Princeton Plasma Physics Laboratory (PPPL) scientists have discovered a remarkably simple way to suppress a common instability that can halt Tokamak fusion reactions and damage the walls of reactors built to create a “star in a jar.”

The findings, published in June in the journal Physical Review Letters, stem from experiments performed on the National Spherical Torus Experiment-Upgrade (NSTX-U), at the Department of Energy’s Princeton Plasma Physics Laboratory.

Sketch of neutral beam geometry. Original NSTX beams in green, new beams for NSTX-U in red. Image Credit: Eric Fredrickson. Click image for the largest view.

The suppressed instability is called a Global Alfvén Eigenmode (GAE) – a common wave-like disturbance that can cause fusion reactions to fizzle out. Suppression was achieved with a second neutral beam injector recently installed as part of the NSTX-U upgrade. Just a small amount of highly energetic particles from this second injector was able to shut down the GAEs.

Such instabilities are akin to a snake or dragon that swallows its own tail. Stirring up GAEs are the same neutral beam particles that heat the plasma, which are ionized into electrons and ions, or atomic nuclei, inside the gas. Once triggered by these fast ions, the GAEs can rise up and drive them out, cooling the plasma and halting fusion reactions.

Suppressing this arousal were beams from the second injector, which flow through the plasma at a higher pitch-angle, in a direction roughly parallel to the magnetic field that confines the hot gas. Physicists call such beams “outboard” to distinguish them from the “inboard” beams that the original NSTX-U injector produces, which flow through the plasma and the magnetic field in a more perpendicular fashion.

Injection of the outboard beam suppressed GAEs in milliseconds. Fast ions from the beam combined with those from the inboard beam to increase the density of the ions and alter their distribution in the plasma. The sudden alteration reduced the gradient, or slope, of the ion density, without which GAEs were unable to form and ripple through the plasma.

These remarkable results were good news for fusion development. “Normally, when you inject energetic particles, you drive up instabilities,” said Jonathan Menard, head of research on NSTX-U. “The fact that the second neutral beam was able to turn them off by varying the fast-ion distribution with a small amount of particles provides our research with flexibility and is a welcome discovery.”

The result validated predictions of a computer code called “HYM,” developed by PPPL physicist Elena Belova, and could prove useful to ITER, the international fusion facility under construction in France to demonstrate the ability to confine a burning plasma and produce 10 times more energy than it consumes.

“This research demonstrates suppression of GAEs with just a small population of energetic particles,” said physicist Eric Fredrickson, lead author of the journal article. “It gives confidence that by using this code, reasonable predictions of GAE stability can be made for ITER.”

Long term readers will recall this writer has a dim view on the ITER project as its a political creature started without the basics understood well enough to trigger a start. Moreover, the project vacuums money by the billions leaving other ideas without resources. Not a great idea, as poorly executed as any government driven exercise ever seen.

But the Princeton effort is worthwhile, if only proving now that its these types of efforts that will give ITER potential. Princeton needs more support, ITER less – until those like Princeton put the legs on the Tokamak.

Okinawa Institute of Science and Technology (OIST) Graduate University researchers have improved perovskite-based technology in the entire energy cycle. The progress ranges from solar cells harnessing power to LED diodes to light the screens of future electronic devices and other lighting applications.

Researchers from the Energy Materials and Surface Unit at OIST. From left to right: Dr. Luis Ono, Dr. Yan Jiang, Dr. Linquiang Meng and Prof. Yabing Qi.  Image Credit: OIST. Click image for the largest view.

Perovskite is a naturally occurring mineral, but the perovskite used in today’s technology is quite different from the rock found in the Earth’s mantle. A designed “perovskite structure” uses a different combination of atoms but keeps the general 3-dimensional structure originally observed in the mineral, which possesses superb optoelectronic properties such as strong light absorption and facilitated charge transport. These advantages qualify the perovskite structure as particularly suited for the design of electronic devices, from solar cells to lights.

The accelerating progress in perovskite technology over the past few years suggest new perovskite-based devices will soon outperform current technology in the energy sector. The Energy Materials and Surface Sciences Unit at OIST led by Prof. Yabing Qi is at the forefront of this development, with now two new scientific publications focusing on the improvement of perovskite solar cells and a cheaper and smarter way to produce emerging perovskite-based LED lights.

Perovskite-based solar cells is a rising technology forecast to replace the classic photovoltaic cells currently dominating the industry. In just seven years of development, the efficiency of perovskite solar cells increased to almost rival – and is expected to soon overtake – commercial photovoltaic cells, but the perovskite structure still plagued by a short lifespan due to stability issues. OIST scientists have made constant baby steps in improving the cells stability, identifying the degradations factors and providing solutions towards better solar cell architecture.

The new finding, reported in the Journal of Physical Chemistry B, suggests interactions between components of the solar cell itself are responsible for the rapid degradation of the device. More precisely, the titanium oxide layer extracting electrons made available through solar energy – effectively creating an electric current – causes unwanted deterioration of the neighboring perovskite layer. Imagine the solar cell as a multi-layered club sandwich: if not properly assembled, fresh and juicy vegetables in contact with the bread slices will make the bread very soggy in a matter of hours. But if you add a layer of ham or turkey between the vegetables and the bread, then your sandwich stays crisp all day in the lunchroom refrigerator.

That metaphor describes what the OIST researchers achieved: they inserted in the solar cell an additional layer made from a polymer to prevent direct contact between the titanium oxide and the perovskite layers. The polymer layer is insulating but very thin, which means it lets the electron current tunnel through yet does not diminish the overall efficiency of the solar cell, while efficiently protecting the perovskite structure.

Dr. Longbin Qiu explained, “We added a very thin sheet, only a few nanometers wide, of polystyrene between the perovskite layer and the titanium oxide layer. Electrons can still tunnel cross this new layer and it does not affect the light absorption of the cell. This way, we were able to extend the lifetime of the cell four-fold without loss in energy conversion efficiency.”

The lifespan of the new perovskite device was extended to over 250 hours – still not enough to compete with commercial photovoltaic cells regarding stability, but an important step forward toward fully functional perovskite solar cells.

At the other end of the energy range:

The bipolar electronic properties of the perovskite structure not only confer them the ability to generate electricity from solar energy but also can convert electricity into vivid light. Light-Emitting Diode technology, omnipresent in our daily life from laptop and smartphone screens to car lights and ceiling tubes, currently relies on semi-conductors that are difficult and expensive to manufacture. Perovskite LEDs are envisaged to become the new industry standard in the near future due to the lower cost and their efficiency to convert power into light. Moreover, by changing the atomic composition in the perovskite structure, perovskite LED can be easily tuned to emit specific colors.

The manufacturing of these perovskite LEDs is currently based on dipping or covering the targeted surface with liquid chemicals, a process which is difficult to setup, limited to small areas and with low consistency between samples. To overcome this issue, OIST researchers reported in the Journal of Physical Chemistry Letters the first perovskite LED assembled with gasses, a process called chemical vapor deposition or CVD.

Professor Yabing Qi noted, “Chemical vapor deposition is already compatible with the industry, so in principle it would be easy to use this technology to produce LEDs. The second advantage in using CVD is a much lower variation from batch to batch compared to liquid-based techniques. Finally, the last point is scalability: CVD can achieve a uniform surface over very large areas.”

Like the solar cell, the perovskite LED also comprises many layers working in synergy. First, an indium tin oxide glass sheet and a polymer layer allow electrons into the LED. The chemicals required for the perovskite layer – lead bromide and methylammonium bromide – are then successively bound to the sample using CVD, in which the sample is exposed to gasses in order to convert to perovskite instead of typically solution-coating processes with liquid. In this process, the perovskite layer is composed of nanometer-small grains, whose sizes play a critical role in the efficiency of the device. Finally, the last step involves the deposition of two additional layers and a gold electrode, forming a complete LED structure. The LED can even form specific patterns using lithography during the manufacturing process.

Dr. Lingqiang Meng explained, “With large grains, the surface of the LED is rough and less efficient in emitting light. The smaller the grain size, the higher the efficiency and the brighter the light. By changing the assembly temperature, we can now control the growth process and the size of the grains for the best efficiency.”

Controlling the grain size is not the only challenge for this first-of-its-kind assembling technique of LED lights.

Dr. Luis K. Ono explained further, “Perovskite is great, but the choice in the adjacent layers is really important too. To achieve high electricity-to-light conversion rates, every layer should be working in harmony with the others.”

The result is a flexible, thick film-like LED with a customizable pattern. The luminance, or brightness, currently reaches 560 cd/m2, while a typical computer screen emits 100 to 1000 cd/m2 and a ceiling fluorescent tube around 12,000 cd/m2.

Dr. Meng added, “Our next step is to improve the luminance a thousand-fold or more. In addition, we have achieved a CVD-based LED emitting green light but we are now trying to repeat the process with different combinations of perovskite to obtain a vivid blue or red light.”

Now this is a very busy group of researchers making remarkable progress. The perovskite LEDs are most likely to be in new products fairly soon. This group has made that prospect even more likely with even better products than one would have expected just days ago.

University of Sydney researchers have found a solution for one of the biggest stumbling blocks of zinc-air batteries. Zinc-air batteries could overtake conventional lithium-ion batteries as the power source of choice in electronic devices.

A University of Sydney researcher holds up a rechargeable zinc-air battery. Image Credit: The University of Sydney. Click image for the largest view.

Zinc-air batteries operate with zinc metal and oxygen from the air. Due to the global abundance of zinc metal, these batteries are much cheaper to produce than lithium-ion batteries, and they can also store more energy (theoretically five times more than that of lithium-ion batteries), are much safer and are more environmentally friendly.

Zinc-air batteries are currently used as an energy source in hearing aids, some film cameras and railway signal devices. They are simply disposed of when discharged. Their widespread use has been hindered by the fact that, up until now, recharging them has proved difficult. This is due to the lack of electrocatalysts that successfully reduce and generate oxygen during the discharging and charging of a battery.

A paper authored by chemical engineering researchers from the University of Sydney and Nanyang Technological University published in Advanced Materials outlines a new three-stage method to overcome this problem.

According to lead author Professor Yuan Chen, from the University of Sydney’s Faculty of Engineering and Information Technologies, the new method can be used to create bifunctional oxygen electrocatalysts for building rechargeable zinc-air batteries from scratch.

“Up until now, rechargeable zinc-air batteries have been made with expensive precious metal catalysts, such as platinum and iridium oxide. In contrast, our method produces a family of new high-performance and low-cost catalysts,” he said.

These new catalysts are produced through the simultaneous control of the: 1) composition, 2) size and 3) crystallinity of metal oxides of earth-abundant elements such as iron, cobalt and nickel. They can then be applied to build rechargeable zinc-air batteries.

Paper co-author Dr Li Wei, also from the University’s Faculty of Engineering and Information Technologies, said trials of zinc-air batteries developed with the new catalysts had demonstrated excellent rechargeability – including less than a 10 percent battery efficacy drop over 60 discharging/charging cycles of 120 hours.

“We are solving fundamental technological challenges to realize more sustainable metal-air batteries for our society,” Professor Chen added.

Its a bit early to say ‘revolution’, but a cell phone battery with four or five times the capacity of lithium-ion would be welcome, indeed. Assuming the phone manufactures have the sense to make swapping in a new one easy, phone potential would jump up another level.

Argonne National Laboratory scientists have engineered a new material to be used in redox flow batteries. Redox flow batteries are particularly useful for storing electricity for the grid. The new material consists of carefully structured molecules designed to be particularly electrochemically stable in order to prevent the battery from losing energy to unwanted reactions.

A new material developed at Argonne shows promise for batteries that store electricity for the grid. The material consists of carefully structured molecules designed to be particularly electrochemically stable in order to prevent the battery from losing energy to unwanted reactions. Image Credit: Robert Horn, Argonne National Laboratory. Click image for the largest view.

The results of the research, some of the best ever recorded for batteries of this type, have been published in Advanced Energy Materials.

To briefly refresh, in this type of battery, called nonaqueous redox flow, energy is stored in negatively and positively charged solutions inside large tanks.

The molecular makeup of the energized solutions in the tanks plays a major role in how much energy the battery is able to produce, and this research focused on designing the ideal molecule to dissolve in the positively charged tank. To maximize efficiency, the researchers had to structure the molecule to hold as much energy as possible while also being stable enough to limit superfluous reactions.

Jingjing Zhang, a postdoc involved in the research said, “We want the stability of the molecules to be high so the battery doesn’t break down prematurely, but we also want it to be able to hold a lot of energy. The two are at odds.”

The molecule’s reversibility, or its ability to be repeatedly charged and discharged, is the very property that allows flow batteries to function. During charging, molecules stored in the positively charged tank shed electrons through a process called oxidation. A problem arises when these now unstable, positively charged molecules begin to react with their surroundings, sapping the charge that would otherwise be stored in the tank and used for power.

Lu Zhang, the leading scientist on the team said, “When it loses an electron, the molecule has a natural tendency to find another electron for a complete pair, and if they form a bond, that means it can’t produce electricity anymore.”

The researchers on this project were able to shut down a common energy-sucking side reaction using a process called bicyclic substitution, which protects the most reactive parts of the molecule’s atomic scaffolding, somewhat like using insulation to cover exposed wires.

Bicyclic substitution itself is not new, but this research was the first to apply it to battery materials. Previously, battery scientists used bulkier protective atomic chains to increase stability. However, these shields tended to suffocate the battery; only half of the reactive molecular regions could be covered without eliminating the molecule’s ability to give off any energy at all.

Lu Zhang explained, “With bicyclic substitution, we finally found a way to protect all of the molecule’s reactive positions without losing its reversibility, and we were able to get very good performance out of it.”

The researchers discovered that the battery suffered only a minimal loss of capacity after 150 cycles of charging and draining the battery, proving the high stability of the molecule.

Jingjing Zhang summed up for the press release, “Bicyclic substitution allows us to avoid compromising between stability and reversibility. Maximizing these two properties is key in engineering more efficient batteries for powering entire buildings and even larger systems in the future.”

This looks like an improvement on an important technology. Redox flow or another technology is critical for energy from things like solar and wind that are economic failures living on politically pressured economics to survive. The sooner one of these gets viable and scalable, the better. Perhaps, and its a long shot, the sub economic energy producers can prosper with low enough cost storage.

Fuzhou University in China scientists report the synthesis of a macroscopic aerogel from carbonitride nanomaterials which is an excellent catalyst for the water-splitting reaction under visible-light irradiation. The study adds new opportunities to the material properties of melamine-derived carbonitrides.

The study has been published in the journal Angewandte Chemie.

Melamine can be polymerized with formaldehyde to give a highly durable and light resin, but it can also condensed to form nanostructures of carbonitride materials. These assemblies made of carbon and nitrogen combine the honeycomb-like electronically active network of graphene with some extra functionality of nitrogen. Searching for ways to assemble these nanostructures into a stable macroscopic architecture, Xinchen Wang and his team at Fuzhou University have now prepared a catalytically highly active and stable lightweight material, which serves well in artificial photosynthesis and offers very interesting structural and electronic properties.

Image Credit: Prof Wang, Fuzhou University. Click image for the largest view.

Aerogels are gels but without water – up to ninety-nine percent of their structure is air. This porosity gives them a huge surface ideal for catalytic or sensory application. As carbonitrides are materials with very interesting nanostructure and graphene-like properties but nitrogen functionality, it has long be sought to bring them into a controlled macroscopic assembly.

The authors said in the study, “Since CN is rich in nitrogen-containing groups, it is expected that CN may have interesting assembly behaviors like proteins or peptides in biological systems.”

The enhanced surface area and higher number of catalytic sites would make these aerogels highly functional macroscopic materials. Employing only physical interparticle forces intrinsic to the nanoparticles, the scientists prepared the aerogel by making a colloidal aqueous solution of carbonitride nanoparticles to settle first into a hydrogel, then converting it into a stable aerogel by a conventional freeze-drying technology.

The authors explained that, “This method has several advantages, including scalability for mass production and low cost.” In combination with a platinum co-catalyst, the aerogel was much better a photocatalyst for hydrogen evolution than the bulk carbonitride, and hydrogen peroxide was generated from pure water under visible-light irradiation when the bulk carbonitride failed.

By joining forces of chemical and physical characteristics from the nano- to the macroscale, they have created a new lightweight material with excellent catalytic prospects. This promising application of melamine building blocks points the way forward to new materials, and is far apart from the well-established mass production of the light and durable, but not so thermostable melamine plastic dishes.

It is interesting to see the Chinese making innovative contributions to the knowledge base. Over the past few years the site has seen more and more non U.S. study and research work make the peer review press. Its great to see them coming on and a disappointment for U.S. folks laboring under low funding – blown by politicians on choosing leader business projects.

The only questions here are just how is the co-catalyst platinum involved and can that be “low cost”?


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