For want of an atom, the space elevator failed
Carbon nanotubes (CNTs) are famed for being a future wonder material that will enable a swathe of super-strong but light applications from racing bikes to computer components.
But now it seems a single out-of-place atom is enough to cut their strength by more than half. That means one of the more outlandish applications for CNT fibres – a sci-fi space elevator – might never happen.
The tubes’ strength is a result of their atomic structure, with walls made from just a single layer of carbon atoms locked in a hexagonal grid. Theoretical studies suggest that a single CNT can have a tensile strength of 100 gigapascals (GPa), making it one of the strongest materials around, but efforts to spin multiple nanotubes into a practical large-scale fibre have only produced ropes with strengths of 1 GPa.
To find out why, Feng Ding of the Hong Kong Polytechnic University and his colleagues simulated CNTs with a single atom is out of place, turning two of the hexagons into a pentagon and heptagon, and creating a kink in the tube. They found this simple change was enough to cut the ideal strength of a CNT to 40 GPa, with the effect being even more severe when they increased the number of misaligned atoms.
Wood makes for better walls than windows — most of the time.
Researchers from the University of Maryland devised a way to strip the colors and and chemicals from a block of wood to leave behind a clear, transparent material that’s stronger and more insulating than glass, and biodegrades better than plastic.
A team led by researchers from the UCLA Henry Samueli School of Engineering and Applied Science has created a super-strong yet light structural metal with extremely high specific strength and modulus, or stiffness-to-weight ratio. The new metal is composed of magnesium infused with a dense and even dispersal of ceramic silicon carbide nanoparticles. It could be used to make lighter airplanes, spacecraft, and cars, helping to improve fuel efficiency, as well as in mobile electronics and biomedical devices.
To create the super-strong but lightweight metal, the team found a new way to disperse and stabilize nanoparticles in molten metals. They also developed a scalable manufacturing method that could pave the way for more high-performance lightweight metals. The research was published today in Nature.
“It’s been proposed that nanoparticles could really enhance the strength of metals without damaging their plasticity, especially light metals like magnesium, but no groups have been able to disperse ceramic nanoparticles in molten metals until now,” said Xiaochun Li, the principal investigator on the research and Raytheon Chair in Manufacturing Engineering at UCLA. “With an infusion of physics and materials processing, our method paves a new way to enhance the performance of many different kinds of metals by evenly infusing dense nanoparticles to enhance the performance of metals to meet energy and sustainability challenges in today’s society.”
Researchers from North Carolina State University have discovered a new phase of solid carbon, called Q-carbon, which is distinct from the known phases of graphite and diamond. They have also developed a technique for using Q-carbon to make diamond-related structures at room temperature and at ambient atmospheric pressure in air.
Phases are distinct forms of the same material. Graphite is one of the solid phases of carbon; diamond is another.
"We've now created a third solid phase of carbon," says Jay Narayan, the John C. Fan Distinguished Chair Professor of Materials Science and Engineering at NC State and lead author of three papers describing the work. "The only place it may be found in the natural world would be possibly in the core of some planets."
Q-carbon has some unusual characteristics. For one thing, it is ferromagnetic – which other solid forms of carbon are not.
"We didn't even think that was possible," Narayan says.
In addition, Q-carbon is harder than diamond, and glows when exposed to even low levels of energy.
"Q-carbon's strength and low work-function – its willingness to release electrons – make it very promising for developing new electronic display technologies," Narayan says.
But Q-carbon can also be used to create a variety of single-crystal diamond objects. To understand that, you have to understand the process for creating Q-carbon.
Hardly a week goes by without somebody proclaiming a new application for graphene, the form of carbon that occurs in single sheets with chicken wire-like structure (see “Research Hints at Graphene’s Photovoltaic Potential”). Roll a graphene sheet into a tube and it forms a carbon nanotube, another wonder material with numerous applications. And wrap it further into a ball and, with a small rearrangement of bonds, it forms buckyballs.
Now there is a new kid on the carbon block. Last month, a team at Pennsylvania State University and elsewhere announced they had created another type of carbon that takes the form of a one-dimensional diamond crystal capped with hydrogen. They call this new material diamond nanothread.
That caused a flurry of excitement and raised some interesting questions. Materials scientists are fascinated by the potential properties of a diamond nanothread and its applications. But one fear is that such a thread would be so brittle that it would shatter like glass under any kind of load, a property that would severely limit its use.
Today, we get some new insight into diamond nanothreads thanks to the work of Haifei Zhan at Queensland University of Technology in Australia and a few pals. These guys have modeled the threads using large-scale molecular dynamics simulations. And they conclude that the material could be more versatile than anyone thought. There are tentative signs that diamond nanothread could be a new a wonder material in its own right.
Two years after physicists predicted that tin should be able to form a mesh just one atom thick, researchers say that they have made it. The thin film, called stanene, is reported on 3 August in Nature Materials. But researchers have not been able to confirm whether the material has the predicted exotic electronic properties that have excited theorists, such as being able to conduct electricity without generating any waste heat.
Stanene (from the Latin stannum meaning tin, which also gives the element its chemical symbol, Sn), is the latest cousin of graphene, the honeycomb lattice of carbon atoms that has spurred thousands of studies into related 2D materials. Those include sheets of silicene, made from silicon atoms; phosphorene, made from phosphorus; germanene, from germanium; and thin stacks of sheets that combine different kinds of chemical elements.
Many of these sheets are excellent conductors of electricity, but stanene is — in theory — extra-special. At room temperature, electrons should be able to travel along the edges of the mesh without colliding with other electrons and atoms as they do in most materials. This should allow the film to conduct electricity without losing energy as waste heat, according to predictions2 made in 2013 by Shou-Cheng Zhang, a physicist at Stanford University in California, who is a co-author of the latest study.
Research from North Carolina State University shows that lightweight composite metal foams are effective at blocking X-rays, gamma rays and neutron radiation, and are capable of absorbing the energy of high impact collisions. The finding means the metal foams hold promise for use in nuclear safety, space exploration and medical technology applications.
"This work means there's an opportunity to use composite metal foam to develop safer systems for transporting nuclear waste, more efficient designs for spacecraft and nuclear structures, and new shielding for use in CT scanners," says Afsaneh Rabiei, a professor of mechanical and aerospace engineering at NC State and corresponding author of a paper on the work.
Rabiei first developed the strong, lightweight metal foam for use in transportation and military applications. But she wanted to determine whether the foam could be used for nuclear or space exploration applications - could it provide structural support, protect against high impacts and provide shielding against various forms of radiation?
To that end, she and her colleagues conducted multiple tests to see how effective it was at blocking X-rays, gamma rays and neutron radiation. She then compared the material's performance to the performance of bulk materials that are currently used in shielding applications. The comparison was made using samples of the same "areal" density - meaning that each sample had the same weight, but varied in volume.
The most effective composite metal foam against all three forms of radiation is called "high-Z steel-steel" and was made up largely of stainless steel, but incorporated a small amount of tungsten. However, the structure of the high-Z foam was modified so that the composite foam that included tungsten was not denser than metal foam made entirely of stainless steel.
The researchers tested shielding performance against several kinds of gamma ray radiation. Different source materials produce gamma rays with different energies. For example, cesium and cobalt emit higher-energy gamma rays, while barium and americium emit lower-energy gamma rays.
The researchers found that the high-Z foam was comparable to bulk materials at blocking high-energy gamma rays, but was much better than bulk materials - even bulk steel - at blocking low-energy gamma rays.
Similarly, the high-Z foam outperformed other materials at blocking neutron radiation.
It's the world's most popular building material, and ever since the Romans built the pantheon from it some 2,000 years ago, we've been trying to find ways to make concrete more durable.
No matter how carefully it is mixed or reinforced, all concrete eventually cracks, and under some conditions, those cracks can lead to collapse.
"The problem with cracks in concrete is leakage," explains professor Henk Jonkers, of Delft University of Technology, in the Netherlands.
"If you have cracks, water comes through -- in your basements, in a parking garage. Secondly, if this water gets to the steel reinforcements -- in concrete we have all these steel rebars -- if they corrode, the structure collapses."
But Jonkers has come up with an entirely new way of giving concrete a longer life.
"We have invented bioconcrete -- that's concrete that heals itself using bacteria," he says.
Imagine a glass window that's tough like armor, a camera lens that doesn't get scratched in a sand storm, or a smart phone that doesn't break when dropped. Except it's not glass, it's a special ceramic called spinel {spin-ELL} that the U.S. Naval Research Laboratory (NRL) has been researching over the last 10 years.
"Spinel is actually a mineral, it's magnesium aluminate," says Dr. Jas Sanghera, who leads the research. "The advantage is it's so much tougher, stronger, harder than glass. It provides better protection in more hostile environments—so it can withstand sand and rain erosion."
As a more durable material, a thinner layer of spinel can give better performance than glass. "For weight-sensitive platforms-UAVs [unmanned autonomous vehicles], head-mounted face shields—it's a game-changing technology."
NRL invented a new way of making transparent spinel, using a hot press, called sintering. It's a low-temperature process, and the size of the pieces is limited only by the size of the press. "Ultimately, we're going to hand it over to industry," says Sanghera, "so it has to be a scalable process." In the lab, they made pieces eight inches in diameter. "Then we licensed the technology to a company who was able then to scale that up to much larger plates, about 30-inches wide."
The sintering method also allows NRL to make optics in a number of shapes, "conformal with the surface of an airplane or UAV wing," depending on the shape of the press.
In addition to being tougher, stronger, harder, Sanghera says spinel has "unique optical properties; not only can you see through it, but it allows infrared light to go through it." That means the military, for imaging systems, "can use spinel as the window because it allows the infrared light to come through."
NRL is also looking at spinel for the windows on lasers operating in maritime and other hostile environments. "I've got to worry about wave slap and saltwater and things like that, and gun blasts going off—it's got to be resistant to all that. And so that's where spinel comes into its own," says Sanghera.
Adaptive optoelectronic camouflage systems with designs inspired by cephalopod skins
Authors:
Yu et al
Abstract:
Octopus, squid, cuttlefish, and other cephalopods exhibit exceptional capabilities for visually adapting to or differentiating from the coloration and texture of their surroundings, for the purpose of concealment, communication, predation, and reproduction. Long-standing interest in and emerging understanding of the underlying ultrastructure, physiological control, and photonic interactions has recently led to efforts in the construction of artificial systems that have key attributes found in the skins of these organisms. Despite several promising options in active materials for mimicking biological color tuning, existing routes to integrated systems do not include critical capabilities in distributed sensing and actuation. Research described here represents progress in this direction, demonstrated through the construction, experimental study, and computational modeling of materials, device elements, and integration schemes for cephalopod-inspired flexible sheets that can autonomously sense and adapt to the coloration of their surroundings. These systems combine high-performance, multiplexed arrays of actuators and photodetectors in laminated, multilayer configurations on flexible substrates, with overlaid arrangements of pixelated, color-changing elements. The concepts provide realistic routes to thin sheets that can be conformally wrapped onto solid objects to modulate their visual appearance, with potential relevance to consumer, industrial, and military applications.
A catalyst made from a foamy form of copper has vastly different electrochemical properties from catalysts made with smooth copper in reactions involving carbon dioxide, a new study shows. The research, by scientists in Brown University's Center for the Capture and Conversion of CO2, suggests that copper foams could provide a new way of converting excess CO2 into useful industrial chemicals.
The research is published in the journal ACS Catalysis.
As levels of carbon dioxide in the atmosphere continue to rise, researchers are looking for ways to make use of it. One approach is to capture CO2 emitted from power plants and other facilities and use it as a carbon source to make industrial chemicals, most of which are currently made from fossil fuels. The problem is that CO2 is extremely stable, and reducing it to a reactive and useful form isn't easy.
"Copper has been studied for a long time as an electrocatalyst for CO2 reduction, and it's the only metal shown to be able to reduce CO2 to useful hydrocarbons," said Tayhas Palmore, professor of engineering and senior author of the new research. "There was some indication that if you roughen the surface of planar copper, it would create more active sites for reactions with CO2."
Copper foam, which has been developed only in the last few years, provided the surface roughness that Palmore and her colleagues were looking for. The foams are made by depositing copper on a surface in the presence of hydrogen and a strong electric current. Hydrogen bubbles cause the copper to be deposited in an arrangement of sponge-like pores and channels of varying sizes.
After depositing copper foams on an electrode, the researchers set up experiments to see what kinds of products would be produced in an electrochemical reaction with CO2 in water. The experiments were performed by Sujat Sen and Dan Liu, graduate students in chemistry working in Palmore's lab at Brown's School of Engineering.
The experiments showed that the copper foam converted CO2 into formic acid — a compound often used as a feedstock for microbes that produce biofuels — at a much greater efficiency than planar copper. The reaction also produced small amounts of propylene, a useful hydrocarbon that's never been reported before in reactions involving copper.
"The product distribution was unique and very different from what had been reported with planar electrodes, which was a surprise," Palmore said. "We've identified another parameter to consider in the electroreduction of CO2. It's not just the kind of metal that's responsible for the direction this chemistry goes, but also the architecture of the catalyst."
[A] phase-changing material built from wax and foam, and capable of switching between hard and soft states, could allow even low-cost robots to perform the same feat.
The material — developed by Anette Hosoi, a professor of mechanical engineering and applied mathematics at MIT, and her former graduate student Nadia Cheng, alongside researchers at the Max Planck Institute for Dynamics and Self-Organization and Stony Brook University — could be used to build deformable surgical robots. The robots could move through the body to reach a particular point without damaging any of the organs or vessels along the way.
Robots built from the material, which is described in a new paper in the journal Macromolecular Materials and Engineering, could also be used in search-and-rescue operations to squeeze through rubble looking for survivors, Hosoi says.
Puritans, Goths,
avant-garde artists, hell-raising poets and fashion icon Coco Chanel all
saw something special in it. Now black, that most enigmatic of colours,
has become even darker and more mysterious.
A British
company has produced a "strange, alien" material so black that it
absorbs all but 0.035 per cent of visual light, setting a new world
record. To stare at the "super black" coating made of carbon nanotubes –
each 10,000 times thinner than a human hair – is an odd experience. It
is so dark that the human eye cannot understand what it is seeing.
Shapes and contours are lost, leaving nothing but an apparent abyss.
In the popular folktale, “The Princess and the Pea,” a young girl proves her princess-like sensitivity after a pea, inserted beneath 20 mattresses and 20 featherbeds, ruins her night of sleep. But if she had slept atop a thin sheet of scientists’ new touch-cloaking nanomaterial, she would have slept like a rock.
Researchers at the Karlsruhe Institute of Technology have created a material that sounds like something from a fictional tale: an elasto-mechanical unfeelability cloak. The polymer-based, scaffold-like structure can mask the presence of an object so it’s imperceptible to the human touch.
Imagine being able to carry all the juice you needed to power your MP3 player, smartphone and electric car in the fabric of your jacket?
Sounds like science fiction, but it may become a reality thanks to breakthrough technology developed at a University of Central Florida research lab.
So far electrical cables are used only to transmit electricity. However, nanotechnology scientist and professor Jayan Thomas and his Ph.D. student Zenan Yu have developed a way to both transmit and store electricity in a single lightweight copper wire.
Their work is the focus of the cover story of the June 30 issue of the material science journal Advanced Materials and science magazine, Nature has published a detailed discussion about this technology in the current issue.
"It's a very interesting idea," Thomas said. "When we did it and started talking about it, everyone we talked to said, "Hmm, never thought of that. It's unique.'"
Copper wire is the starting point but eventually, Thomas said, as the technology improves, special fibers could also be developed with nanostructures to conduct and store energy.
More immediate applications could be seen in the design and development of electrical vehicles, space-launch vehicles and portable electronic devices. By being able to store and conduct energy on the same wire, heavy, space-consuming batteries could become a thing of the past. It is possible to further miniaturize the electronic devices or the space that has been previously used for batteries could be used for other purposes. In the case of launch vehicles, that could potentially lighten the load, making launches less costly, Thomas said.
Internal damage in fiber-reinforced composites, materials used in structures of modern airplanes and automobiles, is difficult to detect and nearly impossible to repair by conventional methods. A small, internal crack can quickly develop into irreversible damage from delamination, a process in which the layers separate. This remains one of the most significant factors limiting more widespread use of composite materials.
However, fiber-composite materials can now heal autonomously through a new self-healing system, developed by researchers in the Beckman Institute's Autonomous Materials Systems (AMS) Group at the University of Illinois at Urbana-Champaign, led by professors Nancy Sottos, Scott White, and Jeff Moore.
Sottos, White, Moore, and their team created 3D vascular networks—patterns of microchannels filled with healing chemistries—that thread through a fiber-reinforced composite. When damage occurs, the networks within the material break apart and allow the healing chemistries to mix and polymerize, autonomously healing the material, over multiple cycles. These results were detailed in a paper titled "Continuous self-healing life cycle in vascularized structural composites," published in Advanced Materials.
"This is the first demonstration of repeated healing in a fiber-reinforced composite system," said Scott White, aerospace engineering professor and co-corresponding author. "Self-healing has been done before in polymers with different techniques and networks, but they couldn't be translated to fiber-reinforced composites. The missing link was the development of the vascularization technique."
"The beauty of this self-healing approach is, we don't have to probe the structure and say, this is where the damage occurred and then repair it ourselves," said Jason Patrick, a Ph.D. candidate in civil engineering and lead author.
Controlling and bending light around an object so it appears invisible to the naked eye is the theory behind fictional invisibility cloaks.
It may seem easy in Hollywood movies, but is hard to create in real life because no material in nature has the properties necessary to bend light in such a way. Scientists have managed to create artificial nanostructures that can do the job, called metamaterials. But the challenge has been making enough of the material to turn science fiction into a practical reality.
The work of Debashis Chanda at the University of Central Florida, however, may have just cracked that barrier. The cover story in the March edition of the journal Advanced Optical Materials, explains how Chanda and fellow optical and nanotech experts were able to develop a larger swath of multilayer 3-D metamaterial operating in the visible spectral range. They accomplished this feat by using nanotransfer printing, which can potentially be engineered to modify surrounding refractive index needed for controlling propagation of light.
"Such large-area fabrication of metamaterials following a simple printing technique will enable realization of novel devices based on engineered optical responses at the nanoscale," said Chanda, an assistant professor at UCF.
The nanotransfer printing technique creates metal/dielectric composite films, which are stacked together in a 3-D architecture with nanoscale patterns for operation in the visible spectral range. Control of electromagnetic resonances over the 3-D space by structural manipulation allows precise control over propagation of light. Following this technique, larger pieces of this special material can be created, which were previously limited to micron-scale size.
What do some high-end golf clubs and your living room window have in common? The answer is glass, but in the golf clubs' case it's a specialized glass product, called metallic glass, with the ability to be bent considerably and spring back into its original form. Your windows, as you know, aren't quite as forgiving of a sudden impact, and they shatter – they are brittle, as opposed to ductile, or more flexible products. For the golf clubs, however, a new generation of flexible metallic glass puts more bounce back into a golf ball, from the metallic glass' high elasticity. They're not unbreakable, but close. And scientists are working toward even stronger and more elastic glass types which would fail in a ductile fashion instead of shattering.
"In glass, localized plastic deformation usually leads to immediate failure," said Seth Imhoff, a Los Alamos National Laboratory materials scientist. "Normally, metal alloys freeze into a collection of crystals in which the atoms line up into very specific patterns. In specially designed metal alloys an amorphous, or random atom arrangement, can be retained in the solid, which can allow us to tailor a wide range of properties such as the ability to be bent severely and spring back into place."
And for scientists, tweaking the shearing characteristics of materials such as glass has important applications well beyond the sporting world, it's a matter of broader impact, aiding such fields as space science, electrical transformers, cell phone cases, and yes, golf clubs, because their mechanical and magnetic properties are highly adjustable.
An international team of scientists from the University of Wisconsin-Madison, Los Alamos National Laboratory, Universitat Autònoma de Barcelona in Spain, and Tohoku University in Japan are hoping their discoveries will lead to glass that can be both stronger and more ductile.
The way that metallic glass deforms plastically is by the formation of what are called shear bands. Shear banding can occur on a macroscopic scale in granular materials, like during an avalanche or landslide, but in glass the bands are generally 10-20 nanometers wide (~3000 times thinner than a human hair!).
In their paper "Nucleation of Shear Bands in Amorphous Alloys" published this week in the Proceedings of the National Academy of Sciences, these researchers are looking at the initiation of shear-banding events in order to better understand how to control the mechanical properties of these materials.
Engineered materials such as chip-grade silicon and fiber-optic glass underpin the modern world. Yet designing new materials has historically involved a frustrating and inefficient amount of guesswork.
Streamlined versions of the equations of quantum mechanics—along with supercomputers that, using those equations, virtually test thousands of materials at a time—are eliminating much of that guesswork.
Researchers are now using this method, called high-throughput computational materials design, to develop new batteries, solar cells, fuel cells, computer chips, and other technologies.
Look out for mass-produced invisibility cloaks thanks to an entirely new way of designing and manufacturing them out of materials such as Teflon
When it comes to invisibility cloaks, one of the trickiest problems is how to make the things.
The materials of choice are known as metamaterials which are created by assembling a repeating pattern of structures that interact with the light they are designed to cloak. This kind of detailed assembly means that making metamaterials is an expensive and time-consuming process. What’s more, the resulting invisibility cloaks are never perfect
So physicists have begun to wonder if they can do just as well with other materials that are easier and simpler to make.
Their approach is entirely different to the theoretical light-bending mathematics physicists have used until now. This current approach works by attempting to steer electromagnetic fields around an object in a way that hides it. The necessary material must be able to repeat this kind of light distortion in real life.
The new approach is to create a computer model of the cloak in the form of a conventional material with fixed light bending properties.
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