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Sanchez C.,CNRS Laboratory of Condensed Matter Chemistry, Paris | Belleville P.,CEA Le Ripault | Popall M.,Fraunhofer Institute for Silicate Research | Nicole L.,CNRS Laboratory of Condensed Matter Chemistry, Paris
Chemical Society Reviews | Year: 2011

Today cross-cutting approaches, where molecular engineering and clever processing are synergistically coupled, allow the chemist to tailor complex hybrid systems of various shapes with perfect mastery at different size scales, composition, functionality, and morphology. Hybrid materials with organic-inorganic or bio-inorganic character represent not only a new field of basic research but also, via their remarkable new properties and multifunctional nature, hybrids offer prospects for many new applications in extremely diverse fields. The description and discussion of the major applications of hybrid inorganic-organic (or biologic) materials are the major topic of this critical review. Indeed, today the very large set of accessible hybrid materials span a wide spectrum of properties which yield the emergence of innovative industrial applications in various domains such as optics, micro-electronics, transportation, health, energy, housing, and the environment among others (526 references). © 2011 The Royal Society of Chemistry. Source

News Article
Site: http://phys.org/chemistry-news/

Modern illuminants are manufactured using a variety of materials. The housing is made of glass or plastic, the heat sink consists of ceramic or aluminum, and the resistors and cables contain copper. The most valuable materials are found within the LEDs themselves. They are indium and gallium inside the semiconductor diode and rare earths like europium or terbium in the phosphor. This makes it relatively expensive to manufacture the diodes, and the margins are small. "Right now recyclers are starting to receive LED products, but currently they are often simply stored as there is no suitable recycling process available yet. The main goal is to recover the valuable materials. It's only a matter of time until recyclers will have to start processing LEDs," says Jörg Zimmermann from the Fraunhofer Project Group for Materials Recycling and Resource Strategies IWKS in Alzenau and Hanau of the Fraunhofer Institute for Silicate Research ISC. Separating components with the help of shock waves Using the "electrohydraulic comminution" process, researchers break the LED lamps into their constituent parts without destroying the LEDs themselves. Shock waves created by electrical impulses in a water bath separate the individual components at their predetermined break points. The components can then be recycled individually. The researchers have adapted their experimental setup to retrofit lamps, which resemble traditional light bulbs or fluorescent tubes and can be used in the same standard sockets. "This method works in principle also for other sizes, for instance with LEDs from television sets or with automobile headlights, as well as with other electronic products," explains Zimmermann. A prerequisite for an efficient recycling process is a neat separation of the components. "To efficiently separate and recycle all components of a LED lamp, an entirely different approach is necessary - one that produces large quantities of semiconductor and phosphor materials," says Zimmermann. If the entire retrofit is shredded, it is much more difficult to separate the resulting mixture of materials. Breaking LED lamps down to the component level also makes it easier to recover greater quantities of the materials contained in them. This is accomplished by collecting large quantities of similar components in which the concentration of individual elements is already higher. Zimmermann clarifies that this reprocessing is only profitable for recyclers and manufacturers, if it involves larger quantities. "We're still testing whether the comminution process can be repeated until the desired materials have been separated," says Zimmerman. The researchers can adjust the parameters of the experimental setup like the type and quantity of the fluid, the container size, or the electric pulse voltage in such a way that separation occurs precisely at the specified break points. "In particular it is the number of pulses that determines how the components will separate," he says. The electrohydraulic comminution process is currently being investigated in detail and improved further, also to gain access to other LED application areas. "Our research has demonstrated that mechanical separation is a viable method for improving the economics of LED lamp recycling," says Zimmermann. Explore further: New technique to make LED lamps even more compact while supplying more light

Mandel K.,Fraunhofer Institute for Silicate Research | Mandel K.,University of Wurzburg | Hutter F.,Fraunhofer Institute for Silicate Research
Nano Today | Year: 2012

Magnetic nanoparticles for adsorption and subsequent magnetic removal of hazardous substances from water, as published in Science in 2006, bears enormous potential for water purification for which there is a growing need all over the world. Many publications followed this idea, but doubts remain whether nanoparticles are really separable and whether the process is really that simple. A closer look reveals uncertainties and the need for more research. © 2012 Elsevier Ltd. Source

News Article
Site: http://phys.org/technology-news/

The earth is 4.57 billion years old – an unimaginable temporal dimension. To understand how the blue planet was first formed long ago, scientists today are analyzing other rock bodies from our solar system, such as fragments of asteroids that have arrived on Earth as meteorites after collisions in space. According to current knowledge, many planetary bodies were formed through the merger of chondrules – which are silicate beads that are about 0.1 to 3 mm wide. How does this cosmic rock formation process work, though? That is what scientists from the Institute of Planetology at the Westphalian Wilhelms University of Münster and the Technical University of Braunschweig are investigating in unique experiments. They are being supported by researchers at the Fraunhofer Institute for Silicate Research ISC in Würzburg. The scientists have developed a special glass for the project and formed tiny beads from it to represent the chondrules as realistically as possible. Previous findings indicate that the original particles had the consistency of hot, liquid glass before they aggregated into larger conglomerates of rock, cooled down and crystallized. "This glass is very different from the material composition of technical glasses with which we are usually working," explains Dr. Martin Kilo, Head of Glass Unit at the ISC. The chemical composition of a glass determines certain physical properties, though, such as the melting and crystallization behavior. Both play a central role in the development process of larger rock bodies. "That's why we have used modeling programs in advance to calculate which melting conditions prevail for the required compositions, how stable the glass particles are, as well as the temperatures and forms at which they crystallize," says Dr. Kilo. Another challenge was to give the glass particles their spherical shape. To do so, the experts use two different procedures. In the first approach, rough glass gravel is prepared, sifted to the right size and then rounded out by thermal treatment. The second solution is to cut glass plates into small cubes and to grind them mechanically – very similar to the marble production. For the experiment, the researchers from Würzburg produced several versions of their beads, each of which differs slightly in material composition. These beads were first heated in special melting units in which the temperature and atmosphere can be adjusted precisely. Those beads which had characteristics closest to the theoretical model after this test melting were selected for the project. The research team from the Universities of Münster and Braunschweig now uses the cosmic glass beads from the ISC in experiments at the Center for Applied Space Technology and Microgravity (ZARM) in Bremen: The drop tower which is operated there surrounds a 120-meter-high steel drop tube, in which a high-vacuum is kept. Through a catapult system, the glass beads are shot in a capsule to the tip of the drop tube. As a result, approximately 9.5 seconds of weightlessness are achieved – the same conditions as in space. During this period, the glass beads are heated up to 1100 °C. During the dropping procedure, the beads can collide and form larger clusters. The experts record the collision behavior with high-speed cameras that colleagues at the TU Braunschweig assess. "Our colleagues from Münster then investigate how the beads merge, whether the clusters are composed of a homogeneous composition or whether the form of the individual beads is still recognizable, and whether and to what extent crystallization results," Dr. Kilo explains. In the next step, the planetologists will compare the results with observations of meteorites to then draw conclusions about the validity of their theoretical models.

Schwarz G.,University of Wurzburg | Hasslauer I.,University of Wurzburg | Kurth D.G.,University of Wurzburg | Kurth D.G.,Fraunhofer Institute for Silicate Research
Advances in Colloid and Interface Science | Year: 2014

Introducing metal ion coordination as bonding motive into polymer architectures provides new structures and properties for polymeric materials. The metal ions can be part of the backbone or of the side-chains. In the case of linear metallo-polymers the repeat unit bears at least two metal ion receptors in order to facilitate metal-ion induced self-assembly. If the binding constants are sufficiently high, macromolecular assemblies will form in a solution. Likewise, polymeric networks can be formed by metal ion induced crosslinking. The metal ion coordination sites introduce dynamic features, e.g. for self-healing or responsive materials, as well as additional functional properties including spin-crossover, electro-chromism, and reactivity. Terpyridines have attracted attention as receptors in metallo-polymers due to their favorable properties. It is well suited to assemble linear rigid-rod like metallo-polymers in case of rigid ditopic ligands. Terpyridine binds a large number of metal ions and are readily functionalized giving rise to a plethora of available ligands as components in metallo-polymers. By the judicious choice of the metal ions, the design of the ligands, the counter ions and the boundary conditions of self-assembly, the final structure and properties of the resulting metallo-polymers can be tailored at all length scales. Here, we review recent activities in the area of metallo-polymers based on terpyridines as central metal ion receptors. © 2013 Elsevier B.V. Source

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