Carbon nanotubes and graphene - properties, applications and market - Page 4

Researchers at Rice University have found that it may be possible to make graphene-carbon nanotube junctions excel at transferring heat, turning these into an attractive way to channel damaging heat away from next-generation nano-electronics. This could, in theory, be done by putting a cone-like chimney between the graphene and nanotube to eliminate the barrier that blocks heat from escaping.

Graphene and carbon nanotubes both excel at the rapid transfer of electricity and phonons, but when a nanotube grows from graphene, atoms facilitate the turn by forming heptagonal (seven-member) rings instead of the usual six-atom rings. Scientists have determined that forests of nanotubes grown from graphene are excellent for storing hydrogen for energy applications, but in electronics, the heptagons scatter phonons and hinder the escape of heat through the pillars.

Researchers at Tsinghua University in China have shown that feeding silkworms mulberry leaves sprayed with an aqueous solution containing a 0.2% (by weight) graphene or carbon nanotubes can result in reinforced silk that could be used in applications like durable protective fabrics, biodegradable medical implants, and wearable electronics.

This carbon-enhanced silk is said to be twice as tough as regular silks, and can withstand at least 50% higher stress before breaking. The team heated the silk fibers at 1,050 °C to carbonize the silk protein and then studied their conductivity and structure. The modified silks conduct electricity, unlike regular silk. Raman spectroscopy and electron microscopy imaging showed that the carbon-enhanced silk fibers had a more ordered crystal structure due to the incorporated nanomaterials.

Lomiko Metals has announced that it will be presenting a summary of the Graphene Energy Storage Devices Corp. (GESD) Graphene Supercapacitor Project at the Battery Material Conference in Toronto September 2016.

GESD is currently working on scale-up of the technology and an in-field evaluation of the energy storage unit with Stony Brook University. The GESD-SBU team demonstrated design and implementation of a sealed high-voltage EDLCs energy storage unit. The unit is internally balanced, there is no need for an external circuit. The electrode is very cost-effective nano-carbon composite either of a commercial carbon or of graphene platelets with carbon nanotubes. The nano-carbon electrode materials were used for deposition and assembly of a working prototype of an internally balanced high-voltage energy storage unit. The bench-top prototype unit, tested up to 10 V, exhibited good discharge characteristics and charge retention. This development enables new compact energy storage solutions for grid and vehicular applications.

Researchers at MIT have found a way to make composite materials using large area graphene films, in which large numbers of layers are stacked in an orderly manner, without having to stack each layer individually. This could enable creating composite materials containing hundreds of layers and open the door to various possibilities for designing new, easy-to-manufacture composites for optical devices, electronic systems, and more.

A major obstacle in creating graphene-based composites has been that graphene sheets and particles have a strong tendency to adhere together, so just stirring them into a batch of liquid resin before it sets is inefficient. The new technique could go a long way in solving this - while the process is more complex than it sounds, at the heart of it is a technique similar to that used to make puff pastry common in many desserts. A layer of material — dough, or graphene, in this case — is spread out flat. Then, the material is doubled over on itself, pounded or rolled out, and then doubled over again, and again, and again. With each fold, the number of layers doubles, thus producing an exponential increase in the layering. Just 20 simple folds would produce more than a million perfectly aligned layers.

Researchers at Rice University have created rivet graphene, 2D carbon that incorporates carbon nanotubes for strength and carbon spheres that encase iron nanoparticles, which enhance both the material’s portability and its electronic properties.

Transferring graphene grown via CVD is usually done with a polymer layer to keep it from wrinkling or ripping, but the polymer tends to leave contaminants behind and degrade graphene’s abilities to carry a current. According to the Rice team, rivet graphene proved tough enough to eliminate the intermediate polymer step, and the rivets also make interfacing with electrodes far better compared with normal graphene’s interface, since the junctions are more electrically efficient. Finally, the nanotubes give the graphene an overall higher conductivity. So for using graphene in electronic devices, this is said to be an all-around superior material.

Researchers from the Israeli Technion University developed a novel and rapid method to optically visualize CNTs and graphene. The idea is that growing pNBA nanocrystals - which are optically visible on top of the CNTs or graphene sheets. This allows the crystals to be viewed by dark-field optical microscopy.

The pNBAs NCs can be easily removed - and the original material is not effected by this process. But it allows much easier study of graphene, and can also be used to aid production processes as it is a scalable, fast and cost-effective process. The video below shows how growing those NCs on carbon nanotubes makes the tubes visible.

Researchers from the University of Illinois at Chicago have used rod-shaped bacteria - precisely aligned in an electric field, then vacuum-shrunk under a graphene sheet - to cause nanoscale ripples in the material, causing it to conduct electrons differently in perpendicular directions. The resulting material can be applied to a silicon chip and may led to various applications in electronics and nanotechnology.

The team explains that the current across the graphene wrinkles is less than the current along them; The key to formation of these wrinkles is graphene's extreme flexibility at the nanometer scale, which allows formation of carbon nanotubes. The wrinkle opens a 'V' in the electron cloud around each carbon atom, creating a dipole moment, which can open an electronic band gap that flat graphene does not have.

Researchers at UNIST in Korea may have overcome the problem of carbon-based electrocatalysts for dye-sensitized solar cells with their new catalyst made from edge-selenated graphene nanoplatelets.

DSSCs consist of a dye-coated titanium oxide photoanode, an electrolyte and a counter electrode (CE). Currently, the most widely used electrolytes in DSSCs are iodide/triode ones, and the most common CE is an optically transparent thin film of platinum (Pt) nanoparticles on fluorine-doped tin oxide (Pt-FTO). While Pt-based materials are among the most efficient CEs, Pt is an expensive precious metal that is in short supply. That is why researchers are constantly looking for alternative CE materials and the best candidates so far appear to be carbon-based. Such materials include carbon nanotubes, porous carbon, carbon spheres, active carbon and graphene. A major problem, however, with carbon-based CEs is that they are active enough in Co(II)/Co(III) electrolytes (and have a high PCE, here), but not sufficiently so in I-/I3- electrolytes.

Graphene ESD has announced the successful completion of its development project, undertaken jointly with the Research Foundation of Stony Brook University (SBU), that explored a novel method for assembly of high-voltage supercapacitor units.

The team assembled and tested a 10 V supercapacitor energy storage unit, thus proving feasibility of the high-voltage design. This development opens the door for new low-cost energy storage products. Currently, GESD is working on scale-up of the technology and an in-field evaluation of the energy storage unit.

Aixtron, a leading global provider of deposition equipment to the semiconductor industry, has announced that the Institute for Microelectronics and Microsystems of the Italian National Research Council (CNR-IMM) in Catania, Italy, has purchased a BM Pro system in a 6-inch wafer configuration.

The equipment will be used to produce carbon nanotubes and graphene for the WATER (Winning Applications of Nano Technology for Resolutive Hydropurification) project, focused on the use of nanomaterials for water purification. In particular, the research is investigating carbon nanostructures, such as nanotubes and graphene, that have turned out to be the most promising nanomaterials for such applications.