Published on October 14th, 2013 | Edited by: Jim Destefani0
Other materials stories that may be of interestPublished on October 14th, 2013 | Edited by: Jim Destefani
A novel bioceramic developed by the Nanomaterials and Nanotechnology Research Center (CINN) of Spain is an alumina–zirconia nanocomposite said to have fracture toughness higher than 9 MPa.m1/2 and high resistance to crack propagation. The material is said to be more reliable than current ceramics and is expected to result in prosthesis life of more than 70 years, thus preventing the need for multiple surgeries. Granted by the US Patent and Trademark Office, the patent has been licensed to the Spanish company Nanoker Research SL. CINN and Nanoker are currently investigating the application of glass-based anti-bacterial coatings on ceramic implants to help prevent the risk of surgical site infections, which currently occur in about 1% of arthroplasty surgeries and lead to revision procedures.
Scientists at HZB Institute for Silicon Photovoltaics, Berlin, say graphene retains its conductivity and transparency even when coated with silicon, making it an excellent candidate material for transparent contact layers in solar cells. The workers grew graphene on thin copper sheets, transferred the material to glass substrates, then coated them with a thin film of either amorphous or polycrystalline silicon. Measurements of carrier mobility using the Hall-effect showed that the mobility of charge carriers within the embedded graphene layer is roughly 30 times greater than that of conventional zinc oxide based contact layers. The researchers say their next challenge will be connecting the atom-thick graphene conducting layer to external contacts.
Researchers at MIT initially thought it must be a mistake: Under certain conditions, putting a cracked piece of metal under tension caused the crack to close and its edges to fuse together. The surprising finding could lead to self-healing materials that repair incipient damage before it has a chance to spread. According to the scientists, the phenomenon is the result of grain boundary migration under stress. The self-healing effect occurs only across a certain kind of boundary that extends partway into a grain, but not all the way through it. This creates defects known as disclinations, which have intense stress fields that can be so strong they actually reverse what an applied load would do, the scientists say. In other words, when the two sides of a cracked material are pulled apart, instead of cracking further, it can heal. The researchers next plan to study how to design metals so cracks would close and heal under loads typical of particular applications.
In an advance that could dramatically shrink particle accelerators for science and medicine, scientists used a laser to accelerate electrons at a rate 10 times higher than conventional technology in a nanostructured glass chip smaller than a grain of rice. The research team, including scientists from the U.S. Department of Energy’s SLAC National Accelerator Laboratory and Stanford University, say the advance could set the stage for new generations of “tabletop” accelerators, matching the accelerating power of SLAC’s 2-mile-long linear accelerator in just 100 feet and delivering a million more electron pulses per second. In the experiments, electrons were accelerated to near light-speed in a conventional accelerator, then focused into a 0.5 μm high channel within a 0.5 mm long piece of fused silica. Infrared light shining on the channel, which is patterned with precisely spaced nanoscale ridges, generates electrical fields that interact with the electrons in the channel to boost their energy. Turning the device into a full-fledged tabletop accelerator will require a more compact way to get the electrons up to speed before they enter the device.
Scientists at the Fraunhofer Institute for Solar Energy Systems ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin recently achieved a new world record for the conversion of sunlight into electricity. Made up of four solar subcells based on III-V compound semiconductors for use in concentrator photovoltaics, the device achieved a conversion efficiency of 44.7% at a concentration of 297 suns. Concentrator photovoltaic technology can achieve more than twice the efficiency of conventional PV setups in locations that receive relatively high amounts of sunlight. The multijunction uses stacked subcells made from different III-V semiconductor materials. Each of the subcells absorbs different wavelength ranges of the solar spectrum. Concentrator modules are produced by Soitec, which currently has CPV installations in 18 countries including Italy, France, South Africa, and the US.
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