Science & Technology News (1016)
Posted: August 27, 2015 06:56AM
A femtosecond is unperceivable to the normal person, but in many fields of science, it is necessary to operate on such short timescales to determine what is happening. In these instances it is a femtosecond laser one often turns to, as the ultrashort pulses of light can illuminate behaviors occurring in those brief windows. Now researchers at the University of Warsaw have succeeded in designing a femtosecond laser that is so resilient to the environment it could find use in industrial settings.
One of the primary components to a normal femtosecond laser is optical resonators made of precision sets of mirrors, but these mirrors are susceptible to external conditions. This new laser does away with those by using an optical fiber as the resonator, which is something other lasers also do. In fact all of the laser-generation is done within the optical fiber, which makes the laser highly resistant to the environment. The researchers tested this by heating a segment of the fiber up to 120 ºC and by placing the laser in a shaker with acceleration above 7 g, but neither test stopped the laser from working.
The laser light produced has a wavelength of 1030 nm, though higher-order harmonics can be generated, and the laser itself can be built from commercial parts, keeping its cost down to just a few thousand euros. By switching to custom designed components, it may be possible to cut the cost down even more. Potentially it could find industrial use as a means of cutting semiconductor panels and diamonds, without incurring thermal stresses, thus minimizing discoloration and cracking.
Posted: August 26, 2015 02:34PM
Energy is only valuable if you can do something with it, and that means getting it where it is useful. Traditionally electrical energy has been carried along copper or aluminum wires, and while these work, we are looking for more efficient systems. Now researchers at the Universities of Bayreuth and Erlangen-Nuremberg have recently developed nanofibers that may be a solution for efficient long-range energy transport.
These new nanofibers are made of carbonyl-bridged triarylamine, which are building blocks that can be made to self-assemble into nanofibers. In this case the over 10,000 blocks assembled into nanofibers 4 micrometers long and 0.005 micrometers (5 nm) wide. Because the triarylamine cores of the building blocks aligned themselves face to face, a phenomenon known as quantum coherence could occur, allowing the energy to carry from one to the next in a wave-like manner. This phenomenon is what makes it very efficient.
While 4 micrometers may not seem very long-range for us, it actually is impressive for what is going on and by demonstrating that materials can be designed to allow this efficiency, this opens up several possibilities. The researchers see this being used to improve methods of transporting energy from solar power systems.
Posted: August 26, 2015 06:03AM
Nobody likes losing data when their computer crashes, so naturally many crash tolerant systems have been developed. Because of the number of ways crashes could lose or corrupt data though, none of these systems can guarantee your data will not be lost. Researchers at MIT are the first to change that though, thanks to a new file system mathematically proven to never lose data due to crashes of any kind.
To prove the file system is so reliable, the researchers applied formal verification, which mathematically represents the bounds a program can work in, and then proves the program will never stray beyond those limits. Instead of working on a high level scheme though, as is normally done, the researchers applied this process to the final code and used a proof assistant to help them. This assisting tool called Coq describes the many parts of the system and the relationships between them in a formal language. From here the researchers got to work developing the new file system and making tweaks to the definitions and relationships in the proof, as some have subtle implications they did not understand at first.
The new file system, though mathematically reliable, is also slow compared to modern systems, but by being the first, it opens the door to more efficient designs. Now that the groundwork has been laid, others can read the study's paper and learn from it how to develop better systems, while maintaining the reliability.
Posted: August 25, 2015 06:01AM
Many people consider the development of the 3D printer the beginning of a new renaissance as anyone could use such a printer to quickly and cheaply construct objects they design or find designs for. While 3D printers do indeed have great potential, we are still developing better ways to tap that potential by bringing in new techniques and technologies. Now researchers at MIT have succeeded in creating a 3D print that can work with 10 materials, and is self-correcting.
Most 3D printers only work with a single material, but there are some that can work with three materials at a time, and these printers can cost $250,000. This new printer, named MultiFab, however costs just $7000 and can work with 10 materials because it utilizes 3D scanning from machine vision techniques. With 3D scanning, it is possible for the printer to examine the shape of the object it is building, or the shape of objects placed inside of it. If it is trying to print a multi-material object, it can work with one material and then see where those components are, for printing other materials around it. If an object is put into the printer though, such as an LED array, the printer can determine where it is and print directly on it, in this case a lens for the LEDs.
By using printheads similar to those of inkjet printers, MultiFab has a resolution of 40 micrometers, which is about half the width of a human hair. Not bad considering the entire printer was built from off-the-shelf components, contributing to its low cost.
Posted: August 24, 2015 04:35AM
We are quickly approaching the fundamental limits of silicon-based electronic computers, which is why many teams around the world are working on replacements. Among these potential replacements are optical computers that would use photons instead of electrons to transmit and process information. Photons can only fit into spaces so small though, due to their wavelength, which is why special means of working with them are required, like those developed by researchers at Lomonosov Moscow State University along with French and Spanish researchers.
Typically people are turning to plasmonics as a means to condense optical signals into smaller spaces, but there is a significant issue with this approach. The best materials for use in plasmonics, like the conductors copper and platinum, exhibit high electrical resistance when at frequencies near those of visible light, which are the frequencies plasmons made from visible light would have. The researchers however turned to electrical insulators that have high refractive indices. Back in the 1980s it was predicted that these materials could exhibit a new kind of light scattering, and this is what the researchers are finally demonstrating.
The researchers created small ceramic spheres that will interact with light to get their electrons vibrating at optical frequencies. By tuning the light correctly, the waves can have their harmonics precisely controlled, allowing the incident radiation to be redirected. This is exactly what is wanted for potential use in optical computers, and to make things better the spheres can be made easily and cheaply.
Posted: August 21, 2015 02:03PM
Researchers at Duke University have happened upon a discovery that could improve water purification systems and more. Initially the researchers were investigating how insect wings with hairy structures clean themselves and noticed a curious phenomenon of two droplets merging jumping off of the hair. As they investigated further they discovered it was more than just some artifact from a breeze.
Droplets store energy along their surface, and when two droplets merge the total surface area decreases, so some energy has to be released. That release can be enough to launch the droplet from the surface it is on. Previous work has shown this with flat surfaces, but those had to be superhydrophobic. The fibers in this study though did not have to be superhydrophobic, but just reasonably hydrophobic, which the researchers achieved by coating them in a Teflon. Superhydrophobic materials tend to be very fragile, so achieving this with a stronger hydrophobic is quite important.
Potentially this could be used in water purifiers that use fibrous webs to collect droplets because you want the droplets off of the web as soon as possible.
Source: Duke University
Posted: August 21, 2015 05:43AM
While many people are replacing magnetic disks with flash memory in computers, some researchers are working to bring magnets back into computers on a whole new level. Spintronics operate on the spin of electrons, a property that leads to magnetism, and by exploiting it computers could run faster and use far less energy. Now researchers at MIT have discovered an exotic phenomenon called proximity-driven magnetic order at the interface between a topological insulator and a ferromagnet.
Topological insulators are unusual materials that are electrical insulating through their bulk, while their surfaces are actually very good conductors. Already there is a lot of interest in them for use in spintronics and quantum computers, and this discovery will help in those applications. When a layer of a topological insulator is bonded to a ferromagnetic layer, the researchers found the proximity-driven magnetic order appeared, which is a localized and controllable magnetic pattern. That control includes the ability to create an energy gap, like those semiconductors have, making transistors a possibility. Because there is also almost no energy dissipation along the interface, it could also be used as a quantum wire.
While both spintronic and quantum computers are still far in the future, this discovery will have an impact in the present by opening up new research possibilities. Among these is the search for Majorana fermions, which were predicted in 1937 and should have some very useful properties, but have not yet been observed.
Posted: August 20, 2015 02:24PM
A lot of technologies are being pushed smaller and smaller all the time, to meet the desires of consumers and to enable new applications. Due to their small size though, some of these technologies, like nanoparticles, can be difficult to control. Researchers at the University of Zurich though have successfully manipulated nanoparticles in a solution, using only electrical and optical signals.
To achieve this level of control, the researchers are taking advantage of the particles' electrical charges. Normally the particles would just be subject to Brownian motion, but the electrical charge means more forces can affect them. By using this, the researchers are able to control the position and orientation of the nanoparticles, enabling them to form nanostructures within the solution. This is achieved without contacting the nanoparticles and at room temperature.
Potentially this discovery could have digital applications, as the nanoparticles could be used to store information. They could also be put to use in displays similar to the e-Ink displays, but with a much smaller pixel size, and thus a higher pixel density, while also speeding up response times.
Source: University of Zurich
Posted: August 20, 2015 05:59AM
Better light sources has been a goal for humanity for a very long time, as brighter light makes it easier to see and more efficient sources means we have the light for longer. Today some of the most advanced lighting technologies utilize LEDs to directly create light from electricity, but these tend to be expensive and put off an unappealing light. Quantum dots could help change that though, especially with the advances Oregon State University has recently made.
Quantum dots are nanocrystals of semiconductors that can have their optical properties tuned as desired, so they can emit whatever color you want. In theory they can be made very easily, but so far this has not quite proven to be the case. The OSU researchers however have developed a new production method that might just do it. It utilizes a continuous flow chemical reactor, so chemicals can be continuously mixed instead of in discrete batches, and a microwave heating technology. This is similar in concept to the microwave ovens we have in our homes, but enables such precise heat control that it is possible to control the size, shape, and composition of the quantum dots. It too can also operate very quickly.
In addition to speeding up the process and cutting costs, the researchers were working with copper indium diselenide instead of cadmium. This change makes the process safe, as cadmium is highly toxic, and copper indium diselenide also has a higher energy conversion efficiency.
Source: Oregon State University
Posted: August 19, 2015 02:03PM
The Great Firewall of China is a rather well-known example of a state censoring the Internet its citizens can view, but it is not unique and not limited to those within China. It has previously been discovered that Internet traffic travelling through China will be modified, indicating some level of censorship, even if the source and destination of the information is not within the nation. To tackle this and similar examples, researchers at the University of Maryland have created a routing method so traffic can avoid regions known to censor the Internet.
Called Alibi Routing, this method uses a peer-to-peer network to send data around censored regions, instead of through them. To prove the data is indeed taking the scenic route, the peers, or alibis, take advantage of how information cannot travel faster than the speed of light. Of course relying on a peer network can be tricky when there are few participants, and some are near the censored regions, but when simulated with just 20,000 peers, the researchers found that with stricter safety parameters, they could find an alibi 85% of the time. With looser parameters, letting the traffic get closer to the censored regions, the success rate rose to 95%.
Now that they have a method to avoid censored regions, the researchers are working to bring it to users by the end of the year, likely via a browser plugin.
Source: University of Maryland
Posted: August 19, 2015 08:43AM
Before a material can really be used in devices, it is critical to understand its properties, and sometimes these properties can surprise you. Researchers at Berkeley Lab have recently examined 2D molybdenum disulfide and found that its edge properties are quite different from other materials. For most other two dimensional materials, a number of properties are determined by their one dimensional edges, but not molybdenum disulfide.
It makes sense that some properties of 2D materials, like their optical and chemical properties, are determined by their edges because that is where the processes happen. What sets molybdenum disulfide, and potentially other transition metal dichalcogenides, apart is that it is an area about 300 nm wide from the edges that determine these properties, and not the 1D edge itself. This could potentially explain why the material has not been living up to theoretical predictions of its properties. The researchers discovered this by using a Campanile probe to break through normal nanospectroscopic imaging limits.
This discovery should help open the door to new applications for molybdenum disulfide and other transition metal dichalcogenides, especially as the researchers also discovered that the amount of sulfur in the edge region affects its properties as well. Less sulfur shortens the amount of time electron-hole pairs, which are necessary for the operation of semiconductors, remain separated.
Source: Berkeley Lab
Posted: August 18, 2015 02:08PM
Lithium ion batteries are a modern marvel thanks to their high energy density enabling even small devices to keep a long charge. Of course we want the charges to last even longer, and for the batteries to be safer, so a lot of work is being done to find new solutions. One possibility is to switch to solid state electrodes, instead of the modern liquid organic solvents, and new research from MIT may make that possibility more real than ever.
Being a liquid allows modern electrolytes to carry charges easily, but that mobility comes with costs, including fire risks. A solid state electrolyte does not burn though, and puncturing it also does not pose a danger. A battery using a solid state electrolyte could also survive hundreds of thousands of power cycles, which is far greater than any modern battery. Actually making such an electrolyte has proven difficult though, but the MIT researchers have managed to identify multiple factors that influence the efficiency of ion conduction within solids. So far the work has focused on superionic lithium-ion conductors including lithium, germanium, phosphorus, and sulfur, but it should be possible to expand the work to other materials. Potentially these other materials could be even better.
In addition to the safety benefits, solid state electrolytes could also operate at lower temperatures and provide a power density 20 to 30% greater. This work was done as part of a partnership with Samsung, so the potential for commercialization has almost certainly been investigated.
Posted: August 18, 2015 06:04AM
For years researchers have been working hard to find applications for graphene, but one of its properties has long posed a challenge. Graphene is an excellent conductor and not a semiconductor as one wants for use in advanced electronics. Graphene did still start a revolution by leading researchers to hunt for other 2D materials that may be useful, and researchers at the Institute for Basic Science have recently made an important discovery to that end.
Black phosphorus is like graphene in that it can be made two dimensional, but it is a natural semiconductor in this state. This means a current running through it can be switched on and off as needed. By doping it with electrons from potassium, the researchers were able to tune its bandgap, the distance between the conducting and nonconducting electron energy levels. Normally 2D black phosphorus, or phosphorene, has a bandgap of 0.35 electron Volts, but the researchers were able to change it to values between 0 and 0.6 eV.
This ability to tune black phosphorus' bandgap opens up many new possibilities for it, as others could use it in specially designed devices.
Source: Institute for Basic Science
Posted: August 17, 2015 02:16PM
There is a lot involved in making a program run, and a lot of places something can go wrong, opening up vulnerabilities. Finding these issues can be difficult though, which is why tools are being created to analyze and find the problems, and awards are being given to support these efforts. The Internet Defense Prize is an example of this and has recently been awarded to researchers from the Georgia Institute of Technology.
The researchers built a tool called CAVER for finding type confusion or bad casting errors. These issues can be used by an attacker to corrupt memory, causing malicious code to run instead of what is intended. It specifically looks at C++ problems, such as Chrome and Firefox and found some 11 vulnerabilities between them. The developers of both browsers confirmed and fixed the issues.
Source: Georgia Institute of Technology
Posted: August 17, 2015 05:17AM
Solid state memory has had a profound effect on the present as it has enabled great speed, efficiency, and mobility in many devices. While traditional hard drives are still very useful, the advantages of SSDs cannot and are not being ignored. Naturally then, ways to improve SSDs are constantly being worked on, and researchers at Rice University have developed a new memory technology that could give Flash memory a run for its money.
This new technology is based on tantalum oxide, which is a common insulator. The device itself is a sandwich of platinum, tantalum, nanoporous tantalum oxide, graphene, and more platinum. The platinum parts are the two electrodes for the device, with the graphene separating them from the rest, preventing it from migrating into the tantalum. The tantalum and tantalum oxide layers are what store the information. An electrical current causes the oxygen ions and vacancies to move, changing the position of the barrier between them. Fortuitously the flow of oxygen ions actually acts as a barrier from crosstalk between the bits, which allows the device to achieve much higher densities than other tantalum oxide memories.
What the researchers have created could store 20 GB to a crossbar array, if suitably dense crossbar devices can be made. It also requires one hundred times less energy than current devices, uses only two electrodes, unlike Flash memory that requires three, and can be made at room temperature, so the dense crossbar array is only major hurdle left to commercialization.
Source: Rice University
Posted: August 14, 2015 05:27AM
Finding ways to utilize waste products is always a good idea, as it can reduce the amount of other resources we rely on. Carbon dioxide is no different than any other waste product in this way, and teams across the planet have been looking for new ways to use it. Researchers at Argonne National Laboratory have recently discovered a new catalyst that could make converting CO2 into methanol easier than it ever has been.
Carbon dioxide is made by a large number of chemical processes, including the combustion of fuels, so the idea of converting it back into a fuel is especially tantalizing. Currently catalysts of copper, zinc oxide, and aluminum oxide help the gas be converted into methanol, but they have a limited number of binding sites, which requires the CO2 is put under pressure. Putting the gas under pressure takes a lot of energy, but this new catalyst, a copper tetramer has all of its binding sites open, allowing it to work at lower pressures. A tetramer is a cluster of four atoms, in this case copper atoms that are on top of a thin film of aluminum oxide.
By not requiring the CO2 to be pressurized, the energy required to convert it to methanol is significantly reduced, and while this research demonstrates the potential of this new catalyst, there is still a lot of work to do. It is possible that the tetramers break down over time, in an industrial setting, and producing them at industrial scales may prove very difficult. Naturally more research is required, but the researchers are also looking to find other catalysts that may perform even better.
Source: Argonne National Laboratory
Posted: August 13, 2015 04:38PM
For most people, the world works in simple and understandable ways, but for those who have to consider quantum mechanics, the world becomes much more difficult to grasp. According to quantum mechanics, particles can exist in multiple places at the same time with the phenomenon called superposition. This is one of the critical phenomena to be used on the quantum bits in quantum computers, but now researchers at the University of Vienna have successfully put the logic gates into superposition as well.
Similar to electronic logic gates, quantum logic gates are a fundamental component to quantum computers and some operations require more of them than others. Typically qubits are run through the gates in a specific sequence, but it was recently theorized that the order photons travel through the gates could be in a superposition. The Vienna researchers put this theory into practice and were successful in having a photon go through two gates (A and B) in both possible orders (A then B, and B then A) at the same time. Analyzing the photon showed that it was impossible to determine which gate was applied first, which confirms they were able to superimpose the quantum gates.
This research is more than just a demonstration of an interest quantum mechanical quirk, as it allowed the researchers to characterize the gates with more efficiently than any previously known algorithm, and the efficiency should increase as gates are added. Potentially other algorithms could be more efficient when run by a system like this, and only more research will determine the applications.
Source: University of Vienna
Posted: August 13, 2015 05:28AM
After the electrical properties of graphene were discovered, many started working on ways to use the atom-thick material. While there are a tremendous number of possible applications, we have been struggling to find ways to grow enough graphene in the proper form to be useful. At least for some applications now, researchers at the University of Wisconsin, Madison have discovered a means to efficiently grow graphene on the semiconductor germanium.
For graphene to be useful in semiconductors applications, it has to be in the form of nanoribbons less than 10 nm wide, and have smooth armchair edges. Typical means of making graphene with this geometry though would involve either cutting apart sheets into the ribbons, leaving rough edges, or growing the ribbons on a metal substrate. The catch with the metal substrate is that the nanoribbons would be too short. The solution the Wisconsin researchers discovered is that when you grow graphene on a germanium substrate, its properties can be controlled by manipulating how much methane, the carbon source in the process, is used. The graphene growing on the germanium naturally forms long nanoribbons with the desirable armchair edges, and can be made less than 10 nm wide.
While this discovery indicates it path to the desired graphene nanoribbons, there is still more work to do as the nanoribbons grow at random spots on the substrate, and in random directions. The researchers are now working to control the growth and alignment of the nanoribbons.
Source: University of Wisconsin, Madison
Posted: August 12, 2015 06:28AM
Electrical insulators, or dielectrics, are essential to many electronic systems, including energy storage and conversion. Typically ceramics are used in these situations, because they can endure the high temperatures involved, but many want to see dielectric polymers used instead. Unfortunately current dielectric polymers cannot survive the temperatures in within large batteries and other systems, but researchers at Penn State may have found a solution.
Instead of working with just a polymer, the researchers added small flakes of boron nitride, which is also known as white graphene. Unlike actual graphene though, boron nitride is an insulator, and adding it to the mix did not reduce the polymer's flexibility. The resulting composite material is also able to withstand the high temperatures normal polymers cannot of over 480 ºF, while maintaining its high-voltage capacity.
Potential applications for this material include electric vehicles, aerospace, and equipment for exploring deep underground, where a dielectric's ability to store electricity and release it quickly will be useful. This release can be enough to start up an engine and can be used to convert the direct current of batteries into the alternating current motors need to operate.
Source: Penn State
Posted: August 11, 2015 02:13PM
An easy way to conserve power on a laptop, tablet, or phone is to turn down the display brightness, as that is one of the primary energy users in these devices. Naturally then, a lot of work is being done to develop displays that are brighter while using the same amount of power. Quantum dots may enable the desired solutions, and now researchers at the University of Illinois have found a way to improve their performance as well.
Quantum dots are nanoscale, semiconductor crystals that can have their optical properties tuned. This capability makes it possible to design the crystals to emit light of specific colors, and so they already being used to enhance some displays. Unfortunately they are not always that bright and can be expensive to produce. What the Illinois researchers have done is add a layer of photonic crystals to the mix. These crystals focus the light from the dots in one direction, doubling their brightness.
To test this discovery, the researchers built a device just one millimeter tall that contains thousands of the quantum dots, with photonic crystals enhancing them. While the device they made was small, it is possible to scale the fabrication process up to create large, flexible plastic sheets, which will prove useful for displays and LED lighting.
Source: University of Illinois
Posted: August 11, 2015 05:25AM
Astronomers working on the Galaxy And Masa Assembly (GAMA) project have recently completed a study indicating that the modern Universe is only producing half as much energy as the Universe was just two billion years ago. This drop in energy output was measured across twenty-one wavelengths from ultraviolet to far-infrared, and looked at over 200,000 galaxies. The energy being measured would be that produced by the nuclear fusion within the cores of stars, where mass is being converted into energy according to E=mc2.
The researchers intend to continue their research into the energy production of the Universe, covering more volume and looking at more points in time. To that end the researchers hope to use many new facilities, including the Square Kilometer Array, which is to be built in Australia and South Africa over the next decade.
Source: European Southern Observatory
Posted: August 10, 2015 05:23AM
Anyone performing an experiment likes it when there are the fewest number of variables involved, but actually achieving this can be very difficult. In the quantum realm where even small phenomena can collapse the system, removing noise and the like is even more important. Researchers at the University of California, Berkeley have successfully created the world's quietest gas by removing the noise of entropy.
For studying various quantum phenomena, researchers will turn to Bose-Einstein condensates, which are clouds of atoms that have been cooled to the point that all the atoms act as one. Such a system is valuable for studying superfluids, superconductors, and quantum magnets. What the Berkeley researchers created is not the coolest condensate on record (at a billionth of a degree above absolute zero, it is actually twice that temperature) but its entropy is a hundredth that of previous experiments. Entropy is a measure of the noise in a system, and so by reducing it, even the most subtle of quantum effects can be detected. It and the temperature were actually so low a new thermometer had to be invented just to measure them.
With this new, quiet gas it should be possible for the researchers to develop a better picture of how high-temperature superconductivity works. With enough study it may be possible to bring superconductors up to room temperature and then revolutionize everything electrical.
Posted: August 7, 2015 06:27AM
Ever since unconventional, or high temperature, superconductors were discovered researchers around the world have been trying to understand how the phenomenon occurs. Now those at Brookhaven National Laboratory and ORNL have discovered that current theories for iron-based superconductors may be wrong. Instead of finding a link between long-range electronic and magnetic order, the researchers found a liquid-like magnetic state exists prior to superconductivity, and may be linked.
Current theories for high temperature superconductors state that long-range electronic and magnetic order, like patterns of electron spins, precede superconductivity. By doping an iron-telluride superconductor with sulfur though, the researchers were able to prevent the long-range order from forming, but the material still became superconducting as temperatures dropped. What they did observe was ordering only on a very local level, which is liquid-like behavior. This behavior comes from two coexisting and competing magnetic phases interacting within the material. Superconductivity came about after the electronic spin correlations changed, which would be like dancers changing partners on the dance floor.
In addition to challenging theories for iron-based unconventional superconductors, the researchers also got results that may require a revision to the model for electron orbitals in metals. The tight binding model has the electrons existing in rigid energy bands, but the spin-liquid state the researchers observed indicate new electron-orbital hybrids. This is likely the result of the sulfur doping and temperature changes.
Source: Brookhaven National Laboratory
Posted: August 6, 2015 02:07PM
Since they entered the commercial market, lithium-ion batteries have proven themselves to be invaluable for mobile technologies, but sadly improving them has been difficult. This is because many possible ways to improve them have serious flaws, such as reduced lifespans and fire dangers. Researchers at MIT and Tsinghua University have recently developed a nanoparticle that could significantly improve batteries, without the problems.
One way to improve lithium-ion batteries is to change the materials used as electrodes. Currently graphite is used for the anode, and it can store about 0.35 ampere-hours per gram (Ah/g), but other materials have much higher charge storage capacities, like aluminum at 2 Ah/g. The issue with aluminum, and many other materials, is that it swells so much when it receives lithium ions that it could cause electrical contacts to disconnect and damage the electrolyte. What the researchers have done to address this problem is create yolk-shell nanoparticles of aluminum and titanium-oxide. In this configuration, the aluminum yolk is free to swell within the shell, as there is plenty of separation between the yolk and the shell, unlike core-shell nanoparticles where the components are bonded together. The new nanoparticles have a charge capacitor of 1.2 Ah/g at a normal charging rate, and 0.66 Ah/g when charged six times faster than normal, after 500 charge-discharge cycles.
The researchers actually created the nanoparticles by accident when they were processing aluminum particles and found the aluminum shrunk within the titanium-oxide shell they formed around it. This is actually very good news too, because the process is so simple it is easily scalable.
Posted: August 6, 2015 06:34AM
Semiconductors are critical to computers because they allow for nanoscale electronic switches to be built. They do have limits though, as the switches can only go so small and they put out a fair amount of heat. For some time now researchers have been working on switches without semiconductors, and those at Michigan Technological University have made an important discovery towards that goal.
This discovery is a hybrid material consisting of a sheet of graphene that has had pinholes put in it so boron nitride nanotubes could grow off of the sheet. Graphene is an atom-thick sheet of carbon that is highly conductive, while boron nitride can be made a single molecule thick and is a great insulator. Both of these materials feature the same hexagonal pattern, so they actually connect very nicely, and where they do heterojunctions are formed. These junctions are what make the hybrid material viable as an electronic switch, due to how the electrons flow near and around them.
Switches made from this hybrid material could potentially operate at very high speeds because of a high switching ratio, thanks to the great difference in conductivity between the two materials.
Posted: August 5, 2015 02:09PM
Flash memory has done a lot to change the state of electronics, as the medium is nonvolatile and much faster than traditional, magnetic HDDs. We are not done with magnets though, especially with the amount of effort being invested into spintronics that will enable computers to boot in an instant and use significantly less power. Researchers at the University of California, Berkeley have recently solved a problem they had in prior research that should help bring about spintronics.
The previous research concerned nanomagnets of tantalum, which the researchers found could have their polarity flipped by an electrical current, and not an external magnetic field. Magnetic fields are large and inefficient to make, so their use has prevented certain magnetic technologies from being integrated into chips. The problem the researchers encountered was that the nanomagnets had to be vertically stacked to pack enough onto a chip, but this orientation negated the polarity switching. It turns out that giving the magnets a slight tilt of even two degrees is enough to re-enable the electrical switching.
By creating a nonvolatile magnetic memory system that can be integrated directly into computer chips, it should be possible to significantly reduce the power consumption of a computer. This is because of how much energy is needed to transmit data between memory devices.
Posted: August 5, 2015 05:31AM
For a great many technologies, transparent electrodes are necessary, but few actually exist. The most commonly used example is indium tin oxide (ITO) and is actually quite expensive because of how rare indium is. Some alternatives involve networks of silver, which is also a rare metal, but researchers at Helmholtz-Zentrum Berlin für Materialien und Energie have created a new conductor that uses so little silver, that the result is cost effective.
A common design for silver transparent conductors arranges strips of the metal into grids, but this new solution instead uses nanowires in a loose mesh. First the silver nanowires are in a suspension with ethanol and then deposited onto a substrate. As the ethanol dries the nanowires organize themselves into that mesh, maintaining transparency and conductivity. Next the researchers deposit a layer of AZO, a wide bandgap semiconductor made of zinc oxide with a heavy dose of aluminum. This composite has proven to be as conductive as the silver grids, though the conductivity can be manipulated by altering the length and concentration of the nanowires.
In the end the new electrode uses just 0.3 grams of silver per square meter, compared to the 15-20 grams per square meter for the silver-grid solutions. Currently the researchers are working to optimize the software used to determine the optimal properties of the nanowires and see the new transparent conductor being used in solar cells.
Posted: August 4, 2015 06:13AM
The two main ways I learned in school to store electricity are capacitors and batteries. These two technologies operate in very different ways and thus have very different applications. Capacitors are able to quickly charge and discharge, giving them a high power density, while batteries are slower to charge but can store large amounts of energy, meaning they have a high energy density. Something that can achieve both high power and energy densities would revolutionary by how much it would simplify technologies, and researchers at the Georgia Institute of Technology may have that solution.
The researchers have created a hybrid material by combining a silica sol-gel thin film with a monolayer of octylphosphonic acid. The silica sol-gel is the part the researchers were first working with and found it acts well as a capacitor, but when they tested it on a mylar film the capacitors suffered high current leakage. This problem was solved by adding the octylphosphonic acid, which acts as an insulator and blocks the leakage, without impairing the capacitor's performance or flexibility.
When measured, the capacitors demonstrated a maximum energy density of 40 joules per cubic centimeters and a power density of 520 watts per cubic centimeter. This exceeds conventional capacitors as well as thin-film lithium ion batteries. The lithium ion batteries used in our devices and electric vehicles though are still superior, but this still marks the first time a capacitor has surpassed a battery for energy density.
Source: Georgia Institute of Technology
Posted: August 3, 2015 01:55PM
Silicon is reaching the end of its days for electronics as we approach fundamental physical limits for its performance. We still have time though, and many are spending it to find replacements. One contender is black phosphorus and researchers at the Institute for Basic Science have discovered a powerful way to control its electronic properties.
For silicon to work as a semiconductor, it has to be doped with certain atoms to give it a positive or negative flavor. It is by combining n-type and p-type semiconductors that basic electronic components are made. What the researchers discovered is that doping is not required to give black phosphorus the extra electrons to be n-type, or the extra electron-holes to be p-type. Instead the thickness of black phosphorus will determine this, as will the metal used to contact it. This gives black phosphorus an interesting advantage as its electronic properties can be so readily tuned. It also has very good carrier mobility, which is the ease at which electrons can travel through it.
While this is all good news for a future for black phosphorus electronics, actually making the material is very difficult. Currently no means exists to make it on a large scale, and thin layers of it can only be made by scraping them off of bulk crystalline black phosphorus. Fortunately while black phosphorus can be a two-dimensional material, just one layer thick, it should be useable when there are more layers, and may even operate better that way.
Source: Institute for Basic Science
Posted: August 3, 2015 05:20AM
In a single day, the Sun dumps far more energy onto Earth than humanity uses, which is one of the reasons many want to see solar energy grow in use. Among the problems with this family of technologies is the cost of the materials used, such as gallium and indium. By shifting to other, cheaper materials, solar power can become more common, and researchers at Rice University have made an important to that end.
This discovery concerns the plasmonic properties of metallic nanoparticles. When light shines on these nanoparticles, some of the photons will couple with electrons to form plasmons, but some electrons will be excited to even higher levels, becoming 'hot electrons.' These hot electrons are what one wants for solar power, but their formation and behavior has not been well understood because they could not be filtered out from less-energetic electrons. This is what the Rice researchers have overcome by placing a gold nanowire on top of titanium dioxide, with a layer of titanium between during some tests. When the titanium was present, all of the excited electrons would flow through, but when it was not, only the hot electrons were collected.
This discrimination between the systems allowed the researchers to correlate systems properties with hot electrons. They found the hot electrons were by a plasmonic mechanism called field-intensity enhancement, and not the total absorption of light by the nanoparticle. With this discovery it should be possible to design and tune metallic nanoparticles for solar power, which will be cheaper than modern solar cells and also more capable, as the nanoparticles can be made to absorb the whole spectrum, and not just specific pieces of it.
Source: Rice University