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Battery charges in a hurry

Engineers at Massachusetts Institute of Technology (MIT) have created a new type of battery that could recharge in seconds rather than hours. This breakthrough could lead to a new generation of batteries for green technologies like hybrid vehicles and wind turbines, say the researchers.

The best lithium batteries on the market can squeeze a lot of electrical charge into a small volume but they are a bit sluggish at gaining and discharging that energy. This drawback can put people off buying an electric car. “They have a lot of energy, so you can drive at 55 mph for a long time, but the power is low. You can’t accelerate quickly,” said Gerbrand Ceder, one of the researchers at MIT.

Now Ceder and his colleagues have revamped a standard lithium battery by speeding up the flow of electric charge. They achieve this by applying a lithium phosphate coating to the material’s outer shell. This “simple” idea followed their recent theoretical work, which showed lithium ions travelling along the surface to be just as important as electron flow within the battery.

“The ability to charge and discharge batteries in a matter of seconds rather than hours may open up new technological applications and induce lifestyle changes,” said Ceder.

Speedy ions

Inside a battery, electricity flows via electrons and lithium ions moving towards the anode and cathode respectively. Previous attempts to improve the power of batteries have focussed on increasing the mobility of electrons. Physicists just assumed that lithium ions travel relatively slowly because of their larger size.

Then about five years ago, Ceder and his colleagues modelled a lithium iron phosphate battery and made the surprising discovery that lithium ions should actually be moving at a similar speed to the electrons. The difference is that the ions can only travel through “tunnels” accessed from the surface. The process however is very inefficient because many of ions have trouble entering these tunnels.

Having established this new theory the scientists set out to maximize access of ions to these tunnels. They designed a system, which allows lithium ions to zip quickly around the surface of the material – analogous to cars avoiding traffic by zipping around the ring road of a city. This created a more efficient system where significantly more ions enter into the tunnels

The researchers then created a small battery that could be fully charged or discharged in 20 seconds; without the coating it took 6 minutes. Reporting their findings in Nature they say there is nothing to prevent this battery being scaled up to a hybrid car battery that could be charged in 5 minutes. The only limiting factor will be the available power – 180 kW would be needed for a 15 kW h battery.

“We will now try to prove the same principle for a range of Lithium battery materials. Maybe there are some that have an even higher energy density,” Ceder told physicsworld.com.

The atlas of science

The map of science (click to see full-sized image)

By Michael Banks

Do you know that when you access a research paper via a “web portal” such as Elsevier’s Science Direct your every “click” is being recorded?

Although this monitoring might at first seem a little scary and possibly unnecessary,
Johan Bollen and colleagues from Los Alamos National Laboratory have put the data to good use.

They have created a “map of science” using over a billion so-called “click-throughs” – produced when going from the web portal to the actual full text paper or the abstract on the journal’s website. The data was taken from 2007 to 2008.

After crunching the data through a so-called “clickstream model” they produced a map (see image above) with each circle representing a journal and the lines reflecting the navigation of users from one journal to another.

Maps showing the connectivity of science subjects have been made before, but they have often used citation data produced using the references in research papers. As it takes years for a new paper to generate lots of citations, the new method promises a more up-to-date map of science. This, the researchers say, can then point more quickly to emerging relationships between difference branches of science.

The researchers also created a table of the most interdisciplinary journals, produced by how many connections it has with other areas of science, which placed Science top followed by Proceedings of the National Academy of Sciences in second place and Environmental Health Perspectives in third.

But don’t worry, as confidentiality agreements prevent any information that could show the identity of the browser being used by a third party, your privacy is protected.

Ig Nobel stars roll into town

Cutting edge science

Ever levitated a frog?
No.
How about, organized an athletics contest between the fleas of a dog and the fleas of a cat?
Thought not.
Ever observed homosexual ducks commit necrophilia?
Ok, I think I need to explain…

These scientific “feats” were amongst the wacky studies presented last night on the latest stop of the Ig Nobel awards tour, in Bristol.

I went along to see if the show lives up to its claim to “first make people laugh, and then make them think”.

Jovial compere Marc Abrahams opened the proceedings telling each speaker they had “5 minutes and NOT A SECOND MORE!”

In the physics category, Sir Michael Berry of Bristol University described how he won the prize in 2000 for explaining how frogs can be levitated with magnets. “Of Flying Frogs and Levitrons” was published in the European Journal of Physics.

Surely the weirdest talk was from 2003 winner for biology Kees Moeliker who talked about homosexual ducks committing necrophilia. So the story goes… he had been sitting in his office when he heard the loud bang of a duck crashing into his window. Rushing out to see if it was ok he was shocked to witness the duck – dead, with a second, live duck, forcing itself upon the corpse. Later observations revealed both ducks to be male and the study was published in the Annual of the Natural History Museum Rotterdam.

A slightly tamer ornithological study addressed the question of “why woodpeckers don’t get headaches?” Apparently it’s because of a millisecond delay between the bird’s beak hitting the tree and its head moving forwards. I caught up with study’s presenter Julian Vincent and his wife after the show. She said he’s “always been full of ideas”.

My favourite act was Dan Meyer – a sword swallower from Tennessee. He eloquently talked us through his 2007 prize-winning paper “Sword Swallowing and Its Side Effects,” before ramming a 17 inch blade down his throat.

A scared looking young girl near the front asked the question everyone was thinking “does it hurt?” To which he replied “a little”

So did the evening make me laugh and then think afterwards?
Well, putting the ancient art of sword-swallowing to one side – I have to say that I found the whole thing a little bit “zany” for my taste.

Having said that, when I looked around the conference room, people were certainly laughing and there was plenty of scientific interest in the after show Q&A session. So perhaps it’s just me becoming an old fuddy-duddy before my time…

US pays price for $500m budget blunder

A $500m accounting error led to the Bush administration scrapping a carbon–capture and storage demonstration plant last year according to a report by the US House of Representatives committee of science and technology. The project was scrapped because costs appeared to have ballooned from $1bn to $1.8bn when in fact it had only risen to $1.3bn.

The report concludes that the Bush administration’s abrupt pull-out “severely” damaged the country’s reputation as an international science partner and “left the country with no coherent strategy for carbon–capture”.

First announced by President George W Bush back in 2003 FutureGen was designed as a coal-fired power plant that would not emit any carbon dioxide by capturing and storing it underground in a technique known as carbon capture and sequestration (CCS). To be built in 2013, the plant was to have been constructed by the FutureGen Alliance — a public–private partnership set up to design, build and operate the plant.

Huge cost overrun?

However, in the 2008 financial year budget, the Department of Energy (DOE), led by Samuel Bodman, cancelled a $1.1bn grant for the project because of the apparent huge cost overrun. “Unfortunately, the Bush Energy Department withdrew their support for FutureGen before the Alliance could complete a new cost estimate in June 2008,” Lawrence Pacheco, a spokesperson for the company told physicsworld.com. However, that figure now seems to be wrong. The report by the House, says that Bodman made an “inexcusable error for the head of a federal agency”. The cause for the mistake was that the initial $1bn estimate was made using constant 2004 dollars, but for the cost estimate last year the DOE factored in inflation through until 2017, which led to the cost ballooning to $1.8bn.

An audit carried out by the US Government Accountability Office in February concluded that the cost of the FutureGen project had actually increased by only 39% to $1.3bn in constant 2005 dollars — $500m less than the DOE calculated.

‘Shovel ready’ projects

Following from President Obama’s $787bn stimulus package announced last month, the DOE gained an extra $1.6bn in funding beyond its 2009 budget of $4.0bn. Some of this may be spent on “shovel ready” projects, which could include FutureGen. “The Alliance will make the case that it is shovel ready,” says Pacheco, “[FutureGen is] the furthest along of any similar project and can deliver much needed CCS technology to the world.”

The FutureGen Alliance now plans to meet with energy secretary Steven Chu to kick-start the project. The Nobel–prize winning physicist has already stated his support of CCS demonstration plants.

Molecular junctions make a switch

Physicists in the US have shown how the electrical current flowing through certain molecular junctions can be switched on and off on by simply stretching or compressing the molecules. The discovery could be exploited to make switches in future molecular devices, and could also help in the understanding of resistance at the nanoscale.

In normal electronic devices, resistance is a well-understood property. When an electric field is applied across a metal, charge–carrying electrons begin to drift but bump into ions and impurities, which slow their motion. At nanometre distances, however, things are not so simple: electrons are able to “tunnel” across small insulating barriers with a finite probability. This means that the electrons can overcome obstacles without losing energy, and therefore without electrical resistance.

Tunnelling is an important consideration in designing nanoscale devices, but measuring its effect is not easy. In 2007, a team led by Latha Venkataraman at Columbia University in New York and Jeffrey Neaton of Lawrence Berkeley National Laboratory (LBNL) in California, managed to measure the conductance of amine-based molecules that were in contact with gold and successfully compare with theory. They touched the gold tip of a scanning tunnelling microscope (STM) onto a gold surface containing amine molecules and then retracted it, so that the tip linked to the surface only by a single, fragile molecular strand. When this strand broke other molecules hopped in to fill the gap, and from this the researchers could calculate the sudden jump in conductance.

Molecular bridge

Now, the researchers at Columbia’s NSF Center for Electron Transport in Molecular Nanostructures, and LBNL’s Molecular Foundry have gone a step further and looked at different conductance states in the molecular strand bridging a STM to a gold surface. Rather than use amines they have used bipyridine, a molecule with twin benzene-like rings that contain nitrogen. They found that bipyridine has two resistance states: when it is bonded to the STM at an angle the resistance is low and the junction is “on”; when it is bonded vertically the resistance is high and the junction is “off”. In fact, the researchers found that they could switch the junction between the on and off resistance states simply by pushing and pulling the STM tip (Nature Nanotechnology doi:10.1038/nnano.2009.10).

Jeffrey Neaton visualizing a molecular bridge

Venkataraman, Neaton, and colleagues believe the different resistance states result from electron tunnelling through the conductive “pi” orbitals of the bipyridine molecule. The different orientations of the molecule change the amount of overlap between the quantum wavefunctions of the pi orbitals and the incident electrons from the gold electrodes. When bipyridine is at an angle the overlap is greater, which increases the chance of tunnelling and therefore decreases the resistance.

A better theory

“One outcome of this study is an improved ‘first principles’ theoretical approach, free of empirical parameters, for conductance in certain classes of nanoscale molecular junctions,” Neaton told physicsworld.com. “Working with experiments, we will continue to develop and extend the range of our theories to junctions and phenomena involving more complex molecules.”

Neaton explains that his team are particularly interested in looking at certain asymmetric molecules with the ability to separate charge, which are used in some organic photovoltaic materials. “Extended studies of such molecular junctions may shed further light on how we might enhance the efficiency of charge separation and transport — and thereby light harvesting — in organic and hybrid organic–inorganic nanomaterials,” he adds.

Sour grapes in the Big Apple

Letting off steam in NYC

What do the president of the Czech Republic and the last living man to walk on the moon have in common?

Answer: they both have a thing about climate change “alarmists”

Both angry men are giving speeches at what’s being billed as the world’s largest ever meeting of climate change sceptics, in New York City.

Organised by the Heartland Institute – a US public policy think tank dedicated to free market solutions – the conference will centre around the question: “Global Warming: Was it Ever Really a Crisis?”

One of the pre-event adverts led with the statement:

Tens of thousands of scientists now say the media and environmental advocacy groups have it all wrong, that global warming is not a crisis. They point to a cooling trend in global temperatures since 2000, past warming and cooling cycles that were not man-made, and new evidence that carbon dioxide is not a very powerful greenhouse gas.

You can also watch a couple of the Institute’s short promos here.

Amongst the keynote speakers is Vaclav Klaus, President of the Czech Republic which currently holds the rotating presidency of the European Union.

Klaus, who has an academic background in economics, is giving a talk this morning (Tuesday) entitled “We Should Not Make Big Changes over Climate Change”.

Other notable presenters include: Jack Schmitt, the last living astronaut to walk on the moon; Roy Spencer, the principal research scientist on NASA’s Aqua satellite; and Richard Lindzen of Massachusetts Institute of Technology, one of the world’s leading experts in dynamic meteorology.

Meanwhile, over in Copenhagen this week more than 2000 climate scientists will be discussing their latest research ahead of the UN Conference on Climate Change that will take place in the city in December.

I’m guessing the outlook at that event will be rather different.

Double graphene coat is slippery stuff

Coating an object with just one or two layers of carbon atoms gives it an extremely slippery yet tough surface, according to physicists in Germany and North America.

What’s more, the friction on a single layer of carbon atoms — known as graphene — is greater than on a double layer, which the researchers say is due to differences in how vibrating carbon atoms interact with surrounding electrons.

The results suggest that such coatings could reduce frictional wear and tear in tiny machines.

The new findings were made by a team led by Roland Bennewitz, who splits his time between McGill University in Montreal and the Leibniz Institute for New Materials in Saarbruecken, Germany. Researchers at McGill, the Lawrence Berkeley National Laboratory, University of Erlangen–Nuremberg and Max Planck Insititute in Berlin were also involved (Phys. Rev. Lett. 102 086102).

Graphene terraces

The team began by carefully heating a single crystal of silicon carbide (SiC), which causes carbon atoms to migrate to the surface of the material. This leads to flat “terraces” on the surface — with each terrace comprising exactly one, two or zero atomic layers of carbon.

The researchers then put the silicon carbide in an ultrahigh-vacuum chamber before studying its surface properties using an atomic–force microscope (AFM). The team measured the friction on the surface simply by dragging the nanometre-sized tip of the AFM along the surface. Friction was measured on bare silicon carbide as well as in the presence of single and bi–layers of graphene.

Bennewitz’s team discovered that both single and bi–layers of graphene are much more slippery than bare silicon carbide. For example, when the AFM tip was pushed down onto the surface with a normal force of 100 nN, the frictional force on single and bi–layer graphene was found to be about 0.6 and 0.2 nN respectively. The friction force on bare silicon carbide, in contrast, was 8 nN.

Surprisingly slippery

Bennewitz told physicsworld.com that the team was “surprised” to find that a bi–layer of graphene is significantly more slippery than a single layer over a wide range of normal forces. They believe this is related to how quantized vibrations of the carbon atoms (called phonons) interacted with the electrons in the graphene — a process that is thought to dissipate some of the heat generated by the sliding tip.

To confirm this the team used a standard technique called angle-resolved photo-emission spectroscopy (ARPES), which revealed that electron-phonon coupling is much stronger in the single layer of graphene than in the bi–layer. Bennewitz likens the effect of the coupling to dragging the tip through sand — with the greater the coupling, the thicker the sand.

The researchers also studied friction in thicker multiple–layer coatings, and found these slightly less slippery than a bi–layer. This could be because the tip is able to dig into a multilayer and become stuck — something that was not seen with the bi-layers.

Hard-wearing as well

The team ended their experiment by trying to damage the graphene coatings using the diamond–coated AFM tip. They were unsuccessful, suggesting that the graphene coatings are hard-wearing as well as slippery.

The team’s results could be good news for researchers that are trying to build micro and nanometre-sized machines using silicon carbide instead of silicon — which is the conventional material for such devices.

These include Roya Maboudian at the University of California Berkeley, who described the discovery as “technologically exciting” and suggested that suggests potential opportunities for improving the reliability of nano and micro machines.

A great day for science in the US

Signing the memorandum

By Hamish Johnston

Yesterday was a great day for scientists in the US.

Barack Obama issued a Presidential Memorandum on Scientific Integrity to US government agencies. The following excerpt says it all…

“The public must be able to trust the science and scientific process informing public policy decisions. Political officials should not suppress or alter scientific or technological findings and conclusions. If scientific and technological information is developed and used by the Federal Government, it should ordinarily be made available to the public. To the extent permitted by law, there should be transparency in the preparation, identification, and use of scientific and technological information in policymaking. The selection of scientists and technology professionals for positions in the executive branch should be based on their scientific and technological knowledge, credentials, experience, and integrity.

While these are noble words (you can read the rest of them here government can never be done by peer review. It remains to be seen how Obama can follow the advice of climate scientists, while dealing with many American’s desire to own a large air-conditioned house in the suburbs with two or more vehicles in the driveway.

Lasers take a measure of halo nucleus

Physicists in Europe and North America have measured the radius of an unusual beryllium isotope containing a single neutron a long way from the rest of the nuclear core. Although the radii of other such “halo” isotopes have been determined before, this is the first time that the measurement has been made on a nucleus with just a single halo neutron. The researchers found that the halo neutron in beryllium–11 is, on average, about 7 fm (7 x 10^-15 m ) from the nuclear core, which itself has a radius of about 2.5 fm.

First discovered in 1985, halo nuclei have a conventional nuclear core plus one or more halo neutrons that spend much of their time a relatively long distance away. The lithium–11 halo nucleus, for example, has about the same diameter as the much more massive uranium nucleus. The reason such nuclei are so large is that the energy that binds halo neutrons to the core is only 100 keV — roughly a tenth of the energy tying neutrons in a conventional nucleus.

But measuring the size of halo nuclei has proven tricky because the nuclei are very short lived — and because they have no electrical charge, the halo neutrons do not interact readily with experimental probes.

Blur of positive charge

The best measurements have involved studying the tiny “volume” shift — of about one part in a billion — of the energy levels of the electrons that are bound to a halo nucleus in an atom or ion. This shift occurs because the halo neutron and the core orbit each other and their relative motion makes the core appear as a blur of positive charge to the electrons. This, for example, means that the electron energy levels of a beryllium atom containing the halo nucleus beryllium–11 are shifted slightly compared to atoms containing the more conventional nuclei beryllium–7, beryllium–9 or beryllium–10.

The volume shift can then be used to calculate the radius of the blur of positive charge, which can then be used to calculate the average separation between the halo and core.

While physicists have already managed to measure this shift in helium and lithium halo isotopes, experiments on beryllium–11 nuclei are further complicated because beryllium has four electrons.

It turns out that electron energy levels are also affected by “mass shifts” that are caused, in part, by interactions between the nucleus and the correlated motion of the electrons. These mass shifts are about 1000 times larger than the volume shift and become increasingly difficult to calculate as the number of electrons increases. The problem is simplified somewhat by studying Be⁺ ions, which only has three electrons.

Measurements and calculations

The new study was carried out at the ISOLDE facility at CERN by Wilfried Nörtershäuser at the University of Mainz and colleagues in Germany, Canada and Switzerland (Phys. Rev. Lett. 102 062503).

The experiment involved producing four different isotopes of beryllium (with 7, 9 10 and 11 nucleons) by firing a 1.4 GeV proton beam into a uranium-carbide target. This created beryllium atoms, which were then ionized using a laser and accelerated to 50 kV. Transitions in electron energy levels were induced by firing two ultraviolet laser beams at the ions. One beam was fired straight at the oncoming ions, while the other was fired in the opposite direction from behind the ions to cancel out the experimental uncertainty in the kinetic energy of the ions.

Some of the laser light is absorbed by the beryllium’s electrons, which jump to a higher energy level. As the electrons fall back down, they emit light at the same wavelength as the laser through the process of “resonance fluorescence”. However, the wavelength of the light absorbed and then emitted by the halo isotope beryllium–11 differs very slightly from the light emitted from conventional beryllium isotopes — the difference being due to the isotope shift, which is the sum of the mass and volume shifts.

The team determined this tiny shift by using a device called a frequency comb, which is capable of making a very accurate measurement of the laser’s wavelength. By comparing the resonant wavelengths of beryllium–11 with the other beryllium isotopes — and then correcting for the mass shift — the team worked out the volume shift. This allowed them to conclude that the halo neutron is about 7 fm from the nuclear core. The core itself has a radius of about 2.5 fm.

Improving mathematical models

“The halo neutron is thus much farther from the other nucleons than would be permissible according to the effective range of strong nuclear forces in the classical model”, explained Nörtershäuser. “The result can now be used by nuclear physicists to improve their mathematical models of nuclei”, he said

Jim Al-Khalili at the University of Surrey in the UK told physicsworld.com, “These measurements tell us quite clearly that the core of the halo nucleus beryllium–11 (namely, beryllium–10) is more tightly packed together than a much lighter nucleus like beryllium–7.” He added. “We learn a lot about the core within the halo with this work, and indirectly we can test our theoretical models of how the halo particles interact with the core”.

Sociologists are too sceptical of science…

Science studies – blending traditional disciplines

By James Dacey

I’m a big fan of The Guardian’s Digested Read in which John Crace reviews new books by condensing them into short narratives. They’re always informative and often satirical. So borrowing his style, I’ve reviewed a new paper by the eminent sociologist Harry Collins, which looks at the changing face of “science studies” since its birth in the post war years. Hope you enjoy…

Back in the Fifties, social scientists were confident in science; in part because of the success of physicists during Second World War. My predecessors developed the naïve view that science works under democratic ideals with scientists interested in nothing but scientific truths. Socio-political realities — like the ongoing debate surrounding Eddington’s ‘clear-cut’ proof of Relativity — were simply ignored.

So hooray for the swinging Sixties! Everything from sex to ideology started to loosen up and even academics wanted in on the action. Sociologists finally realized that even science is underpinned by people power — despite what that stuffy Merton chap had said before.

Sadly though, the party was short-lived as by the late sixties / early seventies, a new scepticism was taking its grip. Terribly inconvenient eco groups were pointing out environmental damage, and after all the post war hype, society was disappointed with science and all its groupies.

At this time, a new way of thinking was sweeping through the humanities. We called it postmodernism and it passionately rejected the ontological hierarchies of modernism. Extremists proposed that all forms of knowledge are shaped equally by faith and politics. Science — previously hailed as the ultimate form of knowledge — became an obvious target and during the Seventies and Eighties we launched a series of attacks.

(more…)

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