thermal stability, as well as outstanding electrochemical properties. The team states, "This strategy may open up an effective way to make other metallic/semiconducting nanomaterials via one-step synthetic reactions through an environmentally benign and cost-effective approach." ### This work was supported by the Basic Science Research Program and Mid-Career Research Program through the National Research Foundation of Korea (NRF) grand, funded by the Korean government (MSIP). For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.


News Article | April 5, 2016
Site: http://www.cemag.us/rss-feeds/all/rss.xml/all

Professor Wan Kyun Chung of Pohang University of Science and Technology’s Department of Mechanical Engineering — together with PhD student Young Jin Heo, MS student Junsu Kang, and postdoctoral researcher Min Jun Kim in the Robotics Laboratory — has developed a novel control algorithm to resolve critical problems induced from a Proportional-Integral-Derivative (PID) controller by automatizing the technical tuning process. Their research was published in Scientific Reports. “Lab-on-a-chip” designates devices that integrate various biochemical functions on a fingernail-sized chip to enable quick and compact biological analysis or medical diagnosis by processing a small volume of biological samples, such as a drop of blood. To operate various functions on a lab-on-a-chip device, the key technology is the precise and rapid manipulation of fluid on a micro-scale. In microfluidic devices, very small and trivial variables can frequently cause a large amount of errors. Up until now, the PID controller has normally been used for the manipulation of fluids in microfluidic chips. To apply the PID controller, a tedious gain-tuning process is required but the gain-tuning is a difficult process for people who are unfamiliar with control theory. In the case of controlling multiple flows, the process is extremely convoluted and frustrating. The developed control algorithm can improve accuracy and stability of flow regulation in a microfluidic network without requiring any tuning process. With this algorithm, microfluidic flows in multiple channels can be controlled in simultaneous and independent way. The team expects that this algorithm has the potential for many applications of lab-on-a-chip devices. For example, cell culture or biological analysis, which are conducted in biology laboratories, can be performed on a microfluidic chip. Physical and chemical responses can be analyzed in the subdivided levels. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP). Source: Pohang University of Science and Technology


The KONNECT project will strengthen STI cooperation between the EU and Republic of Korea, promoting innovation and the enhancement of communication for technology-related policy dialogue. This project brings together seven organizations from the EU and the Republic of Korea to improve and sustain communication between the two regions at the research and policy level and increase the expand the scope of STI networks and activities. The fulfilment of these objectives will improve the overall level of prosperity in both Europe and Korea and contribute to the resolution of natural and societal issues and threats facing the world. The main activities of the KONNECT project will work towards progressing research in four central fields of mutual interest: Information and Communications Technology (ICT), Nanosciences, Nanotechnologies, Materials, and New Production Technologies (NMP), Green Technology and Secure, Clean, and Efficient Energy (GT), and Biotechnologies (BT). The projects consortium will organise important activities within the set parameters of the project, and focus on key issues such as raising awareness for Horizon 2020, advancing innovation as well as R&D, and expanding joint activities under thematic areas. Due to the newly announced EU R&D Framework Programme (Horizon 2020) and Koreas upcoming government changeover in 2013, initiating new collaborative activities between the two sides takes on even greater importance. The KONNECT project will be committed to adhering to the following broad objectives: 1) Developing Knowledge-based Infrastructure, 2) Improving Strategic Communication, 3) Raising Awareness to Facilitate Cooperation between the EU and Korea, 4) Enhancing Networking between Science, Technology, and Innovation-focused Actors, and 5) Fostering Innovation-focused Joint Activities. This project will allow Korea to utilise its assets to assist the EU as it works towards achieving its goals for Europe 2020.

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