Skip to main content

Home/ Advanced Concepts Team/ Group items tagged material

Rss Feed Group items tagged

jcunha

Accelerated search for materials with targeted properties by adaptive design - 0 views

  •  
    There has been much recent interest in accelerating materials discovery. High-throughput calculations and combinatorial experiments have been the approaches of choice to narrow the search space. The emphasis has largely been on feature or descriptor selection or the use of regression tools, such as least squares, to predict properties. The regression studies have been hampered by small data sets, large model or prediction uncertainties and extrapolation to a vast unexplored chemical space with little or no experimental feedback to validate the predictions. Thus, they are prone to be suboptimal. Here an adaptive design approach is used that provides a robust, guided basis for the selection of the next material for experimental measurements by using uncertainties and maximizing the 'expected improvement' from the best-so-far material in an iterative loop with feedback from experiments. It balances the goal of searching materials likely to have the best property (exploitation) with the need to explore parts of the search space with fewer sampling points and greater uncertainty.
Nina Nadine Ridder

Material could harvest sunlight by day, release heat on demand hours or days later - 5 views

  •  
    Imagine if your clothing could, on demand, release just enough heat to keep you warm and cozy, allowing you to dial back on your thermostat settings and stay comfortable in a cooler room. Or, picture a car windshield that stores the sun's energy and then releases it as a burst of heat to melt away a layer of ice.
  •  
    interesting indeed: Such chemically-based storage materials, known as solar thermal fuels (STF), have been developed before, including in previous work by Grossman and his team. But those earlier efforts "had limited utility in solid-state applications" because they were designed to be used in liquid solutions and not capable of making durable solid-state films, Zhitomirsky says. The new approach is the first based on a solid-state material, in this case a polymer, and the first based on inexpensive materials and widespread manufacturing technology. Read more at: http://phys.org/news/2016-01-material-harvest-sunlight-day-demand.html#jCp
johannessimon81

Material that shrinks in heat can weather extreme temperatures - 3 views

  •  
    Meet the incredible shrinking material. Most things swell when they warm up, creating engineering headaches, but now a 3D-printed material has been configured to contract instead. When two interlinked materials expand at different rates, they can warp or crack. It's a problem in buildings, bridges, electronics and anything else that is exposed to a wide temperature swing.
Thijs Versloot

Light brought to a complete stop - 3 views

  •  
    "When a control laser is fired at the crystal, a complex quantum-level reaction turns it the opaque crystal transparent. A second light source is beamed into the crystal before the control laser is shut off, returning the crystal to its opaque state. This leaves the light trapped inside the crystal, and the opacity of the crystal keeps the light trapped inside from bouncing around, effectively bringing light to a full stop." is the simple explanation, but I am not sure how this is actually possible with the current laws of physics
  •  
    There are two ways to make slow light: material slow light and structural slow light, where you either change the material or the structural properties of your system. Here they used EIT to make material slow light, by inducing transparency inside an otherwise opaque material. As you change the absorption properties of a material you also change its dispersion properties, the so-called Kramers-Kronig relations. A rapid positive change in the dispersion properties of a material will give rise to slow light. To effectively stop light they switched off the control beam, bringing back the opaque state. Another control beam is then used to retrieve the probe pulse that was 'frozen' inside the medium. Light will be halted according to the population lifetime on the energy level (~ 100s). They used an evolutionary algorithm to find an optimal pulse preparation sequence to reach close to the maximum possible storage duration of 100s. Interesting paper!
  •  
    So it is not real storage then in a sense, as you are stimulating an excitation population which retains the phase information of your original pulse? Still it is amazing that they could store this up to 100s and retrieve it with a probe pulse, but light has never been halted.
Thijs Versloot

Graphene coated silicon super-capacitors for energy storage - 1 views

  •  
    Recharge in seconds and efficiently store power for weeks between charges. Added bonus is the cheap and abundant components needed. One of the applications they foresee is to attach such a super-capacitor to the back of solar panels to store the power and discharge this during the night
  •  
    very nice indeed - is this already at a stage where we should have a closer look at it? what you think? With experience in growing carbon nanostructures, Pint's group decided to try to coat the porous silicon surface with carbon. "We had no idea what would happen," said Pint. "Typically, researchers grow graphene from silicon-carbide materials at temperatures in excess of 1400 degrees Celsius. But at lower temperatures - 600 to 700 degrees Celsius - we certainly didn't expect graphene-like material growth." When the researchers pulled the porous silicon out of the furnace, they found that it had turned from orange to purple or black. When they inspected it under a powerful scanning electron microscope they found that it looked nearly identical to the original material but it was coated by a layer of graphene a few nanometers thick. When the researchers tested the coated material they found that it had chemically stabilized the silicon surface. When they used it to make supercapacitors, they found that the graphene coating improved energy densities by over two orders of magnitude compared to those made from uncoated porous silicon and significantly better than commercial supercapacitors. Transmission electron microscope image of the surface of porous silicon coated with graphene. The coating consists of a thin layer of 5-10 layers of graphene which filled pores with diameters less than 2-3 nanometers and so did not alter the nanoscale architecture of the underlying silicon. (Cary Pint / Vanderbilt) The graphene layer acts as an atomically thin protective coating. Pint and his group argue that this approach isn't limited to graphene. "The ability to engineer surfaces with atomically thin layers of materials combined with the control achieved in designing porous materials opens opportunities for a number of different applications beyond energy storage," he said.
ESA ACT

NASA - A Telescope Made of Moondust - 0 views

  •  
    Composite materials are synthetic materials made by mixing fibers or granules of various materials into epoxy and letting the mixture harden. Composites combine two valuable properties: ultralight weight and extraordinary strength.
santecarloni

Virus helps build new materials - physicsworld.com - 0 views

  •  
    Scientists in the US have used a common virus to produce materials that resemble skin and bone. In addition to providing new insights into how such materials develop in the natural world, the work also brings synthetic production of tissue in the laboratory closer to reality
jaihobah

Wood windows? Transparent wood material used for buildings, solar cells -- ScienceDaily - 2 views

  •  
    "Windows and solar panels in the future could be made from one of the best -- and cheapest -- construction materials known: wood. Researchers at Stockholm's KTH Royal Institute of Technology have developed a new transparent wood material that's suitable for mass production"
Aurelie Heritier

Lighter-than-air material could drastically change tech - 4 views

  •  
    Aerographite. This post was originally published on Mashable. German scientists have developed a sturdy material called Aerographite made mostly of air, opening up huge implications for the future development of electronics. The jet-black, non-transparent porous carbon material - which was created by scientists at Kiel University and Hamburg University of Technology - was detailed in the July edition of scientific journal Advanced Materials .
Thijs Versloot

Repeated self-healing in composite materials - 1 views

  •  
    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.
ESA ACT

Experimental Observation of an Extremely Dark Material Made By a Low-Density Nanotube A... - 0 views

  •  
    The integrated total reflectance from carbonnanotube arrays is three times lower than the lowest-ever reported values of optical reflectance from any material, making it the darkest man-made material ever.
ESA ACT

Materials Today : The top ten advances in materials science - 0 views

  •  
    What are the defining discoveries, moments of inspiration, or shifts in understanding that have shaped the dynamic field of materials science we know today. Here's what we think are the most significant.
ESA ACT

MRS Special Issue Harnessing Materials for Energy - 0 views

  •  
    "Harnessing Materials for Energy," focuses on the most important materials research challenges that need to be addressed to move toward secure, affordable, and environmentally sustainable energy to meet the world's accelerating energy needs. The issue fol
ESA ACT

MRS Issue on Negative-Index Materials - 0 views

  •  
    How light travels through a material is measured by the index of refraction, a fundamental optical constant long thought to be an intrinsic materials property. However, research has shown that features manipulated through nanofabrication techniques can le
Marcus Maertens

Unsupervised word embeddings capture latent knowledge from materials science literature... - 1 views

  •  
    New results in NLP might allow to automate scientific discoveries by data mining of papers. Work considers 3.3M abstracts from material science, physics and chemistry and claims to discover new materials before they are published later on.
  •  
    ACT did that from diigo post digging in the retreat of 2014! Still without NLP.
  •  
    That's cool! Didn't know.
LeopoldS

Physicists twist water into knots : Nature News & Comment - 3 views

  •  
    More than a century after the idea was first floated, physicists have finally figured out how to tie water in knots in the laboratory. The gnarly feat, described today in Nature Physics1, paves the way for scientists to experimentally study twists and turns in a range of phenomena - ionized gases like that of the Sun's outer atmosphere, superconductive materials, liquid crystals and quantum fields that describe elementary particles.

    Lord Kelvin proposed that atoms were knotted "vortex rings" - which are essentially like tornado bent into closed loops and knotted around themselves, as Daniel Lathrop and Barbara Brawn-Cinani write in an accompanying commentary. In Kelvin's vision, the fluid was the theoretical 'aether' then thought to pervade all of space. Each type of atom would be represented by a different knot.

    Related stories
    Solar magnetism twists braids of superheated gas
    Electron microscopy gets twisted
    Topological insulators: Star material
    More related stories
    Kelvin's interpretation of the periodic table never went anywhere, but his ideas led to the blossoming of the mathematical theory of knots, part of the field of topology. Meanwhile, scientists also have come to realize that knots have a key role in a host of physical processes.
jmlloren

Exotic matter : Insight : Nature - 5 views

shared by jmlloren on 03 Aug 10 - Cached
LeopoldS liked it
  •  
    Trends in materials and condensed matter. Check out the topological insulators. amazing field.
  • ...12 more comments...
  •  
    Aparently very interesting, will it survive the short hype? Relevant work describing mirror charges of topological insulators and the classical boundary conditions were done by Ismo and Ari. But the two communities don't know each other and so they are never cited. Also a way to produce new things...
  •  
    Thanks for noticing! Indeed, I had no idea that Ari (don't know Ismo) was involved in the field. Was it before Kane's proposal or more recently? What I mostly like is that semiconductors are good candidates for 3D TI, however I got lost in the quantum field jargon. Yesterday, I got a headache trying to follow the Majorana fermions, the merons, skyrnions, axions, and so on. Luzi, are all these things familiar to you?
  •  
    Ismo Lindell described in the early 90's the mirror charge of what is now called topological insulator. He says that similar results were obtained already at the beginning of the 20th century... Ismo Lindell and Ari Sihvola in the recent years discussed engineering aspects of PEMCs (perfect electro-megnetic conductors,) which are more or less classical analogues of topological insulators. Fundamental aspects of PEMCs are well knwon in high-energy physics for a long time, recent works are mainly due to Friedrich Hehl and Yuri Obukhov. All these works are purely classical, so there is no charge quantisation, no considerations of electron spin etc. About Majorana fermions: yes, I spent several years of research on that topic. Axions: a topological state, of course, trivial :-) Also merons and skyrnions are topological states, but I'm less familiar with them.
  •  
    "Non-Abelian systems1, 2 contain composite particles that are neither fermions nor bosons and have a quantum statistics that is far richer than that offered by the fermion-boson dichotomy. The presence of such quasiparticles manifests itself in two remarkable ways. First, it leads to a degeneracy of the ground state that is not based on simple symmetry considerations and is robust against perturbations and interactions with the environment. Second, an interchange of two quasiparticles does not merely multiply the wavefunction by a sign, as is the case for fermions and bosons. Rather, it takes the system from one ground state to another. If a series of interchanges is made, the final state of the system will depend on the order in which these interchanges are being carried out, in sharp contrast to what happens when similar operations are performed on identical fermions or bosons." wow, this paper by Stern reads really weired ... any of you ever looked into this?
  •  
    C'mon Leopold, it's as trivial as the topological states, AKA axions! Regarding the question, not me!
  •  
    just looked up the wikipedia entry on axions .... at least they have some creativity in names giving: "In supersymmetric theories the axion has both a scalar and a fermionic superpartner. The fermionic superpartner of the axion is called the axino, the scalar superpartner is called the saxion. In some models, the saxion is the dilaton. They are all bundled up in a chiral superfield. The axino has been predicted to be the lightest supersymmetric particle in such a model.[24] In part due to this property, it is considered a candidate for the composition of dark matter.[25]"
  •  
    Thank's Leopold. Sorry Luzi for being ironic concerning the triviality of the axions. Now, Leo confirmed me that indeed is a trivial matter. I have problems with models where EVERYTHING is involved.
  •  
    Well, that's the theory of everything, isn't it?? Seriously: I don't think that theoretically there is a lot of new stuff here. Topological aspects of (non-Abelian) theories became extremely popular in the context of string theory. The reason is very simple: topological theories are much simpler than "normal" and since string theory anyway is far too complicated to be solved, people just consider purely topological theories, then claiming that this has something to do with the real world, which of course is plainly wrong. So what I think is new about these topological insulators are the claims that one can actually fabricate a material which more or less accurately mimics a topological theory and that these materials are of practical use. Still, they are a little bit the poor man's version of the topological theories fundamental physicists like to look at since electrdynamics is an Abelian theory.
  •  
    I have the feeling, not the knowledge, that you are right. However, I think that the implications of this light quantum field effects are great. The fact of being able to sustain two currents polarized in spin is a technological breakthrough.
  •  
    not sure how much I can contribute to your apparently educated debate here but if I remember well from my work for the master, these non-Abelian theories were all but "simple" as Luzi puts it ... and from a different perspective: to me the whole thing of being able to describe such non-Abelian systems nicely indicates that they should in one way or another also have some appearance in Nature (would be very surprised if not) - though this is of course no argument that makes string theory any better or closer to what Luzi called reality ....
  •  
    Well, electrodynamics remains an Abelian theory. From the theoretical point of view this is less interesting than non-Abelian ones, since in 4D the fibre bundle of a U(1) theory is trivial (great buzz words, eh!) But in topological insulators the point of view is slightly different since one always has the insulator (topological theory), its surrounding (propagating theory) and most importantly the interface between the two. This is a new situation that people from field and string theory were not really interested in.
  •  
    guys... how would you explain this to your gran mothers?
  •  
    *you* tried *your* best .... ??
Tobias Seidl

From ultra-soft slime to hard {alpha}-keratins: The many lives of intermediate filament... - 0 views

  • The diverse mechanisms described here have been employed by animals to generate materials with stiffness values that span an impressive eleven orders of magnitude.
  •  
    One basic molecule allows to achieve a broad range of material stiffness.
ESA ACT

The Transition from Stiff to Compliant Materials in Squid Beaks -- Miserez et al. 319 (... - 0 views

  •  
    Gradient material properties - here in squid beaks - but also in other bio-models are extremely cool.
santecarloni

Three electrons for the price of one - physicsworld.com - 0 views

  •  
    Researchers have created a new material that can produce three or more free electrons every time it absorbs a single photon. This is unlike conventional semiconductors, which produce just one free electron per photon. Based on tiny semiconductor structures called quantum dots, the new material - developed by researchers at Delft University of Technology in the Netherlands and Toyota Europe in Belgium - could someday be used to make more efficient solar cells.
1 - 20 of 227 Next › Last »
Showing 20 items per page