Carbon

This Might Be The Strongest And Lightest Material on Earth

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10 times stronger than steel, with only 5 percent of its density.

For years, researchers have known that carbon, when arranged in a certain way, can be very strong.

Case in point: graphene. Graphene, which was heretofore, the strongest material known to man, is made from an extremely thin sheet of carbon atoms arranged in two dimensions.

But there’s one drawback: while notable for its thinness and unique electrical properties, it’s very difficult to create useful, three-dimensional materials out of graphene.

In January last year, a team of MIT researchers discovered that taking small flakes of graphene and fusing them following a mesh-like structure not only retains the material’s strength, but the graphene also remains porous.

Based on experiments conducted on 3D printed models, researchers have determined that this material, with its distinct geometry, is actually stronger than graphene – making it 10 times stronger than steel, with only 5 percent of its density.

The discovery of a material that is extremely strong but exceptionally lightweight will have numerous applications.

As MIT reports:

“The new findings show that the crucial aspect of the new 3-D forms has more to do with their unusual geometrical configuration than with the material itself, which suggests that similar strong, lightweight materials could be made from a variety of materials by creating similar geometric features.”

Below you can see a simulation results of compression (top left and i) and tensile (bottom left and ii) tests on 3D graphene:

“You could either use the real graphene material or use the geometry we discovered with other materials, like polymers or metals,” said Markus Buehler, head of MIT’s Department of Civil and Environmental Engineering (CEE), and the McAfee Professor of Engineering.

“You can replace the material itself with anything. The geometry is the dominant factor. It’s something that has the potential to transfer to many things.”

Construction may prove to be easier, given that the material used will now be significantly lighter. Because of its porous nature, it may also be applied to filtration systems.

This research, said Huajian Gao, a professor of engineering at Brown University, who was not involved in this work, “shows a promising direction of bringing the strength of 2D materials and the power of material architecture design together”.

Graphene the perfect material for a Lunar Elevator.

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Scientists at Columbia University conducted a study which revealed that graphene retains most of its mechanical properties even when it has been stitched together from small fragments. This discovery may have been the first step toward large scale manufacture of carbon nanotubes, which could be essential in the manufacturing of the first space elevator, light – strong materials, and flexible electronics.

Lunar Elevator

At the present moment, a practical breakthrough in the construction of a lunar elevator has not been realized. However, many scientists have performed experiments which show it will be possible through use of graphene. In these experiments, they have measured the strength of the microscopic carbon nanotube and proved it can indeed support the construction of such elevators.

The space elevator ribbon is constructed out of carbon nanotubes, which are at least 100 times stronger than steel but have flexibility equal to that of plastic. Scientists will only be able to make the ribbon to be used in the space elevator if they manage to make fibers out of carbon nanotubes. In the recent experiments, the materials that were involved were neither strong nor flexible enough to form such a ribbon.

Graphene ribbons have a very high tensile strength and very high elastic modulus, theoretically they are said to make the process of building a space elevator easy. There are two major ways that a lunar elevator ribbon can be built: in the first case a long carbon tube ideally several meters long will be braided into a rope like structure, and in the second case a shorter nanotube will be placed in a selected polymer matrix.

So far graphene is the ideal material for construction of the ribbon, the carbon-carbon bond in graphene is at least 0.142 nm. Scientists have proved that two sheets of graphene are held together by much stronger van de Waals forces than bulk Graphene.

Three-dimensional carbon goes metallic.

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A theoretical, three-dimensional (3D) form of carbon that is metallic under ambient temperature and pressure has been discovered by an international research team.

The findings, which may significantly advance carbon science, are published online this week in the Early Edition of the Proceedings of the National Academy of Sciences.

3-dimensional carbon goes metallic

Carbon science is a field of intense research. Not only does carbon form the chemical basis of life, but it has rich chemistry and physics, making it a target of interest to material scientists. From graphite to diamond to Buckminster fullerenes, nanotubes and graphene, carbon can display in a range of structures.

But the search for a stable three-dimensional form of carbon that is metallic under , including temperature and pressure, has remained an ongoing challenge for scientists in the field.

Researchers from Peking University, Virginia Commonwealth University and Shanghai Institute of Technical Physics employed state-of-the-art theoretical methods to show that it is possible to manipulate carbon to form a three-dimensional metallic phase with interlocking hexagons.

“The interlocking of hexagons provides two unique features – hexagonal arrangement introduces metallic character, and the interlocking form with tetrahedral bonding guarantees stability,” said co-lead investigator Puru Jena, Ph.D., distinguished professor of physics in the VCU College of Humanities and Sciences.

The right combination of these properties could one day be applied to a variety of technologies.

“Unlike high-pressure techniques that require three terapascals of pressure to make carbon metallic, the studied structures are stable at ambient conditions and may be synthesized using benzene or polyacenes molecules,” said co-lead investigator Qian Wang, Ph.D., who holds a professor position at Peking University and an adjunct faculty position at VCU.

“The new metallic  structures may have important applications in lightweight metals for space applications, catalysis and in devices showing negative differential resistance or superconductivity,” Wang said.

According to Jena, the team is still early in its discovery process, but hope that these findings may move the work from theory to the experimental phase.

The study is titled, “Three-dimensional Metallic Carbon: Stable Phases with Interlocking Hexagons.”

Global carbon Cycle.

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global_carbon_cycleMost lakes are oversaturated with CO2 and are net CO2 sources to the atmosphere, yet their contribution to the global carbon cycle is poorly constrained. Their CO2 excess is widely attributed to in-lake oxidation of terrestrially produced dissolved organic carbon. Here we use data collected over 26 years to show that the CO2 in 20 lakes is primarily delivered directly through inflowing streams rather than being produced in situ by degradation of terrestrial carbon. This implies that high CO2 concentrations and atmospheric emissions are not necessarily symptoms of heterotrophic lake ecosystems. Instead, the annual mean CO2 concentration increased with lake productivity and was proportional to the estimated net primary productivity of the catchment. Overall, about 1.6% of net primary productivity (range 1.2–2.2%) was lost to the atmosphere. Extrapolating globally, this is equivalent to CO2 losses of ~0.9 Pg C yr−1 (range 0.7–1.3), consistent with existing estimates. These data and our catchment productivity hypothesis re-enforce the high connectivity found between lakes, their catchment and the global C cycle. They indicate that future concentrations of CO2 in lakes, and losses to the atmosphere, will be highly sensitive to altered catchment management and concomitant effects of climate change that modify catchment productivity.

Atomic bonds between their atoms .

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A pioneering team from IBM in Zurich has published single-molecule images so detailed that the type of atomic bonds between their atoms can be discerned.

The same team took the first-ever single-molecule image in 2009 and more recently published images of a molecule shaped like the Olympic rings.

The new work opens up the prospect of studying imperfections in the “wonder material” graphene or plotting where electrons go during chemical reactions.

The team, which included French and Spanish collaborators, used a variant of a technique called atomic force microscopy, or AFM.

AFM uses a tiny metal tip passed over a surface, whose even tinier deflections are measured as the tip is scanned to and fro over a sample.

The IBM team’s innovation to create the first single molecule picture, of a molecule called pentacene, was to use the tip to pick up a single, small molecule made up of a carbon and an oxygen atom.

This carbon monoxide molecule effectively acts as a record needle, probing with unprecedented accuracy the very surfaces of atoms.

It is difficult to overstate what precision measurements these are.

The experiments must be isolated from any kind of vibration coming from within the laboratory or even its surroundings.

They are carried out at a scale so small that room temperature induces wigglings of the AFM’s constituent molecules that would blur the images, so the apparatus is kept at a cool -268C.

While some improvements have been made since that first image of pentacene, lead author of the Science study, Leo Gross, told BBC News that the new work was mostly down to a choice of subject.

The new study examined fullerenes – such as the famous football-shaped “buckyball” – and polyaromatic hydrocarbons, which have linked rings of carbon atoms at their cores.

The images show just how long the atomic bonds are, and the bright and dark spots correspond to higher and lower densities of electrons.

Together, this information reveals just what kind of bonds they are – how many electrons pairs of atoms share – and what is going on chemically within the molecules.

“In the case of pentacene, we saw the bonds but we couldn’t really differentiate them or see different properties of different bonds,” Dr Gross said.

“Now we can really prove that… we can see different physical properties of different bonds, and that’s really exciting.”

The team will use the method to examine graphene, one-atom-thick sheets of pure carbon that hold much promise in electronics.

But defects in graphene – where the perfect sheets of carbon are buckled or include other atoms – are currently poorly understood.

The team will also explore the use of different molecules for their “record needle”, with the hope of yielding even more insight into the molecular world.

Source: BBC