Guinness record: World's thinnest glass is just two atoms thick

A microscopic photo of a sheet of glass only two atoms thick blends with an artist's conception to show the structural rendering. Credit: Kavli Institute at Cornell for Nanoscale Science.

At just a molecule thick, it's a new record: The world's thinnest sheet of glass, a serendipitous discovery by scientists at Cornell and Germany's University of Ulm, is recorded for posterity in the Guinness Book of World Records.

The "pane" of glass, so impossibly thin that its individual silicon and oxygen atoms are clearly visible via electron microscopy, was identified in the lab of David A. Muller, professor of applied and engineering physics and director of the Kavli Institute at Cornell for Nanoscale Science.

The work that describes direct imaging of this thin glass was first published in January 2012 in Nano Letters, and the Guinness records officials took note. The record will now be published in the Guinness World Records 2014 Edition.

Just two atoms in thickness, the glass was an accidental discovery, Muller said. The scientists had been making graphene, a two-dimensional sheet of carbon atoms in a chicken wire crystal formation, on copper foils in a quartz furnace. They noticed some "muck" on the graphene, and upon further inspection, found it to be composed of the elements of everyday glass, silicon and oxygen.

They concluded that an air leak had caused the copper to react with the quartz, also made of silicon and oxygen. This produced the glass layer on the would-be pure graphene.

Besides its sheer novelty, Muller said, the work answers an 80-year-old question about the fundamental structure of glass. Scientists, with no way to directly see it, had struggled to understand it: it behaves like a solid, but was thought to look more like a liquid. Now, the Cornell scientists have produced a picture of individual atoms of glass, and they found that it strikingly resembles a diagram drawn in 1932 by W.H. Zachariasen – a longstanding theoretical representation of the arrangement of atoms in glass.

"This is the work that, when I look back at my career, I will be most proud of," Muller said. "It's the first time that anyone has been able to see the arrangement of atoms in a glass."

What's more, two-dimensional glass could someday find a use in transistors, by providing a defect-free, ultra-thin material that could improve the performance of processors in computers and smartphones.

Sodium-ion battery cathode has highest energy density to date

This Ragone plot for the new cathode material (red circles) and other cathode materials for Na-ion batteries shows that the new cathode has the highest energy density for a wide range of charge and discharge rates. Credit: Park, et al. ©2013 American Chemical Society

Although sodium-ion (Na-ion) batteries don't perform as well as lithium-ion (Li-ion) batteries, they have the potential to be a cheaper alternative. In a new study, scientists have designed a new cathode for Na-ion batteries that provides an energy density of 600 Wh kg-1, which is the highest reported so far for Na-ion batteries and even rivals the energy densities of some Li-ion batteries. The new cathode material also has a greatly improved cycle life, bringing Na-ion batteries a step closer to realization as part of a large-scale energy storage system.

The researchers, Young-Uk Park, et al., from Seoul National University and KAIST, both in South Korea, have published their paper on the new high-energy cathode in a recent issue of the Journal of the American Chemical Society.

As the researchers explain, Na-ion batteries have the potential to meet and even exceed the performance of today's Li-ion batteries.

"The fascinating thing is that Na chemistry is much richer and has more variety than that of Li," coauthor Kisuk Kang, Professor of Materials Science and Engineering at Seoul National University, told Phys.org. "This makes us believe that there will be unexplored Na battery electrodes out there that can far excel the current Li batteries."

Both Na-ion and Li-ion batteries are candidates for being part of a large-scale system that stores energy generated by new technologies, such as solar, wind, and geothermal technology, where energy is produced intermittently. Although Li-ion batteries' high energy densities enable them to store a large amount of energy in a small space, the downsides of these batteries are their high cost and low stability. Since sodium is abundant in the earth, it is much cheaper than lithium, even though Na-ion batteries face their own challenges.

One of these challenges is a low energy density. Until now, the highest energy density of a Na-ion battery has been about 520 WH kg-1. The root of this problem can be traced to the inherent characteristics of sodium (in particular, a less negative redox potential compared to lithium), which reduces the operating voltage and leads to the lower energy density.

Another major challenge for Na-ion batteries is that, even moreso than Li-ion batteries, they suffer from poor long-term stability. This problem also stems from an inherent characteristic of sodium, which is that sodium ions (1.02 Å) are nearly twice as large as lithium ions (0.59 Å). The large size causes a greater change in the host structure upon insertion and removal, which results in a decrease in capacity after repeated cycles.

The new cathode material improves in both areas. The researchers attribute the 600 Wh kg-1 energy density to the cathode material's open crystal framework with vanadium redox couples, which leads to a high voltage that in turn increases the energy density.

The new cathode material also allows the Na-ion battery to retain 95% of its capacity over 100 cycles and 84% for 500 cycles. This outstanding cycle life arises from the fact that the cathode material has the smallest volume change among Na cathodes so far, which is due to the rigid framework that is less sensitive to Na ion insertion and extraction compared to other frameworks.

In the future, the researchers plan to further improve the electrochemical properties of this Na-ion battery cathode with the goal of designing next-generation Na-ion batteries for new applications.

"Further improvements in the cycle stability need to be accomplished in order to be considered for large-scale systems because it requires exceptionally long cycle life (>10 years), unlike small electronic devices," Kang said. "In this respect, not only the electrode stability, but also other aspects such as the compatibility between electrode and the electrolyte, and the electrolyte stability itself, have to be simultaneously considered."

The researchers plan to address these challenges when designing future electrodes.

"We are currently searching for more new electrode materials that can outperform the material that was reported this time," Kang said. "We have both computational and experimental tools to search for them, which will accelerate the identification of this new material."

First reported self-healing polymer that spontaneously and independently repairs itself

A cylindrical sample of the elastomer mends itself after being cut in two by a razor blade and can be manually stretched without rupture

The researchers have dubbed the material a 'Terminator' polymer in tribute to the shape-shifting, molten T-100 terminator robot from the Terminator 2 film.

The research is published in the Royal Society of Chemistry journal Materials Horizons.

Self-healing polymers that can spontaneously achieve quantitative healing in the absence of a catalyst have never been reported, until now. The scientists prepared the self-healing thermoset elastomers from common polymeric starting materials using a simple and inexpensive approach.

A video shows that the permanently cross-linked poly(urea-urethane) elastomeric network completely mends itself after being cut in two with a razor blade. A metathesis reaction of aromatic disulphides, which naturally exchange at room temperature, causes the regeneration.

The polymer behaves as a Velcro-like sealant or adhesive, displaying an impressive 97 per cent healing efficiency in just two hours. The researchers show that after cutting the material into two separate pieces with a razor blade and allowing it to self-heal, the material is unbreakable when stretched manually.

The authors said: "The fact that poly(urea-urethane)s with similar chemical composition and mechanical properties are already used in a wide range of commercial products makes this system very attractive for a fast and easy implementation in real industrial applications."

Molten air battery offers highest energy storage capacity & is rechargeable

Molten air batteries have been demonstrated to offer highest ever energy storage capacities, making the competition look dwarf. For the first time, researchers have been able to manufacture molten-air batteries that can be recharged - biggest advantage these batteries have over other high capacity batteries. There's however a big challenge that needs to be tackled. The molten electrolyte requires very high temperatures (~800 °C) for the battery to operate. Researchers are optimistic about trying out different compositions and characteristics so that the battery can operate at regular temperatures.

The molten air batteries are the first ones of their kind to use molten salt and free oxygen from air to host multi-electron molecules to store energy. It's this ability to store multiple electrons in a single molecule that gives the massive energy storage capacity to molten-air battery. Traditional batteries, like Li-Ion batteries have single electron per molecule structures which limits their storage capacities. The Vanadium Boride (VB2)-air batteries, which currently have the crown of being the biggest capacity batteries have a serious drawback - they aren't rechargeable.

Researchers have worked out different types of molten air batteries with different storage capacities. The iron, carbon and VB2 -molten air batteries have been developed with intrinsic volumetric energy storage capacities of 10000, 19000, 27000 Wh per liter.

What's yet to be known is the commercial aspect of these batteries. Unless the researchers bring down the costs of manufacturing and operating costs of this battery - they won't get wide adoption. Another important aspect is the overall weight and portability of such batteries, if they were to be used in electric vehicles. The third most important aspect would be the energy required to charge these batteries; which may have significant impact on the operating costs & maintenance.

World record solar cell with 44.7% efficiency

World record solar cell with 44.7% efficiency

German Fraunhofer Institute for Solar Energy Systems, Soitec, CEA-Leti and the Helmholtz Center Berlin announced today that they have achieved a new world record for the conversion of sunlight into electricity using a new solar cell structure with four solar subcells. Surpassing competition after only over three years of research, and entering the roadmap at world class level, a new record efficiency of 44.7% was measured at a concentration of 297 suns. This indicates that 44.7% of the solar spectrum's energy, from ultraviolet through to the infrared, is converted into electrical energy. This is a major step towards reducing further the costs of solar electricity and continues to pave the way to the 50% efficiency roadmap.

Back in May 2013, the German-French team of Fraunhofer ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin had already announced a solar cell with 43.6% efficiency. Building on this result, further intensive research work and optimization steps led to the present efficiency of 44.7%.

These solar cells are used in concentrator photovoltaics (CPV), a technology which achieves more than twice the efficiency of conventional PV power plants in sun-rich locations. The terrestrial use of so-called III-V multi-junction solar cells, which originally came from space technology, has prevailed to realize highest efficiencies for the conversion of sunlight to electricity. In this multi-junction solar cell, several cells made out of different III-V semiconductor materials are stacked on top of each other. The single subcells absorb different wavelength ranges of the solar spectrum.

"We are incredibly proud of our team which has been working now for three years on this four-junction solar cell," says Frank Dimroth, Department Head and Project Leader in charge of this development work at Fraunhofer ISE. "This four-junction solar cell contains our collected expertise in this area over many years. Besides improved materials and optimization of the structure, a new procedure called wafer bonding plays a central role. With this technology, we are able to connect two semiconductor crystals, which otherwise cannot be grown on top of each other with high crystal quality. In this way we can produce the optimal semiconductor combination to create the highest efficiency solar cells."

"This world record increasing our efficiency level by more than 1 point in less than 4 months demonstrates the extreme potential of our four-junction solar cell design which relies on Soitec bonding techniques and expertise," says André-Jacques Auberton-Hervé, Soitec's Chairman and CEO. "It confirms the acceleration of the roadmap towards higher efficiencies which represents a key contributor to competitiveness of our own CPV systems. We are very proud of this achievement, a demonstration of a very successful collaboration."

"This new record value reinforces the credibility of the direct semiconductor bonding approaches that is developed in the frame of our collaboration with Soitec and Fraunhofer ISE. We are very proud of this new result, confirming the broad path that exists in solar technologies for advanced III-V semiconductor processing," said Leti CEO Laurent Malier.

Concentrator modules are produced by Soitec (started in 2005 under the name Concentrix Solar, a spin-off of Fraunhofer ISE). This particularly efficient technology is employed in solar power plants located in sun-rich regions with a high percentage of direct radiation. Presently Soitec has CPV installations in 18 different countries including Italy, France, South Africa and California.

Lexus takes top spot in magazine's auto rankings

Lexus topped all automotive brands in Consumer Reports magazine's 2013 brand report card. Japanese automakers again dominated the rankings, taking eight of the top 10 spots.

Lexus vehicles are rarely sporty, but they earned the top score of 79 points out of 100 because of plush and reliable vehicles, the magazine said Tuesday. Subaru and Mazda were tied for second place with a score of 76. Toyota and Acura, Honda's luxury brand, rounded out the top five tied at 74. Honda and Scion were next at 72, followed by Audi and Nissan's upscale Infiniti brand, both at 70. Mercedes-Benz finished 10th with a score of 69.

The ratings of 26 automotive brands, closely watched by consumers, are based on the magazine's average road tests and predicted reliability scores from surveys of subscribers.

Detroit automakers didn't fare very well in the magazine's rankings. Cadillac was the best U.S.-based brand, tying for 14th place with Hyundai, scoring a 63.

Consumer Reports changed its rankings this year, splitting off individual brands from the companies that make them and scoring them individually. For example, in past years, all three Toyota brands—Lexus, Toyota and Scion—were scored collectively as Toyota.

The magazine said Lexus cars are among the most reliable even though they are "brimming with technology," including hybrid gas-electric power systems and complex information and entertainment systems.

Besides Cadillac, General Motors Co. had two other brands in the top 20: GMC and Chevrolet tied with Volvo for 17th with a score of 58. Buick, with a score of 54, was 21st.

Ford and Lincoln continued to be plagued by problems with the complexity of their touch-screen controls, the magazine said. Ford also has been hampered by "unrefined" automatic transmissions, according to the magazine. Ford finished 23rd with a score of 51, while Lincoln was 24th with 50.

No Chrysler brand fared well. Jeep and Dodge were the bottom two finishers with scores of 47 and 46.

Consumer Reports also released its top pick for 2013 models on Tuesday. The redesigned Honda Accord won in the popular midsize car segment, while Hyundai's Elantra won in the budget car category. The Subaru Impreza was the top pick for compact cars, while the Audi A6 was tops in the luxury segment. Honda's CR-V won the top spot for small crossover SUVs, while BMW's 328i was the top sports sedan, and the Toyota Prius was the top green car pick.

2.15 seconds: Students break 0-100 acceleration world record

The DUT Racing team from TU Delft, The Netherlands, has broken the world record for acceleration from 0 to 100 km/h for electric cars. The previous record stood at 2.68 seconds, but as of today the record is now held by the TU Delft students with 2.15 seconds. 'We thought that under these conditions we'd be happy with 2.30, but we really didn't expect 2.15,' says team manager Tim de Moree.

The students used their self-built racing car from 2012, the DUT12: a compact racing car with full four-wheel drive, weighing only 145 kg. The car was built for the Formula Student competition and the students won the unofficial World Championship with it at Hockenheim.

As light as possible

Every effort was made to break the acceleration record. Gihin Mok, one of the students responsible for the car, explains: 'We made the car a little lighter where possible, but the major difference lies in the electric motors. In the Formula Student competition, they were only allowed to produce 114 horsepower. The motors we used now are actually much more powerful, which means we had to limit them during the race. Now we used the maximum power. That totals 135 horsepower, about 33 horsepower per motor and almost one horsepower for each kilogram of weight.'

A home-made oven, made from an old oil barrel, ensured that the tyres were heated at the start. Even the racing driver was changed to achieve the fastest possible acceleration: Marly Kuijpers, 24, is the lightest member of the DUT Racing team. During the official competition, she had already achieved 2.50 seconds for acceleration from 0 to 100 km/h. Today, she has set her own and the world's fastest time. Talking about the feeling during the drive, Marly says: 'It feels like a roller coaster, that part when you just drop over the edge.'