Stronger or tougher? For designers of advanced materials, this tradeoff may complicate efforts to devise efficient methods for assembling nanometer-scale building blocks into exotic ceramics, glasses and other types of customized materials.
“Not all properties may benefit from microstructural refinement, so due caution needs to be exercised in materials design,” writes the National Institute of Standards and Technology’s (NIST) Brian Lawn in the January issue of Journal of Materials Research.* An expert on brittle materials, Lawn advises that past experience is not always a useful guide for predicting material properties and performance when film thicknesses, grain sizes and other characteristic dimensions shrink toward molecular proportions. At this level, materials designers must reckon with interatomic force laws that are obscured at larger scales, from micrometers (millionths of a meter) on up.
“Generally in brittle materials, strength (resistance to crack initiation) increases and toughness (resistance to crack propagation) decreases as characteristic scaling dimensions diminish,” Lawn concludes from his work to refine ceramics used in biomechanical applications such as dental crowns and orthopedic implants. At the nanoscale, tiny cracks require more load to spread them, but have little resistance to extension once they start and are, therefore, more likely to spread catastrophically. Depending on the application in mind, the decrease in fracture toughness may more than offset initial gains in strength, or the ability to withstand stresses that squeeze, stretch or twist the material.
Mark Bello | NIST
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Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
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An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
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In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
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