Graphene thermal conductivity - introduction and latest news - Page 18

EPFL researchers investigated heat dissipation in graphene and other two-dimensional materials, and have shown that heat can propagate as a wave over very long distances. This discovery can provide a valuable tool for for cooling down circuits at the nanoscale, and contribute to the efforts to replace silicon in next-gen electronics.

2D sheets behave in unexpected ways compared to 3D ones, and understanding the propagation of heat in them is a challenge. The EPFL researchers demonstrated that heat can propagate without significant losses in 2D even at room temperature, thanks to the phenomenon of wave-like diffusion, called "second sound". In that case, all phonons (vibrations of atomes) move together in unison over very long distances. This could be of great value for future electronic components that use 2D materials. 

Cambridge Nanosystems (CNS) was spun-off from the University of Cambridge last year with with an aim to supply graphene and SWCNT materials. The company recently started building a 5-yearly ton graphene factory with the help of a £500,000 grant from the Technology Strategy Board. The new factory is due to open in 2015.

Catharina Paukner, the company's chief scientist, was kind enough to answer a few questions we had on the company and its technology and also share her views on the graphene market.

James Baker, business director at the National Graphene Institute (NGI) in the UK said a technology company (that remained unnamed) is about to open a LED light factory in Manchester.

The factory will produce LED lighting in which graphene will be used to dissipate heat, thanks to its superior heat conductivity trait. 

Researchers from Stockholm University managed to develop a super-insulating and fire retardant foam for house insulation by freezing together graphene oxide, cellulose nanofibers and clay nanorods.

The foam is highly porous and boasts lower thermal conductivity than traditional insulators like polystyrene and polyurethane. It is mechanically stiff, able to sustain great loads and also does not need to be laced with organic fire retardants (it is inherently fire retardant). The researchers believe this foam could even be fitted onto older buildings without tampering with their appearance.

Graphenea has opened a branch in the USA to assist more immediate service of the company's North American customers. The US branch, Graphenea Inc, is based in Cambridge (Boston), MA, due to the close relation that the company has with research giants Massachusetts Institute of Technology (MIT) and Harvard. Apart from developing collaborative projects with those two partners, and acting as a sales outpost for its renown high-quality graphene, Graphenea Inc will set up an Applications Laboratory to help develop custom graphene materials.

The US outpost of Graphenea will continue and enhance the research excellence of the company, with planned hirings of full time R&D and Business Development personnel, says Jesus de la Fuente, CEO of Graphenea. The most pronounced application directions that we will pursue will be advanced polymers, thermal interface materials, energy storage, and (bio)sensors.

Researchers from University of California - Riverside (UCR) report that compressed graphene laminate on PET achieve a higher thermal conductivity compared to non-compressed laminates (for the same average flake size). This is due to better flake alignment.

Graphene has a very high thermal conductivity. At room temperature, a graphene sheet has thermal conductivity of 2000 W/mk to 50000 W/mk. When you place it on a substrate the conductivity is lowered substantially (to around 90 W/mk) - but it is still substantially better than that of plastics.

Researchers from the University of Manchester (with help from an international team of scientists) discovered that if you stack two graphene sheets on on top of the other (bi-layer graphene) in a certain way, it actually cools down when hit with laser light.

The two graphene sheets are aligned so one sheet is rotated by 11.3 degrees. With a specific laser energy, instead of heating up like any "normal" material - it cools down. The researchers explain that the photons of the laser absorb the vibration energy of the atoms - instead of the other way around.

Perpetuus Carbon Group announced another partnership, this time with Cientifica. The two companies aim to bring together graphene technology, market demand and finance to the UK. They also want to create an integrated value chain - from graphene production to consumer and industrial applications. As part of the collaboration, Perpetuus will provide technical support to Cientifica’s planned product development.

As part of the press release, Perpetuus says that Finland's G-Heat Limited developed a new infrared heating technology. G-Heat use flat panel heaters that are based on graphene. Those heaters emit infrared light at wave-lengths precisely tailored for maximum comfort and minimum energy use. G-Heat says that their heaters will maintain the same level of comfort like conventional heaters, but will consume up to 70% less energy. It's not clear from the release, but I guess G-Heat is using Perpetuus' graphene and is being helped by Cientifica.

Aixtron announced today that Shanghai University ordered a BM R&D reactor that will be used for graphene and CNT research at the University's Sino-Sweden Microsystem Integration Technology Center (SMIT).

The University researchers will use this new reactor for their research into CNT and graphene application using thermal- and plasma-based chemical vapor deposition (CVD). The researchers aim to develop next generation thermal interface/dissipating materials, heat spreaders, multi-chip interconnects and through silicon vias (TSV) for semiconductor chip packaging.

Researchers from Germany's Max Planck Institute for Polymer Research and Singapore have shown that the thermal conductivity of graphene changes with the size of the graphene - which actually contradicts Fourier’s law in the micrometer scale. This was shown with computer simulations and later verified in experiments.

The researchers say that "the very concept of thermal conductivity as an intrinsic property does not hold for graphene, at least for patches as large as several micrometers". The researcher found out that the thermal conductivity logarithmically increases as a function of the size of the graphene samples. The longer the graphene patches, the more heat can be transferred per length unit.