September 22, 2016 | 1 Comment
Penn State researchers have made hundreds of observations of individual potassium atoms, cooled to just slightly above absolute zero. The atoms were trapped by lasers in a two-dimensional grid, and interacting with each other in intriguing ways that could help to reveal the behaviors of superconducting electrons.
The team’s scientists suspect that they have observed one of the important dynamics that contribute to producing high-temperature superconductivity; that is, that electrons start forming pairs that “bunch” with empty spaces in the lattice.
The research team’s achievements are an important step in recent efforts to improve today’s superconducting materials, which have superconducting powers only if they are cooled below a critical temperature, hundreds of degrees below the freezing point of water — temperatures at which helium is a liquid — making them impractical for use in most electronic devices.
The team’s research paper has been published in the journal Science. The research is focused on revealing the mysterious ingredients required for high-temperature superconductivity — the ability of a material’s electrons to pair up and travel without friction at relatively high temperatures, enabling them to lose no energy — to be super efficient — while conducting electricity.
The quest to know the mysterious recipe for high-temperature superconductivity, which could enable revolutionary advances in technologies that make or use electricity, just took a big leap forward thanks to the new research by the Penn State led international team of experimental and theoretical physicists.
Marcos Rigol, professor of physics at Penn State University and a theorist on the research team led by Martin Zwierlein, professor of physics and principal investigator at the NSF Center for Ultracold Atoms and the Research Laboratory of Electronics at the Massachusetts Institute of Technology (MIT) said, “We want to understand exactly which ingredients are necessary for high-temperature superconductivity, a beautiful quantum phenomenon with potentially important uses.”
From the research the team’s scientists suspect that they have observed one of the important dynamics that contribute to producing high-temperature superconductivity; that is, that electrons start forming pairs that “bunch” with empty spaces in the lattice.
An important contribution of the theorists on the team is their demonstration that the mathematical model developed to understand real materials (the so-called Hubbard model) could reproduce the behaviors of the atoms in the team’s 2-D experiments within a certain temperature range.
Rigol added, “If we can discover all the essential ingredients for superconductivity, we will have the opportunity to design recipes — theoretical models — for making high-temperature superconducting materials that can have a wide range of practical and innovative uses.”
Zwierlein led the team in building the experimental setup to help identify the ideal conditions for inducing superconductivity. This “quantum simulator” experiment uses atoms in a 2-D gas as stand-ins for electrons in a superconducting solid in order “to understand what’s really going on in these superconductors, and what one should do to make higher-temperature superconductors, approaching hopefully room temperature,” Zwierlein said.
Because of strong interactions, which are thought to be essential for high-temperature superconductivity to occur, not even the most powerful computers in the world have been able to solve the Hubbard model at the temperatures at which electrons are expected to become superconducting. A challenge for physicists, then, is to come up with computational techniques that can solve this model at the lowest possible temperatures in the current supercomputers. Rigol and collaborators developed one such technique, which was able to describe the experimental results.
“Our theoretical results precisely describe how the atoms in our team’s 2-D experiments actually behaved within the accessible temperature range,” Rigol said. “If future experiments are able to demonstrate at lower temperatures that the atoms in the experimental quantum simulator become superconducting — at temperatures at which our equations are just too difficult to solve — then we will know for sure that our theoretical model of high-temperature superconductivity is a good one.”
Rogol makes a useful point as the team’s results are important because, if superconductivity is observed at lower experimental temperatures, “we will know for sure that strong repulsive interactions between the electrons can produce high-temperature superconductivity. Achieving this understanding could have a profound impact in technology, as well, because knowing the features of a material that are necessary for producing high-temperature superconductivity could lead to the engineering of more advanced superconducting materials.”
Other team members with Rigol at Penn State and Zwierlein at MIT, includes Lawrence W. Cheuk, Matthew A. Nichols, Katherine R. Lawrence, Melih Okan, and Hao Zhang at the MIT-Harvard Center for Ultracold Atoms; Ehsan Khatami (a former postdoctoral researcher in Rigol’s group) at San José State University; Nandini Trivedi at Ohio State University; and Thereza Paiva at the Universidade Federal do Rio de Janiero.
Its refreshing to see that basic research looking to understand what is needed is underway with some results at hand. Some might wonder why this is just now getting started, while the fact is the depth of grasping how to get a look and sensors capable of supporting the experiments are only now becoming available.
Electrical line loss by itself is a large number worthy of the research. Yet the breakout will come from using superconductors in ways that have only been imagined so far and even more likely in ideas yet to be born.
September 21, 2016 | Leave a Comment
A Ulsan National Institute of Science and Technology (UNIST) team of researchers claims to have made yet another step towards finding a solution to accelerate the commercialization of silicon anode for lithium-ion batteries.
A new approach developed by a team of researchers, led by Prof. Jaephil Cho (School of Energy and Chemical Engineering) could hold the key to greatly improving the performance of commercial lithium-ion batteries.
Prof. Cho and his research team have developed a new type anode material that would be used in place of a conventional graphite anode, which they claim will lead to lighter and longer-lasting batteries for everything from personal devices to electric vehicles.
Over the course of the study, the research team demonstrated the feasibility of a next-generation hybrid anode using silicon-nanolayer-embedded graphite/carbon. They report that this architecture allows compatibility between silicon and natural graphite and addresses the issues of severe side reactions caused by structural failure of crumbled graphite dust and uncombined residue of silicon particles by conventional mechanical milling.
The newly-developed anode material has been manufactured with an increase in graphite content in the composite by 45%. The research team has also developed new equipment, which is capable of producing 300kg in 6 hours per batch using a small amount of silane gas (SiH4). Such simple procedure is expected to ensure a competitive price.
The team reports that the silicon/graphite composite is mass-producible and it has superior battery performances with industrial electrode density, high areal capacity, and low amounts of binder.
The work has been supported by the IT R&D program of the Ministry of Trade, Industry & Energy (MOTIE) and Korea Evaluation Institute of Industrial Technology (KEIT), 2016 Research Fund of UNIST, and by the Office of Vehicle Technologies, Battery Materials Research Program of the US Department of Energy.
With the certain cell phone battery catching fire, lithium ion is back in the news. While the anode material discussion above isn’t mentioning heat generation one suspects that is very high, if not the top of the list, for device manufacturers. It will be interesting to see if the team follows on with some heat production testing.
With lithium ion technology so widespread now it isn’t a big surprise a model is self igniting. Its been quite some time since the batteries in Boeing’s Dreamliner lit off, and that got solved in pretty short order. One wonders if perhaps manufacturers might want to do more battery testing before shipping millions of them and risking billions of revenue dollars and perhaps, the whole firm.
Purdue University researchers with an international team of collaborators have used a ‘thermal metamaterial’ to control the emission of radiation at high temperatures. The advance that could bring about devices able to efficiently harvest waste heat from power plants and factories.
Generally, its known that about 50 to 60 percent of the energy generated in coal and oil-based power plants is wasted as heat. However, thermophotovoltaic devices that generate electricity from thermal radiation might be adapted to industrial pipes in factories and power plants, as well as on car engines and automotive exhaust systems, to recapture much of the wasted energy.
In new findings, researchers demonstrated how to restrict emission of thermal radiation to a portion of the spectrum most needed for thermophotovoltaic technology.
Zubin Jacob, an assistant professor of electrical and computer engineering at Purdue University explains, “These devices require spectrally tailored thermal emission at high temperatures, and our research shows that intrinsic material properties can be controlled so that a very hot object glows only in certain colors. The main idea is to start controlling thermal emission at record high temperatures in ways that haven’t been done before.”
The thermal metamaterial – nanoscale layers of tungsten and hafnium oxide – was used to suppress the emission of one portion of the spectrum while enhancing emission in another.
Metamaterials are composite media that contain features, patterns or elements such as tiny nanoantennas that enable an unprecedented control of light. Under development for about 15 years, the metamaterials owe their unusual abilities to precision design and manufacture on the scale of nanometers.
Jacob said, “They have been used mainly to manipulate coherent light, as in a laser, but the ability to manipulate infrared thermal radiation at 1,000º C opens up new areas of research. The technique we used to achieve this thermal suppression and enhancement is fundamentally different from existing thermal engineering approaches and harnesses a phenomenon called topological transitions.”
The findings were detailed in a research paper published in the journal Nature Communications. The work was performed by researchers at Purdue, the Hamburg University of Technology in Germany; University of Alberta in Canada; and Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research in Germany. The co-lead authors were Hamburg University of Technology postdoctoral researcherPavel Dyachenko and University of Alberta doctoral student Sean Molesky.
The research represents the first time the approach was used for thermal emission in high-temperature metamaterials, also called refractory metamaterials.
Jacob pointed out, “My student, Sean Molesky, theoretically predicted it in 2012, and it has taken about four years and some exceptional materials engineering from our collaborators to perform the high-temperature experiments and demonstrate the thermal metamaterial.”
The basic operating principle of a photovoltaic cell is that a semiconducting material is illuminated with light, causing electrons to move from one energy level to another. Electrons in the semiconductor occupy a region of energy called the valence band while the material is in the dark. But shining light on the material causes the electrons to absorb energy, elevating them into a region of higher energy called the conduction band. As the electrons move to the conduction band, they leave behind “holes” in the valance band. The region between both bands, where no electrons exist, is called the band gap.
Jacob explained. “If you have energy below the band gap, that is generally wasted,” Jacob said. “So what you want to do for high-efficiency thermal energy conversion is suppress the thermal emission below the band gap and enhance it above the band gap, and this is what we have done. We have used the topological transition in a way that was not done before for thermal enhancement and suppression, enhancing the high-energy part of the emission spectrum and suppressing the low-energy thermal photons. This allows us to emit light only within the energy spectrum above the band gap.”
Future research will include work to convert heat radiation from a thermal metamaterial to electron-hole pairs in a semiconducting material, a critical step in developing the technology. The thermophotovoltaic technology might be ready for commercialization within seven years, Jacob said.
The paper’s authors with Jacob; Hamburg University of Technology researchers Alexander Yu Petrov, Slawa Lang, Manfred Eich, T. Krekeler and M. Ritter; and senior research scientist Michael Störmer from the Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research.
The research was funded by the German Research Foundation, National Science and Engineering Research Council of Canada, Alberta Innovates Technology Futures, and the Helmholtz-Alberta Initiative.
Its often not recalled that half and more of the energy we buy is just lost, usually in heat. It would be quite a change if that energy was not lost, total needs would be cut, costs would go down and use could increase without so much concern. It would really brighten up the future.
So we’ll be watching for this group’s next press release. They don’t have to get it all, just a nice chuck of the losses would be great.
University of Illinois at Urbana-Champaign researchers have identified the active form of an iron-containing catalyst for reducing oxygen gas, the element in a fuel cell that slows the process. Fuel cells have long held promise as power sources, but low efficiency from oxygen presence creates an obstacle to realizing the potential. The finding could help researchers refine better catalysts, making fuel cells a more energy- and cost-efficient option for powering vehicles and other applications.
The U. of I. researchers their and collaborators have identified the active form of an iron-containing catalyst for the process problem of reducing the oxygen gas molecule of two oxygen atoms, so that it can break apart and combine with ionized hydrogen to make H2O water, where only one oxygen atom is used.
Iron-based catalysts for oxygen reduction are an abundant, inexpensive alternative to catalysts containing precious metals, which are expensive and can degrade. However, the process for making iron-containing catalysts yields a mixture of different compounds containing iron, nitrogen and carbon. Since the various compounds are difficult to separate, exactly which form or forms behave as the active catalyst has remained a mystery to researchers. This has made it difficult to refine or improve the catalyst.
Gewirth explained, “Previously, we didn’t know what these catalysts were made of because they had a lot of different things inside them. Now we’ve narrowed it down to one component. Since we know what it looks like, we can change it and work to make it better.”
The researchers used a chlorine gas treatment to selectively remove from the mixture particles that were not active for oxygen reduction, refining the mixture until one type of particle remained: a carbon-encapsulated iron nanoparticle.
Jason Varnell, a graduate student and the first author of the paper described the result, “We were left with only nanoparticles encapsulated within a carbon support, and that allows them to be more stable. Iron oxidizes and corrodes on its own. You need to have the carbon around it in order to make it stable under fuel cell conditions.”
The researchers hope that narrowing down the active form of the catalyst can open new possibilities for making purer forms of the active catalyst, or for tweaking the composition to make it even more active.
Gewirth thinks the problems through with, “What’s the optimal size? What’s the optimal density? What’s the optimal coating material? These are questions we can now address. We’re trying alternative methods for synthesizing the active catalyst and making multicomponent nanoparticles with certain amounts of different metals. Previously, people would add some metal salt into the tube furnace, like cooking – a little of this, a little of that. But now we know we also need to do things at different temperatures to put other metals in it. It gives us the ability to make it a more active catalyst.”
Ultimately, the researchers hope that improved catalyst function and manufacturability will lead to more-efficient fuel cells, which could make them useful for vehicles or other power-intensive applications.
“Now we understand the reactivity better,” Varnell said. “This could lead to the creation of more viable alternatives to precious metal catalysts.”
Even in the midst of an oil glut the fuel cell work goes on with encouraging results. So far only the most lavishly funded projects can have fuel cells like space programs and government mass transit demonstrations. So far the cost sunk into a fuel cell isn’t making anywhere close to economic sense.
But the technology is inching closer and one of the developments or breakthroughs is going to be the tipping point. This may be the one. Then perhaps the market will be ready for a real fuel to energy revolution.
September 14, 2016 | Leave a Comment
Scientists from Forschungszentrum Juelich have developed the first complete and compact design for an artificial photosynthesis system. The team believes this is a decisive step towards applying the water splitting technology. The concept is flexible both with respect to the materials used and in particular, the size of the system.
The researchers expect that over time the sun and wind will supply the lion’s share of our energy. The fluctuating nature of these renewable energy sources means that current research is focusing more intensively on efficient storage technologies. Like the energy sources themselves, these technologies should be environmentally friendly and affordable.
This trend is particularly apparent in research on direct photoelectrochemical water splitting, that is to say artificial photosynthesis employing a combination of solar cell and electrolyser. In this way, solar energy can be directly converted into the universal storage medium of hydrogen. This process was first investigated in the 1970s, but has only begun to attract increasing attention in recent years. As yet, research has focused on materials science for new absorber materials and catalysts to further improve efficiency.
However, Juelich solar cell researchers Jan-Philipp Becker and Bugra Turan are concentrating on an aspect that has so far largely been neglected: a realistic design that can take this technology from the scientists’ laboratories and put it into practical applications. “To date, photoelectrochemical water splitting has only ever been tested on a laboratory scale,” explained Burga Turan. “The individual components and materials have been improved, but nobody has actually tried to achieve a real application.”
The design created by the two experts from Juelich’s Institute of Energy and Climate Research is clearly different from the usual laboratory experiments. Instead of individual components the size of a finger nail that are connected by wires, the researchers have developed a compact, self-contained system – constructed completely of low-cost, readily available materials.
With a surface area of only 64 cm2, their component still appears relatively small. The innovation is in its flexible design. By continuously repeating the basic unit, it will in future even be possible to fabricate systems that are several square meters in size. The basic unit itself consists of several solar cells connected to each other by a special laser technique. “This series connection means that each unit reaches the voltage of 1.8 volt necessary for hydrogen production,” said Jan-Philipp Becker. “This method permits greater efficiency in contrast to the concepts usually applied in laboratory experiments for scaling up.”
At the moment, the solar-to-hydrogen efficiency of the prototype is 3.9 %. “That doesn’t sound like much,” admitted Bugra Turan. “But naturally this is only the first draft for a complete facility. There’s still plenty of room for improvement.” In fact – the scientists add – natural photosynthesis only achieves an efficiency of one percent.
Jan-Philipp Becker is of the opinion that within a relatively short time the Jülich design could be increased to around 10 % efficiency using conventional solar cell materials. However, there are also other approaches. For instance, perovskites, a novel class of hybrid materials, with which it is already possible to achieve efficiencies of up to 14 %.
Becker explained, “This is one of the big advantages of the new design, which enables the two main components to be optimized separately: the photovoltaic part that produces electricity from solar energy and the electrochemical part that uses this electricity for water splitting.”
The Jülich researchers have patented this concept, which can be flexibly applied for all types of thin-film photovoltaic technology and for various types of electrolyzer. “For the first time, we are working towards a market launch,” says Becker. “We have created the basis to make this reality.”
Perhaps the team has nailed the basics for a photoelectrochemical water splitting system. Lots of independent entrepreneurs have taken a run at it and nothing of note is to be seen in the market so far. This tech is lots harder than it seems. And the German team hasn’t got a storage system on board yet. There is a ways to go.
But academic effort with some money, third party oversight, result replication and the credibility that comes with all these basics could be what the market needs.
That would handle the front end, getting the energy available. The devices to store and use the hydrogen are still developing. Once one of these front end systems is economically proven the intensity for results on the back end will grow exponentially.