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Haifa, Israel

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Haifa, Israel
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News Article | May 26, 2017
Site: www.chromatographytechniques.com

The shells of marine organisms take a beating from impacts due to storms and tides, rocky shores, and sharp-toothed predators. But as recent research has demonstrated, one type of shell stands out above all the others in its toughness: the conch. Now, researchers at MIT have explored the secrets behind these shells’ extraordinary impact resilience. And they’ve shown that this superior strength could be reproduced in engineered materials, potentially to provide the best-ever protective headgear and body armor. The findings are reported in the journal Advanced Materials, in a paper by MIT graduate student Grace Gu, postdoc Mahdi Takaffoli, and McAfee Professor of Engineering Markus Buehler. Conch shells “have this really unique architecture,” Gu explains. The structure makes the material 10 times tougher than nacre, commonly known as mother of pearl. This toughness, or resistance to fractures, comes from a unique configuration based on three different levels of hierarchy in the material’s internal structure. The three-tiered structure makes it very hard for any tiny cracks to spread and enlarge, Gu says. The material has a “zigzag matrix, so the crack has to go through a kind of a maze” in order to spread, she says. Until recently, even after the structure of the conch shell was understood, “you couldn’t replicate it that well. But now, our lab has developed 3-D printing technology that allows us to duplicate that structure and be able to test it,” says Buehler, who is the head of the Department of Civil and Environmental Engineering. Part of the innovation involved in this project was the team’s ability to both simulate the material’s behavior and analyze its actual performance under realistic conditions. “In the past, a lot of testing [of protective materials] was static testing,” Gu explains. “But a lot of applications for military uses or sports involve highly dynamic loading,” which requires a detailed examination of how an impact’s effects spread out over time. For this work, the researchers did tests in a drop tower that enabled them to observe exactly how cracks appeared and spread — or didn’t spread — in the first instants after an impact. “There was amazing agreement between the model and the experiments,” Buehler says. That’s partly because the team was able to 3-D print composite materials with precisely controlled structures, rather than using samples of real shells, which can have unpredictable variations that can complicate the analysis. By printing the samples, “we can use exactly the same geometry” as used in the computer simulations, “and we get very good agreement.” Now, in continuing the work, they can focus on making slight variations “as a basis for future optimization,” Buehler says. To test the relative importance of the three levels of structure, the team tried making variations of the material with different levels of hierarchy. Higher levels of hierarchy are introduced by incorporating smaller length-scale features into the composite, as in an actual conch shell. Sure enough, lower-level structures proved to be significantly weaker than the highest level pursued in this study, which consisted of the cross-lamellar features inherent in natural conch shells. Testing proved that the geometry with the conch-like, criss-crossed features was 85 percent better at preventing crack propagation than the strongest base material, and 70 percent better than a traditional fiber composite arrangement, Gu says. Protective helmets and other impact-resistant gear require a key combination of both strength and toughness, Buehler explains. Strength refers to a material’s ability to resist damage, which steel does well, for example. Toughness, on the other hand, refers to a material’s ability to dissipate energy, as rubber does. Traditional helmets use a metal shell for strength and a flexible liner for both comfort and energy dissipation. But in the new composite material, this combination of qualities is distributed through the whole material. “This has stiffness, like glass or ceramics,” Buehler says, but it lacks the brittleness of those materials, thanks to the integration of materials with different degrees of strength and flexibility within the composite structure. Like plywood, the composite is made up of layers whose “grain,” or the internal alignment of its materials, is oriented differently from one layer to the next. Because of the use of 3-D printing technology, this system would make it possible to produce individualized helmets or other body armor. Each helmet, for example, could be “tailored and personalized; the computer would optimize it for you, based on a scan of your skull, and the helmet would be printed just for you,” Gu says. These researchers “ingeniously used 3-D printing and experimentation to elucidate the effect of material hierarchy on bioinspired composites,” says Horacio Espinosa, a professor of mechanical engineering and director of the Theoretical and Applied Mechanics program at Northwestern University, who was not involved in this work. “An interesting remaining question,” he says, “is the applicability of the conch shell design to curved surfaces like those one would encounter in helmets.”


News Article | May 26, 2017
Site: www.sciencedaily.com

The shells of marine organisms take a beating from impacts due to storms and tides, rocky shores, and sharp-toothed predators. But as recent research has demonstrated, one type of shell stands out above all the others in its toughness: the conch. Now, researchers at MIT have explored the secrets behind these shells' extraordinary impact resilience. And they've shown that this superior strength could be reproduced in engineered materials, potentially to provide the best-ever protective headgear and body armor. The findings are reported in the journal Advanced Materials, in a paper by MIT graduate student Grace Gu, postdoc Mahdi Takaffoli, and McAfee Professor of Engineering Markus Buehler. Conch shells "have this really unique architecture," Gu explains. The structure makes the material 10 times tougher than nacre, commonly known as mother of pearl. This toughness, or resistance to fractures, comes from a unique configuration based on three different levels of hierarchy in the material's internal structure. The three-tiered structure makes it very hard for any tiny cracks to spread and enlarge, Gu says. The material has a "zigzag matrix, so the crack has to go through a kind of a maze" in order to spread, she says. Until recently, even after the structure of the conch shell was understood, "you couldn't replicate it that well. But now, our lab has developed 3-D printing technology that allows us to duplicate that structure and be able to test it," says Buehler, who is the head of the Department of Civil and Environmental Engineering. Part of the innovation involved in this project was the team's ability to both simulate the material's behavior and analyze its actual performance under realistic conditions. "In the past, a lot of testing [of protective materials] was static testing," Gu explains. "But a lot of applications for military uses or sports involve highly dynamic loading," which requires a detailed examination of how an impact's effects spread out over time. For this work, the researchers did tests in a drop tower that enabled them to observe exactly how cracks appeared and spread -- or didn't spread -- in the first instants after an impact. "There was amazing agreement between the model and the experiments," Buehler says. That's partly because the team was able to 3-D print composite materials with precisely controlled structures, rather than using samples of real shells, which can have unpredictable variations that can complicate the analysis. By printing the samples, "we can use exactly the same geometry" as used in the computer simulations, "and we get very good agreement." Now, in continuing the work, they can focus on making slight variations "as a basis for future optimization," Buehler says. To test the relative importance of the three levels of structure, the team tried making variations of the material with different levels of hierarchy. Higher levels of hierarchy are introduced by incorporating smaller length-scale features into the composite, as in an actual conch shell. Sure enough, lower-level structures proved to be significantly weaker than the highest level pursued in this study, which consisted of the cross-lamellar features inherent in natural conch shells. Testing proved that the geometry with the conch-like, criss-crossed features was 85 percent better at preventing crack propagation than the strongest base material, and 70 percent better than a traditional fiber composite arrangement, Gu says. Protective helmets and other impact-resistant gear require a key combination of both strength and toughness, Buehler explains. Strength refers to a material's ability to resist damage, which steel does well, for example. Toughness, on the other hand, refers to a material's ability to dissipate energy, as rubber does. Traditional helmets use a metal shell for strength and a flexible liner for both comfort and energy dissipation. But in the new composite material, this combination of qualities is distributed through the whole material. "This has stiffness, like glass or ceramics," Buehler says, but it lacks the brittleness of those materials, thanks to the integration of materials with different degrees of strength and flexibility within the composite structure. Like plywood, the composite is made up of layers whose "grain," or the internal alignment of its materials, is oriented differently from one layer to the next. Because of the use of 3-D printing technology, this system would make it possible to produce individualized helmets or other body armor. Each helmet, for example, could be "tailored and personalized; the computer would optimize it for you, based on a scan of your skull, and the helmet would be printed just for you," Gu says. The research was supported by the Office of Naval Research, a National Defense Science and Engineering Graduate Fellowship, the Defense University Research Instrumentation Program (DURIP), the Institute for Soldier Nanotechnologies (ISN), and the Natural Sciences and Engineering Research Council of Canada.


News Article | May 26, 2017
Site: www.eurekalert.org

CAMBRIDGE, Mass. -- The shells of marine organisms take a beating from impacts due to storms and tides, rocky shores, and sharp-toothed predators. But as recent research has demonstrated, one type of shell stands out above all the others in its toughness: the conch. Now, researchers at MIT have explored the secrets behind these shells' extraordinary impact resilience. And they've shown that this superior strength could be reproduced in engineered materials, potentially to provide the best-ever protective headgear and body armor. The findings are reported in the journal Advanced Materials, in a paper by MIT graduate student Grace Gu, postdoc Mahdi Takaffoli, and McAfee Professor of Engineering Markus Buehler. Conch shells "have this really unique architecture," Gu explains. The structure makes the material 10 times tougher than nacre, commonly known as mother of pearl. This toughness, or resistance to fractures, comes from a unique configuration based on three different levels of hierarchy in the material's internal structure. The three-tiered structure makes it very hard for any tiny cracks to spread and enlarge, Gu says. The material has a "zigzag matrix, so the crack has to go through a kind of a maze" in order to spread, she says. Until recently, even after the structure of the conch shell was understood, "you couldn't replicate it that well. But now, our lab has developed 3-D printing technology that allows us to duplicate that structure and be able to test it," says Buehler, who is the head of the Department of Civil and Environmental Engineering. Part of the innovation involved in this project was the team's ability to both simulate the material's behavior and analyze its actual performance under realistic conditions. "In the past, a lot of testing [of protective materials] was static testing," Gu explains. "But a lot of applications for military uses or sports involve highly dynamic loading," which requires a detailed examination of how an impact's effects spread out over time. For this work, the researchers did tests in a drop tower that enabled them to observe exactly how cracks appeared and spread -- or didn't spread -- in the first instants after an impact. "There was amazing agreement between the model and the experiments," Buehler says. That's partly because the team was able to 3-D print composite materials with precisely controlled structures, rather than using samples of real shells, which can have unpredictable variations that can complicate the analysis. By printing the samples, "we can use exactly the same geometry" as used in the computer simulations, "and we get very good agreement." Now, in continuing the work, they can focus on making slight variations "as a basis for future optimization," Buehler says. To test the relative importance of the three levels of structure, the team tried making variations of the material with different levels of hierarchy. Higher levels of hierarchy are introduced by incorporating smaller length-scale features into the composite, as in an actual conch shell. Sure enough, lower-level structures proved to be significantly weaker than the highest level pursued in this study, which consisted of the cross-lamellar features inherent in natural conch shells. Testing proved that the geometry with the conch-like, criss-crossed features was 85 percent better at preventing crack propagation than the strongest base material, and 70 percent better than a traditional fiber composite arrangement, Gu says. Protective helmets and other impact-resistant gear require a key combination of both strength and toughness, Buehler explains. Strength refers to a material's ability to resist damage, which steel does well, for example. Toughness, on the other hand, refers to a material's ability to dissipate energy, as rubber does. Traditional helmets use a metal shell for strength and a flexible liner for both comfort and energy dissipation. But in the new composite material, this combination of qualities is distributed through the whole material. "This has stiffness, like glass or ceramics," Buehler says, but it lacks the brittleness of those materials, thanks to the integration of materials with different degrees of strength and flexibility within the composite structure. Like plywood, the composite is made up of layers whose "grain," or the internal alignment of its materials, is oriented differently from one layer to the next. Because of the use of 3-D printing technology, this system would make it possible to produce individualized helmets or other body armor. Each helmet, for example, could be "tailored and personalized; the computer would optimize it for you, based on a scan of your skull, and the helmet would be printed just for you," Gu says. The research was supported by the Office of Naval Research, a National Defense Science and Engineering Graduate Fellowship, the Defense University Research Instrumentation Program (DURIP), the Institute for Soldier Nanotechnologies (ISN), and the Natural Sciences and Engineering Research Council of Canada. ARCHIVE: Worm-inspired material strengthens, changes shape in response to its environment ARCHIVE: Researchers design one of the strongest, lightest materials known


News Article | May 26, 2017
Site: phys.org

Now, researchers at MIT have explored the secrets behind these shells' extraordinary impact resilience. And they've shown that this superior strength could be reproduced in engineered materials, potentially to provide the best-ever protective headgear and body armor. The findings are reported in the journal Advanced Materials, in a paper by MIT graduate student Grace Gu, postdoc Mahdi Takaffoli, and McAfee Professor of Engineering Markus Buehler. Conch shells "have this really unique architecture," Gu explains. The structure makes the material 10 times tougher than nacre, commonly known as mother of pearl. This toughness, or resistance to fractures, comes from a unique configuration based on three different levels of hierarchy in the material's internal structure. The three-tiered structure makes it very hard for any tiny cracks to spread and enlarge, Gu says. The material has a "zigzag matrix, so the crack has to go through a kind of a maze" in order to spread, she says. Until recently, even after the structure of the conch shell was understood, "you couldn't replicate it that well. But now, our lab has developed 3-D printing technology that allows us to duplicate that structure and be able to test it," says Buehler, who is the head of the Department of Civil and Environmental Engineering. Part of the innovation involved in this project was the team's ability to both simulate the material's behavior and analyze its actual performance under realistic conditions. "In the past, a lot of testing [of protective materials] was static testing," Gu explains. "But a lot of applications for military uses or sports involve highly dynamic loading," which requires a detailed examination of how an impact's effects spread out over time. For this work, the researchers did tests in a drop tower that enabled them to observe exactly how cracks appeared and spread—or didn't spread—in the first instants after an impact. "There was amazing agreement between the model and the experiments," Buehler says. That's partly because the team was able to 3-D print composite materials with precisely controlled structures, rather than using samples of real shells, which can have unpredictable variations that can complicate the analysis. By printing the samples, "we can use exactly the same geometry" as used in the computer simulations, "and we get very good agreement." Now, in continuing the work, they can focus on making slight variations "as a basis for future optimization," Buehler says. To test the relative importance of the three levels of structure, the team tried making variations of the material with different levels of hierarchy. Higher levels of hierarchy are introduced by incorporating smaller length-scale features into the composite, as in an actual conch shell. Sure enough, lower-level structures proved to be significantly weaker than the highest level pursued in this study, which consisted of the cross-lamellar features inherent in natural conch shells. Testing proved that the geometry with the conch-like, criss-crossed features was 85 percent better at preventing crack propagation than the strongest base material, and 70 percent better than a traditional fiber composite arrangement, Gu says. Protective helmets and other impact-resistant gear require a key combination of both strength and toughness, Buehler explains. Strength refers to a material's ability to resist damage, which steel does well, for example. Toughness, on the other hand, refers to a material's ability to dissipate energy, as rubber does. Traditional helmets use a metal shell for strength and a flexible liner for both comfort and energy dissipation. But in the new composite material, this combination of qualities is distributed through the whole material. "This has stiffness, like glass or ceramics," Buehler says, but it lacks the brittleness of those materials, thanks to the integration of materials with different degrees of strength and flexibility within the composite structure. Like plywood, the composite is made up of layers whose "grain," or the internal alignment of its materials, is oriented differently from one layer to the next. Because of the use of 3-D printing technology, this system would make it possible to produce individualized helmets or other body armor. Each helmet, for example, could be "tailored and personalized; the computer would optimize it for you, based on a scan of your skull, and the helmet would be printed just for you," Gu says. The research was supported by the Office of Naval Research, a National Defense Science and Engineering Graduate Fellowship, the Defense University Research Instrumentation Program (DURIP), the Institute for Soldier Nanotechnologies (ISN), and the Natural Sciences and Engineering Research Council of Canada. Explore further: Materials theory combines strength, stiffness and toughness of composites into a single design map More information: Grace X. Gu et al, Hierarchically Enhanced Impact Resistance of Bioinspired Composites, Advanced Materials (2017). DOI: 10.1002/adma.201700060


News Article | May 26, 2017
Site: www.chromatographytechniques.com

The shells of marine organisms take a beating from impacts due to storms and tides, rocky shores, and sharp-toothed predators. But as recent research has demonstrated, one type of shell stands out above all the others in its toughness: the conch. Now, researchers at MIT have explored the secrets behind these shells’ extraordinary impact resilience. And they’ve shown that this superior strength could be reproduced in engineered materials, potentially to provide the best-ever protective headgear and body armor. The findings are reported in the journal Advanced Materials, in a paper by MIT graduate student Grace Gu, postdoc Mahdi Takaffoli, and McAfee Professor of Engineering Markus Buehler. Conch shells “have this really unique architecture,” Gu explains. The structure makes the material 10 times tougher than nacre, commonly known as mother of pearl. This toughness, or resistance to fractures, comes from a unique configuration based on three different levels of hierarchy in the material’s internal structure. The three-tiered structure makes it very hard for any tiny cracks to spread and enlarge, Gu says. The material has a “zigzag matrix, so the crack has to go through a kind of a maze” in order to spread, she says. Until recently, even after the structure of the conch shell was understood, “you couldn’t replicate it that well. But now, our lab has developed 3-D printing technology that allows us to duplicate that structure and be able to test it,” says Buehler, who is the head of the Department of Civil and Environmental Engineering. Part of the innovation involved in this project was the team’s ability to both simulate the material’s behavior and analyze its actual performance under realistic conditions. “In the past, a lot of testing [of protective materials] was static testing,” Gu explains. “But a lot of applications for military uses or sports involve highly dynamic loading,” which requires a detailed examination of how an impact’s effects spread out over time. For this work, the researchers did tests in a drop tower that enabled them to observe exactly how cracks appeared and spread — or didn’t spread — in the first instants after an impact. “There was amazing agreement between the model and the experiments,” Buehler says. That’s partly because the team was able to 3-D print composite materials with precisely controlled structures, rather than using samples of real shells, which can have unpredictable variations that can complicate the analysis. By printing the samples, “we can use exactly the same geometry” as used in the computer simulations, “and we get very good agreement.” Now, in continuing the work, they can focus on making slight variations “as a basis for future optimization,” Buehler says. To test the relative importance of the three levels of structure, the team tried making variations of the material with different levels of hierarchy. Higher levels of hierarchy are introduced by incorporating smaller length-scale features into the composite, as in an actual conch shell. Sure enough, lower-level structures proved to be significantly weaker than the highest level pursued in this study, which consisted of the cross-lamellar features inherent in natural conch shells. Testing proved that the geometry with the conch-like, criss-crossed features was 85 percent better at preventing crack propagation than the strongest base material, and 70 percent better than a traditional fiber composite arrangement, Gu says. Protective helmets and other impact-resistant gear require a key combination of both strength and toughness, Buehler explains. Strength refers to a material’s ability to resist damage, which steel does well, for example. Toughness, on the other hand, refers to a material’s ability to dissipate energy, as rubber does. Traditional helmets use a metal shell for strength and a flexible liner for both comfort and energy dissipation. But in the new composite material, this combination of qualities is distributed through the whole material. “This has stiffness, like glass or ceramics,” Buehler says, but it lacks the brittleness of those materials, thanks to the integration of materials with different degrees of strength and flexibility within the composite structure. Like plywood, the composite is made up of layers whose “grain,” or the internal alignment of its materials, is oriented differently from one layer to the next. Because of the use of 3-D printing technology, this system would make it possible to produce individualized helmets or other body armor. Each helmet, for example, could be “tailored and personalized; the computer would optimize it for you, based on a scan of your skull, and the helmet would be printed just for you,” Gu says. These researchers “ingeniously used 3-D printing and experimentation to elucidate the effect of material hierarchy on bioinspired composites,” says Horacio Espinosa, a professor of mechanical engineering and director of the Theoretical and Applied Mechanics program at Northwestern University, who was not involved in this work. “An interesting remaining question,” he says, “is the applicability of the conch shell design to curved surfaces like those one would encounter in helmets.”


News Article | May 24, 2017
Site: www.rdmag.com

Materials exposed to neutron radiation tend to experience significant damage, leading to the containment challenges involved in immobilizing nuclear waste or nuclear plant confinements. At the nanoscale, these incident neutrons collide with a material's atoms that, in turn, then collide with each other somewhat akin to billiards. The resulting disordered atomic network and its physical properties resemble those seen in some glassy materials, which has led many in the field to use them in nuclear research. But the similarities between the materials may not be as useful as previously thought, according to new results reported this week in The Journal of Chemical Physics, from AIP Publishing. The disordered atomic networks of glassy substances result from vitrification, the transformation of a substance into glass by its melting and (typically) rapid subsequent cooling. During this cooling, or quenching, atoms don't have time to settle in an organized way, and instead form a disordered atomic network. This led a group of researchers from the University of California, Los Angeles (UCLA) and Oak Ridge National Laboratory to explore the question: Do irradiation and vitrification have the same impact on the atomic structure of materials? To find an answer they explored quartz, a simple yet ubiquitous material in nature used for myriad engineering applications. Traditional experiments don't allow researchers to "see" atoms directly, especially within disordered materials. So, for their study, the group relied on atomistic simulations using the molecular dynamics technique. "The molecular dynamics technique is based on numerically solving Newton's laws of motion for a group of interacting atoms," said Mathieu Bauchy, an assistant professor in the Civil and Environmental Engineering department at UCLA. "All atoms apply a force on each other that can be used to calculate the acceleration of each atom over time." Based on this technique, they were able to simulate the irradiation-induced disordering of quartz by sequentially colliding the atoms of the network with fictitious incident neutrons. "We also simulated quartz's vitrification by heating and quickly quenching the atoms," Bauchy said. "Finally, we compared the resulting atomic structure of these two disordered materials." "Quite unexpectedly, we found that the disordering induced by irradiation differs in nature from that induced by vitrification," Bauchy said. "This is quite surprising because glasses and heavily irradiated materials typically exhibit the same density, so that glasses are often used as models to simulate the effect of the exposure to radiations on materials." In contrast, the researchers' results suggest that irradiated materials are more disordered than glasses. "The atomic structure of irradiated materials is actually closer to that of a liquid than to that of a glass," Bauchy said. The group's findings potentially have serious implications for the selection of materials for nuclear applications. "First, we suggest that present models might be underestimating the extent of the damage exhibited by materials subjected to irradiation, which raises obvious safety concerns," said N.M. Anoop Krishnan, a postdoctoral researcher also at UCLA. "Second, the different natures of irradiation- and vitrification-induced disordering suggest that glasses can also be affected by irradiation." This is a significant discovery because glasses, which are believed to "self-heal" under irradiation, are commonly used to immobilize nuclear waste via vitrification. "These waste forms are expected to remain stable for millions of years once deposited into geological depositories, so our lack of understanding of the effect of irradiation represents a real concern," Krishnan said. Next, the group plans to explore the effect of irradiation on common aggregates found in the concrete of nuclear power plants and on nuclear waste immobilization glasses. "Ultimately, our goal is to develop novel models to predict the long-term effect of irradiation on the structure and properties of materials," Bauchy said.


News Article | May 25, 2017
Site: www.sciencedaily.com

Materials exposed to neutron radiation tend to experience significant damage, leading to the containment challenges involved in immobilizing nuclear waste or nuclear plant confinements. At the nanoscale, these incident neutrons collide with a material's atoms that, in turn, then collide with each other somewhat akin to billiards. The resulting disordered atomic network and its physical properties resemble those seen in some glassy materials, which has led many in the field to use them in nuclear research. But the similarities between the materials may not be as useful as previously thought, according to new results reported this week in The Journal of Chemical Physics, from AIP Publishing. The disordered atomic networks of glassy substances result from vitrification, the transformation of a substance into glass by its melting and (typically) rapid subsequent cooling. During this cooling, or quenching, atoms don't have time to settle in an organized way, and instead form a disordered atomic network. This led a group of researchers from the University of California, Los Angeles (UCLA) and Oak Ridge National Laboratory to explore the question: Do irradiation and vitrification have the same impact on the atomic structure of materials? To find an answer they explored quartz, a simple yet ubiquitous material in nature used for myriad engineering applications. Traditional experiments don't allow researchers to "see" atoms directly, especially within disordered materials. So, for their study, the group relied on atomistic simulations using the molecular dynamics technique. "The molecular dynamics technique is based on numerically solving Newton's laws of motion for a group of interacting atoms," said Mathieu Bauchy, an assistant professor in the Civil and Environmental Engineering department at UCLA. "All atoms apply a force on each other that can be used to calculate the acceleration of each atom over time." Based on this technique, they were able to simulate the irradiation-induced disordering of quartz by sequentially colliding the atoms of the network with fictitious incident neutrons. "We also simulated quartz's vitrification by heating and quickly quenching the atoms," Bauchy said. "Finally, we compared the resulting atomic structure of these two disordered materials." "Quite unexpectedly, we found that the disordering induced by irradiation differs in nature from that induced by vitrification," Bauchy said. "This is quite surprising because glasses and heavily irradiated materials typically exhibit the same density, so that glasses are often used as models to simulate the effect of the exposure to radiations on materials." In contrast, the researchers' results suggest that irradiated materials are more disordered than glasses. "The atomic structure of irradiated materials is actually closer to that of a liquid than to that of a glass," Bauchy said. The group's findings potentially have serious implications for the selection of materials for nuclear applications. "First, we suggest that present models might be underestimating the extent of the damage exhibited by materials subjected to irradiation, which raises obvious safety concerns," said N.M. Anoop Krishnan, a postdoctoral researcher also at UCLA. "Second, the different natures of irradiation- and vitrification-induced disordering suggest that glasses can also be affected by irradiation." This is a significant discovery because glasses, which are believed to "self-heal" under irradiation, are commonly used to immobilize nuclear waste via vitrification. "These waste forms are expected to remain stable for millions of years once deposited into geological depositories, so our lack of understanding of the effect of irradiation represents a real concern," Krishnan said. Next, the group plans to explore the effect of irradiation on common aggregates found in the concrete of nuclear power plants and on nuclear waste immobilization glasses. "Ultimately, our goal is to develop novel models to predict the long-term effect of irradiation on the structure and properties of materials," Bauchy said.


A snapshot of the atomic structure of a partially irradiated quartz sample. Credit: N.M. Anoop Krishnan/UCLA Materials exposed to neutron radiation tend to experience significant damage, leading to the containment challenges involved in immobilizing nuclear waste or nuclear plant confinements. At the nanoscale, these incident neutrons collide with a material's atoms that, in turn, then collide with each other somewhat akin to billiards. The resulting disordered atomic network and its physical properties resemble those seen in some glassy materials, which has led many in the field to use them in nuclear research. But the similarities between the materials may not be as useful as previously thought, according to new results reported this week in The Journal of Chemical Physics. The disordered atomic networks of glassy substances result from vitrification, the transformation of a substance into glass by its melting and (typically) rapid subsequent cooling. During this cooling, or quenching, atoms don't have time to settle in an organized way, and instead form a disordered atomic network. This led a group of researchers from the University of California, Los Angeles (UCLA) and Oak Ridge National Laboratory to explore the question: Do irradiation and vitrification have the same impact on the atomic structure of materials? To find an answer they explored quartz, a simple yet ubiquitous material in nature used for myriad engineering applications. Traditional experiments don't allow researchers to "see" atoms directly, especially within disordered materials. So, for their study, the group relied on atomistic simulations using the molecular dynamics technique. "The molecular dynamics technique is based on numerically solving Newton's laws of motion for a group of interacting atoms," said Mathieu Bauchy, an assistant professor in the Civil and Environmental Engineering department at UCLA. "All atoms apply a force on each other that can be used to calculate the acceleration of each atom over time." Based on this technique, they were able to simulate the irradiation-induced disordering of quartz by sequentially colliding the atoms of the network with fictitious incident neutrons. "We also simulated quartz's vitrification by heating and quickly quenching the atoms," Bauchy said. "Finally, we compared the resulting atomic structure of these two disordered materials." "Quite unexpectedly, we found that the disordering induced by irradiation differs in nature from that induced by vitrification," Bauchy said. "This is quite surprising because glasses and heavily irradiated materials typically exhibit the same density, so that glasses are often used as models to simulate the effect of the exposure to radiations on materials." In contrast, the researchers' results suggest that irradiated materials are more disordered than glasses. "The atomic structure of irradiated materials is actually closer to that of a liquid than to that of a glass," Bauchy said. The group's findings potentially have serious implications for the selection of materials for nuclear applications. "First, we suggest that present models might be underestimating the extent of the damage exhibited by materials subjected to irradiation, which raises obvious safety concerns," said N.M. Anoop Krishnan, a postdoctoral researcher also at UCLA. "Second, the different natures of irradiation- and vitrification-induced disordering suggest that glasses can also be affected by irradiation." This is a significant discovery because glasses, which are believed to "self-heal" under irradiation, are commonly used to immobilize nuclear waste via vitrification. "These waste forms are expected to remain stable for millions of years once deposited into geological depositories, so our lack of understanding of the effect of irradiation represents a real concern," Krishnan said. Next, the group plans to explore the effect of irradiation on common aggregates found in the concrete of nuclear power plants and on nuclear waste immobilization glasses. "Ultimately, our goal is to develop novel models to predict the long-term effect of irradiation on the structure and properties of materials," Bauchy said. Explore further: Scientists gain new insights into atomic disordering of complex metal oxides More information: N. M. Anoop Krishnan et al, Irradiation- vs. vitrification-induced disordering: The case of-quartz and glassy silica, The Journal of Chemical Physics (2017). DOI: 10.1063/1.4982944


News Article | May 13, 2017
Site: www.businesswire.com

RAS AL KHAIMAH, United Arab Emirates--(BUSINESS WIRE)--The American University of Ras Al Khaimah (AURAK) has signed a Memorandum of Understanding with the University of Illinois, converting the U.S.-based university into its latest international partner. The agreement, which was initiated by AURAK’s School of Engineering and the Department of Civil and Environmental Engineering at the University of Illinois’ Urbana-Champaign campus, is centered on the establishment of a ‘3+2’ cooperative academic program in which students can earn a bachelor’s degree at AURAK and a master’s degree in Illinois. Pen was put to paper by Prof. Hassan Hamdan Al Alkim and Prof. Mousa Mohsen, AURAK president and dean of the School of Engineering respectively, as well as Robert J. Jones, chancellor of the University of Illinois, Reitumetse Obakeng Mabokela, vice provost for international affairs and global strategies, and Andreas Cangellaris, dean of the University of Illinois’ College of Engineering. Speaking about the agreement, Prof. Mousa Mohsen stated, “For AURAK students, this arrangement offers a unique opportunity to earn a postgraduate degree at a top university in the United States, as well as experiencing all of the transformative impacts associated with immersion in a new culture and environment. I am so excited at the potential of this agreement.” Prof. Al Alkim added, “We are delighted with this agreement, as it seals a very close relationship with an excellent institution in the United States and provides our students with a wonderful opportunity for further study. Opportunities like this can effectively change lives, and at AURAK, we are immensely proud to offer these possibilities to our students through our own top-class education, as well as our network of partners across the world.” At present, AURAK has a range of international partners across Africa, Asia, Europe and North America, opening a wide spectrum of possibilities to students, including exchange and study abroad programs for up to one year, as well as shorter summer sessions. While AURAK students have travelled abroad to study at the likes of Appalachian State University in North Carolina, AURAK also receives a number of students from the United States and Europe each semester, with international students eager to experience the immersive cultural experience on offer in Ras Al Khaimah.


News Article | May 13, 2017
Site: www.businesswire.com

Initiiert wurde die Vereinbarung von der School of Engineering (Fakultät für Ingenieurwesen) der AURAK und dem Department of Civil and Environmental Engineering (Fakultät für Bau- und Umwelttechnik) am Urbana-Champaign-Campus der University of Illinois. Im Mittelpunkt steht die Einrichtung eines 3+2-Hochschulkooperationsprogramms, in dessen Rahmen Studenten einen Bachelor-Abschluss an der AURAK und einen Master-Abschluss in Illinois erwerben können. Unterzeichner der Absichtserklärung waren bei AURAK Prof. Hassan Hamdan Al Alkim als Präsident und Prof. Mousa Mohsen als Dekan der Fakultät für Ingenieurwesen. Auf US-Seite unterzeichneten Robert J. Jones als Kanzler der University of Illinois, Reitumetse Obakeng Mabokela als Vize-Provost für internationale Angelegenheiten und globale Strategien sowie Andreas Cangellaris als Dekan des College of Engineering (Hochschule für Ingenieurwesen) der University of Illinois. Während AURAK-Studenten sich ins Ausland begeben, um beispielsweise an der Appalachian State University in North Carolina Kurse zu belegen, kommen umgekehrt in jedem Semester Studenten aus den USA und Europa an die AURAK, um in die Kultur von Ras Al Khaimah einzutauchen.

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