Monday, June 6, 2011

Details of new type of electric car battery released

After being spun off from parent company A123 Systems last year; the new offspring, 24M has published a paper in Advanced Energy Materials, ending months of speculation about what it has been working on. It was no secret that the new project was to advance work on a new type of battery that A123 had been working on for a couple of years; namely a battery that could be used to replace the lithium-ion batteries currently used in electric cars. Now, with the paper’s release it's clear that the new battery, similar to a flow battery, uses a liquid material to hold the charge, rather than conventional dry fuel cells, and if successful could do away with a lot of the non-charge holding stuff that makes up nearly three quarters of the bulk of current electric car batteries.

Assisted by a grant from the U.S. Advanced Research Projects Agency-Energy (ARPA-E), to help fund research between the new start-up, MIT and Rutgers University, the new , based on research done by Yet-Ming Chiang who is both a professor at MIT and founder of A123 Systems and 24M, if successful, would allow for upsizing of car batteries without adding any non-chargeable material, greatly increasing its density, which would in turn, theoretically greatly reduce the cost of the battery pack in an electric vehicle. Current battery packs now constitute up to a third of the total vehicle price.

The new battery, as described in the paper, uses a sludge-like material contained in storage tanks, rather than dry cells; one positively charged, the other negative. To get the charge from the battery, the materials are pumped through channels allowing ions to move freely between the two and eventually to an external circuit. To facilitate the transfer of electrons from the sludge, nanoscale particles that help to form networks that give the electrons a path to follow were developed and added to the sludge mix. In this type of battery, the amount of storage capacity goes up as the tank size is increased, with no additional materials needed, in sharp contrast to batteries.

The battery is not yet ready for prime time though, as a current model of the battery would be bulky and the electrical conductivity, according to Change, is still far below what would be needed in a real world battery in an actual electrical vehicle; research is still ongoing, as he and his team try to figure out how to increase the concentration of the active materials in the sludge.

More information: Semi-Solid Lithium Rechargeable Flow Battery, Advanced Energy Materials, Article first published online: 20 MAY 2011 DOI: 10.1002/aenm.201100152

A new kind of flow battery is fueled by semi-solid suspensions of high-energy-density lithium storage compounds that are electrically ‘wired’ by dilute percolating networks of nanoscale conductor particles. Energy densities are an order of magnitude greater than previous flow batteries; new applications in transportation and grid-scale storage may result.

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New mass spectrometry technique clouds early European inflation theories

Using a new coupled mass spectrometry technique that employs multiple collectors, researchers in France have shown that it was not an influx of silver from the America's that caused high inflation in Europe from the early 1500's to mid 1600, as some historians have long believed. Their results, published in the Proceedings of the National Academy of Sciences (PNAS) show that the gradual replacement of coins made from Spanish silver to imported Mexican silver, did not occur until nearly fifty years later.

The research, led by Anne-Marie Desaulty, sought to answer once and for all the question of why the whole of Europe experienced a dramatic, inexplicable rise in overall prices, shortly after the discovery of the new world.

Until now, researchers have had to rely on the results of analysis of lead and copper found in coins to trace its origins, because the results obtained from doing so on silver couldn’t be trusted. Unfortunately, due to the difficulty of reading isotope results for lead, and the fact that copper was used at later dates to re-mint coins, no real conclusions could be drawn from the results of such tests. Now however, using the new technique, the team was able to discern that silver from Mexico didn’t begin appearing in Spanish coins until the inflationary period was over; though it did become the principal source of silver in such coins thereafter.

In the past, mass spectrometry tests on silver were fraught with difficulty due to the ratio of its two stable isotopes, silver-107 and 109; making them extremely difficult to measure. New advances in mass spectrometry devices however, coupled with multiple collectors, has made the process more sensitive; sensitive enough so that the results of such tests can now be trusted; and those findings suggest that it was not the sudden importation of Mexican silver as a means of minting Spanish coins that led to the , because there simply wasn’t enough of it present in during the period in question.

Unfortunately though, because the study was able to rule out the influx of Mexican as a cause for the inflation, a new gap in knowledge has been left behind, which will send scholars and researchers back to the drawing boards to explain why in fact, prices in Europe rose as they did, and why it happened for so long.

More information: Isotopic Ag–Cu–Pb record of silver circulation through 16th–18th century Spain, PNAS, Published online before print May 23, 2011, doi: 10.1073/pnas.1018210108

Estimating global fluxes of precious metals is key to understanding early monetary systems. This work adds silver (Ag) to the metals (Pb and Cu) used so far to trace the provenance of coinage through variations in isotopic abundances. Silver, copper, and lead isotopes were measured in 91 coins from the East Mediterranean Antiquity and Roman world, medieval western Europe, 16th–18th century Spain, Mexico, and the Andes and show a great potential for provenance studies. Pre-1492 European silver can be distinguished from Mexican and Andean metal. European silver dominated Spanish coinage until Philip III, but had, 80 y later after the reign of Philip V, been flushed from the monetary mass and replaced by Mexican silver.


Penn researchers help nanoscale engineers choose self-assembling proteins


Engineering structures on the smallest possible scales -- using molecules and individual atoms as building blocks -- is both physically and conceptually challenging. An interdisciplinary team of researchers at the University of Pennsylvania has now developed a method of computationally selecting the best of these blocks, drawing inspiration from the similar behavior of proteins in making biological structures.

The team was led by postdoctoral student Gevorg Grigoryan and professor William DeGrado of the Department of Biochemistry and in Penn’s Perelman School of Medicine, as well as graduate student Yong Ho Kim of the Department of Chemistry in Penn’s School of Arts and Sciences. Their colleagues included members of the Department of Physics and Astronomy in SAS.

Their research was published in the journal Science last week.  

The team set out to design proteins that could wrap around single-walled carbon nanotubes. Consisting of a cylindrical pattern of carbon atoms tens of thousands of times thinner than a human hair, nanotubes are enticing to nanoengineers as they are extraordinarily strong and could be useful as platform for other nano-structures.

“We wanted to achieve a specific geometric pattern of the that these proteins are composed of on the surface of the nanotube,” Grigoryan said. “If you know the underlying atomic lattice, it means that you know how to further build around it, how to attach things to it. It's like scaffolding for future building.”

The hurdle in making such scaffolds isn’t a lack of information, but a surfeit of it: researchers have compiled databases that list hundreds of thousands of actual and potential structures in atomic detail. Picking the building materials for a particular structure from this vast array and assuring that they self-assemble into the desired shape was beyond the abilities of powerful computers, much less humans.  

“There's just an enormous space of structural possibilities to weed through trying to figure out which are feasible,” Grigoryan said. “To have a process that can do that quickly, that can look at a structure and say ‘that's not reasonable, that can't be built out of common units,’ would solve that problem.”

The researchers’ algorithm works in three steps, which, given the parameters of the desired scaffolding, successively eliminate proteins that will not produce the right shape. The elimination criteria were based on traits like symmetry, periodicity of binding sites  and similarity to protein “motifs” found in nature. 

After separating the wheat from the chaff, the result is a list of thousands of candidate proteins. While still a daunting amount, the algorithm makes the protein selection process merely difficult, rather than impossible.

The research team tested their algorithm by designing a protein that would not only stably wrap around a nanotube in a helix but also provide a regular pattern on its exterior to which gold particles could be attached.

“You could use this to build a gold nanowire, for instance, or modulate the optical properties of the underlying tube in desired ways” Grigoryan said.

Next steps will include applying this algorithm for designing proteins that can attach to graphene, which is essentially an unrolled nanotube. Being able to make scaffolds out of customizable array of proteins in a variety of shapes could lead to advances in everything from miniaturization of circuitry to drug delivery. 

Engineering these materials in the lab requires a tremendous amount of precision and computational power, but such efforts are essentially mimicking a phenomenon found in even the simplest forms of life.  

“The kind of packing that certain viruses have in their viral envelope is similar to what we have here in that they self-assemble. They have protein units that, on their own, form their complicated structures with features that are far beyond the size of any single protein,” Grigoryan said. “Each protein doesn’t know what the final structure is going to be, but it still helps form it. We were inspired by that.”

Provided by University of Pennsylvania (news : web)

Environmentally friendly rockets

Many rockets, satellites, and spacecraft are driven by hydrazine, sometimes with an oxidizing agent like nitric acid or dinitrogen tetroxide. When filling tanks with these highly toxic substances, technicians must wear full protective clothing—and a failed launch can lead to significant environmental damage. Researchers are thus looking for alternatives that are more environmentally friendly and less toxic, but just as powerful—requirements that are hard to meet in a single material.

Stefan Schneider and his co-workers at the Air Force Laboratory (Edwards Air Force Base, USA) have now introduced a new approach in the journal Angewandte Chemie: special hydrogen-rich ionic liquids that self-ignite in the presence of peroxide.

Despite the potential danger, hydrazine is used as a rocket fuel because it delivers high performance, can be stored for a relatively long time, and spontaneously ignites upon contact with an or a suitable catalyst. The oxidizing agents used as fuels are also dangerous. Dinitrogen tetroxide is less corrosive than nitric acid, but it is toxic and highly volatile. Hydrogen peroxide is a promising alternative because it is less corrosive and leads to much less toxic gas at room temperature. Its decomposition produces only water and oxygen.

As an alternative to hydrazine as a fuel component, Schneider and his co-workers propose an ionic liquid. Ionic liquids are compounds that consist of ions, namely positive and negatively charged particles, like a salt. However, they are not crystalline; they remain “molten” as a liquid at room temperature. Ionic liquids essentially do not vaporize, which prevents the formation of toxic vapors. It has previously not been possible to produce an ionic liquid that is flammable when partnered with hydrogen peroxide.

Schneider and his team have now overcome this barrier. The positively charged ion of their ionic liquid is a phosphorus atom bound to four hydrocarbon chains. At the core, however, lies the negatively charged ion made from one aluminum, four boron, and sixteen hydrogen atoms. The hydrogen-rich composition raises the power of the fuel component. “This aluminum borohydride ion can be viewed as a densified form of hydrogen stabilized by metal atoms. In fact, for a given tank size, liquids with this ion contain even more hydrogen than pure liquid hydrogen, without the difficult cooling requirements,” according to Schneider.

In order to test the ignitibility, the researchers applied drops of the novel ionic liquid onto various oxidizing agents. Upon contact with hydrogen peroxide, ignition was nearly instant; with fuming nitric acid it exploded. Says Schneider: “It is thus interesting as a potential component for greener high-performance fuels.”

More information: Stefan Schneider, Green Bipropellants: Hydrogen-Rich Ionic Liquids that Are Hypergolic with Hydrogen Peroxide, Angewandte Chemie International Edition, … ie.201101752

Provided by Wiley (news : web)

Enzymes turn vegetable oils into fuel through a flexible two-step process

Biodiesel is a promising future fuel, particularly because it can be made from a wide variety of renewable sources such as crude vegetable oils and waste fats produced by commercial kitchens. Conventional chemical processes for producing biodiesel, however, require pure and refined feedstock oils, thus negating any potential advantages. To get around this problem, Md. Mahabubur Rahman Talukder and co-workers at the A*STAR Institute of Chemical and Engineering Sciences have developed a two-step biocatalytic process that works well on all sorts of oils -- whether they are refined or not.

Making biodiesel involves breaking down through a reaction with . Although some researchers have tried to use enzymes to catalyze this reaction, their efforts have seen little success because enzymes are deactivated when exposed to droplets of methanol. Various strategies have been developed to overcome this problem -- such as the gradual addition of methanol over time -- but none have proven suitable for industrial production.

Talukder’s approach involves splitting the process of biodiesel production into two separate steps. The first step involves hydrolyzing the oil, for which the researchers use a lipase enzyme called Candida rugosa. Vegetable oils consist of branched molecules known as triglycerides, which have three separate arms. Hydrolysis involves splitting off the arms so that each triglyceride is converted into three molecules of fatty acid.

The second step involves reacting the fatty acids with methanol to produce biodiesel. This step requires Novozym 435, an enzyme that is normally deactivated by methanol droplets. However, because methanol is much more soluble in fatty acids than in the triglyceride, all methanol added at this stage is dissolved in the fatty acids. Thus, because no methanol form, the enzyme remains active.

“Avoiding enzyme deactivation is not the only advantage of our technique. The reaction between methanol and fatty acid progresses faster than the methanolysis of triglycerides,” says Talukder. “However, the key advantage is the flexibility.” In conventional chemical biodiesel production, impurities reduce the yield. This new approach, however, can accept feedstocks with any percentage of free fatty acids and water.

Talukder aims to make the process cheaper so that it can compete with chemical biodiesel production. “The lipase cost is one of the biggest challenges for the commercialization of the two-step process,” he says. “A low-cost lipase preparation technique is under consideration to improve the economic value of the process.” If successful, the technology could greatly help the environment and reduce the cost of fuel.

More information: Talukder, Md. M. R., et al. Two-step lipase catalysis for production of biodiesel. Biochemical Engineering Journal 49, 207–212 (2010) … .2009.12.015

Provided by Agency for Science, Technology and Research (A*STAR)